Elizeu A. Pascon

Clinical, radiographic, and histologic study of endodontic treatment failures

One hundred fifty cases of endodontic treatment failures were studied clinically, radiographically, and histologically. Fifty-seven percent of the teeth were asymptomatic. Pain alone and/or associated with swelling was present in 21% of the teeth. There was no correlation between the size of periradicular rarefaction and the occurrence or severity of clinical signs and/or symptoms. Stainable bacteria were demonstrated in 69% of the teeth and were present mostly in the canal. The severity of periradicular inflammation was related to presence of stainable bacteria in the canal. Swelling and pain or a draining sinus tract was often associated with stainable bacteria inside the canal. The development of a radicular cyst associated with an endodontically treated tooth that has failed is not necessarily the cause of endodontic treatment failure.

Efficacy of chlorhexidine- and calcium hydroxide-containing medicaments against Enterococcus faecalis in vitro

OBJECTIVE We sought to assess the efficacy of chlorhexidine (CHX) and calcium hydroxide, Ca(OH)(2), against Enterococcus faecalis in vitro. STUDY DESIGN The effect of CHX (0.2% and 2% in gel or solution) and Ca(OH)(2) (alone or with 0.2% CHX gel) was evaluated by using the agar diffusion test and an in vitro human root inoculation method, to measure zone of inhibition or bacterial growth with optical density analysis, respectively. For optical density analysis, samples from infected root canals were collected after 7 days of medication and were cultured for 24 hours in brain-heart infusion to detect viable bacteria. RESULTS In the agar diffusion test, CHX was effective against E faecalis in a concentration-dependent fashion, but Ca(OH)(2) alone had no effect. In the root canal inoculation test, CHX was significantly more effective against E faecalis than Ca(OH)(2) was (P < .05), but there were no significant differences between the modes of medication or concentrations of CHX. CONCLUSIONS CHX is effective against E faecalis in vitro. Further in vivo studies are needed to confirm the value of CHX in clinical treatment.

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.

In vitro cytotoxicity of root canal filling materials: 1. Gutta-percha

Gutta-percha (GP) has been the most widely used root canal filling material because of its well-known low toxicity. The inertness of GP, however, was challenged recently. The purpose of this study was to evaluate the toxicity of marketed endodontic GP using the radiochromium release test. Fourteen commercially available and three experimental GP brands were tested. Raw GP, zinc oxide, and barium sulfate, which were considered major components of GP points, and zinc ions were also evaluated. The material was spread to cover the bottom of testing wells after being dissolved in chloroform or warmed. A labeled suspension of L929 cells was added to the wells. After incubation at 37 degrees C for 4 and 24 h, extracellular radiochromium in the culture medium was measured and calculated in percentage of the total intracellular label. Spontaneous release of radiochromium was used as control and the results were considered to be within normal limits either at 4 or 24 h. All chloroform-dissolved GP showed low toxicity at 4 h, whereas warmed GP showed statistically significant differences at 4 h. Both dissolved and warmed GP were toxic at 24 h. The raw materials and barium sulfate were not toxic, whereas zinc oxide and zinc ions showed marked toxicity. All GP points tested were toxic at longer observation periods, and the toxicity was attributed to leakage of zinc ions into the fluids.

The Importance of Material Preparation for the Expression of Cytotoxicity during In Vitro Evaluation of Biomaterials

Biocompatibility of dental materials is routinely evaluated utilizing in vitro methodologies. A wide range of experimental models have been used making comparative literature research very difficult. A study was undertaken which evaluated, under identical culture conditions, the cytotoxicity of seven common endodontic sealers after they had been prepared for the experiment in a variety of ways. The results showed that the preparation of the material for the experiment may significantly alter the apparent cytotoxic effect of a material.

