Analysis of Marginal Adaptation of Porcelain Laminate Veneers Produced by Computer-Aided Design/Computer-Assisted Manufacturing Technology: A Preliminary In Vitro Study.

PURPOSE: To analyze the marginal adaptation of computer-aided design/computer-assisted manufactured (CAD/CAM) porcelain laminate veneers. MATERIALS AND METHODS: A total of 25 three-dimensional (3D) machine-milled laminate veneers were divided into five groups of five each according to fabrication material (E-max; Empress; Lava Ultimate; Suprinity; and Vita Mark II) and cemented in 25 prepared acrylic central incisors. Digital microscopy images (×7.5 magnification) were analyzed for gaps in the mesial/distal surfaces of the prepared tooth and in the cervical, medial, and incisal thirds. RESULTS AND CONCLUSION: All CAD/CAM laminate veneers except for Empress and Suprinity in the middle and incisal thirds showed good results (ie, gaps < 120 µm in the cervical, middle, and incisal thirds).

Development of a device to measure bracket debonding force in vivo.

The purposes of this study were to develop a device to measure bracket debonding force in vivo and to evaluate, in vitro, the bond strength obtained with the device and with tensile and shear bond strength (SBS) tests performed in a universal testing machine. The device was developed using polypropylene pliers (3M Unitek). The basic principle consisted of measuring the applied force to debond, using two strain gauges (Kyowa) bonded to the region of major deformation of the plier handles. The crowns of 75 bovine incisors were embedded in acrylic resin and orthodontic brackets were bonded to the facial surface with Transbond XT (3M Unitek). In group A (n = 25) debonding was carried out with the device, while tensile bond strength testing was performed in group B (n = 25) and SBS testing in group C (n = 25). A universal testing machine (EMIC-DL-2,000) was used for these last two groups. According to analysis of variance and Tukey's test (alpha = 0.05), the mean bond strength for group C (7.71 MPa) was statistically higher than for groups A (2.98 MPa) and B (2.69 MPa). Groups A and B were not statistically different. The device was shown to be feasible to obtain in vivo bond strength values for orthodontic brackets, and that the bond strength values were dependent on the method and direction of debonding.