Ascorbic acid deficiency or scurvy is a rare condition which affects patients who are allergic to fruit juice or found in young children, elderly and disabled individuals whose diets lack fruits and vegetables. These patients may suffer from intraoral pain and spontaneous hemorrhage and/or gingival bleeding upon minor agitation. The oral manifestations include swelling of marginal gingiva and interdental papilla with a bluishred, soft and smooth texture. These conditions should be ruled out from any other general systemic conditions such as bleeding disorders or gingival diseases. Treatment regimen involves daily administration of vitamin C supplementation and intensive oral hygiene care. This paper presents a 9-year-old autistic patient who manifested severe gingivitis and was later on diagnosed as having ascorbic acid deficiency. This was diagnosed as the result of physical and oral manifestations and a review of dietary history. The patient was immediately treated with vitamin C supplementation and showed improvements within the first week. The purpose of this report is to help dentists to recognize and be aware and familiar with the systemic and oral manifestations of this condition. A thorough investigation by questioning patients and/or parents of dietary habit will help dentists to accurately diagnose this condition in the early stages, and prevent worsening symptoms resulting in future major losses.

The purpose of this cross-sectional study was to determine the effect of cigarette smoking on periodontal destruction patterns. The study population included male workers of Electricity Generating Authority of Thailand, aged 50-73 years, who had complete data on periodontal and smoking status. Mean recession, probing depth and clinical attachment level at individual tooth sites were compared between current, former and never smokers. The total sample size was 1,863. The significant differences between groups were tested using analysis of covariance and Bonferroni post hoc test (p < .05). Age and percentage of sites with plaque were adjusted for in all analyses. The subjects were subset according to smoking status into 272 current smokers, 714 former smokers and 477 never smokers. The results revealed that each group had similar periodontal destruction patterns. Current smokers had the most severe periodontal destruction, followed by former and never smokers, respectively. The greatest differences in mean recession between current and never smokers occurred at the palatal sites of upper posterior teeth. The most marked differences in mean probing depth and mean attachment level were observed at the palatal sites of upper teeth. The results of this study support the harmful effect of cigarette smoke, which could be attenuated after quitting smoking. In addition, the effect of smoking was most pronounced at the palatal sites of upper teeth, suggesting that there might be a local effect of cigarette smoke in addition to a systemic effect.

The purpose of the study was to evaluate the skeletal, dental and facial profile changes following orthodontic treatment with extraction and non-extraction. Pretreatment and postreatment cephalograms of 95 Class II division 1 Thai patients, treated with nonextraction (51 patients, mean age 10.5 ± 1.3 years) and extraction (44 patients, mean age 11.8 ± 1.3 years), were superimposed to evaluate the dentoskeletal changes. The effect of treatment on the facial profile was determined by nasolabial angle and Lower lip to E line value. Results of the study showed that cervical headgear can redirect the maxillary growth into more downward direction and enhance the mandibular growth in the anterior and downward direction. There were greater significantly skeletal changes in the non-extraction group than those in the extraction group, whereas dentoalveolar changes in horizontal direction were greater in the extraction group. Lower lip was more retracted in the extraction group. Correction of Class II division 1 malocclusion was accomplished mainly by orthopedic effect in the non-extraction group and by orthodontic effect in the extraction group. Both treatment protocols had the favorable effect on the soft tissue profile.

