Direct versus indirect inlay/onlay composite restorations in posterior teeth. A systematic review and meta-analysis

Abstract

Objective

To evaluate the long-term clinical performance of direct versus indirect composite inlays/onlays in posterior teeth.

Data

Screening for inclusion eligibility, quality assessment of studies and data extraction was performed independently by two authors.

Sources

The electronic databases MEDLINE, EMBASE, Cochrane Oral Health Group’s Trials Register and CENTRAL were searched (14.12.2015), with no restriction to publication date or language. We included only randomised controlled trials (RCTs) and evaluated them according to Cochrane risk of bias tool. The main outcome assessed was the restoration failure, determined by several clinical parameters.

Study selection

Two studies concerning direct and indirect inlays (82 patients with 248 restorations) and one study for onlays (157 patients with 176 restorations) satisfied the inclusion criteria. Two trials, one of unclear and one of high risk of bias, could be mathematically combined. The meta-analysis indicated no statistically significant difference in the risk failure between direct and indirect inlays, after 5 years (RR: 1.54; 95% Cl: 0.42, 5.58; p = 0.52) or 11 years of function (RR: 0.95; 95% Cl: 0.34, 2.63; p = 0.92). Only one parameter, the marginal discoloration, slightly favored direct inlays after 11 years (RR: 0.41; 95% Cl: 0.17, 0.96; p = 0.04). Only one study dealt with onlays; an overall 5-year survival of 87% (95% CI: 81–93%) was reported.

Conclusion

The difference of the two techniques did not reach statistical significance in order to recommend one technique over the other. The scarcity of primary studies support the need for further well-designed long-term studies in order to reach firm conclusions about both techniques.

Clinical significance

Resin composite materials, placed directly or indirectly, exhibit a promising long-term clinical performance when rehabilitation of posterior teeth is needed. Although many years in clinical practice, the selection of the best treatment protocol still remains subjective. The available studies, and their synthesis, cannot provide reliable evidence in this field.

Introduction

Failure of dental restorations presents a major complication in everyday dental practice. It has been reported that about 60% of all operative dental workload refers to placement and replacement of restorations . Correct material manipulation and proper technique selection may be regarded as the key factors that affect restoration success or failure .

Contemporary dentistry evolves along with patient’s demand for high aesthetics. Even though amalgam and gold have been materials with a long history of clinical success and biocompatibility, patients often reject these treatment options, as the desire of a restoration that resembles natural tooth structure, even for posterior teeth, is high .

Conservative restorative dentistry is provided with a wide range of techniques and systems for the rehabilitation of posterior teeth in a minimal invasive way. Resin composite materials, placed directly or indirectly, are among the best alternative non-metallic, tooth-colored restorative treatments .

Composite resin materials usually consist of a matrix (organic polymer) and fillers (combination of inorganic particles) of different types. Some of these resinous materials are based on Bisphenol-A (BPA), which is used as a precursor of BPA glycidyl dimetha-crylate (Bis-GMA) or BPA dimethacrylate (Bis-DMA). The BPA structure assembles a bulk, stiff chain that offers low susceptibility to biodegradation as well as great rigidity and strength . Clinical, physical and mechanical properties of composite resins depend on the percentage of fillers in their volume, the particle size, and load and matrix bonding of the filler. In fact, the more the loading of the filler particle is, the less the wear resistance . However, these resins are less polishable. Resin composites have gone through generations of traditional (macrofilled) composites, microfilled composites, hybrid composites, microhybrid composites and nano-composites. Newer resin formulations of smaller filler particles but higher filler loading percentage (approximately 66% inorganic fillers and 33% resin matrix) have been developed to enhance mechanical characteristics. The submicron-particle fillers provide abrasion resistance, more color stability and less polymerization shrinkage, while increasing flexural and tensile strength. Resins are converted from monomer to polymer by various methods of polymerization devices. The controlled degree of polymerization also enhances tensile strength, wear resistance, fracture toughness and color stability .

