Maximizing esthetic results on zirconia-based restorations

With a flexural strength of approximately 900-1,100 MPa, zirconium oxide is one of the toughest all-ceramic materials available in dentistry.1 It can be used to fabricate both single-unit and long-span bridge frameworks. A moderate level of translucency makes it suitable for esthetically demanding clinical cases, such as restoring maxillary anterior teeth. A variety of well-designed porcelain veneering systems allow technicians to apply their artistic skills to create natural, lifelike restorations. A good balance of strength, precision, and translucency allows zirconia-based restorations to accommodate a variety of clinical situations.     

Current status of zirconia-based fixed restorations

Zirconium dioxide (zirconia) ceramics are currently used for fixed restorations as a framework material due to their mechanical and optical properties. This review article describes the current status of zirconia-based fixed restorations, including results of current in vitro studies and the clinical performance of these restorations. Adaptation of zirconia-based restorations fabricated with CAD/CAM technology is within an acceptable range to meet clinical requirements. In terms of fracture resistance, zirconia-based fixed partial dentures (FPDs) have the potential to withstand physiological occlusal forces applied in the posterior region, and therefore provide interesting alternatives to metal-ceramic restorations. Clinical evaluations have indicated an excellent clinical survival of zirconia-based FPDs and crown restorations. However, some clinical studies have revealed a high incidence of chipping of veneered porcelain. Full-coverage zirconia-based restorations with adequate retention do not require resin bonding for definitive cementation. Resin bonding, however, may be advantageous in certain clinical situations and is a necessity for bonded restorations, such as resin-bonded FPDs. Combined surface treatment using airborne particle abrasion and specific adhesives with a hydrophobic phosphate monomer are currently reliable for bonding to zirconia ceramics. Further clinical and in vitro studies are needed to obtain long-term clinical information on zirconia-based restorations.     

Removable partial denture abutments restored with all-ceramic surveyed crowns.

All-ceramic crowns are used as alternatives to conventional metal-ceramic crowns for the restoration of single teeth. Traditionally all-ceramic restorations possessed physical properties that contraindicated their use in many treatment situations. The strength that zirconia ceramics exhibit seems to support the hypothesis that, in specific situations, an all-ceramic crown may be used to restore removable partial denture (RPD) abutments in areas previously reserved for metal or metal-ceramic restorations. Abutments for RPDs may now be fabricated with Procera AllZirkon with the classically prepared guide planes and rest seats. This article provides an overview of a technique for the fabrication of a zirconia-based crown to be used in conjunction with removable partial dentures using the Procera CAD/CAM technology.     

Zirconium dioxide based dental restorations. Studies on clinical performance and fracture behaviour

