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At least 685 records · Page 38Linked to original sources
PubMed1997

A clinical trial of all-ceramic crown restorations: status, fall 1995.

Although porcelain-fused-to-metal (PFM) restorations are the most widely used full-coverage crown restoration systems, their inherent properties make the achievement of natural aesthetic restorations an elusive task. In contrast, the all-ceramic system (IPS Empress, Ivoclar North America, Amherst, NY) offers excellent translucency and vitality, without the opacity associated with PFM restorations. Its vitality is further enhanced by an adhesive resin cementation method that conducts the color of the underlying tooth structure. This article reports the status of a 5-year investigation, initiated in 1992, of the clinical performance of the IPS Empress all-ceramic system and the resin cementation system used with it.

Adolescent↗
PubMedDate not supplied

Probability of failure of highly filled indirect resin-veneered implant-supported restorations: an in vitro study.

PURPOSE: The study compared the probability of failure of three highly filled resin-veneered restorations to that of conventional metal-ceramic restorations when used as implant-supported prostheses. The effect of the location of load application on the fracture resistance of the restorations was also studied. MATERIALS AND METHODS: Twenty samples each of the three resins, Artglass, Targis, and Estenia, were applied on type IV gold frameworks. Twenty metal-ceramic restorations of equal dimensions (VMK 95 and Degudent Universal) were used as controls. Compressive load was applied vertically at 1 mm (n = 10) and 2 mm (n = 10) from the periphery of the occlusal table until the restorations failed. Weibull analysis was applied to the data. RESULTS: There was no significant difference in the probability of failure among the metal-ceramic restorations and three resin-veneered restoration systems. Loading the resin-veneered restorations at the 1-mm location significantly increased their probability of failure when compared to the 2-mm loading location. The loading location did not significantly change the probability of failure of the metal-ceramic restorations. CONCLUSION: The probability of failure of resin-veneered restorations tested was not significantly different from that of the metal-ceramic restoration under two compressive loading conditions. Eccentric loading of resin-veneered restorations should be minimized in light of the higher probability of failure associated with such a loading condition.

Analysis of Variance↗
PubMed1975

Fluoride application procedures in orthodontic practice, current concepts.

A survey is given of present knowledge of different methods of fluoride administration with emphasis on practical measures of proved value for orthodontic patients. The review covers different F administration procedures by dental personnel and self-application and includes the use of prophylaxis pastes, topical solutions, gels, mouth rinses, dentifrices, tablets, cements, coatings, varnishes, etc. Some recommendations are given as to optimal programs in orthodontic practice based upon evaluations of clinical effectiveness, safety and ease of application. Some caries reduction has been obtained from professional application of F prophylaxis pastes, but F pastes cannot replace topical F application. Treatment with F gels or solutions preceded by thorough cleaning and drying of the teeth is advocated before the placement of appliances and at recementations. Because F solutions are tedious to apply, and not more effective than F gels, the latter are preferable. APF gel application is suited in conjunction with impression taking. Daily self-application of SnF2 gels undoubtedly is effective in reducing caries in orthodontic patients. However, daily NaF or APF mouth rinses may have the dual effect of caries inhibition and stimulating hygiene interest and are more thoroughly tested. In addition to the other forms of F administration, a F dentifrice should be used regularly. Daily F application is appropriate also for orthodontic patients in fluoridated areas. In vitro studies with F cements indicate a great F uptake by the enamel, but controlled, long-term clinical studies are lacking. Also the final judgment of a number of new coating techniques and F varnishes must await further clinical testing, although a beneficial effect of F sealing in orthodontic patients is substantiated. In conclusion, APF gel application before insertion of appliances and at regular recementations plus daily rinsing with dilute NaF or APF solutions throughout the periods of treatment and retention plus the regular use of a F dentifrice is recommended as a routine procedure for all orthodontic patients.

Child↗
PubMed1999

[Reproducible marginal gap measurements of partial ceramic crowns].

Aim of this research was to test the hypothesis that marginal gap measurements by a digital microscopic image processing computer are reproducible. Light microscopic images of the margins of Artglass partial crowns on stone dies were obtained with a 3CCD color video camera, digitized and processed. Ten measuring points were painted on a 0.5 mm section of the finish line of the preparation. The opposite corresponding measuring points on the margin of the partial crown were painted as well. The distance (marginal gap) between two corresponding points was painted and calculated by the computer. Reproducibility (precision) is reflected in the ability to reproduce the same measurement results in repeated measurements (n = 5). The reproducibility error was expressed as the coefficient of variation (CV) in percent (%). The localization of the corresponding measurement points and the calculation of the marginal gap were performed without errors. For a marginal gap between 15-50 microns the average measurement error was 3% or 0.45-1.5 microns. It was concluded that the measurement of the gap between two points by the digital image processing computer was reproducible. The measurement error was neglectable given that a clinically acceptable marginal gap is 100 microns.

Ceramics↗
PubMed2003

Long-term water-aging of whisker-reinforced polymer-matrix composites.

