Objectives:Catastrophic failures in lithium disilicate single-unit prostheses in the mandibular anterior region, particularly when subjected to endodontic access for root canal treatment, represent a significant clinical concern. This in vitro study evaluated the fracture resistance of CAD/CAM-fabricated lithium disilicate intact and endodontically accessed crowns, with and without aging through thermocycling. Methods and Materials:A mandibular right central incisor typodont was prepared and scanned for CAD/CAM fabrication of a lithium disilicate crown. Eighty crowns were milled, treated, etched, primed, and cemented to printed resin dies. The crowns were divided into eight groups based on endodontic access location (facial, incisal, or lingual) and thermocycling condition (presence or absence). All groups underwent vertical loading until fracture, and fracture resistance was measured. Fractured crowns were analyzed for crack patterns and failure modes using scanning electron microscopy. Two-way ANOVA assessed the effects of access type on fracture resistance, while one-way ANOVAs with Tukey's HSD post hoc tests analyzed fracture resistance across aging conditions. Results:Fracture resistance was significantly affected by endodontic access type and thermocycling (p < 0.001). Non-thermocycled, intact crowns had the highest fracture resistance (1218.0 ± 174.8 N), while thermocycled crowns with incisal access demonstrated the lowest resistance (720.9 ± 98.3 N). Lingual access crowns displayed higher fracture resistance than facial and incisal access crowns, although resistance significantly decreased with thermocycling (p = 0.008). SEM analysis revealed that lingual access crowns visually appeared to exhibit less irregular crack patterns compared to facial and incisal access crowns, which displayed more numerous and irregular crack lines. Conclusions:Endodontic access reduced fracture resistance; however, thermocycling had a statistically significant effect only in the lingual access group. A conservative lingual access preserved integrity similarly to intact crowns, making it preferable for mandibular restorations. All crowns met minimum clinical fracture resistance standards, suggesting that crown replacement may not be necessary with conservative access designs. Variations between aged and non-aged specimens should be considered when interpreting in vitro data.
Purpose:The clinical use of universal resin composites for direct restorations has increased significantly in recent years due to their versatility and simplified shade-matching approach. However, limited long-term data exist on their stability under aging conditions. This study evaluated the optical and mechanical properties of six universal resin composites (Omnichroma, Charisma Topaz One, Vittra APS Unique, OptiShade, G-aenial A'Chord, and Neo Spectra ST) after six months of artificial saliva aging, while examining the influence of spectrophotometer type and inorganic filler composition on their performance. Methods:Color differences [CIEDE2000 (ΔE00)], translucency (TP00), gloss (GU), surface roughness (Ra, μm), and flexural strength (MPa) were measured before and after six months of artificial saliva aging. Statistical analysis was performed using non-parametric tests, including Kruskal Wallis, Mann Whitney U, and Wilcoxon signed-rank tests, with a significance level set at α < 0.05. Results:Statistically significant differences were observed in color differences (ΔE00), translucency (TP00), gloss (GU) and flexural strength among the tested resin composites following aging (p < 0.05). Vittra APS Unique exhibited the highest translucency (TP00 = 55.35) and flexural strength (initial = 140.0 MPa, aged = 99.7 MPa), while G-aenial A'Chord demonstrated the lowest surface roughness (Ra = 0.124 μm) and highest gloss (56 GU). The type of spectrophotometer used significantly impacted the color differences (p < 0.05). Conclusions:Optical and mechanical properties of universal resin composites varied significantly after six months of artificial saliva aging. Moreover, this study showed that the type of spectrophotometer utilized had a significant effect on color differences.
Developmental enamel defects can negatively affect esthetics and patient satisfaction. Minimally invasive treatments have emerged as alternatives to conventional restorations, but quantitative evaluation of their outcomes is limited. The objective of this case report was to assess the efficacy of a combined minimally invasive approach in improving enamel appearance using objective color and fluorescence measurements. A 23-year-old male patient presented with enamel hypoplasia and opacities on 24 teeth. The treatment protocol included: (1) three weeks of at-home bleaching with 16% carbamide peroxide using a custom tray; (2) micro-abrasion with 6.6% hydrochloric acid and silicon carbide slurry followed by 5% sodium fluoride varnish; and (3) applications of 15% hydrochloric acid etching, drying, and resin infiltration. The patient was advised to use a remineralization agent for one month. Fluorescence measurements and color contact-spectrophotometer readings were recorded at baseline, after each treatment stage, and during six- and 12-month follow-ups. Marked improvements in enamel color and fluorescence were observed after bleaching and resin infiltration, and despite a slight decline over time, values remained superior to initial measurements during follow-ups. This multistage minimally invasive approach achieved substantial improvements in enamel appearance, demonstrating its effectiveness for managing enamel opacities.
