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BMC Oral Health
BMC Oral Health
BMC Oral Health
1472-6831
BioMed Central London

39267015
4825
10.1186/s12903-024-04825-2
Research
Postoperative sensitivity of composites using novel Bacillus subtilis nanofortified adhesives: a triple-blind study
Amir Nehal 1
Mansoor Afsheen drafsheenqamar@gmail.com

23
Eeman Nabiha 4
Ahmed Muhammad Nouman 5
Mansoor Emaan 6
Hussain Khadim 710
Palma Paulo J. ppalma@uc.pt

89
1 grid.513418.a 0000 0004 4699 2869 Department of Operative Dentistry and Endodontics, School of Dentistry, Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad, Pakistan
2 https://ror.org/04s9hft57 grid.412621.2 0000 0001 2215 1297 Department of Microbiology, Quaid-i-Azam University, Islamabad, 45320 Pakistan
3 grid.513418.a 0000 0004 4699 2869 Department of Dental Material Sciences, School of Dentistry, Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad, 44080 Pakistan
4 https://ror.org/02maedm12 grid.415712.4 0000 0004 0401 3757 Medical Student, Rawalpindi Medical University, Rawalpindi, Pakistan
5 grid.507958.6 0000 0004 5374 437X Medical Student, Army Medical College, National University of Medical Sciences, Rawalpindi, Pakistan
6 https://ror.org/02kdm5630 grid.414839.3 0000 0001 1703 6673 Islamic International Dental College, Riphah International University Islamabad, Islamabad, 46000 Pakistan
7 https://ror.org/002rc4w13 grid.412496.c 0000 0004 0636 6599 CRS Agriculture Department, Islamia University, Bahawalpur, Pakistan
8 https://ror.org/04z8k9a98 grid.8051.c 0000 0000 9511 4342 Faculty of Medicine, Center for Innovation and Research in Oral Sciences (CIROS), University of Coimbra, Coimbra, 3000-075 Portugal
9 https://ror.org/04z8k9a98 grid.8051.c 0000 0000 9511 4342 Faculty of Medicine, Institute of Endodontics, University of Coimbra, Coimbra, 3000-075 Portugal
10 https://ror.org/002rc4w13 grid.412496.c 0000 0004 0636 6599 Department of Statistics, Islamia University, Bahawalpur, Pakistan
12 9 2024
12 9 2024
2024
24 10771 7 2024
28 8 2024
© The Author(s) 2024
2024
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Nanotechnology

is the art and science of dealing with nanoscale particles. This has transformed contemporary dental practices through myriad contributions to biomaterial science. Titanium dioxide nanoparticles procured from Bacillus subtilis, an eco-friendly and biogenic source, can significantly magnify the physiochemical attributes of dental materials. However, postoperative sensitivity is a major drawback of composite restorations. The incorporation of these nanoparticles into dental adhesives can greatly benefit clinical dentistry by resolving this issue. This trial aimed to evaluate the effectiveness of a novel titanium dioxide nanofortified adhesive on the postoperative sensitivity of composite restorations.

Methods

This triple-blind, parallel-group randomized controlled trial was conducted at the Department of Operative Dentistry and Endodontics, School of Dentistry, Islamabad, from May 15, 2023, to November 25, 2023. Participants (n = 60) with Class I and II primary carious lesions with a minimum cavity depth of 3–5 mm were randomly assigned to two groups (n = 30). After obtaining informed consent, the restorative procedure was accomplished using a minimally invasive approach and etch-and-rinse adhesive strategy. In group A, a nanofortified adhesive was used for composite restoration, whereas in group B, an adhesive without nanoparticles was used. Postoperative sensitivity was evaluated using the Visual Analog Scale (VAS) score at follow-up periods: of one day, one week, two weeks and one month. A Chi-square test was used to compare postoperative sensitivity between the two groups. The level of significance was set at p < 0.05.

Results

A noteworthy association was observed between sensitivity and the group variable at all four evaluation periods: after one day (p = 0.002), 1 week (p = 0.002), 2 weeks (p = 0.007) and one month. In conclusion, participants who underwent restorative intervention using titanium dioxide nanoreinforced adhesives reported a notable reduction in sensitivity at all time intervals. Hence, the occurrence and severity of postoperative sensitivity are significantly reduced using Bacillus subtilis-procured nanofortified adhesives as compared to conventional adhesives without nanoparticles.

