Subject(s)
Orthodontic Appliance Design , Orthodontic Brackets , Orthodontic Wires , Adolescent , Alloys/chemistry , Child , Dental Alloys/chemistry , Female , Humans , Male , Malocclusion/therapy , Malocclusion, Angle Class II/therapy , Tooth Eruption, Ectopic/therapy , Tooth Movement Techniques/instrumentation , Young AdultABSTRACT
INTRODUCTION: In indirect bonding, a white surface layer defect sometimes appears on the custom resin base when brackets are bonded to the stone model with a hydrophilic adhesive. It was surmised that this surface layer might be related to oxygen inhibition. METHODS: Scanning electron microscopy and x-ray microanalysis were used to corroborate that this defect is caused by oxygen inhibition during the formation of the resin bases. A series of indirect bonding bases was prepared with both hydrophilic (APC PLUS, 3M Unitek, Monrovia, Calif) and hydrophobic (APCII, 3M Unitek) adhesive-coated metal brackets, sectioned, and imaged in cross section. RESULTS: With the hydrophilic adhesive, a 30- to 40-microm white layer defect was observed on the custom resin base after rinsing and drying. This defect was not observed, however, when the hydrophobic adhesive was used. When the same tests were conducted under an inert nitrogen blanket, the porous white layer was not present on either adhesive. X-ray microanalysis also showed elevated levels of silicon and oxygen in the porous layer compared with the bulk. CONCLUSIONS: These findings indicate that the white layer defect originated from the formation of an oxygen-inhibited surface layer during curing followed by resin leaching when the bonding tray was rinsed. The fact that this layer does not correspond to the normally observed smooth resin-colored surface might be of concern to clinicians; if so, the layer can be eliminated by curing the bonding bases under inert conditions. Moreover, it is not a hindrance to effective bonding.
Subject(s)
Dental Bonding/methods , Oxygen/chemistry , Resin Cements/chemistry , Animals , Cattle , Dental Alloys/chemistry , Dental Cements/chemistry , Electron Probe Microanalysis , Hydrophobic and Hydrophilic Interactions , Materials Testing , Microscopy, Electron, Scanning , Models, Dental , Nitrogen/chemistry , Orthodontic Brackets , Oxygen/analysis , Porosity , Silicon/analysis , Silicon/chemistry , Surface Properties , Temperature , Time Factors , Water/chemistry , WettabilityABSTRACT
The purpose of this article was to introduce the concept of anterior interferences into the dental lexicon and into the thought process of restorative and orthodontic treatment. It certainly seems clear that this information should have a profound impact on the finishing inclinations of the maxillary and mandibular anterior segments. The evidence appears to contraindicate treatment mechanics that would permit anterior interferences during or following orthodontic treatment. Such clinical sequelae could be obviated by controlling the axial inclination of the maxillary and mandibular anterior segments, by interproximal reduction in the mandibular anterior segment, by building up the tooth mass in the maxillary anterior segment, and possibly by occlusal equilibration in patients with heavy lingual marginal ridges on the maxillary incisors.