Loss of teeth can affect a person's appearance and functions such as eating and speaking. There is thus a need for prosthetic rehabilitation to improve quality of life. For many patients, a fixed dental restoration is preferred, and a common restoration is a porcelain-fused-to-metal bridge retained by teeth or implants. Metal-based restorations can potentially cause adverse reactions though, and this is cause for the search for alternative materials. All-ceramic materials are characterized by strong atomic bonds that make them reluctant to react with the environment, and thus unlikely to cause adverse reactions. All-ceramic materials have other attractive material properties and excellent aesthetic properties and have been successfully used in dentistry, mostly for smaller anterior restorations. Ceramics, however, do not withstand tensile forces as well as metals, and are susceptible to brittle fractures with the connector area being especially prone to fracture. More recently, a new type of ceramic material, based on zirconium dioxide, has been developed. Yttria-stabilized tetragonal zirconia polycrystal, Y-TZP, has a unique ability to resist crack propagation by being able to transform from one crystalline phase to another, and the resultant volume increase stops the crack and prevents it from propagating. This material has the potential to be used for larger restorations and in the molar area. Not enough information, however, is available on clinical follow-up of zirconia-based restorations, especially long-term, and information about all-ceramic restorations supported by implants is lacking. The aim of this thesis was to evaluate designs of zirconia-based restorations in relation to achieving increased fracture resistance and evaluate the clinical performance of implant-supported zirconia-based restorations. In paper I implant-supported all-ceramic fixed partial dentures of two different ceramic materials were compared; a zirconia-toughened alumina material (group 1) and a fully-sintered Y-TZP material (group 2). Eighteen patients were randomly divided between the two groups. At the one-year follow-up, all restorations were in function and no complete fractures were noted. However, fractures of the veneering material were noted. There was a significant difference between the two materials: 54% of the restorations in group 2 showed veneer fractures compared to 8% of the restorations in group 1. Paper IV is a five-year follow-up of the same patient groups. All restorations were still in function without complete fractures, but an increase in veneer fractures was noted: 69% of the restorations in group 2 showed veneer fractures compared to 17% in group 1. In paper II the fracture strength was evaluated for 4-unit Y-TZP fixed dental prosthesis frameworks with different connector dimensions: 2.0, 2.5, 3.0, 3.5 and 4.0 mm. The results showed a significant increase in load at fracture for each increase in connector diameter and recommendations for clinically relevant connector dimensions were suggested. In paper III implant-supported Y-TZP fixed full-arch mandibular dentures were evaluated. At the three-year follow-up all restorations were in function and no complete fractures were noted. However, fractures of the veneering material were noted in nine of the ten patients, affecting 34% of the units. In paper V the fracture strength of crowns with different types of Y-TZP core materials and different core design and different veneering materials was evaluated. The crowns were cemented onto tooth-like abutments, except for one group cemented onto implant-like titanium abutments. The results showed significantly higher loads at fracture and less severe veneer fractures for crowns with anatomically shaped cores compared to simple cores of even thickness. Crowns supported by implant-like titanium abutments showed significantly higher loads at fracture than did those supported by tooth-like abutments. The type of core-material and veneering material did not influence the results.     

Recent advances in materials for all-ceramic restorations

The past 3 years of research on materials for all-ceramic veneers, inlays, onlays, single-unit crowns, and multi-unit restorations are reviewed in this article. The primary changes in the field were the proliferation of zirconia-based frameworks and computer-aided fabrication of prostheses, and a trend toward more clinically relevant in vitro test methods. This article includes an overview of ceramic fabrication methods, suggestions for critical assessment of material property data, and a summary of clinical longevity for prostheses constructed of various materials.     

Teaching of all-ceramic restorations in central European dental schools: a survey

The teaching of all-ceramic restorations in Central European dental schools in the mid 1990s has been surveyed. Based on a 65% response, the findings indicate that the majority of undergraduate (pre-doctoral) students receive instruction in all-ceramic restorations with >75% gaining clinical experience in the use of such restorations prior to graduation. When clinical experience was not received, formal instruction, either in the regular curriculum or in elective studies was generally available. All the schools, with one exception, anticipated that the importance of teaching all-ceramic restorations would increase or at least stay the same. In general, the findings were similar to those reported in studies of the teaching of all-ceramic restorations in North America, Scandinavia, and the UK and Ireland, especially in relation to luting systems, contraindications and finishing instrumentation. However, clinical requirements for all-ceramic restorations in Central European dental schools were more common than in dental schools in North America, Scandinavia and the UK and Ireland.     

树脂水门汀颜色稳定性及其对全瓷修复效果影响的研究进展

树脂水门汀广泛用于粘接全瓷修复体,其颜色稳定性与修复体的长期效果有直接关系。树脂水门汀变色的内源性因素通常与材料构成及聚合反应的引发机制相关,树脂水门汀变色的外源性因素主要与口腔局部环境相关。树脂水门汀的颜色稳定性与全瓷修复体长期美学效果关系密切。本综述系统介绍目前临床常用树脂水门汀的颜色稳定性及影响因素,以及其对全瓷...     

