Cuspal deflection and microleakage in premolar teeth restored with bulk-fill flowable resin-based composite base materials

Is use of flowable resin composite an option for occluso-proximal restorations in primary teeth? A fracture strength analysis

BACKGROUND

Use of flowable resin composites for ocluso-proximal restorations in primary molars could improve cervical adaptation, and reduce the failure risk.

AIM

To investigate the fracture strength of occluso-proximal restorations in primary teeth using different flowable resin composites (as an intermediate layer or entire cavity) and a conventional resin composite (incremental technique).

DESIGN

Two standardized occluso-proximal cavities were prepared on mesial and distal surfaces of 50 sound primary molars. The teeth were randomly assigned into five groups (n = 10): 2 mm Filtek Bulk Fill Flow + Z350 XT; 4 mm Filtek Bulk Fill Flow; 2 mm Z350 XT Flow + Z350 XT; 4 mm Z350 XT Flow; and Z350 XT inserted by incremental technique. All restored teeth were subjected to cariogenic challenge and then submitted to fracture strength test. The failure pattern of each specimen was categorized as reparable or irreparable/need for replacement based on the World Dental Federation (FDI) criteria. Fracture strength means were submitted to one-way ANOVA and Tukey's post hoc tests. Failure pattern was analyzed descriptively.

RESULTS

There was no statistically significant difference on fracture strength among groups (p = .48). A similar distribution of reparable (35%-40%) and irreparable (60%-65%) failures was observed among groups.

CONCLUSION

Based on a laboratorial setting, the use of different flowable resin composites (as an intermediate layer or entire cavity) may be an option to restore occluso-proximal cavities in primary molars.

Influence of Different Application Modes of a Universal Adhesive System on the Bond Strength of Bulk-Fill Composite Resin to Enamel and Dentin in Primary Teeth

OBJECTIVES

The objective of this study was to assess how the application mode of a universal adhesive system affects the microshear bond strength (μSBS) of bulk-fill and conventional composite resins to enamel and dentin in primary teeth.

METHODS

A total of 80 caries-free primary second molars were randomly assigned to eight experimental groups (n = 10) based on the bonding substrate (enamel or dentin), the application mode of the universal adhesive system (etch and rinse [E&R], or self-etch [SE]), and the type of composite resin used (bulk-fill or conventional). After bonding the composite resin to enamel or dentin, the μSBS of the bonded composite resins was measured.

RESULTS

The mean μSBS value of bulk-fill composite resin was significantly higher than that of conventional composite resin for both enamel and dentin substrates, regardless of the application mode (p < 0.001). An interaction effect between the bonding substrate and the application mode of the adhesive system was observed, indicating a significant relationship (p < 0.001). The highest μSBS values for primary teeth enamel were achieved using the E&R mode with bulk-fill composite resin, while for dentin specimens, the SE mode with bulk-fill composite resin yielded the highest μSBS values. The μSBS of the E&R group was significantly higher than that of the SE group for enamel specimens (p < 0.001), whereas the μSBS of the SE group was significantly higher than that of the E&R group for dentin specimens (p < 0.001).

CONCLUSION

Bulk-fill composite resin demonstrated higher μSBS in comparison to conventional composite resin. The universal adhesive system exhibited superior performance in the SE mode compared to the E&R mode on primary dentin. Pre-etching the enamel before the application of the universal adhesive enhanced the μSBS to primary teeth enamel, highlighting the importance of selectively acid etching the enamel of primary teeth.

Real-time imaging and quantitative analysis of internal gap formation in bulk-fill and conventional resin composites: An OCT evaluation

BACKGROUND

This study used optical coherence tomography (OCT) to observe real-time internal gap formation in both bulk-fill and conventional resin composites. It aimed to provide a quantitative analysis of variations, addressing the inconclusive nature of microleakage assessment caused by differences in testing methods.

METHODS

Fifty extracted third molars prepared with Class I cavities, were divided into five groups (n = 10). Conventional resin Filtek Z350 XT (FZX) was applied with a double-layer filling of 2 mm per layer. Bulk-fill resins X-tra fil (XTF), Filtek Bulk Fill Posterior Restorative (FBP), Surefil SDR Flow + (SDR), and Filtek Flowable Restorative (FFR) were applied with a single-layer filling of 4 mm. Real-time OCT imaging was conducted during light curing. Post-curing, the entire sample was OCT-scanned. Following this, ImageJ software was used to measure the gap (G1 %). Subsequently, thermal cycling (TC) (5000 times, 5 °C-55 °C) was applied, followed by OCT scanning to calculate the gap (G2 %) and ΔG%. Data were analyzed using two-way repeated measures ANOVA, Kruskal-Wallis test, and Duncan's test (α=0.05).

RESULTS

There was no significant difference in G1 % among the groups (p > 0.05). Following TC, FZX exhibited the highest G2 %, succeeded by FFR, FBP, XTF, and SDR, with SDR demonstrating the lowest G2 % (p < 0.05). FZX showed the highest ΔG% (p < 0.05), while SDR exhibited the lowest ΔG% (p < 0.05).

CONCLUSION

OCT proves to be a promising tool for detecting microleakage. TC exerted a more significant negative impact on conventional resin. Surefil SDR Flow + displayed the least microleakage, both before and after TC.

In-vitro evaluation of fracture resistance of teeth restored with different high-viscosity glass ionomer restorative materials and bulk-fill composite resins

OBJECTIVES

This study aimed to evaluate the effect of restorations made with a glass-hybrid restorative system (GHRS), a high-viscosity glass ionomer restorative material (HVGIC), a high-viscosity bulk-fill composite resin (HVB), a flowable bulk-fill composite resin (FB), and a nanohybrid composite resin (NH), which are commonly preferred in clinical applications on the fracture resistance of teeth in-vitro.

MATERIALS AND METHODS

One hundred intact human premolar teeth were included in the study. The teeth were randomly divided into ten groups (n = 10). No treatment was applied to the teeth in Control group. Class II cavities were prepared on the mesial surfaces of the remaining ninety teeth in other groups. For restoration of the teeth, a GHRS, a HVGIC, a HVB, a FB, and a NH were used. Additionally, in four groups, teeth were restored using NH, GHRS, and HVGIC with open and closed-sandwich techniques. After 24 h, fracture resistance testing was performed. One-way ANOVA and Tukey HDS tests were used for statistical analysis of the data.

RESULTS

The fracture resistance values of Control group were statistically significantly higher than those of GHRS, HVGIC, FB, NH, HVGIC-CS, GHRS-OS, and HVGIC-OS groups(p < 0.05). There was no statistically significant difference observed between the fracture resistance values of Control, HVB, and GHRS-CS groups (p > 0.05).

CONCLUSION

It can be concluded that the use of HVB and the application of GHRS with a closed-sandwich technique may have a positive effect on the fracture resistance of teeth in the restoration of wide Class II cavities.

CLINICAL RELEVANCE

The use of high-viscosity bulk-fill composite resin and the application of glass-hybrid restorative system with the closed-sandwich technique in the restoration of teeth with wide Class II cavities could increase the fracture resistance of the teeth.

Influence of Cavity Lining on the 3-Year Clinical Outcome of Posterior Composite Restorations: A Randomized Controlled Clinical Trial

The purpose of this randomized, split-mouth-designed controlled and single-blinded clinical study was to evaluate the 3-year clinical performance of Class I and Class II resin composite restorations placed with or without cavity lining with a flowable composite. Fifty patients with treatment needs in two premolars or molars were included. One of the teeth was restored using the nanohybrid composite (Grandio®SO, control group), in the test group a high viscosity flowable composite was additionally applied as a first layer. In both groups, the same self-etch adhesive system was applied. Clinical evaluation after 3 years was carried out using the modified USPHS/Ryge criteria. At the 3-year follow-up the recall rate was 92%. Four restorations failed in the test group (8.7%), three due to the loss of vitality and one after fracture. The control group exhibited a cumulative success rate of 100%, while the test group achieved a success rate of 91.3%. This led to significant differences in the annual failure rate (AFR) between the two groups, with rates of 0% and 2.9% (p < 0.05; Mann-Whitney U-test). After 3 years the cumulative survival rate including all restorations was 95.7%. Statistical analysis revealed significant differences for the parameters: tooth vitality, marginal discoloration, success rate, and AFR. The other parameters exhibited no significant differences. Consequently, the nanohybrid composite demonstrated excellent performance over a 3-year period, whereas the utilization of a flowable composite for the cavity lining did not appear to exert a beneficial influence on clinical outcomes.

