Computer-assisted generation of all-ceramic crowns and fixed partial dentures

The successful application of the concept of computer-assisted manufacturing in restorative dentistry requires that computer-assisted design (CAD) and computer-assisted machining (CAM) not only meet but actually exceed currently accepted standards for the material and clinical quality of dental restorations. In addition, the continued development of systems for polyvalent processing of disparate materials and objects must be assured. With these critical requirements in mind, the Precident system is a clinically proven and competitive system. The resolving power of the CCD chip is much improved compared to conventional cameras or charge-coupled devices. The scanner is able to scan entire casts in a fully automated process. In principle, this facilitates the production of frameworks for fixed prosthetic devices (FPD) of any size. It is also possible to create at least partial frameworks for removable prosthetic devices (RPD). A factor of great clinical and economic importance is the polyvalence of the process in materials processing: the numeric control (NC) machine can be programmed for metal alloys and ceramic materials as well as fiber-reinforced resins. At Aeskulap Klinik, the Precident System is routinely used for producing all single crowns and FPDs with up to four units. CAD/CAM all-ceramic crowns and FPDs currently cost about the same as metallo-ceramic or conventional all-ceramic restorations.     

Two-year clinical evaluation of lithia-disilicate-based all-ceramic crowns and fixed partial dentures.

OBJECTIVES: The aim of this study was to evaluate the clinical performance of crowns and fixed partial dentures (FPDs) made with the Empress 2 system over a 2-year period. METHODS: Twenty anterior or posterior all-ceramic (Empress 2) crowns and 20 anterior or posterior, three-unit fixed partial dentures were fabricated for 15 patients. Evaluations of the restorations were performed at baseline and once a year during the 2-year follow-up period. U.S. Public Health Service criteria were used to examine the marginal adaptation, color match, secondary caries and visible fractures in the restorations. Survival rate of the restorations were determined using Kaplan-Meier statistical analysis. RESULTS: U.S. Public Health Service criteria showed 100% Alpha scores concerning recurrent caries for both crowns and FPDs. No crown fractures were observed during the 2-year follow-up, however, 10 (50%) catastrophic failures of FPDs occurred. Five (25%) failures occurred within the 1-year clinical period and the others (25%) within the second year. SIGNIFICANCE: Single unit Empress 2 all-ceramic crowns exhibited a satisfactory clinical performance over 2-year period. Furthermore, the high fracture rate of Empress 2 FPDs limits the usage of Empress 2 for the fabrication of all-ceramic FPD.     

切牙单端铸瓷粘接桥的临床应用初探

目的 探索切牙单端铸瓷粘接桥的治疗方法,观察其临床效果,以期为单端粘接桥的临床应用提供参考.方法 选择单颗切牙缺失病例10例,制作舌侧翼板固位的单端铸瓷粘接桥,共制作10件粘接桥,分别于修复后2周、1年、2年复查,复查内容包括:修复体折裂情况、边缘适合性、继发龋、颜色匹配性.结果 10例患者平均观察14.7个月.10件单端铸瓷粘接桥均无支架及饰瓷折断、裂纹,无松动;10颗基牙和固位体边缘密合,无边缘着色,无继发龋;7例修复体颜色匹配为A级,3例修复体颜色匹配为B级.结论 单端铸瓷粘接桥可修复单颗切牙缺失,牙体组织磨除量小,短期内临床效果良好,但其强度及粘接效果能否满足临床要求尚需进一步观察.     

Adaptation of all-ceramic fixed partial dentures

Objectives

To measure the marginal and internal fit of three-unit fixed partial dentures (FPDs) using the micro-CT technique, testing the null hypothesis that there is no difference in the adaptation between the ceramic systems studied.

Methods

Stainless steel models of prepared abutments were fabricated to design the FPDs. Ten FPDs were produced from each framework ceramic (YZ - Vita In-Ceram YZ and IZ - Vita In-Ceram Zirconia) using CEREC inLab according to the manufacturer instructions. All FPDs were veneered using the recommended porcelain. Each FPD was seated on the original model and scanned using micro-CT. Files were processed using NRecon and CTAn software. Adobe Photoshop and Image J software were used to analyze the cross-sections images. Five measuring locations were used as follows: MG - marginal gap; CA - chamfer area; AW - axial wall; AOT - axio-occlusal transition area; OA - occlusal area. The horizontal marginal discrepancy (HMD) was evaluated in another set of images. Results were statistically analyzed using ANOVA and Tukey tests (α = 0.05).

