Physical properties of some zinc phosphate and polycarboxylate cements

Several physical properties were measured for two zinc phosphate and three polycarboxylate cements. The specimens were tested in compression 24 h after they had been made. Two series of specimens were examined. In one series the cement powders were given a correct treatment, protected from atmospheric humidity. In the other series the powders were exposed for 1 week to ambient conditions with the temperature varying between 20 degrees and 24 degrees C and the relative humidity between 40% and 59%. The zinc phosphate cements were characterized by high values of modulus of elasticity and by plastic deformations less than 0.2%. The polycarboxylate cements were more flexible and also exhibited large plastic deformations. Compared with the zinc phosphate cements, therefore, the polycarboxylate cements had high values of resilience and toughness. The storing of cement powders exposed to atmospheric humidity for 1 week did not change the measured properties of the polycarboxylate cements. However, both strength and resilience were significantly reduced for one phosphate cement.     

Heat treatment of glass ionomer, silicate, zinc phosphate and zinc polycarboxylate cements

Abstract – The compressive strength and erosion resistance of glass ionomer, silicate, zinc phosphate or zinc polycarboxylate cements, submitted to heat treatments at 50° or 70°C after mixing, have been assessed. Zinc phosphate cement specimens showed a marked reduction in compressive strength properties and erosion resistance, while minor improvements in compressive strength were observed for various brands of the other types of cements. For silicate cement a considerable improvement in erosion resistance was noted. One brand showed a reduction in the release of phosphate amounting to approximately a factor of 20. The various improvements observed may be clinically exploited by exposing the restoration after insertion to radiation from an external heat source which deposits radiation energy in the surface or bulk of the restoration.     

Pulpal reaction to a dental adhesive in deep human cavities

Abstract In the last years several dental adhesives have been developed. They are supposed to chemically adhere to dentin and a liner to protect the pulp is not used. The aim of this study was to compare the short-term pulpal reaction, in an intra-toothpair study, between a dental adhesive, Scotchbond 2, and a lining system, Tubulitec, in combination with P-50 in surface-sealed cavities. Deep buccal cavities in 16 human pairs of premolars, 32 teeth, were restored in vivo with a light cured composite resin, P-50. To minimize bacterial contamination all cavities were treated with a cleanser, Tubulicid, and the cavities were surface-sealed with temporary cement, Coltosol. One tooth in each pair, the test, was treated with Scotchprep Dentin Primer and Scotchbond 2 Light Cure Dental Adhesive. In the other tooth in the pair, the control, Tubulitec Primer and Liner were used. The teeth were extracted after 6–14 days. The sections where evaluated for degree of inflammation and the presence of bacteria. Irrespective of treatment of dentin the majority of teeth, 23, including one pulpal exposure, revealed no inflammation or a few inflammatory cells. In four test teeth, including one pulpal exposure, and two controls, growth of bacteria was found on the cavity walls and slight or moderate inflammation was seen in the corresponding pulps. In one test and two control teeth slight inflammation was seen but no bacteria could be detected. In the absence of bacteria Scotchbond 2 did not seem to irritate the pulp. However, in almost one third of the restorations the bond strength to dentin was not sufficient to resist the contraction forces during polymerization as indicated by bacterial growth at the interface between dentin and adhesive/composite.     

A comparative study of retentive strengths of zinc phosphate, polycarboxylate and glass ionomer cements with stainless steel crowns--an in vitro study

This study was conducted on 30 extracted human primary molars to assess the retentive strengths of zinc phosphate, polycarboxylate and glass ionomer cements. The teeth were embedded in resin blocks and were randomly divided into 3 groups of 10 each. The occlusal surfaces of all teeth were reduced uniformly by 1.0 to 1.5 mm. All mesial, distal undercuts were removed and sharp angles rounded. This was followed by cementing pretrimmed and precontoured stainless steel crowns on each tooth with hand pressure and storing in artificial saliva at 37 degrees C for 24 hours. Retentive strength was tested using Instron Universal Testing Machine. The load was applied starting from a zero reading and gradually increased until the cemented stainless steel crowns showed signs of movement and then the readings were recorded. It was found that retentive strengths of zinc phosphate and glass ionomer cements were statistically better (P < 0.05) when compared to the polycarboxylate cement. Negligible difference (0. 59 kg/cm2) was however observed between zinc phosphate and glass ionomer cements.     

