Journal of Dental Medicine

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The purpose of this study was to evaluate Y shape appliance for expansion on maxillary arch of patients in their mixed dentition age. Eight patients, 6 girls and 2 boys, with maxillary constriction, retrusion of maxillary anteriors, and space deficiency of upper canine were treated by Y-plate expansion. For each patient 8 parameters on upper cast and 7 parameters on lower cast were measured. Statistical analysis was conducted by calculating the mean, standard deviation and p-value, of parameters. Since these parameters change during natural growth, the results were compared to normal growth changes of similar patients group form another study as control. Results showed significant increase in maxillary and mandibular cervical and coronal intercanine and intermolar width (P<0.005). The results also showed significant increase in maxillary arch length and perimeter.

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Statement of Problem: Different temperature and moisture around Iran and wide usage of stone type IV in dental laboratories in our country were the reasons for us for doing this study.

Purpose: In this survey the effect of temperature, moisture and time on dimensional change of dental stone type IV (Velmix) were investigated.

Materials and Methods: In this experimental study cube shape Metal models (10×10×10mm) was made for Taking impression. We used special tray, which has ten holes (15×20×25mm) and made impression with condensational silicone in two-step procedure, and poured it with stone type IV. stone cubes were divided to different groups. 3 groups holed in fix moisture and variable tempraure and 5 groups in fix temperature and variable moisture. After 2 hours, 24 hours and one-week dimension of stone cubes were measured. Then analysis was done with ANOVA and dauncan.

Results: The following conclusions were achieved: 1-Time has no effect on dimensional changes. 2-Tempreture and moisture has some effect on dimensional changes in stone IV. Increasing of temperature result in stone contraction and increasing in moisture result in stone expansion.

Conclusion: The best temperature for least dimensional change is 20C and the best moisture for a least dimensional change is 30 %.

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Background and Aim: Among different treatments of patients with Class III malocclusion , orthopedic protraction of maxilla has been known as an effective method in mixed dentition period. The aim of this study was to evaluate the cephalometric changes of Cl III patients in mixed dentition period following face mask therapy and slow maxillary expansion.

Materials and Methods: This was a before-after study which was conducted on 10 children in mixed dentition period, who had class III malocclusion and maxillary deficiency according to the Stiener and Mc Namara's analysis. The patients were all treated by protraction face mask and slow maxillary expansion. The cephalometric changes of maxilla , mandible and dental relations during the treatment were analyzed by Paired sample T Test. P<0.05 was considered as the level of significant.

Results: The overjet increasement was 1.7mm. Co. ANS distance improvement was 5.6mm, Ptm.ANS distance increasing was 3mm, and ultimately improvement of Gf.s distance was 1.5mm which were all statistically significant (p<0.05).

Conclusion: Based on the results of this study, face mask therapy with slow maxillary expansion is able to improve the horizotal position of maxilla, in patients with Cl III malocclusion , in mixed dentition period.