Trial registration

This trial was retrospectively registered at ClinicalTrials.gov (ID: NCT06242184) on 03/02/2024. All procedures involving human participants were performed in conformance with this protocol.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-024-04825-2.

Keywords

Composite resins
Dentin sensitivity
Nanoparticles
Restoration
Titanium dioxide
issue-copyright-statement© BioMed Central Ltd., part of Springer Nature 2024
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pmcBackground

Nanotechnology is the implementation of scientific principles to substantially manipulate matter at the nanoscale to attain the prerequisites of dimensions- and structure-dependent attributes that are distinct from those associated with individual atoms, molecules, or extrapolation from larger sizes of the same material. It has gained immense popularity in clinical dentistry owing to its multitudinous contributions to dental biomaterials [1, 2]. The pinnacle of nanoscience is nanoparticles, which are composed of atoms or molecules that congregate to form nanostructured agglomerates and provide dental materials with remarkable physiochemical and optical-magnetic qualities [3].

Nanoparticles are categorized as having organic, inorganic, or carbon-based lineages. Metal and metal oxide-based materials are exemplary inorganic nanoparticles. The outstanding attributes of metal oxide-based nanoparticles include their dimensions, which range from 10 to 100 nm; their configuration, which is spherical and cylindrical; and their surface qualities, which include pore size, enhanced surface-area-to-volume ratio, and surface charge. Titanium dioxide, also known as titania, is one of the most well-characterized metal-oxide nanoparticles. It has illustrious optical, magnetic, physicochemical, rheological, and biological properties. Titanium dioxide has a high refractive index, biocompatibility, and cost-effectiveness, making it an ideal choice for utilization in dental materials [4, 5].

Composite resin, an esthetic adhesive material, is a paragon in contemporary restorative dentistry. This has transformed the paradigm to minimally invasive dentistry. Among the advantages of composite restorations are their distinguished aesthetics, adhesion to tooth structure, and preservation of healthy dental substrates [6]. Nonetheless, they have explicit shortcomings that jeopardize the long-term viability of posterior restorations. Polymerization shrinkage in composites is primarily responsible for these unfavorable outcomes, including cuspal deflection, postoperative sensitivity, secondary caries, marginal discoloration, restorative fracture, and microleakage at the tooth-restorative junction [7]. Post-operative sensitivity in composite restorations is caused by a multitude of reasons including iatrogenic pulpal damage during caries excavation, inadequate coverage and penetration of adhesives into the dentinal tubules, and the impact of various placement strategies, bonding techniques, curing modes, and the choice of composite material used. Incomplete hybridization is a major cause of sensitivity in composites. This predicament can be resolved by the prospective sealing potential of dental adhesives to occlude patent dentinal tubules at the dentin-adhesive interface. Nevertheless, because of the degeneration and long-term instability of the hybrid layer, this attribute of adhesives is susceptible to time-dependent decline [6–8].

Appreciable improvements in the physio-chemical properties and long-term stability of the tooth-adhesive interface can be achieved by fortifying dental adhesives with nanoparticles.Nano-particles, when incorporated into dental adhesives, enormously magnify the bonding capability of resins into dental substrate by its deeper penetration and sealing capability of the tubular network of dentin. Thus, it could massively reduce post-operative sensitivity in composite restorations [9, 10]. The rationale of this study was to enhance the tubule-sealing ability of dental adhesives by enhancing the bonding performance of resins through the incorporation of nanoparticles, thus minimizing the issue of sensitivity. The objective of this trial was to evaluate the effectiveness of a novel titanium dioxide nanofortified adhesive on the postoperative sensitivity of composite restorations. The hypothesis stated that the occurrence and severity of postoperative sensitivity in composites were lessened using Bacillus subtilis-procured novel nanofortified adhesives compared to dental adhesives without nanoparticles.

Methods

Study design

The present study followed the CONSORT (Consolidated Standards of Reporting Trials) 2010 guidelines. This study was formulated as a triple-blind, parallel-group, randomized clinical trial with a 1:1 allocation ratio. The operator, data analyst, and participants were all blinded to the groups to which they were assigned. The participants were divided into two groups. Group A: Nano-fortified adhesive was employed for restorative treatment, whereas in Group B: Adhesive without nanoparticles was used. All participants were briefed about the study, along with its potential merits and demerits, and a consent form was validated by the principal investigator from each participant.

