Frontiers in Dentistry
Volume:10 Issue: 2, Mar 2013

Accurate delivery of torque to implant screws is critical to generate ideal preload in the screw joint and to offer protection against screw loosening. Mechanical torque-limiting devices (MTLDs) are available for this reason. In this study, the accuracy of one type of friction-style and two types of spring-style MTLDs at baseline, following fatigue conditions and sterilization processes were determined. Five unused MTLDs were selected from each of Straumann (ITI), Astra TECH and CWM systems. To measure the output of each MTLD, a digital torque gauge with a 3-jaw chuck was used to hold the driver. Force was applied to the MTLDs until either the friction styles released at a pre-calibrated torque value or the spring styles flexed to a pre-calibrated limit (target torque value). The peak torque value was recorded and the procedure was repeated 5 times for each MTLD. Then MTLDs were subjected to fatigue conditions at 500 and 1000 times and steam sterilization processes at 50 and 100 times and the peak torque value was recorded again at each stage. Adjusted difference between measured torque values and target torque values differed significantly between stages for all 3 systems. Adjusted difference did not differ significantly between systems at all stages, but differed significantly between two different styles at baseline and 500 times fatigue stages. Straumann (ITI) devices differed minimally from target torque values at all stages. MTLDs with Spring-style were significantly more accurate than Friction-style device in achieving their target torque values at baseline and 500 times fatigue.

The purpose of this study was to evaluate the effect of Er:YAG laser on the shear bond strength of resin modified glass ionomer (RMGI) to enamel. Twenty extracted caries-free human premolars were selected. The teeth were embedded in acrylic resin. The buccal surfaces of each sample were ground to plane enamel with carbonated disc. The teeth were randomly divided in two groups. In the first group, the surfaces were treated by Er:YAG laser (350mJ/10Hz). The second group was prepared by carbide bur. Fuji IX RMGI was adhered to surfaces of the samples in both groups in rod shape. The shear bond strength of samples was measured by a universal testing machine. The results of the two groups were analyzed by T- test. The means and standard deviations of shear bond strength of the laser-treated group and the bur-treated group were 6.75 ± 1.99 and 4.41 ± 1.62 Mpa, respectively. There is significant difference in the shear bond strength of RMGI between the two groups (P-value=0.01). The laser group showed better results. Er:YAG laser can be an alternative technology in restorative dentistry.

Comparative evaluation of the reinforcing effect of different post systems in the restoration of endodontically treated human anterior teeth at two different lengths of post space preparation- an in vitro study 135 extracted human incisors were endodontically treated, out of which 120 teeth were decoronated 2mm above the cementoenamel junction and divided into four experimental groups based on the post system to be used: Glass fiber post (GFP) and stainless steel post (SSP), titanium post (TTP), cast metal post (CMP). Each group was divided into two sub-groups according to the length of post space preparation: 5mm and 10mm. All the samples were restored with metal crowns. The fracture resistance was measured by applying loads at an angle of 135º to the long axis of teeth in an instron universal testing machine. Fracture mode was analyzed for all the samples. Results from the four test groups were compared and analysed using one-way ANOVA test and the Post-hoc Bonferroni test to demonstrate differences between pairs of groups. The results revealed that SSP group at 10mm post space length showed the significantly (“P-value< 0.05”) highest fracture resistance (793.7787 N). Decrease in post length resulted in the decrease in fracture resistance in all the groups reduced to values even lesser than the control (437.8733N). The different post systems used in the study were able to reinforce endodontically treated teeth only at 10mm post space length.

To investigate and compare the amount of fluoride release of conventional, resin modified and nanofilled resin modified glass ionomer cements. Tablets of glass-ionomer cements were immersed in deionized water and incubated at 37◦C. After 1, 2, 7, 15 and 30 days, fluoride ion was measured under normal atmospheric conditions by fluoride ion selective electrode. Buffer (TISAB II) was used to decomplex the fluoride ion and to provide a constant background ionic strength and to maintain the pH of water between 5.0 and 5.5 as the fluoride electrode is sensitive to changes in pH. Statistical evaluation was carried out by one way ANOVA (Analysis of Variance) using SPSS 11.0. The significance level was set at p< 0.05. The release of fluoride was highest on day 1 and there was a sudden fall on day 2 in all three groups. Initially fluoride release from conven-tional glass-ionomer cement was highest compared to the other two glass-ionomer cements, but the amount drastically reduced over the period. Although the amount of fluoride release was less than both the resin modified and nanofilled resin modified glass-ionomer cement, the release was sustained consistently for 30 days The cumulative fluoride release of nanofilled resin modified glass ionomer cement was very less compared to the conventional and resin modified glass ionomer cements and Nanofilled resin modified glass ionomer cement released less but steady fluoride as compared to other resin modified glass ionomer cements.

