Zirconia-based Single Crowns Research Articles

Fifteen-year recall period on zirconia-based single crowns and fixed dental prostheses. A prospective observational study

AimThe aim of this study was to evaluate the long-term clinical outcomes of zirconia-based prostheses used for tooth-supported or implant-supported single crowns and fixed dental prostheses (FPD).MethodsThe authors conducted a prospective analysis of 562 zirconia core restorations supported by endodontically treated teeth or titanium implant in 276 patients in a general dental private practice, with a follow-up period of 15 years. The study was stopped after patients achieved 15 yrs of follow-up. The study analyzed the failure and complication rates of single and multiple crowns, based on Kaplan Meier analysis.ResultsDuring follow-up period, there were 26 complications and 156 failures. The crown level analysis revealed a cumulative failure rate of 28.33% and complication rate of 8.47% for zirconia crowns after 15 years. The complication rate was found to be higher for titanium implant-supported than for natural teeth-supported crowns. The different types of crown-based failure include: veener fracture 5.01% (N = 29), metal zirconia led to 14.85% (N = 86) loss of retention, and 1.73% (N = 10) loss of crown due to extraction.ConclusionBased on these findings, zirconia core restorations appear to be a reliable long-term solution for crowns and fixed dental prostheses.Clinical relevanceThe study suggests that zirconia restorations can be successfully used for long-term prostheses on natural teeth or implants supported. The study results provide clinicians valuable information when selecting prosthetic restorations material.

Fractographic analysis of 35 clinically fractured bi-layered and monolithic zirconia crowns

The aim of this retrieval study was to analyze the fracture features and identify the fracture origin of zirconia-based single crowns that failed during clinical use. Thirty-five fractured single crowns were retrieved from dental practices (bi-layered, n=15; monolithic, n=20). These were analyzed according to fractographic procedures by optical and scanning electron microscopy to identify fracture patterns and fracture origins. The fracture origins were closely examined. The crown margin thickness and axial wall height were measured. Three types of failure modes were observed: total fractures, marginal semilunar fractures, and incisal chippings. Most of the crowns (23) had fracture origins at the crown margin and seven of them had defects in the fracture origin area. The exact fracture origin was not possible to identify due to missing parts in four crowns. The crown wall thickness was 20% thinner and wall height 30% shorter in the fracture origin area compared to the opposite side. The findings in this study show that fractography can reveal fracture origins and fracture modes of both monolithic and bi-layered dental zirconia. The findings indicate that the crown margin on the shortest axial wall is the most common fracture origin site. Crown design factors such as material thickness at the margin, axial wall height and preparation type affects the risk of fracture. It is important to ensure that the crown margins are even and flawless.

Clinical Evaluation of Internal Fit of Milled BioHPP Polyetheretherketone (PEEK) - Based Versus Zirconia-Based Single Crowns

Clinical Evaluation of Internal Fit of Milled BioHPP Polyetheretherketone (PEEK) - Based Versus Zirconia-Based Single Crowns

Clinical performance of tooth- or implant-supported veneered zirconia single crowns: 42-month results.

The objective of this clinical study was to compare and assess the clinical performance of tooth-supported and implant-supported zirconia single crowns with sintered veneering caps. In this prospective study, 118 patients with a total of 220 single crowns placed on 106 teeth (69 vital teeth, 37 endodontically treated teeth) and 114 implants in molar and premolar regions were examined during a mean observation period of 42months. The restorations were evaluated for technical failures such as veneering porcelain fractures (chipping), surface quality, marginal fit, and the interface quality of the coping and sintered veneering. The soft tissue status was assessed using the modified Silness and Löe's plaque and gingival index (mPI) and the modified Muhlemann sulcus bleeding index (mSBI). Tooth-supported crowns were checked for secondary caries and hypersensitivity during the follow-up period. Recalls were performed every 6months. The 3-year Kaplan-Meier success probability was 98.2% and 100% for implant- and tooth-supported crowns, respectively. A significant difference could be detected between the implant-supported and tooth-supported zirconia single crowns, in terms of their chipping rate (p = 0.039). Veneering material fractures were recorded on two implant-supported restorations (1.8%). No veneering fractures occurred on tooth-supported single crowns. The plaque and gingival index and sulcus bleeding index showed stable and healthy soft peri-implant and periodontal tissues. Neither loss of vitality nor secondary caries occurred on tooth-supported crowns. Zirconia-based single crowns with a sintered veneering cap showed promising clinical results on both tooth and implant abutments; however, the dental implants were more prone to complications. In terms of clinical significance, high-strength ceramic with a sintered veneering cap can be recommended for prosthetic treatment of both tooth- and implant-supported single crowns in molar regions. This study provides valuable information for further application of all-ceramic restorations.

Zirconia-based single crowns

Zirconia-based single crowns

Clinical outcomes of zirconia-based implant- and tooth-supported single crowns.

