Clinical efficacy of composite versus ceramic inlays and onlays: A systematic review

Abstract

Objectives

Large tooth substance losses are frequent in posterior teeth because of primary caries or aging restorations. Inlays and onlays are often the minimal invasive solution in such cases, but the efficacy of the composite and ceramic materials used is unknown. We performed a systematic review of randomized controlled trials comparing the efficacy of composite and ceramic inlays or onlays.

Data sources

MEDLINE, Embase and the Cochrane Central Register of Controlled Trials were searched without any restriction on date or language, as were references of eligible studies and ClinicalTrials.gov.

Study selection

Eligible studies were randomized trials comparing the clinical efficacy of composite to ceramic inlays or onlays in adults with any clinical outcome for at least 6 months. From 172 records identified, we examined reports of 2 randomized controlled trials involving 138 inlays (no onlays evaluated) in 80 patients and exhibiting a high-risk of bias. Outcomes were clinical scores and major failures. The 3-year overall failure risk ratio was 2 [0.38–10.55] in favor of ceramic inlays although not statistically significant. The reported clinical scores (United States Public Health Services and Californian Dental Association) showed considerable heterogeneity between trials and could not be combined.

Conclusions

We have very limited evidence that ceramics perform better than composite material for inlays in the short term. However, this result may not be valid in the long term, and other trials are needed. Trials should follow Fédération dentaire internationale recommendations and enhance their methodology. Trials comparing composite and ceramic onlays are needed.

Introduction

Dental caries is still a common disease worldwide and results in tooth substance loss. Inlay or onlay restorations are widely used to treat moderate Class I and II losses. Inlays and onlays can be made of alloy, composite or ceramic material. However, patients often refuse metallic restorations, so practitioners must choose between the 2 esthetic materials: ceramic and composite.

Many studies have compared these materials in vitro . Ceramic inlays and onlays are mainly composed of glass, with some crystals added to increase strength . Composite inlays and onlays are made of a resinous matrix and fillers of different types . Ceramic materials are resistant to compressive forces but are susceptible to tensile stresses and more prone to fracture than are composite materials . However, ceramics are harder than composites and more wear-resistant but can induce more wear than usual with the opposing tooth’s surface . Furthermore, adhesive cement interfaces are made of composite material, so the wear of the interface and restoration material should be closer for composites and marginal integrity could be better . Another disadvantage of composites is their resinous matrix and the possible monomer release if it is incompletely polymerized .

Although in vitro studies generally do not predict in vivo results , few clinical studies have verified these in vitro findings concerning the performance of composite and ceramic for inlays and onlays.

Several clinical studies have evaluated ceramic and composite materials separately . Yet, we can draw no definite conclusions on the best material from these studies. In 1997, Roulet et al. concluded that “very little” was known about the longevity of esthetic inlays. The authors mentioned the difficulty in obtaining a strong bond between the restoration’s surface and the tooth for composite inlays , but this problem has since been solved . In 2001, Hickel and Manhart reported an annual failure rate of 2.3% (range: 0–11.8%) for composite inlays and onlays, as compared with 1.3% (range: 0–7.5%) for ceramic inlays and onlays evaluated in longitudinal studies . In 2004, the same authors reported an annual failure rate of 2.9% (SD 2.6) for composite inlays, as compared with 1.9% (SD 1.8) for ceramic restorations . Note that we have no evidence for linear failure rates of inlays and onlays, so the latter results can be discussed.

Finally, material knowledge has evolved, new materials have been developed, and no systematic review has answered the question posed by practitioners: Is the clinical efficacy of composite or ceramic better for inlay and onlay manufacturing?

We aimed to perform a systematic review of published reports of randomized controlled trials comparing the efficacy of composite and ceramic inlays and onlays for restoring posterior teeth of adults.

Methods

The review is registered, and the protocol can be accessed on the Prospero website .

Eligible studies were randomized controlled trials comparing the clinical efficacy of composite to ceramic inlays or onlays. Any composite or ceramic material was eligible. Patients had to be adults, treated in any dental care center or practice. The follow-up had to be 6 months or more. We searched MEDLINE, Embase and the Cochrane Central Register of Controlled Trials (Central) without any restriction on date or language. The last search was on December 24, 2012. The full electronic search strategy is in Appendix 1. We searched ClinicalTrials.gov to identify ongoing trials. The references of all eligible trials were checked for other relevant studies.