In direct restorations, light-cured resin composite material is placed directly into the prepared cavity. The greatest advantage presented by this procedure, is that it permits the maximum preservation of tooth structure, which collaborates with the modern concept of a minimal-invasion conservative restorative dentistry. In addition, they are usually performed in one treatment appointment, at relatively low costs. However, direct restorations are associated with polymerization shrinkage and low wear resistance .

Indirect technique involves fabricating the restoration outside the oral cavity, using an impression of the prepared tooth. This technique overcomes some of the disadvantages of direct resin composites, such as polymerization shrinkage to the width of the luting gap . Furthermore, it provides better physical and mechanical properties by post-curing the inlay/onlay with light or heat, ideal occlusal morphology, proximal contouring and wear compatibility with opposing natural dentition . However, this technique is more time consuming and requires extra cost and appointments that may, in turn, be out of patient wishes and budget.

As evident in the literature, many in-vitro studies have examined the behavior and durability of direct composite restorations and indirect composite inlays . Although, several studies have verified the long-term in-vivo performance of those materials separately , only few have compared these techniques . In a recent systematic review, Grivas et al. concluded that there was insufficient evidence to make recommendations for the use of indirect composite inlays over direct. In this review, the variety of methodology, the heterogeneity of the trials – 3 randomized controlled trials (RCTs) and 4 controlled clinical trials CCT until 2013 were considered eligible- as long as the unlimited observation time could not permit a valid assessment on the basis of a meta-analysis regarding the longevity of the composite inlays . Even though there is a systematic review that compares clinical effectiveness of composite versus ceramic inlays/onlays , there is no systematic review apparent in the literature that has evaluated effectiveness of direct versus indirect composite inlays/onlays.

The aim, therefore, of this systematic review was to provide updated evidence stemming from randomized controlled trials comparing direct and indirect composite restorations in posterior teeth, with at least 3 years of follow-up after initial restoration. Comparison results relied on the clinical parameters of longevity, secondary caries, post-operative sensitivity, marginal discoloration and color match between intervention modalities.

Materials and methods

This systematic review was based on the guidelines of the PRISMA Statement for reporting Systematic Reviews and Meta Analyses of studies evaluating health-care interventions .

Protocol and registration

Not available.

Selection criteria applied for the review

  • Study design: Only randomized clinical trials were eligible for inclusion in this review. Non-randomized or quasi-randomized controlled trials were not eligible for inclusion

  • Types of participants: Patients of any age who received direct or indirect composite inlays/onlays

  • Type of intervention: All direct/indirect composite inlays/onlays irrespectively of the resin and bonding material and the type of tooth (molar, premolar)

  • Outcome: Failure rate of direct and indirect composite inlays/onlays, (restorations which need replacement or repair) and risk ratio of (1) secondary caries, (2) postoperative sensitivity, and (3) marginal discoloration, color match between the two groups

  • Follow-up: At least three years of observation

  • Exclusion criteria: Animal and in-vitro studies.

Search strategy for identification of studies

Detailed search strategies were developed and appropriately revised for each database, considering the differences in controlled vocabulary and syntax rules. The following elec-tronic databases were searched: MEDLINE (via Ovid and Pubmed, Appendix A , from 1946 to December 14th, 2015), EMBASE (via Ovid), the Cochrane Oral Health Group’s Trials Register and CENTRAL.

Unpublished literature was searched on ClinicalTrials.gov , the National Research Register, and Pro-Quest Dissertation Abstracts and Thesis database. The search attempted to identify all relevant studies irrespective of language. The reference lists of all eligible studies were hand-searched for additional studies.

Selection of studies

Two authors (F.A. and A.G.) of the review independently and in duplicate performed the study selection. The procedure composed of three stages: title-reading, abstract reading and full-text reading in order to identify studies that potentially met the eligibility criteria. After exclusion of not eligible studies, the full report of publication was obtained and assessed independently. Any disagreements were discussed and resolved by discussion and consultation with the other two authors. Reasons of exclusion and all decisions on study identification were recorded.

