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Incidence of straight and angulated screw channel following immediate implant placement in esthetic zone: A simulated cone-beam computed tomography study
Incidence of straight and angulated screw channel following immediate implant placement
https://orcid.org/0009-0004-1978-7373
Radomsutthisarn Watcharapon Data curation Formal analysis Investigation Resources Visualization Writing – original draft 1
Kretapirom Kornkamol Methodology Resources Supervision Visualization Writing – review & editing 2
https://orcid.org/0000-0002-2186-4516
Nakaparksin Pranai Conceptualization Methodology Project administration Supervision Writing – review & editing 1 *
1 Department of Advanced General Dentistry, Faculty of Dentistry, Mahidol University, Bangkok, Thailand
2 Department of Oral and Maxillofacial Radiology, Faculty of Dentistry, Mahidol University, Bangkok, Thailand
Abdullah Johari Yap Editor
Universiti Sains Malaysia, MALAYSIA
Competing Interests: All authors including, Dr. Pranai Nakaparksin, Dr. Watcharapon Radomsutthisarn, Dr. Kornkamol Kretapirom have declared that no competing interests exist.

* E-mail: Pranai.nak@mahidol.ac.th
5 9 2024
2024
19 9 e030815822 9 2023
15 7 2024
© 2024 Radomsutthisarn et al
2024
Radomsutthisarn et al
https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Statement of problem

The demand for immediate implant placement (IIP) in the esthetic zone is rapidly increasing. Despite the treatment’s benefits, the sagittal root position often dictates implant angulation, commonly necessitating the use of cement-retained restorations. This study investigates the impact of angulated screw channel on IIP in the esthetic zone.

Purpose

The purpose of this cone-beam computed tomography (CBCT) study was to determine the probability of IIP in the esthetic zone, using four different implant angulations.

Materials and methods

A retrospective review of CBCT images was conducted and accessed on 9 June 2021. The midsagittal images of maxillary anterior teeth were input into an implant planning software (Implant Studio®). Bone Level X Straumann® implant (BLX 3.5, 3.75, 4.0, 4.5, 5.0 mm) and Bone Level Tapered implant (BLT 2.9, 3.3 mm) were selected for 3D implant planning of IIP in the esthetic zone. The frequency distribution and probability of IIP were recorded and compared among all maxillary anterior teeth.

Results

CBCT images from 720 teeth (120 patient) were evaluated, revealing an overall probability of IIP in the esthetic zone is 76.11% (548/720). Different implant restoration type was evaluated in this study, with the following results; straight screw-retained prosthesis at 3.47% (19/548), cement-retained prosthesis at 14.59% (80/548) and angle screw-retained prosthesis at 85.40% (468/548).

Conclusion

IIP with traditional straight screw-retained prosthesis demonstrated the lowest probability. Nevertheless, the use of angulated screw channels enhances the probability of achieving straight screw-retained prostheses.

Clinical implications

The angulated screw channel is essential for increasing the probability of screw-retained prosthesis in IIP in the esthetic zone. However, limitation in screw angle correction still necessitate the use of cement-retained prostheses for numbers of patients undergoing IIP.

The authors received no specific funding for this work. Data AvailabilityAll relevant data are within the manuscript and its Supporting Information files.
Data Availability

All relevant data are within the manuscript and its Supporting Information files.
==== Body
pmcIntroduction

Immediate implant placement (IIP) and immediate provisionalization following tooth extraction has become a common clinical procedure for the replacement of failing teeth with high survival rate [1–4]. The most recent consensus conference in 2023 has recommended the protocol as the treatment of choice when the ideal conditions are present [4]. However, placement of dental implants in the maxillary anterior esthetic zone is challenging for clinicians, due to the patients’ esthetic expectations and several risk factors that affect overall outcome of the treatment. Therefore, for desired esthetic results and tooth function when performing an IIP [5, 6], this procedure requires strict patient and site-specific selection criteria [3].

To achieve successful tissue integration and minimize risk of complications for IIP, site-specific criteria should be followed, including absence of gingival recession, adequate gingival phenotype, sufficient bone anchorage, presence of facial bone wall, and absence of infection [3]. However, the complexity and technique of the surgical procedure can be challenging. Subsequently, an appropriate implant diameter and length selection has shown to affect both esthetic consequence and primary stability [3, 7, 8]. Smaller diameter implant is recommended for adequate grafting material between facial bone and planned implant position [9]. For predictable implantation in IIP, 4–5 mm implant engagement at apical bone beyond tooth socket is recommended [3].

A preoperative CBCT scan provides valuable information for implant planning including implant position, diameter, length, and angulation [10, 11]. Implant angulation is dictated by sagittal root position (SRP), in turn results in either cement-retained or screw-retained implant prosthesis [12]. Despite the lack of evidence from systematic reviews indicating a difference in peri-implant marginal bone loss between cement-retained and screw-retained implant crowns [13–18], a positive correlation was found between excess subgingival residual cement and peri-implant disease. Thus, clinician commonly plan for implant angulation to accommodate for screw-retained implant prosthesis.

A recent 2-dimentional digital implant template study has demonstrated low possibility of straight screw channel screw-retained restoration for IIP protocol in the esthetic zone [19]. A follow up study using angulated screw channel has shown to increase the frequency of screw-retained implant prosthesis [20].

The purpose of this study was to determine the probability of IIP in the maxillary anterior teeth, using four different implant angulations, traditional screw-retained implant prosthesis (screw-retained), traditional cement-retained implant prosthesis (incisal edge), limited angulation for angulated screw channel (angle screw), and limit restorability angulation for cement-retained implant prosthesis (middle half).

Material and method

Patient selection

This retrospective study was approved by the Institutional Review Board (IRB) of the Faculty of Dentistry/Faculty of Pharmacy, Mahidol University (IRB 2021/052.0906). The sample for this study were patients (39 males and 81 females) with a mean age of 35 years old (range: 21 to 77 years old) who had CBCT scans of the anterior maxilla at the Oral and Maxillofacial Radiology clinic, Faculty of Dentistry, Mahidol University performed during January 2012 –August 2020. CBCT images were performed by 3D Accuitomo 170 (J. Morita®, Japan) and selected for evaluation on 9 June 2021. The design of this study has not been performed. So, there will be no similarity in statistical data for this study. The retrospective study of Asok Velayudhan et al [21], which the objective related to this study have been used for calculated sample size. The sample size calculation for estimating proportion used as shown in the formula:

n=z1−α22p(1−p)d2

α:Confidentinterval=0.05Z1−α/22:StandardNormalscoreatp=1‐α/2p:Proportionfrompreviousstudyd:marginoferror

The output of sample size calculation is 114. The 120 CBCT scans are sufficient for this study.

Inclusion criteria were as follows:

CBCT must have field of view (FOV) 6 cm. x 6 cm. (voxel size 0.125 mm) or FOV 8 cm. x 8 cm. (voxel size 0.160 mm.).

The patient must be at least 18 years old at the time of CBCT scan.

The patient must have all maxillary anterior teeth (canine to canine) with stable posterior occlusal support.

The patient must have a normal alignment of maxillary anterior teeth without periodontal or periapical pathologies as observed on CBCT.

Exclusion criteria were as follows:

Radiographic evidence of periapical inflammatory lesion, periodontally involved teeth, severe root resorption, and/or previous records of trauma, or bone pathology.

Radiographic evidence of artifacts and orthodontic appliances.

Radiographic evidence of surgical (guided bone/tissue regeneration) treatment in the maxillary anterior dentition.

Upper anterior teeth were misaligned.

CBCT images that were distorted or blurred.

Data reconstruction from and CBCT images and digital simulation

CBCT volumetric data was exported to DICOM files and reconstructed by using Implant Studio® (3Shape®, Denmark). For the axial view, the implant was positioned at the center of the selected tooth. In the panoramic view, the implant was aligned parallel to the long axis of the tooth. In the coronal view, the implant was rotated parallel to the long axis of the tooth. The mid-sagittal image, which was located at the bucco-lingual side of the tooth, was used to measure all parameters (Fig 1).