Results

The mean values for MG, CA, AW, OA and HMD were significantly different for all tested groups (p < 0.05). IZ exhibited greater mean values than YZ for all measuring locations except for AW and AOT. OA showed the greatest mean gap values for both ceramic systems. MG and AW mean gap values were low for both systems.

Significance

The ceramic systems evaluated showed different levels of marginal and internal fit, rejecting the study hypothesis. Yet, both ceramic systems showed clinically acceptable marginal and internal fit.     

全瓷粘接桥的临床研究进展

为契合当代微创的治疗理念,粘接桥在口腔修复领域有着较大的应用前景.近年来,随着全瓷材料及粘接技术的发展,全瓷粘接桥在临床上的应用越来越广泛.全瓷粘接桥具有微创、美观、省时和低成本等优势,若适应证选择恰当,能体现出优良的中短期修复效果,但其远期的临床效果仍有待进一步研究.本文综合国内外文献,就全瓷粘接桥及其病例的选择、设计方式、粘接技术和预后情况等临床研究进展作一综述,以供参考.     

全瓷固定桥的应用现状

随着高强度陶瓷材料的出现,全瓷固定桥以其优良的耐腐蚀性、耐磨损性、独特的美学性能和极佳的生物相容性逐步代替金属材料和其他高分子材料,被认为是牙列缺损固定修复发展的方向。但其脆性大,在长期咀嚼力作用下易发生断裂,因此如何通过改良全瓷固定桥的材料性能及临床设计来延长全瓷固定桥的使用寿命成为近年来研究热点之一。本文就全瓷固定桥的材料分类、受力分布及临床设计等研究现状进行综述。     

Clinical long-term survival of two-retainer and single-retainer all-ceramic resin-bonded fixed partial dentures.

OBJECTIVES: All-ceramic resin-bonded fixed partial dentures (RBFPDs) were introduced as a conservative treatment approach 15 years ago. The purpose of this prospective study was to evaluate the long-term clinical survival of RBFPDs made with a conventional two-retainer design or a cantilever single-retainer design. METHOD AND MATERIALS: A total of 37 anterior RBFPDs were made from the glass-infiltrated alumina ceramic In-Ceram. Sixteen RBFPDs with a conventional two-retainer design were inserted in 14 patients, and 21 RBFPDs with a cantilever single-retainer design were inserted in 16 patients. Panavia or Panavia 21 were used as luting agents either after silica-coating and silanation or after air-abrasion only. Patients were recalled every year for a clinical examination to evaluate the restorations with regard to function and possible failures. The mean observation time in the two-retainer group was 75.8 months, and in the single-retainer group it was 51.7 months. RESULTS: No restoration debonded. In the two-retainer group, one restoration was lost because it fractured after 3 months at both connectors and one restoration was removed alio loco accidentally. Also in this group, four RBFPDs fractured within 15 months after insertion at one connector, but the pontic remained in situ as a cantilever RBFPD for several years. In the single-retainer group, only one FPD fractured and was lost 48 months after insertion. The 5-year survival rate was 73.9% in the two-retainer group and 92.3% in the single-retainer group. When unilateral fracture of a FPD was taken as criterion for failure, the five-year survival rate decreased to 67.3% in the two-retainer group. CONCLUSIONS: Cantilever all-ceramic resin-bonded fixed partial dentures made from high-strength oxide ceramics present a promising treatment alternative to two-retainer RBFPDs in the anterior region.     

全瓷固定桥的研究进展

尽管受脆性、抗弯强度和断裂韧性等材料性能的影响,全瓷固定桥目前尚未成为常规的固定修复手段,但其临床应用和研究报道越来越多,并显示出良好的应用前景。本文对硅酸盐陶瓷、玻璃渗透氧化铝陶瓷和氧化锆陶瓷全瓷桥材料的基础研究和临床研究进行了综述。     

Contemporary all-ceramic fixed partial dentures: a review

High-strength all-ceramic systems for fixed partial dentures (FPDs)have become available for replacing missing teeth. New core materials have been developed and have evolved in the last decade,with yttrium tetragonal zirconia polycrystals (Y-TZP)-based materials being the most contemporary. With the emphasis on the use of computer-assisted design/computer assisted-manufacturing technology, various production techniques have been developed for enhancing the fabrication of consistent and predictable restorations in terms of strength, marginal fit, and esthetics. Although initial results are limited, results reported in scientific abstracts of ongoing clinical studies assessing the long-term success of three unit all-ceramic FPDs and anecdotal evidence published in peer reviewed articles on the use of Y-TZP-based restorative systems are encouraging. This article reviews the evolution and development of materials and technologies for all-ceramic FPDs.     

