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At least 19 recordsLinked to original sources
PubMed1998

Microscopic and energy dipersive x-ray analysis of surface adaptation of dental cements to dental ceramic surfaces.

STATEMENT OF PROBLEM: Clinical failure rates reported for acid etched/resin-bonded ceramic restorations are significantly lower than those reported for restorations luted with traditional cements. This improved clinical performance may be associated with greater adaptation of the resin cements to the ceramic surfaces. PURPOSE: The objective of this study was to determine whether the use of resin cements accompanied by acid etching results in improved adaptation when compared with the use of zinc phosphate or glass ionomer cements. RESULTS: The results of this experiment indicate that superior adaptation of cement to ceramic is produced by acid etching and luting with resin cement. In addition, the results lead to the hypothesis that the high clinical failure rates reported for zinc phosphate or glass ionomer luted restorations are due either to incomplete adaptation or to failure within the cement. CONCLUSION: The findings indicate that the use of resin cements accompanied by acid etching of the ceramic surface is the preferred technique for clinical placement of all-ceramic restorations.

Acid Etching, Dental↗
PubMed1989

Kinetic studies on improved phosphate dental cement: the measurement of some improved dental cements containing phosphate polymers by an electric conductance method.

The rate of the setting process of zinc phosphate dental cement with organic phosphate polymers as additives was measured by a conductance technique. There are two rate-determining parameters, namely an induction period and a first-order reaction constant. The values of the latter constant are not affected by the additives.

Chemical Phenomena↗
PubMed1978

[Compressive strength and deformation of dental cements].

Several dental cements have been tested for compressive strength, modulus of elasticity and plastic strain at fracture. Sylindrical specimens (4 x 6 mm) were compressed to fracture with two different crosshead speeds (2 mm/min, 0.1 mm/min) at two temperatures (23 +/- 1 degrees C and 37 +/- 1 degrees C). The results showed that the zinc phosphate cement had relatively high strength and a very small elastic and plastic strain during compression. The luting type of glass-ionomer cements showed properties near to that of the zinc phosphate cement. The other cements had either lower strength or higher elastic and plastic deformation than the zinc phosphate cement. Several cements showed a marked reduction of the mechanical properties when tested at a low crosshead speed or at 37 degrees C.

Composite Resins↗
PubMed1998

Retention of three endodontic posts cemented with five dental cements.

STATEMENT OF PROBLEM: The retention of a post is believed to be a major factor in restoration survival. Therefore the cement with the greatest in vitro retention property should give the best performance for a restoration. PURPOSE: This study compared retentive values of three posts (Flexi-Post, AccessPost, and ParaPost) cemented with five cements (Flexi-Flow, zinc phosphate, Advance, Duet, and Ketac-Cem) plus a control group that consisted of a Flexi-Post No. 2 dowel without cement. MATERIAL AND METHODS: A total of 160 recently extracted human single-rooted teeth with crowns removed at the cementoenamel junction were divided into 16 groups of 10 samples. Post holes were prepared according to manufacturers' instructions. Posts were then cemented with one of the five cements. Each sample was placed into a specialized jig and on a tensile testing machine with crosshead speed of 0.638 cm/minute, applied until failure. A two-way analysis of variance and Newman-Keuls multiple range comparison tests were performed for all cemented groups. A one-way analysis of variance and a Student-Newman-Keuls multiple range comparison test were performed only for the groups with the Flexi-Post dowel, this included the no cement condition, with significant results if p < 0.05. RESULTS: Flexi-Post dowel with Flexi-Flow Natural cement obtained the highest retentive value (303.91 pounds). ParaPost dowel with Duet cement exhibited the lowest retention value (21.23 pounds). The Flexi-Post dowel demonstrated higher mean retention than AccessPost or ParaPost dowels, AccessPost dowel was higher than ParaPost dowel. Flexi-Flow cement had the highest overall mean retention followed, in decreasing order, by zinc phosphate, Advance, Ketac-Cem, and Duet cements. CONCLUSIONS: Flexi-Post dowel was the most retentive post studied with values ranging from 303.91 pounds with Flexi-Flow Natural cements to 150.93 pounds without cement. Flexi-Flow cements had a higher overall mean retention than other cements studied.

Analysis of Variance↗
PubMed2002

Properties of encapsulated and hand-mixed zinc phosphate dental cement.

