Annual review of selected dental literature: report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry.
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Dental Caries↗
Biomedical subjects
W R Hume
Publications and source records attributed to W R Hume.
Component release from light-activated glass ionomer and compomer cements.
The purpose of this study was to identify and quantify any component released from seven commercially available light-cured or resin-modified glass ionomer and compomer cements. Twenty-one separate cylindrical stainless steel moulds 6 mm in diameter and 1.0 mm deep were filled with one of seven glass ionomer or compomer cements, light activated and then immediately immersed in separate containers of distilled water. Water samples were retrieved over a time period of up to 30 days and retained for analysis. An occlusal cavity 6 mm in diameter was prepared in extracted human third molar teeth with a remaining dentin thickness of 1.6-2.0 mm. A polypropylene chamber was attached to the cemento-enamel junction of each tooth to contain 1 mL of distilled water. Ten teeth were each filled with one of three cements and light activated. Water samples (eluates) were retrieved over a period of time. All samples were analysed by high performance liquid chromatography. Only one component, hydroxyethyl methacrylate (HEMA), was detected in the eluates from both tooth and mould samples. Analysis of diffusion of the HEMA through dentin showed a relatively sustained movement into the pulp space during the first day, with exponential decline thereafter. Our data show that HEMA was released from all of the light activated glass ionomer cements studied and from the compomer, both directly into water and through dentin. This release may be relevant both to the risk of adverse pulpal responses in patients and to the risk of allergy in patients and dental personnel.
Chromatography, High Pressure Liquid↗
Rapid and quantitative detection of Streptococcus mutans with species-specific monoclonal antibodies.
Streptococcus mutans is known to be a prime etiologic agent for the initiation and progression of human dental caries. Rapid, accurate, and quantitative detection of S. mutans will help us better understand the pathogenic mechanisms of dental caries and will help to develop methods for caries diagnosis and risk assessment. This study describes the development of three highly species-specific monoclonal IgG antibodies against S. mutans. The antibodies were used to develop a number of methods that quantitatively detect S. mutans in less <1 min and are sensitive enough to detect a single bacterial cell. These methods could be widely used in basic and clinical studies related to S. mutans and in the clinical diagnosis and treatment of caries in humans.
Antibodies, Bacterial↗
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.
Adhesives↗
Restorative dentistry: current status and future directions.
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Dental Caries↗
A study of component release from resin pit and fissure sealants in vitro.
OBJECTIVE: A recent study reported that an estrogenic chemical, bisphenol-A, was released from a fissure sealant. The aim of this study was to identify and quantify the major (or detectable) components released from any of seven commercially-available, light-cured pit and fissure sealants in vitro. METHODS: The fissure systems of ten extracted, third molar teeth were filled with sealant, light-activated and immersed in separate containers of distilled water. Separate, cylindrical stainless steel molds were filled with sealant which was then light-activated and immersed. Each mold or tooth with sealant was moved to a new container of water at defined times and each remaining water sample (eluate) then analyzed by high performance liquid chromatography (HPLC). RESULTS: Triethylene glycol dimethacrylate (TEGDMA) was present in all eluates from each of the sealants tested. 2,2-bis[4'-(2'-hydroxy-3'-methacryloyloxy)phenyl]propane (BisGMA) was detected at much lower levels (about one thousand-fold less) in eluates from one sealant only. Bisphenol-A was not detected in any eluates. The rates of TEGDMA and BisGMA release were highest on first immersion and decreased thereafter. The total amount of TEGDMA released was on the order of 0.25 mg per tooth. Most release occurred during the first day. SIGNIFICANCE: Because bisphenol-A release could not be detected from any of the seven sealants tested, these results call into question earlier concerns expressed about possible adverse effects of bisphenol-A released from resin sealants.
Air Pollutants, Occupational↗
The effect of dentine thickness on diffusion of resin monomers in vitro.
Forty extracted human third molar teeth were divided into four groups, each of 10 teeth, to test the hypothesis that dentine thickness variation influences diffusion of the monomers 2-hydroxyethylmethacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA) from light-cured bonding resin-composite resin restorations to the pulp space. An occlusal cavity 6 mm in diameter was prepared in each tooth of four groups with remaining dentine thickness of 3.4-3.6, 2.4-2.6, 1.4-1.6 and 0.4-0.6 mm, respectively. A polypropylene chamber was attached to the cemento-enamel junction of each tooth to contain 1 mL of distilled water. Each cavity was treated with Scotchbond Multipurpose (3 M, U.S.A.) then restored with Z100 (3 M) and light activated for 30 s. Water samples were retrieved over a time course up to 30 days and analysed by high performance liquid chromatography. Both HEMA and TEGDMA were detected in the pulp samples for all teeth. Decreasing dentine thickness substantially increased pulpward diffusion rate of both HEMA and TEGDMA during the first day after placement, as well as the total release of both components from a bonding resin-composite combination in vitro.
