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Objectives: This retrospective longitudinal study aimed to assess the longevity of single unit crowns placed by several dentists and to investigate risk factors associated with crown failures., Methods: From patient files, longevity of 3404 full crown restorations placed in 1557 patients by 8 Dutch dentists between 1996 and 2011 were analyzed. Annual failure rates (AFRs) were calculated and variables associated with failure (success and survival of crowns) were assessed by multivariate Cox-regressions analysis with shared frailty for patients., Results: Most of crowns were PFM (63.8%) placed in molars (58.1%) and non endodontically treated teeth (65.4%). The observation time of restorations varied from 3 weeks to 11 years with a mean of 7 years, resulting in a mean AFR at 11 years of 2.1% and 0.7% for success and survival of crowns, respectively. Among dentists a relevant variation for type of interventions was observed with AFR varying between 1.2% and 3.5%. The most significant risk factor for failure of crowns was the presence of an endodontic treatment, resulting in Hazard ratios of 1.31 for success [95%CI 1.07-1.61] and 1.89 [95%CI 1.35-2.65] for survival of crowns. Tooth type, tooth position (jaw) and gender showed also a significant influence on success of crowns. For survival, increase in patients' age results in a higher risk for failure., Conclusions: Overall, crowns placed by a selected group of dentist showed a good to acceptable success and survival rates, mainly dependent from the practice. The presence of an endodontically treated tooth was a significant risk factor leading to more failures., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objectives: The aim of this 5-year randomized controlled trial was to compare the longevity and clinical behavior of single posterior crowns made with pressable ceramic on zirconia and on metal frameworks, and if failures occur, to delineate the contributing factors., Methods: 72 patients, who needed the covering of at least a molar and/or premolar, were included in the study. All teeth were endodontically treated, with absence of periapical lesion or active periodontitis. Ninety single crowns were made with zirconia or metal framework and covered with pressable veneering ceramics. Two independent examiners assessed the survival of restorations at 6 months, 1-4 and 5 years after restoration placement including periapical radiographs, intraoral photographs, and USPHS modified criteria. The statistical analyses were performed with the Kaplan-Meier method., Results: One core fracture occurred in Zircad/Zirpress crowns and one metal ceramic crown was lost for root fracture. Chipping fracture of the veneering ceramic was detected in 2 metal-ceramic crowns and in 3 zirconia-based crowns. The Estimate Cumulative Survival (ECS) and the Estimate Cumulative Success (ECSs) with standard deviation (SE) were respectively 97,73±2,19 and 92,64±4,14 for zirconia-based crowns whereas 97,44±2,39 and 91,11±4,27 for porcelain fused to metal crowns., Conclusions: The present randomized controlled trial shows that the survival of zirconia-based and metal-based single crowns is similar over a follow-up period of 5 years. No significant differences in esthetic, functional and biological outcomes were demonstrated between the two groups. The main failure mode was the chipping fracture of the veneering ceramic in both materials. Study number on ClinicalTrial.gov NCT02758457., Clinical Significance: According to the results of this clinical study, zirconia-based rehabilitations with overpressing veneering technique represent a valid alternative to metal-based for posterior single crown restorations., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Objectives: To prospectively evaluate the clinical long-term outcome of tooth-supported crowns (SCs), implant-supported crowns (ISCs), and fixed dental prostheses (FDPs) made of a lithium-disilicate glass-ceramic framework material (IPS Empress 2)., Materials and Methods: Between 1997 and 1999, a total of 184 restorations (106 SCs, 32 ISCs, 33 FDPs, and 13 diverse restorations) were placed in 73 patients. Kaplan-Meier estimation was applied for survival and chipping-free rates. Inter-group comparison of both rates was realized by a log rank test and a 2×2 contingency table. Also, SCs and FDPs were compared regarding adhesive vs. conventional cementation, and anterior vs. posterior positioning, for impact on survival., Results: Due to 14 dropouts (34 restorations) and reasonable exclusion of 19 other restorations, the final dataset included: i) 87 SCs [37 patients, mean observation time 11.4 (±3.8)years]; ii) 17 ISCs [12 patients, mean observation time 13.3 (±2.3)years; and iii) 27 FDPs [19 patients, mean observation time 8.9 (±5.4)years]. The 10-year survival rate/chipping-free rate for SCs were 86.1%/83.4%, for ISCs 93.8%/94.1%, and for FDPs were 51.9%/90.8%. Both ISCs and SCs had a significantly higher survival than FDPs (ISCs vs. FDPs: both tests p=0.001; SCs vs. FDPs: p=0.001 and p=0.005). Differences in the chipping-free rates did not reach significance. Also, neither the cementation mode nor positioning of the restoration had an impact on survival., Conclusions: SCs had a slightly lower outcome than can generally be expected from single crowns. In contrast, ICSs had a favorable outcome and the FDPs predominantly failed., Clinical Significance: The practitioner's choice of dental materials is based (at best) on long-term experience. The present 10-year results are based on comprehensive data analyses and show the high potential of lithium-disilicate as a reliable material, especially for single-unit restoration., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Purpose: This retrospective study investigated the frequency and time history of chipping and facing failures, recurrent caries (RC), periodontitis (PE), and loss of retention (LR) of porcelain-fused-to-metal (PFM) single crowns., Materials and Methods: A total of 997 PFM single crowns had been inserted according to a standardized treatment protocol from January 1984 to May 2009. The frequency and time history of chipping and facing failures were evaluated, as were possible risk factors from historical clinical data. Risk factors were bruxism, the type of antagonist, and the location of crowns (mandible, maxilla, anterior, posterior). The survival times of crowns were estimated using Kaplan-Meier (KM) analysis., Results: The median follow-up time calculated with the inverse KM method was 4.33 years. Anterior and posterior PFM crowns showed 5-year survival rates (time to crown replacement) of 96.4% and 97.5% and 10-year survival rates of 92.3% and 95.9%, respectively. Chipping was found in 17 (1.7%) of the 997 PFM crowns. According to the KM method, the 5- and 10-year free-of-event-rates for chipping of anterior crowns were both 98.9%, and the rates for posterior crowns were 98.2% for 5 years and 97.3% for 10 years. Thirteen patients showed RC (1.3%) and 144 (14.4%) PE. The 5-year free-of-event-rate for RC was 98.7% and the 10-year free-of-event rate was 97.2%. For PE, the 5-year free-of-event-rate was 85.8% and the 10-year free-of-event rate was 72.2%. The 5- and 10-year free of- event-rates for LR were 92.2% each for anterior teeth and 97.1% each for posterior teeth., Conclusions: Patients with PFM crowns may expect long-term survival for their restoration. Clinical complications are rare. Chipping of the veneer or loss of retention may occur during the first few years. While chipping of the veneer may occur during the first few years, the frequency of caries or periodontitis increases with the length of oral service and with age.