Contemporary materials and technologies for all-ceramic fixed partial dentures: a review of the literature

High-strength all-ceramic systems for fixed partial dentures (FPDs) are available for replacing a missing tooth. New core/framework materials have been developed and have evolved in the last decade. With the advancement of CAD/CAM technology, various fabrication techniques have been developed for fabricating improved, consistent, and predictable restorations in terms of strength, marginal fit, and esthetics and for managing core/framework materials that could not otherwise be managed. This article reviews the evolution and development of materials and technologies for all-ceramic FPDs through data published between 1966 and 2004 in the English language. Peer-reviewed articles were identified through a MEDLINE search and a hand search of relevant textbooks and annual publications. The available information suggests that clinical data on the success of these restorations are limited, and that the results of long-term clinical studies are critical to the assessment of these restorations to provide more specific guidelines for usage.     

Clinical considerations for densely sintered alumina and zirconia restorations: Part 1

Densely sintered alumina- and zirconia-based restorations were introduced to dentistry in the early 1990s and became a popular treatment modality, especially in situations requiring complete-coverage restorations. The use of industrial technologies for the fabrication of the restoration, simple clinical management, and pleasing esthetic outcome have made these restorations an attractive treatment alternative. This article reviews the nature of the materials used and the technologies involved and provides indications for clinical case selection and tooth preparation.     

All-ceramic systems: laboratory and clinical performance

Several all-ceramic systems have been developed in dentistry to meet the increased expectations of patients and dentists for highly aesthetic, biocompatible, and long-lasting restorations. However, early bulk fractures or chippings have led the research community to investigate the mechanical performance of the all-ceramic systems. This overview explores the current knowledge of monolithic and bilayer dental all-ceramic systems, addressing composition and processing mechanisms, laboratory and clinical performance, and possible future trends for all-ceramic materials.     

Clinical application of all-ceramic fixed partial dentures and crowns.

The esthetic demands of patients have increased considerably during recent years. Due to this increasing interest in esthetics, as well as concerns about toxic and allergic reactions, the use of all-ceramic restorations has increased. One of the systems introduced for all-ceramic restorations is the IPS Empress system. This article examines one all-ceramic restoration system, IPS Empress, and presents patient cases in which all-ceramic crowns and fixed partial dentures have been utilized.     

All-ceramic silica/glass-based crowns--clinical protocols

The use of all-ceramic crowns offers the potential for improved aesthetic results compared to conventional ceramo-metal crowns. Silica/glass-based all-ceramic crowns are more translucent than alumina- or zirconia-based crowns and therefore have better optical properties. However, they are mechanically weaker and need to be used in conjunction with resin bonding cements. Both these aspects lead to increased clinical and technical demands and as such there are strict guidelines regarding tooth preparation and bonding procedure that need to be followed when using silica/glass-based all-ceramic crowns. The following article describes these preparation, impression and bonding guidelines with the aid of a case presentation.     

Successful use of a single-retainer all-ceramic resin-bonded fixed partial denture for replacement of a maxillary canine: a clinical report.

This clinical report describes the prosthodontic treatment of a 60-year-old woman to close an edentulous space in the region of the maxillary canine. Single-retainer resin-bonded fixed partial dentures (FPD) have shown satisfactory results in different studies. Recent in vivo studies have shown excellent results for all-ceramic anterior FPDs after 5 years. In the present situation, a cantilevered all-ceramic FPD chosen to replace a missing maxillary canine showed success at the 2.5-year follow-up. Special attention was given to functional and minimal restorative considerations. The use of single-retainer all-ceramic FPDs is discussed. The present case does not represent a routine and well-documented approach for the replacement of a missing maxillary canine. Rather, it is a rarity that was successful because of space availability, present occlusal scheme, and patient cooperation. Implant-supported restorations always should be considered as the first treatment option in such a clinical situation.     