Sample size calculation

The sample size was calculated as 60 using the WHO calculator (30 participants in each interventional group). The test had a power of 80% and significance level of 5%. The population mean test result was 1.38, but the population standard deviation was calculated to be 1.6, and the expected population mean was 3.69 [11].

Patient selection and blinding

Participants fulfilling the inclusion criteria were selected from the outpatient department using a consecutive non-probability sampling method and were randomly divided by a trial-autonomous researcher in each study group using a Lottery method. For allocation concealment, an opaque sealed envelope with designated coding was employed for each study group. The dental adhesive used in this intervention had identical bottles with the assigned codes (A and B) for each interventional group. In this study, a trial-autonomous investigator performed both the blinding and allocation concealment. Table 1 presents the inclusion and exclusion criteria of this study.

Table 1 Inclusion and exclusion criteria

Inclusion criteria	Exclusion criteria	
Participants with a good general health status	Patients with a history of temporomandibular disorders	
Class I and II primary carious lesion with a minimum cavity depth of 3 to 5 mm	History of spontaneous pain	
Vital and periodontally sound teeth	Endodontically treated teeth	
Teeth with established occlusion with the natural or prosthetic antagonists and adjacent teeth.	Patients on analgesics within the past two weeks	

Synthesis of microbial titanium dioxide nanoparticles

The strain of Bacillus Subtilis (Accessions No; ATCC®6633TM-Catalog No/ 0486-SPR) was obtained from National Institute of Health Islamabad, Pakistan for preparing the Titanium dioxide nanoparticles. They were fabricated via the methodology available in the reported literature [9]. The supernatant was prepared from fresh Bacillus Subtilis culture after centrifuging it at 10,000 RmP for about 10 min. Then, 80 ml of supernatant and 20 ml of 00.025 m Ti(-OH)2 (Americans Element, 10,884.0 WeYburn AVE/ Los Angeles; CA/90024.0,USA) were mixed together and were placed on metal plate at 60oC for about 20.0 min where white crystal like deposits appeared at the bottom of the flask confirming the Titanium dioxide nanoparticles formation. The characterization techniques involved to identify its original phase, peak form, size, shape, texture, roughness, morphology, elemental composition, functional groups and biocompatibility were performed through equipments: DMAX/2400 Diffractometer (Rigaaku Corpooration: Akishimau Tokyo’s company Japan-), Scanning electron microscope-(NOVA Nanoseme 4300, FEI-company-HillsBoro, ORA, USA), Atomic force microscope (Quesant/Universal SPMS, Ambios-Technology: SantA Cruz’s, C-A, USA), Transmission electron microscope (Jeols JEMS-200CXX-Bioz Star’s: Tokoyo, Japan), Fourier transform infrared spectrophotometery (JASCOS FT/IRR-6600; Utrecht-T, Netherlands) and Spectrometer-(Lambda-A 9500, Perkins Elmer’s, Waltham-MA, USA) [4, 9, 12].

Properties of microbial titanium dioxide nanoparticles

The Titanium dioxide nanoparticles prepared by the microbes displayed mixed anatase-rutile phase having particle size of about 70.00 nm arranged in aggloremates. They possessed smooth texture with minimal roughness in their morphology. Moreover, these nanoparticles revealed pure titanium and oxygen in their elemental composition and confirmed the presence of carboxyl groups, amine groups and titanium-oxygen bendings in their spectrum. These were found to be biocompatible against fibroblast cell lines that enhanced their unique characteristics [4, 9, 12].

Incorporation of nanoparticles into dental adhesive

In this study, synthesized nanoparticles were mixed into a commercially available 5 mL bottle of adhesive (One Coat Bond SL Coltene, Switzerland) at a mass fraction of 30%.

Clinical procedure

The study was conducted at the Department of Operative Dentistry and Endodontics, School of Dentistry, Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad, from May 15, 2023 to November 25, 2023, after acceptance from the Institutional Ethical Committee (SOD/ERB/2023/31 − 01). Before the initiation of the procedure, circumstantial medical and dental history was recorded. Each participant was anesthetized to ensure comfort during the procedure using the local anesthetic solution Lignospan Special-lidocaine hydrochloride 2% with 1:80,000 epinephrine (Septodont, USA). Under rubber dam isolation, carious lesions were excavated using a high-speed handpiece, the cavity design was delineated by the extent of the carious lesion, and the depth of the prepared cavity was estimated using a periodontal probe. Before initiating restorative treatment, a Palodent Plus Sectional Matrix System (Dentsply Sirona, USA) was used to obtain the desired proximal contour of the restoration.

