Conventional bicortical pin substitution with a novel unicortical pin in external fixation: A biomechanical study.

INTRODUCTION: As most patients with polytrauma or open fractures are converted from temporary external fixation to definite stabilization, the prevention of complications such as infection is especially important. To overcome the high risk of infection associated with the use of the conventional bicortical pin for temporary external fixation, the authors developed a novel unicortical pin and analyzed it in a biomechanical study. METHODS: The unicortical pin consisted of an inner screw, purchasing the cortical bone, and an outer sleeve with 6 spikes. A bicortical pin was used for the purpose of comparison. A fracture gap model was stabilized using a monoplanar configuration. Both the unicortical pins (Uni group) and bicortical pins (Bi group) underwent axial compressive and torsional load testing using a servo-hydraulic testing machine. Stiffness, load to failure, and mode of failure were documented. RESULTS: Stiffness and load to failure of the Uni group (average, 40.5 N/mm and 1098.4 N, respectively) were greater than that of the Bi group (average, 33.7 N/mm and 968.6 N, respectively) in the axial compressive load test (P = 0.008 and 0.032). Stiffness and load to failure of the Uni group (average, 1.2 Nm/degree and 1.7 Nm, respectively) were also significantly higher than those of the Bi group (average, 0.8 Nm/degree and 0.6 Nm, respectively) in the torsional load test (P = 0.008 and 0.016). All pins in the Bi group were bent at the pin-synthetic bone interface without synthetic bone failure. Contrarily, the Uni group did not show any pin bending or failure. However, in the axial compression test, partial cracks in the synthetic bone were found at the interface with spikes in the outer shell. In addition, in the torsion test, incomplete fractures were seen through the inner screws' holes. CONCLUSION: Compared with the conventional bicortical pin, the newly designed unicortical pin significantly increased fracture stability under both axial compressive and torsional loads. The unicortical pin can be considered an alternative biomechanical solution to obtain adequate stability when performing external fixation of fractures.

Effect of Indocyanine Green and Infrared Diode Laser to Streptococcus mutans Biofilms.

Objective: The aim of this study was to quantitatively and qualitatively evaluate the effects of the indocyanine green (ICG)-near-infrared (NIR) photoreaction on Streptococcus mutans biofilms. Background: ICG recently emerged as a photosensitive agent for photodynamic therapy. Although the effects of ICG-NIR on S. mutans inhibition are documented, little is known about its influence on biofilms, which are resistant to antimicrobial treatment and a major cause of plaque that leads to dental caries. Methods: ICG was used as a photosensitizer with a diode laser irradiated in a rectangular shape (810 nm, 300 mW) as a light source on S. mutans ATCC 25175 biofilms. Viability was determined by the colony forming unit (CFU) count and confocal laser-scanning microscopy. The biofilm surface temperature was measured with a one-channel thermocouple thermometer. Results: ICG and NIR diode laser significantly decreased the CFU count of S. mutans compared with the control group in a time-dependent manner. When irradiated with light after ICG application, temperature changes of 8.4°C, 12.4°C, and 14.9°C were observed with 10, 30, and 60 sec of irradiation, respectively. Conclusions: The ICG-NIR diode laser photoreaction can inhibit S. mutans biofilms, especially at 60 sec. An optimized protocol is needed for clinical application of ICG-NIR diode laser treatment.

Effect of Photodynamic Therapy on Multispecies Biofilms, Including Streptococcus mutans, Lactobacillus casei, and Candida albicans.

Objective: The aim of this study was to evaluate the effect of photodynamic therapy (PDT) on multispecies oral caries biofilms composed of Streptococcus mutans, Lactobacillus casei, and Candida albicans. Background: The abovementioned microorganisms largely cause dental caries, especially early childhood caries (ECC), by synthesizing of acids in the presence of sugar. PDT is considered an effective process to remove oral biofilms, and erythrosine, an oral bacterial disclosing agent, is an ideal dye that can be used as a photosensitizer in PDT. However, until now, there are no studies that have reported the effect of erythrosine-mediated PDT on biofilms, including the three microorganisms. Methods: The biofilms were formed on hydroxyapatite discs, and erythrosine was used as the photosensitizer, diluted to a concentration of 40 µM for 3 min. Light was irradiated for 10 and 20 sec using a blue light-emitting diode dental curing light. After the experiment, the colony-forming units of each microbial group cultured on blood agar plates were counted, and a confocal laser-scanning microscope was used to evaluate the effect of PDT. Results: The counts of all three microorganisms significantly decreased in the PDT group compared with those in the control group. For S. mutans and L. casei, there was a larger decrease proportional to the amount of energy irradiated. Conclusions: Overall, PDT showed a significant antimicrobial effect against oral biofilms composed of the three microorganisms, suggesting its potential clinical application for infants with ECC.

