Ion concentration adjacent to glass-ionomer restorations in primary molars

Abstract

Objectives

The aim was to compare the levels of fluoride, calcium and phosphorus in enamel and dentin alongside glass-ionomer-based restorations over time.

Methods

This CCT consisted of children with cavities in the occlusal surface of primary molars that were restored with either a high-viscosity (Fuji IX GP ® ) or a resin-modified glass-ionomer (Vitremer ® ), being the test groups. Sound teeth (controls) were harvested from the children belonging to the test groups. Sampled teeth were cut in half and the ion concentration measured using EPMA. ANOVAs, and Newman–Keuls tests were performed to analyze the data. The study sample consisted of 35 children having 29 teeth per group available for analyses.

Results

Although statistically significantly higher, the mean ion-concentration of calcium in enamel and dentin, and that of phosphorous in dentin hardly differed between the tests and control groups. The mean fluoride concentration in enamel (0.20 ppm × 10 3 and 0.24 ppm × 10 3 ) and dentin (0.71 ppm × 10 3 and 0.78 ppm × 10 3 ) surrounding the Fuji IX GP ® and Vitremer ® restored teeth, respectively was statistically significantly higher than in enamel (0.12 ppm × 10 3 ) and dentin (0.12 ppm × 10 3 ) for the control teeth.

Significance

The present in vivo investigation showed that fluoride ions are released from high-viscosity and resin-modified glass-ionomer primary restoration into the restorations’ surrounding enamel and, and in particular, dentin.

Introduction

Contemporary conventional restorative care is governed through the caries management concept of Minimal Intervention Dentistry (MID) . This concept, among other things, seeks to preserve partly demineralized tooth tissues through the use of evidence-based preventive measures and minimally invasive operative techniques. These techniques are characterized by removing decomposed (infected) dentin and leaving demineralized (affected) dentin behind. Fusayama has shown that demineralized dentin left under a resin composite restoration remineralizes over time. This physiological effect was ascribed to the deposition of calcium and phosphate ions on the partly demineralized hydroxyapatite crystals of the demineralized dentin by the living odontoblast process. However, remineralization of demineralized dentin also appears to occur through diffusion of ions (Ca 2+ , Sr 2+ , Mg , F ) from glass-ionomer restorative materials as shown in artificially demineralized dentin in monkey teeth and in naturally occurring demineralized dentin in permanent teeth . Increased fluoride ion concentration has been reported in dentin that surrounded freshly cut cavities in sound dentin and that was restored with an auto-cured glass-ionomer compared to dentin in unrestored teeth in vivo . The same phenomenon was observed in the enamel and dentin surrounding auto-cured glass-ionomer restorations in primary teeth .

Studies on the remineralization of demineralized dentin in primary teeth in vivo are few. Massara et al. , reported an 18% increase in calcium but no increase in fluoride content of demineralized and, most probably, also decomposed dentin under auto-cured glass-ionomer restorations in primary molars after 3 months. Remineralization of demineralized dentin in primary teeth, evidenced by an increase in microhardness over time in the dentin surrounding the restorations, has been reported for high-viscosity glass-ionomer and resin-modified glass-ionomer . Using Electron Probe Micro-Analyzer (EPMA), fluorine and strontium ions were detected in residual (decomposed and demineralized) dentin surrounding high-viscosity glass-ionomer restorations in primary teeth, suggesting that glass-ionomer material is able to remineralize residual dentin . Remineralization of demineralized dentin may be dependent on the concentration of apatite crystals in the collagen matrices of the demineralized dentin .

As insufficient information on the remineralizing potential of glass-ionomers on enamel and demineralized dentin in primary teeth is available, it is important to further investigate this phenomenon. The outcomes will aid dental practitioners in their decision which restorative material to use when treating cavitated dentin lesions in primary teeth under the MID concept. The current study has gained in importance as there is an ongoing discussion at the UNEP (United Nations Environment Programme) about reducing amalgam in the coming decades and, as a result, both FDI and WHO have called for testing environmentally friendly materials to restore tooth cavities in children. Eventually, the present study will contribute to the pool of knowledge on the biological potential of glass-ionomer cement in oral health.

