Journal of Research in Dental Sciences
Year:2009 | Volume:6 | Issue:2 (20)|Papers Count:10

Background and Aim: The biomechanics of implant-retained overdentures can lead to different resorption patterns in the posterior regions of each arch. Two of the most commonly used attachment systems for these type of prostheses are Bar/clip and Ball/rider. The aim of the present study was to compare two types of implant-retained overdenture attachments on the stresses introduced to the mandibular posterior ridge by means of 3D Finite Element Method.Materials and Methods: This experimental study performed with Ansys software. The basic model was generated from data provided by a CT-scan of edentulous patient. Four root form implants were placed in interforaminal region of the mandible. Models were used in order to simulate two situations: In group A, model represented an edentulous mandible supporting an overdenture retained by Four-splinted implants connected with Bar/clip system while in group B, model simulated an edentulous mandible supporting an overdenture retained by Four solitary implants with Ball attachments. The occlusal load of maxillary complete denture was introduced in two directions for each group: vertical load as in centric occlusion, and oblique load as in working lateral excursion.Results: The amount of stress introduced by overdenture using Bar attachment was higher in centric occlusion whereas ball attachment introduced more force in working lateral excursion.Conclusion: If the only determining factor for choosing the attachment system was the amount of stress introduced to the mandibular posterior ridge, then the Ball/rider system would be the attachment of choice.

Background and Aim: The role of 0.2% chlorhexidine in prevention of dry socket followed bysyrgical removal of third molars has been challenged by pervious research. The purpose of this study was to assess the efficacy of this gel on healing and pain after dental extraction at the OMFS Department of Islamic Azad University, school of dentistry.Materials and Methods: This experimental, double blinded study on 123 patients randomly into three groups which are as follows: First group: gel foam with 0.2% chlorhexidine gel placed into the alveolar socket. Second group: gel foam with placebo placed into the alveolar socket. Third group: no material placed into the alveolar socket. Pain level in the three groups after 24 hours and on days three was evaluated using a VAS scale and Healing process on the 3rd and seventh day was investigated with a healing scale. The incidence of dry socket was also evaluated using the diagnostic criteria specified by BLUM. Data were analyzed with Krusal Wallis, Mann-Whitney - U tests.Results: Healing rate on the third and seventh days in the first group had significant statistical differences compared to the second and third groups (P<0.00). Pain rates on the first day and third day in the first group also had significant statistical difference compared to the second and third groups (P< 0.00). Dry Socket was not reported in the first group. In second group and third group two cases and seven cases of dry socket were found respectively.Conclusion: Results from this study show that the use of 0.2% chlorhexidine gel after third molar extraction is effective in healing process, pain reduction and prevention of dry socket.

Background and Aim: The purpose of this study was to assess the diagnostic efficacy of digital radiography paper print compared to original digital radiographs in detection of proximal dentinal caries.Materials and Methods: this diagnostic study was conducted on 320 extracted premolars with no clinical apparent caries. The teeth were arranged to make the radiographs in 2 methods: 1) intra-oral original digital radiography by using a Cygnus media Ritter, CCD sensor.2) paper print of the intra-oral digital radiographs. Dr. Suny software was used to adjust the size of the digital radiographs into the size of a regular film, before printing them on paper using HP color Laser Jet 1600 printer (2400 dpi). Four maxillofacial radiologists observed the original digital & the same radiographs on paper prints to detect proximal dentin caries. The results were then recorded according to a 5 grades scale confidence score method. Microscopic sections were obtained as gold standard for caries detection and were evaluated by a maxillofacial pathologist. P.P.S. and N.P.P of these two methods were compared to histologic standard.Results: Thirty hundred and twenty of samples had caries and half of them did not.P.P.V of the first method was 85.9% and the mentioned value for the second method was 91.7%. N.P.V. of the first method was 74.6% and the value for the print method was 71.4%, (p< 0.9) Conclusion: Paper print of a digital radiograph is almost as efficient as its original digital radiograph in detecting proximal dentinal caries.

