Susceptibility of gamma-irradiated primary teeth to a cariogenic challenge: an in vitro study.

PURPOSE: This study aimed to evaluate whether radiotherapy with gamma radiation changes the susceptibility of primary teeth to a cariogenic challenge. METHODS: Specimens of primary teeth (n = 18) were subjected to gamma radiation simulating the radiotherapy treatment, and 18 specimens were used as control group. A microbiological model of caries induction by S. mutans was used to evaluate the susceptibility of these irradiated specimens to the caries development. The depth, area and volume of caries lesion formed were evaluated using microcomputer tomography analysis (µ-CT) and changes occurring on the enamel surface were evaluated using scanning electron microscopy (SEM). Data of the lesion depth, lesion area and volume were submitted to independent t test with a 5% of significance limit. RESULTS: The lesion depth and the area of caries in the irradiated group (196.61 ± 60.41 µm and 564.52 ± 343.37 µm2, respectively) were significantly higher (p = 0.02 and p = 0.03, respectively) than those in the nonirradiated group (151.70 ± 32.16 µm and 386.64 ± 169.75 µm2, respectively). However, the lesion volume did not differ (p = 0.15) between the groups (7797.89 ± 3675.69 µm3 for irradiated and 6509.03 ± 2902.65 µm3 for nonirradiated group). The SEM images show greater enamel breakdown in the group of irradiated specimens. CONCLUSION: The present study results reveal that the gamma radiation protocol used for cancer treatment renders primary teeth more susceptible to a cariogenic challenge.

Radiotherapy changes salivary properties and impacts quality of life of children with Hodgkin disease.

OBJECTIVE: We aimed to perform a longitudinal investigation of the effects of radiotherapy on salivary flow rate, pH, buffering capacity, and protein composition of saliva and on the quality of life of children with Hodgkin disease. DESIGN: Ten children (6-16-year-old) with Hodgkin disease and 10 matched healthy children were investigated. Stimulated and non-stimulated saliva samples were collected at baseline, after 1080 and 2160cGy of radiation, and 1, 2, and 3 months post-radiotherapy. The salivary flow rate was expressed as mL/min. Buffer capacity was determined by titration. Amylase activity, immunoglobulin A, mucin, and lactoferrin concentrations were determined by ELISA. Quality of life was assessed by Quality of Life - Head and Neck module 35 questionnaire. RESULTS: We found that radiotherapy caused hyposalivation at 1080cGy and 1 month after radiotherapy and reduced buffering capacity at 2160cGy. Mucin concentration and amylase activity in non-stimulated saliva increased 1 month after radiotherapy. Lactoferrin concentration increased during and after radiotherapy. Immunoglobulin A concentration increased at 1080cGy, 1 and 2 months, for non-stimulated saliva and at 2160cGy and 1 month for stimulated saliva. Children reported more pain after radiotherapy and more xerostomia during radiotherapy. CONCLUSION: We concluded that the radiotherapy protocol affected the children's salivary properties and children's quality of life.

Effect of a CO2 Laser on the Inhibition of Root Surface Caries Adjacent to Restorations of Glass Ionomer Cement or Composite Resin: An In Vitro Study.

This study investigated the effect of CO2 laser irradiation on the inhibition of secondary caries on root surfaces adjacent to glass ionomer cement (GIC) or composite resin (CR) restorations. 40 dental blocks were divided into 4 groups: G1 (negative control): cavity preparation + adhesive restoration with CR; G2: (positive control) cavity preparation + GIC restoration; G3: equal to group 1 + CO2 laser with 6 J/cm(2); G4: equal to group 2 + CO2 laser. The blocks were submitted to thermal and pH cycling. Dental demineralization around restorations was quantified using microhardness analyses and Light-Induced Fluorescence (QLF). The groups showed no significant differences in mineral loss at depths between 20 µm and 40 µm. At 60 µm, G2 and G3 ≠ G1, but G4 = G1, G2 and G3. At 80 µm, G4 ≠ G1, and at 100 µm, G4 = G2 = G1. At 140 and 220 µm, G2, G3, and G4 = G1. The averages obtained using QFL in groups 1, 2, 3, and 4 were 0.637, 0.162, 0.095, and 0.048, respectively. QLF and microhardness analyses showed that CO2 laser irradiation reduced mineral loss around the CR restorations but that it did not increase the anticariogenic effect of GIC restorations.

