Rheological characteristics of tooth bleaching materials.

Tooth bleaching materials need to flow easily on insertion but should have high viscosity at low stresses to stay in place on the teeth. Some degree of elasticity may also aid retention on the teeth thereby maximizing efficacy. The present work was undertaken to study the comparative rheology of three tooth bleaching systems: two gels (Opalescence, Ultradent; Perfecta Trio, American Dental Hygienics) and a paste (Colgate Platinum, Colgate). A dynamic stress rheometer (Rheometrics Scientific) with cone and plate geometry was used, with the materials maintained at 37.0+/-0.1 degrees C with a vapour hood to minimize volatilization. Stress creep and recovery experiments were carried out. Steady shear viscosity for all three systems was high (>10(6) Pa s(-1)) for stresses <20 Pa. Between 100 and 200 Pa stress, all three materials showed a large drop in viscosity and flowed readily. The recovery portion of the data showed a marked difference where the elasticity of the gels was nearly two orders of magnitude higher than that of the paste. It was concluded that all materials would flow readily on insertion into the mouth and all have desirable high viscosity at low stress, but the paste material had the lowest elasticity. The effect of elasticity on performance needs to be determined clinically.

Adjunctive treatment of enchondromas with CO2 laser.

STUDY DESIGN/MATERIALS AND METHODS: Fourteen enchondromas, in eight patients, involving the tubular bones of the hand, were treated with curettage, CO2 laser sterilization of the tumor margins followed by autologous bone grafting. Average follow-up time was 35.4 months (14-106 months). Average patients age was 29 years. RESULTS: At follow-up there were no clinical recurrences, none had pain, and all patients reported satisfactory hand function without limitations. Minimal decrease in range of motion without functional limitation was encountered following excision of two lesions (14%) in one patient. One patient reported an increase in range of motion after excision. Grip strength was only minimally decreased. There was no radiographic evidence of recurrence. CONCLUSION: The use of CO2 laser is safe and effective as an adjunct to curettage and bone grafting in the management of relatively large enchondromas of the tubular bones of the hand.