Bacterial, fungal and yeast contamination in six brands of irreversible hydrocolloid impression materials

This study assessed the level of contamination of six commercially available irreversible hydrocolloids (two containing chlorhexidine) and identified the contamination present in the materials. Petri dishes containing selective and enriched culture media were inoculated with alginate powder (0.06 g), in triplicate. After incubation (37 degrees C/7 days), the colony-forming units (CFU) were counted and Gram stained. Biochemical identification of the different morphotypes was also performed. The contamination levels for the materials were: Jeltrate--389 CFU/g; Jeltrate Plus--516 CFU/g; Jeltrate Chromatic--135 CFU/g; Hydrogum--1,455 CFU/g; Kromopan--840 CFU/g; and Greengel--59 CFU/g. Gram staining revealed the presence of Gram-positive bacillus and Gram-positive cocci. The bacteria Staphylococcus epidermidis, Bacillus subtilis, Bacillus sp., Bacillus coagulans, Bacillus licheniformis, Bacillus cereus, Micrococcus luteus, and Nocardia sp.; the filamentous fungi Aspergillus niger, Aspergillus flavus, Rhizopus sp., Neurospora sp.; and the yeast Candida sp. were isolated. The contamination detected in the impression materials points out the need for adopting measures to improve the microbiological quality of these materials. The use of contaminated materials in the oral cavity goes against the basic principles for controlling cross-contamination and may represent a risk for debilitated or immunocompromised patients.

In vitro osteogenesis on a highly bioactive glass-ceramic (Biosilicate®)

One of the strategies to improve the mechanical performance of bioactive glasses for load-bearing implant devices has been the development of glass-ceramic materials. The present study aimed to evaluate the effect of a highly bioactive, fully-crystallized glass-ceramic (Biosilicate) of the system P(2)O(5)-Na(2)O-CaO-SiO(2) on various key parameters of in vitro osteogenesis. Surface characterization was carried out by scanning electron microscopy and Fourier transform infrared spectroscopy. Osteogenic cells were obtained by enzymatic digestion of newborn rat calvarial bone and by growing on Biosilicate discs and on control bioactive glass surfaces (Biosilicate) parent glass and Bioglass(R) 45S5) for periods of up to 17 days. All materials developed an apatite layer in simulated body fluid for 24h. Additionally, as early as 12 h under culture conditions and in the absence of cells, all surfaces developed a layer of silica-gel that was gradually covered by amorphous calcium phosphate deposits, which remained amorphous up to 72 h. During the proliferative phase of osteogenic cultures, the majority of cells exhibited disassembly of the actin cytoskeleton, whereas reassembly of actin stress fibers took place only in areas of cell multilayering by day 5. Although no significant differences were detected in terms of total protein content and alkaline phosphatase activity at days 11 and 17, Biosilicate supported significantly larger areas of calcified matrix at day 17. The results indicate that full crystallization of bioactive glasses in a range of compositions of the system P(2)O(5)-Na(2)O-CaO-SiO(2) may promote enhancement of in vitro bone-like tissue formation in an osteogenic cell culture system.

Dental plaque removal efficacy of three toothbrushes with different designs: A comparative analysis

PURPOSE

This study aimed to compare dental plaque removal efficacy of three manual toothbrushes.

MATERIALS AND METHODS

Three toothbrushes (Colgate Flexível - Colgate (T1), Oral B Advantage Control Grip - Oral B (T2), Comfort Clean - Johnson & Johnson - Reach (T3) were evaluated for dental plaque removal in 17 subjects. Dental plaque was scored before and after seven days' use of each toothbrush, employing an adaptation of Quigley-Hein Index modified by Turesky (Plaque Index). Assessments were performed at days 0, 7, 14, 21, 28, and 35. At the end of the trial each subject was asked which toothbrush was preferred.

RESULTS

Final dental plaque scores for toothbrush T3 were statistically different from toothbrushes T1 and T2, which in turn did not differ from each other. Subjects showed preference towards toothbrush T3.

CONCLUSION

Toothbrush T3 was more efficient in terms of dental plaque removal when compared with toothbrushes T2 and T1.

