In vitro analysis of inhibitory effects of the antibacterial monomer MDPB-containing restorations on the progression of secondary root caries

Objective: This study aimed to analyze in vitro inhibitory effects of restorative materials containing the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) on the formation of artificial secondary root caries lesions. Methods: Class V cavities (2 mm x 2 mm) were prepared in 75 human root fragments. Specimens were randomly divided into five groups (n = 15 fragments per group) and restored as follows: (I) MDPB-free adhesive system + MDPB-free composite (negative control); (II) resin modified glass ionomer (RM-GIC; positive control); (III) MDPB-free adhesive system + MDPB-containing composite (2.83% MDPB); (IV) MDPB-containing adhesive system + MDPB-free composite; M MDPB-containing adhesive system + MDPB-containing composite. Artificial secondary root caries lesions were produced by a biological artificial caries challenge. The restored specimens were immersed into a culture medium containing Streptococcus mutans and sucrose for 15 days. Histological slices (80 +/- 20 mu m) of the specimens were used for measuring the mean depths of the artificial lesions produced in both margins of the restorations using polarized light microscopy. Results were expressed in percentage related to the mean depth of the negative control, considered 100%. Data were compared by ANOVA followed by the Tukey`s test (p <= 0.05). Results: The depths of lesions adjacent to cavities filled with RM-GIC (GII; 85.17 +/- 15.2%) were significantly (p < 0.01) shallower than those adjacent to restorations with MDPB-free composite (GI; 100.00 +/- 10.04%), despite the presence of MDPB in the adhesive system (GIV; 101.95 +/- 21.32%). The depths of lesions adjacent to cavities restored with MDPB-containing composite (GIII; 82.68 +/- 12.81% and GV; 85.65 +/- 15.42%), despite the adhesive system used, were similar to those of RM-GIC (GII). Mean lesions depths in these groups decreased from 13% (GV) to 17% (GIII) in relation to the negative control (GI). Conclusions: MDPB-containing composite inhibits the progression of artificial secondary root caries lesions regardless of adhesive systems. (C) 2009 Elsevier Ltd. All rights reserved.

CO(2) Laser (10.6 mu m) Parameters for Caries Prevention in Dental Enamel

Although CO(2) laser irradiation can decrease enamel demineralisation, it has still not been clarified which laser wavelength and which irradiation conditions represent the optimum parameters for application as preventive treatment. The aim of the present explorative study was to find low-fluence CO(2) laser (lambda = 10.6 mu m) parameters resulting in a maximum caries-preventive effect with the least thermal damage. Different laser parameters were systematically evaluated in 3 steps. In the first experiment, 5 fluences of 0.1, 0.3, 0.4, 0.5 and 0.6 J/cm(2), combined with high repetition rates and 10 mu s pulse duration, were chosen for the experiments. In a second experiment, the influence of different pulse durations (5, 10, 20, 30 and 50 mu s) on the demineralisation of dental enamel was assessed. Finally, 3 different irradiation times (2, 5 and 9 s) were tested in a third experiment. In total, 276 bovine enamel blocks were used for the experiments. An 8-day pH-cycling regime was performed after the laser treatment. Demineralisation was assessed by lesion depth measurements with a polarised light microscope, and morphological changes were assessed with a scanning electron microscope. Irradiation with 0.3 J/cm(2), 5 mu s, 226 Hz for 9 s (2,036 overlapping pulses) increased caries resistance by up to 81% compared to the control and was even significantly better than fluoride application (25%, p < 0.0001). Scanning electron microscopy examination did not reveal any obvious damage caused by the laser irradiation. Copyright (C) 2009 S. Karger AG, Basel

Rehardening of acid-softened enamel and prevention of enamel softening through CO(2) laser irradiation

