Dental Research Journal
Volume:12 Issue: 4, Jul 2015

Implant surgery in mandibular anterior region may turn from an easy minor surgery into a complicated one for the surgeon, due to inadequate knowledge of the anatomy of the surgical area and/or ignorance toward the required surgical protocol. Hence, the purpose of this article is to present an overview on the: (a) Incidence of massive bleeding and its consequences after implant placement in mandibular anterior region. (b) Its etiology, the precautionary measures to be taken to avoid such an incidence in clinical practice and management of such a hemorrhage if at all happens. An inclusion criterion for selection of article was defi ned, and an electronic Medline search through different database using different keywords and manual search in journals and books was executed. Relevant articles were selected based upon inclusion criteria to form the valid protocols for implant surgery in the anterior mandible. Further, from the selected articles, 21 articles describing case reports were summarized separately in a table to alert the dental surgeons about the morbidity they could come across while operating in this region. If all the required adequate measures for diagnosis and treatment planning are taken and appropriate surgical protocol is followed, mandibular anterior region is no doubt a preferable area for implant placement.

The second processing cycle for adding the artifi cial teeth to heat-polymerized acrylic resin denture bases may result in dimensional changes of the denture bases. The aim of this study was to evaluate the dimensional changes of the heat-polymerized acrylic resin denture bases with one and two-cycle processing methods. A metal edentulous maxillary arch was used for making 40 stone casts. Maxillary complete dentures were made with heat-polymerized acrylic resins (Meliodent and Acropars) with one and two stage processing methods (n = 10 for each group). Linear dimensional changes in anteroposterior and mediolateral distances and vertical changes in the fi rst molar region were measured following each processing cycle, using a digital caliper. Mean percentage of the dimensional changes were subjected to two-way analysis of variance and Tukey honest signifi cant difference tests (α = 0.05). Postpolymerization contraction occurred in both anteroposterior and mediolateral directions in all studied groups; however, the vertical dimension was increased. Acropars acrylic resin showed the highest dimensional changes and the second processing cycle signifi cantly affected the measured distances (P < 0.05). Meliodent acrylic resin was not signifi cantly infl uenced by the processing method. Reheating of the acrylic resin denture bases for the addition of denture teeth result in linear dimensional changes, which can be clinically signifi cant based on the acrylic resin used.

The role of retinoblastoma (Rb) protein in cell cycle regulation prompted us to take up this study with the aim of assessing its role in the progression of oral cancer and to correlate with various clinicopathological parameters, including habits such as smoking, Paan chewing, and alcoholism. This observational study included surgical specimens from 10 apparently normal oral mucosa, 14 oral reactive lesions (ORL), 29 precancerous lesions and 43 oral cancers. The expression of Rb protein in tissue samples were evaluated by immunohistochemistry and correlated with clinicopathological data. The percentage and mean expression of Rb protein were statistically analyzed using Student’s t-test and P < 0.05 was considered as statistically signifi cant difference. The expression of Rb protein was found to increase from normal, ORL, precancerous lesions to cancers. A consistently high expression of Rb protein was seen in oral cancers, with an increase in well-differentiated and moderately differentiated tumors. Patients with combined habits of Paan chewing, smoking, and alcohol consumption had a higher expression compared with those without habits. Within the limitations of this study, it seems that overexpression of Rb protein noted in oral cancer, with an increase in well and moderately differentiated tumors suggest a possible role of Rb in differentiation. The high expression of Rb in patients with combined habits of Paan chewing, smoking and alcohol consumption indicates that Rb pathway may be altered in habitrelated oral malignancies.

