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Survival and success of endocrowns: A systematic review and meta-analysis
SYSTEMATIC REVIEW
Survival and success of endocrowns: A systematic review and meta-analysis Raghad A. Al-Dabbagh, BDS, MClinDent Pros, MPros CRS Edin, PhD The successful restoration of ABSTRACT endodontically treated teeth is Statement of problem. Endocrowns are a monoblock type of restoration that use the pulp dependent on the type and chamber and remaining coronal tooth structure as a means of retention. However, data on their quality of the coronal restoralong-term survival and success rates as compared with conventional crowns are lacking. tion.1-4 Endodontically treated Purpose. The purpose of this systematic review and meta-analysis was to collate published work on teeth restored with crowns endocrowns to assist clinicians in making decisions on when and whether they are an appropriate have a 5-year survival rate restorative option with a predictable outcome for extensively damaged endodontically treated similar to vital teeth restored teeth. with crowns (94.2% versus Material and methods. Databases such as PubMed (MEDLINE), Scopus, EMBASE, Cochrane library, 95%).1,5 However, in the and Google Scholar were searched up to June 2019 for clinical and in vitro studies on endocrown absence of cuspal coverage survival and success rates. For the meta-analysis, endocrown and conventional crown survival and (restored with composite resin), success rates were compared, and the pooled effects were presented as relative risks and 95% endodontically treated teeth confidence intervals using a random effects model. have a lower success rate, with Results. Ten studies fulfilled the inclusion criteria (3 clinical and 7 in vitro) and were included in the a 5-year survival rate of 63%.1 systematic review. The meta-analysis of the clinical studies showed an estimated overall 5-year The improved survival of teeth survival rate of 91.4% for endocrowns and 98.3% for conventional crowns. The estimated overall treated endodontically with 5-year success rates were 77.7% for endocrowns and 94% for conventional crowns. There were no significant differences in overall survival or success estimates between the assessed satisfactory coronal cuspal restorations (P>.05). coverage has been attributed to a reduction in microleakages Conclusions. Additional well-designed clinical studies with long-term assessment are needed; however, endocrowns appear to be a promising conservative restorative option with acceptable and the preservation and prolong-term survival for endodontically treated posterior teeth in selected patients. (J Prosthet tection of the remaining tooth 6,7 Dent 2020;-:---) structure. Immediate placement of a satisfactory coronal conservative with advances in adhesive dentistry.8 Such restoration has been reported to reduce microleakage and designs include incorporating fewer mechanical retentive subsequently decrease the risk of endodontic treatment features such as undercuts, grooves, or boxes,8 with failure,6 while cuspal coverage and preservation of the retention being mainly dependent on adhesion to the remaining coronal tooth structure have been reported to tooth structure.8 improve fracture resistance and the outcome of the 2,3,7 Endocrowns are conservative coronal restorations that endodontically treated tooth. have been used to restore endodontically treated teeth Preparation designs for coronal restorations of with significant loss of coronal tooth structure. They are endodontically treated teeth have become more
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Assistant Professor and Consultant in Prosthodontics, Oral and Maxillofacial Rehabilitation Department, Faculty of Dentistry, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia.
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Clinical Implications Limited data suggest that endocrowns can be used as a coronal restoration for endodontically treated posterior teeth with acceptable long-term outcomes when used selectively. Feldspathic computer-aided design and computer-aided manufacturing (CAD-CAM) ceramics appear to be a suitable choice for endocrown fabrication.
monoblock coronal restorations that are retained by the pulp chamber and by bonding to the remaining coronal tooth structure.9 Pissis10 first described the concept in 1995, and Bindl and Mormann9 introduced the term endocrown in 1999. However, only limited data exist on the long-term survival and success of endocrowns as compared with conventional crowns. Therefore, the purpose of this systematic review and meta-analysis was to compare the survival and success rates of endocrowns with conventional crowns for the restoration of endodontically treated teeth. The null hypothesis was that there would be no difference between the 2 restoration types. METHOD AND MATERIALS This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement.11 The population, intervention, control, and outcome (PICO) for this systematic review were defined as follows: the population was participants or teeth undergoing root canal treatment; the intervention was ceramic or composite resin endocrowns; the comparison was conventional post and core crowns; and the outcome measures were survival and success rates, fracture strengths, catastrophic failure rates, and percentage of marginal adaptation. Two investigators (R.A., A.M.) undertook an electronic search of the English language literature in the databases such as PubMed (MEDLINE), Scopus, EMBASE, Cochrane Library, and Google Scholar up to June 2019. The search strategy included the following keywords: crown, endocrown, survival, survival analysis, survival rate, failure rate, failure, compressive strength, materials testing, follow-up studies, prosthesis failure, fracture strength, marginal adaptation, and catastrophic failure. All relevant clinical and in vitro studies were included. No randomized clinical studies published in the Englishlanguage dental literature comparing endocrowns to conventional crowns were identified. Clinical studies considered suitable for this systematic review and metaanalysis included prospective cohort studies or case series, retrospective studies, studies with a mean follow-up THE JOURNAL OF PROSTHETIC DENTISTRY
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of at least 3 years (for the meta-analysis), and the presence of a control group (conventional or classical crowns). The in vitro studies considered in this systematic review were those conducted on extracted teeth and measuring the fracture strength, survival, catastrophic failure, and marginal adaptation as outcome parameters. The intervention of interest included ceramic or composite resin endocrowns, including monoblock-type restorations. Metal alloy restorations were excluded. The comparison included conventional crowns made of ceramic or composite resin excluding crowns made of metal alloys. Survival rate was defined as when endocrowns or conventional crowns were present in the oral cavity but with biological and/or technical complications. Success rate was defined as restorations not associated with any of these complications. Catastrophic failure was defined as nonrestorable or nonrepairable failures in both of the assessed restorations. Two investigators (R.A., A.M.) assessed the article titles and then searched and reviewed the abstracts. Only relevant articles fulfilling the review objectives and inclusion criteria were considered. Full-text articles of potential papers were retrieved and then critically assessed before inclusion in the study if they fulfilled all eligibility criteria. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of the included clinical studies.12 According to the NOS, studies with 5 stars or less have an inherent methodological risk of bias, while those with more than 5 stars have minimal bias. Consequently, only cohort studies with over 5 stars were included in the present review. The risk of methodological bias in the in vitro studies was assessed based on a modification of parameters used elsewhere,13 which included the use of sound teeth for testing, morphologically similar tested teeth, sample size calculation, group randomization, presence of a suitable control group, use of materials according to the manufacturer’s instructions, cavity preparation performed by the same operator (standardization), and blinding of the operator to the testing machine. Studies with 1 to 3 parameters were deemed to be having a high risk of bias; studies with 4 to 5 parameters were of a medium risk of bias; and studies with 6 or more parameters and including a suitable control were classified as having a low risk of bias.13 Only in vitro studies with a low risk of bias were included in the present systematic review. Data were extracted from the included clinical studies and tabulated in a spreadsheet (Microsoft Office Excel 2016; Microsoft Corp) with the following information: authors, year, journal, number of participants, mean age, sex, number of restorations, type of teeth, type of restoration, restoration survival time, restoration success and failure, type of failure, follow-up period, and NOS. When the same data were published more than once, data were obtained from the most complete version. When the Al-Dabbagh
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Inclusion
Eligibility
Screening
Identification
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Application of exclusion criteria and discussion at title and abstract level led to exclusion of 2536 titles
Application of exclusion criteria and critical assessment of methodology led to exclusion of 38 articles
Independent electronic search by 2 investigators yielded 2584 titles
PubMed/MEDLINE 1340 Scopus 547 EMBASE 320 Cochran Library 170 Google Scholar 207
Independent analysis of full text of the 48 selected articles by the investigators
Not endocrown/ unpublished 2476 Finite element analysis 21 Case reports 22 Reviews 5 Alloy based 2 Ongoing clinical trials 10
10 full-articles analyzed for the systematic review of which the 3 clinical articles were included in the meta-analysis
No conventional crown control 6 High risk for bias 22
Figure 1. Flow chart of search strategy and number of included endocrown articles.
