Orthodontic resin under water immersion.

The absorption and desorption of water by a polymer matrix of composite orthodontic resin could cause debonding of the filler-matrix or hydrolytic degradation of fillers and loss of bond strength. In this study, the bond strength of brackets directly bonded with orthodontic composite to the enamel surface of premolars was measured with an Instron machine; the debonding interface distribution was analyzed by scanning electron microscope and energy dispersive x-ray spectrometry following water immersion for 1, 2, and 3 days, and 1, 2, 4, 8, 16, 24, and 32 weeks, respectively. The results show that, under water immersion, bond strength may gradually weaken over time. The greatest loss occurs initially, followed by a period of relative stabilization, and then a weaker reduction after 24 weeks. The greater the time in water immersion, the less the bond strength and the greater the destruction of the composite resin. The debonding interface occurs between bracket and resin.

Effect of H3PO4 concentration on bond strength.

Prior to bonding, the enamel surface of the tooth is normally etched using a solution of 37%-50% phosphoric acid (H3PO4) for 60 seconds. The purpose of this study was to evaluate the tensile bond strength, debonding interface distribution and enamel surface detachment of various concentrations of H3PO4 solution, from 2% to 80%, applied for 15 seconds. Statistically significant differences in bond strength were found among the various concentrations tested: concentrations in the 10% to 60% range produced greater bond strengths than both the weaker and stronger concentrations. The weaker the bond strength, the greater the debonding interface between resin and enamel. The greater the bond strength, the greater the debonding interface between the bracket and resin. Enamel detachment occurred as the H3PO4 concentration rose above 30%. To obtain greater bond strength and less enamel detachment, 10%-30% concentrations of phosphoric acid for 15 seconds etching are suggested for clinical bonding.

Advanced Chinese NiTi alloy wire and clinical observations.

Chinese NiTi wire was studied on the bench with six other nickel-titanium-alloy wires. Bending and torsional tests were conducted and temperatures of phase transformation compared. The Chinese NiTi wire was found to have a low stiffness, high springback and constant bending and torsional moments on unloading, in a very large deformation region. It can produce a gentle, nearly constant force. These factors make it desirable for clinical application. Included in this paper are clinical observations of case selected from over 100 patients in current treatment with Chinese NiTi wires. Chinese NiTi wire reduced the leveling and alignment phase of treatment without discomfort to the patient. Chinese NiTi wire can be used in both children and adults.

Nonextraction treatment of severe Class II, division 2 malocclusions. Part 2.

Nonextraction treatment of a severe Class II, Division 2 malocclusion is presented. Timing, sequencing of appliance therapy, and segmental arch treatment are discussed. The effects of orthodontic treatment, pubertal growth, and postpubertal growth are illustrated with different growth responses. Correction of the handicapping malocclusion was achieved by the development of arch circumference, torque, intrusion of incisors, and vertical buccal dentoalveolar development. Various subtypes of Class II, Division 2 malocclusion are presented. Pretreatment and posttreatment records are evaluated.

Nonextraction treatment of severe Class II, Division 2 malocclusions. Part 1.

Nonextraction treatment of severe Class II, Division 2 malocclusions is presented. Timing, sequencing of appliance therapy, and segmental arch treatment are discussed. The effects of orthodontic treatment, pubertal growth, and postpubertal growth are illustrated with different growth responses. Corrections of the handicapping malocclusions were achieved by the development of arch circumference, torque, intrusion of incisors, and vertical buccal dentoalveolar development. Various subtypes of Class II, Division 2 malocclusion are presented. Pretreatment and posttreatment records are evaluated.

Nonextraction treatment of Class II, Division 1 malocclusions.

Nonextraction treatment of three different types of Class II, Division 1 malocclusions that focused on solving the imbalances of the dentofacial configuration have been presented. Diagnostic features encountered were anterior alveolar hyperplasia that required simultaneous maxillary incisor intrusion and retraction, severe mandibular crowding requiring functional alveolar arch development, and maxillary prognathism requiring distal movement of the maxilla and incisor retraction. Since many factors contribute to the makeup of various types of Class II, Division 1 malocclusions, orthodontic mechanics should address the specific needs of each patient.

Progressive facial asymmetry as a result of early closure of the left coronal suture.

A longitudinal growth analysis of a patient with premature closure of the left coronal suture is presented. The resultant facial asymmetry of patients with unilateral synostosis of the coronal suture is accompanied by diagnostic facial characteristics and radiographic skull distortions. The midfacial structures distort and grow toward the site of synostosis while the lower face grows away from the site of synostosis. Unilateral craniosynostosis of the coronal suture results in distortions and compensations within the cranial vault and the cranial base. Therefore, with growth of the contiguous facial structures, the facial distortions are magnified.

Treatment of severe mandibular retrusion in class II, division 2 malocclusion.

The case of an adult patient with a severe mandibular retrusion of the Class II, Division 2 malocclusion type has been presented. The patient's marked anteroposterior discrepancy was complicated by the severe malocclusion. The solution to this case involved presurgical orthodontic treatment to allow for surgical mandibular advancement by a modified sagittal osteotomy and postsurgical orthodontic care for alignment of the dentition. A discussion of the importance of the patient's facial growth type for stable mandibular advancement has also been presented.

An epidemiologic survey of malocclusions among American Negroes and American Hispanics.

The malocclusions of thirty-six Negro and fifty-six Puerto Rican orthodontic patients from a specific area were surveyed. The population was divided according to sex, age, and skeletal classification. The total Negro malocclusion sample was compared to available Negro norms for both Downs and Steiner analyses. The total Hispanic malocclusion group was compared to available Negro and Caucasian norms for the same analyses. Ranges, means, and standard deviations were developed for each measurement recorded. The comparative frequency of individual skeletal classifications was found to be remarkably similar in both groups, and the percentage of open-bites was greater in both groups than in the general population. The need to expand available material to include a Puerto Rican group is noted.

Treatment of marked anteroposterior and transverse discrepancies in mandibular prognathism.

A case report of a patient with a severe skeletal Class III malocclusion has been presented. The patient's marked anteroposterior discrepancy was complicated by the fact that his buccolingual occlusion was normal. The solution to this case thus involved a correction of the transverse discrepancy in addition to the anteroposterior discrepancy, which required orthodontic and surgical solutions. A discussion of mandibular prognathism has also been presented.

Treatment of anterior skeletal open-bite deformity.

Two patients with severe skeletal anterior open-bite have been presented. Treatment of these patients was accomplished mainly by mandibular repositioning (Case 1 by orthodontic means and Case 2 by a combination of surgery and orthodontics) and by an orthodontic change in the mandibular occlusal plane. A review and a discussion of the cause of this deformity were presented.

Familial generalized delayed eruption of the dentition with short stature.

1. Prolonged retention of the deciduous dentition, subsequent delay in eruption of the permanent dentition, and retardation in dental maturation are displayed outside the limits of normal variation. 2. The pedigree study of this family reveals the trait of noneruption to be distributed in a characteristic pattern of autosomal dominance. 3. Short stature was noted in this family and placed in the lowest limits of short stature as recorded in standard reference charts. 4. Additional findings included concave midfacial appearance, frontal bossing, delayed skeletal maturation, presence of Wormian bones in the lamboidal suture region of the skull, and strikingly large fontanelles in infancy. 5. The pedigree described represents a syndrome of short stature and delayed eruption of the dentition.