Zinc Oxide Cement Research Articles

Retention force of secondary crowns to copings after temporary cementation: the effect of crown material and luting agent

Tooth-implant supported restorations can be temporarily cemented if the natural abutments are protected by permanently cemented copings. This in vitro study investigated the retention forces of pure titanium crowns to milled titanium alloy copings and of cobalt-chromium crowns to copings made of electroplated gold after cementation with different luting agents. Five specimens per group were cemented with acrylic-urethane cement (inner crown surface preisolated with petroleum jelly) and provisional zinc oxide cement. The retention was measured using a universal testing machine and a dental device for crown removal. The differences between groups were compared using analysis of variance. The pull-off forces for the cobalt-chromium secondary crowns cemented on gold copings using zinc oxide cement were significantly higher (mean=144.5 N) than the other crown-cement combinations (32.2-54.4 N), which showed no significant differences in the retention force. The impulse number and magnitude of the dental device was usually low and showed no substantial differences between the crown-cement combinations. It can be concluded that the results of the clinical removal method for prostheses differ from the results of the pull-off test. The question which luting agent is the better choice for retrievable restorations remains unanswered without further clinical and laboratory studies.

Assessment of the tensile strength of hexagonal abutments using different cementing agents

The aim of this study was to assess the uniaxial tensile strength after thermal cycling in replicas of CeraOne abutments (abutment and coping sets), using four types of cements (n = 10). A zinc phosphate cement (Fosfato de Zinco/ SSW), a resin-modified glass ionomer cement (RelyX luting / 3M-ESPE), a zinc oxide-eugenol cement (ZOE/ SSW) and a zinc oxide cement without eugenol (TempBond NE/ KERR) were used. After cementation, the samples were submitted to thermal cycles (1,000 cycles, 5 degrees C +/- 2 degrees to 55 degrees C +/- 2 degrees) for thirty seconds in each bath. Next, the samples were submitted to the tensile test in a universal test machine (0.5 mm/min). The data were submitted to ANOVA and the Tukey-Kramer test (p < 0.05), and statistically significant difference was found among the cements. The highest tensile strength mean value found was for zinc phosphate cement (33.6 kgf) followed by the resin-modified glass ionomer cement (20.5 kgf), zinc oxide-eugenol cement (8.4 kgf) and the temporary cement (3.1 kgf). Therefore, it was found that the permanent cements presented higher tensile strength, and the temporary cement could be used in situations requiring reversibility and the removal of cemented dental implant-supported prostheses.

Complex endodontic treatment of an immature type III dens invaginatus. A case report

To report the endodontic treatment of an immature maxillary central incisor with dens invaginatus. Dens invaginatus is a rare malformation of teeth, probably resulting from an infolding of the dental papilla during tooth development. The present case describes the complex endodontic treatment of a type III dens invaginatus in an immature maxillary central incisor with a necrotic pulp and abscess formation. The initial treatment goal was to achieve apexification of the pseudocanal root and conservative root canal treatment in the main canal. Following 1-year of treatment with calcium hydroxide dressings, radiography revealed a healing response, but no sign of a hard tissue barrier at the apex. Periapical surgery with the placement of a zinc oxide cement (IRM) root-end filling was considered successful at the 4-year follow-up. The complexity of the canal system and open apex in dens invaginatus present a challenge to endodontic treatment. Correct diagnosis and treatment planning are fundamental to treatment of dens invaginatus. Periapical surgery is indicated in cases of unsuccessful apexification in immature teeth with dens invaginatus and nonvital pulp.

The effect of mineral trioxide aggregate on the apexification and periapical healing of teeth with incomplete root formation

