Crown Replacement Research Articles

Second phase strengthening and grain boundary segregation effects on the microstructure and properties of (Ce, Y)-TZP-based ceramics prepared by vat photopolymerization

Immediate implant placement (IIP) has garnered significant attention due to its minimally invasive approach and ability to facilitate immediate crown replacement. Nevertheless, challenges persist in processing complex geometries and selecting suitable materials. This study successfully fabricated high-performance, complex-structured (Ce, Y)-TZP-based composite ceramics using vat photopolymerization (VPP) technology, combining second-phase strengthening and grain boundary segregation effects. The incorporation of α-Al2O3 as a secondary phase led to a progressive refinement of (Ce, Y)-TZP grains, with the most favorable grain size achieved at 20 wt% α-Al2O3, reducing the average grain size to 0.75 μm. However, excessive α-Al2O3 content resulted in micropore formation, compromising the material's mechanical performance. At an optimal concentration of 15 wt% α-Al2O3, the composite exhibited superior mechanical properties, including a Vickers hardness of 11.53 ± 0.27 GPa and a flexural strength of 525.5 ± 21.3 MPa. Despite these improvements, some coarse (Ce, Y)-TZP grains persisted within the ceramic matrix. To further enhance grain refinement at lower α-Al2O3 content, a minimal addition of La3+ (0.1 wt%) was introduced, promoting grain boundary segregation and additional grain refinement. This modification reduced the (Ce, Y)-TZP grain size to 0.74 μm, increased hardness to 13.03 ± 0.31 GPa, and elevated flexural strength to 550.4 ± 39.8 MPa, while maintaining excellent material stability.

Replacement of metal-ceramic crown with fully ceramic: Case report

Dental treatments with aesthetic involvement drive the market towards an increase in the quality and diversity of materials, aiming to provide the highest satisfaction for both the patient and the dentist. Faced with limitations in metal-ceramic treatments, fully ceramic systems have evolved, enabling excellent aesthetic and functional results when appropriately indicated. The purpose of this case report is to describe a clinical case of oral rehabilitation in an aesthetic area through the replacement of a metal-ceramic crown with pure lithium disilicate ceramic (E-Max) for tooth 22. For the clinical success of the treatment, it was necessary to perform teeth whitening and dental recontouring with composite resin of the adjacent teeth prior to the fabrication of the definitive crown. Considering the techniques and materials used, the treatment performed was able to provide a result of clinical excellence, especially in this region that demands higher aesthetic requirements, offering satisfaction and restoring the patient's self-esteem.

Clinical solutions for natural abutments with preexisting defected crown margin in the aesthetic area.

Crown replacement has remained one of the difficult methods for installing fixed prosthesis but is often performed because of aesthetic factors and invasion of biological width. This article focuses on the clinical scenario in which preexisting crown margin has defects. Given that clinical decisions regarding restoration management and perio-dontal tissues have to be made with caution, a decision tree of the decision making process for natural abutments in aesthetic area with preexisting defected crown margin is presented. The re-establishment of a new crown margin is the key to the success of a new restoration, and the new margin should be located at the proper esthetic position and right biological position. It should have fine, smooth, and continuous morphology.

Non-submerged reconstructive approach for peri-implantitis osseous defect with removal of implant crowns: One-year outcomes of a prospective case series study.

The aim of this study was to test a non-submerged reconstructive approach for peri-implantitis osseous defects, by removing the prosthetic components, augmenting of the infraosseous bony compartment, and flap readaptation around the replaced healing abutments, without obtaining a primary wound closure. Twenty-nine implants in 24 patients were treated. Implant suprastructures were removed at the time of the intervention, to aid with the debridement process which included curettage, implantoplasty, air-power driven devices, and locally delivered antibiotics. The infraosseous part of peri-implant defects were augmented using a composite bone graft and an absorbable membrane to be secured around the replaced healing abutments without attempting to submerge the implants. After 8 months, direct peri-implant defect measurements were obtained to serve as the primary outcome. Secondary outcomes included of radiographic bone changes, and probing depth (PD) and bleeding on probing (BOP) changes at 12 months. At the time of the surgical re-entry (8 months), a statistically significant clinical and radiographic defect fill was observed (average of 2.33 and 1.63mm, respectively). Approximately 3 months after crown replacement, 12 months from the surgical intervention, a significant PD (1.51mm) and BOP (65%) reduction were also noted. Considering its limitations, the use of a non-submerged approach (with removal of implant crowns) led to significant improvements in clinical (defect fill, PD, BOP) and radiographic outcomes.

