Adequately Prepared? A Study Using an Innovative Computer Application to Measure Clinical Crown Convergence Angles...

Area of Science:

• Dental Restorative Dentistry
• Prosthodontics
• Biomaterials Science

Background:

• Accurate occlusal convergence angles are crucial for successful full coverage crown retention and stability.
• Variability in preparation angles can lead to challenges in restorative procedures and long-term prognosis.
• Previous studies have highlighted inconsistencies in dental student preparations.

Purpose of the Study:

• To quantify the total occlusal convergence angles in full coverage crown preparations made by dental students.
• To compare these angles across different tooth types (bucco-lingual and mesio-distal).
• To assess the percentage of preparations meeting ideal and clinically acceptable angle ranges.

Main Methods:

• 82 clinical crown preparations from UK dental students were scanned using 3D technology.
• Stereolithographic files were analyzed using specialized crown preparation software (Preppr).
• Bucco-lingual and mesio-distal convergence angles were measured and statistically analyzed.

Main Results:

• Mean bucco-lingual convergence angle was 19.6° (+/-11.7) and mesial-distally 17.8° (+/-11.1).
• Ideal angles (4-14°) were achieved in 23% (bucco-lingual) and 33% (mesio-distal) of preparations.
• Clinically acceptable angles (10-20°) were achieved in 30% (bucco-lingual) and 40% (mesio-distal) of preparations.
• Mesio-distal angles showed statistically significant differences by tooth type (p=0.003), with mandibular molars having higher values.

Conclusions:

• A minority of dental student preparations achieved ideal occlusal convergence angles.
• The findings are comparable to those reported for other student cohorts and clinicians.
• Further education and refinement of preparation techniques are needed to improve accuracy and clinical outcomes.