Journal of Dental School
Volume:28 Issue: 4, 2010

The desirable mechanical properties of nickel-titanium alloy wires have prompted many clinicians to recycle these wires. The purpose of this study was to investigate the changes in mechanical properties of nickel-titanium alloy wires after recycling by electromechanical treatment.

In this experimental study, round 0.018 inch nickel-titanium wires (American Orthodontics trademark) were used. For purpose of determining the behavior of samples in mouth, the transformation temperatures of alloy were carried by electrical resistance test. The types of nickel-titanium wires were separated into three groups: 1- as received condition (control wires), 2- treated by low electrical current, 3- treated by high electrical current. Mechanical properties changes were observed by tensile testing. One-way analysis of variance and Tukey HSD (SPSS statistical package) was used for purpose of comparison.

The results demonstrated significantly greater remained strains after recycling, but plateau stresses and elastic strain energies of the wires were decreased compared with the control wires.

Super elastic property of electromechanical treated nickel-titanium wires is decreased.

Marginal integrity in all ceramic restorations is one of the important elements of the success rate. According to the importance of design preparation in the marginal integrity, in this in-vitro study, decided to compare the marginal integrity between 2 different types of the marginal preparation: shoulder and classic chamfer in IPS e.max press restoration. Methods & Material: This experimental research has been done in vitro with the single blind technique. One standard die with 7mm height, 5mm diameter was prepared by the milling machine. the preparation design consists half shoulder 90 degree & in the other half classic chamfer, with 1mm depth in both of them & 10 degree tapering and then crowns were made of IPS e.max press & after cementation, were ground at the buccolingually direction. Then they were coated by gold &observed under SEM. The data assessed by T-Test.

A difference between 2 types of marginal preparation was significant (p<0.05). Marginal gap in shoulder preparation was 15.45±0.79 & in classic chamfer site was 13.78±0.52.

The marginal fitness in the classic chamfer preparation was better than shoulder preparation in all ceramic restorations.

Gonadal hormones have effect on the growth through increasing the osteoblastic activity of bone. They have influence on the calcium metabolism and therefore, are influential on the calcium level of serum and the strength of the bones. The purpose of this study is to examine the effects of gonadal hormones deficiency on the percentage of bone calcium of the tibia in rats.

In the present experimental study 50 thirty – day – old Wistar rats comprised the sample. 25 male rats were randomly divided into 2 groups: Experimental group, i.e. orchidectomy ORX, (n=15) and control group, sham- operation, (n=10) and also 25 female rats were divided in the same way into 2 groups: Experimental group, i.e. ovariectomy OVX, (n=15) and control group, sham- operation, (n=10). Samples were sacrificed 6 months after the surgery i.e. orchidectomies, ovariectomies, and sham operations. Percentage of bone calcium was determined by atomic absorption spectrophotometry. Serum testosterone, progesterone and estradiol levels were measured by ELISA.

Serum testosterone level significantly decreased in the ORX group as compared with the male sham- operated group. In this study estradiol level was not changed in OVX group, but despite the significant decrease in progesterone level (p<0.001), no significant differences in all variables were found between the OVX group and female sham- operated group. In the ORX group, body length and weight, were significantly smaller than in the male sham- operated group. No significant difference in bone calcium percentage was found (Student’s t-test) between control and experimental groups.

In conclusion, it seems that the suppression of gonadal hormones secretion in the growth phase cannot decrease calcium percentage of tibia bone in rats.

The microbial cause of dental caries has been proved among its multifactorial etiologies. The prevention and control of dental caries is very critical because of high prevalence and cost especially in high risk patient such as xerostomia. Based on the world attraction to traditional treatment and importance of drug extraction of natural material and plants, in this in vitro study effect of hydroalcoholic extract of Salvia officinalis and Menta longifolia which were very useful in traditional treatment of mouth and teeth disease has been determined against cariogenic bacteria.

In this experimental study, hydroalcoholic extracts have been prepared from Salvia officinalis and Menta longifolia with maceration method. Their antibacterial activity against Streptococcus mutans, Lactobacillus rhamnosus and Actinomyces viscosus have been evaluated with broth macrodilution method. Results have been analyzed with Mann-Whitney test.

Minimum inhibitory concentration for Salvia officinalis and Menta longifolia for streptococcus mutans were respectively 6.25 and 12.5 µg/ml, for Lactobacillus rhamnosus 1.56 and 3.12 µg/ml and for Actinomyces viscosus 12.5 and 100 µg/ml.

Both extracts had growth inhibitory effect on all three bacteria. Saliva officinalis had greater effect on inhibition of growth of all three bacteria (p<0.05). Both extracts had bactericidal effect in the range of studied concentrations.