Journal of Dental Medicine

Normal 0 false false false EN-US X-NONE AR-SA Palatal lift appliances are used when the soft palate is anatomically normal but dysfunctional and patients suffer from speech problems while surgical correction is not possible. The aim of these prostheses is lifting soft palate to its normal level in order to achieve palatopharyngeal competence. The prostheses are designed based on maximum retention to keep soft palate in new position without prosthesis displacement. Various methods of constructing these appliances are mentioned and discussed in this article.

Normal 0 false false false EN-US X-NONE AR-SA The theory of designing partial prostheses with rotational path of insertion has been debated for years but most dentists do not consider this treatment method. In conventional partial prostheses, the rests have a single path of insertion while in rotational path of insertion, first the center of rotation sits in the rest then the prosthesis is roated and inserted in final position. In rotational path of insertion prostheses, a rigid retainer is needed as well as conventional clasps. The rigid retainer is inserted in undesirable undercut areas that are not used in conventional method. In current study, methods of rotational partial prostheses as well as their advantages and disadvantages are introduced and discussed.

Normal 0 false false false EN-US X-NONE AR-SA In current study, we reported a research on contamination of instruments and frames of removable partial dentures transmitted from laboratory to the clinic. The instruments and frames were sampled three times and the obtained samples were cultivated in special mediums. Then, the resulted colonies were again sampled to achieve unified bacterial strains and finally the bacteria strains were analyzed in biologic, biochemistry and serological characteristics. The obtained results are presented in this article.

Normal 0 false false false EN-US X-NONE AR-SA Although a full denture cab  replace the teeth and their supporting structures , it commonly develops temporary speech problems that are resolved after a while. In this study, 70 patients were recruited from Prosthodontics department of Tehran and Isfahan dental schools. The patients were analyzed via special questionnaires and oral interview by gender, previous prosthesis and  in 3 phases of edentulous, immediately after denture delivery and a week after delivery. Following data gathering and statistical analysis, it was found that "sh", "s"," Ch" sounds are the most and " m" is the least difficult sound to  pronounce. The study results showed significant difference between 3 stages of denture usage. Also, the effect of previous prosthesis on speech was concluded while gender had not any relation with speech problems.

Preservation of bone-implant interface is vital for maintaining of implant treatment. There are some cases in which crown to fixture ratio is increased due to loss of residual ridge. In this condition knowledge of stresses acting over alveolar bone is important in regard to prognosis of treatment. In this study three different crown to fixture ratios evaluated under lateral forces considering stresses generated in the alveolar bone around the implant.Three different models of crown to implant ratios were designed in a single-tooth implant at anterior maxilla.Model No. 1 with ratio of 1:1, model No. 2 (1.5:1) and model No. 3 (2:1) were designed. Then, the differences between stresses under two horizontal loads (70 and 100 Newton) were analyzed by three-dimensional finite element analysis. Principal normal stresses and Vonmises stress were measured in this study.Results indicated that stress concentration were mainly at the crestal bone.Highest stresses were obtained in third model (2:1 ratio), which was approximately twice as first model (1:1) ratio.

It has been shown that noble alloys require metal collar to resist distortion when subjected to repeat firing cycle of porcelain. Metal collar is undesirable due to esthetic concerns. Since base metal alloys have superior physical properties, it seems that metal collar would not be necessary for obtaining better marginal adaptation of base metal crowns. The Purpose of this study was to evaluate the effect of metal collar on marginal distortion of base metal- ceramic crowns, Twenty base metal copings were constructed and divided into two groups with and without collars. After surface preparation, porcelain was applied onto the surface of specimens. Marginal gap was measured by scanning electron microscope during three stages of crown fabrication: before degassing, after degassing and after glazing. The mean measurements in collarless group were 21.4±13.4, 2I.4±14.9 and 21.9±11.9 u_m, respectively, and in-group with collar 24.7±11.4, 24.0±! 1.5 and 26.6±11.7 urn, respectively. Two- way ANOVA revealed no significant difference in the mean values between two groups and among different stages of crown fabrication. The results of this study showed that base metal alloys did not distort during crown fabrication and metal collar had no effect on the amount of marginal opening (gap).

Background and Aim: According to infection possibility in high risk patients, assessment of microbial contamination in water sources utilized at medico-dental units has become a recent concern. The purpose of this study was to evaluate the microbial contamination in dental units waterlines at the department of operative dentistry, Tehran university of medical sciences in the year 2006.

Materials and Methods: In this cross-sectional study, six dental units in the department of operative dentistry were selected to assess microbial contamination in water sources. Samples were taken on Saturdays (the first working day in a week) and in the midweek, 64 and 16 hours respectively after turning the units off. Moreover, for investigating the effect of flushing, sampling was done at 30, 60, 90 and 120 seconds after flushing and were taken from three parts of each unit including air/water syringe, turbine handpiece and also cup filler water. Samples were transported in closed sterile containers to microbiology laboratory of the school pharmacy. Data were analyzed by Kruskal-Wallis and Dunn tests with p<0.05 as the level of significance.

