2种粘接剂用于前牙断冠再接的剪切力评价

目的比较2种粘接剂用于前牙断冠再接时的剪切力。方法自制上颌恒中切牙冠折模型40个,随机分为A、B组,分别采用日本可乐丽菲露两步法粘接剂Clearfil SE Bond和一步法粘接剂Clearfil S3 Bond及相同的复合树脂Clearfil AP-X进行断冠再接。将再接后的样本置于万能试验机加载台上,持续加力至牙冠折断,记录牙冠断裂时的剪切力值。结果A、B组断冠再接后的剪切力分别为（324.32±65.91）N、（263.08±55.88）N。A组断冠再接后的剪切力明显高于B组,2组间有统计学差异（t=3.17,P=0.000）。结论两步法粘接剂Clearfil SE Bond用于前牙断冠再接后的剪切力优于一步法粘接剂Clearfil S3 Bond。     

用粘接剂及固位钉增强汞合金充填体的剪切粘接强度

作者旨在比较固位钉、粘接剂及两者联合使用时汞合金对牙本质的剪切粘接强度。 材料和方法 使用45颗离体牙(尺寸相似且完整的第三磨牙),磨去部分牙冠直至牙釉骨质界冠向 2 mm 处,于暴露的牙本质表面开窗5 mm~2,然后埋入丙烯酸树脂块中备用,随机分为 3组,每组15个样品。第1组为粘接剂组,首先在牙本质上涂布粘接剂引物,然后在暴露牙釉质表面使用Panavia-Ex粘接剂,最后充填汞合金;第2组为粘接剂加固位钉组,在牙本质中插入2根Pin-     

粘接固定种植冠粘接剂选择的研究进展

粘接固定种植义齿近年来得到广泛的应用，但临床上仍不时有种植修复失败的病例报道。粘接力在种植义齿的功能状态中起固位作用，当种植体中央螺丝松动、折断、种植体周围炎、食物嵌塞等有必要取下牙冠时，可拆卸则需考虑的因素，如何选择一种粘接剂能兼顾粘接力与可拆卸，会影响最终的临床拆卸效果，而目前对于种植牙冠粘接剂的选择尚无统一标准。本文从粘接固位种植牙冠对固位和可拆卸性的要求，固位与可拆卸的统一，机械实验的局限性等方面做一综述，为临床粘接种植修复的取冠及粘接剂的选择提供技术指导和理论依据。     

减少种植修复体周围粘接剂残留方法的体外研究

目的：通过建立体外模型,比较四种减少单颗种植修复体周围粘接剂残留方法的效果。方法：选择一例于河南大学赛思口腔医院行右下第一磨牙种植修复的病例。制取种植体水平印模后,灌注20副相同的超硬石膏模型作为实验模型,分为直接粘接组(n=5)、代型粘接组(n=5)、橡皮障法粘接组(n=5)、凡士林法粘接组(n=5),修复基台边缘均匀设计于龈下0.5mm深度。在模型上模拟粘接操作并清除多余粘接剂后,将基台-牙冠复合体取下,采用称重的方法获得残留粘接剂重量。结果：四种方法均有粘接剂残留,其中代型组、橡皮障组、凡士林组残留粘接剂质量均少于直接粘接组,且具有统计学意义(P<0.05),但其三者间无统计学意义(P>0.05)。结论：代型法、橡皮障法、凡士林法均可有效减少单颗种植修复体周围粘接剂残留,凡士林法是更简便、高效的方法。     

标准牙冠三维模型的建立及其可操作平台的研究

目的 建立标准牙冠的计算机三维模型以及开发其可操作的软件平台。方法 利用三维激光扫描仪扫描全牙列28颗标准牙冠的石膏模型，编写程序对获得的数据进行处理，重建各牙冠的三维图形，并结合国人牙冠的平均测量数据对其进行调整，同时在牙冠表面定义特征区和特征点，利用程序对牙冠进行各种变换和调整。结果 扫描仪获取了牙冠数据，系统重建了各牙冠的标准三维图形，可对牙冠进行各种变换使其产生位移、旋转和整体形变，按照各牙冠的解剖特点及正中He时的咬合接触定义了特征区，特征区可以在空间三个方面上产生指定形变。结论 标准牙冠的三维计算机模型精确可靠，其操作平台实现了多种功能，为进一步开发打下了基础。     

