Tunnel restorations placed in routine practice and observed for 24 to 54 months.

OBJECTIVE: The purpose of this study was to evaluate the feasibility and performance of tunnel restorations placed in routine public dental service. METHOD AND MATERIALS: A total of 420 small approximal lesions received tunnel restorations 12 general practitioners. Three hundred two restorations in 179 patients were available for evaluation after a minimum period of 24 months. The restorations were evaluated by modified US Public Health Service criteria. RESULTS: After service periods up to 54 months, 57% of the restorations were found to be clinically and radiographically acceptable. The remainder had already been replaced or were assessed as unacceptable. High levels of carious activity and internal-type preparations resulted in the poorest prognosis. The success rates varied considerably among the operators, but these differences did not reach statistical significance. CONCLUSION: The indications for use of the tunnel restoration technique for the treatment of primary approximal lesions seem to be limited at present. Partial tunnel restorations may have a somewhat better prognosis than the internal tunnels, but high carious activity has a detrimental effect. Tunnel restorations may be considered for particularly cooperative patients with a low caries rate as a semipermanent treatment for small lesions.

The effect of zinc oxide-eugenol on the shear bond strength of a commonly used bonding system.

It has been claimed that eugenol has a detrimental effect on resin composites and dentin bonding systems. The aim of the present study was to examine whether zinc oxide-eugenol (ZOE) cement would reduce the efficacy of a bonding system. Human third molars were selected for the study, and cylindrical posts of a resin composite (Z100) were bonded vertically to a standardized flat dentinal surface, prepared on the buccal surface of the teeth and treated with Scotchbond Multi-Purpose. The tooth surfaces involved were either freshly cut, or had been exposed to ZOE cement for 6 days, with and without a subsequent thorough cleansing with ethanol. The bond strength in shear was measured after 24 hours. The results showed that ZOE cement had no negative effect on the bond strength of the resin composite (Z100) to dentin when this bonding system was used. The mean shear bond value for the specimens covered with ZOE cement for 6 days was 28.1 MPa. For specimens covered with ZOE cement and cleansed with 96% ethanol, the mean shear bond value was 23.5 MPa. The corresponding value for the controls was 19.0 MPa. These findings suggested that eugenol-containing temporary filling materials may be used safely prior to inserting resin based restorative materials, when Scotchbond Multi-Purpose is employed as the bonding agent.

Pulpal response to prolonged dentinal exposure to sodium hypochlorite.

AIM: The aim of this study was to examine the effect of undiluted NaOCl on vital pulp tissue when applied to freshly cut dentine. METHODOLOGY: Class V cavities were prepared to a depth of 2 mm in 20 teeth in four Beagle dogs. The cavities on one side of each dog were irrigated continuously for 5 min with 5.25% NaOCl, whilst the cavities on the opposite side in each dog were irrigated with saline for the same length of time. Prior to filling each cavity with Cavit, they were again rinsed with saline and gently dried with an air stream. The dogs were sacrificed to allow for investigation of pulpal conditions under the cavities after periods of 24 h, 1 week, and 4 weeks. Histological preparations were made and stained with H & E for evaluation of the pulp subjacent to each cavity. The tissues were examined for presence of inflammatory cells and categorized as (i) no inflammation, (ii) mild, (iii) moderate, and (iv) severe inflammation. RESULTS: The six teeth in the 24 h observation group all showed mild inflammation, both in the NaOCl and the saline groups. After 1 week and 4 weeks, the pulps from all the teeth were free of inflammatory cells. CONCLUSION: Under the conditions of this experiment, the use of NaOCl in a freshly cut cavity in an intact tooth of a dog, with exposed dentinal tubules, does not appear to cause additional pulpal damage to that caused by the physical contact in cutting tooth structure.

Clinical performance of indirect composite resin inlays/onlays in a dental school: observations up to 34 months.