Effect of cervical margin relocation on marginal adaptation and microleakage of indirect ceramic restorations

PURPOSE

This study evaluated the effect of cervical margin relocation (CMR) with two different materials and contamination with hemostatic agents on the margin adaptation and microleakage of ceramic restorations.

MATERIALS AND METHODS

Mesial-occlusal-distal cavities were prepared in 60 human first molars and distributed to 3 groups (n = 20) according to the margin relocation procedure. The groups were: group F; flowable composite applied in two 2 mm increments, group B; bulk-fill flowable composite applied as a bulk increment of 4 mm thickness and group C (control); no CMR was done. Each group was subdivided into two subgroups (subgroup N; no hemostatic agent applied and subgroup H; hemostatic agent was applied). In all groups, ceramic inlays were prepared and cemented. The samples were subjected to thermocycling (10,000 cycles). The adaptation of the cervical margin was evaluated with scanning electron microscopy (200×). Samples were then assessed for microleakage analysis with the dye penetration method. Marginal adaptation data were normally distributed and analyzed using two-way ANOVA followed by Tukey's post hoc test. Ordinal microleakage score data were analyzed using cumulative link models followed by the analysis of deviance using Wald chi-square tests.

RESULTS

Both CMR and contamination with a hemostatic agent had significant effects on the margin adaptation of the cervical margin. Group C showed the highest adaptation with no significant difference from group F. The lowest adaptation was revealed in group B with a significant difference from group C. Subgroup N (in all groups) showed a statistically higher adaptation than subgroup H. Regarding microleakage assessment, CMR had no significant effect but hemostatic agent application showed a significantly higher microleakage score for all groups.

CONCLUSIONS

Both the CMR procedure and contamination with AlCl3 hemostatic agent had a negative effect on marginal adaptation. For microleakage assessment, only contamination with hemostatic agent negatively affected the microleakage with no effect on the margin relocation procedure.

Comparison of two composite resin materials for splinting of dental luxation injuries: A double blind randomized controlled trial

BACKGROUND/AIM

Luxation is a common traumatic dental injury treated with a wire composite (WC) splint. However, bulk-fill flowable composite and conventional packable composite have not been compared for retaining these splints. Therefore, the objectives of this randomized controlled trial were (1) to compare retention of WC splints, and (2) to compare adhesive point dimension, application and removal time, and effect on tooth mobility between the two WC splints.

MATERIALS AND METHODS

In this parallel group, non-inferiority double blind randomized controlled trial, a total of 90 patients, aged 16-50 years participated. They were randomly allocated into two groups, the packable composite group (PC) n = 45 and the bulk-fill flowable composite group (BF-FC) n = 45 by lottery method. Following measurements were taken at the splint application appointment. Horizontal tooth mobility measured via Periotest, splint application time, and frontal images of splinted teeth to measure the percentage composite adhesive point area. After 2 weeks, splints were visually inspected for retention, whereas mobility and removal times were also recorded. Statistically, comparisons were made using independent samples sample T-test, Fisher's exact test, and Mann-Whitney U at p ≤ .05.

RESULTS

A total of 88 patients with 156 luxated teeth completed the trial, as two patients were lost to follow-up. Two patients in the PC group reported with completely de-bonded splints while none de-bonded in the BF-FC group. Both groups were similar in terms of splint retention (p = .352), reduction of mobility (p = .426), and splint removal times (p = .372). The BF-FC group performed significantly better in adhesive point dimension percentages (p < .001) and splint application time (p < .001).

CONCLUSION

Both groups were comparable in most parameters of the study. However, for BF-FC group application time and adhesive point dimension were significantly less.

Evaluation of the color stability of attachments made with different resin composites

INTRODUCTION

Coloring solutions-such as coffee and cola, frequently consumed daily-cause coloration of attachments made with resin composites. This may reduce the motivation for clear aligner treatment, often preferred by patients with esthetic concerns. This study aimed to compare color changes of orthodontic attachments made with 3 different composite resins.

METHODS

A total of 90 premolar teeth (n = 10) extracted for orthodontic reasons were used. All teeth were embedded in plaster models to imitate the arch shape and scanned with an intraoral scanner. Horizontal rectangular attachments were placed on each tooth by printing the attachment template obtained using digital models. Three composite resins: Omnichroma, GC Aligner Connect, and Tetric PowerFlow were used to prepare the attachments. The models prepared in arc-shaped in each composite group were divided into subgroups and kept in 3 different solutions (coffee, cola, and distilled water) in the incubator at 37 ± 1°C. The models were photographed at baseline and 28 days later with the Smile-Lite MDP device. L, a, and b values were obtained with Digital Color Meter (version 5.22; Apple, Cupertino, Calif). CIEDE2000 formula (ΔE00) was used to evaluate color changes. In addition, models were scanned for color determination at baseline and 28 days later with the 3Shape intraoral scanner.

RESULTS

There were significant color differences between solutions (P <0.05).

CONCLUSIONS

Attachments can be colored easily. Patients should be warned against coloring solutions at the beginning of the treatment, and their eating and drinking habits should be regulated.

Interfacial integrity of bulk-fill resin composite restorations in deep Class-II cavities

This study evaluated the interfacial integrity of deep (6 mm) Class-II (OM/OD) restorations placed using different bulk-fill resin composites [Filtek™ Bulk Fill Flowable Restorative (BF) and Filtek™ Bulk Fill Posterior Restorative (BP) (3M ESPE, St. Paul, MN, USA)] of different increment thicknesses (2 or 4 mm). BP was used for capping in all cases, while Filtek™ Z250 Universal Restorative (3M ESPE) was used as the control material. Interfacial debonding was measured during curing through acoustic emission (AE), followed by image analysis using micro-computed tomography and scanning electron microscopy. Microhardness testing was also conducted to assess degree of conversion. Depth of cure was adequate in all restorations. Specimens with 4-mm thick first increment of BF, which had a higher shrinkage strain, produced most AE events and debonding. Thus, bulk filling of deep cavities using bulk-fill resin composites with a high shrinkage strain should be avoided.

Comparison between a bulk-fill resin-based composite and three luting materials on the cementation of fiberglass-reinforced posts

Objectives

This study verified the possibility of cementing fiberglass-reinforced posts using a flowable bulk-fill composite (BF), comparing its push-out bond strength and microhardness with these properties of 3 luting materials.

Materials and Methods

Sixty endodontically treated bovine roots were used. Posts were cemented using conventional dual-cured cement (CC); self-adhesive cement (SA); dual-cured composite (RC); and BF. Push-out bond strength (n = 10) and microhardness (n = 5) tests were performed after 1 week and 4 months of storage. Two-way repeated measures analysis of variance (ANOVA), 1-way ANOVA, t-test, and Tukey post-hoc tests were applied for the push-out bond strength and microhardness results; and Pearson correlation test was applied to verify the correlation between push-out bond strength and microhardness results (α = 0.05).

Results

BF presented higher push-out bond strength than CC and SA in the cervical third before aging (p < 0.01). No differences were found between push-out bond strength before and after aging for all the luting materials (p = 0.84). Regarding hardness, only SA presented higher values measured before than after aging (p < 0.01). RC and BF did not present 80% of the maximum hardness at the apical regions. A strong positive correlation was found between the luting materials' push-out bond strength and microhardness (p < 0.01, R2 = 0.7912).

Conclusions

The BF presented comparable or higher push-out bond strength and microhardness than the luting materials, which indicates that it could be used for cementing resin posts in situations where adequate light curing is possible.

In vitro microleakage at the enamel and dentin margins of class II cavities of primary molars restored with a bulk-fill and a conventional composite

OBJECTIVES

This study assessed the enamel and dentin margin microleakage of class II cavities of primary molars restored with a bulk-fill and a conventional composite.

MATERIALS AND METHODS

In this in vitro, experimental study, standard class II cavities were created in the proximal surfaces of 60 extracted primary molars. The teeth were randomly divided into two groups, and restored with SonicFill bulk-fill and Filtek Z250 conventional composite along with Single Bond 2 adhesive. The teeth were coated with two layers of nail varnish to 1 mm around the restoration margins, and the apices were sealed with wax. The teeth underwent 1500 thermal cycles and incubated at 37°C for 24 h. They were then immersed in 1 M silver nitrate in the dark, rinsed with water, immersed in developing solution for 12 h, and exposed to fluorescent light. Next, they were mesiodistally sectioned, and digitally photographed under a stereomicroscope at ×10 magnification. The dye penetration depth was measured by a blind observer, and analyzed by the Mann-Whitney U test (α = .05).

