Oral bacterial decontamination using an innovative prototype for photocatalytic disinfection.

OBJECTIVES: The aim of this study was to evaluate the effectiveness of a prototype photocatalytic device for bacterial decontaminations of the oral cavity. METHODS: Sixty-four subjects (18-65) were selected and randomly assigned to eight groups (n = 8), according to oral disinfection protocol: (G1): distilled water (control); (G2): 1.5% hydrogen peroxide (HP); (G3): 3.0% HP; (G4): 0.12% chlorhexidine (CHX); (G5): Germinator; (G6): 1.5% HP + Germinator; (G7): 3.0%HP + Germinator; (G8): 0.12% CHX + Germinator. Stimulated saliva was collected before and after a 3-min mouthwash and/or Germinator application. The patients were kept relaxed and retained saliva 5-10 min, spitting out into the tube for 3 min. The percentage bacterial reduction was checked by counting the colony-forming units (CFUs) after culturing on blood agar plates. Data were subjected to one-way ANOVA followed by Tukey's post hoc test (α = 5%) for statistical significance. RESULTS: The highest bacterial reduction was observed in groups 3 (3.0% HP), 6 (1.5% HP + Germinator), and 7 (3.0% + Germinator), with no statistically significant difference between them (p > 0.05). Groups 6 (1.5% HP + Germinator) and 8 (0.12% CHX + Germinator) showed higher bacterial reduction than groups 2 (1.5% HP) and 4 (0.12% CHX) (p < 0.05). Finally, group 5 (Germinator) showed higher bacterial reduction than control group (DW) and group 4 (0.12% CHX) (p < 0.05). CONCLUSIONS: The photocatalytic disinfection was effective against oral bacteria and improved the antimicrobial action of 1.5% HP and 0.12%. CLINICAL SIGNIFICANCE: The photocatalytic disinfection can be an alternative protocol to provide the oral decontamination.

Residual stresses explaining clinical fractures of bilayer zirconia and lithium disilicate crowns: A VFEM study.

OBJECTIVE: To understand the stress development in porcelain-veneered zirconia (PVZ) and porcelain-veneered lithium disilicate (PVLD) crowns with different veneer/core thickness ratios and cooling rates. To provide design guidelines for better performing bilayer restorations with the aid of Viscoelastic Finite Element Method (VFEM). METHODS: The VFEM was validated by comparing the predicted residual stresses with experimental measurements. Then, the model was used to predict transient and residual stresses in the two bilayer systems. Models with two different veneer/core thickness ratios were prepared (2:1 and 1:1) and two cooling protocols were simulated (Fast: ∼300 °C/min, Slow: ∼30 °C/min) using the heat transfer module, followed by stress analysis in ABAQUS. The physical properties of zirconia, lithium disilicate, and the porcelains used for the simulations were determined as a function of temperature. RESULTS: PVLD showed lower residual stresses than PVZ. The maximum tensile stresses in PVZ were observed in the cusp area, whereas those in PVLD were located in the central fossa. The 1:1 thickness ratio decreased stresses in both layers of PVZ. Slow cooling slightly decreased residual stresses in both systems. However, the cooling rate effect was more evident in transient stresses. SIGNIFICANCE: Slow cooling is preferable for both systems. A thinner porcelain layer over zirconia lowers stresses throughout the restoration. The different stress distributions between PVZ and PVLD may affect their failure modes. Smaller mismatches in modulus, CTE, and specific heat between the constituents, and the use of low Tg porcelains can effectively reduce the deleterious transient and residual tensile stresses in bilayer restorations.

Experimental and finite element study of residual thermal stresses in veneered Y-TZP structures.

The main complications of zirconia-based laminated systems are chipping and delamination of veneering porcelain, which has been found to be directly associated with the development of residual thermal stresses in the porcelain layer. This study investigates the effects of cooling rate and specimen geometry on the residual stress states in porcelain-veneered zirconia structures. Bilayers of three different shapes (bars, semi-cylindrical shells, and arch-cubic structures) with 1.5 mm and 0.7 mm thickness of dentin porcelain and zirconia framework, respectively, were subjected to two cooling protocols: slow cooling (SC) at 32 °C/min and extremely-slow cooling (XSC) at 2 °C/min. The residual thermal stresses were determined using the Vickers indentation method and validated by finite element analysis. The residual stress profiles were similar among geometries in the same cooling protocol. XSC groups presented significantly higher tensile stresses (p = 0.000), especially for curved interfaces. XSC is a time-consuming process that showed no beneficial effect regarding residual stresses compared to the manufacturer recommended slow cooling rate.

Nationwide 2.5-Year School-Based Public Health Intervention Program Designed to Reduce the Incidence of Caries in Children of Grenada.