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.

In vitro evaluation of enamel demineralization after several overlapping CO2 laser applications.

This study aimed to evaluate the effects of repeated CO2 laser applications on the inhibition of enamel demineralization. Sixty-five human dental enamel slabs were randomly assigned to the following groups (n = 13): control (C), one application of the CO2 laser (L1), two applications of the CO2 laser (L2), three applications of the CO2 laser (L3), and four applications of the CO2 laser (L4). Enamel slabs were irradiated by a 10.6-µm CO2 laser operating at 5 J/cm(2). The slabs were subjected to a pH-cycling regimen and then analyzed by FT-Raman spectroscopy, energy-dispersive X-ray fluorescence spectrometry (EDXRF), cross-sectional micro-hardness, and scanning electron microscopy (SEM). Statistical analysis was performed using ANOVA and Tukey tests (p < 0.05). FT-Raman spectroscopy showed a reduced carbonate content for L1, L3, and L4 groups when compared to C (p < 0.05). The EDXRF data showed no statistical differences between the control and irradiated groups for calcium and phosphorus components (p > 0.05). Cross-sectional micro-hardness data showed a statistically significant difference between the control and all irradiated groups (p < 0.05), but no difference was found among the irradiated groups (p > 0.05) up to 30-µm depth. A tendency of lower demineralization occurred in deeper depths for L3 and L4 groups. The SEM results showed that with repeated applications of the CO2 laser, a progressive melting and recrystallization of the enamel surface occurred. Repeated irradiations of dental enamel may enhance the inhibition of enamel demineralization.

Relationship among salivary carbonic anhydrase VI activity and flow rate, biofilm pH and caries in primary dentition.

This study aimed to determine the activity of carbonic anhydrase isoenzyme VI (CAVI) in the saliva of preschool children with caries and to investigate the relationship between caries and salivary CAVI activity, salivary flow rate and biofilm pH before and after a 20% sucrose rinse. Thirty preschool children aged 45.3-80.3 months were divided into two groups: a caries-free group and a caries group. Clinical examinations were conducted by one examiner (κ = 0.95) according to WHO criteria (dmfs) and early caries lesions. From each subject, CAVI activity, salivary flow rate and plaque pH were determined before and after a sucrose rinse. The results were submitted to Wilcoxon, Mann-Whitney and Spearman correlation tests (α = 0.05). The results showed that prerinse CAVI activity and its variation were higher in the saliva from caries children than from caries-free children. No difference was found between the two groups in postrinse salivary CAVI activity. After rinsing, biofilm pH differences were lower in both groups (p = 0.0012 and p = 0.0037 for the caries and caries-free groups, respectively). Also, after the sucrose rinse, salivary flow rate significantly increased in caries and caries-free groups (p = 0.0003, p = 0.0037). The variation of salivary CAVI activity was negatively correlated with caries (r = -0.501, p = 0.005). Child's age showed a positive correlation with caries (r = 0.456, p = 0.011). These results suggest that variation of salivary CAVI activity and child's age are associated with dental caries in preschool children.

Influence of the curing mode on fluoride ion release of self-adhesive resin luting cements in water or during pH-cycling regimen.

This study evaluated the effects of curing modes and storage conditions on fluoride release of resin cements. In phase 1, the cumulative fluoride release rate from samples of the resin cements (Panavia F 2.0, RelyX Unicem, MaxCem, and BisCem) was quantified after 15 days storage in water (n=4). In phase 2, the fluoride release profiles from the same materials were analyzed during pH cycling (n=4). In this second phase, fluoride was measured at specific times (one, two, three, five, eight, and 15 days). Disk-shaped specimens were prepared (10 mm × 0.5 mm), and the materials were either light activated or allowed to autopolymerize. For both phases, the fluoride release was measured using a fluoride ion-specific electrode. The fluoride release in water was not affected by the curing mode of RelyX Unicem and Maxcem resin cements. Panavia F. 2.0 and BisCem resin cements, either light cured or autopolymerized modes, released higher amounts of fluoride in water than the other self-adhesive cements. In phase 2, the concentration of fluoride released decreased from the first day of pH cycling until the 15th day for all resin cements, for both curing modes, regardless of the storage solution used (demineralizing/remineralizing). The fluoride release rate during pH cycling by Panavia F 2.0 and MaxCem was not affected by the curing mode. The effect of the curing mode on fluoride ion release in water or during pH cycling was product dependent.

