Biological evaluation of the apical dentin chip plug

Establishing Apical Patency: To be or not to be?

INTRODUCTION

The apical portion of the root canal is very complex and challenging during endodontic treatment. Root canal preparation and obturation to the apical constriction may provide the best prognosis. Incomplete debridement, foramen transportation, and inadequate seal in the apical portion are considered to be responsible for treatment failure. The technique "apical patency" is considered as a way for maintaining the apical part the free of the debris by recapitulation, using a small K-file through the area of the apical foramen. This term was firstly proposed by Buchanan. In this technique, the smallest diameter file is set 1 mm longer than working length and recapitulated after each instrument to prevent packing of debris in the apical part. Apical patency has been found to be effective in achieving an apical seal with gutta-percha. Teeth prepared with a step back method and with maintained apical patency may show less leakage when obturated with cold lateral condensation technique. Data regarding the effect of apical patency on the healing of periapical tissue are very scarce, and it has been shown that the patency file has detrimental effect on the healing of periapical tissues in animal studies. However, using patency file in endodontic treatment is controversial and further studies are needed. The purpose of this article is to review the effect of using a patency file on the extrusion of root canal contents, the apical seal, postoperative pain, and healing of periapical tissues. Furthermore, the effect of establishing patency on reaching irrigation solutions to the apical portion of the canal and prognosis of root canal treatment are discussed.

CLINICAL SIGNIFICANCE

Keywords: Apical patency, Apical seal, Apical transportation, Postoperative pain, Prognosis.

Histological evaluation of the osteoinduction capability of human dentine

Aim To assess whether human dentine has the potential to promote the development of calcified tissues when implanted in the muscle tissue of mice. Methodology Root canals in extracted human teeth were instrumented to produce dentine fragments. The dentine fragments produced were divided into two. In group 1, fragments were demineralized and sterilized. In group 2, the fragments were not submitted to any additional treatment. The dentine fragments were then implanted in the muscle of mice. In group 3, the muscles were implanted with rehydrated lyophilized human bone powder. Animals were killed following test periods of 7, 15, 30, 60, 120 and 180 days, the fragments were removed together with adjacent muscle and examined under light microscopy to assess calcification. Results Areas of calcification were observed in groups 1 and 3 after a period of 180 days. In group 2, the surrounding tissues displayed only chronic inflammatory infiltration. Conclusions On the basis of the experimental model adopted in this study, fibroblast-rich connective tissue formed in groups 1 and 3, which could reflect an osteoinductive process. Further studies are suggested to identify which dentinal factors are capable of inducing the formation of a calcified matrix.

Removal of Organic Debris from Bovine Dentin Shavings

A common problem with root canal failures is chronic inflammation at the apex caused by overfilling of root canal materials. Dentin filings have been suggested as an apical plug to create a biocompatible barrier between the filling material and the periapical tissue. Unfortunately residual organic material, such as pulp remnants or bacteria, still may be part of the filings. Dentin filings removed from the tooth, cleaned, and then used to form a barrier might serve as an effective barrier. The purpose of this study was to evaluate methods of cleaning dentin of organic debris. NaOCl, sodium dodecyl sulfate, and 1% Triton X-100 were used to treat dentin shavings and were evaluated by a micro bicinchoninic acid protein analysis assay. Two series of experiments were performed. One compared the effect of temperature while using phosphate-buffered saline as a control and the second compared exposure times. The percentage of protein extracted from dentin samples increased with temperature. Sodium hypochlorite at room temperature extracted 24.6%, NaOCl at 37 degrees C extracted 26.9%, and NaOCl at 70 degrees C extracted 33.9%. Only NaOCl at 37 degrees C and 70 degrees C showed statistically significant differences from phosphate-buffered saline at room temperature with p-values of 0.028 and 0.019, respectively. The exposure time series showed a difference between a phosphate-buffered saline solution and 6.25% NaOCl. NaOCl removed approximately 90% of protein compared with 60% for the phosphate-buffered saline. A 10-min exposure to 70 degrees C 6.25% NaOCl may be an efficient means of removing organic material from dentin shavings.

Histopathological study of the use of freeze-dried allogenic dentin powder and True Bone Ceramic as apical barrier materials

The biocompatibility of freeze-dried allogenic dentin powder and True Bone Ceramics (TBC), the latter prepared by incineration of bovine bone, as apical barrier materials was evaluated histopathologically in dogs. After pulpectomy, 80 root canals of 53 dog premolar teeth were prepared, and each material was tightly packed to the apical stop area. The remainder of the canal was filled with guttapercha by the lateral condensation method. Control teeth were filled by the lateral condensation method using gutta-percha without constructing apical barriers. In both the teeth filled with the dentin powder and those filled with TBC, multinucleate giant cells appeared on the bone resorption surface and the surface of the root canal wall, and marked bone resorption and positive tartrate-resistant acid phosphate staining were observed. Hard tissue had formed on the root canal wall and the filling material after 3 months. These findings suggest that the test materials are nonirritative and compatible with periapical tissue, and that they may be useful and clinically applicable as apical barrier materials.

