Clinical effectiveness of direct anterior restorations—A meta-analysis

Abstract

Objectives

This is the first meta-analysis on the efficacy of composite resin restorations in anterior teeth. The objective of the present meta-analysis was to verify whether specific material classes, tooth conditioning methods and operational procedures influence the result for Class III and Class IV restorations.

Material and methods

The database SCOPUS and PubMed were searched for clinical trials on anterior resin composites without restricting the search to the year of publication. The inclusion criteria were: (1) prospective clinical trial with at least 2 years of observation; (2) minimal number of restorations at last recall = 20; (3) report on drop-out rate; (4) report of operative technique and materials used in the trial, and (5) utilization of Ryge or modified Ryge evaluation criteria. For the statistical analysis, a linear mixed model was used with random effects to account for the heterogeneity between the studies. p -Values smaller than 0.05 were considered to be significant.

Results

Of the 84 clinical trials, 21 studies met the inclusion criteria, 14 of them for Class III restorations, 6 for Class IV restorations and 1 for closure of diastemata; the latter was included in the Class IV group. Twelve of the 21 studies started before 1991 and 18 before 2001. The estimated median overall success rate (without replacement) after 10 years for Class III composite resin restorations was 95% and for Class IV restorations 90%. The main reason for the replacement of Class IV restorations was bulk fractures, which occurred significantly more frequently with microfilled composites than with hybrid and macrofilled composites. Caries adjacent to restorations was infrequent in most studies and accounted only for about 2.5% of all replaced restorations after 10 years irrespective of the cavity class. Class III restorations with glass ionomer derivates suffered significantly more loss of anatomical form than did fillings with other types of material. When the enamel was acid-etched and no bonding agent was applied, significantly more restorations showed marginal staining and detectable margins compared to enamel etching with enamel bonding or the total etch technique; fillings with self-etching systems were in between of these two outcome variables. Bevelling of the enamel was associated with a significantly reduced deterioration of the anatomical form compared to no bevelling but not with less marginal staining or less detectable margins. The type of isolation (absolute/relative) had a statistically significant influence on marginal caries which, however, might be a random finding.

Introduction

Perfect anterior restorations act as an advertisement for the skills of the dental professional. Most operative interventions in anterior teeth are accomplished with the direct placement of composite resins. The skill of the dentist in achieving a natural anatomical shape and color match with the adjacent teeth are prerequisites to achieving a pleasing aesthetic result, which can also be assessed easily by the patients themselves. Type of composite resin, methods and materials to condition the tooth structure (enamel etching, self-etching, no etching) as well as the operative procedure (bevelling of enamel margin, rubber dam application) may also influence both the aesthetic results and the longevity of the restoration.

Before the development of composite resins and the acid-etch technique of the enamel, carious lesions in anterior teeth were mainly restored with silicate cement, which required a retentive preparation pattern . Restorations that involve the proximal part of an anterior tooth but not the incisal edge are defined as Class III restorations.

In the early days, the building up of fractured teeth was only possible with indirect restorations, such as full-coverage crowns, because bonding to the remaining tooth substance had not yet been established as an operative procedure. Already in the nineteen-fifties, the enamel etch technique with phosphoric acid was developed by Buonocore . However, it took about 20 years until this technique has been introduced into clinical dentistry. This technique made it possible to directly restore fractured anterior teeth with composite resin, to close diastemata or to build up worn teeth. Restorations that involve a part of the incisal edge are defined as Class IV restorations.

At that time, there was a dispute as to whether it is necessary to place an unfilled resin bonding material on the etched enamel or whether high-viscosity resin composites could be placed directly on the etched enamel. The operative procedures have been gradually simplified and the materials improved since then. First, the application times of both enamel etching and rinsing were reduced from 60 to 30 s , dentin bonding agents made liners superfluous and increased the bonding strength to the tooth structure . Then, self-etching adhesive systems were introduced . Capable of establishing a bond to both the enamel and dentin, these materials streamlined the operative procedure because they eliminated the need for a separate rinsing step.

Most contemporary dental composite resins still contain a monomer which was already developed in the late 1950s of the last century by M. Bowen : it is called Bisphenol-A glycidylmethacrylate or simply Bis-GMA or Bowen’s resin Microfilled composites and later hybrid and nano-hybrid composites replaced the macrofilled composites, which were the first dental resins on the market . Polymerization curing lights were first introduced at the end of 1970s of last century . They allowed these materials to be cured on demand, which facilitated the customization of anterior restorations, because they could be built up step-by-step with several layers that have different optical properties.

