利用錐狀電腦斷層掃描量測上下顎骨密度的可信度

The reliability of cone beam computed tomography in measuring jaw bone density

周欣汝(Hsin-Ju Chou)

指導教授 ： 洪純正

高雄醫學大學/口腔醫學院/牙醫學系碩士班/碩士(2017年)

摘要

研究目的：骨質密度的判斷對植體初期穩定度及預後的評估相當重要。本研究分析三種不同廠牌的錐狀電腦斷層掃描(CBCT)及同一廠牌錐狀電腦斷層在不同時間所拍攝的影像，其影像灰階值差異性是否影響以錐狀電腦斷層掃描影像判讀骨密度的準確度並分析各個顎骨區域(前後上下顎)的影像灰階度及最冠部皮質骨厚度的差異。
材料與方法：以三種密度(type I，type II，type III)的聚氨酯人工骨經三種廠牌CBCT(騰協TCT，Vatech，NewTom)照射，並以生物醫學影像軟體ImageJ計算影像灰階值，作為臨床CBCT骨質密度比較標準。另收集40位曾拍攝過兩次以上CBCT病患的斷層影像並分析灰階值及最冠部皮質骨厚度，其中男性24位，女性16位，上顎21例，下顎21例。並以獨立樣本T檢定分析兩廠牌CBCT差異，配對T檢定分析同病患同廠牌CBCT不同次的拍攝差異。
結果：以騰協(TCT)廠牌CBCT拍攝的三種密度人工骨，灰階值分別為type I的64.88 ±1.17 ，type II的42.80 ± 1.83，type III的19.55 ± 1.06，以Vatech廠牌拍攝的灰階值為type I的20.43 ± 0.62，type II的9.63 ± 1.20，type III的8 ± 0.00，而以NewTom CBCT所拍攝的灰階值則分別為35.38 ± 0.74，24.68 ± 0.51，12 ± 0.02，三種廠牌在三種密度的人工骨灰階差異皆具有顯著性(p < 0.001)。四個顎骨區域(前上顎，後上顎，前下顎，後下顎四個區域)在同一廠牌CBCT前後兩次拍攝的灰階值並無顯著差異(p > 0.05)。男性的上下顎灰階平均值分別為110.61 ± 10.17，112.87 ± 9.78，女性的上下顎則分別為105.15 ± 11.73，103.81 ± 8.63，兩性的顎骨灰階平均值並無顯著差異(p > 0.05)。四個顎骨區域灰階值具有顯著差異(p < 0.001)，前上顎區(136.18 ± 14.58 )顯著高於後上顎區(94.39 ± 13.66)和後下顎區(102.23 ± 11.81)，而與前下顎區(125.10 ± 14.55)無顯著差異，前下顎區顯著高於後上顎區與後下顎區，而後上顎與後下顎之間無顯著差異。後上顎區域的最冠部皮質骨厚度(1.15 ± 0.40 mm)顯著小於(p < 0.05)前上顎區(1.70 ± 0.72 mm)，後下顎區(1.75 ± 0.73mm)，前下顎區(1.71 ± 0.67mm)，而其他三個顎骨區域之間的皮質骨厚度無顯著差異。
結論：同一台CBCT所拍攝得到的影像灰階值具有一致性，而灰階值會受顎骨區域影響，但不同廠牌的CBCT的灰階值無法量化客觀比較，不建議目前使用CBCT的灰階值做顎骨密度絕對值的參考。後上顎區域的灰階值與皮質骨厚度皆較其他三個顎骨區域低，在此區域植牙需特別留意初期穩定度是否理想。

