Reaction of bony tissue to implanted silver glass ionomer and a reinforced zinc oxide-eugenol cement.

OBJECTIVE: To evaluate the tissue responses to implants of Ketac Silver and Super EBA cement in the guinea pig mandible. STUDY DESIGN: Sixteen guinea pigs were used for 2 experimental periods of 4 and 12 weeks. Both materials were placed in Teflon applicators and implanted into surgically prepared sites in the mandible. A histologic examination for reaction to the material occurred after the animals were killed and processed. RESULTS: After 4 weeks, minimal inflammatory reactions were observed in Ketac Silver implants, whereas the Super EBA implants showed minimal to moderate inflammation. Localized foreign body reaction was present in areas of fragmented small particles of Ketac Silver. At 12-weeks observation, no inflammatory reactions were present around either material. Direct bone contact was observed in 1 Ketac Silver implant. CONCLUSIONS: Ketac Silver and Super EBA cement elicited mild reactions under the conditions of this model. From a biologic point of view, these 2 materials may offer equal utility in endodontic surgery.

In vitro release of hydroxyl ions from six types of calcium hydroxide nonsetting pastes.

The role of intracanal medication in root canal treatment is very important. Calcium hydroxide (Ca(OH)2) is considered to fulfill many of the properties of an ideal root canal dressing mainly due to its alkalizing pH. It is bacteriocidal and neutralizing to the remaining tissue debris in the root canal(s) and through the continuous release of OH- ions it promotes an alkalizing osteogenic environment for the surrounding tissues. The purpose of this study was to examine the pH values of various Ca(OH)2 based on compounds used as intracanal medicaments over a period of 5 days. The following materials were tested: Calasept, Calcicur, Calxyl blue, Calxyl red, Reogan rapid, and Tempcanal. After a fast OH- release period (2 h) each compound reached an asymptotic pH state. The results showed that all materials exhibited alkalizing pH with Reogan rapid, Calxyl Red, and Calcicur being the most potent (p = 0.05). The final pH of each compound correlated positively with the Ca(OH)2 mass fraction contained in it.

Dentin permeability to bacterial proteins in vitro.

Passage of bacterial components through dentin is a subject of recent research with in vitro as well as with in vivo models. Diffusive transport of Porphyromonas gingivalis ATCC 33277 proteins has been demonstrated by the authors with an in vitro setup closely simulating the pulp chamber. The purpose of this investigation was to study the filtration of these proteins through dentin, measure possible concentration changes resulting from the filtering, and elaborate on the physical aspects of the binding process. The hydraulic conductance (Lp) of 10 dentin specimens was determined in three experiments using standard procedures: initially with phosphate-buffered saline, subsequently with a P. gingivalis ATCC 33277 suspension (200 micrograms/ml of protein), and finally with phosphate-buffered saline. The results showed significant, nonpermanent, alterations of the Lps of the dentin disks, and variable retention of the bacterial proteins among samples. A positive correlation between the bacterial protein retention and reduction of Lps was also demonstrated. The reduction of the Lps of the dentin samples was attributed to microstructural changes of the dentin, while the bacterial protein retention was considered to take place either on the surface of the disk or intratubularly. The intratubular interactions in the present experiment seemed to have a mechanical rather than a chemical basis.

The importance of the culture medium on human dental pulp cell attachment.

Radiochromium-labelled pulpal cells were cultured with nine commercially available media and conditioned minimal essential (MEM) medium. Radiochromium release from the 10 cell cultures was recorded after 4 h of incubation. Cells cultured with MEM and conditioned MEM were examined by scanning electron microscopy (SEM) after 2, 4, 8 and 24 h of incubation to study possible differences in attachment. Radiochromium release from cells cultured with most of the media was very high, indicating damage to the external cell membrane. When cells were cultured with conditioned medium, the radiochromium release was within acceptable limits. SEM showed faster attachment when cells were cultured with conditioned MEM. The data indicate that pulpal cells should be cultured with conditioned medium for better results in short-term cytotoxicity experiments with the radiochromium release method.

Dentin as inhibitor of bacterial toxicity on pulpal cells in vitro.