UNLABELLED: This paper describes an innovative public health intervention, called 'Smile Grenada', targeting the oral health of children in Grenada utilizing the resources of a US dental school, several oral health care companies, local governmental and public health authorities, and Grenadian school personnel. METHODS: Preintervention visual/tactile caries examinations were collected from 1,092 schoolchildren (mean age 9.9 years, standard deviation, SD = 3.7) in 2010. The intervention included: (1) classroom-based toothbrushing with fluoridated toothpaste, (2) fluoride varnish applied by trained dental students, teachers and local providers 3 times a year and (3) glass ionomer sealants placed on first permanent molars in children aged 6-8 years. Postintervention data were collected in May, 2013 (n = 2,301, mean age 9.8 years, SD = 3.7). Decayed and demineralized surfaces were examined for the whole sample and decay/demineralization and sealant retention on 6-year molars were examined separately (ages 6-8 in 2013 cohort). RESULTS: The number of decayed/demineralized surfaces declined across all age groups. The average number of decayed surfaces dropped from 9 at baseline to just over 6 (F1, 3,393 = 69.8, p < 0.0001) and the average number of demineralized surfaces dropped from 6 to less than 2 (1.8 surfaces; F1, 3,393 = 819.0, p < 0.0001). For children aged 6-8 years, there were statistically significantly fewer decayed surfaces (t1, 2,086 = 12.40, p < 0.0001; mean baseline 0.93, SD = 1.75; mean follow-up 0.23, SD = 0.83) and demineralized surfaces (t1, 2,086 = 19.7, p < 0.0001; mean baseline 2.11, SD = 2.74; mean follow-up 0.50, SD = 0.97) on 6-year molars. The Smile Grenada program successfully demonstrated a locally sustainable model for improving oral health in children in a developing country.

The cariogenic dental biofilm: good, bad or just something to control?

This paper discusses the role of dental biofilm and adjunctive therapies in the management of dental caries. Dental biofilm is a site of bacterial proliferation and growth, in addition to being a location of acid production. It also serves as a reservoir for calcium exchange between the tooth and saliva. The salivary pellicle, a protein-rich biofilm layer, regulates the reaction between tooth surface, saliva and erosive acids. The protective effects of this pellicle on enamel are well established. However, understanding the effects of the pellicle/biofilm interaction in protecting dentin from erosive conditions requires further research. Saliva interacts with the biofilm, and is important in reducing the cariogenic effects of dental plaque as acidogenic bacteria consume fermentable carbohydrates producing acids that may result in tooth demineralization. Adequate supplies of healthy saliva can provide ingredients for successful remineralization. Strategies for managing the cariogenic biofilm are discussed with emphasis on the effectiveness of over-the-counter (OTC) products. However, since many toothpaste components have been altered recently, new clinical trials may be required for true validation of product effectiveness. A new generation of calcium-based remineralizing technologies may offer the ability to reverse the effects of demineralization. Nevertheless, remineralization is a microscopic subsurface phenomenon, and it will not macroscopically replace tooth structure lost in a cavitated lesion. Optimal management of cavitations requires early detection. This, coupled with advances in adhesive restorative materials and microsurgical technique, will allow the tooth to be restored with minimal destruction to nearby healthy tissue.

The cariogenic dental biofilm: good, bad or just something to control?

This paper discusses the role of dental biofilm and adjunctive therapies in the management of dental caries. Dental biofilm is a site of bacterial proliferation and growth, in addition to being a location of acid production. It also serves as a reservoir for calcium exchange between the tooth and saliva. The salivary pellicle, a protein-rich biofilm layer, regulates the reaction between tooth surface, saliva and erosive acids. The protective effects of this pellicle on enamel are well established. However, understanding the effects of the pellicle/biofilm interaction in protecting dentin from erosive conditions requires further research. Saliva interacts with the biofilm, and is important in reducing the cariogenic effects of dental plaque as acidogenic bacteria consume fermentable carbohydrates producing acids that may result in tooth demineralization. Adequate supplies of healthy saliva can provide ingredients for successful remineralization. Strategies for managing the cariogenic biofilm are discussed with emphasis on the effectiveness of over-the-counter (OTC) products. However, since many toothpaste components have been altered recently, new clinical trials may be required for true validation of product effectiveness. A new generation of calcium-based remineralizing technologies may offer the ability to reverse the effects of demineralization. Nevertheless, remineralization is a microscopic subsurface phenomenon, and it will not macroscopically replace tooth structure lost in a cavitated lesion. Optimal management of cavitations requires early detection. This, coupled with advances in adhesive restorative materials and microsurgical technique, will allow the tooth to be restored with minimal destruction to nearby healthy tissue.

Clinical evaluation of the ability of CaviStat in a mint confection to inhibit the development of dental caries in children.