With the reduction of caries prevalence in most countries, the prevalence of Class III restorations due to proximal caries has also dropped. However the prevalence of traumatic injuries to anterior teeth has significantly increased over the last 20 years due to an increase in sports activities undertaken during leisure time. In some countries, particularly in Scandinavia, children and adolescents have nowadays more teeth damaged by traumatic injuries than by caries . The restoration of fractured teeth (Class IV) with composite is usually the first treatment option.

The question arises as to how effective such a treatment is in terms of aesthetics, function and longevity. In the databases SCOPUS and PubMed no meta-analysis or systematic review on the efficacy of Class III or Class IV restorations has been found. There are several systematic reviews on posterior composite restorations and cervical restorations . However, it is inadequate to extrapolate from the longevity of posterior composite restoration to that of anterior restorations.

The aim of this review was to systematically evaluate prospective clinical trials on anterior resin composite restorations without restricting the search to the publication year or the type of resin or adhesive system used.

The following factors affecting the clinical outcome were to be specifically evaluated:

  • type of cavity (Class III, Class IV)

  • type of enamel/dentin conditioning

  • type of resin composite

  • operative techniques:

    • bevelling of enamel

    • absolute versus relative isolation

These factors were to be assessed by the following outcome criteria:

  • time elapsed until replacement and reason for replacement (marginal caries, fracture of filling, retention loss, etc.)

  • color match and surface texture

  • marginal integrity and marginal staining

  • anatomical form (shape)

  • chipping and fracture

The following hypotheses were examined:

  • 1.

    Class IV restorations mostly suffer from chippings and fractures and have a reduced longevity compared to Class III restorations.

  • 2.

    The type of composite resin does not influence the overall longevity of Class III restorations.

  • 3.

    Class IV restorations with hybrid composites show a better longevity than Class IV restorations with microfilled composites.

  • 4.

    Restorations based on glass ionomer derivates have a reduced longevity compared to composite resin restorations and compomers.

  • 5.

    Enamel etching with phosphoric acid reduces the number of restorations that show marginal discoloration and defective marginal integrity compared to self-etching systems and compared to those restorations that were placed with enamel etching but without bonding agent.

  • 6.

    The type of isolation or bevelling of the enamel does not influence the clinical outcome.

  • 7.

    Hybrid and microfilled composites show a better color match than macrofilled composites.

  • 8.

    Hybrid composites maintain their anatomical form more effectively than microfilled composites, compomers and glass ionomer derivates.

Materials and methods

Selection of clinical trials on class III/IV restorations

Prospective clinical studies on Class III/IV restorations in permanent teeth were searched in the databases PubMed (search period 1966–2012, search time December 2012). The search terms were “anterior” (or “Class III”) or “anterior” (or “Class IV” or “trauma”) and “composite” and “clinical trial”.

The inclusion criteria were as follows:

  • 1.

    Prospective clinical trial for Class III or Class IV cavities or diastema closures.

  • 2.

    Minimal duration of 2 years.

  • 3.

    Minimal sample size at last recall: 15 restorations per material.

  • 4.

    The study had to report on the following outcome variables: marginal discoloration, marginal integrity, caries adjacent to restorations, material fractures, color match and anatomical form. The variables “surface texture”, “surface staining” were optional variables.

  • 5.

    The study had to report on the materials and hard tissue conditioning technique used (etching of enamel with phosphoric acid yes/no, dentin/enamel bonding agent).

  • 6.

    The study had to report on the operative technique (bevelling of enamel, preparation, isolation technique, type of curing).

Clinical studies on direct composite veneers and studies that used composite materials to correct the vertical dimension were not included in the meta-analysis. Studies with experimental materials that were never launched on the market were not taken into account. There was no restriction with regard to the publication year.

As far as the materials are concerned, studies with polyacid-modified resin composites (compomers or PAMRC) and resin-modified glass ionomer cements (RMGIC) were also included.

