Marinês Nobre-dos-Santos

Effect of sodium hypochlorite on dentine mechanical properties. A review.

OBJECTIVES The aim of this study was to carry out a review on the effect of sodium hypochlorite (NaOCl) on the mechanical properties of root dentine. DATA/SOURCES The authors searched the Cochrane Library, Embase, PubMed and the Web of Science for papers published from 1984 to 2008. The main search terms used were: dentine, root canal dentine, sodium hypochlorite, mechanical analysis, elastic modulus, hardness, roughness, flexural strength, compressive strength. STUDY SELECTION The inclusion criteria were studies that evaluated the effect of NaOCl solution, used as an irrigant in endodontics, on the mechanical properties of root dentine. Those studies that were considered to be unrelated to the question addressed, that had investigated NaOCl as a deproteinizing agent, had not evaluated the effect of NaOCl on the mechanical properties of dentine, and that indirectly verified the effect of NaOCl on endodontically treated teeth were excluded. The selected papers were assigned to a score (A-C), according to predetermined criteria. A total of 16 papers were selected, and nine papers were included in the critical appraisal. Five papers were classified as grade A, 4 as grade B, and no paper was classified as grade C. CONCLUSIONS Based on this review, the authors suggest that there is strong evidence showing that sodium hypochlorite adversely alters the mechanical properties of root dentine, when used as an endodontic irrigant.

Relationship among microbiological composition and presence of dental plaque, sugar exposure, social factors and different stages of early childhood caries

OBJECTIVE This cross-sectional study aimed to investigate the relationship among microbiological composition of dental plaque, sugar exposure and social factors, as well as the presence of visible plaque in preschoolers with different stages of early childhood caries. DESIGN A total of 169 children were clinically examined according to the World Health Organisation criteria + early caries lesions and were divided into three groups: caries-free (n=53), early caries lesions-ECL (n=56), and cavitated caries lesions-CCL (n=60). The presence of clinically visible dental plaque on maxillary incisors was recorded. After that, dental plaque from all buccal and lingual smooth surfaces was collected and the number of colony-forming units of mutans streptococci and total microorganism, as well as the presence of lactobacilli was determined. Daily frequency of meals containing sugar was assessed by a diet chart whereas social factors were evaluated by a questionnaire. The data were analysed by chi-square test followed by multiple logistic regressions (alpha=0.05, confidence interval=95%). RESULTS High levels of mutans streptococci (OR=2.28), high total sugar exposure (OR=5.45) and presence of dental plaque (OR=2.60) showed significant association with ECL (p<0.05). High total microorganism count (OR=5.18), high solid sugar exposure (OR=2.50) and the presence of lactobacilli (OR=24.99) revealed significant association with CCL (p<0.05). CONCLUSIONS These results support the conclusion that dietary sugar experience influenced the microbiological composition of dental plaque. Moreover, the early stage of caries is highly affected by mutans streptococci and visible dental plaque on maxillary incisors whereas cavities are strongly related to lactobacilli and total microorganism.

Effect of a pulsed CO2 laser and fluoride on the prevention of enamel and dentine erosion

OBJECTIVE The hypotheses of this study was that pulsed CO(2) laser (lambda=10.6 microm) treatment in combination (or not) with previous fluoride gel application could increase the resistance of enamel and dentine to erosion, throughout successive erosive challenges. DESIGN Thirty-two bovine specimens of enamel and of root dentine were flattened, polished and randomly assigned to the following treatments (n=8): fluoride (F), laser (L), fluoride+laser (FL) or no treatment as negative control (C). The treated specimens were submitted to demineralization (0.3% citric acid, pH 2.45, for 5 min) and remineralization (artificial saliva, for 60 min) cycles, three times a day, for 3 days. Dental surface loss as well as the concentration of calcium, phosphorus and fluoride in the demineralizing solutions were determined after each cycling day. Enamel and dentine were analysed separately using repeated measures ANOVA for ranks (alpha=0.05). RESULTS The association between fluoride and laser (FL) resulted in the lowest enamel and dentine surface loss values throughout the cycles, differing significantly from the control group. No clear benefit of FL over the F or L treatments was observed. There was a non-significant trend (p>0.05) for FL to release less calcium, phosphorus and fluoride into the demineralizing solutions when compared to the other groups. CONCLUSIONS Pulsed CO(2) laser (lambda=10.6 microm) alone was not able to prevent enamel or dentine surface losses due to erosion. Laser treatment in combination with fluoride showed some protection, but the effect does not appear to be synergistic.

