Geometric analysis of occlusal plane orientation using simulated ear-rod facebow transfer

Area of Science:

• Dental Articulation
• Craniofacial Anatomy
• Orthodontic Technology

Background:

• Ear-rod facebow techniques are crucial for accurate dental cast mounting on articulators.
• Variations in anterior reference points (orbitale or nasion) can lead to inconsistent cast positioning.

Purpose of the Study:

• To assess the impact of altering the anterior reference position on simulated dental cast mountings using an ear-rod facebow.
• To evaluate how different mounting positions (high, midway, low) influence the articulator's parameters.

Main Methods:

• Lateral cephalographs from seven subjects were analyzed and superimposed with a semi-adjustable articulator model.
• Three simulated mounting positions (high, midway, low) were created for each subject's casts.
• Intercuspal and protrusive positions were simulated to determine occlusal planes and condylar guidance.

Main Results:

• No significant changes in intercuspal position were observed across different mounting heights within subjects.
• Angles between the articulator's upper member and condylar guidance varied significantly with mounting position.
• High and low mountings showed greater deviations in condylar guidance angles compared to the midway position.

Conclusions:

• Variability in ear-rod placement relative to skull structures can be compensated by adjustments in horizontal condylar guidance.
• A midway mounting position appears to be a practical and convenient choice for routine dental articulations.
• The findings support optimizing facebow mounting procedures for enhanced accuracy in dental diagnostics.