study data were unclear, the authors were contacted for clarification. Review Manager (RevMan) software version 5.2 (The Nordic Cochrane Centre, The Cochrane Collaboration) was used for the meta-analysis. The success and survival of endocrowns and conventional crowns were measured. Comparisons and pooled effects were presented as relative risks (RR) and 95% confidence intervals (CI) using a random effects model (a=.05). Subgroups were analyzed to compare the effect of tooth type (molars and premolars) on the survival and success of endocrowns versus conventional crowns. Study heterogeneity was measured using the chi-squared test (a=.05). The test of inconsistency (I2) was calculated and interpreted as minimal, moderate, or substantial heterogeneity at levels of <25%, 25% to 50%, and >50%, respectively. RESULTS A total of 2584 potential records were initially identified. The titles and abstracts were screened, and nonqualifying articles and duplicates were removed to leave 48 full articles (9 clinical and 39 in vitro). Excluded articles were omitted because they were not endocrown articles or they were review articles,14-18 case reports,19-39 finite element analysis studies,40-59 alloy-based restoration studies,60,61 or unpublished clinical research. These 48 articles were critically evaluated, and their quality of methodology was assessed. Five more articles were excluded because they did not fulfill the inclusion criteria (absence of comparison with a conventional crown),4,6265 leaving 10 eligible articles for the systematic review and 3 clinical studies for the meta-analysis (Fig. 1). The 38 excluded articles are summarized in Supplementary Al-Dabbagh
Tables 1 and 2 (available online). The article by Otto66 was excluded because the cohort was similar to that of Otto and Mormann.67 Seven in vitro studies compared the fracture strengths and catastrophic failure rates of endocrowns and conventional crowns: 1 in incisors, 4 in premolars, and 2 in molars (Table 1).68-74Additionally, 1 in vitro study assessed marginal adaptation in premolars restored by endocrowns.75 In central incisors, the load to fracture strength of resin ceramic endocrowns and conventional crowns was not significantly different (869 ±247.8 N and 580.0 ±295.4 N), with a catastrophic failure rate of 100% for endocrowns and 0% for conventional crowns.71 Likewise, the load to fracture strength of lithium disilicate ceramic endocrowns (915.9 ±182.1 N) and conventional crowns (646.8 N) was not significantly different, with a catastrophic failure rate of 85% and 0%, respectively.71 In premolars, the fracture strength of composite resin endocrowns (230 N) was higher than for conventional crowns (135 N), 71 while the fracture strength of resin ceramic endocrowns (1522.64 ±352.52 N) was not significantly different from that of conventional crowns (1301.34 ±177.12 N), with a catastrophic failure rate of 30% for endocrowns and 40% for conventional crowns.70 The fracture strength of lithium disilicate ceramic endocrowns (220 N or 933 ±183 N) was similar to that of conventional crowns (200 N or 925 ±186 N), with a catastrophic failure rate of 0 or 80% for endocrowns and 0 or 40% for conventional crowns (Table 1).68,73 When the effect of the type of restorative material was assessed with respect to the fracture strength of endocrowns resin ceramic (1522.64 ±352.5 N), endocrowns had higher load to fracture strengths than lithium disilicate ceramic THE JOURNAL OF PROSTHETIC DENTISTRY
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Table 1. Summary of included in vitro studies
Reference
Objectives of Study
Type of Tooth
No of Samples/ Group
Restoration Material
Type of Sample Preparation and Testing
Load to Fracture Strength (Mn ±SD, N)
Catastrophic Failure Rates (%, Out of Total Failures)
Marginal Adaptation In Vitro (Mn ±SD) Quality Scale (%)
AbdelAziz and AboElmagd68
Compare the Mandibular fracture strength of premolars endocrown and conventional crown in the presence or absence of ferrule
5
Lithium disilicate ceramic (IPS e.Max)
Endocrown and Universal load Endocrown and testing, inspection conventional crown: 933 conventional crown: 0, 0 with digital ±183=925 ±186$ microscope
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Hamdy69
Maxillary Assess various restoration designs first molars fracture strength
10
Lithium disilicate ceramic (IPS e.Max Press)
Thermocycling, universal load testing (axial loading)
Endocrown and Endocrown and conventional crown: 989 conventional crown: 20, 10 ±109.1=1076 ±132
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6
Al-shibri Assess fracture Maxillary and premolars resistance of 70 Elguindy endocrown and conventional crown in 2 different materials
10
Universal load Resin ceramic testing, Visual and (Ceramsmart), lithium disilicate (IPS photographic inspection e.Max CAD)$
Güngör et al71
10
Resin ceramic (Lava Ultimate), lithium disilicate (IPS e.Max CAD)
Reference
Maxillary Assess fracture strength of EC and central CC and 2 types of incisors posts
Objectives of Study
Type of Tooth
Universal load testing (oblique loading)
Resin ceramic, lithium disilicate ceramic endocrowns, and lithium disilicate conventional crowns: 30, 80, 40
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Resin ceramic endocrowns and conventional crowns: 869 ±247.8=580.02 ±295.4 Lithium disilicate endocrowns and conventional crowns: 915.91 ±182.1=646.78
Resin ceramic endocrowns and conventional crowns: 100, 0% Lithium disilicate endocrowns and conventional crowns: 85, 0
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Catastrophic Marginal In Vitro Load to Fracture Survival Time/ Failure Rates Strength (Mn ±SD, Cycles Median (%, out of Total Adaptation Quality Scale (Mn, %) Failures) (95% CI) N)
Sample No of Samples/ Restoration Preparation and Testing Group Material
Lise et al73 Study effect of Single rooted endocrown cavity design and premolars material on fracture strength
Resin ceramic, lithium disilicate ceramic endocrowns, and lithium disilicate conventional crowns: 1522.64 ±352.52>717.33 ±198.59<1301.34 ±177.12
8
Composite resin and Lithium disilicate ceramic CEREC AC CAD-CAM
Fatigue aged, chewing simulator machine, universal load testing (oblique load), stereomicroscope
Composite resin short and long endocrowns, and long conventional crown: 230>140 and 135 Lithium disilicate short and long endocrowns, and long conventional crown: 125=220=200
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Short and long endocrowns, and conventional crown: 93 318 (90 572; 99 176) =90 834 (90 010; 90 834)=85 374 (71 552; 86 552)
Short and long endocrowns, and conventional crown: 50, 41.7, 66.7
Short and long endocrowns, and conventional crown: 73.5, 72.5<82
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Resin ceramic, lithium disilicate ceramic and zirconia reinforced lithium disilicate ceramic endocrowns, and lithium disilicate conventional crowns: 2752 ±242=2914 ±205>2279 ±290>1347 ±185
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Rocca et al74
Study effect of Maxillary premolars endocrown length on marginal adaptation and fatigue strength
12
Lithium disilicate ceramic (IP e.Max CAD)
Thermocycling, SEM, closed loop servo hydraulics, stereomicroscope
El Ghoul et al65
Compare fracture Mandibular molars resistance of endocrown made of different materials to conventional crown
10
Resin ceramic (Cerasmart), Lithium disilicate (IPS e. max CAD), Zirconia reinforced lithium disilicate ceramic (Vita Suprinity)
Thermocycling, Dynamic mechanical loading, SEM
CI, confidence interval; Mn, mean; SD, standard deviation; N, Newton; SEM, scanning electron microscope.
endocrowns (717.33 ±198.6 N), with a catastrophic failure rate of 30% for resin ceramic endocrowns and 80% for lithium disilicate ceramic endocrowns.70 Marginal adaptation of lithium disilicate ceramic
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endocrowns and conventional crowns was assessed in 1 in vitro study, which showed that the marginal adaptation of endocrowns (73%) was less than that of conventional crowns (82%) (Table 1).74
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Table 2. Summary of included clinical studies
Reference
Type of Study
Bindl and Prospective Mormann75
Age (Mn (Range)), Sex (M:F Ratio)
No. of Samples
Mean FollowUp Period Dropout (Mo) Rate
Age: Sex: 1:1.4
136 patients 86 endocrowns, 70 conventional crowns, 52 reduced crowns
55 ±15
0
Roggendorf Prospective Age: 52 et al76 observational (21-80) longitudinal Sex: 2.1:1
35 patients 12 endocrowns, 21 conventional crowns, 44 other restorations
84 ±6
24.4
Otto and Prospective Age: 53 Mormann72 observational (25-79) longitudinal Sex: 1:1.4
55 patients, 25 endocrowns, 8 conventional crowns, 32 reduced crowns
116
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Type of Tooth
Survival Rate Success Rate Failure Rate, (%) (%) (Specific Method of (Endocrown, (Endocrown, Failure Restoration Restoration Conventional Conventional From Total Material Evaluation Crown) Crown) Failures) NOS
Endocrowns: 11 premolars, 70 molars Conventional crowns: 33 premolars, 37 molars
Feldspathic Clinical, porcelain USPHS CAD-CAM (CEREC2)
Premolars: 87.5=96.7% Molars: 87.1=94.6
Molars
Feldspathic Clinical, USPHS porcelain CAD-CAM (CEREC2)
80, 100%
Endocrowns; 5 premolars, 20 molars Conventional crowns: 4 premolars, 4 molars
Feldspathic Clinical, modified porcelain USPHS CAD-CAM (CEREC 3)
Premolars: Endocrowns: 68.8<93.9 Premolars: Molars: 80=73 Loss of retention; 100% Molars: Periodontitis, vertical root fracture each; 14.3%, Loss of retention; 64.3% Conventional crown: Premolars: Crown fracture, vertical root fracture each; 50% Molar: crown fracture, vertical root fracture each; 20%, irreversible pulpitis; 50% 72.7<100
Premolars and Premolars: 80, 100 Molars: Molars: 100=100% 90,100
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Endocrowns: Vertical root fracture: 66.7% Caries: 33.3%
7
Endocrowns: Premolars loss of retention; 100% Molars: loss of retention; 50%, crown fracture; 50%
7
Mn, Mean; NOS, Newcastle-Ottawa scale; USPHS, United States Public Health Service.
