In vivo Dentin Microhardness beneath a Calcium-Phosphate Cement

A minimally invasive caries-removal technique preserves potentially repairable, caries-affected dentin. Mineral-releasing cements may promote remineralization of soft residual dentin. This study evaluated the in vivo remineralization capacity of resin-based calcium-phosphate cement (Ca-PO(4)) used for indirect pulp-capping. Permanent carious and sound teeth indicated for extraction were excavated and restored either with or without the Ca-PO(4) base (control), followed by adhesive restoration. Study teeth were extracted after 3 months, followed by sectioning and in vitro microhardness analysis of the cavity floor to 115-mu m depth. Caries-affected dentin that received acid conditioning prior to Ca-PO(4) basing showed significantly increased Knoop hardness near the cavity floor. The non-etched group presented results similar to those of the non-treated group. Acid etching prior to cement application increased microhardness of residual dentin near the interface after 3 months in situ.

In vivo Dentin Remineralization by Calcium-Phosphate Cement

Minimally invasive caries-removal procedures remove only caries-infected dentin and preserve caries-affected dentin that becomes remineralized. Dental cements containing calcium phosphate promote remineralization. This study evaluated the in vivo remineralization capacity of resin-based calcium-phosphate cement (Ca-P) used for indirect pulp-capping. Carious and sound teeth indicated for extraction were randomly restored with the Ca-P base or without base (control), followed by adhesive restoration. Study teeth were extracted after three months, followed by elemental analysis of the cavity floor. Mineral content of affected or sound dentin at the cavity floor was quantified by electron probe micro-analysis to 100-mu m depth. After three months, caries-affected dentin underneath the Ca-P base showed significantly increased calcium and phosphorus content to a depth of 30 mu m. Mineral content of treated caries-affected dentin was in the range of healthy dentin, revealing the capacity of Ca-P base to promote remineralization of caries-affected dentin.

Osteoconductive Properties of beta-Tricalcium Phosphate Matrix, Polylactic and Polyglycolic Acid Gel, and Calcium Phosphate Cement in Bone Defects

Extensive bone defects in maxillofacial region can be corrected with autogenous grafts; otherwise, the disadvantages of the therapeutics modality take the research for new bone substitutes. The aim of the study was to evaluate and compare the osteoconductive properties of 3 commercial available biomaterials. A total of 30 calvarial defects (5-mm diameter) were randomly divided into 5 treatment groups, with a total of 6 defects per treatment group (n = 6). The treatment groups were as follows: 500 to 1000 Km beta-tricalcium phosphate (beta-TCP), polylactic and polyglycolic acid (PL/PG) gel, calcium phosphate cement, untreated control, and autograft control. The evaluations were based on histomorphometric analysis at 60 postoperative days. The results have shown that beta-TCP and autograft control supported bone formation at 60 postoperative days. beta-Tricalcium phosphate showed the highest amount of mineralized area per total area and statistically significant compared with PL/PG, calcium phosphate cement, and untreated control groups. The PL/PG gel does not have osteoconductive properties and performed similar to empty control. Calcium phosphate cement showed higher number of multinucleated giant cells around the sites of the biomaterial and showed newly formed bone only at the edges of the biomaterial, without bone formation within the biomaterial. The findings presented herein indicate that bone formation reached a maximum level when rat calvarial defects were filled with beta-TCP at 60 postoperative days. Further studies should be conducted with beta-TCP to understand the potential of this biomaterial in bone regeneration.

Utilization of autogenous bone, bioactive glasses, and calcium phosphate cement in surgical mandibular bone defects in Cebus apella monkeys

