Is high-viscosity glass-ionomer-cement a successor to amalgam for treating primary molars?

Abstract

Objectives

To assess and compare the cumulative survival rate of amalgam and atraumatic restorative treatment (ART) restorations in primary molars over 3 years.

Methods

280 children aged 6–7 years old were enrolled in a cluster randomized controlled clinical trial using a parallel group design covering two treatment groups: conventional restorative treatment with amalgam (CRT) and atraumatic restorative treatment (ART) using a high-viscosity glass-ionomer (HVGIC) Ketac Molar Easymix. Three pedodontists placed 750 restorations (364 amalgam and 386 ART in 126 and 154 children, respectively) which were evaluated at 0.5, 1, 2 and 3 years. The proportional hazard rate regression model with frailty correction, ANOVA and Wald tests, and the Jackknife procedure were applied in analysing the data.

Results

The cumulative survival rates over 3 years for all, single- and multiple-surface CRT/amalgam restorations (72.6%, 93.4%, 64.7%, respectively) were no different from those of comparable ART/HVGIC restorations (66.8%; 90.1% and 56.4%, respectively) ( p = 0.10). Single-surface restorations had higher survival rates than multiple-surface restorations for the both treatment procedures ( p < 0.0001). A higher proportion of restorations failed because of mechanical reasons (94.8%) than of secondary caries (5.2%). No difference in reasons for restoration failures between all types of amalgam and ART/HVGIC restorations were observed ( p = 0.24).

Significance

The high-viscosity glass-ionomer used in this study in conjunction with the ART is a viable option for restoring carious dentin lesions in single surfaces in vital primary molars.

Introduction

The importance of restoring cavitated primary teeth, as the most obvious treatment, is debatable since studies have shown that unrestored cavitated teeth exfoliate naturally, without causing pain or sepsis in the majority of cases . Nevertheless, as little evidence is available regarding the effectiveness of non-restoring treatment approaches for managing cavitated primary teeth, restoring them remains the best option in the foreseeable future.

However, which restorative material should be used is unclear, according to a Cochrane systematic review . Amalgam has been used for decades and is considered by many to be the best material for restoring primary molars . Its application requires tooth preparation with rotary instruments and dental equipment that may not be always affordable in many communities . In addition, a number of countries have banned amalgam in response to the treaty agreed by the United Nations Environmental Programme (UNEP) . Both the World Dental Association (FDI) and the World Health Organization (WHO) have called for alternatives to amalgam . One alternative is to use currently available glass-based materials. The most common of these is glass-ionomer cement. Its high-viscosity type has become the material of choice for the atraumatic restorative treatment (ART). This caries management approach, which uses hand instruments only and a high-viscosity glass-ionomer cement (HVGIC), is considered an alternative to conventional restorative treatments . ART does not require use of rotary instruments, dental equipment or electricity and is therefore less painful than conventional restoration and causes less dental anxiety, particularly in children .

In terms of restoration survival, a systematic review concluded that ART/HVGIC and amalgam restorations of the same size, type of dentition, and follow-up period are equally successful. However, because of the limited number of suitable datasets for the analysis, authors suggested that further studies should be carried out to confirm the findings .

A weak feature of glass-ionomer is its fracture toughness. By increasing the powder-to-liquid ratio, the fracture toughness was increased . It was suggested that using an improved glass-ionomer with the ART might increase the survival of ART restorations, especially in multiple-surface cavities .

The aim of the present study was to compare the cumulative survival rates of amalgam and ART restorations using a high-viscosity glass-ionomer with a higher than usual powder-to-liquid ratio in primary molars over a period of 3 years. The null hypothesis tested is that there is no difference between the cumulative survival rates of amalgam and ART restorations in primary molars over a 3-year period.

Materials and methods

Sampling procedure

This cluster-randomized controlled clinical trial used a parallel group design and was carried out in all the available six public primary schools of Paranoá, a deprived suburban area of Brasilia, Brazil. From an oral health epidemiological survey of 6- and 7-year-old children, attending these schools, the sample of the present study was chosen . Inclusion criteria were (1) good general health; (2) at least two cavitated dentin carious lesions in vital pain-free primary molars assessed according to the ICDAS II index. The trial was approved by the Research Ethics Committee of the University of Brasília Medical School (reference number 081/2008) and was registered at the Dutch Trial Registration Centre (reference number 1699). Parents and/or caretakers were informed in writing about the investigation and treatments. Children whose parents or caretakers filled in and signed the consent forms were included in the study.

The main study consisted of three groups: Conventional Restorative Treatment (CRT) protocol, the ART protocol and the Ultra-Conservative Treatment (UCT) protocol group. The UCT protocol was to restore small uncleanable cavities with ART and to clean medium- and large-sized cavities with toothbrush and toothpaste daily . The unit of sampling was the school. As two of the six schools were equipped with a dental unit, these schools were allocated to the CRT group. The remaining four schools were randomly allocated to the ART and UCT groups. The current article concerns a secondary analysis and only reports the outcomes of the comparison between CRT/amalgam and ART/HVGIC restorations, and is a follow-up of a previously published report .

