Comparison of Bennett shift measured at the hinge axis and an arbitrary hinge axis position

Area of Science:

• Dental Mechanics
• Biomechanics
• Prosthodontics

Background:

• The Bennett shift, an important factor in mandibular movement, is influenced by the position of the hinge axis.
• Accurate determination of the kinematic hinge axis is crucial for precise dental restorations.
• Arbitrary hinge axis determination is a common simplification in clinical practice.

Purpose of the Study:

• To evaluate the accuracy of Bennett shift measurements using an arbitrary hinge axis position compared to the true hinge axis position.
• To assess the clinical relevance of discrepancies between arbitrary and true hinge axis measurements.
• To determine the average immediate Bennett shift in subjects with firm guidance.

Main Methods:

• The Bennett shift was measured in 10 subjects at both the arbitrary hinge axis position and the true hinge axis position.
• Sixty percent of arbitrary hinge axis positions were analyzed for their proximity (within 5 mm) to the true hinge axis.
• Measurements were taken in 0.25 mm increments to assess differences in Bennett shift values.

Main Results:

• Sixty percent of arbitrary hinge axis positions were found to be within 5 mm of the true hinge axis position.
• No significant difference was observed in Bennett shift measurements between the true and arbitrary hinge axis positions.
• The average immediate Bennett shift was 1.05 mm on the left and 1.12 mm on the right side with firm guidance.

Conclusions:

• Arbitrary hinge axis positioning can provide sufficiently accurate Bennett shift measurements for clinical applications.
• The findings support the use of simplified arbitrary hinge axis methods in dental practice, potentially improving efficiency.
• The study quantifies the immediate Bennett shift, offering valuable data for prosthetic treatment planning.