10.1371/journal.pone.0308158.g001 Fig 1 User interface of Implant Studio® software showing the implant placement at area 13.

In the axial view, the implant was positioned at the center of the selected tooth. In the panoramic view, the implant was aligned parallel to the long axis of tooth. In the coronal view, the implant was rotated parallel to the long axis of the tooth. The mid-sagittal image, which was been sectioned at the bucco-lingual aspect of the tooth, was used to measure and plan of IIP.

The mid-sagittal of the selected tooth was used for the measurement of the buccal bone thickness and faciopalatal root dimension at the bone crest level. SRP was classified with respect to the alveolar housing according to Kan et al. [12].

Implant planning and determining of implant diameter and length

Implant was planned by Implant Studio® (3Shape®, Denmark) using Bone level X Straumann® implant (BLX 3.5, 3.75, 4.0, 4.5, 5.0 mm) (Straumann®, Switzerland) and Bone Level Tapered implant (BLT 2.9, 3.3 mm) (Straumann®, Switzerland). BLT 2.9 mm was used in lateral incisor only. The angulated screw channel was included in the calculation of all implant diameter except diameter of 2.9 mm was not included.

An implant should be placed 3 mm apical and 2 mm palatal to gingival margin [22]. Thus, the 3 ± 0.02 mm line apical to gingival margin and a 2 ± 0.02 mm line, which perpendicular to the first line were created. The end point was marked as a position of the most buccal aspect of implant platform point P. The line drawn from incisal edge to root apex was long axis of the tooth. The point between incisal edge to CEJ was marked as point M. The point between the center of the most prominent point of cingulum to the incisal edge was marked as point S. The implant component points and lines are shown in Fig 2.

10.1371/journal.pone.0308158.g002 Fig 2 The component points of the implant are marked in the mid-sagittal images.

The implant was positioned in four different angulations (Fig 3) as follows: screw-retained, incisal edge, angle screw and middle half. In traditional cement-retained implant prosthesis (incisal edge), long axis of implant will coincide with incisal edge. In traditional screw-retained implant prosthesis (screw-retained), long axis of implant will coincide with point S. In limit angulation for angulated screw channel (angle screw), long axis of implant will coincide at the point that an angle up to 25° from traditional screw-retained. In limit restorability angulation for cement-retained implant prosthesis (middle half), long axis of implant will coincide with point M.

10.1371/journal.pone.0308158.g003 Fig 3 The four different implant angulations in this study.

A. Screw-retained, B. Incisal edge, C. Angle screw, D. Middle half.

To determine the implant diameter and length, the smallest implant diameter and length were selected. The implant length was increased until engaging a minimum of 4 ± 0.02 mm in distance from the apical to root apex [3], which is considered as the first implant position and increased until the apex of implant is positioned 1 mm away from critical structures. After that, increased the next size implant diameter until it reached the maximum, which calculated by faciopalatal root dimension minus two to ensure sufficient bone grafting gap [3].

All measurements (the buccal bone thickness and faciopalatal root dimension) for the implant planning process were performed by one examiner. The intraexaminer reliability was assessed by repeating the measurement on 10 randomly selected CBCT images 1 month after the first measurement by intra-class correlation coefficient (ICC).

Descriptive statistics were used to report the probability of IIP in the esthetic zone using four different implant angulations as percentages.

Results

120 CBCT images from maxillary anterior teeth (240 central incisors, 240 lateral incisors, 240 canines) in 120 patients were evaluated in this study. The ICC of this study was 0.885, which considered as good according to Cicchetti’s criteria [23].

The result revealed that 84.58% (609/720) of anterior maxillary teeth had buccal bone of less than 1 mm. The SRP with probability of IIP are as follow: class I 87.91% (633/720) with 84.20% (533/633), class II 2.78% (20/720) with 70% (14/20), class III 0.42% (3/720) with 33.33% (1/3) and class IV 8.89% (64/720) with 0% respectively.

The distribution of SRP with probability of IIP are shown in Table 1.

10.1371/journal.pone.0308158.t001 Table 1 Distribution of sagittal root position (SRP) with probability of IIP in the esthetic zone.

SRP	Class I	Class II	Class III	Class IV	
Distribution	633/720 (87.91%)	20/720 (2.78%)	3/720 (0.42%)	64/720 (8.89%)	
Probability	533/633 (84.20%)	14/20 (70%)	1/3 (33.33%)	0/64 (0%)	
	Central incisor	Lateral incisor	Canine	Central incisor	Lateral incisor	Canine	Central incisor	Lateral incisor	Canine	Central incisor	Lateral incisor	Canine	
Distribution	213(88.75%)	183(76.25%)	237(98.75%)	9(3.75%)	11(4.58%)	-	1(0.42%)	2(0.83%)	-	17(7.08%)	44(18.34%)	3(1.25%)	

The probability of IIP in all maxillary anterior teeth are 76.11% (548/720), with consist of central incisor 82.50% (198/240), lateral incisor 64.58% (155/240) and canine 81.25% (195/240). In this study, an individual tooth can have multiple implant positions. The probability of IIP for each relation (10 relations) is shown in Table 2.

10.1371/journal.pone.0308158.t002 Table 2 Detailed probability of IIP by angulation groups and tooth type.

	Central incisor (240 teeth)	Lateral incisor (240 teeth)	Canine (240 teeth)	Total (720 teeth)	
1. Incisal edge (I)	24(10%)	29(12.08%)	7(2.92%)	60(8.33%)	
2. Screw-retained (S)	1(0.42%)	-	-	1(0.14%)	
3. Angle screw (A)	57(23.75%)	52(21.66%)	21(8.75%)	130(18.06%)	
4. Middle half (M)	1(0.42%)	6(2.5%)	73(30.41%)	80(11.11%)	
5. I, S	8(3.33%)	-	-	8(1.11%)	
6. I, A	47(19.58%)	10(4.17%)	6(2.5%)	63(8.75%)	
7. A, M	26(10.83%)	45(18.75%)	78(32.5%)	149(20.69%)	
8. I, S, A	7(2.92%)	-	-	7(0.97%)	
9. I, A, M	24(10%)	13(5.42%)	10(4.17%)	47(6.53%)	
10. I, S, A, M	3(1.25%)	-	-	3(0.42%)	
Total	198/240(82.5%)	155/240(64.58%)	195(81.25%)		
1. I = incisal edge, 2. S = screw, 3. A = angle, 4. M = middle, 5. I, S = incisal edge and screw, 6. I, A = incisal edge and angle, 7. A, M = angle and middle, 8. I, S, A = incisal edge, screw and angle, 9. I, A, M = incisal edge, angle and middle, 10. I, S, A, M = incisal edge, screw, angle and middle

The probability of IIP in screw-retained, incisal edge, angle screw and middle half are 2.64% (19/720), 26.11% (188/720), 55.42% (399/720) and 38.75% (279/720) respectively. The probability of IIP in each angulation is shown in Table 3.

10.1371/journal.pone.0308158.t003 Table 3 Summary of IIP probability by angulation groups and tooth type.

