Journal of Dental Medicine

Discoloration of composite resins is considered to be a major factor in esthetic restoration failures. The aim of this study was to evaluate color stability of IDM composite (both light and self cure samples namely IL and IS), and to compare it with a self-cure composite (Degufill named DS) and a light cure ormocer composite (Definite, called DL in the Report). 60 disk shaped samples of each composite were prepared, according to ISO-7491. The samples were divided into 3 groups and aged as follows: A- (Control) 7 days in dark 37°c chamber B- Foil covered and kept in 100% humidity, and 37°c in xenotest chamber for 24 hours, then transferred to a dark 37°c chamber for 6 more days.C- Kept in 37°c, 100% humidity under the emission of xiiion lamp of xenotest chamber for 24 hours,and then transferred to 37°c dark chamber for 6 more days The lightness and chromaticity values of samples were measured both before and after aging using a spectrophotometer (Data Flash). The total color changes as well as changes in lightness and chromaticity values were measured in the CIE L * a * b * scale, and analyzed. Color change was recorded to be significant in all samples after aging. The maximum change belonged to IL, which was significantly
different from DL and DS. It seems, in order to have a durable esthetic restoration using IDM, more scientific and professional consideration is needed in the production process.

Statement of Problem: Because dental amalgam does not adhere to tooth structure, using adhesive cements in amalgam-bonded restorations have been increased.

Purpose: The goal of this in-vitro study was to compare the effects of three types of glass ionomer as adhesive liners as well as varnish liner in increasing fracture resistance of teeth restored with amalgam.

Materials and Methods: Seventy extracted human maxillary premolars were selected and MOD cavities were prepared on them excluding ten intact teeth as positive control group and ten cavity prepared teeth without restoration as negative control group. All the prepared teeth were then restored with spherical amalgam (gs.80) with one of the following liners silver alloy glass ionomer liner, conventional glass ionomer liner, varnish liner, resin-modified glass ionomer and resin-modified glass ionomer with delayed light curing. The teeth were stored in 37C distilled water for 7 days and were then loaded under compressive strength using an Instron testing machine. The force required to fracture teeth were recorded and the data were analyzed statistically using ANOVA and Tukey HSD tests.

Results: Statistically significant differences were observed in fracture resistance between restored and non-restored samples. Comparisons between groups attributed significant effects to resin-modified glass ionomer in increasing fracture resistance of amalgam restored teeth (P<0.05). In most specimens, one cusp was separated from tooth structure whereas amalgam remained bonded to the intact cusp. Conclusion: According to these findings, resin-modified glass ionomer put a statistically significant effect in fracture resistance of amalgam-restored teeth.

Background and Aims: Considering the application of recycled metallic brackets in orthodontic treatments and probably more resultant metal ion release, which can cause cytotoxic side effects, this study was set up to assess the effect of recycling process of orthodontic brackets on metal ion release.
Materials and Methods: In this experimental study, 80 Discovery direct bond brackets (Dentarum, Germany) were divided into 2 groups, new and recycled brackets (n = 40), then each group was divided into two subgroups (one-week and 6-months subgroups) (n=20). The specimens were maintained in buffered solution of NaNHNo3 (pH=7) at 37°C in an incubator. After periods of one week and 6 months immersion, 0.5 mL of each solution was analyzed by spectrophotometry for the quantity of released Nickel (Ni), Chromium (Cr), and Cobalt (Co) ions. The data were analyzed using two way ANOVA analysis.
Results: After one week, the quantity of Ni, Cr, and Co ions released from new brackets were 0.65, 1.4, and 0.75 (ppb), respectively. The values for recycled brackets were 142, 2.61, and, 1.43 (ppb). These findings indicated significant difference between two groups (P<0.001). After six months, the quantity of Ni, Cr, and Co ions released from new brackets were 1200, 3.4, and 2.4 (ppb) and from recycled brackets were 2330, 6.9, and 10.8 (ppb), which showed significant difference between two groups (P<0.001).
Conclusion: Application of recycled brackets in long fixed orthodontic treatments can lead to metal ion release, specifically Nickel. Thus, the use of recycled brackets in long orthodontic treatments is not recommended.

Background and Aims: Regarding the diversity of reported low- back pain among dentists in different countries and lack of control group in most of the previous studies, the purpose of this study was to compare low- back pain and related risk factors between male general dentists and pharmacists to determine the relation between dentistry and development of low back pain.

Materials and Methods: In this cross-sectional study, 261 male dentists were compared with 193 male pharmacists as a control group with Standardized Nordic Questionnaire (low back section). Subjects were at least one year in clinical practice after becoming qualified and did not suffer from connective tissue diseases and history of a traumatic event causing fracture in spinal column. The data were analyzed by Chi- square, T-test and logistic regression analyses.

Results: The prevalence of low back pain in the past 12 months was 54.8% in male dentists and 36.3% in male pharmacists (P=.001). Logistic regression analyses, adjustmenting for occupation, age, body mass index (BMI), smoking, working years and working hours per week, revealed that there was a significant association between being a dentist and having low- back pain (OR=2.54, P=0.001).

 Conclusion: Dentistry as a profession in male gender is associated with low back pain, independent of age, body mass index (BMI), smoking, working years and working hours per week.