牙冠三维演示模型建立方法的探讨

目的：初步探讨基于普通Windows平台的牙冠三维演示模型建立的方法。方法：通过获取牙冠石膏模型三轴外形轮廓及He龈向层面截面外形，在Windows98下，利用3Dmax软件重建牙冠三维模型。结果：寻求了一套简单、价廉、易操作的牙冠三维教学演示模型建立的方法。结论：该牙冠建模方法简单易行，可应用于实验课教学；建立的牙冠模型可供教学演示，网络教学，多媒体制作，为修复体设计三维预览奠定基础。     

CAD/CAM系统中牙颌数据库的建立

目的：建立CAD／CAM系统中标准牙冠及牙列的三维数据库。方法：利用探针式扫描仪扫描全牙列28颗标准牙冠模型,处理数据,重建各牙冠的三维图形,并结合国人牙冠平均值进行校正。结果：扫描仪所测数据处理、校正后,重建了国人28颗标准牙冠的数据库以及标准牙尖交错He全牙列。结论：单个标准牙牙冠以及标准牙尖交错He全牙列数据精确可靠,为CAD／CAM系统的开发打下基础。     

年轻恒前牙冠折断再接的临床观察

选择2006-02～2007-11来我院儿科就诊的32颗年轻恒前牙冠折的病例,采用日本可乐丽公司生产的帕娜碧亚F双固化粘接材料、3M纳米树脂、3M siglebond-2粘接剂进行自体断冠再接.通过半年至2年的观察,有2颗再接牙冠脱落,其余再接牙冠固位良好,形态美观.断冠再接术是一种简便的、适合于年轻恒前牙冠折的过渡性治疗方法.     

不同制作和粘接方法对铸造金属桩核固位性影响的研究

目的:探索铸造金属桩核制作方法、粘接方法和粘接剂种类对其固位的影响。方法:选择80颗完整的新鲜无龋坏下颌单根管双尖牙,在釉牙骨质界上2 mm处去除临床牙冠,行根管治疗,根管预备和铸造桩核制作及粘接。根据制作方法将80个样本分为两大组(直接法和间接法),每组40个。每组又根据粘接方法(使用螺旋输送器和未使用)和粘接剂(玻璃离子水门汀和磷酸锌水门汀)不同下分4小组,每组10个样本。将样本置于23 ℃室温生理盐水中存放24 h后放置于万能力学测试机上,以0.5mm/min的速度进行拉力试验直到失败,从而得出固位力大小。结果:本实验中影响固位力的最明显因素为粘接方法,使用了螺旋输送器组的固位力明显高于未使用螺旋输送器组(P<0.05);不同制作方法对固位力无明显影响(P>0.05),使用磷酸锌粘接剂组固位力高于使用玻璃离子粘接剂组。然而制作方法,粘接方法和粘接剂种类间是有密切的交互作用的(P<0.05)。结论:制作方法并不影响铸造桩核的固位力,磷酸锌粘接剂性能优于玻璃离子粘接剂,粘接方法对固位力有显著的影响,建议在粘接过程中使用螺旋输送器。     

基于印模扫描数据CAD/CAM一体化纤维桩核的密合度观察

目的 观察基于桩核印模扫描数据CAD/CAM的一体化纤维桩核的密合度.方法 选择上颌侧切牙、尖牙、单根管前磨牙各10颗,按统一标准制备牙冠缺损并预备根管后.按牙位均分为2组,分别采用桩核印模或桩核蜡型三维扫描数据设计一体化桩核CAD模型,并通过CAM方法制成一体化纤维桩核,桩核对应试戴、粘接入根管后分别在根桩颈、中、根尖段中心区垂直牙长轴片切离体牙,测量截面上根桩周围粘接剂的厚度并进行统计分析.结果 基于印模、蜡型扫描数据CAD/CAM的一体化纤维桩核的粘接剂厚度均值范围分别是78.5～102.6μm和75.6 ～96.0 μm,不同数据获取方法或牙根形态对粘接剂厚度无显著影响.结论 基于桩核印模扫描数据CAD/CAM的一体化纤维桩核密合度满足临床要求.     

