Background: Dental implants are frequently applied to unilateral defects in the mandible. However, implant\nplacement in the molar region of the mandible can be difficult due to anatomical structure. The aim of this study\nwas to evaluate the distribution of occlusal force in a mandibular shortened dental arch (SDA) with implants.\nMethods: Three-dimensional finite element (FE) models of the mandible with varying numbers of teeth and implants\nwere constructed. Models Im6 and Im67 contained one and two implants in the defect of the left molar region,\nrespectively. Models Im456 and Im4567 contained three and four implants in the defect of the left premolar and molar\nregions, respectively. Model MT67 contained a defect in the molar region with no implant placed. Model MT7\nrepresented natural dentition without a left second molar, as a control. Modification of the condition of\nocclusal contacts assuming the intercuspal position was performed before analysis under load 400 N; therefore, the\nload condition as total force on the occlusal surface was 400 N. FE analyses were subsequently performed under load\nconditions of loads 100, 200, and 800 N. The distribution of reaction forces on the occlusal surface and the mandibular\ncondyle was investigated.\nResults: Force distribution in models Im67 and Im4567 appeared to be symmetrical under all load conditions. Occlusal\nforce distribution in models Im6 and Im456 was similar to that in model MT7. However, the occlusal force at the\nsecond premolars on the defect side in those models was larger under loads 100 and 200 N. Conversely, the occlusal\nforce on the first molars was much larger than that in model MT7 under load 800 N.\nConclusions: Within the limitations of this theoretical study, we demonstrated that restoration with the same number\nof implants as missing teeth will show almost symmetric occlusal force distribution, and it will produce less\nbiomechanically stress for a unilateral defect of the mandible. However, if restoration of a missing second\nmolar with an implant is impossible or difficult, then an SDA with implants may also be acceptable except\nfor individuals with severe bruxism.
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