OBJECTIVE: The aim of the present study was to determine if a sugarless mint containing CaviStat (an arginine bicarbonate calcium carbonate complex) is capable of preventing the development of dental caries in the primary molars and first permanent molars of 10 1/2- to 11-year-old Venezuelan children. METHODS: Two-hundred children were entered into this one-year study who showed the following: (i) age between 10 1/2 and 11 years; (ii) first and second primary molars still present; (iii) sound primary molars or early caries lesions in any of these teeth; and (iv) at least some caries in the primary or permanent teeth as evidence of caries activity. Out of the 200 children initially selected, 195 finished and provided complete data. Children entered into the study were examined and then randomly divided into two groups (A and B), with distribution performed on the basis of the DMFS levels of the first permanent molars. All subjects were examined visually by a single examiner using good artificial light, mirror, and probe. Group A received a sugarless confection containing CaviStat (BasicMints); Group B received a sugarless mint control that contained all ingredients except for the CaviStat. Packaging and appearance of both types of mints were identical, except for their A and B designations. RESULTS: Mean differences in DMFS, defs, and DMFS + defs scores between Groups A and B were determined. In the first permanent molars and some early erupting premolars and second molars, the data showed 75.6% fewer caries in Group A than in Group B children after six months, and 50.7% fewer after 12 months. Corresponding defs scores showed reduced development of dental caries in deciduous molars of 76.7% after six months and 131.3% after 12 months. Combined DMFS and defs scores showed 76.2 and 74.8% fewer caries lesions at six and 12 months, respectively. As exfoliation of primary molars occurred during the study period (approximately equal in the two groups), a proportion correction was made to allow for caries score reductions due to lesions lost because of such exfoliation. When this was done, the results at the end of the study still showed larger caries reductions in Group A than in the Group B subjects, and statistical analyses showed these differences were still highly significant (p < 0.001). Noncavitated caries lesions in the first permanent molars were also determined. These showed once again less caries development in Group A than in Group B subjects, and did so at both six and twelve months (57.0 and 52.4%, respectively). Levels of statistical significance at these times were p = 0.013 and 0.005. CONCLUSION: It was evident from this clinical trial that mint confections containing CaviStat are able to inhibit both caries onset and caries progression. As a result, one can conclude that CaviStat mint confection technology is a simple and economical means for reducing substantially one of the most prevalent diseases in these children.

The inhibitory effect of an arginine bicarbonate/calcium carbonate CaviStat-containing dentifrice on the development of dental caries in Venezuelan school children.

OBJECTIVE: This study assessed the effect of an arginine bicarbonate/calcium carbonate (CaviStat)-containing dentifrice on caries development, mainly in 11- to 12-year-old Venezuelan children over a two-year period. METHODOLOGY: Children (726) with a DMFT between 3 and 6 were examined at baseline, six months, and one and two years using a mirror, probe, and DMFS scoring. Subjects who completed the study consisted of two groups; 304 test and 297 control. The test group received a CaviStat-containing dentifrice, and the controls used a commercially available 1100 ppm fluoride toothpaste. All subjects were instructed to brush three times a day for 1 minute followed by swishing for 30 seconds. RESULTS: After six months, the mean DMFS scores increased only slightly from baseline in both groups, 6.93 +/- 0.22 in the control and 6.59 +/- 0.22 in the test subjects. After one year, the mean DMFS score in the control group rose to 8.00 +/- 0.24 and leveled off at 7.92 +/- 0.30 at two years. In contrast, the mean DMFS score in the test group decreased to 5.50 +/- 0.24 after one year before rising to 6.99 +/- 0.28 at two years. DMFS difference between the two groups was highly significant (p < 0.001), but mainly due to the large difference seen at one year. Dissection of the data showed that the erupted first molars dominated the overall DMFS changes. At the beginning of this study, first molar scores started at high values and showed a pattern thereafter like that seen for the total data. In contrast, premolars/molars, which erupt 4-6 years later (and at the start of the study had a mean DMFS score slightly above zero), showed a clear rise in the DMFS score in the control group during the first year of the study, which continued to rise until the end of the investigation. In contrast, the CaviStat group showed no change in the premolar/second molar DMFS score from baseline during the first year (giving the impression of 100% inhibition at one year), but showed a delayed rise thereafter that paralleled that seen in the controls between one and two years (58.3% inhibition at two years). Reversal of the development of early dental caries lesions in the CaviStat subjects and limitations of the diagnosis of very early caries lesions with standard dental explorers was suggested for the interesting first molar, first year data. Inhibition of caries initiation and caries progression in the CaviStat group was also observed and easier to see in the premolar/second molar, second year data where the DMFS scores were very low at baseline and reversals are not a significant issue. The results were subjected to statistical analysis including analysis of covariance. Largely because of the first year and first molar data, the difference between control and experimental groups was highly significant (p < 0.001). Similar comparison with the later-erupting premolar/molar teeth showed the CaviStat effect was also significant but at a lower level (p < 0.05). The differences could not be due to examiner error since the Kappa for 10% of the subjects randomly selected and re-examined was 0.898 overall and 0.914 for the first molar data. The data also suggested CaviStat inhibition of caries progression because of a slower rate of rise of missing+filled teeth in the CaviStat vs. the control group (p < 0.05). CONCLUSION: A CaviStat-containing toothpaste was more effective both clinically and statistically in inhibiting caries initiation and progression than the fluoride toothpaste control, and manifested its effects differently in the already-erupted first molars than in the later-erupting premolars and second molars.