人工牙根在牙科領域上的發展及運用，已有長達40 年的時間。人工牙根乃是口腔內植體，代替天生的牙根，恢復牙齒咀嚼、咬合等功能，可謂是人類的第三副牙齒。現今植牙成功率高，但背後存在著對病患骨質條件選擇的問題，因此如何提高骨質條件不佳患者的植牙成功率為日前研究的主要目標。本研究之研究目的為三項：(1)皮質骨厚度及鬆質骨密度對植體初期穩定之影響(2)植體長度及植體寬度對植體初期穩定度之影響(3)有無使用攻牙鑽頭對植體初期穩定度之影響。
本研究於不同皮質骨厚度(0, 1, 2, and 3mm)及鬆質骨密度(0.12, 0.16, 0.20, and 0.32 g/cc)的人造骨及豬下顎骨先進行相同鑽孔步驟，並於最後攻牙程序，分成有無使用攻牙鑽頭。接著透過測量最高鎖入扭力值(peak insertion torque, PIT)及共振頻率(resonance frequency, RF)，作為植體初期穩定度之指標，以進一步討論骨質條件、植體尺寸以及攻牙方法對植體初期穩定的影響。
研究結果顯示，在人造骨以及動物骨中，皮質骨越厚，其植體穩定度越高且具有高度相關(r = 0.63-0.80)；在鬆質骨密度方面，則是低度相關(r = 0.16-0.34)。本實驗使用植體寬度(3.4 and 4.2 mm) 及植體長度 (8, 10, 12, and 14 mm) 中，其與植體穩定度皆呈一低度相關(分別為r = 0.08-0.54, r = 0.04-0.2) 。植體自行攻牙法比攻牙鑽頭攻牙法，其植體初期穩定度較高，且具顯著性的差異(P < 0.05)。
因此透過本研究結果可得知，較厚皮質骨能給予較高之植體初期穩定度，皮質骨厚度為一影響植體穩定度之重要因素，鬆質骨密度則次之；在植體尺寸方面，植體寬度能提高植體穩定度，植體長度則次之；此外，採取植體自行攻牙法能有效提高植體初期穩定度，以補償較差骨質條件下的低植體穩定度。

Implant dentistry has been developed for more than 40 years. Dental implant replaces the root portion of teeth and restores the occlusive function hence is described as the third set of teeth. However, its success depends heavily on the patient’s bone condition. To improve the success rate of dental implantation in patient with poor bone condition is now an important issue. This study investigated: (1) effects of cancellous bone density and cortical bone thickness in primary implant stability (2) effects of implant length and implant width in primary implant stability (3) effect of without tapping drill to compensate poor bone condition.
In this study, implants with four lengths (8, 10, 12, and 14 mm) and two widths (3.4 and 4.2 mm) were implanted into the artificial bone specimens. The artificial bone consisted with cortical bone, with four thicknesses: 0, 1, 2, and 3mm, and cancellous bone,with four densities: 0.12, 0.16, 0.20 and 0.32 g/cc. Two different drilling rocedures, with tapping drill (WTD) and without tapping drill (W/OTD), were used during the implantation. Peak insertion torque (PIT) during implant and resonance frequency (RF)after implant, were measured to evaluate the primary implant stability.
The results showed that cortical bone thickness plays the most important factor in providing the primary implant stability and it had a high correlation (r = 0.63-0.80)with RF and PIT. On the other hand, cancellous bone density only demonstrated a low correlation (r = 0.16-0.34) with RF and PIT which indicated its insignificant role. It was only when there was no cortical bone then the effect of cancellous bone density could be reflected on RF. Width and length of implant again had low correlation (r = 0.08-0.54, r =0.04-0.2, respectively) with both RF and PIT. The role of implant width could be identified only when cortex shell existed. There were significant differences (P < 0.05) between W/OTD and WTD procedure in all evaluated conditions: cortical bone thickness,cancellous bone density, implant length, and implant width.
To conclude, it is confirmed that cortical bone thickness plays an important role in determining implant stability while cancellous bone density is not a key factor for primary implant stability. Wider implant could not provide higher implant stability without the existence of cortical bone. Longer implant could not provide higher implant stability in all cases. By skipping the tapping procedure, it is possible to increase primary implant stability which is important for poor bone condition.

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