Results: E.coli was isolated from contaminated samples. Contamination decreased by flushing. In midweek after 90 seconds flushing, water contamination disappeared. On Saturdays 2 minutes flushing decreased contamination to lower that 200 cfu/ml (the rate recommended by ADA). Samples taken from turbine handpieces showed significantly higher contamination rate compared to air/water syringe and cup filler water (p<0.001).

Conclusion: According to the results of this study, dental units waterlines showed bacterial contamination which was eliminated after 120 seconds of flushing.

Background and Aims: Failure of bonding between artificial teeth and denture base material is a considerable problem for patients who wear dentures. Because of the cost of denture repair and the expensive price of foreign artificial teeth, this study was designed to compare the bond strength of composite and acrylic artificial teeth with heat-cured and auto-polymerized denture base resins.
Materials and Methods: In this experimental and in vitro study, two type of acrylic resin (heat-cured: Selectaplus H/ Trevalon, Dentsply and auto-polymerized: Rapid Repair, Dentsply) and four artificial teeth (acrylic Marjan New, composite Glamour teeth which both of them are Iranian) and Ivoclar acrylic and composite teeth were used. Therefore, 8 groups of 14 specimens each were evaluated. A shear bond strenghth test in a Universal Testing Machine was used. Data were analyzed using the 2-way ANOVA test.
Results: The bond strengths of acrylic teeth (Marjan New and Ivoclar) to heat-cured resin were similar (P=0.632) and statistically higher than those of composite teeth (Glamour and Ivoclar). Acrylic teeth (Marjan New and Ivoclar) and Glamour teeth had similar bond strength to auto-polymerized resin, which showed the highest bond strength values. Ivoclar composite teeth showed significantly the lowest bond strength (P<0.05). All acrylic teeth had the highest mean bond strengths to heat-cured resin which were significantly different from that of
auto-polymerized resin (P<0.05). However, the bond strengths of all composite teeth to both denture base resins were not significantly different (P>0.05).
Conclusion: Based on the results of this study, the type of denture base material and artificial tooth may influence the failure load.

Background and Aims: The aim of this study was to measure the degree of conversion (DC) of three types of composite resins (micro-hybrid, nano-hybrid and Ormocer) with different light curing units (LED LCU and QTH LCU) in two depths.

Materials and Methods: Three commercially available dental resin composites were used in this study: (Tetric Ceram, Ivoclar Vivadent, Liechtenstein-A2 shade), (Tetric Evoceram, Ivoclar Vivadent, Liechtenstein-A2 shade), (Ceram X, Dentsply, Germany-M₂ shade). Specimens were divided into two groups, 5 specimens were photo-activated by QTH unit (Coltolux 75-Colten) and the other five specimens were cured by LED (Demi-Kerr). Then each specimen was sectioned at the top surface and at 2-mm depth. The DC was measured by FT-IR
(Bruker-tensor 27). The data were analyzed by 3-way ANOVA test.

Results: There was significant difference between tested composite resins (P<0.001). The results of top surfaces were significantly different from those observed at 2-mm depth (P<0.001). The type of curing unit affected the polymerization of Ceram X resin composite.

Conclusion: This study showed a significant difference in the degree of conversion in different thicknesses within three groups of resin composites.

  Background and Aims: The importance of quality in medical education makes the need for better standards in educational systems in the center of interest as the basis for certification. Standards needed to be evaluated by program administrators before the implementation phase. The purpose of this study was to evaluate the general dentistry standards program in Islamic republic of Iran from dental schools view point.

  Materials and Methods: This descriptive study was performed during the year 2011 and 2012. A list of 16 faculties was introduced by the dental secretariat of the Ministry of Health and Medical Education. A check list was conducted based on the basic standards of undergraduate dental program that consisted of the importance and feasibility of each standard. The checklist was evaluated by sixteen dental schools representatives and asked their faculty members and reported back to the dental secretariat of the Ministry of Health. Results were reported in descriptive statistics manner.

  Results: Data were collected from 14 dental schools. (Response rate=87%). All of the criteria were essential with more than 85% agreement of the faculties. There were more than 70% of criteria that were not feasible in less than one year.

  Conclusion: The dental standard program was widely accepted by the faculties over the country. However, it seemed that by the faculties it would fail if used as accreditation base line.

Conclusion: The antibacterial effect of the Scrophularia striata extract was significantly lower than chlorhexidine and sodium hypochlorite on Enterococcus faecalis in dental canals viewed as a suitable replacement to the already in use synthetic therapeutic irrigants.