Angulation	Central incisor (240 teeth)	Lateral incisor (240 teeth)	Canine (240 teeth)	Total (720 teeth)	
Incisal edge	113(47.08%)	52(21.67%)	23(9.58%)	188(26.11%)	
1, 5, 6, 8, 9, 10	
Screw-retained	19(7.92%)	0	0	19(2.64%)	
2, 5, 8, 10	
Angle screw	164(68.33%)	120(50%)	115(47.92%)	399(55.42%)	
3, 6, 7, 8, 9, 10	
Middle half	54(22.5%)	64(26.67%)	161(67.08%)	279(38.75%)	
4, 7, 9, 10	
1. I = incisal edge, 2. S = screw, 3. A = angle, 4. M = middle, 5. I, S = incisal edge and screw, 6. I, A = incisal edge and angle, 7. A, M = angle and middle, 8. I, S, A = incisal edge, screw and angle, 9. I, A, M = incisal edge, angle and middle, 10. I, S, A, M = incisal edge, screw, angle and middle

The probability of IIP according to restoration type, cement-retained, straight screw-retained, angle screw-retained are 14.59% (80/548), 3.47% (19/548) and 85.40% (468/548) respectively. The probability of IIP in each restoration type is shown in Table 4.

10.1371/journal.pone.0308158.t004 Table 4 Summary of restoration probability by restoration type and tooth with possible IIP.

Restoration type	Central incisor (198 teeth)	Lateral incisor (155 teeth)	Canine (195 teeth)	Total (548 teeth)	
Cement-retained*	1(0.51%)	6(3.87%)	73(37.43%)	80(14.59%)	
4	
Straight screw-retained	19(9.59%)	0	0	19(3.47%)	
2, 5, 8, 10	
Angle screw-retained	197(99.49%)	149(96.13%)	122(62.56%)	468(85.40%)	
1, 2, 3, 5, 6, 7, 8, 9, 10	
*Cement retained prosthesis is indicated when screw-retained prosthesis can’t be achieved.

1. I = incisal edge, 2. S = screw, 3. A = angle, 4. M = middle, 5. I, S = incisal edge and screw, 6. I, A = incisal edge and angle, 7. A, M = angle and middle, 8. I, S, A = incisal edge, screw and angle, 9. I, A, M = incisal edge, angle and middle, 10. I, S, A, M = incisal edge, screw, angle and middle

Central incisor can position implant with diameter of 3.3 mm, 3.5 mm, 3.75 mm, 4.0 mm and 4.5 mm at 81.67% (196/240), 68.33% (164/240), 54.58% (131/240), 40.83% (98/240) and 5% (12/240) respectively and length of 10 mm, 12 mm, 14 mm, 16 mm and 18 mm at 22.5% (54/240), 62.92% (151/240), 80% (192/240), 73.33% (176/240) and 54.58% (131/240) respectively.

Lateral incisor can position implant with diameter of 2.9 mm, 3.3 mm, 3.5 mm, 3.75 mm and 4.0 mm at 57.92% (139/240), 51.25% (123/240), 36.25% (87/240), 26.67% (64/240) and 15% (36/240) respectively and length of 10 mm, 12 mm, 14 mm, 16 mm and 18 mm at 6.67% (16/240), 30% (72/240), 56.67% (136/240), 43.33% (104/240) and 30.83% (74/240) respectively.

Canine can position implant with diameter of 3.3 mm, 3.5 mm, 3.75 mm, 4.0 mm, 4.5 mm and 5.0 mm at 73.33% (176/240), 77.92% (187/240), 75.42% (181/240), 71.25% (171/240), 55% (132/240) and 23.75% (57/240) respectively and length of 10 mm, 12 mm, 14 mm, 16 mm and 18 mm at 7.5% (18/240), 25.42% (61/240), 49.58% (119/240), 58.75% (141/240) and 55% (132/240) respectively.

The distribution and the percentages of the diameter and length, which were used for IIP are shown in Table 5.

10.1371/journal.pone.0308158.t005 Table 5 Distributions of diameter and length of implant used in immediate implant placement in esthetic zone.

Diameter	Length	
	Central	Lateral	Canine		Central	Lateral	Canine	
incisor	incisor	(240 teeth)		incisor	incisor	(240 teeth)	
(240 teeth)	(240 teeth)			(240 teeth)	(240 teeth)		
2.9 mm	-	-	139	57.92%	-	-	6 mm	-	-	-	-	-	-	
3.3 mm	196	81.67%	123	51.25%	176	73.33%	8 mm	-	-	-	-	-	-	
3.5 mm	164	68.33%	87	36.25%	187	77.92%	10 mm	54	22.5%	16	6.67%	18	7.5%	
3.75 mm	131	54.58%	64	26.67%	181	75.42%	12 mm	151	62.92%	72	30%	61	25.42%	
4.0 mm	98	40.83%	36	15%	171	71.25%	14 mm	192	80%	136	56.67%	119	49.58%	
4.5 mm	12	5%	-	-	132	55%	16 mm	176	73.33%	104	43.33%	141	58.75%	
5 mm	-	-	-	-	57	23.75%	18 mm	131	54.58%	74	30.83%	132	55%	

Discussion

The success criteria for immediate implant placement (IIP) in the esthetic zone including non-acute infection areas, presence of thick gingival biotype, engaging sufficient apical bone, with intact buccal bone [3]. Recent studies have shown that on average, the buccal bone in anterior maxillary teeth was less than 1 mm [24, 25]. This study found similar results with the majority of anterior maxillary teeth, 84.58% (609/720), having less than 1 mm of buccal bone thickness. Canine teeth 29.17% (70/240), were found most frequently to have a buccal bone thickness greater than 1 mm, followed by the lateral incisors and central incisors 11.25% (27/240) and 5.83% (14/240) respectively.

There was a 12.5% (90/720) probability of IIP in the group where the buccal bone is more than 1 mm, which leaves a probability of 63.61% (458/720) for the group of buccal bone that has less than 1 mm. In this group, there is a high risk for recession of the facial mucosa and significant flattening the soft tissue profile at the neck of implant prosthesis [1]. It is important to emphasize that the use of buccal bone augmentation [26], soft tissue graft [27], the combination of bone augmentation and soft tissue graft or alternative option such as partial tooth extraction therapy [28] can contribute to improve the overall esthetic result, and compensate with buccal contour remodeling in IIP.

Sagittal root position (SRP) could directly influence the position of IIP. In the study of Kan et al. [12], the author suggested that class I SRP was favorable and class IV SRP was regarded as a contraindication for IIP [12]. In this study, the distribution with probability results of class I and class IV SRP were in concordance with the study of Kan, the highest distribution and probability is class I 87.42% (633/720) with probability of 84.20% (533/633) and class IV 8.89% (64/720) with the lowest probability of 0% (0/64). Surprisingly, the probability in class II is more than in class III, 70% (14/20) and 33.33% (1/3) respectively, which were different from previous study. These may due to sufficient apical bone to engage in traditional cement-retained implant prosthesis (incisal edge) in class II, whereas in class III inadequate apical bone causing implant to extended outward of alveolar housing.

Direction of implant prosthesis can influence the position of IIP as well. Cement-retained implant prosthesis has more advantages for esthetics, such as absence of screw access hole. In addition, long axis of implant coincides incisal edge, which creates a proper emergence angle that similar to the natural teeth approximately 15° [29]. While a screw-retained implant prosthesis is beneficial for retrievability, reducing complication from the left-over cement, which can further cause inflammation and bone loss [30, 31]. However, the disadvantages such as screw access hole might be esthetically compromised. Therefore, in the esthetic zone, the implant should be placed at cingulum area. However, the more palatal the implant placement, the more emergence angle and therefore makes a greater cervical contour [32]. The mentioned problem caused peri-implantitis and recession on labial surface [33]. Angulated screw channel avoids screw access hole to be placed in palatal area without compromised esthetic [34]. In addition, the position of implant that used of angulated screw channel is on labial aspect, which creates proper emergence angle. The results of this study revealed that if using traditional prosthetic screw with 0-degree compensation the prosthesis is limited to 14.59% (80/548) cement-retained with 3.47% (19/548) straight screw-retained prosthesis. By incorporating angulated screw with 25-degree compensation could increase the probability of screw-retained prosthesis to 85.40% (468/548). In individual tooth, an angulated screw channel could help increase the probability for screw-retained prosthesis in central incisor from 9.59% (19/198) to 99.49% (197/198), in lateral incisors from 0% to 96.13% (149/155), and in canine from 0% to 62.56% (122/195). Nevertheless, it’s important to noted that an angle over 25° above limitation of angulated screw channel, IIP can still be performed but restricted to cement-retained prosthesis. In this study 14.59% (80/548) were restricted to only “middle half” angulation which result in cement-retained prosthesis. It is noteworthy that majority of cement-retained are with canine 91.25% (73/80) which coincide with majority of canine being SRP class I.

