Hypermineralization of dentinal lesions adjacent to glass-ionomer cement restorations

Demineralisation and remineralisation of dentine caries, and the role of glass-ionomer cements

In accordance with the principles of modern operative dentistry, to conserve tooth structure and to use therapeutic restorative materials, an understanding of the carious process in dentine and the biological properties of glass-ionomer cements (GICs) are necessary. Delineation of the outer necrotic from the inner vital and remineralisable carious dentine allows for the preservation of tooth structure. This delineation is not possible when relying on visual and tactile perceptions, but requires the use of a caries detecting dye. GICs are ideal dentine substitutes because of their anticariogenic properties, stable long-term ionic bonding, and ability to assist the process of remineralization. The range of usage of these restorative materials continues to expand with the development of improved products.

Minimal intervention dentistry--a review. FDI Commission Project 1-97

The concept of minimal intervention dentistry has evolved as a consequence of our increased understanding of the caries process and the development of adhesive restorative materials. It is now recognised that demineralised but noncavitated enamel and dentine can be 'healed', and that the surgical approach to the treatment of a caries lesion along with 'extension for prevention' as proposed by G V Black is no longer tenable. This paper gives an overview of the concepts of minimal intervention dentistry, describes suggested techniques for a minimally invasive operative approach, and reviews clinical studies which have been carried out in this area.

Current concepts on the theories of the mechanism of action of fluoride

The caries-preventive effect of fluoride is mainly attributed to the effects on demineralization/remineralization at the tooth oral fluids interface. Sub ppm levels of fluoride in saliva are effective in shifting the balance from demineralization, leading to caries, to remineralization. This is attributed to the fluoride-enhanced precipitation of calcium phosphates, and the formation of fluorhydroxyapatite in the dental tissues. Low fluoride levels are found in saliva after toothbrushing with fluoride containing dentifrices. Similar concentrations are ineffective in interfering with processes of growth and metabolism of bacteria, and also do not result in a significantly reduced dissolution of tooth mineral as a result of (firmly bound) fluoride incorporation. Comparative studies of fluoride efficacy have shown that higher concentrations in solution are needed in pH-cycling studies of dentine than in enamel to maintain the mineral balance or to induce remineralization. This is attributed to the greater solubility of the dentine and the smaller size of the dentine crystallites compared to enamel. Fluoride slow-release devices, in the form of fluoride-releasing restorative materials, may serve to increase the fluoride levels in saliva and plaque to levels at which caries can be prevented, also in high-risk patients. Research questions for the next millennium and future perspectives for fluoride applications should be found in the retention and slow release of fluoride after various combinations of fluoride treatment, the combination of fluoride and anti-microbial treatment, the individualization of caries prevention, and the combination of preventive schemes with new developments in caries diagnosis.

How effective is ART in the management of dental caries?

The ART approach involves excavating cavitated dentine caries with hand instruments, then restoring the cavity and sealing any associated fissures and pits with an adhesive restorative material, resulting in a sealant restoration. Until recently, ART has mainly been used under field conditions, and thus the adhesive restorative material used has been glass ionomer which does not require mixing machines and curing lights. Since the inception of ART, a growing number of studies world-wide have taken place. A total of four studies have reported 3-year survival percentages for one-surface ART restorations. The highest 3-year survival percentage in permanent teeth was 88%, which is comparable to the 85% survival of one-surface amalgam restorations placed under the same field conditions after 3 years. The outcomes depend to some extent on the material used, operator experience and presence of caries. The presence of caries as a reason for failure was higher in the early than in the most recent studies. Only one study has reported on the use of ART restorations in the deciduous dentition. It is concluded that: a very large proportion of dentine lesions in the permanent teeth can be treated using the ART approach; the 3-year survival rate of the more recently placed one-surface ART restorations in permanent teeth was higher than that of ART restorations placed in the beginning; the survival of one-surface ART restorations in the permanent dentition with newer glass ionomers is comparable to that of one-surface conventional restorations placed using amalgam in a comparable setting after 3 years; more studies of longer duration are needed to confirm these findings; ART should be considered a caries treatment modality that benefits people; and educational courses need to be organised before the approach is applied in the clinic.

A 4-year clinical study on amalgam, resin composite and resin-modified glass ionomer cement restorations in overdenture abutments

OBJECTIVE

To assess the performance of three different filling materials in overdenture abutment teeth.

