Effect of preheating on the viscosity of composite resins.

Aim: To determine the effects of time and temperature on the viscosity of preheated composite resins. Materials and Methods: Eleven composite resins were heated to 60°C, and temperature analyses were performed at intervals of 1 min until they had cooled to 25°C. The permanent oscillatory shear test was performed at 25°C, 35°C, 50°C, and 60°C for three composite resins under a shear rate of 1s-1. One- and two-way analysis of variance were used for the analysis (α = 0.05). Results: There was no significant interaction between the composite resin and time (P = 0.9304), and only the main effect time was significantly different (P < 0.0001). A difference was observed between T0 and T6 (P < 0.001), but not after T7. The increase in temperature resulted in a viscosity reduction (P < 0.05). At 25°C, Beautifil II presented higher viscosity. Palfique LX5 showed a significant viscosity reduction with increasing temperature compared with the others (P < 0.05). For Beautifil II and Z100, there was no difference at temperatures of 50°C and 60°C, while for Palfique LX5, no statistical difference was observed at 35°C, 50°C, and 60°C. Conclusions: Ten minutes of preheating were sufficient to reach a temperature of 60°C, reducing viscosity by at least 84%. However, 5 min after removal, the composite resin cooled to room temperature. Clinical Significance: Preheating composite resin has potential benefits. To determine how this approach will work in clinical practice, it is important to define the effects of time and temperature in the protocol of this technique and understand its limitations.

Fragment reattachment or direct restoration? An in vitro study.

BACKGROUND/AIM: The fracture resistance of teeth subjected to fragment reattachment may improve when the technique is performed using intermediate materials. The aim of this study was to evaluate the influence of different bonding materials, including pre-heated composite resin, on the fracture resistance of teeth subjected to the reattachment technique compared with a direct composite resin restoration. MATERIALS AND METHODS: After simulating a tooth fracture, each specimen was reattached by using one of the following intermediate materials (n = 15): G0, negative control (sound teeth); G1, Z100; G2, pre-heated Z100; G3, Filtek Z350 XT; G4, pre-heated Filtek Z350 XT; G5, Filtek Z350 XT Flow; and G6, RelyX Veneer. In G7, direct class IV restorations were performed using Filtek Z350 XT composite resin. The fracture resistance was evaluated using a universal testing machine under a compressive load of 1 mm/min. One-way analysis of variance (ANOVA) and the post hoc Tukey test (5%) were conducted. RESULTS: G0 showed the highest fracture resistance, and this was statistically different from the other experimental groups (p < .05) except for G2 and G4, in which the fragments were bonded using pre-heated resins. A statistically significant difference was found between groups G1 and G6 (one-way ANOVA, p = .04). For G1 and G2, a significant difference was found between bonding with and without pre-heating (p < .05). This difference was not observed in G3 and G4 (p > .05). No statistically significant difference was found between the reattached and directly restored groups (t-test, p = .53). CONCLUSIONS: The tooth reattachment technique using pre-heated composite resin showed fracture resistance values similar to those of the sound tooth group. No difference was found between the fragment reattachment and direct composite resin techniques.

Reattachment of fractured teeth using a multimode adhesive: Effect of different rewetting solutions and immersion time.

BACKGROUND/AIMS: Following coronal tooth fracture, keeping the fragment hydrated is of the utmost importance in the tooth fragment bonding technique. The aim of this study was to evaluate the effects of different immersion times in different storage media on multimode adhesive bonding between reattached fragments and teeth. MATERIALS AND METHODS: A total of 195 bovine incisors were fractured and randomized into the following storage groups (n = 15): G0-control group (sound tooth); GA-saline solution: for 1 hour (A1) or 24 hours (A2); GB-artificial saliva: for 1 hour (B1) or 24 hours (B2); GC-coconut water: for 1 hour (C1) or 24 hours (C2); GD-tap water: for 1 hour (D1) or 24 hours (D2); GE-milk: for 1 hour (E1) or 24 hours (E2); GF-dry (dehydration): for 1 hour (F1) or 24 hours (F2). Tooth fragments were then reattached using a multimode adhesive in a self-mode technique with a flowable resin composite. Fracture resistance was evaluated in a universal testing machine under a compressive load (1 mm/min). The data were submitted to two-way analysis of variance and the post hoc Tukey test (5%). RESULTS: The group submitted to the dehydration factor (GF) exhibited a mean value of 599.1 ± 144.2 N, while those submitted to all hydration protocols (GA, GB, GC, GD, GE) exhibited a mean value of 751.8 ± 285.4 N. Dehydration significantly affected the fracture strength values (P = .005). No significant interaction between the rewetting solutions was observed (P > .05). CONCLUSIONS: Hydration of the tooth fragment increased fracture resistance, regardless of the storage solution and/or immersion time.

Early clinical performance of resin cements in glass-ceramic posterior restorations in adult vital teeth: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Dentists must regularly determine the best adhesive cementation protocol for glass-ceramic restorations on posterior teeth. The authors are aware of few in vivo follow-up studies and no meta-analyses, including clinical trials, regarding this clinically relevant topic, which merits further investigation. PURPOSE: The purpose of this systematic review and meta-analysis was to statistically analyze the clinical performance of glass-ceramic posterior restorations by using a descriptive synthesis based on the integrity of the tooth and restoration under different cementation protocols for self-adhesive or conventional resin cements. MATERIAL AND METHODS: The electronic databases Cochrane, LILACS, PubMed/MEDLINE, SciELO, Scopus, and Web of Science were used to identify relevant clinical trials. Non-peer-reviewed literature searches and hand searching were performed to find additional references. Language, participant's age, or time restrictions were not set. Restoration and tooth integrity were the 2 aspects considered for the meta-analysis. Statistical analyses were performed using a software program in which fixed or random effect models with risk ratios and 95% confidence intervals were applied. RESULTS: Three prospective randomized or quasirandomized clinical trials, published in English from 2012 onward, were selected and statistically analyzed. The integrity of the tooth and restoration was assessed at the baseline and 1 year after the restorative intervention. The statistical analyses did not show any significant differences between the intervention and control groups in terms of the integrity of the tooth and restoration. CONCLUSIONS: This meta-analysis indicated no clinical differences in the ceramic cementation using a self-adhesive or conventional resin cement after the 1-year follow-up period because both resin cements showed adequate properties for tooth and restoration integrity.