When considering in implant length, IIP required the engagement of 4 to 5 mm of bone apical to tooth socket [3], this result is increased implant length than the traditional implant placement. An implant length of 14 mm is the most frequently used in central incisor and lateral incisor 80% (192/240) and 56.67% (136/240) respectively. An implant length of 16 mm is the most frequently used for canine teeth 58.75% (141/240), as canine has the longest root length of 15.83 ± 1.49 mm [35]. Beyond the mentioned implant length could result in over extrusion of implant. When considering implant diameter, a diameter of 3.3 mm is the most frequently used for central incisors 81.67% (196/240). A diameter of 2.9 mm is the most frequently used in lateral incisor 57.92% (139/240), due to the least faciopalatal root dimension. For canine teeth with widest faciopalatal 6.67 mm [36], a diameter of 3.5 mm is the most frequently used 77.92% (187/240). Noteworthy in this study, the diameter of 2.9 mm is used in lateral incisor only, due to the manufacturer’s recommendation. Previous study had shown that narrow diameter implant with < 3 mm has decrease survival rate [37] with increases the risk of implant fracture, abutment and screw failure [38, 39]. Even though, when simulating 2.9 mm diameter in central incisors and canines can increase the probability from 82.50% (198/240 teeth) to 87.50% (210/240) and 81.25% (195/240) to 82.08% (197/240).

In recent years, there are two very similar studies Kan et al. [19] and Erin et al. [40]. In Kan [19] study investigate the probability of using straight screw-channel screw-retained restoration for IIP in maxillary anterior teeth. The method was 2D implant planning using digital template. The digital template for 3.5 mm diameter was used in central incisor and lateral incisor. The digital template for 4.3 mm diameter was used in central incisor and canine. The implant length was 13, 15 and 18 mm. In Erin [40] study was virtual implant planning in screw-retained implant direction using straight or angled screw channel abutment with different angulation (5°, 10°, 15°). The process is not IIP and the implant diameter for each site was fix based on standards for each tooth type (canine and central incisor 4.3 mm, lateral incisor 3.5 mm). The implant length was 10 mm for all implant.

In this study was virtual implant planning to determine the probability of IIP in the esthetic zone. The additional implant angulations mentioned in more than two studies were cement-retained implant prosthesis, angulated screw channel at the 25° angulation and positioning of implant at the middle of individual tooth. Various size of diameter (2.9, 3.3, 3.5, 3.75, 4.0, 4.5, 5 mm) and length (6, 8, 10, 12, 14, 16, 18 mm) were included in this study to promote adaptability and suitability in IIP in the esthetic zone.

For limitation of this study to standardized the method, implant planning is limited to static predetermined angulation to anatomical relation and implant size. This could limit the probability as clinician can increase the depth of implant placement, modified implant angulation within restorable position. Future study is suggested to study the effect of probability associated with dynamic implant planning.

Conclusion

Within the limitation of this CBCT study, thorough treatment planning and precise evaluation a probability of 76.11% (548/720) perform IIP. Straight screw-retained prosthesis allows for the lowest probability 3.47% (19/548) to perform IIP in the esthetic zone. Moreover, the use of angulated screw channel demonstrated to increase the probability of straight screw-retained prosthesis to 85.40% (468/548). However, the limit of angulated screw could not compensate for all IIP position with 14.59% (80/548) restricted to cement-retained prosthesis. A careful individual site planning is advised to maximize treatment outcome.

Supporting information

S1 Data (XLSX)

10.1371/journal.pone.0308158.r001
Decision Letter 0
Abdullah Johari Yap Academic Editor
© 2024 Johari Yap Abdullah
2024
Johari Yap Abdullah
https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Submission Version0
1 Dec 2023

PONE-D-23-29819Incidence of straight and angulated screw channel following immediate implant placement in esthetic zone: A CBCT studyPLOS ONE

Dear Dr. Nakaparksin,

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Johari Yap Abdullah, B.S. & I.T, GradDip ICT, M.Sc, Ph.D.

Academic Editor

PLOS ONE

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Reviewer #1: Yes

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

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Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #2: Yes

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Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This study was conducted to determine the probability of immediate implant placement in the esthetic zone using four different implant directions. In general, the findings can be potentially applied for dental implant treatment planning.

Comments:

1. Manuscript is well written but it can be further improved with adequate proofreading (e.g. paragraph from line 66 to 77). Please do the needful.

2. Table 2: 'each relation' - can be more specific (e.g. anatomical relation, etc)

3. Conclusion: The authors state that "the use of angulated screw is essential to increase the probability of screw retained implant prosthesis".

Can the authors explain further on the relevance of this statement in relation to the statement problem and the purpose of this study?

Reviewer #2: The authors conducted a CBCT study, aiming to determine the probability of IIP in the esthetic zone, using four different implant directions. The topic is clinically relevant and the manuscript is well presented. However, some sections may need further clarification.

Abstract

1. Line 14: Please specify the number of patients as well.

2. Line 15: Please specify the method used to come up with the probability of 76.11%. What’s the diameter of the implants? Was angulated screw channel (ASC) included in this calculation?

3. Line 18: What is “limited restorability angulation for cement retained implant prosthesis (middle half)”? This description is confusing. Please revise.

Material and Method

1. Line 90: How did you determine a number of 120 CBCT scans is sufficient for the study?

2. For the inclusion/exclusion criteria, did you have any criteria to assess if the patient’s anterior teeth were misaligned?

3. Line 132: Any citations you could provide to support the use of 4 mm as the threshold?

4. The authors should elaborate on the methods used to determine the long axis of the tooth, the angulation/direction of the planned implant, etc.

Results

1. How did you decide the implant length and diameter for central incisors, lateral incisors and canines? For example, is it practical to place a 5mm-diameter implant at a canine location, or to place a 16mm- or even 18mm-long implant?

Discussion

1. There are two very similar studies published in 2022 and 2023. The authors must provide comments on these two studies, and elaborate on how the current study can add more information to the currently available evidence.

Erin K Edmondson, Pedro M Trejo, Nikolaos Soldatos, Robin L Weltman. The ability to screw-retain single implant-supported restorations in the anterior maxilla: A CBCT analysis. J Prosthet Dent. 2022 Sep;128(3):443-449.

Joseph Y K Kan, Kitichai Rungcharassaeng, Pongrapee Kamolroongwarakul, Guo-Hao Lin, Hiroyuki Matsuda, Shi Yin, Hom-Lay Wang, Dennis Tarnow, Jaime L Lozada. Frequency of screw-retained angulated screw channel single crown following immediate implant placement and provisionalization in the esthetic zone: A cone beam computed tomography study/ Clin Implant Dent Relat Res. 2023 Oct;25(5):789-794.

2. The authors should comment on the limitations of the current study.

**********

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Reviewer #1: No

Reviewer #2: No

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10.1371/journal.pone.0308158.r002
Author response to Decision Letter 0
Submission Version1
30 Jan 2024

Reviewer #1:

1. Manuscript is well written but it can be further improved with adequate proofreading (e.g.paragraph from line 66 to 77). Please do the needful.

Answer: Line 66-70 have been revised in the introduction.

2. Table 2: 'each relation' - can be more specific (e.g.anatomical relation, etc)

Answer: Table 2 and table 3 have been revised and adjusted in page 10 and 11 respectively.

3. Conclusion: The authors state that "the use of angulated screw is essential to increase the probability of screw retained implant prosthesis".

