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Frontiers in Dentistry - Volume:13 Issue: 6, Nov 2016

Frontiers in Dentistry
Volume:13 Issue: 6, Nov 2016

  • تاریخ انتشار: 1395/07/27
  • تعداد عناوین: 10
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  • Mohammad Hossein Toodehzaeim, Alireza Haerian, Ali Alesaeidi Pages 383-387
    Objectives
    Proper diagnosis and prevention of malocclusion are superior to treatment. Discrepancy between arch length and tooth size in mixed dentition period is a condition requiring timely diagnosis. Estimating the mesiodistal width of unerupted teeth according to the size of erupted ones can lead to earlier diagnosis of malocclusion. On the other hand, the best timing for serial extractions is before the eruption of lateral incisors. The aim of this study was to present prediction formulas for mesiodistal width of unerupted lateral incisors, canines and premolars in an Iranian population based on the width of erupted permanent mandibular central incisors and maxillary first molars.
    Materials And Methods
    A total of 120 dental models (60 males, 60 females) of orthodontic patients between 11-25 years were evaluated in Yazd city. The measurements were made by a digital caliper on the widest mesiodistal width of teeth at the interproximal contacts. Data were analyzed to calculate the prediction equation.
    Results
    The prediction equation in the upper jaw was y=0.57x.82 for males, y=0.7x.37 for females and y=0.64x.46 for both sexes. The equation for the lower jaw was y=0.76x.86 for males, y=0.74x.53 for females and y=0.77x.7 for both sexes.
    Conclusions
    The prediction equations suggested in this study can predict the mesiodistal width of unerupted lateral incisors, canines and premolars in an Iranian population in early mixed dentition period without taking radiographs.
    Keywords: Dentition, Mixed, Dentition, Permanent, Tooth, Unerupted
  • Amir Hossein Mirhashemi, Mohammad Sadegh Ahmad Akhoundi, Rezvaneh Ghazanfari, Shahroo Etemad, Moghadam, Mojgan Alaeddin, Azam Khorshidian, Ahmad Reza Dehpour, Nafiseh Momeni Pages 388-393
    Objectives
    Nitric oxide (NO) is a signaling molecule that mediates mechanical bone loading. Cyclic guanosine 3', 5' monophosphate (cGMP) is a NO-induced effector molecule. The aim of this study was to assess the effect of NO-cGMP pathway on orthodontic tooth movement (OTM) in rats by use of two phosphodiesterase 5 (PDE5) inhibitors namely sildenafil and tadalafil as chemical tools.
    Materials And Methods
    Forty-five male Wistar rats were divided into three equal groups (n=15) based on the substance they received. The first group received daily injections of tadalafil; the second group received daily injections of sildenafil and the third group received daily injections of normal saline. The orthodontic appliances consisted of nickel-titanium closed-coil spring ligated between the maxillary right incisor and the first molar of the animals for 21 days. The amount of tooth movement was measured in all three groups at the end of this period. Histological analysis was performed to assess root resorption lacunae, osteoclast number and periodontal ligament (PDL) thickness.
    Results
    All appliance-treated molars in the experimental and control groups showed evidence of tooth movement. The mean OTM was calculated to be 0.39±0.16, 0.32±0.16 and 0.26±0.16mm in tadalafil, sildenafil and control groups, respectively and there were no significant differences in OTM among the study groups (P>0.05). In the tadalafil group, significantly greater root resorption on the tension side was seen when compared with controls (P≤0.05).
    Conclusions
    Tadalafil and sildenafil PDE-5 inhibitors affecting the NO-cGMP pathway did not affect OTM in rats.
    Keywords: Nitric Oxide_Phosphodiesterase 5 Inhibitors_Tooth Movement Techniques
  • Maryam Ehsani, Robab Farhang, Azadeh Harandi, Saeid Tavanafar, Maryam Raoof, Saeedeh Galledar Pages 394-399
    Objectives
    During root canal preparation, apical extrusion of debris can cause inflammation, flare-ups, and delayed healing. Therefore, instrumentation techniques that cause the least extrusion of debris are desirable. This study aimed to compare apical extrusion of debris by five single-file, full-sequence rotary and reciprocating systems.