The restorative materials and adhesive systems (AS) were grouped as follows:

  • Restorative material (RM)

    • 1 = macrofiller

    • 2 = microfiller

    • 3 = hybrid

    • 4 = polyacid-modified resin composite (compomer)

    • 5 = resin-modified glass ionomer cements (RMGIC)

  • Adhesive system (AS)

    • 1 = enamel etch + enamel bonding

    • 2 = enamel etch + no bonding

    • 3 = enamel etch–3 steps

    • 4 = enamel etch–2 steps

    • 5 = self-etch–2 steps

    • 6 = self-etch–1 step

    • 7 = no etch + no bond

To further reduce the number of categories and to increase the statistical power, four adhesive classes were defined:

  • 1 = enamel etch with phosphoric acid + bonding

  • 2 = enamel etch with phosphoric acid + no bonding

  • 3 = self-etch

  • 4 = no etch + no bond

The following binary variables were considered, where the percentage of the category given in brackets will be analyzed in what follows:

  • 1.

    MD marginal discoloration (not visible).

  • 2.

    MI marginal integrity (no clinically detectable margins (with explorers).

  • 3.

    CAR caries adjacent to restorations (no caries).

  • 4.

    F material fracture (no chipping, no bulk fracture; alternatively with slight chipping or fracture).

  • 5.

    AF anatomical form (good/very good).

  • 6.

    C color match (good/very good).

  • 7.

    ST surface texture (good/very good).

  • 8.

    R retained restoration.

For most of these variables (MD, MI, F, C, ST and AF) the data were originally graded into three categories (1 = good or very good, corresponds to Ryge criterion “Alpha”; 2 = acceptable or repairable, corresponds to Ryge criteria “Beta” or “Charlie”; 3 = inacceptable which needs replacement, corresponds to Ryge criterion “Delta”), but since the category 3 occurred only rarely, the variables were dichotomized for the analysis, as given above. However, category 3 was taken into account when defining and analyzing the longevity of a restoration. The percentage of restorations still in function refers to those restorations which did not have to be replaced due to one (or more) of the following reasons:

  • 1.

    CAR = caries adjacent to restorations (secondary or marginal caries)

  • 2.

    F = material fracture

  • 3.

    R = loss or partial loss of restoration

  • 4.

    C = inacceptable color match

  • 5.

    MI = inacceptable marginal integrity

  • 6.

    AF = inacceptable anatomical form

To assess the possible influence of the polishing system, the various polishing methods were categorized in the following way:

  • 1 = disc

  • 2 = silicone instrument

  • 3 = stone

  • 4 = disc + glaze

  • 5 = etch + bonding

Materials and methods

Selection of clinical trials on class III/IV restorations

Prospective clinical studies on Class III/IV restorations in permanent teeth were searched in the databases PubMed (search period 1966–2012, search time December 2012). The search terms were “anterior” (or “Class III”) or “anterior” (or “Class IV” or “trauma”) and “composite” and “clinical trial”.

The inclusion criteria were as follows:

  • 1.

    Prospective clinical trial for Class III or Class IV cavities or diastema closures.

  • 2.

    Minimal duration of 2 years.

  • 3.

    Minimal sample size at last recall: 15 restorations per material.

  • 4.

    The study had to report on the following outcome variables: marginal discoloration, marginal integrity, caries adjacent to restorations, material fractures, color match and anatomical form. The variables “surface texture”, “surface staining” were optional variables.

  • 5.

    The study had to report on the materials and hard tissue conditioning technique used (etching of enamel with phosphoric acid yes/no, dentin/enamel bonding agent).

  • 6.

    The study had to report on the operative technique (bevelling of enamel, preparation, isolation technique, type of curing).

Clinical studies on direct composite veneers and studies that used composite materials to correct the vertical dimension were not included in the meta-analysis. Studies with experimental materials that were never launched on the market were not taken into account. There was no restriction with regard to the publication year.

As far as the materials are concerned, studies with polyacid-modified resin composites (compomers or PAMRC) and resin-modified glass ionomer cements (RMGIC) were also included.

The restorative materials and adhesive systems (AS) were grouped as follows:

  • Restorative material (RM)

    • 1 = macrofiller

    • 2 = microfiller

    • 3 = hybrid

    • 4 = polyacid-modified resin composite (compomer)

    • 5 = resin-modified glass ionomer cements (RMGIC)

  • Adhesive system (AS)

    • 1 = enamel etch + enamel bonding

    • 2 = enamel etch + no bonding

    • 3 = enamel etch–3 steps

    • 4 = enamel etch–2 steps

    • 5 = self-etch–2 steps

    • 6 = self-etch–1 step

    • 7 = no etch + no bond

To further reduce the number of categories and to increase the statistical power, four adhesive classes were defined:

  • 1 = enamel etch with phosphoric acid + bonding

  • 2 = enamel etch with phosphoric acid + no bonding

  • 3 = self-etch

  • 4 = no etch + no bond

The following binary variables were considered, where the percentage of the category given in brackets will be analyzed in what follows:

  • 1.