The aim of this retrospective clinical study was to evaluate the clinical performance of indirect composite resin inlays and onlays. Patients among the dental school clientele in need of posterior approximal filings and preferring esthetic restorations were included. Clinical teachers or trained students under supervision carried out the preparations, made impressions and prepared stone casts. Inlays made from either Tetric, Z100 or Maxxim were light-cured and placed in a light oven for secondary curing, before being luted with a dual cure cement. At recall, the inlays were evaluated using slightly modified US Public Health Service (USPHS) criteria. Twenty-two patients with 50 fillings presented for the assessment. The right censored observation periods ranged from 12 to 34 months, with a mean of 20. With the only exception of an early fracture of one onlay, all restorations were classified as successful. This was based on 15 "A" (optimal) and 34 "B" (acceptable) ratings, each of which representing the lowest rating for the individual restoration. The major reason for the "B" ratings was imperfect gingival marginal adaptation due to a small surplus of bonding material and/or luting cement.

Pronase digestion of carious dentin.

The aim of this study was to investigate the individual capabilities of the proteolytic enzyme preparation Pronase, the enzyme collagenase and sodium hypochlorite to disintegrate and solubilize carious dentin. Samples of carious dentin, and samples of sound dentin for comparison, were extracted 4 times in succession for 24 h with buffered solutions of Pronase. Separate carious dentin samples were extracted in the same manner with buffered solutions of collagenase or with aqueous sodium hypochlorite. The extracts, the solid residues left over after the extractions and untreated samples of carious and sound dentin were digested with sulfuric acid-H(2)O(2) and then analyzed for nitrogen content by a special adaptation of the Berthelot color reaction. Although Pronase did not attack sound dentin, it solubilized more than 90% of the nitrogen present in carious dentin. Collagenase solubilized approximately 66% of the nitrogen, whereas sodium hypochlorite released only 12-20% of the nitrogen of carious dentin. In clinical dentistry, chemical disintegration of carious dentin may reduce the need for mechanical removal of sound tooth structure.

Saucer-shaped cavity preparations for posterior approximal resin composite restorations: observations up to 10 years.

OBJECTIVE: This clinical trial aimed at studying the long-term performance in routine clinical practice of saucer-shaped Class II resin composite restorations. METHOD AND MATERIALS: Fifty-one preparations were completed and filled with either of two light-cured posterior composites by seven dentists of the Public Dental Service. The restorations were evaluated annually, using the US Public Health Service criteria, bitewing radiographs, and dies based on replica impressions. At the final evaluation, the recall rate was 100%. RESULTS: After a mean of 7.2 +/- 1.3 years of service (censored maximum of 9.6 years), 70% of the restorations were acceptable for continued use. Caries and technical deficiencies were the main causes of failure. CONCLUSION: The saucer configuration, by respecting and utilizing inherent properties of the resin composites, spares sound dentin and is preferable to the box preparation.

In vitro shear bond strength of two resin composites to dentin with five different dentin adhesives.

OBJECTIVE: The aim of this in vitro study was to evaluate the shear bond strength to dentin of five different dentin bonding agents in combination with two resin composites (Tetric and Z-100). METHOD AND MATERIALS: Human third molars were selected for the study, and cylindrical posts of either Tetric or Z-100 were bonded vertically to a standard flat dentinal area, prepared on the buccal surface of the teeth. A chisel-shaped shearing blade, attached to the crosshead of a universal testing machine, was positioned so that its edge was immediately adjacent to the adhesive joint. The shear bond strengths to dentin of 10 resin composite-dentin adhesive combinations were measured. RESULTS: The results showed that the bond strength of dentin bonding agents may depend on the choice of restorative material. The in vitro bond strength of dentin bonding agents also differed significantly. In several cases, the bond strength exceeded the cohesive strength of dentin. CONCLUSION: It seems important for clinicians to be acquainted with the variation in bond strength values that is experienced with any bonding system.

Detection of microbial-derived fatty acids in carious dentin by gas chromatography and gas chromatography-mass spectrometry.

The aim of the present study was to analyze the fatty acid content of carious and sound human dentin. Gas chromatography and gas chromatography-mass spectrometry revealed the presence of fatty acids of C10-C18 size in the carious dentin, whereas fatty acids of C16 size were present in minute amounts in three samples of the corresponding sound dentine controls. No fatty acids were detected in the other sound dentin control samples. The source of fatty acids was considered to be microorganisms invading the dentin during the progression of the caries lesion. The presence of bacterial fatty acids in carious dentin may serve as a marker for the pathological process and thus contribute to the understanding of the mechanisms involved.

