Review on fluoride-releasing restorative materials--fluoride release and uptake characteristics, antibacterial activity and influence on caries formation.

This review discusses current trends in the development of dentin adhesives and the possibility that some classes of currently available adhesives are too hydrophilic. Manufacturers have reformulated dentin adhesives to make them more compatible for bonding to intrinsically moist, acid-etched dentin by adding 2-hydroxyethyl methacrylate and other hydrophilic resin monomers. These 3-step adhesives work well but are more time consuming to use and more sensitive to technique than the newer, simplified adhesives. When primers are mixed with adhesives in 2-step single-bottle adhesives and self-etching primers, the adhesives are more permeable to water and hence absorb more water over time than previous generations of adhesives. The most recent single-step self-etching adhesives are even more hydrophilic and hence more permeable to water derived from the underlying bonded dentin. This permeability can lead to a wide variety of seemingly unrelated problems, including incompatibility of chemically or dual-cured composites with simplified adhesives and expedited degradation of resin-dentin bonds.

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Have dentin adhesives become too hydrophilic

BACKGROUND: Fissure sealants used on occlusal tooth surfaces were introduced in the 1960s for protecting pits and fissures from dental caries. Although sealants have demonstrated to be effective in preventing caries, their efficacy may be related to the background caries prevalence in the population. OBJECTIVES: The primary objective of this review was to evaluate the caries prevention of resin based pit and fissure sealants and glass ionomer cements or sealants in children and adolescents. SEARCH STRATEGY: We searched the Cochrane Oral Health Group's Trials Register (last update December 2002), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2002), MEDLINE via OVID (1966 to December 2002), EMBASE (1974 to February 2002), SCISEARCH, SIGLE, CAplus, INSPEC, JICST-EPLUS, NTIS, PASCAL (February 2002) and DARE, NHS EED, HTA (March 2002). Reference lists from included articles and review articles were searched for additional relevant articles. All relevant studies in most languages were considered and translated. SELECTION CRITERIA: Randomised or quasi-randomised controlled trials of at least 12 months in duration in which sealants were used for preventing caries in children and adolescents under 20 years of age were included. The primary outcome was the increment in the numbers of carious occlusal surfaces of premolars and molars. DATA COLLECTION AND ANALYSIS: In the first phase, two reviewers independently examined whether a given study was likely to be relevant on the basis of the title, key words and abstract. In the second phase, four of the reviewers independently classified studies to be included in final analyses. Study authors were contacted for additional information. In the split-mouth studies relative risk ratios were calculated for the paired differences of tooth surfaces being carious or not. In studies comparing resin based sealant with no treatment, fixed effect meta-analyses were used to combine the estimates of relative risk ratios. In one parallel group study, the mean DFS data as continuous data, the effect estimate being the difference in mean DFS, was calculated from data of occlusal surfaces of teeth included in the test and control groups. MAIN RESULTS: Eight trials were included in this review of which seven trials were split-mouth studies and one a parallel group study. Six studies provided data for comparing sealant with no treatment and three studies for comparing glass ionomers with resin based sealants. The overall effectiveness of resin based sealants in preventing dental decay on first molars was high. Based on five split-mouth studies with 5 to 10 year old children there were significant differences in favour of the second-generation resin sealant compared with no treatment with pooled relative risk values of 0.14, 0.24, 0.30, 0.43 at 12, 24, 36 and 48 to 54 months respectively. The reductions in caries therefore ranged from 86% at 12 months to 57% at 48 to 54 months. The 24 month parallel group study comparing second-generation resin sealant with control in 12 to 13 year old children found also significantly more caries in the control group children with DFS = 0.65 (95% CI 0.47 to 0.83). Allocation concealment was classified adequate in three of these six studies. However the information on background levels of caries in the population was insufficient to conduct further analyses to estimate the effectiveness of resin based sealants related to baseline caries prevalence.Only one study provided data for the comparison between glass ionomer sealant and control. Based on this, there is not enough information to say whether ionomer sealants are effective, or not. The results of three studies comparing resin sealants with glass ionomer sealants were conflicting and the meta-analyses were not carried out. REVIEWERS' CONCLUSIONS: Sealing with resin based sealants is a recommended procedure to prevent caries of the occlusal surfaces of permanent molars. However,

Pit and fissure sealants for preventing dental decay in the permanent teeth of children and adolescents.