Purpose: the purpose of the present study was to evaluate the histologic results of bone cavities that were surgically created in the mandibles of Cebus apella monkeys and filled with autogenous bone, PerioGlas, FillerBone, or Bone Source. Materials and Methods: Surgical cavities 5 mm in diameter were prepared through both mandibular cortices in the mandibular angle region. The cavities were randomly filled, and the animals were divided into groups according to the material employed: Group 1 cavities were filled with autogenous corticocancellous bone; group 2 cavities were filled with calcium phosphate cement (BoneSource); and group 3 and group 4 cavities were filled with bioactive glass (FillerBone and PerioGlas, respectively). After 180 days the animals were sacrificed, and specimens were prepared following routine laboratory procedures for hematoxylin/eosin staining and histologic evaluation. Results: the histologic analysis showed that autogenous bone allowed total repair of the bone defects; bioactive glasses (FillerBone and PerioGlas) allowed total repair of the defects with intimate contact of the remaining granules and newly formed bone; and the cavities filled with calcium phosphate cement (BoneSource) were generally filled by connective fibrous tissue, and the material was almost totally resorbed. Discussion: the autogenous bone, FillerBone, and PerioGlas provided results similar to those in the current literature, showing that autogenous bone is the best Choice for filling critical-size defects. Synthetic implanted materials demonstrated biocompatibility, but the bioglasses demonstrated osteoconductive activity that did not occur with calcium phosphate (BoneSource). Conclusion: According to the methodology used in this study, it can be concluded that the utilization of autogenous bone and bioactive glasses permitted the repair of surgically created critical-size defects by newly formed bone; the synthetic implanted materials demonstrated biocompatibility, and the bioactive glasses demonstrated osteoconductive activity. The PerioGlas was mostly resorbed and replaced by bone and the remaining granules were in close contact with bone; the FillerBone showed many granules in contact with the newly formed bone; BoneSource did not permit repair of the critical-size defects, and the defects were generally filled by connective fibrous tissue.

Intra-articular calcium phosphate cement: Its fate and impact on joint tissues in a rabbit model

Clinical application of injectable ceramic cement in comminuted fractures revealed penetration of the viscous paste into the joint space. Not much is known on the fate of this cement and its influence on articular tissues. The purpose of this experimental study was to assess these unknown alterations of joint tissues after intra-articular injection of cement in a rabbit knee. Observation periods were from 1 week up to 24 months, with three rabbits per group. Norian SRS cement was injected into one knee joint, the contralateral side receiving the same volume of Ringers' solution. Light microscopic evaluation of histologic sections was performed, investigating the appearance of the cement, inflammatory reactions, and degenerative changes of the articular surface. No signs of pronounced acute or chronic inflammation were visible. The injected cement was mainly found as a single particle, anterior to the cruciate ligaments. It became surrounded by synovial tissues within 4 weeks and showed signs of superficial resorption. In some specimens, bone formation was seen around the cement. Degeneration of the articular surface showed no differences between experimental and control side, and no changes over time became apparent. No major degenerative changes were induced by the injected cement. The prolonged presence of cement still seems to make it advisable to remove radiologically visible amounts from the joint space.

Cytotoxicity of two novel formulations of calcium phosphate cements: A comparative in vitro study

The purpose was to evaluate the cytotoxicity of two novel formulations (alpha and beta) of calcium phosphate cements. Positive control, represented by a commercial hydroxyapatite cement, and negative control were included for comparative purposes. A continuous lineage of fibroblastic cells was used, and the effect of the tested materials on both cell proliferation and viability was assessed by counting cell number on hemocytometer and by the trypan blue exclusion test, respectively. Study design attempted to simulate clinical use by allowing direct and indirect contact of cells and cements. Results were analyzed by the Kruskal-Wallis test and indicated that the beta formulation was extremely cytotoxic (P < 0.001), because this material induced the greatest reduction on cell proliferation and viability. The alpha formulation behaved similarly to the positive control regarding its effect on cell proliferation and viability. Thus, it is concluded that alpha formulation has promise for further evaluation of its behavior in vivo.

Application of impedance spectroscopy to evaluate the effect of different setting accelerators on the developed microstructures of calcium phosphate cements

