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PubMedDate not supplied

[Motives for placement and replacement of dental restoration].

Aiming to evaluate placement and replacement of dental restorations, a questionnaire has been elaborated and distributed in Clinics of the Operative Dentistry Department, Bauru Dental Scholl--USP, for the students to point out some information about the operatory procedures performed. The analysis of the results made possible the observation that of the 241 restorations achieved, 45.64% were made due to primary caries and 54.36% were replacement of deficient restorations. The reasons for replacement as well as the possible factors responsible for failure of tooth-colored and amalgam restorations are analyzed and discussed.

Composite Resins↗
PubMed1978

Temporary restorative materials: properties and uses.

Various materials used for temporary restorations are reviewed, with reference to their chemical and physical properties. Research and standard specifications should be instituted in order to standardize and improve the many products now available to the profession. Knowledge of the materials and their properties will enable the dentist to arrive at correct selection of the material for each case, thus promoting more successful clinical procedures.

Acetates↗
PubMed1993

An in vitro assessment of cavity margin finishing and marginal adaptation of tunnel restorations.

Reasons for the failure of tunnel restorations include fracture of weak carious enamel at the cavity margins, poor adaptation of the restoration approximally, incomplete removal of caries and fracture of the marginal ridge. Four methods of cavity margin finishing were investigated. A round steel bur in a slow handpiece was found to give the best finish. Four materials were used for the restoration of tunnel cavities. In this study posterior resin composite gave the best marginal adaptation; however, a glass ionomer (polyalkenoate) may be preferable as it is impossible to guarantee removal of all carious tooth tissue from these preparations and glass ionomers have the benefit of fluoride release.

Cermet Cements↗
PubMed2006

EXAFS study of U(VI) uptake by calcium silicate hydrates.

Among the different cement minerals, calcium silicate hydrates (C-S-H) are the prime candidates for heavy metal binding because of their abundance and appropriate structure. Immobilization processes of heavy metals by cementitious materials, and in particular C-S-H phases, thus play an important role in multibarrier concepts developed worldwide for the safe disposal of hazardous and radioactive wastes. In this study, the uptake of U(VI) by C-S-H has been investigated using X-ray absorption fine structure (XAFS) spectroscopy. C-S-H phases were synthesized using two different procedures: One is based on the mixing of CaO and SiO2 solids ("direct reaction" method); for the other one starting solutions of Ca and Si are used ("solution reaction" method). XAFS investigations were carried out on samples doped with U(VI). U(VI) was either sorbed onto previously precipitated C-S-H phases (sorption samples) or added during C-S-H synthesis (coprecipitation samples). The coordination environment of U(VI) in the sorption samples was found to be independent of the procedure used for C-S-H synthesis. A split equatorial oxygen shell (Oeq1: R=2.23-2.27 A; Oeq2: R=2.36-2.45 A), neighboring silicon atoms at short (R=3.07-3.11 A) and long (R=3.71-3.77 A) distances, and neighboring Ca atoms (R=3.77-3.81 and 4.15-4.29 A) were observed for all the samples. The structural parameters resemble those reported for uranophane. The coordination environment of U(VI) in the coprecipitation samples depends on the method used for C-S-H synthesis, and further, the spectra differ from those determined for the sorption samples. UU backscattering contributions were observed in the samples prepared using the direct reaction method, whereas no split equatorial shell appeared in the samples prepared using the solution reaction method.

Absorptiometry, Photon↗
PubMed1993

Pulpal healing and dentinal bridge formation in an acidic environment.

This study was designed to observe the healing and bridging capacity of mechanically exposed pulps that were capped with silicate or zinc phosphate cements and biologically sealed with zinc oxide-eugenol cement to exclude bacteria. In six monkeys, Class V facial cavities with pulpal exposures were randomly distributed throughout 105 teeth, of which 80 were directly capped, 40 with silicate cement and 40 with zinc phosphate cement. Twenty of each group were filled to the cavosurface margin with the respective cement and 20 were surface sealed to the cavosurface margin with zinc oxide-eugenol cement. The remaining 25 exposures were capped with calcium hydroxide and amalgam as controls. Tissues were obtained by perfusion fixation after intervals of 21, 14, 10, 5 and 3 days. The 25 pulps capped with calcium hydroxide showed cell migration and organization at 5 days and dentinal matrix deposition at 10 days. At 3 and 5 days, all exposures in the experimental groups showed clot resolution. At 10 days, fibroblasts had stratified against the cement interface. At 14 days, pulps in both experimental groups showed new dentinal bridge formation directly adjacent to the acidic cements. The 21-day experimentally capped and sealed pulps presented healing similar to the controls. This study indicates that acidic components of silicate and Zinc phosphate cements are not directly responsible for pulpal inflammation or necrosis. The exposed dental pulp possesses an inherent healing capacity for cell reorganization and dentinal bridge formation when a bacterial seal is provided.