Background:The mechanical action of toothbrushing can lead to the wear of restorations, and the extrinsic characterization layer applied to enhance their esthetics may also experience degradation over time. Therefore, it is essential to evaluate the effectiveness of surface treatments and the durability of this layer in new restorative materials. Objective:This study evaluated the effects of simulated toothbrushing on the optical and mechanical properties of one 3D-printed and two CAD/CAM resin composite materials, considering different surface treatments. Methods and Materials:Disks of a 3D-printed material (VarseoSmile Crownplus) and two CAD/CAM resin composite materials (Grandio Blocs and Vita Enamic) were divided into three groups (n = 10) based on surface treatment: control (no treatment after polishing), self-etching primer (Monobond Etch & Prime [MEP]), and hydrofluoric acid with silane. A pigment layer followed by glaze was applied to the surface, which was then evaluated for roughness, color, translucency, and gloss. Specimens were subjected to 3,650, 18,250, and 36,500 cycles of simulated toothbrushing, with measurements taken after each interval. Surface characteristics were analyzed using scanning electron microscopy. Translucency and color difference data were subjected to Two-Factor ANOVA and Tukey's test, while roughness and gloss were analyzed using repeated measures ANOVA and Tukey's test. Results:Repeated measures ANOVA revealed statistically significant differences (p < 0.05) across the tested factors (time, surface treatment, and their interaction), depending on the material and parameter evaluated. Surface treatment and toothbrushing had a significant impact on roughness, gloss, and translucency (p < 0.05), with varying effects across different materials. Overall, MEP is preferred for VarseoSmile Crownplus, while acid conditioning is most suitable for Grandio Blocs and Vita Enamic. Two-way ANOVA indicated statistically significant differences for color and translucency difference, with higher values after applying the characterization layer. Conclusion:Surface treatment played a key role in maintaining the longevity of the characterization layer. Although simulated toothbrushing led to progressive wear, the application of surface treatment before characterization effectively mitigated this degradation.
Introduction:The restorative strategies for cracked teeth vary considerably, and both direct and indirect restorations, with and without cuspal coverage have been proposed. However, the literature has shown no consensus among authors, and long-term clinical studies focusing on the direct restorative treatment of cracked teeth remain limited. This five-year retrospective clinical study aimed to evaluate the survival rate of teeth affected by coronal cracks, treated with cuspal coverage direct resin composite restorations, and to evaluate the risk factors associated with tooth loss. Methods and Materials:The study was conducted following the principle of the Declaration of Helsinki and good clinical practice after the approval by the Ethics Committee of the University. Clinical charts, photographs, and videos of 321 patients were retrospectively evaluated. The inclusion criteria were as follows: only posterior cracked teeth with at least five-year follow-up and no pre-existing endodontic treatment. The patients were treated in a private practice between January 1991 and December 2018. Two types of direct resin composite restorative techniques were performed based on the fracture and tooth type. One approach involved a cavity design with full cusp coverage; the other utilized partial cusp coverage, in which only the cracked cusp was covered, and box-shaped restorations were performed to reinforce the opposing walls. No indirect restorations were performed in any of the groups. All treatments were provided by a single operator. The primary outcome was to assess tooth survival at five years. Stepwise logistic regression analysis was performed to identify variables as potential predictors of tooth loss. Results:A total of 321 teeth and 321 patients were included (mean follow-up: 63 months, mean age: 53.9 years). The sample consisted of 79 maxillary and 21 mandibular premolars and 78 maxillary and 143 mandibular molars. At the five-year follow-up, the survival rate was 94.1% (302/321 teeth), with only 19 teeth extracted; 126 root canal treatments were performed (39.2%), and 41 teeth (12.8%) developed periodontal lesions during the follow-up, due to the deepening of the crack. Endodontic treatment (OR: 2.67, 95% CI 1.04-6.89, p = 0.04) and development of a periodontal lesion (OR: 10.52, 95% CI 4.1-27.1, p < 0.0001) were independent risk factors for tooth loss. The type of fracture and other tooth-related factors (ie, pulp calcification, tooth vitality, apical periodontitis) were not statistically significant (p > 0.05). Conclusions:The different restorations exhibited similar clinical performance. Our results suggest that the treatment of coronal cracks with direct resin composite restorations may achieve the remission of symptoms and stop the progression of the crack pattern, improving long-term durability. However, when endodontic treatment is required for a cracked tooth, its long-term prognosis may be reduced.