    Materials And Methods
    One hundred twenty human mandibular premolars with similar root lengths, apical diameters, and canal curvatures were selected and randomly assigned to six groups (n=20): Reciproc R25 (25, 0.08), WaveOne Primary (25, 0.08), OneShape (25, 0.06), F360 (25, 0.04), Neoniti A1 (25, 0.08), and ProTaper Universal. Instrumentation of the root canals was performed in accordance with the manufacturers’ instructions. Each tooth's debris was collected in a pre-weighed vial. After drying the debris in an incubator, the mass was measured three times consecutively; the mean was then calculated. The preparation time by each system was also measured. For data analysis, one-way ANOVA and Games-Howell post hoc test were used.
    Results
    The mean masses (±standard deviation) of the apical debris were as follows: 2.071±1.38mg (ProTaper Universal), 1.702±1.306mg (Neoniti A1), 1.295±0.839mg (OneShape), 1.109±0.676mg (WaveOne), 0.976±0.478mg (Reciproc) and 0.797±0.531mg (F360). Compared to ProTaper Universal, F360 generated significantly less debris (P=0.02). The ProTaper system required the longest preparation time (mean=88.6 seconds); the Reciproc (P=0.008), OneShape (P=0.006), and F360 (P=0.001) required significantly less time (P
    Conclusions
    All instruments caused extrusion of debris through the apex. The F360 produced significantly less debris than did the ProTaper Universal.
    Keywords: Dentistry, Endodontics, Root Canal Preparation, Instrumentation
  • Vahideh Nazari, Safoura Ghodsi, Marzieh Alikhasi, Majid Sahebi, Ahmad Reza Shamshiri Pages 400-406
    Objectives
    Fracture strength is an important factor influencing the clinical long-term success of implant-supported prostheses especially in high stress situations like excessive crown height space (CHS). The purpose of this study was to compare the fracture strength of implant-supported fixed partial dentures (FPDs) with excessive crown height, fabricated from three different materials.
    Materials And Methods
    Two implants with corresponding abutments were mounted in a metal model that simulated mandibular second premolar and second molar. Thirty 3-unit frameworks with supportive anatomical design were fabricated using zirconia, nickel-chromium alloy (Ni-Cr), and polyetheretherketone (PEEK) (n=10). After veneering, the CHS was equal to 15mm. Then; samples were axially loaded on the center of pontics until fracture in a universal testing machine at a crosshead speed of 0.5 mm/minute. The failure load data were analyzed by one-way ANOVA and Games-Howell tests at significance level of 0.05.
    Results
    The mean failure loads for zirconia, Ni-Cr and PEEK restorations were 2086±362N, 5591±1200N and 1430±262N, respectively. There were significant differences in the mean failure loads of the three groups (P
    Conclusions
    According to the findings of this study, all implant supported three-unit FPDs fabricated of zirconia, metal ceramic and PEEK materials are capable to withstand bite force (even para-functions) in the molar region with excessive CHS.
    Keywords: Dental Implants, Polyetheretherketone, Zirconium oxide, Dental Restoration Failure, Dental Porcelain
  • Masumeh Hasani Tabatabaei, Sakineh Arami, Farnaz Farahat Pages 407-414
    Objectives
    Dental composite wear in posterior restorations is a concern and is affected by different factors. This study was conducted to evaluate the effect of polishing and mechanical loads on wear of silorane-based and methyl methacrylate-based composites resins.
