ABSTRACT
AIM: the aim of the study was to study the effect of stress distribution on the bone around an implant using angled abutments by means of finite element analysis in the anterior maxillary region. MATERIALS AND METHODS: A three-dimensional (3D) model of the of patient's maxilla of right central incisor: tooth, bone, crown, implant, and abutment system were used in this study. The models were designed for three situations with straight abutment, i.e. 0°, 15°, and 20° angled abutment. The load of 178N was applied on the cingulum area of the prosthesis at an angle of 130° in relationship with the long axis of the implant. After applying the static loads on each model, the stress generated in the bone and the implant was recorded. The results will be analyzed by analysis of variance test. RESULTS: The cortical and cancellous on Mises stresses in 20° abutment model were found to be maximum as compared to 15° abutment followed by 0° abutment. The stress was concentrated in the implant-abutment joint area. The overall stresses in 20° abutment model were found to more than 15° abutment followed by 0° abutment. The magnitude of stresses increased as the angulations increased. CONCLUSION: From the conclusions of this study, the stress is more multiplied in angled abutments, hence care needs to be taken when restoring implants using angled abutments, especially in patients with heavy masticatory load or when planning for cantilevering of restorations in these angled implant restoration.
ABSTRACT
AIM: One of the common dental procedures employed these days in patients with irreversible pulpitis is root canal therapy. In retreatment cases, it is necessary for complete removal of obturate gutta-percha (GP) from obturate root canal system. Various methods and techniques are available these days for this purpose. This study was aimed to assess the efficacy of D-RaCe files, ProTaper retreatment files, Mtwo retreatment files, and manual Hedstrom files (H-files) in removing filling materials from the root canals of the endodontically treated teeth. MATERIALS AND METHODS: The present study included comparative evaluation of efficacy of nickel-titanium (NiTi) retreatment instruments and H-files in removing GP and sealer from root canals. All the samples were randomly and broadly divided into four study groups based on the instrumentation technique for removing the root canal fillings. Evaluation of the results was done based on operating time and remaining root canal filling material. Stereomicroscopic evaluation of the samples was done at 8* magnification. RESULTS: All the results were assessed and analyzed by Statistical Package for the Social Sciences (SPSS) software. Least quantity of filling material was left by ProTaper retreatment files. When put together in decreasing order, the efficacy of different study groups, in terms of mean time taken for retreatment, was found to be as follows: D-RaCe > ProTaper Retreatment > Mtwo Retreatment > H-file. CONCLUSION: No single technique can completely remove obturating fillings from the root canals of endodontically treated teeth. However, rotary instruments are better in comparison with hand instruments for removing the GP from obturate root canals. CLINICAL SIGNIFICANCE: ProTaper retreatment files and D-RaCe files are recommended over other instrument systems in terms of quality for managing retreatment root canal cases.
