Journal of Dental School, Shahid Beheshti University of Medical Sciences

Objective: Antibacterial properties of silver nanoparticles have recently come into the spotlight in endodontic therapy. This study was conducted aiming at comparing the antimicrobial activity of a new irrigation solution containing nanosilver particles with that of sodium hypochlorite and chlorhexidine against Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa and Candida albicans with direct culture technique.

Methods: In this in vitro experimental study, Mueller Hinton agarmedium was prepared for cultivation of E. coli, C. albicans and P. aeruginosa species and Bile-Esculin agar culture medium was used for E. faecalis. Understudy irrigation solutions were chlorhexidine 2%, chlorhexidine  0.2%,  sodium hypochlorite  5.25%,  sodium hypochlorite  2.5%,  sodium hypochlorite  1.125%  and

nanosilver solutions of 25, 50, 100, 150, 200, 400 and 4000 ppm. After preparation, the bacteria  were exposed to these solutions and the culture media were stored in an incubator at 37°C for 24 hours.The diameter of growth inhibition zone was determined for different microbial species and data were analyzed using Kruskal-Wallis and Dunnett’s tests.

Results: Significant differences were found between various irrigation solutions based on the diameter of growth inhibition zones for E. faecalis, E. coli, C. albicans and P. aeruginosa (P<0.0001). The greatest antimicrobial activity against microbial species belonged to sodium hypochlorite 5.25% and 2.5%. Silver nanoparticle solution had an acceptable antimicrobial activity  in comparison to other solutions and its antimicrobial property constantly improved by increased concentration of Ag ions. The nanosilver containing irrigation solution at different concentrations up to 100 ppm did not show a significant difference with sodium hypochlorite 1.25% in terms of antimicrobial efficacy. Furthermore, the greatest antibacterial activity against P.aeruginosa was observed at different concentrations of nanosilver up to 100 ppm; whereas, chlorhexidine showed no antimicrobial activity against this microorganism.

Conclusion: Based on the obtained results, nanosilver canal irrigation solution had a lower but acceptable antimicrobial activity against various bacterial species compared to conventional irrigation solutions. Therefore, once other characteristics of nanosilver are approved, further studies can be performed to improve its properties and use it as an alternative to conventional root canal irrigation solutions.

Objective: Knowledge about the internal anatomy of the root canal and apical foramen is a critical prerequisite for root canal therapy and is necessary for the success of endodontic treatment. This study aimed to determine the distance of apical foramen from the anatomical apex and apical constriction, evaluate the deviation of apical foramen from the anatomical apex and specify the most common canal types in maxillary premolar teeth using stereomicroscope.

Methods: In this laboratory experimental study, 100 extracted first and second maxillary premolars of patients presenting to dental clinics in Tehran were selected. After the disinfection of roots and access cavity preparation, apical foramen deviation and its distance from the anatomical apex were determined by introducing a #10 hand file into the canal and observation under stereomicroscope; 2% methylene blue was then injected into the canals and demineralization and clearing process were carried out to measure the distance of apical foramen from the apical constriction and evaluate the canal type.

Results: The mean distance of apical foramen from the anatomical apex and apical constriction was 0.4-0.5 and 0.5-0.7 mm, respectively in maxillary first premolars and 0.3-0.7 and 0.6-1 mm, respectively in maxillary second premolars. In less than 17% of first premolars and 37% of second premolars, the canal followed a straight path to the anatomical apex without any deviation towards the mesiodistal or buccolingual directions. The most common canal type according to Vertucci’s classification was type IV in the first and type I in the second premolars. In general, 94% (n=47) of the first premolars and 46% (n=23) of the second premolars had 2 canals while the remaining teeth had a single canal.

Conclusion: This study showed that the apical foramen in premolar teeth is located at a 0.3-0.7 mm distance from the anatomical apex and 0.5-1 mm distance from the apical constriction. In more than 83% of first premolars and 63% of second premolars the apical foramen did not correspond to the anatomical apex. First and second premolars had 2 canals in 94% and 46% of cases, respectively.

Objective: Iron deficiency anemia is among the most common types of childhood anemia. According to the World Health Organization, approximately 5 billion people were suffering from iron deficiency anemia worldwide in 2001. Aside from causing anemia, iron deficiency can negatively affect the physical and mental development of children and adolescents. Several studies have discussed the consequences of inadequate iron intake among which we may name changes in deciduous teeth. Considering the importance of iron supplementation, the present in-vitro study aimed at assessing the surface roughness of deciduous teeth following exposure to three different iron drops.