Can the authors explain further on the relevance of this statement in relation to the statement problem and the purpose of this study?

Answer: In our study screw retained implant prosthesis allows for the lowest probability 2.64% (19/720) to perform IIP in esthetic zone. By incorporating angulated screw with 25-degree compensation could increase the probability of screw retained implant prosthesis to 55.42% (399/720). In individual tooth, an angulated screw channel could help increase the probability for screw retained implant prosthesis in central incisor from 7.92% (19/240) to 72.08% (173/240), in lateral incisors from 0% to 50% (120/240), and in canine from 0% to 47.92% (115/240). So, the use of angulated screw channel is essential to increase the probability of screw retained implant prosthesis.

Reviewer #2:

Abstract

1. Line 14: Please specify the number of patients as well.

Answer: 120 patients have been added to the abstract.

2. Line 15: Please specify the method used to come up with the probability of 76.11%. What’s the diameter of the implants? Was angulated screw channel (ASC) included in this calculation?

Answer: 548 teeth from 720 teeth (548/720) can be performed IIP in esthetic zone. The diameter of 3.3, 3.5, 4.1, 4.5 and 5 mm were used in all maxillary anterior teeth (central incisor, lateral incisor, canine). The diameter of 2.9 mm is used in lateral incisor only. The angulated screw channel was included in the calculation of all implant diameter except diameter of 2.9 mm was not included.

3. Line 18: What is “limited restorability angulation for cement retained implant prosthesis (middle half)”? This description is confusing. Please revise.

Answer: It is the most buccal angulation that allow for IIP in esthetic zone in cement retained implant prosthesis, which often in the middle of individual tooth, hence referred to as “middle half”. Even though, there are some possibilities to restore implant in more extreme buccal angulation with implant platform being more apical and palatal, there is an increased risk of complication.

Material and Method

1. Line 90: How did you determine a number of 120 CBCT scans is sufficient for the study?

Answer: Sample size calculation

The purpose of this study is to determine the probability of IIP in esthetic zone using four different implant directions. This design of the study has not been performed yet. So, there will be no similarity in statistical data for this study.

The sample size calculation for estimating proportion will be used as shown in the formula (in Response to reviewers):

According to the retrospective study of Ashok Velayudhan et al. in 2020 that the objective related to the current study showed that in a total of 77 implants placed in the anterior maxilla, with 21 of them being immediate implants, 6 (or 7.8%) of 21 immediate implants were placed in the anterior maxilla alone.

The output of the sample size calculation is 114. The 120 patients are sufficient for our study.

2. For the inclusion/exclusion criteria, did you have any criteria to assess if the patient’s anterior teeth were misaligned?

Answer: Upper anterior teeth (canine-canine) misaligned is considered to exclusion criteria, which did not include in the sample size of our study.

3. Line 132: Any citations you could provide to support the use of 4 mm as the threshold?

Answer: The citation has been added to line 132.

4. The authors should elaborate on the methods used to determine the long axis of the tooth, the angulation/direction of the planned implant, etc

Answer: The line drawn from incisal edge to root apex was long axis of the tooth.

The point between incisal edge to CEJ was marked as point M. The point between the center of the most prominent point of cingulum to the incisal edge was marked as point S.

- In traditional cement retained implant prosthesis (incisal edge), long axis of implant will coincide with incisal edge.

- In traditional screw retained implant prosthesis (screw retained), long axis of implant will coincide with point S.

- In limit angulation for angulated screw channel (angle screw), long axis of implant will coincide at the point that an angle up to 25° from traditional screw retained.

- In limit restorability angulation for cement retained implant prosthesis (middle half), long axis of implant will coincide with point M.

Results

1. How did you decide the implant length and diameter for central incisors, lateral incisors and canines? For example, is it practical to place a 5mm-diameter implant at a canine location, or to place a 16mm- or even 18mm-long implant?

Answer: In our study, the guideline for implant positioning includes, positioning implant platform at 3 mm apical and 2 mm palatal to gingival margin, a minimum distant of 1.5 mm from adjacent teeth, implant engaging at least 4 mm of apical bone, with at least 2 mm of buccal bone to implant gap to accommodate the grafting material to minimize bone remodeling. In our study was digital implant planning to determine the probability of IIP in esthetic zone by using different diameter (2.9, 3.3, 3.5, 3.75, 4.0, 4.5, 5 mm) and length (6, 8, 10, 12, 14, 16, 18 mm). To determine the diameter and length, select the smallest diameter and length and gradually increase the diameter and length until reaching a size where the implant exist in alveolar housing while respecting aforementioned guideline. It is possible to placed implant with diameter 5 mm and length 16-18 mm in canine since it is allowed by the guideline. However, it does not explicitly state that using these diameter and length is the first choice for IIP in esthetic zone.

Discussion

1. There are two very similar studies published in 2022 and 2023. The authors must provide comments on these two studies, and elaborate on how the current study can add more information to the currently available evidence.

Erin K Edmondson, Pedro M Trejo, Nikolaos Soldatos, Robin L Weltman. The ability to screw-retain single implant-supported restorations in the anterior maxilla: A CBCT analysis. J Prosthet Dent. 2022 Sep;128(3):443-449.

Joseph Y K Kan, Kitichai Rungcharassaeng, Pongrapee Kamolroongwarakul, Guo-Hao Lin, Hiroyuki Matsuda, Shi Yin, Hom-Lay Wang, Dennis Tarnow, Jaime L Lozada. Frequency of screw-retained angulated screw channel single crown following immediate implant placement and provisionalization in the esthetic zone: A cone beam computed tomography study/ Clin Implant Dent Relat Res. 2023 Oct;25(5):789-794.

Answer: In Erin K Edmondson study was virtual implant planning by Simplant® Pro17.01; Dentsply Sirona in screw retained implant direction using straight or an angled screw channel abutment with different angulation (5°, 10°, 15°). The process is not IIP, therefore the method to placed implant was different from our study. The implant diameter for each site was fix based on standards for each tooth type (canine and central incisor 4.3 mm, lateral incisor 3.5 mm). The implant length was 10 mm for all implant.

In Joseph Y K Kan study investigate the probability of using straight screw-channel screw-retained restoration for immediate implant placement in maxillary anterior teeth. The method of this study was different from our study. The mid sagittal image of each maxillary teeth with vertical and horizontal scale bars was screen-captured and transferred to Keynote. The digital template for 3.5 mm diameter was used in central incisor and lateral incisor. The digital template for 4.3 mm diameter was used in central incisor and canine. The implant length was 13, 15 and 18 mm. Additional line added to digital template as a guide for IIP. All CBCT images were classified as contraindicated or indicated by two examiners.

In our study was virtual implant planning by Implant Studio® to determine the probability of IIP in esthetic zone. The directions of implant that added for more than the two mentioned study (Erin K Edmondson and Joseph Y K Kan) were cement retained implant prosthesis, angulated screw channel at the 25° angulation and the middle of individual tooth. Various size of diameter (2.9, 3.3, 3.5, 3.75, 4.0, 4.5, 5 mm) and length (6, 8, 10, 12, 14, 16, 18 mm) were included in our study to promote adaptability and suitability in IIP in esthetic zone.

2. The authors should comment on the limitations of the current study.

Answer: In our study, to standardized the method, implant planning is limited to static predetermined angulation to anatomical relation and implant size. This could limited the probability as clinician can increase the depth of implant placement, modified implant angulation within restorable position. Future study is suggested to study the effect of probability associated with dynamic implant planning.

Attachment Submitted filename: Response to Reviewers.docx

10.1371/journal.pone.0308158.r003
Decision Letter 1
Abdullah Johari Yap Academic Editor
© 2024 Johari Yap Abdullah
2024
Johari Yap Abdullah
https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Submission Version1
26 Feb 2024

PONE-D-23-29819R1Incidence of straight and angulated screw channel following immediate implant placement in esthetic zone: A CBCT studyPLOS ONE

Dear Dr. Nakaparksin,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Apr 11 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Johari Yap Abdullah, B.S. & I.T, GradDip ICT, M.Sc, Ph.D.