Objective:Single-shade materials are favored for simplifying clinical workflows without compromising the esthetics of restorations, although evidence supporting their use remains limited. Therefore, this laboratory evaluated color match of single-shade versus group-shade resin composites. Methods:Sixty sound human molars were divided into three subgroups (n = 20), based on the tooth-shade correspondence for the tested group-shade resin composite: L (light) including A1, B1, B2, C1 and D2; M (medium) including A2, A3, C2, D3 and D4, and D (dark) including A3.5, A4, B3, B4, C3 and C4 shaded teeth. Standardized class V cavities (4 × 4 × 2 mm) were prepared. Half of the specimens within each subgroup were restored with single-shade (Omnichroma), while the other half was restored with group-shade resin composite (SimpliShade). Tooth/restoration ΔE00 color differences were calculated at 24 hours (T1), and after seven days (T2) by a spectrophotometer (VITA Easyshade V). A visual analysis was performed after 14 days (T3). Also, a novel computer vision algorithm (CVA) analysis, was employed to evaluate color match at three weeks (T4). Student's t-test was used to compare the two groups within each subgroup and time point and one-way ANOVA was used to compare the values between subgroups, within each group and time point. Results:Instrumental analysis at T1 showed higher mean ΔE00 for single-shade compared to group-shade resin composites (p < 0.05), within each subgroup. Within single-shade specimens, significantly higher mean ΔE00 differences were found at T2 between D (8.24 ± 1.85) vs L (5.65 ± 2.24) (p = 0.007) and M (6.49 ± 2.5) (p = 0.03). Within group-shade specimens, a significant difference was found between L (4.16 ± 2.19) and M (2.17 ± 1.05) at T1 (p = 0.034). Visual analysis reported a significant difference (p = 0.0153) between L-group shade (1.03 ± 1.04) and L-single shade (1.97 ± 0.78) restorations (p = 0.0153). No significant differences were detected when CVA analysis was employed. Conclusions:Overall, group-shade showed better color match than single-shade resin composites, especially when spectrophotometric and visual evaluation were employed.
Objective:Charcoal-based mouthwashes have recently gained popularity, but current evidence on their effects on the color change (ΔE00) and surface properties of resin composites is limited. This study aimed to evaluate the effects of five charcoal-based mouthwashes on the color change and surface roughness (Ra) of a stained resin composite. Methods and Materials:Seventy disc-shaped resin composite specimens (Filtek Z250) were prepared and immersed in coffee for 12 days. The specimens were then randomly distributed into seven groups (n = 10), based on mouthwash used: five charcoal-based mouthwashes (Hello Activated Charcoal Extra Freshening Mouthwash, My Magic Mud Activated Charcoal Alcohol-Free Oral Rinse, Dr. Jones' Naturals Activated Charcoal Mouthwash, The Humble Co. Natural Mouthwash Charcoal, and Colgate Plax White + Charcoal), one hydrogen peroxide-based mouthwash (Crest 3D White), and artificial saliva. Each specimen was immersed in the relevant mouthwash for 60 seconds, rinsed with water for 30 seconds, and then immersed again in a fresh mouthwash solution for 60 seconds to simulate daily mouthwash use. This cycle was repeated to represent 1, 2, 3, 4, and 12 weeks of use. Color measurements were performed at baseline, after staining, and after 1, 2, 3, 4, and 12 weeks. Surface roughness was evaluated after staining and after 1, 2, 3, 4, and 12 weeks of immersion. The surface morphology of the specimens was examined using a scanning electron microscope. The data were analyzed using repeated measures ANOVA and Tukey's test (α = 0.05). Results:After immersion in coffee, the resin composite exhibited discoloration above the 50:50% acceptability threshold (AT) (ΔE00: 1.8). After 12 weeks of use, only one charcoal-based mouthwash, Colgate Plax White + Charcoal, and Crest 3D White reduced the ΔE00 of the resin composite below the AT, but both showed a significant increase in Ra (p < 0.001) and caused changes in surface morphology of the resin composite. The other charcoal-based mouthwashes did not cause an increase in Ra (p > 0.05) but failed to reduce the ΔE00 of the material below this threshold. Conclusions:All charcoal-based mouthwashes, except Colgate Plax White + Charcoal, maintained surface integrity but failed to reduce the color change below the AT. The hydrogen peroxide-based mouthwash provided color improvement on the resin composite but led to increased surface roughness.
