Effect of Thickness on Light Transmission and Vickers Hardness of Five Bulk-fill Resin-based Composites Using Polywave and Single-peak Light-emitting Diode Curing Lights.

OBJECTIVES:: This study compared light transmission through different thicknesses of bulk-fill resin-based composites (RBCs) using a polywave and a single-peak light-emitting diode light-curing unit (LCU). The effect on the surface hardness was also evaluated. METHODS:: Five bulk-fill RBCs were tested. Specimens (n=5) of 1-, 2-, 4-, or 6-mm thickness were photopolymerized for 10 seconds from the top using a polywave (Bluephase Style) or single-peak (Elipar S10) LCU, while a spectrophotometer monitored in real time the transmitted irradiance and radiant exposure reaching the bottom of the specimen. After 24 hours of storage in distilled water at 37°C, the Vickers microhardness (VH) was measured at top and bottom. Results were analyzed using multiple-way analysis of variance, Tukey post hoc tests, and multivariate analysis (α=0.05). RESULTS:: The choice of LCU had no significant effect on the total amount of light transmitted through the five bulk-fill RBCs at each thickness. There was a significant decrease in the amount of light transmitted as the thickness increased for all RBCs tested with both LCUs ( p<0.001). Effect of LCU on VH was minimal (ηp2=0.010). The 1-, 2-, and 4-mm-thick specimens of SDR, X-tra Fill, and Filtek Bulk Restorative achieved a VHbottom/top ratio of approximately 80% when either LCU was used. CONCLUSIONS:: The total amount of light transmitted through the five bulk-fill RBCs was similar at the different thicknesses using either LCU. The polywave LCU used in this study did not enhance the polymerization of the tested bulk-fill RBCs when compared with the single-peak LCU.

Nanofilled Resin Composite Properties and Clinical Performance: A Review.

The aim of this review was to compile recent evidence related to nanofilled resin composite materials regarding the properties and clinical performance. Special attention was given to mechanical properties, such as strength, hardness, abrasive wear, water sorption, and solubility. The clinical performance of nanocomposite materials compared with hybrid resin composites was also addressed in terms of retention and success rates, marginal adaptation, color match, and surface roughness. A search of English peer-reviewed dental literature (2003-2017) from PubMed and MEDLINE databases was conducted using the terms "nanocomposites" or "nanofilled resin composite" and "clinical evaluation." The list was screened, and 82 papers that were relevant to the objectives of this work were included in the review. Mechanical properties of nanocomposites are generally comparable to those of hybrid composites but higher than microfilled composites. Nanocomposites presented lower abrasive wear than hybrids but higher sorption values. Their clinical performance was comparable to that of hybrid composites.

Effect of bulk-fill base material on fracture strength of root-filled teeth restored with laminate resin composite restorations.

OBJECTIVES: To evaluate the effect of using a bulk-fill flowable base material on fracture strength and fracture patterns of root-filled maxillary premolars with MOD preparations restored with laminate restorations. METHODS: Fifty extracted maxillary premolars were selected for the study. Standardized MOD cavities with endodontic treatment were prepared for all teeth, except for intact control. The teeth were divided randomly into five groups (n=10); (Group 1) sound teeth, (Group 2) unrestored teeth; (Group 3) MOD cavities with Vitrebond base and resin-based composite (Ceram. X One Universal); (Group 4) MOD cavities with 2mm GIC base (Fuji IX GP) and resin-based composite (Ceram. X One Universal) open laminate, (Group 5) MOD cavities were restored with 4mm of bulk-fill flowable base material (SDR) and resin-based composite (Ceram. X One Universal). All teeth were thermocycled and subjected to a 45° ramped oblique load in a universal testing machine. Fracture load and fracture patterns were recorded. Data were analyzed using one-way ANOVA and Dunnett's T3 test. RESULTS: Restoration in general increased the fracture strength compared to unrestored teeth. The fracture strength of group 5 (bulk-fill) was significantly higher than the fracture strength of the GIC laminate groups and not significantly different from the intact teeth (355±112N, P=0.118). The type of failure was unfavorable for most of the groups, with the majority being mixed failures. CONCLUSIONS: The use of a bulk-fill flowable base material significantly increased the fracture strength of extracted root-filled teeth with MOD cavities; however it did not improve fracture patterns to more favorable ones. CLINICAL SIGNIFICANCE: Investigating restorative techniques that may improve the longevity of root-filled premolar teeth restored with direct resin restorations.

The Silorane-based Resin Composites: A Review.