Purpose: To assess the survival outcomes and reported complications of screw- and cement-retained fixed reconstructions supported on dental implants., Materials and Methods: A Medline (PubMed), Embase, and Cochrane electronic database search from 2000 to September 2012 using MeSH and free-text terms was conducted. Selected inclusion and exclusion criteria guided the search. All studies were first reviewed by abstract and subsequently by full-text reading by two examiners independently. Data were extracted by two examiners and statistically analyzed using a random effects Poisson regression., Results: From 4,324 abstracts, 321 full-text articles were reviewed. Seventy-three articles were found to qualify for inclusion. Five-year survival rates of 96.03% (95% confidence interval [CI]: 93.85% to 97.43%) and 95.55% (95% CI: 92.96% to 97.19%) were calculated for cemented and screw-retained reconstructions, respectively (P = .69). Comparison of cement and screw retention showed no difference when grouped as single crowns (I-SC) (P = .10) or fixed partial dentures (I-FDP) (P = .49). The 5-year survival rate for screw-retained full-arch reconstructions was 96.71% (95% CI: 93.66% to 98.31). All-ceramic reconstruction material exhibited a significantly higher failure rate than porcelain-fused-to-metal (PFM) in cemented reconstructions (P = .01) but not when comparing screw-retained reconstructions (P = .66). Technical and biologic complications demonstrating a statistically significant difference included loss of retention (P ≤ .01), abutment loosening (P ≤ .01), porcelain fracture and/or chipping (P = .02), presence of fistula/suppuration (P ≤ .001), total technical events (P = .03), and total biologic events (P = .02)., Conclusions: Although no statistical difference was found between cement- and screw-retained reconstructions for survival or failure rates, screw-retained reconstructions exhibited fewer technical and biologic complications overall. There were no statistically significant differences between the failure rates of the different reconstruction types (I-SCs, I-FDPs, full-arch I-FDPs) or abutment materials (titanium, gold, ceramic). The failure rate of cemented reconstructions was not influenced by the choice of a specific cement, though cement type did influence loss of retention.

