With the development of science and technology,cosmetic tooth medical science becomes a new developing subject.This article discusses the professional qualities needed as a cosmetic tooth doctor,the pschological characteristics of patients and its corresponding countermeasures from the point of view of medical ethics to obtain satisfactory result for both doctor and patient.

objective: To study the stress distribution of abutment dentin of mandibular complete overdenture based on post core abutment(COBPA). Methods: 3 D FEM was employed to investigate the stress distribution of abutment dentin of mandibular COBPA and natural abutment(NA) on standard model, the data were compared. Results: In the same loading condition, stress concentration was observed at the root end area of dentin in both COBPA and NA. When post core was applied decreased stress distribution area and increased stress value were found aroud tooth neck, decreased stress concentration was found at root end. Conclusion: In COBPA and NA the stress may be transferred to the root end along the axis. Apart from retention, post core can transfer and buffer the stress, change the way of stress transfer, and may result in cervical fracture.

Objective To study the effect of different palatal vault shape on the stress distribution of edentulous maxilla surface.Methods Using three-dimensional finite element method(3-D FED),we simulated five bite states,putting five loading conditions on 3-D FED model of maxillary edentulous with three different palatal vault shapes.Results We obtained the stress value and multicolor picture of 3-D FE model.Labial frenal notch zone and alveolar ridge zone were the stress concentration zone of the maxillary edentulous with three different palatal vault shapes under five kinds of loading conditions.The deep palatal vault maxillary edentulous almost had the maximum stress values in labial frenal notch zone,palate zone and alveolar ridge zone,and upper edentulous jaw with palatal torus was the minimum.Conclusion Palatal vault shape can change the stress value of edentulous maxilla surface,but cannot change the stress distribution.Loading condition can change the stress distribution and stress value.

Objective To construct a temporomandibular joint (TMJ) model including mandible by means of three-dimensional finite element methods and to investigate the stress distribution of the condyle during clenching of edentulous jaw with complete denture.Methods The three-dimensional model (3-DFEM) of TMJ including mandible of edentulous jaw patient was constructed by helix-CT scanned transverse sections.The stress distribution of the condyle was analyzed under load.Results The three-dimensional finite element model of TMJ including mandible of edentulous jaw was established,then loaded and calculated on the corresponding situs of posterior tooth of the model.Analytic results showed the stress on the neck of condyle obviously surpassed that on the top of condyle.The stress decreased from external to interior on anterior and posterior incline,and decreased from anterior to posterior on interior and external incline of the condyle.Compressive stress was dominant in the anterior incline and upper 12 of lateral part (near the top of the condyle),and tensile stress was dominant in the inferior 12 (near the neck),so the lateral inferior part was featured by high stress distribution.In the posterior and interior part,tensile stress occupied the upper 12 and compressive stress was main in inferior 12.Conclusion The edentulous jaw of patients had the compressive stress and tensile stress simultaneously on the whole condyle.But the stress is different in level and feature of distribution.The external anterior incline is featured by the highest stress distribution,and it is consistent with the feature of the TMJ of healthy people.

Objective To find the characteristics of stress distribution on condyle during different vertical distances of edentulous jaw.Methods Three dimensional finite element models of the mandible and temporomandibular joint were established with the complete dentures in different heights by helix-CT scanned transverse sections.The stress distribution of the condyle was analyzed under load.Results The compressive stress and tensile stress coexisted on the whole condyle with the different vertical distances.The trend of distribution was consistent practically,but the stress presented a large difference on different locum.With the decrease of the vertical distance(from H-2 to H-6),the stress presented a decreasing trend but an increasing trend at H-8.Conclusion Changes in the vertical distance produce different effects of stress on edentulous jaw under the same load.

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Objective To investigate the stress distribution in various tooth heights of ferrule effect in post crown,and to evaluate the biomechanical mechanism in post crown.Methods The three-dimensional finite element entity grid model was constructed,which was a maxillary central incisor restored with post and porcelain fused to metal crown (PFM crown).By imitating the various tooth heights under static loading,the dentin stress was analyzed.Results The stress distribution had an increasing tendency from tooth cervix to root,but it could be decreased by ferrule structures and the decrease degree accorded with the region and height of ferrule.The ferrule effect of the wrapping 1 cm coronal tooth could decrease the stress of the tooth cervix obviously but 2 cm decreased a little.Conclusion The crown wrapping 1 cm coronal can produce ferrule effect obviously and protect the tooth.We can choose to use crown wrapping 2 cm coronal to care the tooth condition.

Objective To study the stress distribution on the base of mandibular complete overdenture based on post-core abutment and its su pporting tissues, and to offer experimental foundation and guidance for clinic. Methods 3-D FEM was used to study the stress distribution on the base of mandibular complete overdenture based on post-core abutment and its supporting tissues, calculate the stress values of denture base, mucosality and cortex of bone, then we compared these values with those of natural abutment . Results Base plate of mandibular complete overdenture had stress concentration phenomenon at abutment zone. The stress value of mucosa on bilateral molar teeth alveolar ridge crest was relatively larger. Cortex of bon e mainly bore compressive stress; cortex of bone around the abutment had obvious stress concentration. Conclusion Denture base may fracture at abutment zone; cort ex of bone around abutment relatively bears more stress, so bone absorption may easily arise. Post-core has little influence on stress distribution of denture base and of mucosa ,while it does have some influence on that of cortex of bone.

Objective To study the stress distribution of mandibular complete overdenture based on post-core abutment with various height of core and its supporting tissues, and to offer experimental foundation and guidance for clinical work. Methods 3-D FEA models of mandibular complete overdenture were set up based on post-core abutment and its supporting tissues; vertical loading was imposed on denture; the stress values of denture and its supporting tissues were calculated and analyzed, with the height of core as 3 mm, 4 mm, 5 mm and 6 mm, respectively. Results With the height of core increasing, the stress in dentine, parodontal membrane, denture base plate and cortical bone increased, while the stress in mucosality hardly changed. Conclusion Under the premise of retention, the height of core should be decreased as much as possible to maintain the health of the tissues.

Objective To construct three-dimensional finite element model (3-D FEM) of maxillary complete denture and its supporting tissues with different shapes of palatal vault and different teeth cusp inclination. Methods Based on the data of 3-D measurement, using MATLAB 6.1 and ALGOR FEAS software, 3-D FEM was constructed by computer. Results 3-D FEM of maxillary complete denture was constructed with three different palatal vault and three different teeth cusp inclination (10?, 20?, 30?) and supporting tissues. Conclusion 3-D FEM can be used for the analysis of the effect of different shapes of palatal vault and different teeth cusp inclination on the stress distribution of maxillary complete denture under different loading conditions.