Evaluating the color stability of temporary crowns fabricated by 3-dimensional printing and manual methods.

This in vitro study aimed to compare the color stability of temporary crowns fabricated by 3-dimensional (3D) printing with that of crowns fabricated with 2 manual methods. An impression was made of a prepared central incisor, from which 90 dies were fabricated. The dies were randomly assigned to 3 groups (n = 30) based on crown fabrication method: 3D printing, automix bis-acryl resin, or powder-and-liquid polymethyl methacrylate. All specimens were immersed in a coffee, soft drink, or distilled water solution for 1 week (n = 10 per subgroup). Color change was measured using a spectrophotometer and the International Commission on Illumination's CIE L*a*b* method, and the values were converted to the National Bureau of Standards (NBS) index for assessment and comparison. When color change was assessed according to fabrication method, the highest (mean [SD]) ΔE* value was reported for the automix specimens (3.39 [2.86]), and the lowest was recorded for the powder-and-liquid specimens (2.05 [2.33]) (P < 0.05; Kruskal-Wallis test). The difference between ΔE* values of the 3D printing group (2.46 [1.75]) and the powder-and-liquid group was not statistically significant. When color change was assessed according to the immersion solution, the coffee solution showed a significantly higher (mean [SD]) ΔE* value (5.04 [2.67]) than the soft drink (1.43 [0.92]) and distilled water (3.41 [7.93]) solutions (P < 0.05; Kruskal-Wallis test). The color changes associated with the 3 methods were statistically equal in terms of the NBS index ranges, most frequently falling in the range of very minor to acceptable change. The powder-and-liquid method seems to be most suitable for fabricating temporary prostheses for long-term use.

Determination of strain around distal implants as abutments for partial and fixed implant-supported prostheses with posterior cantilever.

This study aimed to compare strain around implants used as abutments for removable partial dentures with wrought wires and fixed partial dentures with ball attachments and fixed dentures with posterior cantilever. An edentulous mandibular model was constructed using epoxy resin with four parallel implants in the area between the two mental foramina. Four strain gauges were attached to the buccal, lingual, mesial, and distal aspects of each implant. One fixed prosthesis with cantilever and two removable partial dentures were considered as prosthetic treatments. A vertical 500-N force was applied with 10-N intervals. The maximum strain in the fixed prosthesis was higher than that of the partial removable denture; in the removable denture with a wrought wire arm, it was higher than that in the denture with a ball attachment (P < 0.001). The lowest rate of strain was recorded on the mesial aspect (P < 0.05). However, the highest rate of strain was recorded on the lingual and distal aspects of the removable denture with a wrought wire in the buccal aspect and the removable prosthesis with the ball attachment on the buccal and lingual aspects (P < 0.05). Finally, despite minor differences in the maximum strain rate in each implant position, the differences were not statistically significant (P > 0.05). Partial removable denture with a ball attachment decreased strain more than that by the removable portal denture with a wrought wire arm. The worst type of prosthesis in terms of the overall strain rate was the fixed prosthesis with cantilever.

Color changes of three different brands of acrylic teeth in removable dentures in three different beverages: An in vitro study.

Background. The best prosthetic appliances exhibit a high level of similarity to the lost organ. Color should exhibit favorable stability, as a critical factor in the esthetic appearance of dental prostheses and materials used in fabricating prostheses. The present in vitro study was undertaken to evaluate color changes of three different brands of acrylic resin teeth in three different beverages. Methods. In this in vitro study, 10 samples from each brand of acrylic resin tooth (Ivoclar, Italy; BStar, Iran; and BetaDent, Iran) were immersed in the following beverages for one week: tea, orange juice, natural carrot juice, and distilled water (control). The color parameters were measured using the spectrophotometry technique before and after immersion, and changes were calculated. The same procedures were carried out with the same number of samples at 30-day interval. Data were analyzed with multivariate ANOVA and post hoc Tukey tests. Results. After seven days, Ivoclar and BStar brands exhibited the minimum (1.78) and maximum (3.39) color changes, respectively (P<0.05). At the 30-day interval, the Ivoclar and BetaDent brands exhibited the minimum (3.03) and maximum (4.27) color changes, respectively (P<0.05). At the 7-day interval, carrot juice, orange juice and tea, in descending order, caused the maximum and minimum color changes. At the 30-day interval, carrot juice resulted in maximum color changes (P<0.05); orange juice, and tea caused similar color changes (P>0.05). Conclusion. Different beverages resulted in color changes with different patterns in different brands of acrylic resin teeth. Overall, the Ivoclar brand exhibited less color changes compared to BStar and BetaDent brands. In the first week, all the three brands and in 30 days, Ivoclar and BStar brands exhibited clinically acceptable color changes.