PURPOSE: Dental cements can be supplied as loose powder and liquid or as encapsulated syringes. This study assessed the compressive strength of a recently marketed zinc phosphate encapsulated cement compared with a hand-mixed system according to the American Dental Association Specification. MATERIALS AND METHODS: The mean fracture strength, standard deviations and associated Weibull Moduli (m) of the encapsulated and hand-mixed cements were determined by compressive fracturing 30 cylindrical specimens (height 6.0 +/- 0.1 mm, diameter 4.0 +/- 0.1 mm). Scanning electron microscopy was employed to assess crack growth from indentations and cement morphology. Image analysis was used to investigate the influence of mixing regime on pore distribution within the cement samples. RESULTS: The compressive strength data showed variation in magnitude and reliability ranging from 42 +/- 8 MPa (m = 5.2 +/- 1.0) for the encapsulated cement filled directly from the capsule to 71 +/- 11 MPa (m = 6.3 +/- 1.3) for the hand-mixed cement. The encapsulated cement matrix was extensively porous, consisting of pores between 0.1-0.5 microm diameter, compared with the non-porous hand-mixed cement matrix. Larger pores (over 18 microm diameter) were related to air entrapment in the encapsulated cement on mixing while small pores (0.1-0.5 microm diameter) were indicative of vaporization porosity commonly seen with exothermic reactions.

Air↗
PubMed1999

Contemporary evaluation of dental cements.

Today, the clinician has numerous dental cements available for luting of restorations to prepared teeth. Compared to traditional cements, many of the newer cements have improved physical properties. In this article, we analyze available cements in terms of these physical properties based on scientific data and attempts to determine their effect on long-term clinical performance. We conclude that these improved physical properties do not necessarily result in improved clinical performance. We also conclude that although these newer cements have specific clinical applications, they should not be routinely used for the cementation of metal castings because they are clearly more technique-sensitive than traditional luting agents. Zinc-phosphate cement remains the cement of choice for cementing cast gold and metal-ceramic restorations.

Biocompatible Materials↗
PubMed1976

The effect of varnish on dentinal bonding strength of five dental cements.

1. The following dental cements are listed in order of decreasing mean bonding strenghts on varnish-free dentin: polycarboxylate, zinc phosphate, EBA, Fynal, and CBA. 2. The application of either Copalite or Varnal decreased the dentinal bonding strength of polycarboxylate and zinc phosphate cements. There was no change for CBA cement. 3. The application of Copalite and Varnal increased the dentinal bonding strength for Fynal to the level of zinc phosphate cement on varnish-free dentin. 4. The dentinal bonding strength of EBA cement increased with the application of Varnal but not with Copalite.

Dental Bonding↗
PubMed2006

Cytotoxicity of a calcium aluminate cement in comparison with other dental cements and resin-based materials.

The objective of this study was to compare the cytotoxic effects of a calcium aluminate cement with several currently used direct restorative materials. Specimens of three composites (QuiXfil, Tetric Ceram, Filtek Supreme), one zinc phosphate cement (Harvard Cement), one glass ionomer cement (Ketac Molar), and one calcium aluminate cement (DoxaDent), were used fresh or after 7-days' preincubation in cell culture medium at 37 degrees C, pH 7.2. PVC strips for ISO 10993-5 cytotoxicity test were used as positive control and glass specimens as negative control. L-929 fibroblasts (5-ml aliquots, containing 3 x 10(4) cells/ml), cultivated in DMEM with 10% FCS, 1% glutamine, and 1% penicillin/streptomycin at 37 degrees C/5% CO2 and trypsinized, were exposed to the specimens for 72 h. The cells were harvested, centrifuged, and resuspended in 500 microl DMEM and then counted in 500 microl DMEM for 30 s with a flow cytometer at 488 nm. The analysis of variance comparing the six materials showed different influences on L-929 fibroblast cytotoxicity (p <0.0001). The cytotoxicity of all specimens diminished with increasing preincubation time (p <0.0001). Fresh DoxaDent exhibited the lowest cytotoxicity, followed by QuiXfil. Ketac Molar showed the highest cytotoxicity. After 7 days of preincubation, Harvard Cement and Filtek Supreme demonstrated more cytotoxicity than the other materials (p <0.005).

Aluminum Compounds↗