This article aims to review the research done on the silorane-based resin composites (SBRC) regarding polymerization shrinkage and contraction stresses and their ability to improve the shortcomings of the methacrylate-based resin composites (MRBC). Special attention is given to their physical and mechanical properties, bond strength, marginal adaptation, and cusp deflection. The clinical significance of this material is critically appraised with a focus on the ability of SBRC to strengthen the tooth structure as a direct restorative material. A search of English peer-reviewed dental literature (2003-2015) from PubMed and MEDLINE databases was conducted with the terms "low shrinkage" and "silorane composites." The list was screened, and 70 articles that were relevant to the objectives of this work were included.

Fracture strength of root filled premolar teeth restored with silorane and methacrylate-based resin composite.

OBJECTIVES: To compare fracture characteristics of root-filled teeth with variable cavity design restored with a low shrinkage silorane and methacrylate-based resin composite. METHODS: 77 extracted maxillary premolars were divided randomly into seven groups: (Group 1) intact teeth; (Groups 2-4) MOD plus endodontic access with the buccopalatal width of the occlusal isthmus equals one third of the intercuspal width; (Groups 5-7) MOD plus endodontic access with the buccopalatal width of the occlusal isthmus equals one half of the intercuspal width. Groups 2 and 5 were left unrestored, Groups 3 and 6 were restored with a silorane-based resin composite (Filtek P90) and Groups 4 and 7 with a methacrylate-based resin composite (Z250). Teeth were loaded in a universal testing machine; load and fracture patterns were recorded and compared statistically using 2-way ANOVA and t-test for pairwise comparisons and 1-way ANOVA with Dunnett test for multiple comparisons. RESULTS: Unrestored teeth became progressively weaker with more extensive preparations, Group 5 (unfilled ½) showed the lowest fracture load among the groups (71±22N, P<0.001). Restorations increased the fracture strength of unrestored teeth regardless of cavity size (P<0.001), but was still significantly weaker than sound teeth, with no significant difference between silorane and methacrylate groups. Failure of restored teeth was mostly adhesive at the tooth restoration interface. CONCLUSIONS: Silorane-based resin composite have no superior strengthening effect over the conventional methacrylate-based resin composite in restoration of root filled teeth. Both materials showed similar fracture patterns. CLINICAL SIGNIFICANCE: Root filled teeth are considerably weakened via restorative and endodontic procedures. A direct adhesive restoration will aid in preserving tooth structure as far as it provides enough strength.

Assessment of the effect of casein phosphopeptide-amorphous calcium phosphate on postoperative sensitivity associated with in-office vital tooth whitening.

The aim of this study was to evaluate the efficacy of tooth mousse containing 10% casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) in reducing tooth sensitivity associated with in-office vital tooth whitening. In-office tooth whitening was performed for 51 participants using 35% hydrogen peroxide gel in a single visit. After the procedure, each participant was randomly assigned to one of three groups: gel without desensitizing agent (n=17), gel with 2% sodium fluoride (n=17), gel with 10% CPP-ACP (n=17). A small amount of the desensitizing gel assigned for each participant was applied directly on the labial surfaces of teeth and left undisturbed for three minutes. The participants were asked to apply the gel assigned to them for three minutes twice daily after brushing their teeth, and to continue this for 14 days. The participants were asked to return for follow-up visits after 24 hours and on days 3, 7, and 14, at which time teeth shade changes were assessed by one evaluator using a value-oriented Vita classic shade guide. The incidence, duration, and intensity of tooth sensitivity experienced was self-assessed on a daily basis for the 14-day study period using a visual analog scale (VAS). The effect of the three gels on tooth sensitivity was assessed using one-way analysis of variance and a χ (2) test (α=0.05). The general linear model was used to compare intensity-level differences in the three studied groups and for shade stability over the follow-up period. The results of this study showed that all three gels decreased the intensity of sensitivity associated with tooth whitening. The intensity of sensitivity was lower in the fluoride group than in the other two groups; however, it was not statistically significant (p=0.112 and p=0.532 on day 1 and day 2, respectively). The average shade change was 6.8. None of the tested materials affected the efficacy of tooth whitening, but the shade change among the fluoride group showed more color stability than that of the other two groups. This study suggested that using a gel after tooth whitening can reduce the intensity of tooth sensitivity associated with in-office whitening procedures without affecting the efficiency of tooth whitening. However, it failed to demonstrate that using a 10% CPP-ACP could provide additional therapeutic benefits.