Simplifying management of the posterior maxilla using short, porous-surfaced dental implants and simultaneous indirect sinus elevation.

This article describes the use of short, porous-surfaced root-form dental implants and an indirect, simultaneous, osteotome-mediated sinus elevation procedure to restore the posterior maxilla when as little as 3 mm of bone remain below the sinus floor. Results with 16 patients who are part of an ongoing prospective clinical trial using the Endopore implant show 100% success (using established criteria) with a mean implant length of 6.9 mm and a mean functional time of 11.1 months. This treatment approach greatly simplifies the management of the posterior maxilla with minimal bone height below the sinus floor.

Epithelial cell invasion by Actinobacillus actinomycetemcomitans strains from restriction fragment-length polymorphism groups associated with juvenile periodontitis or carrier status.

The epithelial cell invasiveness of Actinobacillus actinomycetemcomitans strains of different restriction fragment-length polymorphism (RFLP) groups associated with disease conversion and asymptomatic carrier status in localized juvenile periodontitis was examined. Twenty clinical isolates were studied for their ability to invade KB monolayers, using the quantitative gentamicin killing assay. Five isolates were found to be invasive, five were not invasive; and the other 10 did not invade better than an invasion negative control Haemophilus aphrophilus strain ATCC 19415. Using probe-specific DNA fingerprinting. 11 strains were assigned to RFLP group II (disease-associated); 4 to RFLP type XIII (carrier status associated); and the other to groups III, IV, V and VII. Eight isolates, all RFLP group II, were leukotoxin producers as determined by PCR amplification of the lkt promoter region. No correlation was found between invasiveness and RFLP group. Leukotoxin production was more associated with noninvasive than invasive strains.

Characterization of a 4.2-kb plasmid isolated from periodontopathic spirochetes.

Oral anaerobic treponemes are assoicated with active periodontal disease and may comprise up to 57% of the microbiota in periodontal pockets. Four treponeme strains (designated U2a, U2b, U9b, and U9c) isolated from clincial cases were found to harbor a new 4.2-kb plasmid when plasmid DNA was extracted and purified employing the Qiagen Plasmid Kit. This plasmid differs from the smaller plasmids (2.0-, 2.6-, and 2.7-Kb) reported previously by others in Treponema denticola. The newly discovered 4.2-kb plasmid was found to be the same in all four treponeme strains by restriction endonuclease analysis. It is a circular plasmid since restriction with PstI, Pvu II, Sma I, Xma I, Ava 1 or Bam HI produced a single band of the same size. Bacterial strain U2b was shown to be Treponema socranskii and U9c to be T. denticola. The plasmid is designated "pTS1". The presence of the same plasmid in different species of the treponemes isolated from the same patient suggests the possibility of a naturally occurring genetic transfer system within the oral spirochetes or their ability to take up and maintain mobilizable plasmids.

Contaminated toothbrushes and their disinfection.

Twenty toothbrushes used by healthy subjects were screened for the presence of microorganisms. Microbes were dislodged from the brushes by vortexing, and an average of 4 x 10(3) CFU/mL were recovered from the suspending fluid. Bristles removed from the vortexed brushes still yielded confluent bacterial growth on brain-heart infusion agar medium. Virkon (one per cent), Listerine, Cepacol, Scope, and Plax were tested for their bactericidal effects on microorganisms sedimented from the suspending fluid, on toothbrush bristles and proxabrushes, and on various test species including Candida albicans, Mycobacterium smegmatis, M. bovis, and Streptococcus mitis. Virkon and Listerine killed all the test species and virtually all the microorganisms on the toothbrush bristles and proxabrushes. Six volunteers tested the efficacy of a Listerine soaking regime to prevent the bacterial contamination of toothbrushes. Soaking the toothbrush head (bristles) in Listerine for 20 minutes after brushing was sufficient to eliminate bacterial contamination.

Distribution and characterization of plasmids in oral anaerobic spirochetes.

Fifteen oral spirochete strains belonging to the species Treponema denticola, Treponema vencentii and Treponema socranskii as well as 9 fresh clinical isolates were screened for the presence of extrachromosomal plasmid DNA by a modified alkaline lysis procedure. A 2.6-kb plasmid was detected in both T. denticola ATCC 33520 and T. denticola e'. The 2.6-kb plasmid from T. denticola e' was shown to be similar to pTD1, previously reported by Ivic et al. in T. denticola ATCC 33520 on the basis of molecular weight, restriction endonuclease profile and DNA:DNA hybridization. T. denticola ATCC 33520 and T. denticola e' share 65% DNA homology and belong to different serological groups. This dissimilarity has been reconfirmed by specific immunofluorescence using polyclonal and monoclonal antibodies. A plasmid-free T. denticola ATCC 33520 was identified. Comparative studies have shown no antigenic, morphological, or genetic differences between the plasmid-bearing and the plasmid-free strain. In addition, screening of fresh clinical isolates of spirochetes revealed the presence of a 4.2-kb plasmid in 4 of these strains.

Incorporation of tRNA into normal and mutant HIV-1.

During retroviral assembly, tRNAs are incorporated into the virion, one of which serves as a primer for the reverse transcription reaction. Using two dimensional polyacrylamide gel electrophoresis, we have studied the patterns of tRNAs incorporated into HIV-1 (3B) produced either in the lymphoid cell line H-9 or in the monocytic cell line U937. We have also examined viral tRNA patterns incorporated in a non-infectious, mutant virion which lacks pol gene products and processed gag protein. Our results lead to the following conclusions: 1) tRNA incorporated into HIV-1 is a select subpopulation of the host-cell's tRNA. 2) The type of tRNA incorporated into the virion is dependent upon cell type. 3) There can be multiple species of tRNA of similar mobilities tightly associated to the viral genome. 4) The packaging of putative primer tRNA into virions requires either the synthesis of pol gene products, the processing of gag proteins, or both, while the incorporation of non-primer tRNAs does not.

Incidence of antibiotic-resistant Escherichia coli associated with frozen chicken carcasses and characterization of conjugative R plasmids derived from such strains.

Escherichia coli were isolated at concentrations of about 10(2)/ml from the fluid obtained after thawing each of five frozen chicken carcasses. Between 13 and 89% of the E. coli were resistant to mercury(II) or to at least one of eight antibiotics tested. Multiple resistance was more common than single resistance, and resistances to tetracycline, streptomycin, sulfathiazole, or chloramphenicol were more frequently encountered than was resistance to ampicillin or mercury(II). Resistance to kanamycin, gentamicin, or trimethoprim occurred rarely. Upwards of 30% of the E. coli apparently carried conjugative plasmids and could transfer at least one of their resistance determinants to E. coli K-12. Twenty-five conjugative R plasmids obtained in this way were characterized within strain K-12 by a variety of phenotypic criteria. Twenty could be assigned to the incompatibility groups Inc X, Inc N, Inc FI, or Inc I alpha.