CAD/CAM systems,materials, and clinical guidelines for all-ceramic crowns and fixed partial dentures

Advances in dental ceramic materials and the development of computer-aided design/computer-aided manufacturing (CAD/CAM) and milling technology have facilitated the development and application of superior dental ceramics. CAD/CAM allows the use of materials that cannot be used with conventional dental processing techniques. This article reviews the main techniques and new materials used in dentistry for CAD/CAM-generated crowns and fixed partial dentures. Also covered are the clinical guidelines for using these systems.     

Fracture strength of all-ceramic posterior inlay-retained fixed partial dentures

OBJECTIVES: The purpose of this in vitro study was to compare the quasi-static (QSFS) and fatigue fracture strength of all-ceramic resin-bonded three unit inlay-retained fixed partial dentures (IRFPDs) made from a heat-pressed lithium-disilicate based glass-ceramic (LDGC) and a CAD/CAM-manufactured yttrium-oxide partially stabilized zirconia framework (YPSZ). METHODS: Identical IRFPD-models of the maxilla were used. They consisted of a second premolar, a missing first molar and a second molar (Co-Cr-Mo alloy) integrated in a low melting alloy base. Roots were covered with a soft silicone-layer to simulate an artificial parodontium. Premolars had an occlusal-distal inlay-preparation and molars a mesial-occlusal inlay-preparation. Thirty-two IRFPDs were made from each ceramic using two different connector dimensions: 3mmx3mm (LDGC_9, YPSZ_9); 4mmx4mm (LDGC_16, YPSZ_16). All IRFPDs were cemented adhesively to the IRFPD-models, using composite resin cement. QSFS was tested in a universal-testing-machine (UTM) for six specimens. The other specimens were fatigued either with cyclic loading at 250N (n=4) in a chewing simulator or at 600N (n=6) using the UTM, and group YPSZ additionally at 1500N. RESULTS: The medians of QSFS (N) were 960 (LDGC_9), 1316 (LDGC_16), 3180 (YPSZ_9) and 3120 (YPSZ_16). For both QSFS and cyclic loading significant differences were found between LDGC_9 and LDGC_16 (p0.05). Differences between LDGC and YPSZ were significant for both connector sizes (p相似文献   

Clinical outcome of glass-fiber-reinforced crowns and fixed partial dentures: a three-year retrospective study.

OBJECTIVE: Glass-fiber-reinforced resin composites for the fabrication of esthetic single crowns and fixed partial dentures have been developed recently. However, little data on the clinical outcome of such restorations have been published. The purpose of this retrospective study was to evaluate the clinical outcome of crowns and fixed partial dentures made from the glass-fiber-reinforced resin composite material Targis/Vectris. METHOD AND MATERIALS: Between 1995 and 1997, 39 patients were treated with 67 single crowns and 83 fixed partial dentures. Twenty-five crowns and 28 fixed partial dentures were cemented with temporary cement, while 42 crowns and 55 fixed partial dentures were cemented with either zinc-phosphate cement or glass-ionomer cement. RESULTS: In September 2001, 57 restorations in 17 patients were still in function. The three-year survival rate calculated according to the Kaplan-Meier method was 58.8% for all restorations. However, after this time, it was 37.5% for crowns and 59.9% for fixed partial dentures cemented with temporary cement, and 55.1% for crowns and 67.9% for fixed partial dentures cemented with zinc phosphate or glass ionomer. The differences between the restoration groups were not statistically significant. CONCLUSION: Glass-fiber-reinforced crowns and fixed partial dentures made with the glass-fiber-reinforced resin composite material Targis/Vectris showed a lower survival rate than that published for metal-ceramic crowns and fixed partial dentures. Therefore, the use of this material for the fabrication of single crowns or fixed partial dentures as permanent restorations cannot be recommended.     

Survival rates of IPS empress 2 all-ceramic crowns and fixed partial dentures: results of a 5-year prospective clinical study.

