Amir Reza Rokn, DDS, MSc
Mohammad-Sadegh Ahmad-Akhoundi, DDS, MSc.
Shahroo Etemad-Moghadam, DDS, MSc.
Abbas Mirzaei, PhD
Vol 13, No 3 (2016)
During dental education, dental students learn how to examine patients, make diagnosis, plan treatment and perform dental procedures perfectly and efficiently. However, progresses in computer-based technologies including virtual reality (VR) simulators, augmented reality (AR) and computer aided design/computer aided manufacturing (CAD/CAM) systems have resulted in new modalities for instruction and practice of dentistry. Virtual reality dental simulators enable repeated, objective and assessable practice in various controlled situations. Superimposition of three-dimensional (3D) virtual images on actual images in AR allows surgeons to simultaneously visualize the surgical site and superimpose informative 3D images of invisible regions on the surgical site to serve as a guide. The use of CAD/CAM systems for designing and manufacturing of dental appliances and prostheses has been well established.
This article reviews computer-based technologies, their application in dentistry and their potentials and limitations in promoting dental education, training and practice. Practitioners will be able to choose from a broader spectrum of options in their field of practice by becoming familiar with new modalities of training and practice.
Objectives: The aim of this study was to assess the effect of tube current, kilovoltage peak (kVp), metal type, and the position of metal objects on metal artifacts in cone-beam computed tomography (CBCT) images.
Materials and Methods: Titanium and cobalt-chromium rods were fabricated and placed in a dry human mandible. Samples were scanned using a Promax 3D CBCT unit with different milli-amperages and kVp. The artifacts induced by metal objects were evaluated using the Image J software in four regions of interest (ROIs) on each image.
Results: A higher kVp decreased artifacts of the buccal surface of the rods in 97% of the cases (P=0.046) but did not affect the severity of artifacts between the two metal objects (P>0.05). Increasing the tube current had no effect on metal artifacts in 93% of the cases (P>0.05). Artifacts induced by a cobalt-chromium alloy were more severe than those with titanium (P<0.001). Artifacts were more intense in the buccal surface of anterior rods compared to the posterior rods (P<0.003).
Conclusions: Tube voltage, metal type and the position of metal objects affected the severity of metal artifacts on CBCT images. The metal type had the greatest effect on metal artifact intensity in this study.
Objectives: Obstructive sleep apnea (OSA) can lead to various cardiovascular disorders (CVD) such as hypertension. There is no documented data about this relationship among the Iranian population. The aim of this study was to obtain comprehensive information about the severity of OSA as a cause of CVD and its relationship with other important risk factors.
Materials and Methods: In this cross sectional study, we studied patients with OSA and apnea/hypopnea index of 5 or more. The data were collected from the patients’ polysomnography report and medical files. Data analysis was done with SPSS version 18.
Results: The majority of patients were males (71.9%). Among the studied individuals, 26.5% showed at least one sign of CVD, and hypertension was the most common condition (74.5%). Multiple regression analysis showed that the odds ratios for one unit increase in BMI and one year increase in age were 1.13 and 1.12, respectively (P<0.001).
Conclusions: In our study, BMI and age had the strongest relationship with CVD. Thus, public health care providers should implement weight control strategies and improve diagnostic and treatment procedures for the elderly patients.
Objectives: Scientometric methods and the resulting citations have been applied to investigate the scientific performance of a nation. The present study was designed to collect the statistical information of dental articles by Iranian authors published in PubMed.
Materials and Methods: We searched the PubMed database for dental articles of Iranian authors until June 31, 2015. All abstracts were manually reviewed in order to exclude false retrievals. The number of articles per dental subspecialties, distribution of research designs, Scopus/Google Scholar citation of each article, number of authors and affiliation of the first/corresponding author were extracted and transferred to Microsoft Excel. The data were further analyzed to illustrate the related scientometric indicators.