Survival analysis of crown margin repair: A retrospective study in a dental school setting

BackgroundRepairing crowns with defective margins is minimally invasive and cost-effective compared with replacement. The authors’ objectives were to examine the survival trajectory of crown margin repairs and to determine the factors associated with survival. MethodsRecords of adult patients from January 2008 through August 2019 were reviewed for crown margin repairs completed at University of Iowa College of Dentistry. A total of 1,002 crown margin repairs were found. Each repair was followed through the end of study in 2019 or until an event (for example, additional repair, endodontic treatment, crown replacement, or extraction). A Cox proportional hazards model was used to study the relationship between selected covariates and time to event. ResultsDuring the follow-up period, 32.8% of the repairs needed reintervention. In the final model, repair material was the only significant covariate. No difference was found between the survival of repairs done with resin-modified glass ionomer and amalgam. However, the repairs done with resin-based composite and conventional glass ionomer were more likely (1.5 times: 95% CI, 1.02 to 2.10 times; and 2 times: 95% CI, 1.40 to 2.73 times, respectively) to need reintervention than were those done with amalgam. ConclusionsMedian survival time of crown margin repairs was 5.1 years (95% CI, 4.48 to 5.72 years). Median survival times for amalgam, resin-modified glass ionomer, resin-based composite, and glass ionomer repair materials were 5.7 years (95% CI, 4.80 to 6.25 years), 5.3 years (95% CI, 4.73 to 6.34 years), 3.2 years (95% CI, 2.51 to 6.19 years), and 3.0 years (95% CI, 2.53 to 3.62 years), respectively. Practical ImplicationsWhen considering crown margin repairs, resin-modified glass ionomer or amalgam is preferable to resin-based composite or glass ionomer.

Effect of Repairing Endodontic Access Cavities on Survival of Single Crowns and Retainer Restorations

IntroductionThis retrospective study aimed to analyze the effect of repairing endodontic access cavities with composite on the survival of single crowns and retainer restorations of fixed or removable dental prostheses. MethodsDental records of patients attending a university dental clinic were retrospectively screened for single crowns and retainer restorations receiving endodontic treatment after crown placement. Survival (no further intervention) and failure (removal, loss or replacement of crown, replacement of access restoration, or recementation of restoration) of crowns and retainers with repaired endodontic access cavities were recorded. The mean annual failure rates were calculated, and the effect of individual-, tooth-, and restoration-related variables on survival was assessed by univariate log-rank tests and multivariate Cox regression analyses with shared frailty (P < .05). ResultsOne hundred eighty repaired crowns/retainers placed in 151 patients were included (4.5 ± 3.3 years follow-up). Survival after 2, 5, 7, and 10 years amounted to 82.7%, 71.5%, 67.3%, and 48.8% (mean annual failure rate = 9.0%, 6.5%, 5.5%, and 6.9%), respectively. Although tooth type, kind of restoration, endodontic irrigant, repair conditioning methods, and kind of composite affected survival in the univariate regression analyses, only the kind of restoration (single crown vs retainer restoration) remained significant in the multivariate Cox regression model. ConclusionsRepairing endodontic access cavities with composite increases the longevity of single crowns and retainer restorations.

Randomized Clinical Trial on Single Zirconia Crowns with Feather-Edge vs Chamfer Finish Lines: Four-Year Results.

The objective of this study was to evaluate the influence of two finish lines on the fracture resistance and periodontal response of porcelain zirconia crowns. Ethical committee approval was obtained, and 50 zirconia single crowns were placed in posterior regions. Abutments were randomly distributed into two groups: Group 1 (feather-edge preparation) and Group 2 (chamfer preparation). Patients were recalled after 1 month, 6 months, and 1, 2, 3, and 4 years. The function, esthetics, and marginal adaptation of the restorations were evaluated. Bleeding on probing (BoP) and distance of margins from the bone crest were recorded. Statistical analyses were performed for survival and success rates. Group 1 had an 80% success rate (21/25 crowns) and a 96% survival rate (24/25 crowns; 1 encountered irreparable fracture of ceramic layer); Group 2 had a 76% success rate (20/25 crowns) and a 100% survival rate (25/25 crowns). Chippings were noticed on 4 crowns in Group 1 (one crown replacement). Five chippings occurred in Group 2, without any replacement. There were no statistically significant differences between the two groups. BoP was found in 18 of the 25 crowns in Group 1 (72%) and in 12 of the 25 crowns in Group 2 (48%). A statistically significant correlation between BoP and the distance of the margin to the bone crest was found. It was concluded that: (1) clinical survival and success rates of the two preparation methods on crowns are not significantly different; (2) due to the statistically significant correlation between BoP and the distance of the margin to the bone crest, margins should be placed at least 3 mm from the bone crest; and (3) higher probability of BoP is expected in cases with feather-edge preparation.