A precise impression is mandatory to obtain passive fi t in implant-supported prostheses. The aim of this study was to compare the accuracy of three impression materials in both parallel and nonparallel implant positions. In this experimental study, two partial dentate maxillary acrylic models with four implant analogues in canines and lateral incisors areas were used. One model wassimulating the parallel condition and the other nonparallel one, in which implants were tilted 30° bucally and 20° in either mesial or distal directions. Thirty stone casts were made from each model using polyether (Impregum), additional silicone (Monopren) and vinyl siloxanether (Identium), with open tray technique. The distortion values in three-dimensions (X, Y and Z-axis) were measured by coordinate measuring machine. Two-way analysis of variance (ANOVA), one-way ANOVA and Tukey tests were used for data analysis (α = 0.05). Under parallel condition, all the materials showed comparable, accurate casts (P = 0.74). In the presence of angulated implants, while Monopren showed more accurate results compared to Impregum (P = 0.01), Identium yielded almost similar results to those produced by Impregum (P = 0.27) and Monopren (P = 0.26). Within the limitations of this study, in parallel conditions, the type of impression material cannot affect the accuracy of the implant impressions; however, in nonparallel conditions, polyvinyl siloxane is shown to be a better choice, followed by vinyl siloxanether and polyether respectively.

According to the development of resistant strains of pathogenic bacteria following treatment with antimicrobial chemotherapeutic agents, alternative approaches such as lethal photosensitization are being used. The aim of this study was to evaluate the effect of visible light and laser beam radiation in conjugation with three different photosensitizers on the survival of two main periodontopathogenic bacteria including Porphyromonas gingivalis and Fusobacterium nucleatum in different exposure periods. In this in vitro prospective study, strains of P. gingivalis and F. nucleatum were exposed to visible light at wavelengths of 440 nm and diode laser light, Gallium-Arsenide, at wavelength of 830 nm in the presence of a photosensitizer (erythrosine, curcuma, or hydrogen peroxide). They were exposed 1-5 min to each light. Each experiment was repeated 3 times for each strain of bacteria. Data were analyzed by two-ways ANOVA and least significant difference post-hoc tests. P < 0.05 was considered as significant. After 4 days the colonies were counted. Viability of P. gingivalis was reduced 10% and 20% subsequent to exposure to visible light and diode laser, respectively. The values were 65% and 75% for F. nucleatum in a period of 5-min, respectively. Exposure to visible light or laser beam in conjugation with the photosensitizers suspension caused signifi cant reduction in the number of P. gingivalis in duration of 5-min, suggesting a synergic phototoxic effect. However, the survival rate of F. nucleatum following the exposure to laser with hydrogen peroxide, erythrosine and rhizome of Curcuma longa (curcumin) after 5-min was 10%, 20% and 90% respectively. Within the limitations of this study, the synergic phototoxic effect of visible light in combination with each of the photosensitizers on P. gingivalis and F. nucleatum. However, the synergic phototoxic effect of laser exposure and hydrogen peroxide and curcumin as photosensitizers on F. nucleatum was not shown.

The aim of this study was to evaluate and compare the in vitro biofi lm forming capacity of Enterococcus faecalis on Gutta-percha points disinfected with four disinfectants. A total of 50 Gutta-percha points used in this study were divided into four test groups based on disinfectant (5.25% sodium hypochlorite, 2% chlorhexidine gluconate, 20% neem, 13% benzalkonium chloride [BAK]), and one control group. The Gutta-percha points were initially treated with corresponding disinfectants followed by anaerobic incubation in Brain Heart Infusion broth suspended with human serum and E. faecalis strain for 14 days. After incubation, these Gutta-percha points were stained with Acridine Orange (Sigma – Aldrich Co., St. Louis, MO, USA) and 0.5 mm thick cross section samples were prepared. The biofi lm thickness of E. faecalis was analyzed quantitatively using a confocal scanning laser microscope. Results statistically analyzed using analysis of variance. P < 0.05 was considered to be signifi cant. Confocal scanning laser microscope showed reduced amount of E. faecalis biofi lm on Guttapercha points treated with BAK and sodium hypochlorite. Post-hoc (least square differences) test revealed that there is no statistically signifi cant difference between BAK and sodium hypochlorite groups (P > 0.05). This study illustrates that the Gutta-percha points disinfected with sodium hypochlorite and BAK showed minimal biofi lm growth on its surface.

