Vol 15, No 3 (2018)

Published: 2018-06-13

Original Article

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    Objectives: The use of zirconia as a framework for prosthetic restorations is increasing due to its favorable mechanical properties. Zirconia also has remarkable aesthetic properties when used as a framework and covered with a layer of cosmetic ceramic. The aim of this study was to compare the fracture toughness of three types of aesthetic ceramics, namely VITA VM®9, ceraMotion® Zr, and IPS e.max® Ceram.
    Materials and Methods: Three groups of aesthetic ceramics (n=10) were subjected to three-point bending tests. The force leading to fracture was recorded for each sample to measure the impact of the ceramic type on the solidity of the framework. The type of fracture has not been studied in this work. One-way analysis of variance (ANOVA) was used to statistically analyze the results.
    Results: The statistical analysis showed significantly different fracture toughness values among the three groups. IPS e.max® showed the lowest fracture toughness (25.42 MPa) compared to VITA VM®9 and ceraMotion® Zr (respectively 40.39 MPa; P<0.001, and 48.78 MPa; P<0.005).
    Conclusions: Within the limitations of the present study, it can be concluded that aesthetic ceramics play an important role in the fracture toughness of all-ceramic restorations.

  • XML | PDF | downloads: 315 | views: 872 | pages: 143-150

    Objectives: Obtaining an adequate ceramic thickness to mask the substructure color is not always feasible, and appropriate use of a cement may be the only solution. This study aimed to evaluate the effect of the color of Variolink II resin cement on the final color of lithium disilicate glass ceramic restorations.
    Materials and Methods: In this in-vitro study, 90 discs of IPS e.max Press ceramic were evaluated. The ceramic discs were cemented to composite and amalgam blocks. The effect of the cement color and substructure on the final color of ceramic was analyzed by calculating the color change (∆E) value using a spectrophotometer. Data were analyzed via three-way analysis of variance (ANOVA) and Tukey’s test.
    Results: The cement color had a statistically significant effect on the final color of ceramic (P≤0.001). The white, yellow, and translucent cements caused the highest color change (ΔE=4.558, 3.308, and 2.649, respectively). The effect of composite substructure and the yellow cement on the final color was less prominent compared to other combinations of cement and substructure (ΔE=2.043). The white cement over amalgam substructure showed the greatest effect on the final color (ΔE=4.890). The ΔE in HO group was less than that of other combinations (P<0.05), and the greatest ΔE was reported in MO group with the white cement (∆E=6.255).
    Conclusions: The final color of the restoration is influenced by the cement color. Therefore, when IPS e.max Press is used over a metal core, it is recommended to use a cement with an HO ceramic.

  • XML | PDF | downloads: 325 | views: 1016 | pages: 151-160

    Objectives: The purpose of this in-vitro study was to determine and compare the shortest period needed for a triple antibiotic paste (TAP) and calcium hydroxide (Ca(OH)2) plus 2% chlorhexidine (CHX) to eradicate the biofilm of Enterococcus faecalis (EF) from the root canal system.
    Materials and Methods: Sixty-five extracted single-rooted human teeth with straight root canals were selected. The crowns were cut from the cementoenamel junction (CEJ), and canal preparations were done by step-back technique. The smear layer was removed by 17% ethylenediaminetetraacetic acid (EDTA) and 5.25% sodium hypochlorite (NaOCl). Afterwards, the samples were sterilized with gamma ray and were placed inside microtubes for one week. During this week, the teeth were infected with EF. Then, a TAP and Ca(OH)2 mixed with 2% CHX were inserted into the canals. The roots were cut longitudinally, and dentin chips were collected from the apical part of the roots by a round bur to the depth of 400 μm. The vital bacterial load was assessed by counting the numbers of colony-forming units (CFUs).
    Results: The paste of Ca(OH)2 mixed with 2% CHX was able to eradicate the EF biofilm in three days. The TAP was able to eradicate the biofilm of EF in seven days.
    Conclusions: It seems that Ca(OH)2 mixed with 2% CHX is more potent than the TAP against EF biofilm.

