利用CBCT、Micro CT對骨結構分析與植體穩定度相關參數於豬骨模型上之探討

Comparision of microstructure for Cone Beam Computed Tomography and Micro Computed Tomography and Investigating Implant Stability Parameter in Iliac Bone Blocks of Swine

林彥佑(Yen-Yu Lin)

指導教授 ： 林立德

國立臺灣大學/醫學院/臨床牙醫學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201703290

摘要

實驗目的
牙科植體的初期穩定度是決定植體是否能夠進行立即受力的條件之一，也是植體成功的因素之一。影響牙科植體最重要的因素是缺牙區的骨頭條件，也就是骨質，骨質的評估分為骨密度和骨微結構。過去對骨質的評估多是利用Multislice CT (MSCT) 或CBCT影像來得到HU值，以代表放射線骨密度。但是MSCT輻射劑量太高，CBCT得到的HU值又不是那麼可靠。而隨著CBCT解析度的進步，而且對長度的測量準確，因此我們對骨質的分析，從骨密度漸漸轉向為希望從利用CBCT來對骨小樑微結構做分析。本實驗利用MicroCT到的影像作為標準，希望找出利用CBCT影像得到的骨小樑微結構與標準值之間的關聯性，並且分析得到的骨小樑微結構參數與植體穩定度之間的關係。

實驗材料與方法
將豬髂骨切成約15-20mm寬的骨塊，選取皮質骨厚度約0-1mm的骨塊總共七塊，分別標示為Bone 1、Bone 2、Bone 3、Bone 4、Bon 5、Bone 6、Bone 7。在這七塊骨模型上分別製作手術定位模板(surgical stent)，並於手術定位模板上每隔5mm鑽孔做記號，作為預計要鑽孔的位置。
進行鑽孔前，先將骨模型及手術定位版以3M紙膠帶固定起來分別先去照Micro CT和CBCT，來進行植體種植區骨小樑微結構分析。研究中Micro CT的微結構分析採用：SkyScan micro-CT (Bruker micro CT, Belgium). 掃描的條件設為 80 kVp, voxel size 35μm, 180 scanning。CBCT採用：3D Accuitomo 170(Morita, Osaka, Japan),掃描條件設為 FOV 60mm ✕60mm，voxel size 125μm ✕ 125μm✕125μmm，90kVp，5.0mA，30.8s。MicroCT的影像利用CT-Analyser (Bruker, Kontich, Belgium)，CBCT的影像利用ImageJ plugin, BoneJ (Rasband, W.S., ImageJ, U.S. National Institutes of Health, Bethesda, MD, USA) 得到每個鑽孔位置的骨體積分數bone volume fraction (BV/TV)、骨表面積密度bone surface density(BS/TV)、骨小樑厚度trabecular thickness (Tb. Th)、structural model index、connectivity density。最後選擇十個位置來進行植體種植和植體穩定度的測量。
植體種植選擇Nobelbiocare MKIV (4.0mm x 10mm; ø × length)，依照廠商建議的軟骨質鑽孔規則進行鑽孔、種植。植體穩定度測量記錄鑽孔過程中最大置入扭力(insertion torque, IT)，植體種植完成後的植體共振頻率(implant stability quotient, ISQ)、敲擊阻尼值(periotest value, PTV)，最後再用線性位移計測量植體在受10N側向力時的側向位移。
實驗結果
CBCT與Micro CT的骨微結構係數相關性較高的是：骨體積分數 (BV/TV) 的Spearman相關係數是0.346 (p < 0.05)，骨表面積密度 (BS/TV) 的Pearson相關係數為0.383 (p < 0.05)，Spearman相關係數為0.371 (p < 0.05)。
Micro-CT所得到的骨結構相關參數與植體穩定度相關參數的相關性為：骨體積分數(BV/TV)與微移動量的Spearman相關係數為-0.636 (p< 0.05)。皮質骨厚度與最大置入扭力的Pearson相關係數為0.963 (p< 0.01)、 Spearman相關係數為0.794 (p < 0.01)，與ISQ的Pearson相關係數為0.632 (p < 0.05)。
CBCT所得到的骨結構相關參數與植體穩定度相關參數的相關性為骨小樑厚度(Tb.Th)與PTV的Pearson相關係數為0.632 (p< 0.05)、 Spearman相關係數為0.782 (p< 0.01)，與微移動量的Pearson相關係數為0.790 (p< 0.01)、 Spearman相關係數為0.697(p < 0.05)。骨體積分數(BV/TV)與最大置入扭力的Pearson相關係數為-0.776 (p < 0.01)、 Spearman相關係數為-0.782 (p < 0.01)。骨表面積密度(BS/TV)與PTV的Pearson相關係數為-0.754 (p< 0.05)、 Spearman相關係數為-0.818 (p< 0.01)。骨表面積密度(BS/TV)與微移動的Pearson相關係數為-0.701(p< 0.05)、 Spearman相關係數為-0.745 (p< 0.01)。皮質骨厚度與最大置入扭力的Pearson相關係數為0.942 (p< 0.01)、 Spearman相關係數為0.763 (p< 0.01)。
植體穩定度之相關性，在Pearson相關係數方面，最大入扭力與ISQ的為0.635 (p < 0.05)，ISQ與PTV的為-0.659 (p <0.05)，PTV與微移動的為0.872 (p <0.01)。在Spearman相關係數方面，最大入扭力與ISQ的為0.685 (p < 0.05)，PTV與微移動的為0.685 (p <0.05)。
結論
CBCT與Micro-CT的骨小樑結構相關性較高的是骨體積分數(BV/TV)，骨表面積密度(BS/TV)。
在本實驗中，MK IV植體的最大置入扭力與皮質骨的厚度呈現高度正相關。
骨體積分數(BV/TV)，皮質骨體積，骨表面積密度(BS/TV)跟植體微移動量呈負相關，相關性較高的是骨體積分數。
在本實驗的豬骨模型及鑽孔規則下，置入扭力與植體微移動量呈負相關，ISQ與植體微移動量呈負相關，但是相關性都較小；PTV與植體微移動量呈正相關，相關性最大。而與置入扭力的相關性最高的是ISQ。