Data extraction and management

Data extraction was performed independently and in duplicate by the first two authors. In order to record the desired information, the following customized data collection forms were used.

  • Author/title/year of study

  • Design of study

  • Number/age/gender of patients recruited

  • Type of restoration, direct or indirect technique

  • Number of tooth

  • Composite used

  • Bond system used

  • Observation period (Follow up of patients)

  • Outcome assessed

  • Failure rate of direct and indirect inlays/onlays

Measures of treatment effect

For continuous outcomes, mean differences and standard deviations were used to summarize the data from each study. For dichotomous data, number of participants with events and total number of participants in experimental and control groups were analyzed. Regarding meta-analysis for dichotomous data risk ratios (RR) and their 95% confidence intervals (Cls) were calculated. For continuous data mean difference (MD) and 95% Cls were calculated.

Unit of analysis issues

In all cases, the unit of analysis was the restored tooth (number of teeth treated).

Dealing with missing data

We contacted study authors via e-mail to request information where missing. In case of no response, only the available data were reported and analyzed. Following our request, Dr. Fennis provided additional data, concerning the exact time-point that onlays’ failures had occurred during her trial .

Assessment of heterogeneity

We assessed clinical heterogeneity by examining the characteristics of the studies, the similarity between the types of participants, the interventions and the outcomes as specified in inclusion criteria.

Quality assessment

The methodological quality of RCTs was assessed by two review authors, independently and in duplicate, using the Cochrane risk of bias tool . Risk of bias was assessed and judged for seven separate domains.

  • Sequence generation: was the allocation sequence adequately generated?

  • Allocation concealment: was allocation adequately concealed?

  • Blinding of participants and investigators: was knowledge of the allocated intervention adequately prevented during the study?

  • Blinding of outcome assessors: was knowledge of the allocated intervention adequately prevented before assessing the outcome?

  • Incomplete outcome data: were incomplete outcome data adequately addressed?

  • Selective outcome reporting: were reports of the study free of suggestion of selective outcome reporting?

  • Other sources of bias: was the study apparently free of other problems that could put it at a high risk of bias?

Each study received a judgment of low risk, high risk or unclear risk of bias (indicating either lack of sufficient information to make a judgment or uncertainty over the risk of bias) for each of the seven domains. Studies were finally grouped into the following categories:

  • Low risk of bias (plausible bias unlikely to seriously alter the results) if all key domains of the study were at low risk of bias.

  • Unclear risk of bias (plausible bias that raises some doubt about the results) if one or more key domains of the study were unclear.

  • High risk of bias (plausible bias that seriously weakens confidence in the results) if one or more key domains were at high risk of bias.

Assessment of reporting bias

In the presence of more than 10 studies in a meta-analysis, the possible presence of publication bias was investigated.

Data synthesis

We planned to conduct meta-analyses if there were studies of similar comparisons reporting the same outcomes at the same follow-up periods. Risk ratios were combined for dichotomous data using fixed-effect models, unless there were more than three studies in the meta-analysis, when random-effects models would have been used.

Materials and methods

This systematic review was based on the guidelines of the PRISMA Statement for reporting Systematic Reviews and Meta Analyses of studies evaluating health-care interventions .

Protocol and registration

Not available.

Selection criteria applied for the review

  • Study design: Only randomized clinical trials were eligible for inclusion in this review. Non-randomized or quasi-randomized controlled trials were not eligible for inclusion

  • Types of participants: Patients of any age who received direct or indirect composite inlays/onlays

  • Type of intervention: All direct/indirect composite inlays/onlays irrespectively of the resin and bonding material and the type of tooth (molar, premolar)

  • Outcome: Failure rate of direct and indirect composite inlays/onlays, (restorations which need replacement or repair) and risk ratio of (1) secondary caries, (2) postoperative sensitivity, and (3) marginal discoloration, color match between the two groups

  • Follow-up: At least three years of observation

  • Exclusion criteria: Animal and in-vitro studies.

