Demineralization resistance and tensile bond strength of four luting agents after acid attack

Resistance to acid demineralization provided by luting agents adjacent to enamel was evaluated for four different luting agents: composite resin, glass ionomer, polycarboxylate, and zinc phosphate cement. Cement solubility and enamel demineralization after acid attack at pH 3.0 were measured radiographically and calculated using computer-aided design. Tensile bond strength of a miniature crown seated on an accurately prepared preparation was evaluated after acid attack using an Instron instrument. Crown retention after 12 days was greater for the polycarboxylate (2,000 kg/m2) than the zinc phosphate cement (500 kg/m2). Crown retention for the glass ionomer (1,100 kg/m2) and composite resin luting agent (1,400 kg/m2) were similar statistically after 21 days of acid exposure. Cement washouts for zinc phosphate and polycarboxylate were similar, and were greater than either glass ionomer or composite resin luting agent. The amount of demineralization related to cements was, from greatest to least: zinc phosphate, polycarboxylate, composite resin, glass ionomer. Fluoride release was concluded to be initially effective in reducing enamel solubility in spite of cement solubility.     

Effects of evaporation on the properties of water-based dental luting agents

The most commonly used luting agents for fixed prosthodontics are water-based cements: zinc phosphate, zinc polycarboxylate, glass ionomer, and resin-modified glass ionomer. Properties were tested at baseline and after the cement liquids were allowed to evaporate for 10, 20, and 30 minutes. Viscosity, pH, contact angle, and surface tension were determined using the cement liquids only; tensile strength, hardness, film thickness, and working/setting times were determined after the cements had been mixed with the various liquids. pH decreased over 30 minutes, while viscosity, contact angle, and film thickness all increased, especially for the zinc polycarboxylate and glass ionomer cements. Changes in mechanical properties depended upon time and material.     

强化氟水门汀物理性能及释放氟研究

目的：探讨市售磷酸锌水门汀、聚羧酸锌水门汀、玻璃离子水门汀粉末中添加复合氟化物制剂（Co-F）对其物理性能及氟释放的影响。方法：在上述各水门汀粉末中按质量分数添加复合氟化物0％～20％，调和水门汀测定其固化时间、抗压强度、氟离子释放量。结果：添加适量复合氟化物对水门汀的抗压强度没有影响，添加复合氟化物的玻璃离子水门汀释放氟量增加，添加复合氟化物的聚羧酸锌水门汀、磷酸锌水门汀也能够释放氟离子。添加复合氟化物对聚羧酸锌水门汀及玻璃离子水门汀固化时间有明显影响。结论：强化氟水门汀通过释放氟，使充填材料附近牙齿发挥防治继发龋作用，基于此观点强化氟水门汀是牙科应用有希望的材料。     

Comparative study on cytotoxicity of main components of three luting cements in vitro (author's transl)

In order to elucidate cytotoxicity of main components of glass ionomer, polycarboxylate and zinc phosphate cements, cell culture method was utilized. Criteria of cellular responses were made on the basis of cell growth and changes in cell morphology. The results obtained were as follows: 1. SiO2, AlF3, Al2O3, Ca3(PO4)2 and NaAlF6 of powder components in glass ionomer cement did not yield any unfavourable effects on either cell growth nor morphology. On the other hand, AlPO4 yielded moderate cytotoxic reaction and CaF2 marked reaction. 2. ZnO and MgO of powder components in polycarboxylate and zinc phosphate cements yielded marked cytotoxic reaction. Moreover, CaO of zinc phosphate cement brought very marked cytotoxic reaction. On the other hand, SiO2 and Bi2O3 did not yield any unfavourable effects on either cell growth nor morphology. 3. All the liquids of three cements brought cytotoxic reaction ranging from marked to very marked levels. The present results seemed to reveal that mild cytotoxic reaction of glass ionomer cement, which had been reported, was due to inclusion of less cytotoxic components compared to polycarboxylate or zinc phosphate cements. It was also discussed the relationship between biocompatibility of the cements and dissolution of the components. It is considered that the present results could shed a light on biocompatibility of dental cements.     

