下顎インプラントオーバーデンチャーの後方残存歯根の吸収と再植がインプラント周囲の曲げ歪みに及ぼす影響

Effect of Posterior Residual Ridge Resorption and Relining for Mandibular Implant Overdentures on Bending Strain Around Implants.

抄録

目的:

オーバーデンチャー下のインプラント周囲の曲げ歪みに及ぼす後方残骨吸収（PRRR）とリライニングの影響を検討する。

PURPOSE: To examine the influence of posterior residual ridge resorption (PRRR) and relining on bending strain around implants under an overdenture.

材料および方法:

上顎と下顎の無歯顎模型を作製し、白色シリコーンで覆った。各インプラントの4面に歪みゲージを設置した．下顎の側切歯と犬歯の間の部分に2本の組織レベルインプラントを両側から埋入した．上顎のコンベンショナルデンチャーと下顎のオーバーデンチャーを作製し，模型に装着した．インプラント周囲の骨吸収を3段階で評価した．0mm，0.8mm，1.5mmとした．インプラント遠位側近傍から後臼歯部にかけて残存隆起面を一様に除去し，PRRRを0，1，1.5mmの3水準で作成した．測定後，PRRRが1mmと1.5mmの実験用義歯を再装着した．ロケーターアタッチメントを使用した．98Nの咬合力を負荷し，インプラント周囲の曲げひずみを測定した．データの解析には，Kruskal-Wallis検定とBonferroni補正を用いた．

MATERIALS AND METHODS: Maxillary and mandibular edentulous models were made and covered with white silicone. Four strain gauges were placed on four sides of each implant. Two tissue-level implants were placed bilaterally in the part between the lateral incisors and canines of the mandible. A maxillary conventional denture and a mandibular overdenture were fabricated to fit the models. Three levels of bone resorption around the implant were created: 0, 0.8, and 1.5 mm. The surface of the residual ridge was uniformly removed from the area near the distal side of the implant to the retromolar section, and three levels of PRRR were created (0, 1, and 1.5 mm). After the measurement, the experimental denture of the PRRR of 1 mm and 1.5 mm were relined. Locator attachments were used. A 98-N occlusal force was applied, and bending strains around the implant were measured. The Kruskal-Wallis test and Bonferroni correction were employed to analyze the data.

結果:

リライニングを行わない場合、インプラント周囲の各骨吸収レベルにおいて、曲げ歪みはPRRR0mmで最も小さく、PRRR1.5mmで最も大きくなった。リライニング後の曲げひずみは、稜線吸収がある場合の曲げひずみよりも小さかった。リライニング後の曲げひずみは、尾根の吸収がない場合の曲げひずみよりも小さかったが、これら3群間に曲げひずみの有意差は認められなかった。

RESULTS: Without relining, at each bone resorption level around the implant, the bending strain was smallest with PRRR of 0 mm and largest with PRRR of 1.5 mm. The bending strain after relining was smaller than the bending strain with ridge resorption. Bending strains after relining were smaller than bending strains with no ridge resorption, but there was no significant difference in bending strain between these three groups.

結論:

PRRRが増加すると、リライニングを行わなくても曲げひずみが増加した。インプラント周囲の骨吸収が進行すると、PRRRはインプラント周囲の曲げひずみの増加を促進した。リライニングを行うと曲げひずみは軽減された．

CONCLUSION: As PRRR increased, the bending strain increased without relining. As bone resorption around the implant progressed, PRRR enhanced the increase in the peri-implant bending strain. Bending strain was reduced when relining was performed.