RESULTS

No significant difference existed in microleakage between the two composite groups at the enamel (p = .76) or dentin (p = .16) margins. In both composite groups, microleakage at the dentin margins was significantly greater than that at the enamel margins (p = .000).

CONCLUSION

Considering the absence of a significant difference in microleakage, SonicFill bulk-fill composite can be used as an alternative to Filtek Z250 conventional composite for restoration of primary molars to benefit from its advantages such as simpler and faster application.

Crack propensity of different direct restorative procedures in deep MOD cavities

OBJECTIVE

The purpose was to evaluate the crack formation associated with different direct restorative procedures of the utilized resin composites (RC) right after and 1 week later of the restoration.

MATERIALS AND METHODS

Eighty intact, crack-free third molars with standard MOD cavities were included in this in vitro study and randomly divided into four groups of 20 each. After adhesive treatment, the cavities were restored either with bulk (group 1) or layered (group 2) short-fiber-reinforced resin composites (SFRC); bulk-fill RC (group 3); and layered conventional RC (control). Right after the polymerization and a week later, crack evaluation on the outer surface of the remaining cavity walls was performed with a transillumination method utilizing the D-Light Pro (GC Europe) with the "detection mode." Between- and within-groups comparisons Kruskal-Wallis and Wilcoxon tests were used, respectively.

RESULTS

Post-polymerization crack evaluation showed significantly lower crack formation in SFRC groups compared to the control (p<0.001). There was no significant difference within SFRC groups and non-SFRC groups (p=1.00 and p=0.11, respectively). Within group comparison revealed significantly higher number of cracks in all groups after 1 week (p≤0.001), however, only the control group differed significantly from all the other groups (p≤0.003).

CONCLUSIONS

Post-polymerization shrinkage induced further crack formation in the tooth 1 week after the restoration. SFRC was less prone to shrinkage-related crack formation during the restorative procedure; however, after 1 week, besides SFRC, bulk-fill RC also showed less prone to polymerization shrinkage-related crack formation than layered composite fillings.

CLINICAL RELEVANCE

SRFC can decrease the shrinkage stress-induced crack formation in MOD cavities.

Evaluation of Glass-Ionomer versus Bulk-Fill Resin Composite: A Two-Year Randomized Clinical Study

Background: The aim of this split-mouth design research was to compare the clinical performance of a glass-ionomer cement system on Class I/II cavities against the clinical performance of bulk-fill resin composite restoration materials. Methods: Thirty-five patients were randomized and enrolled in the study, aged between 10 and 12 years, all of whom had a matched pair of permanent mandibular carious molars with similar Class I/II. A total of 70 restoration placements were performed. The patients were each given two restorations consisting of either a glass-ionomer cement with a nano-filled coating or a bulk-fill resin composite after the use of a self-etch adhesive. The cumulative survival rates were estimated using log-rank test and the Kaplan−Meier method. For comparison of the restorative materials in line with the modified Ryge, the McNemar test and the Wilcoxon signed rank test were employed. Results: With regard to retention, the glass-ionomer cement system and bulk-fill resin composite performed similarly in permanent molars in Class I/II cavities over a period of up to 24-months (p > 0.05). Over the 24-month period, Class I restorations showed statistically better survival rates than Class II restorations (p < 0.05). In the case of glass-ionomer cement systems, over the two-year period, more common chipping and surface degradations were observed. Conclusions: The glass-ionomer cement system and bulk-fill resin composite restorative materials display good clinical performance over a period of 24-months.

Deep Margin Elevation: Current Concepts and Clinical Considerations: A Review

Dietschi and Spreafico first proposed deep margin elevation (DME) in 1998 to address the multiple clinical problems associated with sub-gingival margins, where sub-gingival margins will be repositioned coronally using composite resin restorations. Given that dentistry is directing towards conservatism, its use is currently trending. Materials and Methods: a search was performed through PubMed, Scopus, and Google Scholar search engines to obtain relevant articles with no time restriction. Results: With biological width taken into consideration, well-defined and polished sub-gingival restorations are compatible with periodontal health. Marginal integrity in the DME technique seems to be affected by the type of adhesive, restoration, and incremental layering of the restoration. Regarding fracture resistance, DME has no significant effects. Conclusion: The DME technique seems to be a minimally invasive alternative to surgical crown lengthening (SCL) and orthodontic extrusion (OE) with respect to biological width. Well-controlled clinical trials are limited in this field; further long-term follow-up studies emphasizing the periodontal outcomes and prevention of complications are needed.

Deep proximal margin rebuilding with direct esthetic restorations: a systematic review of marginal adaptation and bond strength

This review aimed to characterize the effect of direct restorative material types and adhesive protocols on marginal adaptation and the bond strength of the interface between the material and the proximal dentin/cementum. An electronic search of 3 databases (the National Library of Medicine [MEDLINE/PubMed], Scopus, and ScienceDirect) was conducted. Studies were included if they evaluated marginal adaptation or bond strength tests for proximal restorations under the cementoenamel junction. Only 16 studies met the inclusion criteria and were included in this review. These studies presented a high degree of heterogeneity in terms of the materials used and the methodologies and evaluation criteria of each test; therefore, only a descriptive analysis could be conducted. The included studies were individually evaluated for the risk of bias following predetermined criteria. To summarize the results of the included studies, the type of restorative material affected the test results, whereas the use of different adhesive protocols had an insignificant effect on the results. It could be concluded that various categories of resin-based composites could be a suitable choice for clinicians to elevate proximal dentin/cementum margins, rather than the open sandwich technique with resin-modified glass ionomers. Despite challenges in bonding to proximal dentin/cementum margins, different adhesive protocols provided comparable outcomes.

Effect of a fiber-reinforcing technique for direct composite restorations of structurally compromised teeth on marginal microleakage

OBJECTIVES

To evaluate if the marginal microleakage of extensive Class I composite resin restorations can be affected by applying ultra-high-molecular-weight polyethylene (UHMWPE) fibers with the wallpapering technique combined with different restorative materials and methods.

MATERIALS AND METHODS

A 120 human molars were selected and one extensive Class I cavity was prepared on the occlusal surface of each tooth. The specimens were divided into 12 groups (n = 10) according to the type of restorative material (Filtek Z550, Beautifil II LS or Beautifil Bulk Restorative), the use or not of reinforcing fibers (ribbond) and the applied restorative technique (incremental or bulk). The specimens were subjected to thermocycling and then immersed into a 50 wt% silver nitrate solution following a dying protocol. Subsequently, the teeth were prepared for SEM observations to evaluate the extent of marginal microleakage.

RESULTS

Three-way ANOVA revealed that the type of material, the use of ribbond fibers and the type of restorative technique significantly affected marginal microleakage (p < 0.001). Application of ribbond fibers decreased marginal microleakage to all tested restorative materials, regardless of the restorative technique, in a range of 31.2-81.4%. In the groups with no-use of ribbond fibers, among the materials there were no significant differences in microleakage when the teeth were restored with the incremental technique (p > 0.05).

CONCLUSIONS

The use of UHMWPE fibers with wallpapering technique in Class I composite restorations may be an effective method to reduce marginal microleakage, regardless of the selected restorative technique or the material.

CLINICAL RELEVANCE

Clinicians may be encouraged to utilize reinforcing fiber restorative techniques for direct restorations of structurally compromised teeth as a valid alternative to indirect restorations.

Degradability of bulk-fill resin composites after cyclic immersion in different distilled alcoholic beverages

OBJECTIVES

To investigate effect of distilled alcoholic beverages on surface hardness, roughness, and erosion of bulk-fill resin composites.

MATERIALS AND METHODS

Sixty eight specimens of each bulk-fill resin composite (Filtek One Bulk Fill Restorative, SonicFill 2, and Tetric N-Ceram Bulk Fill) were prepared. Baseline data of surface hardness and roughness value were recorded. The specimens were divided into five groups: vodka, whisky, tequila, brandy, and deionized water (served as a control). Specimens were then alternately immersed in 25 ml of a storage agent for 5 s and in 25 ml of artificial saliva for 5 s over 10 cycles. This process was repeated for 14 days. After immersion, specimens were subjected to evaluation of surface hardness, roughness, and erosion on days 7 and 14. The data were statistically analyzed by two-way repeated analysis of variance, Tukey's honestly significant difference, and a t test (p < 0.05).