Methods: This in-vitro experimental study was conducted on 90 sound anterior deciduous teeth that were divided into 6 groups. After surface preparation, the teeth were placed in cariogenic environment. Different ferrous sulfate compounds were added to 4 media and the remaining two groups were  considered as positive and negative controls. Fourteen days later, the specimens were removed from the media, sectioned labiolingually, polished and enamel and dentin microhardness were evaluated. The  mean microhardness value for the 15 specimens in each group was recorded. ANOVA was applied for comparison of data and LSD test was used for multiple comparisons.

Results: No statistically significant differences were found in enamel microhardness of the 6 understudy groups. The mean microhardness of dentin was significantly different in the three understudy depths. Dentin microhardness immediately below the DEJ, at 250 Mm distance from the DEJ and at 450 Mm distance from the DEJ was (kgf/m2) 68.72 (10.00), 67.75 (8.75) and 68.75 (11.86) in group 1, 69.22

(12.46), 73.06 (9.36) and 69.29 (8.01) in group 2, 68.533 (12.27), 64.63 (10.64) and 69.64 (10.15) in

group 3, 83.033 (11.22), 71.68 (16.01) and 70.88 (17.60) in group 4, 60.080 (9.83), 63.52 (14.46) and

65.49 (11.20) in group 5 and 91.91 (43.76), 88.62 (20.47) and 85.04 (26.56) in group 6 (p=0.001 for all three), respectively. Pair-wise comparison of groups revealed that the mentioned difference is due to the statistically significant differences between group 6 and other groups and the remaining groups were not significantly different.

Conclusion: This study showed that iron supplementation had no effect on demineralization of tooth structure.

Objective: Propolis is a resinous material produced by honeybees that has recently gained fame as an antimicrobial agent. This study sought to assess the effects of propolis as an intra-canal medicament on tooth discoloration. The effect of its application technique on the degree of discoloration was investigated as well.

Methods: This experimental study was conducted on 40 intact anterior human teeth. After access cavity and canal preparation, the teeth were randomly divided into three groups. In group A, propolis was placed inside the canals and pulp chamber. In group B, propolis was used as an intracanal medicament. Group C was considered as the control group and saline solution was injected into the canals. Labial surfaces of all teeth were digitally photographed using a digital camera (Fujifilm at one day, one week, 2 weeks, one month and 2 months time points. Color of teeth was assessed and measured at incisal, middle, and cervical segments using the CIELab system and Photoshop  software. Collected data at different time points were statistically analyzed.

Results: The overall color change in the two groups of A and B was significantly different from the control group (P<0.001). Significant changes in color were also noticed in follow up sessions in groups A and B (P<0.001). At 2 months, the difference in overall color change between incisal, middle and cervical thirds of teeth in groups A and B was not statistically significant.

Conclusion: Based on the obtained results, application of propolis as an intracanal medicament can lead to clinical color changes in tooth crown. Its application technique has no effect on the degree of discoloration.

Objective: The present study assessed the association of size, axial angulation, developmental stage and bud position of the mandibular third molar with the second molar impaction in patients with mandibular second molar impaction.

Methods: In this descriptive-analytical study (Case-Control Design), dental records of 5,420 patients in the age range of 12-15 years who underwent orthodontic treatment were assessed out of which 20 patients (14 females and 6 males) with lower second molar impaction were studied. Twenty control patients with erupted second molars were selected from the same centers and matched with the case group. Total sample size was 40 (Case and Control) and had normal distribution for the determined measurements. Third molar axial angulation towards the second molar, first molar and mandibular base, mesiodistal width of 3rd molar /2nd molar ratio, Nolla developmental stage and third molar bud position were measured and calculated in patients with impacted and erupted second molars and analyzed using student t and chi-square tests.

Results: The mean degree of third molar angulation towards the second molar, first molar and mandibular base was 30.20, 53.6, and 51.3 degrees in cases and 21.4, 34.65 and 45.15 degrees in controls, respectively. Significant differences were found between the two groups in terms of third molar angulation towards the second molar (30.2 Vs 21.4 degrees p<0.047), and first molar (53.6 Vs

34.65 degrees p<0.0001); while no differences were found between the two groups in terms of third molar angulation towards the mandibular base (51.3 Vs 45.15 degrees). The mean mesiodistal width of third molar/ second molar ratio was 0.99 in cases and 0.95 in controls with no significant difference. Nolla developmental stage and position of the marginal ridge of the third molar bud towards the second molar showed no definite relation with second molar impaction.

