Patterns Of Microbial Colonization In Untreated And Fail-treated Infected Root Canals

Objective: To study the morphology, distribution and relative position of microorganisms in situ in untreated and fail-treated root canal using scanning electron microscopy and light microscopy.Methods: 18 recently extracted roots were studied. They were divided into three groups. The roots on group 1 were untreated. Group 2 were failed in root canal therapy. Group 3 were failed in resinfying therapy. Each group had six roots. All cases demonstrated evidence of periapical radiolucencies. The root was split into two halves along the gena-lingua axis. One half was studied under scanning electron microscopy. The other half was observed under light microscopy for histology and microorganisms.Results: (1) Microorganisms were found in all untreated roots. However, the patterns of microbial colonization were different in individual roots and varied in different areas of the same root. The microbial colonization in root canals was made up of cocci and/or bacilli that often blended together in a community. The depth of the invasion of bacteria in dental tube was about 100 um. However, in some roots we did find that it could be up to 300um. Infiltration of chronic inflammation cell was discovered in periapical tissues with no microorganism observed. (2) In the group that failed in the root canal therapy, bacteria, mostly cocci were found in 3 cases and fungus was found in one case solely. The invasion of bateria was within 100um. Colonies can be found dispersedly in dental tubes with unitary morphology. Chronic inflammation cell infiltration was discovered in the perapical tissue of 5 specimens. Scar tissue was found in one specimens. No microorganism was found in the perapical tissue. (3) In the group that failed in resinfying therapy, cocci were found mostly in 2 cases and fugi were found solely in the other 2 cases. The invasion of bateria was within 100um. Colonies can be found dispersedly in dental tubes with unitary morphology. Chronic inflammation cell infiltration was discovered in the perapical tissue of 3 specimens, and scartissue was found in 2 specimens. No microorganism was found in the perapicaltissue.Conclusions: (1) Severe infection occurs in untreated root canals. The pattern ofmicrobial colonization is characterized as climax community. (2) The pattern ofmicrobial colonization in failed-treated root canals of root canal therapy andresinfying therapy dramatically differ from that of the untreated, which can becharacterized as unitary morphology, smaller dispersed islet-like colonies. (3) Thecontinuant existence of microorganisms is due to the failure of root canal therapyand resinfying therapy. (4) In the asymptomatic infected root canals of failuretreatments, the coccus is the mostly common microorganism. (5) The eukaryoticmicroorganism is related to the chronicle continuant infection and its reoccurrence.(6) It is possible that little microorganisms exist in the perapical tissue ofasymptomatic infected root canals.