Microleakage of Porcelain and Composite Machined Crowns Cemented with Self‐Adhesive or Conventional Resin Cement

Purpose: Resistance of machined crowns to microleakage when cemented with new self‐adhesive cements has not been fully investigated. This study evaluated microleakage of machined crowns milled from porcelain and composite blocks and bonded to teeth with self‐adhesive and conventional resin cement. Materials and Methods: Thirty‐two freshly extracted premolars of similar shape and size were sterilized and mounted in resin blocks. Teeth received standard crown preparations with 1‐mm circumferential shoulder finish line, flat occlusal surface reduced by 2 mm, and ideal angle of convergence. Prepared teeth were divided into two equal groups and assigned to either porcelain (Vita Mark II, Vident) or composite (Paradigm MZ100, 3M ESPE) blocks for crown fabrication. Optical impressions were captured for each tooth with the intraoral camera of a CEREC 3D machine. Crowns were designed and milled from both materials. Each group was then subdivided into two subgroups (n = 8) according to cement used (self‐adhesive resin cement, RelyX Unicem, 3M ESPE or resin cement with self‐etching adhesive, Panavia F 2.0, Kuraray). Following seating, a 5‐kg weight was applied on the occlusal surface of the crown for 5 minutes. Specimens were then stored in water at 37°C for 24 hours. Specimens were thermocycled for 3000 cycles between 5°C and 55°C, then coated with nail varnish and immersed in a 2.0% basic red fuchsine dye solution for 24 hours. Teeth were then rinsed and sectioned mesiodistally and assessed under magnification for microleakage. A five‐point scale was used to score degree of microleakage. Data were statistically analyzed with 2‐way ANOVA and Kruskal‐Wallis nonparametric test. Results: Crown material had no significant effect on microleakage (p= 0.67); however, cement type had a significant effect (p < 0.0001), with Panavia F 2.0 resulting in lower microleakage scores than RelyX Unicem. Conclusions: Compared to the self‐adhesive cement, the resin cement with separate primer/bonding agent resulted in significantly lower microleakage scores, irrespective of crown material.     

Comparing the Effect of a Resin Based Sealer on Crown Retention for Three Types of Cements: An In Vitro Study

To determine the effect of resin based sealer on retention of casting cemented with three different luting agents. 55 extracted molar teeth were prepared with a flat occlusal surface, 20° taper and 4 mm axial height. The axial surface of each specimen was determined. The specimen were then distributed into five groups based on decreasing surface area, so each cementation group contained 11 specimens with similar mean axial surface area. A two-step, single bottle universal adhesive system (One-Step—Resinomer, Bisco) was used to seal dentin after the tooth preparation. Sealer was not used on the control specimens except for the modified-resin cement (Resinomer, Bisco) specimens that required use of adhesive with cementation. Using ceramometal (Wirobond^®, BEGO), a casting was produced for each specimen and cemented with either zinc phosphate (Harvard), glass ionomer (Vivaglass) or modified resin cement (Resinomer) with single bottle adhesive. All the castings were cemented with a force of 20 kg. Castings were thermal cycled at 5 and 55 °C for 2,500 cycles and were then removed along the path of insertion using a universal testing machine at 0.5 mm/min. A single-factor ANOVA was used with a = 0.05. The nature of failure was also recorded. The mean stress removal for non sealed zinc phosphate, sealed zinc phosphate, non sealed glass ionomer, sealed glass ionomer and modified resin cement was found to be 3.56, 1.92, 2.40, 4.26, 6.95 MPa respectively. Zinc phosphate cement remained principally on the castings when the tooth surface was treated with the sealer and was found on both the tooth and the casting when the sealer was not used. Fracture of root before dislodgement was seen in 9 of 11 specimens with modified resin cement. Resin sealer decreases the retention of the castings when used with zinc phosphate and increases it when used with glass ionomer cement. The highest mean dislodgement force was measured with modified resin cement.     

树脂加强型玻璃离子水门汀的涂布方式对锆瓷冠与种植体基台粘固效果的影响

目的 分别应用传统涂布法和预压薄法,比较树脂加强型玻璃离子水门汀在种植体支持的氧化锆单冠粘固修复中水门汀残留和粘接力的差别。方法 应用Sinora CEREC系统扫描Ankylos标准B型6mm种植体基台替代体,设计厚度为1mm的单冠,切割和烧结氧化锆瓷块,制作氧化锆单冠。应用树脂加强型玻璃离子水门汀,分别通过传统涂布法和水门汀预压薄法,将单冠粘固在种植体基台替代体上。观察水门汀的残留情况,评价2种粘固方法的粘接效果。结果 预压薄法粘固组的氧化锆单冠和基台周围水门汀残留明显少于应用传统涂布法的粘固组。但是预压薄法组的平均粘接力（247.95N）明显小于传统涂布法组（428.79N）,其差异具有统计学意义（P<0.01）。结论 树脂加强型玻璃离子水门汀预压薄法能有效减少树脂加强型玻璃离子水门汀的残留,但其粘接力明显降低。     