Influence of shaft design on the shaping ability of 3 nickel-titanium rotary systems by means of spiral computerized tomography

OBJECTIVE To evaluate the influence of shaft design on the shaping ability of 3 rotary nickel-titanium (NiTi) systems. STUDY DESIGN Sixty curved mesial canals of mandibular molars were used. Specimens were scanned by spiral tomography before and after canal preparation using ProTaper, ProFile, and ProSystem GT rotary instruments. One-millimeter-thick slices were scanned from the apical end point to the pulp chamber. The cross-sectional images from the slices taken earlier and after canal preparation at the apical, coronal, and midroot levels were compared. RESULTS The mean working time was 137.22 +/- 5.15 s. Mean transportation, mean centering ratio, and percentage of area increase were 0.022 +/- 0.131 mm, 0.21 +/- 0.11, and 76.90 +/- 42.27%, respectively, with no statistical differences (P> .05). CONCLUSIONS All instruments were able to shape curved mesial canals in mandibular molars to size 30 without significant errors. The differences in shaft designs seemed not to affect their shaping capabilities.

Evaluation of tissue reaction to endodontic materials

Teflon tubes containing freshly mixed AH26 and Hydron were implanted in subcutaneous tissue of 48 rats using an injection technique. Equal size empty Teflon tubes and solid rods were implanted as controls. Tissue reaction to test and control materials were histologically studied and morphometrically analyzed under the light microscope. Necrosis and inflammation occurred around test materials at all observation periods. This method was convenient for qualitative testing of the materials but did not allow accurate ranking of biocompatibility of the materials.

Biological evaluation of Hydron.

The root canal filling material, Hydron, was evaluated for its biocompatibility in a subcutaneous implant test in rats, in an intraosseous implant test in guinea pigs, and in root canal fillings in subhuman primates. A discrepancy between the manufacturers claims and findings in this study occurred regarding physical/clinical properties as well as the biocompatibility of Hydron.

An in vivo comparison of working length determination of two frequency-based electronic apex locators

AIM To compare in vivo the accuracy of two electronic apex locators (EALs) by means of digital radiographic imaging system. METHODOLOGY Electronic working lengths of 831 canals were determined with the DentaPort ZX and Raypex 5 apex locators and confirmed radiographically. The radiographic images acquired with the aid of a digital radiographic imaging system (VisualiX eHD; Gendex Dental Systems, Des Plaines, IL, USA) were blindly analysed by two independent evaluators. The distance between the file tip and the radiographic apex was measured using dedicated software (VixWin Pro, Gendex Dental Systems, Des Plaines, IL, USA) and the mean distance achieved between different tooth type and EALs were compared statistically. Statistical analyses were performed using the t-test for independent samples and one-way anova with the null hypothesis set as 5%. Positive or negative values were recorded when the file tip was detected beyond or short of the radiographic apex, respectively. RESULTS The mean distance between file tip and radiographic apex were -1.08 +/- 0.73 and -1.0 +/- 0.67 mm considering DentaPort ZX and Raypex 5 groups, respectively, with no significant differences (P > 0.05). No statistically significant differences were found amongst the same tooth type when comparing both groups (P > 0.05) or amongst different teeth type in the same group (P > 0.05). CONCLUSIONS Within the limitations of this in vivo study, the DentaPort ZX and Raypex 5 were similar in terms of accuracy.

Biological evaluation of the apical dentin chip plug

Autologous dentin chips were packed in the apical part of root canals of baboon teeth. Root canals were then filled with Hydron using a pressure syringe technique. Histological periapical response was evaluated up to 114 wk. Complete apical closure did not occur and material particles were observed in periapical tissues. All root canal sealers studied until now are known to be toxic (1, 2). Extrusion of root filling materials into the periapical tissue causes an inflammation, including foreign body reaction, and contributes to poor prognosis and failures in root canal treatment (3). Apical dentin chip plugs are suggested to prevent overfilling during root canal obturation (4, 5) and, at least in noninfected root canals, appear to be compatible to periapical tissues (6–11). A technique for pulpectomy and the simultaneous creation of an autologous dentin plug is described by Baume et al. (12). The purpose of the present study was to examine periapical tissue reaction to a dentin chip plug and to investigate if such a plug can act as a biocompatible barrier between periapical tissue and root canal filling material.