Begg Mechanics ORTHO / orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMYLeader in continuing dental educationwww.indiandentalacademy.com

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BEGGS MECHANICS

INTRODUCTION

• Last 5 decades• Sudden negative growth• Little knowledge of Biomechanics• Efficiency in bite opening• Works like a simple machine• Base arch wire-main component


• Edgewise -two point contact at both the ends-moment at both the ends-two couple system

• Begg –two point contact at one end ,one point contact at other end-force at one end and moment at other end-one couple system


• V-bend principle


Special features of Begg mechanics

The difference between the design of the Begg bracket and the edgewise bracket, as also the difference in the philosophies of the two treatment modalities must be taken into account for enunciating the Begg biomechanics.

Begg MechanicsDr. Srinivas


Behavior of the Begg bracket in the first, second and third order

mechanics ‘Unipoint’ bracket Bracket slot behaves differently in the three planes First order mechanicsSecond order mechanicsThird order mechanics


Differences between the mechanics of the two therapies


When groups of teeth are rigidly held together forces are applied on the tooth surface away

from the bracket Forces and moments employed are relatively

lowThe Begg slot is closer to the tooth than the

edgewise slot


Vertical deflection in the arch wire will generate a force but no moment unlike in an edgewise bracket


Rotational Control in Refined Begg

• In the horizontal plane (First order) is the least (especially with full size wires).

• For second order (mesio-distal) is relatively greater (more so with Stage I pins).

• The freedom for third order displacement on a round wire is maximum


Basic Begg Movements

• Incisor intrusion • Tipping • Root movements


Mechanics of intrusion

More easily understood by considering the net intrusive force magnitude and direction instead in terms of M/F ratio

Lack of true intrusion of the maxillary incisors was one of the major weaknesses of traditional Begg (bite opening was mainly on account of molar extrusion and some intrusion of the lower incisors)


Anterior teeth can be intruded by orthodontic means only to the extent of 3-4 mm.

An adult case of gummy smile requiring surgery cannot be converted to a non surgical orthodontic treatment

However, cases of gummy smile during childhood can be successfully treated by partly intruding the incisors and partly by preventing the downward displacements of the alveolus / maxilla.


six anterior teeth are intruded together in Begg practice


Bite opening force from the anchor bendsvarying amounts of intrusion (translation) and labial crown-lingual root tipping (rotation). Such rotational displacement is generally undesirable (the exception being lingually inclined incisors as in Cl. II div. 2 cases), Interplay between the wire generated intrusive force and the elastic force determines both the magnitude and direction of the net resultant force acting on the teeth


Consideration of the magnitude of intrusive force

• Optimal intrusive force value• For active intrusion the upper anteriors

should receive approximately 60 gm net force in the midline after negating the extrusive component of Cl II elastics


• Role of light Class II elastics• light elastic force for longer periods (from 2 to 5

days), a very light Cl. II force is provided most of the time

• Sims has suggested the use of 3/8 ultra light elastics e.g., “road-runner elastics”

• suggested force values are only a rough estimate

• many variables


Consideration of the direction of the resultant force

Hocevar: teeth respond only to the resultant of the forces, and not to the individual components of the force system

• The direction and the magnitude of the resultant force both depend upon the interplay between

• 1.The magnitude of the intrusive force • 2.The magnitude and direction both of the

elastic force.


Arch wire design • mild gingival curve • incorporating a vertical step up bend-

Swain• posterior segments of the archwire are

kept gingival and the anterior segment is kept occlusal

• likely to tip the anchor molars distally


distal vertical elastics


Summary of Intrusion Mechanics

• Application of force is through the concerned centre of resistance (or very close to it).

• Careful manipulation of these two forces the magnitude and the direction of the resultant force can be so adjusted as to obtain a predominantly intrusive action, a predominantly retrusive action or a combination of the two


• Extreme cases of proclination or retroclination

• After the inclination corrects, a varied strategy is employed which helps in keeping the resultant force close to the C Res


•TPA elastics


Mechanics of Begg tipping • uncontrolled tipping is undesirable

because it can hasten root resorption, as emphasized by Reitan

• The few exceptions wherein uncontrolled tipping is beneficial for one or two visits


Controlled Lingual tipping of upper anteriors

• Intrusion and tipping of upper incisors are intimately related

• the moments generated by both of them are in the same labio-lingual plane but act in opposite directions

• retractive force is crown lingual - root labial. • intrusive force is crown labial - root lingual,