Background and Aim: Considering the high failure rate of bracket bonding in orthodontics treatment, in the event of either the patient accidentally applying inappropriate forces to the bracket or poor bonding techniques, the objective of this study was to determine the effect of resin removal methods on enamel surface and shear bond strength of rebonded brackets.Materials and Methods: A total of 76 fresh human premolars were used in this experimental (in vitro) study, seventy of which were divided into three experimental groups (N:20) and one control group (N:10). (Simple random sampling). After the bonding procedure in the experimental groups using No-mix composite and mesh base brackets, debonding was performed with use of plier. Buccal surface of each sample was examined by an optical microscope (×10) to determine the location of the bond failure interface, using an Adhesive Remnant Index (ARI). The remnant adhesives were cleaned up with three methods: 1- High speed-Tungsten Carbide Bur (TCB), 2- Low speed-TCB, 3- Sandblast with Microetcher. For rebounding procedure each experimental group divided into two subgroups of 10. A- With use of new bracket, B- Sandblasted bracket. Rebounding was performed on 70 samples in experimental and control groups and the second set of SBS and ARI were calculated and statistically evaluated. In six samples, the buccal surface of each tooth divided into four groups for bonding composite to observe the effect of the above interventions on the enamel structure by SEM (×1000). The data was analyzed with (One-way & Two-way) ANOVA, Dunnett t and Kruskul-Wallis.Results: No significant difference was found between control and experimental groups reading Shear Bond Strength (SBS) and ARI detachment levels with respect to resin cleanup methods and bracket type. (P>0.6) But SEM studies showed complete destruction of enemal surface as a result of sandblasting with micro etcher. enamel surface preservation was found to be closest to it normal morphology in TCB group.Conclusion: Enamel damage after rebounding seems to be inevitable but with TCB it can be reduced and also reasonable SBS should be achieved.

Background and Aim: Nowdays, there are several whitening toothpastes claiming to be able to remove external tooth stains. The goal of this study was to compare the efficacy of Crest and Pooneh whitening toothpastes in the prevention of extrinsic tooth discolorations. Materials and Methods: Following scaling and prophylaxis, a total number of 25 volunteers were asked to avoid all types of oral hygienic care during a 4-day period and limit themselves to the use of mouthrinses including 0.2% chlorhexidine, tea and a solution prepared from the experimental tooth pastes. The first two mouthrinses were used on minute per hour from 9 oclock to 16 oclock, one minute per hour and at 9 AM to 4 PM; and subjects were instructed to apply one of the prepared experimental solutions once at 9 AM and once at 4 PM for 2 minutes prior to the use of two mouthrinses. The amount of stain was recorded on the fifth day based on Lobene index . Following a nine-day wash out, the procedure Ws repeated in a similar fashion for the other experimental tooth paste and and the control tooth paste (Pooneh).Results: Significant difference was observed between Crest whitening toothpaste and Pooneh toothpaste (P<0.001). The difference between Pooneh whitening toothpaste and the Pooneh toothpaste was not significant. However, the difference in stain removal between two tooth pastes was also significant.Conclusion: Crest whitening tooth paste is more efficient in reducing extrinsic tooth discoloration compared to Pooneh whitening tooth paste.

Background and Aim: There are major issues of concern regarding of blood pressure & heart rate changes due to injection of local anesthesia and contradictory. According to different reports about exists the effect of local anesthesia agents on cardiovascular system. The purpose of this study was to compare the effect of anesthetic agent: lidocaine 2% with epinephrine and mepivacaine 3% on blood pressure & heart rate changes after inferior alveolar nerve block injection.Methods and Materials: In the present randomized single blind cross over clinical trial study 35 patient (70 models) were participated. In the first visit the patients were injected with one of the aesthetics agents and on their second visit, the other aesthetic agent was injected. Patients were asked to complete the stress questionnaire and then the blood pressure and heart rate were recorded. Afterwards, the injection was made and B.P and heart rate were recorded immediately after the injection and 10 minutes later. Paired T-test was used for data analysis.Results: there was no significant difference between the effect of lidocaine and mepivacaine on blood pressure & heart rate before, right after and 10 minutes after inferior alveolar nerve block injection. Also, no statistically significant difference was found between the two groups in terms of systolic and diastolic BP and pulse rate, although there was a genered increase in the group injected with lidocaine. In the present study, there was a significant positive linear correlation between the score of DAS (stress of dental) and systolic & diastolic blood pressure& heart rate changes before, right after & 10 minutes after the injection.Conclusion: There were no major changes in systolic & diastolic blood pressure& pulse rate immediately & 10 minutes after injection in & among groups, which indicates that use of lidocaine & mepivacaine will not make any systemic difference in healthy patients. However more research is recommended for the systemically compromised patients.

Background and Aim: Increasing demand for esthetic restorations, esp for the anterior teeth has led to a greater use of all ceramic materials. In order to decrease technique sensivity of cementing, self-etch resin cements were offered that need no pretreatment of the tooth. In this paper we compared the shear bond strength of self-etch and total-etch cements of the same brands.Materials and Methods: 60 third human molar divided to 6 experience groups: 1-Rely XUnicem (3M ESPE), 2-RelyXARC (3M ESPE) +Acid etch 37%+SingleBond (3M ESPE), 3- Nexus2 (KerrHawe) Acid etch 37%+Optibond Solo (KerrHawe), 4-Maxcem (KerrHawe), 5-RelyXUnicem (3M ESPE) +Acid etch 37%+SingleBond (3M ESPE), 6- Maxcem (KerrHawe)+Acid etch 37%+Optibond Solo (KerrHawe).The shear bond strength of the specimens were then measured. The surfaces of the dentines were examined using an stereomicroscope.Results and Conclusion: Shear bond strength of the specimens were as followed: (1) 5.27 ±2.91 MPa (2) 9.33±4.83 MPa (3) 3.28±1.12 MPa (4) 10.45±4.82 MPa (5) 5.72±2.29 MPa (6) 11.75±4.01 MPa The shear bond strength of the total-etch resin cements was significantly higher than of the self-etch resin cements (p<0.001).Using pretreatments for self-etch cements was significantly effective for Maxcem (p<0.05).