4种玻璃离子水门汀对ITI基台与金属内冠之间粘接力的比较研究

目的：研究4种玻璃离子类水门汀对ITI种植系统标准颈粘接固位基台和金属内冠之间的粘接力。方法将10只金属内冠与10只I T I标准颈粘接固位基台分别使用以下4种水门汀进行交叉粘固：A组为玻璃离子水门汀（日本）;B组为树脂加强型玻璃离子水门汀（美国）;C组为暂时粘固用玻璃离子水门汀（日本）;D组为玻璃离子水门汀（德国）;粘固后测试并记录样本粘接力（N）,同时观察并记录粘固界面的断裂模式,最后,对粘接力进行统计学处理。所有内冠和基台经清洗后重复使用。结果4种水门汀的粘接力及由大至小的排列顺序为C组（183.6±29.4） N〉D组（153.4±36.2） N〉B组（144.4±41.1） N〉A组（109.9±25.7）N,其中C组的粘接力最高,A组的粘接力最低,A组显著低于其它3种水门汀（P〈0.05）。对样本的断裂面观察显示,A组和D组样本断裂面发生在水门汀和基台表面之间,而B组和C组样本的断裂面则呈现混合断裂的模式。结论2种玻璃离子水门汀和树脂加强型玻璃离子水门汀都具有临床可接受的粘接力,而暂时粘固用玻璃离子水门汀因粘接力太大,不适用对种植牙冠进行暂时粘固。     

玻璃离子水门汀与银汞粘接的剪切力测试

探讨了玻璃离子水门汀增强银汞充填体与牙体之间的粘结作用。取新鲜离体人磨牙制成3mm厚的牙块,在其中央制备直径3mm的圆柱形洞,分别以玻璃离子、银汞粘结剂涂于洞壁,再充填银汞合金,另设空白对照组。两周后测各组的剪切力并作统计学分析。结果表明:玻璃离子与银汞粘结剂组的剪切力比空白对照组大,并有显著差异;说明玻璃离子与银汞粘结剂均有相似的增强银汞修复体与牙体之间粘结力的作用。     

(牙合)面厚度与肩台宽度连续变化的下颌第一磨牙全瓷冠三维有限元分析

目的 探讨(牙合)面厚度和肩台宽度同时连续变化情况下下颌第一磨牙全瓷冠的优化设计,以期为全瓷冠的临床设计提供理论基础.方法 运用逆向工程及计算机辅助设计技术建立(牙合)面厚度和肩台宽度连续变化的下颌第一磨牙三维有限元模型,设定(牙合)面厚度变化范围为1～3 mm,肩台宽度变化范围为0.4～1.2 mm,并在全瓷冠颊尖垂直向(牙合)面加载225 N的力,观察验面厚度和肩台宽度同时变化对全瓷冠、粘接剂、基牙、牙周膜和牙槽骨等效应力峰值的影响,同时进行灵敏度分析.结果 随着(牙合)面厚度和肩台宽度的增加,除牙周膜和牙槽骨的等效应力峰值无明显变化外,全瓷冠、粘接剂和基牙的等效应力峰值均下降.当(牙合)面厚度≥1.87 mm、肩台宽度≥0.66 mm时,全瓷冠、粘接剂和基牙的应力响应曲线斜率均位于-1～1之间,即在此区间内等效应力峰值变化相对较小.灵敏度分析显示,肩台宽度对全瓷冠和基牙等效应力峰值的影响较大,(牙合)面厚度对粘接剂等效应力峰值的影响较大.结论 在本项研究所设定的参数范围内,下颌第一磨牙全瓷冠的(牙合)面厚度应不小于1.87 mm,肩台宽度应不小于0.66 mm.     

