The aim of this study is to assess the effect of shade and light-curing intensity on the heat generation and degree of conversion of bulk-fill composite. A commercially available bulk-fill composite resin was used in this study. A total of 250 cylindrical specimens of each composite shade (n = 25/group) were prepared (125 for testing heat generation and 125 for testing degree of conversion, then cured using a monowave light-curing unit (LCU) with a single light intensity of 1470 mW/cm² and a polywave LCU with three different light intensities (1200, 2000, and 3000 mW/cm²). Heat generation during polymerization was measured by five K-type thermocouples placed in each 1 mm layer from top to bottom. FTIR was used for evaluating the degree of conversion. Regarding heat generation, significant differences were seen in layers 4 and 5. Curing types and times also showed significant impacts on heat generation and the degree of conversion. Heat generation relates more to curing time than light intensity. Darker shades generate and retain more heat. Lighter shades exhibit higher degrees of conversion with longer curing.

Purpose: To estimate the prevalence of three-rooted mandibular deciduous second molars (3RME) and three-rooted mandibular permanent first molars (3RM6) in Iraqi children and to evaluate their association using cone-beam computed tomography (CBCT). Methods: This retrospective cross-sectional study analyzed CBCT scans of Iraqi children aged 7– 12 years (N = 196). Root morphology was assessed in axial, coronal, and sagittal planes. Prevalence was calculated at the patient level (presence of ≥ 1 affected tooth). Associations between 3RME and 3RM6 were tested using the chi-square test, and age/sex were explored as predictors using logistic regression. Intra- and inter-examiner reliability were assessed with Cohen’s kappa. Results: Three-rooted morphology was identified in 3/196 children for 3RME (1.53%; 95% CI 0.52– 4.40) and 10/196 children for 3RM6 (5.10%; 95% CI 2.80– 9.14). A significant association was observed between 3RME and 3RM6 (χ²(4, N = 196) = 96.48, p < 0.001; Cramér’s V = 0.50). Age and sex were not significant predictors (p > 0.05). Conclusion: Three-rooted mandibular molars were uncommon in this Iraqi pediatric sample; however, 3RME co-occurred significantly with 3RM6, indicating a strong association that may be clinically useful for anticipatory diagnosis and treatment planning.

Accurate knowledge of the root canal system is essential for successful endodontic treatment. The position of the apical foramen, which frequently deviates from the anatomical apex, impacts treatment precision. While advances like electronic apex locators have enhanced accuracy, discrepancies with radiographic readings still arise due to foramen position variations. Factors such as age, race, and ethnicity contribute to these differences. This study examines the distance and direction of deviation between the major apical foramen and the anatomical apex in an Iraqi subpopulation. It aims to highlight local anatomical variations, aiding better treatment outcomes. A total of 238 extracted permanent human teeth were examined. The teeth were sectioned transversely at the cemento-enamel junction, mounted on a calibrated microscopic slide, and analyzed to identify the location of the major apical foramen. The major foramen was defined as the largest-diameter opening at the root apex. The assessment was conducted using a dental operating microscope. The distance between the major apical foramen and the anatomical apex was calculated using Image J software. The mean distance between the major apical foramen and the anatomical apex across all teeth was 0.52 mm. This distance was consistent in both anterior and posterior teeth, with notable variations observed among different tooth types. The mandibular canine exhibited the greatest deviation, with a mean distance of 0.77 mm, followed by mandibular molars, which showed a mean distance of 0.6 mm. The most common direction of deviation was distal, with a frequency of 25.65% across all tooth types. The study’s findings indicated that in 85% of all tooth types, the major foramen deviated from the anatomical and/or radiographic apex. The distal deviation was the most frequent, with an average distance of 0.52 mm. These results underscore the importance of understanding apical anatomy for accurate endodontic treatment and highlight notable anatomical variations in this subpopulation.

Background/Objectives: Achieving durable intraoral repairs of fractured metal and zirconia restorations requires optimal adhesion. This in vitro study evaluated the effects of mechanical surface treatments and commercial repair systems on the shear bond strength (SBS) of composite resin to nickel–chromium (Ni-Cr) alloy and zirconia, including the influence of thermocycling aging. Methods: In this study, 144 Ni-Cr and zirconia discs (12 × 12 × 2 mm) were randomly assigned to three surface treatments: untreated control, airborne particle abrasion (50 µm Al₂O₃), and medium grit diamond bur grinding. Each group was further subdivided to assess two intraoral repair kits (GC Corp (Tokyo, Japan). and Bisco Inc. (Schaumburg, IL, USA)). Composite resin cylinders were bonded following the manufacturer’s instructions. Half of the specimens (n = 12/subgroup) underwent 5000 thermocycles (5–55 °C). Micro-shear bond strength testing was performed, and failure modes were analyzed. Data were analyzed using three-way ANOVA and post hoc tests (p < 0.05). Results: Air abrasion significantly increased SBS compared to control and bur grinding for metal (p < 0.001). For zirconia, both air abrasion and bur grinding yielded similarly improved SBS over the control (p < 0.001). The GC repair kit demonstrated significantly superior bond stability after thermocycling across both substrates. Aging significantly reduced SBS in all groups (p < 0.001), with the most substantial reductions observed in untreated controls and groups repaired with the Bisco system. Conclusions: Airborne particle abrasion combined with a HEMA-free, 10-MDP-containing universal adhesive achieved the strongest and most durable resin bonds to both metal and zirconia, supporting its clinical use for the intraoral repair of ceramic and metal restorations.

Background: The restorative material used to seal the screw access channel in screw-retained implant-supported crowns may influence the biomechanical behavior and mechanical performance of the restoration. Objective: To evaluate the influence of different screw access channel restorative materials on stress distribution and deformation in porcelain-fused-to-metal (PFM) and monolithic zirconia implant-supported crowns using three-dimensional finite element analysis (FEA). Materials and Methods: Three-dimensional finite element models of screw-retained PFM and monolithic zirconia implant-supported crowns were developed. Four restorative materials—direct composite resin, resin matrix ceramic (RMC), lithium disilicate (LDS), and zirconia inlays—were used to restore the screw access channel. Each model was subjected to 200 N vertical and oblique occlusal loads. Equivalent von Mises (EVM) stress and total deformation were calculated and compared among the different restorative materials and crown types. Results: In PFM crowns, lithium disilicate and zirconia inlays produced lower stress transfer under vertical loading than direct composite resin and resin matrix ceramic. Under oblique loading, the differences in stress distribution among restorative materials were less pronounced. Zirconia inlays exhibited the highest internal stress concentrations but the lowest deformation, whereas direct composite resin demonstrated the greatest deformation. In monolithic zirconia crowns, deformation values were comparable among zirconia, lithium disilicate, and resin matrix ceramic inlays, indicating that the high stiffness of the zirconia crown largely governed the biomechanical response. Conclusions: Both the crown material and the restorative material used to seal the screw access channel affected the biomechanical performance of implant-supported restorations. Lithium disilicate and zirconia demonstrated more favorable mechanical behavior than direct composite resin, which exhibited greater deformation. These findings suggest that indirect restorative materials may provide biomechanical advantages over direct composite resin, particularly in restorations subjected to higher occlusal loads.