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At least 613 records · Page 34Linked to original sources
PubMed2002

The influence of hygroscopic expansion of resin-based restorative materials on artificial gap reduction.

PURPOSE: This study compared the effect of water sorption on the extent of marginal gap reduction in two resin-modified glass-ionomer cements (RMGICs), two giomers, two compomers, and two resin composites over a twelve-week storage period. MATERIALS AND METHODS: Artificial gaps were created in 160 borosilicate glass cylinders. One-half of the internal surface of each cylinder was blocked out with wax and the other half was sandblasted. The bonding surface was further treated with 4% hydrofluoric acid, rinsed, and then coated with silane. After removal of the wax, one coat of dentin adhesive was applied to the silane-treated surface of the cylinder, briefly air dried and light cured. Eight light-cured restorative materials were placed incrementally: Vitremer (V), Fuji II LC (FJ), Beautifil (B), Reactmer Paste (R), Compoglass F (C), F2000 (F), Filtek Z250 (Z), and Tetric-Ceram (T). For each material, ten specimens were stored in deionized water (W), and ten (control) in nonaqueous silicone fluid (O) at 37 degrees C. The dimension of the same maximum gap created in each specimen was repeatedly measured at 0, 1, 2, 4, 6, 8, 10, and 12 weeks. RESULTS: R-W exhibited extensive hygroscopic expansion that resulted in cracking of 40% of glass cylinders after the 2nd week and 70% after the 4th week. One-way ANOVA of the other seven water groups showed significant differences (p < 0.001) among gap widths measured at different time intervals in V-W, FJ-W, C-W, F-W. Both RMGICs had the most significant gap reduction during the first week (p < 0.001). Both compomers exhibited delayed water-sorption characteristics, with more significant gap reduction observed in C-W. B-W was similar to the two resin composites Z-W and T-W and exhibited the least gap reduction. After the first week, there were no significant differences in the percentage reduction in marginal gaps for any of the groups (p > 0.05). CONCLUSION: Marginal gap reduction that results from water sorption is more extensive and rapid in RMG-ICs, followed by compomers, whereas composites are relatively stable. Reactmer Paste exhibits rapid and extensive expansion and should probably be avoided in tooth preparations that involve thin unsupported enamel.

Acid Etching, Dental↗
PubMed1999

[Comparative study of the effect on stress distribution of porcelain laminate complex with different elastic moduli].

Porcelain laminate has been a kind of popular treatment modality for its aesthetics and less tooth reduction. The models of 3-D FEA of left upper permanent central incisor were designed by microtomy. Comparative studies of stress distribution were carried out to reveal the stress of three designs of tooth preparation with two kinds of occlusions. The results showed that under loads imitating of central occlusion, the stress level increased a little with the rising of elastic modulus of the porcelain material, while the stress values of type II veneer seemed the highest under loads imitating of protruding occlusion. For the designing of laminate, it implies that porcelain material with low elastic modulus should be used in case of type II veneers.

Dental Porcelain↗
PubMed2002

Color stability of resin cements--an in vitro study.

The long-term success of an aesthetic restoration is predicated on numerous factors that include its color stability. As clinicians incorporate conservative tooth preparation into their restorative designs, the color stability of the underlying cement material increases in importance. This in vitro study evaluated the color stability of several commercially available resin cements under accelerated conditions. The investigation demonstrated that, under the experimental conditions, resin cements tended to change color between 1 week and 14 weeks, and their color change values increased with accelerated aging times.

Bisphenol A-Glycidyl Methacrylate↗
PubMedDate not supplied

Pit and fissure sealant: review of the literature.

For this literature review of pit and fissure sealant, 1,465 references were selected by a search for "sealants" on PubMed. References were limited to dental journals and papers in the English language. The search comprised papers from 1971 to October 2001. Additional papers of historical significance prior to 1971 were added from memory and from reference lists published in early papers. This paper reviewed the literature on pit and fissure sealants under the following subheadings: (1) laboratory studies, (2) clinical technique and tooth preparation, (3) etching time, (4) auxiliary application of pit and fissure sealant, (5) retention and caries prevention, (6) fluoride used with sealants and fluoride-containing sealant, (7) glass ionomer materials as sealants, (8) options in sealant: filled vs unfilled; colored vs clear; autocure vs light-initiated, (9) sealant placed over caries in a therapeutic manner, (10) cost effectiveness of sealant application, (11) underuse of pit and fissure sealant, (12) the estrogenicity issue, (13) use of an intermediate bonding layer to improve retention, (14) new developments and projections, and (15) summary and conclusions. From a careful and thorough review of peer-reviewed publications on pit and fissure sealant, it is clear that sealants are safe, effective and underused (at least underused in the United States). Pit and fissure sealant is best applied to high-risk populations by trained auxiliaries using sealant that incorporates the benefit of an intermediate bonding layer, applied under the rubber dam or with some alternative short-term, but effective, isolation technique, onto an enamel surface that has been cleaned with an air polishing technique and etched with 35% phosphoric acid for 15 seconds. The dental profession awaits with enthusiasm, and some impatience, the incorporation of dentin-bonding technology into the development of a modern, more durable, resin-based sealant.

