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

Clinical Relevance All insertion techniques using composite materials caused measurable cusp deflection during polymerization, with little difference between different incremental techniques. The silorane-based composite produced significantly less cuspal movement.

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Effect of Composite Insertion Technique on Cuspal Deflection Using an In Vitro Simulation Model

This study evaluated the influence of dentin adhesive application technique (pre-curing vs non precuring) on microtensile bond strength (microTBS) to dentin and adhesive layer thickness in indirect resin restorations. Seven proprietary dentin adhesives were tested, including one-step and multistep products. Experimental groups included adhesive pre-cure (PC) with a halogen light source and no pre-cure (NPC) prior to resin cement insertion. Thirty caries-free molars received an MO inlay preparation. Inlays made with Tetric Ceram resin composite were cemented using a dual-cured resin luting agent. Prior to inlay cementation, each tooth was treated with one dentin bonding agent, using pre-cure (PC) or no pre-cure (NPC). After storage in distilled water at 37 degrees C for 24 hours, the teeth were sectioned along their long axis to produce serial sticks for microtensile bond strength testing at 0.5 mm/minute. The results were subjected to statistical analysis by one-way and two-way analysis of variance (ANOVA) and Tukey's multiple comparison test (p < or = 0.05). For the film thickness evaluation, 10 additional teeth were restored and sectioned mesiodistally. The thickness of the adhesive layer was evaluated by SEM at 1000x magnification at the pre-selected locations. The microTBS varied from 11.7 +/- 4.5 MPa to 43.4 +/- 9.8 MPa. The effect of pre-curing the adhesive was material specific. No adhesive layer was visualized for the adhesives used without the pre-curing step. The thickness of the adhesive layer for the pre-cured groups varied according to the different areas analyzed.

The effect of dentin adhesive and cure mode on film thickness and microtensile bond strength to dentin in indirect restorations.

Retention problems have been reported with the clinical use of indirect microfilled resin veneers. This study used 24-hour shear tests to assess the bond strengths of such a resin veneer compared with other veneer types. The effect of different resin luting cements and resin veneer surface treatments were analyzed to elucidate factors by which retention could be increased. The six resin luting systems investigated showed a range of bond values. Debonding occurred primarily at the veneer/cement interface. G-Cera material produced the weakest bonds to Isosit-N resin. Surface treatment of Isosit-N veneers resulted in bond strength changes. Sandblasting reduced the force required for bond failure; Special Bond resin increased it slightly. Improving retention of prefabricated resin veneers proved difficult. Etched hybrid resin veneers delivered higher bond strengths than microfilled resin veneers but not significantly. Etched porcelain veneers, however, provided consistently the strongest bond strengths with cohesive, as opposed to adhesive, bond failure.

Shear bond strengths of resin luting cements to laboratory-made composite resin veneers

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 x 2 x 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 (Fluage, résistance, rigidité et radio-opacité des résines composites à faible viscosité)

In response to public concern, Health Canada recently conducted a review of amalgam safety and released a position statement entitled The Safety of Dental Amalgam. Essentially, the department has concluded that the levels of mercury absorbed by the body due to the release of mercury vapor from amalgam restorations, while detectable, do not approach those recognized to cause illness. It has therefore confirmed that amalgam restorations can be used safely in most patients, with some notable caveats. Despite Health Canada's position statement in support of amalgam, patient doubts about amalgam safety remain, including the tenuous hypothesized link between amalgam restorations and specific diseases. This article reviews the available studies of dentist mortality to identify possible links between mercury exposure and negative health effects. A lack of evidence to suggest a detrimental health outcome in dentists who are occupationally exposed to higher levels of mercury than their patients, and are known to have higher levels of mercury in their blood, provides an important reassurance concerning the safety of amalgam. The reviewed data indicates that the 10 leading causes of death in the United States and Canada are the same for both dentist and non dentist population groups, and that the percentage of deaths by the same cause are remarkably similar. By 1975, the year of the most recent U.S. study, the average age at death for white male dentists was about three years higher than for all adult white males. Although suicide standard mortality rates are known to be higher for dentists, suicide deaths have also been shown to be a factor in many other occupations, particularly those where there is easy access to drugs. Although updated actuarial data for dentist mortality are needed, the available data indicate no reduction in the life expectancy of practising dentists, nor any specific or disproportionate rates of disease associated with high mercury exposure. In fact, the available mortality studies are generally optimistic about the health of dentists, which should reassure patients about the safety of dental amalgam.

Dorothy McComb

Papers

Effect of Composite Insertion Technique on Cuspal Deflection Using an In Vitro Simulation Model

The effect of dentin adhesive and cure mode on film thickness and microtensile bond strength to dentin in indirect restorations.

Shear bond strengths of resin luting cements to laboratory-made composite resin veneers

Flow, Strength, Stiffness and Radiopacity of Flowable Resin Composites (Fluage, résistance, rigidité et radio-opacité des résines composites à faible viscosité)

Occupational exposure to mercury in dentistry and dentist mortality