Zirconia-based restorations have been increasingly used on implant and teeth abutments, but the evidence about clinical outcomes of these restorations is limited. The aim of this study was to assess up to 7-year clinical outcomes of implant- and tooth-supported zirconia-based single crowns. In this retrospective study, 261 patients with 556 single crowns supported by either teeth (324) or implants (232) were examined during 3- to 7-year follow-up (mean observation of 60.70 months for tooth and 59.20 months for implant-supported crowns). California Dental Association (CDA) quality evaluation system was used to evaluate the restorations. Soft tissue status was assessed using plaque and gingival index scores, bleeding on probing, and pocket depth. Patient and professional satisfaction were evaluated by visual analog scale (VAS). The 5-year Kaplan-Meier survival probability was 98.3 and 97.3 for implant- and tooth-supported crowns, respectively. In regard to CDA rating, most of the crowns were ranked as either excellent or acceptable (99.5 %). The recorded failures were replacement of the crown due to porcelain chipping (3), implant failure (1), and teeth extraction (5). Soft tissue parameters were not affected by the restorations compare to control teeth. The VAS was high for both patients and clinicians. Zirconia-based single crowns on both tooth and implant abutments showed promising clinical performance in this up to 7-year follow-up. The zirconia-based single crowns can be used clinically for tooth- and implant-supported restorations.

Technical complications and failures of zirconia-based prostheses supported by implants followed up to 7 years: a case series.

To evaluate technical complications and failures of zirconia-based fixed prostheses supported by implants. Consecutive patients received zirconia-based single crowns (SCs) and fixed dental prostheses (FDPs) on implants in a private clinical setting between 2005 and 2010. One dentist performed all surgical and prosthetic procedures, and one master technician performed and coordinated all laboratory procedures. One-piece computer-aided design/ computer-assisted manufacture technology was used to fabricate abutments and frameworks, which were directly connected at the implant level, where possible. All patients were involved in a recall maintenance program and were finally reviewed in 2012. Data on framework fractures, chipping of veneering ceramics, and other technical complications were recorded. The primary endpoint was failure of the prostheses, ie, the need for a complete remake. A life table analysis was calculated. A total of 289 implants supported 193 zirconia-based prostheses (120 SCs and 73 FDPs) in 127 patients (51 men, 76 women; average age: 62.5 ± 13.4 years) who were reviewed in 2012. Twenty-five (13%) prostheses were cemented on 44 zirconia abutments and 168 (87%) prostheses were screw-retained directly at the implant level. Fracture of 3 frameworks (1 SC, 2 FDPs) was recorded, and significant chipping resulted in the remake of 3 prostheses (1 SC, 2 FDPs). The 7-year cumulative survival rate was 96.4% ± 1.99%. Minor complications comprised 5 loose screws (these were retightened), small chips associated with 3 prostheses (these were polished), and dislodgement of 3 prostheses (these were recemented). Overall, 176 prostheses remained free of technical problems. Zirconia-based prostheses screwed directly to implants are clinically successful in the short and medium term.

Seven-year prospective clinical study on zirconia-based single crowns and fixed dental prostheses.

Zirconia-based prostheses are used for esthetic crown and fixed restorations, but follow-ups are still limited. The authors evaluated the 7-year clinical results of 303 zirconia core restorations, performed in a general dental private practice. Clinical events (fracture and loss of retention, gingivitis, tenderness, excess cement, and temporary pain) were recorded in 303 zirconia core restorations positioned in 88 patients. Kaplan-Meier survival probability estimates were computed for failures (needed the replacement or removal of the prosthesis) and complications (resolved without replacing the prosthesis). One hundred and fifty single crowns (130 tooth-supported, 20 implant-supported) and 153 multiple units up to 6 elements (49 tooth-supported, 104 implant-supported) were followed-up for 7 years in 88 patients (40 men, 48 women), aged 35-89 years (mean 57). During the follow-up period, there were no complications for 287 (95 %) of the restorations. Sixteen restorations/abutment teeth (5 %) had some complication: extraction of abutment tooth (7, 2 %); caries (2, 1 %), porcelain veneer fracture (3, 1 %), loss of retention (4, 1 %). Nine (3 %) restorations were recorded as failures. The overall 7-year survival probability estimate for failures was 0.966 (95 % confidence limits, 0.932 and 0.983), for complications was 0.976 (95 % confidence limits 0.947 and 0.989), with a cumulative survival rate of 94.7 %. Within the analyzed follow-up, zirconia core restorations appear a good clinical solution, with favorable functional properties. All ceramic restorations can be successfully used for both single-and multiple-unit prostheses, either teeth or implants supported.