Two authors independently and in duplicate screened the titles of records retrieved by the search, then screened the selected abstracts to identify studies that potentially met the eligibility criteria. Any disagreements were resolved by discussion and the reasons for exclusion were recorded. The full text of potentially eligible studies was retrieved and assessed for eligibility by the same authors. Again, the reasons for exclusion were recorded.

A standardized, pre-piloted form was used to extract data from the included studies for assessment of study quality and synthesis of evidence. Data were extracted on (1) general trial information (publication year, number of patients treated, number of inlays or onlays manufactured, and number of operators); (2) intervention characteristics (rubber dam isolation, base or liner application, inlay/onlay materials and manufacturing technique(s), adhesive and cement), and (3) outcome data (clinical scores [United States Public Health Services (USPHS) or Californian Dental Association (CDA) or Fédération dentaire internationale (FDI) criteria] and restoration failures). The clinical scores are usually ordinal variables that measure the quality of the restoration according to a variety of dimensions. When published, in 1971, the USPHS scale comprised 3 grades (Alfa, Bravo and Charlie: Charlie being pejorative and Alfa being favorable) and 5 items (color match, cavosurface marginal discoloration, anatomic form, marginal adaptation, and caries). A fourth grade (Delta) was later added. The CDA scale is similar (except the grades are Romeo, Sierra, Tango and Victor) . The consensus FDI score, published in 2007, comprises 5 grades (from 1 to 5, 1 being ideal and 5 corresponding to a restoration that needs replacement) and 18 items that comprise the 5 initial USPHS items . Any event that required replacement of the inlay or onlay was defined as a failure. Failure types were also extracted and classified according to failure cause: inlay fracture, tooth fracture, recurrent caries, persisting hypersensibility and endodontic treatment.

The risk of bias for each study was assessed by the Cochrane Collaboration Risk of Bias tool, which includes the following domains: methods for sequence generation and maintaining allocation concealment, blinding, and incomplete outcome data . Each domain was rated as low, high, or unclear risk of bias. Within-study selective outcome reporting was not assessed because we did not have access to study protocols. Blinding of dental staff (operators and clinical evaluators) is not possible because both materials can easily be recognized by an experienced eye, so this domain was not assessed and the tool was slightly modified to take into account intervention standardization and the risk of bias during clinical outcome assessment. The standardization risk was high if the cavity preparation or the adhesion procedure differed between treatment groups; it was low otherwise and unclear if these aspects were insufficiently or not reported. The clinical outcome assessment risk was low if 2 independent evaluators or 1 evaluator distinct from the operator had completed the clinical follow-up examinations; it was high otherwise and unclear if these aspects were insufficiently or not reported. The source of funding was also extracted.

The unit of analysis was the tooth. For clinical score outcomes, we reported only percentages of restorations assessed with the best grade (i.e., 1 for FDI criteria, A for USPHS criteria, R for CDA criteria). For each item, we estimated risk ratios for the restoration to be assessed with the best grade (considered the event). To take into account patients with missing outcome data, we assumed that the proportion of patients with the best grade was the same in complete cases and in patients with missing outcome data. For the dichotomous failure outcome, the measure of treatment effect was the risk ratio. To allow for an intention-to-treat analysis, we imputed missing outcome data as success.

When a study included multiple composite or multiple ceramic groups, all composites were combined into a single composite group and/or all ceramics were combined into a single ceramic group . We synthesized trials comparing at least one composite and one ceramic with the same outcome (item score or failure) at a given follow-up time. The decision whether or not to combine the results of individual studies depended on the assessment of heterogeneity in forest plots and by I 2 coefficients. Combined estimates and associated 95% confidence intervals were calculated by use of Mantel–Haenszel fixed-effect methods.

Methods

The review is registered, and the protocol can be accessed on the Prospero website .

Eligible studies were randomized controlled trials comparing the clinical efficacy of composite to ceramic inlays or onlays. Any composite or ceramic material was eligible. Patients had to be adults, treated in any dental care center or practice. The follow-up had to be 6 months or more. We searched MEDLINE, Embase and the Cochrane Central Register of Controlled Trials (Central) without any restriction on date or language. The last search was on December 24, 2012. The full electronic search strategy is in Appendix 1. We searched ClinicalTrials.gov to identify ongoing trials. The references of all eligible trials were checked for other relevant studies.

