Diode laser debonding of ceramic brackets.

INTRODUCTION: Our objective was to investigate the effectiveness of debonding ceramic brackets with a diode laser. METHODS: Two types of ceramic brackets (monocrystalline and polycrystalline) were bonded to bovine maxillary central incisors. The diode laser was applied to brackets in the experimental groups for 3 seconds. Shear bond strength and thermal effects on the pulp chamber were assessed at 2 laser energy levels: 2 and 5 W per square centimeter. Analysis of variance (ANOVA) was used to determine significant differences in shear bond strength values. RESULTS: The diode laser was ineffective with polycrystalline brackets and effective with monocrystalline brackets in significantly (P <0.05) lowering the shear bond strength. There were no significant adhesive remnant index score differences between any groups tested. CONCLUSIONS: Diode laser use significantly decreased the debonding force required for monocrystalline brackets without increasing the pulp chamber temperature significantly. Diode lasers did not significantly decrease the debonding force required for polycrystalline brackets.

The neuroanatomic basis of facial perception and variable facial discrimination ability: implications for orthodontics.

INTRODUCTION: Because of familial, ethnic-racial, cultural, and emotional preferences, achieving common facial understanding among orthodontist, patient, parents, and other health care professionals is a daunting communication challenge. Research into the neuroanatomic basis of human facial perception, including the roles of visual short-term memory and long-term memory, might apply to orthodontic facial learning. METHODS: In this article, we review findings from functional magnetic resonance imaging and electrophysiology studies of the brain during visual perception and mental imaging of faces, and integrate these findings with facial learning needs in orthodontics. RESULTS: Research distinguishes specialized brain areas for whole face and face feature perception, the spatial relationship of face features, and facial memory stores. The right anterior temporal lobe's fusiform face area helps recognize facial identity, whereas the bilateral superior temporal sulcus assists in perception of facial expression. The amygdala, hippocampus, and bilateral inferior occipital gyrus help process familiar, unfamiliar, and famous faces. Because visual perceptual experience and processing are individually variable, along with visual short-term memory and long-term memory capacities, it is likely that facial discrimination ability is variable. CONCLUSIONS: Neuroanatomic research shows that each person's brain is as unique as his or her face. Due to variable neural hard-wiring, what the clinician sees facially might not be what the patient or parent sees, and vice versa. Enhanced facial learning is related to creation of a distinctive mental context associated with a facial stimulus and rich mixing between memory and visual perception. This context can be formed by information from clinical examinations, patient databases, patient-parent facial preference questionnaires, and functional face viewing. The more extensive the long-term memory facial links, the better the person knows the face. Facial discrimination exercises with electronic and hard-copy tools might improve facial learning and should be based on defined facial learning objectives. Tools should use facial prototypes and facial-feature spatial-relationship information, and emphasize categorization of whole faces and facial components. These are proven methods of expert recognition of objects having prototypical spatial configuration.

Current concepts in the biology of orthodontic tooth movement.

Adaptive biochemical response to applied orthodontic force is a highly sophisticated process. Many layers of networked reactions occur in and around periodontal ligament and alveolar bone cells that change mechanical force into molecular events (signal transduction) and orthodontic tooth movement (OTM). Osteoblasts and osteoclasts are sensitive environment-to-genome-to-environment communicators, capable of restoring system homeostasis disturbed by orthodontic mechanics. Five micro-environments are altered by orthodontic force: extracellular matrix, cell membrane, cytoskeleton, nuclear protein matrix, and genome. Gene activation (or suppression) is the point at which input becomes output, and further changes occur in all 5 environments. Hundreds of genes and thousands of proteins participate in OTM. Gene-directed protein synthesis, modification, and integration form the essence of all life processes, including OTM. Bone adaptation to orthodontic force depends on normal osteoblast and osteoclast genes that correctly express needed proteins at the right times and places. Cell membrane receptor-ligand docking is an important initiator of signal transduction and a discovery target for new bone-enhancing drugs. Despite progress in identification of regulatory molecules, the genetic mechanism of "orchestrated synthesis" between different cells, tissues, and systems remains largely unknown. Interpatient variation in mechanobiological response is most likely due to differences in periodontal ligament and bone cell populations, genomes, and protein expression patterns. Discovery of mutations in OTM-associated genes of orthodontic patients, including those regulating osteoclast bone-matrix acidification, chloride channel function, and osteoblast-derived mineral and protein matrices, will permit gene therapy to restore normal matrix and protein synthesis and function. Achieving selectivity in targeting abnormal genes, cells, and tissues is a major obstacle to safe and effective clinical application of gene engineering and stem-cell mediated tissue growth. Orthodontic treatment is likely to evolve into a combination of mechanics and molecular-genetic-cellular interventions: a change from shotgun to tightly focused communication with OTM cells.

Predicting skeletal maturation using cervical vertebrae.

This study's objective was to familiarize the profession with determining skeletal maturation and skeletal age, and predicting growth potential by using cervical vertebrae images of lateral cephalograms. The investigation was done through repeated evaluations of 30 randomly selected, pretreatment lateral cepaholometric radiographs. The accuracy of determining skeletal age and growth potential with lateral cephalograms was found to be R=0.98 (highly accurate) by statistical analysis.