Changes in retention strength of luting cements by repeated loading

The retention of crowns cemented on abutment tooth model was examined for three types of luting cements when compressive loads of 2.5 to 10.0 kg were repeatedly applied to the occlusal plane. The chamfer type Ni-Cr alloy crown and abutment tooth model were prepared, and their surfaces to be cemented were sandblasted with glass beads. Loads were applied 7,200 times a day for 1, 3, or 7-day period after cementing. The polycarboxylate and zinc phosphate cements showed higher crown retentions than glass ionomer cements. Although retention strength of glass ionomer cements was significantly increased by storing the cemented specimen in water for 7 days, repeated loading tended to decrease retention. In polycarboxylate cements and one brand of zinc phosphate cement employed, retention strengths were decreased when stored in water over 3 days. However, their highest levels were maintained or even positively impacted by repeated loading for 7 days.     

Evaluation of glass ionomer luting cements

In the present study the three glass ionomer luting cements available on the Scandinavian market in June, 1982 were evaluated by comparison with a zinc phosphate and a zinc carboxylate cement. The following properties were tested: effective maximum grain size, retention, strength, bond strength to dentin, disintegration in and absorption of water and solubility in 0.001 n lactic acid. The glass ionomer cements proved to be fully acceptable luting materials.     

Evaluation of glass ionomer luting cements

Abstract – In the present study the three glass ionomer luting cements available on the Scandinavian market in June, 1982 were evaluated by comparison with a zinc phosphate and a zinc carboxylate cement. The following properties were tested: effective maximum grain size, retention, strength, bond strength to dentin, disintegration in and absorption of water and solubility in 0.001 n lactic acid. The glass ionomer cements proved to be fully acceptable luting materials.     

Effect of dental luting cements from the viewpoint of cell recovery (in vitro)

Cell recovery of four cell lines [L-929 cells, HEp-2 cells, Gin-1 cells and the cells from human dental pulp tissues (Hp cells)] was examined after exposure to four zinc phosphate cements, five polycarboxylate cements, three glass ionomer cements, five resin based cements and one zinc oxide-eugenol.EBA cement. Phosphate cements, glass ionomer cements and zinc oxide-eugenol.EBA cement were markedly cytotoxic to the four cell lines 3 hours and 24 hours after mixing. Polycarboxylate cements considerably inhibited cell recovery of the three types of cells except Hp cells even 24 hours after mixing, compared to the gradual recovery of Hp cells after mixing. Two of the resin based cements inhibited cell recovery, while the three others allowed moderate cell recovery. The pH values of the medium used for the experiments was 6.6-6.8 for phosphate cements, glass ionomer cements and zinc oxide-eugenol.EBA cements. Polycarboxylate cements had no effect on the pH. On the other hand, in resin based cements the pH was shifted from acidic to basic. The solubility of the materials used was, in decreasing order: glass ionomer cements, zinc oxide-eugenol.EBA cement and one of the resin based cements, polycarboxylate cements, phosphate cements and another resin based cement, and the other three of resin based cements (lowest). The difference in cell recovery was considered to be due to composition and solubility of the materials.     

Retention of orthodontic bands with new fluoride-releasing cements

The prevalence of enamel decalcification beneath orthodontic bands has indicated the need for a fluoride-releasing, enamel-adhesive orthodontic luting cement. The purpose of this study was to compare the retentive bond strengths of orthodontic bands cemented with two new fluoride-releasing cements, a zinc polycarboxylate and a glass ionomer, with the retentive bond strength of bands cemented with the standard orthodontic cement zinc phosphate. The site of cement failure was also evaluated. One hundred eighty extracted human molar teeth were embedded in resin blocks and randomly assigned to three cement groups. Adapted bands were cemented by a clinically acceptable technique. The cemented teeth were then assigned to one of three time intervals--24 hours, 7 days, and 60 days--and thermocycled in synthetic saliva. The force required to initially fracture the cement bond was used as a measure of cement retention. By means of the Instron, a tensile load was applied to each cemented band. The maximum retentive strength (cement failure) was interpreted from the stress-strain curve at the point where linearity deviated. The failure site was judged subjectively: between cement and enamel, within the cement, or between cement and the band. Using stress at failure, an analysis of variance showed no significant differences among the retentive strengths of the three cements. The chi-square test revealed a significant difference (P less than 0.01) between failure sites of the zinc phosphate and glass ionomer cements. Significantly more bands cemented with the glass ionomer failed at the cement/band interface, leaving the cement adhered to the tooth.(ABSTRACT TRUNCATED AT 250 WORDS)     