關鍵字

錐狀電腦斷 ； 骨密度 ； 灰階值 ； 人工植牙

並列摘要

Objectives: Bone density and quality are crucial for primary stability and prognosis of dental implant. This study was aimed to investigate the discrepancies of gray value recruited from images of three CBCT systems (TCT , Vatech , NewTom), gray value and crestal cortical bone thickness of four jaw bone area(anterior maxilla and mandible, posterior maxilla and mandible), and the consistency of gray value recruited from different times of scan by the same CBCT systems.
Material and methods: Three artificial bones of different density (type I, type II, type III) were scanned by three CBCT systems(TCT , Vatech, NewTom).On the other hand, CBCT images of 40 patients including 24 males, 16 females, 21 maxilla and 21 mandible, received more than two times of CBCT scan were collected. All the CBCT images were analyzed by biomedical image software ImageJ to calculate their gray value, and the cortical bone thickness of crestal jaw bone were also measured.
Results: There were statistically significant discrepancies (p < 0.001) of gray value between the three CBCT systems, the mean gray value of artificial bone scanned by TCT CBCT were 64.88 ± 1.17 for type I , 42.80 ± 1.83 for type II, 19.55 ± 1.06 for type III artificial bone, while those scanned by Vatech CBCT were 20.43 ± 0.62, 9.63 ± 1.20, 8 ± 0.00 and by NewTom were 35.38 ± 0.74 , 24.68 ± 0.51 , 12 ± 0.02 respectively. No statistically significant discrepancies of gray value (p > 0.05) between two times of scan by same CBCT system in four jaw bone area (anterior maxilla, posterior maxilla, anterior mandible, posterior mandible)were found. The mean maxillary gray value of male was 110.61 ± 10.17, and 105.15 ± 11.73 for female. The mean mandibular gray value of male was 112.87 ± 9.78, and was 103.81 ± 8.63 for female. There was no statistically significant discrepancies (p > 0.05) of gray value between male and female. Significant discrepancies (p < 0.001) of gray value were noted among the four jaw bone areas. The gray values of anterior maxilla (136.18 ± 14.58) and anterior mandible (125.10 ± 14.55) were significant higher (p < 0.001) than posterior maxilla (94.39 ± 13.66) and posterior mandible (102.23 ± 11.81); there were no significant discrepancies (p >0.05) between anterior maxilla and anterior mandible and between posterior maxilla and posterior mandible. Crestal cortical bone thickness of posterior maxilla, anterior maxilla, posterior mandible, and anterior mandible were 1.15 ± 0.40, 1.70 ± 0.72, 1.75 ± 0.73, 1.71 ± 0.67 mm respectively, and cortical bone thickness of posterior maxilla were statistically significant lower than the others.
Conclusion: The gray values of the images obtained by the same CBCT system are consistent, and there were significant differences of the gray values in different jaw areas, but the discrepancies of gray values obtain -ed by CBCT of different systems were difficult to compare. Therefore, using gray values of CBCT as absolute jaw bone density reference is not feasible and the inconsistencies among different CBCT systems still need to be concerned. Gray values and cortical bone thickness are least over posterior maxillary area, primary stability and prognosis of implant in this area must be concerned.

並列關鍵字

CBCT ； bone density ； gray value ； dental implant

參考文獻

1. Chee, W., & Jivraj, S. (2007). Failures in implant dentistry. British Dental Journal, 202(3), 123-129.

2. Goodacre, C. J., Bernal, G., Rungcharassaeng, K., & Kan, J. Y. (2003). Clinical complications with implants and implant prostheses. The Journal of Prosthetic Dentistry, 90(2), 121-132.

3. Molly, L. (2006). Bone density and primary stability in implant therapy. Clinical Oral Implants Research, 17(S2), 124-135.

4. Jaffin, R. A., & Berman, C. L. (1991). The excessive loss of Bränemark fixtures in type IV bone: a 5-year analysis. Journal of Periodontology, 62(1), 2-4.

5. Fuster-Torres, M. Á., Peñarrocha-Diago, M., Peñarrocha-Oltra, D., & Peñarrocha-Diago, M. (2011). Relationships between bone density values from cone beam computed tomography, maximum insertion torque, and resonance frequency analysis at implant placement: a pilot study. International Journal of Oral & Maxillofacial Implants, 26(5).