  • XML | PDF | downloads: 140 | views: 508 | pages: 161-168

    Objectives: Cleft lip and palate (CLP) is the most common congenital anomaly of the head and neck region. The upper airway in CLP patients is affected by retarded maxillary growth. Small size of the nasopharynx can also lead to mouth breathing. This study aimed to compare the size of nasopharynx and adenoids in non-syndromic unilateral CLP (NSUCLP) patients and healthy controls two-dimensionally on lateral cephalograms.
    Materials and Methods: This retrospective study was performed on 30 children with NSUCLP (mean age of 11.3 years) and 30 sex- and age-matched healthy controls with class I skeletal relationship. The bony boundaries of the nasopharynx, nasopharyngeal airway and adenoids were outlined on lateral cephalograms and their surface area was calculated and compared between the two groups. The percentage of nasopharynx occupied by the adenoids was calculated for each individual and compared between the two groups using independent t-test.
    Results: Size of nasopharynx in NSUCLP children was significantly smaller than that in healthy controls (P=0.0001). Size of adenoids was significantly larger in NSUCLP children (P=0.0001). Size of nasopharyngeal airway was smaller in NSUCLP patients than controls (P=0.0001). Percentage of nasopharynx occupied by the adenoids was significantly greater in NSUCLP patients (P=0.0001).
    Conclusions: The size of nasopharynx is smaller while the size of adenoids is larger in NSUCLP children compared to healthy controls; this can lead to mouth breathing and velopharyngeal incompetence.

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    Objectives: Periodontitis is an inflammation of periodontal tissues that is caused by the biofilm of periodontal pathogens. Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) is an opportunistic periodontopathogen that can be the cause of periodontal diseases via fimbriae as a virulence factor. In this study, we aimed to determine the expression level of A. actinomycetemcomitans rcpA gene as a virulence factor associated with biofilm formation after antimicrobial photodynamic therapy (aPDT) as a relatively new therapeutic modality.
    Materials and Methods: To determine sub-lethal doses of aPDT against A. actinomycetemcomitans ATCC 33384 strain, we used curcumin (CUR) as a photosensitizer at a final concentration of 40 µmol/ml, which was excited with a light-emitting diode (LED) at the wavelength of 450 nm. Quantitative real-time polymerase chain reaction (qRT-PCR) was then applied to monitor rcpA gene expression in A. actinomycetemcomitans.
    Results: 10-40 μmol/ml of CUR caused a significant reduction in the growth of A. actinomycetemcomitans compared to control group (P<0.05). Also, the cell viability of A. actinomycetemcomitans was significantly decreased after more than four minutes of LED irradiation. Therefore, the sub-lethal dose of aPDT against A. actinomycetemcomitans was 5 μmol/ml of CUR with three minutes of LED irradiation at a fluency of 180-240 J/cm2, which reduced the expression of the rcpA gene by approximately 8.5-fold.
    Conclusions: aPDT with CUR leads to decreased cell survival and virulence of A. actinomycetemcomitans. Thus, CUR-aPDT can be used as an alternative approach for the successful treatment of periodontitis in vivo.

  • XML | PDF | downloads: 197 | views: 888 | pages: 178-186

    Objectives: Successful root treatment depends on elimination of microorganisms from the root canal. Considering incomplete removal of bacteria from the canal by usual methods, lasers have been suggested as a new modality. Despite their anti-bacterial properties, lasers can cause thermal changes. This study assessed the thermal changes of root surface in pulpectomy of primary teeth following the use of Er:YAG laser.
    Materials and Methods: Sixty primary anterior teeth were collected and prepared by K-file up to number 50. Then, they were randomly divided into two groups and were irradiated with Er:YAG laser. The first group was irradiated with 1 W laser and the second group with 1.5 W laser. The laser irradiation time was two 10-second cycles with a 2-second interval in both groups. Thermal changes were measured by a thermometer in the apical and coronal areas per second. The results were analyzed by repeated measures ANOVA considering the laser power as between-subject variable.
    Results: There was a temperature increase in the coronal and apical areas in use of 1 W power. There was a temperature rise in the coronal and apical areas in use of 1.5 W power. The temperature rise in the apical third was more than that in the coronal third; also, the average temperature rise was more in use of 1.5 W power than 1 W power.
    Conclusions: As the average temperature increase was not more than 7°C in any group, this type of laser seems to be suitable for root treatment of primary anterior teeth.

Case Report

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    This article describes the prosthetic treatment of a patient suffering from a hemimaxillary defect after surgical resection of an adenoid cystic carcinoma (ACC) in the palate. The patient had also received therapeutic irradiation. One year after radiotherapy, three implants were placed in the remaining maxillary bone without any bone augmentation. One of the implants failed during the osseointegration period. The implant replacing the failed one also failed during prosthetic procedures. The patient was unwilling to undergo another surgical episode, and the final prosthesis was completed on the two remaining implants.

  • XML | PDF | downloads: 220 | views: 825 | pages: 193-196

    The management of traumatic dental injuries as well as crown-root fractures is always challenging in everyday general dental practice. A number of treatment modalities are available for crown-root fractures, depending on the position, extent and severity of the fracture. The aim of this case report was to describe a clinical case of rehabilitation of a complicated crown-root fracture of the maxillary left central incisor, successfully treated by a multidisciplinary approach including orthodontic extrusion. The final result was esthetically pleasant and periodontally sound in the follow ups.