五种黏固剂下纤维/树脂复合材料桩钉固位力的研究

目的 比较纤维/树脂复合材料(FRC)桩钉在5种黏固剂下的固位力。方法 将FRC桩钉用5种黏固剂(磷酸锌水门汀、玻璃离子水门汀、聚羧酸水门汀、EB复合树脂、AB组份复合树脂)分别黏固于新鲜离体上前牙牙根内,在电子力学试验机上测试其固位力。结果 FRC桩钉在不同黏固剂下与根管的固位力由大到小的顺序是:AB组份复合树脂>玻璃离子水门汀>EB复合树脂>聚羧酸锌水门汀>磷酸锌水门汀。AB组份复合树脂的固位力最大,为(418.14±23.40)N。结论 新研制的FRC桩钉的固位力可以满足临床需要。     

Mechanical properties of dental luting cements

STATEMENT OF PROBLEM: Dental luting cements fail by microcrack formation and bacterial ingress or by gross failure and crown dislodgment. Both of these failure modes are related to mechanical properties and deformation. PURPOSE: This study evaluated those mechanical properties of cements. METHODS AND MATERIAL. Elastic modulus for 8 representative cements (zinc phosphate, polycarboxylate, glass ionomer, encapsulated glass ionomer, resin-modified glass ionomer, resin composite, and adhesive resin composite) was measured by using a nondestructive technique and evaluated for cement type and storage time (1 hour, 1 day, 1 week, 1 month, 1 year) by 2-way ANOVA (P <.05). Compressive properties (proportional limit, resilience, and toughness), ultimate strengths (compressive, diametral tensile, and flexural), and flexural toughness were determined and evaluated by 2-way ANOVA for 2 crosshead testing rates (5 and 0.5 mm/min) and cement type (P <.05). RESULTS: Cements varied with respect to elastic moduli, compressive proportional limit, compressive resilience, compressive strength, compressive toughness, diametral tensile strength, flexural strength, and flexural toughness. Storage time affected the elastic moduli of different materials in different ways. Elastic moduli of polycarboxylate and glass ionomer cements increased over time, whereas the other materials changed little after the first day. Crosshead rate only significantly affected compressive proportional limit and resilience. CONCLUSIONS: Luting cements differed considerably with respect to mechanical properties.     

Retention forces and seating discrepancies of implant-retained castings after cementation

PURPOSE: The purpose of this in vitro study was to evaluate the influence of cement type and application technique on seating discrepancies and retention forces of noble alloy castings cemented on titanium abutments. MATERIALS AND METHODS: Eugenol-free zinc oxide (Freegenol), zinc phosphate (Harvard), glass ionomer (KetacCem), polycarboxylate (Durelon), and self-adhesive resin (RelyX Unicem) cements were used. The inner surfaces of the castings were either completely coated or half-coated with cement. Abutments were used as delivered with a machined surface for the first part of the study. Groups of 8 castings were cemented in both ways. For the second part of the study, the abutments were air-abraded (aluminum oxide, 50 microm particle size), and groups of 8 completely coated castings were cemented with all cements. Marginal discrepancies were measured before and immediately after cementation. Tensile tests were conducted to measure the retention forces. Statistical analysis was performed with pair-wise comparison using the Wilcoxon rank sum test modified by Bonferroni-Holm. RESULTS: Change in seating discrepancies did not differ significantly among the different application techniques. The median retention forces for completely-coated castings were 177 N for eugenol-free zinc oxide, 346 N for zinc phosphate, 469 N for glass ionomer, 813 N for polycarboxylate, and 653 N for self-adhesive resin. With respect to retention force, 3 significantly different groups (P < .05) were identified: (1) zinc oxide, (2) zinc phosphate/glass ionomer, and (3) polycarboxylate/self-adhesive resin. No differences in retention between the 2 coating techniques were found for any cement. However, air abrading the abutments resulted in increased retention of the castings for some of the cements. CONCLUSIONS: Half-coating of the restorations with cements did not result in reduced retention values compared to the complete coating technique, but air abrasion resulted in increased retention with some cements.     

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.     

Study on dental cements. 1. The cored structure of three luting cements obtained by using Cryo-SEM and image analyzer

The polished surfaces of three set dental cements for luting (zinc phosphate cement, polycarboxylate cement, and glass ionomer cement) were observed by cryo-SEM at a specimen temperature of -160 degrees C to prevent damage of the cement specimens and also the specimens were analyzed by EDX. Furthermore, the SEM composition images of the polished cement surface were transferred to an image analyzer to obtain the core/matrix area ratio of the set cements. 1. The polished surface of set dental cement could be clearly observed by cryo-SEM without damaging the cement specimens. 2. The image analyzer showed that the core/matrix area ratio of the zinc phosphate cement and the glass ionomer cement was approximately 2 to 8, whereas that of the polycarboxylate cement was approximately 3 to 7. 3. The elements detected in the zinc phosphate cement were Ca, Zn, Mg, Al, and P, in the polycarboxylate cement were Ca, Zn, Mg, Si, and Sr, and in the glass ionomer cement were Al and Si.     