Adolescent↗
PubMed2003

Reliability and validity of eight dental age estimation methods for adults.

This paper evaluates the reliability and validity of eight published dental age estimation methods for adults that may aid in victim identification. Age was calculated on 20 Caucasian teeth of known age according to the methods of Kvaal (for in situ and extracted teeth), Solheim (for in situ and sectioned teeth), Lamendin (for extracted teeth), Johanson (for sectioned teeth) and Bang (for extracted and sectioned teeth) by one independent observer. For each method, mean age error and standard error were assessed as the measures of accuracy and precision. In addition, method simplicity, requirements for tooth preparation and the equipment necessary were assessed and recommendations given for forensic use in various situations. Methods for sectioned teeth gave more reliable results when compared to methods for intact teeth.

Adolescent↗
PubMedDate not supplied

A clinical evaluation of ceramic laminate veneers.

The objective of this study was to make a clinical quality evaluation of resin-bonded ceramic veneers placed in general practice. Ceramic veneers were evaluated by four independent examiners according to the California Dental Association guidelines for evaluation of dental care. In addition, bleeding and margin index and mode of tooth preparation were recorded. None of the veneers had been replaced and only two had fractured. Almost all veneers received a satisfactory rating regarding surface, color, and margin integrity. More than half of the veneers had a satisfactory anatomical form. The bleeding index was comparable to that reported for other types of crowns. An equigingival or subgingival margin was most common.

Adolescent↗
PubMed1992

Resin-bonded bridges: 2. Treatment planning, clinical gases and failures.

This is the second paper in the two-part series which considers the developments and clinical techniques of resin-bonded bridges with the emphasis on methods for increasing success from a functional and aesthetic view point. Part 1 focused on the development and types of resin-bonded bridge and tooth preparation. This article describes the clinical application of this type of bridge and discusses failures.

Adolescent↗
PubMed2003

Method for immediate measurement of in vitro bond strength of bonded direct esthetic restorations.

There are many different ways to measure the bond strength of direct esthetic restorations to various dental substrates. Unfortunately, most methods cannot measure bond strengths immediately after a restoration has been placed. This lack of clinically-relevant information seriously affects the clinician's ability to select and use various bonding agents and procedures. The aim of this article is to provide a very detailed method for immediate measurement of in vitro bond strengths of direct bonded esthetic restorations. It focuses on the steps that should be taken to select and prepare various tooth substrates for bond strength testing, the steps to "restore" various tooth substrates, and to measure the immediate in vitro bond strength. A fundamental understanding of a standardized testing protocol should provide clinicians with a clearer appreciation of bond strengths associated with various bonding procedures.

Dental Bonding↗
PubMedDate not supplied

[Clinical and technical measures to improve the fit of whole-cast fixed dentures to the denture bed].

Basing on the literature data and their clinical experience, the authors analyze the following factors influencing the union of whole-cast permanent dentures and denture bed: shape of the prepared tooth, use of various types of benches, presence of free space for cement, compensation for the alloy shrinkage, simplification of placing the dentures by perforating the crowns, use of vibration, lesser volumes of cement put into the crown, and various methods of transferring the masticatory pressure to the denture over the course of denture fixation. Practical significance of these factors is estimated.

Crowns↗
PubMed2003

Bond strengths of tooth-colored posts, effect of sealer, dentin adhesive, and root region.

PURPOSE: To evaluate the effect of sealer, dentin bonding agent, and root region on the push-out bond strengths of three tooth colored posts. METHODS: 24 extracted human single rooted maxillary central incisors and canines were endodontically-treated using gutta percha and Roth's 801 or AH26 sealer. Posts (Cosmopost, Fibrekor, or Parapost Fiber White) were placed using one of two adhesive systems (Parapost Cement Conditioner with Parapost Cement, or One-Step with Hi-X Post self-cure resin cement). The push-out test was performed on different sections of the root to measure bond strengths. RESULTS: Cosmopost showed significantly lower mean bond strengths than either Fibrekor or Parapost. Bond strengths of the posts in the crown section were significantly higher than those in any of the three root areas measured. Neither the eugenol-containing sealer nor the bonding agent type had any effect on bond strength. Post type and root region significantly affected bond strength while sealer type or bonding agent had no effect on bond strength.

