The effects of low level laser (LLL) irradiation on the proliferation of human buccal fibroblasts were studied. A standardized LLL set-up was developed (812 nm, 4.5 +/- 0.5 mW/cm2). Cultures in petridishes were divided into eight groups (1 group served as control). On day 6 after seeding, routine growth medium was replaced with PBS for 1/2 hour. At the beginning of this period, LLL irradiation was performed for 0, 1, 3, 10, 32, 100, 316, or 1,000 seconds, respectively--corresponding to the radiant exposures 0, 4.5, 13.5, 45, 144, 450, 1,422, 4,500 mJ/cm2. Subsequently the cells received 3H-dT in fresh medium for 16 hours DNA-incorporation. Scintillations from tritium and total protein concentration per culture dish were determined. The individual 3H-cpm/protein-concentration ratios were calculated in % of control. Three experiments were performed (N = 151). Following LLL exposure the 3H-cpm/protein ratio was increased with maximum cpm/protein ratio (132.5% +/- 10.6% SEM) in the group receiving 450 mJ/cm2 (P < 0.03 nonparametric Kruskal Wallis one-way ANOVA-test). This study demonstrated an increased incorporation on tritiated thymidine in cultured human oral fibroblasts following LLL exposure and suggests that LLL irradiation can induce increased DNA synthesis.

Recently, it was reported that Bisphenol-A (BPA) was released from one fissure sealant (Delton) into saliva causing estrogenic activity in vitro. The aim of this study was to chemically analyze the BPA content of different fissure sealant resin monomers and their release of BPA under hydrolytic conditions. BPA content was first measured in commercially available monomers of bisphenol-A glycidyldimethacrylate (Bis-GMA), bisphenol-A dimethacrylate (Bis-DMA) and bisphenol-A diglycidylether (BADGE). Then, Bis-GMA-monomer and Bis-DMA-monomer in methanol were subjected to pH values of 0 to 11 for 30 minutes at 50 degrees C, to porcine liver esterase, and to pooled saliva for up to 24 hours. The BPA-content was determined by high-performance liquid chromatography (HPLC). Bis-GMA-monomer and BADGE-monomer from one manufacturer did not contain any detectable amounts of BPA (< or = 2 ppm); Bis-DMA and BADGE-monomer from a second manufacturer contained BPA quantities of 4-155 ppm. For Bis-GMA-monomer, no BPA could be detected under any hydrolytic conditions chosen (detection limit: < or = 1%). For Bis-DMA-monomer an increase of BPA was observed at pH 11, resulting in a conversion of approx. 100% Bis-DMA to BPA. When Bis-DMA was subjected to esterase, a conversion of 82.5% resulted after 24 h; saliva led to an 81.4% conversion of Bis-DMA after 24 h. Hence, we conclude that the results reported in the literature may be attributed to the Bis-DMA-content of the fissure sealant tested (Delton). No BPA-release is expected under physiologic conditions from fissure sealants based on Bis-GMA if pure base monomers are used.

No abstract

It was recently reported that estrogenic activity was detected in saliva samples collected during 1 h after placement of one fissure sealant (Delton) and this related to Bisphenol-A (BPA) content. The aim of the present study was to determine the time-related BPA content and estrogenic activity in saliva samples collected before and after placement of two fissure sealants each with a different monomer composition. Eight healthy male volunteers with no history of prior placement of fissure sealants or composite resin fillings had four molars sealed with either Delton LC (four people) or Visio-Seal (four people). Base-line saliva samples were collected preexperimentally, in the morning when fasting. Fissure sealants were placed and saliva samples collected immediately, 1 h and 24 hs after placement of the fissure sealant. BPA was found in saliva samples collected immediately after placement of Delton LC (range 0.3-2.8 ppm). No detectable amounts of BPA were determined 1 h and 24 h after Delton treatment (detection limit < or = 0.1 ppm). In base-line samples and in all samples collected from Visio-Seal treated individuals, no BPA was detected. In a recombinant yeast cell assay, significantly increased estrogenic activity was found in saliva samples collected immediately after placement of Delton LC sealant (P < 0.05; ANOVA) whereas no statistically significant estrogenic activity was observed in the remaining groups. In conclusion, minute amounts of BPA, however considerably lower than previously reported, were detected in saliva samples collected immediately after but not 1 and 24 h(s) after placement of Delton LC fissure sealant. BPA was not detected after placement of Visio-Seal fissure sealant.

No valid animal or in vitro model exists to assess the potential mucosal irritancy of dental materials. However, recently, a commercially available model system based on a recombined co-culture of human fibroblasts and human epithelial cells has been introduced for evaluating the time-dependent irritancy of cosmetic products. Cell viability and prostaglandin E2 (PGE2) release from the cells were used as markers for the irritative potential of test materials. The objective of the present study was to evaluate the suitability of this model for monitoring the irritative potential of metals and cast alloys used in dentistry. The human fibroblast-keratinocyte co-cultures were exposed to test specimens fabricated from copper, zinc, palladium, nickel, tin, cobalt, indium, a high noble cast alloy, and from a dental ceramic. Cell survival rates decreased after exposure to copper (14-25%), cobalt (60%), zinc (63%), indium (85%), nickel (87%), and the non-oxidized and oxidized high noble cast alloy (87%/90%) compared to untreated control cultures. Dental ceramic, palladium and tin did not influence cell viability. In parallel, the PGE2 release was continuously monitored up to 24 h using a competitive displacement enzyme immunoassay. PGE2 release increased most highly in the cultures exposed to copper (6-25 fold), cobalt (7 fold), indium (4 fold), and zinc (2 fold) compared to untreated control cultures. The PGE2 determination proved to be a non-destructive method for continuous monitoring of cell reactions in the same culture. The model used seems promising for evaluating the time-dependent mucosal irritancy of dental cast alloys.