The aim of this study was to compare the apical seal of curved canals obturated with Resilon/Epiphany with gutta-percha/AH Plus. Thirty-four extracted human mandibular molars with 25-40 degree canal curvature of the mesial root were selected for this study. After preparation, the mesiobuccal canals were obturated with gutta-percha and AH- Plus sealer (group G) or Resilon and Epiphany sealer (group R). Four specimens served as control. Microleakage was evaluated after passing 3 and 30 days using the fluid filtration technique. The data were analyzed statistically using parametric tests. In the 3-day evaluation, the mean microleakage in group R was significantly less than in group G (P< 0.05). After 30 days, there was no significant difference between the two groups (P> 0.05). In group G, the leakage values at the end of 30 days were significantly less than values at the end of 3 days. Although in group R the mean leakage decreased after 30 days, this reduction was not statistically significant. Resilon/Epiphany provided a better seal than gutta-percha/AH-Plus in severely curved root canals immediately after obturation, although with the passage of time, Resilon/Epiphany was equivalent to gutta-percha/AH Plus in sealing properties.

Handling of endodontic sealers is greatly dependent on their elasticity and flow ability. We compared the viscoelastic properties of three root canal sealers. AH Plus (Dentsply, De Trey, Konstanz, Germany), Endofill (Dentsply Hero, Petrópolis, Rio de Janeiro, Brazil) and AH26 (Dentsply, De Trey, Konstanz, Germany) were mixed according to the manufacturer's instructions. The resulted pastes were placed on the plate of a rheometer (MCR 300, Anton-Paar, Graz, Austria). The experiments were performed at 25˚C and 37˚C. Viscoelastic properties of the sealers including loss modulus (G"), storage modulus (G´) and complex viscosity (η*) were studied using dynamic oscillatory shear tests. The shear module versus frequency (from 0.01 to 100 S-1) curves were gained using frequency deformation sweep test. Three samples of each material were examined at each temperature. The mean of these three measurements were recorded. The storage modulus of AH plus was higher than its loss modulus at two temperatures. Endofill exhibited a crossover region in which the storage modulus crosses the loss modulus in both temperatures. At 25ºC the loss modulus of AH26 was higher than the storage modulus (G">G¢). In contrast, at 37ºC G¢was greater than G² (G¢>G²). Both shear modules of AH Plus and Endofill decreased as the temperature raised from 25ºC to 37ºC. On the contrary, the loss modulus and storage modulus of AH26 increased at 37ºC. In both test temperatures, AH Plus behaved like viscoelastic solids and Endofill exhibited a gel-like viscoelastic behavior. AH26 at 25ºC behaved like liquids, while at 37ºC it was an elastic solid-like material.

Crestal bone loss is a biologic complication in implant dentistry. The aim of this study was to compare the effect of progressive and conventional loading on crestal bone height and bone density around single osseointegrated implants in posterior maxilla by a longitudinal radiographic assessment technique. Twenty micro thread implants were placed in 10 patients (two implants per patient). One of the two implants of each patient was assigned to progressive and the other to conventional loading groups. Eight weeks after surgery, conventional implants were restored with a metal ceramic crown and progressive group underwent a progressive loading protocol. The progressive loading group takes different temporary acrylic crowns at 2, 4 and 6 months. After eight months, acrylic crowns were replaced with metal ceramic crown. Computer radiography of both progressive and conventional implants was taken at 2, 4, 6, and 12 months. Image analysis was performed to measure height of crestal bone loss and bone density. The mean values of crestal bone loss at month 12 were 0.11 (0.19) mm for progressively and 0.36 (0.36) mm for conventionally loaded implants, with a statistically significant difference (P < 0.05) using Wilcoxon sign rank. Progressively loaded group showed a trend for higher bone density gain compared to conventionally loaded group but when tested with Repeated measure ANOVA, the differences were not statistically significant (P > 0.05). Progressive group showed less crestal bone loss in single osseointegrated implant than conventional group. Bone density around progressively loaded implants showed increase in crestal, middle and apical.

Despite the current use of radiography for quantifying sagittal skeletal measurements, it is an unsuitable way for screening or epidemiologic purposes. Although not fully approved, anthropometric measurements have been suggested as a substitute, and considering displacement of soft tissues, could possibly lead to more consistent results. The purpose of this study was to evaluate the reliability of anthropometric anteroposterior facial measurements under soft tissue compression using a special ruler. Anthropometric measurements were done with a specifically designed sliding ruler twice on 36 adult patients with a 14 day lag between two measurements. The ruler measured the distance between the external acoustic meatus and the nasion (Na), subnasal (Sn) point and the soft tissue pogonion (Pog). The soft tissue was displaced during measurements only to the extent that the underlying hard tissue resistance was felt subjectively by each assessor. The intraclass correlation coefficient (ICC) was calculated for both inter- and intra- rater measurements using SPSS software. All measurements had inter- and intrarater agreements above 0.9, with only a few parameters having lower bound confidence intervals below 0.9, but more than 0.8. Sagittal facial anthropometric measurements under soft tissue displacement using the specific ruler are valid and reliable and could possibly aid orthodontists in chairside craniofacial assessments.

