Methods: Human extracted teeth (44 and 47) with prepared post-spaces were duplicated by composite resin. Composite resin cores with glass fiber posts were fabricated and bonded using adhesive composite resin cement. Five 4-unit zirconia FPD frameworks were fabricated and bonded to the specimens using adhesive composite resin cement. Each root was surrounded with a layer of vinyl polysiloxane as artificial periodontal ligament, and all specimens were embedded in acrylic resin. The rosette strain gauges were cemented at mesiobuccal (MB) and mesiolingual (ML) root surfaces of molar, distobuccal (PB) and distolingual (PL) root surfaces of premolar with strain-gauge cement. Specimens were loaded (200N) on the occlusal surface. The loading points were center of premolar (CP), pontic (CD), and molar (CM). Then the magnitude and direction of principal strain were calculated. The data were statistically analyzed (two-way ANOVA, Bonferroni correction, Bonferroni test, p<0.05).
Results: The magnitude of maximum principal strain (με) of PB, PL, MB, ML when loaded CD were 237.5±43.7, 211.2±23.9, 127.0±38.4, 140.7±42.0, respectively. Those of minimum principal strain of PB, PL, MB, ML when loaded CD were -960.1±264.7, -986.0±169.6, -565.9±78.9, -506.1±183.3, respectively. PB and PL showed significantly higher magnitude of maximum and minimum principal strain than MB and ML (p<0.05).The magnitude of maximum principle strain of PB, ML when loaded CP were 119.2±24.9, 57.5±27.5, respectively. PB showed significantly higher magnitude of maximum principal strain than ML (p<0.05).
Conclusions: In this study, the strain values of abutment root surface of premolar were larger than those of molar during loading.