Immediate Crown Replacement: a case report of extensive radicular fracture with intra-canal anchorage

Aim: Fracture by trauma is one of the most common type of dental injury in the permanent dentition. The purpose of this case report is to present the multidisciplinary management of a subgingival crownroot fracture in one patient. Summary: In this article we report one case of complicated crown-radicular fractures reattachment, in a traumatized maxillary permanent central incisor, which was treated with a novel method preserving coronal integrity after fiber post placement.

The use of retraction paste to simplify impression and cementation of ceramic veneers and crowns: 3-year follow-up report.

Proper gingival displacement is an important prerequisite to obtain good quality impressions. Retraction pastes could eliminate the need for retraction cords, as they have advantages such as comfort reported by patients, faster technique, ease of use, no need for anesthesia, and reduced tissue trauma. The objective of this paper was to present a clinical case of ceramic veneers and crowns in which a retraction paste was used for gingival displacement during both the impression and cementation stages, with 3 years of follow-up. Treatment planning consisted of the replacement of preexisting crowns and ceramic veneers on the anterior teeth. After finishing the preparations, gingival displacement with Astringent Retraction Paste was performed without anesthesia or the use of cords and the impression was taken. Before cementation of the crowns and veneers, the Astringent Retraction Paste was applied. Avoiding the use of cords during cementation prevented trauma. The soft tissue margins remained stable and healthy after a period of 3 years. It can be concluded that retraction pastes could be indicated for displacement of soft tissue when preparation margins are at the gingival level or slightly intrasulcular prior to impressions, restoration cementations, direct restorations, and before relining provisional restorations. Clinical significance: The impression appointment can be traumatic to some patients. The use of cords for gingival displacement usually requires local anesthesia and is time consuming. Retraction astringent pastes instead of cords seems to be a good option for some cases in gingival tissue displacement.

Reasons for placement and replacement of crowns in general dental practice.

The aim of this study was to investigate the reasons for placement and replacement of crowns in general dental practice. Forty general dental practitioners recorded the principal reason for the provision of new (initial) and replacement crowns for a maximum of up to 20 patients over a 20-week period. A total of 664 patients received 783 crowns during the period of this study. Of these, 69% (n = 542) were new (initial) placements and 31% (n = 241) were replacements. Overall, tooth fracture (45%, n = 241) was the most frequently reported reason for new/ initial crown placements. Aesthetics (21%, n = 53) and secondary/recurrent caries (20%; n = 47) were the most frequent reasons for crown replacement. Maxillary premolars (27%, n = 145) and mandibular molars (25%, n = 137) were the teeth that received most initial crown placements. In contrast, maxillary incisors (50%, n = 115) were the most common teeth to receive a replacement crown. Dentists were more likely to replace a crown if they had not placed the original crown: 74% of replacement crowns (n = 178) were placed by a different dentist. Most patients had only one crown placed or replaced per course of treatment (n = 611; 90%). The results of this study reveal the prescribing habits of dentists in relation to provision of initial and replacement crowns. The vast majority of patients had only one crown provided per course of treatment, which is probably a reflection of funding schemes and changing patterns of oral health. This sample reported fewer replacement crowns than previous studies. In keeping with existing literature, crowns were more frequently replaced when the treating dentist had not placed the initial crown. However, against this, more replacements were provided for more long-standing patients (5+ years attendance) compared to those with shorter attendance history (<5 years). In an area where high quality evidence is lacking, further consensus on the need for placement and replacement crowns is needed. Such information would assist dentists to provide high-quality care and commissioners in developing an evidence-based service.

