Aim:Endodontic treatment generally reduces the fracture resistance of teeth. The purpose of this study was to evaluate the fracture resistance and the mode of fracture of endodontically treated human premolars with different amounts of remaining tooth structure.Materials and Methods:Seventy non-carious human premolars were randomly assigned into 7 groups. Group 1 (ST) did not receive any preparation. The teeth in groups 2-7 received root canal treatment and different preparations. Group 2 (MO-NF): Mesio-occlusal preparation without filling; Group 3 (MOD-NF): Mesio-occluso-distal preparation without filling; Group 4 (MO-F): Mesio-occlusal preparation with direct composite restoration (Z250); Group 5 (MOD-F): Mesio-occluso-distal preparation with direct composite restoration (Z250); Group 6 (CC-D): Mesio-occluso-distal preparation with cusp reduction and direct composite restoration (Z250); Group 7 (CC-InD): Mesio-occluso-distal preparation with cusp reduction and indirect composite restoration (Gradia GC). The fracture resistance (N) was assessed under compressive load in a universal testing machine (Zwick) perpendicular to the occlusal surface at a cross-head speed of 1 mm/min, and the mode of fracture was assessed under stereomicroscope.Statistical analysis:Data was analyzed by Kruskal – Wallis and Mann – Whitney tests and the mode of fracture was analyzed by Chi-square test (P < 0.05).Results:Statistical analysis showed that MO and MOD cavity preparations significantly reduced the fracture resistance of sound teeth. Direct composite restorations can improve the fracture resistance, and Groups 7 and 6 presented the highest fracture resistance values.Conclusions:Teeth with adhesive restorations showed significantly higher fracture resistance values as compared with the non-restored ones.

Introduction:A correct diagnosis and optimal treatment planning is essential for success in implant dentistry. Proper diagnosis of bone quality is an important part of the diagnostic procedure.Objective:The purpose of this study was to correlate the tactile sense of the surgeon in the assessment of bone density to the histomorphometric analysis of bone quality.Methods:In this study, 56 bone samples from 33 patients were harvested from implant sites with trephine drills. The samples were analyzed with Image J software. In the samples following parameters were measured: BV/TV, superficial cortical plate thickness, the number and thickness of haversian canals in cortical bone and the number, thickness and distance of trabecules in cancellous bone. The clinical hardness of bone during drilling was evaluated by surgeon according to Misch. GEE analysis with exchangeable correlation structure and linear model was used to evaluate the relationship between the tactile sense of the surgeon and histomorphometric parameters and all analysis was adjusted for two confounding variables: gender and location.Results:There were 51.79% implants in D2 samples and 48.21% in D3. Bone classification according to Misch was significantly correlated to distance of trabecules in cancellous bone (P-value=0.05), and shown marginally significant correlation with mean superficial cortical bone thickness (P-value =0.07) and number of haversian canals (P-value =0.005) in cortical bone.Discussion:There were differences between our results and others. The authors believed that these differences mainly are because of confounding factors, that in this study were eliminated. The clinical finding during surgery can approximately explain the histologic properties of bone.Conclusion:It is concluded that tactile sense of the surgeon can exhibit the histologic properties of the bone, and we are able to estimate the healing prognosis of the bone in implant placement.