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At least 559 records · Page 31Linked to original sources
PubMed2004

Effects of surface treatment and joint shape on microtensile bond strength of reattached root dentin segments.

STATEMENT OF PROBLEM: An effective bonding technique for reattaching vertical root fracture segments has not yet been established. PURPOSE: The purpose of this study was to investigate the effects of surface treatment and joint shape on bond strength of reattached root dentin segments. MATERIAL AND METHODS: Microtensile dentin specimens (n=120, cross-sectional area=1.5 mm2) were obtained from 12 bovine teeth roots, and fractured under a tensile force. The segments of each group (n=6) were reattached by a 4-META/MMA-TBB adhesive resin after different treatments (etching or polishing, a 50-microm or 500-microm gap space, butt or wedge joint). The group with a 50-microm gap space and butt joint, which was not etched or polished, served as the control. After 24 hours of storage in 0.9% normal saline solution or thermal cycling (3000 cycles, 4 degrees C and 60 degrees C), the specimens were fractured in a universal testing machine at a crosshead speed of 1.0 mm/min. The microtensile bond strengths (MPa) were recorded. The bonded interface and fractured surface were observed by SEM (original magnification x 1000). The results were analyzed by a 2-way analysis of variance and the Fisher protected least significant difference post-hoc test (alpha=.05). RESULTS: Significantly higher bond strengths (P=.0001) were shown for the nonpolished group (9.78 +/- 4.44 MPa) and the etched group (9.31 +/- 1.23 MPa) than for the polished group (fractured before test). The wedge-shaped joint exhibited the highest bond strength (18.57 +/- 3.40 MPa, P=.0017). SEM observations showed that the penetration of resin tags along the oblique dentinal tubules was within the wedge joint. CONCLUSION: Etching and oblique tubule orientation contributed to significantly high bond strength of reattached segments to dentin after vertical root fracture.

Acid Etching, Dental↗
PubMed2004

Survival rates of resin-bonded, glass fiber-reinforced composite fixed partial dentures with a mean follow-up of 42 months: a pilot study.

STATEMENT OF PROBLEM: Although short-term clinical data exist for resin-bonded, glass fiber-reinforced composite fixed partial dentures (FPDs), long-term data are needed. PURPOSE: The survival rates of 29 resin-bonded, glass fiber-reinforced composite fixed partial dentures were evaluated in this clinical study for periods of up to 42 months. MATERIAL AND METHODS: FPDs were fabricated to replace 1 to 3 missing maxillary or mandibular teeth of 29 patients not able to be treated with conventional FPDs. Originally, there were 37 patients (the drop-out rate was 22%). The FPDs were retained with wings, inlays, complete coverage crowns, or combinations of these that were bonded to tooth structure. The FPD frameworks were made of continuous unidirectional E-glass fibers with a multiphase polymer matrix and light-polymerized particulate composite veneer. The patients were recalled for examinations, where a general dental examination was performed, 1 to 3 times per year for up to 63 months (minimum 24 months, mean 42 months). Partial or complete total debonding of the FPD or the framework fracture was considered a treatment failure. The data were analyzed with the Kaplan-Meier survival test (alpha=.05). RESULTS: Two resin frameworks fractured, and 3 frameworks were debonded. Kaplan-Meier survival probability at 63 months was 75%. Three of the failed FPDs were rebonded or repaired in situ, producing a functional survival rate of 93% after rebonding or repairing (mean survival time was 55 months). CONCLUSION: The results of this clinical study of 29 prostheses suggest that glass fiber-reinforced FPDs may be a possible alternative to cast metal resin-bonded FPDs. These restorations were successfully used as multiple-unit prostheses that employed a variety of abutment tooth preparation designs.

Composite Resins↗
PubMed2006

Considerations for services from dental technicians in fabrication of fixed prostheses: A survey of commercial dental laboratories in Thessaloniki, Greece.

