Influence of S. mutans on base-metal dental casting alloy toxicity.

We have highlighted that exposure of base-metal dental casting alloys to the acidogenic bacterium Streptococcus mutans significantly increases cellular toxicity following exposure to immortalized human TR146 oral keratinocytes. With Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), S. mutans-treated nickel-based (Ni-based) and cobalt-chromium-based (Co-Cr-based) dental casting alloys were shown to leach elevated levels of metal ions compared with untreated dental casting alloys. We targeted several biological parameters: cell morphology, viable cell counts, cell metabolic activity, cell toxicity, and inflammatory cytokine expression. S. mutans-treated dental casting alloys disrupted cell morphology, elicited significantly decreased viable cell counts (p < 0.0001) and cell metabolic activity (p < 0.0001), and significantly increased cell toxicity (p < 0.0001) and inflammatory cytokine expression (p < 0.0001). S. mutans-treated Ni-based dental casting alloys induced elevated levels of cellular toxicity compared with S. mutans-treated Co-Cr-based dental casting alloys. While our findings indicated that the exacerbated release of metal ions from S. mutans-treated base-metal dental casting alloys was the likely result of the pH reduction during S. mutans growth, the exact nature of mechanisms leading to accelerated dissolution of alloy-discs is not yet fully understood. Given the predominance of S. mutans oral carriage and the exacerbated cytotoxicity observed in TR146 cells following exposure to S. mutans-treated base-metal dental casting alloys, the implications for the long-term stability of base-metal dental restorations in the oral cavity are a cause for concern.

Cuspal deflection and microleakage in premolar teeth restored with bulk-fill flowable resin-based composite base materials.

OBJECTIVES: To assess the cuspal deflection and cervical microleakage of standardised Class II cavities incrementally filled with a dimethacrylate RBC or bulk-fill flowable RBC bases. METHODS: Twenty-four sound upper premolar teeth with Class II cavities were allocated to three groups (n=8). Restoration of the teeth involved the placement of an RBC (GrandioSO) in eight oblique increments (Group A) or Groups B and C were restored to within 2 mm of the palatal cusp in a single increment with bulk-fill flowable RBC bases (SDR and x-tra base) before the two occlusal cavity increments were placed with GrandioSO. Buccal and palatal cusp deflections were recorded postirradiation using a twin channel deflection measuring gauge. Following restoration, the teeth were thermocycled, immersed in 0.2% basic fuchsin dye for 24h, sectioned and examined for cervical microleakage. RESULTS: The mean total cuspal deflection for the oblique incremental restoration technique was 11.26 (2.56) µm (Group A) and 4.63 (1.19) µm (Group B) and 4.73 (0.99) µm (Group C) for the bulk-fill flowable RBC bases. A significant increase in the mean total cuspal deflection for the incrementally filled GrandioSO compared with the SDR (P=0.007) and x-tra base (P=0.005) restored teeth was evident. No significant difference in the cervical microleakage scores was recorded between groups AC (P>0.05). CONCLUSIONS: The bulk-fill flowable RBC bases significantly reduced cuspal deflection compared with a conventional RBC restored in an oblique incremental filling technique with no associated change in cervical microleakage recorded.

Disinfection procedures: their efficacy and effect on dimensional accuracy and surface quality of an irreversible hydrocolloid impression material.

OBJECTIVES: This study investigated the antibacterial efficacy and effect of 0.55% ortho-phthalaldehyde (Cidex OPA(®)) and 0.5% sodium hypochlorite (NaOCl) on the dimensional accuracy and surface quality of gypsum casts retrieved from an irreversible hydrocolloid impression material. METHODS: A simulated clinical cast and technique was developed to compare the dimensional accuracy and surface quality changes of the test gypsum casts with controls. Dimensional accuracy measurements were completed between fixed points using a travelling microscope under low angle illumination at a magnification of ×3. Surface quality changes of "smooth" and "rough" areas on the cast were evaluated by means of optical profilometry. The efficacy of the disinfection procedures against Pseudomonas aeruginosa was evaluated by determining the number of colony forming units (cfu) recovered after disinfection of alginate discs inoculated with 1×106cfu for defined intervals. RESULTS: The dimensional accuracy of the gypsum casts was not significantly affected by the disinfection protocols. Neither disinfectant solution nor immersion time had an effect on the surface roughness of the "smooth" area on the cast, however, a significant increase in surface roughness was observed with increasing immersion time for the "rough" surface. Complete elimination of viable Pseudomonas aeruginosa cells from alginate discs was obtained after 30 and 120 s immersion in Cidex OPA(®) and NaOCl, respectively. CONCLUSIONS: Immersion of irreversible hydrocolloid impressions in Cidex OPA(®) for 30 s was proved to be the most effective disinfection procedure.

Visual and anatomic outcomes associated with posterior segment complications after ganciclovir implant procedures in patients with AIDS and cytomegalovirus retinitis.

PURPOSE: To determine anatomic and visual acuity outcomes of posterior segment complications after ganciclovir implant surgery. METHODS: We reviewed the medical records of 63 patients with acquired immunodeficiency syndrome who had active cytomegalovirus retinitis in 82 eyes and who underwent 110 consecutive ganciclovir implant procedures. Preoperative and postoperative visual acuity, type of postoperative complication, treatment, and lines of visual acuity change were determined. RESULTS: Thirty-eight eyes of 19 patients had bilateral ganciclovir implant procedures, and 25 eyes of 19 patients underwent two or more ganciclovir implant procedures. Thirteen (12%) of 110 ganciclovir implant procedures developed posterior segment complications: rhegmatogenous retinal detachment in six, vitreous hemorrhage in four, endophthalmitis in two, and cystoid macular edema with epiretinal membrane in one. Treatment included pars plana vitrectomy with silicone oil in two cases and without silicone oil in three cases, scleral buckling in one, intravitreal antibiotic injection in two, and laser photocoagulation in two. Overall, median visual acuity was 20/25 preoperatively. Median follow-up was 6 months for all eyes and 7 months for eyes with complications. Postoperative median visual acuity was 20/25 for eyes without complications vs 20/40 at 1 month, 20/60 at 3 and 6 months, and 20/100 at 12 months in eyes with complications (P < .001). More eyes with than without complications lost 2 or more lines of visual acuity (P < .001). CONCLUSION: Postoperative complications occurred in 12% of the ganciclovir implant procedures and were associated with decreased visual acuity despite treatment.