Animals↗
PubMed2004

Flexural fatigue behavior of machinable and light-activated hybrid composites for esthetic restorations.

The purpose of this study was to determine the flexural strength and flexural fatigue strength of a machinable composite (GN-I) and three hybrid composites (Artglass, Estenia, and Gradia). Specimens (2 x 2 x 25 mm) were polymerized in a laboratory photo-curing unit and then immersed in water at 37 degrees C for 24 h, 6 months, and 1 year. After each immersion period, flexural strengths (4-PFS) were measured at a cross-head speed of 1 mm/min in 4-point bending (span = 20 mm; distance between inside loading points = 10 mm). The cyclic fatigue test was performed at 2.0 Hz on a fatigue tester. The staircase method was employed for flexural fatigue strength (FFS) using a 5000 cyclic load limitation, 5-MPa stress increment, and 20 specimens for each material. Both 4-PFS and FFS of the machinable composite after all immersion periods were significantly greater than those of the three hybrid composites. The FFS results followed the same pattern as those of the 4-PFS. The Estenia material exhibited the highest 4-PFS and FFS after 24 h of immersion among three hybrid composites, whereas after 1 year of immersion, all three composites showed almost identical 4-PFS and FFS statistically. A strong correlation was observed between 4-PFS and FFS of the machinable composite and three hybrid resin composites.

Composite Resins↗
PubMed1988

Evaluation of the retention of endodontic implants.

The study investigated the retentive strength of endodontic implants measured by forced removal (pull-out or push-out tests) as a function of implant design and cement type. Smooth-tapered, threaded, and an innovative porous-surfaced implant were evaluated. Specimens were cemented in single-rooted human teeth with five different cements: zinc phosphate, polycarboxylate, glass ionomer, silicophosphate, or AH-26. The results indicated superior retention for the threaded and porous-surfaced implants, and stronger retention with glass-ionomer and AH-26 cements.

Bismuth↗
PubMed1992

Cytotoxicity evaluation of a new radiopaque resin additive--triphenyl bismuth.

Triphenyl bismuth (Ph3Bi) is a promising new additive for making biomedical resins visible on x-ray images. We evaluated the cytotoxicity of Ph3Bi, both alone and as a component of a denture resin, as an initial step in determining its biocompatibility. These experimental materials were compared with several types of dental materials that are in current clinical use (PMMA denture acrylic resin, two photo-cured sealants, and two glass-ionomer cements). Human embryonic lung fibroblast tissue cultures (WI-38 cells) were exposed to 24-hour aqueous extracts of the materials. Changes in cell growth, cell viability, and the visual appearance of cells were used for the assessment of toxic response. Only a slight degree of cytotoxicity was observed for Ph3Bi, both alone and in combination with self-cured PMMA. All clinical materials showed a higher level of cytotoxicity than did Ph3Bi. The sealants and cements exhibited the most cytotoxicity and PMMA acrylic the least. The cytotoxicity of PMMA was elevated slightly by inclusion of Ph3Bi, probably due to decreased monomer conversion. When stored in water, the already low levels of cytotoxicity of both PMMA and PMMA with added Ph3Bi were reduced even further. From these results, we can predict a high level of safety for Ph3Bi as a radiopaque additive for biomedical resins. Any toxicity associated with Ph3Bi-containing resins can be reduced or avoided by prior extraction. Alternatively, curing conditions can be selected that would drive the polymerization reaction to a higher level of conversion.

Acrylic Resins↗
PubMed1994

Glass polyalkenoate bond strength to dentine after chemomechanical caries removal.

The bond strength of a glass polyalkenoate cement after chemomechanical caries removal of dentine with or without the use of a conditioning agent and the mode of bond failure using scanning electron microscopy was examined. Forty extracted carious human teeth were divided into four groups of ten. Conventional caries removal was carried out on two groups and chemomechanical caries removal on the other two groups. Surface conditioner was applied to the dentine in one conventionally treated and one chemomechanically treated group. Glass polyalkenoate cement was applied via a metal holder to the dentine. The samples were stored for 7 days in a moist environment at 37 degrees C. The samples were subjected to a shearing-type stress at a cross-head speed of 0.5 mm min-1. The mean bond strength for each group, in MPa (standard deviation), was: conventional caries removal alone 1.32 (0.51), conventional caries removal and conditioner application 2.43 (0.47), chemomechanical caries removal alone 2.47 (0.99) and chemomechanical caries removal and conditioner application 2.76 (0.96). Mean bond strengths for both the chemomechanically treated groups and the conventionally treated group, coupled with the use of the conditioning agent, were significantly greater than for the conventionally treated groups alone at the 0.05 level. There was no significant difference between the chemomechanically treated groups or the group conventionally treated with conditioner application. SEM examination revealed a combination of cohesive and adhesive bond failure. Different morphologies between the conventionally and chemomechanically treated surfaces were also evident.

