The polarized light microscopic appearance of caries-like lesions adjacent to restored cavities in the crowns and roots of extracted human teeth

Longitudinal clinical studies indicate consistently that secondary caries is the major cause of failure of restorations. Recently there has been an increase in the number of fluoride-containing materials coming to the market place and this has renewed the debate about the cariostatic effectiveness of such materials. The present study examined the histologic appearance of caries-like lesions adjacent to a non-fluoride-containing material (amalgam), a low fluoride-containing material (composite) and a moderate fluoride-containing material (glass-ionomer). The artificial caries system used to produce lesions has been previously reported and is a microbial system using Streptococcus mutans NCTC 10832. The lesions produced were similar to naturally occurring lesions in many respects, indicating the usefulness of this in vitro technique. Variations in the appearance of lesions were found adjacent to the different materials and the effect of the fluoride contained within two of the materials is discussed.     

Variability in cytotoxicity and fluoride release of resin-modified glass-ionomer cements

New-generation glass-ionomer cements contain resin to improve their restorative properties. These resin-modified glass-ionomer cements vary considerably in their chemistry, which could result in corresponding variability in their physical and biological properties. This study investigated the cytotoxicity and the fluoride release of two resin-modified glass ionomers, a conventional glass-ionomer cement, and a resin composite. Samples were prepared and extracted in distilled water for 1, 4, and 7 days; eluates were filtered and tested by means of 3T3 mouse fibroblasts. Cytotoxicity (MTT assay) values were low for all materials and extraction times, indicating minimal cytotoxicity of all materials (less than 30% inhibition). Cytotoxicity of one resin-modified glass ionomer was significantly higher than for the other materials (p < 0.001). One resin-modified glass ionomer and the conventional glass-ionomer cement released significantly more fluoride at each time interval (p < 0.001) than the other resin-modified glass-ionomer cement and the resin composite. Fluoride release and cytotoxicity were correlated (r2 = 0.60; p < 0.001), although the fluoride release does not account for the cytotoxicity observed. Cytotoxicity and fluoride release suggest that one hybrid behaved more like a conventional glass ionomer, and the other like a resin composite. These differences may have implications for material selection in specific clinical situations.     

Ultrastructural evaluation following catheterization of the fallopian tube with a hysteroscopic catheter

PURPOSE: The purpose of this study was to determine the in vitro effects of a resin-modified glass-ionomer restorative material on human enamel. METHODS: Enamel specimens were restored with Photac-Fil, a resin-modified glass ionomer; Ketac-Fil, an autopolymerizing glass ionomer and silver amalgam. The samples were pH cycled and then subjected to an artificial caries challenge. Specimens were evaluated by fluoride microdrill biopsy and quantitative microradiography at 1, 2, and 3 mm from restorations. Data on fluoride content, lesion depth, and mineral content were analyzed by one-way ANOVA, Student's t test, Neuman-Keuls procedure (multiple [pairwise] comparison), and Pearson's product-moment correlation tests. RESULTS: There were significant differences in fluoride uptake, lesion depth, and mineral density between groups. Significant correlational relationships were also determined. CONCLUSION: This study demonstrates that Photac-Fil and Ketac-Fil prevent in-vitro demineralization of enamel and suggests different mechanisms of action for each material.     

Artificial caries formation around fluoride-releasing restorations in roots

Secondary caries is one of the most important factors leading to replacement of dental restorations. This investigation assessed the capacity of fluoride-releasing restorative materials to resist caries in vitro when used in roots. Class 5 cavities were prepared in the buccal and lingual surfaces of 30 extracted premolars. The six materials used were: glass-ionomer cement (Fuji), glass-ionomer cement with silver particles added (Ketac-silver), fluoride-containing composite resin (Tetric), composite resin (Silux plus), fluoride-containing amalgam (Fluor-Alloy) and high-copper amalgam (Dispersalloy). After 5 weeks in an acid gel for caries-like lesion formation, the teeth were sectioned longitudinally and examined with polarized light. The results showed that repair with glass-ionomer materials of a carious lesion may be of great importance in the prevention of secondary caries around the restorations in roots.     