Two authors independently and in duplicate screened the titles of records retrieved by the search, then screened the selected abstracts to identify studies that potentially met the eligibility criteria. Any disagreements were resolved by discussion and the reasons for exclusion were recorded. The full text of potentially eligible studies was retrieved and assessed for eligibility by the same authors. Again, the reasons for exclusion were recorded.

A standardized, pre-piloted form was used to extract data from the included studies for assessment of study quality and synthesis of evidence. Data were extracted on (1) general trial information (publication year, number of patients treated, number of inlays or onlays manufactured, and number of operators); (2) intervention characteristics (rubber dam isolation, base or liner application, inlay/onlay materials and manufacturing technique(s), adhesive and cement), and (3) outcome data (clinical scores [United States Public Health Services (USPHS) or Californian Dental Association (CDA) or Fédération dentaire internationale (FDI) criteria] and restoration failures). The clinical scores are usually ordinal variables that measure the quality of the restoration according to a variety of dimensions. When published, in 1971, the USPHS scale comprised 3 grades (Alfa, Bravo and Charlie: Charlie being pejorative and Alfa being favorable) and 5 items (color match, cavosurface marginal discoloration, anatomic form, marginal adaptation, and caries). A fourth grade (Delta) was later added. The CDA scale is similar (except the grades are Romeo, Sierra, Tango and Victor) . The consensus FDI score, published in 2007, comprises 5 grades (from 1 to 5, 1 being ideal and 5 corresponding to a restoration that needs replacement) and 18 items that comprise the 5 initial USPHS items . Any event that required replacement of the inlay or onlay was defined as a failure. Failure types were also extracted and classified according to failure cause: inlay fracture, tooth fracture, recurrent caries, persisting hypersensibility and endodontic treatment.

The risk of bias for each study was assessed by the Cochrane Collaboration Risk of Bias tool, which includes the following domains: methods for sequence generation and maintaining allocation concealment, blinding, and incomplete outcome data . Each domain was rated as low, high, or unclear risk of bias. Within-study selective outcome reporting was not assessed because we did not have access to study protocols. Blinding of dental staff (operators and clinical evaluators) is not possible because both materials can easily be recognized by an experienced eye, so this domain was not assessed and the tool was slightly modified to take into account intervention standardization and the risk of bias during clinical outcome assessment. The standardization risk was high if the cavity preparation or the adhesion procedure differed between treatment groups; it was low otherwise and unclear if these aspects were insufficiently or not reported. The clinical outcome assessment risk was low if 2 independent evaluators or 1 evaluator distinct from the operator had completed the clinical follow-up examinations; it was high otherwise and unclear if these aspects were insufficiently or not reported. The source of funding was also extracted.

The unit of analysis was the tooth. For clinical score outcomes, we reported only percentages of restorations assessed with the best grade (i.e., 1 for FDI criteria, A for USPHS criteria, R for CDA criteria). For each item, we estimated risk ratios for the restoration to be assessed with the best grade (considered the event). To take into account patients with missing outcome data, we assumed that the proportion of patients with the best grade was the same in complete cases and in patients with missing outcome data. For the dichotomous failure outcome, the measure of treatment effect was the risk ratio. To allow for an intention-to-treat analysis, we imputed missing outcome data as success.

When a study included multiple composite or multiple ceramic groups, all composites were combined into a single composite group and/or all ceramics were combined into a single ceramic group . We synthesized trials comparing at least one composite and one ceramic with the same outcome (item score or failure) at a given follow-up time. The decision whether or not to combine the results of individual studies depended on the assessment of heterogeneity in forest plots and by I 2 coefficients. Combined estimates and associated 95% confidence intervals were calculated by use of Mantel–Haenszel fixed-effect methods.

Results

Description of studies

Results of the search

In all, 172 records were identified by a search of MEDLINE, Embase and Central databases (Appendix 2). We discarded 27 duplicates, and thus screened and assessed 145 record titles for eligibility. Finally, 84 abstracts (Appendix 3) and 12 full-text articles were screened: 4 records met all eligibility criteria, but 3 records concerned a single study, so only 2 prospective randomized clinical studies were finally included in the review (Appendix 4 and Fig. 1 ). For the Fasbinder et al. trial, 3-year results were published in 2005 and for the Thordrup et al. trial, 1-year, 5-year and 10-year results were published in 1994, 2001 and 2005, respectively. We did not identify any additional trial from ClinicalTrials.gov.

