Functional Remodelling Of Mandibular Bone Induced By Fxed Partial Dentures

After FPD treatment, abutments and restoration would be connected as a whole, andthe occlusal loading on restoration will be transmitted to periodontal supporting tissuesby abutments and the parodontium of abutments. Therefore the occlusal loading onsupporting tissues and the stress/strain of supporting bone will be changed after FPDrestoration. As a consequence, the remodeling process of bone will happen under themechanical stimulus. So it is important to know the remodeling process and influencingfactors of it, and it will have a guiding significance to clinical procedures. However theprevious researches mainly focus on biocomplexity of the surrounding tissues and theanalysis of stress distribution of supporting tissues based on different FPD design, andreports about the remodeling of bone surrounding abutments induced by FPD restorationwere rare. The bone remodeling process includes the changes of density and shape of the bone,and the density change is closely related to mechanical stimulus. Researching on boneremodeling under the biological forces by numerical simulation analysis is prevalent inthe field of implant restoration and orthodontics. According to the theory, based on thestrain energy density of the bone alterations,3D finite element analysis (FEA) techniqueswill be employed in this study to understand the remodeling process of bone surroundingabutments under different occlusal loading after FPD restoration, a series ofthree-dimensional (3D) fnite element models which simulate the situation of a three-unitfxed partial denture for the loss of the mandibular first molar with various periodontalattachment levels were presented, and hope the results could provide a theoreticalguidance to clinical practice.There are four parts in this study:1. Three-dimensional (3D) fnite element models for functional remodeling ofalveolar bone induced by FPD restoration were built.Select a normal anatomy of complete mandible with integral dentition, little absorptionof alveolar bone and no defect and wear of posterior tooth as a modeling basis. Thenscanned by100μm thickness using Micro CT, and saved by DICOM format for next step.Mimics10.01, Geomagic stuio11.0, CATIA V5software were used to access to modelsof pre-and post-FPD restoration with five different levels of periodontal attachment (theabutment dentition used herein was the mandibular right second premolar and rightsecond molar, where the edentulous area was the mandibular right first molar). Aftersmoothing, models were conducted ABAQUS CAE6.10. the new models were consistedof quadratic tetrahedral solid mesh.The results show that the shape of models built in this study is similar to restorationand alveolar bone. Construction of models is clear and can reveal the structure ofrestoration and alveolar bone. Region of stress concentration is buccal and lingual area ofcortical bone and cancellous bone, and apical area. The trend of bone density’s variationwas in accordance with the trend of stress’ variation, which could be proved by the outcome of remodeling. So this result is similar to the previous report and it couldcontribute to the research of bone remodeling process and pattern under occlusal force inpre-and post-FPD.2. Research on alveolar bone remodeling process induced by FPDBased on the method and models in part1, situation that the abutments withoutperiodontal attachment loss level and the restoration under the same loading before andafter FPD treatment, analyzed the trends of abutments bone densities among24months,in order to investigate the effect on bone remodeling process caused by FPD restoration.The result show that region of bone density’s variation is in accordance with region ofstress concentration under the same loading. However, Stress in alveolar bone after FPDrestoration is bigger than that before restoration. After restoration, remodeling of bonedensity happens earlier and its extent is larger at the same time.3. Research on the effect of different loadings on bone remodeling induced by FPD.Based on models and method in part1, simulate the situation that the abutmentswithout periodontal attachment loss level and the restoration under the different loadingsbefore and after FPD treatment, analyzed the trends of abutments bone densities among24months, in order to investigate the effect on bone remodeling process caused byvarious occlusal forces after FPD restoration.The results show that after FPD restoration, region of stress concentration is buccaland lingual area of cortical bone and cancellous bone, and apical area. Bone densityvariation is closely related to the loading on abutments, and with the growth of loading,stress in bone density’s variation will be larger. When load is too large, alveolar boneremodeling happens and shows bone absorption. Additionally, bone remodeling happensearlier with the higher load, and the speed of remodeling will be more rapid at the sametime. This result reveals that mastication loading on restoration should be control in theclinical practice.4. Research on the effect of different periodontal attachment loss levels on boneremodeling induced by FPD. Based on models and method in part1, simulate the situation that the abutments withdifferent periodontal attachment loss levels and the restoration under the same loadingbefore and after FPD treatment, analyzed the trends of abutments bone densities among24months, in order to investigate the effect on bone remodeling process caused byvarious periodontal attachment loss levels after FPD restoration.The results show as follows: Stress in alveolar bone increased dramatically with theperiodontal attachment levels’ drop. When periodontal attachment loss levels are over10%, stress in bone will be grow rapidly and the bone density decreases. At that time,pathological remodeling of alveolar bone appears. In the process of remodeling, variationof bone surrounding the second premolar is the largest. this results point out that whenthe periodontal attachment levels’ loss happens, stress will be increased and stressconcentration will appear even under the normal occlusal force, and this would inducebone absorption. So if there is bone absorption, load on abutment should be reduced oradd other abutment to prevent absorption of alveolar bone in clinical practice.