The effect of a resin-modified glass ionomer restorative material on artificially demineralised dentine caries in vitro

OBJECTIVES: Recurrent caries is one of the most common reasons for the replacement of restorations. One method of reducing the frequency of this problem may be by using fluoride-releasing restorative materials. The aim of this in vitro study was to evaluate the progression of artificial lesions around resin-modified glass ionomer (Vitremer) restorations placed in root surfaces. Class V cavities were prepared on the mesial and distal surfaces of 28 human premolar teeth. Artificial carious wall lesions were created in all cavities. The root of each tooth was then hemisected through the middle of the two cavities, before being restored with either the glass ionomer or amalgam, while the opposing cavities on the same root portion were varnished as negative controls. Forty-eight specimens were pH-cycled in remineralising and demineralising solutions for 20 h and 4 h, respectively, each day for 4 weeks, whilst in a smaller control group of eight specimens, the demineralising solution was replaced with deionised water. Mineral changes in the carious lesions were evaluated using contact microradiography. RESULTS: Results showed that varying degrees of subsurface demineralisation and remineralisation were evident, with a laminated appearance in lesions adjacent to the glass ionomer. There was higher remineralisation in the glass ionomer-filled cavities compared with the amalgam-filled cavities. In the water-cycled group, glass ionomer showed an increase in mineral content (p < 0.05), while no changes were observed in the amalgam-filled cavities. CONCLUSIONS: This model has shown that glass ionomer has a greater potential than amalgam for remineralisation of artificially created wall lesions within an acidic environment.     

The epidemiology of Neisseria gonorrhoeae isolates in Greenland 1979-1990: the emergence, spread and disappearance of non-PPNG strains carrying the conjugative 38.9 kb plasmid

The aim of this study was to compare the clinical performance of an amalgam, a glass polyalkenoate (ionomer) cerment material and a resin-based composite material used in small Class II cavities in permanent teeth. All restorations were inserted under rubber dam. They were examined yearly for 3 years. One clinician continued the study up to 5 years. The clinical examination focused on two criteria: clinically acceptable and failure. In addition, impressions were taken of the prepared cavities immediately before restoration and at each clinical examination using an elastomeric material. The study comprised 274 Class II restorations (88 amalgams, 95 cerments and 91 resin composites) placed in 142 adolescent patients. One hundred and sixty-seven restorations were in molar and 107 in premolar teeth. Patient dropout after 5 years resulted in the loss of 161 restorations, evenly distributed for restorative material and type of tooth involved. Four amalgam restorations, 22 glass ionomer cerment and nine resin composite restorations failed. The glass ionomer cerment and amalgam restorations failed primarily due to bulk fractures, while the resin composite restorations failed due to secondary caries and bulk fractures.     

Ten-year longitudinal clinical evaluation of a visible light cured posterior composite resin

Using modified USPHS criteria, we evaluated annually for ten years 91 cases restored with visible light cured posterior composite resin LFP (Base resin: UDMA; filler: micro crushed type, alumino-silicate, barium glass and silica, 85 wt%, 74 vol%). The 91 cases restored with LFP decreased to 68 in ten years. Of the 23 cases that were lost, one resulted from a pulpal reaction immediately following restoration, four were extracted owing to periodontal disease or extrusion of third molars, two became abutments owing to loss of an adjacent tooth, eight had recurrent caries, and eight were lost owing to caries on a surface having no relationship to the composite resin restoration. Because we observed comparatively little wear, good marginal adaptability, and no discoloration, we concluded that the ten-year clinical success of LFP was on the whole very good, and that this resin has adequate clinical merit as a restorative material for posterior teeth when restricted to restorations covering comparatively small areas.     

Fluoride release from tooth-colored restorative materials: a 12-month report

BACKGROUND: This study measured the amount of fluoride released from three light-activated glass polyalkenoate (ionomer) cements, a conventional glass polyalkenoate, a compomer and a fluoridated composite over a period of 12 months. METHODS: Five discs (7 x 2 mm) of each material were sequentially immersed in 4 mL portions of deionized water at 37 degrees C and before each measurement, the test specimen was rinsed with 1 mL of deionised water. An Orion Model 901 microprocessor digital Ionalyzer was used for the measurements and the data obtained were converted into microgram/cm2. The amount of fluoride released was measured 86 times during the 12-month test period. RESULTS: It was found that the pattern of fluoride release from the light-activated glass polyalkenoates was similar to that of the conventional glass polyalkenoate. The light-activated glass polyalkenoates, however, released significantly more fluoride than the conventional material. The composite and the compomer released significantly less fluoride than any glass polyalkenoate tested and the difference between the composite and the compomer was not significant. CONCLUSION: It was concluded that the light-activated glass polyalkenoates tested released more fluoride than a conventional glass polyalkenoate, a compomer or a composite, and that with regard to fluoride release the compomer behaved more or less like the composite.     