Fatigue Failure of External Hexagon Connections on Cemented Implant-Supported Crowns

To evaluate the probability of survival and failure modes of different external hexagon connection systems restored with anterior cement-retained single-unit crowns. The postulated null hypothesis was that there would be no differences under accelerated life testing. Fifty-four external hexagon dental implants (∼4 mm diameter) were used for single cement-retained crown replacement and divided into 3 groups: (3i) Full OSSEOTITE, Biomet 3i (n = 18); (OL) OEX P4, Osseolife Implants (n = 18); and (IL) Unihex, Intra-Lock International (n = 18). Abutments were torqued to the implants, and maxillary central incisor crowns were cemented and subjected to step-stress-accelerated life testing in water. Use-level probability Weibull curves and probability of survival for a mission of 100,000 cycles at 200 N (95% 2-sided confidence intervals) were calculated. Stereo and scanning electron microscopes were used for failure inspection. The beta values for 3i, OL, and IL (1.60, 1.69, and 1.23, respectively) indicated that fatigue accelerated the failure of the 3 groups. Reliability for the 3i and OL (41% and 68%, respectively) was not different between each other, but both were significantly lower than IL group (98%). Abutment screw fracture was the failure mode consistently observed in all groups. Because the reliability was significantly different between the 3 groups, our postulated null hypothesis was rejected.

Audit of Crown and Fixed Partial Denture in a Nigerian Teaching Hospital

Aim: The purpose of this investigation was to document the reasons for placement, and replacement of crowns and fixed partial denture in a Nigerian Teaching Hospital. Methods: a retrospective review of patients that had advanced conservative procedures. A data collection form was used to gather the relevant information from the patients’ case notes. Section A sought information on age , gender, educational level, patients’ occupation etc. Section B recorded information on tooth/teeth involved, reason for fabrication of prosthesis and material used. Results: Three hundred and twenty six had 398 crowns while 23 patients received bridges. Patients’ ages ranged from 16-85 years with a mean of 47.7± 17.2years and a male to female ratio of 1:1.3. Thirty five percent of the crowned teeth were in the upper right quadrant, followed by the upper left quadrant with 29.4%. Upper right central incisors were the most frequently (15.6%) crowned teeth. Endodontics and esthetics were the most common reasons for initial crown placement and replacement respectively. About 60% of bridges fabricated were new, while 22.2% of replaced bridges were due to fracture of porcelain and unacceptable marginal adaptation. Conclusion: Endodontics and esthetics were the most common reasons for initial crown placement and replacement.

Audit of Crowns and Fixed Partial Dentures in a Nigerian Teaching Hospital

Aim: The purpose of this investigation was to document the reasons for placement, and replacement of crowns and fixed partial denture in a Nigerian Teaching Hospital. Methods: a retrospective review of patients that had advanced conservative procedures. A data collection form was used to gather the relevant information from the patients’ case notes. Section A sought information on age, gender, educational level, patients’ occupation etc. Section B recorded information on tooth/teeth involved, reason for fabrication of prosthesis and material used. Results: Three hundred and twenty six had 398 crowns while 23 patients received bridges. Patients’ ages ranged from 16-85 years with a mean of 47.7 ± 17.2 years and a male to female ratio of 1:1.3. Thirty five percent of the crowned teeth were in the upper right quadrant, followed by the upper left quadrant with 29.4%. Upper right central incisors were the most frequently (15.6%) crowned teeth. Endodontics and esthetics were the most common reasons for initial crown placement and replacement respectively. About 60% of bridges fabricated were new, while 22.2% of replaced bridges were due to fracture of porcelain and unacceptable marginal adaptation. Conclusion: Endodontics and esthetics were the most common reasons for initial crown placement and replacement

Patients' Values Related to Treatment Options for Teeth with Apical Periodontitis

IntroductionThis study aimed to explore patients' values when selecting treatment for a tooth with apical periodontitis (AP), namely retention via root canal treatment (RCT) and extraction without replacement or replacement with implant-supported crowns or fixed or removable partial prostheses. MethodsThrough 2 surveys of patients (800 university patients and 200 community patients, response rate = 43%) and dentists (498 Ontario endodontists, periodontists, prosthodontists, oral and maxillofacial surgeons, response rate = 40% and 1983 Ontario general dentists, response rate = 15%), the importance of values that might be considered important to patients when selecting treatment options for a tooth with AP were recorded. Chi-square and Kendall's tau tests were used to respectively compare the importance rating frequency by each surveyed group and its correlation to their demographic variables (P ≤ .05). ResultsPatients considered communication and trust (94%), tooth retention (90%), esthetic outcome (84% regardless of location), cost (83%), longevity (83%), and preoperative pain (81%) as the most important decision values. Dentists overrated the importance of patients' previous experience with the treatment options (94% vs 72%), dental insurance (90% vs 70%), and intraoperative pain (79% vs 60%) while underestimating the importance of maintenance cost (60% vs 79%). ConclusionsDentists should respect patients' views about esthetic outcome, longevity, and cost associated with treatment options for a tooth with AP. In particular, this survey highlights the value of communication and trust between patient and dentist and preservation of the natural tooth through RCT over implant-supported crown replacement when planning treatment for a tooth with AP.

