Journal of Research in Dental and Maxillofacial Sciences
Volume:2 Issue: 4, Autumn 2017

Dental implants with angled abutments are often inserted in the anterior maxillary region due to the status of the residual ridge and aesthetic considerations. The purpose of this study was to assess stress and strain distributions in the premaxillary bone around dental implants by means of finite element analysis (FEA). Four three-dimensional (3D) finite element models were designed by using ANSYS 14.5 software: (1) a straight titanium abutment, (2) a straight zirconia abutment, (3) a 20° angled titanium abutment, and (4) a 20° angled zirconia abutment in the anterior maxilla. Standard Straumann® implants with regular necks (4.8×12 mm) were selected. Premaxillary bone with type 3 bone quality was modelled with a 0.5-mm-thick cortical layer. A 178-N oblique load was applied to the cingulum of the models. Afterwards, stress and strain distributions were measured by using ANSYS 14.5 software. Maximum stress and strain concentrated at the implant-abutment joint at the cervical one-third of crestal bone, mainly in the labial surface. The abutment's material had a less substantial effect on the distribution of stress and strain compared to the angle of the abutment. Stress and strain concentration in angled abutments was higher than that in straight abutments. However, angled abutments transferred lower levels of stress and strain to the bone compared to straight abutments. It can be concluded that an angled abutment might decrease the stress and strain in the anterior maxillary bone in comparison with straight abutments.

The Gow-Gates (GG) block and the inferior alveolar nerve block (IANB) can be used interchangeably for anesthetizing mandibular molars. The aim of this study was to compare these two injections in root canal therapy of mandibular molars with regard to heart rate (HR) and blood oxygen saturation (BOS) changes. Thirty patients between the ages of 18-70 years having mandibular molars on both sides of their jaw and in need of root canal therapy were recruited after signing a consent form. The patients' HR and BOS were measured 5 minutes before and immediately, 2, 5, 10, 15, and 20 minutes after injection by using a pulse oximeter. Paired t-test and Friedman test were used for statistical analysis of the data. This study was done on 30 patients (60 teeth). The results of HR and BOS showed no significant differences between the two injection techniques (P=0.6 and 0.7, respectively). Also, HR and BOS in each group were not significantly changed during the follow-ups (P=0.7 and 0.6, respectively). According to the results, IANB and GG block by using 2% lidocaine and 1:80000 epinephrine had no significant different effects on HR and BOS.

Discolored teeth are among the most common reasons behind seeking esthetic dental treatments. Resin infiltration is a new technique for treatment of white spot lesions (WSLs). In this technique, 15% hydrochloric acid (HCl) is used to cause surface erosion. The aim of this study was to compare the enamel erosion caused by 15% and 18% HCl gels after different application times. In this experimental study, sixty sound enamel surfaces were randomly divided into six groups of 10 (G1-G6). G1 specimens were subjected to 15% HCl gel for 75 seconds. G2 and G3 samples were subjected to 15% HCl for 90 and 120 seconds, respectively. G4, G5, and G6 specimens were subjected to 18% HCl for 75, 90, and 120 seconds, respectively. The specimens were then evaluated under a scanning electron microscope (SEM), and the depth of erosion was recorded. Data were analyzed by using one-way analysis of variance (ANOVA) and Tukey’s post-hoc test with a 95% confidence interval. The depth of erosion in 18% HCl groups was greater than that in 15% HCl groups after the same application times (P<0.05). The depth of erosion was not significantly different between G3 and G4 samples (P>0.05). The results of this study showed that the application of 18% HCl for 75 seconds is a suitable alternative to the application of 15% HCl for 120 seconds in the resin infiltration technique.