Surface roughness of a dental ceramic after polishing with different vehicles and diamond pastes

During fabrication of bonded ceramic restorations, cervical adaptation, occlusal adjustment and final finishing/polishing are procedures to be performed at the dental office after adhesive cementation. Final adjustments may result in loss of ceramic glaze, which requires new polishing of the ceramic surface, with special attention for selection of adequate materials and instruments. The purpose of this study was to evaluate the efficiency of different vehicles associated with diamond pastes indicated for dental ceramic polishing. Two polishing pastes (Crystar Paste and Diamond Excell) associated with four vehicles (rubber cup, Robinson bristle brush, felt wheel and buff disc) were evaluated. Disc-shaped specimens were fabricated from Ceramco II dental ceramic. Surface roughness means (Ra) of the ceramic specimens were determined with a rugosimeter. Data were analyzed statistically by two-way ANOVA and Tukey's test at 5% significance level. There was no statistically significant difference (p>0.01) between the polishing pastes. However, there were statistically significant differences (p<0.01) among the tested vehicles. Vehicle-paste interaction showed statistically significant difference (p<0.05) as well. It may be concluded that: 1) Robinson bristle brush, felt wheel and buff disc were efficient vehicles to be used in association with a diamond polishing paste; 2) The use of rubber cup as a vehicle showed poor efficiency for mechanical polishing of the ceramic surfaces; 3) Both pastes provided similar and efficient polishing and may be recommended for use with an appropriated vehicle.

Bond strength of three dental porcelains to Ni-Cr and Co-Cr-Ti alloys

Ceramometal bond strength has played an important role for the replacement of gold alloys by nickel-chromium alloys in dentistry. This study evaluated the metal/porcelain bond strength of three ceramic systems (Vita VMK 88, Williams and Duceram) associated with three nickel-chromium alloys (Durabond, Lite Cast B and Resistal P) and one experimental cobalt-chromium-titanium alloy. Thirty cast cylinder specimens (15 mm in height; 6 mm in diameter) were obtained for each alloy, in away that 10 specimens of each alloy were tested with each porcelain. Bond strength was measured with an Emic screw-driven mechanical testing machine by applying parallel shear forces to the specimens until fracture. Kruskal-Wallis and Mann-Whitney U tests were used for statistical analysis of the alloy/ceramic combinations (p<0.05). Resistal P/Duceram had significantly higher bond strength (44.38±9.12 MPa) (p<0.05) than the other combinations, except for Co-Cr-Ti alloy/Vita VMK 88 (38.41±12.64 MPa). The association of the experimental Co-Cr-Ti alloy with Williams porcelain had significantly higher bond strength (28.20±3.86 MPa) than the combination of other alloys with the same porcelain (p<0.05). Based of these results and within the limitations of an in vitro study, it may be concluded that the bond strength of the three ceramic systems to the Ni-Cr and Co-Cr-Ti alloys varied significantly, indicating that metal/ceramic compatibility was very important to the bond strength.

Permeability of remaining endodontic obturation after post preparation

This study assessed the correlation between leakage from the cervix to the apex and from the apex to the cervix for different post preparation techniques. Sixty roots were obturated with gutta-percha lateral condensation and AH Plus sealer and divided into two groups of 30 roots each. Immediate post preparation was used for one group and delayed preparation was used for the other. Two subgroups of 15 roots each were formed to investigate leakage from cervix-to-apex and from apex-to-cervix. The extent of leakage was determined using a dye, India ink, and a clearing technique that rendered the teeth transparent. Linear measurement of the dye penetration was recorded and examined with a stereomicroscope. Eight teeth were used as positive and negative controls. Leakage was observed in all samples. No statistically significant differences were found between the immediate and delayed post preparation techniques regarding apex-to-cervix leakage; however, the values of cervix-to-apex leakage were significantly lower for the immediate technique than for the delayed technique.