Analysis of Variance↗
PubMed2000

[Three dimensional Finite Element Analysis of the Effects of Posts and Cores with Different Angles]

OBJECTIVE:The test is an analogue of the conditions that cast post and core can be made with different angles to get the core incline lingually or facially in clinic, so that the arrangement of the anterior teeth may be improved.METHODS:Analyse the stress distribution and concentration in the dentin of posts and cores with different angles by Ansys three dimensional finite element stress analysis method.RESULTS:The stress in root was positively related to the angles between the load and the axis of the tooth, the stress distributoin in dentin was related to the direction of the core but not related to the angles. The closer the distance from the load to cemento enamel junction,the greater the effect of the load on the stress in dentin.CONCLUSION:When the cast post and core with angle was used to rectify the facially malpositional maxillary anterior teeth, the core should not be inclined lingually excessively. It is important to assure the thickness of the facial and lingual canal wall during tooth preparing and to adjust the occlusion so that the root fracture can be avoided.

Journal Article↗
PubMedDate not supplied

Influence of finish-line form on crown cementation.

Studies reporting the influence of finish-line configuration on the fit of cemented crowns have had conflicting conclusions. This study examined the effect of finish-line configuration on the fit of cemented complete crowns. Three identical tooth preparations were made, each with a different facial finish line: shoulder, shoulder-bevel, and chamber. The prepared teeth were replicated to produce 45 epoxy resin teeth, 15 for each finish-line design. Thirty cast crowns were fabricated and seated on their respective epoxy resin teeth--fifteen without cement and fifteen with zinc phosphate cement. An additional set of fifteen castings, seated on their working dies, was used for control measurements. All specimens were embedded, sectioned, and measured at predetermined sites. Results showed that finish-line form does not affect the fit of cemented crowns.

Cementation↗
PubMed1992

Sealed restorations: 5-year results.

This clinical study determined the feasibility of a sealed resin composite restoration to arrest dental caries using a minimal tooth preparation: a bevel in enamel only without removal of the carious lesion. These ultra-conservative sealed composite restorations placed over caries (CompS/C) were compared with ultra-conservative sealed amalgam restorations (AGS) that had no "extension for prevention". The CompS/C restorations were also compared with the traditional (unsealed) amalgam restorations (AGU) with the "extension for prevention" outline form. Caries progress, as determined by standardized radiographs, revealed that after 5 years caries remained arrested under the CompS/C restorations; the marginal integrity was similar for the CompS/C and the AGS groups, and exhibited highly significant superiority to the AGU restorations (Chi square, P less than = 0.00004). Complete sealant retention over the amalgam restorations (AGS group) was less than over the composite restorations (CompS/C), and conversely, partial sealant retention was higher for the AGS group. Sealants also appeared to protect the posterior composite restorations against wear.

Adolescent↗
PubMed2004

Are there acceptable alternatives to amalgam?

Amalgam has been the material of choice for restoring posterior teeth for more than 100 years. The past 25 years have witnessed significant advances in restorative materials themselves and in the bonding systems for retaining a restoration in the prepared tooth. As a result, there has been a shift toward resin composite materials during this same period because of concerns about the esthetics and biocompatibility of dental amalgam. In addition, other materials such as glass ionomer cements, ceramic inlays and onlays, and gold alloys have been used as alternatives to amalgam. This article will review recent studies on the longevity and biocompatibility of these alternatives to dental amalgam.

Biocompatible Materials↗
PubMed2005

Evaluation of the interface between one-bottle adhesive systems and dentin by Goldner's trichrome.

PURPOSE: To evaluate the hybrid layers in interfaces between dentin and six contemporary one-bottle adhesive systems using a nondestructive differential staining micro-technique. METHODS: The adhesive systems used in this study were divided to three groups based on hydrophilic/hydrophobic component ratios (i.e. ability to dissolve in water), from highest to lowest as follows: Group 1 (Dentastic UNO.DUO, PermaQuick PQ1) > Group 2 (One-Step, Primer&Bond NT) > Group 3 (Optibond Solo, Single Bond). The occlusal third of the crown was removed from 36 extracted, unerupted human 3rd molars. Smear layers were created by abrading the dentin with 600 grit SiC under water. The exposed dentin was treated with one of the adhesive systems per manufacturer's instructions. After 24 hours in water, 3-5 microm thin sections of the adhesive/dentin (adhesive/dentin ) interface were cut with a microtome and stained with Goldner's trichrome. Stained thin sections from each prepared tooth were imaged with light microscopy. RESULTS: The thickness and color difference of adhesive/dentin interfaces among these one-bottle adhesive systems were clearly visualized. The width of the hybrid layers varied, ranged from 4.1-9.2 microm for six adhesive systems. The color differences in the stained sections are reflected to the extent and degree to which the adhesive envelops the exposed collagen. Among these six bonding systems, resin encapsulation of collagen varied from highest to lowest as follows: Group 1 (UNO, PQ1) > Group 2 (OS, PBNT) > Group 3 (OP, SB). The differences in collagen encapsulation are dependent on the adhesive composition, or the ability to tolerate water during the infiltration of the wet demineralized matrix.

Azo Compounds↗