Purpose: The aim of this clinical retrospective study was to evaluate the clinical quality, estimated survival rate, and failure analysis of different all-ceramic restorations in a long-term analysis of up to 20 years., Materials and Methods: Different all-ceramic restorations (crowns [n = 470], veneers [n = 318], onlays [n = 213], and inlays ]n = 334[) were placed in 302 patients (120 men, 182 women) between 1987 and 2009 at Medical University Innsbruck, Innsbruck, Austria. Clinical examination was performed during patients' regularly scheduled maintenance appointments. Esthetic match, porcelain surface, marginal discoloration, and integrity were evaluated following modified California Dental Association/Ryge criteria. Number of restoration failures and reasons for failure were recorded. The study population included 106 (35.1%) individuals diagnosed with bruxism. The success rate was determined using Kaplan-Meier survival analysis., Results: The mean observation time was 102 ± 60 months. Ninety-five failures were recorded. The main reason for failure was fracture of the ceramic (33.68%). The estimated survival rate was 97.3% after 5 years, 93.5% at 10 years, and 78.5% at 20 years. Nonvital teeth showed a significantly higher risk of failure (P < .0001). There was a 2.3-times greater risk of failure associated with existing parafunction (bruxism, P = .0045). Cementation using Variolink showed significantly fewer failures than Optec Cement (P = .0217) and Dual Cement (P = .0099). No significant differences were found for type of restoration and distribution in the mouth., Conclusion: All-ceramic restorations offer a predictable and successful restoration with an estimated survival probability of 93.5% over 10 years. Significantly increased failure rates are associated with bruxism, nonvital teeth, and specific cementation agents.

Purpose: The aim of this study was to evaluate the clinical fracture rate of crowns fabricated with the pressable, leucite-reinforced ceramic IPS Empress, and relate the results to the type of tooth restored., Materials and Methods: The database SCOPUS was searched for clinical studies involving full-coverage crowns made of IPS Empress. To assess the fracture rate of the crowns in relation to the type of restored tooth and study, Poisson regression analysis was used., Results: Seven clinical studies were identified involving 1,487 adhesively luted crowns (mean observation time: 4.5+/-1.7 years) and 81 crowns cemented with zinc-phosphate cement (mean observation time: 1.6+/-0.8 years). Fifty-seven of the adhesively luted crowns fractured (3.8%). The majority of fractures (62%) occurred between the third and sixth year after placement. There was no significant influence regarding the test center on fracture rate, but the restored tooth type played a significant role. The hazard rate (per year) for crowns was estimated to be 5 in every 1,000 crowns for incisors, 7 in every 1,000 crowns for premolars, 12 in every 1,000 crowns for canines, and 16 in every 1,000 crowns for molars. One molar crown in the zinc-phosphate group fractured after 1.2 years., Conclusion: Adhesively luted IPS Empress crowns showed a low fracture rate for incisors and premolars and a somewhat higher rate for molars and canines. The sample size of the conventionally luted crowns was too small and the observation period too short to draw meaningful conclusions.

The purpose of this study was to determine radiographically the prevalence of periapical periodontitis in teeth restored with crown in a Senegalese population. Full mouth periapical radiographs were obtained from 208 consecutive adult patients (6234 teeth) presenting as new patients to the Dental Service of the University. The presence of crown restorations, the periapical status and technical quality of root fillings associated were evaluated. 7.69% (n = 16) of patients had at least one tooth that was crowned. The total number of crowns assessed was 0.95% (n = 59). The molars were the teeth most crowned 40.67% (n = 24) followed by anterior teeth 30.50% (n = 18) and premolars 28.81% (n = 17). All the crowned teeth had previous root canal treatment of which only 16.94% (n = 10) were acceptable. 53 % (n = 32) of the teeth had apical periodontitis (PAI > 2). Unacceptable root fillings were associated with a higher prevalence of periapical disease (p < 0.05). Crown with a post extending more than 4 millimetres from the apex were associated with more periapical lesions 64.28% (p < 0.05). The results indicate a low prevalence of crowned teeth, an absence of vital preparation, a high prevalence of radiographic periapical disease and unacceptable root fillings associated.