The use of liners under amalgam restorations: an in vitro study on marginal leakage

OBJECTIVE: Marginal leakage of amalgam restorations may lead to secondary caries and pulpal damage. The purpose of this study was to determine the effect various cavity liners might have on microleakage. METHOD AND MATERIALS: Mesio-occlusodistal amalgam restorations with margins on enamel and dentin were treated with different liner materials (an adhesive system, a topical fluoride gel, a cavity varnish, and a glass-ionomer cement) in vitro. Following restoration, the teeth were submitted to thermocycling in a stained solution and sectioned to allow assessment of microleakage. RESULTS: On enamel, the control group (no liner) and the glass-ionomer-lined group had equivalent leakage scores and were superior to every other group. On dentin, only the glass-ionomer specimens had superior performance. The cavity varnish and fluoride-lined specimens exhibited the highest leakage scores. CONCLUSION: The use of liners does not reduce microleakage on amalgam restorations when the cavity margins remain on enamel. On dentin margins, a glass-ionomer liner can reduce microleakage.     

Effectiveness of caries removal by the partial tunnel preparation method

The tunnel preparation method is designed to remove approximal caries through a channel from the occlusal surface while preserving the marginal ridge. This method entails reduced access to the caries lesion and thereby uncertainty as to the complete removal of caries. The purpose of the present investigation was to study the effectiveness of caries removal in 60 extracted premolars and molars by the partial tunnel preparation method. The glass polyalkenoat (ionomer) filling and the distance to the pulp were also examined. Examination of the sectioned teeth showed residual caries in the axial wall of two teeth and in dentin close to the enamel lesion in 10 teeth. Very few porosities were found within the glass polyalkenoat material and at the interface between the filling and the cavity walls.     

Uptake and release of fluoride by saliva-coated glass ionomer cement

The 'recharging' of aged glass ionomer cement restorations with fluoride by exposing them to a concentrated NaF solution has been suggested to improve their performance as devices with slow fluoride release. We have studied the interference of salivary coatings on glass ionomer cement with the uptake of fluoride in vitro. Freshly prepared glass ionomer discs were leached in distilled water for 14 weeks, then incubated in human saliva for 2 h, 24 h or 1 week before exposure to 0.53 M NaF (1% fluoride) for 5 min. Fluoride uptake by the cement was measured indirectly as the subsequent increase in fluoride release. A 2-hour incubation in saliva reduced the fluoride uptake by half, a 24-hour incubation by 74%. The major part (93-95%) of the fluoride that was taken up was released on the first day. A 1-week salivary coating reduced the uptake by 49%, but also caused some retardation of the fluoride release: 80% of the total release was on the first day. It was concluded that despite the considerable interference by salivary coating, the amount of fluoride that can be taken up by aged glass ionomer cement remains significant. However, the fast release will limit the usefulness of such recharging in vivo.     

Pulp response in primary teeth with deep residual caries treated with silver fluoride and glass ionomer cement ('atraumatic' technique)

Histological assessment of the dental pulps of 55 carious primary teeth was carried out 3 to 58 months after treatment by the 'atraumatic' technique involving application of 40 per cent silver fluoride to residual caries followed by restoration with glass ionomer cement. Fifty of the 55 teeth examined showed a favourable pulpal response, inducing presence of abundant reparative dentine and a wide odontoblast layer. Histological comparisons were made between these teeth and others not treated with silver fluoride but restored with glass ionomer cement, amalgam or zinc oxide and eugenol. Possible mechanisms of the action of silver fluoride in arresting residual caries are discussed. The question of whether or not treatment of carious dentine with silver fluoride represents a biologically acceptable clinical procedure cannot be answered on the basis of pulpal histology alone. The very high concentration of fluoride in commercial preparations of silver fluoride raises several questions concerning its clinical safety.     