Objectives:Although the repair of partially defective resin composite restorations is promoted as a minimally invasive alternative to full replacement, existing evidence remains fragmented across systematic reviews with differing scopes and conclusions. This umbrella review synthesized current systematic reviews on the topic, focusing on clinical longevity, adhesive protocols, professional attitudes, and patient acceptance. Methods and Materials:A comprehensive search was conducted in five databases up to April 2025. Eligible systematic reviews assessed clinical or in vitro outcomes, patient or professional perspectives, or decision-making protocols related to resin composite repair. Methodological quality was assessed using AMSTAR 2, and study overlap was evaluated with corrected covered area (CCA). Findings were interpreted across five thematic domains using the PROPS framework (Patient-centeredness, Risk of bias, Outcomes, Protocols, Significance). Results:Seven systematic reviews were included. A meta-analysis found no significant difference in failure rates between repaired and replaced restorations (RR= 1.21; 95% CI: 0.51-2.83), though evidence certainty was low. A network meta-analysis of laboratory studies identified that diamond bur + silane + adhesive yielded the highest bond strength (mean: 24.5 MPa). Surveys reported high patient acceptance (> 86%) and professional endorsement of repair, yet only 31.3% of defective restorations were repaired. Standardized decision-making tools were lacking. Conclusions:Repair is a clinically sound, conservative option that can offer outcomes comparable to full replacement when appropriately indicated and proper protocols are used. Broader implementation requires guideline standardization, clinical training, and studies incorporating patient-reported outcomes and cost-effectiveness.
Weakened roots remain a significant restorative challenge. Conventional cast metal posts are limited by factors such as stress concentration and unfavorable fracture patterns. While glass fiber posts and bulk-fill resin composites provide benefits in terms of stress distribution and simplified application, evidence supporting their combined use to reinforce compromised roots is still limited. Purpose: The aim of this study was to compare the resistance and patterns of fracture of weakened anterior roots, without ferrule, restored with different techniques. Methods and Materials: A total of 40 human maxillary anterior teeth were selected, endodontically treated, weakened, and divided into four groups (n = 10): G1: cast metal post (NiCr [nickel-chromium] alloy, control); G2: glass fiber post and a thick layer of resin cement; G3: root reinforced with bulk-fill flowable resin composite and glass fiber post; G4: anatomical glass fiber post relined with bulk-fill flowable resin composite. Whitepost DC 0.5 (FGM) and Opus Bulk Fill flow (FGM) were used. Cast metal posts and glass fiber posts were cemented with conventional resin cement (All Cem Core, FGM). The coronal portion of the roots restored with fiber posts was built-up with bulk-fill resin composite (Opus Bulk Fill, FGM), and all roots received an indirect resin composite crown (Opus Bulk Fill, FGM). All specimens were stored in distilled water at 37 degrees C for 60 days to simulate aging and then subjected to compressive loading (1.0 mm/minute at an angle of 45 degrees to the long axis of the tooth) until fracture. Failure modes were analyzed using a stereomicroscope. Fractures were classified as reparable or catastrophic. One-way ANOVA was used to compare fracture resistance of the groups, and Fisher Exact test was used to compare the failure mode (alpha = 0.05). Results: Mean (standard deviation) failure loads (in newtons [N]) were G1: 307.3 (77.4); G2: 250.4 (64.4); G3: 288.3 (50.4); G4: 189.4 (82.0). One-way ANOVA revealed significant differences among groups (p < 0.05), with G4 significantly lower than G1 and G3. The percentage of specimens with catastrophic fracture was 45.0% and ranged from 40.0% to 60.0% per group, with no significant difference (p > 0.05) among groups. Conclusion: Root reinforcement with bulk-fill flowable resin composite associated with a glass fiber post showed adequate mechanical performance, making it an alternative for restoring weakened roots. The fracture resistance of this technique was comparable to that of cast metal posts and superior to that of the direct anatomical post with bulk-fill flowable resin composite. There were no significant differences in failure mode among the evaluated techniques.