Objectives: The objective of this systematic review was to assess the 5-year survival of implant-supported single crowns (SCs) and to describe the incidence of biological and technical complications., Methods: An electronic MEDLINE search complemented by manual searching was conducted to identify prospective and retrospective cohort studies on SCs with a mean follow-up time of at least 5 years. Failure and complication rates were analyzed using random-effects Poisson's regression models to obtain summary estimates of 5-year proportions., Results: Twenty-six studies from an initial yield of 3601 titles were finally selected and data were extracted. In a meta-analysis of these studies, survival of implants supporting SCs was 96.8% [95% confidence interval (CI): 95.9-97.6%] after 5 years. The survival rate of SCs supported by implants was 94.5% (95% CI: 92.5-95.9%) after 5 years of function. The survival rate of metal-ceramic crowns, 95.4% (95% CI: 93.6-96.7%), was significantly (P=0.005) higher than the survival rate, 91.2% (95% CI: 86.8-94.2%), of all-ceramic crowns. Peri-implantitis and soft tissue complications occurred adjacent to 9.7% of the SCs and 6.3% of the implants had bone loss exceeding 2 mm over the 5-year observation period. The cumulative incidence of implant fractures after 5 years was 0.14%. After 5 years, the cumulative incidence of screw or abutment loosening was 12.7% and 0.35% for screw or abutment fracture. For supra-structure-related complications, the cumulative incidence of ceramic or veneer fractures was 4.5%., Conclusion: It can be concluded that after an observation period of 5 years, high survival rates for implants and implant-supported SCs can be expected. However, biological and particularly technical complications are frequent.

Unlabelled: This study evaluated the long-term survival of inlays and partial crowns made of IPS Empress. For this purpose, the patient data of a prospective study were examined in retrospect and statistically evaluated., Materials and Methods: All of the inlays and partial crowns fabricated of IPS-Empress within the Department of Operative Dentistry at the School of Dental Medicine of Philipps University, Marburg, Germany were systematically recorded in a database between 1991 and 2001. The corresponding patient files were revised at the end of 2001. The information gathered in this way was used to evaluate the survival of the restorations using the method described by Kaplan and Meyer., Results: A total of n = 1624 restorations were fabricated of IPS-Empress within the observation period. During this time, n = 53 failures were recorded. The remaining restorations were observed for a mean period of 18.77 months. The failures were mainly attributed to fractures, endodontic problems and cementation errors. The last failure was established after 82 months. At this stage, a cumulative survival probability of p = 0.81 was registered with a standard error of 0.04. At this time, n = 30 restorations were still being observed. Restorations on vital teeth (n = 1588) showed 46 failures, with a cumulative survival probability of p = 0.82. Restorations performed on non-vital teeth (n = 36) showed seven failures, with a cumulative survival probability of p = 0.53. Highly significant differences were found between the two groups (p < 0.0001) in a log-rank test. No significant difference (p = 0.41) was found between the patients treated by students (n = 909) and those treated by qualified dentists (n = 715). Likewise, no difference (p = 0.13) was established between the restorations seated with a high viscosity cement (n = 295) and those placed with a low viscosity cement (n = 1329).

Objective: The aim of this long-term follow-up was to collect up to 17-year survival data of different metal post-and-core restorations with a covering crown., Methods: At initiation of the study, a controlled clinical trial, single tooth was provided with an artificial covering crown, by 18 operators. Restorations under investigation were the post-and-core restorations: cast post-and-core restorations, prefabricated metal post and resin composite core restorations, and post-free all-composite core restorations. Before treatment allocation, the recipient tooth was categorized according to the expected dentin height after tooth preparation. A tooth was assessed to have "substantial dentin height" (Trial 1) or "minimal dentin height" (Trial 2). The study sample consisted of 257 patients that received 307 core restorations. The performance of the restorations was based on data collected from the files of the current dentists monitoring the oral health of the patients. The survival probability was analyzed at different levels: on the restoration level (S(R)), and on the level of the tooth carrying the restoration (S(T)). Kaplan Meier analyses were used to compare survival probabilities., Results: "Type of post-and-core restoration" showed no influence on the survival probability (at both levels) in both trials (P-value>0.05). The 17-year survival rates at restoration level varied from 71% to 80%, and at tooth level from 83% to 92%., Conclusions: The results of this study showed no difference in survival probabilities among different core restorations under a covering crown of endodontically treated teeth. The preservation of substantial remaining coronal tooth structure seems to be critical to the long-term survival of endodontically treated crowned teeth.