Results: A total of 3,835 articles were retrieved according to the selection criteria. The number of PubMed-indexed publications between 2008 and 2015 showed a seven-fold increase. The majority of articles were written by four authors (24.56%). Systematic reviews and clinical trials constituted 9.20% of all publications. The number and percentage of articles with ≥4 citations from Google Scholar (n=2024; 52.78%) were higher than those from Scopus (n=1015; 26.47%). According to affiliated departments of the first authors, the top three dental subspecialties with the highest number of publications belonged to endodontics (19.82%), orthodontics (11.13%) and oral and maxillofacial surgery (10.33%). Moreover, the majority of articles originated from Shahid Beheshti- (14.47%), Tehran- (13.72%) and Mashhad- (12.28%) University of Medical Sciences.
Conclusions: Analysis of PubMed-indexed dental publications originating from Iran revealed a growing trend in the recent years.
Objectives: The aim of this study was to assess the effect of artificial accelerated aging (AAA) on color change of direct and indirect fiber-reinforced composite (FRC) restorations.
Materials and Methods: Direct (Z250) and indirect (Gradia) composite resins were reinforced with glass (GF) and polyethylene fibers (PF) based on the manufacturers’ instructions. Forty samples were fabricated and divided into eight groups (n=5). Four groups served as experimental groups and the remaining four served as controls. Color change (∆E) and color parameters (∆L*, ∆a*, ∆b*) were read at baseline and after AAA based on the CIELAB system. Three-way ANOVA and Tukey’s test were used for statistical analysis.
Results: Significant differences were found in ΔE, ΔL*, Δa* and Δb* among the groups after AAA (P<0.05). Most of the studied samples demonstrated an increase in lightness and a red-yellow shift after AAA.
Conclusions: The obtained ∆E values were unacceptable after AAA (∆E≥ 3.3). All indirect samples showed a green-blue shift with a reduction in lightness except for Gradia/PF+ NuliteF.
Objectives: Microbial leakage through the implant-abutment (I-A) interface results in bacterial colonization in two-piece implants. The aim of this study was to compare microleakage rates in three types of Replace abutments namely Snappy, GoldAdapt, and customized ceramic using radiotracing.
Materials and Methods: Three groups, one for each abutment type, of five implants and one positive and one negative control were considered (a total of 17 regular body implants). A torque of 35 N/cm was applied to the abutments. The samples were immersed in thallium 201 radioisotope solution for 24 hours to let the radiotracers leak through the I-A interface. Then, gamma photons received from the radiotracers were counted using a gamma counter device. In the next phase, cyclic fatigue loading process was applied followed by the same steps of immersion in the radioactive solution and photon counting.
Results: Rate of microleakage significantly increased (P≤0.05) in all three types of abutments (i.e. Snappy, GoldAdapt, and ceramic) after cyclic loading. No statistically significant differences were observed between abutment types after cyclic loading.
Conclusions: Microleakage significantly increases after cyclic loading in all three Replace abutments (GoldAdapt, Snappy, ceramic). Lowest microleakage before and after cyclic loading was observed in GoldAdapt followed by Snappy and ceramic.
Objectives: Gingival recession can lead to root exposure and discomfort for patients. There are various techniques for root coverage. The aim of this study was to compare the use of gingival unit graft (palatal graft including the marginal gingiva and papillae) with free gingival graft for treatment of localized gingival recession.
Materials and Methods: In this randomized controlled clinical trial, 18 bilateral localized recessions of Miller class I and II were treated in nine systemically healthy patients. Recessions were randomly treated with gingival unit graft in one side and conventional free gingival graft in the other side. Clinical parameters including clinical attachment level, keratinized tissue width, probing depth and vertical recession depth (VRD) were recorded at baseline and at one, three and six months after surgery. The healing index and patient satisfaction were also evaluated. One-way and two-way repeated measures ANOVA and paired t-test were used for statistical analyses.
Results: Both techniques caused significant improvement in clinical parameters. Gingival unit graft produced higher satisfaction esthetically (P=0.050, 0.024 and 0.024, respectively at the three time points), higher healing index (P<0.001), higher root coverage percentage at one month after surgery (34.04%, P=0.011) and greater reduction of recession width three months after surgery (P=0.007) but the reduction in VRD at this side was not significantly greater.
Conclusions: Gingival unit graft might be an acceptable modality in Miller Class I/II recession defects. This technique may have advantages over free gingival graft such as significantly superior clinical and esthetic results.