The purpose of this study was to investigate the effect of tooth anatomy, education qualification, and organized learning experience on the ability of dental students and dentists to evaluate the values of total occlusal convergence (TOC) prepared on crown abutments. Acrylic resin teeth (abutment); No. #11, #16, #41, and #46 were prepared with five different TOCs: 0, 6, 12, 20, and 30 degree arranged on 5 set. Each set had five different angle of each abutment. Exceptionally, all abutment of the first set were prepared with the same angle’s value of 6 degrees. The subjects (thirty of the sixth year dental student (DS), thirty of general practitioners (GP), and seventeen of prosthodontist, restorative dentist and master degree candidates who have entered the course for more than one year (SP)were evaluated TOC, then learned the standard value and followed by evaluated TOC again. The tooth percentage which each group evaluated correctly and nearly match the standard total occlusal convergence were calculated and the recorded TOCs were analyzed by the Chi-square and the One-sample t-test analyses at α= .05. The results showed that all groups of subjects have shown the ability to assess the TOCs without statistically significant difference (p > .05) and they could demonstrate the ability to effectively identify 0 degree of TOC, virtually reached the standard value. The DS have shown the efficient ability in identifying 0 and 6 degree of TOCs. The SP showed the best performance in identifying the values, especially those equal or above 12 degree while the second most efficient group were the GP, while the DS showed the most misidentified values. Comparing the mean assessed TOCs and the standard ones, all groups of subjects have shown more efficient ability in identifying more accurate values for all teeth, compared to the values of mandibular posterior teeth (p < .05). All groups of subjects with different experiences have not shown significant difference in the latter assessment compared to the previous one (p > .05). However, the DS showed the better ability in identifying the values of TOC than other groups. Within the limitation of this study, therefore, it could be concluded that tooth anatomy has influenced the ability to assess TOCs while the different levels of educational qualification and organized learning experience may enhance the ability to efficiently identify the TOCs.

The objective of this pilot study was to compare the caries increments in a group of preschoolers between an oral health education of schoolteachers to correctly brush the children’s teeth and fluoride varnish application by a dentist. The subjects included 36 two-to-four years old preschoolers in Piraya-Navin school that taking children from lowincome families. The children were randomly assigned into 2 groups after being stratified into 1) no caries, 2) 1 to 10 dmfs, and 3) more than 10 dmfs groups. The control group received brushing by teachers and the experiment group received fluoride varnish by a dentist. Data were analyzed using the t-test to compare the incremental dmft/s of the two groups. The results showed that mean age of the children was 39.8 ± 2.3 months and 13 were females. Eighteen of them were randomly assigned into fluoride varnish group including 6 females. Another 18 in the brushing group included 7 females. Only 24 of all subjects completed the 6-month study, which 10 were randomly assigned into the fluoride varnish group. This group had mean age of 39.5 ± 2.0 months and the mean dmfs was 13.1 ± 10.3 in which 3 of whom were females. The brushing group had 7 females and 7 males. They had the mean age of 39.8 ± 2.6 months and the mean dmfs was 9.9 ± 13.6. The t-test comparing incremental dmfs of both groups found that the fluoride varnish group had greater incremental dmfs than the brushing group (10.7 ± 13.3 and 3.6 ± 7.4, respectively). The finding was statistically significant with 90% confidence interval (p = .093). In conclusion, with a 6- month follow-up, oral health education to schoolteachers may help prevent dental caries and promote oral health of this group of preschoolers as compared to fluoride varnish application. Future studies are needed to confirm the findings of this pilot study.

The purpose of this study was to evaluate the effect of three metal adhesive primers, ALLOY PRIMER (AP), ML PRIMER (ML), ALLBOND PRIMER B (AB) on the shear bond strength of metal brackets bonded to enamel surfaces with composite resin (System1+). Sixty extracted premolar teeth were obtained and divided into four groups. The brackets in the first, control, group were coated with bonding agent before bonding on the teeth with composite resin. In the other three groups, AP, ML or AB was applied to the bracket bases before bonding as group one. All teeth were stored in distilled water for 24 hours at 37 ± 2 oC, then subjected to thermocycling between 5 ± 2 oC and 55 ± 2 oC for 5000 thermal cycles. The shear bond strength was then tested by an Instronฦ testing machine at a crosshead speed of 0.5 mm/min. The result of this study revealed no significant difference in the means of the shear bond strengths between the four groups as determined by one-way ANOVA (p > .05). Under the conditions of this experiment, using metal adhesive primer before application of the composite resin to bond metal bracket with enamel did not increase the shear bond strength.