In molars, the load to fracture strength of resin ceramic endocrowns (2752 ±242 N) was higher than that of conventional crowns (1347 ±185 N).72 The fracture strength of lithium disilicate ceramic endocrowns (989 ±109.1 N or 2914 ±205 N) was consistently either similar to or higher than conventional crowns (1076 ±132 N or 1347 ±185 N), with a catastrophic failure rate of 20% and 10%, respectively.69,72 Comparisons of the fracture resistance of endocrowns made of various materials showed that resin ceramic endocrowns (2752 ±242 N) had a fracture strength that was not significantly different from that of lithium disilicate ceramic endocrowns (2914 ±205 N) and a higher fracture strength than that of zirconia-reinforced ceramic endocrowns (2279 ±290 N).72 Taken together, from in vitro studies, the fracture strength of endocrowns restoring posterior teeth was either similar to or higher than that of conventional Al-Dabbagh
crowns, yet the overall rate of catastrophic failures of endocrowns and conventional crowns restoring molars was less than for the same restorations restoring anterior teeth or premolars (Table 1). Clinical studies included in the systematic review and meta-analysis were prospective studies with a population average age of 53 years (range: 21-80), a male-to-female ratio of 1:1, and an average follow-up period of 85 ±10 months (Table 2).67,75,76 The estimated overall 5-year survival rates were 93.8% for endocrowns and 98.4% for conventional crowns restoring premolars, and the 5-year survival rates were 89.1% for endocrowns and 98.2% for conventional crowns when restoring molars. The estimated overall 5year success rates of endocrowns and conventional crowns restoring premolars were 74.4% and 97%, respectively, and the 5-year success rates in tests and THE JOURNAL OF PROSTHETIC DENTISTRY
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Weight
Risk Ratio M-H, Random, 95% CI
Premolars Bindl et al. 2005 Otto and Mormann 2015
21.2% 5.6%
0.90 [0.74, 1.10] 1.00 [0.68, 1.46]
Subtotal (95% CI)
26.8%
0.92 [0.78, 1.10]
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Risk Ratio M-H, Random, 95% CI
Heterogeneity: τ2=0.00; χ2=0.22, df=1 (P=.64); I2=0% Test for overall effect: Z=0.92 (P=.36) Molars Bindl et al. 2005 Otto and Mormann 2015 Roggendorf et al. 2012
57.3% 9.0% 6.9%
0.92 [0.82, 1.04] 1.00 [0.74, 1.35] 0.84 [0.60, 1.19]
Subtotal (95% CI)
73.2%
0.92 [0.83, 1.02]
Heterogeneity: τ2=0.00; χ2=0.54, df=2 (P=.76); I2=0% Test for overall effect: Z=1.50 (P=.13) Overall (95% CI)
100.0%
0.92 [0.84, 1.01]
Heterogeneity: τ2=0.00; χ2=0.77, df=4 (P=.94); I2=0% Test for overall effect: Z=1.76 (P=.08) Test of subgroup differences: χ2=0.00, df=1 (P=.99); I2=0%
0.05
0.2 Conventional crowns
1
5 Endocrowns
20
Survival Rate Figure 2. Forest plot of survival rates of endocrowns compared with conventional crowns in molars and premolars
controls restoring molars were 80.9% and 91%, respectively. However, the overall survival (RR=0.92; 95% CI: 0.84, 1.01) and success rates (RR=0.91; 95% CI: 0.77, 1.08) of endocrowns and conventional crowns were not significantly different (Figs. 2, 3). Moreover, subgroup analysis revealed that the survival rates of endocrowns and conventional crowns were similar when restoring molars (RR=0.92; 95% CI: 0.83, 1.02) and premolars (RR= 0.92; 95% CI: 0.78, 1.10). However, this analysis demonstrated an improved but nonsignificant success outcome favoring conventional crowns when restoring premolars (RR= 0.76; 95% CI: 0.57, 1.01) (Figs. 2, 3). Heterogeneity was minimal for both assessed outcomes (I2= 0 and 22%). DISCUSSION The main objective of this review was to assess the survival and success rates of endocrowns. The analysis showed that the fracture strength of endocrowns restoring posterior teeth was either similar to or higher than conventional crowns. However, there was a higher catastrophic failure rate of lithium disilicate ceramic endocrowns compared with conventional crowns. Consistently, clinical survival and success rates of endocrowns and conventional crowns were similar when used to restore endodontically treated molars and premolars, supporting acceptance of the null hypothesis. The analysis revealed several deficiencies in the current literature, including a lack of randomized controlled studies, clinical studies with sufficient
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numbers of test and control restorations, and clinical studies with long-term survival analysis over 3 years. Most of the studies included in this review were, accordingly, in vitro studies. Most of the articles published to date were on endocrowns used to restore endodontically treated molars and premolars.68,70,72-76 However, endocrowns were shown to perform better when placed in posterior teeth.76 This is possibly because of the larger pulp chamber in premolars and molars and their axial loading under function. In clinical studies, endocrowns were mainly used in teeth with minimal remaining coronal tooth structure, where establishing a ferrule would be difficult, yet margins were mainly equigingival.68,75 In these teeth, crown lengthening could be avoided because it may further compromise the tooth, rendering it nonrestorable. Endodontically treated teeth are susceptible to biomechanical failure and should be restored with a coronal restoration to protect them from fracture and failure.1-3Ideally, an endocrown should be fabricated from a material with a low modulus of elasticity (similar to that of the tooth structure), high mechanical strength, and sufficient bond strength to the underlying tooth structure.53 A modulus of elasticity comparable with dentin helps to distribute occlusal forces along the bonded surface and possibly improves fracture resistance,53 while high mechanical strength helps in withstanding occlusal load and resisting material fracture.53 Al-Dabbagh
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Subgroup
Weight
Risk Ratio M-H, Random, 95% CI
Premolars Bindl et al. 2005 Otto and Mormann 2015
20.0% 9.0%
0.73 [0.52, 1.03] 0.83 [0.48, 1.44]
Subtotal (95% CI)
29.0%
0.76 [0.57, 1.01]
Risk Ratio M-H, Random, 95% CI
Heterogeneity: τ2=0.00; χ2=0.16, df=1 (P=.69); I2=0% Test for overall effect: Z=1.87 (P=.06) Molars Bindl et al. 2005 Otto and Mormann 2015 Roggendorf et al. 2012
34.9% 20.9% 15.2%
1.10 [0.87, 1.38] 0.98 [0.70, 1.36] 0.76 [0.50, 1.13]
Subtotal (95% CI)
71.0%
0.98 [0.80, 1.20]
Heterogeneity: τ2=0.01; χ2=2.56, df=2 (P=.28); I2=22% Test for overall effect: Z=0.18 (P=.85) Overall (95% CI)
100.0%
0.91 [0.77, 1.08]
Heterogeneity: τ2=0.00; χ2=5.14 , df=4 (P=.27); I2=22% Test for overall effect: Z=1.06 (P=.29) Test of subgroup differences: χ2=2.05, df=1 (P=.15); I2=51.2%
0.05
0.2 Conventional Crowns
1
5 Endocrowns
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Survival Rate Figure 3. Forest plot of success rates of endocrowns compared with conventional crowns in molars and premolars
The published prospective and retrospective clinical studies on the clinical performance and survival of endocrowns used feldspathic computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic endocrowns.67,75,76 However, most of the in vitro studies used either resin ceramic or lithium disilicate ceramics to fabricate endocrowns.68-74 In these in vitro studies, endocrowns made of resin ceramic restoring premolars had higher fracture strengths and lower catastrophic failure rates than those of endocrowns made of lithium disilicate ceramics. A possible explanation for this is that the modulus of elasticity of the resin ceramic is comparable with dentin and thus may better distribute occlusal forces along the bonded surface of premolars, thereby improving fracture resistance and reducing catastrophic failure rates.53 For feasibility and to improve the mechanical properties, most studies used CAD-CAM blocks (resin ceramic, feldspathic, and lithium disilicate) to fabricate endocrowns.66,70,71,73,74 The results of most in vitro studies on endocrown CAD-CAM restorations were positive.69,74 Clinical studies on the long-term serviceability of endocrowns are scarce. Although there were no significant differences in the overall survival rates of endocrowns compared with conventional crowns in this meta-analysis, there was a trend toward better survival with conventional crowns, a trend that was more pronounced in premolars. This failure to detect a significant difference was possibly attributable to the small number Al-Dabbagh
of assessed restorations. In their prospective study, Bindl et al75 reported that the cumulative survival rates of endocrowns (feldspathic CAD-CAM CEREC2) in molars were similar to those of conventionally prepared and minimally prepared crowns (87.9%, 94.6%, and 92.1%, respectively). This study included 208 crowns in 136 participants, of which 109 were endocrowns (70 molars, 39 premolars). Among the endocrown restorations, 19 failed, mainly from adhesive failure (14 restorations) after 5 to 6 years of service.75 In another prospective study, the same group showed that the 12-year survival rates of the same type of endocrowns and crowns (with post and core crowns or in vital teeth with deficient preparation) were similar (85.7%, 90.3%, and 94.4%, respectively). The difficulty in detecting a significant difference in survival between test (25 endocrowns) and control (40 crowns) could be because of the small sample size. However, in general, the failure rates were low, which may also reflect participant selection and the standardized procedure or that endocrowns could be a promising restorative option.67 In summary, clinical evidence on the longevity of endocrown restorations is still lacking. Most existing in vivo and in vitro studies focused on CAD-CAM endocrowns made of resin ceramics and feldspathic or lithium disilicate ceramics and demonstrated the possibility of using endocrowns in specific clinical scenarios such as endodontically treated molars with minimal remaining coronal tooth structure. When endocrowns failed in molars, this was usually a restoration failure or THE JOURNAL OF PROSTHETIC DENTISTRY
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repairable failure. However, regular maintenance visits should be recommended to assess the susceptibility of marginal leakage and debonding for immediate intervention. CONCLUSIONS Based on the findings of this systematic review and meta-analysis, the following conclusions were drawn: 1. There remains a need for large, well designed, clinically controlled studies with long-term assessment. 2. However, endocrowns appear to be a promising, conservative, and inexpensive restorative option with acceptable long-term survival for endodontically treated posterior teeth in selected patients using standardized clinical procedures. REFERENCES 1. Stavropoulou AF, Koidis PT. A systematic review of single crowns on endodontically treated teeth. J Dent 2007;35:761-7. 2. Suksaphar W, Banomyong D, Jirathanyanatt T, Ngoenwiwatkul Y. Survival rates against fracture of endodontically treated posterior teeth restored with full-coverage crowns or resin composite restorations: a systematic review. Restor Dent Endod 2017;42:157-67. 3. Tang W, Wu Y, Smales RJ. Identifying and reducing risks for potential fractures in endodontically treated teeth. J Endod 2010;36:609-17. 4. Gregor L, Bouillaguet S, Onisor I, Ardu S, Krejci I, Rocca GT. Microhardness of light- and dual-polymerizable luting resins polymerized through 7.5-mmthick endocrowns. J Prosthet Dent 2014;112:942-8. 5. Sailer I, Makarov NA, Thoma DS, Zwahlen M, Pjetursson BE. All-ceramic or metal-ceramic tooth-supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates. Part I: single crowns (SCs). Dent Mater 2015;31:603-23. 6. Saunders WP, Saunders EM. Coronal leakage as a cause of failure in rootcanal therapy: a review. Endod Dent Traumatol 1994;10:105-8. 7. Mannocci F, Cowie J. Restoration of endodontically treated teeth. Br Dent J 2014;216:341-6. 8. Sofan E, Sofan A, Palaia G, Tenore G, Romeo U, Migliau G. Classification review of dental adhesive systems: from the IV generation to the universal type. Ann Stomatol (Roma) 2017;8:1-17. 9. Bindl A, Mormann WH. Clinical evaluation of adhesively placed cerec endocrowns after 2 years–preliminary results. J Adhes Dent 1999;1:255-65. 10. Pissis P. Fabrication of a metal-free ceramic restoration utilizing the monobloc technique. Pract Periodontics Aesthet Dent 1995;7:83-94. 11. Moher D, Liberati A, Tetzlaff J, Altman DG, Group P. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. J Clin Epidemiol 2009;62:1006-12. 12. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomized studies in meta-analysis. [Internet]. 2013. Available at: http:// www.ohri.ca/programs/clinical_epidemiology/oxford.asp. Accessed August 15, 2018. 13. Sarkis-Onofre R, Skupien JA, Cenci MS, Moraes RR, Pereira-Cenci T. The role of resin cement on bond strength of glass-fiber posts luted into root canals: a systematic review and meta-analysis of in vitro studies. Oper Dent 2014;39:E31-44. 14. Sevimli G, Cengiz S, Oruc MS. Endocrowns: review. J Istanb Univ Fac Dent 2015;49:57-63. 15. Sedrez-Porto JA, Rosa WL, da Silva AF, Munchow EA, Pereira-Cenci T. Endocrown restorations: a systematic review and meta-analysis. J Dent 2016;52:8-14. 16. Carvalho MA, Lazari PC, Gresnigt M, Del Bel Cury AA, Magne P. Current options concerning the endodontically-treated teeth restoration with the adhesive approach. Braz Oral Res 2018;32:e74. 17. Menezes-Silva REC, Atta MT, Navarro MF, Ishikiriama SK, Mondelli RF. Endocrown: a conservative approach. Braz Dent J 2016;19:121-31. 18. Sobczyk M, Godlewski T. The possibility of application of endocrowns in prosthetic treatment. Norwa Stomatol 2018;23:116-20. 19. Valentina V, Aleksandar T, Dejan L, Vojkan L. Restoring endodontically treated teeth with all-ceramic endo-crowns: case report. Stomatol Glas Srb 2008;55:54-64.