METHODS

In 49 patients amalgam, resin composite and resin-modified glass ionomer cement were used to seal the root canal orifices of 155 overdenture abutment teeth. After initial preparation of the cavities, the three restorative materials were randomly assigned to the abutment teeth using a number of balancing criteria. All patients were reviewed every six months and received the same preventive regimen. Survival was assessed at two levels: Sorig (survival of the restoration independent from eventual maintenance treatments) and Scomp (restorations survived even without maintenance treatments).

RESULTS

The calculated overall survival percentage of the original restorations (Sorig) after four years was 63 +/- 6% (mean +/- SE). Calculation for the overall complete survival (Scomp) revealed a percentage survival of 57 +/- 6%. At both levels, the differences between the survivals of the investigated materials were not statistically significant (p-values > 0.05). Two abutments were lost, severe caries was the reason for one extraction and another abutment tooth was extracted for periodontal reasons.

CONCLUSIONS

The results of this study did not point out a superior restorative material for the seal of root canal orifices of overdenture abutments. The distribution of failures over the patients indicates a certain patient dependency.

Clinical performance and caries inhibition of resin-modified glass ionomer cement and amalgam restorations

BACKGROUND

The authors clinically examined two restorative materials to evaluate their effectiveness in Class II restorations in primary molars and their ability to inhibit recurrent caries.

METHODS

Forty subjects, each in need of two Class II restorations in primary molars, took part in this study. Each patient received one Class II restoration of resin-modified glass ionomer cement and one of amalgam. The authors evaluated the restorations at six-month, one-year, two-year and three-year recall appointments. On exfoliation, teeth with experimental restorations were retrieved and microscopically examined for inhibition of demineralization at restoration margins.

RESULTS

The results of the clinical evaluation demonstrated no significant differences between the resin-modified glass ionomer cement restorations and the amalgam restorations (P < .05). Polarized light microscopic examination of the returned teeth that were restored as a part of this study indicated that the resin-modified glass ionomer cement had significantly less enamel demineralization at restoration margins than did amalgam (P < .0001).

CONCLUSIONS

The resin-modified glass ionomer cement functioned clinically as well as amalgam for Class II restorations in primary molars. However, the resin-modified glass ionomer exhibited significantly less enamel demineralization at restoration margins than did amalgam.

CLINICAL IMPLICATIONS

Resin-modified glass ionomer cement restorative material functions well for Class II restorations in primary molars and exhibits less recurrent caries at restoration margins than does amalgam.

Fluoride release from restorative materials and its effects on dentin demineralization

As the use of adhesive restorative materials has increased during the last several years, interest in adhesive materials that release fluoride has also grown. The purpose of this study was to measure fluoride release from several adhesive restorative materials and to evaluate its effect on dentin resistance to demineralization and on bacterial metabolism in a modified in vitro system. Standardized cavities (1.8 mm in diameter) were prepared in bovine teeth that had been ground to dentin. One cavity in each tooth was restored with one of the following restorative systems: (a) Single Bond and Z100; (b) Single Bond and Tetric Ceram; (c) Fuji Bond LC and Z100; (d) Fuji Bond LC and Tetric Ceram; (e) Fuji II LC; or (f) Fuji IX GP. The other cavity in each tooth was "restored" with wax as a control. For each restorative system, 12 specimens were evaluated for fluoride release during the first 24 hrs after restoration placement. Dentin adjacent to the restored sites was subjected to lactic acid challenge (pH 4.3) for 3 hrs, after which calcium release was measured. Another 12 specimens in each group were stored for 24 hrs in de-ionized water, and were exposed to an S. mutans suspension (1:1 THB/de-ionized water and 50 mM glucose, A660 = 0.2) for 6 hrs, followed by calcium release and pH measurement. Bulk specimens of each material were also made and stored in water. Fluoride released from Fuji Bond LC, Fuji IX GP, and Fuji II LC in bulk was significantly greater than from the other materials. In the restored dentin specimens, increased resistance to demineralization from a lactic acid challenge was directly related to fluoride release. The same effects were seen as a result of the S. mutans challenge. While fluoride release from restorative materials increased the resistance of dentin to demineralization in this system, the clinical relevance of the findings is not known.

Fluoride release of glass ionomer-based luting cements in vitro

STATEMENT OF PROBLEM

There is considerable variation in generic formulation and in reported fluoride release from resin-modified glass ionomer luting cements.