Fluoride release and uptake in vitro from a composite resin and two orthodontic adhesives.

The aim of this study was to investigate the fluoride release and uptake characteristics of a composite resin (Tetric) and two orthodontic adhesives (VP 862 and Saga Bond), with a type-II glass ionomer cement (Ketac Fil) as a control. Test specimens in 2 ml deionized water released fluoride over a period of 33 days. Ketac Fil released 54 and 15 times more fluoride than Tetric after 24 h and 1 month, respectively, whereas the two adhesives released amounts between these values. Specimen exposure to 1000-ppm NaF solution increased the 24-h fluoride release from all materials, with near pre-exposure levels reached after 2-3 days. Ketac Fil had a tendency to recharge not seen with the other materials. The ytterbium trifluoride filler in Tetric has a very low water solubility, and it is therefore suggested that the increases in fluoride release from Tetric after exposure to fluoride were most probably due to release of surface-retained fluoride.

A 3-year clinical study of tunnel restorations.

Tunnel restorations (n = 161) performed by 4 dentists were evaluated after a mean of 35 months in situ. Demineralized enamel was to be spared during preparation. The preparations were filled with a cermet glass ionomer (polyalkenoate) cement. Evaluation was carried out using clinical and radiographical criteria. During the observation period, approximately 16% of the restorations were replaced due to caries in dentin and 14% due to marginal ridge fracture. Cavitation in the approximal surface and/or increased radiolucency of the approximal enamel were observed in 34% of the remaining tunnel-restored teeth. A significantly higher frequency of failures were registered when treating patients with a high caries activity, where the initial lesion was large, and where the restoration did not reach the approximal surface.

Severe dental aberrations in familial steroid dehydrogenase deficiency: a new association.

Severe numerical dental aberrations are rare, and are most often seen as a part of certain syndromes. We here report on a Saudi Arabian family where first-cousin marriages have caused numerical and structural dental abnormalities linked to autosomal recessively inherited liver diseases. The two latest affected children in this family have had their liver defect successfully treated with fat-soluble vitamins and chenodeoxycholic acid, enabling us to study their dental development. One boy exhibits 11 supernumerary teeth, a general hypomineralisation and enamel hypoplasia, while an affected cousin successfully diagnosed at an early age, so far, only suffers from structural enamel defects. The children are otherwise healthy. There is no resemblance to any known syndromes. We suggest that the supernumerary teeth and the liver disease are caused by the same genetic defect, and represent a new association. The hypomineralisation, however, is most likely to result from vitamin deficiency secondary to malabsorption during the first years of life, before successful treatment was instituted.

Chemical treatment of cavity walls following manual excavation of carious dentin.

PURPOSE: To improve the conditioning of cavity walls resulting from minimal mechanical preparation of carious lesions, such as is done in modified Class II tunnel preparations. MATERIALS AND METHODS: Proximal carious lesions in premolars and molars were excavated manually and the cavity walls studied using a stereomicroscope and by scanning electron microscopy (SEM) following treatment with either polyacrylic acid, sodium hypochlorite, the enzyme preparation Pronase, or sequential combinations of the agents. Polyacrylic acid (10%) was used according to the manufacturer's instructions, while concentrated sodium hypochlorite (5.25%) was applied with either intermittent scrubbing or with ultrasonic energy for 5-10 minutes, or the cavity wall was incubated with the agent at +/- 37 degrees C for periods up to 24 hours. Incubation with the proteolytic enzyme preparation Pronase was carried out at 37 degrees C for a period up to 48 hours. RESULTS: Manual excavation did not remove all carious dentin, neither did treatment with polyacrylic acid. Scrubbing or sonication with ample amounts of sodium hypochlorite, followed by treatment with polyacrylic acid, or prolonged incubation with sodium hypochlorite, removed most of the remaining carious dentin. However, the "cleanest" surfaces were obtained after 48 hours of incubation with Pronase. Spots of thicker, soft layers of decayed dentin that were left intentionally at some locations could be disintegrated only by the Pronase treatment. It was concluded that treatment with sodium hypochlorite and polyacrylic acid in tandem, or with Pronase may represent potential supplements to conventional cavity cleaning that deserve further investigation. In the clinic more efficient cavity cleaning may improve the bonding ability and thus reduce the risk of marginal ridge fracture in teeth with Class II tunnel restorations.

