Effect of Tribochemical Coating on Composite Repair Strength

Clinical Relevance

Tribochemical treatment of existing composite surfaces is highly effective for composite repair. When repairing an old composite restoration, the clinician should try to use the same composite originally used for the restoration. If the information about the original restoration is not known, a composite with strong mechanical properties should be used for the repair restoration.

SUMMARY

This study evaluated the effect of tribochemical coating on composite-to-composite repair interfacial fracture toughness (iFT). Sixty beam-shaped specimens (21×4×3 ± 0.2 mm) were prepared with a nanofill composite (Filtek Supreme Ultra [FSU]) and a nanohybrid composite (Clearfil Majesty ES-2 [CME]) and aged for 50,000 thermocycles (5°C-55°C, 20-second dwell time) and then sectioned in half. The resulting 120 hemispecimens (60 for each composite) were randomly assigned to different repair methods (n=10): universal adhesive (Clearfil Universal Bond Quick [CUB]), sand-blasting followed by CUB, or tribochemical coating (CoJet, CoJet sand, Espe-Sil, and Visio-Bond). The repair surface was prepared with a diamond bur (Midwest #471271), rinsed, and dried. Each aged composite brand (FSU, CME) was repaired with either the same composite or the opposite composite. All adhesives and composites were light cured with a high-irradiance LED curing light (Elipar DeepCure-S). After postrepair storage in 100% humidity and at 37°C for 24 hours, iFT was measured as KIc (MPa m½). Data were analyzed for statistical significance using two-way analysis of variance (ANOVA) and the Tukey honest significant difference post hoc test (α=0.05). Regardless of the substrate composite, ANOVA showed significant differences for surface treatment (p<0.0001) and repair composite (p<0.0001). Mean iFT values (SD) ranged from 0.91 (0.10) MPa·m½ to 2.68 (0.12) MPa·m½. Repairs made with FSU after CoJet resulted in significantly higher iFT (FSU: 2.68 MPa·m½; CME: 2.21 MPa·m½) when compared to the other experimental groups. The repair iFT was higher with CoJet treatment and when the nanofill composite FSU was used as the repair composite.

Does the addition of potassium nitrate to carbamide peroxide gel reduce sensitivity during at-home bleaching?

BACKGROUND

A systematic review with meta-analysis was conducted to assess the effect of adding potassium nitrate to carbamide peroxide gels on bleaching efficacy and on reducing the risk and intensity of tooth sensitivity.

METHODS

PubMed, Scopus, Web of Science, LILACS, BBO, and Cochrane Library databases and the gray literature were searched. IADR abstracts, records of trials, dissertations and theses were also searched. The Cochrane Collaboration risk of bias tool was used to assess the quality of the studies.

RESULTS

Six studies were included in the systematic review and most of them had unclear risk of bias for the key domains, and of these only five were included in the meta-analysis. The risk ratio (RR) for sensitivity was 0.93 (95% CI = 0.73 to 1.19, P = 0.56). The standardized mean difference for pain intensity was -0.10 (95% CI = -0.36 to 0.16, P = 0.45), and for colour change was 0.12 (95% CI = -0.22 to 0.46; P = 0.49).

CONCLUSIONS

No significant differences were observed between the groups with and without addition of the desensitizer in the gel. The addition of potassium nitrate to carbamide peroxide gel did not reduce the risk and intensity of tooth sensitivity during at-home bleaching. Colour change was not influenced by the addition of potassium nitrate to the gel.

Efficacy of a Light-cured Tetracaine-based Anesthetic Gel for Rubber Dam Clamp Placement: A Triple-blind Randomized Clinical Trial

OBJECTIVES

To evaluate the efficacy of a new light-cured anesthetic gel for pain control in adults undergoing rubber dam isolation for the restorative treatment of noncarious cervical lesions (NCCLs).