Acid etching was performed using Phosphoric acid 35% (Etchant gel S Coltene, Switzerland) for 15–30 s. The enamel surface was etched for 30 s while dentin substrate was etched for 15 s. Afterwards, the area was rinsed with water for 20 s and allowed to air-dry for 5 s. The subsequent steps were executed in conformance with the fundamentals of adhesive dentistry (Fig. 1).

Group A (nanofortified dental adhesive): In this interventional group, titanium dioxide nanoparticles were incorporated in 5 mL adhesive (One Coat Bond SL Coltene, Switzerland). Using a microbrush, the etched surface was vigorously coated with adhesive for 20 s. This was followed by another application for 20 s. For 40 s, the adhesive coating was light-cured using an LED curing light (Woodpecker DTE LUX E Plus, Woodpecker, China). Subsequently, the restorative material (Brilliant NG Universal Nano Composite Coltene, Switzerland) was placed using the incremental packing strategy and light-cured for 40 s using a curing light Woodpecker DTE LUX E Plus (Woodpecker, China).

Group B (adhesive without nanoparticles): In this experimental group, a commercially available adhesive (One Coat Bond SL Coltene, Switzerland) without nanoparticles was employed, followed by the application of composite (Brilliant NG Universal Nano Composite Coltene, Switzerland) using the incremental packing strategy and light-curing for 40 s with curing light Woodpecker DTE LUX E Plus (Woodpecker, China).

Subsequently, the rubber dam was removed, the restoration was assessed for any occlusal modifications and the adequacy of inter-proximal contacts. Afterwards, the finishing was completed. The restoration was polished using a Jiffy Original Composite System (Ultradent, USA).

Fig. 1 Clinical intervention for the restorative treatment

Assessment of postoperative sensitivity

The Visual Analog Scale (VAS) score was used to assess sensitivity after one day, one week, two weeks, and one month. VAS is a psychometric tool for measuring subjective attributes that cannot be measured. It is a 10 cm long scale with markings from 0 to 10, calibrated for sensitivity scores of 0 (none), 1–3 (mild), 4–6 (moderate), and 7–10 (severe) (Fig. 2) [11, 13, 14]. Moreover, participants were directed to rate whether their sensitivity was spontaneous or stimulated. They were instructed to mention the provoking stimuli.

Fig. 2 Visual Analog Scale (VAS) score

Statistical analysis

The data were analyzed using SPSS software version 26. A Chi-square test was employed to compare the postoperative sensitivity between the two groups at the follow-up period. The level of significance was set at p < 0.05.

Results

A total of 112 participants were enrolled in this interventional study. Of these, 30 participants did not satisfy the inclusion criteria, 10 refused participation, and 12 had other reservations about this trial. The study comprised 60 participants, who were designated into two groups (n = 30). Table 2 provides a detailed overview of the critical variables based on the 60 participants. Figure 3 illustrates the CONSORT 2010 Flow Diagram.

Table 2 Characteristic variables of study participants

Variables	Frequency	Percent	
Gender			
Male	37	61.7	
Female	23	38.3	
Tooth Distribution			
Premolar	27	45	
Molar	33	55	
Black Classification			
Class I	30	50	
Class II	30	50	
Arch Distribution			
Maxillary arch	30	50	
Mandibular arch	30	50	

Fig. 3 CONSORT 2010 flow diagram

Postoperative sensitivity levels after one day, one week, two weeks, and one month show distinct patterns. After one day, the sensitivities ranged from none (25%) to severe (6.7%). After one and two weeks, the patterns of none, mild, moderate, and severe sensitivity persisted. After one month, 81.7% indicated no sensitivity, 15% indicated mild sensitivity, and 3.3% indicated moderate sensitivity. Table 3 depicts the cross-tabulations and chi-square tests that investigated the relationship between sensitivity at different time intervals and several categorical variables.