Glass ionomer cement is a common material used in pediatric dentistry. The aim of this study was to evaluate the microleakage of high-viscosity glass ionomer restorations in deciduous teeth after conditioning with four different conditioners. Fifty intact primary canines were collected. Standard Class V cavities (2 mm × 1.5 mm × 3 mm) were prepared by one operator on all buccal tooth surfaces, including both enamel and dentin. The samples were divided into fi ve groups with different conditioners (no conditioner, 20% acrylic acid, 35% phosphoric acid, 12% citric acid, and 17% ethylenediaminetetraacetic acid [EDTA]). Two-way — ANOVA, Kruskal–Wallis and Mann–Whitney tests were used to compare the means of microleakage between the fi ve groups. The signifi cance level was set at P < 0.05. There was no signifi cant difference between the means of microleakage in incisal (enamel) and gingival (dentin) margins (P = 0.34). Furthermore, there was no signifi cant difference between the means of microleakage in enamel and dentin margins (P = 0.4). There was a signifi cant difference between the means of microleakage in different groups (P = 0.03). Within the limitations of this study, it is suggested that 20% acrylic acid and 17% EDTA be used for cavity conditioning which can result in better chemical and micromechanical adhesion.

Keratocystic odontogenic tumor (KCOT) is a developmental odontogenic cyst on which various investigations have been focused due to its biological activities, high tendency to recur and different growth mechanisms in comparison with other cystic lesions. Previous studies have shown different biological and proliferative activities for the lining epithelium of KCOT. The aim of this study was immunohistochemical evaluation of Bcl-2 and epidermal growth factor receptor (EGFR) expression in KCOT compared with dentigerous cyst and ameloblastoma. Formalin-fi xed and paraffi n-embedded tissue sections of 16 cases of KCOT, 16 cases of dentigerous cyst and 16 cases of ameloblastoma were immunohistochemically analyzed to determine Bcl-2 and EGFR proteins’ expression. Biotin-Stereotavidin method was used. It was observed by two oral pathologists separately, and the data were analyzed by Mann–Whitney and Kruskul–Wallis. P < 0.05 was considered as signifi cant. Regardless of staining intensity, all cases of ameloblastoma and KCOT except dentigerous cases were positively stained for Bcl-2. Expression of Bcl-2 was higher in the peripheral layer of ameloblastoma and basal layer of KCOT. Furthermore, all cases of ameloblastoma and dentigerous cysts except KCOT samples were positively stained for EGFR. Expression of EGFR was higher in the peripheral layer of ameloblastoma and basal layer of dentigerous cysts. According to the expression of — Bcl-2 in ameloblastoma and KCOT, and no expression of EGFR in KCOT, it can be concluded that the biological activity and growth mechanisms of KCOT are different compared with other cystic lesions. However, the aggressive potential of KCOT is not as severe as that of a neoplasm such as ameloblastoma.

Elastomeric chains are commonly used in orthodontics. Force decay in these materials poses clinical problems. The aim of this study was to evaluate the effects of three different mouthwashes on the force decay of orthodontic chains. In this experimental study, elastomeric chains with two different confi gurations were divided into eight groups (two control and six test groups). After 10 s of prestretching up to 100% of their initial length, the chains were stretched for 25 mm on jig pins and then immersed in artifi cial saliva, persica, chlorhexidine 0.2% and sodium fl uoride 0.05% mouthwashes. Ten cycles of thermocycling between 5°C and 55°C were conducted daily during the test period. In order to reach a 200-g initial force, seven loop closed chains, and fi ve-loop short chains were selected. Forces were recorded by digital force gauge (Lutron) at initial, 24 h, 1, 2, and 4 weeks for all groups. The amount of force loss was compared among different mouthwashes and times using one-way analysis of variance (post-hoc, Tukey, α = 0.05). About 20% of the force decay occurred during the fi rst 24 h, but after that and up to the 4th week the rate of force loss was gradual and steady. After 4 weeks, persica and chlorhexidine caused the lowest and the highest percentage of force loss, respectively. These two mouthwashes showed statistically signifi cant differences at all points of time (P < 0.05). Within the limitations of this study, during the orthodontic treatment, persica is preferred to chlorhexidine for oral health control.