Objectives: To test the hypothesis that the placement of a crown is associated with improved (long term) survival of root canal treated teeth, using a systematic review process of clinical studies., Data Sources: Papers referring to single crowns on endodontically treated teeth were located by a MEDLINE search and hand searching. One thousand six hundred and nine references were found, and they were subjected to a systematic review procedure., Study Selection: A three-step inclusion-exclusion procedure was applied to identify papers that represented; good scientific practice (GSP), reported results of all patients, restorations on root canal treated teeth (RCT) for more than 2 years and had sufficient data to generate life table analyses. The outcomes were 'survival of RCT restored with crowns' and 'survival of RCT with direct restorations'. Ten studies survived. These data showed an overall mean GSP of 0.605 with a 10-year survival of 81% for crowned RCT and a 10-year survival of 63% for RCT with direct restorations (resin composites, amalgam, cements)., Conclusion: RCTs restored with crowns show an acceptable long-term survival of 10 years, while direct restorations have a satisfactory survival only for a short period.

Statement of Problem: Limited clinical data exist on the survival of teeth relative to their treatment history., Purpose: This study evaluated failure of teeth relative to their treatment history., Material and Methods: Longitudinal data were collected for 3071 teeth from 148 fully compliant patients from 1 private practice in Yamagata, Japan. Follow-up times ranged from 15 to 23 years, with a mean of 19.2 years (SD 2.4). In this study, every tooth and its restoration were evaluated by one of the authors at the time of each maintenance visit. Treatment history of the teeth was categorized at baseline as follows: (1) sound, unrestored tooth (SUT); (2) 1-surface restoration (RT1); (3) 2-surface restoration (RT2); (4) 3-surface restoration (RT3); (5) 4+-surface restoration (RT4); (6) complete crown (CCT); (7) abutment for fixed partial dental prosthesis (AFT); (8) abutment for removable partial dental prosthesis (APDT); and (9) root canal treatment (RCT). Three types of failure modes were evaluated in this study: (1) restorative failure (secondary caries and/or fracture), (2) extraction, and (3) any failure (restorative failure or extraction). Multivariate survival analysis was used to determine the impact of the treatment history on failure (alpha=.05)., Results: Teeth with multi-surface restorations experienced the highest incidence of any failure (P<.001). For secondary caries, similar risks were noted for the different treatment histories. For failures resulting in extraction, the only teeth with an increased risk were abutments for removable partial dental prostheses (relative risk=5.5) (P=.008)., Conclusions: The data demonstrated that restored teeth experienced a higher incidence of failure compared with unrestored teeth. Complete crowns and abutments for fixed partial dental prostheses had fewer restorative failures when compared with teeth with complex multisurface restorations. Removable partial denture abutments experienced the highest failure rate.

Aims: To prospectively report on the survival of resin-modified glass ionomer cement (RMGIC), photac-fil and pre-formed stainless steel crown (SSC) restorations in primary molar teeth placed over a seven-year period in a specialist paediatric dental practice under private contract of remuneration., Method: All primary molar restorations placed by a specialist paediatric dentist over a seven-year period were reviewed and the outcome results recorded. Data were recorded at review visits until June 30, 2003. Data recorded included Class I restorations, Class II restorations and SSC. The Class II cavities were either mesial or distal, with or without buccal/palatal extensions. If both proximal surfaces were decayed or if after cavity preparation the resultant outline form was significantly larger than the minimal classical form, RMGIC was not used; an SSC was placed instead. Stainless steel crown preparation followed conventional guidelines. The crowns were cemented with reinforced zinc oxide and eugenol (Kalzinol). The status was recorded as satisfactory restoration, tooth exfoliated, tooth extracted for orthodontic reasons with the date of extraction, or needing replacement. If replaced then the reason for replacement was also recorded., Results: A total of 544 Class I RMGICs, 962 Class II RMGICs, and 1,010 SSCs were placed. At the last review of each restoration, 98.3% of Class I, 97.3% of Class II RMGICs and 97.0% of SSCs were either satisfactory or withdrawn intact., Conclusion: Under the conditions of private specialist practice-based study SSCs continued to prove very successful for the restoration of larger cavities and for pulp-treated primary molar teeth. For the smaller cavities RMGIC were also very successful.

