mahasti sahabi

Cases of antimicrobial resistance are increasing, partly due to inappropriate prescribing practices by dentists. The purpose of this study was to investigate the prescribing practices and knowledge of dentists with regards to antibiotics. Moreover, this study aimed to determine whether the prescriptions comply with the recommended guidelines and whether clinical audit can alter the prescribing practices of dentists leading to better use of antibiotics in the dental service. A clinical audit (before/after non-controlled trial) was carried out in two dental clinics in the northeast of England. Retrospective data were collected from 30 antibiotic prescriptions, analysed and compared with the recommended guidelines. Data collected included age and gender of patients, type of prescribed antibiotics and their dosage, frequency and duration, clinical condition and reason for prescribing. The principles of appropriate prescribing based on guidance by the Faculty of General Dental Practice in the United Kingdom (UK), FGDP, were discussed with the dental clinicians. Following this, prospective data were collected and similarly managed. Pre and post audit data were then compared. Changes were tested for significance using McNemar''s test and P value<0.05 was considered statistically significant. After intervention, data revealed that antibiotic prescribing practices of dentists improved, as there was an increase in the percentage of prescriptions that were in accordance with the FGDP (UK) guidelines. In view of the limited data collected, this study concludes that there are inappropriate antibiotic prescribing practices amongst general dental practitioners and that clinical audit can address this situation, leading to a more rational use of antibiotics in dental practice.

Resin cements, regardless of their biocompatibility, have been widely used in restorative dentistry during the recent years. These cements contain hydroxy ethyl methacrylate (HEMA) molecules which are claimed to penetrate into dentinal tubules and may affect dental pulp. Since tooth preparation for metal ceramic restorations involves a large surface of the tooth, cytotoxicity of these cements would be more important in fixed prosthodontic treatments. The purpose of this study was to compare the cytotoxicity of two resin cements (Panavia F2 and Rely X Plus) versus zinc phosphate cement (Harvard) using rat L929-fibroblasts in vitro. In this experimental study, ninety hollow glass cylinders (internal diameter 5-mm, height 2-mm) were made and divided into three groups. Each group was filled with one of three experimental cements; Harvard Zinc Phosphate cement, Panavia F2 resin cement and Rely X Plus resin cement. L929- Fibroblast were passaged and subsequently cultured in 6-well plates of 5×105 cells each. The culture medium was RPMI_ 1640. All samples were incubated in CO2. Using enzyme-linked immune-sorbent assay (ELISA) and (3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) (MTT) assay, the cytotoxicity of the cements was investigated at 1 hour, 24 hours and one week post exposure. Statistical analyses were performed via two-way ANOVA and honestly significant difference (HSD) Tukey tests. This study revealed significant differences between the three cements at the different time intervals. Harvard cement displayed the greatest cytotoxicity at all three intervals. After 1 hour Panavia F2 showed the next greatest cytotoxicity, but after 24-hours and one-week intervals Rely X Plus showed the next greatest cytotoxicity. The results further showed that cytotoxicity decreased significantly in the Panavia F2 group with time (p<0.005), cytotoxicity increased significantly in the Rely X Plus group with time (p<0.001), and the Harvard cement group failed to showed no noticeable change in cytotoxicity with time. Although this study has limitations, it provides evidence that Harvard zinc phosphate cement is the most cytotoxic product and Panavia F2 appears to be the least cytotoxic cement over time.

Fixed splinting of abutment teeth can alter the stress distribution characteristics of removable partial denture (RPD). However, periodontally compromised abutments may complicate free end RPD treatment plans. The purpose of this study was to determine the effects of fixed splinting of periodontally compromised abutments on load distribution in free end RPD. Three-dimensional finite element models were designed for mandibular first and second premolars including their PDL and surrounding bony structures. In the first model the teeth had no periodontal involvement; in the second model, the first premolar was healthy, the second premolar had periodontal involvement (C/R=1); and, in the third model both teeth had periodontal involvement (C/R=1). Likewise, before and after fixed splinting, situations were defined for each model. The Von misses stress in surrounding bone was analyzed after applying 50 N loads on the specimens. In all three models the maximum Von misses stress before splinting were found to be in the apical area of teeth and the minimum was detected near the mesial crest of first premolar and distal crest of second premolar. After splinting the teeth together, a stress reduction was observed in the interdental crest areas; while in model 1 and 2, increase in the stress was observed in apical areas. The greatest remedy was demonstrated in model 2 where a periodontally compromised tooth was splinted to a healthy one. Fixed splinting of periodontally compromised teeth can reduce the stress concentration in the interdental crest areas and it can improve the stress distribution in the surrounding bone.

Nowadays various types of dental cements are used in fixed prosthetic treatments with different indications. On the other hand, these indications may be changed over a lot every day and new materials are being produced. The aim of this study was to determine the practice of dentists (included general practitioners and prosthodontists) about applications and manipulations of dental cements in fixed prosthetic treatments. Methods & Materials: The study was designed as a cross-sectional, descriptive method. Samples were 362 general practitioners (GP) and 32 (academic and non-academic staff) specialists worked in Great Tehran in 2004. Sampling was done in a simple random method. The questionnaire consisted of 11 questions. After determining the validity of questionnaire, it's reliability was confirmed by means of a test – retest exam. Zinc phosphate was the most frequent cement in fixed partial denture restorations (FPDs) in non-vital teeth (54.4% of GPs and 51.3% of specialists). In vital teeth, both in preparations near and distant to the pulp, polycarboxylate were used frequently by GPs (50.8% and 56.4%, respectively) and specialists (531% and 34.4%, respectively). The most of dentists in both groups were using zinc oxide with eugenol in temporary restorations near the pulp (55.5% and 62.5%, respectively). Zinc phosphate was frequently used for post and core cases (54.5% and 71.9%, respectively). The choices of general practitioners were relatively similar to specialists.

