| Refractory periapical periodontitis generally refers to the chronic that keep persistent infections after the conventional root canal therapy. It includes symptomatic periapical periodontitis and the asymptomatic radiolucent post-treatment. Compared with the non-treated teeth ,the tooth with refractory periapical periodontitis are more complicated in the etiology and treatment . Some studys showed that no bacteria or individual advantage bacteria can be detected in the infected root canals,the bacteria were mainly Gram-positive facultative anaerobic bacteria, which were different from untreated infected root canals with chronic periodontitis,.Are the extraradicular infection of refractory periapical periodontics the same with the other conditions? And how does the micro-flora exist? Which is the most effective way to treat the refractory periapical periodontitis? The subject will discuss the pathogenesis and treatment prognosis of the refractory periapical periodontitis through studying of periapical microbiology, morphology and treatm- ent. We hope this study can provide a reference for clinical diagnosis and treatment. about refractory apical periodontitis.1. The detection of pathogenic microorganisms with refractory periapical periodontitis Eighteen patients with refractory peiapical periodontitis who accepted the root-end surgery were selected, and the periapical sample were collected in two ways,and then through traditional bacterial culture, isolating and identifying to study of them.The results showed that 16 of 18 cases yielded microbial growth(88.8%),17 different microbial species and 57 bacteria strains were detected, with an average 3.5 per case detected,.the rate of Gram-positive bacteria detection was 77.8%,the ratio of constitution was 50.9%;the rate of gram-negative bacteria detection was 83.3%, the ratio of constitution was 49.1%,there is no significant differences in the detection rate and the ratio of constitution.between Gram-positive bacteria and gram-negative bacteria have no significant differences in the detection rate and the ratio of constitution (P> 0.05). The rate of facultative anaerobic bacteria detection was 66.6%, the ratio of constitution was 38.5%,.the rate of obligate anaerobes detection was 72.2%, the ratio of constitution was 61.5%.Through statistical analysis, there is no significant difference in the detection rate between the obligate anaerobic bacteria and facultative anaerobic bacteria (P> 0.05), but there is significant differences in the the ratio of constitution between the obligate anaerobic bacteria and facultative anaerobic bacteria (P <0.05), the ratio of constitution obligate anaerobic bacteria was significantly higher than that of facultative anaerobic bacteria, Streptococcus sanguis, Porphyromonas endodontics, Bacteroides vulgatus were more frequently detected.In 8 cases with fistula,,facultative anaerobic bacteria were the prominent bacteria.,including Streptococcus mutans,Enterococcus faecalis, Actinomyces israell,and Porphyr- omonas endodontics. The result is significantly different from the previous study of refractory periapical periodontitis with root canal infection,but in agreement with the untredted root canals and periapical inflammatory tissue of chronic periapical periodontitis. 2. The morphological study of refractory periapical periodontitisTwenty-five cases were collected to observe the periapical biofilm morphology and ultrastructure by scanning electron microscopy, the samples weie divided into three groups according to their pathological state,group A (10 cases): refractory periapical periodontitis; group B (11cases): chronic periapical periodontitis with post-core crown;group C (5cases):control group (normal orthodontic extracted tooth).Periapical specimens were collected through the root-end surgery in group A and, B; 5 cases of normal periapical specimens were collected through orthodon- tic extracted in group C. The Results showed that there was no periapical biofilm on the tooth used as controls in guoup C, only a lot of collagen fibers of periodontal ligament and normal cementum.can be seen. The periapical biofilm was found in every cases in groupAandB,In groupB,we can see a lot of bacterial,and the morphology, type,the amount of the baterial were different in different cases, most of the baterial were cocci and bacilli, the morphology of bacteria was clear, a large number of bacteria distributed around the periodontal collagen fibers.The peri- apical biofilm of group A was more diverse and dense comparing with group B.There are a large number of periodontal fibers,and stack-like structure was found.Therefore,there can be observed a large number of bacteria ,or integrate into gobbet each other,or with the calcification of matrix like extracellular polysacchar ide-protein together into integration, little free bacteria can be observed occasionally .Most of the bateria coverd with or inlayed in the"network"consisted of collagen fibers, shows a semi-dense or fully dense state, and formed a mature biofilm. Bacterial virulence and pathogenicity can be enhanced gradually due to Mature biofilm's resistance to antibiotics, resistance to immune function and resistance to the liquid erosion,and become the causes for poor efficacy of periapical periodontitis. Because the existence of apical biofilm, the conventional root canal therapy can not achieve a satisfactory effect, the periapical surgery was probably the effective treatment.3. The observation of clinical efficacy of 122 periapical surgery cases122 periapical surgery cases operated from 2001 to 2008 were selected.Most of them were teeth with refractory apical periodontitis, chronic periapical periodontiti -s with post-core crown ,foreign bodies in root canals, extruded gutta-percha, and apical morphological variation.The cases found the existence of serious crack of root and serious periodontics are not included in this study. In accordance with the various stages of using different surgical instruments, methods and filling mate- Rious we divided them into three groups,: group A (n = 38): traditional equipment + amalgam; group B (n=38 ): Micro-ultrasound equipment + amalgam; group C (n=46): Micro-ultrasound equipment+MTA.Time of follow-up review was one year, The statistic result showed that the success rate of group A was significantly higher than that of group B (P<0.05), the success rate of group B was no statistically significant. different than that of group C(P>0.05) ,indicating the effect of microscopic and ultrasonic instrument is superior to that of the traditional instruments,and as for root-end filling materials in this clini- al prospective study , MTA and amalgam had the same clinical effectiveness in the rate of success of one year. |
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