Adhesion of polycarboxylate cements to dental casting alloys.

The adhesive strengths of four commercial polycarboxylate cements to five dental casting alloys were compared with the strength of a conventional zinc phosphate cement. The following results were obtained. (1) The polycarboxylate cements showed adhesion that was four to 12 times greater than that of the zinc phosphate cement to all alloys tested. (2) The adhesive strength of the polycarboxylate cements was greater to the chemically active substitute alloys, such as the copper, nickel-chromium, and silver-tin-zinc alloys. The adhesion of the polycarboxylate cements to the chemically stable gold and silver-palladium alloys was not as great, but was four to six times that of the zinc phosphate cement. (3) The difference in adhesive strength between the brands of polycarboxylate cement was generally slight or statistically insignificant.     

Elements in minor or trace quantities in zinc phosphate cements.

Eight powders and two liquids of zinc phosphate cements have been analyzed by optical emission spectrography for the purpose of characterizing elements in minor or trace quantities. The following elements were measured: bismuth, boron, cadmium, chromium, copper, iron, lead, silver and titanium. The content of any of these elements did not exceed the level of 0.1%. The amounts of such elements which might be transferred to the gastrointestinal tract associated with dissolution from unsuccessful restorations have been considered.     

A comparative study of retentive strengths of zinc phosphate, polycarboxylate and glass ionomer cements with stainless steel crowns - an in vitro study

An in vitro study was conducted to compare the retentive strengths of zinc phosphate, polycarboxylate and glass ionomer cements using Instron universal testing machine. Thirty preformed and pretrimmed stainless steel crowns were used for cementation on 30 extracted human primary molars which were divided into three groups of 10 teeth in each group. Then the teeth were stored in artificial saliva and incubated at 37°C for 24 h. A load was applied on to the crown and was gradually increased till the crown showed dislodgement, and then the readings were recorded using Instron recorder and analyzed for statistical significance. The surface area of crown was measured by graphical method. The retentive strength was expressed in terms of kg/cm 2 , which was calculated by the equation load divided by area. Retentive strengths of zinc phosphate (ranged from a minimum of 16.93 to amaximum of 28.13 kg/cm 2 with mean of 21.28 kg/cm 2 ) and glass ionomer cement (minimum of 13.69 - 28.15 kg/cm 2 with mean of 20.69 kg/cm 2 ) were greater than that of polycarboxylate cement (minimum of 13.26 - 22.69 kg/cm 2 with mean of 16.79 kg/cm 2 ). Negligible difference (0.59 kg/cm 2 ) of retentive strength was observed between zinc phosphate (21.28 kg/cm 2 ) and glass ionomer cements (20.69 kg/cm 2 ). Glass ionomer cements can be recommended for cementation of stainless steel crowns because of its advantages and the retentive strength was almost similar to that of zinc phosphate cement.     

Pulpal tissue reaction to buffered glutaraldehyde.

Pulpal tissue changes following pulpotomies with 2% w/v buffered glutaraldehyde in primary teeth were observed. A 3 minute single application of 2% w/v buffered glutaraldehyde was able to produce effective surface fixation. Limited penetration of the medicament left the remaining pulp tissue unaffected. The zone of fixation did not proceed apically. With time, macrophages and fibroblasts appear apical to the zone of fixation indicating the onset of replacement resorption.     

