Effect of Different Heating Protocols of Resin Composites on Pulp Condition (Randomized Controlled Trial)

1. Background and Rationale Pre-heating of resin-based composites decreases viscosity, enhances flow characteristics, and improves monomer conversion rates [1,2]. Specialized devices including the VisCalor delivery system have been introduced to standardize prewarming methodologies [3,4]. However, the utilization of preheated substances in deep preparations raises legitimate thermal concerns for the pulp-dentin interface. Zach and Cohen [5] demonstrated that a 5.5°C elevation in pulpal temperature induces irreversible pulpitis or necrosis in 15% of teeth.

   Cytokines represent pivotal inflammatory mediators and have been examined in gingival crevicular fluid (GCF) as diagnostic markers of pulpal inflammation [6,7]. Tumor necrosis factor-alpha (TNF-α) functions as a pleiotropic pro-inflammatory cytokine central to initiating and amplifying pulpal inflammatory cascades [8,9]. Celik et al. [10] established that diverse restorative materials significantly influence GCF concentrations of IL-6, IL-8, and TNF-α, demonstrating material-specific temporal variations.

   Despite accumulating evidence, no clinical investigation has evaluated varying preheating protocols on pulpal inflammatory status utilizing objective biomarkers. Consequently, this randomized controlled study aims to examine the influence of different prewarming regimens on pulpal inflammatory status through GCF TNF-α quantification and VAS pain assessment.

2. Study Design This is a randomized, single-blinded, parallel-group controlled clinical trial conducted at the outpatient facility of the Faculty of Dentistry, Ain Shams University. The study adheres to the Consolidated Standards of Reporting Trials (CONSORT) guidelines [11]. Ethical approval was obtained from the Research Ethics Committee of the Faculty of Dentistry, Ain Shams University (approval number: [to be inserted]), and the study is performed in accordance with the Declaration of Helsinki [12]. Written informed consent is secured from all participants.

3. Eligibility Criteria

   Inclusion Criteria:

   Patients aged 18-45 years in good general health

   Asymptomatic deep occlusal carious lesions with ICDAS scores 5 and 6, confirmed by preoperative periapical radiographs

   Healthy gingiva with probing depths ≤ 3 mm, normal occlusion, and no radiographic evidence of periodontal bone loss

   No anti-inflammatory or antibiotic therapy within the preceding six months

   Willingness to complete the full trial period with signed informed consent

   Exclusion Criteria:

   Vulnerable populations (pregnant or nursing women, incarcerated individuals, those with mental health disorders)

   Current tobacco users

   Patients with systemic conditions (e.g., diabetes mellitus, immunocompromise)

   Teeth with prior endodontic intervention

   Periodontal pockets >3 mm

   Use of medications influencing inflammatory responses

   Orthodontic appliance wearers

4. Interventions Group I (Test Group 1): Thermoviscous bulk-fill composite (VisCalor, VOCO, Germany) preheated to 65°C using VisCalor Dispenser, placed as a single bulk increment (4 mm thickness).

   Group II (Test Group 2): Conventional nanohybrid composite (Ivoclar Vivadent, Liechtenstein) preheated to 55°C using Composite Heater (Cicada Dental, China), placed incrementally (2 mm thickness per increment).

   Group III (Control Group): Conventional nanohybrid composite (Ivoclar Vivadent, Liechtenstein) at room temperature (23°C), placed incrementally (2 mm thickness per increment).

   All restorations are performed by a single operator. Selective enamel etching combined with universal bonding (Bisco) is applied across all groups following manufacturer specifications. Cavity preparations are executed with diamond burs in a high-speed handpiece under continuous water coolant.

5. Outcome Measures

   Primary Outcome:

   Pulpal inflammatory response assessed by GCF TNF-α levels (pg/mL) at baseline, immediately post-treatment, and 7 days post-treatment, measured using ELISA [10].

   Secondary Outcomes:

   Postoperative pain assessed using Visual Analog Scale (VAS) at baseline and 7 days post-treatment