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20. Biacchi GR, Mello B, Basting RT. The endocrown: an alternative approach for restoring extensively damaged molars. J Esthet Restor Dent 2013;25: 383-90. 21. Carlos RB, Thomas Nainan M, Pradhan S, Roshni S, Benjamin S, Rose R. Restoration of endodontically treated molars using all ceramic endocrowns. Case Rep Dent 2013;2013:210763. 22. Rocca GT, Rizcalla N, Krejci I. Fiber-reinforced resin coating for endocrown preparations: a technical report. Oper Dent 2013;38:242-8. 23. da Cunha LF, Mondelli J, Auersvald CM, Gonzaga CC, Mondelli RF, Correr GM, et al. Endocrown with leucite-reinforced ceramic: case of restoration of endodontically treated teeth. Case Rep Dent 2015;2015:7503-13. 24. Mahesh B, Vandana G, Sanjay P, Jaykumar G, Deepika C, Aatif N. Endocrown: conservative treatment modality for restoration of endodontically treated teeth: a case report. Endodontology 2015;27:188-91. 25. Sowmya B, Mathew S, Narayana I, Hedge S. Management of mutilated molars with altered canal morphology: a case report. Endodontology 2015;27: 66-70. 26. Desai P, Tailor K, Patel P, Thakkar P. Post endodontic restoration with novel endocrown approach: a case series. J Res Adv Dent 2016;5:129-36. 27. Bilgin MS, Erdem A, Tanriver M. CAD-CAM endocrown fabrication from a polymer-infiltrated ceramic network block for primary molar: a case report. J Clin Pediatr Dent 2016;40:264-8. 28. Chaudhary S, Rathod A, Yadav P, Talwar S, Verma M. Restorative management of grossly mutilated molar teeth using endocrown: a novel concept. J Restor Dent 2016;4:97-100. 29. Soares R, de Ataide Ide N, Fernandes M, Lambor R. Fibre reinforcement in a structurally compromised endodontically treated molar: a case report. Restor Dent Endod 2016;41:143-7. 30. Fernandes da Cunha L, Gonzaga CC, Pissaia JF, Correr GM. Lithium silicate endocrown fabricated with a CAD-CAM system: a functional and esthetic protocol. J Prosthet Dent 2017;118:131-4. 31. Rao BS, Bandekar S, Kshirsagar S, Naman S. Endocrown-a unique way of retention-case report. J Adv Med Med Res 2017;22:1-5. 32. Shah RJ, Lagdive S, Verma V, Shah S, Saini S. Rehabilitating endodontically treated mandibular molar having inadequate coronal length with “endocrown”- a neoteric clinical approach. J Dent Med Sci 2017;16:29-33. 33. Singh S, Rajkumar B, Gupta V, Bhatt A. Endocrown: conservative approach for restoration of endodontically treated teeth: a case report. Int J Curr Innov Res 2017;3:595-7. 34. Rocca GT, Krejci I. Crown and post-free adhesive restorations for endodontically treated posterior teeth: from direct composite to endocrowns. Eur J Esthet Dent 2013;8:156-79. 35. Fages M, Bennasar B. The endocrown: a different type of all-ceramic reconstruction for molars. J Can Dent Assoc 2013;79:d140. 36. Zoidis P, Bakiri E, Polyzois G. Using modified polyetheretherketone (PEEK) as an alternative material for endocrown restorations: a short-term clinical report. J Prosthet Dent 2017;117:335-9. 37. Tzimas K, Tsiafitsa M, Gerasimou P, Tsitrou E. Endocrown restorations for extensively damaged posterior teeth: clinical performance of three cases. Restor Dent Endod 2018;43:e38. 38. Dablanca-Blanco AB, Blanco-Carrion J, Martin-Biedma B, Varela-Patino P, Bello-Castro A, Castelo-Baz P. Management of large class II lesions in molars: how to restore and when to perform surgical crown lengthening? Restor Dent Endod 2017;42:240-52. 39. Dogui H, Abdelmalek F, Amor A, Douki N. Endocrown: an alternative approach for restoring endodontically treated molars with large coronal destruction. Case Rep Dent 2018;2018:1-7. 40. Zarone F, Sorrentino R, Apicella D, Valentino B, Ferrari M, Aversa R, et al. Evaluation of the biomechanical behavior of maxillary central incisors restored by means of endocrowns compared to a natural tooth: a 3D static linear finite elements analysis. Dent Mater 2006;22:1035-44. 41. Aversa R, Apicella D, Perillo L, Sorrentino R, Zarone F, Ferrari M, et al. Nonlinear elastic three-dimensional finite element analysis on the effect of endocrown material rigidity on alveolar bone remodeling process. Dent Mater 2009;25:678-90. 42. Lim DY, Kim HC, Hur B, Kim KH, Son K, Park JK. Stress distribution of endodontically treated maxillary second premolars restored with different methods: three-dimensional finite element analysis. J Kor Acad Con Dent 2009;34:69-80. 43. Lin CL, Chang YH, Pa CA. Estimation of the risk of failure for an endodontically treated maxillary premolar with MODP preparation and CAD-CAM ceramic restorations. J Endod 2009;35:1391-5. 44. Lin CL, Pai CA. Numerical investigation of failure risk of CAD-CAM ceramic restoration for an endodontically treated maxillary premolar with MO preparation. Biomed Eng Appl Basis Commun 2009;22:327-35. 45. Lin CL, Chang YH, Chang CY, Pai CA, Huang SF. Finite element and Weibull analyses to estimate failure risks in the ceramic endocrown and classical crown for endodontically treated maxillary premolar. Eur J Oral Sci 2010;118:87-93. 46. Lin CL, Chang YH, Pai CA. Evaluation of failure risks in ceramic restorations for endodontically treated premolar with MOD preparation. Dent Mater 2011;27:431-8.