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.

Association of polymorphisms in the carbonic anhydrase 6 gene with salivary buffer capacity, dental plaque pH, and caries index in children aged 7-9 years.

Carbonic anhydrase VI is a secreted enzyme that catalyzes the hydration of carbon hydroxide in saliva and other body fluids. This enzyme has been implicated in taste and gastrointestinal dysfunctions, tooth erosion, and caries. The purpose of this study was to analyze the allele and genotype distribution of three polymorphisms in the coding sequences of (CA6) gene and check for possible associations with salivary buffer capacity, number of decayed, missing, and filled teeth in deciduous and permanent teeth (dmft/DMFT, Decayed/Missing/Filled Teeth), plaque index (PI), and the plaque pH variation (DeltapH) in children aged 7-9 years. Two hundred and forty-five children from both genders, residents in area with fluoridated water (Piracicaba, São Paulo, Brazil) were divided into two groups: caries free and with caries. The clinical examinations were conducted by a single previously calibrated examiner (kappa=0.91) in an outdoor setting using a mirror and a probe, according to WHO criteria index (dmft/DMFT). Approximately 2 h after the first daily meal, the buffer capacity (BC) and the plaque pH were analyzed by means of a pH meter and an ion selective electrode. Plaque pH was measured immediately and 5 min after a mouth rinse with a 10% sucrose solution. The data were submitted to chi(2), Student's, and Mann-Whitney tests (alpha=0.05). The PI and DeltapH of the upper and lower teeth were significantly higher in the carious group than control (P<0.05). There was no difference between the groups in relation to BC. There was no association between the alleles and genotypes distributions for polymorphisms in the CA6 gene exons 2 and 3 and caries experience (P>0.05). There was a positive association between buffer capacity and the rs2274327 (C/T) polymorphism. The allele T and genotype TT were significantly less frequent in individuals with the highest buffer capacity (P=0.023 and 0.045, respectively). This finding encourages future studies relating CA6 gene polymorphisms and their association with malfunctions, such as taste and gastrointestinal alterations, or the differential effect of chemical modulators on the protein products originated from the distinct genotypes of the CA6 gene.

Effect of the CO2 laser combined with fluoridated products on the inhibition of enamel demineralization.

AIM: This in vitro study evaluated the combined effects of a 10.6 microm CO2 laser, fluoridated dentifrice, and mouthrinse on the reduction of lesion progression in carious human enamel. METHODS AND MATERIALS: Slabs of previously demineralized dental enamel were assigned to nine groups, either treated with/without a CO2 laser, with/without fluoridated dentifrice, and with/without fluoridated mouthrinse. After a pH-cycling regime, fluoride concentrations were determined in the demin- and remineralizing solutions. A qualitative polarized light analysis was performed on enamel, and enamel mineral loss was determined by cross-sectional microhardness testing. RESULTS: All treatments were able to decrease mineral loss, and the inhibition of demineralization progression ranged from 48% to 60%. CONCLUSION: The 10.6 microm CO2 laser irradiation alone or combined with fluoridated products reduced demineralization progression in enamel. However, there was no significant additional demineralization inhibitory effect with the use of the combined laser-fluoride treatments. CLINICAL SIGNIFICANCE: CO2 lasers have proven to be efficient in reducing subsurface enamel demineralization. Its association with a high frequent fluoride therapy may enhance this protective effect.

Combined effects of carbon dioxide laser and fluoride on demineralized primary enamel: an in vitro study.

