Stress and strain distribution in the lower jaw with shortened dental arch: A finite element method study

Abstract

Introduction/Objective The absence of functional loading due to molar loss might cause changes to the microstructure of the bone. Therefore we investigated and visualized deformation and strain pattern distribution of the mandibule with full arch dentition (FDA) and shortened dental arches (SDA) during occlusion. Methods A 3D model of an adult cadaveric dentate mandible, without pathological and traumatic damages, was developed based on CT scan images, set to 0.7 mm slice thickness. The scanned slices were imported into software where the bone and teeth were identified and modelled separately based on image density thresholding. Using the software and based on the grey-scale analysis of the slices initial meshes for the cortical, cancellous bone and teeth were generated. Results Highest stress/strain values were registered in the structures adjacent to molars i.e. molar region of processus alveolaris assigned by blue color in FDA model. Similar to FDA, the SDA models exibited deformation with evident highest strain (9.33%) at the processus coronoideus and mandibular angle. The highest overall stress (5 MPa) and strain (6.67%) was found in the mandibular intercanine segment of the SDA model, considering the mandibular body. Conclusion Finite element method can be employed as a powerfull tool for visualization of the stress and strain of the loaded mandible models with full and shortened dental arches. It was registered that molar support loss caused higher stress and strain in SDAs compared to FDA model.

Uvod/Cilj Odsustvo funkcionalnog opterećenja usled gubitka molara može izazvati promene u mikrostrukturi kosti. Cilj ovog istraživanja je bio da se ispitaju i vizuelizuju naponi i deformacije u mandibulama sa intaktnim zubnim lukom (IZL) i skraćenim zubnim lukom (SZL) u toku okluzije. Metod 3D model kadaverske donje vilice odrasle osobe (procenjena vizuelnim pregledom bez patoloških i traumatskih oštećenja) razvijen je na osnovu KT slike, debljine sloja od 0,7 mm. Skenirani preseci su uneti u softver gde su identifikovana i modelirana tvrda tkiva kosti i zubi pojedinačno na osnovu segmentacije slike. Početne mreže za kortikalnu kost, spongioznu kost i zube su proizvedene korišćenjem softvera i na osnovu analize sive skale preseka. Rezultati Najveće vrednosti napona i deformacija su registrovane u strukturama donje vilice neposredno uz molare u tzv. molarnom regionu alveolarnog nastavka, što je označeno plavom bojom na IZL modelu. Slično IZL, i SZL modeli su pokazali najveće vrednosti deformacija (9,33%) u koronoidnom nastavku i mandibularnom uglu. Najveći napon (5 MPa) i deformacija (6,67%) pronađeni su u interkaninom regionu SZL modela, ukoliko se razmatra telo donje vilice. Zaključak Metodom konačnih elemenata su vizuelizovane slike napona i deformacija modela donje vilice sa punim i skraćenim zubnim lukovima. Uočeno je da gubitak molarne potpore izaziva jače napone i deformacije u SZL modelima u poređenju sa IZL modelom.