Myoung Uk Jin

An ultrastructural evidence for the expression of transient receptor potential ankyrin 1 (TRPA1) in astrocytes in the rat trigeminal caudal nucleus

The transient receptor potential ankyrin 1 (TRPA1) is implicated in the mechanical and cold hyperalgesia following inflammation and nerve injury. Its expression has been presumed to be confined to primary afferent terminals. Here, we show that TRPA1 is expressed in astrocytes in the superficial laminae of the rat trigeminal caudal nucleus by use of electron microscopic immunoperoxidase and immunogold labeling techniques. Immunoreactivity for TRPA1 was consistently observed in somata and process of astrocytes and was weaker than that in presumed nociceptive primary afferent terminals, but increased significantly in the fine process of astrocyte in rats with experimental inflammation of the temporomandibular joint. Thus, we provide ultrastructural evidence that TRPA1 is expressed in astrocytes in the brain stem and propose a novel pathway of its involvement in the central mechanism of inflammatory hyperalgesia.

Effect of dual treatment with SDF-1 and BMP-2 on ectopic and orthotopic bone formation.

Purposes The potent stem cell homing factor stromal cell-derived factor-1 (SDF-1) actively recruits mesenchymal stem cells from circulation and from local bone marrow. It is well established that bone morphogenetic protein-2 (BMP-2) induces ectopic and orthotopic bone formation. However, the exact synergistic effects of BMP-2 and SDF-1 in ectopic and orthotopic bone regeneration models have not been fully investigated. The purpose of this study was to evaluate the potential effects of simultaneous SDF-1 and BMP-2 treatment on bone formation. Materials and Methods Various doses of SDF-1 were loaded onto collagen sponges with or without BMP-2.These sponges were implanted into subcutaneous pockets and critical-size calvarial defects in C57BL/6 mice. The specimens were harvested 4 weeks post-surgery and the degree of bone formation in specimens was evaluated by histomorphometric and radiographic density analyses. Osteogenic potential and migration capacity of mesenchymal cells and capillary tube formation of endothelial cells following dual treatment with SDF-1 and BMP-2 were evaluated with in vitro assays. Results SDF-1-only-treated implants did not yield significant in vivo bone formation and SDF-1 treatment did not enhance BMP-2-induced ectopic and orthotopic bone regeneration. In vitro experiments showed that concomitant use of BMP-2 and SDF-1 had no additive effect on osteoblastic differentiation, cell migration or angiogenesis compared to BMP-2 or SDF-1 treatment alone. Conclusions These findings imply that sequence-controlled application of SDF-1 and BMP-2 must be further investigated for the enhancement of robust osteogenesis in bone defects.

Diastema closure using direct bonding restorations combined with orthodontic treatment: a case report

Closure of interdental spaces using proximal build-ups with resin composite is considered to be practical and conservative. However, a comprehensive approach combining two or more treatment modalities may be needed to improve esthetics. This case report describes the management of a patient with multiple diastemas, a peg-shaped lateral incisor and midline deviation in the maxillary anterior area. Direct resin bonding along with orthodontic movement of teeth allows space closure and midline correction, consequently, creating a better esthetic result.

Expression of Vesicular Glutamate Transporters VGLUT1 and VGLUT2 in the Rat Dental Pulp and Trigeminal Ganglion following Inflammation

Background There is increasing evidence that peripheral glutamate signaling mechanism is involved in the nociceptive transmission during pathological conditions. However, little is known about the glutamate signaling mechanism and related specific type of vesicular glutamate transporter (VGLUT) in the dental pulp following inflammation. To address this issue, we investigated expression and protein levels of VGLUT1 and VGLUT2 in the dental pulp and trigeminal ganglion (TG) following complete Freund’s adjuvant (CFA) application to the rat dental pulp by light microscopic immunohistochemistry and Western blot analysis. Results The density of VGLUT2− immunopositive (+) axons in the dental pulp and the number of VGLUT2+ soma in the TG increased significantly in the CFA-treated group, compared to control group. The protein levels of VGLUT2 in the dental pulp and TG were also significantly higher in the CFA-treated group than control group by Western blot analysis. The density of VGLUT1+ axons in the dental pulp and soma in the TG remained unchanged in the CFA-treated group. Conclusions These findings suggest that glutamate signaling that is mediated by VGLUT2 in the pulpal axons may be enhanced in the inflamed dental pulp, which may contribute to pulpal axon sensitization leading to hyperalgesia following inflammation.

Endodontic treatment of maxillary lateral incisors with anatomical variations

Maxillary lateral incisors usually exhibit a single root with a single canal. However, maxillary lateral incisor teeth with unusual morphology of root canal system are frequently reported. These cases of variable root canal anatomy can be treated well by nonsurgical endodontic methods. A detailed description of root canal morphology is fundamental for successful endodontic treatment. Treatment using an operating microscope, radiographs from different angles, and cone-beam computerized tomography (CBCT) can produce more predictable endodontic outcomes.