RESULTS

Distilled alcoholic beverages caused significant hardness decrement, roughness and erosion increment (p < 0.05), where the greatest degradation was found in brandy group. Tetric N-Ceram Bulk Fill had the most significant decrement in hardness and increment in roughness and erosion than the other resin composites (p < 0.05).

CONCLUSION

Distilled alcoholic beverages affected hardness, roughness, and erosion of all the bulk-fill resin composites.

CLINICAL SIGNIFICANCE

Regarding the bulk-fill resin composites tested, Filtek One Bulk Fill Restorative was the most appropriate restorative material in patients who consume distilled alcoholic beverages.

In vitro evaluation of marginal adaptation in medium- and large size direct class II restorations using a bulk-fill or layering technique

OBJECTIVES

to test if cavity dimensions and restorative protocol have potential to influence in-vitro adaptation of class II restoration after simulated thermo-occlusal stressing.

METHODS

A total of 32 prepared teeth were randomly assigned to one of the 4 experimental groups depending on cavity size, composite system and filling technique; group 1: small cavity and multi-layered conventional restorative composite (Tetric Evo-ceram: TEC), group 2: small cavity and flowable bulk-filled composite (SDRFlow: SDR) + one single occlusal layer of conventional restorative composite (TEC), group 3: large cavity and multilayered conventional restorative composite (TEC) and group 4: large cavity and bulk-filled flowable composite (SDR) + one single occlusal layer conventional restorative composite (TEC). All specimens were submitted to 500'000 cycles of thermomechanical loading (50 N, 5 to 55 °C). The proximal tooth-restoration interface was analyzed quantitatively by SEM, prior and after thermomechanical loading.

RESULTS

Before loading, continuous enamel adaptation varied from 61.49% (Gr 1) to 68.39% (Gr 4) proximally and from 50.93% (Gr2) to 68.65% (Gr1) cervically, with no statistical difference among groups for both segments. After thermomechanical loading, continuous enamel adaptation varied from 36.6% (Gr2) to 46.6% (Gr1) proximally, without significant difference, and from 20.2% (Gr4) to 51.3% (Gr1) cervically; statistical differences in cervical enamel adaptation were found in-between groups 1 and 2 (p = 0.0479), 1 and 4 (P = 0.0116), 2 and 3 (p = 0.0028) and 3 and 4 (p = 0.001). Before loading, dentin continuous adaptation varied from 55.32% (Gr3) to 81.82% (Gr4) with statistical difference in-between those groups (p = 0.045); after loading, dentin continuous adaptation varied from 31.56% (gr2) to 51% (Gr4) with a statistical difference between those 2 groups (p = 0.019). The drop in adaptations values after loading was significant in all groups and segments.

CONCLUSIONS

The impact of the restorative technique and cavity size on marginal adaptation appeared essentially after simulated fatigue for enamel adaptation. Cervical enamel and dentin continuous adaption of small and large bulk-filled restorations dropped significantly while the change was lower in layered restorations made of conventional restorative composite.

CLINICAL SIGNIFICANCE

Restorations made with bulk-filled flowable composite behaved differently from layered ones using conventional resin composite, according to cavity size and loading.

Effect of Stress Generated by Occlusal Cyclic Force on Class I Bulk-Fill Composite Restoration Microleakage

Objective  This study aimed to evaluate the effects of different types and restorative techniques of Class I composite restorations with a single loading force on stress distribution and cyclic loading force on microleakage formation.

Materials and Methods  Class I cavities were prepared in premolars with 4 mm depth and divided into six groups of different restorations with: (1) Filtek Z250; (2) a 3-mm-thick layer of Filtek Bulk Fill Flowable Restoration and covered with Z250; (3) a 1.5-mm-thick layer of flowable composite and covered with Z250; (4) lining all cavity with flowable composite and restored with Z250; (5) Filtek Bulk Fill Posterior Restoration; and (6) lining all cavity with flowable composite and restored with bulk-fill composite. The specimens with and without cyclic occlusal loading were subjected to microleakage observation. In addition, six different models of Class I restorations corresponding to the microleakage study were generated. Finite element analysis (FEA) was used to identify the stress distribution under a single loading force.

Statistical Analysis Data were statistically analyzed by two-way analysis of variance and multiple comparison. The significance level set at 0.05.

Results  Cavity lining or restoration with flowable composite underneath conventional composite reduced stress on composite resin based on FEA (groups 2 and 3). The cyclic stress on composite increased microleakage. Restoration with flowable composite underneath conventional composite reduced the microleakage in Class I restoration (groups 2, 3, and 4).

Conclusion  The most effective cavity lining with a flowable composite underneath conventional composite restoration was stress reduction under loading force resulting in microleakage reduction.

Marginal quality of a full-body bulk-fill composite placed with an universal adhesive system in etch-and-rinse and self-etch mode: An in vitrostudy

Background

Marginal seal of a nanohybrid bulk-fill composite compared to a nanohybrid conventional composite, using a universal adhesive (UA) applied in etch-and-rinse (ER) and self-etch (SE) mode was investigated.

Material and Methods

Thirty-six intact molars were selected and two standardized cavities in each tooth were prepared and allocated into four groups according to restorative material and etching strategy. All samples were placed in a 1% methylene blue solution for 24 h, then cut in the middle of the restorations obtaining two parts (n=144) and used for microscopic evaluation (50x) for dye penetration measurements.

Results

The data were analysed by ANOVA and Tukey post-hoc test (p<0.05). Marginal seal was influenced by adhesive strategy (p<0.05) but not from the composite used (p>0.05).

Conclusions

Simplified restorations with nanohybrid bulk-fill composite showed comparable marginal leakage to incrementally placed nanohybrid composite. The UA used with a ER technique resulted in better marginal seal irrespective of the restorative material used.

Key words:Bulk-fill composite, universal adhesive, self-etching, etch-and-rinse, marginal seal.

Fracture strength of extended class I composite restorations with different restorative techniques

To evaluate the fracture strength of extended Class I restorations with different restorative techniques using nanofilled and nanohybrid composites. Sixty extracted human third molars were prepared with extended Class I cavities and divided into six groups: groups FS-F (Filtek bulk-fill Flow + Filtek Supreme Ultra, 3 M) and GR-F (X-tra base + GrandioSO, VOCO), restored with a flowable bulk-fill composite as a base covered by a nanofilled or nanohybrid composite; groups FB (Filtek One Bulk-Fill, 3 M) and AF (Admira Fusion X-tra, VOCO), restored with a bulk-fill resin composite; and groups FS (Filtek Supreme Ultra, 3 M) and GR (GrandioSO, VOCO), restored incrementally with a nanofilled or nanohybrid composite. Sound extracted teeth (n = 10) were used as a control group (CTL). The specimens were axially loaded until failure. Data were analyzed using one-way ANOVA and Games Howell test (α = 0.05). Groups CTL and GR-F demonstrated significantly higher mean fracture strength when compared to FS, AF, and GR (p < 0.05). Group AF obtained more repairable fractures than the other groups. Restorations made with a nanofilled bulk-fill composite or with conventional resin composites associated with a flowable bulk-fill base were able to reestablish the fracture strength to that of sound teeth.

Comparing the Ability of Various Resin-Based Composites and Techniques to Seal Margins in Class-II Cavities

Background: Resin-based composites (RBCs) provide excellent esthetics but the marginal micro-leakage in the proximal cavities remains a major concern. The aim of the present study was to assess the ability of various dental RBCs and techniques utilized for sealing deep dentin margin in class-II cavities. Methods: Box-cavities (class-II) on the distal and mesial surfaces of extracted (premolar) teeth were prepared with a gingival margin placed 1mm apical to the cemento-enamel junction. Teeth with prepared class II cavities were randomly divided into four study groups according to the type of restorative materials (conventional RBC; bulk-fill RBC; conventional RBC lined with flowable RBC and conventional RBC lined with resin-modified glass-ionomer-cement (GIC) as open sandwich-technique). Each group was further subdivided into a total-etch subgroup in which a separate etching step was performed before applying the bonding agent and a self-etch subgroup in which a self-etch adhesive system was used (n = 10). For each group, cavities were restored using the respective restorative materials and techniques, subjected to 1000 thermocycles, and placed in the methylene-blue dye. The specimen teeth were sectioned for further microscopic examination for micro-leakage. Results: The least dye penetration values were reported for group 4 (GIC) followed by the group Bulk-fill using the self-etch adhesive system (group 2b). The highest dye penetration was reported for the group Bulk-fill using the total-etch adhesive system (2a), followed by the group conventional RBC using the total-etch adhesive system). The total-etch adhesive system had significantly greater micro-leakage compared to the self-etch adhesive system (1a) (p = 0.026). Conclusions: The self-etch adhesive system significantly reduced the micro-leakage compared to the total-etch system. Bulk-fill RBC when bonded with the self-etch adhesive provided good marginal sealing ability comparable to open sandwich-technique using GIC.

