Tissue reactions induced by dental pulp capping materials: a histological study Ovidiu Cristea, Romeo Brezeanu, Alexandra Stoica, Rania Seserman (Lecturer Cosmin Moldovan,Assoc. Prof. Monica Monea)

Background Biocompatibility is a condition that must characterize all materials used in conservative dentistry, which means no risk of side effects on contact with host tissues. In the case of pulp capping materials, this is expressed by many variables such as carcinogenesis, cytotoxicity, biocompatibility and antimicrobial effect.

Aim of the study The purpose of our study is to evaluate the biocompatibility of materials used in pulp capping procedures, such as MTA and calcium hydroxide, by measuring the degree of inflammation induced by these products after subcutaneous implantation in experimental animals.

Material and method We used 12 animals divided in 3 study groups and 1 control group in which subcutaneous implants with MTA and calcium hydroxide containing products (Life, Calxyl)were placed; the histological evaluation was carried out after 7, 14 and 21 days. Our test was conducted according to international law (ISO/Tc 194)

Material and method Local anesthesia with 2ml Mebumal 10%, under rules of asepsis and antisepsis; Postoperatively, the animals were not isolated and no antibiotherapy was applied, in order to avoid any effect on tissue inflammatory reactions.

Material and method Preparation of cotton implants containing dental materials on a sterile table. On a skin surface of 2 cm² a pocket was created, after a tissue incision of 1- 1,4 cm, which was than elevated; The subcutaneous implant was placed and sutured. Histopathological evaluation was carried out after 7, 14 and 21 days.

Histopathological evaluation The histologic specimens were obtain according to a specific protocol; sections of 4 µm were stained with Hematoxylin-Eosin and /or PAS and prepared for optical microscopic analisys. The examination was carriede out by the same person, who did not know the type of material or moment of sample preservation.

Criteria for histopathological evaluation 0 = no inflammation: reaction zone similar to control, with none or only a few inflammatory cells; 1= mild inflammation: presence of plasma cells and macrophages; 2= moderate inflammation: inflammatory reaction with granulocites and limfocites beside macrophages and plasma cells. 3= severe inflammation: areas of necrosis, many inflammatory cells in the surrounding tissue.

Results Control group 7 days Moderate inflammatory infiltrate, multinucleated cells, enlarged blood vessels(HE stain 20X).

Results MTA at 7 days Moderate reaction, with an important inflammatory infiltrate. The implant placed in epithelial tissue is surrounded by a limited necrotic zone (HE stain, 20X).

Results Calxyd paste at 7 days Large necrotic zone, severe inflammatory infiltrate, numerous hyperemic blood vessels (HE stain, 20X).

Results Life cement at 14 days A connective tissue barrier is developing arround the implant; The inflammatory reaction is moderate; There are many collagen fibres and fibroblasts as signs of tissue healing.

Results MTA at 14 days Slight tendency of tissue healing and reduced inflammatory infiltrate; A connective tissue barrier is formed with the presence of collagen fibres and a few macrophages.

Results Control at 21 days The implant placed in subcutaneous tissue shows healing, with the development of a fibrous barrier. Absence of inflammatory cells.

Results MTA at 21 days Tendency to tissue healing and absence of inflammatory infiltrate. The implant was rarefied due to macrophages activity and a thin fibrous capsule had developed (PAS, 20X).

Results Calxyde paste at 21 days The implant is surrounded by a fibrous capsule, there is no inflammation and the tissue is considered healed. (HE stain, 10X).

Results Life cement at 21 days A thick fibrous barrier with a septum surrounds the implant; The adjacent tissue is considered healed, free of inflammation. (HE stain, 20X).

Discussion Conservative treatment of the dental pulp is still a subject of intense debate, as there are many methods that totally or partially preserve the vitality of this tissue. The most used material for capping procedures is calcium hydroxide, due to its antibacterial and neodentinogenetic effects. Same effects were noted for MTA, which offers a tight seal and stimulated dentin bridge formation, with very good results in direct pulp capping procedures.

Discussion Our investigation was based on an experimental method widely used for in vivo studies, beeing currently considered the most accurate approach in evaluating the biocompatibility of dental materials. Regarding the effect of surgical procedure upon experimental animals, we found no difficulty in the placement of subcutaneous implants, with no interference with the general health of the study groups.

Conclusions The inflammatory reactions induces by MTA and Life cement are comparable, showing that there are no major differences in the biocompatibility of these materials. Anyway, this is not enough to rule out calcium hydroxide containing materials from every day dental practice, due to its excellent results. Further clinical studies are necessary in order to evaluate the potential of MTA to induce dentin bridge formation on exposed dental pulps and its long-term clinical outcome.

Selective refferences Modena da Silva KC, Atta MT, Costa K, Santos CF. Cytotoxicity and biocompatibility of direct and indirect pulp capping materials. J Appl Oral Sci. 2009: 17 (6); 544-554. Bogen G, Kim JS, Bakland LK. Direct pulp capping with Mineral Trioxide Aggregate: an observational study. J Am Dent Assoc. 2008, 139; 305-315. Pelka M, Danzl C, Distler W. A new screening test for toxicity testing for dental materials. J Dent 2008, 28: 341-345. Perirokh M, Torabinejad M. Mineral Trioxide Aggregate, a comprehensive literature review: part II. Leakage and biocompatibility investigations. J Endod 2010, 36: 190-202. Tuna D, Olmez A. Clinical long-term evaluation of MTA as a direct pulp capping material in primary teeth. Int Endod J 2008, 41(4): 273-278.

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