STATEMENT OF PROBLEM: Effective communication and cooperation between dentists and dental technicians are essential in providing quality services. There has been a lack of information regarding dentist-dental technician communications and current methods and materials used for the fabrication of fixed partial dentures (FPDs). PURPOSE: This cross-sectional study identified the materials and techniques used for fabrication of FPDs, as well as the status of communication between dentists and dental technicians in Thessaloniki, Greece. MATERIAL AND METHODS: A questionnaire was developed with 7 sections pertaining to procedures and materials used for the fabrication of fixed prostheses: general questions, infection control, impressions/interocclusal records, die technique/mounting, information from final casts, prostheses design/materials, and communication/shade selection. The questionnaire was anonymous and distributed by the Association of Dental Technicians of Thessaloniki to all member laboratories (228) in the wider province of Thessaloniki, Greece. Due to the absence of normal distribution of the results, frequencies and medians were reported. RESULTS: Ninety-six of 228 dental laboratories responded (42.1% response rate). Twenty-six percent of dental laboratories did not routinely disinfect incoming items. The dental technicians considered 30% of incoming final impressions and 20% of interocclusal registrations as inadequate. Half of the time (55%) final casts were mounted by technicians on simple hinge articulators. Only 20% of tooth preparations had adequate finish lines. The majority (70%) of fixed restorations were metal-ceramic. Fifty-seven percent of dental technicians considered the delivery time requested by dentists as insufficient. CONCLUSION: The information provided in this study indicates areas of weakness in communication between dentists and dental technicians, along with areas where both parties should use greater care during clinical and laboratory procedures.

Communication↗
PubMed1995

Seating accuracy and fracture strength of vented and nonvented ceramic crowns luted with three cements.

Methods to facilitate the seating of artificial crowns can improve the gingival margins and ensure longevity. This study examined the effects of venting and different luting agents on the seating accuracy and compressive strength of Dicor ceramic crowns. Vented and unaltered anterior restorations were tested using zinc phosphate cement (ZnPO4), glass ionomer, and composite resin cement. Rexillium metal dies of a tooth preparation of a maxillary canine were provided and standardized crowns were fabricated. The artificial crowns were evaluated for adaptation of the finish line before and after cementation, then were compressively loaded to failure. Under the conditions of this study, neither the design of the artificial crown nor the luting agent had a significant effect on the compressive strength. Composite resinous cement appeared to enhance seating of the crown, whereas ZnPO4 cement inhibited seating.

Cementation↗
PubMed1995

In vivo marginal adaptation of cast crowns luted with different cements.

Large marginal crown discrepancies are deleterious. Although previous studies have examined casting seating in vitro, few have evaluated the effects of different luting cements on in vivo seating. Hence this in vivo study compared marginal discrepancies created by different cements on cast crowns. Tooth preparations were completed according to acceptable procedures on previously intact human molars that were severely periodontally compromised and scheduled for extraction. Castings were made by conventional techniques. The castings were randomly assigned to the following luting agents: zinc phosphate cement, resin-modified glass-ionomer cement, and the same resin-modified glass-ionomer cement with a dentinal bonding agent. After 6 months the teeth were carefully extracted, embedded, and sectioned, and vertical and horizontal discrepancies were measured. Analysis of variance revealed that all cements resulted in similar discrepancies. Vertical discrepancies were considerably greater than horizontal discrepancies, and the distributions of marginal discrepancies were skewed towards upper ranges.

Analysis of Variance↗
PubMed1982

Influence of cementing medium on the accuracy of the remount procedure.

In light of the results of this study, a number of conclusions can be made with reference to full coverage castings. 1. Dental cement causes occlusal displacement. Zinc phosphate cement results in a greater displacement than does temporary zinc oxide-eugenol cement. 2. The disparity in seating of cast restorations obtained with no cement, temporary zinc oxide-eugenol cement, and zinc phosphate cement tends to reduce in magnitude with increasing taper of the tooth preparations. 3. Venting of crowns is an effective way of reducing the disparity in seating between no cement, temporary zinc oxide-eugenol cement, and zinc phosphate cement. 4. Remount records should be made with the restorations cemented with temporary zinc oxide-eugenol cement rather than held to the teeth by friction alone.