Chromatography, High Pressure Liquid↗
Diffusion of resin monomers through human carious dentin in vitro.
The diffusion of 2-hydroxyethylmethacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA) from light cured bonding resin-composite resin restorations through human carious dentin was investigated. Extracted human molar teeth with different degrees of caries were obtained from consenting donors. Teeth were classified into three groups according to caries severity (mild, moderate and severe) using subjective criteria. The outer carious lesions were then removed guided by a proprietary caries detector dye. Teeth with exposure of the pulp space after caries removal were excluded from the study. A polypropylene chamber was attached to the cemento-enamel junction of each tooth to contain 1 ml distilled water. Each cavity was restored with a HEMA containing bonding resin then a TEGDMA-containing resin composite. Water samples were retrieved over a time course and analyzed by high performance liquid chromatography. There was great variation between teeth in HEMA and TEGDMA permeability. The cumulative amounts released were of similar magnitude to those observed in non-carious teeth for the mild and moderately-severe groups. However, the cumulative amounts released were markedly greater in severely carious teeth than in those with moderate or mild caries.
Adult↗
A revised classification of carious lesions by site and size.
The present classification used by the profession for the identification of carious lesions was devised by Black about 100 years ago. It was based, in part, on the location of the lesion but was modified to take into account the materials that were available for restoration. Over the last 20 years, there has been considerable modification of these materials; adhesion between the restoration and tooth structure is now possible, and the understanding of the relevance of fluoride and other ions in the prevention and repair of caries has improved. It would be logical at this time to adopt a new classification based on the site of the carious lesion and the extent to which it has progressed. More relevant detail could be recorded for each restoration, and this would be of value both for personal records and epidemiologic studies. The proposal is a simple digital system that is compatible with the use of computers for record keeping.
Dental Caries↗
Bioavailability of components of resin-based materials which are applied to teeth.
Chemical components of many materials used in dental practice can move into the local biophase, where they can have beneficial or adverse effects. The strongest indirect evidence that components of resin-based materials used in dentistry can move into the biophase are the many reports of allergic dermatitis in dental personnel. Direct measurement of component release has shown that triethylene glycol dimethacrylate (TEGDMA), hydroxyethyl methacrylate (HEMA), and, in the case of some orthodontic cements, bis-glycidyl methacrylate and benzoyl peroxide can move into an aqueous medium from a range of resin-based materials which are applied to teeth as part of oral care. In the case of resin composite restorations, HEMA and TEGDMA are available in microgram quantities via the salivary surface in the minutes and hours after clinical placement and via dentin and pulp in the hours and days after placement. Fortunately, moderate thickness of dentin protects pulp tissue against local toxicity. There are no data which suggest that systemic toxicity is a risk with any of these materials. There are some case reports of allergic responses to the monomers in patients, but the incidence of such responses appears at present to be much lower than that in dental personnel.
Benzoyl Peroxide↗
Variation in phosphoric acid concentration and treatment time and HEMA diffusion through dentin.
PURPOSE: The effects of phosphoric acid concentration and time of dentin treatment on the movement of 2-hydroxyethylmethacrylate (HEMA) from a bonding resin-resin composite combination through dentin were investigated in vitro. MATERIALS AND METHODS: Freshly extracted human third molar teeth were divided into seven groups each of 10 teeth. A closed chamber was attached to the CEJ of each tooth to contain 1 ml distilled water. An occlusal cavity of 6 mm diameter and remaining dentin thickness of 1.0-1.5 mm was prepared in each tooth. Dentin was treated with either 10% phosphoric acid for 15, 30 or 60 seconds or with 37% phosphoric acid for 15, 30 or 60 seconds. A control group not treated with acid was also prepared. The cavities were rinsed, dried and then treated with the HEMA-containing Scotchbond Multi-Purpose bonding resin which was light-cured for 10 seconds. The cavities were then restored with Z100 and light-cured for 30 seconds. Water samples were retrieved from the chambers over a time course (4.32, 14.4, 43.2, 144 & 432 minutes; 1, 3 and 10 days) and analyzed by high performance liquid chromatography. RESULTS: HEMA was detected in the pulp chambers of all teeth from 4.32 minutes after resin placement. Mean total (cumulative) release at 10 days for all groups was in the 2-4 mumol range. The highest HEMA diffusion rate was 4.32 minutes after placement and were in the range 6-13 times greater than control in the 10%-15 seconds, 10%-30 seconds, 10%-60 seconds, 37%-15 seconds, and 37%-30 seconds groups. Unexpectedly, by far the lowest early rate at 4.32 minutes was in the 37%-60 seconds group (0.6 times of no-acid control).
Acid Etching, Dental↗
Effect of hydrostatic pressure on the diffusion of monomers through dentin in vitro.