The main goal of the present study was to evaluate the effect of different setting accelerator agents on the developed microstructures of calcium phosphate cements (CPCs) by employing the impedance spectroscopy (IS) technique. Six compositions of CPCs were prepared from mixtures of commercial dicalcium phosphate anhydrous (DCPA) and synthesized tetracalcium phosphate (TTCP) as the solid phases. Two TTCP/DCPA molar ratios (1/1 and 1/2) and three liquid phases (aqueous solutions of Na(2)HPO(4), tartaric acid (TA) and oxalic acid (OA), 5% volume fraction) were employed. Initial (I) and final (F) setting times of the cement pastes were determined with Gillmore needles (ASTM standard C266-99). The hardened samples were characterized by X-ray powder diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and apparent density measurements. The IS technique was employed as a non-destructive tool to obtain information related to porosity, tortuosity and homogeneity of the cement microstructures. The formulation prepared from a TTCP/DCPA equimolar mixture and OA as the liquid phase presented the shortest I and F (12 and 20 min, respectively) in comparison to the other studied systems. XRD analyses revealed the formation of low-crystallinity hydroxyapatite (HA) (as the main phase) as well as the presence of little amounts of unreacted DCPA and TTCP after 24 h hardening in 100% relative humidity. This was related to the proposed mechanisms of dissolution of the reactants. The bands observed by FTIR allowed identifying the presence of calcium tartrate and calcium oxalate in the samples prepared from TA and OA, in addition to the characteristic bands of HA. High degree of entanglement of the formed crystals was observed by SEM in samples containing OA. SEM images were also correlated to the apparent densities of the hardened cements. Changes in porosity, tortuosity and microstructural homogeneity were determined in all samples, from IS results, when the TTCP/DCPA ratio was changed from 1/1 to 1/2. The cement formulated from an equimolar mixture of TTCP/DCPA and OA as the liquid phase presented setting times, degree of conversion to low-crystallinity HA and microstructural features suitable to be used as potential bone cement in clinical applications. The IS technique was shown to be a very sensitive and non-destructive tool to relate the paste composition to the developed microstructures. This approach could be very useful to develop calcium phosphate bone cements for specific clinical demands.

In vivo biological behavior of calcium phosphate cements with different Ca/P ratio

Bioceramics with different Ca/P ratio were prepared from a mechanical mixture of NaPO3, CaCO3, Ca(OH)2 and phosphate buffer solution and implanted in rats subcutaneous tissues. The cements were characterized by Thermo gravimetric analysis (TG-TDA), X-ray diffraction and 31P-NMR. The implant sites were excised after 1, 4 and 16 weeks, fixed, dehydrated, included in paraffin wax for serial cutting and examined under the light transmitted microscope. They were biocompatible and biodegradable when implanted in rat subcutaneous. None of the materials induced ectopic osteogenesis. According to the results, the studied materials seem to be able for manufacturing reabsorbable bone implants.

Effects of a novel calcium aluminate cement on the early events of the progression of osteogenic cell cultures

The present study evaluated the progression of osteogenic cell cultures exposed to a novel calcium aluminate cement (CAC+) in comparison with the gold standard mineral trioxide aggregate (MTA). Cells were enzimatically isolated from newborn rat calvarial bone, plated on glass coverslips containing either CAC+ or a control MTA samples in the center, and grown under standard osteogenic conditions. Over the 10-day culture period, roundening of sample edges was clearly noticed only for MTA group. Although both cements supported osteogenic cell adhesion, spreading, and proliferation, CAC+-exposed cultures showed significantly higher values in terms of total cell number at days 3 and 7, and total protein content and alkaline phosphatase activity at day 10. The present in vitro results indicate that the exposure to CAC+ supports a higher differentiation of osteogenic cells compared with the ones exposed to MTA. Further experimental studies should consider CAC+ as a potential alternative to MTA when the repair of mineralized tissues is one of the desired outcomes in endodontic therapy.

Effect of ultrasonic instrumentation on the bond strength of crowns cemented with zinc phosphate cement to natural teeth. An in vitro study

