Journal of Dentistry, Shiraz University of Medical Sciences
Volume:24 Issue: 1, Mar 2023

Statement of the Problem: 

Medial depression of the mandibular ramus (MDMR) as a normal anatomical variation might complicate orthognatic surgeries that involve ramus. When planning an orthognatic surgery, it is clinically valuable to notice MDMR in osteotomy site to decrease the risk of failure.

The aim of present study was to evaluate the prevalence as well as characteristics of MDMR in three skeletal sagittal classifications.

This cross sectional study evaluated 530 cone beam computed tomography (CBCT) scans, of which 220 were enrolled. The skeletal sagittal classification, the presence of MDMR, the shape, depth, and width of MDMR were recorded for each patient by two examiners. Chi-square test was performed to determine the differences between three skeletal sagittal groups and between two genders.

The overall prevalence of MDMR was 60.45%. MDMR was mostly detected in class III (76.92%), followed by class II (76.66%), and class I (54.87%). In the analyzed CBCT scans, semi-lunar was the most common shape detected (42.85%), followed by triangular (30.82%), circular (18.04%), and tear-drop (8.27%). The depth of MDMR was not significantly different between three sagittal groups and between genders; however, the width of MDMR was higher in class III group and in male patients. In the present study, MDMR was found to be more common in patients with class II and class III skeletal classifications. Although, MDMR was more frequent in class III, the difference between class II and class III was not significant.

More caution is needed during orthognatic surgery in patients with dentoskeletal deformities during the splitting of the ramus. Moreover, higher width of MDMR in class III and male patients should be concerned when planning an orthognatic surgery for these patients.

Statement of the Problem: 

Gubernacular canal (GC) is a canal that extends from the follicle of unerupted permanent teeth to the alveolar bone crest filled with remnants of the dental lamina. This canal is thought to guide tooth eruption and be related to some pathologic conditions.

This study aimed to determine the presence of GC and its anatomical characteristics in teeth, which failed to erupt normally on cone beam computed tomography (CBCT) images.

This cross-sectional study evaluated CBCT images of 77 impacted permanent and supernumerary teeth obtained from 29 females and 21 males. The frequency of GC detection, its location in relation to the crown and root, the anatomical surface of the tooth from which the canal has originated, and the adjacent cortical table to which the canal opens, along with the length of the GC were studied.

GC was observed in 53.2% of teeth. The anatomical tooth aspect of origin was occlusal/ incisal in 41.5% and crown in 82.9% of teeth. Moreover, 51.2% of GCs opened in palatal/lingual cortex and 63.4% of canals were not located along the tooth long axis. Finally, GC was detected in 85.7% of teeth undergoing the crown formation stage.

Although GC was introduced as an eruption pathway, this canal is also present in impacted teeth. This means that presence of this canal does not promise the normal eruption of tooth and the anatomical characteristics of GC may influence the eruption process.

Statement of the Problem:

 Eichner index is a dental index, which is based on the occlusal contacts between naturally existing teeth in premolar and molar regions. One controversial topic is the association between occlusal status and temporomandibular joint dysfunction (TMD) and its associated degenerative bony changes.

Through the use of cone-beam computer tomography (CBCT), the current study sought to ascertain the relationship between the Eichner index and condylar bone alterations in TMD patients

In this retrospective study, the CBCT images of bilateral temporomandibular joints (TMJs) of 107 patients with TMD were evaluated. The patients’ dentition was classified into three groups of A (71%), B (18.7%), and C (10.3%), according to the Eichner index. Radiographic indicators of condylar bone alterations, including as flattening, erosion, osteophytes, marginal sclerosis, subchondral sclerosis, and joint mice, were either present or absent and registered as 1 or 0, respectively. Chi-square test was used to evaluate the link between the condylar bony changes and the Eichner groups

According to the Eichner index, the most prevalent group was group “A”. The most prevalent radiographic finding was “flattening of the condyles” (58%). Condylar bony changes were found to be statistically related to age (p= 0.00). However, no significant relationship was found between sex and condylar bony changes (p= 0.80). There was a significant relationship between the Eichner index and condylar bony changes (p= 0.05).

Patients with greater loss of tooth supporting zones have more condylar bony changes.

Statement of the Problem:

 Camelia Sinenis or green tea (GT) and Teucrium polium (TP) are known to have a great antimicrobial potential on salivary Streptococcus mutans (S. mutans).Their efficacy should be examined compared to the gold standard antimicrobial agents.

To evaluate the effects of Camelia Sinenis or green tea (GT) and Teucrium polium (TP) extracts in comparison with chlorhexidine gluconate (CHG) on salivary S. mutans levels.

This double-blinded randomized clinical trial study was conducted on 90 preschool children aged 4 to 6 years and assigned randomly (simple randomization) to three groups as GT, TP, and CHG. Unstimulated saliva samples were then collected in three times as before application of agents, after half an hour, and after one week. To determine S. mutans levels, quantitative polymerase chain reaction (qPCR) technique was additionally utilized. Statistical analysis was also fulfilled using Shapiro-Wilk test, Friedman test, Chi-square test, paired sample t-test, repeated measures analysis of variance (ANOVA), and Mann-Whitney U test at a significance level of 0.05.

