Crown Of Maxillary First Molar Research Articles

Stress distribution on implant- supported zirconia crown of maxillary first molar: effect of oblique load on natural and antagonist tooth

This study evaluated the stress distribution on an implant-supported zirconia crown of a mandibular first molar subjected to oblique loading by occlusal contact with the natural maxillary first molar by using the 3D finite element method. Two virtual models were made to simulate the following situations: (1) occlusion between maxillary and mandibular natural first molars; (2) occlusion between zirconia implant-supported ceramic crown on a mandibular first molar and maxillary natural first molar. The models were designed virtually in a modeling program or CAD (Computer Aided Design) (Rhinoceros). An oblique load of 100 N was uniformly applied to the zirconia framework of the crown. The results were obtained by the Von Mises criterion of stress distribution. Replacement of the mandibular tooth by an implant caused a slight increase in stress on portions of the maxillary tooth roots. The crown of the maxillary model in occlusion with natural antagonist tooth showed 12% less stress when compared with the maxillary (model in occlusion with the) implant-supported crown. The mandibular crown of the implant show 35% more stress when compared with the mandibular antagonist crown on the natural tooth. The presence of the implant to replace the mandibular tooth increased the stresses on the maxillary tooth, especially in the region of the mesial and distal buccal roots.

Physiological drift of teeth in upper arch after bi-maxillary first premolar extraction

Objective To study the distance and pattern of the movement of the maxillary teeth after 6 months driftodontics for dental crowding.Methods 20 dental crowding children,according to the treatment plan,who were required to removal four first premolars,were involved in this study (8 males,12 females,aged 11-14 years old).All of the children did not wear appliance in six months after teeth extraction.X-ray image data before and six months after teeth extraction were collected.The width of extraction space,the anterior irregular index and inclination of the axis of each tooth were recorded before and six months after tooth extraction.The data were analyzed by t-test and Pearson relative analysis.Results The study model showed that bilateral maxillary space of extraction pre-and pro-driftodontics decreased (5.79 ± 4.9) mm (P ＜ 0.01) ; anterior crowding decreased (5.79± 4.12) mm,irregular index was significantly reduced (P＜0.01).Cephalometric film measurement showed that canine crown moved distally (4.87±3.54) mm after the drift (P＜0.01).Canine tooth axis changed from mesial to upright.The crown of maxillary first molar moved mesially (1.18± 0.52) mm (P ＜ 0.01).There were no significant changes in apical position.Conclusions After 6 months of the physiological drift,upright moving of canine relieves anterior teeth crowding.The molar anchorage is saved. Key words: Physiological drift; First premolar; Maxillary