Objective: Temporomandibular disorders (TMDs) are among the most common disorders of the maxillofacial region and are often characterized by pain and dysfunction of the temporomandibular joint(TMJ) and muscles of mastication. Due to the presence of several diagnostic criteria for such disorders, the reported prevalence rates for TMDs have been variable in different communities. The aim of this study was to determine the prevalence of TMDs in patients presenting to the Prosthodontics Department of Shahid Beheshti Dental School (SBDS) in fall 2010.

Methods: In this descriptive study, 150 patients presenting to the Prosthodontics Department of SBDS (86 females and 64 males) were randomly selected and evaluated by using a questionnaire (subjectively) and clinical examinations (objectively). Presence and prevalence of various symptoms of TMDs such as clicking and tenderness on palpation in the muscles of mastication and the TMJ were evaluated in patients. Statistical comparisons were carried out using chi-square test.

Results: Clicking, masticatory muscle and joint tenderness, TMDs, and limitation of mouth opening were found in 21.3%, 18.7%, 5.3%, 18.7% and 1.3% of patients, respectively. Despite the higher prevalence of TMDs in females, the difference in this regard between males and females was not statistically significant (39.3% in men versus 60.7% in women).

Conclusion: Based on the obtained results, the prevalence of TMDs and its related symptoms was 18.7% in patients presenting to the Prosthodontics Department of SBDS in fall 2010. This value was lower than the rates reported in the literature.

Objective: At present, treatment of edentulous areas with implant-supported prosthesis has greatly increased. The aim of this study was to assess the survival rate of implants with different diameters. Methods: This retrospective study was conducted on 239 warfare victims presenting to Qazi Tabatabaie Clinic during 2000-2010. A total of 1,649 implants were placed. The success criteria included presence of osteointegrated implants with no sign of infection, mobility, or lucency around them. Data were extracted from patients’ records and recorded in questionnaires. Statistical analysis was carried out using Chi-square or Log-Rank test.

Results: A total of 1,533 implants were evaluated out of which, 61 (4%) had failed. Survival rate of implants of different brands had a significant association with implant diameter as the highest failure rate was observed in implants with 5-6.5 mm diameter and the lowest failure rate belonged to 3-3.5 mm diameter implants.

Conclusion: Study results demonstrated that the survival of implants may be affected by their diameter as the failure rate was higher in implants with greater diameters.

Objective: In comparison to clinical oral health indices, perceived oral health measures are less applied in large-scale epidemiological oral health studies in Iran. The aim of this study was to measure perceived oral health among adults in Tehran, Iran.

Methods: In this cross-sectional study, perceived oral health was measured in 1100 adults in Tehran by two measures: 1- non-replaced extracted teeth, and 2- revised Rand dental health questions including pain, chewing problems and communication problems. Data was gathered by telephone interview using gender, age and level of education as socio-demographic information.

Results: The mean number of non-replaced extracted teeth was 1.28 with 53.8% of adults reporting no extracted teeth. Extracted teeth was significantly less in younger (p<0.001) and more educated people (p<0.001). Rand dental health scores increased by age (p<0.001) but had no significant changes in different educational levels. The three items of Rand dental health were highly correlated (p<0.01) with Chronbach’s Alpha=0.73 but were not correlated with extracted teeth.

Objective: Zirconium oxide has gained the spotlight during the recent years as a high strength ceramic material. However, despite its mechanical superiorities, it forms a weak bond with different synthetic substrates and tissues due to its neutral nature and resistance against chemical agents. Therefore, it is important to improve the bonding technique in order to prevent microleakage and increase retention and fracture resistance of the restoration.

Literature Review: Since the discovery of zirconium oxide, several surface treatment methods have been evaluated to increase its bond strength to resin cement such as surface grinding with micro- abrasion, burs or abrasive papers, tribochemical silica coating, silicoating, glass micropearls, glaze- on technique, selective infiltration etching, hot etching and use of phosphate ester monomers. The mentioned techniques and related articles are reviewed and discussed in the present study.