Objectives: This study aimed to assess the effect of storage time and temperature on dimensional stability of impressions made with Cavex Outline zinc oxide impression paste.
Materials and Methods: A round stainless steel mold with five grooves (three horizontal and two vertical) was used in this in-vitro experimental study. Cavex Outline impression paste was prepared according to the manufacturer’s instructions and applied to the mold. The mold was placed on a block and stored at 35°C and 100% humidity for setting. The impressions were poured with stone immediately and also after 30, 120, 240 and 420 minutes and 24 hours. The distance between the vertical lines on the casts was measured and compared with that in the immediately poured cast.
Results: Storage in a refrigerator and at room temperature for zero to seven hours had no significant effect on dimensional stability of the impressions; however, 24 hours of storage in a refrigerator or at room temperature decreased the dimensional stability of Cavex Outline (P=0.001). Also, a significant association was found between dimensional changes following 24 hours of storage in a refrigerator (4°C) and at room temperature (23°C; P<0.01).
Conclusions: The optimal pouring time of Cavex Outline impressions with stone is between zero to seven hours, and 24 hours of storage significantly decreases the dimensional stability.
Objectives: This study was designed to assess the changes of the mandible of patients who underwent orthodontic treatment with or without extraction of four premolars.
Materials and Methods: Eighteen Class I bimaxillary protrusion patients treated with extraction of four first premolars and retraction of anterior teeth and 18 Class I non-extraction patients with a mean age of 16.38±0.4 years were selected. Cephalometric analysis was performed before and after treatment. Twenty-four variables for analyzing the hard and soft tissues of the mandible were compared between the two groups. Repeated measures ANOVA was used for the comparison of the two groups fallowed by paired t-test. The relationship between the soft and hard tissue variables was studied using the Pearson’s correlation coefficient.
Results: In both groups, the mean value of angular measurements related to B point and Pogonion (Pog) decreased with treatment (P<0.05). Similarly, the symphysis depth of soft tissue decreased (P=0.008). The mean angular value of Y-axis increased in both groups after treatment (P=0.007). The mean changes in hard tissue symphysis depth after treatment were different in the two groups (P=0.021). Vertical, horizontal and rotational changes in soft tissue B point (B’) and Pogonion (pog’) followed their underlying hard tissue changes (P<0.05).
Conclusions: Points B and Pog showed backward movement after orthodontic treatments in both extraction and non-extraction patients. Changes in B’ and Pog’ were directly influenced by the changes in the corresponding points of the underlying hard tissue. Orthodontic treatments with and without extraction of premolars produced insignificant changes in vertical facial dimension.
Keywords: Chin; Tooth Extraction; Mandible
Objectives: This study sought to compare the push-out bond strength of two bulk-fill and one conventional composite to intracanal dentin in primary anterior teeth.
Materials and Methods: This in vitro, experimental study was conducted on 39 primary anterior teeth, which were randomly divided into three groups. After cleaning and shaping, the root canals were filled with Metapex in such a way that after the application of 1mm light-cure liner on top of it, the coronal 3mm of the canal remained empty for composite post space. Z250 conventional composite was used in group 1 and SonicFill and Filtek bulk-fill composites along with Single Bond 2 were used in groups 2 and 3, respectively. The samples were subjected to thermocycling. One-millimeter thick sections were made of the mid-root and subjected to push-out bond strength test. Mode of failure was determined under a stereomicroscope at ×25 magnification. The data were analyzed using one-way ANOVA.
Results: The mean (±standard deviation) push-out bond strength was 11.40±4.23MPa, 10.94±6.69MPa and 8.79±4.12MPa in the conventional, SonicFill and Filtek groups, respectively. The difference in this regard among the three groups was not statistically significant (P=0.397).
Conclusions: Based on the results, bulk-fill composites, similar to conventional types, can be successfully used for the fabrication of composite intracanal posts in primary teeth to decrease the treatment time in children.
Amir Reza Rokn, DDS, MSc
Mohammad-Sadegh Ahmad-Akhoundi, DDS, MSc.
Shahroo Etemad-Moghadam, DDS, MSc.
Abbas Mirzaei, PhD
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