Table 3 Cross-tabulation and chi-square tests for sensitivity after different time intervals and categorical variables

Variables	Sensitivity after One Day	Sensitivity after One Week	Sensitivity after 2 Weeks	Sensitivity after 1 month	
Group	χ² = 14.357

p = 0.002

	χ² = 14.732

p = 0.002

	χ² = 9.797

p = 0.007

	χ² = 13.469

p = 0.001

	
Black Classification	χ² = 1.640

p = 0.650

	χ² = 2.404

p = 0.493

	χ² = 6.007

p = 0.050

	χ² = 0.132

p = 0.936

	
Tooth Distribution	χ² = 2.380

p = 0.497

	χ² = 4.729

p = 0.193

	χ² = 0.830

p = 0.660

	χ² = 0.022

p = 0.989

	

A noteworthy correlation was found between sensitivity after one day and the group variable (p = 0.002) (Fig. 4). The majority of participants in the “Adhesive with Nanoparticles” group reported no or mild sensitivity, whereas the “Adhesive without Nanoparticles” group reported a higher number of participants experiencing moderate and severe sensitivity. The analysis of sensitivity after one day and Black classification showed no statistically significant relationship between these variables (p = 0.65). The distribution of sensitivity levels was comparable between the Class I and Class II restorations. Analysis of sensitivity after one day and tooth distribution revealed no statistically significant correlation (p = 0.497). The sensitivity levels appeared to be similar for both the premolar and molar tooth distributions.

Fig. 4 Distribution of sensitivity between group variables after one day

Sensitivity after one week in the group showed a significant correlation (p = 0.002). The group utilizing the “Adhesive with Nanoparticles” has a greater proportion of participants reporting no or mild sensitivity in comparison to the group using the “Adhesive without Nanoparticles” Adhesive without nanoparticles. Sensitivity after one week and black classification were analyzed using cross-tabulation. (Fig. 5) The results showed no statistically significant association between the two variables (p = 0.493). Sensitivity after one week did not show a statistically significant association with tooth distribution (p = 0.193). The sensitivity levels appear to be similar in both premolar and molar tooth distributions.

Fig. 5 Distribution of sensitivity between group variables after one week

There were notable connections between sensitivity after two weeks and the group, as indicated by the statistical analysis (p = 0.007) (Fig. 6). The majority of participants in the “Adhesive with Nanoparticles” group reported either no sensitivity or mild sensitivity. In contrast, the “Adhesive without nanoparticles group had a higher percentage of participants experienced moderate sensitivity. The contingency table analysis for sensitivity after two weeks and black categorization revealed a weakly significant correlation (p = 0.05). However, there was no significant correlation between tooth distribution and sensitivity after two weeks (p = 0.66).

Fig. 6 Distribution of sensitivity between group variables after two weeks

A strong correlation between the sensitivity after one month and the group (p = 0.001) was observed. The majority of the participants in the “Adhesive with Nanoparticles” group reported no sensitivity. Moreover, sensitivity after one month does not show any significant correlation with black classification (p = 0.936) and tooth distribution (p = 0.989 ) (Fig. 7).

Fig. 7 Distribution of sensitivity between the group variables after 1 month

Table 4 shows that participants who used “adhesives with nanoparticles” consistently exhibited reduced levels of sensitivity in comparison to those who used “adhesives without nanoparticles” at all four time points. After one day, a significant percentage of patients who had restorative treatment with nano-reinforced adhesives claimed that they did not experience any sensitivity (13 versus 2), and the group that did not have nanoparticles was the only one that experienced severe sensitivity. At the end of one week, the pattern was maintained, with a greater number of participants expressing no sensitivity (17 rather than 5), while a smaller number reported moderate sensitivity (2 rather than 12). At two weeks, this tendency became more obvious, with 22 patients with nanofortified adhesives reporting no sensitivity, compared to 11 participants in the group that did not use nanoparticles, and there were no reports of moderate sensitivity in the group that used titanium dioxide nanoparticles. Based on the results of this study, it can be deduced that adhesives containing titanium dioxide reinforced nanoparticles resulted in significantly decreased levels of postoperative sensitivity over time when compared to adhesives without nanoparticle fortification.