Immunological and Microbiologic Changes during Caries Development in Young Children

We explored the association between caries development, colonization with caries-associated microflora, and immunity as children begin the transition to mixed dentition. Forty children received dental examinations at 3–4 years of age, repeated a year later. Children were grouped into caries-free (n = 23; CF) and caries-active (n = 17; CA ≧3 new lesions on follow-up). Salivary IgA and IgA antibody to Streptococcus mutans virulence epitopes were measured by Luminex assay. Mutans streptococci (MS), lactobacilli and total microorganisms were enumerated on selective media from plaque samples. There was no significant difference in baseline levels of MS or lactobacilli between CF and CA groups. However, both MS and lactobacilli levels were higher at follow-up in the CA group. Furthermore, children with detectable lactobacilli at baseline had significantly higher caries risk. Salivary IgA concentrations increased significantly in both groups during the study. Both CF and CA groups also displayed significant increases in salivary IgA antibody levels to glucosyltransferase, glucan-binding protein (Gbp) and antigen I/II salivary binding region. CF antibody levels to seven peptides associated with domains of biological importance increased at follow-up, in contrast to increases to only three peptides in CA saliva samples. Multivariate modeling showed that a lower baseline level of salivary IgA anti-GbpB was associated with higher caries risk. These data indicate that MS and lactobacilli are associated with caries in this population, that the secretory immune system is undergoing significant maturation during this period, and that the breadth of mucosal IgA response to epitopes of S. mutans virulence components may influence the degree to which these cariogenic microorganisms can cause disease.

Physical and compositional changes on demineralized primary enamel induced by CO2 Laser.

OBJECTIVE This in vitro study aimed to evaluate the physical and chemical changes promoted by a CO(2) laser at 10.6-microm wavelength on primary dental enamel with artificial caries-like lesions. BACKGROUND DATA Several previous investigations have shown that enamel can be modified by CO(2) laser to obtain a caries-preventive effect, but the specific mechanism remains uncertain. MATERIALS AND METHODS Twenty-seven primary molars were randomly assigned to three groups as follows: control, carious, and laser (n = 9). The specimens from the carious and laser groups were demineralized and treated with or without CO(2) laser, according to the group. Enamel surface changes after treatments were monitored using Fourier transform Raman spectroscopy and scanning electron microscopy (SEM). RESULTS The Raman spectra showed a statistically significant reduction of mineral content in carious and laser groups when compared to control group. Additionally, carbonate content was reduced in irradiated specimens when compared to the other groups. No physical change was observed in specimens evaluated by SEM. CONCLUSION The results suggest that CO(2) laser irradiation may reduce the carbonate content of enamel, which is likely to make this substrate more acid-resistant.

In vitro photodynamic antimicrobial chemotherapy in dentine contaminated by cariogenic bacteria

The development of a method to ensure bacterial-free substrates without extensive cavity preparation would be highly useful to dentistry, since there is no currently available effective method for killing residual bacteria in dentinal tissue. This randomized in vitro study determined parameters for using toluidine blue O (TBO) with a light-emitting diode (LED) for dentine caries disinfection and monitored intrapulpal/periodontal temperatures during irradiation. Occlusal human dentine slabs were immersed in Streptococcus mutans culture for demineralization induction. Slabs were allocated to 10 groups (n = 15), which were treated with 0.1 mg ml−1 TBO with 5 min of incubation time or 0.9% NaCl solution for 5, 10 or 15 min, and submitted or not to irradiation for 5, 10 or 15 min (47, 94, and 144 J/cm2). Before and after treatments, dentine samples were analyzed with regard to S. mutans counts. In whole teeth, temperature in pulp and periodontium was measured by thermocouples during irradiation. Kruskal-Wallis/Student-Newman-Keuls, and ANOVA/Tukey test were respectively utilized to compare log reductions and temperature rises between groups. Bacterial reduction was observed when dentine was exposed to both TBO and LED at all irradiation times, as well as to LED alone for 10 and 15 min. Temperature increases lower than 2°C were observed for either pulp or periodontium. Concluding, LED combined with TBO is a safe and effective approach for dentine caries disinfection. Nevertheless, additional studies should be conducted to determine the influence of the irradiation in S. mutans viability in dentinal surface/tubules.