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47. Hasan I, Frentzen M, Utz KH, Hoyer D, Langenbach A, Bourauel C. Finite element analysis of adhesive endo-crowns of molars at different height levels of buccally applied load. J Dent Biomech 2012;3:1-11. 48. Dejak B, Mlotkowski A. 3D-finite element analysis of molars restored with endocrowns and posts during masticatory simulation. Dent Mater 2013;29: e309-17. 49. Lin CL, Chang YH, Hsieh SK, Chang WJ. Estimation of the failure risk of a maxillary premolar with different crack depths with endodontic treatment by computer-aided design/computer-aided manufacturing ceramic restorations. J Endod 2013;39:375-9. 50. Chen B, Ma Y, Wu K, Chen H, Li L, Liang L, et al. Influence of various materials on biomechanical behavior of endocrown-restored, endodonticallytreated mandibular first molars; a 3D finite element analysis. J Wuhan Univ Technol-Mater Sci Ed 2015;30:643-8. 51. Helal MA, Wang Z. Biomechanical assessment of restored mandibular molar by endocrown in comparison to a glass fiber post-retained conventional crown: 3D finite element analysis. J Prosthodont 2017;25:1-9. 52. Gulec L, Ulusoy N. Effect of endocrown restorations with different CADCAM materials: 3D finite element and Weibull analyses. Biomed Res Int 2017;2017:1-10. 53. Zhu J, Rong Q, Wang X, Gao X. Influence of remaining tooth structure and restorative material type on stress distribution in endodontically treated maxillary premolars: a finite element analysis. J Prosthet Dent 2017;117: 646-55. 54. Dejak B, Mlotkowski A. Strength comparison of anterior teeth restored with ceramic endocrowns vs custom-made post and cores. J Prosthodont Res 2018;62:171-6. 55. Tribst JPM, Dal Piva AMO, Madruga CFL, Valera MC, Borges ALS, Bresciani E, et al. Endocrown restorations: influence of dental remnant and restorative material on stress distribution. Dent Mater 2018;34: 1466-73. 56. Chen G, Fan W, Mishra S, El-Atem A, Schuetz MA, Xiao Y. Tooth fracture risk analysis based on a new finite element dental structure models using micro-CT data. Comput Biol Med 2012;42:957-63. 57. Schmidlin PR, Stawarczyk B, DeAbreu D, Bindl A, Ender A, Ichim IP. Fracture resistance of endodontically treated teeth without ferrule using a novel H-shaped short post. Quintessence Int 2015;46:97-108. 58. da Fonseca GF, de Andrade GS, Dal Piva AM, Tribst JP, Borges AL. Computer-aided design finite element modeling of different approaches to rehabilitate endodontically treated teeth. J Indian Prosthodont Soc 2019;18: 329-35. 59. Dartora NR, de Conto Ferreira MB, Moris ICM, Brazao EH, Spazin AO, Sousa-Neto MD, et al. Effect of intracoronal depth of teeth restored with endocrowns on fracture resistance: in vitro and 3-dimensional finite element analysis. J Endod 2018;44:1179-85. 60. Li H, Liu L, Li X, Wang X, Gao Y, Jing G. Influence of three pattern materials on the marginal adaption of Co-Cr alloy inner crown of PFM endocrown. Adv Mater Res 2014;887-888:407-10. 61. Wang Z, Guo J, Li X, Zhao T, Li H. Evaluation of the marginal microleakage of endocrowns fabricated with three different processing technologies. J Resid Sci Technol 2016;13:316.1-4. 62. Ozyoney G, Yan Koglu F, Tagtekin D, Hayran O. The efficacy of glass-ceramic onlays in the restoration of morphologically compromised and endodontically treated molars. Int J Prosthodont 2013;26: 230-4. 63. Decerle N, Bessadet M, Eschevins C, Veyrune J, Nicolas E. Evaluation of cerec endocrowns: a preliminary cohort study. Eur J Prosthodont Restor Dent 2014;22:1-7. 64. Belleflamme MM, Geerts SO, Louwette MM, Grenade CF, Vanheusden AJ, Mainjot AK. No post-no core approach to restore severely damaged posterior
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teeth: an up to 10-year retrospective study of documented endocrown cases. J Dent 2017;63:1-7. Sedrez-Porto JA, Munchow EA, Valente LL, Cenci MS, Pereira-Cenci T. New material perspective for endocrown restorations: effects on mechanical performance and fracture behavior. Braz Oral Res 2019;33:e012. Otto T. Computer-aided direct all-ceramic crowns: preliminary 1-year results of a prospective clinical study. Int J Periodontics Restorative Dent 2004;24: 446-55. Otto T, Mormann WH. Clinical performance of chairside CAD-CAM feldspathic ceramic posterior shoulder crowns and endocrowns up to 12 years. Int J Comput Dent 2015;18:147-61. Abdel-Aziz M, Abo-Elmagd AA. Effect of endocrowns and glass fiber prostretained crowns on the fracture resistance of endodontically treated premolars. Egypt Dent J 2015;61:3203-10. Hamdy A. Effect of full coverage, endocrowns, onlays, inlays restorations on fracture resistance of endodontically treated molars. J Dent Oral Health 2015:1-5. Al-Shibri S, Elguindy J. Fracture resistance of endodontically treated teeth restored with lithium disilicate crowns retained with fiber posts compared to lithium disilicate and cerasmart endocrowns: in vitro study. Dentistry 2017;7:12. Güngör MB, Bal BT, Yilmaz H, Aydin C, Nemli SK. Fracture strength of CADCAM fabricated lithium disilicate and resin nano ceramic restorations used for endodontically treated teeth. Dent Mater J 2017;36:135-41. El Ghoul W, Ozcan M, Silwadi M, Salameh Z. Fracture resistance and failure modes of endocrowns manufactured with different CAD-CAM materials under axial and lateral loading. J Esthet Restor Dent 2019. doi: 10.1111/jerd. 12486. Lise DP, Van Ende A, De Munck J, Suzuki TY, Vieira LC, Van Meerbeek B. Biomechanical behavior of endodontically treated premolars using different preparation designs and CAD-CAM materials. J Dent 2017;59:54-61. Rocca GT, Daher R, Saratti CM, Sedlacek R, Suchy T, Feilzer AJ, et al. Restoration of severely damaged endodontically treated premolars: the influence of the endo-core length on marginal integrity and fatigue resistance of lithium disilicate CAD-CAM ceramic endocrowns. J Dent 2018;68:41-50. Bindl A, Richter B, Mormann WH. Survival of ceramic computer-aided design/manufacturing crowns bonded to preparations with reduced macroretention geometry. Int J Prosthodont 2005;18:219-24. Roggendorf MJ, Kunzi B, Ebert J, Roggendorf HC, Frankenberger R, Reich SM. Seven-year clinical performance of CEREC-2 all-ceramic CADCAM restorations placed within deeply destroyed teeth. Clin Oral Investig 2012;16:1413-24.
Corresponding author: Dr Raghad A. Al-Dabbagh, Oral and Maxillofacial Rehabilitation Department Faculty of Dentistry King Abdulaziz University Al Fayha’a District Jeddah 22252-3646 KINGDOM OF SAUDI ARABIA Email: [email protected] Acknowledgments The author thanks Dr Mona Al-Dabbagh for her guidance and support in the methodology of this systematic review and meta-analysis and Dr Alaa Manna for being the second investigator in this review. She as well thanks editorial assistance from Nextgenediting (www.nextgenediting.com). Copyright © 2020 by the Editorial Council for The Journal of Prosthetic Dentistry. https://doi.org/10.1016/j.prosdent.2020.01.011
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Survival and success of endocrowns: A systematic review and meta-analysis Raghad A. Al-Dabbagh, BDS, MClinDent Pros, MPros CRS Edin, PhD The successful restoration of ABSTRACT endodontically treated teeth is Statement of problem. Endocrowns are a monoblock type of restoration that use the pulp dependent on the type and chamber and remaining coronal tooth structure as a means of retention. However, data on their quality of the coronal restoralong-term survival and success rates as compared with conventional crowns are lacking. tion.1-4 Endodontically treated Purpose. The purpose of this systematic review and meta-analysis was to collate published work on teeth restored with crowns endocrowns to assist clinicians in making decisions on when and whether they are an appropriate have a 5-year survival rate restorative option with a predictable outcome for extensively damaged endodontically treated similar to vital teeth restored teeth. with crowns (94.2% versus Material and methods. Databases such as PubMed (MEDLINE), Scopus, EMBASE, Cochrane library, 95%).1,5 However, in the and Google Scholar were searched up to June 2019 for clinical and in vitro studies on endocrown absence of cuspal coverage survival and success rates. For the meta-analysis, endocrown and conventional crown survival and (restored with composite resin), success rates were compared, and the pooled effects were presented as relative risks and 95% endodontically treated teeth confidence intervals using a random effects model. have a lower success rate, with Results. Ten studies fulfilled the inclusion criteria (3 clinical and 7 in vitro) and were included in the a 5-year survival rate of 63%.1 systematic review. The meta-analysis of the clinical studies showed an estimated overall 5-year The improved survival of teeth survival rate of 91.4% for endocrowns and 98.3% for conventional crowns. The estimated overall treated endodontically with 5-year success rates were 77.7% for endocrowns and 94% for conventional crowns. There were no significant differences in overall survival or success estimates between the assessed satisfactory coronal cuspal restorations (P>.05). coverage has been attributed to a reduction in microleakages Conclusions. Additional well-designed clinical studies with long-term assessment are needed; however, endocrowns appear to be a promising conservative restorative option with acceptable and the preservation and prolong-term survival for endodontically treated posterior teeth in selected patients. (J Prosthet tection of the remaining tooth 6,7 Dent 2020;-:---) structure. Immediate placement of a satisfactory coronal conservative with advances in adhesive dentistry.8 Such restoration has been reported to reduce microleakage and designs include incorporating fewer mechanical retentive subsequently decrease the risk of endodontic treatment features such as undercuts, grooves, or boxes,8 with failure,6 while cuspal coverage and preservation of the retention being mainly dependent on adhesion to the remaining coronal tooth structure have been reported to tooth structure.8 improve fracture resistance and the outcome of the 2,3,7 Endocrowns are conservative coronal restorations that endodontically treated tooth. have been used to restore endodontically treated teeth Preparation designs for coronal restorations of with significant loss of coronal tooth structure. They are endodontically treated teeth have become more
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Assistant Professor and Consultant in Prosthodontics, Oral and Maxillofacial Rehabilitation Department, Faculty of Dentistry, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia.
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Clinical Implications Limited data suggest that endocrowns can be used as a coronal restoration for endodontically treated posterior teeth with acceptable long-term outcomes when used selectively. Feldspathic computer-aided design and computer-aided manufacturing (CAD-CAM) ceramics appear to be a suitable choice for endocrown fabrication.
monoblock coronal restorations that are retained by the pulp chamber and by bonding to the remaining coronal tooth structure.9 Pissis10 first described the concept in 1995, and Bindl and Mormann9 introduced the term endocrown in 1999. However, only limited data exist on the long-term survival and success of endocrowns as compared with conventional crowns. Therefore, the purpose of this systematic review and meta-analysis was to compare the survival and success rates of endocrowns with conventional crowns for the restoration of endodontically treated teeth. The null hypothesis was that there would be no difference between the 2 restoration types. METHOD AND MATERIALS This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement.11 The population, intervention, control, and outcome (PICO) for this systematic review were defined as follows: the population was participants or teeth undergoing root canal treatment; the intervention was ceramic or composite resin endocrowns; the comparison was conventional post and core crowns; and the outcome measures were survival and success rates, fracture strengths, catastrophic failure rates, and percentage of marginal adaptation. Two investigators (R.A., A.M.) undertook an electronic search of the English language literature in the databases such as PubMed (MEDLINE), Scopus, EMBASE, Cochrane Library, and Google Scholar up to June 2019. The search strategy included the following keywords: crown, endocrown, survival, survival analysis, survival rate, failure rate, failure, compressive strength, materials testing, follow-up studies, prosthesis failure, fracture strength, marginal adaptation, and catastrophic failure. All relevant clinical and in vitro studies were included. No randomized clinical studies published in the Englishlanguage dental literature comparing endocrowns to conventional crowns were identified. Clinical studies considered suitable for this systematic review and metaanalysis included prospective cohort studies or case series, retrospective studies, studies with a mean follow-up THE JOURNAL OF PROSTHETIC DENTISTRY
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of at least 3 years (for the meta-analysis), and the presence of a control group (conventional or classical crowns). The in vitro studies considered in this systematic review were those conducted on extracted teeth and measuring the fracture strength, survival, catastrophic failure, and marginal adaptation as outcome parameters. The intervention of interest included ceramic or composite resin endocrowns, including monoblock-type restorations. Metal alloy restorations were excluded. The comparison included conventional crowns made of ceramic or composite resin excluding crowns made of metal alloys. Survival rate was defined as when endocrowns or conventional crowns were present in the oral cavity but with biological and/or technical complications. Success rate was defined as restorations not associated with any of these complications. Catastrophic failure was defined as nonrestorable or nonrepairable failures in both of the assessed restorations. Two investigators (R.A., A.M.) assessed the article titles and then searched and reviewed the abstracts. Only relevant articles fulfilling the review objectives and inclusion criteria were considered. Full-text articles of potential papers were retrieved and then critically assessed before inclusion in the study if they fulfilled all eligibility criteria. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of the included clinical studies.12 According to the NOS, studies with 5 stars or less have an inherent methodological risk of bias, while those with more than 5 stars have minimal bias. Consequently, only cohort studies with over 5 stars were included in the present review. The risk of methodological bias in the in vitro studies was assessed based on a modification of parameters used elsewhere,13 which included the use of sound teeth for testing, morphologically similar tested teeth, sample size calculation, group randomization, presence of a suitable control group, use of materials according to the manufacturer’s instructions, cavity preparation performed by the same operator (standardization), and blinding of the operator to the testing machine. Studies with 1 to 3 parameters were deemed to be having a high risk of bias; studies with 4 to 5 parameters were of a medium risk of bias; and studies with 6 or more parameters and including a suitable control were classified as having a low risk of bias.13 Only in vitro studies with a low risk of bias were included in the present systematic review. Data were extracted from the included clinical studies and tabulated in a spreadsheet (Microsoft Office Excel 2016; Microsoft Corp) with the following information: authors, year, journal, number of participants, mean age, sex, number of restorations, type of teeth, type of restoration, restoration survival time, restoration success and failure, type of failure, follow-up period, and NOS. When the same data were published more than once, data were obtained from the most complete version. When the Al-Dabbagh
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Application of exclusion criteria and discussion at title and abstract level led to exclusion of 2536 titles
Application of exclusion criteria and critical assessment of methodology led to exclusion of 38 articles
Independent electronic search by 2 investigators yielded 2584 titles
PubMed/MEDLINE 1340 Scopus 547 EMBASE 320 Cochran Library 170 Google Scholar 207
Independent analysis of full text of the 48 selected articles by the investigators
Not endocrown/ unpublished 2476 Finite element analysis 21 Case reports 22 Reviews 5 Alloy based 2 Ongoing clinical trials 10
10 full-articles analyzed for the systematic review of which the 3 clinical articles were included in the meta-analysis
No conventional crown control 6 High risk for bias 22
Figure 1. Flow chart of search strategy and number of included endocrown articles.