Search strategy for identification of studies

Detailed search strategies were developed and appropriately revised for each database, considering the differences in controlled vocabulary and syntax rules. The following elec-tronic databases were searched: MEDLINE (via Ovid and Pubmed, Appendix A , from 1946 to December 14th, 2015), EMBASE (via Ovid), the Cochrane Oral Health Group’s Trials Register and CENTRAL.

Unpublished literature was searched on ClinicalTrials.gov , the National Research Register, and Pro-Quest Dissertation Abstracts and Thesis database. The search attempted to identify all relevant studies irrespective of language. The reference lists of all eligible studies were hand-searched for additional studies.

Selection of studies

Two authors (F.A. and A.G.) of the review independently and in duplicate performed the study selection. The procedure composed of three stages: title-reading, abstract reading and full-text reading in order to identify studies that potentially met the eligibility criteria. After exclusion of not eligible studies, the full report of publication was obtained and assessed independently. Any disagreements were discussed and resolved by discussion and consultation with the other two authors. Reasons of exclusion and all decisions on study identification were recorded.

Data extraction and management

Data extraction was performed independently and in duplicate by the first two authors. In order to record the desired information, the following customized data collection forms were used.

  • Author/title/year of study

  • Design of study

  • Number/age/gender of patients recruited

  • Type of restoration, direct or indirect technique

  • Number of tooth

  • Composite used

  • Bond system used

  • Observation period (Follow up of patients)

  • Outcome assessed

  • Failure rate of direct and indirect inlays/onlays

Measures of treatment effect

For continuous outcomes, mean differences and standard deviations were used to summarize the data from each study. For dichotomous data, number of participants with events and total number of participants in experimental and control groups were analyzed. Regarding meta-analysis for dichotomous data risk ratios (RR) and their 95% confidence intervals (Cls) were calculated. For continuous data mean difference (MD) and 95% Cls were calculated.

Unit of analysis issues

In all cases, the unit of analysis was the restored tooth (number of teeth treated).

Dealing with missing data

We contacted study authors via e-mail to request information where missing. In case of no response, only the available data were reported and analyzed. Following our request, Dr. Fennis provided additional data, concerning the exact time-point that onlays’ failures had occurred during her trial .

Assessment of heterogeneity

We assessed clinical heterogeneity by examining the characteristics of the studies, the similarity between the types of participants, the interventions and the outcomes as specified in inclusion criteria.

Quality assessment

The methodological quality of RCTs was assessed by two review authors, independently and in duplicate, using the Cochrane risk of bias tool . Risk of bias was assessed and judged for seven separate domains.

  • Sequence generation: was the allocation sequence adequately generated?

  • Allocation concealment: was allocation adequately concealed?

  • Blinding of participants and investigators: was knowledge of the allocated intervention adequately prevented during the study?

  • Blinding of outcome assessors: was knowledge of the allocated intervention adequately prevented before assessing the outcome?

  • Incomplete outcome data: were incomplete outcome data adequately addressed?

  • Selective outcome reporting: were reports of the study free of suggestion of selective outcome reporting?

  • Other sources of bias: was the study apparently free of other problems that could put it at a high risk of bias?

Each study received a judgment of low risk, high risk or unclear risk of bias (indicating either lack of sufficient information to make a judgment or uncertainty over the risk of bias) for each of the seven domains. Studies were finally grouped into the following categories:

  • Low risk of bias (plausible bias unlikely to seriously alter the results) if all key domains of the study were at low risk of bias.

  • Unclear risk of bias (plausible bias that raises some doubt about the results) if one or more key domains of the study were unclear.

  • High risk of bias (plausible bias that seriously weakens confidence in the results) if one or more key domains were at high risk of bias.