Clinical performance of large, all-ceramic CAD/CAM-generated restorations after three years: a pilot study

BACKGROUND: Adhesively luted all-ceramic restorations preserve and stabilize weakened tooth structure, but there is little published information about the clinical performance of large, all-ceramic restorations. METHODS: In this pilot study, the authors placed 58 large, single-tooth, all-ceramic restorations in 26 patients using a computer-aided design/computer-aided manufacturing, or CAD/CAM, system (CEREC 2, Sirona Dental Systems GmbH, Bensheim, Germany). They documented the maximum height of the restoration and remaining cementoenamel junction, or CEJ. In 21 cases, rubber dam isolation was not possible during adhesive luting. They re-evaluated the restorations after three years according to the U.S. Public Health Service criteria. RESULTS: After three years, the authors rated 56 (97 percent) of the 58 restorations as Bravo or better in regard to marginal integrity, secondary caries (four could not be rated), discoloration and anatomical form. One restoration was rated as Charlie because of poor marginal integrity, and one restoration had to be replaced owing to a bulk fracture. The authors rated the adequacy of proximal contact and occlusal relationships as acceptable-to-good for all restorations. Neither the extent of the remaining enamel at the cavity margin nor application of a rubber dam had any statistically significant influence (chi2 test, P > .05) on the clinical performance of the restorations after three years. CONCLUSIONS: At the three-year recall appointment, the authors found that the adhesively luted all-ceramic restorations had successfully repaired large coronal defects, irrespective of the cavity margin location (that is, coronal or apical to the CEJ). CLINICAL IMPLICATIONS: Tooth-colored, all-ceramic CAD/CAM-generated restorations are an alternative to conventional restorations if large coronal defects need to be treated.     

Preparation guidelines for full and partial coverage ceramic restorations

Aesthetic awareness of dental patients has produced a growing demand for posterior tooth-coloured restorations. This has led to the development of posterior composite resins and, more recently, posterior all-ceramic restorations. In the last decade, modern technological advances have allowed the production of stronger ceramics and better luting techniques, which have led to the use of all-ceramic restorations in posterior sites. The preparation guidelines for posterior ceramic restorations outlined in this paper emphasize rounded internal line angles and a chamfer or rounded shoulder finish-line.     

椅旁CAD/CAM(CEREC AC~(TM))全瓷修复的临床回顾性研究

目的评价椅旁CAD/CAM系统(CEREC AC~(TM))进行全瓷修复的临床效果。方法针对619例患者的667颗各类牙体缺损患牙采用西诺德的瓷睿刻系统(CEREC AC~(TM))进行临床即刻椅旁CAD/CAM全瓷修复,1年后对597例患者的603颗瓷睿刻修复体进行临床效果评价。采用USPHS修订版指标检查,包括美观——解剖形态、颜色匹配、边缘变色、表面质地;功能——边缘吻合性、磨耗(邻接、动静态咬合关系);生物学性能——牙髓活力、继发龋。结果 1年的随访结果发现,临床存留率达到95.11%,失败病例中修复体折裂占比为83%。93%的全瓷修复体表现出较高的美学评分,82%的修复体保持了较好的功能评分,而100%的修复体未见生物学并发症。结论不同牙体缺损患牙的瓷睿刻椅旁CAD/CAM全瓷修复,可获得理想的临床效果,但仍需长期随访。     

CAD/CAM氧化锆全瓷冠修复临床疗效评价

目的：探讨CAD／CAM氧化锆全瓷冠的修复效果。方法：选择82例（192颗患牙）,分别在CAD／CAM氧化锆全瓷冠粘接后1、3、6、12个月进行随访观察。采用美国公共健康协会的修订标准对修复体的临床效果进行评价。结果：观察期间失访4例,随访78例共181件修复体,结果显示CAD／CAM全瓷冠颜色达到好以上91．2％,CAD／CAM氧化锆全瓷冠的崩瓷率2．76％,与修复体部位有明显相关性（P〈0．01）,在粘接12个月后有1个修复体的边缘密合度欠佳,所有复诊患者在12个月的临床观察中均未见边缘着色,继发龋和基牙松动。结论：氧化锆全瓷修复体具有良好的稳定性和生物相容性,近期临床效果满意。     