   Correlation between TNF-α levels and pain scores

6. Sample Size and Power Sample size was calculated using G*Power software version 3.1.9.7 (Heinrich Heine University, Dusseldorf, Germany) [13] based on prior investigations [10]. The minimally acceptable sample size was 5 per group, calculated from the mean ± standard deviation of TNF-α levels pre-restoration (5.83 ± 0.25) and post-restoration (7.15 ± 0.7), yielding a 2.8 effect size. With power set at 95% and type I error probability at 0.05, the sample size was increased to 10 per group to enhance statistical power and accommodate anticipated attrition. Consequently, 30 patients (10 per group) are enrolled.
7. Statistical Analysis The normality of data distribution and homogeneity of variances are verified using Shapiro-Wilk's test. Intergroup comparisons are performed using Kruskal-Wallis test with Dunn's post-hoc correction. Intragroup temporal changes are analyzed using Friedman test with Nemenyi post-hoc analysis. Baseline versus 7-day comparisons utilize Wilcoxon signed-rank test. Correlation between TNF-α and pain scores is assessed using Spearman's rank correlation coefficient. Significance is established at p < 0.05. Calculations are performed using SPSS software version 26.0 (IBM, NY, USA) and R statistical software.
8. Study Timeline Phase Duration Description Screening 1 week Medical history, clinical examination, radiographs, eligibility confirmation Baseline Day 0 Informed consent, demographic data, baseline VAS, baseline GCF collection Intervention Day 0 Anesthesia, rubber dam, cavity preparation, composite placement, light curing Immediate Post-op Day 0 Immediate GCF collection (T1) Follow-up Day 7 Clinical examination, VAS, GCF collection Data Analysis 2-4 weeks ELISA analysis, statistical analysis
9. Data Management All data are entered into a password-protected Excel spreadsheet. Patient identification is coded (e.g., G1_P01 for Group I, Patient 1). A separate master linking file (password-protected) maintains codes linked to patient identities. Data are backed up weekly to an external encrypted hard drive. All records are retained for five years following publication of study results.
10. Safety and Adverse Events This study uses commercially available dental materials with established safety profiles. Participants are closely monitored throughout the follow-up period. Any patient who discontinues follow-up or undergoes extraction of the involved tooth is excluded from the final analysis. Patients experiencing persistent or severe postoperative pain receive appropriate clinical management.
11. Dissemination of Results Results will be published in a peer-reviewed journal (BMC Oral Health) and presented at national and international conferences.

References for Detailed Description Daronch M, Rueggeberg FA, De Goes MF, Giudici R. Polymerization kinetics of pre-heated composite. J Dent Res. 2006;85(1):38-43.

Lovell LG, Newman SM, Bowman CN. The effects of light intensity, temperature, and comonomer composition on the polymerization behavior of dimethacrylate dental resins. J Dent Res. 1999;78(8):1469-76.

Ates H, Iscan Yapar M. The effect of different preheating methods on the intrapulpal temperature of bulk-fill composite resins. BMC Oral Health. 2025;25(1):1977.

El-Saeed AS, Elerian FA, Hamama HH, Mahmoud SH. Impact of resin composite restorative material pre-heating on dental pulp temperature: A laboratory study. Mansoura J Dent. 2022;9(3):128-32.

Zach L, Cohen G. Pulp response to externally applied heat. Oral Surg Oral Med Oral Pathol. 1965;19(4):515-30.

Champagne CM, Buchanan W, Reddy MS, Preisser JS, Beck JD, Offenbacher S. Potential for gingival crevice fluid measures as predictors of risk for periodontal diseases. Periodontol 2000. 2003;31:167-80.

Lamster IB, Hartley LJ, Vogel RI. Development of a biological profile for gingival crevicular fluid. J Periodontol. 1985;56(Special Issue):13-21.

Pezelj-Ribaric S, Anic I, Brekalo I, Miletic I, Hasan M, Simunovic-Soskie M. Detection of tumor necrosis factor alpha in normal and inflamed human dental pulps. Arch Med Res. 2002;33(5):482-4.

Kokkas AB, Goulas A, Varsamidis K, Mirtsou V, Tziafas D. Irreversible but not reversible pulpitis is associated with up-regulation of tumour necrosis factor-alpha gene expression in human pulp. Int Endod J. 2007;40(3):198-203.

Celik N, Askin S, Gul MA, Seven N. The effect of restorative materials on cytokines in gingival crevicular fluid. Arch Oral Biol. 2017;84:139-44.

Moher D, Hopewell S, Schulz KF, Montori V, Gøtzsche PC, Devereaux PJ, et al. CONSORT 2010 explanation and elaboration: updated guidelines for reporting parallel group randomised trials. Int J Surg. 2012;10(1):28-55.

World Medical Association. World Medical Association Declaration of Helsinki: Ethical principles for medical research involving human subjects. JAMA. 2013;310(20):2191-4.

Faul F, Erdfelder E, Buchner A, Lang AG. Statistical power analyses using G*Power 3.1: tests for correlation and regression analyses. Behav Res Methods. 2009;41(4):1149-60.