The restoration of endodontically treated teeth is always a topic of crucial attention for dentists. If until a few years ago, the therapeutic choice of rehabilitating these elements with a post and a crown was unquestionable, nowadays adhesive dentistry is becoming increasingly popular and has proposed other therapeutic solutions, as partial indirect restorations, with the aim to preserve as much healthy dental tissue as possible.
The therapeutic choices discussed and evaluated in the study of Dejak et al. was performed by evaluating the masticatory stresses that endocrowns and crowns with posts underwent in endodontically treated mandibular molars.
Materials and Methods
Four three-dimensional models of first mandibular molars were created and divided into 4 groups:
1) intact tooth as control group;
2) tooth restored by leucite-reinforced ceramic endocrown;
3) tooth with fiber posts, composite core and leucite reinforced ceramic crown;
4) tooth with cast post and leucite-reinforced ceramic crown.
Crowns and endocrowns were cemented by Variolink II composite luting cement (Ivoclar).
The study was performed using finite element analysis, with contact elements. The computer simulations of mastication were conducted. The equivalent stresses of modified von Mises failure criterion (mvM) in models were calculated, Tsai-Wu index for FRC post was determinate. Maximal values of the stresses in the ceramic, cement and dentin were compared between models and to strength of the materials. Contact stresses in the cement–tissue adhesive interface around restorations were considered as well.
During masticatory simulation, these were the maximal mvM stress values (MPa) showed during the test:
-intact tooth (as control group): 10.7 (vs Enamel/ceramic restoration); 3.4 (vs dentin); / (vs posts); / (vs resin composite luting cement);
-tooth with endocrown: 16.5 (vs Enamel/ceramic restoration); 2.6 (vs dentin); / (vs posts); 1.8 (vs resin composite luting cement);
-tooth with FRC post and resin composite cores: 21.0 (vs Enamel/ceramic restoration); 3.7 (vs dentin); 0.18 (vs posts); 2.9 (vs resin composite luting cement);
-tooth with cast post and cores: 17.6 (vs Enamel/ceramic restoration); 3.2 (vs dentin); 49.5 (vs posts); 2.1 (vs resin composite luting cement).
The lowest stressed values were recorded in molar restored with endocrown. So we can conclude that molars restored by endocrowns are potentially more resistant to failure than those with FRC posts. Under physiological loads, ceramic endocrowns ideally cemented in molars should not be demaged or debonded.
For additional informations: 3D-Finite element analysis of molars restored with endocrowns and posts during masticatory simulation
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