مجله دانشکده دندانپزشکی مشهد
سال سی و نهم شماره 1 (پیاپی 92، بهار 1394)

It has been demonstrated that nanoparticle-containing mouthrinses could be effective for plaque control. This study aimed to evaluate the color stability of a dental composite after exposure to several colloidal solutions containing nanoparticles. The composite specimens were prepared and immersed in distilled water for 24 hours. Then, the colors of all specimens were assessed according to the CIELAB system (First stage; baseline). Afterwards, the specimens were immersed for 24 hours in mouthrinses containing nanoTiO2, nanoZnO, nanoAg, nanoCuO, chlorhexidine (positive control) or distilled water (negative control) and color assessment was performed again (second stage; after immersion in mouthrinse). Finally, the teeth were brushed with an electrical toothbrush for 1minute, and color measurement was performed again. The level of color change between different treatments stages was compared among the study groups using ANOVA and Tukey test (α=0.05) ANOVA showed significant between-group differences in the color change among different treatment stages (P<0.05). The color change between the first and second stages was significantly lower in chlorhexidine and silver mouthwash compared to CuO and TiO2 mouthwashes. Discoloration in all groups was significantly greater than distilled water (P<0.05). The color change between the first and third stages was statistically comparable in all mouthrinse groups, and was significantly greater than distilled water (P<0.05). Nanoparticle-containing mouthwashes exhibited the same or even greater staining effect compared to chlorhexidine. Tooth brushing had little effect on stain removal from the composite specimens.

because of problems associated with dentures nowadays implant supported overdentures are used widely. Despite the high success of implants, implant failure remains a major challenge. Implant overload is a factor for cortical bone loss and implant failure. This study, evaluated 3 designs used in overdentures with three implants, using finite element analysis for their stress distribution. Using finite element method, a geometrical model of the mandible was produced with CT data and three ITI implants were placed at the midline and at the first premolar teeth. All conditions were simulated using finite element software. Three treatment bar-ball, bar and ball were considered to support the overdenture. Maximum von Mayzz stress levels were compared for all attachments and supporting bone and mandibular flexure attachment was compared in different designs. Results showed that the greatest amount of stress on the bone was around the upper thread and the neck of the implants. Attachment of the ball and the bar-ball induced the greatest and the least amounts of stress to the bone around the implants respectively. The maximum stress could be seen on the ball attachment in the bar-ball design. The maximum amount of the movement was show in bar-ball attachment. According to the results, the bar-ball treatment plan with reducing the stability of over denture will reduce the stress around the bone of implant and ball treatment plan with increasing bone stress around the implant will increse the stability of overdenture.

In addition to successful osseointegration, the goal of the modern implant therapy is to provide an esthetic and functional restoration similar to natural dentition. To this end, lots of problems still remain, including a loose abutment which often leads to patient dissatisfaction. Herein, it is aimed to investigate the mechanical properties, contact surface design in screw type abutments. In the present study, five implant systems were evaluated through 103 finite element complex models subjected to static, dynamic, thermal, and cyclic loads to simulate stress distribution in abutments and fixtures in the lateral incisor position. Between the two types of the threaded abutments, one-piece screw abutments showed higher stiffness than two-piece abutments with retain screws. Despite the higher resistance of one-piece abutments compared to the two-piece abutments in internal connection implant systems, due to the diverse designs of implants, the results may vary in different systems. Hence, improvements in the design of the connection between the internal fixture and the abutment, holds a significant role in the loosening resistance.

Quarternary ammonium compounds are a group of chemical compounds that are antiseptic and are used to disinfect surfaces and dental devices nowadays. In this study, the antimicrobial effects of disinfectant Disept, Micro10 enzyme and Helvemed forte on dental instruments contaminated with Staphylococcus aurous and Candida albicans were compared. In this experimental study, 88 drills were divided into four equal groups and and using on autoclave, were sterilized. Burs were immersed in Staphylococcus aurous and Candida albicans suspension. Burs contaminated with the microorganisms in group A were placed in the antiseptic solution Helvemed forte, Group B in Micro10 enzyme and Group C in Disept and were them Set in BHI culture environment. Next, the polluted environment was cultivated with candida albicans in sabouro dextrose agar and in SBA for staphylococcus aurous. Group D as controls were cultured without exposure to the disinfectant solution. The data were analyzed usage SPSS software and chi square test. P<0.05 were considered significant. No microbial growth was observed in the first 3 groups but in group D (control), culture was positive. Disinfectant Iranian solution Disept at a concentration of 5% is similar to products Micro10 enzyme and Helvemed forte. Disept is cheaper and more available compared to the other products.