(牙合)面厚度与肩台宽度连续变化的下颌第一磨牙全瓷冠三维有限元分析

目的 探讨(牙合)面厚度和肩台宽度同时连续变化情况下下颌第一磨牙全瓷冠的优化设计,以期为全瓷冠的临床设计提供理论基础.方法 运用逆向工程及计算机辅助设计技术建立(牙合)面厚度和肩台宽度连续变化的下颌第一磨牙三维有限元模型,设定(牙合)面厚度变化范围为1～3 mm,肩台宽度变化范围为0.4～1.2 mm,并在全瓷冠颊尖垂直向(牙合)面加载225 N的力,观察验面厚度和肩台宽度同时变化对全瓷冠、粘接剂、基牙、牙周膜和牙槽骨等效应力峰值的影响,同时进行灵敏度分析.结果 随着(牙合)面厚度和肩台宽度的增加,除牙周膜和牙槽骨的等效应力峰值无明显变化外,全瓷冠、粘接剂和基牙的等效应力峰值均下降.当(牙合)面厚度≥1.87 mm、肩台宽度≥0.66 mm时,全瓷冠、粘接剂和基牙的应力响应曲线斜率均位于-1～1之间,即在此区间内等效应力峰值变化相对较小.灵敏度分析显示,肩台宽度对全瓷冠和基牙等效应力峰值的影响较大,(牙合)面厚度对粘接剂等效应力峰值的影响较大.结论 在本项研究所设定的参数范围内,下颌第一磨牙全瓷冠的(牙合)面厚度应不小于1.87 mm,肩台宽度应不小于0.66 mm.

Abstract：

Objective To investigate the effect of different occlusal thickness and shoulder finish line depth on stress distribution of all-ceramic crowns and to select optimal occlusal thickness and shoulder finish line depth using continuous variation of parameters. Methods This analysis was performed using mandibular first molar finite element modl. The range of occlusal thickness was set from 1 mm to 3 mm, and that of shoulder finish line depth was from 0. 4 mm to 1.2 mm. Load of 225 N was applied perpendicularly to the occlusal surface of the tooth at all buccal cusps to simulate functional occlusal force. The maximum equivalent stresses in crown, cement layer, abutment, periodontal ligament, alveolar bone were calculated, and the sensitivities of stresses to the variables were also evaluated. Results The maximum equivalent stresses in crown, cement layer and abutment decreased as occlusal thickness and shoulder finish line depth were increased, while no obvious change were found in maximum equivalent stresses in periodontal ligament and alveolar bone. When occlusal thickness exceeded 1.87 mm and shoulder finish line depth exceeded 0. 66 mm,the tangent slope rate of the maximum equivalent stress response curves ranged from - 1 to 1. Data indicated that occlusal thickness played a more important role in reducing maximum equivalent stress in cement layer than finish line depth did, and shoulder finish line depth was a more effective parameter in reducing maximum equivalent stress in crown and abutment than occlusal thickness was. Conclusions Occlusal thickness exceeding 1.87 mm and shoulder finish line depth exceeding 0. 66 mm are optimal design for ceramic crown on mandibular first molar from biomechanical point of view.     

The effect of a resin-based sealer on crown retention for three types of cement

STATEMENT OF PROBLEM: In an effort to control postoperative sensitivity, dentin sealers are being applied following crown preparation with little knowledge of how crown retention might be affected. A previous study demonstrated no adverse effect when using a glutaraldehyde-based sealer, and existing studies have shown conflicting results for resin-based products. PURPOSE: This study determined if a resin sealer applied to prepared dentin affected retention of cemented castings when using 3 common types of luting agents. MATERIAL AND METHODS: Extracted human molars (n=55) were prepared with a flat occlusal, 20-degree taper, and 4-mm axial length. The axial surface area of each preparation was determined and specimens were distributed equally among groups (n=11). A 2-step, single-bottle adhesive system (One Step) was used to seal dentin following tooth preparation. Sealer was not used on the control specimens except for the modified-resin cement (Resinomer) specimens that required use of adhesive with cementation. Using ceramometal high noble alloy (Olympia), a casting was produced for each specimen and cemented with a seating force of 20 Kg using either zinc phosphate (Fleck's), glass ionomer (Ketac-Cem) or modified-resin cement (Resinomer) with the single-bottle adhesive. Castings were thermal cycled at 5 degrees C and 55 degrees C for 2500 cycles; then removed along the path of insertion using a universal testing machine at 0.5 mm/min. A single-factor ANOVA was used with alpha=.05. The nature of failure was also recorded and the data analyzed with a chi-square test. RESULTS: Mean dislodgment stresses for unsealed and sealed conditions were 3.7 +/- 1.0 and 2.2 +/- 0.8 MPa for zinc phosphate; 2.7 +/- 1.2 and 4.2 +/- 0.9 MPa for glass ionomer, respectively (P<.001). Retentive stress of castings cemented with modified-resin cement was 6.4 +/- 1.7 MPa. With resin sealer in combination with zinc phosphate, cement resided totally on castings in 82% of the situations and was on both surfaces without sealer. The tooth failed before casting dislodgment in 9 of 11 specimens cemented with modified-resin cement. CONCLUSIONS: Resin sealer decreased casting retentive stress by 42% when used with zinc phosphate. However, sealer use resulted in 55% increased retention when used with glass ionomer. The modified-resin cement produced the highest mean dislodgment stress, nearly always exceeding the strength of the tooth.     

