Clinical performance of a new glass ionomer based restoration system: A retrospective cohort study

Abstract

Objectives

This retrospective clinical study evaluated the suitability of a glass ionomer system as a permanent restoration material in posterior cavities.

Methods

26 Class I (1-surface (S1)) and 125 Class II (84 2-surface (S2), 41 3- and 4-surface (S3+)) restorations were placed in permanent molars (n = 94) and premolars (n = 57) in 43 patients in 6 dental practices. Restorations were evaluated at 4.5× magnification using modified USPHS criteria. Statistical analysis was performed using the Pearson's Chi-square-test (p ≤ 0.05).

Results

The median age of the restorations was 24 months. No failures were observed. The original volume of the restoration was retained in 88.5% of the S1, in 64.2% of the S2 and in 53.7% of the S3+ restorations. A distinct volume loss in S1 restorations was evident in 3.8%. A visible and perceptible roughness was shown in 11.5% of the S1, in 14.3% of the S2 and in 24.4% of the S3+ restorations. Marginal disintegrities occurred in none of the S1, in 1.2% of the S2 and in 7.3% of the S3+ restorations. A distinct marginal discoloration was found less than 1%.

Conclusions

Within the limitations of this study it can be concluded that EQUIA can be used as a permanent restoration material for any sized Class I and in smaller Class II cavities. However, results of ongoing prospective studies shall provide a more exact indication definition in Class II situations.

Significance

Modern glass ionomer systems may not only serve as long-term temporaries, but also as permanent restorations in posterior teeth.

Introduction

In modern operative dentistry focus is on minimal removal of tooth tissues and on application of adhesive restorative materials that possibly perform therapeutic actions on demineralized dentin. Glass ionomer cements (GIC) have been shown to have the potential for release and uptake of fluoride ions. While it is supposed that these materials may have caries preventive and remineralizing effects, it is still unclear what the clinical implications of this phenomenon might be [1], [2]. The major drawbacks of conventional GIC have been the relatively low fracture toughness and higher rate of occlusal wear, compared to amalgam and modern composite restorative materials. For use in Class II restorations, conventional and metal modified GIC were previously not considered materials of choice, neither in primary nor in permanent molars [3], [4], [5], [6]. Although the highly viscous glass ionomer materials, which were introduced in the market not before 1995, achieved superior physical properties compared to traditional GIC by optimizing polyacid and particle size distribution and resulting in a high cross-linkage in the GIC matrix [7], the reputation of glass ionomers did not change significantly: they are nowadays mostly still considered a semi-permanent restoration material for Class I and Class II fillings in permanent teeth.

However, some promising prospective longitudinal data of highly viscous GIC were shown in the ART (atraumatic restorative treatment) approach, e.g. in a prospective longitudinal study a total of 1117 Class I and Class II GIC (Fuji IX [GC Europe, Leuven, Belgium] and Ketac Molar [3MEspe, Seefeld, Germany]) and amalgam restorations which were placed in permanent teeth of 370 and 311 children, respectively, by 8 dentists. The cumulative survival rates after 6.3 years were 66.1% for GIC and 57.0% for amalgam. Differences between the GIC were not significant [8]. However, it has to be considered that the relationship between Class I and Class II restorations was around 10:1 and ART conditions are not comparable to private practice conditions. Studies on highly viscous GIC not performed under ART conditions in Class I and II cavities are scarce, but also promising. In a study on 169 Class I (n = 67) and Class II (n = 102) GIC restorations (Fuji IX) in 116 patients placed by 3 dentists the survival rate was 98% after 2 years. The main reason for replacement was fracture of the filling [9]. In a 6-year retrospective clinical study 116 Class II GIC restorations (Fuji IX GP) in 72 patients placed by 2 dentists in a private practice were examined. Until 1.5 years no failures were observed. From 1.5 to 3.5 years survival dropped to 93%. After 3.5 years failure rate increased and at 6 years survival was 60% [10].

Nowadays, GIC may also be an interesting alternative in terms of economical aspects which are very important in public health systems with a kind of basic and economic approach. They may be a valuable solution for the dentist and the patient in cases, where the patient does not accept an amalgam filling, but is not able or willing to pay additional costs for layered composite resin restorations.

To overcome the disadvantages of classical GIC, a unique concept called EQUIA (GC Europe, Leuven, Belgium) was introduced in 2007 which tries to combine the main advantages (self-adhesion, bulk application, improved mechanical properties) of the highly viscous GIC (Fuji IX GP Extra) with a nano-filled, light curing varnish (G-Coat Plus) to provide protection in the early maturation phase for improved strength [11] and an improved surface hardness. So far, only results of one clinical prospective short-term study under ideal university environment conditions have been published [12].

The aim of the present retrospective cohort study was to evaluate the clinical performance of EQUIA used in a private practice environment in order to clarify, if a highly viscous GIC protected with a nano-filled, light curing varnish might be suitable as a permanent restoration material in Class I and/or Class II cavities under private practice conditions.