On the genetics of hypodontia and microdontia: synergism or allelism of major genes in a family with six affected members.

Familial severe hypodontia of the permanent dentition is a rare condition. The genetics of this entity remains unclear and several modes of inheritance have been suggested. We report here an increase in the number of congenitally missing teeth after the mating of affected subjects from two unrelated Norwegian families. This condition may be the result of allelic mutations at a single gene locus. Alternatively, incompletely penetrant non-allelic genes may show a synergistic effect as expected for a multifactorial trait with interacting gene products. This and similar kindreds may allow identification of genes involved in growth and differentiation of dental tissues by linkage and haplotype association analysis. Brittle nails, delayed growth of the hair, and delayed teething in the probands support the grouping of these conditions among the ectodermal dysplasias.

Clinical performance of porcelain laminate veneers without incisal overlapping: 3-year results.

The aim of this clinical trial was to evaluate the performance of 135 porcelain laminate veneers placed on anterior teeth without incisal preparation. Only 0.3-0.5 mm of the facial enamel was removed using a tapered round-ended diamond bur. The veneers were fabricated from a sintered feldspathic porcelain, etched and silanized and then bonded with a light-cured composite lute. The veneers were yearly examined clinically for debonding, chipping, marginal integrity and staining. After 3 years of service all veneers were retained. Incisal chipping occurred in seven veneered teeth. Wear and staining were negligible. It was concluded that this minimal porcelain veneer restoration with no incisal overlapping was conservative, predictable and successful.

Saucer-shaped cavity preparation for composite resin restorations in class II carious lesions: three-year results.

This study determined the feasibility of saucer-shaped cavity preparations for composite resins in class II lesions. Saucer-shaped class II cavity preparations were restored with composite resin and subjected to clinical, radiographic, and replica cast evaluation (39 restorations) after 6, 18, and 36 months. The results indicated that the retention, resistance form, and wear resistance of the class II saucer-shaped cavity preparations were satisfactory after 3 years.

The clinical performance of two groups of functioning class-II cast gold inlays.

The length of service and the clinical performance of two groups of functioning class-II cast gold inlays in patients attending a private practice were assessed by conventional clinical and radiographic examination. In one group all inlays were older than 25 years (median age, 34 years), and they had an extended outline form. The impression technique was based on a thermoplastic material in a copper ring. In the other group, comprising inlays inserted during the past 25 years (median age, 16.5 years), the outline form was minimal and an elastic impression material in a copper ring was used. The inlays in the older group appeared to perform better than those in the younger group. In both groups recurrent caries appeared to be the predominant reason for repair.

Amelogenin gene similarity in vertebrates: DNA sequences encoding amelogenin seem to be conserved during evolution.

Mouse amelogenin cDNA was used in hybridization assays with genomic DNA, cut with the restriction enzyme Eco RI, from the edentulous chicken (Gallus domesticus), the monophyodont mouse (as control), diphyodont man, and the polyphyodont fishes Atlantic salmon (Salmo salar) and seawolf (Anarrhichas lupus). The hybridization assay was performed under stringent conditions with non-radioactive probes. Hybridization was obtained with mouse (6.4-kb band), man (9-kb and 13-kb bands), and seawolf (18-kb band) genomic DNA. This demonstrates DNA sequence similarities between these species, and supports the theory that DNA sequences encoding enamel proteins appear to be highly conserved during the evolution of vertebrates. Lack of hybridization in salmon and chicken may be due to sequence divergences or structural differences in an amelogenin gene analog, or it may be that no amelogenin gene is present in these animals.

[Light-cured glass ionomer cements]. / Lysherdende glassionomersementer.

An attempt at improving the properties of glass-ionomer cements is represented by the incorporation of light-cure resin systems. This produces materials which have mechanical properties and moisture sensitivity superior to those of present glass-ionomer cements. Such hybrid materials cure by two different mechanisms: polymerization and salt formation. In particular, the early mechanical properties and water sensitivity of the materials are improved due to the formation of a polymer matrix. The tendency to undergo surface crazing during desiccation is also reduced. Three commercially available products are shortly described.