To evaluate the influence of mineral trioxide aggregate (MTA) on apexification and periapical healing of teeth in dogs with incomplete root formation and previously contaminated canals and to verify the necessity of employing calcium hydroxide paste before using MTA. Twenty premolars from two 6-month old dogs were used. After access to the root canals and complete removal of the pulp, the canal systems remained exposed to the oral environment for 2 weeks. Canal preparation was then carried out using Hedström files, under irrigation with 1% sodium hypochlorite, 1 mm short of the radiographic apex. After drying, the canals of two premolars in each dog were left empty (control group). The other eight teeth in each animal were divided into two experimental groups. The apical thirds of the canals of group 1 were filled with MTA. In the teeth of group 2, the canals were dressed with a calcium hydroxide-propylene glycol paste. After 1 week, the paste was removed and the apical third was filled with MTA. All teeth were restored with reinforced zinc oxide cement (IRM) and amalgam. The animals were killed 5 months later, and blocks of the teeth and surrounding tissues were submitted to histological processing. The sections were studied to evaluate seven parameters: formation of an apical calcified tissue barrier, level of barrier formation, inflammatory reaction, bone and root resorption, MTA extrusion, and microorganisms. Results of experimental groups were analysed by Wilcoxon's nonparametric tests and by the test of proportions. The critical value of statistical significance was 5%. Significant differences (P < 0.05) were found in relation to the position of barrier formation and MTA extrusion. The barrier was formed in the interior of the canal in 69.2% of roots from MTA group only. In group 2, it was formed beyond the limits of the canal walls in 75% of the roots. MTA extrusion occurred mainly in roots from group 2. There was similarity between the groups for the other parameters. Mineral trioxide aggregate used after root canal preparation favoured the occurrence of the apexification and periapical healing. The initial use of calcium hydroxide paste was not necessary for apexification to occur, and has shown to be strongly related to the extrusion of MTA and formation of barriers beyond the limits of the root canal walls.

The effect of the renewal of calcium hydroxide paste on the apexification and periapical healing of teeth with incomplete root formation

To evaluate the influence of renewing calcium hydroxide paste on apexification and periapical healing of teeth in dogs with incomplete root formation and previously contaminated canals. Forty premolars from four 6-month-old dogs were used. After access to the root canals and complete removal of the pulp, the canal systems remained exposed to the oral environment for 2 weeks. Canal preparation was then carried out using Hedströem files, under irrigation with 1% sodium hypochlorite, 1 mm short of the radiographic apex. After drying, the canals of one premolar in each dog were left empty (group 4-control), and those of the other nine teeth in each animal were filled with a calcium hydroxide-propylene glycol paste. All teeth were restored with reinforced zinc oxide cement (IRM) or IRM and amalgam (group 4). The paste was renewed and the teeth restored again 1 week later. Then, the nine teeth in each animal were divided into three experimental groups: group 1 - paste not changed; group 2 - paste renewed every 4 weeks for 5 months; and group 3 - paste renewed after 3 months had elapsed. The teeth were restored with IRM and amalgam (groups 1 and 3) or IRM (group 2). The animals were killed 5 months later, and blocks of the teeth and surrounding tissues were submitted to histological processing. The sections were studied to evaluate six parameters: apical calcified tissue barrier, inflammatory reaction, bone and root resorption, paste extrusion and microorganisms. Results of experimental groups were analysed by Kruskal-Wallis nonparametric tests and by the test of proportions. The critical value of statistical significance was 5%. Significant differences (P < 0.05) were found in relation to the presence of bone resorption and paste in the periradicular area, the formation of a calcified tissue barrier at the apex, and the intensity of the apical inflammatory reaction. Bone resorption was more evident in group 1 (medicament not changed), and the presence of paste in the periodontal tissues was more common in groups 2 and 3. Renewal of the paste reduced the intensity of the inflammatory reaction (groups 2 and 3), but the formation of apical calcified tissue was more noticeable in the teeth where the paste had not been renewed. Replacement of calcium hydroxide paste was not necessary for apexification to occur, however, it did reduce significantly the intensity of the inflammatory process. Monthly renewal of calcium hydroxide paste reduced significantly the occurrence of apexification.

Inhibition of human pulpal gelatinases (MMP-2 and MMP-9) by zinc oxide cements.

The interaction between metal ions and the oral environment is a major subject matter in dental research. Matrix metalloproteinases (MMPs) have been implicated in several pathological and physiological processes such as, periodontal tissue destruction, root caries, dentin calcification and pulpal inflammation. The aim of this work was to test the effect of zinc released from zinc oxide-eugenol (ZOE) cements, on the activity of the major pulpal gelatinolytic MMPs. Pulpal explants were cultured overnight in Dulbecco's Modified Eagle Medium and the activity of secreted enzymes was analysed by gelatin zymography in buffer conditioned with diverse ZOE cements. Phenanthroline, a zinc chelator, was used to revert the inhibition of MMPs caused by zinc. The major gelatinolytic proteinases present in the conditioned media were characterized as MMP-2 and MMP-9 by immunoprecipitation. All ZOE cements inhibited MMPs activity, whereas phenanthroline could partially revert the inhibition caused by plain ZOE and Intermediate Restorative Material (IRM).