Effect of an elastomeric urethane monomer on BisGMA-free resin composites containing different co-initiators

OBJECTIVES

The aim of this study was to investigate the mechanical, chemical, optical, and adhesive properties of BisGMA-free experimental resin composites containing Exothane-24-an elastomeric urethane monomer-and different co-initiators.

MATERIALS AND METHODS

A blend of urethane dimethacrylate (UDMA), extended dimethacrylate urethane (PEG 400), triethylene glycol dimethacrylate (TEGDMA), and camphorquinone was prepared. Two different co-initiators-dimethyl aminoethyl methacrylate (DMAEMA) or 4-N alcohol, N-dimethylamine phenylethyl (DMPOH)-were added to the blend. Exothane-24 monomer was added to the blend for each co-initiator and four groups were established as follows: DMAEMA; DMAEMA + Exothane; DMPOH; and DMPOH + Exothane. Specimens were photo-activated using a multi-wave LED light-curing unit (VALO; 954 mW/cm² of irradiance). Mechanical (ultimate tensile strength, flexural strength, flexural modulus and hardness), chemical (degree of conversion, hardness reduction, water sorption and solubility), optical (color change), and adhesive (microtensile bond strength) properties were analyzed. Data were submitted to two-way ANOVA and Tukey's test (α = 0.05).

RESULTS

The resin composite containing DMPOH and Exothane-24 showed similar or superior performance to those of the other experimental composites for mechanical and chemical properties, except for flexural strength. It also showed less color change and greater micro-tensile bond strength.

CONCLUSIONS

Among the combinations tested, the BisGMA-free resin composite containing Exothane-24 combined with the DMPOH co-initiator showed the best mechanical, chemical, optical, and adhesive properties. Clinical relevance Exothane-24 monomer and DMPOH co-initiator could be useful in the formulation of BisGMA-free resin composites in order to minimize exposure to BPA.

Effect of proximal box elevation on fracture resistance and microleakage of premolars restored with ceramic endocrowns

Background

Restoration of endodontically treated premolar is in high risk for biomechanical failure, and often presents with subgingival margins. Proximal box elevation (PBE) has been used to relocate subgingival cavity outlines.

Objective

To evaluate the influence of PBE on fracture resistance and gingival microleakage of premolars with endodontic access cavities following ceramic endocrown.

Methods

Eighty sound maxillary premolars with standardized Class II cavities on mesial surfaces were randomly assigned to four groups (n = 20 in each group). Groups E1, E2 and E3, with proximal margins located in dentin/cementum, 2 mm below the cemento-enamel junction (CEJ), simulated subgingival location. Group E4 (supragingival group), with proximal margins located in enamel, 1 mm above the CEJ, was used as the positive control. For margin elevation of the proximal cavities, bulk-fill Smart Dentin Replacement (SDR), a visible light cured resin composite, was applied in group E1, and conventional resin composite (3M Z350 XT, a light-activated composite) was placed in group E2. Group E3 was only treated with a ceramic crown and served as the negative control. In all groups, computer-aided design (CAD) ceramic endocrowns were adhesively inserted, and fracture resistance, failure mode and microleakage were evaluated.

Results

A higher fracture resistance value was observed in PBE groups E1 and E2, regardless of the materials used (P = 0.038, and 0.010, respectively, vs E3), and fracture resistance in group E1 was higher than that in group E2. In teeth without PBE, the percentage of catastrophic failures reached 70%. Compared to group E3, a lower frequency distribution of microleakage was detected in supragingival group E4 (P = 0.031). No increased percentage of microleakage was observed in groups treated with PBE.

Conclusion

For endodontically treated maxillary premolars restored with ceramic endocrowns, PBE increases fracture resistance but not microleakage.

Clinical performance of class I cavities restored with bulk fill composite at a 1-year follow-up using the FDI criteria: a randomized clinical trial

Objectives

The present study aimed to evaluate the survival rate and clinical performance of class 1 composite restorations restored with the Filtek Bulk Fill composite material using either the bulk fill technique or the incremental technique at baseline (1 week) and at 3, 6 and 12 months of follow-up.

Materials and Methods

Forty-two patients with at least 2 carious teeth were selected. Following randomization, one tooth was restored with the Filtek Bulk Fill composite using the incremental fill technique, and the other tooth was restored with the same material using the bulk fill technique. Patients were recalled for follow-up at baseline (1 week) and 3, 6, and 12 months and evaluated using the FDI criteria.

Results

The data were analyzed using the McNemar χ² test. No statistically significant differences were found between the scores of teeth restored with either technique. At baseline and at 3, 6, and 12 months of follow-up; there were no significant difference in the clinical status of both groups of restorations.

Conclusions

Within the limitations of this study, using the bulk fill technique for restorations with the Filtek Bulk Fill material seems to be equally efficient to using the incremental fill technique.

Trial Registration

Clinical Trials Registry-India Identifier: CTRI/2017/07/008961.

Effects of cuspal compliance and radiant emittance of LED light on the cuspal deflection of replicated tooth cavity

The aim was to investigate effects of compliance and radiant emittance on cuspal deflection. A mesio-occluso-distal cavity was replicated using a flowable composite and steel rods with different diameters. To investigate the effect of cuspal compliance on deflection, the replicated tooth and extracted human tooth cavities were bulk-filled with a micro-hybrid composite. The replicated cavities with 2.0-mm-diameter steel rods were restored with bulk-filling of the micro-hybrid or a nano bulk-fill composite and photo-cured with four protocols. The cuspal deflection was the highest in the replicated tooth without steel rod, followed by with 1.0-, 1.5-, and 2.0-mm steel rods, and significantly lower in the human tooth. Cuspal deflections showed no significant differences among light-curing protocols, and that in the micro-hybrid composite were higher than the nano bulk-fill composite. To reduce cuspal deflection of a high compliance cavity, selecting the proper composite based on physical properties is more important than light-curing protocol.

Tridimensional Evaluation of the Interfacial Gap in Deep Cervical Margin Restorations: A Micro-CT Study

CLINICAL RELEVANCE

Using a material that optimizes marginal seal when using a margin elevation technique to manage deep class II cavities should enhance clinical outcomes.

SUMMARY

Objectives: The purpose of this laboratory study was to perform a tridimensional interfacial gap evaluation of class II cavities with enamel and dentin cervical margins, before and after cyclic fatigue, restored with different nanohybrid resin composites.Methods and Materials: Standardized class II cavities were performed on 48 intact maxillary premolars, placing the mesial cervical margin 1 mm above the cement-enamel junction (CEJ) and the distal cervical margin 1 mm below the CEJ. Specimens were treated with two-step self-etch adhesive (Clearfil SE Bond2) and divided into six groups according to the restoration technique. Microcomputed Tomography imaging was executed before and after 1,000,000 cycles of chewing simulation at 50 N. Tridimensional interfacial gaps, expressed as cubic millimeters, were analyzed through a standardized software flowchart (Mimics). Data were analyzed with a two-way analysis of variance and Tukey post hoc tests (α=0.05).Results: Restoration technique (p=0.001) and chewing simulation (p=0.00001) significantly influenced interfacial gap on dentin but not on enamel. The post hoc test showed that, on dentin margins, flowable resins had a lower gap at baseline but a higher gap after chewing simulation, especially when a 2-mm-thick layer was applied, compared with nanohybrid and bulk-fill composites.Conclusions: Based on the obtained results, no differences in interfacial gap volume were found on enamel margins. On dentin margins, flowable resins showed better marginal seal at baseline, but they seem to be more prone to interfacial degradation during chewing simulation than traditional composites.

Comparative Assessment of Cuspal Deflection in Premolars Restored with Bulk-Fill and Conventional Composite Resins

Objectives:

It has been reported that bulk-fill composites simplify tooth restoration with no adverse effect on the success rate. This study sought to assess the cuspal deflection of premolars with mesio-occluso-distal (MOD) cavities restored with bulk-fill and conventional posterior composite resins.