Long-term water exposure may degrade polymer-matrix composites. This study investigated the water-aging of whisker composites. It was hypothesized that whiskers would provide stable and substantial reinforcement, and that whisker type would affect water-aging resistance. Silica-fused Si(3)N(4) and SiC whiskers were incorporated into a resin. The specimens were tested by three-point flexure and nano-indentation vs. water-aging for 1 to 730 days. After 730 days, SiC composite had a strength (mean +/- SD; n = 6) of 185 +/- 33 MPa, similar to 146 +/- 44 MPa for Si(3)N(4) composite (p = 0.064); both were significantly higher than 67 +/- 23 MPa for an inlay/onlay control (p < 0.001). Compared with 1 day, the strength of the SiC composite showed no decrease, while that of the Si(3)N(4) composite decreased. The decrease was due to whisker weakening rather than to resin degradation or interface breakdown. Whisker composites also had higher moduli than the controls. In conclusion, silica-fused whiskers bonded to polymer matrix and resisted long-term water attack, resulting in much stronger composites than the controls after water-aging.

Analysis of Variance↗
PubMed2005

Maxillary tooth splinting in periodontally compromised patients using fiber-reinforced composite: the Targis-Vectris method.

AIM: To show the Targis-Vectris retention technique, illustrating its features and clinical applications in periodontally compromised patients. METHODS: The Targis-Vectris technique is constituted by an esthetic external layer (Targis) combined with and supported by a metal-free structure (Vectris). An adult female with a full Class II malocclusion and compromised periodontal condition with significant bone loss on the maxillary central incisor was treated. Before debonding, a fiber-reinforced splint was placed on the palatal surface of the maxillary anterior teeth, using the Targis-Vectris method, to permit long-term stability. The final result remained stable at 5 years posttreatment. RESULTS: The correction of the Class II malocclusion took 24 months. The Targis-Vectris method ensured maintenance of tooth position and periodontal condition. CONCLUSION: The Targis-Vectris technique represents a useful procedure for splinting maxillary teeth in selected periodontally compromised patients. The 5-year posttreatment follow-up visit showed no relapse. Correct occlusal relationships are necessary to reduce the risk of breakage.

Adult↗
PubMed2001

Kinetics of fluoride release from zinc oxide-based cements.

Considerable attention has been given to the release of the cariostatic fluoride ion from glass-based dental cements (dental silicate and glass ionomer). In these, the total available fluoride content is not precisely known since fluorine is distributed between the cross-linked aqueous salt matrix, partially dissolved glass, and undissolved glass. In analogous cements based on zinc oxide the fluoride is added as highly soluble SnF2. The object of this study is to compare the F- ion release profiles of commercial zinc polycarboxylate and zinc phosphate containing 4.4 and 3.6% SnF2, respectively. Mixed cements were clamped in split ring moulds to produce discs of 10 mm x 1 mm after storage at 37 degrees C for 1 h. Each was weighed and immersed in 10 ml of deionised water. When this changed, at 13 time intervals up to 98 days, the fluoride content was measured using an ion selective electrode. The mean (N = 3) values obtained were expressed cumulatively [F] in micromol F ion/g cement. The total [F] released was 111 for the zinc polycarboxylate and 286 for zinc phosphate compared with total F in the cements of 561 and 464, respectively. When the cumulative [F] was plotted versus t(1/2) close associations were found for both cements. For the polycarboxylate the regression line [F] = 10.6t(1/2) + 9.9 fitted well over the whole 98 days (R = 0.997). For the phosphate a better fit regression line was obtained using results up to 32 days only; [F] = 36.8t(1/2) - 8.4 (R = 0.999). For t > 32 days results increasingly deviated from this line. These results fitted a regression line of the form [F] = 81.7log(e) t - 87.3 (R = 0.9997). Comparisons are made with data from previous authors both for zinc phosphate cement and glass-based cements and with diffusion theory of F ion release. It is concluded that zinc-based cements provide some indications of how glass-based cements may behave over long periods of release and that zinc phosphate is the material of clinical choice for orthodontic cementation if maximal fluoride release is the prime criterion.

Cariostatic Agents↗
PubMed1998

Fluoride release from glass-ionomer and compomer restorative materials: 6-month data.

OBJECTIVES: To investigate the daily fluoride release of two glass ionomers (Ketac-Fil and ChemFil Superior) and two compomers (Compoglass and Dyract Restorative) over 6 months. METHODS: A pilot study evaluated the time taken for sample solutions to equilibrate to establish an appropriate time period for sample solution storage between fluoride ion measurements. In the main study storage water replacement and fluoride ion determination was made daily using a specific ion electrode, TISAB buffer and standard solutions for calibration. RESULTS: Equilibration of fluoride concentration in aqueous solution occurred in under 48 h for all materials. Total fluoride released (microgram mm-2) after 6 months by Ketac-Fil (30.6, s.d. 4.9) was significantly greater than ChemFil Superior (12.7, s.d. 2.5), Compoglass (10.4, s.d. 1.0) and Dyract Restorative (7.7, s.d. 1.7) (P < 0.05). Daily fluoride release at 24 h and 10 days was significantly higher for the glass ionomers than the compomers (P < 0.05). After 40 days the daily fluoride release (microgram mm-2) from ChemFil Superior (0.05, s.d. 0.01) was not significantly different from Compoglass (0.04, s.d. 0.01) and Dyract Restorative (0.03, s.d. 0.00) (P > 0.05). Daily fluoride release from Ketac-Fil remains significantly higher than the compomers at 3 and 6 months (P < 0.05). CONCLUSIONS: Specimens stored in water equilibrate rapidly, suggesting the rate at which storage water is changed may alter the relative fluoride release rates of materials. This important fact is often overlooked. Fluoride release from the glass ionomers is initially higher than for the compomers. Fluoride release from glass ionomers falls rapidly to approach levels released by compomers. Compomers produce no initial burst of fluoride and levels of release remain relatively constant.

Aluminum Silicates↗