Load bearing capacity of minimal invasive direct and indirect veneers bonded to maxillary incisors with severe wear: effect of preparation design and material type

Abstract

This study evaluated the load bearing capacity of direct and indirect veneers vs. full-coverage crowns and classified the failure types after fracture load. Sound human maxillary incisors (N = 108, n = 12 per group) were randomly divided into nine groups to receive one of the following restoration types: Group 1: Intact tooth, Group 2: Direct resin composite, Group 3: Lingual: Indirect composite veneer, Labial: Ceramic veneer, Lingual overlap: Ceramic, Group 4: Lingual: Indirect composite, Labial: Ceramic, Lingual overlap: Indirect composite, Group 5: Lingual: Direct composite, Labial: Ceramic, Group 6: Lingual: Ceramic, Labial: Ceramic, Group 7: Feldspathic ceramic crown, Group 8: Metal-ceramic Crown, Group 9: Lithium disilicate crown. Teeth were prepared simulating the erosion/wear conditions in each group. After cementing, the specimens were stored in distilled water at 37 °C for 2 months and then loaded to failure from the lingual surface at 105° inclination in the Universal Testing Machine (1 mm/min). Failure types were classified as irreparable or repairable. Data were analyzed using one-way ANOVA, Sheffe and Bonneferroni tests (α = 0.05). Mean fracture strength (N) of Groups 1, 4, 8, and 9 (558 ± 278 – 880 ± 319) were significantly higher than those of other groups (348 ± 101–421 ± 162) (p < 0.05). Lingual veneering with direct/indirect resin composite or ceramic did not significantly affect the results (p > 0.05) but lingual overlap with indirect composite increased the results (p < 0.05). Group 1, 2, 4 and 5 presented more repairable failures. Restoration of eroded teeth could best be achieved with direct composite veneer at the lingual and ceramic veneer on the labial surface.

Keywords:

• Erosion
• laminates
• minimal invasive
• static loading
• veneers
• wear

Acknowledgements

The authors acknowledge Mr. A. Trottmann, V. Fehmer, A. Keller, CDT, for their assistance with the specimen preparation, Dr. M. Roos from the Division of Biostatistics, Institute of Social and Preventive Medicine, University of Zurich, for her support with the statistical analysis.