Biodegradable rigid fixation is highly predictable in orthognathic surgery. In the mid-1980s, most oral and maxillofacial surgeons began using rigid fixation with titanium plates and screws rather than transosseous wire fixation after orthognathic surgery. The change to rigid fixation gave patients much greater postoperative stability and virtually eliminated the traditional 6 weeks of intermaxillary fixation. But the disadvantage of the plates and screws is that the patient must retain this metal in their skull indefinitely. To overcome this problem, researchers developed biodegradable screws and plates during the 1990s, and their use has expanded gradually. But are these biodegradable means

Abstract

We objectively and automatically classified arch wire blank forms represented by a series of facial surface points on tooth crowns in human adults with normal occlusions using a vector quantization algorithm on the basis of the generalized Lloyd algorithm. We investigated also the descriptive dental arch form parameters that were most effective in distinguishing the classified groups of dental arch wire blanks and examined if they were associated with specific anatomical traits. Dental casts, taken from 79 adults with complete dentitions, were laser scanned with a computer-assisted stereotaxic device. Coordinates of the tooth crown points (FA points) were measured for each dental arch expressed as a vector having positional elements in a series of 14 FA points and categorized into several codes (ie, patterns) according to the similarity of the quantized vector patterns. We found that classifying the dental arches into four patterns maximized the difference between arch wire blank patterns. The classified patterns were differentiated by a gradual broadening of the interarch widths posterior to the lateral incisor. The code with the narrowest arch had the longest coronal arch, whereas the code with the widest arch had the shortest coronal arch (P < .01). The interpremolar and intermolar basal arch widths determined for the code showing the widest arch were significantly greater than those for the code with the narrowest width (P < .01).

Abstract

This study investigates the differences in condylar position between centric relation (CR) and centric occlusion (CO) in Japanese orthodontic patients before treatment. We employed 150 consecutive cases (age range: 6–57 years) for the study. Dental casts were mounted on a Panadent articulator with a power centric CR bite record. The differences in condylar position between CR and CO in all three spatial planes were measured using the Panadent Condyle Position Indicator (CPI). The subjects were divided into groups by age, gender, mandibular plane angle or angle classification. No significant differences in the magnitude of CPI measurements were found among the groups. The three-dimensional distances of condylar displacement on both sides were almost identical, and the superoinferior displacement (S-I) was greater (P < .0001) than the anteroposterior displacement (A-P). The S-I was greater (P = .02) on the left side than on the right side, while the A-P displacement was smaller (P < .0001) on the left side than that on the right side. Significant condylar displacement (2.0 mm for S-I and A-P, 0.5 mm for the lateral displacement, L) was found frequently in L (31.3%), S-I, and A-P, in that order. Fifty-eight (38.7%) of the subjects had significant displacement in L, S-I, or A-P. Moreover, Angle Class III subjects tended to have significant condylar displacement toward the left side. The results suggest that orthodontists should be aware of a high incidence of condylar displacement in Japanese orthodontic patients and measure condylar displacement before the start of comprehensive orthodontic treatment to unmask real jaw relationships and avoid possible misdiagnoses.

