Tissue reactions to endodontic materials implanted in the mandibles of guinea pigs

Safety Assessment of Polyfluorinated Polymers as Used in Cosmetics

The Expert Panel for Cosmetic Ingredient Safety (Panel) reviewed the safety of 12 polyfluorinated polymers in cosmetic products; most of these ingredients have the reported function of film former in common. However, PTFE, the only ingredient that is reported as currently used in cosmetics, functions as a bulking agent and slip modifier, but not as a film former. The Panel reviewed data relevant to the safety of these ingredients under the intended conditions of use in cosmetic formulations, and concluded that PTFE and Hexafluoropropylene/Tetrafluoroethylene Copolymer are safe in cosmetics in the present practices of use and concentration described in the safety assessment; the data are insufficient to determine the safety of the 4 fluorinated-side-chain polymers and 6 fluorinated polyethers.

Microscopic analysis of subcutaneous reactions to endodontic sealer implants in rats

The reaction of subcutaneous tissues to Endofill, Endomethasone, Sealer 26, and AH-Plus was investigated microscopically after implantation of in rats polyethylene cannulae, obturated with gutta-percha cones and sealers, in rats. Empty polyethylene cannulae and cannulae filled with gutta-percha cones alone were used as controls. The inflammatory reactions caused by the sealers were evaluated 7, 14, and 30 days after implantation using a descriptive, histopathological analysis. Inflammatory reactions at each implant site were gauged as either absent, discreet, moderate, or intense, and scores from 0 to 3 were attributed, respectively. Microscopic analysis revealed that Endomethasone showed the best biological behavior for all postimplant periods, followed by Sealer 26 and AH Plus, which produced an irritating effect only during the initial pos-implant period. Endofill caused the severest irritation, producing an inflammatory reaction that ranged from moderate to intense over the entire experimental period. Reactions were more intense near those parts of the cannulae containing more sealer. These results reveal that the root canal sealers tested cause inflammation in rat, subcutaneous conjunctive tissue, the intensity of which may be related to the type and quantity of sealer used, and to postimplant period.

Biocompatibility of an experimental glass-ionomer cement sealer in rat mandibular bone

OBJECTIVE

The purpose of this study was to compare an experimental glass-ionomer cement sealer, KT-308, with a conventional zinc oxide-eugenol sealer, Canals, in terms of tissue compatibility and solubility.

STUDY DESIGN

Tissue reactions were examined under light and electron microscopes at 3 and 20 days after the implantation of either freshly mixed KT-308 sealer or Canals sealer into prepared cavities in rat mandibles.

RESULTS

At 3 days after implantation, no inflammatory reaction was seen around KT-308 sealer, which was in direct contact with the bone surface. In contrast, Canals sealer elicited an initially severe inflammation in the surrounding tissue. At 20 days, the majority of KT-308 sealer remained in the bone cavity. Canals sealer was largely absorbed and surrounded by fibrous tissue with many macrophages. An ultrastructural examination also revealed that no intervening tissue was present between the cut bone surface and the glass-ionomer cement sealer and that disintegrated zinc oxide-eugenol particles were engulfed by macrophages.

CONCLUSIONS

KT-308 sealer possesses better tissue compatibility and lower solubility compared with a conventional zinc oxide-eugenol sealer, suggesting its potential for use as a root canal sealant.

Reactions of connective tissue to compomers, composite and amalgam root-end filling materials

AIM

To evaluate the subcutaneous connective tissue reaction to compomers, composite and amalgam root-end filling materials.

METHODOLOGY

This study was conducted in 30 Wistar albino rats. The materials were mixed or light-cured according to the manufacturer's directions and placed in polyethylene tubes. Group 1 - Dyract compomer (Dentsply); group 2 - F2000 compomer (3M); group 3 - Valux Plus composite (3M); group 4 - Oralloy high-copper amalgam (Coltene). The tubes containing the materials were implanted into the dorsal connective tissue of rats, which were killed 7, 15, 30, 60 and 90 days after the implantation procedure. Thirty extra empty tubes were also placed as controls. The implant sites were excised and prepared for histological evaluation. Sections of 6-microm thickness were stained with haematoxylin and eosin and assessed under light microscopy. The presence of inflammation, predominant cell type and thickness of fibrous connective tissue adjacent to each implant were recorded. Reactions were scored as: 0: none or few cells and no reaction; 1: less than 25 cells and mild reaction; 2: between 25 and 125 cells and moderate reaction; 3: 125 and more cells and severe reaction. Fibrous capsules were considered to be thin if their thickness was less than 150 microm and thick if it was more than 150 microm. Necrosis and formation of calcification were categorized as 'yes' or 'no'.

RESULTS

All four materials caused moderate or severe inflammatory reactions in the first 7-day period, but these reactions decreased by the 60th and 90th days. No significant difference in inflammatory cell numbers between the materials could be detected at the 90th day.