study data were unclear, the authors were contacted for clarification. Review Manager (RevMan) software version 5.2 (The Nordic Cochrane Centre, The Cochrane Collaboration) was used for the meta-analysis. The success and survival of endocrowns and conventional crowns were measured. Comparisons and pooled effects were presented as relative risks (RR) and 95% confidence intervals (CI) using a random effects model (a=.05). Subgroups were analyzed to compare the effect of tooth type (molars and premolars) on the survival and success of endocrowns versus conventional crowns. Study heterogeneity was measured using the chi-squared test (a=.05). The test of inconsistency (I2) was calculated and interpreted as minimal, moderate, or substantial heterogeneity at levels of <25%, 25% to 50%, and >50%, respectively. RESULTS A total of 2584 potential records were initially identified. The titles and abstracts were screened, and nonqualifying articles and duplicates were removed to leave 48 full articles (9 clinical and 39 in vitro). Excluded articles were omitted because they were not endocrown articles or they were review articles,14-18 case reports,19-39 finite element analysis studies,40-59 alloy-based restoration studies,60,61 or unpublished clinical research. These 48 articles were critically evaluated, and their quality of methodology was assessed. Five more articles were excluded because they did not fulfill the inclusion criteria (absence of comparison with a conventional crown),4,6265 leaving 10 eligible articles for the systematic review and 3 clinical studies for the meta-analysis (Fig. 1). The 38 excluded articles are summarized in Supplementary Al-Dabbagh
Tables 1 and 2 (available online). The article by Otto66 was excluded because the cohort was similar to that of Otto and Mormann.67 Seven in vitro studies compared the fracture strengths and catastrophic failure rates of endocrowns and conventional crowns: 1 in incisors, 4 in premolars, and 2 in molars (Table 1).68-74Additionally, 1 in vitro study assessed marginal adaptation in premolars restored by endocrowns.75 In central incisors, the load to fracture strength of resin ceramic endocrowns and conventional crowns was not significantly different (869 ±247.8 N and 580.0 ±295.4 N), with a catastrophic failure rate of 100% for endocrowns and 0% for conventional crowns.71 Likewise, the load to fracture strength of lithium disilicate ceramic endocrowns (915.9 ±182.1 N) and conventional crowns (646.8 N) was not significantly different, with a catastrophic failure rate of 85% and 0%, respectively.71 In premolars, the fracture strength of composite resin endocrowns (230 N) was higher than for conventional crowns (135 N), 71 while the fracture strength of resin ceramic endocrowns (1522.64 ±352.52 N) was not significantly different from that of conventional crowns (1301.34 ±177.12 N), with a catastrophic failure rate of 30% for endocrowns and 40% for conventional crowns.70 The fracture strength of lithium disilicate ceramic endocrowns (220 N or 933 ±183 N) was similar to that of conventional crowns (200 N or 925 ±186 N), with a catastrophic failure rate of 0 or 80% for endocrowns and 0 or 40% for conventional crowns (Table 1).68,73 When the effect of the type of restorative material was assessed with respect to the fracture strength of endocrowns resin ceramic (1522.64 ±352.5 N), endocrowns had higher load to fracture strengths than lithium disilicate ceramic THE JOURNAL OF PROSTHETIC DENTISTRY
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Table 1. Summary of included in vitro studies
Reference
Objectives of Study
Type of Tooth
No of Samples/ Group
Restoration Material
Type of Sample Preparation and Testing
Load to Fracture Strength (Mn ±SD, N)
Catastrophic Failure Rates (%, Out of Total Failures)
Marginal Adaptation In Vitro (Mn ±SD) Quality Scale (%)
AbdelAziz and AboElmagd68
Compare the Mandibular fracture strength of premolars endocrown and conventional crown in the presence or absence of ferrule
5
Lithium disilicate ceramic (IPS e.Max)
Endocrown and Universal load Endocrown and testing, inspection conventional crown: 933 conventional crown: 0, 0 with digital ±183=925 ±186$ microscope
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6
Hamdy69
Maxillary Assess various restoration designs first molars fracture strength
10
Lithium disilicate ceramic (IPS e.Max Press)
Thermocycling, universal load testing (axial loading)
Endocrown and Endocrown and conventional crown: 989 conventional crown: 20, 10 ±109.1=1076 ±132
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Al-shibri Assess fracture Maxillary and premolars resistance of 70 Elguindy endocrown and conventional crown in 2 different materials
10
Universal load Resin ceramic testing, Visual and (Ceramsmart), lithium disilicate (IPS photographic inspection e.Max CAD)$
Güngör et al71
10
Resin ceramic (Lava Ultimate), lithium disilicate (IPS e.Max CAD)
Reference
Maxillary Assess fracture strength of EC and central CC and 2 types of incisors posts
Objectives of Study
Type of Tooth
Universal load testing (oblique loading)
Resin ceramic, lithium disilicate ceramic endocrowns, and lithium disilicate conventional crowns: 30, 80, 40
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7
Resin ceramic endocrowns and conventional crowns: 869 ±247.8=580.02 ±295.4 Lithium disilicate endocrowns and conventional crowns: 915.91 ±182.1=646.78
Resin ceramic endocrowns and conventional crowns: 100, 0% Lithium disilicate endocrowns and conventional crowns: 85, 0
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Catastrophic Marginal In Vitro Load to Fracture Survival Time/ Failure Rates Strength (Mn ±SD, Cycles Median (%, out of Total Adaptation Quality Scale (Mn, %) Failures) (95% CI) N)
Sample No of Samples/ Restoration Preparation and Testing Group Material
Lise et al73 Study effect of Single rooted endocrown cavity design and premolars material on fracture strength
Resin ceramic, lithium disilicate ceramic endocrowns, and lithium disilicate conventional crowns: 1522.64 ±352.52>717.33 ±198.59<1301.34 ±177.12
8
Composite resin and Lithium disilicate ceramic CEREC AC CAD-CAM
Fatigue aged, chewing simulator machine, universal load testing (oblique load), stereomicroscope
Composite resin short and long endocrowns, and long conventional crown: 230>140 and 135 Lithium disilicate short and long endocrowns, and long conventional crown: 125=220=200
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Short and long endocrowns, and conventional crown: 93 318 (90 572; 99 176) =90 834 (90 010; 90 834)=85 374 (71 552; 86 552)
Short and long endocrowns, and conventional crown: 50, 41.7, 66.7
Short and long endocrowns, and conventional crown: 73.5, 72.5<82
6
Resin ceramic, lithium disilicate ceramic and zirconia reinforced lithium disilicate ceramic endocrowns, and lithium disilicate conventional crowns: 2752 ±242=2914 ±205>2279 ±290>1347 ±185
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Rocca et al74
Study effect of Maxillary premolars endocrown length on marginal adaptation and fatigue strength
12
Lithium disilicate ceramic (IP e.Max CAD)
Thermocycling, SEM, closed loop servo hydraulics, stereomicroscope
El Ghoul et al65
Compare fracture Mandibular molars resistance of endocrown made of different materials to conventional crown
10
Resin ceramic (Cerasmart), Lithium disilicate (IPS e. max CAD), Zirconia reinforced lithium disilicate ceramic (Vita Suprinity)
Thermocycling, Dynamic mechanical loading, SEM
CI, confidence interval; Mn, mean; SD, standard deviation; N, Newton; SEM, scanning electron microscope.