Materials and Methods:

This in-vitro experimental study was conducted on 64 human maxillary premolars. MOD cavities were prepared on teeth and restored with Filtek P60 conventional composite and Filtek Bulk Fill flowable, X-tra fill, and X-tra base bulk-fill composites in four groups (n=16). Distance between the cusp tips was measured before, five minutes, 24 hours, 48 hours, and one week after restoration. The data were analyzed using repeated-measures analysis of variance (ANOVA) and Tukey’s test (α=0.05).

Results:

The mean±standard deviation (SD) of cuspal deflection at five minutes after the restoration was 13.5±5.3, 12.2±3.5, 11.3±4.4, and 10.4±3.7 μm for Filtek P60, Filtek Bulk Fill, X-tra fill, and X-tra base, respectively. ANOVA showed that bulk-fill composites did not cause a significant reduction in cuspal deflection compared to P60 (P>0.05). Cuspal deflection in all groups significantly decreased with time (P<0.05).

Conclusion:

Bulk-fill composites have no superiority over P60 in the reduction of cuspal deflection. The cuspal deflection was variable at different time points in all groups and decreased over time.

Margin Integrity of Bulk-Fill Composite Restorations in Primary Teeth

This in vitro study examined the margin integrity of sculptable and flowable bulk-fill resin composites in Class II cavities of primary molars. Standardized Class II cavities were prepared in human primary molars and restored with the following resin composite materials after application of a universal adhesive: a sculptable bulk-fill composite (Tetric EvoCeram Bulk Fill (TEC) or Admira Fusion x-tra (AFX)), a flowable bulk-fill composite (Venus Bulk Fill (VBF) or SDR), or a conventional composite (Filtek Supreme XTE (FS)). The bulk-fill materials were applied in 4 mm layers, while the conventional composite was applied in either 2 mm (FS2, positive control) or 4 mm layers (FS4, negative control). The specimens were exposed to thermo-mechanical loading (TML) in a computer-controlled masticator. A quantitative margin analysis was performed both before and after TML using scanning electron microscopy, and the percentage of continuous margins (margin integrity) was statistically analyzed (α = 0.05). All composites showed a significant decline in margin integrity after TML. AFX exhibited the significantly highest margin integrity of all materials after TML (97.5 ± 2.3%), followed by FS2 (79.2 ± 10.8%), TEC (73.0 ± 9.1%), and FS4 (71.3 ± 14.6%). SDR (43.6 ± 22.3%) and VBF (25.0 ± 8.5%) revealed the lowest margin integrity. In conclusion, the tested sculptable bulk-fill materials show similar or better margin integrity in primary molars than the conventional resin composite placed in 2 mm increments.

Shrinkage vectors in flowable bulk-fill and conventional composites: bulk versus incremental application

OBJECTIVES

Sufficient depth of cure allows bulk-fill composites to be placed with a 4-mm thickness. This study investigated bulk versus incremental application methods by visualizing shrinkage vectors in flowable bulk-fill and conventional composites.

MATERIALS AND METHODS

Cylindrical cavities (diameter = 6 mm, depth = 4 mm) were prepared in 24 teeth and then etched and bonded with OptiBond FL (Kerr, Italy). The composites were mixed with 2 wt% radiolucent glass beads. In one group, smart dentin replacement (SDR, Dentsply) was applied in bulk "SDR-bulk" (n = 8). In two groups, SDR and Tetric EvoFlow (Ivoclar Vivadent) were applied in two 2-mm-thick increments: "SDR-incremental" and "EvoFlow-incremental." Each material application was scanned with a micro-CT before and after light-curing (40 s, 1100 mW/cm²), and the shrinkage vectors were computed via image segmentation. Thereafter, linear polymerization shrinkage, shrinkage stress and gelation time were measured (n = 10).

RESULTS

The greatest shrinkage vectors were found in "SDR-bulk" and "SDR-increment2," and the smallest were found in "SDR-increment1-covered" and "EvoFlow-increment1-covered." Shrinkage away from and toward the cavity floor was greatest in "SDR-bulk" and "EvoFlow-increment2," respectively. The mean values of the shrinkage vectors were significantly different between groups (one-way ANOVA, Tamhane's T2 test, p < 0.05). The linear polymerization shrinkage and shrinkage stress were greatest in Tetric EvoFlow, and the gelation time was greatest in "SDR-bulk."

CONCLUSIONS

The bulk application method had greater values of shrinkage vectors and a higher debonding tendency at the cavity floor.

CLINICAL RELEVANCE

Incremental application remains the gold standard of composite insertion.

Vickers Hardness and Shrinkage Stress Evaluation of Low and High Viscosity Bulk-Fill Resin Composite

The aim of this in vitro study was to evaluate the hardness and shrinkage stress (SS) of six bulk-fill resin composites. To evaluate microhardness (MH), ten 6 mm specimens were prepared using a metal mold for each selected bulk-fill resin composite and irradiated from the top side for 40 s using an LED light. After 24 h of storage, Vickers MH was evaluated on the upper, lower and lateral sides of the specimens. SS evaluation was then performed with a universal machine, which evaluated the contraction force generated by a bulk-fill composite specimen placed between two metal cylinders during and after light curing. The results were evaluated with a one-way ANOVA test with a post-hoc Bonferroni test and linear regression analysis (p < 0.05). All materials showed a significant MH decrease between the top and bottom surfaces. However, the bulk-fill materials tested performed differently when considering lateral depth progression. ANOVA tests for SS evaluation showed that both SDR and Venus Bulk Fill had significantly lower stress during irradiation than other tested materials. Further, MH decrease became significantly lower from the top surface at different depths in each tested group. Among the different resins, Venus Bulk Fill and SDR showed not only inferior hardness, but also a significant reduction in SS.

The effect of two composite placement techniques on fracture resistance of MOD restorations with various resin composites

OBJECTIVE

The aim of this in vitro study was to compare the effect of two restorative placement techniques, centripetal incremental technique (CIT) and bulk-fill technique (BT) on the fracture resistance of Class II MOD restorations with various resin composites in molar teeth.

MATERIALS AND METHODS

Fifty-six extracted, caries free third molars were prepared with MOD preparations and restored with resin composites. The specimens were divided into two groups by placement technique, centripetal incremental technique (CIT) and bulk-fill technique (BT). Each group was subdivided into four groups according to resin composite: hybrid (Aelite LS), nano-hybrid (Virtuoso Universal), bulk fill (Filtek One Bulk Fill) and the micro-hybrid (Herculite XRV) as the control.

RESULTS

Two-way analysis of variance test (ANOVA) followed by the multiple comparison procedure, Student-Newman-Keuls Method showed no a statistically significant difference between placement techniques and fracture resistance of Class II resin composite restorations (P > 0.05). Herculite XRV resisted a significantly higher load before fracture than the other three materials at a 0.05 level of significance, while Virtuoso Universal scored the lowest load.

CONCLUSIONS

There was no significant effect of the two placement techniques on the fracture resistance of Class II resin composite restorations CLINICAL SIGNIFICANCE: Resin composite restorations in Class II MODs using a simplified bulk fill placement technique showed no significant difference in fracture resistance with the centripetal technique in molar teeth.

Comparison of the Depth of Cure of Flowable Composites Polymerized at Variable Increment Thicknesses and Voltages: An In vitro Study

Objectives

The aim of this study is to compare the depth of cure of two composite materials (SDR and Filtek bulk-fill) cured at variable increment depths (2, 4, and 6 mm) and voltages (180 and 220 volts).

Materials and Methods

Each sample of the composite material was packed in a mold of 2 mm, 4 mm, and 6 mm and curing light (quartz tungsten halogen) of optimal intensity was exposed for 20 s at 2 different voltages on each specimen. After curing, the specimens were removed and the composite on the nonexposed end was scraped with a plastic instrument. The remaining composite thickness was measured using a digital Vernier caliper. The reading was divided by half to follow the ISO 4049 method. Independent sample t-test, one-way ANOVA, and linear regression analysis were applied. Level of significance was kept at 0.01.

Results

The mean DOC of SDR and Filtek were 1.93 ± 0.82 and 1.77 ± 0.65 mm. Lowering the voltage from 220 to 180 volts reduced the depth of Filtek from 1.87 ± 0.74 to 1.67 ± 0.54 mm, whereas the DOC of SDR remained unchanged at 1.93 mm at the two voltages. The adjusted R ² for the depth of cure was 0.93 when the increment thickness, voltage, and restorative material were taken together in the regression model.

Conclusions

There was no statistically significant difference between SDR and Filtek for the depth of cure at 2 and 4 mm increments. However, at 6 mm increment, the SDR cured significantly deeper than the Filtek. Around 91% variation in the depth of cure of these composites materials is explained by increment thickness alone.