Background and Aim: considering the limitations of conventional loading time and reported failures of immediate load protocol and on one hand, report of an article starting the success of Sargon expandable implant system, the aim of this study was to evaluate the short-term success rate of immediately loaded expandable implants placed in fresh extraction sockets.Materials and Methods: This quasi clinical trial study included 24 Sargon implants placed in fresh extraction sockets in 20 patients, aged from 23 to 70 years (average: 14.79 ± 13.99 years) which were immediately provisionalized. The final restorations were delivered at 3rd week follow up if the implants were stable. Data were collected at 1, 2, 3 weeks and 1, 2, 3 and 6 months. Sex, region, bruxism and clenching and smoking status were studied as related factors. The failure rate and influence of the related factors were analyzed using Fisher's exact test.Results: Due to leak of patent compliance, 2 of the 24 implants were excluded from the study. The load was removed off of 10 implants (45.4%) that were unstable after immediate loading, and the expansion mechanisms were reactivated for those cases. All the cases became stable later on and they were reloaded. Lower bone quality was statistically associated with a nine fold increase in risk of loosing stability (p<0.001). After a 6-month follow-up period, a success rate of 100% was reported for all implants.Conclusion: The results indicate that immediate loading of expandable implants in fresh extraction socket can be a predictable procedure. A true clinical trial study to evaluate the efficacy of this implant over a longer follow up period is necessary.

Background and Aim: With respect to the concerns regarding non-conformity of practical training with theoretical training and its subsequent negative effects on educational quality and absence of information of such a situation and in order to collect students’ opinions to the above subject, the research was performed on students in 12th semester and up in the faculty of Dentistry in Azad University in 2008.Materials and Methods: This research was done based on the cross sectional method on all students in 12th semester and Up. The number of students who were being studied on were 144.All the members of the list filled a consent form and their opinions regarding conformity of clinical trainings with theoretical subjects were studied. All the subjects which were offered in theory and practice were selected as practical courses. These practical courses were 15 units and the students were asked weather they had any opinion regarding the titles of these practical and theoretical trainings and to evaluate the training within four different categories of full conformity, conformity, little conformity, and none conformity. The parameters related to this research include sex, age, marital status, level of likeness towards the program, semester, grades of general science, final average, employment, social status (with or without immediate family) and parents’ level of education. The level of conformity of the students’ opinions towards theoretical or practical training was evaluated by Sperman test and the role and the role of non-conformity parameters were evaluated by the kaido test.Results: Out of 144 students whom the research was based on, 136 (94.4%) Were qualified. To them, conformity of the training were from 97% to 99%. based on the given results, one could come up with the conclusion that the conformity between these 2 types of training is well correlated.The level of dissatisfaction in the diagnosis section from the quality of the the theoretical training based on the semester curriculum was maximum 63% and 10% in fixed protease. Again, dissatisfaction of practical training in the diagnosis section was maximum 78% and minimum 10% in fixed protease. employed students as well as those living on their own, made a higher evaluation of the level of conformity (p< 0.001).Conclusion: It seems that conformity of theoretical and practical trainings were low according to the students and they were all unanimous and were seriously asked to cope with the proposed issues.

Background and Aim: The level of fluoride in drinking water has always been an issue of concern in dentistry. Too much water fluoridation can result in undesirable conditions such a dental flourosis and low levels of intelligence, whereas too little fluoride can lead to dental caries and increased DMFT. The purpose of this study was to deference the level of fluoride in Shiraz drinking water in the spring of 2009.Materials and Methods: This descriptive research was performed on 36 water samples of all drinking water sources in the city of Shiraz. The sampling process was conducted at nearest home surrounding each source. All obtained water samples were delivered to quality control laboratories at Islamic Azad University, dental branch, Tehran. The level of fluoride in each sample was determined using potentiometer method and the desired fluoride level at specific temperature for the source was calculated using the formula (f=0.34/E, E=- 0.039+0.0062). The samples were then classified into three categories of deficient, efficient and over efficient according to latest WHO standards.Results: This study was performed on 36 samples. The total volume of shiraz water source was two hundred twenty six thousand and two hundred cubic meters and the total amount of fluoride in shiraz drinking water was 0.35±0.15 ppm .The amount of fluoride in 100% of the total drinking water was less than standardized level.Conclusion: The amount of fluoride in shiraz drinking water is significantly lower than the standard level.