Multiple adhesive coating is a controversial topic, especially in primary dentition that should be clarified. We evaluated the effect of multiple consecutive adhesive resin coatings on the microshear bond strength (µSBS) of composite resin to primary tooth dentin utilizing a filled (Adper Single Bond Plus) and an unfilled (Adper Single Bond) adhesive resin.

Thirty extracted primary canines were randomly allocated into two groups based on the adhesive used. Dentin occlusal surfaces were exposed and further polished on 400, 600 and 800-grit silicon-carbide paper. The surfaces were divided into two halves in the labial-lingual orientation. After etching, the adhesives were used either in double coats, or four coats on the halves of the same tooth followed by air evaporation for each layer and finally light curing. Cylinders of composite were bonded to the dentin surfaces. After 24 h shear bond testing was evaluated by Bisco tensile tester. ANOVA, Student t test and paired t test were used for statistical analysis.

The mean (standard deviation) for double coats or four coats in single bond were 31.99 (2.94) and 30.25 (2.69), while they were 29.18 (3.35) and 31.26 (2.07) in single bond plus, respectively. No significant differences were found between the double coated specimens and those receiving four coatings with both adhesives (p>0.05). Micro SBS values of Single Bond double coated specimens were significantly higher than Single Bond Plus (p=0.02). In four-coated specimens, there were no significant differences between Single Bond and Single Bond Plus (p=0.26).

Applying four coats of adhesive did not improve the µSBS to primary tooth dentin.

To compare three various methods in the diagnosis of dentinal cracks formed in the apical third after root resection. One hundred extracted human maxillary central incisors were selected. The root canals were prepared with step-back technique. Then 3mm from the apical end of all roots was cut perpendicular to the long axis of the tooth. The apical end of each root was evaluated to make sure there were no cracks. Fifty specimens were randomly chosen and connected to an apparatus especially designed for application of force (50-60N) by a universal testing machine for crack formation. The cracked (no=50) and non-cracked (no=50) specimens were examined by three methods of fiber optic transillumination, methylene blue staining and combination of the two. Sensitivity and specificity of the methods were evaluated. The most suitable method for detecting cracks was determined using Youden index. To compare agreement between studied methods with the gold standard, kappa statistics and odds ratio of McNemar were utilized. The sensitivity of transillumination, staining and the combination method were 82.0, 50.0 and 90.0%, respectively. The staining technique had the lowest sensitivity and the highest specificity. Both transillumination and the combination method had Youden index of 0.56, but the combination method diagnosed truly cracked samples more than the other techniques. The efficacy of transillumination in identification of apical root-end cracks undetectable by unaided vision was similar to the combination method. However, the efficacy of 2% methylene blue without transillumination was significantly lower than the other two methodologies.

Because of the great challenges in the diagnosis and treatment of "C" configuration and lack of any systematic information about its occurrence, the purpose of the present study is to determine the prevalence of C shaped root canals in Iranian population. An exhaustive search was undertaken to identify published and unpublished researches related to the C-shaped canals by using key words. The search of the MEDLINE database included all publications from 1966 to May 2012.Then selected articles were obtained and reviewed. Data evaluated and summarized in the data sheet included methodology, population, number of teeth per study (power), number of root canals, type of root canal configuration, and c-shaped canals. Six studies were included with total of 1062 teeth, all in mandibular second molars. The total incidence of C-shaped canals in Iranian population was obtained 6.96%, The incidence of C-shaped canals in Iranian population is 6.96%, which seems much less than Asian populations but nearer to Middle East countries.

Primary immune thrombocytopenia is an acquired bleeding disorder with no clinically apparent cause of thrombocytopenia. Clinical indicators of ITP include easy bruising of the skin, prolonged bleeding on injury, mucocutaneous lesions such as petechiae and ecchymosis, epistaxis, gastrointestinal bleeding, hematuria and bleeding from the gums. It is important for a dentist to be aware of the clinical manifestations of ITP as it may not only lead to successful management of the patient, but in some cases it may even lead to formation of a provisional diagnosis of the condition in previously undetected cases. However, very few cases of ITP have been reported in dental practice making it difficult for a dentist to identify the disorder when a patient suffering from ITP reports for dental treatment. A case report of a female patient with ITP is thus described with emphasis on the importance of periodontal health in such patients to prevent consequent unwanted sequelae. It is followed by discussion of oral manifestations of the disorder and dental management of such patients.