三單位植體補綴物不密合度對於植體螺釘關節
內部應力分佈的影響

礙於臨床上及製作技術上的限制，要製作一個完全密合的補綴物幾乎是不可能的。因此，決定一個臨床可以接受的補綴物密合度是有必要的。本有限元素分析實驗的目的在於比較三單位牙橋補綴物與支台間的垂直不密合度，對於植體螺釘關節內應力分部的影響。實驗中採用NobleBiocare植體系統的MK IV植體、Multi-unit支台與TorqTite植釘為觀察對象。補綴物是模擬由兩支植體支撐的三單位螺釘固定牙橋，並在遠心支台與補綴物間設定0μm、50μm、100μm、150μm的垂直間隙，來模擬補綴物的不密合度。實驗步驟為依序鎖緊近心支台螺釘、遠心支台螺釘、近心補綴固位螺釘與遠心補綴固位螺釘(支台螺釘的預負載力設為550N；補綴固位螺釘的預負載力設為350N)，再於遠心支台上方補綴物施予300N的模擬垂直咬合力。實驗結果顯示在支台螺釘部分最大應力分部於螺紋部與螺釘頭部間的連接體處，當密合度愈大時，應力數值愈大，並集中在螺釘連接體接近螺紋部分。近心支台螺釘最大的Von Mises應力發生在施加模擬咬合力後，依密合度小到大的順序為：24.0%, 26.7%, 34.1%, and 41.8% of the ultimate tensile strength(1100 N)。在補綴固位螺釘方面，應力也是主要集中在螺釘的連接體處，而且數值明顯比支台螺釘大許多。最大Von Mises應力發生在近心補綴固位螺釘的連接體處，在四支螺釘都鎖緊後，其數值依密合度小到大的順序為：72.3%, 75.1%, 75%, and 88% of the ultimate tensile strength(1100 N)。在施加模擬咬合力後，唯有150μm不密合度這組的最大Von Mises應力明顯提高至0.94 GPa (90.7% of the ultimate tensile strength)。其餘三組則變化不明顯。在本實驗的條件限制下顯示三單位牙橋補綴物的垂直不密合度在150μm這組對近心補綴固位螺釘造成的最大應力明顯大於其餘三種密合度。另外，在支台螺釘方面，最大應力皆沒有大過ultimate tensile strength。

關鍵字

植體；補綴物；密合度；螺釘關節；應力分部

並列摘要

Purpose: The purpose of this study was to use finite element analysis to investigate the effect of misfit prostheses on the stress distribution in the abutment screws and prosthetic screws. Materials and Methods: A 3-dimensional finite element models, including two 4.0-mm-diameter MK IV implant fixtures, two 2.0-mm-height / 4.0-mm-diameter Multi-unit abutment with TorqTite abutment screws and TorqTite prosthetic screws, suprastructure, and bone block were constructed. The geometries of four suprastructures were designed to simulate 0μm、50μm、100μm、150μm gaps between suprastructure and distal abutment. The loading procedure is in the sequence : mesial abutment screw, distal abutment screw, mesial prosthetic screw, distal prosthetic screw, and adding 300N simulated biting force on distal area of suprastructure. Results: When the implant system got balance without external loading, the maximum Von Mises stress of mesial abutment screw were 23.5%, 25.6%, 32.5%, and 40.0% of the ultimate tensile strength(1100 N) in sequence of 0 to 150μm gap. With a simulated biting force of 300N, they became 24.0%, 26.7%, 34.1%, and 41.8%. Regarding two prosthetic screws, the maximum Von Mises stress occurred in mesial one, the values were 72.3%, 75.1%, 75%, and 88% of the ultimate tensile strength in sequence of 0 to 150μm gap. After simulated biting load, the value increased to 90.7% of the ultimate tensile strength in 150μm-gap model. Conclusions: Prosthesis misfit influenced the pattern and magnitude of stress distribution in the abutment and prosthetic screws. The stress of mesial prosthetic screw in 150μm-gap model was obviously different from the other three models. All the three vertical discrepancy, 50μm, 100μm, and 150μm, between prosthetic and abutment could be closed after the screws were locked.

並列關鍵字

Three Unite Suprastructure Misfit ； Stress Distribution ； Implant Screw Joints

參考文獻

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三單位植體補綴物不密合度對於植體螺釘關節內部應力分佈的影響

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