Objectives: To investigate the variations of buccal/labial tooth margin configuration for metal-ceramic crowns between clinicians with varying experience; fourth and fifth year undergraduate dental students, clinical teaching staff (CTS) and general dental practitioners (GDPs). Methods: A total of 80 dies, 20 from each group were examined from impressions taken of clinical preparations. All were cast in class IV die stone before being trimmed and sectioned in three bucco-lingual planes (mesial, midline and distal). Each die section was placed with the buccal/labial axial wall at approximately 5º to the vertical using a crosshair eyepiece. The margin dimensions and configurations were examined using a Mitutoyo travelling microscope at 30 X magnification. All results were recorded before being analysed statistically using a One-way Analysis of Variance and two sample t-test. Results: In total 76% of preparations were under-prepared around the buccal/labial aspect with only 23% falling within the ideal range of 1.0 to 1.5 mm. The results show mean margin widths of 0.72mm for year four students, 0.73mm for year five students, 0.96mm for clinical teaching staff and 0.79 for general dental practitioners. A two sample t-test comparing margin widths prepared by the different groups investigated, revealed a significant difference (p < 0.05) between both fourth year undergraduates and CTS (p = 0.021) and fifth year undergraduates and CTS (p = 0.011). Shoulder finish lines were observed with greatest frequency as 50% of all preparations, followed by chamfers (~43.8%) and non-standard configurations (~6.3%). Conclusion: The results from this study have shown there to be differences in preparation width between operators of varying experience and overall deficiencies in buccal/labial preparation relative to that recommended in the literature.

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