Aim: Although the production of plastic teeth has developed but separation of these teeth from acrylic resin base because of the improper occlusal forces or errors in laboratory procedures is still a problem. In this study the effect of different preparation methods of ridge lap surfaces of acrylic teeth (Berelian teeth) in bonding to acrylic resin base (Acropars) was evaluated.Method & Material: For this study, 84 acrylic teeth (premolars Berelian teeth) were selected. These teeth were divided in four groups according to the method of changes in ridge lap surfaces (control, application of monomer, retention groove and removing the glaze surface). The teeth processed on acrylic blocks. They loaded by instron set until the fracture. The forces of fracture of the teeth were recorded and analaysed. Analysis of variances and Duncan test were used for data analysis.Results: The results showed that the application of monomer to the ridge lap surfaces of acrylic teeth increased the bonding strength between these teeth and acrylic resin denture base, but retention groove and removing the glaze surface were not effective in the bonding strength. The fractures were occured inside the teeth in the most cases.Conclusion: With the limitation of this study, it seems that application of monomer to ridge lap surfaces can increase the bonding strength of berelian teeth to Acropars resin base.

Aim: Because the pathogenic microbes can be transmitted through blood and saliva, therefore the dental personal are more likely to be exposed to infectious diseases than other people. Transmission of INFECTION from a patient to another one is high probability. Through dental treatment, the importance of the INFECTION control would be more lighted when we know it is not impossible to define all the patients with infectious diseases. Therefore apply the standard methods of INFECTION control is very necessary. In this study we intended to examine the methods of prevention and INFECTION control in Tehran general dental offices.Method & Material: This investigation is descriptive which is CROSS sectional. Samples in every class were selected by systemic random sampling included general dental offices. The study was done in winter 2001. Information gathered by two ways observation and questionnaire, observing the dentist treating the patient personal protection such as gloves, masks, glasses, ... and decoration of office. Questionnaire was included 50 question items about vaccination, personal protection; ways of sterilization, disINFECTION the surfaces, ways of discarding of contaminated wastes and INFECTION control in radiology.Results: The most important obtained results are a following:- vaccinated against hepatitis B: 97.5% dentists - 56.41% personal in the offices.- used 75.4% gloves, 61% mask and 53% protective glass by dentist.- 18.7% of dentists sterilized hand pieces for every patient, 42.3% sterilized their burs by heat.- 87.7% of dentists did not disinfect radiology set.- 49.5% of dentists disinfected the orders delivered by the laboratory before apply them to patients.Conclusion: The obtained results show the applied methods in general dental offices in Tehran are very far from the standard recommendation be ADA, CDC in views quantity and quality. Therefore it is very necessary to bring up the- knowledge about the principle of INFECTION control and to make available the essential equipment to reduce the seriously risk of CROSS INFECTION spread in our society.

Blood- borne INFECTIONs such as hepatitis B, C, and HIV INFECTIONs are proved to be transmittable by dental procedures. Sterilization and protective measures are known as a critical part in CROSS INFECTION control in dental practice. This study looks at INFECTION control measures taken by 450 dentists who participated in this survey. Dentists attended to the 38th annual congress of Iranian Dental Association were questioned using a comprehensive questionnaire. Results showed that more than 69.4% of the participants "always" used gloves during dental treatments. Accordingly, 82.1% of them "always" used facemask. Dry heat was the most common method of sterilization, used by 95% of the dentists. However, only 10.4% of these practitioners knew the proper timing and temperature setting for dry heat sterilization.

The traditional method for studying non-stationary signals is spectrogram based on the short-time Fourier transform (STFT). The well known limitation of the STFT is the inherent trade-off between time and frequency resolution. The Wigner-Ville (WV) distribution has the best time-frequency resolution, but its draw back is generating CROSS-terms. The matching pursuit (MP) distribution based on using the Gaussian atom is always positive, does not include CROSSterm, and has convenient resolution. In this paper, we have shown in addition to the known properties, the MP distribution can also remove the additive noise inherently. On the other words, we are able to remove the noise just by limiting the algorithm iterations and without paying any additional cost. Although the MP distribution based on using the Gaussian atoms is always positive and it has convenient resolution, according to the MP the time marginal and the frequency marginal will not be obtained accurately. In this paper, it has been shown that by implementing the minimum CROSS entropy (MCE) technique according to the MP distribution as a priory positive distribution, the new extracted distribution has the most similarity to the MP distribution and it also satisfies the correct time and frequency marginal.

Introduction: Effective plaque removal is an important factor in the long-term clinical success of dental implants. The aim of this study was to compare the clinical efficacy of a powered toothbrush (Power CROSS-Action) and a manual toothbrush (CROSS-Action) in the control of plaque and soft tissue inflammation around implants supporting mandibular overdentures.Materials and Methods: This study was a CROSS-over clinical trial. The subjects included 10 edentulous subjects, aged 47-73 years, with removable mandibular overdentures supported by 2 unsplinted implants, all the subjects wore maxillary complete dentures. The study consisted of two 4-week phases separated by a 2-week interval. In each phase each subject randomly used one toothbrush type. Two days prior to each phase, the implants were polished. Plaque and bleeding indices were recorded before and after brushing. Data was analyzed by t-test using SPSS software (a=0.05).Results: Both toothbrushes reduced the indices under study. Means of plaque index decreases were 0.5 in manual toothbrush and 0.44 in powered toothbrush. Means of bleeding index decreases were 0.27 in manual toothbrush and 0.3 in powered toothbrush. There were no statistically significant differences between the two toothbrush types in changing plaque index (p value=0.88) and bleeding index (p value=0.91).Conclusion: Both toothbrushes were efficient in plaque control around implants which supported mandibular overdentures and there was no difference between them. Patients can use one of these toothbrushes depending on personal preference and comfort.