Zirconia-based crowns up to 5 years in function: a retrospective clinical study and evaluation of prosthetic restorations and failures.

The purpose of this retrospective study was to evaluate the 5-year clinical performance and failure rate of single- or multiple-unit zirconia-based crowns. A total of 148 patients (39 men and 109 women, mean age: 46.9 ± 10.6 years) treated in university and private practices with 618 single- or multiple-unit zirconia-based (Lava) crowns made on natural teeth from January 2007 to December 2008 were included. Two hundred fifty-nine anterior and 359 posterior crowns were examined. A core and/or veneer fracture that required replacement of the restoration was considered to be a failure. The cumulative survival rate (CSR) was described with Kaplan-Meier survival functions. The crowns replaced for other reasons were deemed lost to follow-up, and esthetic, functional, and biologic complications were rated. At the 5-year follow-up, no zirconia core fractures were observed. Twelve veneer fractures that required crown replacement were detected. The CSR was 98.1%. There was a statistically significant difference between survival of the anterior and posterior restorations (P < .001). In total, 116 crowns experienced biologic and technical complications. The most common complications were smooth veneer fracture (4, 0.6%), loss of retention (7, 1%), staining because of smoking (24, 4%), and gingival recession (48, 8%). According to the 5-year CSR (98.1%) observed in this study, zirconia-based single or multiple crowns may be considered an acceptable treatment modality for the replacement of anterior and posterior teeth. RESULTS from the current study should be supported by additional randomized clinical trials.

Fracture behavior of zirconia implant abutments is influenced by superstructure-geometry

The purpose of this in vitro study was to evaluate the influence of the superstructure-geometry on the fracture behavior of zirconia abutments (Compartis, DeguDent GmbH, Hanau, G). Four different groups (n = 8) representing anterior single crown replacement were prepared. In groups 1 and 2, the implants were restored with customized all-ceramic abutments and anatomically shaped crowns (chromium cobalt alloy). Groups 3 and 4 received crowns with a geometry according to the international standard ISO 14801 (dynamic fatigue test for endosseous dental implants) with a spherical contact area. Groups 2 and 4 were subjected to mechanical aging in a chewing simulator (50 N × 1,200,000 cycles). Static loading until fracture was performed using a universal testing device at an angle of 30° to the implant axis. Fracture patterns were analyzed using SEM. In group 2, only one specimen survived mechanical aging. In group 4, one specimen fractured during the chewing simulation. Groups 1 and 2 showed significantly lower load-bearing capacity than groups 3 and 4. Artificial aging did not influence the fracture resistance. The SEM analysis revealed fatigue-related fracture patterns in those specimens, which failed during artificial aging. Drawing conclusions from ISO testing concerning clinical performance appears to be critical as anatomic superstructure geometries induce different fracture behaviors. ISO testing of zirconia abutments should be accompanied by load-bearing capacity testing under simulated clinical conditions to predict clinical performance.

Long‐Term Follow‐Up of CeraOne™ Single‐Implant Restorations: An 18‐Year Follow‐Up Study Based on a Prospective Patient Cohort

Knowledge on long-term clinical performance of more than 5 years on the single-implant CeraOne™ (Nobel Biocare AB, Gothenburg, Sweden) concept is limited. The aim of this study is to report the long-term clinical performance of the first CeraOne single-implant restorations, installed 17 to 19 years ago. The group comprised 57 patients provided with 65 CeraOne single-tooth restorations. Sixty-two all-ceramic and three metal-ceramic crowns were cemented between 1989 and 1991. Patients were followed up clinically and with intraoral radiographs at placement, after 1, 5, and between 17 and 19 years after placement. Data were available for altogether 48 patients, followed up on an average time of 18 years. Excluding deceased patients (n=2) and failed implant patients (n=2), only five patients were lost to follow-up (8.8%). Two implants failed, resulting in an 18-year implant cumulative success rate (CSR) of 96.8%, and altogether eight original single-crown restorations were replaced (CSR 83.8%). The most common reason for crown replacement was infra-position of the implant crown (n=3). Many of the remaining original crowns showed various signs of implant crown infraposition at the termination of the study. In general, the soft tissue at the restorations was assessed to be healthy and comparable with the gingiva at the adjacent natural teeth. Bone levels were on an average stable with only few patients exhibiting bone loss of more than 2mm during 18 years in function. This long-term follow-up study of single-implant restorations shows encouraging results with few implant failures and minimal bone loss over an 18-year period. Original single-crown restorations were replaced more frequently, because of, for example, implant crown infraposition and veneer fractures. The CeraOne concept proved to be a highly predictable and safe prosthodontic treatment.

