Identity of 1:2:1 and 2:4:2 subgingival spirochetes by DNA hybridization

A group of 1:2:1 and 2:4:2 subgingival spirochetes, well characterized by transmission electron microscopy, biochemical tests, cellular fatty acid and carbohydrate analyses, and ribotyping, was recently suggested to represent new treponemal species. The present study used DNA hybridization to examine this possibility. When DNA of a representative strain (no. 16) of the 8 1:2:1 spirochetes examined was labeled by iodination, it showed, after SI nuclease treatment, from 58 to 104% (average 76%) homology with DNA from the 1:2:1 spirochetes. 94% homology with DNA from the type strain of Treponema socranskii and of T. socranskii subsp. socranskii , i.e., ATCC 35536T, and 62% homology with DNA from T. socranskii subsp. buccale , strain ATCC 35534^T. Similarly treated DNA from a representative strain (no. 3) of 8 2:4:2 spirochetes exhibited from 90 to 105% (average 97%) homology with DNA from the 2:4:2 spirochetes, and 85% and 87% homology, respectively, with DNA from Treponema denticola strains ATCC 33520 and FDC T1. There was a negligible degree of homology between the 1:2:1 and 2:4:2 spirochetes. Thus, all the 2:4:2 spirochetes belonged to T. denticola . 1:2:1 strains with DNA homology levels >70% (5 strains) belonged to T. socranskii or T. socranskii subsp. socranskii , while those with homology levels from 58 to 63% (3 strains) most likely belonged to other subspecies of T. socranskii .     

Visions and viewpoints: promises and reality

The immediate past chair of the ADA Council on Ethics, Bylaws and Judicial Affairs, who is also an attorney, explains why, after a thirty-year absence, he went back to treating Medicaid patients. It is easy to identify the social, political, bureaucratic, and financial shortcomings of our imperfect system. But how else, besides participating, can one educate patients so the dentist and the patient can both accept responsibility? How else can the profession make a difference except one patient at a time?     

Associateships: trends and opportunities

Interest in associateship dental practice arrangements has increased rapidly in recent years. Surveys by the American Association of Dental School indicate most new graduates who go directly into private practice are now doing so as associates. Although the percentage of Texas graduates planning to immediately enter solo private practice is higher than the national average, the trend toward associateship preference for the Texas graduate follows the same curve as the national average. Associateships can be rewarding, stimulating experiences and dentists who already own established practices should be aware that there are many well-educated young graduates seeking associateships. The Texas Dental Association has a well organized, systematized placement service (TDA Placement Service). Students review the Placement Service computer printout regularly, and practitioners seeking an associate should consider utilizing this same free listing service.