Shear bond strength of dental porcelains to nickel-chromium alloys

The continuous technological advance and increasing availability of new base metal alloys and ceramic systems in the market, coupled to the demands of daily clinical practice, have made the constant evaluation of the bond strength of metal/porcelain combinations necessary. This study evaluated the metal/porcelain shear bond strength of three ceramic systems (Duceram, Williams and Noritake) in combination with three nickel-chromium (Ni-Cr) alloys (Durabond, Verabond and Viron). Thirty cast cylinder specimens (15 mm high; 6 mm in diameter) were obtained for each alloy, in a way that 10 specimens of each alloy were tested with each porcelain. Bond strength was measured with an Emic screw-driven mechanical testing machine by applying parallel shear forces to the specimens until fracture. Shear strength was calculated using the ratio of the force applied to a demarcated area of the opaque layer. Mann-Whitney U test was used for statistical analysis of the alloy/ceramic combinations (p<0.05). Viron/Noritake had the highest shear bond sregnth means (32.93 MPa), while Verabond/Duceram (16.31 MPa) presented the lowest means. Viron/Noritake differed statistically from other combinations (p<0.05). Viron/Duceram had statistically significant higher bond strengths than Verabond/Duceram, Verabond/Williams and Durabond/Noritake (p<0.05). It was also found significant difference (p<0.05) between Verabond/Noritake, Verabond/Duceram and Durabond/Noritake. No statistically significant difference (p>0.05) were observed among the other combinations. In conclusion, the Noritake ceramic system used together with Viron alloy presented the highest resistance to shear forces, while Duceram bonded to Verabond presented the lowest bond strength. Viron/Duceram and Verabond/Noritake provided intermediate results. The combinations between the Williams ceramic system and Ni-Cr alloys had similar shear strengths among each other.

Antimicrobial spray for toothbrush disinfection: an in vivo evaluation

OBJECTIVE

The aim of this study was to evaluate the efficacy of a spray containing an antimicrobial solution for toothbrush disinfection.

METHODS AND MATERIALS

Three different solutions were sprayed on toothbrush bristles among 30 adults after they had brushed: (1) basic formulation (base) plus chlorhexidine; (2) base only, and (3) sterile tap water (control). Each solution was tested for 1 week. After that, the toothbrushes were collected and sonicated in Letheen Broth, diluted in 10-fold series, and plated on selective and nonselective media for detection of anaerobes, aerobes, streptococci, and gram-negative bacilli. After incubation, the colonies of those microorganisms were counted. Presence of mutans streptococci on the bristles was also confirmed.

RESULTS

Spray 1 produced a significant reduction in the microbial contamination of toothbrushes for all the microorganisms, spray 2 provided some reduction of contaminants, and spray 3 demonstrated the least antimicrobial effect.

CONCLUSION

The antimicrobial spray with chlorhexidine proved to be an effective and practical means for toothbrush disinfection.

Comparison of two cleansing pastes for the removal of biofilm from dentures and palatal lesions in patients with atrophic chronic candidiasis

The efficacy of 2 oral hygiene products, an experimental toothpaste specific for complete denture cleansing and a regular standard toothpaste, was compared in terms of denture biofilm removal and cure of palatal lesions in patients with atrophic chronic candidiasis. The degree of correlation between presence of biofilm and mucosa erythema was also evaluated. Twenty-four complete denture wearers (45-80 years old) were divided into 2 groups: experimental paste and standard toothpaste (Sorriso-Kolynos, Brazil). Both groups received soft toothbrushes. The internal surfaces of upper dentures were stained using 1% sodium fluorescein and photographed at a 45 masculine angle at 0, 15, 30 and 60 days. The slides were scanned and the areas of interest (denture total area and biofilm area) were measured (Image Tool software). The degree of erythema was evaluated on slides according to the Prosthesis Tissue Index. There was a significant reduction (1%) in the degree of biofilm (ANOVA/Tukey) between the two initial visits (0 and 15 days) and the two final visits (30 and 60 days), and in the average erythema scores (Kruskal-Wallis) between 0 and 60 days, in both groups. The Mann-Whitney test showed a significant difference (1%) between pastes in terms of biofilm degree, but no difference was found for the erythema score. Correlation values between biofilm and erythema degree were 0.3801 (experimental paste) and (0.3678 (standard toothpaste). We may therefore conclude that the experimental product was efficient for the removal of denture plaque biofilm.