METHODS AND MATERIALS

This study was a randomized, split-mouth, triple-blind, controlled trial. The sample comprised 50 adults with at least one pair of NCCLs located in the same arch but on opposite sides. Simple randomization defined the tooth to receive the light-cured tetracaine-based anesthetic gel or the placebo gel. After cotton roll isolation, the gels were applied in the gingival tissue around the tooth with the aid of the applicator tip of a syringe, left in place for 15 seconds, and light-cured for 15 seconds. Then, a #212 clamp was positioned on the tooth. If the patient reported pain, the clamp was removed, the patient filled out a pain intensity form (a 0-10 visual analog scale [VAS] and a 0-4 verbal rating scale [VRS]) and an injectable anesthetic was applied before rubber dam isolation for the restorative procedure. The absolute risk, intensity of pain, and need for rescue anesthesia were analyzed by the McNemar test and the Wilcoxon signed rank test (α=5%).

RESULTS

The odds ratio [OR] for pain (OR=3.5; 95% confidence interval [CI]=1.1 to 14.6; p=0.03) showed lower reports of pain for the light-cured anesthetic gel. One in five patients will benefit from placement of the light-cured anesthetic gel. On average, pain intensity was one VAS unit lower in those using the light-cured anesthetic gel than in those using the placebo gel. For the VRS, the pain intensity for the light-cured anesthetic gel was 0.4 units lower than the pain intensity for the placebo gel (95% CI=-0.9 to 0.07). The OR for rescue anesthesia was 2.5 (95% CI=0.7 to 10.9; p=0.18).

CONCLUSIONS

The light-cured, tetracaine-based anesthetic gel reduced the absolute risk of pain by 20% in NCCLs.

Composite-composite Adhesion as a Function of Adhesive-composite Material and Surface Treatment

OBJECTIVE

To evaluate the composite-to-composite repair interfacial fracture toughness (iFT) as a function of adhesive and composite repair material.

METHODS AND MATERIALS

Beam-shaped composite specimens (21×4×3±0.2 mm) were prepared for each substrate material (Filtek Supreme Ultra [FSU] or Clearfil Majesty ES-2 [CME]) and artificially aged for 50,000 thermocycles (5-55°C, 20-second dwell time). Aged specimens were sectioned in half, and the resulting hemispecimens were randomly assigned to one of the different repair methods (n=10) based on the following variables: type of substrate composite (FSU or CME), acid etch (yes or no), adhesive type (Scotchbond Universal or Clearfil SE Bond 2), and type of repair composite (FSU or CME). The repair surface was prepared with a course diamond bur (Midwest #471271). When used, 37% phosphoric acid was applied for 20 seconds, rinsed, and dried. All adhesives and composites were applied according to manufacturers' instructions. After postrepair storage (100% humidity, 37°C, 24 hours), iFT was measured and expressed as MPa. Data were analyzed for statistical significance using a three-way analysis of variance and Tukey post hoc tests (α=0.05).

RESULTS

iFT values ranged from 0.64 ± 0.19 MPa to 1.28 ± 013 MPa. Significantly higher iFT values were achieved when FSU was used as the repair composite resin regardless of the substrate composite resin (p<0.001). Clearfil SE Bond 2 adhesive was associated with significantly higher iFT values for FSU substrate (p<0.001). The etching procedure had no significant effect on the iFT values of the repair procedures (p>0.05).

CONCLUSIONS

Composite repair strength is adhesive and composite dependent. Repair strength appears to be higher when FSU is the repair composite regardless of the adhesive used.

