Splints and stress transmission to teeth: an in vitro experiment

Objective. To determine the influence of hard and soft splints with two thicknesses on the stress transmission to the tooth supporting the splint and the opposite tooth. Methods. Continuous vertical forces up to 500 N were applied to two opposite first molar phantom teeth using a universal loading machine. Deformation was detected by strain gauges attached to the cervical area of the buccal and lingual aspects of the lower tooth. Strain, as a function of force, was collected and the slope, defined as the compliance (in μS/N) of the system, was calculated. Results. The highest compliance was found with hard splints. When splints were constructed on the upper molar, the highest compressive compliance was registered on the buccal side (2.8 μS/N) and tension compliance on the lingual side (−0.35 μS/N). When constructed on the lower tooth, the opposite was found. Soft splints resulted in compression on both the buccal and lingual sides when adjusted to the upper or lower tooth. A higher compliance was found on the buccal side (1.26 μS/N), while on the lingual side, the values varied (0.48–0.78 μS/N). Conclusions. Soft splints are more efficient in protecting teeth against the damage of bending forces although there is an increase of compression forces. The tooth opposing a hard splint is exposed to a higher risk of bending forces.