Current ceramic materials and systems with clinical recommendations: a systematic review

STATEMENT OF PROBLEM: Developments in ceramic core materials such as lithium disilicate, aluminum oxide, and zirconium oxide have allowed more widespread application of all-ceramic restorations over the past 10 years. With a plethora of ceramic materials and systems currently available for use, an overview of the scientific literature on the efficacy of this treatment therapy is indicated. PURPOSE: This article reviews the current literature covering all-ceramic materials and systems, with respect to survival, material properties, marginal and internal fit, cementation and bonding, and color and esthetics, and provides clinical recommendations for their use. MATERIAL AND METHODS: A comprehensive review of the literature was completed seeking evidence for the treatment of teeth with all-ceramic restorations. A search of English language peer-reviewed literature was undertaken using MEDLINE and PubMed with a focus on evidence-based research articles published between 1996 and 2006. A hand search of relevant dental journals was also completed. Randomized controlled trials, nonrandomized controlled studies, longitudinal experimental clinical studies, longitudinal prospective studies, and longitudinal retrospective studies were reviewed. The last search was conducted on June 12, 2007. Data supporting the clinical application of all-ceramic materials and systems was sought. RESULTS: The literature demonstrates that multiple all-ceramic materials and systems are currently available for clinical use, and there is not a single universal material or system for all clinical situations. The successful application is dependent upon the clinician to match the materials, manufacturing techniques, and cementation or bonding procedures, with the individual clinical situation. CONCLUSIONS: Within the scope of this systematic review, there is no evidence to support the universal application of a single ceramic material and system for all clinical situations. Additional longitudinal clinical studies are required to advance the development of ceramic materials and systems.     

Integration of all-ceramic restorations in reconstructive prosthetic dentistry: a case report.

A male patient presented for maxillary and mandibular complete-arch prostheses. A total of eight all-ceramic restorations, eight metal-ceramic crowns, and four metal-ceramic fixed partial dentures were placed. The restorations were examined for marginal integrity, anatomic form, surface, and color for a period of 12 months. All restorations were in function at the end of the evaluation period. There was no adverse event. No substantial difference between the all-ceramic onlays and the metal-ceramic crowns was apparent. The all-ceramic restorations exhibited the least plaque growth. Bleeding on probing was minimal at both restoration types. The marginal integrity of the all-ceramic restorations was considered to be nearly as precise as that of the metal-ceramic crowns.     

Esthetic techniques and restorative systems used in the second-year undergraduate dental curriculum

Metal-free tooth-colored restorative systems for fabricating indirect intracoronal and extracoronal restorations have been developed because of patients' demand for superior esthetics. During the past decade, long-term clinical studies have demonstrated the success of many of these types of restorations in terms of function and esthetics. Ceramic veneers, all-ceramic crowns, ceramic onlays, and composite-resin inlays are becoming an integral part of contemporary clinical practice. The constant evolution in bonding techniques, adhesive systems, and cements plays a major role in the success of these metal-free restorations. In addition, home-bleaching procedures have become an integral part of the esthetically oriented dental practice. This article discusses the rationale, scientific basis, and implementation of a new undergraduate preclinical esthetics course for second-year dental students at the Louisiana State University Health Sciences Center School of Dentistry.
CLINICAL SIGNIFICANCE
Changes in the undergraduate dental curriculum are ultimately necessary to provide undergraduate students with the adequate theoretic knowledge and clinical skills they require to face challenging practice demands and patients' requests for esthetic restorations. The implementation of the Preclinical Esthetics course at Louisiana State University School of Dentistry gives undergraduate dental students a foundation for restoring patients with indirect tooth-colored restorations, such as composite-resin inlays, ceramic onlays, ceramic veneers, and all-ceramic crowns, and vital bleaching procedures.