Histopathological and cell enzyme studies of calcium phosphate cements.
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New types of self-setting calcium phosphate cement (N-CPC), which do not contain tetracalcium phosphate, were recently developed. N-CPCs harden in 10 minutes with phosphate solution as the cement liquid, and form hydroxyapatite as the set product. The objectives of the present study were to evaluate the biocompatibility (Study I) and cell enzyme activity of N-CPCs and a conventional CPC (Study II). Four experimental cements were tested: (1) dicalcium phosphate anhydrous (DCPA) and calcium oxide; (2) DCPA and calcium hydroxide; (3) tricalcium phosphate and calcium carbonate; and (4) DCPA and tetracalcium phosphate. Phosphate solution was used as the cement liquid for cements (1)-(3), and water for cement (4). Sintered hydroxyapatite particles (5) were used as a control. The test materials were implanted subcutaneously in rats. Four weeks after operation, the animals were sacrificed and histopathological observations were performed. Cements (2) and (3) showed no inflammatory reaction, and were surrounded only by very thin fibrous connective tissues. The histopathological reactions of N-CPCs were nearly identical and were similar to (4) and (5). In addition, effects of alkaline phosphatase (ALP-ase) activity--invoked by the presence of cements (3) and (4)--on osteoblast-like cells derived from dog alveolar bone were also examined because ALP-ase activity is closely related to new bone formation. These results indicated that (3) and (4) were highly compatible with subcutaneous tissues and suggested that these cements may enhance new bone formation. (+info)
The effect of luting agents on the retention of dental implant-supported crowns.
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BACKGROUND: This study was designed to evaluate the retentive strength of 7 different luting agents on cement-retained implant abutment/analog assemblies. METHODS: Fifty-six Steri-Oss implant abutment/analog assemblies and cast superstructures were randomly divided into 7 groups: definitive cements included zinc phosphate cement, Advance, All-Bond 2, Panavia F, and Durelon, while provisional cements included Temp Bond and ImProv. After the superstructures were cemented onto the implant abutments, the specimens were subjected to 100,000 cycles on a chewing machine (75 N) and 1000 cycles on a thermocycling machine (0-55 degrees C). A universal testing machine was used to test the cement failure load values for each specimen. One-way ANOVA and Duncan's multiple-range analysis were used to determine the effects of luting agents on cement failure load values. RESULTS: The following values for the mean and standard deviation of cement failure loads for each group were obtained: zinc phosphate, 1.225 +/- 0.229 MPa; Advance, 1.205 +/- 0.197 MPa; All Bond 2, 1.752 +/- 0.211 MPa; Panavia F, 1.679 +/- 0.176 MPa; Durelon, 0.535 +/- 0.161 MPa; Temp Bond, 0.274 +/- 0.079 MPa; and ImProv, 0.319 +/- 0.107 MPa. CONCLUSIONS: There were significant differences in cement failure loads among the various cements tested. Values significantly differed among 4 groups consisting of All-Bond 2 and Panavia F resin cements, zinc phosphate cement and Advance hybrid ionomer cement, Durelon carboxylate cement, and ImProv and Temp Bond provisional cements (p < 0.0001). All-Bond 2 and Panavia F resin cements had statistically significantly higher values for cement failure loads compared to the other 5 types of cement. (+info)
Histological analysis of rat dental pulp tissue capped with propolis.
