فریده بحرانی

One of the complications of removable partial dentures is debonding of the acrylic resin from the cobalt-chromium framework. Several factors are involved in this chemical and physical bond. The aim of this study was to investigate the effect of applying primers and sandblasting on bond strength between the metal and the acrylic resin in mesh and ladder-like frameworks. In this in vitro study، 30 frameworks with ladder-like design (A) and 30 frameworks with mesh-like design (B) were fabricated. The mesh-like and ladder-like frameworks were each subdivided into three subgroups: 10 specimens in each subgroup were un-treated as the control group (A1 and B1); 10 specimens were sandblasted (A2 and B2)، and 10 were both primed and sandblasted (A3 and B3). Then the acrylic resin base was bonded to metal surfaces and the metal‒resin bond strength was examined by an Instron testing machine and recorded in Newton. Data were analyzed using two-way ANOVA and Tukey test (α = 0. 05). There were significant differences between the three preparation techniques (p value < 0. 001). There were no significant differences between the mean bond strength values of ladder (785. 90 ± 207. 24N) and mesh type (718. 60 ± 216. 83N) frameworks (p value = 0. 133). Mean bond strength values of sandblasting and primer (947. 38 ± 86. 18 N) were significantly higher than those of sandblasting (749. 5 ± 142. 11 N) (p value < 0. 001). Sandblasting resulted in a significantly higher bond strength values compared to the control group (539. 47 ± 164. 09 N) (p value < 0. 001). Sandblasting alone resulted in a 38% increase in bond strength whereas applying primers with sandblasting increased bond strength by 75%. Sandblasting and primer significantly influence resin‒metal bond strength. Subjecting frameworks to a combination of priming and sandblasting produces the highest bond strength.

Considering the professional position of physicians, ethics is of great significance in medical society and being among medical sciences, dentistry is not an exception. This research evaluates the Shiraz dentists’ knowledge of professional ethics especially in regard to patients’ rights, which is recommended by American Dentists Association. This research is of descriptive/observational and cross-sectional type. The society studied in this research included all dentists in Shiraz who owned an office, out of which 97 individuals were selected through simple random sampling. To collect the data, a 20-question questionnaire was used. The reliability and validity of this questionnaire was approved, and collected data was analyzed by SPSS software. ANOVA test was used as a method of gaining correlation of age and knowledge, and T-test was used to gain correlation of gender and knowledge.Results revealed that the score of dentists’ knowledge was 61%, which is equal to 11 out of 18 scores. There was no relationship between knowledge and age (P=0.67) or gender (P=0.68).Dentists must be aware of patients’ rights, and reviewing ethical education in the faculty of dentistry is essential, and reaching this goal requires public participation and proper planning for training on this issue in Iran.

Statement of Problem: Orientation of the occlusal plan in complete denture prostheses therapies plays an important role, leading to appropriate esthetics, stability and mastication. The aim of the present study was to define the best soft tissue index, by which the location and inclination of the occlusal plane in complete dentures could be established. This cross-sectional study consisted of 200 individuals (76 male, 124 female), with the mean age of 26.05 (SD±4.39). In order to determine the relationship between maxillary occlusal plane and ala-tragus line, fox plane and J plane were used. The relationships between maxillary occlusal plane and ALT1 (ala-superior border of tragus), ALT2 (ala-mid-tragus) and ALT3 (ala-inferior border of tragus) were evaluated. In the lower jaw, the occlusal plane was evaluated with the line between the upper and middle parts (ret1) and that between the middle and lower part of retromolar pad (ret2). Data were analyzed by Chi-square test. Evaluation of the difference between the number and percentage using Chi–square test (p < 0.05) showed that there were significant differences between ALT1, ALT2, ALT3 (ALT3 < ALT2 ret2).

Conclusion

Superior one third of the tragus and the upper and middle one third of the retromolar pad are suggested as a reference points for determining the posterior part of the occlusal plane in comparison with the middle and lower one third of the tragus and middle and inferior one third of the retromolarpad.

Statement of Problem: Utilization of denture cleaning solutions and toothpastes are common methods of cleaning the denture surfaces, which can increase the surface roughness of acrylic dentures. The aim of this study was to evaluate the effect of two cleaning agents in the form of solution and paste on the surface roughness value of denture following tooth brush application. Thirty acrylic discs with 20 mm diameter and 2 mm thickness were made and uniformly polished. These discs were randomly divided into three groups, each comprising ten discs. The roughness value (Ra) was measured, using talysurf.10. The discs in the first group were brushed using tooth paste and brush. The discs in the second group were first brushed using water and tooth brush, and then immersed in cleaning solution for 92 hours. The discs in the third group (control) were only brushed using water and tooth brush. For all the groups, tooth brushing abrasion test was performed with 200gr weight applied. The surface roughness of each specimen after 10.000 strokes was determined. Data were analyzed with ANOVA and post hoc Tukey test (α =0.05). An increase in the surface roughness was observed for all groups. However, surface roughness in the first group, for which tooth paste had been used was significantly increased as compared to the other groups (p =0.01). But there was no significant difference between the other two groups (p >0.05). Denture cleaning materials in the form of solution produce less surface roughness as compared to the ones in the form of pastes.