Objective: To address the limited evidence regarding the performance of various matrix systems, this study investigated proximal contact quality and surface characteristics across systems differing in structural design and component configuration. Methods and Materials: Forty Frasaco mandibular left first molars (ANKA-4 ZE 100, Frasaco GmbH, Tettnang, Germany) were used to prepare mesial proximal box cavities with standard dimensions. Cavities were restored with a bulk-fill light-cured resin composite using four different matrix systems (n = 10): precontoured stainless steel (Palodent V3, Dentsply Sirona, York, PA, USA), copper (TECCI Copper, TECCI Dental, Istanbul, Turkey), and polyester (TECCI Transparent, TECCI Dental) sectional, and non-dead soft steel circumferential (SuperMat Adapt SuperCap, KerrHawe, Bioggio, Switzerland) matrix systems. Pre-and post-operative scans were obtained using an intraoral scanner (Trios 3, 3Shape, Copenhagen, Denmark). Mesiodistal (MD) diameters were measured on the scans. Proximal contour and marginal adaptation were assessed by two blinded examiners. Surface roughness was evaluated using a profilometer (Mitutoyo SJ 301, Mitutoyo Corp., Kawasaki-shi, Kanagawa, Japan). Data were analyzed using One-Way ANOVA with Tukey's post hoc test for parametric comparisons, and Wilcoxon Signed-Ranks, Kruskal-Wallis with Dunn's post hoc test, Fisher's Exact test with Bonferroni correction, and Cohen's kappa for nonparametric analyses, with significance set at alpha = 0.05. Results: Significant differences were observed among matrix systems for MD diameters, proximal contour, marginal adaptation, and surface roughness (all p < 0.049). The stainless steel sectional matrix system produced the greatest MD diameter change and the highest incidence of cervical and lateral overhang. Only stainless steel and copper sectional matrix systems generated convex contours. Copper and stainless steel sectional matrices also exhibited greater surface roughness than the other systems (both p < 0.03). Conclusion: Precontoured metal sectional matrices with rings achieve proper proximal contours and increase MD diameter. However, they require precise placement to avoid distortion, which may compromise surface smoothness.
Objectives:Loss of cervical tooth structure due to noncarious cervical lesions (NCCLs) can weaken teeth and increase tooth strain. Therefore, the aim of this study was to evaluate the in vivo microstrain variations in human maxillary premolars with NCCLs before and after restoration with resin composite (RC) and resin-modified glass ionomer cement (RMGIC). Methods and Materials:This study was a split-mouth, randomized controlled clinical trial. Twenty patients aged 40-60 years with NCCLs in maxillary premolars were selected. Bite force was measured bilaterally. In Stage I, 10 patients with unilateral NCCLs were randomized and restored with RC and RMGIC. In Stage II, 10 patients with bilateral NCCLs received RC and RMGIC restorations after maxillary quadrant randomization. Bonded strain gauges recorded the coronal buccal microstrain after maximum intercuspation before and after restoration and at the six-month recall visit. Data were analyzed with the Wilcoxon signed-rank test, Mann-Whitney test, Fisher exact test, and Friedman test. Results:In Stage I, there was a significant reduction in mean coronal buccal microstrain immediately after restoration with RMGIC and RC (both p = 0.048) to values similar to that of intact control teeth (p = 0.486, p = 0.686); this reduction remained evident at the six-month recall (RMGIC: p = 0.014, RC: p = 0.040). In Stage II, there was a bilateral, significant reduction in mean coronal buccal microstrain immediately after restoration with RMGIC (p = 0.022) and RC (p = 0.011), which remained evident at the six-month recall visit (both p < 0.001). Conclusion:Coronal buccal microstrain in teeth with NCCLs was significantly reduced after restoration with RMGIC and RC.