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The aim of the present study was to assess the response of rat dental pulp to direct pulp capping with propolis. Flavonoid and non-flavonoid materials were purified from an ethanol extract of propolis obtained from South Sulawesi, Indonesia. A Class I cavity was prepared on the occlusal surface of the right maxillary first molar in Sprague Dawley rats. The dental pulp was exposed and then capped with a zinc oxide-based filler as a control (group I), or with propolis flavonoids (group II) or non-flavonoids (group III). The animals were sacrificed at week 1, 2 or 4, biopsy samples were obtained, and these were stained and viewed by light microscopy. The results showed that pulp inflammation occurred in groups I and III as early as week 1. No dentin bridge formation was seen in these groups. In contrast, there was no evident inflammatory response in group II at week 1. Mild and moderate pulp inflammation in this group occurred at 2 and 4 weeks after treatment, respectively. Partial dentinal bridge formation was seen in group II at week 4. Therefore, the present results suggest that direct pulp capping with propolis flavonoids in rats may delay dental pulp inflammation and stimulate reparative dentin. (+info)
Early biofilm formation and the effects of antimicrobial agents on orthodontic bonding materials in a parallel plate flow chamber.
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Decalcification is a commonly recognized complication of orthodontic treatment with fixed appliances. A technology, based on a parallel plate flow chamber, was developed to investigate early biofilm formation of a strain of Streptococcus sanguis on the surface of four orthodontic bonding materials: glass ionomer cement (Ketac Cem), resin-modified glass ionomer cement (Fuji Ortho LC), chemically-cured composite resin (Concise) and light-cured composite resin (Transbond XT). S. sanguis was used as it is one of the primary colonizers of dental hard surfaces. Artificial saliva was supplied as a source of nutrients for the biofilms. The effects of two commercially available mouthrinses (i.e. a fluoride containing rinse and chlorhexidine) were evaluated. Initial colonization of the bacterium was assessed after 6 hours of growth by the percentage surface coverage (PSC) of the biofilm on the disc surfaces. There were statistically significant differences in bacterial accumulation between different bonding materials (P < 0.05), Concise being the least colonized and Transbond XT being the most colonized by S. sanguis biofilms. All materials pre-treated with 0.05 per cent sodium fluoride mouthrinse showed more than 50 per cent reduction in biofilm formation. The 0.2 per cent chlorhexidine gluconate mouthrinse caused significant reduction of biofilm formation on all materials except Ketac Cem. This in vitro study showed that the use of a chemically-cured composite resin (Concise) reduced early S. sanguis biofilm formation. Also, fluoride had a greater effect in reducing the PSC by S. sanguis biofilms than chlorhexidine. Rinsing with 0.05 per cent sodium fluoride prior to placement of orthodontic appliances is effective in reducing early biofilm formation. (+info)
Three-dimensional finite element analysis of weakened roots restored with different cements in combination with titanium alloy posts.
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BACKGROUND: It is very difficult and relatively unpredictable to preserve and restore severely weakened pulpless roots. To provide much needed benefit basis for clinical practice, this study was carried out to analyze the stress distribution in weakened roots restored with different cements in combination with titanium alloy posts. Finite element analysis (FEA) was employed in the study. METHODS: A pseudo three-dimensional model of a maxillary central incisor with flared root canal, theoretically restored with titanium alloy posts in combination with different cements, was established. The analysis was performed by use of ANSYS software. The tooth was assumed to be isotropic, homogenous and elastic. A load of 100 N at an angle of 45 degrees to the longitudinal axis was applied at the palatal surface of the crown. The distributions of stresses in weakened roots filled with cements of different elastic modulus were analyzed by the three-dimensional FEA model. RESULTS: Several stress trends were observed when the stress cloud atlas obtained in the study was analyzed. With the increase of the elastic modulus of cements from 1.8 GPa to 22.4 GPa, the stress values in dentin decreased from 39.58 MPa to 31.43 MPa and from 24.51 MPa to 20.76 MPa (respectively, for maximum principle stress values and Von Mises stress values). When Panavia F and zinc phosphate cement were used, the stress peak values in dentin were very small with no significant difference observed, and the Von Mises stress values were 20.87 MPa and 20.76 MPa respectively. On the other hand, maximum principle stress value and Von Mises stress value in cement layer increased with the increase of the elastic modulus of cements. CONCLUSIONS: The result of this study demonstrated that elastic modulus was indeed one of the important parameters to evaluate property of the cements. Our three-dimensional FEA model study also found that the cement with elastic modulus similar to that of dentin could reinforce weakened root and reduce the stress in dentin. Thus, it may be a better choice for the restoration of weakened roots in clinical practice. (+info)
Resin tag length of one-step and self-etching adhesives bonded to unground enamel.
