Effect of Magnification on the Precision of Tooth Preparation in Dentistry.

OBJECTIVES:   To evaluate the impact of magnification aids on the precision of tooth preparation under simulated clinical conditions.

METHODS AND MATERIALS:   Two plastic blocks marked with a geometric shape were fixed in a dental phantom head: a circle as the distal surface of tooth 16 (UNS 3) and a y-shaped figure as the occlusal surface of tooth 36 (UNS 19). Sixteen dentists (mean age: 39 years; range: 26-67 years) prepared the geometric shapes from the inside to the boundary line with a cylindrical bur and water-cooling. The boundary line had to be touched but not erased. Chair-side assistance was provided to simulate the clinical situation. Tooth 16 was prepared under indirect vision via a dental mirror. Tooth 36 was prepared under direct vision A) without magnification aids, B) with Galilean loupes, 2.5× and light-emitting diode light, and C) with a microscope, 6.4× and coaxial light. The preparation procedure was performed three times in different sequences of the magnification devices and with a break of at least 1 week between each procedure. The correctly prepared contour and the incorrectly prepared areas were evaluated in relation to the whole circumference of the geometric shapes.

RESULTS:   For both values the precision was significantly higher when a microscope was used, followed by preparation using loupes; precision was lowest without magnification aids ( p<0.0001). This was true for both indirect and direct vision ( p<0.05).

CONCLUSIONS:   Magnification devices improved the precision of tooth preparation under simulated clinical conditions.