Objectives: The addition of film-forming polymers to fluoride varnishes may enhance their protective effect against erosive tooth wear. This study evaluated experimental varnishes combining fluoride with polymethacrylate copolymers for controlling enamel wear under erosive-abrasive conditions. Methods and Materials: Polished bovine enamel specimens were demineralized (0.3% citric acid, pH 2.6, 5 minutes) and assigned to six groups (n = 15) based on treatment: amino methacrylate copolymer (AMC); methyl methacrylate copolymer (MMC); AMC with sodium fluoride (AMC+NaF); MMC with sodium fluoride (MMC+NaF); ultrapure water (negative control, NC); and a commercial varnish (positive control; Duraphat, Colgate-Palmolive Company). Experimental varnishes contained 15% polymer, and fluoride-containing groups had 5% NaF. Specimens underwent nine-day erosive-abrasive cycling consisting of five minutes immersion in 0.3% citric acid, 60 minutes in artificial saliva, repeated four times daily, combined with toothbrushing for 15 seconds twice daily. Surface loss (SL) was measured after treatment to confirm varnish thickness standardization and at the end of cycling using contact profilometry. KOH-soluble fluoride (& micro;g/cm2) on enamel was also quantified. Data were analyzed using One-way ANOVA for surface loss, and Kruskal-Wallis and Dunn post hoc tests for KOH-soluble fluoride (alpha = 0.05). Results: AMC+NaF, MMC+NaF, and the commercial varnish (Duraphat) significantly reduced SL compared to the negative control and polymer-only varnishes (p = 0.001). No significant differences were observed between Duraphat and AMC+NaF (p = 0.139) or MMC+NaF (p = 0.166). For KOH-soluble fluoride, AMC+NaF showed lower values than MMC+NaF (p = 0.001), while Duraphat did not differ significantly from either. Conclusions: Varnishes formulated with polymethacrylate copolymers and sodium fluoride provided in vitro protection against enamel erosive-abrasive wear, with efficacy comparable to the commercial varnish tested.
Objective:Resin composite restorations in deep subgingival cavities involving cementum margins often exhibit early adhesive debonding and marginal failure. Conventional resin adhesive systems are prone to hydrolysis in these situations. However, evidence on the optimal adhesive systems for deep margins is limited. Therefore, this study evaluated the effect of HEMA-containing and HEMA-free adhesives in deep proximal margin restorations after simulated long-term aging. Methods and Materials:Class II box-only cavities were prepared on the distal surfaces of 48 extracted upper premolars, with the gingival margins placed 2 mm apical to the cemento-enamel junction. The teeth were randomly divided into three study groups (n = 16) based on the type of adhesive system: two-step HEMA-containing, two-step HEMA-free, and one-step HEMA-containing. Cavities were restored using a preheated nanohybrid resin composite and cured using a polywave LED light at 1200 mW/cm2. Each group was subdivided into an immediate subgroup (n = 8), in which teeth were examined after 24 hours, and a delayed subgroup (n = 8), in which teeth were examined after an aging process comprising 10,000 thermal cycles (5-55°C). Resin composite/cementum interfaces were evaluated quantitatively by scanning electron microscopy at 200× magnification. Marginal integrity was statistically analyzed by the percentage of continuous margin (%CM). Results:The Kruskal-Wallis test revealed that the two-step HEMA-containing and two-step HEMA-free adhesive systems showed significantly better marginal integrity than the one-step HEMA-containing system for both the immediate and aged groups (all p < 0.005). A Wilcoxon rank-sum test showed that the aging process affected the one-step HEMA-containing adhesive system (p = 0.002), but not the two-step systems (p < 0.05). Conclusion:Two-step adhesive systems had better performance at cementum margins than the one-step adhesive system. The presence of HEMA in the two-step adhesive did not degrade marginal quality compared to the two-step HEMA-free adhesive systems.
Purpose:There is limited information in the literature regarding when overhanging restorations should be replaced, and the topic remains underexplored. Therefore, the aims of this study were to investigate, using fractal analysis, whether overhanging restorations cause microtrabecular alterations in the adjacent alveolar bone even in the absence of radiographically visible changes, and to evaluate whether the size of the overhang contributes to the extent of these bone changes. Methods:In periapical radiographic images of 85 individuals with overhanging restorations, regions of interest (ROIs) were selected from the interdental trabecular bone adjacent to the overhanging edge and the normal side of the same tooth. Fractal dimension (FD) values were obtained using the box-counting method developed by White and Rudolph, implemented with ImageJ software version 1.52 (National Institutes of Health, Bethesda, MD, USA). Compliance with the normal distribution was analyzed using the Kolmogorov-Smirnov test. The relationship between FD values was assessed using the paired two-sample t-test and expressed using the Pearson correlation coefficient. The angle between the lines drawn from the cementoenamel junction of the tooth to the mesio-distal extreme point of the overhanging restoration and the contact point with the adjacent tooth was determined. The effect the of overhanging restoration angle on FD value was analyzed using linear regression analysis. Results:The overhanging restorations were most commonly found in the maxillary molar regions and in disto-oclusal cavity types. The FD obtained on the overhang side was 0.99 ± 0.06, and the FD obtained on the control side was 1.04 ± 0.06. When FD on the overhang side and FD on the control side were compared using the dependent t-test, the difference between them was statistically significant (p < 0.001). The effect of angle on the FD ratio was evaluated using linear regression analysis, and no significant result was found (F = 0.072, p = 0.789). Conclusion:According to the results of this study, overhanging restorations can cause radiographically undetectable alveolar bone loss, and this effect can be demonstrated using fractal analysis.
