PubMed Health⌕ Search

Biomedical subjects

R A Hocevar

Publications and source records attributed to R A Hocevar.

16 recordsLinked to original sources
PubMed1996

The nonsurgical treatment of a Class II open bite malocclusion.

This case was treated by residents in the postgraduate orthodontic program at the University of Florida under the supervision of Dr. Hocevar. A treatment regimen that he developed to increase the strength and endurance of the masticatory muscles was used. The patient performed prescribed daily clenching and chewing exercise with resilient posterior bite-blocks and wore a hard acrylic posterior biteplane the remainder of the time. It was hoped that this approach would increase the chances of treatment success and stability.

Adolescent↗
PubMed1992

A study of reference lines for mandibular plane angles.

Four mandibular plane angles, MP-sella nasion, MP-Frankfort horizontal, MP-articulare nasion, and MP-gnathion occiput, were compared. Highly significant correlations were found among all four. The relation of an extension of the mandibular plane to the posterior inferior outline of the cranium was found to provide a valid indication of mandibular plane angle. Articulare nasion was found to be the reference line most likely to provide a true indication of the mandibular inclination rather than a reflection of a variation in the reference line itself.

Cephalometry↗
PubMed1990

The timing of treatment for Class II malocclusions in children: a literature review.

Two basic strategies for the timing of treatment for Class II malocclusions in children are common: (1) correction achieved in two phases, one during pre-adolescence (early treatment) and the other during the teen years; and (2) correction accomplished in one phase of active treatment during the adolescent years. The issues of efficacy and cost(risk)-benefit of these strategies have not been well delineated. Most clinical studies examining these issues have suffered serious methodological deficiencies, such as being retrospective, lacking adequate controls, and evaluating only successfully treated cases. However, despite a lack of objective data, clinicians have shown considerable interest in recent years in two-phase treatment. This paper reviews major issues of two-phase Class II treatment and concludes by delineating several important clinical questions which could be resolved by a carefully controlled prospective study.

Adolescent↗
PubMed1988

Indirect versus direct bonding: bond strength and failure location.

Bond strengths and failure locations in direct and indirect bonding of orthodontic brackets with foil-mesh bonding pads were compared in an in vitro study that used extracted human premolars. The direct technique comprised bonding the attachments directly to the premolars with composite resin. The indirect technique comprised bonding the attachments to die-stone models of the teeth with composite resin, making silicone positioners to transfer the attachments from the models to the teeth, and bonding to the teeth with the use of two-part unfilled resin. One part of the unfilled resin was applied to the teeth and the other part to the composite resin that was already bonded to the attachments. Placing the positioners on the teeth brought the two parts together to initiate setting. Inspection after bonding disclosed marginal voids in two thirds of the indirect bonds. Of these, two thirds were then sealed with unfilled resin and one third were left defective. There were no significant differences in strength among direct, void-free indirect, and sealed indirect bonds. Indirect bonds with voids were only half as strong. This seems to indicate that sealing around brackets immediately after positioner removal might be a worthwhile clinical routine. Forty-four percent of the direct bonds fractured predominantly at the bracket-adhesive interface, whereas 72% of the indirect bonds failed mainly at the enamel-resin interface. Grouping the data according to failure location showed no difference in bond strength between those that failed at the enamel and those that failed at the bonding pad. Thus the indirect bonding promised similar bond strength and easier debonding because less resin was left on the teeth.

Dental Bonding↗
PubMed1987

Moment/force ratios.

Explore the source record for details and available documents.

Biomechanical Phenomena↗
PubMed1985

Begg-edgewise diagnosis-determined totally individualized orthodontic technique: foundations, description, and rationale.