Convergence angle, occlusal reduction, and finish line depth of full-crown preparations made by dental students.

OBJECTIVE: To measure the convergence angle, incisal/occlusal clearance, and finish line depth, which indicate the amount of axial reduction of full metal-ceramic crown preparations made by final-year dental students. METHOD AND MATERIALS: A total of 157 preparations were assessed. Convergence angle and finish line depths were measured by Tool Maker Microscope, while crown height was measured using a digital caliber. RESULTS: The mean convergence angle, faciolingually and mesiodistally, was 22.4 and 25.3 degrees, respectively. The mean for molars was statistically significantly greater than that for other teeth. The incisal/occlusal reduction ranged from 1.8 to 2.2 mm and averaged 2 mm. Buccal shoulder finish line depth averaged 0.86 mm, and mean chamfer finish line depth was 0.74 mm lingually, 0.7 mm mesially, and 0.66 mm distally. The buccal shoulder for mandibular anterior teeth was significantly smaller than for other teeth and averaged only 0.45 mm. CONCLUSION: The mean convergence angle was clinically acceptable. However, shoulder depth was less than the recommended depth of 1.0 to 1.5 mm for metal ceramic crowns. Incisal/occlusal reduction was clinically adequate to provide enough structural durability and color matching.     

Tooth structure removal associated with various preparation designs for anterior teeth

STATEMENT OF PROBLEM: The conservation of sound tooth structure helps preserve tooth vitality and reduce postoperative sensitivity. Innovative preparation designs, like those for porcelain laminate veneers, are much less invasive than conventional complete-coverage crown preparations. However, no study has quantified the amount of tooth structure removed during these preparations. PURPOSE: The purpose of this study was to quantify and compare the amount of tooth structure removed when various innovative and conventional tooth preparation designs were completed on different teeth. MATERIAL AND METHOD:. A new comprehensive tooth preparation design classification system was introduced. Typodont resin teeth representing the maxillary left central incisor, maxillary left canine, and mandibular left central incisor were prepared with the following designs: partial (V1), traditional (V2), extended (V3), and complete (V4) porcelain laminate veneer preparations; resin-bonded retainer preparation with grooves (A1) and with wing/grooves (A2); all-ceramic crown preparation with 0.8 mm axial reduction and tapering chamfer finish line (F1), all-ceramic crown preparation with 1.0 mm axial reduction and rounded shoulder finish line (F2), and metal-ceramic crown with 1.4 mm axial reduction and facial shoulder finish line (F3). After tooth preparations (10 per group), the crown was separated from the root at the CEJ. The removed coronal tooth structure was measured with gravimetric analysis. Means and standard deviations for tooth structure removal with different preparation designs were calculated and analyzed with analysis of variance at a significance level of P<.05. RESULTS: Significant differences in the amount of tooth structure removal were noted between preparation designs. Ceramic veneers and resin-bonded prosthesis retainers were the least invasive preparation designs, removing approximately 3% to 30% of the coronal tooth structure by weight. Approximately 63% to 72% of the coronal tooth structure was removed when teeth were prepared for all-ceramic and metal-ceramic crowns. For a single crown restoration, the tooth structure removal required for an F3 preparation (metal-ceramic crown) was 4.3 times greater than for a V2 preparation (porcelain laminate veneer, facial surface only) and 2.4 times greater than for a V4 preparation (more extensive porcelain laminate veneer). CONCLUSION: Within the limitations of this study, tooth preparations for porcelain laminate veneers and resin-bonded prostheses required approximately one-quarter to one-half the amount of tooth reduction of conventional complete-coverage crowns.