Background:Immediate dentin sealing (IDS) has been widely used to enhance adhesive bonding in indirect restorations. However, the influence of different bonding agents, temporary materials, and surface cleansing protocols on shear bond strength (SBS) remains unclear. Previous studies have reported conflicting results, and no consensus exists on the optimal combination of these factors for maximizing adhesive performance. This study aimed to evaluate how these variables affect SBS in IDS-based restorations. Methods:Occlusal dentin surfaces of 80 human third molars were prepared and treated with either an etch-and-rinse adhesive (OptiBond FL, Kerr, Orange CA, USA) or a universal adhesive (G2 Bond, GC Corporation, Tokyo, Japan) to create an IDS layer. Specimens were then divided based on the type of temporary material used: eugenol-free cement (TempBond NE, Kerr) or resin-based material (Structur 2 SC, Voco GmbH, Cuxhafen, Germany). After 24-hour water storage, temporary materials were removed using either airborne aluminum oxide (Al2O3) particle abrasion or waterborne Al2O3 particle abrasion (AquaCare, Velopex, London, UK). Ceramic discs were cemented with resin cement, and SBS was measured using a universal testing machine. Failure modes were analyzed under a stereomicroscope, and structural changes on dentin surfaces were examined using scanning electron microscopy (SEM). Data were analyzed using three-way ANOVA with Bonferroni post hoc tests (α = 0.05). Results:Three-way ANOVA revealed a significant interaction among adhesive system, temporary material, and cleansing method (p < 0.001). Due to this interaction, only select pairwise comparisons were interpreted. The highest SBS was observed in the OptiBond FL-Structur 2 SC-AquaCare group, significantly higher than all other combinations (p < 0.05). AquaCare-treated groups consistently outperformed air-abraded groups in bond strength (p < 0.001). Within the air-abraded subgroup, G2 Bond Universal-Structur 2 SC yielded significantly higher SBS than G2-TempBond NE and OptiBond FL-Structur 2 SC (p < 0.05). Failure mode analysis showed a predominance of mixed failures across groups, with no significant differences among failure types (p = 0.729). Conclusion:Cleansing method, adhesive system, and temporary material significantly and interactively influenced SBS in IDS-based restorations. AquaCare waterborne Al2O3 abrasion consistently yielded higher bond strengths than conventional Al2O3 air abrasion. The highest SBS was achieved with the combination of OptiBond FL-Structur 2 SC-AquaCare. These findings highlight the importance of optimizing all procedural steps to enhance bonding effectiveness.
Objective:Because the application of violet light-emitting diode (LED) light may enhance the release of reactive oxygen species, and its combination with a high-concentration bleaching agents may accelerate collagen degradation, this study aimed to evaluate its impact on the mechanical properties of demineralized dentin matrix exposed to high or low concentrations of hydrogen peroxide used in in-office treatments. Methods:The evaluation included changes in mass, modulus of elasticity, ultimate tensile strength, hydroxyproline release, and total matrix metalloproteinase (MMP) activity. Demineralized collagen matrices were assigned to groups (n = 10): 35% hydrogen peroxide, 7.5% hydrogen peroxide, or simulated body fluid (SBF, control) with or without violet LED light. Treatments were conducted over three 30-minute sessions. During each session, violet LED light was applied in 20 cycles of 60 seconds of light, followed by a 30-second rest interval. Dentin matrix mass variation, modulus of elasticity, ultimate tensile strength after treatments, and hydroxyproline release were evaluated. Additionally, other dentin collagen matrices were evaluated for total MMP activity before and after the bleaching protocols (n = 10). Results:Violet LED light caused a significant mass loss in the 35% hydrogen peroxide group (p = 0.007; Mann-Whitney test) compared to the other treatments. There were no significant treatment-related differences in modulus of elasticity (p = 0.527; generalized linear models). The 35% hydrogen peroxide group showed lower ultimate tensile strength and higher hydroxyproline release than the 7% hydrogen peroxide and control groups (p < 0.0001; generalized linear models). All experimental groups exhibited lower percentages of MMP inhibition than the control inhibitor group (p < 0.0001; generalized linear models). Conclusions:Violet LED light and different in-office bleaching agent concentrations did not reduce the modulus of elasticity. Violet LED light combined with 35% hydrogen peroxide reduced dentin mass and ultimate tensile strength, and increased hydroxyproline release and total MMP collagen activity.