The aim of this study was to evaluate the hypothesis that budesonide increases the susceptibility of teeth to root resorption during the course of orthodontic treatment. A randomized controlled trial design (animal study) was employed. Budesonide was administered in test group for 14 days during which orthodontic force was applied to upper right molar. Afterwards, root resorption was measured on mesio-cervical and disto-apical parts of the mesial root on transverse histological sections. ANOVA and Bonfferoni tests were used. Statistical signifi cance was considered to be P ≤ 0.05. In general, the subgroups in which the force was applied showed signifi cantly greater root resorption. Where force was applied there was no signifi cant difference, whether budesonide was administered or not. While where there was no force, a group who received budesonide showed signifi cantly greater root resorption than the other, unless at the coronal level where the difference was not signifi cant. Within the limitations of this study, it seems budesonide could increase root resorption, but in the presence of orthodontic force this effect is negligible.

The fi nal position of the abutment changes with the amount of tightening torque. This could eventually lead to loss of passivity and marginal misfi t of prostheses. The aim of this study was to evaluate the effect of three different tightening torques on the marginal adaptation of 3-unit cement-retained implant-supported fi xed dental prostheses (FDPs). Two implants (Straumann) were inserted in an acrylic block so that one of the implants was placed vertically and the other at a 15° vertical angle. A straight abutment and a 15° angulated abutment were connected to the vertically and obliquely installed implants, respectively, so that the two abutments were parallel. Then, 10 cement-retained FDPs were waxed and cast. Abutments were tightened with 10, 20, and 35 Ncm torques, respectively. Following each tightening torque, FDPs were luted on respective abutments with temporary cement. The marginal adaptation of the retainers was evaluated using stereomicroscope. FDPs were then removed from the abutments and were sectioned at the connector sites. The retainers were luted again on their respective abutments. Luting procedures and marginal adaptation measurement were repeated. Data were analyzed by ANOVA and least signifi cant difference tests (α = 0.05). After cutting the FDP connectors, the independent samples t-test was used to compare misfi t values (α = 0.05). Following 10, 20, and 35 Ncm tightening torques, the marginal discrepancy of the retainers of FDPs signifi cantly increased (P < 0.05). There was no signifi cant difference between the marginal discrepancies of these two retainers (P > 0.05). The marginal gap values of angulated abutment retainers (ANRs) were signifi cantly higher than those of the straight abutment after cutting the connectors (P = 0.026). Within the limitations of this study, the marginal misfi t of cement-retained FDPs increased continuously when the tightening torque increased. After cutting the connectors, the marginal misfi t of the ANRs was higher than those of the straight abutment retainers.

For improving the quality of endodontic performance of practitioners in clinical practice, their basic, preclinical performance and knowledge must be taken into consideration. This study aimed to radiographically evaluate the technical quality of preclinical molar root canal treatments (RCTs) performed by undergraduate dental students at a dental school in Iran. Further, the effect of using Gates-Glidden (GG) drills on the fi nal quality of RCTs was evaluated. In this retrospective cross-sectional study, 315 roots of 105 endodontically treated teeth in preclinical practice were evaluated radiographically. The analyzed quality parameters included length, taper and density of fi llings, which were scored as S2 (adequate standard), the S1 (slight deviation), or S0 (considerable deviation). For all the parameters, acceptable, moderate and poor fi llings received total scores of 6, 3-5 and 0-2, respectively. There were two groups of students: One group had used only K-fi les, and the other had used K-fi les along with GG drills. The quality of RCTs between these groups was evaluated using the aforementioned scoring protocol. The results were analyzed using Chi-square, Mann–Whitney and Fisher’s exact tests (α = 0.05). Under-fi llings (P = 0.001) and under-shapings (P = 0.007) occurred mostly in mandibular root fi llings. A lower density was found in maxillary fi llings (P < 0.001). No relationship was observed between the technique used (irrespective of GG drills usage) and length (P = 0.499) and taper of fillings (P = 0.238). The roots instrumented with GG drills had a higher fi lling density (P = 0.004).The quality mean score of RCTs was improved when GG drills were used (P = 0.008). The technical quality of preclinical molar RCTs performed by undergraduate dental students was considered acceptable in 35.6% of the cases. When GG drills were used along with K-fi les, the technical quality of RCTs was enhanced.