endocrowns (717.33 ±198.6 N), with a catastrophic failure rate of 30% for resin ceramic endocrowns and 80% for lithium disilicate ceramic endocrowns.70 Marginal adaptation of lithium disilicate ceramic
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endocrowns and conventional crowns was assessed in 1 in vitro study, which showed that the marginal adaptation of endocrowns (73%) was less than that of conventional crowns (82%) (Table 1).74
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Table 2. Summary of included clinical studies
Reference
Type of Study
Bindl and Prospective Mormann75
Age (Mn (Range)), Sex (M:F Ratio)
No. of Samples
Mean FollowUp Period Dropout (Mo) Rate
Age: Sex: 1:1.4
136 patients 86 endocrowns, 70 conventional crowns, 52 reduced crowns
55 ±15
0
Roggendorf Prospective Age: 52 et al76 observational (21-80) longitudinal Sex: 2.1:1
35 patients 12 endocrowns, 21 conventional crowns, 44 other restorations
84 ±6
24.4
Otto and Prospective Age: 53 Mormann72 observational (25-79) longitudinal Sex: 1:1.4
55 patients, 25 endocrowns, 8 conventional crowns, 32 reduced crowns
116
5.5
Type of Tooth
Survival Rate Success Rate Failure Rate, (%) (%) (Specific Method of (Endocrown, (Endocrown, Failure Restoration Restoration Conventional Conventional From Total Material Evaluation Crown) Crown) Failures) NOS
Endocrowns: 11 premolars, 70 molars Conventional crowns: 33 premolars, 37 molars
Feldspathic Clinical, porcelain USPHS CAD-CAM (CEREC2)
Premolars: 87.5=96.7% Molars: 87.1=94.6
Molars
Feldspathic Clinical, USPHS porcelain CAD-CAM (CEREC2)
80, 100%
Endocrowns; 5 premolars, 20 molars Conventional crowns: 4 premolars, 4 molars
Feldspathic Clinical, modified porcelain USPHS CAD-CAM (CEREC 3)
Premolars: Endocrowns: 68.8<93.9 Premolars: Molars: 80=73 Loss of retention; 100% Molars: Periodontitis, vertical root fracture each; 14.3%, Loss of retention; 64.3% Conventional crown: Premolars: Crown fracture, vertical root fracture each; 50% Molar: crown fracture, vertical root fracture each; 20%, irreversible pulpitis; 50% 72.7<100
Premolars and Premolars: 80, 100 Molars: Molars: 100=100% 90,100
8
Endocrowns: Vertical root fracture: 66.7% Caries: 33.3%
7
Endocrowns: Premolars loss of retention; 100% Molars: loss of retention; 50%, crown fracture; 50%
7
Mn, Mean; NOS, Newcastle-Ottawa scale; USPHS, United States Public Health Service.
In molars, the load to fracture strength of resin ceramic endocrowns (2752 ±242 N) was higher than that of conventional crowns (1347 ±185 N).72 The fracture strength of lithium disilicate ceramic endocrowns (989 ±109.1 N or 2914 ±205 N) was consistently either similar to or higher than conventional crowns (1076 ±132 N or 1347 ±185 N), with a catastrophic failure rate of 20% and 10%, respectively.69,72 Comparisons of the fracture resistance of endocrowns made of various materials showed that resin ceramic endocrowns (2752 ±242 N) had a fracture strength that was not significantly different from that of lithium disilicate ceramic endocrowns (2914 ±205 N) and a higher fracture strength than that of zirconia-reinforced ceramic endocrowns (2279 ±290 N).72 Taken together, from in vitro studies, the fracture strength of endocrowns restoring posterior teeth was either similar to or higher than that of conventional Al-Dabbagh
crowns, yet the overall rate of catastrophic failures of endocrowns and conventional crowns restoring molars was less than for the same restorations restoring anterior teeth or premolars (Table 1). Clinical studies included in the systematic review and meta-analysis were prospective studies with a population average age of 53 years (range: 21-80), a male-to-female ratio of 1:1, and an average follow-up period of 85 ±10 months (Table 2).67,75,76 The estimated overall 5-year survival rates were 93.8% for endocrowns and 98.4% for conventional crowns restoring premolars, and the 5-year survival rates were 89.1% for endocrowns and 98.2% for conventional crowns when restoring molars. The estimated overall 5year success rates of endocrowns and conventional crowns restoring premolars were 74.4% and 97%, respectively, and the 5-year success rates in tests and THE JOURNAL OF PROSTHETIC DENTISTRY
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Volume
Subgroup
Weight
Risk Ratio M-H, Random, 95% CI
Premolars Bindl et al. 2005 Otto and Mormann 2015
21.2% 5.6%
0.90 [0.74, 1.10] 1.00 [0.68, 1.46]
Subtotal (95% CI)
26.8%
0.92 [0.78, 1.10]
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Risk Ratio M-H, Random, 95% CI
Heterogeneity: τ2=0.00; χ2=0.22, df=1 (P=.64); I2=0% Test for overall effect: Z=0.92 (P=.36) Molars Bindl et al. 2005 Otto and Mormann 2015 Roggendorf et al. 2012
57.3% 9.0% 6.9%
0.92 [0.82, 1.04] 1.00 [0.74, 1.35] 0.84 [0.60, 1.19]
Subtotal (95% CI)
73.2%
0.92 [0.83, 1.02]
Heterogeneity: τ2=0.00; χ2=0.54, df=2 (P=.76); I2=0% Test for overall effect: Z=1.50 (P=.13) Overall (95% CI)
100.0%
0.92 [0.84, 1.01]
Heterogeneity: τ2=0.00; χ2=0.77, df=4 (P=.94); I2=0% Test for overall effect: Z=1.76 (P=.08) Test of subgroup differences: χ2=0.00, df=1 (P=.99); I2=0%
0.05
0.2 Conventional crowns
1
5 Endocrowns
20
Survival Rate Figure 2. Forest plot of survival rates of endocrowns compared with conventional crowns in molars and premolars
controls restoring molars were 80.9% and 91%, respectively. However, the overall survival (RR=0.92; 95% CI: 0.84, 1.01) and success rates (RR=0.91; 95% CI: 0.77, 1.08) of endocrowns and conventional crowns were not significantly different (Figs. 2, 3). Moreover, subgroup analysis revealed that the survival rates of endocrowns and conventional crowns were similar when restoring molars (RR=0.92; 95% CI: 0.83, 1.02) and premolars (RR= 0.92; 95% CI: 0.78, 1.10). However, this analysis demonstrated an improved but nonsignificant success outcome favoring conventional crowns when restoring premolars (RR= 0.76; 95% CI: 0.57, 1.01) (Figs. 2, 3). Heterogeneity was minimal for both assessed outcomes (I2= 0 and 22%). DISCUSSION The main objective of this review was to assess the survival and success rates of endocrowns. The analysis showed that the fracture strength of endocrowns restoring posterior teeth was either similar to or higher than conventional crowns. However, there was a higher catastrophic failure rate of lithium disilicate ceramic endocrowns compared with conventional crowns. Consistently, clinical survival and success rates of endocrowns and conventional crowns were similar when used to restore endodontically treated molars and premolars, supporting acceptance of the null hypothesis. The analysis revealed several deficiencies in the current literature, including a lack of randomized controlled studies, clinical studies with sufficient
THE JOURNAL OF PROSTHETIC DENTISTRY
numbers of test and control restorations, and clinical studies with long-term survival analysis over 3 years. Most of the studies included in this review were, accordingly, in vitro studies. Most of the articles published to date were on endocrowns used to restore endodontically treated molars and premolars.68,70,72-76 However, endocrowns were shown to perform better when placed in posterior teeth.76 This is possibly because of the larger pulp chamber in premolars and molars and their axial loading under function. In clinical studies, endocrowns were mainly used in teeth with minimal remaining coronal tooth structure, where establishing a ferrule would be difficult, yet margins were mainly equigingival.68,75 In these teeth, crown lengthening could be avoided because it may further compromise the tooth, rendering it nonrestorable. Endodontically treated teeth are susceptible to biomechanical failure and should be restored with a coronal restoration to protect them from fracture and failure.1-3Ideally, an endocrown should be fabricated from a material with a low modulus of elasticity (similar to that of the tooth structure), high mechanical strength, and sufficient bond strength to the underlying tooth structure.53 A modulus of elasticity comparable with dentin helps to distribute occlusal forces along the bonded surface and possibly improves fracture resistance,53 while high mechanical strength helps in withstanding occlusal load and resisting material fracture.53 Al-Dabbagh
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Subgroup
Weight
Risk Ratio M-H, Random, 95% CI
Premolars Bindl et al. 2005 Otto and Mormann 2015
20.0% 9.0%
0.73 [0.52, 1.03] 0.83 [0.48, 1.44]
Subtotal (95% CI)
29.0%
0.76 [0.57, 1.01]
Risk Ratio M-H, Random, 95% CI
Heterogeneity: τ2=0.00; χ2=0.16, df=1 (P=.69); I2=0% Test for overall effect: Z=1.87 (P=.06) Molars Bindl et al. 2005 Otto and Mormann 2015 Roggendorf et al. 2012
34.9% 20.9% 15.2%
1.10 [0.87, 1.38] 0.98 [0.70, 1.36] 0.76 [0.50, 1.13]
Subtotal (95% CI)
71.0%
0.98 [0.80, 1.20]
Heterogeneity: τ2=0.01; χ2=2.56, df=2 (P=.28); I2=22% Test for overall effect: Z=0.18 (P=.85) Overall (95% CI)
100.0%
0.91 [0.77, 1.08]
Heterogeneity: τ2=0.00; χ2=5.14 , df=4 (P=.27); I2=22% Test for overall effect: Z=1.06 (P=.29) Test of subgroup differences: χ2=2.05, df=1 (P=.15); I2=51.2%
0.05
0.2 Conventional Crowns
1
5 Endocrowns
20
Survival Rate Figure 3. Forest plot of success rates of endocrowns compared with conventional crowns in molars and premolars
The published prospective and retrospective clinical studies on the clinical performance and survival of endocrowns used feldspathic computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic endocrowns.67,75,76 However, most of the in vitro studies used either resin ceramic or lithium disilicate ceramics to fabricate endocrowns.68-74 In these in vitro studies, endocrowns made of resin ceramic restoring premolars had higher fracture strengths and lower catastrophic failure rates than those of endocrowns made of lithium disilicate ceramics. A possible explanation for this is that the modulus of elasticity of the resin ceramic is comparable with dentin and thus may better distribute occlusal forces along the bonded surface of premolars, thereby improving fracture resistance and reducing catastrophic failure rates.53 For feasibility and to improve the mechanical properties, most studies used CAD-CAM blocks (resin ceramic, feldspathic, and lithium disilicate) to fabricate endocrowns.66,70,71,73,74 The results of most in vitro studies on endocrown CAD-CAM restorations were positive.69,74 Clinical studies on the long-term serviceability of endocrowns are scarce. Although there were no significant differences in the overall survival rates of endocrowns compared with conventional crowns in this meta-analysis, there was a trend toward better survival with conventional crowns, a trend that was more pronounced in premolars. This failure to detect a significant difference was possibly attributable to the small number Al-Dabbagh