Acrylic Resins↗
PubMed2004

Effect of fiber position and orientation on fracture load of fiber-reinforced composite.

OBJECTIVES: The aim of this study was to determine the effect of fiber position and orientation on the initial and final fracture loads of fiber-reinforced composite (FRC). METHODS: Test specimens made of two indirect particulate composites (BelleGlass HP, Kerr, Orange, CA) or (Targis, Ivoclar Vivadent, Amherst, NY) were reinforced with ultra high molecular weight polyethylene (UHMWPE) fiber ribbon (Connect, Kerr, Orange, CA), woven E-glass fibers (Vectris Frame, Ivoclar Vivadent, Amherst, NY) or unidirectional R-glass fibers (Vectris Pontic, Ivoclar Vivadent, Amherst, NY). Fibers were placed with different positions, orientations or geometry into the rhombic test specimens (2 x 2 x 25 mm3). Control specimens did not contain fiber reinforcement. The test specimens (n=6) were stored in distilled water for 1 week at 37 degrees C before testing in a three-point loading test to determine the initial and final fracture load values. RESULTS: Initial failure loads varied from 22.6 to 172.1 N. The lowest value resulted from one UHMWPE reinforcement fiber located in diagonal orientation and the highest from two unidirectional glass fiber reinforcements, one located on the tension side and the second on the compression side. SIGNIFICANCE: Position and fiber orientation influenced the load to initial and final failure, and specimen deflection. Tension side reinforcement was most effective in increasing the load to initial and final fracture.

Analysis of Variance↗
PubMed2005

Morphological and functional rehabilitation of severely infra-occluded primary molars in the presence of aplasia of the permanent premolar: a clinical report.

This clinical report describes the fixed prosthodontic rehabilitation of an infra-occluded primary molar. Diagnostic considerations included the patient's age, occlusal status, condition of the infra-occluded tooth including the degree of infra-occlusion and root resorption, as well as adjacent alveolar bone levels. Due to the patient's young age, an invasive prosthetic approach was delayed in favor of an onlay restoration, which represented a more rapid and conservative therapeutic choice. The treatment involved the design and fabrication of a composite onlay on the deciduous molar using a ceramic optimized polymer on a fiber-reinforced composite framework. Three years later, intraoral radiography showed satisfactory marginal adaptation. No change was observed in periodontal tissues.

Adolescent↗
PubMed1991

Orthodontic bonding using glass ionomer cement: an in vitro study.

The aim of this study was to investigate the in vitro 24-hour tensile/peel bond strength of glass ionomer cement (GIC) together with the amount of cement left attached to the enamel surface after bond failure. The effect of contamination with moisture during setting/hardening and changing the powder/liquid mixing ratio of the GIC was also studied. Five GIC's (Intact, Fuji II, Orthocem B, ChemFil II, and Ketac Fil[capsulated]) and one composite resin (Concise) were tested by bonding GAC eyelets, with a curved photo-etched base, to the buccal surface of human premolars. Bond strength testing was performed on an Instron 1185 testing machine and the amount of cement left attached to the enamel surface quantified using the ARI index. The tensile/peel bond strengths achieved with all the GIC's were significantly lower than the composite resin (P less than 0.0002). Increasing the powder/liquid ratio resulted, in general, in higher bond strengths, the increase being significant for Intact and Orthocem B (P less than 0.05). Protection from moisture did not significantly affect the bond strength with the exception of Fuji II, for which, there was a significant decrease when the material was mixed at the recommended powder/liquid ratio.

Acrylic Resins↗
PubMed1992

Three-year evaluation of effect of surface conditioning on bonding of glass ionomer cement in cervical abrasion lesions.

Cervical abrasion/erosion lesions were restored without any form of mechanical cavity preparation with an anhydrous glass ionomer cement. To study the effect of dentin pretreatment on the bonding between dentin and glass ionomer cement three cleaning methods were tested: 1) mechanical cleaning with a prophylaxis paste, 2) scrubbing with a surface active cavity cleanser (Tubulicid) for 60 seconds, or 3) a 10-15 s application of a 40% polyacrylic acid solution. During a 3-yr period, 193 restorations were evaluated every 6 months. Cumulative loss rates after 3 yr were 11.6%, 12.3%, and 17.9% respectively. One restoration showed secondary caries during the evaluation period.

Acrylic Resins↗
PubMed1999

Nonmetal crowns.

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Crowns↗