The purpose of this study was to evaluate the influence of direct base and indirect inlay materials on stress distribution and fracture resistance of endodontically treated premolars with weakened cusps. Forty healthy human premolars were selected; five were left intact as controls (group C+), and the others were subjected to endodontic treatment and removal of buccal and lingual cusp dentin. Five teeth were left as negative controls (group C-). The remaining 30 teeth were divided into two groups according to the direct base material (glass ionomer [GIC] or composite resin [CR]). After base placement, each group was subjected to extensive inlay preparation, and then three subgroups were created (n=5): no inlay restoration (GIC and CR), restored with an indirect composite resin inlay (GIC+IR and CR+IR), and restored with a ceramic inlay (GIC+C and CR+C). Each specimen was loaded until fracture in a universal testing machine. For finite element analysis, the results showed that the removal of tooth structure significantly affected fracture resistance. The lowest values were presented by the negative control group, followed by the restored and based groups (not statistically different from each other) and all lower than the positive control group. In finite element analysis, the stress concentration was lower in the restored tooth compared to the tooth without restoration, whereas in the restored teeth, the stress concentration was similar, regardless of the material used for the base or restoration. It can be concluded that the inlay materials combined with a base showed similar behavior and were not able to regain the strength of intact tooth structure.
<p><strong>Objectives: </strong>The aim of this study was to evaluateby electromyography the activity of the temporalisand masseter muscles in removable partial dentures(RPDs) users, before and after new RPDs installation.<strong>Material and Methods: </strong>Ten patients were selectedfor this study. All subjects were edentulous in theposterior mandibular region (Kennedy class I orII), fully dentate in the antagonist arch, and dentalprosthesis users, which needed to be replaced. Theelectromyographic activity (EMG) recorded thesuperficial masseter and temporalis muscles, duringthe maximum voluntary bite force and the restposition. Maximum mouth opening was also verified.The measurements were recorded at four specifictimes: using the old prosthesis (T0), right after thenew prosthesis installation (T1), two weeks (T2) andfour weeks (T4) after installing the new prosthesis.All the RPDs were made by an experienced dentistand the same laboratory. Data were statisticallyanalyzed by ANOVA and Tukey tests (α = 0.05).<strong>Results: </strong>EMG values had high standard deviation atthe time T0. Generally, the mean values decreasedafter new prosthesis installation, especially aftertwo weeks from the installation (T2). During therest position, the left masseter and left temporalismuscles showed statistically significant gradualdecrease in their activities over time. <strong>Conclusion:</strong>New prostheses have positive effect on the patient’smuscular activity. However, an adaptation period ofthe muscle fibers to the new prosthesis is needed.</p><p>Keywords<br />Electromyographic activity; Dental occlusion; Masseter; Removable partial dentures; Temporalis.</p>
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