Evaluation of the marginal fit of three margin designs of resin composite crowns using CAD/CAM

Abstract 

Objectives

To examine the marginal fit of resin composite crowns manufactured with the CEREC 3 system employing three different margin designs; bevel, chamfer and shoulder, by means of a replica technique and a luting agent.

Methods

Three master casts were fabricated from an impression of a typodont molar tooth and a full-coverage crown prepared with a marginal finish of a bevel, a chamfer and a shoulder. Each cast was replicated 10 times (n=10). Scanning of the replicas and crown designing was performed using the CEREC Scan™ system. The crowns were milled from Paradigm MZ100™ composite resin blocks. The marginal fit of the crowns was evaluated with a replica technique (Aquasil™ LV, Dentsply), and with a resin composite cement (RelyX™ Unicem, Aplicap™) and measured with a travelling microscope. Statistical analysis was performed using two-way ANOVA.

Results

For the replica technique the average marginal gaps recorded were: Bevel Group 105±34μm, Chamfer Group 94±27μm and Shoulder Group 91±22μm. For the resin composite cement the average marginal gaps were: Bevel Group 102±28μm, Chamfer Group 91±11μm and Shoulder Group 77±8μm. Two-way ANOVA analysis showed that there was no statistically significant difference between the three groups of finishing lines regardless of the cementation technique used.

Conclusions

The marginal gap of resin composite crowns manufactured with the CEREC 3 system is within the range of clinical acceptance, regardless of the finishing line prepared or the cementation technique used.

Keywords: Resin composite, Resin composite crowns, Dental materials, CAD/CAM, CEREC, Marginal gap, Replica technique