• The Korean Journal of Physiology and Pharmacology
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• v.24 no.1
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• pp.11-18
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• 2020

The present study was aimed to explore the neuroprotective role of imatinib in global ischemia-reperfusion-induced cerebral injury along with possible mechanisms. Global ischemia was induced in mice by bilateral carotid artery occlusion for 20 min, which was followed by reperfusion for 24 h by restoring the blood flow to the brain. The extent of cerebral injury was assessed after 24 h of global ischemia by measuring the locomotor activity (actophotometer test), motor coordination (inclined beam walking test), neurological severity score, learning and memory (object recognition test) and cerebral infarction (triphenyl tetrazolium chloride stain). Ischemia-reperfusion injury produced significant cerebral infarction, impaired the behavioral parameters and decreased the expression of connexin 43 and phosphorylated signal transducer and activator of transcription 3 (p-STAT3) in the brain. A single dose administration of imatinib (20 and 40 mg/kg) attenuated ischemia-reperfusion-induced behavioral deficits and the extent of cerebral infarction along with the restoration of connexin 43 and p-STAT3 levels. However, administration of AG490, a selective Janus-activated kinase 2 (JAK2)/STAT3 inhibitor, abolished the neuroprotective actions of imatinib and decreased the expression of connexin 43 and p-STAT3. It is concluded that imatinib has the potential of attenuating global ischemia-reperfusion-induced cerebral injury, which may be possibly attributed to activation of JAK2/STAT3 signaling pathway along with the increase in the expression of connexin 43.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.4
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• pp.301-309
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• 2015

Purpose: When the edentulous area is restored by implant prostheses, the opposing hypofunctioned teeth will receive physiologic mechanical stimuli. This study evaluated the bone changes around the maxillary teeth opposing an implant restoration installed in the mandibular posterior area. Materials and Methods: Radiographs of the opposing teeth were taken at prostheses delivery (baseline), 3 and 6 months later. A customized film holding device was fabricated to standardize the projection geometry for the serial radiographs of the opposing teeth. The gray values of the region of interest of each digital image were compared according to time. Repeated measured analysis of variance was performed at the 95% significance level. Results: The gray values of the alveolar bone around the antagonist teeth of implants increased with time. The changes in gray values of the middle area were greater than those of the crestal area. However, the gray values of the mesial and distal areas were not different. The changes in gray values were different according to the unloaded time. Conclusion: A change in bone tissue will occur if a proper physiologic load is again applied to the bone tissues around a hypofunctioned tooth.

• Journal of Dental Rehabilitation and Applied Science
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• v.17 no.4
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• pp.245-256
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• 2001

The purpose of this study is to analyze the mechanical stress and displacement on the jaws during the simulated bilateral clenching task on the three-dimensional finite element model of the dentated skull with unilateral molar loss. For this study, the computed tomography(G.E.8800 Quick, USA) was used to scan the total length of human skull in the frontal plane at 2.0mm intervals. The fully assembled finite element model consists of the articular disc, maxilla, mandible, teeth, periodontal ligament and cranium. The FE model was used to simulate the bilateral clenching in intercuspal position. The loading condition was the force of the masseter muscle exerted on the mandible as reported by Korioth et al. degrees of freedom of the zygomatic region where the masseter muscle is attached were fixed as restraints. In order to reflect the actual action of the muscles force, the displacement of the region was attached where the muscle is connected to the temporal bone and restraint conditions were given values identical to values at the attachment region of the masticatory muscle but with the opposite direction of the reaction from when the muscle force is acted on the mandible. Although the mandible generally has higher displacement and von Mises stress than the maxilla, its mandibular corpus on the molar-loss side has a higher stress and displacement than the molar-presence side. Because the displacement and von Mises Stress was the highest on the lateral surface of mandibular corpus with molar loss, the stress level of the condyle on the molar-loss side is greater than that of the molar-presence side, which in turn caused the symphysis of the mandible to bend. In conclusion, the unilateral posterior bite collapse with molar loss under para-functional activities such as bruxism and clenching can affect the stress concentration on the condyle and mandibular corpus. It is therefore necessary to consider the biomechanical function of dento-skeleton under masticatory force while designing the occlusal scheme of restoration on alveolar bone with the posterior collapse.

• Journal of Dental Rehabilitation and Applied Science
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• v.34 no.2
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• pp.89-96
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• 2018

Purpose: The aim of this study was to evaluate the effect of delayed time, surface treatment, and repair materials on repair of bis-acryl composite resin through comparison of shear bond strength and to evaluate the utility of bis-acryl composite resin repair using polymethyl methacrylate resin. Materials and Methods: A total of 90 bis-acryl composite resin specimens were fabricated and classified into 9 test groups, each of 10 pieces according to delayed time, surface treatment and repair material. The shear bond strength of each specimen was measured using a universal testing machine immediately after fabrication and analyzed using a statistical analysis program (IBM SPSS statistics 20). After the shear bond strength measurement, the fracture surface of the specimen was observed. Results: The highest shear bond strength ($17.54{\pm}3.14MPa$) was observed in the experimental group bonded immediately with a light-curing flowable composite resin using a bonding agent. Conclusion: When repairing bis-acryl composite resin, it is necessary to consider whether to remake according to the delayed time. For effective repair, it is desirable to consider appropriate materials and surface treatment methods according to the site or purpose of use.

• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.1
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• pp.41-47
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• 2020

Purpose: The purpose of this study was to evaluate the flexural strength and reliability of highly translucent colored zirconia for all ceramic restoration. Materials and Methods: Bar-shaped specimens (25 × 4 × 2.5 mm) were prepared from highly translucent monolithic zirconia. Three experimental groups were set up according to color (shade A0, A1, and A3). For each group, 20 specimens were prepared. Flexural strength was determined using a 3-point flexural test and results were analyzed with one-way ANOVA test. Weibull statistical analysis provided 2 parameter estimates: Weibull modulus and characteristic strength. X-ray diffraction (XRD) analysis was performed. Results: There was statistically significant difference between uncolored (Shade A0) and colored (shade A1 and A3) (P < 0.05), but there was no difference between colored groups (P > 0.05). The uncolored group had higher reliability compared with colored study groups. On x-ray diffraction analysis of each group, typical peaks of tetragonal phase appeared in all groups. Conclusion: Within the limitations of this in vitro study, coloring highly translucent zirconia had significant effect on flexural strength and reliability. Therefore, clinicians should be careful when using highly translucent colored zirconia to prevent breakage of veneering ceramic and enhance aesthetics.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.2
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• pp.81-91
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• 2002

Dental implant systems have shown many post-surgical problems and One of the most frequent problem is screw loosening. To reduce screw loosening, a number of methods have been tried and recently fundamental modification of fixture-abutment connection structure was developed and used the most frequently. Former implant system structure, such as Br${\aa}$nemark, had external hex with the height of 0.7 mm and later, fixture with external hex of 1.0 mm height and internal hex structure were developed. In addition, the method of morse taper application was introduced to reduce screw loosening. In this study, the level of screw loosening of each implant systems was compared based on the vibration loosening measurement of abutment screw of each implant systems. Analysis of measured value was performed using 3 kinds of methods, (i) Percentage of average of initial 3 times loosening-torque value(initial loosening value) to tightening-torque of 30 Ncm, (ii) Percentage of loosening-torque value after 200 N strength loaded(experimental value) to initial loosening value and (iii) Percentage of experimental value to 30 Ncm of tightening-torque. Each result of analyses shows the value of initial loosening, loosening by repetitive load and final loosening level. The results of this study were as follows. (1) Percentage of initial loosening value to tightening-torque was increased in order of 0.7 mm external hex, 1.0 mm external hex, internal hex and internal taper and all values between each groups showed statistical significance (p<0.05). (2) Percentage of experimental value to initial loosening value was increased in order of internal hex, 0.7 mm external hex, 1.0 mm external hex and internal taper. Value of internal taper showed significant difference with that of 0.7 mm external hex and internal hex (p<0.05). (3) Percentage of experimental value to tightening torque was increased in order of 0.7 mm external hex, 1.0 mm external hex, internal hex and internal taper. Values of all groups showed statistical significance (p<0.05) except between the groups of 1.0 mm external hex and internal hex. Based on those results, there was no significant difference of loosening-torque by repetitive loading except internal taper. It is supposed that implant system with high resistant capability against initial loosening could be recommended for clinical use. In addition, in case of single implant restoration, 1.0 mm external hex or internal hex could be recommended rather than 0.7 mm external hex, and the use of internal taper would be the most useful way to reduce screw loosening.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.3
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• pp.311-322
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• 2010

The purpose of this study was to evaluate the bond strengths between IPS e.max Press and four different types of resin cements that often used for esthetic restoration. Disc shaped IPS e.max Press blocks(N=40, diameter: 12mm, thickness: 3mm) were fabricated according to the manufacture's instruction and cleaned with ultrasonic cleaner. They were embedded into an autopolymerizing acrylic resin. Fourty cylinder shaped resin block(Filtek Z350, diameter: 4.5mm, thickness: 3mm) were fabricated using a plastic tube. Each specimens were randomly divided into 4 experimental group and bonded each other using 4 different resin cements(Variolink II(light-cure), Variolink II(dual-cure), Calibra, Super-Bond C&B) according to the manufactures' recommendations. All the specimens were stored in normal saline at $37^{\circ}C$ for 24 hours before test. Universal testing machine at a crosshead speed of 1mm/min was used to evaluate the shear bond strength. The data were statistically analyzed using one-way ANOVA(P<.01). Multiple comparison was done by the Tukey HSD test. The shear bond strength of Super-Bond C&B to e.max was significantly lower than those of Calibra, Variolink II(light-cure), Variolink II(dual-cure) (P<.01). The shear bond strength of Calibra, Variolink II(light-cure), Variolink II(dual-cure) to e.max were not significantly different. The shear bond strengths of light-cure/dual-cure cement were higher than that of self-cure cement.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.3
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• pp.189-198
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• 2017

