Akira Komori

Evaluation of Light Curing Units Used for Polymerization of Orthodontic Bonding Agents

This study evaluated the light intensity of various light curing units, the effect of distance of the light guide, and the validity of a tapered light guide. Light curing units tested included (1) four blue light-emitting diode curing units, Lux-O-Max, LEDemetronl, Ortholux LED, and The Cure; (2) two tungsten-quartz halogen curing units, Optilux 501 and Co-bee; and (3) one plasma arc curing unit, Apollo95E. The Optilux 501 was also evaluated for combinations of normal mode and boost mode and Standard tip and Turbo tip light guide. The spectral output of each unit was measured from 300 to 600 nm with a spectroradiometer. The light intensities at distances of zero, five, 10, 15, and 20 mm were determined with the radiometer. The peak value of Ortholux LED and The Cure surpassed that of Apollo95E. The light intensity significantly decreased with distance. Although The Cure showed a higher light intensity than the LEDemetron1 at zero-mm distance, the light intensity of the LEDemetron1 was higher than that of The Cure at five to 20 mm, resulting in no significant difference. The boost mode increased light intensity at any distance. Although the Turbo tip enhanced light intensity at zero-mm distance, reduction of light intensity by Turbo tip was demonstrated at five- to 20-mm distance.

Evaluation of a new 2-paste glass ionomer cement.

A new 2-paste resin-reinforced glass ionomer cement, Fuji Ortho Band Paste Pak (GC Corporation, Tokyo, Japan), for the placement of orthodontic bands, has been developed for easier handling. The aim of this study was to compare the fluoride release and uptake characteristics of this cement with that of 3 others commonly used to cement orthodontic bands: a conventional resin-reinforced glass ionomer cement, a polyacid-modified composite resin, and a conventional glass ionomer cement. Fluoride release was measured during a 28-day period. After the measurement on day 28, experimental samples were exposed to 1000 ppm sodium fluoride solution for 5 minutes, and fluoride release was then measured for 7 days. Initially, the new 2-paste resin-reinforced glass ionomer cement released the greatest amount of fluoride; the polyacid-modified composite resin released the least initially, and it continued to show the lowest values throughout the study. The fluoride uptake and release values of the new 2-paste resin-reinforced glass ionomer cement were statistically significantly higher than those of the conventional resin-reinforced glass ionomer cement or the conventional glass ionomer cement. The new 2-paste resin-reinforced glass ionomer cement might be a good alternative to conventional products for cementing orthodontic bands.

Tensile and shear bond strength of resin-reinforced glass ionomer cement to glazed porcelain.

The purpose of this study was to measure the tensile and shear bond strength of resin-reinforced glass ionomer cement (RGIC) to glazed porcelain, to evaluate the durability of RGIC by thermal cycling, and to examine the RGIC remaining on the surface of the porcelain after the bond strength test to evaluate bonding conditions. Three adhesives were used in this study: Concise (CO) as a chemically cured composite resin, Fuji ORTHO (FO) as a chemically cured RGIC, and Fuji ORTHO LC (FOLC) as a light-cured RGIC. Tensile and shear bond strengths were measured 24 hours after bonding orthodontic brackets and also after thermal cycling. Tensile bond strength after 24 hours was 6.6 +/- 3.2 MPa in CO, 7.3 +/- 1.4 MPa in FO, and 8.6 +/- 1.9 MPa in FOLC, and the strength significantly decreased after the thermal cycling test. Shear bond strength after 24 hours was 32.5 +/- 8.9 MPa in CO, 23.3 +/- 6.8 MPa in FO, and 24.7 +/- 6.5 MPa in FOLC, and in contrast to tensile bond strength, no decreases in the strength were detected after the thermal cycling test. CO showed significantly higher shear bond strength than did FO and FOLC. When using the shear bond strength test and CO, destruction of porcelain surfaces frequently occurred after 24 hours and was observed in every specimen after the thermal cycling. RGIC was found to be an advantageous alternative to resin adhesive for bracket bonding to porcelain and to enamel.

KommonBase for precise direct bonding of lingual orthodontic brackets

On account of the morphological variations of lingual dental surfaces, indirect bonding systems have been used for bonding lingual orthodontic brackets. Improvements in bracket seating and bonding systems have enabled the development of KommonBase, a precise direct bonding system. KommonBase is characterized by a large bonding base, which can achieve a good bracket fit and precise bracket positioning while also enhancing bond strength. Furthermore, transfer trays are not required because of its self-positioning shape. KommonBase offers an advantageous alternative to conventional indirect bonding systems for the bonding of lingual orthodontic brackets.