The null hypotheses tested were that there is no difference in the concentration of fluoride, calcium and phosphate ions in (1) enamel and (2) demineralized dentin in primary molars after restoring the cavity with a high-viscosity and a resin-modified glass-ionomer cement in vivo and (3) between the two glass-ionomer cements in enamel and dentin.

Material and methods

Subjects

Subjects were selected from children who attended the pediatric dental clinic of the University Hospital of Brasília for dental care. Children were clinically and radiographically examined. The inclusion criteria were children with: (1) an active dentin cavitated lesion in the occlusal surface of a primary molar without pulp involvement but with the following characteristics: the base of the radiographic carious lesion be situated within in the middle-1/3 of the dentin thickness; the buccal-lingual width of the carious lesion be no greater than 1/4 of the intercuspal width, and the tooth is not expected to exfoliate within the next 6 months, and with: (2) at least one sound primary molar with at least 2/3 of the root resorbed, or a primary molar that is indicated for extraction due to orthodontics reasons. After an intake period of 9 months, 40 children complied with the inclusion criteria. The study was approved by the Ethical Committee of the Health Sciences Center of the University of Brasília (045/2001) and only children whose parents signed the informed consent form were enrolled in the study.

Study design

The study was a controlled clinical trial were the control group (GC) consisted of sound teeth from the same children belonging to either of two experimental groups. All selected cavities were restored either (1) with a powder-liquid mixed high-viscosity glass-ionomer cement Fuji IX GP ® (GC, Tokyo, Japan) (GHv), or (2) with a resin-modified glass-ionomer cement, Vitremer ® (3 M/ESPE, MN, USA) (GRm). Following their sequence of appearance at the dental clinic, children were allocated alternatively to GHv or GRm.

Treatment procedures

All children were born and had lived all their live in Brasília, Brazil whose water supply system is artificially fluoridated (0.7 ppm). They had brushed their teeth with a 1100 ppm fluoridated toothpaste regularly. All children were submitted to the same oral health preventive scheme that consisted of oral hygiene instructions and diet counseling at the beginning of the treatment session(s) and of fluoride varnish (Fluorniz, SS White, Rio de Janeiro, Brazil) application at the final restoration session.

Restorations in primary molars were performed under local anesthesia and rubber dam isolation by one dentist (RCN). If needed, the cavity opening was widened with a high-speed handpiece and a round diamond point number 1011 or 1012 (KG Sorensen, Rio de Janeiro, Brazil) cooled with air/water spray. Decomposed dentin was removed using hand instruments until resistance was felt. The cavities were then conditioned either for 15 s using the glass-ionomer liquid in GHv, or for 10 s using the supplied primer in GRm. The high-viscosity glass-ionomer was hand-mixed, inserted in the cavity, and after bite check and removal of excess material, the restoration was protected from saliva through application of the supplied varnish (GHv). Resin-modified GIC was syringed into the cavity, cured for 40 s using the Ultralux light curing unit (Dabi Atlanti, Ribeirão Preto, Brazil), polished with a fine-grade diamond point (KG Sorensen) and finished through applying the supplied liquid gloss (GRm).

Parents were provided with marked bottle(s) containing 0.9% saline solution to store exfoliated teeth at home and were instructed to take the bottle(s) to the pediatric dental clinic at the monthly recall visit. Oral hygiene instructions were then provided and very mobile sound and restored teeth, without visible signs of cavitated dentin lesions, were carefully removed and kept in 0.9% saline solution.

Laboratory procedures

Sampled teeth were cut in halves in a mesio-distal direction with a diamond coated disc (KG Sorensen, Rio de Janeiro, Brazil), from which one half was cut into ten slices and used for ion content measurement. The slices were ground using a 3000 silicium carbide disc (M Almeida Com Ltda, São Paulo, Brazil) to produce a flat surface of 0.04 mm thickness. Surface polishing was performed with a 120 aluminum oxide and 3000 silicium carbide disc under water spray and was completed using a diamond paste (Tyrolit Lt, São Paulo, Brazil). The polished slices were mounted on glass slabs and coated with pure carbon-graphite (Edwards High Vacuum International, Crawley, England) and stored for analysis.