One of the best methods for reconstruction of bone defects in the area of dental patients is using autogenously bone grafts that is considered the gold standard for bone defect augmentation. Different intraoral donor sites to harvest the bone graft are available and the maxillary tuberosity due to its convenient surgical access and fewer complications is a perfect place for taking a limited amount of bone. The aim of this study was to evaluate maxillary second molar periodontal problems after tuberosity bone graft harvesting. 15 patients admitted to the Department of Oral and Maxillofacial surgery at Mashhad Dental School with ages ranging from 20 to 40 years, were studied. For each patient, pocket depth index, gingival attachment loss index, plaque index, gingival index and bleeding on probing at four areas including middistal, disto buccal, disto lingual of each tooth, both before and 6 months after surgery were measured and recorded. Paired t test and Wilcoxon and Mc Nemar tests were used for data analysis (α=0.05). The data showed that the mean pocket depth of distal of maxillary second molar, both before and 6 months after surgery, showed a rate of 15.4% reduction which was significant (P=0.002). Plaque index, gingival attachment loss index and gingival index were ordinal evaluated as and all three had declined significantly over time (P-value=0.002, 0.025 and 0.077 respectively. Bleeding rate observed at 6 months after surgery showed a 21.4% decrease which was not significant (P=0.250). The removal of bone from the maxillary tuberosity, will not cause any periodontal problems for second molar maxillary and if the supporting bone distal to it is damaged during surgery, would be restored so that there will be a normal biologic width and pocket depth.

Stainless steel crowns are valuable materials for the restoration of primary second molars. Luting cements provide the connection between crowns and prepared tooth structure so the aim of this study was to evaluate and compare the retentive strength of stainless steel crowns to the teeth after using luting cements including poly carboxylate, zinc phosphate, glass ionomer and adhesive resin cements. A total 48 primary second molars were randomly divided into 4 groups, the standard crown preparation (stainless steel crown) was done on each tooth and a crown with suitable size and retention were selected for each tooth before cementation. A U shape orthodontic wire was soldered to the crown and then the crowns of each group were cemented with one of the four cements. Next, the teeth were kept in artificial saliva and incubated for 24 hours at 37ᵒc. After that using a specially designed Instron Universal Testing Machine, the teeth were pulled away with 2mm/min speed. The load was gradually increased so that the signs of dislodgement of the crown from tooth would be observed. The surface area of SSC was measured by a graphical method. The retentive strength was measured in terms of load/area (kg/cm2). The mean retentive strength (kg/cm2) of poly carboxylate cement was 17.2±3.3, 19.8±3.8, zinc phosphate 17.01±3.8 for glass ionomer and 19.27±3.7 for resin cement. Based on statistical analysis of One Way ANOVA, there was no significant statistical difference among 4 groups. (P=0.1) The retentive strength of these four cements showed non-significant difference. Therefore, the selection of the cement could depend on the individual patient’s needs and decision of practitioner.

Cervical vertebrae morphology is used in planning orthodontic patients’ treatment for assessing skeletal maturation. The aim of this study was to investigate the relationship between chronological age and Cervical Vertebral Maturation (CVM) stages. In this descriptive-analytical study, 320 lateral cephalograms over an age range of 7-15 years (160 boys and 160 girls) were investigated in the city of Babol, Iran. The subjects were divided into eight age groups. The Baccetti modified version of CVM method was used for the assessment. The assessment consisted of visual analysis of morphological characteristics of the three cervical vertebrae (C2, C3, C4). Data analysis was done using SPSS (version 20) software. P≤0.05 was considered significant. The spearman correlation coefficient between chronological age and cervical vertebral maturation stages was 0.841 (P<0.001) in total sample size, 0.839 (P<0.001) in boys and 0.873 (P<0.001) in girls. The positive likelihood ratio for detecting cervical vertebral stages was low in all age groups; except for age range of 7-8 in boys and girls, and age ranges of 8-10 and 14-15 in the girls. The results of this study demonstrated that the CVM method is reliable for the determination of onset of puberty and despite the high correlation coefficient between chronological age and cervical vertebral maturation stages, the low positive likelihood ratio in most age groups results that the chronological age is a poor indicator for detecting maturation stages.