Background The DIAGNOdent, or DD (KaVo America, Lake Zurich, Ill.), a device for detecting caries using laser fluorescence, has been growing in popularity during the past three years. Although several evaluations of its diagnostic performance have appeared in the literature, the range of reported performances is extensive. Types of Studies Reviewed The authors conducted a systematic review of the literature to assess the diagnostic performance of the DD. Of 115 articles identified in the search, 25 studies were included in the review according to criteria requiring histologic validation and outcomes expressed as sensitivity and specificity values. Results For detection of dentinal caries, sensitivity values ranged widely (0.19 to 1.0), although most tended to be high. Specificity values exhibited a similar pattern, ranging from 0.52 to 1.0. In comparison with visual assessment methods, the DD exhibited a sensitivity value that was almost always higher and a specificity value that was almost always lower. The body of evidence is characterized largely by in vitro studies, so that generalization to the clinical setting is uncertain. Because caries thresholds varied substantially across the studies, synthesized estimates of performance were not possible. Conclusions and Clinical Implications The DD clearly is more sensitive than traditional diagnostic methods; however, the increased likelihood of false-positive diagnoses compared with that with visual methods limits its usefulness as a principal diagnostic tool.

A systematic review of the performance of a laser fluorescence device for detecting caries

Statement of problem Endodontically-treated, dowel-restored teeth may experience fracture, but investigations of variables related to fracture are often inconclusive and occasionally contradictory. Purpose The finite element method was used to analyze the stresses in dowel-restored teeth. The variables studied were material, shape, bonding, modulus of elasticity, diameter, and length of the dowel. Material and methods The model of the dowel-restored tooth involved dentin, ligament, cortical and trabecular bone, gingiva, and gutta-percha. The dowels were made of glass fiber, titanium, or zirconia and modeled as an approximation of the brands ParaPost Fiber White, ParaPost XH, and Cerapost, respectively. The dowel was cemented with zinc-phosphate cement or with bonded or nonbonded resin luting agents, and an approximation of the material properties of these 2 materials were used in the modeling. The restoration included a composite resin core and a gold crown. Other variables included taper versus parallel-sided posts, modulus of elasticity, diameter, and length of post. The model was axisymmetrical in 3 dimensions. A load of 100 N was applied to the crown at an angle of 45 degrees, and tensile, shear, and von Mises stresses were calculated. Results The generated stresses decreased with respect to the dowel material in the following order: glass fiber, titanium, and zirconia. Stresses were in general higher with tapered than with parallel-sided dowels. Stresses were reduced by bonding and with an increasing modulus of elasticity, increasing diameter, and increasing length of the dowel. Conclusions Within the limitations of this study, it was found that all investigated dowel-related factors influenced the stress field generated in dowel-restored teeth.

Finite element analysis of stresses in endodontically treated, dowel-restored teeth

