Conceptual orthodontics

Bite-opening Mechanics as Applied in the Begg Technique

In the Begg Technique, factors controlling the anterior intrusive force provided by the archwire have yet to be fully clarified. The rationale for bite opening with very light forces, the effect of Class II elastics on intrusive force magnitude and the intrinsic quality of ‘Australian’ wire in bite opening are examined in this paper. A formula is presented which allows the intrusive force that archwires exert in different individuals to be predicted. The values derived from the formula were compared with case model measurements. It was found that the intrusive force of the archwire was affected by the length of the individual dental arch. The magnitude of this intrusive force was seen to increase gradually during the period of bite opening and appeared to be related to the use of Class II elastics. The study revealed factors which affected the magnitude of the intrusive force.

The effects of archwire forces on incisor intrusion

The forces exerted by archwires were measured in association with both Begg and Straight-Wire attachments. Seven stainless steel and three nickel-titanium wires were tested at vertical deflections equivalent to 20, 30, and 40 degrees, these being incorporated via anchor bends or reverse curve of Spee as appropriate to each system. All seven brands of stainless steel arches demonstrated similar performance. An increase in archwire diameter from 0.016 to 0.018 inch increased intrusive forces by 64 per cent for stainless steel and 58 per cent for nickel-titanium. Increasing anchor bend or reverse curve of Spee produced considerable force increases across the range of specimens. Begg archforms produced more force than Straight-Wire archforms of similar deflection when attached to molars only. Attachment of archwires to second premolars in addition to molars reduced the intrusive forces produced by Begg arches, but increased the forces of Straight-Wire arches.

The anchorage bend in the Begg technique

The anchorage bend is an essential feature of the Begg technique. The factors which affect the degree of the anchorage bend include operator preferences as well as certain mechanical features of the case being treated. A test jig was constructed so as to be able to measure on the bench the intrusive forces developed by an anchorage bend over the six anterior teeth for a selection of different archwires. The amount of force developed was proportional to the degree of anchorage bend and also to the diameter of the archwire. The jig was modified in order to measure the frictional resistance to distal movement generated by the anchorage bend. The resistance was found to be greater than the usually quoted forces designed to slide the upper archwire distally. An oval tube was placed on to the test jig and doubled back archwires used. A reduction in intrusive force for a particular degree of anchorage bend was seen although frictional resistance was not affected when using doubled back archwires.

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.

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.

Begg and straight wire: a combination approach to treatment

Orthodontic appliances should be designed to satisfy goals for denture, patient, and doctor. An appliance that is able to achieve these goals more closely approaches the ideal treatment system. Analysis of appliances of the Begg and straight wire types indicates that each treatment system has significant advantages and that the advantages of one system frequently are the disadvantages of the other. A technique that uses both the tipping principles of Begg and the bodily movement principles of the straight wire type of appliance has been designed and clinically evaluated. The unique capability of the combined treatment approach is in the mechanical design of the new combination four-stage bracket. A description of the appliance and the technique, as well as a clinical case presentation, is included in this article.