A comparison of cuspal movement of premolar teeth restored with bulk-filled composite resins combined with universal adhesives

BACKGROUND

The aim of the present study was to compare bulk-filled composite resins with conventional composites in terms of cuspal movement and micro-leakage scores.

METHODS

Ninety-six maxillary premolar teeth with mesial-occclusal-distal cavities were allocated to four groups. Twelve teeth in each group was treated etch-and-rinse, self-etch or selective-etch (N.=8) protocols with respective adhesive system. Bucco-palatal cusp measurements were performed before and after preparation, and 180s after curing and then subjected to 5000 thermocyclws. After immersed in 0.2% basic fuchsin dye for 24h, cervical micro-leakage was evaluated. The data was analyzed by One-way ANOVA and post-hoc Tukey's honest Test (P<0.05).

RESULTS

All groups and bonding protocols revealed no significant differences in total cuspal deflection measurement and micro-leakage scores. After preparation, a significant increase was found in bucco-palatal width of the teeth compared to baseline (P=0.002). There were no significant relationship among composite resins and adhesives (P>0.05).

CONCLUSIONS

Cuspal relief after cavity preparation should be taken into account when evaluating deflection.

Influence of the degree of conversion and Bis-GMA residues of bulk fill resins on tissue toxicity in an subcutaneous model in rats

AIM

To analyse the influence of the degree of conversion (DC) and light curing residues of different bulk fills (BFs) composites on the inflammatory profile in the subcutaneous tissue of rats.

MATERIALS AND METHODS

Resin disks of BF-resins and their active conventional resins (CR; 3M®, Ivoclar®, and Kerr®) were light-cured at 2 mm (BF-superficial) and 4 mm (BF-deep) thicknesses and analyzed by infrared spectroscopy (FTIR; n = 3/group; DC and light curing residues). Then, the disks were implanted in four quadrants in the subcutaneous tissue of Wistar rats (sham, CR, BF-superficial and RF-deep), and after 7, 14, and 28 days, the animals (n = 6/day) were euthanized for histological analysis of the intensity of the inflammatory process (scores 0-3). Kruskal-Wallis/Dunn and ANOVA/Bonferroni tests were used (p < 0.05, Graph Pad Prism 5.0).

RESULTS

The DC of CR 3M® did not differ significantly compared to BF-superficial and BF-deep resins (p = 0.235). The Ivoclar® and Kerr® resins showed a higher DC with CR and BF-superficial compared to the BF-deep (p = 0.005 and p = 0.011, rctively). Kerr® resins showed a higher Bis-GMA/UDMA ratio, especially in BF-deep resin (p < 0.05). 3M® and Ivoclar resins did not show high inflammation scores, but for Kerr® BF resins (superficial and deep), the inflammatory process was significantly higher than that in the CR and sham quadrants (p = 0.031).

CONCLUSION

The tissue inflammatory response after resin inoculation depends on the DC and light curing residues of Bis-GMA.

Microleakage of "Bulk-Fill" Composite Resin for Class II Restorations Pretreated With CO2 Laser in Deciduous Molars: An In Vitro Study

Introduction: Microleakage has been reported to cause dentin hypersensitivity because of the passage of bacteria and their products through the restoration-tooth interface and is one of the main reasons for replacement of restorations. CO₂ laser can be used for treatment of dentin hypersensitivity. Thus, this study aimed to evaluate in vitro the microleakage in composite restorations following surface pretreatment with acid etching and CO₂ laser. Methods: Twelve human caries-free primary molars were selected. Class II cavities were prepared on occlusal mesial and occlusal distal surfaces. Specimens were randomly divided into four groups (n=6): Group 1 (G1) - 37% phosphoric acid gel etching + Beautiful-Bulk Restorative - Giomer (Shofu Inc); Group 2 (G2) - 37% phosphoric acid gel etching + SDR Bulk-Fill Flow (Dentsply); Group 3 (G3) - CO₂ laser irradiation + Beautiful-Bulk Restorative - Giomer (Shofu Inc); Group 4 (G4) - CO₂ laser irradiation + SDR Bulk-Fill Flow (Dentsply). Surfaces were restored with bonding agent (Natural Bond DE, DFL). Specimens were cut longitudinally and immersed in 0.5% methylene blue solution for 4 hours. Microleakage scores were assessed under a magnifying glass at x3,5 and qualitatively analyzed by scanning electron microscope (SEM). Data were analyzed using nonparametric Wilcoxon test (P < 0.05). Results: Scores prevailed between 0 and 2, however, no statistically significant difference was found among the groups (P = 0.05). Conclusion: It could be concluded that all composite resins bulk fill did not show significant difference among them regarding microleakage using either CO₂ laser or 37% phosphoric acid etching.

Fracture Resistance and Marginal Adaptation of Capped and Uncapped Bulk-fill Resin-based Materials

OBJECTIVES

This study tested the fracture resistance of capped and uncapped bulk-fill composite restorations and compared them to a conventional composite. Also, the effect of different radiant exposure was investigated.

METHODS AND MATERIALS

Flowable and high-viscosity bulk-fill composites (SureFil SDR, Filtek Bulk-Fill Posterior, and Tetric N-Ceram Bulk-Fill) and a nanohybrid resin composite (Filtek Z350 XT) were used. Standardized class II cavities were prepared on extracted premolars, and different restoration protocols were used. In protocol 1 (control), restoration was applied using a layering technique; in protocol 2, restoration was applied in bulk with a capping layer; in protocol 3, restoration was applied in bulk without a capping layer; and in protocol 4, restoration was applied in bulk without a capping layer, and the light curing time was extended. After thermocycling, the restorations were examined for marginal gaps and then subjected to the fracture resistance test using a universal testing machine. Statistical analysis was carried out using two-way analysis of variance (ANOVA) followed by one-way ANOVA at a significance level of α = 0.05.

RESULTS

A statistically significant difference in the fracture resistance of the tested materials and protocols was detected. Filtek Bulk-Fill Posterior achieved the highest fracture resistance values regardless of the protocol used, and its results were comparable to those of Filtek Z350. SDR and Tetric N-Ceram Bulk-Fill achieved their highest strengths when a capping layer was added. Tetric N-Ceram Bulk-Fill showed improvement in fracture resistance with extended light curing, while SDR and Tetric N-Ceram Bulk-Fill achieved similar results with the addition of a capping layer. The uncapped bulk-fill group showed more gap-free margins than the capped group.

CONCLUSION

The new high-viscosity bulk-fill composite restorations seem to have adequate fracture resistance. However, the results are material dependent, and some materials perform better with a capping layer and extended light curing.

Validation of a method of quantifying 3D leakage in dental restorations

STATEMENT OF PROBLEM

A reliable and validated protocol for nondestructive analysis of the entire restorative interface that could be applicable in studies assessing the adaptation of direct and indirect restorations is lacking.

PURPOSE

The purpose of this in vitro study was to validate a 3D protocol for microleakage assessment in class II mesio-occluso-distal (MOD) cavities restored with composite resin.

MATERIAL AND METHODS

Sixteen human third molars received standardized class II MOD preparations with cervical margins located 1 mm apical to the cemento-enamel junction. The specimens were restored with Filtek Bulk Fill Posterior (FBP) or Filtek Bulk Fill Flowable (FBF) and submitted to 10 000 thermocycles (5 °C and 55 °C with a 30-second dwell time at each temperature and 5-second transfer time). The specimens were scanned with microcomputed tomography (μCT) before and after immersion in 50% ammoniacal silver nitrate solution for 12 hours. Scanned data were processed, and the 3D amount of infiltrated silver nitrate was analyzed through the entire adhesive interface. In addition, the linear distance of silver nitrate infiltration was assessed using 3 axial images obtained from each specimen proximal box (2D analysis). Data were tested for homogeneity by using the Shapiro-Wilk test and evaluated by using 1-way ANOVA, followed by the post hoc Tukey HSD test (α=.05).

RESULTS

FBP showed significantly lower leakage than FBF for both 2D and 3D analyses. A low correlation was observed between the assessment methods.

CONCLUSIONS

Three-dimensional analysis of microleakage using μCT is a predictable and more reliable method for nondestructive and comprehensive analysis of the entire specimen.

Clinical performance and chemical-physical properties of bulk fill composites resin -a systematic review and meta-analysis

OBJECTIVES

The objective of this study was to perform a meta-analysis of clinical and laboratory studies to compare the performance of bulk-fill and conventional composite resins in terms of polymerization shrinkage, polymerization stress, cusp deflection, marginal quality, degree of conversion, microhardness, flexural strength, fracture strength and clinical performance.