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Length of resin tags yielded by utilization of an one-step conventional adhesive system and self-etching adhesive system on unground enamel was observed. In study Groups I and III, the enamel surface was etched for 60 seconds with 35% phosphoric acid gel and adhesive systems PQ1 (Ultradent Products, Inc) and Adper Prompt L Pop (3M/ESPE) were applied. Adper Prompt L Pop (3M/ESPE) was also applied in Group II in accordance with the manufacturer's recommendations. After application of these adhesive systems to dental enamel, specimens were prepared for light microscopy analysis to ascertain degree of penetration (x400). The results were submitted to an analysis of variance at the 5% level; whenever there was significance, the Tukey test was applied at the 5% level. It was found that acid etching prior to application of conventional and self-etching adhesive materials provided higher penetration of the adhesive into the unground enamel surface compared to that achieved solely by application of self-etching adhesive. (+info)
OBJECTIVES: Calcium phosphate cement (CPC) is a promising material for dental, periodontal, and craniofacial repairs. However, its use requires on-site powder-liquid mixing that increases the surgical placement time and raises concerns of insufficient and inhomogeneous mixing. The objective of this study was to determine a formulation of premixed CPC (PCPC) with rapid setting, high strength, and good in vitro cell viability. METHODS: PCPCs were formulated from CPC powder+non-aqueous liquid+gelling agent+hardening accelerator. Five PCPCs were thus developed: PCPC-Tartaric, PCPC-Malonic, PCPC-Citric, PCPC-Glycolic, and PCPC-Malic. Formulations and controls were compared for setting time, diametral tensile strength, and osteoblast cell compatibility. RESULTS: Setting time (mean+/-S.D.; n=4) for PCPC-Tartaric was 8.2+/-0.8 min, significantly less than the 61.7+/-1.5 min for the Premixed Control developed previously (p<0.001). On 7th day immersion, the diametral tensile strength of PCPC-Tartaric reached 6.5+/-0.8 MPa, higher than 4.5+/-0.8 MPa of Premixed Control (p=0.036). Osteoblast cells displayed a polygonal morphology and attached to the nano-hydroxyapatite crystals in the PCPCs. All cements had similar live cell density values (p=0.126), indicating that the new PCPCs were as cell compatible as a non-premixed CPC control known to be biocompatible. Each of the new PCPCs had a cell viability that was not significantly different (p>0.1) from that of the non-premixed CPC control. SIGNIFICANCE: PCPCs will eliminate the powder-liquid mixing during surgery and may also improve the cement performance. The new PCPCs supported cell attachment and yielded a high cell density and viability. Their mechanical strengths approached the reported strengths of sintered porous hydroxyapatite implants and cancellous bone. These nano-crystalline hydroxyapatite cements may be useful in dental, periodontal, and craniofacial repairs. (+info)
Laser-Raman Spectroscopic study of the adhesive interface between 4-MET/MMA-TBB resin and hydroxyapatite or bovine enamel.
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The possible chemical interaction between synthetic hydroxyapatite or bovine enamel and a functional monomer of 4-methacryloxyethyl trimellitic acid (4-MET) diluted in methyl methacrylate (MMA) was examined by measuring the Raman spectra. It was concluded that the carboxyl group of 4-MET reacted with the calcium in the substrate to form a salt that was detected by the Raman band at around 1,380 cm-1. However, formation of the salt on the surface of the hydroxyapatite (HAP) with the carboxyl group, and polymerization of the 4-MET in the methacryl group near the surface were mutually exclusive reactions for the same 4-MET molecule. (+info)