Influence of repair procedure on composite-to-composite microtensile bond strength.

PURPOSE: To investigate the effect of different repair procedures and storage time on microtensile bond strength (µTBS) of a resin composite to an older one from a simulated previous restoration. METHODS: Composite disks were made by layering 2 mm-thick increments of a nanohybrid composite (Grandio) shade A1 in a Teflon mold (4 x 8 mm). Afterwards, they were light-cured and stored (37 degrees C/7 days) in a saline solution. Specimens were randomly divided into groups according to the surface treatment applied: (1) Composite surface was roughened with a bur (Cimara) and Solobond Plus adhesive was applied; (2) Sandblasting with 27 µm aluminum oxide particles (KaVo Rondoflex), and adhesive application; (3) Air-abrasion with 30 µm alumina particles coated with silica (CoJet Sand), silane (Monobond-S) and adhesive application; (4) Negative control group with only adhesive application. Afterwards, Grandio composite (shade A3.5) was packed incrementally on the treated surface obtaining another disk (4 x 8 mm). Repaired blocks were stored (24 hours or 6 months) and afterwards µTBS test was performed and failure mode was evaluated. Also, beams obtained from 8 mm-high composite blocks without any surface treatment were immediately submitted to µTBS test to determine Grandio composite cohesive bond strength (positive control group). Data were analyzed using ANOVA and Tukey's test (P < 0.05). RESULTS: The repair procedure affected µTBS values (P < 0.001) while neither storage time nor interactions did (P > 0.05). All repair procedures achieved bond strength values higher than the negative control group but they did not reach the composite's cohesive bond strength. The overall conclusion was that an increased superficial roughness by means of a bur, silica coating or alumina sandblasting improved µTBS of the repaired composite and bond strength remained stable after 6 months.

Microhardness of different resin cement shades inside the root canal

Objectives: To compare microhardness along the root canal post space of two resin cements in different shades and a dual-cure resin core material. Study Design: Root canals of 21 bovine incisors were prepared for post space. Translucent posts (X·Post, Dentsply DeTrey) were luted using one the following resin luting agent: Calibra (Dentsply DeTrey) in Translucent, Medium and Opaque shades, RelyX Unicem (3M ESPE) in Translucent, A2 and A3 shades and the dual-cure resin core material Core·X flow. All materials were applied according to manufacturers’ instructions and were all photopolymerized (Bluephase LED unit, Ivoclar Vivadent, 40s). After 24 hours, roots were transversally cut into 9 slices 1 mm thick from the coronal to apical extremes, three corresponding to each root third. Then, VHNs were recorded (100gf, 30 s) on the resin luting materials along the adhesive interface in all sections. Data were analyzed by twoway ANOVA and SNK tests (á=0.05). Results: A significant influence on microhardness of resin luting material in their respective shades (p<0.001), root third (p<0.001) and interactions between them was detected (p<0.001). RelyX Unicem cement showed the highest microhardness values and Calibra the lowest, regardless of the shade selected. All resin luting materials tested exhibited a significantly higher microhardness in the cervical third. Conclusions: Microhardness of resin luting agents tested inside the canal is dependent on material brand and resin cement shade seems to be a less relevant factor. Microhardness decreased along the root canal, regardless of the shade selected (AU)

Microhardness of different resin cement shades inside the root canal.

OBJECTIVES: To compare microhardness along the root canal post space of two resin cements in different shades and a dual-cure resin core material. STUDY DESIGN: Root canals of 21 bovine incisors were prepared for post space. Translucent posts (X∘Post, Dentsply DeTrey) were luted using one the following resin luting agent: Calibra (Dentsply DeTrey) in Translucent, Medium and Opaque shades, RelyX Unicem (3M ESPE) in Translucent, A2 and A3 shades and the dual-cure resin core material Core∘X flow. All materials were applied according to manufacturers' instructions and were all photopolymerized (Bluephase LED unit, Ivoclar Vivadent, 40s). After 24 hours, roots were transversally cut into 9 slices 1 mm thick from the coronal to apical extremes, three corresponding to each root third. Then, VHNs were recorded (100gf, 30 s) on the resin luting materials along the adhesive interface in all sections. Data were analyzed by two-way ANOVA and SNK tests (α=0.05). RESULTS: A significant influence on microhardness of resin luting material in their respective shades (p<0.0001), root third (p<0.0001) and interactions between them was detected (p<0.0001). RelyX Unicem cement showed the highest microhardness values and Calibra the lowest, regardless of the shade selected. All resin luting materials tested exhibited a significantly higher microhardness in the cervical third. CONCLUSIONS: Microhardness of resin luting agents tested inside the canal is dependent on material brand and resin cement shade seems to be a less relevant factor. Microhardness decreased along the root canal, regardless of the shade selected.

Influence of the menstrual cycle on the pressure pain threshold of masticatory muscles in patients with masticatory myofascial pain.

OBJECTIVE: The aim of this study was to investigate the influence of the menstrual cycle and oral contraceptive (OC) intake on the pressure pain threshold (PPT) of masticatory muscles in patients with masticatory myofascial pain (MFP). STUDY DESIGN: The sample was composed of 36 women, divided into 4 groups, according to the presence of MFP and the intake of OC (15 patients had MFP [7 taking OC] and 21 were pain-free controls [8 taking OC]). The algometer-based PPT of masseter and temporalis, and the record of subjective pain by visual analog scale (VAS) were determined during 2 consecutives menstrual cycles at 4 phases (menstrual, follicular, periovulatory, and luteal). A 3-way ANOVA for repeated measurements, Kruskal-Wallis, Friedman, and Dunn tests, with a 5% significant level analyzed the data. RESULTS: PPT was significantly lower in MFP patients when compared with controls throughout the experiment (P < .001). The menstrual phases did not influence PPT (P > .05), while the intake of OC seems to raise PPT levels for the left temporalis (P = .01) and right masseter (P = .04). VAS was, in general, higher at the menstrual phase CONCLUSIONS: Different phases of the menstrual cycle have no influence on PPT values, regardless of the presence of a previous condition, as masticatory myofascial pain, while the intake of OC is associated with decreased levels of reported pain.