評估CEREC 3D 全瓷冠蓋體之邊緣及內部的密合度及咬合面的精確度

Marginal discrepancy, internal fitness, and occlusal accuracy of CEREC 3D ceramic onlays

何偉宏(Wei-Hong He)

指導教授 ： 洪純正

高雄醫學大學/口腔醫學院/牙醫學研究所/碩士(2007年)

https://doi.org/10.6832/KMU.2007.00111

摘要

研究目的：
CEREC 3D系統是屬於牙科診間 CAD/CAM系統的一種，病人可在一次的診療時間內完成治療。但所製作出來的復形物在精準度方面尚有改善的空間。本研究目的是想測量CEREC 3D系統所製作的全瓷冠蓋體復形物，在咬合面高度、邊緣密合度、內部密合度各方面的精準度。
材料與方法：
以一顆46的樹脂牙做為樣本，包埋於咬合器上，和對咬牙呈均勻的咬合關係，並以三維立體測量床定位及記錄咬合面咬點的三維座標。在樣本牙上設計一個BOD方位的冠蓋體窩洞，窩洞壁為10°外展，深度為2mm，肩部寬度及高度為1.5mm，咬合面曲線依照牙齒解剖構造設計，並在此曲線上設定曲率半徑分別為1.0mm、3.5mm、10.0mm的線段。窩洞外形以牙科用硬石膏翻模十次。
以CEREC光學取模專用石膏分別對窩洞車磨前後及對咬記錄進行翻模再進行光學取模，表面不需進行噴粉處理。使用CEREC 3D系統(V 2.80 R2400, step bur 10 & cylinder pointed bur 1.6)，進行窩洞復形物製作，依照軟體中所提供的咬合面設計方式分成C組(correlation: 依照未車磨窩洞前的外形製作)及F組(function: 依照對咬牙的咬合記錄來製作)兩組，使用瓷塊為Vita Mark II，樣本數目兩組各為5個。
將復形物定位於原本窩洞模型中後，測得咬合高度變化。再以複合樹脂黏著劑將復形物固定於翻製的石膏模窩洞，利用三維立體測量床加以測量，再以多面向切割方式直接觀測內部及邊緣的密合度。
分別針對咬合高度、內部密合度、邊緣密合度設定統計模組進行分析。使用多因子變異數分析模組內含區集及巢式設計(multi-factor ANOVA (including block and nested design))，並將各因子之間交互作用(interaction)併入統計模組(α=0.05)。
樣本數若有未達常態分布或未能滿足中央極限定理的項目，則再以無母數統計法(Wilcoxon / Kruskal-Wallis Tests (Rank Sums))加以分析比較(α=0.05)。
結果：
在C組中，咬合高度提高100.25± 53.72µm，而在F組中，咬點高度提高90.80 ± 31.39µm，都顯著比程式內設定的數值高。
在邊緣密合度方面，平均值為94.23 ± 34.33μm，其中以牙齦邊緣的密合度最好(61.23 ± 25.68µm)，顯著優於頰側(157.40 ± 50.87µm)及遠心側(121.00 ± 39.30µm)的垂直邊緣，咬合邊緣密合度僅次於牙齦邊緣(95.97 ± 35.49µm)。曲率半徑大小並不顯著影響邊緣密合度，但呈曲率半徑越大，密合度越好的趨勢。
在內部密合度方面，平均值為115.60 ± 29.51µm，在頰側及遠心側的轉角處(269.66 ± 315.31µm)縫隙值顯著大於其他位置。而若以縱切面觀，則在肩部內緣線角處密合度(462.27 ± 312.67µm)顯著不如其他位置。
結論：
以CEREC 3D系統製作出來的冠蓋體復形物，能夠符合臨床精準度的要求，而垂直邊緣線的精準度及內部的密合度則有待加強。窩洞設計時要避免尖銳的內部線角及太過複雜彎曲的邊緣曲線。

