[Analysis of the movement of long axis and the distribution of principal stress in abutment tooth retained by conical telescope].

OBJECTIVE: To study the movement of long axis and the distribution of principal stress in the abutment teeth in removable partial denture which is retained by use of conical telescope. METHODS: An ideal three dimensional finite element model was constructed by using SCT image reconstruction technique, self-programming and ANSYS software. The static loads were applied. The displacement of the long axis and the distribution of the principal stress in the abutment teeth was analyzed. RESULTS: There is no statistic difference of displacenat and stress distribution among different three-dimensional finite element models. Generally, the abutment teeth move along the long axis itself. Similar stress distribution was observed in each three-dimensional finite element model. The maximal principal compressive stress was observed at the distal cervix of the second premolar. CONCLUSION: The abutment teeth can be well protected by use of conical telescope.

[Comparative evaluation of the tiled abutment teeth restored with or without fixed bridge on stress distribution by anisotropic finite element method].

OBJECTIVE: To compare the tilted abutment teeth restored with or without fixed bridge on stress distribution by anisotropic finite element method when the vertical and the oblique loads are simulated. METHODS: Three-dimensional finite element model was constructed by using SCT image reconstruction technique, self-programming and ANSYS software with the anisotropic elasticity data. The static loads were simulated according to the restored and unrestored situation. The stress distribution and stress level of the second molar was recorded. RESULTS: When the vertical static load was simulated, the stress distribution of the tilted abutment teeth was much improved. Tensile stresses appeared dominantly on the mesial apex of the second molar (31.0 Mpa) before restoration and on the distal apex of the second molar (20.2 Mpa) after restoration. When the oblique load was simulated, the stress distribution changed a little. CONCLUSION: The stress distribution of the tilted abutment can be improved by restorative techniques with the use of fixed bridge; however, the clinician should lower the height of the cusp to reduce the oblique load of the abutment.

[Three-dimensional finite element stress distribution and displacement analysis of alveolar ridge retained by conical telescope].

OBJECTIVE: To study the stress distribution and displacement of edentulous alveolar ridge of removable partial denture which is retained by using conical telescope. METHODS: An ideal three dimensional finite element model was constructed by using SCT image reconstruction technique, self-programming and ANSYS software. The static load was applied. The stress and displacement characteristics of these different types of materials which form the metal part of the conical telescope were compared and analyzed. RESULTS: Generally, the four materials produced almost the same stress and displacement at the site of the edentulous alveolar ridge. CONCLUSION: From the viewpoint of dynamics, the application of different materials in making the metal part of conical telescope is feasible.

[Stress distribution on periodontium of separated removable partial denture assembly].

OBJECTIVE: The objects of the present study were to construct a computer model and to evaluate the load and stress of denture by means of three dimensional finite element analysis in order to provide evidence for clinic application. METHODS: The study utilized CT to scan the maxilla of a healthy man to receive the primal data, and then used Materialise Mimics 9.1 to establish a series of two-definite images artificially and automatically. The three dimensional finite element model of partial maxilla, including teeth, bone and softy tissue, could be constructed in Pro/Engineer WF 2.0 software by using related commands. The separated removable partial denture assembly was finally set up according to the denture design in Pro/Engineer WF 2.0. After converting data into Ansys Workbench 9.0, the command of meshing was fulfilled. Applying different loads on artificial teeth, the data about the stress on the periodontium, abutment and supporting tissue were obtained. RESULTS: Statistical comparisons showed that the stresses of periodontal membranes had no significant differences, but the periodontium under saddle changed greatly under different loads. CONCLUSION: This study shows that the separated removable partial denture assembly can undertake the retention and load respectively due to special design. It is the two layers of bases that can protect the healthy of abutments. This design may be applicable for the restoration of the tooth with poor periodontium around abutments.

The relationship between IL-1 gene polymorphism and marginal bone loss around dental implants.

PURPOSE: Early marginal bone loss around dental implants has been found during the bone healing period before stage II surgery despite a lack of apparent cause, and the etiology of this bone loss is unclear. This study was designed to investigate whether interleukin-1 gene polymorphism is associated with the marginal bone loss around the implants before stage II. MATERIALS AND METHODS: One hundred forty-three implants were placed in 59 patients. The patients were divided into 2 groups: 1) test group: with 1 or more marginal bone loss greater than 0.5 mm; and 2) control group: with marginal bone resorption less than 0.5 mm. Polymorphisms of the IL-1alpha and IL-1beta genes (IL-1A-889, IL-1B-511, and IL-1B+3954) were detected by restriction fragment length polymorphism using Ncol, AvaI, and TaqI digestion after polymerase chain reactions. RESULTS: The frequency of IL-1B-511 II/II was significantly higher among patients in early marginal bone loss (+) group than those in early marginal bone loss (-) group (P < .05). Multiple logistic regressions showed the OR of the II/II versus the I/I+I/II of the IL-1B-511 genotype was 3.933 between the 2 groups. The difference was statistically significant (P < .05). There was no significant difference between the other risk factors. CONCLUSION: These results suggest that the IL-1B-511 II/II genotype in individuals is associated with early marginal bone loss around implants.

[Determination and analysis of masticatory performance of nonfree-end removable partial denture].

OBJECTIVE: The purpose of this study was to evaluate the changes of masticatory performance of the cases wearing dentures and relative factors. METHODS: The changes of masticatory performance of the cases wearing dentures were studied before and after wearing by using the light absorption method and peanuts as test food. RESULTS: The mastication performance of the experimental groups was predominantly lower than that of the control groups. The masticatory performance was gradually improved with wearing denture period increasing. Factors relating to the masticatory performance were age, number of occlusal units lost and the kind of denture, and the number of chewing etc. CONCLUSION: The mastication performance of the experimental groups was dominantly lower than that of the control groups, but gradually improved with wearing denture period increasing. Varied factors affect the masticatory performance of experimental groups.