OBJECTIVE: The aim of this prospective clinical study was to evaluate the survival rates of IPS Empress 2 (Ivoclar Vivadent) all-ceramic crowns and fixed partial dentures (FPDs) after an observation period of up to 5 years. METHOD AND MATERIALS: Forty-three patients (19 women and 24 men) were included in this study. The patients were treated with a total of 58 adhesive bonded IPS Empress 2 restorations. A total of 27 single crowns were placed on molars and premolars, and 31 three-unit FPDs were placed in the anterior and premolar regions. Clinical follow-up examinations took place at 6, 12, 24, 36, 48, and 60 months after insertion. Statistical analysis of the data was calculated using the Kaplan-Meier method. RESULTS: Results of the 50-month analysis (interquartile range, 33 to 61 months) showed that the survival rate was 100% for crowns and 70% for FPDs. Six failures that occurred exclusively in the three-unit FPDs were observed. Framework fractures were recorded in three FPD units where the connector dimensions did not meet the manufacturer specifications. Only one FPD exhibited an irreparable partial veneer fracture, and 2 FPDs showed evidence of biologic failures. The accuracy of fit and esthetic parameters were clinically satisfactory for crowns and FPDs. CONCLUSION: The results of this 5-year clinical evaluation suggest that IPS Empress 2 ceramic is an appropriate material for the fabrication of single crowns. Because of the reduced survival rates, strict conditions should be considered before the use of IPS Empress 2 material for the fabrication of three-unit FPDs.     

Fracture resistance of different zirconium dioxide three-unit all-ceramic fixed partial dentures

OBJECTIVE: This study evaluated the fracture resistance of different zirconia three-unit posterior all-ceramic fixed partial dentures before and after fatigue loading. MATERIAL AND METHODS: Forty-eight zirconia three-unit posterior all-ceramic fixed partial dentures were fabricated using different manufacturing systems and conventionally cemented on human teeth. The restorations were divided according to the system used for manufacturing the frameworks into 3 groups of 16 specimens each (DCS, Procera and Vita CerecInlab). Half of each group was artificially aged through dynamic loading and thermal cycling, whereas the other half was left with no artificial aging. Afterwards, all specimens were tested for fracture resistance using compressive load on the occlusal surface. Non-parametric ANOVA using the Kruskal-Wallis and Wilcoxon rank tests was performed to test for differences in fracture resistance values with a global significance level of 0.05. RESULTS: All artificially aged specimens survived with no failures. The median fracture resistance values (before; after artificial aging) were: DCS (1683 N; 1618 N), Procera (1522 N; 1256 N), and Vita CerecInlab (1702 N; 1556 N). No significant differences were found for comparisons between different groups before artificial aging. Artificial aging did not significantly influence the fracture resistance of different groups. After artificial aging, group Procera showed significantly lower fracture resistance than the Vita CerecInlab (p=0.015) and DCS (p=0.038) groups. CONCLUSIONS: All tested restorations have the potential to withstand occlusal forces applied in the posterior region and can therefore represent interesting alternatives for replacing porcelain-fused-to-metal restorations. Further assessment is needed before recommending such restorations in daily practice.     

A preliminary prospective evaluation of all-ceramic crown-retained and inlay-retained fixed partial dentures

PURPOSE: The purpose of this preliminary prospective study was to evaluate the clinical outcome of crown-retained and inlay-retained fixed partial dentures (FPDs) made from a new lithium-disilicate glass-ceramic (IPS e.max Press, Ivoclar Vivadent). MATERIALS AND METHODS: Eighty-one 3-unit FPDs were placed in 68 patients. The FPDs replaced teeth in the anterior (8%) and posterior region (92%). All teeth were prepared according to a standardized protocol. The size of the proximal connector of the FPDs was 12 mm2 (anterior) or 16 mm2 (posterior), respectively. Crown-retained FPDs were cemented either with glass ionomer (n = 20) or resin composite (n = 16), while all inlay-retained FPDs (n = 45) were cemented with resin composite. Initial follow-up was performed at 6 and 12 months and annually thereafter. RESULTS: The mean observation periods were 48 months (for crown-retained FPDs) and 37 months (for inlay-retained FPDs). None of the crown-retained FPDs failed during the observation period, while 6 inlay-retained FPDs (13%) had to be replaced. Six cases failed because of debonding (n = 3) or a combination of debonding and fracture (n = 3). During the observation period, 2 patients died and the status of another 5 patients is unknown. The 4-year survival rate according to Kaplan-Meier was 100% for crown-retained FPDs and 89% for inlay-retained FPDs. The differences between the groups were statistically significant. CONCLUSION: Crown-retained 3-unit FPDs made from a new glass-ceramic have a significantly better outcome up to 5 years than inlay-retained 3-unit FPDs over the observation period.