Laboratory strength of glass ionomer and zinc phosphate cements

PURPOSE: The present in vitro study examined 3 mechanical properties, namely compressive, flexural, and diametral tensile strength, of various commercially available cements and core materials as a function of time after mixing. MATERIALS AND METHODS: The examined materials were 2 cermet cements (Ketac Silver [ESPE, Seefeld, Germany] and Chelon Silver [ESPE]), 1 metal-reinforced glass ionomer cement (Miracle Mix [GC Dental Industrial Corp, Tokyo, Japan]), 2 conventional glass ionomer cements (Ketac Bond [ESPE] and Ketac Cem [ESPE]), 1 standard cure zinc phosphate cement (Harvard Cement [Richter and Hoffmann, Berlin, Germany]), and 1 zinc phosphate cement with the addition of 30% silver amalgam alloy powder (Harvard Cement 70% with Dispersalloy 30% [Richter and Hoffmann/Johnson and Johnson, East Windsor, NJ]). Properties were measured using a universal testing machine at 15 minutes, 1 hour, and 24 hours after first mixing. RESULTS: Compressive strengths varied widely between the 3 times of measurement from 5.8 +/- 6.6 MPa for Ketac Cem to 144.3 +/- 10.2 MPa for Ketac Silver. Twenty-four hours after mixing, the Bonferroni test showed significant (p 相似文献   

Pulpal response to restoration of deep cavities with high-copper amalgam.

The effect on the pulp of a high-copper amalgam was studied in buccal cavities in 16 pairs of human premolars, 32 teeth, restored with ANA 2000. To minimize the risk of bacterial contamination, the cavities were treated with a cleanser, Tubulicid, and the outer portion of the filling was replaced by zinc oxide-eugenol cement (ZOE), i.e. surface-sealing. In one cavity in each pair, the control, a thin lining was used. The teeth were extracted after 5-13 days, sectioned, stained with hematoxylin-eosin or Brown and Brenn and evaluated for the degree of pulpal inflammation and presence of bacteria. The results showed that regardless of whether lining was used or not, no inflammation or only a very few inflammatory cells were found in the 21 teeth in which the thickness of the remaining dentin varied from 0.15 mm to 0.5 mm, except for one pair showing slight to moderate inflammation. However, in this pair bacterial growth were found on the cavity walls. No other teeth showed bacterial growth. In the remaining eleven teeth the thickness of the remaining dentin was less than 0.08 mm, including five pulpal exposures. Slight to severe inflammation occurred in eight of these teeth. ANA 2000 per se did not seem to irritate the pulp except in very deep cavities or on direct exposures. The reason for this reaction is not known, but it might be attributable to the zinc content of the amalgam.     

Elements in minor or trace quantities in zinc phosphate cements

Abstract – Eight powders and two liquids of zinc phosphate cements have been analyzed by optical emission spectrography for the purpose of characterizing elements in minor or trace quantities. The following elements were measured: bismuth, boron, cadmium, chromium, copper, iron, lead, silver and titanium. The content of any of these elements did not exceed the level of 0.1%. The amounts of such elements which might be transferred to the gastrointestinal tract associated with dissolution from unsuccessful restorations have been considered.     

Retentive [correction of Preventive] efficacy of glass ionomer,zinc phosphate and zinc polycarboxylate luting cements in preformed stainless steel crowns: a comparative clinical study

This study was undertaken to assess the efficacy of three luting cements, namely, glass ionomer, zinc phosphate and zinc polycarboxylate in retainng the preformed stainless steel crowns in-vivo. Twenty subjects, with an indication for restoration of three primary molars with stainless steel crowns, were selected. Sixty teeth were taken up for the study, and twenty crowns were cemented with each of the three luting cements. After an eight month follow up the crowns were assessed for their presence/ absence or "rocking". Statistical analysis was done using Chi-square test. The results have shown no significant difference in retentivity of stainless steel crowns with the use of either of the three luting agents.     

Strength properties of three zinc phosphate cements mixed to two different consistencies

When hand-mixing is used, clinicians mix zinc phosphate cement to consistencies which allow proper seating of restorations. Slump tests have indicated that the same two preferred consistencies (one for cementing a single unit restoration, the other for cementing a multiple unit restoration) could be obtained at different slab temperatures for three cements by mixing to certain powder-liquid ratios which were different for each cement. Each cement could be repeatedly mixed to the preferred consistency by using the appropriate powder-liquid ratio. The compressive and tensile strengths of the cements varied, although mixed to the same consistency. Selection of a cement for clinical use should be based on its strength properties when mixed to a preferred consistency.