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: All comments and recommendations have been satisfactorily addressed.

Clear clarification was made on issues raised from the first review.

The amendments are well highlighted in the manuscript. Thank you.

Reviewer #2: While the authors adequately addressed most concerns in the "Author's Response to Reviewer Comments," it is noted that the manuscript itself has undergone only minimal revision. It is requested to incorporate the information provided in the Author's Response directly into the manuscript to ensure a more comprehensive presentation.

The specific details from the "Author's Response to Reviewer Comments" that need to be included in the manuscript are as follows:

Answer for using angulated screw channel of not: 548 teeth from 720 teeth (548/720) can be performed IIP in esthetic zone. The diameter of 3.3, 3.5, 4.1, 4.5 and 5 mm were used in all maxillary anterior teeth (central incisor, lateral incisor, canine). The diameter of 2.9 mm is used in lateral incisor only. The angulated screw channel was included in the calculation of all implant diameter except diameter of 2.9 mm was not included.

Answer for clarifying “limited restorability angulation for cement retained implant prosthesis": It is the most buccal angulation that allow for IIP in esthetic zone in cement retained implant prosthesis, which often in the middle of individual tooth, hence referred to as “middle half”. Even though, there are some possibilities to restore implant in more extreme buccal angulation with implant platform being more apical and palatal, there is an increased risk of complication.

Answer for sample size calculation:

The purpose of this study is to determine the probability of IIP in esthetic zone using four different implant directions. This design of the study has not been performed yet. So, there will be no similarity in statistical data for this study.

The sample size calculation for estimating proportion will be used as shown in the formula (in Response to reviewers):

According to the retrospective study of Ashok Velayudhan et al. in 2020 that the objective related to the current study showed that in a total of 77 implants placed in the anterior maxilla, with 21 of them being immediate implants, 6 (or 7.8%) of 21 immediate implants were placed in the anterior maxilla alone.

The output of the sample size calculation is 114. The 120 patients are sufficient for our study. --> This must be mentioned in the manuscript.

Answer for misaligned teeth as an exclusion criterion: Upper anterior teeth (canine-canine) misaligned is considered to exclusion criteria, which did not include in the sample size of our study.

Answer to elaborate on the methods used to determine the long axis of the tooth, the angulation/direction of the planned implant:

The line drawn from incisal edge to root apex was long axis of the tooth.

The point between incisal edge to CEJ was marked as point M. The point between the center of the most prominent point of cingulum to the incisal edge was marked as point S.

- In traditional cement retained implant prosthesis (incisal edge), long axis of implant will coincide with incisal edge.

- In traditional screw retained implant prosthesis (screw retained), long axis of implant will coincide with point S.

- In limit angulation for angulated screw channel (angle screw), long axis of implant will coincide at the point that an angle up to 25° from traditional screw retained.

- In limit restorability angulation for cement retained implant prosthesis (middle half), long axis of implant will coincide with point M. --> Please add all of them to your manuscript.

Discussion

Answer related to the two recent studies:

In Erin K Edmondson study was virtual implant planning by Simplant® Pro17.01; Dentsply Sirona in screw retained implant direction using straight or an angled screw channel abutment with different angulation (5°, 10°, 15°). The process is not IIP, therefore the method to placed implant was different from our study. The implant diameter for each site was fix based on standards for each tooth type (canine and central incisor 4.3 mm, lateral incisor 3.5 mm). The implant length was 10 mm for all implant.

In Joseph Y K Kan study investigate the probability of using straight screw-channel screw-retained restoration for immediate implant placement in maxillary anterior teeth. The method of this study was different from our study. The mid sagittal image of each maxillary teeth with vertical and horizontal scale bars was screen-captured and transferred to Keynote. The digital template for 3.5 mm diameter was used in central incisor and lateral incisor. The digital template for 4.3 mm diameter was used in central incisor and canine. The implant length was 13, 15 and 18 mm. Additional line added to digital template as a guide for IIP. All CBCT images were classified as contraindicated or indicated by two examiners.

In our study was virtual implant planning by Implant Studio® to determine the probability of IIP in esthetic zone. The directions of implant that added for more than the two mentioned study (Erin K Edmondson and Joseph Y K Kan) were cement retained implant prosthesis, angulated screw channel at the 25° angulation and the middle of individual tooth. Various size of diameter (2.9, 3.3, 3.5, 3.75, 4.0, 4.5, 5 mm) and length (6, 8, 10, 12, 14, 16, 18 mm) were included in our study to promote adaptability and suitability in IIP in esthetic zone.

--> These are great discussion points. Please add them to your manuscript. You should compare your study with these two recently published articles since these points are clinically relevant.

Answer related to the study limitation: In our study, to standardized the method, implant planning is limited to static predetermined angulation to anatomical relation and implant size. This could limited the probability as clinician can increase the depth of implant placement, modified implant angulation within restorable position. Future study is suggested to study the effect of probability associated with dynamic implant planning.

--> This answer needs to be added as the last paragraph of your Discussion.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

**********

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10.1371/journal.pone.0308158.r004
Author response to Decision Letter 1
Submission Version2
26 Mar 2024

To Editor:

- All references have been reviewed and corrected to ensure completeness.

- Citation [37. Erin K Edmondson, Pedro M Trejo, Nikolaos Soldatos, Robin L Weltman. The ability to screw-retain single implant-supported restorations in the anterior maxilla: A CBCT analysis. J Prosthet Dent. 2022 Sep;128(3):443-449. Available from: https://doi.org/10.1016/j.prosdent.2021.01.004] has been added to line 273-274 in the discussion part of manuscript.

- Citation [38. Joseph Y K Kan, Kitichai Rungcharassaeng, Pongrapee Kamolroongwarakul, Guo-Hao Lin, Hiroyuki Matsuda, Shi Yin, Hom-Lay Wang, Dennis Tarnow, Jaime L Lozada. Frequency of screw-retained angulated screw channel single crown following immediate implant placement and provisionalization in the esthetic zone: A cone beam computed tomography study/ Clin Implant Dent Relat Res. 2023 Oct;25(5):789-794. Available from: https://doi.org/10.1111/cid.13227] has been added to line 274 and 278 in the discussion part of manuscript.

Reviewer #2:

1. Answer for using angulated screw channel of not: 548 teeth from 720 teeth (548/720) can be performed IIP in esthetic zone. The diameter of 3.3, 3.5, 4.1, 4.5 and 5 mm were used in all maxillary anterior teeth (central incisor, lateral incisor, canine). The diameter of 2.9 mm is used in lateral incisor only. The angulated screw channel was included in the calculation of all implant diameter except diameter of 2.9 mm was not included.

- The angulated screw channel was included in the calculation of all implant diameter except diameter of 2.9 mm was not included. The following sentence has been added to line 121-122 in the material and method part of manuscript. The remaining sentences are already included in line 118-121 in the material and method part of manuscript.

2. Answer for clarifying “limited restorability angulation for cement retained implant prosthesis": It is the most buccal angulation that allow for IIP in esthetic zone in cement retained implant prosthesis, which often in the middle of individual tooth, hence referred to as “middle half”. Even though, there are some possibilities to restore implant in more extreme buccal angulation with implant platform being more apical and palatal, there is an increased risk of complication

- The “middle half” has been explained for better comprehension and understanding in line 254-256 in the discussion part of manuscript.

3. Answer for sample size calculation:

The purpose of this study is to determine the probability of IIP in esthetic zone using four different implant directions. This design of the study has not been performed yet. So, there will be no similarity in statistical data for this study.

