Clinical significance of dental root canal microflora.

OBJECTIVES: Previous work by this group has shown that a significant association exists between pain and the presence of either Prevotella or Peptostreptococcus spp. in dental root canals. The aim of this study was to examine a more extensive series of canals microbiologically, to determine whether any other particular endodontic symptoms or clinical signs showed specific associations with individual bacterial species. METHODS: Seventy root canals were examined microbiologically and clinical data collected to investigate in detail such associations. RESULTS: Of the canals studied, 37 were associated with pain, 49 with tenderness to percussion, 23 with swelling, six with purulent exudate and 57 presented with wet root canals. Anaerobes were isolated from 70.3% of painful canals and from 29.7% of pain-free canals. Significant associations were found between (a) pain and either Prevotella spp. or peptostreptococci, both with P < 0.01; (b) tenderness to percussion and Prevotella spp. (P < 0.01) or anaerobes (P < 0.05); (c) swelling and Eubacterium spp. (P < 0.01), or with Prevotella spp. or Pstr. micros, both with P < 0.05; (d) purulent exudate and any one of F. necrophorum (P < 0.01), Prev. loescheii, Streptoccoccus constellatus or Bacteroides spp. (each P < 0.05); (e) wet canal and facultative anaerobes (P < 0.01), and any one of the genera of Eubacterium, Peptostreptococcus, Prevotella or Propionibacterium (each P < 0.05). CONCLUSION: It was concluded that several different endodontic clinical signs and symptoms are significantly associated with specific bacterial species.

A role for computers in the management of dental education.

The dental educator confronts increasing demands for technically demanding training against a background of factors working to reduce the clinical experience of students: less dental disease, new educational emphases and greater cost-consciousness. A computer system is described which has run successfully for 7 years in the Department of Conservative Dentistry at Manchester University. This system enables better use to be made of declining teaching resources; it allows the department to make more accurate and timely assessments of student progress; it can also provide information on current workload and clinical commitments. Some possible lines of future development are discussed, including use of the system to collect Korner data-sets and to support a more integrated approach to treatment.

Associations of endodontic symptoms and signs with particular combinations of specific bacteria.

Significant associations have been reported between (a) specific bacterial species isolated from root canals and (b) between individual bacterial species and endodontic symptoms and signs. The prime objective of this study was to determine whether particular combinations of specific bacteria are associated with individual endodontic symptoms and signs. Seventy root canals were investigated microbiologically taking care to maintain the viability of obligate anaerobes, which accounted for 64% of the total species isolated, including Peptostreptococcus micros, Prevotella melaninogenica, Prevotella oralis, Eubacterium aerofaciens, Eubacterium lentum, Fusobacterium nucleatum, Prevotella buccae and Prevotella intermedia. Significant associations were found between individual clinical features and the following pairs of species: (a) pain (37 cases) and Peptostreptococcus spp./Prevotella spp., Peptostreptococcus spp./Prevotella melaninogenica, Pstr. micros/Prev. melaninogenica (all P < 0.01); (b) swelling (23 cases) and Pstr. micros/Prevotella spp. (P < 0.01); (c) 'Wet' canal (57 cases) and Prevotella spp./Eubacterium spp. (P < 0.01), Peptostreptococcus spp./Eubacterium spp. (P < 0.05). Thus data from this investigation suggests that statistically significant associations exist between individual endodontic symptoms and signs and particular combinations of specific bacteria.

Variations in the susceptibilities of components of the endodontic microflora to biomechanical procedures.

The role of the endodontic microflora in pulpal disease and in endodontic treatment failures is well established. Thus the need for effective microbial control is one of the important justifications for biomechanical procedures. However the efficacy of this stage of treatment is dependent upon the vulnerability of the involved species, which may not be uniform. The aim of this study was to investigate variations in the susceptibilities of members of the root canal microflora to routine biomechanical procedures. Forty-two root canals were investigated microbiologically. Samples were collected before and after instrumentation and the bacterial findings were compared. In 15 cases of 'primary' root canal therapy, despite changes in the population size, no significant change in the species composition of the microflora was observed. However in 27 cases 'secondary' treatment, a decrease in the number of isolations of Peptostreptococcus spp. was found (P = 0.008). When all 42 cases were considered together, significant decreases were found between first and second samples for anaerobes (P = 0.0117) and for Grampositive species (P = 0.008), especially Peptostreptococcus spp. (P = 0.02). It was therefore concluded that certain species are more resistant to the biomechanical procedures than others.

