Reliability and validity of a transverse horizontal axis location instrument

Area of Science:

• Dental prosthetics
• Biomechanics
• Craniometry

Background:

• Accurate landmark identification is crucial in prosthodontics.
• Previous instruments for locating the transverse horizontal axis (THA) show variable accuracy.
• Evaluating the reliability and validity of specific instruments is essential for clinical application.

Purpose of the Study:

• To statistically evaluate the reliability and validity of a specific instrument system for locating the transverse horizontal axis (THA).
• To assess the accuracy and consistency of THA location using a standardized mannequin model.

Main Methods:

• Three experienced prosthodontists used a specific instrument to locate a known THA on a mannequin.
• Operators utilized a 15 mm interincisal arc, with the mandibular stylus aligned to the known horizontal axis.
• Vertical microdot flags were used to position the stylus over known coordinates, with variations across four trials.

Main Results:

• The highest coefficient of reliability observed was 0.25 for subjects 1 and 3.
• The 95% confidence intervals for linear deviation were 0.44 ± 0.10 mm (right) and 0.97 ± 0.10 mm (left).
• Statistically significant differences were found, with better accuracy on the right side (p = 0.0014).

Conclusions:

• The evaluated instrument system demonstrates a random error factor of 0.3 to 1.2 mm in clinical use.
• Clinical application of this instrument may lead to deviations in transverse horizontal axis location, particularly on the left side.
• Further refinement or alternative methods may be needed for precise THA determination in prosthodontics.