Statement of problem. New luting agents, particularly with adhesive capability, are being introduced in an attempt to improve clinical success. Independent studies of basic comparative data are necessary to characterize these materials in relation to mechanical and physical properties. Purpose. The purpose of this study was to compare the flexural strength, modulus of elasticity, and radiopacity and pH of representatives of 5 types (categories) of luting agents. Material and methods. The luting agents included a zinc phosphate, a conventional and a resin-modified glass ionomer, 2 dual-polymerizing resins ("photopolymerized" after mixing and "unphotopolymerized" conditions), and an auto-polymerizing resin. The specimens were prepared and the testing was conducted by 1 person to maximize standardization. Flexural strength (MPa) and modulus of elasticity (GPa) were determined on bar-shaped specimens (2 × 2 × 20 mm) at 24 hours and 3 months (n = 8). Radiopacity (mm Al) was measured by exposing 1 mm thick specimens along with an aluminum step wedge (n = 4). pH was measured using a pH electrode immediately after mixing; at 1, 5, 15, 30 minutes; and at 1, 2, 4, 6, and 24 hours (n = 4). The data were subjected to statistical analyses with analysis of variance and Duncan's multiple range test ( P Results. The resin luting agents (64 to 97 MPa) showed higher flexural strength than all other materials tested (7 to 27 MPa), with the "photopolymerized" (83 to 97 MPa) conditions higher than "unphotopolymerized" (64 to 81 MPa) ( P P P P P Conclusion. Within the limitations of this study the data showed a wide variation of material properties. The dual-polymerization resin luting agents tested showed the best combination of mechanical and physical properties combined with the highest setting pH. Photopolymerization of these resin-based materials was necessary to maximize strength and rigidity. (J Prosthet Dent 2003;89:127-34.)

Mechanical and physical properties of contemporary dental luting agents

Objective: This study was undertaken to characterize 9 currently available proprietary flowable composites with respect to key properties of flow, flexural strength, stiffness (modulus of elasticity) and radiopacity Methods: Seven proprietary flowable composites (Aelite Flo, Filtek Flow, Heliomolar Flow, PermaFlo, Revolution Formula 2, Tetric Flow, Wave) and 2 flowable compomers (Compoglass Flow, Dyract Flow) were evaluated A universal hybrid composite (Filtek Z250) and a restorative compomer (Dyract AP) were used as controls Standard mechanical testing of 25 · 2 · 2 mm bar specimens was carried out at 24 hours and 1 month Flow testing used a fixed volume of material under consistent loading, and radiopacity was measured simultaneously for all materials using disk specimens of 1 mm thickness Results: As expected, flowable composites showed higher flow and lower mechanical properties than the controls Moduli of the composites were approximately 50% or less of the moduli of control materials, which indicates high flexibility Flexural strengths approached that of the control composite Flow properties varied widely The material Tetric Flow had the highest radiopacity, above that of enamel and the control composite Lowest radiopacity, below or equivalent to that of dentin, was shown by Wave and Revolution Formula 2 Conclusions: The flowable materials possessed a wide range of mechanical and physical properties Their lower mechanical properties suggest that they should not be used in bulk in areas of high occlusal loading Within intracoronal restorations, clinicians are advised to use materials with high radiopacity A wide range of fluidity options is available The clinical applications and performance of these materials require further study

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Flow, strength, stiffness and radiopacity of flowable resin composites.

Purpose: To determine the flexural strength, modulus of elasticity, and 24-hour pH profile of three self-etching resin luting cements and to obtain comparative data for representative conventional resin and resin-modified glass ionomer luting cements



Materials and Methods: Three self-etching resin luting cements [RelyX Unicem (3M ESPE), Maxcem (Kerr), Embrace Wetbond (Pulpdent)] were tested and compared with two conventional resin cements [RelyX ARC (3M ESPE), Linkmax (GC)] plus two resin-modified glass ionomer luting cements [Fuji Plus (GC), RelyX Luting Plus (3M ESPE)] Flexural strength and modulus of elasticity were determined using bar-shaped specimens (2 × 2 × 25 mm3) at 24 hours, using an Instron universal testing machine Setting pH was measured using a flat-surface pH electrode at 0, 2, 5, 15, and 30 minutes and 1, 2, 4, 6, and 24 hours after mixing Testing was performed under both dual-cured and self-cured conditions for all dual-cure cements Data analysis included ANOVA and Tukey's test (p < 005)



