Comparison of resin-bonded prosthesis groove parallelism with the use of four tooth preparation methods

Abstract

Statement of problem. A precise preparation is required to develop resistance form resulting in mechanical stability of the framework for resin-bonded prostheses (RBPs). Purpose. The effects of 4 methods of tooth preparation (freehand, guiding pin, extraoral parallelometer, and intraoral parallelometer) on the deviation of proximal grooves from a preestablished path of insertion (guide planes) were investigated under clinical conditions. Material and methods. Tooth preparation of proximal grooves was performed by 32 dentists on resin substitutes of posterior segments intraorally with a single test patient. A Latin-square randomized cross-over design was selected as the experimental design. Results. The significant least angular deviation of proximal grooves from path of insertion was achieved with an intraoral parallelometer (mean ± SD 3.15 ± 1.67 degrees). Compared with freehand tooth preparations (4.37 ± 2.11 degrees), neither use of a guiding pin (4.10 ± 1.62 degrees) nor an extraoral parallelometer (5.06 ± 2.33 degrees) improved the results. Conclusion. Divergence of guiding grooves from path of insertion was reduced with the use of an intra-oral parallelometer. This should improve mechanical stability of posterior RBPs. (J Prosthet Dent 1999;82:398-409.)