Acrylic Resins↗
PubMed1989

Microleakage of core materials for complete cast gold crowns.

This study evaluated the microleakage patterns of complete cast-gold crowns cemented onto teeth rebuilt with pin-retained cores made from cast gold, amalgam, composite resin, and silver-reinforced glass ionomer by using three different cements (zinc phosphate, glass ionomer, and resin cement). Crowns cemented onto unrebuilt tooth preparations with zinc phosphate cement served as controls. The cemented specimens were thermocycled between 4 degrees and 50 degrees C in waterbaths. They were then embedded in epoxy resin and sectioned. The extent of marginal microleakage was evaluated with a stereomicroscope and scored. The findings indicated that the type of luting agent used appeared to affect microleakage more than the core material. No significant differences in the degree of microleakage were found under crowns cemented onto teeth rebuilt with the four core materials when cemented with the same luting cement.

Composite Resins↗
PubMed1996

A longitudinal study of resin-bonded prostheses.

Resin-bonded fixed partial dentures, without definitive tooth preparation and current resinous cements and perceptive treatment, have had an inordinate number of dislodgments in initial restorative efforts. A longitudinal examination of resin-bonded prostheses was performed after a mean observation time exceeding 6 years. To prevent stress fatigue fractures of the cement bondings, one proximal groove was prepared in dentin for each anterior abutment and the inner surfaces of the frameworks were silicoated. Five of 34 prostheses debonded, and the bond strength between resin and high gold alloys was too low to resist fatigue fractures during this study. The results of this study and other reports suggested a need for increased retention and resistance form of the frameworks to improve longevity of resin-bonded prostheses.

Adult↗
PubMed1996

Biaxial flexural strength and indentation fracture toughness of three new dental core ceramics.

The traditional gold and porcelain fused to metal crowns have been challenged by the esthetic all-ceramic crown materials. Only previous experience with poor mechanical properties, lack of standardized tooth preparation, and processing challenges have prevented universal acceptance of all-ceramic crowns. However, stronger and tougher ceramics and unique processing methods for ceramics have been developed in the past 20 years. In this study, three new ceramic crown core materials were tested to compare their biaxial flexural strength and indentation fracture toughness. Ten specimens of Empress, In-Ceram, and Procera AllCeram ceramics were prepared according to their manufacturers' recommendations. The results revealed significant differences in flexural strength for the three materials (p < or = 0.05). The average flexural strengths of AllCeram, In Ceram, and Empress ceramics were 687 MPa, 352 MPa, and 134 MPa respectively. There was no statistically significant difference between the fracture toughness of Procera (4.48 MPa x m1/2) and In-Ceram ceramics (4.49 MPa x m1/2); however, both ceramics had significantly higher fracture toughness (p < 0.005) than Empress ceramic (1.74 MPa x m1/2).

Aluminum Oxide↗
PubMed1997

Adherence of "stuck" restorations to demineralized dentin following use of experimental primers.

PURPOSE: This in vivo study histopathologically evaluated the biocompatibility of four self-conditioning dentinal primer formulas in four bonding systems and evaluated the pulpal responses of the self-conditioning dentinal bonding systems for Class V tooth preparations in primates. MATERIAL AND METHODS: The basic formula consisted of proprietary carboxylic diacid monomer, dipentaerythritol pentaacrylate phosphoric acid ester, acetone, and ethanol that was used alone or mixed with other commercial priming agents. After application of primers, Prisma Universal Bond 3 was selected to restore the cavity preparations. RESULTS: All systems were judged histopathologically biocompatible. "Stuck" restorations that were resistant to acid demineralization necessary for processing of histologic slides, occurred more frequently with intact smear layers and increasing use of dehydrating agents. CONCLUSIONS: Tests should be performed to determine whether "stuck" restorations in in vivo studies that maintain dentin-pulpal relationships can support in vitro shear bond strength tests.