The objectives of this study was to determine the level of bacterial contamination of water in dental unit water lines (DUWL) and to study the relationship between the decontamination policy and the quantity of bacterial found in DUWL. DUWL cleaning policies were collected from 36 out of 1,209 dental clinics in Bangkok. The water samples, both inward and outward from DUWL, were collected and cultured to quantify the microbial contamination levels. The results were analyzed using Mann-Whitney U-test. The results showed that ninety percent of dental clinics claim to have DUWL cleaning policy; however, the majority of dental clinics (97%) have never checked for bacterial contamination of their DUWL. There is no relationship between dental units’ used-life and the quantity of aerobic bacteria recovered from DUWL. The results show that the number of aerobic bacteria emitted from aerotor pipe-lines is significantly higher (p < .05) than the inward water, indicating that pipe-lines inside dental units are the major source of microbial contamination in DUWL. Dental units using unprocessed water seem to have slightly higher amount of microbial contamination than those using filtered/boiled/RO water. Moreover, dental units using chemical agents in the cleaning process tend to have less microbial agents than those without chemical use, though the difference are statistically insignificant. In conclusion, significant microbial contaminations in DUWL among dental clinics in Bangkok were found. The current decontamination policies are insufficient to control the microbial contamination in DUWL to meet the American Dental Association’s (ADA) standard.

Flow under loading is an important property of denture adhesive. The adhesive with good flow should provide a thin layer of material to adhere the denture together with gum. The objective was to study the flow property of 24 formulated gels comparing to 2 commercial denture adhesive pastes (Polident and Fitty dent). The testing was performed by applying the adhesive on the non-reflection glass sheet then covered with clear acrylic plate and compressed with 1 kilogram weight. The picture of the flow was recorded from the underneath using digital camera at 30 seconds, 1, 3 and 5 minutes. The area of material flow was calculated using photo analyzing program (Image Pro Plus 4.5). The data were analyzed using one way analysis of variance (ANOVA) and multiple comparison (α=0.05). The result showed that the flow areas of all formulated gels were higher than that of Polident significantly in all period of time. When compared with Fitty dent at 5 minutes, the flow areas of 6 formulated gels were not significantly different from that of Fitty dent; gum tragacanth gel (GT1, 2 and 3) carbopol gel (CP3 and 4) and carboxymethyl cellulose gel (C5). Furthermore, the flow areas of gum tragacanth gel (GT4) and carbopol gel (CP5) were lower than that of Fitty dent significantly. It was concluded that gel was an interesting form of denture adhesive because of its very good flow property.

Neurofibroma is a benign nerve sheath tumor. Oral neurofibroma is uncommon particularly at the upper labial mucosa location. A case of upper labial mucosa neurofibroma of a 35-year-old man is presented. The tumor was completely excised. Histopathological examination revealed many spindle-shaped tumor cells with wavy nuclei scattering in fine collagenous fibers. The diagnosis of neurofibroma was made. The immunohistochemical staining using an antibody against S-100 protein was performed to support the diagnosis. It was found that many tumor cells showed positive staining. After additional body examination and familial history taking, signs of neurofibromatosis were not found. There has been no recurrence after 1 year of follow-up.

This study’s objectives were to study opinions and practices of non-orthodontic dentists on referral and basic orthodontic treatments of orthodontic patients, as well as the factors associated with these practices. The samples were 600 non-orthodontic dentists who were selected by random sampling from all 8,478 non-orthodontic dentists in Thailand. The mailing questionnaire consisted of questions about the opinions and experiences of non-orthodontists regarding their orthodontic referral, and basic orthodontic treatments. Descriptive statistics and the Chi-square test were used to analyse the data. The results showed that 304 non-orthodontic dentists in Thailand returned the questionnaires (51% response rate). 74.7% of the samples had referred patients to see orthodontists. About three quarters (78%) of the respondents agreed that basic orthodontic treatment should be provided by non-orthodontic dentists. Although most respondents thought that non-orthodontists should provide basic orthodontic treatment, only 35.9% had performed basic orthodontic treatments. The results showed that types of basic orthodontic treatments which the respondents thought that non-orthodontists should practice were all types of preventive orthodontics, some types of interceptive orthodontics (correction of abnormal oral habits, correction of anterior cross bite, space regainer, and serial extraction), and some types of limited corrective orthodontics (minor tooth movement in adult patients for anterior crossbite correction, correction of minor mal-alignment, and placing obtulators in cleft child). The results showed that factors that significantly increased referral of orthodontic patients were increased age, increased experience of practice, being a specialist, practicing in an urban area, and having graduated from early established institutes (p < .01). Perceived sufficiency of orthodontic knowledge at the undergraduate study level was the only factor that significantly influenced basic orthodontic treatments of non-orthodontic dentists (p < .01). In conclusion, almost all non-orthodontic dentists in this study referred orthodontic patients and agreed that the basic orthodontic treatments should be provided by non-orthodontists. However, only one third of them had experience in providing basic orthodontic treatments. Sufficient orthodontic knowledge and practice at the undergraduate study level could promote the basic orthodontic treatment of non-orthodontists.