    MD marginal discoloration (not visible).

  • 2.

    MI marginal integrity (no clinically detectable margins (with explorers).

  • 3.

    CAR caries adjacent to restorations (no caries).

  • 4.

    F material fracture (no chipping, no bulk fracture; alternatively with slight chipping or fracture).

  • 5.

    AF anatomical form (good/very good).

  • 6.

    C color match (good/very good).

  • 7.

    ST surface texture (good/very good).

  • 8.

    R retained restoration.

For most of these variables (MD, MI, F, C, ST and AF) the data were originally graded into three categories (1 = good or very good, corresponds to Ryge criterion “Alpha”; 2 = acceptable or repairable, corresponds to Ryge criteria “Beta” or “Charlie”; 3 = inacceptable which needs replacement, corresponds to Ryge criterion “Delta”), but since the category 3 occurred only rarely, the variables were dichotomized for the analysis, as given above. However, category 3 was taken into account when defining and analyzing the longevity of a restoration. The percentage of restorations still in function refers to those restorations which did not have to be replaced due to one (or more) of the following reasons:

  • 1.

    CAR = caries adjacent to restorations (secondary or marginal caries)

  • 2.

    F = material fracture

  • 3.

    R = loss or partial loss of restoration

  • 4.

    C = inacceptable color match

  • 5.

    MI = inacceptable marginal integrity

  • 6.

    AF = inacceptable anatomical form

To assess the possible influence of the polishing system, the various polishing methods were categorized in the following way:

  • 1 = disc

  • 2 = silicone instrument

  • 3 = stone

  • 4 = disc + glaze

  • 5 = etch + bonding

Statistical analysis

All the clinical outcomes could be expressed as percentages of restorations retaining a given property across the defined period of time, for example the percentage of restorations without a visible marginal discoloration, the percentage of restorations with a good or a very good anatomical form, or the percentage of restorations which did not need replacement, as defined above. To permit a comparison of the rate of deterioration among the various experiments, the percentages observed at the various points of time were divided by the percentage observed at baseline for those experiments where the latter was below 100%.

Let Y ( t ) be a percentage measured at time t (expressed in years). To model the rate of deterioration, we were looking for a model where Y ( t ) is a decreasing function of t ranging from Y (0) = 100% down to 0% for large values of t. A linear model of the form Y ( t ) = 100 − beta × t would for example not be convenient since it would have become negative for large values of t, which was not sensible in our context. We considered instead a deterioration model of the form Y = 100 × exp(−lambda × t ˆalpha) with positive values of alpha and lambda, which is equivalent to stating that Log(−Log Y /100) = beta + alpha × Log( t ), with beta = Log(lambda).

To study how the deterioration process depends on a given factor of interest, we then considered the following statistical model for our empirical percentages Y ( t ):

Log(−Log( Y ( t )/100)) = beta_ j + alpha × Log( t ) + study_effect + experiment_effect + random error.

In this model, beta_ j is a fixed parameter characterizing the rate of deterioration for the level j of the factor of interest, such that the higher the parameter, the faster the deterioration (a value of beta_ j = −2 indicates for example a faster deterioration than a value of beta_ j = −3). The parameter alpha characterizes the shape of the deterioration which does not depend on the factor of interest. A random experiment effect was included to account for the obvious dependencies among the repeated percentages observed in the same experiment along time, while a random study effect was included to account for the fact that the subjects involved in different experiments from the same study were partly the same (split-mouth design).

In our model, the deterioration curve is thus assumed to be different from study to study and from experiment to experiment. Figs. 1–9 below show some of our fitted models as Y = 100 × exp(−lambda_ j × t ˆalpha), with lambda_ j = exp(beta_ j ), which can be interpreted as a median deterioration curve for the level j of the factor of interest (estimated over all studies and experiments).

Fig. 1
Estimated median percentage of restorations across the studies and experiments with good or very good color match in relation to the type of restorative material and to the observation time. (Left) Class III, (right) Class IV.

