Recording dowel pin position with plastic logs.

Six readily available plastic materials were evaluated for use as a log for locating the ends of die dowel pins. Seven criteria were divided into two main categories of adherence qualities of the material and useability. Cost was the third category evaluated and compared. Color and availability were also considered. Forty-two sophomore dental students accomplished 84 evaluations. Plasticine and Weatherstrip Caulking Cord were found to meet all criteria best.

Fracture resistance of mandibular molars with occlusal class I amalgam preparations.

The finding that large occlusal Class I restorations weaken premolars is not confirmed for natural mandibular molars because no statistically significant difference was found in the mean loads needed to fracture mandibular molars that were unprepared, minimally prepared, or prepared with a large occlusal amalgam restorations. Similarly, there was no statistically significant change in the amount of force necessary to fracture natural mandibular molars prepared with sharp vs round internal line angles (a no. 56 vs a no. 330 bur). Duplication of the experiment in acrylic resin mandibular molars confirmed the results of a previous experiment by Re and Norling as well as the results relating to sharp vs round internal line angles found in this experiment on natural mandibular molars. Acrylic resin teeth of homogeneous shape and substance overcome some of the sampling problems inherent in obtaining suitable human teeth for testing purposes; however, further testing of this material is indicated.