植體支台之抗旋轉設計及抗扭力裝置於預載力施與過程後對於植體周圍應變的影響

Abstract

施加於植體支台螺釘的預載力可以在植體與支台之間形成鉗夾力，避免螺絲的過早鬆動來達到穩定植體與支台間關節的效果，但卻也可能會造成植體的變形，或將過多的應變傳導至植體－骨頭界面而影響到骨整合。本實驗的目的是為了解旋緊支台螺釘過程中，支台之抗旋轉設計有無，或抗扭力裝置的使用與否於植體－骨頭界面之扭力的影響，以及在植體－支台界面產生之鉗夾力對於植體應變的影響。 本研究分成三個部分：第一部分：旋緊支台螺釘時，支台是否具有抗旋轉設計或有無使用抗扭力裝置，在植體－骨頭界面處扭力的影響；第二部分：以植體類比體為測試對象，旋緊支台螺釘時，支台是否具有抗旋轉設計或是有無使用抗扭力裝置所產生之植體－支台界面鉗夾力對於植體應變的影響；第三部分：以植體為測試對象，鎖緊支台螺釘時，支台是否具有抗旋轉設計或是有無使用抗扭力裝置所產生之植體－支台界面鉗夾力對於植體應變的影響。 第一部分的研究是將一5 mm之植體類比體( Brånemark system )固定於扭力測量器上，測試的植體支台共有兩種：具抗旋轉設計的MirusCone abutment ( MC )及不具抗旋轉設計的Multiunit abutment ( MU )。以扭力控制器施加20 Ncm的扭力旋緊支台螺釘，並配合抗扭力裝置的使用有無( wct, woct )，共計四種測試組合：MC+woct, MC+wct, MU+woct, MU+wct，每種測試組合各測試五次，紀錄扭力測量器所得到的數值。 第二部分研究中，是將一具有三組電極線圈的應變計貼於直徑為5 mm之植體類比體上，應變計電極線圈中心點距離植體－支台界面約1.5 mm，令其中一組電極線圈( SG 1 )與待測物之長軸平行。接著將貼好應變計的植體類比體以環氧樹脂包埋。一共建立了五組模型，共計四種測試組合( MC+woct, MC+wct, MU+woct, MU+wct )、每種測試組合各測試五次。 第三部分的研究是架設三組直徑為4 mm、高度為10 mm之植體，重複上述實驗步驟。利用Spike 2軟體紀錄分析測得的數據，再依照應變計原理，算出maximum principle strain及minimum principle strain (Єp,q )及其與SG 1（即待測物長軸方向）所夾的角度(øp,q )。 20 Ncm的預載力且併用抗扭力裝置的情況下，扭力測量器紀錄的扭力數值約減少了90 %左右。應變計數據顯示，SG 1量測到的數值往往是最高的、且大小與maximum principle strain ( MPS )相近，由此可知施加於支台螺釘上的預載力，的確會造成近乎平行待測物的應變。另外在一前驅實驗中，分別以20 Ncm及32 Ncm的扭力旋緊Multiunit abutment的支台螺釘時，發現當以較大的預載力旋緊支台螺釘時，會在植體－骨頭界面產生較大的應變，而且與待測物長軸所夾的角度（順時鐘方向）也越大。植體類比體及植體皆得到下述結果：以各個測試組合的MPS平均值來看，MC+woct大於MU+woct、MC+wct大於MU+wct（植體類比體之應變值：MC+woct = -242.48±14.65 μє, MC+wct = -231.71±27.72 μє , MU+woct = -215.95±17.79 μє , MU+wct = -221.00±7.59 μє；植體之應變值：MC+woct = -976.76±172.16 μє, MC+wct = -868.09±207.38 μє , MU+woct = -919.49±147.17 μє , MU+wct = -839.72±101.40 μє ）。抗扭力裝置的使用與否並沒有統計學上的差異，支台之抗旋轉設計的影響則不明顯。施加預載力於支台螺釘上會產生近乎平行待測物長軸的應變，而未來的研究方向著重在施力過程中動態分析。