Fig. 2
Estimated median percentage of Class III restorations across the studies and experiments with good or very good surface texture in relation to the type of restorative material and to the observation time.

Fig. 3
Estimated median percentage of Class III restorations across the studies and experiments with adequate anatomical form in relation to the type of restorative material and to the observation time.

Fig. 4
Estimated median percentage of restorations across the studies and experiments without material chipping/fracture to the restoration in relation to the type of restorative material. (Left) Class III, (right) Class IV.

Fig. 5
Estimated percentage of restorations across the studies and experiments based on all data without caries adjacent to the restoration in relation to the type of cavity category (Class III/IV).

Fig. 6
Estimated median percentage of Class III restorations across the studies and experiments without caries adjacent to the restoration in relation to the type of isolation.

Fig. 7
Estimated median percentage of restorations across the studies and experiments without marginal staining in relation to the adhesive technique and adhesive system and to the observation time. (Left) Class III, (right) Class IV.

Fig. 8
Estimated median percentage of Class III restorations across the studies and experiments without detectable margins in relation to the composite material (left) and the adhesive technique (right).

Fig. 9
Estimated median percentage of restorations across the studies and experiments that were not replaced in relation to the type of restorative material. (Left) Class III, (right) Class IV.

Such a linear mixed model could be fitted using the restricted maximum likelihood method implemented in the routine lme , which can be found in the package nlme from the statistical software R. In this routine, it was also possible to weight each empirical percentage by the corresponding number of restorations (the denominator of the percentage). To test for the statistical significance of the factor of interest, a maximum likelihood ratio test was used, with the number of levels of the factor of interest minus one as number of degrees of freedom. p -Values smaller than 0.05 were considered to be significant.

Results

Study search

The initial search revealed 85 clinical studies on Class III/IV anterior restorations. However, only 21 studies met the criteria to be included in the review, 14 of them for Class III restorations, 6 for Class IV and 1 for diastema closure; the latter was included in the group of Class IV restorations ( Table 1 ). Furthermore, prospective studies that missed to report on one or several of the clinical outcome variables listed above, e.g. color match or marginal staining, were also included, which led to more statistical power.

Table 1
Clinical studies and their characteristics that are included in the meta-analysis.
First author Reference Publication year Number of restorations at baseline Number of restorations at last recall Observation period (years) Bevelling
Class III
Osborne 1990 50 46 3 No
1990 50 47 3 no
Schlapbach 1982 111 97 2 yes
1982 43 39 2 yes
1982 61 53 2 yes
van Dijken 1986 29 29 6 yes
1986 28 28 6 yes
1986 20 20 6 yes
1986 28 28 6 yes
1986 47 47 6 yes
Qvist 1993 52 37 11 yes
1993 52 38 11 no
Davis 1986 28 17 3 yes
1986 28 17 3 yes
1986 28 17 3 yes
Crumpler 1988 28 17 5 no
1988 28 16 5 no
1988 28 15 5 no
1988 28 18 5 no
Osborne 1990 24 22 3 no
1990 24 22 3 no
1990 24 22 3 no
van Dijken 1999 53 49 5 yes
1999 49 44 5 yes
1999 49 44 5 yes
van Dijken 1999 52 50 5 no
1999 45 42 5 no
1999 57 52 5 yes
Araujo 1998 21 21 2 yes
1998 21 21 2 no
Reusens 1999 28 23 2 yes
1999 28 23 2 yes
Demirci 2006 62 57 5 no
Demirci 2008 32 29 2 yes
2008 32 29 2 no
2008 32 29 2 no
Ermis 2010 51 40 3 yes
2010 51 40 3 yes
Class IV
Sheykholeslam 1977 33 33 2 No
1977 31 30 2 No
Dogon 1980 161 27 4 Yes
1980 161 27 4 Yes
Roberts 1978 52 37 2 Yes
1978 52 38 2 Yes
1978 52 29 2 Yes
Shey 1979 25 19 2 Yes
1979 25 19 2 Yes
Tyas 1990 25 15 3 No
1990 29 17 3 No
1990 22 21 3 No
1990 26 24 3 No
Peumans 1997 61 61 5 Yes
van Dijken 2010 43 40 12 Yes
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Nov 23, 2017 | Posted by in Dental Materials | Comments Off on Clinical effectiveness of direct anterior restorations—A meta-analysis
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