مجله دندانپزشکی دانشگاه علوم پزشکی تهران
سال شانزدهم شماره 2 (پیاپی 35، تابستان 1382)

Statement of Problem: Ultrasonic Scaling is one of the main sources of producing infected aerosols in dentistry. These aerosols are able to spread pathogens such as microorganisms associated with tuberculosis, conjunctivitis, influenza and other respiratory diseases, herpetic and other skin diseases, ADIS and hepatitis B. The aim of this study was to investigate the clinical effectiveness of an aerosol- reduction device attaching to ultrasonic scaler handpiece. In this experimental study 18 patients participated. Randomly, mandibular and maxillary quadrants of one side, in each subject, were scaled using an ultrasonic scaler with aerosol-reduction device for 5 minutes. After 30 minutes, another quadrant was scaled by ultrasonic scaler without aerosol- reduction device. In order to determine the effectiveness of aerosol- reduction device, blood agar plates attached to the surgical mask of the operator, 30 cm far from the patient's mouth, were incubated in 37°c for three days and the colonies were counted. Median, Interquartile eange and Wilcoxon test, at the 0.05 level of significance, were used to analyze the data. The median and interquartile range for the number of colony forming units (CFUS) without aerosol- reduction device was 17.5 (8, 24), while the median for the number of CFUS when using aerosol-reduction device was 0 (0, 1), indicating significant statistical difference (PO.001) The aerosol- reduction device significantly reduces the amount of aerosols produced during ultrasonic scaling.

Statement of Problem: The construction of dental materials has been developing inside the country.Cold- cured acrylic resins are of such materials which are used in removable prostheses. The aim of this study was to compare the dimensional changes of two types of cold-cured acrylic resins, Acropars and Meliodent. Forty acrylic discs, with diameter of 13.7 mm, were made of Acropars and Meliodent acrylic resins (20 samples in each group). Then, each group was randomly divided into two parts. The first group was kept in usual environment, whereas the samples of the second group were placed in the boiling water for five minutes. The dimensional changes of the samples, at different intervals and seven days post curing, were measured by light microscope and recorded. Variance analysis was used to analyze the results. Acropars resins, comparing to Meliodent ones, showed a considerable dimensional changes,which was statistically significant. Boiling of Acropars resins, for five minutes, lead to a significant shrinkage. The maximum shrinkage occured at 24 hours post curing. If the tray is made of Acropars acrylic resin, it is recommended to take impression, 24 hours after its setting.

Statement of Problem: Recently, investigators have presented new methods to reduce polymerization shrinkage of composite resin restorations. It is claimed that more powerful light cure systems associated with a change in radiation patterns, lead to improved mechanical properties and reduced microleakage. The aim of the present study was to evaluate the effects of two curing systems, known as Soft-Start, Pulse-Delay, on microleakage and degree of conversion of composite resin restorations. To evaluate microleakage, dye penetration method in class V cavities was applied. 30 extracted human molars filled with three different curing techniques, namely conventional, Soft-Start and Pulse-Delay, were compared. Degree of conversion was measured by FTIR Spectroscopy method immediately after sample curing. Kruskal- Wallis and Mann-Whitney test were used to compare groups. The degree of microleakage in enamel and dentin among three groups was not significantly different, however, microleakage in gingival and occlusal walls showed a significant difference among Pulse-Delay curing (P=0.001) and Soft-Start curing (P=0.28) groups, meaning that leakage gingival in wall was significantly higher than occlusal wall. This difference was not significant in conventional group. Moreover, the degree of conversion was not statistically significant among three groups (P-0.909). Soft-Start and Pulse-Delay curing systems, with a two intensity start curing light, do not provide better marginal adaptation in class V composite resin restorations. It should be mentioned that polymerization degree is not also reduced in these methods.