The purpose of this study was to determine the prevalence and characteristics of oral and dental anomalies in children with Down syndrome. One hundred and four children (52 males, 52 females), who registered at Queen Sirikit National Institute of Child Health (QSNICH) were examined. The result showed that children with Down syndrome had stair palate, angle of the mouth pulled down, lower lip everted, lingual diastasis, scalloped and fissured tongue. In this study, the children had mouth closed and no tongue protrusion at rest, which resulted from manual stimulation on lips, cheek and tongue daily when they were infants. Tooth eruption was delayed in timing and sequence. For the majority of children, the first tooth erupted between age 9 to 16 months. The primary dentition was complete at the age 41 months or older. Missing teeth were found in 21.2% of the patients. Primary lateral lower incisors were the most frequently absent. Dental anomalies in shape such as peg shaped and geminated teeth were found at 4.8% and 2.8%. An irregular sequence of teeth eruption was common. In conclusion, Down syndrome children had abnormalities of palate, lips, tongue, an irregular sequence of teeth eruption, shape, size and number of teeth.

The study’s objective was to evaluate prevalence and characteristics of zygomatic air cell defect in Thai population on panoramic radiograph. The panoramic radiographs of 838 cases were examined for gender and age distribution, location and type of zygomatic air cell defect classified as unilocular and multilocular type. All data were analyzed by descriptive statistics. The results showed that zygomatic air cell defect was found on panoramic radiographs 2.3% (19 cases) with a mean age of 29.5±14.5 years. Eight cases occurred in male, while 11 cases occurred in female. In seven cases, the zygomatic air cell defect was bilateral which composed of unilocular 2 cases and multilocular 5 cases. Twelve cases were unilateral which composed of unilocular 5 cases and multilocular 7 cases. All zygomatic air cell defect on this finding were not beyond the zygomaticotemporal suture. In conclusion, the prevalence of zygomatic air cell defect in Thai population is similar to those of previous studies. The unilateral and multilocular types were found mostly.

The objective of this study was to determine volume loss due to physiological wear of natural anterior teeth at one year and two years. Eighteen subjects with good medical and dental health, average age 37 ± 9 years, were recruited for this study. Impressions of maxillary and mandibular arches were taken using polyvinyl siloxane impression material at baseline, one-year, and two-year appointments. Replica models were made using synthetic stone. Volume loss or wear of both maxillary and mandibular natural central incisors and canines was obtained by comparing the surface of the original model with those of the one-year and two-year models using 3D laser scanner. Statistical analysis of the mean values was performed using Student’s t-test at a significant level of 0.05. The results showed that the means volume loss of maxillary central incisor and canine after two years were 0.46 ± 0.27 mm3 and 0.31 ± 0.07 mm3, respectively. The means volume loss of mandibular central incisor and canine after two years were 0.09 ± 0.06 mm3 and 0.07 ± 0.02 mm3, respectively. The increases in means volume loss of maxillary central incisor and canine were observed after two years, and significant differences were found between the means volume loss of all maxillary anterior teeth at one year and the means volume loss at two years (p < .05). The means volume loss of maxillary anterior teeth were significantly higher than those of mandibular anterior teeth at two years (p < .05). In conclusion, significant differences were found between the means volume loss of all maxillary anterior teeth at one year and the means volume loss at two years. The means volume loss of maxillary anterior teeth were significantly higher than those of mandibular anterior teeth at two years.

