Space Closure Efficiency with Modified Ceramic Brackets : A Comparative Study

The purpose of this study was to determine if the rate of extraction site closure was determined by the type of ceramic bracket used. A new ceramic bracket with a metal archwire slot was compared with a conventional ceramic bracket. Twenty patients were randomly assigned the metal slot ceramic bracket and conventional ceramic to one half of their maxillary arch respectively. The distribution was even left and right. Retraction was started and completed on an 0.016 stainless steel round continuous archwire. One hundred gram sentalloy springs provided a uniform retraction force and were reactivated every four weeks to maintain a constant force measured at 100 grams. Retraction continued until contact occurred between the retracted tooth and the most posterior tooth adjacent to the space. At this point retraction was considered complete and final records were taken. The initial lateral cephalagram was compared to the progress cephalagram. Measurements from PTV to each first molar and to each anterior tooth being retracted were used in a subgroup of eight patients with essentially identical treatment methods. These were used to determine if binding or resistance to space closure occurred more frequently with one bracket type. The results of space closure were analyzed using a regression analysis to evaluate millimeters of movement per month for each bracket and tooth measurement for each patient. Correlation was high in all cases and rate of retraction of the 17 patients that completed the study showed no significant difference from one bracket type to the other (p=0.61). When the values to PTV were compared using a Paired T Test, no indication of increased binding or friction could be shown from one bracket type to the other (p=0.25). While there may be other advantages to the metal slot insert, such as improved resistance to fracture or ease of wire placement, there appears to be no specific advantage regarding rate of retraction or reduction of friction according to the results obtained from this study