Several studies have reported the benefits of sonic and/or ultrasonic instrumentation for root debridement, with most of them focusing on changes in periodontal clinical parameters. The present study investigated possible alterations in the tensile bond strength of crowns cemented with zinc phosphate cement to natural teeth after ultrasonic instrumentation. Forty recently extracted intact human third molars were selected, cleaned and stored in physiologic serum at 4°C. They received standard preparations, at a 16º convergence angle, and AgPd alloy crowns. The crowns were cemented with zinc phosphate cement and then divided into four groups of 10 teeth each. Each group was then subdivided into two subgroups, with one of the subgroups being submitted to 5,000 thermal cycles ranging from 55 ± 2 to 5 ± 2°C, while the other was not. Each group was submitted to ultrasonic instrumentation for different periods of time: group 1 - 0 min (control), group 2 - 5 min, group 3 - 10 min, and group 4 - 15 min. Tensile bond strength tests were performed with an Instron testing machine (model 4310). Statistical analysis was performed using ANOVA and Tukey's test at the 5% level of significance. A significant reduction in the tensile bond strength of crowns cemented with zinc phosphate and submitted to thermal cycles was observed at 15 min (196.75 N versus 0 min = 452.01 N, 5 min = 444.23 N and 10 min = 470.85 N). Thermal cycling and ultrasonic instrumentation for 15 min caused a significant reduction in tensile bond strength (p < .05).

Evaluation of several protocols for the application of ultrasound during the removal of cast intraradicular posts cemented with zinc phosphate cement

To evaluate several protocols for the application of ultrasound during removal of cast posts with varying core configurations cemented with zinc phosphate. Sixty maxillary canines were distributed into three groups (n = 20): group 1 - core with 5 mm diameter/height and post diameter of 1.3 mm; groups 2 and 3 - core with the same diameter as the post (1.3 mm) and heights of 5 mm and 3 mm, respectively. Posts/cores were cemented using a standard technique with zinc phosphate cement. Each group was divided into two subgroups according to the ultrasonic vibration mode: point vibration - ultrasonic vibration applied to the core surface for 5 s, on each face totalling 25 s; alternate vibration - intermittent application of ultrasonic vibration for 10 s to the labial and lingual surfaces, 10 s to the mesial and distal surfaces and 5 s to the incisal surface, totalling 25 s. The specimens were submitted to the tensile test using an Instron machine (1 mm min(-1)) and results were analysed by anova and t-test. The failure type was also analysed. Statistical analysis showed significant differences between groups relating to the core preparations (P < 0.05). The lowest mean values of traction force were obtained for group 3 (46.1 +/- 7.7 N), followed by group 2 (89.0 +/- 2.7 N) and group 1 (160.4 +/- 7.5 N). Regarding ultrasonic vibration, the lowest mean was observed with alternate vibration (81.1 +/- 10.1 N), which was significantly lower than the point vibration (115.9 +/- 9.5 N) (P < 0.05). Cohesive failure occurred in all cases. A reduction in core diameter/height and intermittent ultrasonic application improved the removal of cast posts cemented with zinc phosphate.

Radiopacity Evaluation of Calcium Aluminate Cement Containing Different Radiopacifying Agents

Introduction: The aim of this study was to evaluate the radiopacity of calcium aluminate cement (Endo Binder) with 3 different radiopacifiers (bismuth oxide, zinc oxide, or zirconium oxide) in comparison with gray mineral trioxide aggregate (GMTA), white MTA, and dental structures (enamel and dentin). Methods: Eighteen test specimens of each cement with thicknesses of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm (n = 3) were made by using a stainless steel matrix and were adapted to a standardizing device (8 x 7 cm) with a graduated aluminum stepwedge varying from 2.0-16.0 mm in thickness. To compare the radiopacity of the cements with that of dental structures, slices of first molars with a thickness increasing from 0.5-3.0 mm were obtained and placed on the standardizing device. One occlusal radiograph for each tested cement was taken, with exposure time of 0.1 seconds and focus-film distance of 20 cm. Films were processed in an automatic device, and the mean radiopacity values were obtained by using a photodensitometer. Results: Mean values showed that the thicker the specimen was, the greater was its radiopacity. Only EndoBinder + bismuth oxide (EBBO) and GMTA demonstrated radiopacity values greater than 3.0 mm of the aluminum scale for all thicknesses. When zinc oxide was used as radiopacifier agent, EndoBinder only reached the desired radiopacity with a thickness of 2.0 mm, and with zirconium oxide it was 2.5 mm. Conclusions: Bismuth oxide was the most efficient radiopacifier for EndoBinder, providing adequate radiopacity in all studied thicknesses, as recommended by ISO 6876, being similar to GMTA. (J Endod 2011;37: 67-71)