    Materials And Methods
    Of each dental composite (Filtek P90 and Filtek P60), 40 samples were fabricated in a polyethylene mold (4mm diameter, 10mm height). According to the finishing and/or polishing protocols (180-grit or 2500-grit silicon carbide papers), the samples of each composite were divided into two groups. Surface roughness (Rₔ) was measured and recorded using a contact profilometer. The weight of each sample was also measured in grams. The wear test was performed in a pin-on-disc device under two different loads (70N, 150N). Afterwards, samples were subjected to profilometry and their weight was measured again. Data were analyzed using t-test and univariate ANOVA. P
    Results
    Higher mechanical load resulted in greater weight loss (P
    Conclusions
    Results showed that wear of posterior composite restorations depends on mechanical load, type of composite resin and surface properties.
    Keywords: Dental Restoration Wear, Surface Properties, Silorane Composite Resin
  • Hossein Najafi, Hakimeh Siadat, Solmaz Akbari, Amirreza Rokn Pages 415-422
    Objectives
    The purpose of this study was to compare the outcomes of immediate and delayed rehabilitation of edentulous jaws by means of two straight and two tilted implants after one year of function.
    Materials And Methods
    Thirty consecutive patients (16 males, 14 females) were enrolled in this study. Two anterior straight and two posterior tilted implants were placed in each patient. According to the implant insertion torque and the need for bone grafting, implants were loaded immediately (at 72 hours) or delayed (after four months) using a fixed metal resin prosthesis.
    Results
    One axial implant failed in the delayed group after one year of loading, resulting in cumulative implant survival rate of 99.3%. The mean marginal bone loss was 0.84mm. No significant difference was found between axial and tilted implants in the two groups (P>0.05)
    Conclusions
    Based on the results, immediate or delayed fabrication of final prosthesis on two tilted and two axial implants did not result in significant differences in survival rates or marginal bone loss.
    Keywords: Dental Implants, Immediate Dental Implant Loading, Prospective Studies
  • Javad Chalipa, Yasamin Farajzadeh Jalali, Fatemeh Gorjizadeh, Pedram Baghaeian, Mohammad Hashem Hoseini, Omid Mortezai Pages 423-430
    Objectives
    The aim of this study was to evaluate the effect of conventional and high-power light emitting diode (LED) light curing units on shear bond strength (SBS) of metal and ceramic brackets to tooth surface.
    Materials And Methods
    Forty sound bovine maxillary central incisors were used for the study. The teeth were divided into four groups (n=10). Teeth surfaces were etched with 37% phosphoric acid for 20 seconds. After applying a uniform layer of adhesive primer on the etched enamel, composite was placed on the base of brackets. The samples were light cured according to the manufacturer’s instructions and thermocycled. The SBS was measured. The failure mode was scored using the adhesive remnant index (ARI).
    Results
    The mean SBS of samples in groups A (high-power LED, metal bracket), B (high-power LED, ceramic bracket), C (conventional LED, metal bracket) and D (conventional LED, ceramic bracket) was 23.1±3.69, 10.7±2.06, 24.92±6.37 and 10.74±3.18MPa, respectively. The interaction effect of type of LED unit (high-power/conventional) and bracket type on SBS was not statistically significant (P=0.483). In general, type of LED unit did not affect SBS. Type of bracket significantly affected SBS (P
    Conclusions
    The obtained SBS is the same for both bracket types by use of high-power and conventional LED light curing units. Regardless of the type of LED unit, SBS of ceramic brackets was significantly lower than that of metal brackets.
    Keywords: Orthodontic Brackets, Shear Strength, Light-Curing of Dental Adhesives
  • Mahshid Mohammadi Basir, Mohammad Bagher Rezvani, Elham Tabatabai Ghomsheh, Zahra Malek Hosseini Pages 431-437
    Objectives
    This study aimed to determine the effect of surface treatments such as tooth reduction and extending the etching time on microtensile bond strength (µTBS) of composite resin to normal and fluorotic enamel after microabrasion.