Purpose: The objective of this study was to assess the relationship between the number of stainless steel crowns (SSCs) placed, number of surfaces at risk (SAR) post dental surgery, and the risk for relapse in patients treated for Early Childhood Caries (ECC)., Methods: The study population consisted of 57 children treated for ECC under general anesthesia, ranging in age from 2.3 to 7.3 years old at the time of entry. Dental surgery utilized an aggressive approach: teeth that had necrotic pulps or were nonrestorable were extracted; decayed primary mandibular incisors that could not be treated by stripping were extracted; primary maxillary incisors with 3 or more carious surfaces were extracted; single-surface lesions of primary molars that did not compromise cusp integrity were restored with intracoronal amalgam restorations; primary maxillary, incisors and canines with smooth-surface lesions affecting 2 or less surfaces were treated with intracoronal composites; primary molars and canines requiring vital pulp therapy were restored with SSCs; primary molars with caries lesions affecting 2 or more surfaces (including smooth-surface, white-spot lesions) were restored with SSCs; primary canines with caries affecting 3 or more surfaces were restored with stainless steel crowns; topical fluoride was applied after all restorative therapy was completed. The cohort was examined for new caries lesions 6 months post dental surgery. Relapse was defined as the presence of new smooth-surface caries lesions as defined by Radike. Comparisons between relapse (R) and nonrelapse (NR) groups, with respect to the number of SSCs placed and the number of SAR, were performed using t tests and Wilcoxon tests. A 0.05 level of significance was employed in all statistical tests., Results: Twenty-one of the 57 (37%) patients relapsed. No statistically significant difference for the number of SSCs placed or SAR existed between the R group (SSCs: mean = 4.57, median = 4 +/- 2.18; SAR: mean = 39.76, median = 40 +/- 13.62) and NR group (SSCs: mean=5.44, median = 5.5 +/- 2.62; SAR: mean = 39.98, median = 39.5 +/- 15.19)., Conclusions: The risk for relapse in children treated for ECC is not associated with the number of SSCs placed or SAR; aggressive dental surgery for ECC does not result in acceptable clinical outcomes.

The aim of this study was to estimate whether the survival ratios after 20 years of fixed prosthodontics made of alginate impressions was higher, equivalent or lower, compared to the survival ratios, shown in studies, where different impression materials were used. 151 females and 104 males were screened regarding the condition and age of the restorations at the annual check-up in one of the author's surgeries. Average ages were 55 and 54 years respectively, when the fixed prosthodontics were seated. A total of 1.271 units were produced during the twenty years, 911 abutment teeth and 360 pontics. The type of prosthetic work was divided into three groups: 1) larger fixed prosthodontics 6-14 units (469), 2) smaller fixed prosthodontics 2-5 units (541) and 3) single crowns (261). The results show that alginate impressions can produce fixed prosthodontics with survival ratios similar to those presented in other studies, after 5 years (99%), 1o years (93-96%) and 15 years (74-96%). After 20 years the survival ratio was 61-63%. In conclusion, fixed prosthodontics made according to the syringe-tray alginate impression method may have the same success rates after 20 years compared to that of fixed prosthodontics presented in previous longitudinal clinical studies where other impression materials had been used. In this study, caries and root fractures were the main reasons for removing abutment teeth and pontics.

