Objective. To determine the influence of hard and soft splints with two thi
cknesses 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 opposit
e first molar phantom teeth using a universal loading machine. Deformation
was detected by strain gauges attached to the cervical area of the buccal a
nd lingual aspects of the lower tooth. Strain, as a function of force, was
collected and the slope, defined as the compliance (in mu S/N) of the syste
m, was calculated.
Results. The highest compliance was found with hard splints. When splints w
ere constructed on the upper molar, the highest compressive compliance was
registered on the buccal side (2.8 mu S/N) and tension compliance on the li
ngual side (-0.35 mu S/N). When constructed on the lower tooth, the opposit
e was found. Soft splints resulted in compression on both the buccal and li
ngual sides when adjusted to the upper or lower tooth. A higher compliance
was found on the buccal side (1.26 mu S/N), while on the lingual side, the
values varied (0.48-0.78 mu S/N).
Conclusions. Soft splints are more efficient in protecting teeth against th
e damage of bending forces although there is an increase of compression for
ces. The tooth opposing a hard splint is exposed to a higher risk of bendin
g forces. (C) 2000 Elsevier Science Ltd. All rights reserved.