PURPOSE

This study compared fluoride release from 2 generically similar resin-modified glass ionomer luting cements (Vitremer and Advance) with release from 2 conventional glass ionomer luting cements (Ketac-Cem and Fuji I).

MATERIAL AND METHODS

Ten specimen disks of each of the 4 luting cements were fabricated and immersed in deionized water in individual polystyrene jars. The jars were stored in a humidor at 37 degrees C between test periods. At the same time each day, for 28 days, fluoride release from each specimen disk was measured in parts per million by testing the storage water.

RESULTS

The 4 luting cements tested showed an initial high concentration of fluoride release during the first week, followed by a gradual decrease over the study period. Vitremer luting cement demonstrated the greatest mean cumulative fluoride release in parts per million over the study period (198), followed by Fuji I (140), Ketac-Cem (110), and Advance (99) luting cements.

CONCLUSIONS

Resin-modified glass ionomer luting cements showed fluoride release comparable to the conventional glass ionomer luting cements. Vitremer luting cement released more fluoride over the 28-day period than the other cements.

Longevity of extensive class II open-sandwich restorations with a resin-modified glass-ionomer cement

Several new techniques have been introduced for use in the esthetic restoration of posterior cavities to substitute for the presumed toxicity of amalgam. Composite-laminated glass-ionomer cement restorations, the sandwich technique, have been recommended for caries-risk patients. Clinical evaluation of the use of conventional glass-ionomer cements in the open-sandwich restoration has shown a high failure rate. The aim of this study was to evaluate the durability and cariostatic effect of a modified open-sandwich restoration utilizing a resin-modified glass-ionomer cement (RMGIC) in large cavities. The materials consisted of 274 mostly extensive Class II Vitremer/Z100 restorations performed by four dentists in 168 adults. Six experimental groups were investigated. In four groups a thick and in two groups a thin layer of cement was placed. Cavity conditioning before application of the RMGIC self-etching primer was done in 3 groups with polyacrylic acid and in one group with maleic acid; in two groups, only water rinsing was performed. The restorations were evaluated at baseline and after 6, 12, 24, and 36 months according to modified USPHS criteria (van Dijken, 1986). After 3 years, 239 restorations were evaluated. Twelve (5%) were estimated as non-acceptable. Two were replaced, and seven were repaired with resin composite. Tooth fractures were observed in 2.5%. Slight erosion of the RMGIC part was seen in 4%, and in one case operative treatment was indicated. Post-operative sensitivity was reported for 9 teeth. Forty-three percent of the patients were considered as caries-risk patients. Only one restoration showed secondary caries. The three-year results indicated that the modified open-sandwich restoration is an appropriate alternative to amalgam including extensive restorations.

The influence of luting cements on the fermentation of sucrose by oral microorganisms

OBJECTIVES

Three luting cements based on zinc oxide phosphate, glass ionomer or composite resin were compared with respect to their influence on the anaerobic fermentation of sucrose by human oral bacteria.

METHODS

Fifteen standardized samples of each of the three luting cements were prepared according to the manufacturer's instructions and stored for 72 h at 37 degrees C in distilled water, which was also used as elution medium. After removing the samples solutions were incubated with human fasting saliva, sucrose and a bicarbonate buffer in a Warburg apparatus. Intermediary organic acids resulting from anaerobic fermentation of sucrose were quantified indirectly by manometric measurement of CO2, released from the buffer.

RESULTS

The materials did not indicate either an accelerating or an inhibiting effect on the formation of organic acids from sucrose.

CONCLUSION

In the case of bacterial microleakage along the interface between cavity and luting cement, an inhibition of acid induced dentin or enamel demineralisation--using the materials investigated--cannot be expected.

