小林 義和

Abstract Background The COVID-19 pandemic led to concerns about the potential airborne transmission of the virus during dental procedures, but evidence of actual transmission in clinical settings was lacking. This study aimed to observe the behavior of dental sprays generated from dental rotary handpieces and to evaluate the effectiveness of high-volume evacuators (HVEs) using laser light sheets and water-sensitive papers. Methods A dental manikin and jaw model were mounted in a dental treatment unit. Mock cutting procedures were performed on an artificial tooth on the maxillary left central incisor using an air turbine, a contra-angle electric micromotor (EM), and a 1:5 speed-up contra-angle EM (×5EM). Intraoral vacuum and extraoral vacuum (EOV) were used to verify the effectiveness of the HVEs. The dynamics and dispersal range of the dental sprays were visualized using a laser light sheet. In addition, environmental surface pollution was monitored three-dimensionally using water-sensitive papers. Results Although the HVEs were effective in both the tests, the use of EOV alone increased vertical dispersal and pollution. Conclusions The use of various types of HVEs to reduce the exposure of operators and assistants to dental sprays when using dental rotary cutting instruments is beneficial. The study findings will be helpful in the event of a future pandemic caused by an emerging or re-emerging infectious disease.

近年，口唇口蓋裂患者に対する二次的顎裂部骨移植術の術後評価に，CT画像を用いた検討が報告されている．われわれは，二次的顎裂部骨移植術による骨架橋容積の評価と，骨架橋成立に寄与する予後規定因子を明らかにするため，CT画像を用いた検討を行ったので報告する．二次的顎裂部骨移植術を行った片側性唇顎裂（unilateral cleft lip and alveolar: UCLA），片側性唇顎口蓋裂児（unilateral cleft lip, alveolar, and palate: UCLP）の各30例，計60例を対象とし，術前後にCT画像を撮影した．骨欠損腔の容積から顎裂部骨架橋率を算出し，その予後規定因子について検討を行った．骨架橋率の中央値は片側性唇顎裂で83.6%，片側性唇顎口蓋裂で66.3%となった．単変量解析，多変量解析双方において，口蓋裂の有無および術前の顎裂部骨欠損腔容積の大きさが有意な予後規定因子として抽出された．顎裂部誘導歯の種類や萌出状況は予後に関連しなかった．

Objective The usefulness of computed tomography (CT) for measuring bone defect volume in the alveolar cleft has attracted considerable attention in recent years. Moreover, 320-row area detector CT (320-ADCT) is currently widely utilized. This technology helps to acquire smooth three-dimensional images, with a reduced exposure dose and improved image resolution, similar to those of dental cone-beam CT (CBCT). We compared the exposure dose of 320-ADCT with that of dental CBCT, and analyzed the reliability of a volumetric method for measuring bone defects in the alveolar cleft using 320-ADCT, both experimentally and clinically. Methods We performed thermoluminescent dosimeter measurements using an anthropomorphic RANDO phantom. Additionally, we evaluated the reproducibility of the volumetric measurement method for the bone defective volume using CT images of simulated bone defects in pigs. In addition, we evaluated the inter-rater reliability of the volumetrically measured values of bone defects in 20 patients with a unilateral cleft. Results The exposure doses of 320-row area detector CT and CBCT were similar. The errors of volumetric values between calculated and actual bone defects created in pigs were up to 7.6%. Inter-rater reliability of the calculated volumes of bone defect was evaluated as high, according to Bland–Altman analysis. Conclusions CT examination with a low exposure dose and precise analysis is feasible without the use of highly specialized dental CBCT.

近年，口唇口蓋裂患者に対する二次的顎裂部骨移植術の術後評価に，CT画像を用いた検討が報告されている。今回われわれは，二次的顎裂部骨移植術による骨架橋の成立に寄与する予後規定因子を明らかにするため，CT画像を用いた後方視的検討を行った。<br>13例に対し，患側上顎中切歯の根尖部，歯根中央部，歯槽骨頂部の高さに相当する断層面において，唇側，歯槽中央，口蓋側の，計9ヶ所で術後の骨架橋について評価した。骨架橋は，歯根中央部唇側では全例で認められ，以下，歯根中央部歯槽中央9例（69.2%），根尖部唇側および歯槽骨頂部歯槽中央8例（61.5%），歯槽骨頂部唇側6例（46.2%），歯根中央部口蓋側5例（38.5%），歯槽骨頂部口蓋側4例（30.8%），根尖部歯槽中央および口蓋側3例（23.1%）と続いた。また，単変量ロジスティック回帰分析の結果，歯根中央部の高さにおいて，歯槽中央および口蓋側では術前の顎裂幅径が術後の骨架橋成立に対する予知性の高い指標となることも明らかとなった。