Replacements of restorations in the primary and young permanent dentition

The present study focused on the type of restorative material used and the reasons for replacements of restorations in the primary and the young permanent dentition. All patients with restorations and who were 8 and 19 years of age in 1995 and were regularly treated at 11 Public Dental Health clinics in J?nk?ping County, Sweden, participated in the study. Data were extracted from the records for all types of restorations in canines and molars for the preceeding of 5 years for the 8-year-olds (i.e. from 3 to 8 years of age; n = 546) and for approximal restorations in premolars and molars for the preceeding 13 years for the 19-year-olds (i.e. from 6 to 19 years of age; n = 606). In all, 6012 restorations were evaluated. The two most common restorative materials used in the primary dentition were compomer and glass ionomer cement and in the young permanent dentition composite and amalgam. In the primary dentition, 29% of the restorations had been replaced and 4% of the teeth with restorations had been extracted. Thus, 33% of the restorations in the primary dentition failed. The corresponding figure for the young permanent dentition was 13%. The most common reason for replacements in the permanent dentition was secondary caries. That restorations often fail because of caries and that the development of secondary caries is not prevented by replacement of an old restoration indicate that more attention should be paid to preventive dental care for patients with restorations in the primary as well as in the young permanent dentition.     

Root surface treatment with glass ionomers and resin composites

Recommendations for restorative treatments of root surfaces are made difficult by a lack of information on the etiology of root conditions and on the clinical performance of available materials used to treat these conditions. Resin composite and glass ionomer materials are popular restorative materials because they are esthetic and can bond to tooth structure. However, the role each can play in restoration of root surface lesions is not well documented. This article presents a rationale for using these materials for a number of restorative situations.     

Low-frequency ultrasound treatment of chronic venous leg ulcers in an outpatient therapy

An in vitro dye leakage study was performed to compare the sealing ability of glass ionomer, composite resin and glass ionomer/resin cement when used as restorative materials for G.V. Black class V cavities. In this research, standard Class V cavities were prepared in sound premolar teeth extracted for orthodontic reasons. The cavities were randomly divided into 3 groups. After filling the cavities with glass ionomer cement, composite resin and light curing glass ionomer/resin cement, the specimens were immersed in silver nitrate solution. Marginal microleakage at the interface between the cavity wall and restoration was evaluated. The results were analyzed by using Kruskal-Wallis and Mann Whitney U tests. Result of this in vitro study indicate that composite resin and glass ionomer/resin cement provide a better seal than glass ionomer cement.     

Effect of peroxide bleaches on fluoride release of dental materials

PURPOSE: To investigate the effect of two bleaching agents, 35% hydrogen peroxide (Superoxal) and 10% carbamide peroxide (Opalescence), on the release of fluoride from Ketac-Fil, a glass ionomer cement, Photac-Fil, a glass ionomer/resin hybrid; and Tetric, a resin composite with fluoride. MATERIALS AND METHODS: Seven disks (9 x 3 mm) of each material were immersed in Superoxal for 1 hour to simulate an in-office application; seven other disks of each material were immersed in Opalescence 1 hour daily for 7 days to simulate a week of home bleaching regimen; and seven additional disks of each material without bleach served as a control. The disks were kept in deionized water and the water was tested for fluoride released every 24 hours for 14, 21, 28, and 35 days, respectively. RESULTS: Repeated measures ANOVA showed that the mean daily release of fluoride did not differ significantly (P > 0.05) between the bleaching agents or the control: Superoxal 6.17 ppm, Opalescence 6.45 ppm, and control 6.50 ppm. Statistically significant differences (P < 0.05) occurred for mean daily fluoride (+/- standard error) released from the three materials over the 35-day period: Photac-Fil 12.31 +/- 0.48 ppm > Ketac-Fil 7.07 +/- 0.66 ppm > Tetric 0.12 +/- 0.01 ppm, respectively.     

Tunnel restorations. A 3 1/2-year follow up study of Class I and II tunnel restorations in permanent and primary teeth

During 1988-89, 224 patients with approximal caries in the premolar/molar regions were provided with 318 tunnel restorations. In case of perforation of the enamel in the enamel/dentin border, (23%), complete Class II-tunnel restorations with glass ionomer cement and composite resin were made. In case of "intact" enamel, (77%), partial Class I-tunnel restorations were made. The restorations were controlled at annual routine recalls and the success rate after 3 1/2 years was 74% for permanent teeth, and 10% for primary teeth. Restorations in permanent teeth, made during the second year of the study were successful in 82%, as compared with 62% for restorations made during the first year, indicating a learning effect. Failures in the permanent dentition were due to marginal ridge fracture (35%), cavitation in the approximal enamel (31%), and recurrent caries (38%). Failures in primary teeth were predominantly due to marginal ridge fractures (84%). A comparison with the longevity of conventional Class II restorations is made and the possible advantages of the present method are presented.     