ART restorations and glass ionomer sealants in Zimbabwe: survival after 3 years

Atraumatic restorative treatment (ART) consists of removing demineralised tooth tissues with hand instruments only, restoring the prepared cavity and sealing the adjacent pits and fissures with an adhesive filling material. This relatively painless, no-handpiece, minimal intervention approach to controlling dental caries is described. ART was applied in an oral health care programme in Zimbabwe that was carried out amongst secondary school students from 1994 to 1997. A new glass ionomer (Fuji IX) was used as the restorative and sealant material. Sealants were placed in high caries risk students using the 'press-finger' technique. A total of 297 one-surface ART restorations and 95 glass ionomer sealants were placed in 142 and 66 students, respectively. After 3 years, the lost-to-follow-up percentages for one-surface ART restorations and glass ionomer sealants were 30.6% and 30.5%, respectively. Actuarial (life table) analysis resulted in 3-year survival rates of one-surface ART restorations of 88.3% (95% CI: 92.4%-84.2%), ranging from 94.3% to 65.4% per operator. A total of 28 ART restorations placed in 25 students failed. Reasons for failure related to the material and the operator (11 restorations or 5.3% each), and to caries adjacent to the restoration (one restoration or 0.5%). Reasons for failure were not recorded for five restorations (2.3%). Sealants were placed on surfaces diagnosed as early enamel lesions. After 3 years, 71.4% (95% CI: 81.7%-61.1%) of the fully and partially retained sealants survived with a range of 100% to 55.6% per operator. Of the sealed surfaces 96.3% (95% CI: 100%-92.2%) survived 3 years without developing caries. Experienced operators placed better ART restorations than inexperienced operators. This study has demonstrated that ART with a glass ionomer restorative material and sealants provided high quality preventive and restorative dental care to this student population. ART has become one of the treatment modalities available to oral health workers in managing dental caries.

Dental luting agents: A review of the current literature

STATEMENT OF PROBLEM

The practice of fixed prosthodontic has changed dramatically with the introduction of innovative techniques and materials. Adhesive resin systems are examples of these changes that have led to the popularity of bonded ceramics and resin-retained fixed partial dentures. Today's dentist has the choice of a water-based luting agent (zinc phosphate, zinc polycarboxylate, glass ionomer, or reinforced zinc oxide-eugenol) or a resin system with or without an adhesive. Recent formulations of glass ionomer luting agents include resin components (resin-modified glass ionomers), which are increasingly popular in clinical practice.

PURPOSE

This review summarizes the research on these systems with the goal of providing information that will help the reader choose the most suitable material.

MATERIAL

The scientific studies have been evaluated in relation to the following categories: (1) biocompatibility, (2) caries or plaque inhibition, (3) microleakage, (4) strength and other mechanical properties, (5) solubility, (6) water sorption, (7) adhesion, (8) setting stresses, (9) wear resistance, (10) color stability, (11) radiopacity, (12) film thickness or viscosity, and (13) working and setting times. In addition, guidelines on luting-agent manipulation are related to available literature and include: (1) temporary cement removal, (2) smear layer removal, (3) powder/liquid ratio, (4) mixing temperature and speed, (5) seating force and vibration, and (6) moisture control. Tables of available products and their properties are also presented together with current recommendations by the authors with a rationale.

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.

Microhardness of in vitro caries inhibition zone adjacent to conventional and resin-modified glass ionomer cements

OBJECTIVE

This study was conducted to correlate Knoop and triangular hardness numbers by measuring the microhardness of in vitro caries-inhibited and -demineralized dentin adjacent to a conventional and two resin-modified glass ionomer cements.

METHODS

Box-shaped cavities were prepared on bovine root dentin and restored with either Fuji II, Fuji II LC, or Vitremer. The teeth were then decalcified in an acid buffered solution of 50 mmol l-1 acetic acid adjusted to pH = 4.5 for 3 days. Knoop and triangular microhardness indentations were performed perpendicular to the surface and parallel to the cavity wall, in the demineralized lesion and inhibition zone. Calcium and phosphorous contents of the outer lesions and inhibition zones were compared using energy-dispersive X-ray spectrometry (EDS). The correlation between Knoop and triangular hardness was analyzed by correlation coefficient. The statistical significance of hardness data was analyzed by one-way ANOVA and Fisher's PLSD test (p < 0.05).

RESULTS

Triangular hardness (HT) correlated well with Knoop hardness number (KHN) (r2 = 0.81, p < 0.05). The microhardness of the inhibition zone created by Fuji II was of 59.2 +/- 3.8 HT and was statistically significantly higher than the zone produced by Fuji II LC and Vitremer. Fuji II LC and Vitremer produced inhibition zones with similar microhardness [48.3 +/- 3.5 HT and 44.0 +/- 7.6 HT, respectively (p > 0.05)]. Calcium and Phosphorous were present in the inhibition zone, but did not exist in the demineralized lesion.

SIGNIFICANCE

Knoop and triangular hardness numbers correlated significantly (p < 0.05), and the latter seems to be a promising alternative method for measuring very narrow surfaces. Despite the fact that all glass ionomer materials used in this study were effective in producing an acid-resistant layer, microhardness and intensity of these layers were material dependent.