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.     

Influence of types and surface treatment of dental alloy and film thickness of cements on bond strength of dental luting cements

The goal of this study was to test the influence of the type and oxidation treatment of dental casting alloys on the tensile bond strength of luting cements. Also, the influence of film thickness of luting cements on the tensile bond strength of different dental casting alloys was examined. Four different luting cements (zinc phosphate, polycarboxylate, glass ionomer and adhesive resin cements) and four different dental casting alloys (Au-Ag-Cu, Ag-Pd, hardened Ag-Pd and Ni-Cr alloys) were used. Cylindrical alloy rods for the tensile bond strength test were casted, and then, top surfaces of the rods were cemented with each luting cement to the bottom surfaces of other rods, using the film thickness adjustment apparatus. The film thickness of luting cement was adjusted to 20, 30, 50, 75 or 100 microns. The tensile bond strengths of each cement to different casting alloys at each film thickness were measured one day after the rods had been cemented. The tensile bond strength of the zinc phosphate cement could not be determined in this study due to the separation of the alloy rods cemented with the zinc phosphate cement in water before the tensile test. The tensile bond strength to the adhesive resin cement to any alloy showed the greatest strength; however, that of the glass ionomer cement to any alloy was the lowest strength among the cements examined. The Ni-Cr alloy had the highest bond strength of any luting cement, compared to other alloys. The tensile bond strengths of luting cements significantly decreased with the increase in film thickness of cement layer. The adhesive resin cement had the greatest bond strength, and the glass ionomer cement was the lowest bond strength at any film thickness. The oxidation treatment significantly increased the bond strength of the adhesive resin cement to both Au-Ag-Cu and Ag-Pd alloys. The tensile bond strength of the adhesive resin cement was most dependent upon the film thickness of cement layer, and that of the polycarboxylate cement was least dependent upon the film thickness of cement layer among the cements examined. In addition, the oxidation treatment for precious alloys could be a factor contributing to the increase in the bond strength of the adhesive resin cement.     

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.     

Leakage of various types of luting agents

Freshly extracted molar teeth were prepared for complete cast gold crowns cemented with either zinc phosphate cement, polycarboxylate cement, glass ionomer cement, a resin luting agent, or a zinc oxide-eugenol temporary cement. The specimens were tested at 1-, 6-, and 12-month intervals with radioactive 45Ca. The specimens were sectioned, autoradiographs were made, and the marginal leakage was evaluated on a scale of 0 to 3. The results showed that zinc phosphate, polycarboxylate, and glass ionomer cements are equally suited for permanent cementation of restorations. The resin luting agent showed high initial leakage, indicating that it is not as desirable for permanent cementation purposes. The zinc oxide-eugenol cement showed increased leakage with time but is well suited for its indicated purpose, temporary cementation.     

Early erosion of dental cements

The disintegration in water of various unset glass ionomer cements, a polycarboxylate and a zinc phosphate cement was measured gravimetrically after exposure of the cements to a constant water jet. The test gave reproducible results with significant variations between the various types and brands of cements. For zinc phosphate and polycarboxylate cements, no weight loss was observed in the period from 4 to 8 min after commencement of mixing. All the glass ionomer cements showed a significant loss of weight at 4 min and a somewhat reduced weight loss at 6 min after start of mixing. Two cements, a filling and a luting material, showed reduced weight when exposed to a water jet even 8 min after start of mixing. The early erosion as recorded in the present study conforms with the setting of the glass ionomer cements.     

Early erosion of dental cements

The disintegration in water of various unset glass ionomer cements, a polycarboxylate and a zinc phosphate cement was measured gravimetrically after exposure of the cements to a constant water jet. The test gave reproducible results with significant variations between the various types and brands of cements. For zinc phosphate and polycarboxylate cements, no weight loss was observed in the period from 4 to 8 min after commencement of mixing. All the glass ionomer cements showed a significant loss of weight at 4 min and a somewhat reduced weight loss at 6 min after start of mixing. Two cements, a filling and a luting material, showed reduced weight when exposed to a water jet even 8 min after start of mixing. The early erosion as recorded in the present study conforms with the setting of the glass ionomer cements.