Tongue-cleaning methods: a comparative clinical trial employing a toothbrush and a tongue scraper

BACKGROUND

It is estimated that approximately 85% of all halitosis cases have their origin within the mouth; of these, 50% are caused by tongue residues. Previous studies have established that hydrogen sulfide and mercaptans are the primary components of halitosis. Thus, tongue cleaning gains importance as a means of halitosis management.

METHODS

This investigation compared the efficacy of two mechanical methods for tongue cleaning through a handheld sulfide monitor. This crossover trial was carried out with 10 healthy subjects, 20 to 50 years old. Before the baseline measurement of the volatile sulfur compounds (VSCs), the subjects were instructed to refrain from any tongue cleaning method for 48 hours. The 10 participants were then placed in one of two groups (five each): 1) first week: tongue scraper, second week: soft-bristle toothbrush; 2) first week: toothbrush, second week: tongue scraper, with a 48-hour wash-out period between each week.

RESULTS

The baseline measurements were compared with those of the end of each week using the Dunn method (alpha = 0.01). The tongue scraper showed a 75% reduction in VSCs, while the toothbrush only achieved a 45% reduction in VSCs.

CONCLUSION

Although the tongue coating was removed by both methods, the tongue scraper performed better in reducing the production of volatile sulfur compounds.

Assessing the surface roughness of a posterior resin composite: effect of surface sealing

This study assessed the in vitro influence of surface sealing on the surface roughness of a posterior resin composite before and after toothbrushing. Thirty specimens (13 mm diameter x 1 mm high) were fabricated from Filtek-P60 resin composite and randomly assigned to three groups (n = 10): a non-sealed control and two groups sealed with one of the tested materials-a surface-penetrating sealant (Protect-it!-PI) and a one bottle adhesive system (Single Bond-SB). The samples were subjected to a surface roughness reading to determine the initial roughness, then submitted to simulated toothbrushing with 35,600 cycles for 100 minutes. Specimens were then cleaned and a post-abrasion surface roughness reading accomplished. Means (microm), recorded before (B) and after (A) toothbrushing, and standard deviations were: Control--(B): 0.032 (+/- 0.005), (A): 0.054 (+/- 0.005); PI-(B): 0.034 (+/- 0.005), (A): 0.060 (+/- 0.034); SB (B): 0.031 (+/- 0.004), (A): 0.047 (+/- 0.007). Data were tabulated and submitted to two-way ANOVA. No statistically significant difference was observed when the control and experimental groups were compared. However, a significant difference (p < 0.05) was found between the measurements performed before and after toothbrushing. Based on these results, it may be concluded that using either a surface penetrating sealant or a one bottle adhesive system did not provide the optimization of superficial integrity. The use of a dentifrice and toothbrush resulted in significant alterations to the surface smoothness of the resin composite.

Tensile bond strength of a polymeric intra-buccal bioadhesive: the mucin role

The intra-bucal polymeric bioadhesive systems that can stay adhered to the oral soft tissues for drug programmed release, with the preventive and/or therapeutic purpose have been employed for large clinical situations. A system based on hydroxypropyl methyl cellulose/Carbopol 934TM/magnesium stearate (HPMC/Cp/StMg), was developed with the sodium fluoride as an active principle. This kind of system was evaluated according to its resistance to the removal by means of physical test of tensile strength. Swine buccal mucosa extracted immediately after animals' sacrifice was employed as a substrate for the physical trials to obtain 16 test bodies. Artificial saliva with or without mucin was used to involve the substrate/bioadhesive system sets during the trials. Artificial salivas viscosity were determined by means of Brookfield viscometer, and they showed 10.0 cP artificial saliva with mucin, and 7.5 cP artificial saliva without mucin. The tensile strength assays showed the following averages: 12.89 Pa for the group "artificial saliva with mucin", and 12.35 Pa for the group "without mucin". Statistical analysis showed no significant difference between the assays for both artificial salivas, and we can conclude that the variable mucin did not interfere with the bioadhesion process for the polymeric devices.