In previous work, the diffusion of monomers from composite and bonding resins through dentin was demonstrated in vitro. The monomers triethylene glycol dimethacrylate (TEGDMA) and 2-hydroxyethyl methacrylate (HEMA) were identified in samples from the pulp space. In the current study, we examined the effects of two levels of positive hydrostatic pressure on the passage of resin monomers through dentin in vitro from a composite-resin/bonding-resin combination to test the hypothesis that monomer diffusion is prevented by such pressure. An occlusal cavity prepared in the tooth crown was restored with the resins. Distilled water samples from the pulpal space were removed over time and analyzed for monomer content by high-performance liquid chromatography and mass spectrometry. Positive pulpal pressure reduced but did not prevent pulpward movement of diluent monomers that leach from bonding agents and from resin composites through dentin in vitro. The degree of reduction of diffusion was greater with TEGDMA than with the lower-molecular-weight monomer HEMA.
Adolescent↗
Effect of dentine on release of TEGDMA from resin composite in vitro.
Triethylene glycol dimethacrylate (TEGDMA) is a component of some resin composites which contributes to their cytotoxicity. The presence of dentine between resin composite and test cells reduces the cytotoxicity in vitro. To determine why dentine has this protective effect, the diffusion of TEGDMA from a composite resin through dentine to the pulp space was compared with release directly into aqueous solution in vitro. Both release rate and total cumulative release of TEGDMA for the two groups, at times up to 100 days, were determined using reversed-phase HPLC. Release rate directly into water was highest in the minutes immediately after immersion and declined thereafter. However, in the tooth model, using an equivalent mass and surface area of composite resin, no TEGDMA was detectable in the pulp space until 43 min after restoration placement. The rate of diffusion through dentine from that time until day 1 was less than 1% of the highest (initial) direct release rate. The rate declined thereafter. It is relevant, however, that by day 3 the total cumulative release of TEGDMA through dentine was 60% of the direct release. Dentine therefore appears to exert its protective effect principally by retarding or 'damping' the initial high release of TEGDMA to a substantial degree.
Bisphenol A-Glycidyl Methacrylate↗
Influence of dentine on the pulpward release of eugenol or acids from restorative materials.
The diffusion gradient which develops across dentine and the clearance into the capillary circulation at the pulpal side of the tissue both reduce the concentration of potential toxins applied to dentine, thus protecting pulpal cells. The data presented on eugenol indicates that when release of a potential toxin from a solid material is hydrolytic the limited wetness of dentine, i.e. the limited availability of water for hydrolysis, contributes to the protective effect of the tissue. The data on strong acids indicates that a third protective mechanism, buffering by hydroxyapatite, can contribute to dentine's protective effect in situations where the potential toxin is strongly acid. There may be other mechanisms by which dentine protects the pulp against chemical toxins from restorative materials. However, the three described: diffusion limitation; limited wetness for hydrolysis; and buffering by dentinal hydroxyapatite, appear to allow the relatively safe use of a wide range of tooth restorative materials.
Acids↗
Movement of resin cement components through acid-treated dentin during crown cementation in vitro.
This study examined the hypothesis that components of crown cements may be forced through acid-treated dentin during cementation. Freshly extracted, human third molar teeth were prepared to accept full crowns. Roots were removed to allow irrigation of the pulp chamber with saline before, during, and after crown placement with resin dentin bond and resin composite cement. Saline samples were collected and analyzed by high performance liquid chromatography to identify and quantify resin components arriving in the pulp space. Two components of the bond-cement system used were identified in the pulp space samples immediately after crown cementation. These were 2-hydroxyethylmethacrylate and 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane. The amounts of these components in the pulp space decreased when the bonding agent was cured prior to crown placement. The results of this study supported the hypothesis that crown cementing components may flow through acid-treated dentin during crown cementation.
Adolescent↗
The association of carious dentin microflora with tissue changes in human pulpitis.
Correlations were sought between the number and type of microorganisms recovered from sampled carious dentin and the cellular responses observed in dental pulpal tissues from a sample of 65 vital, carious teeth extracted from adult humans who had declined the option of tooth restoration. Standardized homogenates of carious dentin were plated using selective and nonselective media under anaerobic and microaerophilic conditions. Pulpal responses were characterized histopathologically on the basis of the nature of the cellular infiltrate and the extent of degenerative changes. A significant association between the number of Prevotella intermedia and Prevotella melaninogenica in carious dentin and extensive, principally mononuclear, inflammatory infiltration was evident despite a high degree of complexity and intersubject variability in the microbial flora. There was no apparent association between other microorganisms or total microbial load and the histopathological category.
Actinomyces↗
Need for change in standards of caries diagnosis--perspective based on the structure and behavior of the caries lesion.
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Dental Caries↗