Acetone↗
PubMed1994

Dentin ablation by Ho: YAG laser: correlation of energy versus volume using stereophotogrammetry.

The future use of lasers in endodontics is dependent upon predictable and consistent ablation of dentin. In this pilot study we used an Ho:YAG laser fiberoptic delivery system to apply laser energy to prepared tooth sections in vitro. Longitudinally sectioned single-rooted human teeth were subjected to single-energy pulses varying from 25 to 1750 mJ at a focal length of 1 mm. At different energy levels we observed changes in the dentin surface ranging from minute surface pitting to the formation of large craters. Scanning electron microscopy and stereophotogrammetry were used to determine the relationship between the amount of energy applied to dentin and the extent of dentin ablation. Dentin crater formation was quantified by determining surface area, depth, and volume of craters produced. Increases in laser energy were compared with increases in surface area, depth, and volume of craters produced within the range of 150 to 1200 mJ. The Ho:YAG laser fiberoptic delivery system used in this study provides an effective means of ablating dentin. Three-dimensional stereophotogrammetry may prove to be a useful method for further studies on the effects of laser energy on mineralized tissues.

Dentin↗
PubMed2001

Rheological properties of vinyl polysiloxane impression pastes.

OBJECTIVES: Some vinyl polysiloxane impression (VPS) materials are claimed to be 'thixotropic' so that they will have 'non-drip' properties and not flow off an impression tray during insertion of the material into the mouth. This work was carried out to investigate rheological properties of VPS materials by determination of their flow properties under different experimental conditions relevant to their dental application. METHODS: The rheological characteristics of each component paste of two low viscosity VPS materials were assessed by a Dynamic Stress Rheometer using cone and plate geometry. RESULTS: Both pastes of one product (Imprint II) showed a yield stress of around 40 Pa in addition to some degree of true thixotropy. In contrast, both Examix pastes had no yield stress value, but the catalyst paste was markedly thixotropic, as shown by a drop in viscosity as a result of application of shear force over time. Both products had thixotropic properties. The Imprint II in addition showed a yield stress that would also contribute to the 'non-drip' properties. SIGNIFICANCE: Combination of yield stress and thixotropy will prevent the undesirable drip of the materials once it has been injected around the tooth preparation until the impression tray is loaded and seated. After seating the tray, a thixotropic material will not flow.

Chemical Phenomena↗
PubMed2000

Porcelain veneers: a review of the literature.

OBJECTIVES: Porcelain veneers are steadily increasing in popularity among today's dental practitioners for conservative restoration of unaesthetic anterior teeth. As with any new procedure, in vitro and in vivo investigations are required to assess the ultimate clinical efficacy of these restorations. The current literature was therefore reviewed in search for the most important parameters determining the long-term success of porcelain veneers. DATA SOURCES: Laboratory studies focusing on parameters in prediction of the clinical efficacy of porcelain veneers such as the tooth preparation for porcelain veneers, the selection and type of the adhesive system, the quality of marginal adaptation, the resistance against microleakage, the periodontal response, and the aesthetic characteristics of the restorations have been reviewed. The clinical relevance of these parameters was then determined by reviewing the results of short and medium to long-term in vivo studies involving porcelain veneers performed during the last 10 years. CONCLUSIONS: The adhesive porcelain veneer complex has been proven to be a very strong complex in vitro and in vivo. An optimal bonded restoration was achieved especially if the preparation was located completely in enamel, if correct adhesive treatment procedures were carried out and if a suitable luting composite was selected. The maintenance of aesthetics of porcelain veneers in the medium to long term was excellent, patient satisfaction was high and porcelain veneers had no adverse effects on gingival health inpatients with an optimal oral hygiene. Major shortcomings of the porcelain veneer system were described as a relatively large marginal discrepancy, and an insufficient wear resistance of the luting composite. Although these shortcomings had no direct impact on the clinical success of porcelain veneers in the medium term, their influence on the overall clinical performance in the long term is still unknown and therefore needs further study.