This study aimed to evaluate the effect of repeated bonding by self-etching primers (SEPs) and a conventional phosphoric acid-etchant on shear bond strength (SBS), adhesive remnant index (ARI), and enamel morphology at different debonding time points. In this experimental study, 120 premolars were randomly divided into six groups of 20. In the first three groups, the brackets were bonded by Transbond XT, Transbond Plus, and Beauty Ortho Bond, and were debonded after 30 minutes. Adhesive remnants were removed from the enamel surface by a tungsten carbide bur. Rebonding was done with new brackets as described. The remaining three groups were debonded after aging. The SBS, ARI, and enamel surface morphology were evaluated. The SBS data were analyzed by two-way analysis of variance (ANOVA). The ARI scores were compared by using Mann-U-Whitney and Kruskal-Wallis tests. The SBS of Transbond XT in the first debonding was significantly higher than that of Transbond Plus. Transbond Plus showed a higher SBS than Beauty Ortho Bond. In the second debonding, the SBS values of Transbond XT and Transbond Plus were not significantly different, but their SBS values were significantly higher than that of Beauty Ortho Bond. SEPs showed a higher bond strength in the second bonding compared to the first bonding. Scanning electron microscopy (SEM) showed more porosity in the enamel surface before the second bonding compared to the first bonding. The SBS of Beauty Ortho Bond significantly decreased after aging, and SEM images showed a gap at the resin-enamel interface. SEPs are recommended for secondary bonding in the clinical setting due to a decreased chair time, less damage to enamel, and an adequate bond strength.

Debris and the smear layer that remain after root canal preparations may result in failure of root canal therapies. The aim of this study was to compare the smear layer formation and the amount of residual debris following the use of WaveOne and ProTaper rotary files in mesiobuccal root canals of upper first molars by scanning electron microscopy (SEM). In this experimental study, 34 mesiobuccal root canals of human maxillary first molars with 20°-40° curvatures (according to Schneider technique) were randomly distributed in two experimental groups (15 each) and two control groups. The canals in test groups were instrumented according to the manufacturers’ instructions. Five ml of 5.25% sodium hypochlorite (NaOCl) and 5 ml of normal saline were used as irrigants. The roots were split longitudinally, and apical, middle, and coronal radicular sections were randomly scanned by an SEM at ×1000 magnification. Two endodontists scored the data according to Schäfer and Schlingemann scoring system. Data of the amount of debris and smear layer were separately analyzed by Kruskal-Wallis test. Although there was a slight difference in mean scores between the two groups (3.28 for WaveOne and 3.6 for ProTaper), no significant differences in debris amount were noted. The overall mean smear layer formation was not significantly different between the two groups (4.11 for WaveOne and 3.95 for ProTaper). There was no significant difference in remaining debris and smear layer in coronal, middle, and apical parts of root canals. However, ProTaper system appeared to produce less debris during preparation.

Considering the consequences of false positive (FP) and false negative (FN) diagnoses as well as the lack of information on the diagnostic ability of photostimulable phosphor plate (PSP) and complementary metal oxide semiconductor (CMOS) sensors in the detection of secondary caries, this study aimed to compare the diagnostic ability of these two sensors in the detection of secondary caries adjacent to amalgam restorations. This diagnostic study was performed on 40 intact permanent premolars. Class II cavities were prepared and restored with amalgam. Periapical radiography was performed by using PSP and CMOS sensors via parallel technique. A 0.5-mm round bur was used to create another cavity under amalgam restorations. To simulate secondary gingival caries at the cementoenamel junction (CEJ), the samples were placed inside 0.1M lactic acid solution and were incubated at 37°C for three weeks. The teeth were placed in gypsum blocks and were radiographed again by CMOS and PSP sensors. The presence of decay was determined by an oral and maxillofacial radiologist, and the results were recorded in datasheets and were statistically analyzed by the ratio test. The sensitivity and specificity of PSP in caries detection were 52.5% and 77.5%, respectively. The sensitivity and specificity of CMOS in caries detection were 57.5% and 82.5%, respectively. Incorrect diagnoses (FP+FN) were equal to 35% for PSP and 30% for CMOS (P=0.89). The results indicated that PSP and CMOS sensors have similar abilities in the detection of secondary caries under amalgam restorations, while none of the two sensors has the adequate ability for a precise and thorough diagnosis of secondary caries.

A correct diagnosis of the morphology of the root canal system is crucial in order to ensure a successful root canal treatment. The incidence of mandibular first premolars with three root canals has been reported to be low. This clinical case report describes a case of a successful nonsurgical endodontic management of a mandibular first premolar with three root canals. A 27-year-old man presented to our clinic with pain in the left mandibular premolar. The diagnosis was irreversible pulpitis based on the clinical and radiographic examinations. Hence, root canal treatment was recommended. After preparing the access cavity, the orifices were found by removing the dentinal shelves. The root canals were treated by rotary files and were obturated using the cold lateral compaction technique. Mandibular premolars can present with an extremely complex root canal morphology, which if not considered during the treatment, it can lead to post-treatment complications, failure, or flare-ups.