Chemical analyses were performed at the Electronic Micro Probe Laboratory of the Geology Institute of the University of Brasília, by an experienced technician who was blinded to the origin of the samples. All readings were made in triplicate and the mean score was used in the analyses. The fluoride, calcium and phosphorus concentrations (ppm) in enamel and dentin were measured by means of an Electron Probe Micro-Analyzer (CAMECA SX50, Courbevoie-Cedex, France) equipped with 4 WDS (wavelength dispersive system) spectrometers, operating with an electronic beam energy of 20 kV and an electron beam flow of 25 mA. The electron beam diameter was equal to 10 μm.

Fluorapatite was the reference point. The readings in enamel were based on 5 spots for G1 and 10 spots for both GHv and GRm, the reading in dentin on 3 spots for GC and 5 spots for both GHv and GRm, which are illustrated approximately in Fig. 1 a and b. The spots were marked on enamel and dentin with the aid of a ruler under an optical microscope at 400× magnification, in the following manner. GC – enamel: the first spot was marked near the enamel–dentin junction (EDJ), the second spot in the middle of the enamel thickness and the third spot near the outer surface. Two other spots were positioned to the right of the second spot. GC – dentin: The three spots were positioned in the middle of the dentin thickness ( Fig. 1 a). GHv and GRm – enamel: following the same pattern as described for GC, five spots were positioned at each side of the restoration. GHv and GRm – dentin: three spots were positioned equidistant underneath the floor of the restoration. One spot was also positioned near the axial wall and another spot to the right of it ( Fig. 1 b).

Fig. 1
Position of measuring spots in enamel and dentin in GC (a) and in GHv and GRm (b).

Statistical analysis

The JPM 9 software (SAS Institute, USA) was used for statistical analysis of data. The ion concentrations for each tooth were averaged, and the means were used for statistical analyzes. Logarithmical transformation was applied to data from fluoride and calcium concentrations in enamel to obtain normality. Descriptive statistics were reported as means and standard errors of non-transformed data. ANOVAs were used to test the null-hypothesis of no difference among groups. Newman–Keuls tests were used to perform multiple comparisons. The level of statistical significance was set at 5%.

Material and methods

Subjects

Subjects were selected from children who attended the pediatric dental clinic of the University Hospital of Brasília for dental care. Children were clinically and radiographically examined. The inclusion criteria were children with: (1) an active dentin cavitated lesion in the occlusal surface of a primary molar without pulp involvement but with the following characteristics: the base of the radiographic carious lesion be situated within in the middle-1/3 of the dentin thickness; the buccal-lingual width of the carious lesion be no greater than 1/4 of the intercuspal width, and the tooth is not expected to exfoliate within the next 6 months, and with: (2) at least one sound primary molar with at least 2/3 of the root resorbed, or a primary molar that is indicated for extraction due to orthodontics reasons. After an intake period of 9 months, 40 children complied with the inclusion criteria. The study was approved by the Ethical Committee of the Health Sciences Center of the University of Brasília (045/2001) and only children whose parents signed the informed consent form were enrolled in the study.

Study design

The study was a controlled clinical trial were the control group (GC) consisted of sound teeth from the same children belonging to either of two experimental groups. All selected cavities were restored either (1) with a powder-liquid mixed high-viscosity glass-ionomer cement Fuji IX GP ® (GC, Tokyo, Japan) (GHv), or (2) with a resin-modified glass-ionomer cement, Vitremer ® (3 M/ESPE, MN, USA) (GRm). Following their sequence of appearance at the dental clinic, children were allocated alternatively to GHv or GRm.

