Effects of Thermocycling and Occlusal Force on Adhesive Composite Crowns

Abstract

The aim of this in vitro study was to provide first quantitative data on the marginal adaptation and the required load to fracture of adhesive composite crowns with and without adhesive composite cores. Eighteen caries-free extracted human premolars were restored using fine hybrid composite crowns with margins located entirely in dentin. Six crowns were adhesively luted to dentin stubs, six to endodontically treated teeth with adhesive titanium posts and adhesive composite cores, and six to adhesive composite cores without posts. Another ten unprepared teeth served as a control. All restored teeth were subjected to long-term occlusal and thermal stresses. The marginal adaptation was evaluated in the SEM before and after loading. Load to fracture was recorded at the end of the stress. Before stressing, 72.2 to 85.0%, and after stressing, 51.9 to 66.2% of "continuous margin" were recorded at the dentin-luting composite interface. The best results after stressing were achieved with crowns luted to adhesive composite cores without titanium posts. At the luting composite-composite crown interface, 61.6 to 88.7% of "continuous margin" before and 57.7 to 75.5% after stressing were recorded. The required load to fracture the restored teeth ranged from 72.0 to 89.2% of the unrestored, unloaded control. Adhesive composite cores without titanium posts yielded the best results.

Biomechanical Evaluation of a Tooth Restored with High Performance Polymer PEKK Post-Core System: A 3D Finite Element Analysis

“…For a fatigue analysis in the FEA study, S - N (stress versus number of cycles to failure) curves of the materials are required. The S - N curve of dentine was referenced from a previous study [27]. Generally, the S - N curves of materials, when no experimental data are available, can be estimated by the following formula (flexural strength ( S f ) versus number of cycles): (0.9 · S f versus 10 3 ), (0.5 · S f versus 10 6 ), and (0.5 · S f versus a number of cycles greater than those tested) [25].…”

Fracture strengths of endocrown restorations fabricated with different preparation depths and CAD/CAM materials

“…Whereas metal posts may cause non-repairable fracture of the root because of higher stress distribution 8) , fiber posts which have similar elasticity moduli with dentine may overcome this problem 9) . Moreover, several studies in the literature have reported that the application of the posts causes weakening of the roots, in addition to the perforation risk during the preparation of the post space 10,11) . As of yet, there is no established consensus on whether the post length affects the fracture resistance of teeth.…”

Premolars restored with posts of different materials: fatigue analysis

“…These conditions are believed to simulate, approximately, 5 years of clinical service 35) . This number of cycles have been used in several fatigue studies [12][13][14][15][16]36,37) .…”