Factors determining the retentiveness of luting agents used with metal- and ceramic-based implant components

To investigate the factors that determine the retentiveness of copings made of cobalt-chromium (CoCr)-alloy or zirconia luted with permanent (solid-body like) and provisional (viscous, elastic-body-like) luting agents. We manufactured titanium implant analogs with four-, six-, and eight-taper degrees and copings of CoCr-alloy and zirconia and luted the copings according to a standardized protocol. Samples were thermally cycled, and we investigated the various degrees of roughness of the copings' inner surfaces as well as the various cement mixing ratios on the retentiveness. Copings were either pulled out slowly (by means of a universal testing machine) or knocked out quickly (using a CORONAflex crown replacement device). The highest level of retentiveness was achieved with a four-taper degree for polycarboxylates followed by zinc-oxide-phosphates and glass ionomers or composite cements. Provisional cements and composite cements containing a plastifier showed significantly lower retentiveness levels. The pull-out and knock-out tests showed a relationship between retentiveness level and taper degree. However, the influence of taper degree was reduced with higher taper degrees as well as with cements that do not set as a solid body due to ingredients such as oily liquids or plastifiers. Thermal cycling further reduced the retentiveness level of these cements. Higher degrees of roughness only improved the retention force of cements setting as a solid body. Mixing errors may alter retentiveness levels in an unpredictable manner. When used within the same group of cements, metal-alloy, and zirconia copings did not differ with regard to their level of retentiveness. Copings made of metal-alloy and zirconia showed no different level of retentiveness when set onto titanium abutments fixed with permanent or provisional cements. Only cements setting as a solid body showed a clear relationship between retentiveness level and taper degree. In contrast, the retentiveness of provisional (viscous, elastic-body-like) luting agents was less predictable.

Avoiding and managing the failure of conventional crowns and bridges

The replacement of crowns and bridges is a common procedure for many dental practitioners. When correctly planned and executed, fixed prostheses will provide predictable function, aesthetics and value for money. However, when done poorly, they are more likely to fail prematurely and lead to irreversible damage to the teeth and supporting structures beneath. Sound diagnosis, assessment and technical skills are essential when dealing with failed or failing fixed restorations. These skills are essential for the 21st century dentist. This paper, with treated clinical examples, illustrates the areas of technical skill and clinical decisions needed for this type of work. It also provides advice on how the risk of premature failure can, in general, be further reduced. The article also confirms the very real risk in the UK of dento-legal problems when patients experience unexpected problems with their crowns and bridges. This paper outlines clinical implications of failed fixed prosthodontics to the dental surgeon. It also discusses factors that we can all use to predict and reduce the risk of premature restoration failure. Restoration design, clinical execution and patient factors are the most frequent reasons for premature problems. It is worth remembering (and informing patients) that the health of the underlying supporting dental tissue is often irreversibly compromised at the time of fixed restoration failure.

Reliability and failure modes of anterior single‐unit implant‐supported restorations

Failures of implant-abutment connections have been observed clinically, especially in single-tooth replacements. This study sought to evaluate the reliability and failure modes of implant-supported anterior crowns restored with different implant systems. Forty-two Ti-6Al-4V dental implants (~4 mm diameter) were used for single anterior crown replacement and divided into two groups according to tested system: (NB) Replace Select system, Nobel Biocare (n = 21); and (IL) Internal connection system, Intra-Lock International (n = 21). Proprietary abutments were screwed to the implants and anatomically correct maxillary central incisor metal crowns were cemented and subjected to step-stress-accelerated life testing in water. Use-level probability Weibull curves and reliability for a mission of 50,000 cycles at 200 N (95% 2-sided confidence intervals) were calculated. Polarized-light and scanning electron microscopes were used for failure analyses. The Beta values for NB and IL (2.09 and 2.05, respectively) indicated that fatigue accelerated the failure of both groups. The calculated reliability for the NB system (0.81) was lower than for the IL system (0.96), but no significant difference was observed between groups. Screw and abutment fracture was the chief failure mode in group NB, while screw fracture was most representative in specimens of group IL. Reliability of implant-supported maxillary central incisor crowns was not significantly different between NB and IL abutments. Failure modes differed between implant systems.