Implementation

Restorations were performed by three trained and calibrated pedodontists, aided by trained dental assistants, from May to July 2009 on the school premises, using a portable bed and an operating light. Children received an oral hygiene kit containing a toothbrush, fluoridated dentifrice, plaque-disclosing dentifrice, and dental floss. They were instructed on how to use each element of the kit and were encouraged to brush their teeth twice daily. In the UCT group a trained dental assistant supervised children every school day during tooth brushing sessions.

Conventional restorative treatment (CRT) protocol . Dentin carious cavities in primary molars were prepared with rotary instruments and restored, using a high-copper non-gamma 2 spherical and lathe cut amalgam (Permite Regular set ® ; SDI, Melbourne, Australia). The floors of the cavity and walls were prepared according to modified Black’s principles, but the ‘extension for prevention’ concept was not followed up. Demineralized dentin was removed with a slow speed round bur. The bite was checked with articulation paper and excess material was removed with a carver.

Atraumatic restorative treatment (ART) protocol . Dentin carious cavities in primary molars were accessed and cleaned with hand instruments only (ART Kit; Henry Schein ® , Chicago, USA), conditioned for 10 s with a wet cotton wool pellet saturated with the GIC liquid (polyacrylic acid), washed for 5 s, dried for 5 s with dry cotton wool pellets, and restored, using a high-viscosity glass-ionomer (Ketac Molar Easymix ® , 3M ESPE, Seefeld, Germany) mixed according to manufacturer’s instructions. The glass-ionomer was inserted into the cavity, using an applier/carver instrument (ART Kit; Henry Schein ® ), overfilled and pressed down with a petroleum-jelly-coated finger. Bite-check was performed and the applier/carver instrument was used to remove excess material.

In each treatment group, isolation was obtained through use of cotton wool rolls, local anesthesia was administered when children indicated pain or whenever the operator judged it necessary. A calcium hydroxide liner (Hydro C ® , Dentsply, Petrópolis, Rio de Janeiro, Brazil) covered with a glass-ionomer liner (Vidrion F ® , SS White, Rio de Janeiro, Brazil) was applied on deep cavities. A wooden wedge and steel matrix band (Injecta ® , Diadema, São Paulo, Brazil) in a Tofflemire matrix retainer (Golgran ® , São Paulo, Brazil) were used for restoring proximal cavities.

Evaluation

Two independent evaluators (dentists) assessed restorations according to the ART restoration criteria ( Table 1 ) on the school premises after 6 months, 1, 2 and 3 years. Evaluators were trained and calibrated before each evaluation session by an experienced epidemiologist (JF). Secondary caries was defined as an obvious dentin carious cavity. Battery-illuminated dental mirrors (Kudos ® , Hong Kong, China), CPITN probe (Golgran ® ) and compressed air aided the evaluation. A total of 198 restorations, presenting 543 surfaces, were re-examined for reproducibility testing. The inter-evaluator kappa coefficient value for assessing restoration failure over the four evaluation times was 0.75. The percentage of agreement was 92.6%.

Table 1
ART restoration criteria used in the present study.
Code Criteria
0 Present, satisfactory
1 Present, slight deficiency at cavity margin of less than 0.5 mm a
2 Present, deficiency at cavity margin of 0.5 mm or more a
3 Present, fracture in restoration
4 Present, fracture in tooth
5 Present, overextension of approximal margin of 0.5 mm or more a
6 Not present, most or all of restoration missing
7 Not present, other restorative treatment performed
8 Not present, tooth is not present
9 Unable to diagnose

a Assessed using the 0.5 mm ball-end of CPITN probe.

Statistical analysis

The sample size was based on a power calculation using an α of 0.05 and a 1 − β of 0.8. On the basis of an expected increase in the survival rate of multiple-surface ART restorations after two years from 65% to 70%; the survival rate of amalgam restorations of 80% ; a 10% correction for dependency of restorations; and an estimated annual loss of children of 8%, the required sample size was 365 restorations for each treatment group.

Statistical analyses were performed by a biostatistician using SAS version 9.2-software. Restorations coded 0 and 1 were considered to have survived, those coded 2–6 were considered failures and codes 7–9 were considered censored observations. Presence of a dentin carious cavity alongside the restoration (secondary caries) was considered a failure. The presence of secondary caries prevailed over a mechanical failure in the same restoration, except for failure coded 6 (restoration not present, most or all of restoration missing), since a complete displacement of the restoration is very unlikely to be justified by the occurrence of secondary caries but would rather be due to the restorative material used.

The dependent variable was the survival rate of restorations. Independent variables were type of restoration (amalgam, ART/HVGIC); type of surface (single-surface, multiple-surfaces); gender; operator (1–3). ANOVA and chi-square tests were used to test for differences between independent variables at baseline and for non-response. The Proportional Hazard Rate Regression Model (PHREG) with frailty correction was used to estimate cumulative survival rates of amalgam and ART/HVGIC restorations over the total survival period. The Wald test (chi-square) was used to test for differences in survival rates and for estimating effects of the independent variables. The Jackknife method was applied to calculate standard errors for use in the comparison of survival rates among restorations at one time point. Statistical significance was set at α = 0.05.