The results of this study established a significant difference between mean salivary S. mutans levels after administration of the three compounds. Although the mean of S. mutans levels reduced significantly following the application of CHG and TP after half an hour, the mean salivary S. mutans levels in the group receiving GT declined in a significant manner only one week later (p< 0.05).

The results of this study indicated that GT and TP extracts had considerable effects on salivary S. mutans levels compared with CHG.

Statement of the Problem: 

New calcium silicate base cements are introduced as root repair materials in order to defeat the problems of early root repair materials. Their mechanical properties such as solubility and porosity should be concerned.

This study was conducted to evaluate the solubility and porosity of the NanoFastCement (NFC) as a new calcium silicate base cement comparing to mineral trioxide aggregate (MTA).

In this in vitro study, scanning electron microscope (SEM) was used to evaluate the porosity at five different magnifications (200×, 1000×, 4000×, 6000× and 10000×) in secondary backscattered electron mode. All analyses were performed at 20kV. The obtained images were subjected to qualitative evaluation regarding the porosity. Solubility was determined following the international standards organization (ISO) 6876 method. Twelve specimens in specially fabricated stainless steel ring molds were weighed, initially and after 24 hour and 28 days of immersion in distilled water. Each weight was measured three times to record the average weight. Solubility was measured by calculating the difference of the initial and final weight.

Solubility of the NFC in comparison with MTA showed no statistical difference (p Value > 0.05) after one day and 28 days. NFC acted like MTA and showed an acceptable solubility value at exposure time intervals. In both groups, solubility increased as time went on (p Value<0.05).The porosity of NFC was comparable to MTA, and NFC presented a less porous and a slightly smoother surface compared to MTA.

NFC has similar solubility and porosity to Proroot MTA. Therefore, it can be a good, more available and less expensive substitute for MTA.

Statement of the Problem: 

By development of adhesive dentistry and noble mechanical strength of ceramics, reconstruction of posterior teeth with partial coverage restorations such as ceramic endocrowns is possible. Different ceramics may show different mechanical properties which should be investigated.

The aim of this experimental in vitro study was to compare the tensile bond strength of endocrowns made by CAD-CAM using 3 types of ceramics.

In this in vitro study, 30 fresh extracted human molars were prepared to evaluate the tensile bond strength of endocrowns made by IPS e.max CAD, Vita Suprinity, and Vita Enamic blocks (n=10). The specimens were mounted and endodontically treated. Standard preparations were done with 4.5±0.5 mm intracoronal extensions into the pulp chamber and the restorations were designed and milled by CAD-CAM technique. All specimens were cemented with a dual polymerizing resin cement according to the manufacturer's instructions. The specimens were incubated for 24 hours and then thermocycled for 5000 cycles at 5-55°C and underwent the tensile strength test by universal testing machine (UTM). Shapiro-Wilk and one-way ANOVA test were used to statistically analyzed (α= 0.05).

The highest tensile bond strength values were achieved in IPS e.max CAD (216.39 ±22.67N) and Vita Enamic (216.22±17.72N) followed by Vita Suprinity (211.54±20.01N). There was no significant statistical difference between retention of endocrowns made by CAD-CAM technique among ceramic blocks (p= 0.832).

Within the limitation of this study, there was no significant difference between retention of endocrowns made by IPS e.max CAD, Vita Enamic, and Vita Suprinity as ceramic blocks.

Statement of the Problem:

 One of the rare adverse effects in patients who take bisphosphonates is the osteonecrosis of the jaw in the oral cavity following any trauma such as tooth extraction.

The aim of this study is the histopathological evaluation of the jaw following intra-ligament anesthesia injection in Zoledronate-treated rats.

In this descriptive-experimental study, rats weighing 200-250 g were divided into 2 groups. The first group received a 0.6 mg/kg dose of zoledronate and the second group received normal saline. Five injections with a 28-day interval were performed. At the end of the injection, the animals were sacrificed. Then, five-micrometer histological slides were prepared from the first maxillary molars and the surrounding tissues. Hematoxylin and eosin staining was performed to evaluate osteonecrosis, infiltration of inflammatory cells, fibrosis, and root and bone resorption.

There was no difference between the macroscopic and clinical features in both groups and no evidence of osteonecrosis of the jaw was observed in the samples. From the histological point of view, all the samples had normal tissues and none of them showed any evidence of inflammation, tissue fibrosis, disorder, or pathological root resorption.

According to the histological findings, the periodontal ligament space, the bone adjacent to the roots, and the dental pulp conditions were similar in both groups. Osteonecrosis of the jaw did not develop in the rats that took bisphosphonates after intraligamental injection.

Statement of the Problem:

 Various default values in each software can eventually lead to different crown thicknesses and affect their compressive strength.

This study aimed to compare the compressive strength of temporary crowns made with the milling machine, designed in Exocad and 3Shape Dental System software.