Denture adhesive was dental product that uses to promote the adherent of denture for a century. Denture adhesives powder and paste were generally commercial available. Gel was an interested form because it could provides comfort in usage. The objective of this study was to study the adhesion properties of adhesive gels formulate from 9 gel former as follow pregel -starch, konjak, gum tragacanth, guar gum, xanthan gum, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropylmethyl cellulose and carbopol comparing with 3 commercial denture adhesive (1 powder and 2 pastes). The 39 gels were prepared by mixing gel former with distill water. The adhesion testing was performed using the Pi 2 method. The result showed that the adhesion forces of all gels were in a range of 4.7 to 34.3 Newton that cover the adhesion force of commercial denture adhesive tested (powder = 10.5 ± 1.7 N, paste = 19.0 ± 1.0 and 20.2 ± 2.1 N). The data was analyzed statistically with one way analysis of variance (ANOVA) and multiple comparisons (p= .05) The problems in gels preparation and the characteristic of gels were evaluated. This was concluded that there was 7 gel formers was selected for further study and development as follow konjak, gum tragacanth, guar gum, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxypropylmethyl cellulose and carbopol.

The aims of this study were to investigate the effects of green and white tea on surface roughness of various resin composites including nanofill resin composite (Premisa, Kerr, Califf., USA; Filtek Z350, 3M ESPE, Minn., USA), hybrid resin composite (Point 4, Califf., USA; Filtek Z250, 3M ESPE, Minn., USA) and microfill resin composite (Clearfil ST, Kurary Medical, Osaka, Japan; Durafil VS, Hareeus Kulzer, Wehrheim, Germany) and to compare the differences in surface of holes of various resin composites after being immersed in the same and different types of tea. Fourteen disc specimens of resin composites were prepared. Baseline data of surface roughness (surface of holes) and surface characteristics were recorded. Specimens were alternately immersed in tea for 5 seconds and in artificial saliva for 5 seconds in 10 cycles. After that specimens were stored in artificial saliva for 24 hours. These processes were repeated 5 times. After immersions, surface roughness measurements and surface characteristics were assessed. The data were analyzed by two-way repeated ANOVA, Tukey HSD test and paired t-test at the significance level of .05. The results of this study showed that after being immersed in green and white tea, surface roughness of all resin composites were significantly increased (p < .05) except for Filtek Z350 (p > .05). The differences in surface of holes of nanofill resin composite were less than microfill resin composite and hybrid resin composite, respectively. The surface of holes of resin composites after being immersed in the green tea were more than white tea but there were no significant differences (p > .05) except Filtek Z350 and Clearfil ST groups. This study concluded that after being immersed in green and white tea, the surface roughness of all resin composites were increased.

Beside an indication of poor oral health, oral malodor has also tremendous effects to the patient’s mental status and social activities. More than 90% of the oral malodor is associated with intra-oral etiology. Oral cavities are habitats of hundreds of bacterial species. Mostly those who are able to produce volatile sulfur compounds are involving in oral malodor. A great majority of them are anaerobic bacteria found in periodontal pockets and tongue coating. This article reviews the causes of oral malodor associated with intra-oral bacterial communities, the methods which can be used to identify those species involved, and the future roles of probiotics in oral malodor treatment.