Objectives: The aims of the present study were to investigate whether irradiation with a CO(2) laser could prevent surface softening (i) in sound and (ii) in already softened enamel in vitro. Methods: 130 human enamel samples were obtained and polished with silicon carbide papers. They were divided into 10 groups (n = 13) receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C); and submitted to 2 different procedures: half of the groups was acid-softened before surface treatment and the other half after. Immersion in 1% citric acid was the acid challenge. Surface microhardness (SMH) was measured at baseline, after softening and after treatment. Additionally, fluoride uptake in the enamel was quantified. The data were statistically analysed by two-way repeated measurements ANOVA and post hoc comparisons at 5% significance level. Results: When softening was performed either before or after laser treatment, the L group presented at the end of the experiments SMH means that were not significantly different from baseline (p = 0.8432, p = 0.4620). Treatment after softening resulted for all laser groups in statistically significant increase in SMH means as compared to values after softening (p < 0.0001). Enamel fluoride uptake was significantly higher for combined laser-fluoride treatment than in control (p < 0.0001). Conclusion: Irradiation of dental enamel with a CO(2) laser at 0.3J/cm(2) (5 mu s, 226 Hz) not only significantly decreased erosive mineral loss (97%) but also rehardened previously softened enamel in vitro. (C) 2011 Elsevier Ltd. All rights reserved.

Effect of Iron on Matrix Metalloproteinase Inhibition and on the Prevention of Dentine Erosion

It is known that some metal salts can inhibit matrix metalloproteinase (MMP) activity, but the effect of iron has not been tested yet. On the other hand, it has recently been suggested that MMP inhibition might influence dentine erosion. Based on this, the aims of this study were: (1) to test in vitro the effect of FeSO(4) on MMP-2 and -9 activity, and (2) to evaluate in situ the effect of FeSO(4) gel on dentine erosion. MMP-2 and -9 activities were analysed zymographically in buffers containing FeSO(4) in concentrations ranging between 0.05 and 1.5 mmol/l or not. Volunteers (n = 10) wore devices containing bovine dentine blocks (n = 60) previously treated with the following gel treatments: FeSO(4) (1 mmol/l FeSO(4)), F (NaF 1.23%; positive control) and placebo (negative control). The gels were applied once and removed after 1 min. Erosion was performed extraorally with Coca-Cola 4 times per day for 5 min over 5 days. Dentine wear was evaluated by profilometry. The data were analysed by Kruskal-Wallis and Dunn`s tests (p < 0.05). FeSO(4) inhibited both MMP-2 (IC(50) = 0.75 mmol/l) and MMP-9 (IC(50) = 0.50 mmol/l) activities. In the in situ experiment, the mean wear (+/- SD) found for the F gel (0.79 8 +/- 0.08 mu m) was significantly reduced in more than 50% when compared to the placebo gel (1.77 +/- 0.33 mu m), but the FeSO(4) gel completely inhibited the wear (0.05 +/- 0.02 mu m). Since FeSO(4) was able to inhibit MMP in vitro, it is possible that the prevention of dentine wear by the FeSO(4) gel in situ might be due to MMP inhibition, which should be investigated in further studies. Copyright (C) 2010 S. Karger AG, Basel

Emerging technologies for the prevention of dental caries. Are current methods of prevention sufficient for the high risk patient?

Fluorides and chlorhexidine are technologies that are 65 and 40 years old, respectively. This overview argues that current methods of caries prevention are not effective for the high caries risk patient. In this review examples, arguments and recommendations are provided to address the high caries risk patient that include: failure of comprehensive chemical modalities treatments to address the high caries risk patient; ecological alteration - would this be an effective approach?; and biomaterials and oral microbiome research to address the high caries risk patient.

Study on the potential inhibition of root dentine wear adjacent to fluoride-containing restorations

The purpose of this in vitro study was to determine whether the vicinity of root dentine that had been restored with fluoride-releasing materials was at reduced risk for erosive/abrasive wear compared to root dentine restored with a non-fluoride-containing material. According to a randomized complete block design, standardized cavities prepared on the surface of 150 bovine root dentine slabs were restored with glass-ionomer cement, resin-modified glass ionomer, polyacid-modified resin composite, fluoride-containing or conventional composite. Specimens were coated with two layers of an acid-resistant nail varnish exposing half of the dentine surface and half of the restoration. Subsequently, specimens were either eroded in an acidic drink or left uneroded, then exposed to artificial saliva and abraded in a toothbrushing machine. Wear depth in the vicinity of restorations was quantified by a stylus profilometer, based on the nonabraded areas surrounding the erosion/abrasion region. Two-way ANOVA did not demonstrate significant interaction between restoratives and eroded-uneroded dentine (p = 0.5549) nor significant difference among restorative materials (p = 0.8639). Tukey`s test ascertained that the wear depth was higher for eroded than for uneroded groups. Fluoride-releasing materials seemed to negligibly inhibit wear in the vicinity of restored root dentine subjected to erosive/abrasive challenges.