Capacity of denture plaque/biofilm removal and antimicrobial action of a new denture paste

The efficacy of a paste for complete dentures was analyzed in terms of denture plaque/biofilm removal and antimicrobial action against specific microorganisms by determination of colony forming units of mutans group streptococci and yeast from 120 full denture wearers with a healthy palatine mucosa. The patients were given a questionnaire to evaluate the experimental product in terms of important characteristics. The paste was widely accepted by the patients, and effective in denture plaque removal and antimicrobial action. The species of yeasts most frequently isolated were C. albicans, C. tropicalis and C. glabrata. We conclude that it is possible for complete denture wearers to keep their dentures clean with the regular use of a paste-like hygienic product.

[In vitro assessment of antibacterial activity of ozonized water against Staphylococcus aureus]

Staphylococcus aureus belongs to the normal flora of the skin, mucosa and nasopharynx of several animal species, including man, but it is also associated to illnesses such as abscesses, bacteremia, endocarditis and osteomyelitis, besides showing resistance to multiple drugs. The purpose of this paper was to evaluate the disinfecting ability of ozone when dissolved in water. Suspensions of Staphylococcus aureus with concentrations varying from 10(6) to 10(16) microorganisms/ml were prepared. One milliliter of each recently prepared suspension was added to 99 ml of distilled water (with or without previous ozonization) contained in a crystal reactor. Aliquots of 0.1 ml of this new suspension were taken at various time intervals and, then, serially diluted and inoculated on plaques. The data indicated that there was difference in the disinfecting effect when distilled water was used with and without previous ozonization.

Comparative study of the direct-lift and platinum foil techniques in the marginal discrepancy of collarless metal ceramic restorations

This study was carried out to evaluate the marginal discrepancy of collarless metal ceramic restorations, using a combination of three different techniques to manufacture the porcelain butt margin with two brands of body porcelain. Statistical analysis showed no significant difference between the techniques or brands of body porcelain used in this study.

Optical transmittance of reflecting wedges

This study quantified the light intensity transmitted by the reflecting wedges perpendicularly to the growth axis. The results demonstrated that the cervical wedges did reflect the light of 180 degrees and original light intensity diminished by 83.9%. The maximal light intensity transmitted to the resin by the wedge was less than 8% of that receiving direct exposure to the curing wand. Differential measurements made on points closely spaced along the sides of the wedge indicated a maximal intensity at approximately 2 mm from the base of the wedge.

[Emission microspectrometric study of the amalgam restoration-tooth interface]

Optical Emission Microspectroscopy was used to identify the corrosion products in the amalgam tooth interface with and without cavity varnish use in different times. The factor time determined new chemical elements in the older specimens. A major mercury concentration was found in the restoration interface which used cavity varnish, at the initial twenty-four hours. The first corrosion product had the tin in its composition, possibly from the degradation of 2 phase.

[Resistance and deformation of acrylic resin reinforced with cut and ground fiberglass. 3. Modus of elasticity]

With respect to the elasticity module, it was observed that the incorporation of fiberglass to acrylic resin makes the test bodies more rigid, decreasing their rupture lengthening. The presence of fibers confers on the material a greater capacity of elastic recovery.

[Resistance and deformation of acrylic resin reinforced with cut and ground fiberglass. 2. Rupture lengthening]

The rupture lengthening test demonstrated the addition of fiberglass to acrylic resin tends to make the test bodies more rigid, making them fracture with a shorter lengthening than unloaded resin. The greatest rigidity was observed with a 20% load.

[Resistance and deformation of acrylic resin reinforced with cut and ground fiberglass. 1. Rupture tension]

Traction trials were carried out on acrylic resin test bodies for denture frames reinforced with cut and ground fiberglass, to determine rupture tension. The results demonstrated that: 1--Cut fibers tend to increase the resistance of acrylic to traction forces, and the increase in load percentage of these fibers also increase resistance. 2--This increase was more marked when treatment with SILANE A 174 was combined with the use of cut fibers, at all concentrations tested.

[Quantitative evaluation of reflectance of some acrylic resins mixed with powdered enamel and/or natural quartz]

Autopolymerizing acrylic resins for temporary prothesis and crown veneering have been mixed with dental enamel and/or quartz in powder form in different percentages, to simulate optical properties of the tooth. The analysis of our measurements of apparent reflectance of those mixings show that is possible to approximate several of those values to the ones corresponding to natural tooth; being sufficient to follow the formulation given++ in this paper.