Table 4 Comparison of postoperative sensitivity between the two groups at follow-up periods

Sensitivity	Adhesive to Nanoparticles	Adhesive without Nanoparticles	Total	
After one day				
 None	13	2	15	
 Mild	12	13	25	
 Moderate	5	11	16	
 Severe	0	4	4	
Total	30	30	60	
After one week				
 None	17	5	22	
 Mild	11	12	23	
 Moderate	2	12	14	
 Severe	0	1	1	
Total	30	30	60	
After two weeks				
 None	22	11	33	
 Mild	8	15	23	
 Moderate	0	4	4	
Total	30	30	60	
After one month				
 None	30	19	49	
 Mild	0	9	9	
 Moderate	0	2	2	
Total	30	30	60	

Discussion

With the inception of resin composites in clinical practice, the field of restorative dentistry has blossomed. Resin composites, which embody the fundamentals of minimally invasive and adhesive dentistry, provide high-quality esthetic and durable posterior restorations. Despite its long-track record of clinical success, it has several shortcomings. Polymerization shrinkage during the free radical addition reaction produces many undesirable outcomes, one of which is postoperative sensitivity. The drawback of sensitivity subsequent to composite restoration is primarily explained by the hydrodynamic theory, as the fluctuations in tubular hydrostatic pressure cause stimulation of nerve endings in the dental pulp. Many strategies have been employed over the decades to counteract this pitfall of resin composites, such as modifications in placement techniques, variations in restorative materials, utilization of low-viscosity materials, and alterations in curing modes. However, no single treatment modality has completely eliminated this issue [15–17].

Amid this predicament, a silver lining of hope has emerged from the instigation of nanoscience in clinical dentistry. The philosophy of nanoscience has proven to be a ground-breaking step in the development of dental biomaterials. A multitude of advancements has been made in dental materials through the incorporation of fundamental principles of nanotechnology. Reinforced composites of nano-fortified adhesives encompass the field of restorative dentistry. The core of a successful composite restoration is the establishment of a durable hybrid layer. Incomplete infiltration of adhesives into demineralized dentin is the main culprit for nanoleakage, which is mainly responsible for the postoperative sensitivity of composites. Thus, by fortifying the adhesives with nanoparticles, significant enhancements in physio-chemical attributes can be attained. These reinforced adhesives have better permeability into the dentin matrix, resulting in longevity and stability in the hybrid layer [18–20].

Thus, the principles of nanoscience can resolve the issues of postoperative sensitivity in composites by utilizing the superlative permeability and mechanical attributes of nanofillers. In this interventional study, nanoparticles were mixed with a commercially available adhesive (One Coat Bond SL Coltene, Switzerland) at a mass fraction of 30% [20, 21]. This was attributed to the fact that reinforced nanofillers have a significant impact on the viscoelasticity and flowability of adhesives into dentinal tubules [4, 11]. Hence, the percentage of incorporated titanium dioxide nanoparticles was deliberately set at moderate levels to avoid any detrimental impact on the dentin adhesives while upgrading their physio-chemical properties. In this study, titanium dioxide nanoparticles procured from a biogenic source, Bacillus subtilis, were employed to reinforce dental adhesives. The superior physio-chemical, biological, and optical properties of titanium dioxide nanoparticles have already been elucidated in various studies conducted recently [22–24]. Moreover, an in vitro study has supported the safety profile of these biogenically synthesized nanoparticles as being non-cytotoxic and eco-friendly [25].

In accordance with the findings of this study, a noticeable association was observed between sensitivity and the group variable at all four evaluation periods: after one day (p = 0.002), one week (p = 0.002), two weeks (p = 0.007) and one month (p = 0.001). The majority of participants in the “Adhesive with Nanoparticles” group reported none or mild sensitivity, whereas the “Adhesive without Nanoparticles” group reported a higher number of participants experiencing moderate to severe sensitivity. The results of this trial go hand in gloves with a study conducted at the Department of Operative Dentistry, Faculty of Dentistry, Cairo University [11] that shows a significant reduction in postoperative sensitivity using bioglass-incorporated nanoparticles in dentin adhesives.

An etch-and-rinse adhesive strategy was used in this interventional study. This was chiefly due to the increased prevalence of postoperative sensitivity in the composites when this adhesive technique was employed. Several studies have shown promising results in favor of the self-etch adhesive technique in terms of sensitivity [26, 27]. However, the findings of the systemic review negated the impact of the adhesive strategy on postoperative sensitivity in posterior composites [28, 29]. Additionally, an incremental placement technique was utilized for this intervention owing to the proposition that the bulk-fill strategy has a more successful clinical outcome and reduced sensitivity compared to the incremental layering technique [14, 30]. This was mainly used to judge the impact of reinforced nanoparticles in adhesives on the sensitivity of the composites. Nonetheless, various studies have highlighted that the placement techniques do not influence the postoperative sensitivity of composite restorations [31, 32].