Statement of Problem: A lot of efforts have been made to create a complete adaptation between tooth and amalgam restorations. The aim of this study was to evaluate microleakage and interfacial micromorphology of amalgam restorations lined with dentin adhesives, namely One Coat Bond, Syntac, Excite and Copalite,as liners. 144 intact human canine teeth were selected. Then class V cavities, with enamel and dentinal margins, were prepared on each of them. Cavities were lined with different dentin bonding systems (Syntac, One Coat Bond and Excite) according to the manufacturer's instructions and restored with Oralloy and Cinalloy, non gamma 2 spherical amalgams and Aristaloy a non gamma 2 Admixed alloy. Copalite was used in the group, served as controls. After thirty days storage in synthetic saliva at 37°c, the specimens were thermocycled in saliva (4000 cycles). The degree of microleakage was assessed by means of basic fushin dye penetration and recorded. The gap width was evaluated with Scanning Electron Microscope. Pearson and %2 tests were used to analyze the results. None of the systems, tested in this study, eliminated microleakage completely, Pearson's correlation coefficient showed a positive correlation between gap and microleakage (P<0/05).Statistical significant differences were revealed among the liners regarding gap and microleakage (P<0.05).One Coat Bond and Syntac appeared to leak less than other groups. The gap width by One Coat Bond and Syntac were respectively 0.35 and 0.3 urn in dentine, 0.2 and 0.1 in enamel. Excite and copalite gap width in dentine and enamel were 1,3-1.36 urn and 0.3-0.6, respectively. The type of amalgam did not have any effect in the degree of microleakage and gap width (P>0/05). One Coat Bond and Syntac, comparing to Excite and Copalite, showed less microleakage and gap width.

Statement of Problem: Menopause can exert extensive somatic and psychological effects on women at this stage including: oral complaints such as dry mouth, glossodynia, viscous saliva, although these findings should be studied further. The aim of this study was to investigate the stimulated salivary flow rate of 158 menopause and post menopause women. In this cross- sectional and analytic- descriptive study, 158 women, at post menopause stage, were selected as case group. The controls consisted of 83 same aged men. None of the subjects had any systemic disease and did not use any drugs. Age range, in both groups, was 50-69 years old. Psychical condition of two groups, were compared by HADSCALE test. Oral symptoms were also compared and evaluated. In order to analyze the results, "t" and "Mann- Whitney" tests were used. No significant difference was found between two groups regarding the quantity of stimulated saliva and psychological condition, but the incidence of oral symptoms in case group was significantly higher than the control group (P=0.002). Based on this study, although oral symptoms have a significant relation with menopause, can not be attributed to the quantity of saliva or psychical condition. In order to find the underlying reasons, more investigations should be performed on quality changes of saliva or other factors.

Statement of Problem: Previous experiences and clinical observations indicate that enamel hypoplasia and hypocalcification of first permanent molars, among infants born in Cessarian Section Delivery (C/S) is more common than those born in Normal Vaginal Delivery (NVD). Moreover, the first permanent molar is the only tooth that its "cusp tip calcification" starts exactly at the time of delivery. The aim of this research was to investigate the relationship between delivery type and clinical feature of the first permanent molar. Meanwhile, the different effects of the elective and selective types of cessarian, on the clinical feature of first permanent molar, were studied. Birth files, relation to the year 1994 and before, were extracted from a gynecologist clinic. One hundred patients with NVD, 50 patients with selective cessarian delivery and 50 patients with elective cessarian delivery were chosen to examine clinical feature of the first permanent molars of their children. The children, 6 years old or more, were examined. The medical information of the mother were extracted from her file and that of child, were asked from the mother. To analyze the result, X lest- was used. The prevalence of enamel defects (hypoplasia and hypocalcification) of the first permanent molar among children born by C/S, were significantly different from the children born by NVD (P=0.0002). Mean while, the prevalence of these enamel defects in the selective cessarian delivery was more than elective cessarian delivery (17% vs. 9%), which was not statistically significant (P-0.07) It is suggested that gynecologists, pediatricians and pedodontists provide the parents with necessary information about the child's first permanent tooth and ask them to pay enough attention to keep this tooth which is considered as the key of occlusion.

Statement of Problem: One of the easiest and most practical methods to predict the size of permanent canines and premolars, is of Tanaka-Johnston, but their research has been only performed on white skin North Europeans and it should be noted that the size of teeth, in various races, differ from each other. The aim of this study was to determine the validity of Tanaka-Johnston method, in a sample population taken from Ghazvin city. The numbers of 235 pairs of study casts, prepared before any kind of treatment, were selected. The size of lower permanent incisors and permanent canines and premolars of both arches were measured. To analyze the results, "regression analysis" and "t test" were used. Based on the findings obtained from this study, new prediction equations as Y=12.9+0.4(X) and Y=]0.6+0.5(X) were presented for maxilla and mandible, respectively. However, these equations did not differ from Tanaka-Johnston equations statistically. Tanaka- Johnston equations can be acceptably applied for the sample population taken from Ghazvin city, if the predictions are not overestimated.

