Evaluation of a natural resin-based new material (Shellac F) as a potential desensitizing agent.

OBJECTIVES: To evaluate the cytotoxicity of Shellac F, a new fluoride varnish, and its effects on human dentin hydraulic conductance. METHODS: Shellac F was compared to another fluoride varnish (Duraphat) and a fluoride containing desensitizing agent (Isodan). The cytotoxicity test was performed on human gingival fibroblasts and through dentin slice on human pulp fibroblasts. The hydraulic conductance (Lp) was recorded by fluid filtration with a Flodec device under a constant pressure (15 cm H2O). The treated surface of the dentin disks and their sections were also investigated with SEM. RESULTS: The cytotoxicity test on gingival fibroblasts revealed that Duraphat was the least cytotoxic material, followed by Shellac F then Isodan. With dentin slice interposition, a lower level of cytotoxicity was obtained. All of them showed a lower cytotoxicity decreasing on further dilutions (p<0.001). The measurement of hydraulic conductance showed that all materials resulted in a significant decrease in dentin permeability after 24h comprising between 60 and 76%, but there was no statistically significant difference among the materials. This decrease was still over 50% of the initial values after 7 days for all three materials. SEM investigation showed dentin tubules covered with a thick layer of Shellac F or Duraphat whilst no material was observed on dentin surfaces treated with Isodan. SIGNIFICANCE: Shellac F showed an adequate cellular compatibility and a significant effect on human dentin hydraulic conductance. This indicates that the new material is safe and seems to be effective as a potential desensitizing agent.

A new method to extract dental pulp DNA: application to universal detection of bacteria.

BACKGROUND: Dental pulp is used for PCR-based detection of DNA derived from host and bacteremic microorganims. Current protocols require odontology expertise for proper recovery of the dental pulp. Dental pulp specimen exposed to laboratory environment yields contaminants detected using universal 16S rDNA-based detection of bacteria. METHODOLOGY/PRINCIPAL FINDINGS: We developed a new protocol by encasing decontaminated tooth into sterile resin, extracting DNA into the dental pulp chamber itself and decontaminating PCR reagents by filtration and double restriction enzyme digestion. Application to 16S rDNA-based detection of bacteria in 144 teeth collected in 86 healthy people yielded a unique sequence in only 14 teeth (9.7%) from 12 individuals (14%). Each individual yielded a unique 16S rDNA sequence in 1-2 teeth per individual. Negative controls remained negative. Bacterial identifications were all confirmed by amplification and sequencing of specific rpoB sequence. CONCLUSIONS/SIGNIFICANCE: The new protocol prevented laboratory contamination of the dental pulp. It allowed the detection of bacteria responsible for dental pulp colonization from blood and periodontal tissue. Only 10% such samples contained 16S rDNA. It provides a new tool for the retrospective diagnostic of bacteremia by allowing the universal detection of bacterial DNA in animal and human, contemporary or ancient tooth. It could be further applied to identification of host DNA in forensic medicine and anthropology.

Bartonella quintana in a 4000-year-old human tooth.

Bacteria of the genus Bartonella are transmitted by ectoparasites (lice, fleas, ticks) and have mammalian reservoirs in which they cause chronic, asymptomatic bacteremia. Humans are the reservoir of B. quintana, the louse-borne agent of trench fever. We detected DNA of B. quintana in the dental pulp of a person who died 4000 years ago.

Bartonella quintana in domestic cat.

We recovered Bartonella quintana DNA from dental pulp of a domestic cat. This study, the first to detect B. quintana in a nonhuman mammal, changes our understanding of the epidemiology of this infection and proposes that cats may be an emerging source of human infection.

Genotyping, Orientalis-like Yersinia pestis, and plague pandemics.

Three pandemics have been attributed to plague in the last 1,500 years. Yersinia pestis caused the third, and its DNA was found in human remains from the second. The Antiqua biovar of Y. pestis may have caused the first pandemic; the other two biovars, Medievalis and Orientalis, may have caused the second and third pandemics, respectively. To test this hypothesis, we designed an original genotyping system based on intergenic spacer sequencing called multiple spacer typing (MST). We found that MST differentiated every biovar in a collection of 36 Y. pestis isolates representative of the three biovars. When MST was applied to dental pulp collected from remains of eight persons who likely died in the first and second pandemics, this system identified original sequences that matched those of Y. pestis Orientalis. These data indicate that Y. pestis caused cases of Justinian plague. The two historical plague pandemics were likely caused by Orientalis-like strains.