Evaluation of resistance form of different preparation features on mandibular molars.

AIMS

Resistance form of full metal-ceramic crown is an important feature that determines longevity of these restorations. This study evaluated the resistance form of full metal-ceramic prepared with four different design features.

MATERIALS AND METHODS

An acrylic tooth was prepared with 20° total occlusal convergence (TOC) angle, 2.5 mm of occlusocervical dimension and a shoulder finishing line. This design lacked resistance form. The crown preparation was subsequently modified by preparing Mesial Occlusal Distal isthmus, placing occlusal inclined plane, and reducing TOC. Four metal dies from these designs were constructed by lathe machine and then 10 metal copings were fabricated for each preparation. Metal coping were cemented on metal dies with temp-bond cement. Force was applied at 45° from lingual to buccal direction with universal testing machine.

STATISTICAL ANALYSIS USED

The data were evaluated by Kruskal-Wallis and non-parametric Mann-Whitney test.

RESULTS

All features increased resistance form when compare to control group. However, reduce TOC group showed greatest value of resistance.

CONCLUSION

Within the limitation of this study, reducing the tapering of occlusocervival dimension is the most effective way in increasing resistance form, although, other features were also effective.