Applying a force onto abutment screws within its preloading limit can induce a clamping force between the implant-abutment interfaces and can prevent screws from loosening, thereby reaching a more stable implant-abutment joint. However, overload or overstrain may cause implant deformation which may induce excessive strains around peri-implant bones and affect osseointegra-tion. The purpose of the study was to evaluate whether the use of an antirotational design at implant-abutment interface and the application of a counter-torque device could affect the development of peri-implant bone strain with a preloading force onto the abutment screws. Three parts of experiment were included in the study. The first part focused on the effect of the antirotational design of the abutments and the counter-torque device to the implant-bone interface when tightening the abutment screws. The second part is done to clarify the effect the clamping force between the implant-abutment interface caused by tightening the abutment screw to the implant-bone interface. The implant replica was chosen for testing. The effect of the antirotational design of the abutments and the counter-torque device were also discussed. In the third part of the experiment, the implant replica was replaced with implant for testing. In the first part of the experiment, a 5 mm diameter implant replica of Brånemark system was fixated onto a torque gauge. There were two types of implant abutment designs chosen for testing: an anti-rotary based MirusCone abutment (MC) design and a rotary, or without anti-rotary, based Multiunit abutment (MU) design. An abutment screw was placed and tightening the screw with an electronic torque controller with 20 Ncm torque. The preloads were also conducted under the conditions of with and without the use of counter-torque device (wct and woct respectively). Therefore, the measure-ments were done under four different combinations: MC+woct, MC+wct, MU+woct, MU+wct. Each of these combinations was repeated five times and the torque transmitted to implant surface were recorded by the torque gauge. In the second part of the experiment, a snacked delta rosette strain gauge was bonded on a 5 mm of diameter implant replica of Brånemark system. The strain gauge was bonded at approximately 1.5 mm away from the implant-abutment junction with one strain gauge ( SG 1 ) parallel to the longitudinal axis of the replica. Then the replica assembly was embedded in an epoxy resin block. Five models were set up and the four measurement combinations: MC+woct, MC+wct, MU+woct, MU+wct were tested 5 times for each measurement condition accuracy and precision. In the third part of the experiment, three models of implant fixture of 4mm in diameter and 10mm in height were constructed and the tests were repeated. Spike2 software was used to analyze the results of the second and third parts of the experiment. The maximum and minimum principle strains (Єp,q ) as well as the angle (øp,q ) between strains and the longitudinal axis of the implant/replica were calculated with the formulas provided by the manufacture. Under the condition of the 20 Ncm torque applied with counter-torque device, the torque transmitted to the replica surface recorded by the torque gauge was lessened about 90 % in comparison with the condition without counter-torque device. According to the strain gauge data, the value of the SG 1 was highest and almost equal to maximum principle strain (MPS). According to a preliminary study, a Multiunit abutment was tightened with 20 Ncm and 32 Ncm torque forces. From the results, there was a direct correlation between the strength preloaded upon the abutment screw and the strain value imposed onto the object under test. The larger the preload, the higher the reaction observed between the peri-implant and the bone and the wider the longitudinal axis of the device under test (clockwise direction). Both the replica and fixture models showed that MC+woct had greater change than MU+woct, and MC+wct had greater change than MU+wct ( in replica group: MC+woct = -242.48±14.65 μє, MC+wct = -231.71±27.72 μє , MU+woct = -215.95±17.79 μє , MU+wct = -221.00±7.59 μє ; in implant group: MC+woct = -976.76±172.16 μє, MC+wct = -868.09±207.38 μє , MU+woct = -919.49± 147.17 μє , MU+wct = -839.72±101.40 μє ). The use of counter-torque device did not statistically affect the strain value. More, the different results from the antirotational designs of the abutment were insignificant. The data showed that preloading the abutment screw may directly induce peri-implant bone strain towards the direction along the longitudinal axis of the implant replica and fixture. Future research will focus in the area of dynamically changing the force of preload affecting the result.