The sample size calculation for estimating proportion will be used as shown in the formula (in Response to reviewers):

According to the retrospective study of Ashok Velayudhan et al. in 2020 that the objective related to the current study showed that in a total of 77 implants placed in the anterior maxilla, with 21 of them being immediate implants, 6 (or 7.8%) of 21 immediate implants were placed in the anterior maxilla alone.

The output of the sample size calculation is 114. The 120 patients are sufficient for our study. --> This must be mentioned in the manuscript.

- This retrospective study of Ashok Velayudhan et al. has been mentioned and cited in line 92-93 in the material and method part of manuscript.

4. Answer for misaligned teeth as an exclusion criterion: Upper anterior teeth (canine-canine) misaligned is considered to exclusion criteria, which did not include in the sample size of our study.

- Misaligned upper anterior teeth has been added to exclusion criteria in line 104 in the material and method part of manuscript.

5.Answer to elaborate on the methods used to determine the long axis of the tooth, the angulation/direction of the planned implant:

The line drawn from incisal edge to root apex was long axis of the tooth.

The point between incisal edge to CEJ was marked as point M. The point between the center of the most prominent point of cingulum to the incisal edge was marked as point S.

- In traditional cement retained implant prosthesis (incisal edge), long axis of implant will coincide with incisal edge.

- In traditional screw retained implant prosthesis (screw retained), long axis of implant will coincide with point S.

- In limit angulation for angulated screw channel (angle screw), long axis of implant will coincide at the point that an angle up to 25° from traditional screw retained.

- In limit restorability angulation for cement retained implant prosthesis (middle half), long axis of implant will coincide with point M.

- All following sentences have been added to line 126-135 in the material and method part of manuscript.

6. Discussion

- The two mentioned studies have been added and compared to our study to line 273-289 in the discussion part of manuscript.

7. Answer related to the study limitation: In our study, to standardized the method, implant planning is limited to static predetermined angulation to anatomical relation and implant size. This could limited the probability as clinician can increase the depth of implant placement, modified implant angulation within restorable position. Future study is suggested to study the effect of probability associated with dynamic implant planning.

- All following sentences have been added to line 290-294 in the discussion part of manuscript.

Finally, I appreciate your feedback. They are accommodating and explicitly more reliable to my work. I am open to revising and improving my manuscript based on your suggestions. Thank you again for your time and consideration.

I look forward to your reply,

Attachment Submitted filename: Response to Reviewers.docx

10.1371/journal.pone.0308158.r005
Decision Letter 2
Abdullah Johari Yap Academic Editor
© 2024 Johari Yap Abdullah
2024
Johari Yap Abdullah
https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Submission Version2
30 Apr 2024

PONE-D-23-29819R2Incidence of straight and angulated screw channel following immediate implant placement in esthetic zone: A CBCT studyPLOS ONE

Dear Dr. Nakaparksin,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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We look forward to receiving your revised manuscript.

Kind regards,

Johari Yap Abdullah, B.S. & I.T, GradDip ICT, M.Sc, Ph.D.

Academic Editor

PLOS ONE

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #3: (No Response)

Reviewer #4: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #3: No

Reviewer #4: Partly

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #3: No

Reviewer #4: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #3: Yes

Reviewer #4: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #3: Yes

Reviewer #4: (No Response)

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #3: Dear authors,

I am evaluating the R2 version of the article titled "Incidence of straight and angulated screw channel following immediate implant placement in esthetic zone: a CBCT study”. The purpose of this “cone-beam computed tomography (CBCT) study was to determine the probability of IIP in the esthetic zone, using four different implant directions.”

After reading the results session, I understood the study. No patient received dental implants.

There are biases in the study.

The probability depends on many factors which must be considered and were abandoned. Moreover, there was no statistical to prove the superiority of any type over another one.

SPECIFIC COMMENTS

ABSTRACT:

- “Statement of problem: What are the incidences of immediate implant placement (IIP) in the esthetic zone, using four different implant directions?” - It is wrongly developed.

- The methodology was weakly presented.

INTRODUCTION

- This session is long.

M&M

- there is a time problem in the study “The sample criteria for this study were patients who had CBCT scans of the anterior maxilla at the Oral and Maxillofacial Radiology clinic, Faculty of Dentistry, Mahidol University performed during January 2012 – August 2022. CBCT images were performed by 3D Accuitomo 170 (J. 91 Morita®, Japan) and randomly selected for evaluation on 9 June 2021.”

- Exclusion criteria is incomplete

- Statistics was poorly presented

RESULTS

- What was the foundation/parameter to support the probability suggested? “The distribution of SRP with probability of IIP are shown in Table 1."

CONCLUSION

- I suggest to rethink and adjust it after revision.

Reviewer #4: Thank you for the authors of this work. The study aim to determine the probability of IIP in the esthetic zone without perioperative complications, using four different implant placement directions. The study is considered Novel and of interest. However, some concerns were addressed in the Word file attached. Please correct them all and comment when needed.

To mention some of the comments here:

1. Title needs to be improved

2. Abstract: The problem statement is not clear and is almost the same as what is mentioned in the purpose.

3. Introduction: A. In my opinion, you can shorten your introduction by removing unnecessary details; B. Your introduction needs to be strengthened. You need to add a paragraph of other studies that used simulations like yours and describe their findings in a very short and meaningful way. C. Some references were missing; D. Add your study hypothesis.

4. Material: A. Please specify the population?, which ethnicity? Age (Mean age)? Gender? B. Figure 1 showed misaligned anterior central incisor. One of your exclusion criteria is misaligned teeth, so how come you have included this in your study. This is contradicting and may be translated into bias in your study. Please comment on this. C. In your figure 3, I noticed that there are some issues in your alignment of your Implant. It is clearly evident to the readers in this figure that you are not following exactly Point M or Point S when placing your implants. Even the incisal edge is not followed 100%.

The points mentioned in figure 2 are not exactly followed in figure 3

This can affect all your study results and can be considered invalid outcomes. Please comment on this.

Other comments and suggestions were mentioned in the word file. Please correct and comment on them all.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #3: No

Reviewer #4: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Attachment Submitted filename: PONE-D-23-29819-reviewer comments.docx

10.1371/journal.pone.0308158.r006
Author response to Decision Letter 2
Submission Version3
14 Jun 2024

Reviewer #3:

Abstract:

“Statement of problem: What are the incidences of immediate implant placement (IIP) in the esthetic zone, using four different implant directions?” - It is wrongly developed.

- The methodology was weakly presented

Introduction:

- This session is long.

Answer: All suggestions have been applied and incorporated into the abstract section of manuscript.

Material and Method:

- there is a time problem in the study “The sample criteria for this study were patients who had CBCT scans of the anterior maxilla at the Oral and Maxillofacial Radiology clinic, Faculty of Dentistry, Mahidol University performed during January 2012 – August 2022. CBCT images were performed by 3D Accuitomo 170 (J. 91 Morita®, Japan) and randomly selected for evaluation on 9 June 2021.”

Answer: The sample criteria for this study were patients who had CBCT scans of the anterior maxilla at the Oral and Maxillofacial Radiology clinic, Faculty of Dentistry, Mahidol University performed during January 2012 – August 2020. CBCT images were performed by 3D Accuitomo 170 (J. 91 Morita®, Japan) and randomly selected for evaluation on 9 June 2021.

- Exclusion criteria is incomplete

Answer: - “CBCT images that were distorted or blurred” have been added in exclusion criteria.

- Statistics was poorly presented

Answer: This study is descriptive study without comparison group. Descriptive statistics were used to present the probability of IIP in the esthetic zone as percentages.

Results

- What was the foundation/parameter to support the probability suggested? “The distribution of SRP with probability of IIP are shown in Table 1."