Effects of abutment size and luting cement type on the uniaxial retention force of implant-supported crowns

Statement of problem. The assumption that increasing the diameter of the abutment/crown components will provide greater resistance to crown loosening forces than standard-sized components has not been reported either with clinical trials or in the laboratory. Purpose. This study attempted to determine what effect abutment dimension and type of luting agent have on the retention of the prosthetic crown. Methods and material. Test specimens consisted of standard, wide, and “experimental” CeraOne titanium abutments and matching CeraOne gold cylinders cemented with a zinc phosphate permanent or a zinc oxide eugenol provisional cement. The mean uniaxial force (Newtons) and the load (MPa) required to dislodge the cylinder from the abutment was determined. Statistical analysis of the sample data was performed using a 2-way analysis of variance test (α=.05). Results. Mean uniaxial resistance force (Newtons) was significantly greater for zinc phosphate cement than for zinc oxide cement ( P <.001). Abutment size was a significant factor when permanent luting cement is used ( P <.001). Retention strength per unit area (MPa) of the wide abutments was lower than the standard size and “experimental” abutments. Conclusion. Permanent luting cement produced uniaxial retention forces approximately 3 times greater than provisional cement. The increase in surface area provided by a wide abutment did not result in an improvement in retention strength over the standard abutment. (J Prosthet Dent 2000;83:344-8.)

Mineral trioxide aggregate — a new experimental material for retrograde filling

Objective To compare apical microleakage of MTA following reverse retrograde root filling with that following amalgam and EBA retrofilling. Design Prospective random control trial. Setting It was conducted at the University of Jordan in 1998. Materials and methods The root canals of 79 extracted teeth were instrumented and obturated with vertically condensed gutta-percha. Each tooth was apically resected and the apex was prepared ultrasonically to 3 mm depth and the root surface isolated with nail varnish. Teeth were divided randomly into three groups of 25 teeth each. First group was retrofilled with amalgam, second group with EBA and the third group with MTA. Following immersion in 1% methylene blue dye for 72 hours, the roots were sectioned and the depth of dye penetration was evaluated by a stereomicroscope at x10 magnification. Interventions Super EBA is a reinforced zinc oxide cement based on a mixture of 32% eugenol and 68% ethoxy benzoic acid (EBA). MTA is a mineral trioxide aggregate cement (MTA) based on a mixture of sterile water. Main outcome measures The sealing effectiveness of the retrograde filling materials used in this study was determined by their ability to inhibit dye penetration. Results 56% of the group filled with amalgam and 20% of the group filled with EBA showed dye leakage beyond the retrofilling material whereas the MTA group showed none, two samples from MTA group were eliminated because of their fractured roots. The chi-squared test revealed a statistically significant difference among all three groups (P < 0.05). Conclusion MTA cement provides a better seal than amalgam and EBA cement when used as retrograde filling, but the extrapolation of this result into a clinical practice may be questionable.

Cement coating of osteoarticular allografts in rats to prevent the immune response.

Recently, more attention is being paid to the treatment of the articular surface defect in the young, active individual. Resurfacing or "shell" allografts are being considered as one of the alternatives for treatment. The immune response by the host may be the chief obstacle to the successful use of fresh osteoarticular allografts. Since proteins on the surfaces of allograft bone cells are considered to be the principal antigens eliciting the immune response, we hypothesized that mechanical masking of these cells by a biodegradeable blocking agent might prevent the immune response. Osteoarticular allografts of the distal femur were performed in rats and the cut surfaces of the graft were coated with cement before implantation. In a preliminary experiment, six biodegradeable cement materials were tried (bone wax, zinc polycarboxylate, collodion, fibrin adhesive, zinc oxide, and isobutyl-cyanoacrylate). Of these, the zinc oxide cement and isobutyl-cyanoacrylate were effective in inhibiting the immune response observed in control rat distal femur allografts. A second experiment was performed using nine rats with zinc oxide and nine rats with isobutyl-cyanoacrylate cements. These were compared with 20 control rats that had allografts without cement coating. Eighteen of the control rats (90%) developed an immune response, while only 22% (2/9) of the rats with zinc oxide coating and 33% (3/9) of the rats with isobutylcyanoacrylate developed an immune response. In a third experiment distal femur allografts were performed in 13 rats using only the liquid component of the zinc oxide cement.(ABSTRACT TRUNCATED AT 250 WORDS)

An evaluation of the significance of the impinging jet method for measuring the acid erosion of dental cements

An extensive review has been made of the impinging jet method for evaluating the durability of dental cements. A comprehensive range of 28 dental cements was examined. The initial rate of erosion was found to be essentially constant. Zinc oxide cements were found to be markedly less durable than aluminosilicate cements. Results broadly correlate with those found in clinical studies.