of assessed restorations. In their prospective study, Bindl et al75 reported that the cumulative survival rates of endocrowns (feldspathic CAD-CAM CEREC2) in molars were similar to those of conventionally prepared and minimally prepared crowns (87.9%, 94.6%, and 92.1%, respectively). This study included 208 crowns in 136 participants, of which 109 were endocrowns (70 molars, 39 premolars). Among the endocrown restorations, 19 failed, mainly from adhesive failure (14 restorations) after 5 to 6 years of service.75 In another prospective study, the same group showed that the 12-year survival rates of the same type of endocrowns and crowns (with post and core crowns or in vital teeth with deficient preparation) were similar (85.7%, 90.3%, and 94.4%, respectively). The difficulty in detecting a significant difference in survival between test (25 endocrowns) and control (40 crowns) could be because of the small sample size. However, in general, the failure rates were low, which may also reflect participant selection and the standardized procedure or that endocrowns could be a promising restorative option.67 In summary, clinical evidence on the longevity of endocrown restorations is still lacking. Most existing in vivo and in vitro studies focused on CAD-CAM endocrowns made of resin ceramics and feldspathic or lithium disilicate ceramics and demonstrated the possibility of using endocrowns in specific clinical scenarios such as endodontically treated molars with minimal remaining coronal tooth structure. When endocrowns failed in molars, this was usually a restoration failure or THE JOURNAL OF PROSTHETIC DENTISTRY
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repairable failure. However, regular maintenance visits should be recommended to assess the susceptibility of marginal leakage and debonding for immediate intervention. CONCLUSIONS Based on the findings of this systematic review and meta-analysis, the following conclusions were drawn: 1. There remains a need for large, well designed, clinically controlled studies with long-term assessment. 2. However, endocrowns appear to be a promising, conservative, and inexpensive restorative option with acceptable long-term survival for endodontically treated posterior teeth in selected patients using standardized clinical procedures. REFERENCES 1. Stavropoulou AF, Koidis PT. A systematic review of single crowns on endodontically treated teeth. J Dent 2007;35:761-7. 2. Suksaphar W, Banomyong D, Jirathanyanatt T, Ngoenwiwatkul Y. Survival rates against fracture of endodontically treated posterior teeth restored with full-coverage crowns or resin composite restorations: a systematic review. Restor Dent Endod 2017;42:157-67. 3. Tang W, Wu Y, Smales RJ. Identifying and reducing risks for potential fractures in endodontically treated teeth. J Endod 2010;36:609-17. 4. Gregor L, Bouillaguet S, Onisor I, Ardu S, Krejci I, Rocca GT. Microhardness of light- and dual-polymerizable luting resins polymerized through 7.5-mmthick endocrowns. J Prosthet Dent 2014;112:942-8. 5. Sailer I, Makarov NA, Thoma DS, Zwahlen M, Pjetursson BE. All-ceramic or metal-ceramic tooth-supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates. Part I: single crowns (SCs). Dent Mater 2015;31:603-23. 6. Saunders WP, Saunders EM. Coronal leakage as a cause of failure in rootcanal therapy: a review. Endod Dent Traumatol 1994;10:105-8. 7. Mannocci F, Cowie J. Restoration of endodontically treated teeth. Br Dent J 2014;216:341-6. 8. Sofan E, Sofan A, Palaia G, Tenore G, Romeo U, Migliau G. Classification review of dental adhesive systems: from the IV generation to the universal type. Ann Stomatol (Roma) 2017;8:1-17. 9. Bindl A, Mormann WH. Clinical evaluation of adhesively placed cerec endocrowns after 2 years–preliminary results. J Adhes Dent 1999;1:255-65. 10. Pissis P. Fabrication of a metal-free ceramic restoration utilizing the monobloc technique. Pract Periodontics Aesthet Dent 1995;7:83-94. 11. Moher D, Liberati A, Tetzlaff J, Altman DG, Group P. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. J Clin Epidemiol 2009;62:1006-12. 12. The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomized studies in meta-analysis. [Internet]. 2013. Available at: http:// www.ohri.ca/programs/clinical_epidemiology/oxford.asp. Accessed August 15, 2018. 13. Sarkis-Onofre R, Skupien JA, Cenci MS, Moraes RR, Pereira-Cenci T. The role of resin cement on bond strength of glass-fiber posts luted into root canals: a systematic review and meta-analysis of in vitro studies. Oper Dent 2014;39:E31-44. 14. Sevimli G, Cengiz S, Oruc MS. Endocrowns: review. J Istanb Univ Fac Dent 2015;49:57-63. 15. Sedrez-Porto JA, Rosa WL, da Silva AF, Munchow EA, Pereira-Cenci T. Endocrown restorations: a systematic review and meta-analysis. J Dent 2016;52:8-14. 16. Carvalho MA, Lazari PC, Gresnigt M, Del Bel Cury AA, Magne P. Current options concerning the endodontically-treated teeth restoration with the adhesive approach. Braz Oral Res 2018;32:e74. 17. Menezes-Silva REC, Atta MT, Navarro MF, Ishikiriama SK, Mondelli RF. Endocrown: a conservative approach. Braz Dent J 2016;19:121-31. 18. Sobczyk M, Godlewski T. The possibility of application of endocrowns in prosthetic treatment. Norwa Stomatol 2018;23:116-20. 19. Valentina V, Aleksandar T, Dejan L, Vojkan L. Restoring endodontically treated teeth with all-ceramic endo-crowns: case report. Stomatol Glas Srb 2008;55:54-64.
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20. Biacchi GR, Mello B, Basting RT. The endocrown: an alternative approach for restoring extensively damaged molars. J Esthet Restor Dent 2013;25: 383-90. 21. Carlos RB, Thomas Nainan M, Pradhan S, Roshni S, Benjamin S, Rose R. Restoration of endodontically treated molars using all ceramic endocrowns. Case Rep Dent 2013;2013:210763. 22. Rocca GT, Rizcalla N, Krejci I. Fiber-reinforced resin coating for endocrown preparations: a technical report. Oper Dent 2013;38:242-8. 23. da Cunha LF, Mondelli J, Auersvald CM, Gonzaga CC, Mondelli RF, Correr GM, et al. Endocrown with leucite-reinforced ceramic: case of restoration of endodontically treated teeth. Case Rep Dent 2015;2015:7503-13. 24. Mahesh B, Vandana G, Sanjay P, Jaykumar G, Deepika C, Aatif N. Endocrown: conservative treatment modality for restoration of endodontically treated teeth: a case report. Endodontology 2015;27:188-91. 25. Sowmya B, Mathew S, Narayana I, Hedge S. Management of mutilated molars with altered canal morphology: a case report. Endodontology 2015;27: 66-70. 26. Desai P, Tailor K, Patel P, Thakkar P. Post endodontic restoration with novel endocrown approach: a case series. J Res Adv Dent 2016;5:129-36. 27. Bilgin MS, Erdem A, Tanriver M. CAD-CAM endocrown fabrication from a polymer-infiltrated ceramic network block for primary molar: a case report. J Clin Pediatr Dent 2016;40:264-8. 28. Chaudhary S, Rathod A, Yadav P, Talwar S, Verma M. Restorative management of grossly mutilated molar teeth using endocrown: a novel concept. J Restor Dent 2016;4:97-100. 29. Soares R, de Ataide Ide N, Fernandes M, Lambor R. Fibre reinforcement in a structurally compromised endodontically treated molar: a case report. Restor Dent Endod 2016;41:143-7. 30. Fernandes da Cunha L, Gonzaga CC, Pissaia JF, Correr GM. Lithium silicate endocrown fabricated with a CAD-CAM system: a functional and esthetic protocol. J Prosthet Dent 2017;118:131-4. 31. 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Aversa R, Apicella D, Perillo L, Sorrentino R, Zarone F, Ferrari M, et al. Nonlinear elastic three-dimensional finite element analysis on the effect of endocrown material rigidity on alveolar bone remodeling process. Dent Mater 2009;25:678-90. 42. Lim DY, Kim HC, Hur B, Kim KH, Son K, Park JK. Stress distribution of endodontically treated maxillary second premolars restored with different methods: three-dimensional finite element analysis. J Kor Acad Con Dent 2009;34:69-80. 43. Lin CL, Chang YH, Pa CA. Estimation of the risk of failure for an endodontically treated maxillary premolar with MODP preparation and CAD-CAM ceramic restorations. J Endod 2009;35:1391-5. 44. Lin CL, Pai CA. Numerical investigation of failure risk of CAD-CAM ceramic restoration for an endodontically treated maxillary premolar with MO preparation. Biomed Eng Appl Basis Commun 2009;22:327-35. 45. Lin CL, Chang YH, Chang CY, Pai CA, Huang SF. Finite element and Weibull analyses to estimate failure risks in the ceramic endocrown and classical crown for endodontically treated maxillary premolar. Eur J Oral Sci 2010;118:87-93. 46. Lin CL, Chang YH, Pai CA. Evaluation of failure risks in ceramic restorations for endodontically treated premolar with MOD preparation. Dent Mater 2011;27:431-8.
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Corresponding author: Dr Raghad A. Al-Dabbagh, Oral and Maxillofacial Rehabilitation Department Faculty of Dentistry King Abdulaziz University Al Fayha’a District Jeddah 22252-3646 KINGDOM OF SAUDI ARABIA Email: [email protected] Acknowledgments The author thanks Dr Mona Al-Dabbagh for her guidance and support in the methodology of this systematic review and meta-analysis and Dr Alaa Manna for being the second investigator in this review. She as well thanks editorial assistance from Nextgenediting (www.nextgenediting.com). Copyright © 2020 by the Editorial Council for The Journal of Prosthetic Dentistry. https://doi.org/10.1016/j.prosdent.2020.01.011
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