This article presents an appliance system designed to facilitate efficient treatment by the use of the biomechanical approach considered most suitable by the orthodontist for the individual patient. The system described uses narrow, single brackets with 0.022 X 0.028 inch edgewise arch wire slots and 0.020 X 0.020 inch vertical slots for various auxiliaries. There are five brackets that differ only in the torque of the arch wire slot-0 degree, 5 degrees, 10 degrees, 15 degrees, and 20 degrees. Thus, an appropriate bracket can be selected for any tooth in any situation. The brackets and bonding pads are small in all dimensions to ensure optimal appearance and interbracket arch wire spans and minimal lip and cheek irritation. This also lessens occlusal interference, enamel surface involved in bonding, and problems with gingival proximity and oral hygiene. The basic buccal tubes are conventional 4.5 mm long, 0.022 X 0.028 inch torqued edgewise tubes. A buccal tube assembly with a similar additional rectangular tube carried diagonally at a 15 degree angle across the buccal surface of the basic tube (its mesial end pointing gingivally) is used in extraction cases with deep overbites or moderate-to-severe anchorage requirements. The angulated outer tube carries the main (working) arch wire during the bite-opening and retraction phases of treatment. A rectangular sectional wire in the inner tube and second premolar bracket locks the molar and premolar teeth together so that neither can tip independently. As a unit they provide anchorage for bite opening and retraction. The gingivally positioned and angulated outer tube directs the arch wire out of danger of distortion from mastication and provides a built-in biteopening effect. The molar and premolar teeth, in effect, become a single large tooth with its center of resistance (CR) further mesial than the CR of the molar. Sectional wires result in a more favorable system of moments created by arch wires and elastics. This delivers more intrusive force to the incisors with less tendency to tip the anchor units. The appliance provides the orthodontist with an extensive range of options in treatment mechanics--from anchorage conservation and rapid movement of limited tipping by light forces to translation or stabilization with precise three-dimensional control.

Adolescent↗
PubMed1982

Orthodontic force systems: individualized treatment with open-minded "Begg" technique.

Conventional Begg technique is efficacious for alignment, overbite reduction, and anchorage conservation, but it has a number of deficiencies. Biomechanical systems should be determined by the characteristics of each individual malocclusion, not by habitual application of the same recipe to every patient. Check elastics can increase the bite-opening potency of the appliance, thus permitting control of root movement at any stage. Ribbon arch wires can provide torque control for either bolstering or expending anchorage. Extraoral traction can provide anchorage, control of orientation of the dentition within the face, and simplify and/or shorten treatment in some cases.

Adolescent↗
PubMed1982

Orthodontic force systems: technical refinements for increased efficiency.

The efficiency of the Begg technique suffers because Class II elastics overwhelm anchor bends, which normally do not yield enough force for vertical control of maxillary incisors. This can be improved by attention to detail and modifications. Bite-opening bends in the arch wires distal to canines and lateral incisors, long (6.5 mm.) mesiogingivally angulated molar tubes, and placement of intermaxillary elastics at the distal ends of the tubes are all helpful. Intermaxillary "check elastics," having one end over the posterior end of the maxillary arch wire, both strands under the end of the mandibular arch wire, and the other end up to the maxillary anterior teeth, reinforce anchor bends and extrude upper and lower molars while keeping them upright. They augment bite opening in Stage I and counteract the adverse affects of the auxiliaries in Stage III.

Biomechanical Phenomena↗
PubMed1981

Understanding, planning, and managing tooth movement: orthodontic force system theory.

A simple force may cause translation and/or rotation of the tooth upon which it acts. The closer the line of force to the tooth's center of resistance, the greater is the proportion of translation relative to rotation, and vice versa. When a tooth is subjected to a tipping moment, strain is concentrated in the areas of the alveolar crest and root apex. This may explain how a light force can tip a tooth readily, while translation, involving a more even distribution of strain throughout the length of the root, requires more force with little or no moment. It is difficult to sustain a desired combination of rotational and translational movement over any significant distance. Couples induce rotation only. Couples and simple forces can be used in combinations to effect movements that are not possible with either one alone. Molars provide anchorage for incisor intrusion. This "vertical anchorage" can be reinforced by elastics producing moments opposite those produced by arch wire anchor bends. Calculation of the elastics' contribution provides an indication of the intrusive force that may be applied to incisors without reciprocal molar tipping. The common use of the term center of rotation in orthodontics may be inappropriate and/or confusing. It may be more accurate and straightforward to view most tooth movements as combinations of linear translation with rotation about the center of resistance.

Adolescent↗