Abstract
BackgroundDental implants are frequently applied to unilateral defects in the mandible. However, implant placement in the molar region of the mandible can be difficult due to anatomical structure. The aim of this study was to evaluate the distribution of occlusal force in a mandibular shortened dental arch (SDA) with implants.MethodsThree-dimensional finite element (FE) models of the mandible with varying numbers of teeth and implants were constructed. Models Im6 and Im67 contained one and two implants in the defect of the left molar region, respectively. Models Im456 and Im4567 contained three and four implants in the defect of the left premolar and molar regions, respectively. Model MT67 contained a defect in the molar region with no implant placed. Model MT7 represented natural dentition without a left second molar, as a control. Modification of the condition of occlusal contacts assuming the intercuspal position was performed before analysis under load 400 N; therefore, the load condition as total force on the occlusal surface was 400 N. FE analyses were subsequently performed under load conditions of loads 100, 200, and 800 N. The distribution of reaction forces on the occlusal surface and the mandibular condyle was investigated.ResultsForce distribution in models Im67 and Im4567 appeared to be symmetrical under all load conditions. Occlusal force distribution in models Im6 and Im456 was similar to that in model MT7. However, the occlusal force at the second premolars on the defect side in those models was larger under loads 100 and 200 N. Conversely, the occlusal force on the first molars was much larger than that in model MT7 under load 800 N.ConclusionsWithin the limitations of this theoretical study, we demonstrated that restoration with the same number of implants as missing teeth will show almost symmetric occlusal force distribution, and it will produce less biomechanically stress for a unilateral defect of the mandible. However, if restoration of a missing second molar with an implant is impossible or difficult, then an SDA with implants may also be acceptable except for individuals with severe bruxism.
Highlights
Dental implants are frequently applied to unilateral defects in the mandible
Dental implant treatment has been frequently applied in dental practice as the most important prosthodontic procedure with long-term predictability to restore oral function, maintain occlusion, and improve the quality of life (QoL) of a patient [1]
Lingual concavities in an edentulous mandible appear to be related to risk of perforation in the lingual cortical bone during dental implant insertion, which may lead to hemorrhages or infections in the parapharyngeal space [3, 4]
Summary
Dental implants are frequently applied to unilateral defects in the mandible. Implant placement in the molar region of the mandible can be difficult due to anatomical structure. Implant placement in the molar region of a mandible occasionally has some anatomical difficulties, such as lingual concavity of a mandible, small distance to the mandibular canal, insufficient space between the alveolar ridge and opposing teeth, and lack of keratinized mucosa. Lingual concavities have a prevalence of 68% in the molar region and occur at a significantly higher rate in the second molar (90%) than in the first molar (56%) [5] To avoid these risks, implants may not always be suitable to repair second molar defects
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