Effect of mouth-motion fatigue and thermal cycling on the marginal accuracy of partial coverage restorations made of various dental materials

Objectives. To investigate the influence of mouth-motion fatigue on marginal-accuracy of partial-coverage-restorations-(PCRs) of various dental materials. Methods. Eighty molars were prepared equally and divided into five groups (n = 16). PCRs were fabricated of following dental materials: Group-GO = Gold-Pontor-MPF double dagger, Group-TA = Targis*, Group-EX = IPS-e.max-Press*, Group-EM = IPS-Empress*, Group-PC = ProCAD*/Cerec 3(dagger) ((double dagger)Metalor/*Ivoclar-Vivadent/(dagger)Sirona-Denral-System). Gold-PCRs were cemented conventionally. Residual 64 PCRs were adhesively luted and subjected to masticatory loading (1.2million-cycles, 1.6 Hz, 49 N) and thermal cycling (5 degrees C/55 degrees C, 60s, dwell-time, 5500cycles). Discrepancies in marginal-accuracy were examined on epoxy replicas (200x magnification). Statistical analysis was performed by unpaired and paired t-tests (alpha=0.05). Results. After cementing, marginal-accuracy (geometrical mean)[95% confidence limits] was recorded: GO-47[43-51]mu m, TA-42[38-45]mu m, EX-60[52-67]mu m, EM-52[45-60]mu m and PC-75[59-94] mu m. No significant differences were found between groups GO, TA and EM. Values of Group-EX were significantly higher compared to Group-TA (p = 0.04). Group-PC demonstrated significantly decreased marginal-accuracy towards groups GO (p = 0.03) and TA (p = 0.02). Except for Group-GO (p = 0.01), no significant changes in marginal-accuracy were observed after mouth-motion fatigue and thermal cycling (GO-42[38-45] mu m, TA-42[38-47] mu m, EX-56[49-65]mu m, EM-54[46-64] mu m and PC-71[59-84]mu m Lm). However, Group-GO and Group-EM showed significant deviations in marginal-accuracy after aging (P = 0.04). Marginal discrepancies of groups EX and EM were similar (p=1.0). Values of Group-PC were significantly higher when compared to groups GO (p = 0.01) and TA (p = 0.02). Buccal-lingual marginal discrepancies were significantly higher than mesial-distal in all groups and stages. Significance. Cast-gold-PCRs demonstrated superior marginal-accuracy, followed by indirect ceromer PCRs. All-ceramic PCRs showed in vitro clinical acceptable marginal widths, even though CAD/CAM fabrication slightly compromised marginal-accuracy. Since preparation margins were not exposed to occlusal loading directly, increased marginal discrepancies due to marginal chipping during mouth-motion fatigue were not experienced. (c) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.