Arrest of root surface caries in situ

This study tests the hypothesis that daily oral hygiene combined with topical fluoride arrests active root-surface caries lesions without changing the mineral content of the lesions. Therefore, changes in mineral content and distribution were studied in root surfaces during caries lesion development and subsequent arrest of lesion progression in situ. In 18 subjects, lesions were developed during 3 months in sound root-surface specimens inserted into lower partial dentures. After 3 months, ground sections were prepared from each lesion prior to re-insertion of the specimens into the dentures. In addition, one sound root specimen was added per subject. During the following 3 months, half of the subjects cleaned both sound and carious specimens once a day with an 1100-ppm fluoride toothpaste, and the specimens were treated twice with 2% NaF for 2 min in situ. The other half of the subjects continued the experiment without cleaning. During the initial three-month period, all specimens developed subsurface lesions extending 187 to 583 microm into the dentin. Lesion depth increased somewhat in both experimental groups during the following 3 months (P > or = 0.1). There was a non-significant increase in mineral loss in the plaque-covered specimens (P = 0.08). However, the total mineral content of specimens subjected to plaque removal and topical fluoride did not change. This treatment resulted in an increased mineral content in the surface layer (P < 0.01) and formation of a zone of higher mineral content within the body of the lesion. The sound root surfaces which had been cleaned for a three-month period showed mineral uptake in the surface layer, occasionally associated with subsurface demineralization extending 20 to 70 microm into the tissue. The mineral loss of these specimens was significantly smaller than that of plaque-covered surfaces (P < 0.001). It is concluded that daily plaque removal and topical fluoride use influence the distribution of mineral in sound and carious root surfaces and may arrest lesion progression without affecting the total mineral content.     

Bond strengths of fluoride-releasing restorative materials

PURPOSE: To compare the shear bond strengths to dentin of four tooth-colored fluoride-releasing restorative materials that utilize different mechanisms of dentin-bonding. MATERIALS AND METHODS: Four materials were tested: a chemically-cured glass ionomer (Ketac-Fil); a light-cured resin-modified glass ionomer (Photac-Fil); a light-cured resin-modified glass ionomer in conjunction with a resin dentin-bonding agent (Vitremer); and a light-cured resin composite in conjunction with a resin dentin-bonding agent (Tetric). The enamel was removed from four sides of the twenty human noncarious extracted molars which had their roots embedded in acrylic blocks. Cylindrical samples of the materials were prepared in plastic molds and bonded to the dentin surface according to the manufacturers' instructions. After 24 hours of storage in a humidor, the samples were sheared with an Instron testing machine at a crosshead speed of 0.5 mm/minute. RESULTS: Statistical evaluation (ANOVA and Duncan's test) suggests that the fluoride-releasing resin composite material utilizing a resin dentin-bonding agent provided a significantly greater mean shear bond strength (16.5 MPa) after 24 hours storage than any of the selected glass ionomer materials. Of the three glass ionomer materials compared, the light-cured resin-modified material with a resin dentin-bonding agent provided a significantly greater mean shear bond strength (6.7 MPa) than the light-cured resin-modified material without a resin dentin-bonding agent (3.0 MPa) or the chemically-cured material (3.8 MPa).     

In vitro inhibition of caries around a resin composite restoration containing antibacterial filler

Class V cavities were prepared and restored with resin composite containing antibacterial filler powder (Apacider-AW, Ap-AW) using experimental restorations. The restored teeth were incubated in vitro with the cariogenic bacteria Streptococcus mutans IFO 13955. Ground sections were then prepared and examined using macrophotography. Lesions of the outer and inner wall were noted, and the depths of which the lesions penetrated were measured. We found that, in restorations containing 1-5 wt% Ap-AW, caries penetrated the marginal area, while in restorations containing 10 wt% Ap-AW the margin remained free of caries out to a distance of about 1.1 and 1.8 mm on the occlusal and gingival sides, respectively.