In this in vitro study, 90 temporary crowns were made and evaluated based on each software settings. For this purpose, a sound premolar was first scanned as a pre-operative model by 3Shape laboratory scanner. The standard tooth preparation and scanning were performed, and then the temporary crown files (designed by each software) were transferred to the Imes-icore 350i milling machine. A total of 90 temporary crowns (45 based on the file of each software) were made using poly methyl methacrylate (PMMA) vita cad-temp block. The value of compressive force displayed on the monitor was recorded at the first crack and the ultimate failure of the crown.

The first crack and the ultimate strength of crowns designed with the Exocad software was 903.5±96N and 1490±139.3N and for crowns designed with 3Shape Dental System software was 1060.4±160.2N and 1691.1±73.9N, respectively. The amount of compressive strength of temporary crowns made with 3Shape Dental System was significantly higher than those made with Exocad software and this difference was statistically significant(p= 0.000).

The compressive strength of temporary dental crowns made by both softwares is in a clinically acceptable range, but considering that the average compressive strength in the 3Shape Dental System group was slightly higher than of the other group, it is preferable to design and fabricate with 3Shape Dental System software to increase the compressive strength of these crowns.

Statement of the Problem: 

For many years, practitioners have been encountered with dental rehabilitation of atrophic jaws. Among many of alternatives, free iliac graft can be a reasonable and also problematic choice to be accomplished.   

The aim of this study was to evaluate the implant survival rate and bone loss in implants inserted in reconstructed jaws with free iliac graft.

In this clinical trial study, twelve patients that underwent bone reconstruction with free iliac graft were included in this retrospective study. The patients underwent surgery over a 6-year period from September 2011 to July 2017. Panoramic images were taken immediately after implant insertion and at the follow-up session. The parameters that were assessed included implant survival rate, bone level changes, and surrounding tissue conditions.

One hundred and nine implants were placed in eight female and four male patients, of which 65 (59.6%) were inserted in the reconstructed maxilla and 44 (40.3%) in the reconstructed mandible. The interval between the reconstruction surgery and follow-up session was 28.75 months and the mean interval between implant insertion and the follow-up session was 21.75 months, ranging from 6 to 72 months. The total average of crestal bone resorption was 2.44 mm (range: 0 to 5.43 mm).

This study found that rehabilitation of atrophic jaws with dental implants placed in free iliac graft was associated with acceptable marginal bone loss, survival rate, satisfaction, and esthetic results among the patients.

Statement of the Problem:

 Distribution of stress along endodontic instruments determines their fracture resistance during instrumentation of root canals. The cross-sectional design of instruments and root canal anatomy are of the most important factors affecting the stress distribution.

The purpose of this study was to evaluate the stress distribution in different cross-sectional design of nickel-titanium (NiTi) endodontic instruments operating in different canal anatomies using finite element analysis (FEA).

In this original finite element analysis study, 3-dimensional models of convex triangle (CT), S-type (S), and triple-helix (TH) cross-sectional designs with the size of 25/04 simulated rotational movements through 45ᵒ and 60ᵒ angled root canals with 2- and 5-mm radii using ABAQUS software. The stress distribution was evaluated by the means of FEA.

CT showed the lowest stress values followed by the TH and S ones. The most stress concentration was detected in the CT apical third while, TH revealed better stress distribution all along its length. 45ᵒ curvature angle and 5-mm radius applied the lowest stress to the instruments.

Higher value of radius and smaller curvature angle apply lower stress values to the instrument. CT design shows the lowest stress level with the most stress concentration in its apical third while the triple-helix design has a better stress distribution. Thus, it is safer to use convex triangular cross-section mostly for coronal and middle thirds in initial steps of shaping and triple-helix for the apical third in final steps.

Arteriovenous malformation of head and neck is a rare vascular anomaly but when present, it is persistent and progressive in nature. It can also represent a lethal benign disease due to massive hemorrhage. There are several indications for treatment including age, location, extension and type of vascular malformation. Endovascular therapy can effectively cure most lesions with limited tissue involvement. Surgery can be used in selected cases in combination with embolization. Here, we present a rare case of arteriovenous malformation of mandible with floating tooth appearance in an 11-year-old boy patient. Given the spectrum of imaging presentations seen and the crossover with other lesions, microscopic histopathological examination is the gold standard for diagnosis.

Open reduction and internal fixation (ORIF) of mandibular condylar fracture with a three dimensional stabilization has been a controversial topic in oral and maxillofacial surgery. Miniplates and many 3D plates have been used till now for fixation of condylar fracture and delta plate is one of them. Present literature has less evidence about which one is superior over another. We have tried to evaluate the clinical performance of the delta miniplate in this study. A total of 10 patients presenting mandibular condylar fracture were treated by ORIF using delta miniplate. Dimensional details were measured of 10 dry human mandibles. At the end of 1-year follow-up period, all patients had satisfactory results, both clinically and radiologically. Delta plate showed better stability in the condylar region and less complication associated with plating system.