Results: The self-etching cements showed similar flexural strength to the conventional resin cements, except for Embrace Wetbond self-cured, which was considerably lower Modulus of elasticity results were both higher and lower than for conventional resin cements All photopolymerized conventional and self-etch dual-cure cements showed markedly higher flexural strength and modulus than when solely self-cured The resin-modified glass ionomer cements were characterized by lower flexural strength and elastic modulus Self-etching resin cements showed lower initial pH (20 to 24) than conventional resin cements (48 to 52) and a wide range of final pH values (39 to 73) at 24 hours One self-etching cement (Unicem) revealed a unique pH profile characterized by a more rapid rise in pH to neutrality both when dual-cured (15 minutes) and when auto-cured (1 hour)



Conclusions: The self-etching resin cements evaluated in this study displayed disparate properties and cannot be considered a homogeneous group Flexural strength properties were most uniform and were similar to those of the conventional resin cements, whereas moduli of elasticity showed greater variation Setting pH profiles differed, depending on the brand and mode of cure, even within the same category of luting cement All cements with dual-cure capability, both conventional and self-etch, showed significantly superior properties when photopolymerized

Flexural strength, elastic modulus, and pH profile of self-etch resin luting cements.

Controversy exists as to whether there is less secondary caries at the margins of glass ionomer restorations compared with other materials that do not release fluoride. This study examined the incidence of secondary caries for three types of restorative materials in Class V restorations in xerostomic patients. The study group consisted of 45 high caries-risk adult patients who had undergone head and neck irradiation for the treatment of cancer. All were substantially xerostomic and in need of at least three restorations in the same arch. Every patient received a restoration with each of the test materials, a conventional glass ionomer (GI), a resin modified glass ionomer (RMGI) and a resin composite (C). Patients were instructed in the daily use of a neutral pH sodium fluoride gel in custom trays. Recall appointments were made at 6, 12, 18 and 24 months, and the restorations were examined for material loss, marginal integrity and recurrent caries at the restoration margin. Fluoride compliance was determined at each recall period and recorded as the percentage of recommended use during that interval. Patients were categorized at the end of the study as fluoride non-users if their average compliance was 50% or less. Those with greater than 50% compliance were categorized as fluoride users. In the latter group, no recurrent caries was found for any of the restorations, whereas a material-dependent incidence of recurrent caries was found in the fluoride non-user group. None of the GI, one RMGI and eight C restorations failed due to recurrent caries. For the fluoride non-user patients, Fishers exact test (p=0.05) showed no statistical difference between GI and RMGI but statistical differences were found among those materials and resin composite at each recall period. Recurrent caries reductions for GI and RMGI relative to C were greater than 80% in xerostomic patients not using topical fluoride supplementation.

A clinical comparison of glass ionomer, resin-modified glass ionomer and resin composite restorations in the treatment of cervical caries in xerostomic head and neck radiation patients.

Commercially available caries-detector dyes are purported to aid the dentist in differentiation of infected dentin, yet research has established that these dyes are not specific for infected dentin. They are non-specific protein dyes that stain the organic matrix of less mineralized dentin, including normal circumpulpal dentin and sound dentin in the area of the amelo-dentinal junction. A considerable body of evidence indicates that conventional tactile and optical criteria provide satisfactory assessment of caries status during cavity preparation. There is reason for concern that subsequent use of a caries-detector dye would result in unnecessary removal of sound tooth structure. The use of caries-detector dyes has also been suggested as a diagnostic aid for occlusal caries. Although diagnosis of carious dentin beneath apparently sound enamel can be challenging, there is a lack of substantive evidence supporting the use of dyes for this purpose and false positives are a significant concern. Careful visual inspection combined with bitewing radiographic diagnosis has been shown to be the most reliable diagnostic method for the presence of infected dentin requiring operative treatment.

Dorothy McComb

Papers

Mechanical and physical properties of contemporary dental luting agents

Flow, strength, stiffness and radiopacity of flowable resin composites.

Flexural strength, elastic modulus, and pH profile of self-etch resin luting cements.

A clinical comparison of glass ionomer, resin-modified glass ionomer and resin composite restorations in the treatment of cervical caries in xerostomic head and neck radiation patients.

Caries-detector dyes--how accurate and useful are they?