Can insoluble polysaccharide concentration in dental plaque, sugar exposure and cariogenic microorganisms predict early childhood caries? A follow-up study

BACKGROUND Insoluble polysaccharide (IP) has been associated with caries prevalence in young children. However, the power of IP to predict ECC needs to be demonstrated. AIMS To assess the relationships between early childhood caries (ECC) and extracellular insoluble polysaccharides (IP) in dental plaque, sugar exposure and cariogenic microorganisms. DESIGN Visible plaque on maxillary incisors was recorded, followed by caries diagnosis in 65 preschoolers (3-4 years) at baseline and after 1 year. Plaque was collected for mutans streptococci (MS), total microorganism (TM) and lactobacilli (LB) enumerations in selective media, as well as for IP analysis, which was later assessed by colorimetry. Sugar/sucrose exposure was assessed by a diet chart. RESULTS Positive correlations were found among the prevalence of caries and MS, TM, LB, solid sucrose and visible dental plaque. Additionally, children with IP concentrations in dental plaque higher than 2.36 μg/mg (odds ratio-OR=6.8), with visible plaque on maxillary incisors (OR=4.3), harbouring LB (OR=13) and exposed to solid sugar more than twice/day (OR=5) showed higher risk of developing caries (p<0.05). CONCLUSION Extracellular insoluble polysaccharides, solid sugar/sucrose, visible dental plaque and cariogenic microorganisms could predict caries development, partially explaining the ECC pattern.

An in vitro microbial model associated with sucrose to produce dentin caries lesions

The complexity of the oral environment and ethical issues have prompted the development of an in vitro bacterial model to evaluate the effect of frequency of sucrose exposure on dentin caries formation, biofilm composition, and pH changes. In the experiment, dentin specimens (n=45) were randomly divided into four groups: control (C), negative control (0S), 3S (three sucrose baths), and 6S (six sucrose baths). The specimens then were inoculated with Streptococcus mutans and treated according to the protocol described below. Dentin demineralization and lesion depth were assessed by transverse microradiography. Extracellular polysaccharides that formed in the biofilm were analyzed and counts of microorganisms in the carious dentin were measured. After a 7-day period of growth, the biofilm pH was assessed before and after sucrose baths (n=5). The addition of sucrose led to dentin caries development regardless of the number of sucrose baths performed. The number of colony forming units (cfu) from the carious dentin did not differ among the treatment groups, though the extracellular polysaccharides from both 3S and 6S differed from 0S. The pH decreased immediately after the sucrose bath but increased again after 5 min. We demonstrate here that the in vitro microbial model for the study of dentin caries formation is reproducible and able to produce dentin caries, irrespective of the frequency of sucrose exposure.

Assessment of cavitated and active non-cavitated caries lesions in 3- to 4-year-old preschool children: a field study.

BACKGROUND The prevalence of early childhood caries (ECC) is high in developing countries; thus, sensitive methods for the early diagnosis of ECC are of prime importance to implement the appropriate preventive measures. AIM To investigate the effects of the addition of early caries lesions (ECL) into WHO threshold caries detection methods on the prevalence of caries in primary teeth and the epidemiological profile of the studied population. DESIGN In total, 351 3- to 4-year-old preschoolers participated in this cross-sectional study. Clinical exams were conducted by one calibrated examiner using WHO and WHO + ECL criteria. During the exams, a mirror, a ball-ended probe, gauze, and an artificial light were used. The data were analysed by Wilcoxon and Mc-Nemars tests (α=0.05). RESULTS Good intra-examiner Kappa values at tooth/surface levels were obtained for WHO and WHO+ECL criteria (0.93/0.87 and 0.75/0.78, respectively). The dmfs scores were significantly higher (P<0.05) when WHO+ECL criteria were used. ECLs were the predominant caries lesions in the majority of teeth. CONCLUSIONS The results strongly suggest that the WHO+ECL diagnosis method could be used to identify ECL in young children under field conditions, increasing the prevalence and classification of caries activity and providing valuable information for the early establishment of preventive measures.

Caries resistance of lased human root surface with 10.6 μm CO2 laser-thermal, morphological, and microhardness analysis

Although the cariostatic effects of CO2 laser on enamel have been shown, its effects on root surface demineralization remains uncertain. The objectives of this in vitro research was to establish safe parameters for a pulsed 10.6 μm CO2 laser and to evaluate its effect on morphological features of the root surface, as well as on the reduction of root demineralization. Ninety-five human root surfaces were randomly divided into five groups: G1-No treatment (control); G2—2.5 J/cm2; G3—4.0 J/cm2; G4—5.0 J/cm2; and G5—6.0 J/cm2. Intrapulpal temperature was evaluated during root surface irradiation by a thermocouple and morphological changes were evaluated by SEM. After the surface treatment, the specimens were submitted to a 7-day pH-cycling model. Subsequently, the cross-sectional Knoop microhardness values were measured. For all irradiated groups, intrapulpal temperature changes were less than 1.5°C. Scanning electron microscopy images indicated that fluences as low as 4.0 J/cm2 were sufficient to induce morphological changes in the root surface. Additionally, for fluences reaching or exceeding 4.0 J/cm2, laser-induced inhibitory effects on root surface demineralization were observed. It was concluded that laser energy density in the range of 4.0 to 6.0 J/cm2 could be applied to a dental root to reduce demineralization of this surface without compromising pulp vitality.