Cementation↗
PubMed2001

A method of age estimation using Raman microspectrometry imaging of the human dentin.

The aim of this work is to establish a correlation between ageing and Raman spectra imaging of human teeth. Raman spectrum of an analysed sample is characteristic of its chemical components. By exploring the different dentinal areas on each tooth, we sought to find a correlation between noticeable variability on Raman spectra and the stages of dentinal evolution with advancing age. A study on 30 teeth analysed by Raman microspectrometry was used to select predictors of age, and it allowed us to determine a regression formula, with age as a dependent variable. Our data were computed by means of a statistical method called partial least squares (PLS) regression. This method was specially adapted for this kind of situation, where we have numerous predictors and relatively few observations. The regression formula was performed on a test sample of four more teeth, and we obtained a correct age estimation, with a mean error of more or less than 5 years. The main benefits of this method was a minimal and non-destructive tooth preparation, which led to an efficient age prediction, for any age group.

Adolescent↗
PubMed2001

Palatal radicular multigrooves associated with severe periodontal defects in maxillary central incisors.

BACKGROUND: This case report describes a rare condition of palatal radicular multigrooves on teeth 11 and 21 with severe periodontal defects and the findings at 3-year follow-up. METHOD: Radiculoplasty using hand curettes and rotary burs were used to remove the multigrooves on the root surfaces and change the wrinkled root form to the relatively flat and smooth normal root morphology. Minor tooth movement and frenotomy were performed for a diastema between teeth 11 and 21. Supportive periodontal therapy started immediately after completion of the active treatment. RESULTS: Improved healthy periodontal tissues and adequate plaque control have been maintained.

Adult↗
PubMed1993

Dental anomalies--are adhesive castings the solution?

Adhesive cast restorations placed without tooth preparation were used to restore the teeth of patients affected by either amelogenesis or dentinogenesis imperfecta. Twelve patients aged between 7 and 18 years were treated and in total 64 cast restorations were placed. At the time of cementation, the vertical dimension was increased by the thickness of restorative material placed on the functioning surfaces of the restored teeth. Full occlusion was restored for all individuals, with only one casting being lost. The castings have been placed for intervals between 10 and 54 months.

Acrylic Resins↗
PubMed1997

Film thickness of various dentine bonding agents.

Curing dentine bonding agents create a film thickness on the surface of teeth which are prepared for all-ceramic crowns. The aim of this study was to investigate if the film thickness of dentine bonding agents (DBAs) is acceptable with the fit of definitive restorations of 50-100 microm. AllBond 2, Syntac, ART Bond, P-Bond (an experimental DBA), and the Primer of AllBond 2 were applied onto teeth which were prepared with standardized all-ceramic crown preparations. The DBAs were applied onto the prepared tooth surfaces according to manufacturers' instructions and under a standardized simulation of intrapulpal pressure. After curing the DBAs, the teeth were cut mesiodistally and orolingually and the film thickness was measured under a light microscope. Only the film thicknesses of AllBond 2 and P-Bond were low enough and, therefore, would enable curing to take place immediately after their application.

Acid Etching, Dental↗
PubMed1997

Clinical and histological evaluation of thermal injury thresholds in human teeth: a preliminary study.

The effect on healthy dental pulp of thermal increases ranging from 8.9 to 14.7 degrees C was evaluated. These temperature increases correspond approximately to those caused by certain restorative procedures, such as tooth preparation with high-speed instruments and the fabrication of direct provisional crowns. Two criteria of evaluation have been used in conjunction, a clinical (symptomatic) and a histological one, to assert with greater precision potential damage to the pulp. The results suggest a low susceptibility of cells to heat, which does not appear to be a major factor of injury, at least in the short term. The main cause of postoperative inflammation or necrosis of the pulp is probably the injury of the dentine, a tissue in direct functional and physiological connection with the pulp.

Adolescent↗