Commercially available archwire forms compared with normal dental arch forms in a Japanese population.

INTRODUCTION: The objective of this research was to evaluate commercially available preformed archwire forms compared with normal dental arch forms. METHODS: Thirty mandibular dental casts were made of orthodontically untreated subjects with the most ideal occlusions, selected from among approximately 3500 students at Nippon Dental University. Canine and first-molar widths were measured on the dental casts with a 3-dimensional laser scanning system. Twenty preformed mandibular archwires were scanned by using a flatbed scanner. The archwire widths were measured at the level of the mean canine and first-molar depths, and then compared with the natural dental arch widths, considering bracket thickness, measured with a modified caliper. The results were statistically analyzed with the Mann-Whitney test. RESULTS: The preformed archwires that most closely matched the normal dental arch forms were the Orthos (Ormco, Glendora, Calif) and Vari-Simplex large (Ormco) types. The preformed archwires were significantly narrower than the normal dental arches at both the canine (P <0.05) and molar (P <0.01) levels. CONCLUSIONS: The variations in current preformed archwires do not correspond entirely with various arch forms in a group with ideal occlusion. The most commonly used archwires are similar and can be considered imitations of the Roth arch form, which was designed primarily for extraction patients in the 1970s. Therefore, preformed archwires that are approximately 1 to 3 mm wider at the canine level and 2 to 5 mm wider at the first-molar level might be required for today's orthodontic needs.

Influence of shovel-shaped incisors on the dental arch crowding in Mongolian females.

The aim of this study was to investigate the influences of shovel-shaped incisors on the dental arch crowding in the samples of modern young female adult Mongolians (belonging to the Khalkha-Mogol grouping) ranged between 18.5 and 25.0 years, with a mean age of 20.7 years. Materials in this study comprised of 33 dental casts. Plaster replicas of the A.S.U. system plaques were used to facilitate standardization in scoring and classify shoveling regarding both upper central and lateral incisors. Dimensions of the dental arch namely, overjet, overbite, arch depth, arch width and irregularity index were measured. The correlation between the shovel shape of the central incisor and the lateral incisor was highly significant. Significantly relations were found between the grades of shoveling and the mesiodistal diameters of upper first molars and lower incisors. Positive correlation was admitted between the shoveling and upper arch depth anterior, and upper arch depth. It may be considered that the grades of shoveling are indirectly related with upper and/or lower anterior crowding. Although crowding is looks like an expression of disharmony between teeth and alveolar arch, it may be caused by multiple etiologic factors interacted directly and/or indirectly.

Characteristics of the tooth in the initial movement: the influence of the restraint site to the periodontal ligament and the alveolar bone.

It is critical to clarify orthodontic load transfer mechanism from tooth to alveolar bone, and to determine the influence of applied orthodontic force on tooth behaviour. In this study, two dimensional (2-D) finite element (FE) models were constructed to simulate to mechanical behaviour observed during the initial movement of periodontal ligament (PDL) deformation, and to evaluate the effects of the presence of PDL and various restraint sites on tooth behaviour.A 2-D solid FE model of the tooth-PDL-alveolar bone system was constructed and investigated into stress distribution pattern and displacement. The first analysis was carried out with combinations of FE model with and without PDL. The second analysis was compared with three different sites restraint of alveolar bone. By incorporating PDL in FE models, excessively large stress values and deformation generated in a tooth and alveolar bone were relieved. Since restraint conditions did not affect a tooth and PDL, but had an effect on alveolar bone, orthodontic force necessary for tooth displacement was transmitted correctly. The results of this study revealed that inclusion of PDL in FE models is indispensable to transmit orthodontic force appropriately when investigating tooth behaviour for orthodontic treatment. Restrained sites affected stress distribution in alveolar bone.

Face mask therapy and conventional orthodontic treatment for anterior crossbite with cleft lip and palate: a case report.

AIM: To demonstrate a conventional orthodontic approach to anterior crossbite with unilateral cleft lip and palate. METHODS: Initially, maxillary expansion and face mask therapy was provided to widen the maxilla and improve the sagittal skeletal relation. Bone grafting to the maxillary left alveolar cleft then was performed, prior to treatment with a multibracket appliance. A multibracket appliance and intermaxillary elastics were used to align the dentition and establish a Class I relationship. RESULTS AND CONCLUSIONS: The combined orthodontic treatment of maxillary expansion, face mask therapy, bone grafting, and tooth alignment with a multibracket appliance resulted in a stable occlusion. The mandibular growth appeared after face mask therapy in adolescence; however, positive overjet and overbite were maintained throughout the retention phase.

A study on craniofacial morphology of Japanese subjects with normal occlusion and esthetic profile.

This study was designed to properly characterize the cephalometric values of Japanese individuals with both normal occlusion and esthetic profiles. Multivariate statistics were applied to analyze the collected data. Cephalometric values identified are expected to help in the simplification of orthodontic diagnosis. Lateral cephalometric radiographs from 50 men and 50 women with normal occlusion were traced and the dimensions of hard and soft tissues recorded. The corresponding values were classified by cluster analysis, and selected representative values were subjected to principal component analysis. From these values, characteristics of hard and soft tissue morphology were extracted. The subjects were grouped by sex, and subdivided into esthetic and unesthetic profile groups. The principal component scores from each group were plotted on a scattergram and the characteristics of each group investigated. The hard tissue characteristics in men with esthetic profiles were primarily vertical factors, including a tendency for smaller lower facial heights, a smaller mandibular plane angle, and a larger Nasion-ANS/ANS-Menton (N-ANS/ANS-Me). Soft tissue features included a more posteriorly placed maxilla and a high nasal crest. These features yield a less marked maxillary prognathism and a greater nose prominence. In females, hard tissue characteristics associated with esthetic profiles primarily involved the cranial base and posterior facial area. These included a smaller saddle angle, larger articulare angle, and smaller Sella-Articulare/Articlare-Gonion (S-Ar/Ar-Go). Female soft tissue characteristics primarily included retracted upper and lower lips, a shallow inferior sulcus with a smaller lower lip-Frankfort plane angle, and a shorter mentolabial sulcus and subnasale perpendicular-upper lip.

Shear bond strength and FEM of a resin-modified glass ionomer cement--effects of tooth enamel shape and orthodontic bracket base configuration.

The objective of this study was to evaluate the influences of enamel shape and bracket base configuration on shear bond strength from a biomechanical point of view. To this end, shear bond test and stress analysis using finite element method (FEM) were performed. Results obtained from both tests were then comprehensively investigated. Maxillary incisors were prepared for plane specimens, while mandibular premolars were prepared for curvature specimens. Shear bond test was carried out with three different test conditions. Two finite element models of enamel shape and bracket base configuration were also created. An approximate mean load of 200 N was applied. Results revealed that the shear bond strength of plane model was higher than that of curvature model. In conclusion, the present study revealed that shear bond strength was significantly influenced by enamel shape and bracket base configuration, whereby a curvature configuration tended to have lower bond strength.

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.

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.