DATA

One hundred three articles were included in this study, and the Peto method was used to compare the bulk-fill and conventional composites using the RevMan software.

SOURCES

Searches were performed in the PubMed and Scopus databases.

STUDY SELECTION

Laboratory studies and randomized clinical trials comparing one of the previous detailed outcomes between bulk-fill and control composites were included.

CONCLUSIONS

The bulk-fill composite resins showed less shrinkage, polymerization stress, cusp deflection and microhardness than conventional composites, while both materials presented a similar marginal quality, flexural strength and fracture strength. Also, bulk-fill materials with regular viscosity showed similar shrinkage. The conversion of bulk-fill materials with flowable consistency were similar to conventional composite resins with a thickness of up to 2mm and greater than conventional composites with a thickness greater than 2mm. Despite these in vitro differences, the clinical performance of bulk-fill and conventional composite resins was similar in randomized clinical trials, with one to ten years of follow up. In conclusion, the bulk-fill materials show better or similar performance to the conventional materials in clinical trials and laboratory studies in terms of volumetric shrinkage, polymerization stress, cusps deflection and marginal quality, with the only exception being the lower level of microhardness observed for bulk-fill composites with thickness up to 2mm.

Volumetric Cuspal Deflection of Premolars Restored With Different Paste-like Bulk-fill Resin Composites Evaluated by Microcomputed Tomography

OBJECTIVES

The aim of this study was to measure the volumetric cuspal deflection of premolars restored with different paste-like bulk-fill resin composites using microcomputed tomography (micro-CT).

METHODS AND MATERIALS

A total of 35 freshly extracted human maxillary second premolars were selected for this study. Standardized large MOD cavities were prepared in each premolar with a bucco-lingual width of 4 mm and a cavity depth of 4 mm measured from the palatal cusp tip. After cavity preparation, all samples were scanned immediately using a micro-CT system. After the initial micro-CT scanning, restorative procedures were performed. Four groups received different paste-like bulk-fill composites-Beautifil-Bulk Restorative (BBR), Admira Fusion x-tra (AFX), x-tra fill, and Sonic Fill-and the control group received a conventional universal composite and Clearfil Majesty Esthetic (CME). Immediately after the restorative procedure, each tooth was scanned by micro-CT in the same manner as the initial scanning. The buccal and palatal regions of each restoration were evaluated separately in terms of cuspal deflection. One-way analysis of variance was used to compare the effect of the composite resin, and multiple comparisons were performed by the Tukey test with a level of significance of α = 0.05.

RESULTS AND DISCUSSION

Multiple comparisons showed that teeth restored with the conventional paste-like composite and CME (control) had significantly different cuspal deflection from those filled with paste-like bulk-fill composites (p<0.05). Among the bulk-fill composites, a significant difference was observed between BBR and AFX (p<0.05).

CONCLUSIONS

Paste-like bulk-fill resin composites had significantly lower cuspal deflection than the conventional paste-like resin composite tested.

Comparison of the fracture resistance of three different recent composite systems in large Class II mesio-occlusal distal cavities: An in vitro study

BACKGROUND

The present study was undertaken to evaluate the most suitable recent restorative material for extensively mutilated teeth.

AIM

This study aims to evaluate and compare the fracture resistance of maxillary premolars with Class II mesio-occlusal distal (MOD) cavities restored with recent Ever X posterior, bulk-fill composite, and Estelite sigma quick composite systems.

MATERIALS AND METHODS

Sixty human maxillary premolars were selected. Fifteen intact teeth served as positive control (Group 1). MOD cavities were prepared in the remaining 45 teeth with standardized dimensions and were randomly divided into three experimental groups (Group 2, 3, and 4) (n = 15). Teeth in Group 2, 3, and 4 were reinforced with 3M ESPE Filtek Bulk-fill posterior, GC Ever X posterior, and Tokuyama Estelite sigma quick composites, respectively. Fracture resistance was measured in Newton (N).

RESULTS

Group 4 (1432.60 N) showed the highest mean fracture resistance followed by Group 3 (1326.20 N), Group 1 positive controls (1288.53 N), and Group 2 (946.66N), respectively. One-way analysis of variance (ANOVA) test revealed a statistically significant difference between all the groups (P = 0.005). Post hoc Tukey test revealed a statistically significant difference in mean fracture resistance between the Group 2 and Group 4 (P = 0.004), as well as between the Group 2 and Group 3 (P = 0.033). However, there were no significant differences among the other groups.

CONCLUSION

Among the experimental groups, Estelite sigma quick composite showed the highest fracture resistance. Statistically, a significant difference was seen between all groups.

Shrinkage stress and elastic modulus assessment of bulk-fill composites

Bulk-fill composites were introduced in dentistry to accelerate clinical procedures while providing adequate outcomes. Concerns regarding the use of bigger composite increments rely on the polymerization shrinkage and shrinkage stress, which may generate gaps on the adhesive interface and result in a reduced success rate. Objective: To evaluate the polymerization shrinkage stress of different bulk-fill resin composites and their elastic modulus. Materials and Methods: Fourteen specimens were made for each of the nine different resin composites (seven with 12 mm³ and seven with 24 mm³): Surefill SDR flow (SDR), X-tra Base (XB), Filtek Bulk Fill Flowable (FBF), Filtek Z350XT Flow (Z3F); Tetric Evo Ceram Bulk Fill (TBF), X-tra Fil (XF), Filtek Bulk Fill (FBP), Admira Xtra Fusion (ADM) and Filtek Z350 XT (Z3XT). Linear shrinkage stress was evaluated for 300 s with the aid of a linear shrinkage device adapted to a Universal Testing Machine. For each composite group, seven additional specimens (2x2x25 mm) were made and Young's modulus was evaluated with a 3-point bending device adapted in a Universal Testing Machine with 0.5 mm/min crosshead speed and 50 KgF loading cell. Results: For 12 mm³ specimens, three-way ANOVA showed that only SDR and TBF generated lower stress after 20 s. Considering 300 s, TBF, SDR, and XF generated the lowest stress, followed by ADM, FBP, XB, and FBF, which were similar to Z3XT. Z3F generated the highest stress values for all time points. Considering 24 mm³ specimens after 20 s, all bulk fill composites generated lower stress than Z3XT, except XB. After 300 s, SDR, FBP, and ADM generated the lowest stress, followed by TBF and XF. For elastic modulus, one-way ANOVA showed that FBF, SDR, Z3F, and ADM presented the lowest values, followed by XB and TBF. FBP, Z3XT, and XF presented the highest elastic modulus among the evaluated composites. Conclusions: Bulk-fill resin composites presented equal to lower shrinkage stress generation when compared to conventional composites, especially when bigger increments were evaluated. Bulk-fill composites showed a wide range of elastic modulus values, but usually similar to “regular” composites.

Comparison of Internal Adaptation of Bulk-fill and Increment-fill Resin Composite Materials

Objectives:

To evaluate 1) the internal adaptation of a light-activated incremental-fill and bulk-fill resin-based composite (RBC) materials by measuring the gap between the restorative material and the tooth structure and 2) the aging effect on internal adaptation.

Methods and Materials:

Seventy teeth with class I cavity preparations were randomly distributed into five groups; four groups were restored with bulk-fill RBCs: Tetric EvoCeram Bulk Fill (TEC), SonicFill (SF), QuiXX Posterior Restorative (QX), and X-tra fil (XF); the fifth group was restored with incremental-fill Filtek Supreme Ultra Universal Restorative (FSU). One-half of the specimens of each group were thermocycled. Each tooth was sectioned, digital images were recorded, and the dimensions of any existing gaps were measured. Data were analyzed using analysis of variance (α=0.05).

Results:

FSU had the smallest gap measurement values compared with the bulk-fill materials except QX and TEC (p≤0.008). FSU had the smallest sum of all gap category values compared with the bulk-fill materials, except QX (p≤0.021). The highest gap incidence and size values were found at the composite/adhesive interface. All aged groups had greater gap values in regard to the gap measurement and the sum of all gap categories compared with non-aged groups.

Significance:

The incrementally placed material FSU had the highest internal adaptation to the cavity surface, while the four bulk-fill materials showed varied results. Thermocycling influenced the existing gap area magnitudes. The findings suggest that the incremental-fill technique produces better internal adaptation than the bulk-fill technique.