關鍵字

CEREC ； CAD/CAM ； 邊緣密合度 ； 內部密合度 ； 咬合精準度

並列摘要

Objective:
CEREC 3D is one of the chair-side dental CAD/CAM systems, patients can get their treatments finish in one appointment. The accuracy of the prostheses fabricated with chair-side dental CAD/CAM systems is not perfect yet. The purpose of this study is to measure the occlusal accuracy, marginal discrepancy, and internal fitness of the full ceramic onlay produced by CEREC 3D CAD/CAM system.
Materials &Methods:
Used a right mandibular first molar resin tooth as the sample of this study. This sample tooth and the neighbor teeth were mounted on an articulator with an even occlusion relationship against the antagonist teeth. Used the 3D coordinate measuring machine to locate and recode the three-dimension coordinates of the occlusal points on the sample tooth. A BOD(buccal-occlusal-distal) onlay cavity was set on this tooth with 2 mm in depth, 10°flared axial wall, and a shoulder with 1.5mm in width and height. The occlusal marginal line of this cavity went according to the occlusal morphology of the sample tooth with three pre-set curvatures. The radiuses of those curvatures pre-set on the occlusal marginal line are 1.0mm, 3.5mm, and 10.0mm. Ten duplicates of the cavity were made with dental hard stone.
Duplicates of the original tooth, the cavity, and the occlusal registry were made with special modeling plaster for CEREC optical impression. The data of this cavity was taken with optional impression without powdering procedure. Used CEREC 3D system (V 2.80 R2400, step bur 10 and cylinder pointed bur 1.6) to produce restorations for the onlay cavity, the occlusal surfaces were designed with ‘correlation’ (Group C: according to the original tooth) and ‘function’ (Group F: according to the occlusal registry) programs of CEREC 3D software. Vita Mark II ceramic blocks were used to produce the restorations. Both groups includes 5 samples.
Fix the restorations into the original tooth model to exam the changes of occlusal height. Then fixed the restorations into duplicates with resin composite cement and measure those samples with 3D coordinate measuring machine. Marginal discrepancy and internal fitness were observed directly with multiple cutting methods.
Used statistic models to analyze the data of occlusal accuracy, internal fitness, and marginal discrepancy. The models set as multi-factor ANOVA including block design, nested design, and interaction effect (α=0.05).
If the sample size of statistic models cannot reach normal distribution and Central Limit Theorem, the non-parametric statistics (Wilcoxon / Kruskal-Wallis Tests (Rank Sums)) were used to analyze the data (α=0.05).
Results:
In group C, the average occlusal height increases 100.25 ± 53.72µm. In group F, the average occlusal height increases 90.80 ± 31.39µm. There is no statistically significant difference between two groups. The occlusal height of both two groups is statistically significantly larger than the settings in programs.
The average marginal discrepancy is 94.23 ± 34.33μm. The gingival margin has the smallest discrepancy (61.23 ± 25.68µm), which is statistically significantly smaller than the discrepancies of buccal (157.40 ± 50.87µm) and distal (121.00 ± 39.30µm) vertical margin . The occlusal marginal discrepancy (95.97 ± 35.49µm) is just larger than the discrepancy of gingival margin. There is no statistically significant difference amount the radiuses of curvatures, but there is a tendency that curvatures with smaller radiuses have larger marginal discrepancy.
The average gap size of internal fitness is 115.60 ± 29.51µm. The gap size of buccal-distal corner area (269.66 ± 315.31µm) is statistically significantly larger than others. Longitudinal section planes show that the largest internal gap (462.27 ± 312.67µm) is at the internal line angle of the gingival shoulder.
Conclusion:
The full ceramic onlays fabricated with CEREC 3D system can reach the clinical requirements of accuracy, but need to improve the fitness of the vertical margin and the internal area. When preparing the cavity for a CAD/CAM restoration, the operator should avoid any internal sharp line angles and reduce complex marginal curvatures.

並列關鍵字

CEREC ； CAD/CAM ； marginal discrepancy ； internal fitness ； occlusal accuracy

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