Answer: The mid-sagittal images were used to classify SRP with respect to the alveolar housing according to Kan et al. [Kan JY, Roe P, Rungcharassaeng K, Patel RD, Waki T, Lozada JL, et al. Classification of sagittal root position in relation to the anterior maxillary osseous housing for immediate implant placement: a cone beam computed tomography study. Int J Oral Maxillofac Implants. 2011 Jul-Aug;26(4):873-6.]

In table 1 show distribution of SRP with probability of IIP as percentages.

In this study have 120 CBCT scans, which focus on upper anterior teeth (720 teeth).

SRP class l have 633 teeth, which perform IIP 533 teeth.

The distribution of SRP class l is 633/720*100 = 87.91%. The probability of IIP in SRP class l is 533/633*100 = 84.20%.

SRP class ll have 20 teeth, which perform IIP 14 teeth.

The distribution of SRP class ll is 20/720*100 = 2.78%. The probability of IIP in SRP class ll is 14/20*100 = 70%.

SRP class lll have 3 teeth, which perform IIP 1 teeth.

The distribution of SRP class lll is 3/720*100 = 0.42%. The probability of IIP in SRP class lll is 1/3*100 = 33.33%.

SRP class lV have 64 teeth, which perform IIP 0 teeth.

The distribution of SRP class lV is 64/720*100 = 8.89%. The probability of IIP in SRP class lV is 0/64*100 = 0%.

Conclusion

- I suggest to rethink and adjust it after revision.

Answer: The conclusion section has been revised.

Reviewer #4:

1. Title needs to be improved

Answer: The title has been improved.

2. Abstract: The problem statement is not clear and is almost the same as what is mentioned in the purpose.

Answer: The problem statement has been improved: the demand for immediate implant placement (IIP) in the esthetic zone is rapidly increasing. Despite the treatment’s benefits, the sagittal root position often dictates implant angulation, commonly necessitating the use of cement-retained restorations. This study investigates the impact of angulated screw channel on IIP in the esthetic zone.

3. Introduction: A. In my opinion, you can shorten your introduction by removing unnecessary details; B. Your introduction needs to be strengthened. You need to add a paragraph of other studies that used simulations like yours and describe their findings in a very short and meaningful way. C. Some references were missing; D. Add your study hypothesis.

Answer:

A. The content in the introduction section has been revised to more concise, following the recommendations.

D. This study is descriptive study without comparison group, so there is no study hypothesis.

4. Material: A. Please specify the population?, which ethnicity? Age (Mean age)? Gender? B. Figure 1 showed misaligned anterior central incisor. One of your exclusion criteria is misaligned teeth, so how come you have included this in your study. This is contradicting and may be translated into bias in your study. Please comment on this. C. In your figure 3, I noticed that there are some issues in your alignment of your Implant. It is clearly evident to the readers in this figure that you are not following exactly Point M or Point S when placing your implants. Even the incisal edge is not followed 100%.

The points mentioned in figure 2 are not exactly followed in figure 3

This can affect all your study results and can be considered invalid outcomes. Please comment on this.

Answer:

A. Details regarding the population have been added to the material and method section.

B. The old image presented in Fig 1 is a CBCT scan section as described in the caption of Fig 1 (In the axial view, the implant was positioned at the center of the selected tooth. In the panoramic view, the implant was aligned parallel to the long axis of tooth. In the coronal view, the implant was rotated parallel to the long axis of tooth. The mid-sagittal image, which was been sectioned at the bucco-lingual aspect of the tooth, was used to measure and plan of IIP). However, it was not used in the planning of IIP and was not included in this study. The image has been revised and replaced for Fig 1.

C. The placement of dental implant at each site will be conducted as described in the material and method section. The position of point M, point S and point P will vary depending on each individual tooth. Nevertheless, there may be some placements that deviate from the reference points in Fig 2. However, this does not affect the outcome of this study, as the determination of whether a tooth is suitable for IIP is based on the implant being surrounded by bone, assessed on an area basis rather than specific points. The image has been revised and replaced for Fig 3.

Attachment Submitted filename: Response to Reviewers final .docx

10.1371/journal.pone.0308158.r007
Decision Letter 3
Abdullah Johari Yap Academic Editor
© 2024 Johari Yap Abdullah
2024
Johari Yap Abdullah
https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Submission Version3
18 Jul 2024

Incidence of straight and angulated screw channel following immediate implant placement in esthetic zone: A CBCT study

PONE-D-23-29819R3

Dear Dr. Nakaparksin,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. If you have any questions relating to publication charges, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Johari Yap Abdullah, B.S. & I.T, GradDip ICT, M.Sc, Ph.D.

Academic Editor

PLOS ONE

Summary of Reviews

The manuscript received a total of four reviews. Two reviewers recommended acceptance, praising the paper for its originality and significant contribution to the field. They highlighted the following points:

• Reviewer 1 commended that the manuscript is well written, with few comments to improve the overall manuscript.

• Reviewer 3 emphasized the novelty of the study, which follows the trend toward digital investigation in dentistry. The reviewer commented on many things, however, after the revision, all the comments were addressed according to this reviewer’s feedback.

However, two reviewers recommended rejection. Their concerns were primarily focused on:

• Reviewer 2 pointed out perceived methodological flaws and suggested comparative statistical testing. The reviewer’s comments were reduced from the first revision to the second revision. However, still the reviewer insisted on the poor statistical analysis.

• Reviewer 4 commented on the statistical method followed by the authors as it is only descriptive analysis.

Evaluation and Justification

After a thorough evaluation of the manuscript and considering the reviewers' comments, I believe that the strengths of the paper justify its acceptance. Here are my reasons:

1. Originality and Contribution: The manuscript presents novel findings that offer significant insights into digital guided implantology. The originality of the research aligns with the high standards of PLOS ONE, contributing valuable knowledge that can advance the field.

2. Robust Methodology: While two reviewers raised concerns about the statistical analysis, the authors have provided a detailed explanation addressing these points. In the era of digital research, studies with only descriptive data are not abnormal incidence. I have encountered many studies published in very prestigious journals with only descriptive data. The novelty claims superiority over the strength of the statistical analysis.

3. Despite the fact that the authors have made the necessary corrections, one of the reviewers failed to take into account the fact that the authors had made the correction. This reviewer continued to point out that the correction is needed.

4. Clarifications and Revisions: In response to all reviewers’ comments, the authors have revised the manuscript to clarify their interpretations and enhance the readability of key sections. These revisions address the concerns raised and improve the manuscript's quality.

5. Positive Reviewer Feedback: The positive feedback from Reviewers 1 and 3 cannot be overlooked. Their endorsement of the paper's strengths and its potential impact underscores the value of this research.

Conclusion

Given the substantial revisions made by the authors and the manuscript's contribution to the field, I recommend accepting this paper for publication in PLOS ONE. I believe that the positive aspects of the research, as highlighted by the accepting reviewers, outweigh the concerns raised by the rejecting reviewers. I am confident that this manuscript will be a valuable addition to PLOS ONE.

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #4: All comments have been addressed

Reviewer #5: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #4: Yes

Reviewer #5: No

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #4: Yes

Reviewer #5: No

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #4: Yes

Reviewer #5: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #4: Yes

Reviewer #5: No

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #4: Thank you to the authors. All the previous comments have addressed and the figures were replaced. No further comments from my side.

Reviewer #5: The manuscript is poorly designed and statistically analysis is very weak. Probability is mentioned and any other comparative statistics or advance tools have not been used. The Manuscript is not suitable for publication as per PLOS ONE journal standards.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #4: No

Reviewer #5: No

**********

10.1371/journal.pone.0308158.r008
Acceptance letter
Abdullah Johari Yap Academic Editor
© 2024 Johari Yap Abdullah
2024
Johari Yap Abdullah
https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
25 Jul 2024

PONE-D-23-29819R3

PLOS ONE

Dear Dr. Nakaparksin,

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now being handed over to our production team.

At this stage, our production department will prepare your paper for publication. This includes ensuring the following:

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