In order to improve the retention and stability of the mandibular removable prosthesis with distal extension, it is usually required to make a secondary impression (the altered cast impression). This study was designed to clinically evaluate the conventional method of altered cast technique with modified altered cast technique. This prospective experimental study was conducted with 15 patients. They were treated with two methods of conventional and modified altered cast techniques. Following an oral examination, a questionnaire was used to collect clinical information on the occurrence of ulceration on the ridge, denture border areas, buccal shelf and retromolar pad areas, as well as the sufficiency of denture base extension. Patients were followed up 24 hours and one week after using the partial dentures. In conventional altered cast impression technique, it is required to dissect the casts and form the impression boxing in order to make sure that the master cast is properly registering the distal extension ridge anatomical features. Separation of the edentulous portion from the master cast is eliminated in the modified altered cast impression technique. This makes it more efficient, convenient for patient and less time consuming procedure. The X2 and fisher’s exact tests were used to detect significant levels. The percent of ulceration on the ridge, denture border areas, and buccal shelf as well as the retromolar pad areas were lower in modified altered cast impression technique compared with the conventional altered cast impression method. The percentage of the denture base extension in the modified altered cast impression technique was better than the conventional altered cast impression method. The extension of denture base in distolingual areas of modified altered cast impression technique was the same as the conventional altered cast technique. The difference between the two procedures was not statistically significant. The modified alerted cast technique can result in saving time, increasing the patient’s satisfaction and comfort, which makes it the recommendable procedure for making removable partial dentures with distal extensions.

One of the most important structural factors that facilitate patient’s acceptance of full denture, is adequate and appropriate retention. The objective of this study was to evaluate the retentive ability of four denture adhesives in vitro: Safe Saze-Gum Sealing-Denstet-Corega. This experimental study was conducted in vitro on the basis of measurement of adhesion and cohesion forces between acrylic disk and glass, with denture adhesive applied between them. At first the retentive ability of alcohol, water and artificial saliva was measured and recorded as control. Then the retention ability of different adhesives mixed once with water and next with artificial saliva was measured and compared. The procedure was repeated 7 times for each denture adhesive with 7 similar acrylic disks. Data were analyzed using. ANOVA and paired t test with p<0.05 as the limit of significance. Comparison of four powder denture adhesives showed that the highest retentive ability was observed in Denstet and the lowest in Safe-Saze. The retentive ability of Gum-Sealing was higher than Corega. Based on the results of this study, significant differences exist among the retention ability of different denture adhesives.

Statement of Problem: Difficulties in sterilizing impressions by traditional methods have led to chemical disinfections as an alternative, and some studies have shown that some methods may adversely affect impressions. This study evaluated the effectiveness of 5.25% sodium hypochlorite spray and immersion disinfection methods on irreversible hydrocolloid impressions (Iralgin alginate). In this study, twenty normal individuals were randomly selected. Impressions were made by a sterile tray from the maxillary arch and then were contaminated with the following organisms: staphylococcus aureus, streptococcus mutans, β-hemolytic streptococcus type A, Pseudomonas aeruginosa, Escherichia coli and Candida albicans. Impressions were cut and divided into three sections anterioposteriorly and longitudinally. Then, sections were randomly placed in three groups as 1) control (without disinfection), 2) immersion and 3) spray. Then, the provided samples (pieces) of impression materials were cultured and microbial count of the three groups were compared. All of agar models from 20 alginate pieces in control group showed a positive microbial growth. Ten agar models form 20 alginate pieces which were disinfected by spraying method, showed also positive microbial growth and only 2 agar models out of 20 alginate pieces which were disinfected by immersion method showed a positive microbial growth. The mean number of organisms recovered form the surface of the impressions in control group was 3.52×108 CFU/ml while in spay and immersion groups it was 132217 CFU/ml and 1915 CFU/ml respectively. According to the results of this study, disinfection by immersion method with 5.25% sodium hypochlorite was more effective than the spray method.

This research was conducted in the academic year 2002-2003 in the Department of Prosthodontics of School of Dentistry, Shiraz University of Medical Sciences to investigate patients post complications after delivery of R.P.D.

50 Patients who were psychologically healthy and withoutsystemic diseases were selected. The dentures were made and delivered by sixth yeardental students. They were evaluated twice using questionaires one day and one weekafter the delivery of their dentures. Responses of patients to the proposed questions were evaluated.

Statistical analysis of the data showed that denture soreness on residual ridge and vestibule was maximum (72%), which was reduced to 12% after one week. Lack of retention in centric and eccentric was 44%, which was reduced to 15% one week later. Gag reflex and speaking inability was reduced from 44% to 4% in one week. Herpis and apthus lesion were low.

It is recommended that more precise attention be given to impression stages and occlusion adjustment while making R.P.D.