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In this clinical trial, we examined the efficacy of intra-articular hyaluronic acid (HA) treatment in 38 patients with reducing displaced disc of the temporomandibular joint (TMJ). Subjects received two unilateral upper space injections of HA or physiological saline solution with 1 week apart. Efficacy was based on the following measurements: pain and sound intensity of the joint measured by visual analogue scale (VAS), modified Helkimo's clinical dysfunction index and the intensity of joint vibration during opening and closing the mouth measured by accelerometers. These measurements were performed before the first injection and 1 and 6 months after the last injection. In the treatment group (n=19), all measurements improved significantly at month 1 and at month 6 compared with the baseline (P < 0.01). The same measurements, in the placebo group (n=19), did not show any change, except for the pain intensity which improved at month 1 and month 6 (P < 0.05). The change in baseline measurements of all of the efficacy criteria at month 1 and at month 6 in the treatment group was significantly better compared with the change obtained with placebo at the same time intervals. This study demonstrates that intra-articular sodium hyaluronate (Orthovisc) injection into the TMJ is an effective treatment for a reducing displaced disc.

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This in vitro study was conducted to evaluate the interaction between the shear bond strength and the surface treatment method for a commercial dental ceramic. Ninety bonded ceramic units were manufactured for this study. Each unit was made by luting two cylinder-shaped ceramic samples to each other with a resin-composite luting agent. The units were then divided into nine groups, containing 10 units in each group. Samples from each group were treated with one of the following: etching with 4.9% hydrofluoric acid for 10, 20 and 40 s, 9.5% hydrofluoric acid for 10, 20 and 40 s, 40% orthophosphoric acid for 40 s, air abrasion with alumina in 50-microm particles, and grinding with a high-speed diamond bur. The treated samples were then silanated and luted with a resin-composite luting agent. The luted units were then loaded to failure. Two samples from each group were neither silanated nor luted after the surface treatment procedure, and morphological changes obtained by various surface treatment regimens were investigated by scanning electron microscopy. A statistically significant difference was observed among the mean shear bond strengths of the groups prepared with different surface treatment techniques (P = 0.00). Hydrofluoric acid appeared to be the most suitable chemical medium to produce a reliable ceramic bond. Etching time and concentration of the acidic medium were also observed as important prognostic variates. Orthophosphoric acid treatment was observed to be the least effective surface treatment method on the heat-pressed ceramic samples. Physical applications such as bur grinding and air blasting maintained stronger bonds than the orthophosphoric acid, while producing weaker bonds than surfaces treated with hydrofluoric acid in all concentrations and etching periods. The effect of the silane priming agent was not considered in this study.

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