Secondary trauma from occlusion Threedimensional analysis using finite element method

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Slide 1 : Secondary trauma from occlusion: Three-dimensional analysis using finite element method Allahyar Geramy DDS,MSc Associate Professor, Orthodontic department Tehran University of Medical Sciences Dental research Center, (DRC-TUMS) Tehran University of Medical Sciences (TUMS)
Slide 2 : This lecture is based on: Geramy A, Faghihi Sh. Secondary trauma from occlusion: three-dimensional analysis using finite element method. Quintessence Int 2004;35:835-843.
Slide 3 : Occlusal trauma is defined as an injury to the attachment apparatus as a result of excessive occlusal force. The role of occlusal trauma in the pathogenesis of periodontal disease has been studied since the beginning of the 20th century. Research on the effects of occlusion on periodontal health has been challenging and the results are often inconclusive and contradictory.
Slide 4 : “Does occlusal trauma modify the progression of attachment loss in periodontitis?” A question to be answered in details
Slide 5 : Researches to study the effects of trauma from occlusion are divided into 3 categories: 1- Human Cadaver Investigation 2- Animal Studies 3- Human Clinical Studies
Slide 6 : Human Cadaver Investigation Published between 1960s and 1970s. They were inconclusive Better to say, almost nothing was added to our information upon which to decide what to do!
Slide 7 : Animal Studies Different animal models were studied. A list of famous researchers can be formed who worked on this topic in animal models. “ In the presence of inflammation, trauma from occlusion may enhance the rate of disease progression , acting as a destructive co-factor .” “Glickman” As a conclusion to these literature:
Slide 8 : Human Clinical Studies Few clinical studies have identified a clear relationship between trauma from occlusion and inflammatory periodontitis in human. A major problem with this type of clinical studies is the lack of a reliable index for measuring the degree of occlusal trauma to which a tooth is subjected. According to some studies, when trauma from occlusion is superimposed on progressive periodontitis, there is both an increase in amplitude of mobility and a prolonged phase of progressively increasing mobility.
Slide 9 : According to the categories defined and their limitations: Finite element method of analysis is the unique method by which an accurate quantitative answer can be obtained to explain the importance of the alveolar bone loss in patients who may be referred for treatment
Slide 10 : What is finite element method (analysis) The limitations Of human mind are such that it cannot grasp the behavior of its complex surroundings and creations in one operation. Thus the process of subdividing all systems into their individual components or ‘elements’, whose behavior is readily understood … and then rebuilding the original system from such component to study its behavior is a natural way in which the engineer, scientist, economist,… proceeds.
Slide 11 : The finite-element method originated from the needs for solving complex elasticity, structural analysis problems in civil engineering andaeronautical engineering..
Slide 12 : Its development can be traced back to the work by Alexander Hrennikoff (1941) and Richard Courant (1942).
Slide 13 : While the approaches used by these pioneers are dramatically different, they share one essential characteristic: mesh discretization of a continuous domain into a set of discrete sub-domains
Slide 14 : Materials & Method
Slide 15 : 5 Three-dimensional FEMs were designed of a central incisor With normal alveolar bone height With 1.0 mm of alveolar bone loss With 2.5 mm of alveolar bone loss With 5.0 mm of alveolar bone loss With 6.5 mm of alveolar bone loss With 8.0 mm of alveolar bone loss
Slide 16 : Normal model Frontal view Mesial view
Slide 17 : Alveolar Bone Loss Model Mesial view Frontal view
Slide 18 : Different Materials Used
Slide 19 : Mechanical Properties for the structural element of the study Material Data According to my Previous Studies
Slide 20 : Applied force 1.5 N 45 degrees to Horizontal Plane In palatal side of the incisal edge In a palato-labial Magnitude Direction Point of application Sense
Slide 21 : Maximum Principal (S1)Minimum Principal Stress(S3)were evaluated in PDL In a Path of nodes from apex up to the cervical part in the labial surface
Slide 22 : results
Slide 23 : Output data for S1 and S3 in varying degrees of alveolar bone loss in PDL (N/mm2)
Slide 24 : Stress pattern in normal alveolar height
Slide 25 : S1 & S3 modification
Slide 26 : S1 & S3 modification
Slide 27 : S1 & S3 modification
Slide 28 : S1 & S3 modification (6.5 mm of alveolar bone loss)
Slide 29 : S1 & S3 modification
Slide 30 : Discussion
Slide 31 : To view what is going on really! All the curves were superimposed
Slide 32 : No need to explain!
Slide 33 : Some points concerning the superimposed curves An increase in the apical and cervical stress produced Modification of the location of center of rotation in gradual steps of bone loss Apical stress increase is higher than coronal stress increase
Slide 34 : Stress increase in different stages of alveolar bone loss (N/mm2)
Slide 35 : A non-linear change in cervical stress can be noticed in alveolar bone loss
Slide 36 : A non-linear change in apical stress can be noticed in alveolar bone loss
Slide 37 : So… Approximately 2.5 mm (19.2%) of alveolar bone loss can be considered as a limit of the attachment apparatus loss beyond which the stress increase accelerates
Slide 38 : According to Linhe, Karring and Lang application of equal forces in normal and reduced alveolar bone height causes an equal amount of root displacement at the level of the alveolar crest. The findings of this study is against this idea which is shown by lines not superimposing each other
Slide 39 : Conclusion The more alveolar bone loss that occurs, the greater the stress increase in the PDL. This is verification for Secondary Trauma from Occlusion qualitatively and quantitatively. It can be assumed that each layer of the alveolar bone protects lower layer from stress. Approximately, 2.5 mm of alveolar bone loss is assumed to be the starting point for dramatic changes in stress level.
Slide 40 : Nowadays… My 3d models have much better views due to better methods of modeling present in SolidWorks. I use SolidWorks in all new models in a top to bottom strategy which makes the models much better in shape and in meshing. The relationship between designing and calculating phases are improved.

 


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