Restoration of anterior primary teeth with severe caries lesion is a big challenge. The aim of this study was to compare the fracture resistance of three types of post, including composite resin, customized quartz fi ber and prefabricated glass fi ber in restoration of severely damaged primary anterior teeth. Sixty extracted human primary maxillary incisors were randomly divided into three groups: Group 1: Customized quartz fi ber post, Group 2: Composite post and Group 3: Prefabricated glass fi ber post. Due to the effect of bonded area on the fracture resistance, the bonded surface of each sample was measured 1 mm above cementoenamel junction. An increasing force was subjected with a crosshead speed of 0.5 mm/min by a universal testing machine until fracture occurred, and the failure mode was assessed afterwards. Data were analyzed using One-way analysis of variance and Kruskal–Wallis tests. The level of signifi cance was considered at P < 0.05. The mean fracture resistance values of three groups were 343.28 N, 278.70 N and 284.76 N, respectively. Although customized quartz fi ber post showed the greatest fracture resistance, statistical analysis revealed no signifi cant difference between groups (P = 0.21). The mean fracture strength values of three groups were 12.82 N/mm−2, 11.93 N/mm−2 and 11.31 N/mm−2, respectively; however, the differences were not statistically signifi cant (P = 0.72). Favorable failure mode was more frequent in all groups (P = 0.12). Within the limitations of this study, it can be concluded that all three types of studied posts can be successfully used to restore badly destructed primary anterior teeth.

With the introduction of skeletal anchorage system, recently it is possible tosuccessfully intrude molar teeth. On the other hand, there have been concerns about periodontal changes associated with intrusion and there are few studies on this topic, especially for posteriorteeth. Ten female patients were enrolled in this study. Maxillary molar intrusion was achieved by inserting two miniscrews and a 17 × 25 titanium molybdenum alloy spring. Crestal height changes were evaluated at three intervals including: Baseline (T0), end of active treatment (T1) and 6 months after retention (2). Other variables including probing depth, gingival recession, attachment level and bleeding on probing were evaluated by clinical measurements in the three above mentioned intervals. One-sample Kolmogrov-Smirnov test ascertained the normality of the data. For all patients, the changes in tooth position and crestal height were evaluated using onesample t-test. (P < 0.05) Supra-erupted molars were successfully intruded a mean of 2.1 ± 0.9 mm during active treatment (T0-T1). A mean bone resorption of 0.9 ± 0.9 mm in mesial crest and 1 ± 0.8 mm in distal crest had occurred in total treatment (T0-T2). A mean of 0.6 ± 1.4 mm bone was deposited on mesial crest during the retention period (T1-T2) following tooth relapse. On average, 0.8 ± 0.4 mm attachment gain was obtained. Gingival margin coronalized a mean of 0.8 ± 0.6 mm throughout the entire treatment. Probing depth showed no signifi cant change during treatment. Within the limitations of this study, these results suggest that not only periodontal status was not negatively affected by intrusion, but also there were signs of periodontal improvement including attachment gain and shortening of clinical crown height.

Mandibular canal is the most important anatomical landmark in the body of mandible which always must be considered for implant surgery in posterior mandibular region. Damage to vessels and inferior alveolar nerve that passes through the mandibular canal can cause problems such as hemorrhage and neurosensory disturbances. Damage to the mandibular canal can occur during implant surgery. Depending on the severity of injuries, it would result in temporary or permanent neurosensory disturbances. We have reported a case that mandibular canal narrowing occurred following implant surgery and resulted in anesthetic and hypoesthetic areas in the lower lip. Patient had a history of implant surgery in the region of teeth numbered 3 and numbered 31. The inserted implant failed after 6 years, and reimplantation was done in this area, but due to lower lip numbness in the right side, the second implant was removed, and another implant was inserted in the region of the tooth numbered 3. After 2 years, right lower lip numbness was reported again by the patient. Cone beam computed tomography images showed canal narrowing in the region of the tooth numbered 31 where the second implant was inserted. It seems that the main cause for anesthesia and hypoesthesia in this patient is canal narrowing due to damage during implant replacement and removal.