Abstract

Based on a recent investigation that modeled the elastic properties (ie, strength, stiffness and range) of multistranded wires made from linearly elastic materials, three-stranded (triple) and six-stranded coaxial (coax) stainless steel (SS) wires were compared to single-stranded (single) SS and conventional nickel titanium (NiTi) leveling wires. To measure Young's modulus of elasticity (E), flexural tests were performed with an Instron mechanical testing machine in a three-point bending arrangement having a span length of 8.9 mm or 12.5 mm. A strong correlation between wire stiffness and the area moment of inertia demonstrated that strand interaction was negligible at low activations and that E = 199 GPa was constant even for the heavily drawn coax strands. Using the Instron with an extensometer, the 0.1% yield strengths (σ_YS) of the single SS wires and the straight inner strands within the coax wires were tested. The ratio of the σ_YS to the ultimate tensile strength averaged 0.81 for the single wires, 0.88 for the coax wires, and was subsequently assigned 0.85 for the triple wires. The average σ_YS values were 1.88, 1.83, and 1.78 GPa for the single, triple, and coax SS wires, respectively. For each NiTi wire, both the σ_YS and the elastic limit (σ_EL) via cyclic loading were measured. The conventional NiTi wires displayed nonlinear elasticity, as the average σ_EL values (1.10 GPa) were 50% higher than the average σ_YS values (0.73 GPa). Compared to the elastic properties of the conventional NiTi wires, the triple and coax SS wires generally matched the stiffness, but had only one-third to one-half of the strength and range. Since the properties of strength and range are both proportional to σ_YS, fabrication using alloys with enhanced σ_YS values would allow multistranded SS archwires to compete better against conventional NiTi products.

RE: Kim, J, Nielsen, I. A Longitudinal Study of Condylar Growth and Mandibular Rotation in Untreated Subjects with Class II Malocclusion.

It was incorrectly stated in that Vol. 72, No. 2 April 2002 that the material for the study came from Malmäo, Sweden. The material originated in Uppsala, Sweden.

RE: Agaoglu, Gäunseli; Arun, Täulin; Izgi, Belgin; Yarat, Aysen

Dr. Belgin Izgi's name was spelled incorrectly in Volume 71 (5), 2001, p. 375–379, [“Nickel and chromium levels in the saliva and serum of patients with fixed orthodontic appliances”].

Lip incompetence resolved by active vertical control in nonsurgical treatment of a protrusion case with vertical maxillary excess

Johnny JL Liaw,

Jae Hyun Park,

Fang Fang Tsai,

Betty MY Tsai, and

Wendy WT Liao

Smiles, Faces, and Straight Teeth

What's New in Dentistry

Patterning of Human Dental Arch Wire Blanks Using a Vector Quantization Algorithm

Abstract

The Difference in Condylar Position Between Centric Relation and Centric Occlusion in Pretreatment Japanese Orthodontic Patients

Abstract

Elastic Flexural Properties of Multistranded Stainless Steel Versus Conventional Nickel Titanium Archwires ^*

Abstract

Reproducibility of Characteristics Assessing the Occlusion of Young Adults

Abstract

An Improved Version of the Cervical Vertebral Maturation (CVM) Method for the Assessment of Mandibular Growth

Abstract

Comparison of Linear Cephalometric Dimensions in Americans of European Descent (Ann Arbor, Cleveland, Philadelphia) and Americans of African Descent (Nashville)

Abstract

Modeling Rabbit Temporomandibular Joint Torques During a Power Stroke

Abstract

Microbial Profile on Metallic and Ceramic Bracket Materials

Abstract

The Effects of Nitanium Maxillary Expander Appliances on Dentofacial Structures

Abstract

Maxillary Expansion and Protraction in Correction of Midface Retrusion in a Complete Unilateral Cleft Lip and Palate Patient

Abstract

An Adult Case of Skeletal Open Bite with a Severely Narrowed Maxillary Dental Arch

Abstract

Treatment of Condylar Hypoplasia with Distraction Osteogenesis: A Case Report

Abstract

ERRATA

Lip incompetence resolved by active vertical control in nonsurgical treatment of a protrusion case with vertical maxillary excess

Changes in glenoid fossa of adult female patients with Class II division 1 malocclusion during premolar extraction treatment and mini-implant anchorage: a cone-beam computed tomography study

Differences in the cooperation of teenagers for orthodontic treatment: Z Generation versus Y Generation

Miniscrew-assisted slow palatal expansion with bone borne expander in adult patients: a case control study on consecutively treated patients

Influence of personalized replacement protocol and low-level laser therapy combined with vibration on tooth movement rate and tooth movement accuracy in clear aligner treatment: a randomized clinical trial