Fig. 1
Study flow diagram.

Characteristics of trials, patients, teeth and interventions

The 2 trials investigated 138 teeth for 80 patients. Characteristics of each trial are presented in Table 1 . In both trials, patients had low caries risk (Fasbinder et al. “scored all enrolled patients as having a low caries risk” while “patients with […] high caries progression” were excluded in Thordrup’s study), all teeth were vital at inclusion and all restorations were inlays; no onlay was evaluated.

Table 1
Patient, teeth and intervention characteristics of included studies.
Fasbinder study Thordrup study
Trial characteristics
No. of operators 2 1
No. of centers 1 1
Patient characteristics
Number 43 37
Gender (% women) 81
Age (years) 23–69
Teeth characteristics
Number 80 58
Maxillary/mandibular (%) 55/45
Primary/secondary caries Primary or secondary Secondary
Cavity type Occluso-proximal or mesio-occluso-distal Mesio-occluso-distal
Interventions characteristics
Base application No Yes (Dycal, Caulk and Vitra Bond, 3M)
Composite materials [no. of inlays] Paradigm MZ100 (3M Espe): 85 wt% nanocrystalline zirconia-silica spherical ceramic fillers; polymer matrix: bisGMA, TEGDMA, patented ternary initiator Estilux (Heraeus Kulzer): 77 wt% glass particle fillers; polymer matrix: bisGMA, pigments
Brilliant D.I. (Coltene): 77–78 wt% glass particle fillers, polymer matrix
Ceramic materials [no. of inlays] Mark II (Vita): fine particle feldspar ceramic (SiO 2 , Al 2 O 3 , Na 2 O, K 2 O, CaO, TiO 2 , pigments) Cerec blocks (Sirona): fine particle feldspar ceramic (SiO 2 , Al 2 O 3 , Na 2 O, K 2 O, CaO, TiO 2 , pigments)
Vita Dur N (Vita): fine particle feldspar ceramic (SiO 2 , Al 2 O 3 , K 2 O, B 2 O 3 , Na 2 O, pigments)
Rubber dam isolation Yes No
Adhesive Single Bond (3M Espe) Gluma 2 and 3 (Bayer), Durabond resin
Cement Rely X ARC (3M Espe) Cerec Dual Cement (Kulzer)

The Fasbinder trial was two-arm; all inlays were direct (chairside) CAD–CAM manufactured, with the Cerec 2 unit. Cavity preparation involved butt joint margins (without bevels) and a wall divergence of 6°–8°.

The Thordrup trial was four-arm: Cerec and Brilliant D.I. inlays were directly manufactured (by the operator, with the Cerec Cos 2.0 for Cerec inlays) and Vita Dur N and Estilux inlays were indirectly manufactured (by a dental technician). Margins and wall divergence were not detailed, but divergence was greatest for the Brilliant D.I. composite and least for the Cerec. A noneugenolic temporary filling (Fermin, Detax dental) was placed between visits for indirect inlays.

Risk of bias of trials

The risk of bias for each study is in Fig. 2 ; risk of bias tables are in Appendix 5. The risk of bias was high overall for both studies. The random sequence generation was not reported in either study. For the Thordrup study, the randomization was mentioned in the 10-year report but not in the 1- and 5-year reports. The allocation was concealed only in the Fasbinder study. Cementation standardization was correct in both studies, but preparation was standardized only in the Fasbinder study. Patients were not blinded in the Thordrup study and no information was given for the Fasbinder study. Concerning clinical outcome assessment, the risk of bias was low in the Fasbinder study and unclear in the Thordrup study because the process differed between assessment times. Radiographs were taken in the Thordrup study, but the report gave no information concerning radiograph assessment; no radiographic examination was reported for the Fasbinder study. Both studies exhibited attrition bias according to the Cochrane’s Risk of Bias tool. The Fasbinder study was supported by Septodont and 3M. The source of funding was not mentioned for the Thordrup study.

Nov 25, 2017 | Posted by in Dental Materials | Comments Off on Clinical efficacy of composite versus ceramic inlays and onlays: A systematic review
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