Associations of specific bacteria with some endodontic signs and symptoms.

Although a wide range of bacterial species has been isolated from infected dental root canals it remains necessary to determine whether any particular group of such bacteria is associated with specific endodontic symptoms and clinical signs. In this study 30 root canals were examined microbiologically; of these, 14 were associated with pain, 20 with tenderness to percussion, 23 presented with wet root canals, seven with swelling, five with purulent exudate and four with a sinus. Clinical and microbiological correlation was observed particularly with regard to pain where anaerobes were isolated from 93% of painful canals and only from 53% of painfree canals. The former yielded means of 2.5 anaerobic species and 1.6 facultative species per canal, compared with 1.5 and 2.4 in painfree canals. Prevotella spp. were isolated from 64.2% of painful canals and 12.5% of painless canals (P < 0.01) similarly, peptostreptococci were isolated from 71.4% of painful and 31.3% of painless canals (P < 0.05). It was concluded that a significant association exists between pain and the presence of Prevotella and Peptostreptococcus spp. in dental root canals.

Positive and negative associations between bacterial species in dental root canals.

Significant associations have been previously reported between certain pairs of bacterial species isolated from human dental root canals. The aim of this study was to examine microbiologically a more extensive series of cases, with particular reference to obligate anaerobes which accounted for 64% of total isolations. A total of 65 different species was isolated and individual root canals yielded a maximum of eleven bacterial species. Highly significant positive associations (p < 0.001) were found between Peptostreptococcus spp. and Prevotella spp., between Peptostreptococcus spp. and P. melaninogenica, between P. micros and Prevotella spp., P. micros and P. melaninogenica and between Prevotella spp. and Eubacterium spp., all with an ODDS ratio of > 9.0. In contrast, negative and highly significant associations (p < 0.01) were found only between the four species pairs: B. vulgatus/F. necrophorum, P. magnus/Bifidobacterium spp., B. gracilis/F. nucleatum and between B. gracilis/Fusobacterium spp.; all with an ODDS ratio of < 0.5. Some previously published associations were confirmed and some new associations were found, while some negative associations became apparent.

Effect of thermal placement techniques on some physical properties of gutta-percha.

Some clinical techniques for the placement of gutta-percha root fillings involve the application of heat. This study was undertaken to assess the effects of intracanal heating techniques on the following properties of gutta-percha: coefficient of thermal expansion, softening temperature, phase transition temperature and organic content. Samples from each of four products were prepared by three different methods. The materials were studied by thermomechanical analysis, simultaneous thermogravimetry and differential thermal analysis, and by measurement of weight loss on ashing. It was shown that the techniques of gutta-percha placement involving heating in the root canal caused reversible physical changes in the materials without any apparent change in chemical composition. The average coefficient of thermal expansion was 137 x 10(-6)/degrees C, the softening temperature was 55.5 degrees C, there were two characteristic phase changes, and the organic content was 25%.

The endodontic microflora revisited.

The microbial flora of 35 dental root canals were examined, taking care to maintain the viability of obligate anaerobes which accounted for 45% of total isolations, while streptococcal species accounted for 24% of the total species isolated. Individual root canals yielded a maximum of eight bacterial species. A total of 40 different species was isolated of which the most prevalent were the facultative anaerobe Streptococcus sanguis and the obligate anaerobe, Peptostreptococcus micros (both in 23% of root canals), followed by Eubacterium aerofaciens and the 'Streptococcus milleri group' (both 17%) then Prevotella melaninogenica (formerly Bacteroides melaninogenicus), Enterococcus faecalis and Prevotella oralis (formerly Bacteroides oralis), which were each isolated from 14% of root canals. Highly significant associations were discovered between four pairs of species, viz P. melaninogenica with P. micros, P. melaninogenica with P. oralis, Prevotella corporis with Streptococcus morbillorum and Actinomyces odontolyticus with E. faecalis.