Passiri Nisalak

Type IV Dental Stone Incorporated with Antimicrobial Agents and its Physical Properties

Contamination of dental casts can occur via direct contact with impression materials that are contaminated by patients fluids. Thus, the development of dental stone with antimicrobial activity to reduce cross-contamination between patients and laboratory personnel is needed. This study aims to evaluate the influence of incorporation of disinfectants into type IV dental stone on its antimicrobial activities and physical properties such as setting time and dry compressive strength. Type IV dental stone incorporated with 4 types of disinfectants; Diamond Rock D (3-iodo-2-propynylbutylcarbamate), Diamond Rock B (zeolite), Diamond Rock Z (thiabendazole) and Diamond Rock T (2-benzimidazole carbamic acid), were tested in this study compared with the control, Diamond Rock O (type IV dental stone without disinfectant). Microorganisms tested were Staphylococcus aureus ATCC 6538, Pseudomonas aeruginosa ATCC 27853 and Candida albicans ATCC 1023. One hundred μL of each microbial suspension (108 CFU/mL) was dropped on hydrocolloid impression (Jeltrate; Caulk/Dentsply, Milford, DE) and left dry. All types of stone mixes were prepared and poured into the impressions and allowed to set for 60 min. Then the stone samples were removed and the microbial contact surfaces were imprinted on Brain Heart Infusion agar plates. After incubation, colonies appeared on agar were gram-stained and counted. The setting time and dry compressive strength were tested in accordance with International Standard (ISO) 6873: 1998 (E). Dental stone incorporated with 4 types of disinfectants showed antimicrobial activity against all tested microorganisms with the percentage of microbial reduction ranging from 83% to 100%. Among all types of dental stone, no significant difference in setting time was observed. In dry compressive strength testing, the disinfectant-containing dental stone had significant higher strength than that without the disinfectant. The newly developed type IV dental stone incorporated with disinfectants had antimicrobial effects against all tested microorganisms. The physical properties of the modified dental stones were within the ISO standards. However, further investigation on other properties such as dimensional stability, detail reproduction and clinical usage are still needed.

Antimicrobial Properties of Ag Nanoparticle-Incorporated Irreversible Hydrocolloid Impression Material

Irreversible hydrocolloid impressions are easily contaminated with saliva and blood that are potentially capable of cross-infection. Disinfection with addition of Silver (Ag) nanoparticles into the impression material has been explored recently. This research aims to evaluate the in-vitro efficacy of Ag nanoparticle-incorporated irreversible hydrocolloid impression material. Ag nanoparticles (AgZrPO4, National Direct Network Company, Thailand) at concentrations of 0.50%, 1.00% and 1.50% w/w were added to powder of impression material (Kromopan, Lascod, Italy). Impression material samples were prepared on sterile plate in accordance with manufacturer’s instruction. After setting, a 100 microliter of P. aeruginosa ATCC 6538 and C. albicans ATCC 13803 suspension (106 cells/mL) were inoculated on the surface of the impression sample and left for 10 minutes. The amount of the P. aeruginosa and C. albicans on the surface was quantified using imprint technique on the individual culture media respectively. Impression materials incorporated with AgZrPO4 showed antimicrobial property against microbes compared with control (impression material without AgZrPO4). This beneficial effect can be used to reduce cross contamination. However, further investigations are required to study the physical properties of the Ag nanoparticle-incorporated impression material.

Physical Properties of Irreversible Hydrocolloid Impression Material Incorporated with Silver-Nanoparticles

Dental impression is a source of cross infection and transmission of diseases. Conventional disinfection may lead to a change in physical properties. Self-disinfectant irreversible hydrocolloid is an alternative to the disinfection and can prevent microbial cross contamination. The present study evaluates the physical properties of irreversible hydrocolloid impression material incorporated with 0.5%, 1.0% and 1.5% w/w silver nanoparticles (AgZrPO4, Sunshine Factory Co.,Ltd, China). The working time and detail reproduction were tested according to ISO 21563:2013 with some modification. The result showed that AgZrPO4 did not significantly affect the physical properties of the impression material. Based on this in vitro study, AgZrPO4 can be added to the impression material for its antimicrobial benefit without significant changes in the physical properties of the material.

Shear Bond Strength of Orthodontic Bonding Materials Polymerized by High-Intensity LEDs at Different Intensities and Curing Times

To evaluate and compare shear bond strength (SBS) and Adhesive Remnant Index (ARI) of orthodontic brackets polymerized by high-intensity light-emitting diode (LED) curing units at different intensities and curing times. Sixty extracted human upper premolar teeth were divided into 3 groups of 20 each. The tooth surfaces were prepared and the brackets were bonded on the teeth with light-cured adhesive and cured with 3 different light-curing units and conditions; Group 1 (Bluephase, 1,200 mW/cm2, 20 seconds), Group 2 (VALO, 3,200 mW/cm2, 6 seconds), Group 3 (FlashMax P3, 4,000-6,000 mW/cm2, 3 seconds). Shear bond strength of the specimens were tested after bracket bonding for 5 minutes. The means of shear bond strength among groups were compared by Kruskal-Wallis and Mann-Whitney U tests. ARI were tested by the Fishers exact test (p < 0.05). The means and standard deviations of SBS in groups 1, 2 and 3 were 21.80 ± 2.85, 21.04 ± 2.87 and 4.75 ± 2.82 MPa, respectively. Group 3 had significantly lowest mean SBS. Significant difference of ARI was found between Bluephase and VALO groups (p = .010). FlashMax P3 curing at 3 seconds generated significantly lowest mean SBS among 3 groups. The SBS generated by VALO curing at 6 seconds was not significantly different from Bluephase curing at 20 seconds. Therefore, VALO can be an option for orthodontic bracket bonding benefited in reducing clinician chairtime and patient discomfort.

Evaluation of facial asymmetry measurements on simulation model

Abstract Objective To study the correlation between 3 types of facial deformation and 2 groups of measurements using (1) ratio parameters and (2) center of mass based parameters, in asymmetric computerized simulation models. Materials and methods Three groups of facial deformation were constructed which were (1) proportion deformation, (2) shearing deformation and (3) rotation deformation. Computerized facial models were divided into 3 zones which were (1) total zone (maxillo-mandibular complex), (2) upper zone (maxilla) and (3) lower zone (mandible). Three ratio parameters: (1) area ratio, (2) compactness ratio, (3) perimeter ratio, and 4 center of mass based parameters: (1) difference center milieu, (2) Ci milieu, (3) difference milieu and (4) difference vertical milieu were used to measure incremental deformation figures. The results were evaluated using SPSS program. Slope and coefficient of determination (R2) values were obtained. Correlation of deformation amount and 7 measurements were considered high and significant if R2 was greater than 0.8 with p-value less than 0.05. Results For the proportion deformation and shearing deformation, the center of mass based parameters and area ratio were highly and significantly correlated with the deformation amount. However, difference vertical milieu was the only measurement with significant R2 in the rotation deformation group for all 3 facial zones. Conclusion The correlation of the ratio and the center of mass based parameters can be differently influenced by type of deformations and facial anatomical zones. Center of mass based parameters may be used in conjunction with ratio parameters in order to differentiate type of asymmetry.