Assessment of reporting bias

In the presence of more than 10 studies in a meta-analysis, the possible presence of publication bias was investigated.

Data synthesis

We planned to conduct meta-analyses if there were studies of similar comparisons reporting the same outcomes at the same follow-up periods. Risk ratios were combined for dichotomous data using fixed-effect models, unless there were more than three studies in the meta-analysis, when random-effects models would have been used.

Results

Description of studies

A total number of 42 studies were identified as relevant, as screened from the electronic searches and after the specific inclusion criteria were applied. Many studies concerning direct or indirect composite inlays separately or in comparison with ceramic inlays as well as in-vitro studies and studies assessing veneers were found, but their outcome was not relevant for this review. After exclusion of all duplicates, the studies were screened and assessed for eligibility. 24 studies were discarded after the title-reading stage and finally 18 abstracts were screened. 4 records met all eligibility criteria but one was excluded after full text reading, leaving 3 RCTs (2 regarding direct versus indirect inlays and 1 regarding direct versus indirect onlays ) to be included in this review ( Table 1 ). The process of study identification is presented in Fig. 1 .

Table 1
Characteristics of included studies ordered by study design and date.
Reference
type of study
Country
Operator-evaluation
Assessment criteria
Statistical analysis
No of patients No of restorations Tooth Materials Cement Follow up
Pallesen and Qvist Modified USPHS 28 140 88 Premolars
52 Molars
Briliant Dentin (BD) by Coltene. For inlays and direct restorations Cements: BD by Coltene 11 y
(2-5-8-11y).
RCT X 2 and sign test (20 female, 8 male) 28 sets (2 direct, 3 inlays) 85 MO/DO (two surfaces cavities-class II) Estilux Posterior (EP) by Kulzer. For direct restorations EP by Microfil Pontic C, Heraeus
Denmark University of Copenhagen Range: 19–64 years old (av35) 84 inlays
56 direct
SR-Iso-sit (ISO) by Ivoclar. For indirect inlays ISO by Vivadent
Operator:One clinician (UP) 55 MOD (3 surfaces cavities)
Evaluation by either UP or UP and VQ Vital teeth
Fennis et al. Authors criteria 157 92 direct
84 onlays
176 Premolars hybrid resin composite 70% vol, 86% wt filler load; AP-X, Kuraray(direct) Clearfil Photobond,Kuraray Mean follow-up time was 5.6 yrs (SD, 0.9 yrs; range, 4.5–8.8 yrs) for the direct and 6.0 yrs (SD, 1.3 yrs; range, 4.5–8.5 yrs) for the inlays
RCT Kaplan-Meier 77 males, 80 females Vital teeth All Class II,
Radbound university Nijmegen,
The Netherlands
Evaluated by two clinicians
Mean age 54.9 yrs (range, 35.0–81.0 yrs) Fracture of buccal or palatal cusps Estenia(indirect)
Cetin et al. Modified USPHS, 54 108 Molars Indirect:
1.(Estenia [E]
2.Tescera ATL [TATL])
DC for E inlays (Panavia) 5yrs
RCT Statistical analysis fisher exact test and McNemar x2test 22 males and 32 females
20–28yo, mean:23yo
41 Indirect inlays
21(Estenia [E] and 20Tescera ATL [TATL])
57 Class I
51 Class II
Direct:
1. Filtek SupremeXT [FSXT],
2. Tetric Evo Ceram [TEC
3. AELITE Aesthetic [AA])
Talt with Duo Link (Bisco)
Selcuk university Konya,Turkey
One clinician
Evaluation by two independent dentists (blind)
Each patient 1 class one and 1 class II resto-ration 67Direct inlays
(Filtek SupremeXT [FSXT], Tetric Evo Ceram [TEC], AELITE Aesthetic [AA])
Vital teeth
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Jun 19, 2018 | Posted by in General Dentistry | Comments Off on Direct versus indirect inlay/onlay composite restorations in posterior teeth. A systematic review and meta-analysis
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