The efficacy of zinc augmentation in children with attention deficit hyperactivity disorder under treatment with methylphenidate: A randomized controlled trial.

INTRODUCTION: Regarding to the role of the zinc in the metabolism of the central nervous system and the correlation of zinc supplementation in the treatment of any Attention deficit hyperactivity disorder (ADHD) symptoms, this study was conducted to evaluate the complementary effects of this nutrient. METHOD: This was a double-blind randomized clinical trial study and 60 children with ADHD who were treated with methylphenidate were chosen by random allocation and were divided in the two groups: 30 for the case and 30 for the control group. The treatment in case group was augmented with zinc. Duration of study was six weeks. RESULT: Forty eight (80%) of participants were boy and 12 (20%) were girl. The mean age of patients was 9.6 ± 1.70 years. There was no significant difference between the two groups after the intervention in terms of total score, hyperactivity and impulsivity subscales during variance analysis, but there was a significant difference between the mean of inattention score. CONCLUSION: Augmentation with zinc can enhance the improvement of inattention.

Evaluation of strain in mandibular denture-supporting area in three different occlusal schemes during jaw movements.

Background. Various occlusal schemes have been introduced over the years to enhance the stability, comfort, beauty and function of complete denture, of which lingualized, bilateral balanced and monoplane occlusions are the most recommended. The aim of this study was to compare the strain in mandibular denture-supporting structures in three different occlusal schemes. Methods. Two mandibular and maxillary models were simulated using epoxy resin, and strain gauges were embedded on each side of the mandible in mental foramen, buccal shelf and distolingual area. Strain values were measured in three occlusal schemes at centric occlusion protrusive and lateral movements. Data were analyzed with one-way and three-way ANOVA, followed by post-hoc Tukey tests. The significant level was set at 0.05. Results. The mean strain in denture-supporting area was lower in monoplane occlusion than the two other occlusal schemes, and the mean of values in the buccal shelf was higher than that of mental foramen and distolingual area. In all the three occlusal schemes, the mean strain values on the working side were higher than those on the non-working side during eccentric movements. Conclusion. Monoplane occlusal scheme imposed lower strain on denture-supporting area, with the buccal shelf being the primary strain-bearing area to tolerate more pressure than the rest of the denture-supporting areas. In terms of strain distribu-tion scheme, in all the three occlusal schemes, the working side received more strain than the non-working side during eccen-tric movements.

Prevalence of Head and Neck Tumors in Children under 12 Years of Age Referred to the Pathology Department of Children's Hospital in Tabriz during a 10-year Period.

Background and aims. Head and neck tumors are the most common complaints of people referring to different medical sections, especially in children. The aim of this study was to evaluate the prevalence of these tumors in children less than 12 years of age to provide a better perspective for future studies. Materials and methods. All the files in Department of Pathology at Tabriz Pediatric Hospital from 2001 to 2011 were screened for head and neck tumors in children under 12 years of age. Data including age and gender as well as the type, the location, and benign/malignant characteristic of the tumor were recorded. Data were analyzed by SPSS 15 statistical software, using descriptive statistics and chi-square test. Results. A total of 160 cases were identified. Most of the tumors were benign (68%) and most of the tumors occurred in the neck region (41%). The most frequent benign and malignant tumors were lymphangioma and non-Hodgkin lymphoma, respectively. The majority of benign tumors were found in children younger than 2 years old (P=0.007), but there was no age predilection for malignant tumors. Conclusion. According to our results, benign tumors were more prevalent than malignant ones. Although a low rate of benign tumors in males shows that more attention should be paid to the early diagnosis of head and neck tumors.