Purpose: This study aims to analyze the stress distribution of mandibular molar restoration supported by the implants with external hex and internal taper abutment connection design. Materials and Methods: Models of external connection (EXHEX) and internal connection (INCON) implants, corresponding abutment/crowns, and screws were developed. Supporting edentulous mandibular bony structures were designed. All the components were assembled and a finite element analysis was performed to predict the magnitude and pattern of stresses generated by occlusal loading. A total of 120 N static force was applied both by axial (L1) and oblique (L2) direction. Results: Peak von Mises stresses produced in the implants by L2 load produced 6 - 15 times greater than those by L1 load. The INCON model showed 2.2 times greater total amount of crown cusp deflection than the EXHEX model. Fastening screw in EXHEX model and upside margin of implant fixture in INCON model generated the peak von Mises stresses by oblique occlusal force. EXHEX model and INCON model showed the similar opening gap between abutment and fixture, but intimate sealing inside the contact interface was maintained in INCON model. Conclusion: Oblique force produced grater magnitudes of deflection and stress than those by axial force. The maximum stress area at the implant was different between the INCON and EXHEX models.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.1
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• pp.77-102
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• 1994

Many studies have been made on the masticatory and esthetic effects of prosthodontic treatments, but few on the restoration of pronunciation, especially in complete denture wearers. The purpose of this study is to provide a basis that could be of help to the complete denture wearers' speech adaptation by analyzing the influence of the palatal coverage upon the duration of consonants and vowels with the method of experimental phonetics. For this study, metal plates and resin plates were made for 3 male subjects in their twenties, who have good occlusion, and do not have speech and hearing disorders. Then 8 Korean consonants and 4 Korean vowels were selected, systemically considering phonetic variants such as the place and manner of articulation, lenis/fortis, mutual effect of each phoneme, etc. They were combined into meaningless tested words in the form of /VCV/, and were included in the carrier sentences. Each informant uttered the sentences 1) without the plate, 2) with the metal plate, 3) with the resin plate. The recorded data were analyzed through the waveform of sounds and spectrogram by using the program SoundEdit, Signalize, Statview 512+for the Macintosh computer. The duration of each segment was measured by searching for the boundaries between the preceding vowels and consonants, and between the consonants and the following vowels. The study led to the conclusion that. 1. With the palatal plate, the duration of all the tested words increased and the duration increased more with the resin plate than with the metal plate. 2. With the palatal plate, the duration of all the preceding vowels, consonants, and following vowels increased, but the temporal structure of the tested words was maintained. 3. As for the manner of articulation, fricative /s/(ㅅ) was greatly influenced by both kinds of palatal plates. 4. As for the place of articulation, alveolar sounds /d/(ㄷ), /n/(ㄴ) were greatly influnced by the kinds of palatal plates, and the velar sounds /n/(ㅇ), /g/(ㄱ) were influenced by the platal plates, but the kind of the palatal plates did not show any significance. 5. As for the lenis/fortis, lenis was influenced more by the kind of the palatal plates. 6. As for the influence of vowels upon each segment in the tested words, palatal vowel /i/(ㅣ) had greater influence than pharyngeal vowel /a/(ㅏ), and following vowels than preceding vowels.

• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.4
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• pp.335-341
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• 2013

Impacted maxillary canines are the most frequently impacted teeth after the third molars. The exact etiology of impacted maxillary canines is unknown, but several complications may result from impacted maxillary canines. An early detection of ectopically erupting teeth can lead to performing interceptive treatment such as early extraction of primary canine and provide the best long-term results. In the absence of prevention, clinicians should consider orthodontic treatment followed by surgical exposure of the canine to bring it into occlusion. However, in cases when the finding ectopically erupting teeth and severe root resorption of adjacent teeth are found late, malposed canine can replace the injured teeth. In these presented cases, early diagnosis and treatment of ectopic eruption and root resorption were not performed. The maxillary incisor replacement with ectopically erupting canine can be the alternative treatment of choice with successful results. The reconstructed canine is planned to be checked periodically for the condition of composite resin restoration. Orthodontic treatment and dental implant are planned. This report shows that when early diagnosis was not done, maxillary incisor replacement with ectopically erupting canine could prevent uncertain prognosis of the adjacent teeth with root resorption and provide esthetic satisfactory with time saved and cost reduced.