The Study Of The Prevalence Of Temporomandibular Disorders In Edentulous Individuals

Objective: To study the prevalence of temporomandibular disorders(TMD) in352aged edentulous individuals and to evaluate stress distribution of condyle in edentulousjaw and compare the strength of the condyle in edentulous jaw with different occlusiontypes using three-dimensional finite element analysis (3D-FEA). To analyze thecorrelative risk factors of TMD．Subjects and Methods: Three hundred and fifty-two aged edentulous subjects wereincluded in the study(198males and154females)．The adopted questionnaire wasdesigned according to Helkimo index，and the subjects were examined by the sameexaminer who would record every result as well．A three-dimensional(3D) finiteelement model (FEM) of the edentulous mandible and TMJ was created by helix-CTscanned and mimics l0.01(Materialise’s Interactive Medical Image Control System，Belgium) and analyzed by Abquas6.11to obtain the condition of the stress distribution.Compare the value of the two kinds of occlusion types. The FEM model was appliedwith hibateral molars loads(100N) by perpendicular to molars(L1) and30oblique in abuccal direction(L2). The top of the condyle and mandibular angle were fixed in alldegrees of freedom.Results: Results: The prevalence of TMD’s clinical positive signs in the edentuloussubjects was43.2％(152/352)，among which temporomandibular joint(TMJ) noise [34.1％(120/352)] was the highest prevalent sign while TMJ pain on movemert was thelowest．The prevalence of mandibular movement deviation[18.2％(64/352)] fitted inbetween．The prevalence of TMD’S clinical positive signs of male individuals was36.9％(73/198)，and the female was51.3％(79/154)．There was a significant difference in prevalence of TMD’S clinical positive signs between males andfemales(P=0.0067<0.01)．The prevalence of TMD’s clinical positive signs in denturewearing group was38.6％(91/236) and that in no denture group was52.6％(61/116)．There was a significant correlation between the prevalence of TMD’s clinicalpositive signs and wearing denture [P=0.0125<0.05, OR=1.767(1.130-2.763)]．Theprevalence of TMD’s clinical positive signs in cross bite(malocclusion) grouop was59.03%(36/61)，and normal occlusion group was39.86%(116/291). There was asignificant correlation between the prevalence of TMD’s clinical positive signs andmalocclusion[P=0.0060<0.01, OR=2.172(1.248～3.779)]. The von mises concentratedthe condyle neck area. Compression stress was more evident than tensile stress on thetop of the condyle and anterior incline; Tensile stress was more evident thancompression stress on the neck of the condyle; The mean stress value of L1conditionwas4.68Mpa and that was7.20Mpa in L2condition.Conclusion: Gender and malocclusion may be the risk factors of TMD inedentulous individuals．The mean stress value of the condyle in edentulous jaw withcrossbite occlusion was greater than that of normal occlusion.