This study was conducted to evaluate the compressive strength of 3 brands of Zinc Phosphate Cements determining the influences of eye estimated (rough measurement) of powder/liquid ratios on the compressive strengths of these cements. The three tested Zinc phosphate cements were Hoffmann's [Harvard Dental GmbH], DeTrey Zinc [Densply] and Ariadent [Asia Cherri Teb]. The specimens were divided into 6 groups, each one containing 10 samples. These samples were prepared according to ISO 9917 (2003) and stored in distilled water at the temperature of 37 ºC for 24 hours. The compressive strengths of samples were measured with the Zwick testing machine. The ANOVA and Tukey statistical tests were used to identify the significant differences between these groups. There were significant differences between compressive strengths of cements prepared with manufacturer suggested mixing ratios and clinically used (eye estimated) ratios. The least compressive strength was recorded for Ariadent samples with clinical mixing ratio and the highest was recorded for Hoffmann's samples with manufacturer’s suggested ratio. In clinically used ratios, Hoffmann's cement had the highest compressive strength. The differences between the strengths of manufacturer suggested mixing ratios and clinically used ones were the most in DeTrey Zinc cement.

Color research has shown that shade guides do not always represent the color of natural tooth. Moreover, visual evaluation has been found to be unreliable and inconsistent. This study evaluated the effects of 2 shade guides and 2 light sources on the intrarater repeatability of prosthodontists, postgraduate students and laboratory technicians with regard to shade selection. Methods & Materials: Three prosthodontists, three postgraduate students and three laboratory technicians participate in this descriptive – analytic study. Examiners were tested to eliminate color blindness by Eshihara Test. Each clinician used Vita Classic and Vitapan 3 D- master shade guides under two light sources (sun light and corrected Dialite lamp) to determine the shades of the maxillary left canines of 20 patients following a standard protocol. The identification codes of the shade tabs were masked to prevent shade memory. All teeth were polished before each shade selection. Shade selection was randomly repeated 1 month later by the same practitioners on the same group of patients. Data were analyzed with two way analysis of variance (Anova). Significant interactions were found between the effects of shade guide system and specially training on intrarater repeatability (P<0.05). The intrarater repeatability of prosthodontists was significantly higher than that of postgraduate students and laboratory technicians when the Vita Classic shade guide was used (P<0.05). Use of the Vitapan 3 D – master shade guide significantly improved the intrarater repeatability of postgraduate students compared with Vita Classic shade guide (P<0.05). This improvement was not significant, however, among prosthodontists and laboratory technicians (P>0.05). Light sources didnt show any significant effects on intrarater repeatability of examiners. The prosthodontists demonstrated superior intrarater repeatability in shade selection, especially when the Vita Classic shade guide was used. Use of the Vitapan 3 D – master Shade guide notably improved intrarater repeatability among the postgraduate students.

Through selection of accurate bite registration materials, the error in the interocclusal relationship of mounted casts on the articulator, can be minimized during fabrication of fixed restorations. Thus this study was done to determine the three-dimensional accuracy of four interocclusal recording materials. Method & Material: This quasi - experimental study measured and compared the three dimensional errors of a wax, a polyether, an impression compound and an autopolymerizing acrylic resin. A dentoform was mounted on a semiadjustable arcon articulator. Ten records of each material were produced and stored for 24 hours. Following a variety of modifications on the articulator, the three dimensional deviations of maxillary dentoform member due to interocclusal records, were measured. There was significant difference between accuracy of materials tested in all dimensions. The least three dimensional changes were recorded by polyether. The accuracy of the remaining materials was, in descending order, compound, wax and acrylic resin.

The aim of this study was to compare tensile strength of pre-solder and post-solder joints for three dental alloys. 45 rods, 32 mm in length and 25mm in diameter were made from degubond 4 (Au-Pd-Ag), person 4 (Pd-Ag) and verabond (ni-Cr-Be).Methods & Materials: 15 rods for each alloy randomly divided in to three groups of control, presolder and postsolder. 10 rods of each alloy were cut in half with a custom made cutting Jig and then positioned and stabilized at 13 mm gap distance in an indexing Jig. Rods of deubond 4 and porson 4 were given a heat treatment to simulate porcelain firing. Specimens were soldered with manufacturers recommended solder with gas-oxygentorch (pre-soldering). Verabond speciments were soldered with gold and base-metal solder.Tensile testing was done on an instron machine. Model AB 725-AM.SM.At cross head speed of 2mm/min and result were recorded in kilogram. 1- For degubond 4, techniques of soldering has no significant effect on tensile strength of solder joints. 2- For porson 4, tensile strength of presolder joints are significantly stronger than post-solder joints. 3- The tensile strength of presolder joints for degubond 4 and porson 4 are significantly stronger than verabond. Tensile strength of solder joints depends on different factors such as type of alloy and soldering technique however this is not dearly predictable.