Treatment procedures

All children were born and had lived all their live in Brasília, Brazil whose water supply system is artificially fluoridated (0.7 ppm). They had brushed their teeth with a 1100 ppm fluoridated toothpaste regularly. All children were submitted to the same oral health preventive scheme that consisted of oral hygiene instructions and diet counseling at the beginning of the treatment session(s) and of fluoride varnish (Fluorniz, SS White, Rio de Janeiro, Brazil) application at the final restoration session.

Restorations in primary molars were performed under local anesthesia and rubber dam isolation by one dentist (RCN). If needed, the cavity opening was widened with a high-speed handpiece and a round diamond point number 1011 or 1012 (KG Sorensen, Rio de Janeiro, Brazil) cooled with air/water spray. Decomposed dentin was removed using hand instruments until resistance was felt. The cavities were then conditioned either for 15 s using the glass-ionomer liquid in GHv, or for 10 s using the supplied primer in GRm. The high-viscosity glass-ionomer was hand-mixed, inserted in the cavity, and after bite check and removal of excess material, the restoration was protected from saliva through application of the supplied varnish (GHv). Resin-modified GIC was syringed into the cavity, cured for 40 s using the Ultralux light curing unit (Dabi Atlanti, Ribeirão Preto, Brazil), polished with a fine-grade diamond point (KG Sorensen) and finished through applying the supplied liquid gloss (GRm).

Parents were provided with marked bottle(s) containing 0.9% saline solution to store exfoliated teeth at home and were instructed to take the bottle(s) to the pediatric dental clinic at the monthly recall visit. Oral hygiene instructions were then provided and very mobile sound and restored teeth, without visible signs of cavitated dentin lesions, were carefully removed and kept in 0.9% saline solution.

Laboratory procedures

Sampled teeth were cut in halves in a mesio-distal direction with a diamond coated disc (KG Sorensen, Rio de Janeiro, Brazil), from which one half was cut into ten slices and used for ion content measurement. The slices were ground using a 3000 silicium carbide disc (M Almeida Com Ltda, São Paulo, Brazil) to produce a flat surface of 0.04 mm thickness. Surface polishing was performed with a 120 aluminum oxide and 3000 silicium carbide disc under water spray and was completed using a diamond paste (Tyrolit Lt, São Paulo, Brazil). The polished slices were mounted on glass slabs and coated with pure carbon-graphite (Edwards High Vacuum International, Crawley, England) and stored for analysis.

Chemical analyses were performed at the Electronic Micro Probe Laboratory of the Geology Institute of the University of Brasília, by an experienced technician who was blinded to the origin of the samples. All readings were made in triplicate and the mean score was used in the analyses. The fluoride, calcium and phosphorus concentrations (ppm) in enamel and dentin were measured by means of an Electron Probe Micro-Analyzer (CAMECA SX50, Courbevoie-Cedex, France) equipped with 4 WDS (wavelength dispersive system) spectrometers, operating with an electronic beam energy of 20 kV and an electron beam flow of 25 mA. The electron beam diameter was equal to 10 μm.

Fluorapatite was the reference point. The readings in enamel were based on 5 spots for G1 and 10 spots for both GHv and GRm, the reading in dentin on 3 spots for GC and 5 spots for both GHv and GRm, which are illustrated approximately in Fig. 1 a and b. The spots were marked on enamel and dentin with the aid of a ruler under an optical microscope at 400× magnification, in the following manner. GC – enamel: the first spot was marked near the enamel–dentin junction (EDJ), the second spot in the middle of the enamel thickness and the third spot near the outer surface. Two other spots were positioned to the right of the second spot. GC – dentin: The three spots were positioned in the middle of the dentin thickness ( Fig. 1 a). GHv and GRm – enamel: following the same pattern as described for GC, five spots were positioned at each side of the restoration. GHv and GRm – dentin: three spots were positioned equidistant underneath the floor of the restoration. One spot was also positioned near the axial wall and another spot to the right of it ( Fig. 1 b).

Nov 28, 2017 | Posted by in Dental Materials | Comments Off on Ion concentration adjacent to glass-ionomer restorations in primary molars
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