Materials and methods

Sampling procedure

This cluster-randomized controlled clinical trial used a parallel group design and was carried out in all the available six public primary schools of Paranoá, a deprived suburban area of Brasilia, Brazil. From an oral health epidemiological survey of 6- and 7-year-old children, attending these schools, the sample of the present study was chosen . Inclusion criteria were (1) good general health; (2) at least two cavitated dentin carious lesions in vital pain-free primary molars assessed according to the ICDAS II index. The trial was approved by the Research Ethics Committee of the University of Brasília Medical School (reference number 081/2008) and was registered at the Dutch Trial Registration Centre (reference number 1699). Parents and/or caretakers were informed in writing about the investigation and treatments. Children whose parents or caretakers filled in and signed the consent forms were included in the study.

The main study consisted of three groups: Conventional Restorative Treatment (CRT) protocol, the ART protocol and the Ultra-Conservative Treatment (UCT) protocol group. The UCT protocol was to restore small uncleanable cavities with ART and to clean medium- and large-sized cavities with toothbrush and toothpaste daily . The unit of sampling was the school. As two of the six schools were equipped with a dental unit, these schools were allocated to the CRT group. The remaining four schools were randomly allocated to the ART and UCT groups. The current article concerns a secondary analysis and only reports the outcomes of the comparison between CRT/amalgam and ART/HVGIC restorations, and is a follow-up of a previously published report .

Implementation

Restorations were performed by three trained and calibrated pedodontists, aided by trained dental assistants, from May to July 2009 on the school premises, using a portable bed and an operating light. Children received an oral hygiene kit containing a toothbrush, fluoridated dentifrice, plaque-disclosing dentifrice, and dental floss. They were instructed on how to use each element of the kit and were encouraged to brush their teeth twice daily. In the UCT group a trained dental assistant supervised children every school day during tooth brushing sessions.

Conventional restorative treatment (CRT) protocol . Dentin carious cavities in primary molars were prepared with rotary instruments and restored, using a high-copper non-gamma 2 spherical and lathe cut amalgam (Permite Regular set ® ; SDI, Melbourne, Australia). The floors of the cavity and walls were prepared according to modified Black’s principles, but the ‘extension for prevention’ concept was not followed up. Demineralized dentin was removed with a slow speed round bur. The bite was checked with articulation paper and excess material was removed with a carver.

Atraumatic restorative treatment (ART) protocol . Dentin carious cavities in primary molars were accessed and cleaned with hand instruments only (ART Kit; Henry Schein ® , Chicago, USA), conditioned for 10 s with a wet cotton wool pellet saturated with the GIC liquid (polyacrylic acid), washed for 5 s, dried for 5 s with dry cotton wool pellets, and restored, using a high-viscosity glass-ionomer (Ketac Molar Easymix ® , 3M ESPE, Seefeld, Germany) mixed according to manufacturer’s instructions. The glass-ionomer was inserted into the cavity, using an applier/carver instrument (ART Kit; Henry Schein ® ), overfilled and pressed down with a petroleum-jelly-coated finger. Bite-check was performed and the applier/carver instrument was used to remove excess material.

In each treatment group, isolation was obtained through use of cotton wool rolls, local anesthesia was administered when children indicated pain or whenever the operator judged it necessary. A calcium hydroxide liner (Hydro C ® , Dentsply, Petrópolis, Rio de Janeiro, Brazil) covered with a glass-ionomer liner (Vidrion F ® , SS White, Rio de Janeiro, Brazil) was applied on deep cavities. A wooden wedge and steel matrix band (Injecta ® , Diadema, São Paulo, Brazil) in a Tofflemire matrix retainer (Golgran ® , São Paulo, Brazil) were used for restoring proximal cavities.

Evaluation

Two independent evaluators (dentists) assessed restorations according to the ART restoration criteria ( Table 1 ) on the school premises after 6 months, 1, 2 and 3 years. Evaluators were trained and calibrated before each evaluation session by an experienced epidemiologist (JF). Secondary caries was defined as an obvious dentin carious cavity. Battery-illuminated dental mirrors (Kudos ® , Hong Kong, China), CPITN probe (Golgran ® ) and compressed air aided the evaluation. A total of 198 restorations, presenting 543 surfaces, were re-examined for reproducibility testing. The inter-evaluator kappa coefficient value for assessing restoration failure over the four evaluation times was 0.75. The percentage of agreement was 92.6%.

Table 1
ART restoration criteria used in the present study.
Code Criteria
0 Present, satisfactory
1 Present, slight deficiency at cavity margin of less than 0.5 mm a
2 Present, deficiency at cavity margin of 0.5 mm or more a
3 Present, fracture in restoration
4 Present, fracture in tooth
5 Present, overextension of approximal margin of 0.5 mm or more a
6 Not present, most or all of restoration missing
7 Not present, other restorative treatment performed
8 Not present, tooth is not present
9 Unable to diagnose
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Nov 25, 2017 | Posted by in Dental Materials | Comments Off on Is high-viscosity glass-ionomer-cement a successor to amalgam for treating primary molars?
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