Analysing the effect of the crown/implant ratio on stresses at two different bone type by finite element analyses

ABSTRACTAnalysing The Effect Of The Crown/İmplant Ratio On Stresses At TwoDifferent Bone Type By Finite Element AnalysesDental implants are widely used in the treatment of complete or partialedentulous patient. As a result of tooth losses, atrophy is observed in alveolar bonesover time. The atrophy develops in maxilla in vertical and buccopalatinal direction.The density of maxillary bone deficiency, in comparison with mandible, brings aboutthe difficultness of implant anchorage and loading conditions in this area. Theamount of existing bone is an important criterion for the success of implants applied.The inner bone structure is defined as quality or density. Generally, in maxilla thebone types of 3 and 4 were observed. One of the important factors in the success ofimplant supported prosthesis is to comply with biomechanical principles. Implantsupported prosthesis could be subject to external or internal forces. For the purposeof measuring the functional stresses in the bones, implant, and restorations, variousanalysis methods are employed. Finite element method is an appropriate way toassess the relation between implant and bone and for modeling of the bone. Singletooth deficiency is generally seen in posterior area. Due to the in evitable bonedestruction as a result of tooth extraction, the ratio of crown/implant is alwaysdifferent from the one observed in natural dentition.The purpose of this study is to assess the stresses to be derived by threedifferent bone losses in the bone-implant system of type 3 and type 4 bones in casemaxillary first molar tooth is lost.For this purpose, the model of posterior maxilla has been created by usingMarc 2005 (MSC Software) programme from the computerized tomography imagesof an actual patient. Through this programme, we created different vertical boneresorptions in the first molar tooth zone, modeled the loading conditions andperformed the stress analyses.The highest stresses have been observed around the implant neck at thecrown/implant ratio of 2/1(430,57MPa). As the crown/implant ratio increases, thezone where the stress spreads and amount of deformation have extended. As for theivstresses in the bone, they have been generally accumulated in the cortical bone that isadjacent to the implant neck. The highest values for the cortical bone have beenobserved in type 4 bone (145,92MPa) when the crown/implant ratio is 2/1. theincrease in crown/implant ratio has decreased the stresses observed in implant-bonesystem. The modification made to the bone density mainly affected the stressesobserved in spongios bone. The lowering of density increases the amount ofdeformation in spongios bone.Key Words: crown-implant ratio, FEA, maxillary molar, crown lengthv