The influence of moisture control on bond strength of composite resin treated with self-etching adhesive system

A goal of restorative dentistry is to develope adhesive restorative materials that are durable and provide an effective seal at the restoration/ tooth interface. To achieve this purpose, many enamel-dentin bonding systems were introduced and improved in a new formula. These new adhesive materials not only attempt to improve the quality of the bond, but also simplifying the clinical procedures. Most recent innovative changes of bonding concept are the “total-etch”and “wet-bonding”techniques, and these methods have been used for many years. However, when using the wet bonding technique it is difficult to maintain the optiThe influence of moisture control on bond strength of composite resin treated with self-etching adhesive system

Polymerization of dual cured composites by different thickness

The purpose of this study was to evaluate the effect of thickness, filling methods and curing meth-ods on the polymerization of dual cured core materials by means of microhardness test. Two dual cured core materials, MultiCore Flow (Ivoclar Vivadent AG, Schaan, Liechtenstein) andBis-Core (Bisco Inc., Schaumburg, IL, USA) were used in this study. 2 ㎜(bulky filled), 4 ㎜(bulkyfilled), 6 ㎜(bulky and incrementally filled) and 8 ㎜(bulky and incrementally filled)-thicknessspecimens were prepared with light cure or self cure mode. After storage at 37℃for 24 hours, theKnoop hardness values (KHN) of top and bottom surfaces were measured and the microhardnessratio of top and bottom surfaces was calculated. The data were analyzed using one-way ANOVA andScheffe multiple comparison test, with α= 0.05.The effect of thickness on the polymerization of dual cured composites showed material specificresults. In 2, 4 and 6 ㎜groups, the KHN of two materials were not affected by thickness. However,in 8 ㎜group of MultiCore Flow, the KHN of the bottom surface was lower than those of othergroups (p< 0.05). The effect of filling methods on the polymerization of dual cured composites wasdifferent by their thickness or materials. In 6 ㎜thickness, there was no significant differencebetween bulk and incremental filling groups. In 8 ㎜thickness, Bis-Core showed no significant dif-ference between groups. However, in MultiCore Flow, the microhardness ratio of bulk filling groupwas lower than that of incremental filling group (p< 0.05). The effect of curing methods on the poly-merization of dual cured composites showed material specific results. In Bis-Core, the KHN of dualcured group were higher than those of self cured group at both surfaces (p< 0.05). However, inMultiCore Flow, the results were not similar at both surfaces. At the top surface, dual cured groupshowed higher KHN than that of self cured group (p< 0.05). However, in the bottom surface, dualcured group showed lower value than that of self cured group (p< 0.05).

Root Canal Shaping Effect of Instruments with Offset Mass of Rotation in the Mandibular First Molar: A Micro–computed Tomographic Study

Introduction: The aim of this study was to evaluate the root canal shaping effect of 2 nickel‐titanium rotary instruments with offset mass of rotation compared with an instrument with a conventional centered mass of rotation. Methods: Thirty‐six extracted human mandibular first molars with 2 independent mesial canals and 1 oval distal canal were selected and divided equally into 3 groups for instrumentation with ProTaper Next (PTN; Dentsply Maillefer, Ballaigues, Switzerland), Revo‐S (RS; Micro‐Mega, Besançon, France), and ProTaper Universal (PTU, Dentsply Maillefer) systems (n = 12). For apical preparation, PTN X2 (#25/0.06), RS SU (#25/0.06), and PTU F2 (#25/0.08) were used in the mesial canals and PTN X3 (#30/0.07), RS AS30 (#30/0.06), and PTU F3 (#30/0.09) were used in the distal canals. Specimens were scanned before and after instrumentation using a SkyScan 1272 scanner (Bruker micro‐CT, Kontich, Belgium) at 10‐&mgr;m isotropic resolution. Changes in the canal area, volume, structure model index (SMI), and untouched canal area were evaluated. Canal transportation and centering ratio were measured at 1, 3, 5, and 7 mm from the apical foramen. Data were statistically analyzed using 1‐way analysis of variance with the Tukey post hoc test. Results: The PTN and RS systems showed significantly less transportation and better centering ability compared with the PTU system at 1 mm from the apical foramen (P < .05). All instrumentation increased the canal area, volume, and SMI values without significant differences among the 3 groups (P > .05). Conclusions: Regardless of the differences in the cross‐sectional design, alloy type, and taper variation, instruments with offset mass of rotation showed better root canal shaping ability compared with an instrument with a centered mass of rotation. HIGHLIGHTSInstruments with offset mass of rotation showed less canal transportation and better centering ability and a comparable amount of dentin removal compared with a system with a conventional centered mass of rotation.The resultant swaggering motion of the systems with offset mass of rotation might have a beneficial effect on dentin removal but not on untouched canal areas.

EFFECT OF PRE-HEATING ON SOME PHYSICAL PROPERTIES OF COMPOSITE RESIN

The purpose of this study was to evaluate the effect of pre-heating on some physical properties of composite resin. Eighty extracted, noncarious human molars were used in the present study. Four different temperatures of composite resin were used: 4℃, 17℃, 48℃, and 56℃. The 4℃ and 17℃ values represented the refrigerator storage temperature and room temperature respectively. For 48℃ and 56℃, composite resin was heated to the temperatures. As physical properties of composite resin, shear bond strength, microhardness, and degree of conversion were measured. The data for each group were subjected to one-way ANOVAs followed by the Tukeys HSD test at 95% confidence level. Both in enamel and dentin, among composite resin of 4℃, 17℃, 48℃, and 56℃, the pre-heated composite resin up to 56℃ revealed the highest shear bond strength, and pre-heated composite resin to the higher temperature revealed higher shear bond strength. Microhardness value was also higher with composite resin of higher temperature. Degree of conversion was also higher with composite resin of the higher temperature. In this study, it seems that pre-heating composite resin up to the higher temperature may show higher shear bond strength, higher microhardness value, and higher degree of conversion. Therefore, when using composite resin in the clinic, preheating the composite resin could be recommended to have enhanced physical properties of it.