Retentores Intraradiculares Estéticos Fabricados por CAD/CAM: Resistência à Fratura e à União Após Fadiga

Os objetivos do estudo foram avaliar a resistência à fratura (RF) após fadiga e a resistência de união ao push-out (RU) com e sem fadiga, em retentores intrarradiculares personalizados fabricados com diferentes materiais estéticos em CAD/CAM. Noventa dentes foram selecionados, preparados endodonticamente e submetidos ao preparo do espaço intraradicular. Os dentes foram distribuídos aleatoriamente em 3 grupos de acordo com o material do retentor: fibra de vidro experimental (FV) cerâmica híbrida Vita Enamic (CH) e resina composta nano cerâmica Lava Ultimate (RC). Os restentores foram fabricados em CAD/CAM e cimentados com cimento resinoso autoadesivo (Rely X U200). Um subgrupo de 30 espécimes (n10) foi submetido a fadiga (1.000.000 ciclos a       5 Hz) e, em seguida, ao ensaio de RF. Outro subgrupo com 60 espécimes foi submetido ao ensaio de RU, com e sem fadiga. Os dados foram submetidos à análise de variância (RF - ANOVA 1 fator RU - ANOVA 2 fatores) e teste de Tukey (a0,05). As médias de RF (N±DP) para os materiais foram 407,61±109,04 (FV), 414.52±83.95 (CH), and 621,38±100,35 (RC), com RC apresentando valores de RF significativamente superiores (p<0,05). Para RU, não houve diferença estatisticamente significante entre os materiais, com e sem fadiga (p>0,05). Pode-se concluir que o tipo de material utilizado para confecção do retentor personalizado influenciou significativamente na RF, mas não na RU dos espécimes. A realização da fadiga não influenciou na RU para os diferentes materiais.Palavras-chave: CAD-CAM. Pino Intrarradicular. Materiais Dentários.

Mechanical properties of resin cements with different activation modes

Dual-cured cements have been studied in terms of the hardness or degree of conversion achieved with different curing modes. However, little emphasis is given to the influence of the curing method on other mechanical properties. This study investigated the flexural strength, flexural modulus and hardness of four proprietary resin cements. Materials tested were: Enforce and Variolink II (light-, self- and dual-cured), RelyX ARC (self- and dual-cured) and C & B (self-cured). Specimens were fractured using a three-point bending test. Pre-failure loads corresponding to specific displacements of the cross-head were used for flexural modulus calculation. Knoop hardness (KHN) was measured on fragments obtained after the flexural test. Tests were performed after 24 h storage at 37 degrees C. RelyX ARC dual-cured showed higher flexural strength than the other groups. RelyX ARC and Variolink II depended upon photo-activation to achieve higher hardness values. Enforce showed similar hardness for dual- and self-curing modes. No correlation was found between flexural strength and hardness, indicating that other factors besides the degree of cure (e.g. filler content and monomer type) affect the flexural strength of composites. No statistical difference was detected in the flexural modulus among the different groups.

Tensile bond strength of filled and unfilled adhesives to dentin

PURPOSE

To determine the tensile bond strength of three filled and two unfilled adhesives applied to bovine dentin.

MATERIALS AND METHODS

Fragments of the labial dentin of bovine incisors were embedded in PVC cylinders with self-cure acrylic resin, and ground flat using 200 grit and 600 grit sandpaper. The following adhesive systems were tested (n=10): Prime & Bond NT, Prime & Bond NT dual cure, Prime & Bond 2.1, OptiBond Solo and Single Bond. A 3 mm-diameter bonding surface was delimited using a perforated adhesive tape. After etching with 37% phosphoric acid and adhesive application, a resin-based composite truncated cone (TPH, shade A3) was built. Tensile test was performed after 24 hrs storage in distilled water at 37 degrees C. Failure mode was accessed using a x10 magnification stereomicroscope.

RESULTS

Weibull statistical analysis revealed significant differences in the characteristic strength between Single Bond and Prime & Bond NT dual cure, and between Single Bond and Prime & Bond 2.1. The Weibull parameter (m) was statistically similar among the five groups. Single Bond and Prime & Bond NT showed areas of dentin cohesive failure in most of the specimens. For OptiBond Solo, Prime & Bond NT dual cure and Prime & Bond 2.1 failure was predominantly adhesive.