A new cavity classification

With the development of adhesive restorative materials and a far better understanding of the action of the fluoride ion it is suggested that the time has arrived for a reassessment of the traditional cavity classification as set out by G.V. Black over one hundred years ago. When preventive measures and remineralization fail and a carious lesion has progressed through the enamel into the dentine there is a need to remove the infected dentine, and possibly some of the affected dentine as well, to eliminate cavitation and avoid further accumulation of plaque. In most situations this will involve removal of enamel to achieve access to the infected dentine but, in the presence of fluoride, both enamel and dentine are capable of being remineralized and therefore conserved, at least to a degree. The principle of minimal extension must be encouraged to allow maximum preservation of natural tooth structure. A new cavity classification is proposed which is designed to make the most of the potential for healing which is inherent in both enamel and dentine. However, it must be accepted that a considerable proportion of restorative dentistry is carried out to replace failed restorations and, in this case, cavity design will be complicated by existing loss of tooth structure.

New direct restorative materials. FDI Commission Project

People worldwide have become increasingly aware of the potential adverse effects on the environment, of pollution control and of toxic effects of food, drugs and biomaterials. Amalgam and its potential toxic side effects (still scientifically unproven) continue to be discussed with increasing controversy by the media in some countries. Consequently, new direct restorative materials are now being explored by dentists, materials scientists and patients who are searching for the so-called 'amalgam substitute' or 'amalgam alternative'. From a critical point of view some of the new direct restorative materials are good with respect to aesthetics, but all material characteristics must be considered, such as mechanical properties, biological effects, and longterm clinical behaviour.

Longevity and cariostatic effects of everyday conventional glass-ionomer and amalgam restorations in primary teeth: three-year results

The aim of this study was to compare the longevity and cariostatic effects of everyday conventional glass-ionomer and amalgam restorations in primary teeth. The materials consisted of 515 Ketac-Fil glass-ionomer restorations and 543 Dispersalloy amalgam restorations prepared in 666 children, from 3 to 13 years of age, by 14 dentists within the Danish Public Dental Health Service in the municipalities of Vaerløse and Hillerød. The restorations, of which 79% were of the Class II type, were in contact with 593 unrestored surfaces in adjacent primary and permanent teeth. After 3 years, 6% of the patients had dropped out of the study, and 33% of the teeth were exfoliated with the restoration in situ. A further 37% of the glass-ionomer and 18% of th amalgam restorations were recorded as failed (p < 0.001). The frequency of failures was highest for Class II glass-ionomer restorations, which showed a 50% median survival time of only 34 1/2 months, because of many fractures, while the 75% survival time for Class II amalgam restorations just exceeded the actual 36 months (p < 0.001). Caries progression was most often recorded in surfaces adjacent to amalgam restorations, and 21% of these surfaces needed restorative treatment vs. 12% of the surfaces adjacent to glass-ionomer restorations (p < 0.001). The three-year results indicated that conventional glass ionomer is not an appropriate alternative to amalgam for all types of restorations in primary teeth. In particular, the short longevity of Class II glass-ionomer restorations could not be compensated for by the reduced caries progression and need for restorative therapy of adjacent surfaces.

The physical and adhesive properties of dental cements used for atraumatic restorative treatment

Atraumatic restorative treatment (ART), a recently reported field dentistry technique, involves removal of carious debris using only hand instruments and placement of a glass-ionomer cement (GIC) restoration. While small ART-GIC restorations are effective short-term replacements for lost tooth form, many larger ART-GIC restorations are defective after two years. Presently, resin-modified GICs (R-M GIC) are available which require no special activation equipment and handle easily in field settings. This study measured the compressive, tensile, and shear bond strengths to enamel and dentin of a conventional ART-GIC (Fuji IX) and two R-M GICs (Fuji Plus and Advance) at a powder-to-liquid ratio of 3.6:1. The compressive strengths of the GICs tested were significantly different. Fuji IX had the highest compressive strength, and Advance had the lowest strength (p < 0.05). The tensile strength of the R-M GICs was greater than that of the ART-GIC. Fuji Plus showed the highest shear bond strength to enamel and dentin and was significantly different from both Fuji IX and Advance. A clinical protocol is presented followed by case reports where the ART technique was used for management of acute caries in a modern dental setting.