關鍵字

錐狀射束電腦斷層掃描 ； Micro-CT ； 骨小樑微結構 ； 植體穩定度 ； 植體微移動量

並列摘要

Research goal
The purpose of this study was to investigate the correlation of trabecular microstructure parameter obtained from micro computed tomography (micro-CT) and cone beam computed tomography (CBCT), and the relationship between trabecular microstructure parameters and implant stability parameters on iliac bone blocks of swine.
Material and method
1. 7 iliac bone blocks of swine (15mm in width). Surgical stents of each bone block were fabricated.
2. Trabecular microstructures of implant sites were evaluated with MicroCT SkyScan micro-CT (Bruker micro CT, Belgium) and CBCT 3D Accuitomo 170(Morita, Osaka, Japan) before implant drilling. 3D morphometric quantification of micro CT was performed in a CT-Analyser (Bruker, Kontich, Belgium). 3D morphometric quantification of CBCT was performed in a ImageJ plugin, BoneJ (Rasband, W.S., ImageJ, U.S. National Institutes of Health, Bethesda, MD, USA).
3. 10 sites were chosen for implantation according to the bone volume fraction (BV/TV).
4. Nobelbiocare MK IV (4.0mm x 10mm; ø x length) were used.
5. Implant site preparations were performed according to manufacturer’s instruction: MK IV by step drilling with 2-mm, 2.4/2.8-mm, 3-mm drill in 10 mm depth, Counterbore drill was used with laminated blocks.
6. MK IV implants were inserted into swine bone blocks by hand torque wrench.
7. Final insertion torque (FIT), resonance frequency analysis (ISQ), perio-test valuae and micromotion were recorded.
Results:
(1) The correlation coefficient between CBCT and Micro CT in BV/TV was Spearman correlation coefficient 0.346 (p < 0.05), in BS/TV was Pearson correlation coefficient0.383 (p < 0.05), Spearman0.371 (p < 0.05).
(2) The correlation coefficient between bone microstructure parameters measured by Micro-CT and primary stability parameters were: Pearson correlation coefficient of cortical bone thickness and insertion torque 0.963 (p < 0.01), cortical bone thickness and ISQ 0.632 (p < 0.05). Spearman correlation coefficient of BV/TV and micromotion -0.636 (p < 0.05); cortical bone thickness and insertion torque 0.794 (p < 0.01).
(3) The correlation coefficient between bone microstructure parameters measured by CBCT and primary stability parameters were: Pearson correlation coefficient of Tb. Th and PTV 0.632 (p < 0.05); BV/TV and insertion torque -0.776 (p < 0.01); BS/TV and PTV -0.754 (p < 0.05); BS/TV and micromotion -0.701(p < 0.05); Cortical bone thickness and insertion torque 0.942 (p < 0.01). The correlation coefficient between bone structure of CBCT and primary stability parameters were: Spearman correlation coefficient of Tb. Th and PTV 0.782 (p < 0.01); BV/TV and insertion torque -0.782 (p < 0.01); BS/TV and PTV -0.818 (p < 0.01); BS/TV and micromotion -0.745(p < 0.05); Cortical bone thickness and insertion torque 0.763 (p < 0.01).
(4) The correlation coefficient between primary stability parameters were: Pearson correlation coefficient of insertion torque and ISQ 0.635 (p < 0.05); ISQ and PTV -0.659 (p <0.05); PTV and micromotion 0.872 (p <0.01). Spearman correlation coefficient of insertion torque and ISQ 0.685 (p < 0.05); PTV and micromotion 0.685 (p <0.05).

Conclusions:
There were high correlation in BV/TV and BS/TV between CBCT and Micro CT.
Insertion torque was highly correlated with cortical bone thickness.
BV/TV, BS/TV, cortical bone thickness were negative correlated with micormotoion. BV/TV was highly correlated with micromotion.
Under swine iliac bone model: PTV was highly correlated with micromotion and ISQ was correlated with insertion torque.

並列關鍵字

CBCT ； Micro CT ； trabecular bone structure ； primary stability ； implant micromotion

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