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Kakehashi S, Stanley HR, Fitzgerald RJ. The effects of surgical exposures of dental pulps in germ- free and conventional laboratory rats. Oral Surg Oral Med Oral Pathol 1965
Rats, in vivo study. The purpose of this study was to observe the pathologic changes resulting from untreated experimental pulp exposures in germ-free rats as compared with conventional rats with a normally complex microflora. By the eighth day, vital pulp tissue remained only in the apical half of the roots in the conventional animals. Complete pulpal necrosis with granulomas and abscess formation occurred in all older specimens. Evidence of repair was uniformly lacking. In contract, no devitalized pulps, apical granulomas, or abscesses were found in the germ-free animals. Dentinal bridging began at 14 days and by 21 and 28 days was complete, regardless of the angle or severity of the exposure. Presence or absence of a microbial flora is the major determinant in the healing of exposed rodent pulps.
Zach L, Cohen G. Pulp response to externally applied heat. Oral Surg Oral Med Oral Pathol 1965;19:515–30.
5 monkeys, in vivo study. Rises in temperature as low as 10 degrees F can cause damage to the pulp and anything above 20 degrees will most likely render the pulp nonvital.
Sjogren U, Hagglund B, Sundqvist G, Wing K. Factors affecting the long-term results of endodontic treatment. J Endod 1990;16:498–504.
Radiograph study. The results of treatment were directly dependent on the preoperative status of the pulp and periodical tissues. K files, 0.5% sodium hypochlorite. In vital cases, an apical pulp stump of about 2mm was left. The pulp was completely removed in necrotic cases. Calcium hydroxide was used as an intracanal dressing between appointments. Lateral condensation. Performed by undergrad students. Negative bacterial culture was the prerequisite for filling the canals in the cases studied here. 356 patients 8 to 10 yr after treatment. The overall success rate is 91%. The rate of success for cases with vital or nonvital pulps but having no periapical radiolucency exceeded 96%, whereas only 86% of the cases with pulp necrosis and periapical radiolucency showed apical healing. Retreat with PA lesions, 62% healed.
Full length till apical Constriction: 90%, 69% when it was not.
Not causality study but assumes failure.
Sundqvist G, Figdor D, Persson S, Sjo€gren U. Microbiologic analysis of teeth with failed endodontic treatment and the outcome of conservative re-treatment. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;85:86–93.
In vivo, 5 year follow-up. The microbial flora isolated in canals after failed endodontic therapy were Enterococcus faecalis, gram-positive. Differed markedly from the flora in untreated teeth. The overall success rate of re-treatment was 74%. At the time of root filling, without bac. success rate 80%, with bac. 33%. Two factors that were shown to have a negative influence on the prognosis are the presence of infection at the time of root filling and the size of the periodical lesion.
Schneider SW. A comparison of canal preparations in straight and curved root canals. Oral Surg Oral Med Oral Pathol 1971;32:271–5.
In vitro, roots were classified as straight <=5, moderate 10-20, severe 25-70. Hand files. Perfectly round (1mm level) 80% chance of making round prep in straight canals, 40% moderate, 33%severe; Perfectly round (5mm level) 40% straight, 10% moderate, 0 severe. Once a definite curve existed, can’t make round prep either at 1 or 5mm levels. Straight canals were much more readily prepared round than were curved canals. Round preparations were obtained 51 per cent of the time at the 1 mm. level, as compared to 17 per cent at the 5 mm. level.
Sjo€gren U, Figdor D, Persson S, Sundqvist G. Influence of infection at the time of root filling on the outcome of endodontic treatment of teeth with apical periodontitis. Int Endod J 1997;30:297–306.
Complete periapical healing occurred in 94% of cases that yielded a negative culture. Where the samples were positive prior to root filling, the success rate of treatment was just 68%. Actinomyces were recovered in failure cases. Strindberg’s (1956) criteria were used to judge the success rate of treatment. considered successful when (i) the contours, width and structure of the periodontal margin were normal, or when (ii) the periodontal contours were widened mainly around an excess of filling material.
Molander A, Reit C, Dahlen G, Kvist T. Microbiological status of root-filled teeth with apical periodontitis. Int Endod J 1998;31:1–7.
It is concluded that the microflora of the obturated canal differs from that found normally in the untreated necrotic dental pulp, quantitatively as well as qualitatively. There was a predominance of Gram-positive facultative anaerobes (69%). The most frequently isolated species belonged to the Enterococcus group,