Effect of various polishing burs on surface roughness and bacterial adhesion in pediatric zirconia crowns.

To evaluate the effect of various polishing points on surface roughness of pediatric zirconia crowns and to correlate findings with bacterial adhesion. Zirconia discs (n=40) were fabricated and divided into five groups according to point type used to roughen and polish: I (negative control [not roughened]); II (positive control [roughened]); and III-V, representing three commercially available point brands. Atomic force and scanning electron microscopy were used to assess surface roughness. The number of colony forming units were counted after biofilm formation. A statistically significant difference was found in surface roughness and bacterial adhesion between the positive control and the other four groups, with no difference between negative control and the three point groups. Surface roughness and bacterial adhesion were significantly and positively correlated. Surface roughness and bacterial adhesion in pediatric zirconia crowns were not significantly different from other materials regardless of polishing system.

Antimicrobial activity of isothiocyanates (ITCs) extracted from horseradish (Armoracia rusticana) root against oral microorganisms.

The antimicrobial activity of isothiocyanates (ITCs) extracted from horseradish root was investigated against oral microorganisms: 6 strains of facultative anaerobic bacteria, Streptococcus mutans, Streptococcus sobrinus, Lactobacillus casei, Staphylococcus aureus, Enterococcus faecalis and Aggregatibacter actinomycetemcomitans; one strain of yeast, Candida albicans, and 3 strains of anaerobic bacteria, Fusobacterium nucleatum, Prevotella nigrescens, and Clostridium perfringens. The ITCs extracted from horseradish root showed antimicrobial activity against all oral microorganisms by the paper disk method. The minimum bactericidal concentration (MBC) of the ITCs extracted from horseradish root ranged from 1.25 to 5.00 mg/ml against 6 strains of facultative anaerobic bacteria and one strain of yeast, and 4.17 to 16.67 mg/ml against 3 strains of anaerobic bacteria. The ITCs extracted from horseradish root showed the strongest antimicrobial activity, with a MBC of 1.25 mg/ml, against C. albicans among facultative microorganisms, and 4.17 mg/ml against F. nucleatum among anaerobic bacteria. These results suggest that the ITCs extracted from horseradish root may be a candidate for use as an antimicrobial agent against oral microorganisms.

The photodynamic therapy on Streptococcus mutans biofilms using erythrosine and dental halogen curing unit.

The purpose of our study was to evaluate the effect of photodynamic therapy (PDT), using erythrosine as a photosensitizing agent and a dental halogen curing unit as a light source, on Streptococcus mutans in a biofilm phase. The S. mutans biofilms were formed in a 24-well cell culture cluster. Test groups consisted of biofilms divided into four groups: group 1: no photosensitizer or light irradiation treatment (control group); group 2: photosensitizer treatment alone; group 3: light irradiation alone; group 4: photosensitizer treatment and light irradiation. After treatments, the numbers of colony-forming unit (CFU) were counted and samples were examined by confocal laser scanning fluorescence microscopy (CLSM). Only group 4 (combined treatment) resulted in significant increases in cell death, with rates of 75% and 55% after 8 h of incubation, and 74% and 42% at 12 h, for biofilms formed in brain-heart infusion (BHI) broth supplemented with 0% or 0.1% sucrose, respectively. Therefore, PDT of S. mutans biofilms using a combination of erythrosine and a dental halogen curing unit, both widely used in dental clinics, resulted in a significant increase in cell death. The PDT effects are decreased in biofilms that form in the presence of sucrose.

Quantitative localization of impacted mesiodens using panoramic and periapical radiographs.

PURPOSE: The purpose of this study was to evaluate a new technique for localizing impacted mesiodens using its horizontal magnification ratio on panoramic radiographs. MATERIALS AND METHODS: Location-magnification equation of a panoramic equipment was obtained from horizontal magnification ratio of a metal ball which was located variable positions from the center of image layer at interval of 2 mm. Panoramic radiographs were obtained from a skull phantom with a metal ball which was a substitute for impacted mesiodens and was embedded 10mm(Group 1), 15mm(Group 2), and 20mm(Group 3) posterior to the central incisor. Each group obtained 7 panoramic radiographs at variable positions and one periapical radiograph. Three methods were used to estimate the actual width of the incisors and the balls which were used to calculate the magnification ratio. The methods included using the actual incisor width and the calculated ball width (Method 1), using the actual incisor width and the ball widths measured on periapical radiograph (Method 2), and using the incisor and the ball widths measured on periapical radiograph (Method 3). The location of the metal ball was calculated by using the location-magnification equation. RESULTS: The smallest difference between the calculated and the actual distance was 0.1±0.7 mm in Group 1/Method 3. The largest difference was -4.2±1.6 mm in Group 3/Method 2. In all groups, method 3 was the most accurate. CONCLUSION: Quantitative localization of impacted mesiodens is possible by using panoramic radiograph.