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Azerbaycan Saytlari

 »  Home  »  Endodontic Articles 8  »  Periapical healing of endodontically treated teeth in one and two visits obturated in the presence or absence of detectable microorganisms
Periapical healing of endodontically treated teeth in one and two visits obturated in the presence or absence of detectable microorganisms
Discussion - References.



Discussion.
The presence of bacteria in the root canal results in the development of apical periodontitis. In the present study, no correlation was seen between the healing of endodontic lesions and the presence orabsence of a positive canal culture after proper cleaning and shaping, and no correlation was seen between healing of endodontic lesions and treatment in one or two visits with intracanal dressing of calcium hydroxide. It is widely accepted that inclusion of calcium hydroxide renders the canal sterile and ready for obturation (Tronstad 1991, Friedman 1998).However, studies have shown that calciumhydroxide is not always effective and that its action is unreliable (Reit & Dahle. n 1988, Orstavik et al. 1991,Yared & Bou Dagher 1994, Peters et al. 2002). Comparisons of the success rate between the two-visit endodonticswith calcium hydroxide as an intracanal interappointment dressing and the one-visit endodontic treatment of teeth with necrotic pulps in this and other prospective studies do not show significant differences (Friedman et al. 1995,Trope et al.1999,Weiger et al. 2000). Other studies evaluating the healing of teeth with necrotic pulps after either one or two-visits report success rates between 75 and 90% for both treatment options (Bystrom et al. 1987, Murphy et al. 1991, Jurcak et al. 1993, Caliskan & Sen1996).
It seems more reliable to evaluate infection at the time of root filling. Studies by Zeldow & Ingle (1963) and Engstrom et al. (1964) showed inferior results for teeth with a positive culture at the time of root filling. On the other hand, Seltzer et al. (1963) and Matsumoto et al. (1987) could not ¢find any significant differences in healing results. All these studies are limited in bacteriological technique, because no strict anaerobic techniques were used and contamination cannot be ruled out in some reports owing to a lack of information about the treatment procedures. Sjogren et al. (1997) using strict anaerobic techniques, related infection at the time of obturation and success. They showed inferior healing results for root canals with a positive culture at the time of obturation. Our results do not indicate such differences. It is stressed that, in both studies, the number of CFU left in the canal at the time of obturation was very low. In our study, six out of the eight positive root canals contained <102 CFU mL_1, one canal contained 2 x103 and one canal harboured 8 _104 CFU mL_1. The latter case scored a treatment outcome B. In the study by Sjogren et al. (1997), 22 (40%) root canals contained bacteria at the time of obturation. In eight cases, bacteria could only be detected after the enrichment growth in fluid media, nine samples contained 102_103 CFU, three samples contained >104 CFU, and in two samples, no data were available. Of these 22 positive samples 7 failed. The authors did not relate the failed cases to the number of CFU found. If the failures are related to higher number of CFU (>103) in the canal, it could provide an explanation for the reason why cases with a positive culture appeared successful in both studies, 15/22 (Sjogren et al. 1997) and 7/8 in our study.
Comments have been made previously about the uncertainty of the bacteriological sampling procedure immediately after the removal of a calcium hydroxide dressing (Reit&Dahle. n1988). It has been suggested (Reit et al. 1999) that the microbiological samples should be taken after filling the canal with a sampling fluid (after removal of the calcium hydroxide) for 7 days. However, when the authors applied this procedure, culture reversals were seen in both directions. Thus, Reit et al. (1999) reported seven canals that turned from a negative to a positive culture after 1week, but also the seven canals that changed from a positive culture to a negative culture over the same period. It cannot be ruled out completely that some negative canals in the present study after calcium hydroxide removal (S3), may have become positive if evaluated 1 week later. The studies of Reit & Dahlen (1988) and Reit et al. (1999) demonstrated the limitations of microbiological root-canal sampling, and this should be taken into account when evaluating all root-canal procedures. Because it was found that removal of calcium hydroxide from the root canal with the aid of the operating microscope was enhanced, and because it has been shown previously that a second culture taken 7 days later did not result in more reliable data (Reit & Dahlen 1988, Molander et al. 1990, Reit et al. 1999), cultures were taken immediately after removal of the calcium hydroxide. This process was also less demanding for the patients, as it reduced the number of appointments.
Differences in healing can also be created because the size of the preoperative radiolucency, between canals with detectable and non-detectable microorganisms, is different in both groups. In the present study, these differences were not found.
Sjogren et al. (1997) found 60% negative root-canal samples after similar preparation of the root canals. The difference with our findings (79% negative) could be a result of the concentrations of sodium hypochlorite (0.5% vs. 2%) and different delivery systems used for irrigation. In addition, the sampling techniques and transport media used may have also created differences.
A question that remains to be answered is the reason for failure in cases of root canals from which no bacteria could be cultured. In Sjogren’s study (1997), two of those cases failed. In one of these, bacteria were found at the time of surgery in a lateral canal. This points to the in ability of current cleaning and shaping techniques to reach microorganisms present in lateral canals and dentinal tubules (Peters et al. 2001). These bacteria cannot be identified using current endodontic sampling procedures and seem inaccessible to an intracanal disinfectant like calcium hydroxide (Siqueira & Lopes1999).
The number of patients available in our study as well as most other prospective studies is limited. Given the high-success rates of both treatment options, the sample size per group required to detect a difference is very high. Weiger et al. (2000) showed that the probability for complete periapical repair over 5 years was 93%for two-visit root-canal treatment and 92% for one-visit root-canal treatment. When we calculate power statistics (power set at 80%) with these proportions, the numbers per group would have to exceed 10 000. Trope et al. (1999) calculated the need for a group size of 354 (power set at 80%) to show significance for the differences he found (74 vs. 64%) in comparing one- versus two-visit rootcanal treatment. However, the short observation period of 52 weeks in that study may lead to an underestimation of periapical healing over longer observation periods, as was shown by Weiger et al. (1998). In the present study, the probability for healing increased gradually to 91 and 94% over a period of 4 years, indicating the need for a group size of 1275 teeth to show significance at P ј 0.05. However, the cases that were selected in these studies, all present a relatively simple anatomy resulting in high success rates. The numbers that are needed in a prospective study with more complex cases maybe much lower because of lower success rates.

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