Reliability of Various Depth Guiding Methods in Preparation of Full Crowns Used by Dental Undergraduates

This study compares the effects of different depth guiding techniques used by undergraduates on improving the reliability of full crown tooth preparation.

A primary virtual model was designed by making a 3-dimensional print of a scanned standard artificial tooth #11 and the base. Thirty undergraduate students were divided into three groups based on different depth guiding techniques tested: depth groove group (G), silicone indices group (S) and depth hole group (H). The participants prepared the teeth 10 times after being informed of the required amount of preparation at different sites. The prepared models were matched virtually with the primary model. The preparation depth of three groups at twenty-nine sites per tooth was measured and compared against the recommendation. Additionally, curves showing the relationship between preparation depth and preparation count were obtained.

The depth guiding technique and preparation count had different effects on the preparation depth in different sites. Excluding the finish line, the different methods had a significant impact on the preparation depth at other measured sites (p < 0.05). Comparing the actual preparation depth for each group with the recommendation, the qualified ratio was 45.29% in group H, 38.00% in group S and 26.57% in group G. The preparation count also had a significant impact on the preparation depth (p < 0.05).

The depth hole method was the most effective in controlling the preparation depth for undergraduate dental students, while the depth groove method performed the least effectively. In the finish line area, the operators' proficiency in tooth preparation appeared to be more dominant than the guiding method for the reliability of its preparation.