The most striking attribute of this intervention was its novelty. No previous study has utilized Bacillus subtilis-procured nanoparticles in dentin adhesives. This study is the first of its kind to demonstrate the impact of biogenically synthesized titanium dioxide nanoparticles on the sensitivity of composite restorations. Titanium dioxide nanoparticles can significantly improve the properties of adhesives. Due to their biogenic origin, these nanoparticles are eco-friendly, and their cytotoxicity profile has also been authenticated [33]. Additionally, naturally prepared titanium dioxide nanoparticles displayed outstanding antimicrobial features that might play a significant role in the adhesive dentistry as well [34, 35]. Moreover, the triple-blind nature of this intervention rendered the study unbiased, and ratified its authenticity. However, this study had certain limitations. One of the major shortcomings of this trial is that one month could be a short evaluation period to remark the appreciable impact of nano-reinforced adhesives on post-restorative sensitivity in composites. This trial did not evaluate the influence of variables such as cavity depth, arch distribution, adhesive techniques, or different placement strategies on postoperative sensitivity after composite restorations. Moreover, this trial was conducted in a single hospital setting. To authenticate the findings and practicability of this study, it should have been executed at multiple clinical setups. Thus, further research is warranted to validate the efficacy of novel titanium dioxide nanofortified adhesives in restorative dentistry.

Nanotechnology is a cynosure in contemporary science. This study paves the way for further research on nanoscience to synthesize ecologically secure nanoparticles and incorporate them into biomaterials. It can drastically improve the final treatment outcome and benefit healthcare practitioners by providing high-quality dental care to patients.

Clinical relevance

This study shed light on one of the major issues in restorative dentistry, which is post-operative sensitivity. By embodying composite restorative material with nanoparticles, significant enhancement in bonding performance could be achieved. This could enormously improve the longevity of restorations by providing premium dental treatment to patients.

Conclusion

A noteworthy association was observed between sensitivity and the group variable at all four evaluation periods: after one day (p = 0.002), one week (p = 0.002), two weeks (p = 0.007) and one month (p = 0.001). The majority of participants in the “Adhesive with Nanoparticles” group reported none or mild sensitivity whereas the “Adhesive without Nanoparticles” group had a higher number of participants experiencing moderate to severe sensitivity. It could be deduced that participants who underwent restorative intervention using titanium dioxide nanoreinforced adhesives reported a notable reduction in sensitivity at all time intervals. Hence, the incidence and severity of postoperative sensitivity are significantly reduced by using Bacillus subtilis-procured nano-fortified adhesives as compared to conventional adhesives without nanoparticles.

Limitations of the study

A limited sample size was used in this clinical trial to investigate patient sensitivity. Therefore, future studies with a larger number of patients involved in the clinical trial are required to clarify any ambiguity regarding the limited sample size.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary Material 1

Acknowledgements

Authors acknowledge School of Dentistry for their help and support in the research.

Author contributions

Conceptualization: N.A, A.M.; Methodology: N.A., A.M.; Data Collection: N.A., N.E., M.N.A., E.M.; Data Processing: N.A., N.E., M.N.A., E.M, K.H.; Data Analysis & Interpretation: K.H, N.A.; Writing - Original Draft: N.A.; Writing - Review & Editing: A.M., P.J.P.; Validation and Critical Review: A.M., P.J.P.; Supervised by: A.M.

Funding

None.

Data availability

All data generated or analyzed during the study is available in this manuscript.

Declarations

Ethics approval and consent to participate

The study was conducted after the approval from Institutional Ethical Research Committee, School of Dentistry, Shaheed Zulfiqar Ali Bhutto Medical University with the reference number (SOD/ERB/2023/31 − 01). An informed consent was obtained from all of the participants included in this trial.

Consent for publication

A consent for publication was obtained from allthe participants involved in the study.

Conflict of interest

The authors declare no conflicts of interest.

Competing interests

The authors declare no competing interests.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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