Antiplaque properties of sustained release SnF2: pilot studies.

Pilot studies examining the physical and clinical properties of an intracoronal sustained release fluoride delivery system were performed. After testing various percentages of SnF2 incorporated into polycarboxylate, zinc phosphate, and zinc oxide cements, 70% SnF2 polycarboxylate cement was found to have adequate compressive strength while releasing the greatest amount of fluoride in vitro. A 30-day in vivo trial, in which this fluoride cement was used as a temporary intracoronal restoration, produced elevated salivary fluoride levels with only transient elevation in urinary fluoride levels. Plaque scores decreased during the experimental period, suggesting that the released SnF2 affected bacterial growth or attachment. The SnF2-polycarboxylate cement was an adequate temporary restorative material without significant side effects.

Resolution of periapical radiolucency following pulpotomy

There is evidence in the literature that some periapical lesions can be resolved by conservative management of the pulpal tissues rather than by traditional endodontic therapy (1-4). Moore (1) showed apparent resolution of periapical lesions radiographically in three of eight vital carious teeth after treatment by various direct and indirect capping techniques. Jordan et al. (2) treated 24 vital nonexposed teeth in 19 patients with gross caries and periapical radiolucencies by indirect pulp capping with fortified calcium hydroxide (Dycal; L. D. Caulk Co.) and zinc oxide cement. Eleven of the 24 teeth remained vital and showed resolution of the periapical radiolucency during observation times ranging from 11 months to 7 years. The remaining 13 teeth were either extracted or root filled. Recently, Foreman (3) reported some resolution of a periapical area in a second molar tooth following a calcium hydroxide (Calxyl; Exceldent Ltd., United Kingdom) pulpotomy and fortified zinc oxide dressing, and Russo et al. (4) showed reduction (2 teeth) or complete disappearance of abnormal radiolucency (28 teeth) in a group of 30 first permanent molars with carious pulp exposures and periapical radiolucencies after treatment by pulpotomy, corticosteroid-nitrofurazone dressing (48 h) followed by calcium hydroxide. The following case shows complete resolution of a periapical area 1 year following pulpotomy and dressing with a corticosteroid-antibiotic dressing material (Ledermix cement; Ledermix Pharmaceuticals, Wolfratshausen).

Modulus of elasticity and strength properties of dental cements

The modulus of elasticity of commercial dental cements was determined by an optical strain gauge method. Values of compressive and tensile strengths also were measured. Of the cements of primary consistency tested, a noneugenol zinc oxide cement had the lowest mechanical properties. A zinc phosphate cement had the highest value of compressive strength and modulus, but a zinc polyacrylate cement had the highest tensile strength. A zinc polyacrylate cement base had the highest tensile strength, but a zinc phosphate cement base had the highest compressive strength and modulus of elasticity. A calcium hydroxide liner had higher mechanical properties than an unmodified ZOE liner.

Permeability beneath orthodontic bands: Variations dependent on cement type and cement-removal method

The permeability of the margins of five dental cement seals was evaluated, by using 45Ca, after five different procedures for removing excess cement. The five dental cements varied significantly ( P < 0.001) in amount of penetration by 45Ca. From least penetration to greatest penetration, the order was (1) zinc oxide cement, (2) zinc phosphate cement No. 1, (3) silicophosphate cement No. 1, (4) silicophosphate cement No. 2, and (5) zinc phosphate cement No. 2. The five treatments also varied significantly ( P < 0.001). From least to greatest penetration, the order was (1) wiping the cement off the tooth and band prior to initial set, (2) hand scaling after complete set, (3) ultrasonic application directed only on the tooth surface, (4) ultrasonic application directed only on the band surface, and (5) ultrasonic application on tooth and band indiscriminately. The relationship among cements did not remain the same for all treatments; there was significant cement-treatment interaction ( P < 0.025). The buccal and lingual surfaces demonstrated less penetration than did the proximal surfaces ( P < 0.05). The two factors that emerged most clearly from this study were that the method of wiping or hand scaling the cement tended to prevent disruption of the integrity of the tooth-band cement bond, irrespective of the cement used, and, perhaps more important, that the zinc oxide-eugenol type of cement was able to withstand the effects of ultrasonic instrumentation.

Reaction of dog tissue to immediate root filling with zinc oxide cement and gutta percha.

Reaction of dog tissue to immediate root filling with zinc oxide cement and gutta percha.