Purpose:Low-temperature plasma (LTP) has been used as an option for dentin surface treatment prior to adhesion due to its antibacterial effect without causing substantial changes to the dentin surface. However, few studies have reported the influence of argon combined with oxygen on the degree of conversion of resin cements or the adhesive luting procedure. Thus, this study aimed to evaluate the effect of LTP pretreatment of dentin on the degree of conversion of resin cements, as well as the effect on bond strength to dentin of different adhesion luting protocols. Methods and Materials:The dentin surfaces of 72 sound human molars were exposed. Specimens were divided into three groups according to LTP pretreatment (argon-based LTP, argon/oxygen-based LTP, and no LTP application). These groups were then divided into three subgroups (n = 8) and resin composite blocks (Te-Econom Plus, Ivoclar Vivident) were cemented to the dentin according to one of three adhesive luting protocols (Single Bond 2 [Solventum] + RelyX ARC [Solventum], Single Bond Universal [Solventum] + RelyX Ultimate [Solventum], and RelyX U200 [Solventum]). Microtensile bond strengths were measured before and after thermocycling (10,000 cycles between 55°C and 5°C). Degree of conversion was measured using a Raman spectrometer (Senterra, Bruker Optik GmbH). All data were submitted to ANOVA and Tukey post hoc tests (α = 0.05). Results:RelyX ARC exhibited higher dentin bond strength than RelyX U200 regardless of LTP treatment. RelyX Ultimate showed intermediate bond strength and higher degree of conversion than the other materials. The application of argon-based LTP resulted in bond strength and degree of conversion similar to those of the control group for all cements used. The addition of oxygen to argon to generate LTP resulted in lower bond strength, especially when RelyX U200 was used. Conclusion:The application of Argon plasma did not cause any damage to the adhesive interface. However, neither Argon alone nor the addition of oxygen to argon to generate LTP was beneficial for the properties evaluated.
Introduction:Resin infiltration is an effective minimally invasive treatment for white spot lesions, but post-treatment discoloration remains a significant clinical challenge with limited evidence-based management protocols. Objectives:This study evaluated the effectiveness of polishing and bleaching techniques in enhancing the color of resin-infiltrated teeth. Methods and Materials:Fifty caries-free, extracted permanent human teeth were randomly allocated to control and study groups (n = 25). All specimens were cleaned, sectioned mesiodistally, mounted in acrylic resin, and examined for surface imperfections. The study group underwent standardized artificial demineralization to create 50-µm white spot lesions, followed by ICON resin infiltration. Both groups completed a 30-day staining protocol with twice-daily 15-minute immersions in standardized coffee solution and brushing. Interventions included (1) mechanical polishing and (2) 14-day bleaching (9.5% H2O2 gel, 30-minute daily applications). Color changes were quantitatively assessed at baseline, post-polishing, and post-bleaching using spectrophotometry (Vita Easyshade) with CIELAB/CIEDE2000 systems and Vitapan Classical shade scores. Statistical analysis employed paired t-tests, ANOVA, and mixed ANOVA (α = 0.05). Results:At baseline, resin-infiltrated teeth were significantly darker (lower L*) and redder (higher a*) compared to untreated controls (p < 0.005). Mechanical polishing improved color parameters in both groups and effectively minimized intergroup differences (ΔE00: 6.90 vs 6.84; p = 0.49). Bleaching produced significantly greater color change in resin-infiltrated teeth compared to controls (ΔE00 from baseline: 17.6 vs 11.4, p < 0.001). Vitapan shade scores improved significantly across sequential treatment stages (baseline, post-polishing, post-bleaching; p < 0.001), with no significant intergroup differences in final scores (p = 0.49). Conclusions:Polishing reduced surface stains and color differences, but bleaching achieved greater whitening, especially in resin-infiltrated teeth. Together, they offer an effective approach for managing post-infiltration discoloration.