Aim: This study aimed to examine clinically and radiographically the survival of primary root canal treatment completed in a dental teaching hospital between 10 and 20 years previously., Methodology: A data collection form was used to collate all information obtained from the written patients' records along with the results from clinical and radiographic examination of 608 teeth, out of a total of 986 randomly selected teeth that had been root filled in the Prince Philip Dental Hospital (PPDH), Hong Kong, between 1981 and 1989. The criteria for failure were extractions (except for documented nonendodontic reason), retreatments and presence of a periapical radiolucency. The survival function of the treated teeth was plotted against the calculated date of failure using the Kaplan-Meier (K-M) method. Covariables were examined further by Cox Regression analysis with a backward stepwise method., Results: A total of 314 teeth (52%) were either documented or deemed to have failed after examination. The median survival time was 111 months. Cox Regression analysis indicated that the survival of root-filled teeth was significantly influenced by the tooth type, preoperative periapical status and the type of coronal restoration. The survival function declined with time, with a rapid drop in the first 18 months or so. The rate at which failures occurred appeared to slow down with a longer observation time., Conclusions: There was a nonlinear decline in the cumulative survival probability of primary root canal treatment. Tooth type, preoperative periapical status and type of post and final restoration significantly affected the long-term survival of the treated teeth.

Purpose: The failure rates of restorative procedures for children undergoing dental rehabilitation under general anesthesia, performed by pediatric dental residents in advanced educational programs, were evaluated in order to determine treatment outcomes and best practices., Methods: Retrospective review of 504 dental records of children receiving comprehensive dental treatment under general anesthesia at children's hospitals in Boston between 1990-1992 and in Washington, DC, between 1994-1998, were undertaken. Data regarding restoration outcomes were evaluated using chi square tests with correction for continuity. Only records of patients who returned for follow-up at least six months after their rehabilitations were evaluated. T-tests were performed on parametric data., Results: Two-hundred and forty-one (48%) of the records were evaluated. Stainless steel crowns (SSCs) had significantly lower failure rates than amalgams (P<0.001, chi2=63). The highest failure rates were seen in composites (P<0.001, chi2=112) and composite strip crowns (P<0.001, chi2=121)., Conclusions: SSCs are the most reliable restorations while composite restorations are the least durable. Failure of restorations appears to be related to follow-up length.

Purpose: The study compared the probability of fracture of 4 systems of all-ceramic crowns fabricated on maxillary central incisors., Materials and Methods: The 4 all-ceramic crown systems were: (1) a glass-infiltrated, sintered alumina system (In-Ceram) fabricated conventionally, (2) the same system with machine-milled alumina cores (CEREC 2), (3) a heat-press, leucite-reinforced glass-ceramic system (IPS Empress), and (4) a high-purity, high-density alumina system (Procera). Ten crowns of each system were fabricated and compressed at 45 degrees at the palatal surface until failure. The data were analyzed with the Weibull method., Results: There were no significant differences in the probability of fracture among the 4 systems studied., Conclusion: The likelihood of fracture of these crown systems on central incisors should be similar.

Purpose: The purpose of this study was to retrospectively evaluate leucite reinforced-glass ceramic crowns (Empress) placed in patients who regularly visit general practices., Materials and Methods: One hundred ten Empress crowns, placed in 29 patients who visited a general practice on a regular basis, were evaluated according to the California Dental Association's (CDA) quality evaluation system. In addition, the occurrence of plaque and certain gingival conditions was evaluated. All crowns were luted with resin composite cement. The mean and median years in function for the crowns were 3.6 and 3.9 years, respectively., Results: Based on the CDA criteria, 92% of the 110 crowns were rated "satisfactory." Eighty-six percent were given the CDA rating "excellent" for margin integrity. Fracture was registered in 6% of the 110 crowns. Of the remaining 103 crowns, the CDA rating excellent was given to 74% for anatomic form, 86% for color, and 90% for surface. No significant differences (P > 0.05) were observed regarding fracture rates between anterior and posterior crowns. With regard to the occurrence of plaque and bleeding on probing, no significant differences (P > 0.05) were observed between the Empress crowns and the controls., Conclusion: Most of the fractured crowns had been placed on molars or premolars. Although the difference between anterior and posterior teeth was not statistically significant with respect to the fracture rates obtained, the number of fractured crowns placed on posterior teeth exceeded that of those placed on anterior teeth. The difference between the fracture rates may have clinical significance, and the risk of fracture has to be taken into consideration when placing crowns on teeth that are likely to be subjected to high stress levels.