This in vitro study aimed at evaluating the efficacy of a CO(2) laser (10.6 microm) alone or combined with acidulated phosphate fluoride (APF) on the inhibition of lesion progression in primary enamel. The specimens were treated with/without CO(2) laser and/or APF and submitted to pH cycling. Microhardness analysis was performed and the enamel mineral loss values were obtained. The groups treated with laser and/or APF presented lower mineral loss when compared to the control group (p < 0.05). Laser irradiation alone or combined with APF decreased lesion progression in primary enamel. However, the combined treatment did not show any significant additional effect.

In situ mineral loss inhibition by CO2 laser and fluoride.

Laser and fluoride treatments have been shown to inhibit enamel demineralization in the laboratory. However, the intra-oral effects of this association have not been tested. This study assessed in situ the effect of a Transversely Excited Atmospheric CO2 laser (lambda = 9.6 mum) and the use of pressure fluoridated dentifrice on enamel demineralization. During two 14-day phases, 17 volunteers wore palatal appliances containing human enamel slabs assigned to treatment groups, as follows: (1) non-fluoride dentifrice, (2) CO2 laser irradiation plus non-fluoride dentifrice, (3) fluoride dentifrice, and (4) CO2 laser irradiation plus fluoride dentifrice. A 20% sucrose solution was dripped onto the slabs 8 times per day. The specimens treated with laser and/or fluoridated dentifrice presented a significantly lower mineral loss when compared with those from the non-fluoride dentifrice group. The results suggested that CO2 laser treatment of enamel inhibits demineralization in the human mouth, being more effective when associated with fluoride.

Masticatory performance and bite force in relation to signs and symptoms of temporomandibular disorders in children.

AIM: The aim of this study was to compare and correlate the masticatory performance (MP) and maximum bite force (BF) in children with and without signs and symptoms of temporomandibular disorders (TMD). METHODS: Thirty-six children aged 7-12 years in the mixed or beginning of permanent dentition where divided into 2 groups: with signs and symptoms of TMD (SS group, n=21) and without signs and symptoms (Control group, n=15). The signs were evaluated in the clinical exam and the symptoms through a questionnaire. The evaluated criteria were: presence of postcanine teeth in occlusion, the Angle's classification for first permanent molars, canine relationship, crossbite, midline deviation, overbite and overjet. The MP was determined by chewing a silicone tablet during 20 cycles and the particles were analyzed by an optical system. The BF was determined by a pressurized transducer placed between the upper and lower permanent first molars. The statistical tests were Student's t, Mann-Whitney, Fisher's Exact and Pearson's correlation. RESULTS: MP and BF were statistically smaller for SS group. Body variables did not show significant differences between groups. There was no correlation among the variables within each group demonstrating that MP was independent on the BF, as well as BF and MP were independent on the body variables. There was no difference in the proportion on occlusal characteristics between groups. Overbite was significantly larger for SS group. CONCLUSIONS: It is possible to infer that signs and symptoms of TMD can interfere in the proper masticatory function and muscle strength in children.

Relationship among dental plaque composition, daily sugar exposure and caries in the primary dentition.

The relationship among daily sugar exposure, dental plaque composition and caries patterns in the primary dentition is not known. Three groups of 20 children (18-48 months old) were studied: (1) caries-free (CF), (2) presenting pit and fissure caries (PFC), and (3) with nursing caries (NC). Dental caries index (dmfs) was assessed and the frequency of daily sugar exposure (TS) and its forms were estimated by questionnaires. Fluoride (F), calcium (Ca), inorganic phosphorus (P(i)), insoluble polysaccharide (IP) and mutans streptococci were quantified in dental plaque. The three groups of children were statistically different regarding daily sugar exposure. Concentrations of F, Ca and P(i) were lower and the IP and mutans streptococci statistically higher in dental plaque from NC children than those from CF children. PFC children also showed statistically lower F and P levels in their plaque than CF children. Statistically significant correlations were found between IP, TS and dmfs from NC and PFC children. A statistically significant correlation between mutans streptococci in plaque from anterior teeth and dmfs for NC children was also observed. These results suggest that the dietary sugar experience changes the biochemical and microbiological composition of dental plaque, which could partly explain the different caries patterns observed in primary dentition.