The objective of this study was to describe the history of systemic diseases, medication use, drug allergy and cigarette smoking in a group of Thai dental patients at the Faculty of Dentistry, Mahidol University, between July 2003 to February 2008. By systematic random sampling, 1,787 dental chart records were selected to study retrospectively. Data on age, gender, medical and smoking history were collected and analyzed. The results showed that, of these 1,787 dental patients, 581 (32.5%) were men and 1,206 (67.5%) were women. Age range was between 9-80 years with an average of 33.6ฑ10.1 years. Three hundred and ninety-eight (22.3%) dental patients, 110 (6.2%) men and 288 (16.1%) women, had systemic diseases. The most common systemic condition was cardiovascular disease (8.9%), gastrointestinal/liver disease (6.4%), and disease of endocrine system (3.9%), respectively. Prevalence of systemic diseases increased with age. Four hundred and eighty-four (27.1%) dental patients were taking medication. The common types of drug taken were antihypertensive drug (5.8%), analgesic/anti-inflammatory/ antibiotics drugs (5.3%), vitamin and other supplements (4.5%). One hundred and seventy-three (9.7%) dental patients gave history of drug allergy mostly from antibiotics, i.e. penicillin group (3.3%), followed by analgesic/anti-inflammatory drugs (2.2%) and sulfonamides (1.4%), respectively. One hundred and seventy-eight patients (9.9%) were cigarette smoker, with 138 (7.7%) men and 40 (2.2%) women. Men had a significant greater smoking history than women (p = .000). In conclusion, about one fourth of dental patients had history of systemic diseases and taking medication. Smoking and drug allergy were found in one tenth of dental patients. This study suggests that a thorough medical history taking is necessary to provide proper treatment plan and dental care.

The aims of the present study were to compare the dental knowledge, attitude and plaque score of students in Border Patrol Police Schools via a community participation of teachers, students and other networks. This study was a participatory action research using a quasi-experimental technique. Three schools were purposive sampled. Thungsabaijai and Baroey Border Patrol Police school students were identified as the experiment group, while students in Sangwanwit primary school were in the control group. Sixty students, stratified by class grade 1-2, 3-4 and 5-6, were randomly selected from those schools. Each school conducted different activities of community participation of teachers, students and other networks for three years. The results showed that students, grades 1-2 in the experimental group had significantly greater knowledge than the control group. Students in grades 1-2, 3-4 had in the experiment group significantly better attitude than the control group. Moreover, students in the experimental group had statistically significantly lesser mean plaque score than the control group (p < .05). In conclusion, oral health promotion and prevention of oral diseases in the Border Patrol Police schools via a community participation of teachers, students and other networks were successful in changing the behavior of students. The important factors for behavioral change were the participation of school administrators, health teachers and school teachers. In addition, parents should be encouraged to continuously participate in the oral health activities in their children’s schools.

The objective of this crossectional descriptive study was to compare the oral impact on quality of life of grade 6 students between the gold and bronze health promoting schools in Muangsamsib district, Ubonratchatani. 174 students from gold-level and 206 students from bronze-level health promoting school were interviewed using a questionnaire measuring an oral impact on quality of life by The CHILD–OIDP index. The result showed that 56.3% of students in the gold-level and 60.7% of students in the bronze-level health promoting schools had one or more oral impact. Eating was the most common performance affected of both groups. Similarly, the major clinical cause of oral impact was toothache. The prevalence of oral impacts between the two groups of students was not statistically different. The present finding supports the view that the gold level schools’ health promotion activities do not reflect the better oral health related quality of life comparing to the bronze-level schools. Therefore, dental health indicator should be compulsing for the evaluation of the gold-level schools.

This study aimed to survey on tobacco use including knowledge, attitude and practice on tobacco control among Thai dental students in 2006. The data collection used anonymous self-administered questionnaire recommended by WHO as part of The Global Health Professional Survey project, were sent to all dental students from 8 public dental faculties. The response rate was 83% including 2,425 students. The findings indicated that 17% of dental students had ever smoked cigarettes. Three percent of the respondents were current cigarette smokers. Prevalences of smokers were 8% in males and 0.8% in females. Twenty nine percent of smokers wanted to quit smoking now. More than 90% of students had positive attitude towards tobacco control including banning of cigarette sales to adolescent under 18 years of age, banning of all tobacco advertising and banning of smoking in public places. Ninety percent of the respondents stated they have been educated on tobacco hazard. However, only 17% received a specific training on tobacco cessation techniques. Eighty four percent of students desired to be trained on tobacco cessation counseling technique. It was also found that 2% of dental students reported that they regularly consumed alcohol. In conclusion, prevalence of smokers was low in Thai dental students. A majority of students requested a tobacco cessation training program in dental schools.