    Materials And Methods
    Fifty non-carious anterior teeth were classified into two groups of normal and fluorotic (n=25) using Thylstrup and Fejerskov index (TFI=4-6). Teeth in each group were treated with five modalities as follows and restored with OptiBond FL and Z350 composite resin: 1-Etching (30 seconds), bonding, filling (B); 2-Tooth reduction (0.3mm), etching, bonding, filling (R-B); 3-Microabrasion (120 seconds), etching, bonding, filling (M-B); 4- Microabrasion, tooth reduction, etching, bonding, filling (M-R-B); and 5- Microabrasion, etching (60 seconds), bonding, filling (M-2E-B). Ten experimental groups (n=5) were designed; 150 rectangular samples (10 in each group) with a cross-sectional area of 1×1mm2 were prepared for µTBS test. Failure mode was determined under a stereomicroscope and one specimen was selected from each group for scanning electron microscopy (SEM) analysis. Data were analyzed using two-way ANOVA and Tukey’s test.
    Results
    The µTBS to normal enamel was higher than to fluorotic enamel in all groups except for group (R-B). The Maximum and minimum µTBS were noted in the group (normal, reduction, bonding) and (fluorosed, microabrasion, bonding), respectively. Tooth reduction increased µTBS more effectively than extended etching time after microabrasion.
    Conclusions
    Fluorosis may reduce µTBS of composite resin to enamel. Microabrasion reduced the bond strength. Tooth reduction and extended etching time increased µTBS of composite resin to both normal and fluorotic enamel.
    Keywords: Fluorosis, Dental, Enamel Microabrasion, Dental Bonding, Composite Resins
  • Mandana Naseri, Mohammad Javad Kharazifard, Sepanta Hosseinpour Pages 438-447
    Objectives
    It is essential for clinicians to have adequate knowledge about root canal configurations; although its morphology varies largely in different ethnicities and even in different individuals with the same ethnic background. The current study aims to review the root canal configurations of mesiobuccal roots of maxillary first molars in an Iranian population based on different epidemiological studies.
    Materials And Methods
    A comprehensive search was conducted to retrieve articles related to root canal configuration and prevalence of each type of root canal based on Vertucci’s classification for the mesiobuccal root of maxillary first molars. An electronic search was conducted in Medline, Scopus and Google Scholar from January 1984 to September 2015. The articles were evaluated and methods, population, number of teeth and percentage of each root canal type evaluated in each study were summarized in the data table. Websites such as www.iranmedex.com, www.magiran.com and www.sid.ir were used to search all related studies published in Persian.
    Results
    Totally, out of nine studies conducted on the Iranian populations in nine provinces of Iran and 798 teeth, the Vertucci's type I was the most common type (35.70%), followed by type II (30.37%), type IV (16.66%), type III (7.93%) and type V (2.61%).
    Conclusions
    From this review article, it is concluded that the root canal morphology of mesiobuccal roots of maxillary first molars in the Iranian population predominantly has more than one canal. Therefore, careful evaluation of radiographs and anatomy of the pulp chamber is essential in order to achieve a successful root canal therapy.
    Keywords: Anatomy, Dental Pulp Cavity, Molar, Maxilla, Review Literature as Topic
  • Behnam Bolhari, Salma Pirmoazen, Ensieh Taftian, Somayeh Dehghan Pages 448-452
    Trauma to primary teeth can lead to devastating sequels in development of permanent successors. The disturbance may range from enamel hypoplasia and/or hypo-calcification to arrest of dental bud development. Crown dilaceration of permanent teeth is one of the consequences of trauma to deciduous teeth mainly due to intrusion or avulsion. This report presents a mandibular central incisor with dilacerated crown and yellowish discoloration with symptomatic apical abscess. History revealed avulsion of primary mandibular central incisors. The purpose of this report is to present: 1. Reasons of dilacerated crown, yellowish discoloration and necrotic pulp in this case, 2. Treatment options in different types of crown dilacerations and also in this case. The tooth was successfully managed by nonsurgical root canal therapy and restoration with composite resin to restore esthetics. We emphasize that trauma to deciduous teeth should not be understated, and regular follow up is essential.
    Keywords: Tooth, Deciduous, Tooth Avulsion, Tooth, Tooth Abnormalities