CONCLUSIONS

Valux Plus composite, Dyract and F2000 compomers and Oralloy amalgam were biocompatible.

Relation of dental composite formulations to their degradation and the release of hydrolyzed polymeric-resin-derived products

This article reviews the principal modes of dental composite material degradation and relates them to the specific components of the composites themselves. Particular emphasis is placed on the selection of the monomer resins, the filler content, and the degree of monomer conversion after the clinical materials are cured. Loss of mechanical function and leaching of components from the composites are briefly described, while a more detailed description is provided of studies that have considered the chemical breakdown of materials by agents that are present in the oral cavity, or model the latter. Specific attention will be given to the hydrolysis process of monomer and composite components, i.e., the scission of condensation-type bonds (esters, ethers, amides, etc.) that make up the monomer resins, following reaction of the resins with water and salivary enzymes. A synopsis of enzyme types and their sources is outlined, along with a description of the work that supports their ability to attack and degrade specific types of monomer systems. The methods for the study of biodegradation effects are compared in terms of sensitivity and the information that they provide. The impact of biodegradation on the ultimate biocompatibility of current materials is discussed from the perspective of what is known to date and what remains to be studied. The findings of the past decade clearly indicate that there are many reasons to probe the issue of biochemical stability of composite resins in the oral cavity. The challenge will now be to have both industry and government agencies take a pro-active approach to fund research in this area, with the expectation that these studies will lead to a more concise definition of biocompatibility issues related to dental composites. In addition, the acquired information from such studies will generate the development of alternate polymeric chemistries and composite formulations that will require further investigation for use as the next generation of restorative materials with enhanced biostability.

Tissue reaction to implanted root-end filling materials in the tibia and mandible of guinea pigs

The purpose of this study was to examine the tissue reaction to implanted mineral trioxide aggregate (MTA), amalgam, Intermediate Restorative Material, and Super-EBA in the tibias and mandibles of guinea pigs. After anesthetizing 20 guinea pigs, raising tissue flaps, and preparing bony cavities, the test materials were placed in Teflon cups and implanted in the tibias and 10 days later in the mandibles. The animals were euthanized 80 days later and the tissues prepared for histological examination. The presence of inflammation, predominant cell type, and thickness of fibrous connective tissue adjacent to each implant were recorded. The tissue reaction to MTA implantation was the most favorable observed at both sites; as in every specimen, it was free of inflammation (p < 0.01). In the tibia, MTA was the material most often observed with direct bone apposition. Based on these results, MTA seems to be a biocompatible material.

Evaluation of a combined surgical repair and guided tissue regeneration technique to treat recent root canal perforations

This study evaluated a technique that included retrofill to repair molar root canal perforations and guided tissue regeneration to restore the periodontium that was removed from the furcation area for access to the sites. Six dogs had root canal therapy on mandibular fourth premolars and first molars. The distal root of each tooth was perforated on the furcation aspect halfway between the furcation and the apex. Replaced flap surgery was performed for access to prepare and fill the perforation site with intermediate Restorative Material. A bone xenograft was placed in the access ostectomy site and covered with GoreTex Augmentation Material (GTAM). Controls included unfilled perforations and not using bone grafts and/or GTAM. Dogs were killed at 6, 12, and 24 wk postsurgery. Complications were more common when root perforations were left unfilled. Histomorphometry revealed a statistically significant decrease in inflammation and more bone fill when root perforations were filled and GTAM was used, respectively.

Root end filling materials: a review

When non-surgical attempts prove unsuccessful or are contraindicated, surgical endodontic therapy is needed to save the tooth. The procedure usually consists of exposure of the involved area, root end resection, root end preparation and insertion of a root end filling material. Numerous materials have been suggested as root end filling materials. This article is a review of the literature on the suitability of various root end filling materials based on their leakage assessment, marginal adaptation, cytotoxicity, and usage test in experimental animals and humans.

Tissue reaction to implanted super-EBA and mineral trioxide aggregate in the mandible of guinea pigs: a preliminary report

In vitro sealing ability and biocompatibility tests on mineral trioxide aggregate (MTA) have shown similar or better properties for this material than for existing root-end filling substances. The purpose of this study was to examine the tissue reaction of implanted Super-EBA and MTA in the mandibles of guinea pigs. After anesthetizing seven guinea pigs, raising a tissue flap and preparing two bony cavities, the test materials were placed in Teflon cups and implanted in the mandibles. Two bony cavities without implanted materials were left to heal and used as negative controls. The presence of inflammation, predominant cell type, and thickness of fibrous connective tissue adjacent to each implant was recorded. The tissue reaction to MTA implantation was slightly than that observed with Super-EBA implantation. Based on these results , it seems that both Super-EBA and MTA are biocompatible.

Formocresol and alternative primary molar pulpotomy medicaments: a review

This paper reviews the history, clinical success and concerns regarding the safety of formocresol as a primary molar pulpotomy medicament. The alternatives to formocresol are discussed and their advantages and disadvantages evaluated.