Statement of Problem: Anecdotal reports based on clinical observation have recently linked resin-modified glass ionomer luting agents with postcementation fracture of all-ceramic crowns., Purpose: This study evaluated the fracture incidence of In-Ceram and VitaDur Alpha porcelain jacket all-ceramic crowns cemented with 5 luting agents (Fuji I, Fuji Plus, Vitremer, Advance, and Panavia 21) during 2 months storage in 0.8% NaCl solution., Material and Methods: Fifty human maxillary premolar teeth were prepared for each ceramic system and divided into 5 subgroups of 10 teeth to be cemented with 5 luting cements. Specimens were observed for fracture lines and crack initiation at storage times up to 2 months. Incidence of fracture was analyzed with Fisher's Exact test. Specimens that did not fracture during storage were loaded in compression to failure. Failure loads were analyzed by analysis of variance and multiple pairwise comparisons., Results: Only all-ceramic crowns cemented with Advance cement fractured during the 2-month observation period, and porcelain jacket crowns were found to fracture earlier and more frequently than In-Ceram crowns. Cracks initiated at the crown margin, and multiple crack lines were found as the time of storage increased. In-Ceram crowns were significantly stronger (140 +/- 21.5 kg) than porcelain jacket crowns (98.6 +/- 17.8 kg) at P <.05. For In-Ceram crowns, cement type did not influence failure load while for porcelain jacket crowns, Fuji I (110.5 kg) was significantly higher than Vitremer (86.6 kg) at P <.05., Conclusions: For the cements studied, only crowns cemented with Advance cement demonstrated fracture during 2-month storage. Results for the true resin-modified glass ionomer cements do not support anecdotal reports of fracture of all-ceramic crowns cemented with these materials.

Thirty-six maxillary central incisors were endodontically treated and restored with a post and core and cast crown. Three different post and core systems were evaluated. Restored teeth were fatigue-loaded until preliminary failure of the casting occurred as detected by a strain gauge bonded across the lingual margin of the cast crown. After preliminary failure, fatigue loading was continued for 100,000 load cycles with the crown margin exposed to basic fuschin dye. Teeth were then immersed in dye for 24 h, sectioned, and evaluated for leakage. There was no significant difference in the number of load cycles required to cause preliminary failure among the three post and core systems. Leakage occurred in all three groups, with no significant difference between groups. The occurrence of preliminary failure is clinically undetectable, yet it allows leakage between the restoration and tooth that may extend down the prepared post space.

This in vitro study investigated the fracture resistance of dentin-bonded crowns constructed from four ceramic materials: feldspathic porcelain, aluminous porcelain, a glass-ceramic core material (Dicor), and a leucite-enriched ceramic (Empress). Forty sound maxillary premolar teeth were chosen and divided at random into four equal groups. The teeth were prepared with a standardized crown minimal preparation. The restored teeth were subjected to compressive loading. When the mode of fracture of the specimens was examined, it was found that four mode V (severe) fractures occurred in the Empress group, compared with none in the aluminous porcelain group and one each in the feldspathic porcelain and Dicor groups. Statistical analysis indicated that the loads required to fracture Dicor specimens were significantly greater than those required to fracture the feldspathic and aluminous porcelain crowns but were not significantly different from the loads achieved by the Empress specimens.

Very little is known of dentist and patient factors which may influence the survival or longevity of dental restorative materials placed in private practices. The present retrospective study investigated during 1992 the effects of six factors on the long-term survivals of five types of restorations placed by 20 male dentists in 100 adult patients, at 3 selected Adelaide dental practices. There were no significant effects on restoration survival from change, of dentist, and generally only one or two types of restorations had their survivals influenced significantly either by dental practice location, or by patient age, frequency of patient attendance, experience of dentist, and whether or not the restorations were replacements during the study period. Restoration survival was not influenced significantly by whether, or not, any replacements were made by the dentist who placed the initial restorations. The median survival times for amalgams were 22.52 years, resin composites 16.72 years, castings 13.75 years, and crowns an estimated 26 years. For glass-ionomers, 75 per cent were still present at 11.25 years.

Although the good appearance and biocompatibility of dental porcelains, failures are still of considerable concern because of the limited properties to all ceramic system. Physical properties that might be considered ideal include high strength, resistance to abrasion, and resistance to the hostile oral environment. Porcelain has been considered by many of its physical characteristic are similar to those of enamel. In 1983 a new modality of treatment, the etched porcelain restoration was introduced by Simonsen and Calamia. Numerous investigations have shown the strength of the etched porcelain bonded to composite resin and also the clinical success of this porcelain to be used as laminated veneers and etched inlays and onlays.