Many studies have shown that the major cause of pulpal disease is the presence of bacteria or their by-products in the dentinal tubules. The purpose of this investigation was to develop an in vitro model, simulating the pulp chamber, that would permit the study of the transport of bacterial by-products through dentin and their effect on pulpal cells. Human pulpal cells were cultured in a modified Sykes-Moore chamber and exposed through dentin to sonicated extracts of Porphyromonas gingivalis ATCC 33277. The cell response was evaluated with the thymidine incorporation method. The results were compared with the cell response obtained after direct exposure to the same irritant. It was found that dentin significantly restricts the diffusion of bacterial proteins in a 24-h experimental period. The time needed for the first bacterial protein molecule to cross the dentin barrier was 6 h. The "diffusion velocity" of the bacterial proteins was 0.023 microns/s. The proposed model has further applications in biocompatibility and microleakage research.

Toxicity of sonicated extracts of Bacteroides gingivalis on human pulpal cells and L929 cells in vitro.

Human pulpal fibroblasts and L929 cells were treated with sonicated extracts of two strains of Bacteroides gingivalis (W83 and ATCC 33277). The cell reaction was evaluated by monitoring cell growth and DNA synthesis. Light and scanning electron microscopic analysis were used to evaluate morphological changes of the cells. Extracts from both bacterial strains exerted a growth inhibitory effect on the cells. The pulpal cells were more sensitive than L929 cells. The ATCC 33277 strain of B. gingivalis was more cytotoxic than the W83 strain. Pulpal cells appeared to be markedly affected on the microscopic level. The diffusion of these toxic bacterial by-products, through dentin to the pulp, may account for pulpal cell damage that contributes to the initiation of pulpal pathosis.

Toxicity of Pulpispad using four different cell types.

The cytotoxic effect of a zinc oxide-eugenol-based paste (Pulpispad) was evaluated in vitro after setting for 1 day and 1 week. Target cells were L929 cells, gingival, periodontal ligament and pulpal fibroblasts. The material was incubated with the cells for 4 and 24 hours, and its toxicity was evaluated with the 51Cr-release method. Pulpispad was highly cytotoxic to all cell lines even after setting for 1 week. The use of Pulpispad is not recommended for future clinical application. The various responses among the four cell lines indicated that diploid cell lines can, under certain circumstances, be less sensitive than aneuploid cell lines. It is therefore suggested that in the evaluation of biomaterials the choice of cell lines should be carefully considered, as they can display varying sensitivities.

Silver glass ionomer cement as a retrograde filling material: a study in vitro.

Comparison was made of the apical microleakage of retrograde fillings with amalgam and with silver glass ionomer cements using a modified dye penetration method. Forty instrumented human teeth were divided into four groups. Each group was characterized by a different retrograde filling material or technique: Group 1--silver glass ionomer (SGI); group 2--SGI with previous acid wash of the cavity; group 3--SGI in a previously acid washed cavity, protected with varnish; and group 4--zinc-free amalgam. A paper cone for dye adsorption analysis was placed in contact with retrofill and the main canal was obturated with thermoplasticized gutta-percha. All teeth were coated, immersed in methylene blue dye, and evacuated to assure complete penetration of the dye in any possible void. Later the teeth were cleared and evaluated under stereomicroscope. Statistical analysis showed that group 1 had the least microleakage of all. In addition, the biocompatibility of the SGI and varnish was compared with that of amalgam using the 51Cr release evaluation method. The results showed that SGI and varnish were less cytotoxic than amalgam. It was concluded that SGI cement can be considered an alternative retrograde filling material.

Biological evaluation of collagen gels containing calcium hydroxide and hydroxyapatite.

Dentinal chips and different biocompatible materials have been used in the past as apical plugs to enhance healing and simplify obturation. The purpose of this study was to evaluate bone reactions to implants of hydroxyapatite, collagen, and calcium hydroxide, alone or in different combinations. The materials were implanted bilaterally in the mandibles of 36 guinea pigs and the reactions were compared histologically over a period of 16 wk. No major inflammatory reactions were observed in any of the implant combinations. Hydroxyapatite was not resorbed over the examination periods, but calcium hydroxide and collagen implants were partially or totally resorbed and replaced by bony tissue. The results indicate that cylinders which may be useful as apical plugs can be performed and will heal with minimal biological reactions.