A 3 years retrospective study of survival for zirconia-based single crowns fabricated from intraoral digital impressions

ObjectiveTo evaluate the clinical performance of glass-ceramic/zirconia crowns fabricated using intraoral digital impressions – a retrospective study with a three-year follow-up. Methods70 consecutive patients with a total of 86 glass-ceramic/zirconia crowns were treated by a single clinician using standardized clinical and laboratory protocols. A complete digital workflow was adopted for the purpose except for the veneering procedure for the glass-ceramic crowns. Occlusal adjustments were made before the ceramic glazing procedure. Before cementation, all abutments where carefully cleaned with a 70% alcoholic solution and air dried. Cementation was performed using dual-curing, self-adhesive resin cement. Patients were re-examined after 12, 24 and 36 months, to assess crown chipping/fractures. ResultsAfter the three-year follow-up, none of the zirconia-based restoration was lost (“apparent” survival rate 100%) otherwise, the chipping rate of the veneering material increased from 9.3% after 12 months, to 14% after 24 months to 30.2% after 36 months. As a consequence, the “real” success rate after 3 years was 69.8%. ConclusionsAfter 3 years the success rate of zirconia-based crowns was 69.8%, while the incidence of the chipping was 30.2%. Assuming an exponential increase in chipping rate between 12 and 36 months it can be argued that, among others, the fatigue-mechanism could be advocated as the main factor for the failure of glass-ceramic veneered zirconia especially after 24 months.

Sehr gute Erfolgsraten vollkeramischer Einzelkronen in der Praxis

Monaco C, Caldari M, Scotti R. Clinical evaluation of 1,132 zirconia-based single crowns: a retrospective cohort study from the AIOP clinical research group. Int J Prosthodont 2013; 26 : 435–442

A critical appraisal of evidence-based dentistry: The best available evidence

The principle of evidence-based dentistry requires that relevant scientific literature be integrated into the dentist's practice and the patient's treatment needs and wishes. This approach involves critically appraising the scientific literature for the best available evidence in order to make clinical decisions. The purpose of the study was to critically appraise the process by which a practitioner attempts to make an evidenced-based clinical decision. This process is illustrated by evaluating the clinical literature pertaining to zirconia-based single crowns. An electronic search was performed in PubMed and the Cochrane Library by using Boolean operators for articles published in English between January 1950 and October 2012 to address the PICO (patients, intervention, comparison, outcome) question, "In adults, how does the long term prognosis of zirconia-based single crowns compare to conventional single crowns on natural teeth?" Comparisons were made across the publications to determine the quality of relevant information. Three systematic reviews included 4 clinical trials. Two randomized clinical trials and 1 retrospective study met the search criteria but were not identified in the systematic reviews. The definitions of the outcomes and the presentation of the data varied among studies. The lack of standardization of reporting data, the nonstandardized definitions of outcomes, and the impact of the length of the research study were identified as problems that need to be addressed to improve the quality of systematic reviews and other clinical trials.

A critical appraisal of the systematic review process: Systematic reviews of zirconia single crowns

Systematic reviews analyze the data of published research in an effort to assemble the scientific evidence to help clinicians apply evidence-based information in decision making. The quality of systematic reviews varies greatly. The purpose of this study was to critically appraise the current systematic review process by evaluating systematic reviews that pertain to zirconia-based single crowns. The following PICO (patients, intervention, comparison, outcome) question was formulated: "In adults, how does the long-term prognosis of zirconia-based single crowns compare with conventional single crowns on natural teeth?" An electronic search was performed in PubMed and the Cochran Library for articles published in English between 1950 and October 2012. Additional manual searches were completed. To be included in the analysis, the study must have been a systematic review, published in an English-speaking peer-reviewed journal, and evaluated zirconia crowns on teeth. Two examiners qualitatively evaluated the publications with an Assessment of Multiple Systematic Reviews checklist and the Oxford Systematic Review Appraisal form. Three systematic reviews were identified that met the search criteria. Two studies met 5 of the 11 Assessment of Multiple Systematic Reviews criteria, whereas the third met only 1 criterion. The same 2 studies met 3 of the 5 Oxford Systematic Review Appraisal criteria and the third met only 2 criteria. Because of the variation in methodologies, systematic reviews should be interpreted cautiously. The Assessment of Multiple Systematic Reviews Checklist and the Oxford Systematic Review Appraisal Sheet are practical tools for appraising and determining the quality of systematic reviews.

Clinical Evaluation of 1,132 Zirconia-Based Single Crowns: A Retrospective Cohort Study from the AIOP Clinical Research Group

The aim of this retrospective cohort study was to gather the outcomes of zirconia single crowns made by 16 members of the Italian Academy of Prosthetic Dentistry (AIOP) over a time period of up to 5 years. A total of 398 patients treated in private practices with 1,132 zirconia-based single-crown restorations made on natural teeth from January 2005 to July 2010 were included. Three hundred forty-three anterior restorations (30.3%) and 789 posterior crowns (69.7%) were made with 16 types of zirconia, using primarily chamfer or knife-edge tooth preparation, and examined according to the esthetic, functional, and biologic criteria. To evaluate the relationship of parafunction with mechanical failure, patients with clenching or bruxism were not excluded from the study group. The cumulative survival rate of all restorations was 98.1%, while the cumulative success rate was 94.3%. Functional criteria had the highest number of failures. The odds ratio (OR) for all restorations was calculated to clarify the relationship between patients who were subject/not subject to parafunctions and technical complications; the OR was 2.60. An association between parafunction and mechanical failure was found in patients with severe parafunction. Porcelain-veneered zirconia single crowns with chamfer and knife-edge preparations showed good clinical results over a period of up to 5 years. Technical complications were few and were limited primarily to patients with parafunction.