Statement of Problem: Rapid increases in the population of hemodialyzed patients induce the dentists to acquire a complete understanding of the special therapeutic considerations for such patients. The goal of this research was to study the amount of DMF in hemodialyzed patients, age ranging from 12-20 years, in the city of Tehran. In this cross- sectional and analytic- descriptive research, 50 kidney patients (27 mail and 23 females), with the age range of 12-20 years were selected. They had referred to one of the following hospitals for hemodialysis: Imam Khomeini, Children Medical Center Fayyazbakhsh, Haft-e-Tir, Ashrafi Esfahani, Labafinejad and Hasheminejad. The data, based on clinical examination, patient's answers, patient's medical files, parents replies, were collected and analyzed by Chi- Square test. The average DMF, for. patients under study was 2.46, comparing to the normal subjects of the society, no significant difference was observed. Factors such as sex, Mother's education, oral hygiene and the number of daily brushing did not show any statistically significant difference about this index. The results also showed a 38% prevalence of severe gingivitis and 32% of moderate gingivitis. This restricted study emphasizes the necessity to use proper preventive methods and to improve the patient's and parent's knowledge about oral and dental health.

Statement of Problem: The correlation between the activity of aspartate aminotransferase (AST) and alkaline phosphatase (ALP) enzymes in gingival sulcular fluid (GCF) with inflammation and periodontal attachment loss has been proved, however there are not adequate studies about dental implants. The aim of present study was to investigate the presence and activity level of AST & ALP and their correlation with pocket depth (PD) and bleeding of peri-implant slcular fluid (PISF), and to evaluate the possibility of using these assessments as a diagnostic index in oral implantology. In this study, 41 implants as test group and 41 contralateral teeth as control group, in 21 patients were evaluated. At first visit, the general information about implants and the values of pocket probing depth (PPD), modified sulcus bleeding index (mSBl) and modified plaque index (mPI) were recorded. At the second visit, samples of GCF/PISF were collected. AST & ALP activity was determined spectrophotometrically and data were analyzed by "t", "Mann-Whitney" tests and Pearson Spearman correlation coefficient. The results showed that there was a significant difference in the activity of AST between two study groups (P<0.0001). The average activity of ALP in test group was more than control group but the difference was not significant. After elimination of the confounding variables, the average AST in test group was 54.6 (S£=2.3) and in control groups was 44.8 (SE=2.3) (P=0.004). The average ALP in test group (SE=2.2) and in control (SE=2.2) were 36.6 and 35.4, respectively. Values of AST and ALP were positively correlated with other clinical parameters such as PD and mSBI which was significant in test group. The present study suggests that PISF analysis could be considered as a proper diagnostic strategy in the evaluation of dental implant success.

The health of habitants, living in un-fluoridated drinking water areas, can be endangered through fluoride intake from food, beverages, tooth paste and dentistry products. Fluoride is used in mouthwash, toothpaste, juice fruits, conserved foods and Teflon dishes. Water exposure to fluoride occurs through fertilizers, aluminum industries, insecticides, pesticides, herbicides and fungicides used for fruits and vegetables which ultimately lead to environmental fluoride pollution. Some side effects.caused by chronic fluoride intake are as follows: decrease of hemoglobin concentration, gastrointestinal disorders, and tooth loss at young age, osteofluorosis, hip fracture among aged people, osteosclerosis,osteoporosis, special forms of arthritis and joint ankylosis, metaphysial osteomalacia, mottling and weak structure of tooth, insulin secretion and glucose tolerance test disorders, decrease of urine concentration,immune system disorders, genetic defects and cancer, learning disabilities and IQ(intelligence quotient)deficits and thyroid dysfunction The present article was to investigate the side effect of excessivefluoride intake and to discuss different preventive and diagnostic ways.

Chlorhexidine is bonded well to the oral mucosa and dental pellicle and is poorly absorbed from the astrointestinal tract, but in high concentration it is absorbed enough to produce liver necrosis. In this case a dentistry student accidentally ingested a shot of 20% chlorhexidine gluconate solution. Treatments included washing the oral cavity with lots of tooth paste, drinking of 5% alginate syrup and ingestion of 5g small pieces of cork. The following adverse effects were experienced: headache, giddiness, mild mist, euphoria, stomachache, diarrhea and complete loss of taste sensation for 8h, which recurred gradually during the last 48 hours. According to the poor absorption, low toxicity and low concentration of conventional mouthwashes, systemic toxicity following drinking of some shots of this solution is rare. Ultimately if may cause gastritis. Other treatments which are helpful in the same cases are: drinking of hard water, kaolin and tragacant syrup, bicarbonates such as baking soda, carbonates such as beverage, citrates such as lemon-juice and chlorides such as brine and so on.