Tensile bond strength of light-cured resin-reinforced glass ionomer cement with delayed light exposure

Abstract In the clinical situations, the time intervals between material mixing and light exposure during bracket bonding, using light-cured resin-reinforced glass ionomer cement (LCGIC), may vary for each individual bracket. This study determined the tensile bond strengths of LCGIC subjected to various time intervals, and evaluated the durability with thermocycling. Comparisons were made between LCGIC and light-cured composite resin (LCR). Two hundred and forty bovine teeth were chosen as specimens. Light exposure was performed 5, 10, 20, and 40 min after the commencement of powder/liquid mixing. The durability was evaluated by thermocycling for 2000 times at temperatures between 5°C and 55°C, with a 30-s dwell time. Tensile bond strengths of LCGIC and LCR after 5 min, representing the general condition in clinical use, equaled 5.7 ± 1.5 MPa and 5.1 ± 2.6 MPa, respectively. For the LCGIC groups, no significant differences were seen between bond strengths with and without thermocycling. Also, no significant differences were noted among any time intervals. For the LCR groups, there were also no significant differences with and without thermocycling. The tensile bond strength of LCR showed highly significant differences within groups across time. Compared with LCR, the failure sites for brackets bonded with LCGIC appeared to be predominantly at the bracket/adhesive interface. The standard deviations of LCR were high when compared with those of LCGIC. The bond strength of LCGIC with or without thermocycling surpassed the clinically required minimum. LCGIC may be an advantageous alternative to LCR for orthodontic bracket bonding.

Time-related bond strength of resin-reinforced glass ionomer cement under various light exposure conditions

Abstract Purpose This studys purpose was to determine the time-related bond strengths of light-cured resin-reinforced glass ionomer cement (LCGIC) under various conditions of light exposure. Materials and methods 480 freshly extracted bovine mandibular incisors were randomly divided into 32 groups. The study was performed in 4 light curing conditions, at 4 bond-testing times, and by 2 bond testing methods. For dental curing lights, LED using a source consisting of high intensity light-emitting diode, TQH (tungsten quartz halogen lamp) and PAC (plasma arc lamp) were used. Light exposure from 2 directions was performed under 4 conditions: for 5 s with LED (LED-5s), for 10 s with LED (LED-10s), for 20 s with TQH, and for 3 s with PAC. Tensile and shear bond tests were performed at 4 time-points after light exposure, i.e. 0 min, 3 min, 30 min, and 24 h. Results LED had the highest peak output by 44.7 mW/cm2 at 458 nm. Significant increase over time of tensile and shear bond strength was observed in all of the groups. TQH and PAC had low tensile bond strength just after the exposure. LED-10s demonstrated significantly higher tensile and shear bond strength compared with other groups. Conclusion Although LED and PAC showed approximately peak irradiance five times higher than TQH, there is no significant difference in tensile and shear bond strength between TQH and PAC. It appears that LCGIC would have provided greater bond strength under various conditions of LED-10s.

A case treated with simultaneous orthodontic traction of deeply impacted mandibular first and second molars

approximately one-half and one-third those of stainless steel wire and cobalt–chromium–nickel alloy wire, respectively. For a cyclic bending test, stainless steel wire, cobalt–chromium– nickel alloy wire, and beta-titanium alloy-2 wire did not fracture even after 10,000 times of bending cycles, although beta-titanium alloy-1 wire fractured after 4500 bending cycles. Orthodontic forces delivered by a quad helix made from both betatitanium alloy wires were lower than those for stainless steel wire and cobalt–chromium–nickel alloy wire.

Conventional orthodontic treatment for isolated cleft palate with bilateral mild crossbite

Abstract This is a case report of a female patient who demonstrated bilateral posterior crossbite with isolated cleft palate. Molar relation was Class I on the right side and Class II on the left side. Maxillary dental midline was deviated 1.0 mm to the left. To establish the Class I relation, comprehensive orthodontic treatment without extraction was planned. Initially, an open coil spring was activated between the first premolar and the first molar to make space for the second premolar. Subsequently, Class II elastics were used to align the dentition and establish Class I relation. Bilateral crossbite was significantly improved, and the molar relation improved to Class I. Although the maxillary arch width was slightly decreased post-retention, intercuspation was maintained during the retention phase.

A modified transpalatal arch with customized bonding base

Abstract In orthodontic treatment using fixed appliances, a transpalatal arch acts as an anchorage to stabilize against the movement of other teeth. However, due to the usage of multiple bands, this appliance requires complicated laboratory procedures, and often involves technical errors. A modified transpalatal arch (M-TPA) was developed for simple laboratory procedures and for versatile designs. M-TPA can be attached by using direct bonding with resin-reinforced glass ionomer cement. M-TPA contacts over a large area, which allows a tight fit. Since M-TPA is bonded only on the lingual side, it can be removed according to anchorage requirements without disturbing labial fixed appliances.

An experimental study on the direct bonding method to reduce the risk of porcelain fracture

Abstract To evaluate resin-reinforced glass ionomer cement (RGIC) for bracket bonding to the enamel and porcelain surfaces employing the direct bonding system, the tensile and shear bond strengths of RGIC were measured. At the same time, the surfaces of the bonded materials were observed before the bond strength test. In addition, residual bonding agents on the bonded surfaces were investigated after the bond strength test to evaluate the bonding condition. The results were as follows:(1) The silane-treated porcelain surface was smooth, and no deposit was noted.(2) There was no significant difference in the tensile bond strength between the composite resin and RGIC.(3) The shear bond strength of composite resin was significantly greater than that of RGIC.(4) No significant difference was noted in tensile and shear bond strength between the porcelain and enamel.(5) The porcelain surface bonded using the composite resin was frequently destroyed after the shear bond strength test, indicating that it is desirable to load a tensile force during bracket removal.(6) The risk of destroying porcelain bonded with RGIC is low even when a tensile or shear force is loaded.(7) RGIC also showed favorable bond strength on porcelain, as well as on enamel, suggesting that its characteristics are clinically useful.