The in vitro adhesion testing is a valuable measurement for the effectiveness assessment of denture adhesives. The objective of this study was to assess the adhesion forces of adhesives powder, paste and gels. The test was performed with the Pi 3 methods. One way ANOVA and Dunnett T3 were used at 95% confident interval. The result showed that the adhesion forces of resin acrylic palatal plate in normal situation (without adhesive) were 9.9ฑ0.6 N. The adhesion forces were increased after using denture adhesives. Immediately after insertion, the adhesion force of gels was greater than paste and powder significantly. For a longer period of wearing, the adhesion force of paste were increased, as opposed to those of gels that decreased continuously. After wearing for 2 hours, the adhesion force of paste was highest and significantly different from the others, while the adhesion forces of gels (carbopol, carboxymethyl cellulose and gum tragacanth) and one powder were similar to without adhesive. Within the limitation of this study, it was concluded that well-fitting resin acrylic palatal plates could adhere to tissue without using any adhesives. The adhesive gels could increase the adhesion forces up to 3-4 times immediately, but they decreased continuously and was similar to without adhesive within 2 hours. The adhesion forces of paste increased with time of wearing. The increased adhesion forces of adhesive powder were lower than the paste.

The aim of this study was to investigate the mechanical properties and microstructure of cobalt-chromium alloy cast circumferential clasps recycled in 50:50 mixing ratios by weight of used alloy and new alloy. Thirty circumferential clasp samples made from cobalt-chromium alloy were divided into 3 groups (n = 10 per group) : 100% new alloy, 50% used alloy mixed with 50% new alloy, and 100% used alloy; the used alloy was melted only once. Ten samples per group were tested on the universal testing machine with a crosshead speed of 0.5 mm/min. The load to fracture and load to permanent deformation were recorded. One-way analysis of variance and LSD multiple comparison tests were used to compare the results of the 3 groups (a= 0.05). Three selected samples from each group were examined the fractured surface using a Scanning Electron Microscope (SEM) and analyzed elements with Energy dispersive spectroscopy (EDS). The results showed that the mean load to fracture of the three groups were not significantly different (p < .05). The mean load to permanent deformation of the 100% new alloy cast clasps was not significantly different from that of the 50% used alloy mixed with 50% new alloy cast clasps but was significantly greater than that of the 100% used alloy cast clasps (p < .05). SEM examination revealed that contamination increased with the ratio of used alloy. In conclusion, the use of used cobalt-chromium alloy reduces the mechanical property of the cast clasp which may result from contamination of the inclusions in the alloy.

The purpose of this study was to develop wax cubes having the desired physical properties, for evaluating the chewing ability. The manufacturing and evaluating process can be done in a short time. The developed wax cubes can be used to evaluate the chewing ability among various subject age groups. Four types of wax were blended until they achieved the desired physical properties to create 10 mm. x 10 mm. x 10 mm. wax cubes. Forty-five subjects (21 males and 24 females) with normal occlusion were classified into 3 groups (Group 1: 20-29 years old, Group 2: 30-39 years old, and Group 3: 40-49 years old). The wax cubes were disinfected and stored in an incubator (37oC) for 24 hours then soaked in a water bath (37oC) for 10 minutes prior to testing. Each subject was assigned to chew four pieces of the wax cubes, one by one for ten chewing strokes each using habitual chewing patterns. The chewed wax was captured and analyzed by the Image J program (NIH) which calculated the percent of well mixed color areas. The results showed the average percentage of chewing ability based on well mixed areas in Group 1, 2 and 3 were 25.3±4.4, 23.6±5.7, and 16.5±5.5 (mean±s.d.), respectively. One-way ANOVA showed the differences between Group 1 and 3, Group 2 and 3 were statistical significance (p < .05). However, no statistically significance (p > .05) was obtained between gender in each group when analyzed by Independent t-test. In conclusion, the wax cubes developed in this study using an uncomplicated manufacturing and evaluating process can be used to identify chewing ability among different groups. Also, this study indicates chewing ability and age of subjects are negatively correlated.