Medicinal application of plants has been after used for the treatment of different diseases throughout human history. There is an increasing need for antiviral drugs since the treatment of viral infections with the available antiviral drugs often leads to the problem of viral resistance. In the present study, Echinacea purpurea plant with ethnomedical background was tested for its inhibitory effect on HSV-1 multiplication at different exposure times. Root part of Echinacea purpurea plant was extracted with decoction method to obtain crude aqueous extract. This extract was screened for its cytotoxicity against Hep II cell line by CPE assay. Antiviral property of the plant extract was determined by Neutralization Test (NT) at one, two and three hours after extract oxposufe following inoculation of HSV-1. Echinacea purpurea plant did not have toxic effect at 50-900 μg/ml concentrations to the cell lines used. Findings indicated that plant extract had the highest inhibitory property when used one hour after virus inoculation that was completely inhibitory for virus replication in concentrations500-900μg/ml, but this anti-herpes specificity decreased in two and three hours. Echinacea purpurea extract exhibited significant antiherpes effect on HSV-1 at nontoxic concentrations to the cell line used. Further research is needed to find action the mechanism of this plant before it could be used in conformation of antiherpes drugs.

Gingivitis is an inflammatory disease involving gums. Saffron contains various forms of flavonoids, glycosides and anthocyanin compounds that are proved to have anti-inflammatory and antioxidant effects. This study evaluates the anti-inflammatory effects of Saffron on gingival indices in patients with marginal generalized plaque induced gingivitis. For this study, we used toothpastes containing aqueous extract of Saffron flower. 22 patients with generalized marginal gingivitis were chosen. Patients were randomly divided into two equal groups of test and placebo each group, pocket depth index (PD), gingival index (GI), plaque index (PI) and bleeding of probing index (BOP) were measured before and one month after use. Independent t test, Mann–Whitney test and Wilcoxon test were used for statistical analysis (P<0.05). The comparison between gingival indices before and one month after tooth paste use showed significant decrease in all measured indices at the end of study (P<0.01). Saffron treated group had a significant difference in reducting GI and BOP indices in comparison with placebo group (P<0.05). However, for PD and PI indices in the difference was not statistically significant (P>0.05). In this study, it was found that using aqueous extract of Saffron flower containing toothpastes may have a positive effect in some gingival indices in patients with gingivitis.

Application of a lubricant material at the abutment screw interface has been proposed to reduce the possibility of screw loosening. The aim of this study was to compare removal torque values (RTVs) of one-piece and two-piece abutments tightened in three different conditions: dry, saliva impregnated and filled with saliva. 10 ITI implants were inserted in acrylic blocks. 10 one-piece abutments were connected on their corresponding implants and tightened with 10, 20 and 35 NCm torques. After each tightening, RTV of the abutment was measured. This experiment was conducted in three different conditions: dry environment, abutment screws impregnated with artificial saliva, and the fixture holes filled with artificial saliva. These procedures were repeated for two-piece abutments. Data were analyzed by repeated measure ANOVA and LSD tests. One-sample test was used to compare the RTVs with respective tightening torques (α=0.05). The RTVs of one- piece and two piece abutments increased continuously when the environment changed from dry to impregnated and filled with saliva respectively (P<0.001). The RTVs of one-piece abutments were higher than those of two-piece abutments in three applied torques (P<0.001). The RTVs of both one-piece and two-piece abutments increased when the abutment screw was impregnated with artificial saliva and the fixture hole was filled with artificial saliva, respectively.