An experimental study of the sealing ability of a dentinal apical plug treated with bonding agent

The purpose of this study was to evaluate the sealing ability of a dentinal apical plug treated with a bonding agent. Ninety human lower premolars were used. The teeth were divided into three groups. in groups 1 and 2, to prepare an apical isthmus of 1 mm in length, the first apical seat was prepared with a #45 K file 1 mm short of the anatomical apex and with a #60 K file 2 mm short for the second apical seat. Dry dentin fillings were packed in the apical isthmus with a #60 K file. In group 1, the root canal was obturated with gutta-percha and Canals root canal sealer by the lateral condensation method. In group 2, following an application of the bonding agent to the plug, the root canal was obturated in the same way. In group 3 (control), a single apical seat was prepared with a #60 K file 1 mm short of the apex and the root canal was obturated similarly. The teeth of three groups were immersed in a 1% methylene blue solution for 1, 2, and 4 wk. Dye penetration depth from the apical foramen was determined. Group 2 showed no leakage after 4 wk. Groups 1 and 3 showed dye penetration into the root canal, and in these two groups dye penetration increased with time.

Tissue reaction to endodontic materials: methods, criteria, assessment, and observations

The purpose of this study was to develop methods and criteria for the testing of the biocompatibility of endodontic materials. One hundred twenty-one teeth from 12 baboons (Papio anubis) were used to test three sealers: AH26, Kerr pulp canal sealer, and Kloroperka N.O. Gutta-percha cones were used as solid core in all cases. Under disinfected conditions, access preparation was performed, and with working length approximately 1.0 mm short of the foramen, the instrumentation of the root canal was started, using sodium hypochlorite (1%) for irrigation. After the root canals were cleaned and shaped, they were obturated with gutta-percha cones and the sealer, and by lateral condensation technique. Histologic periapical reactions were evaluated at 1, 7, 30, 365, 730, and 1095 days. The methods and criteria used were adequate for ranking of the biocompatibility of the tested materials in the short and long periods. At short observation periods (1 to 7 days) AH26 caused severe reactions, and Kerr pulp canal sealer and Kloroperka N.O., moderate and mild reactions, respectively. At 2- and 3-year observation periods the ranking was AH26, mild; Kerr pulp canal sealer, moderate; and Kloropercha N.O., severe.

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.

In vivo findings associated with heat generation during thermomechanical compaction of gutta-percha. 2. Histological response to temperature elevation on the external surface of the root

An in vivo investigation is described and a histological evaluation made of the effect of canal obturation by thermomechanical compaction of gutta-percha and sealer on the cementum on the lateral surface of the root and adjacent periodontal membrane and alveolar bone of the ferret canine after time intervals of 24 hours, 20 days and 40 days. These tissue reactions were compared with those in the roots of control teeth filled by lateral condensation of cold gutta-percha and sealer. Iatrogenic damage was apparent in a minority of the experimental specimens 20 and 40 days after obturation.

Clinical evaluation of low-temperature thermoplasticized injectable gutta-percha: a preliminary report

An injectable thermoplasticized gutta-percha system (Ultrafil) was used to fill 50 teeth which were monitored radiographically over a period of 24 months. An equal number of teeth were filled with the lateral condensation technique and used as controls. Radiographic evidence of success was determined at a 24-month recall. The results were subjected to a 2 x 2 analysis of variance (control versus experimental/before and after treatment. There was a significant amount of repair irrespective of obturation procedure (p greater than 0.0001). Thirteen teeth in the experimental group randomly filled with sealer showed that the sealer did not influence repair.

Biologic evaluation of SPAD. I. A comparison between the tissue reactions to SPAD, Gelfoam, and silver amalgam

The biologic properties of Traitement SPAD, a material suggested for filling root canals and the periapical region in cases of periapical involvement, were tested and compared with those of Gelfoam and silver amalgam. Empty polyethylene tubes were used as a negative control. The reactions of the subcutaneous tissues of rats to the test and to the control materials are reported. The initial tissue reaction to SPAD was very mild. However, this reaction increased with time to become moderate and persisted throughout the period of the study with no signs of absorption of the material. The inflammatory response to Gelfoam was initially greater. However, it decreased with time and the material was removed by the macrophages with subsequent reduction in the size of the surgical gap. The greatest inflammatory reaction was recorded after the use of silver amalgam, with the formation of capsules around the specimens, indicating that the material was extremely irritant before it had set. The longer the silver amalgam remained in situ, the milder the tissue reaction became.