MAA • Provides a moment in the labio – lingual

plane by creating a force couple


Light forces generated by MAA against the crown surfaces

Wire Canine Lateral Central

0.009 16.5 15 15.25

6 Boxes

0.010 34.25 29.5 29.5

0.009 18.75 19.5

4 Boxes

0.010 27.75 29.5


Preventing Uncontrolled Tipping of Lower Incisors

• Intrusive force alone can flare the teeth• Such flaring can be avoided by: a.Minimise the moment by reducing the

intrusive force, or by placing the brackets as much gingivally as is permitted by hygiene considerations.


b.Provide a holding force by bending the diatal ends of the arch wire as suggested by Hocevar.

c.Provide a counter moment by using a MAA for labial root torque or a reverse torquing auxiliary


Mechanics of root movement Predominantly root movements in a

labiolingual or mesiodistal directionAuxiliary commonly used is the one made in

0.012 premium plus wire


• Forces generated (in grams) by the commonly used four spur and two spur torquing auxiliaries with 5 mm spur length

Wire Horizontal Vertical

Lateral Central

010 14 18 11

4 Spurs 012 26 30 19

014 48 53 23

016 96 103 77

010 22 14

2 Spurs 012 42 28

014 64 28

016 112 78www.indiandentalacademy.com

• Forces produced by a 4 spur torquing auxiliary made in 0.012” wire are approximately twice of those from a MAA made in 0.009” wire

• The M/F ratio for root movements is about twice of that employed in controlled tipping during the initial stages


Activation 75o 60o 45o 25o

Minispring 142.5 97.5 72.5 < 37.5

0.000 (s) 137.5 82.5 52.5 < 37.5

0.010 (s) 157.5 97.5 57.5 < 37.5

0.012 (s) 282.5 162.5 112.5 57.5

0.012 (p) 257.5 157.5 107.5 57.5

0.014 (sp+) 387.5 297.5 197.5 97.5

0.016 (p) 437.5 307.5 207.5 107.5

Spring pin 787.5 637.5 487.5 287.5

Forces generated by the uprighting springs (2 1/2 turns, the inner diameter of helical 0.036”, length of the arm 4 mm and angulation 135o )


• Nikolai-greater moments are required for the mesio-distal root movements than for the bucco-lingual root movements

• Action of uprighting springs and torquing auxiliaries is in all the three planes namely sagittal, vertical and transverse


Does Begg appliance satisfy the appliance design criteria ?

Burstone has set the following criteria for an efficient appliance design :

• Force system • Precise M/F ratios for different types of tooth

movement.• Constancy and low magnitude of moments and

forces.• Ease of use.• Patient comfort.• Minimal patient co-operation


• Refined Begg appliance admirably satisfies all the above requirements.

• provide the required M/F ratios for controlled tipping in the initial stages and for root movements in the final stage.

• forces used are light and fairly constant. In fact the ultra-light forces advocated by Refined Begg are physiologically more acceptable.

• easy to practice and manipulate.• The light forces are comfortable for the patient.

Finally, one has to depend on patient’s co-operation only to a limited extent.


Problems in stage III• Multiple complex moments and forces• Tends to the generation of unintentional

force systems• Anchor loss,bite deepening,flaring of

molars ,space opening distal to molars


• Modification of materials: high L/D wires as base arch wire low L/D wires for springs and auxillaries• Design modifications: bends mesial and distal to canines constricted arch wires class II elasticsAll these add a new set of forces which can further

complicate the mechanics www.indiandentalacademy.com

• Solution : Balancing of forces at either ends of the base arch wire

• Distal tipping of molar-excellent anchorage preservation modality


Orthodontic force systems: Technical refinements for increased efficiency

Richard A. Hocevar.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.www.indiandentalacademy.com

Vector analysis of forces. a, Arch wire anchor bend. b, Class II elastic. c, Vertical component of Class II elastic. d, Resultant of a and c. e, Horizontal component of elastic. f, Total resultant force. Vector lengths are proportional to force magnitudes. www.indiandentalacademy.com

Reducing this overjet without allowing the edge of the upper incisor to drop would require a balance of forces that is probably impracticable with conventional Begg technique.


Class II, Division 2 incisor relation. Force a, would produce only further retroclination in this situation. Intrusion would require that the total resultant force on the incisors act in direction b. Following intrusion, a posteriorly directed force and a couple to produce lingual root torque would be required to achieve the desired final position indicated by the shaded incisor.


Typical Begg arch wire tends to intrude canines and extrude incisors relative to each other.


Slight bite-opening bends (at arrows) mesial and distal to the canines help ensure efficient bite opening, level occlusal planes, and even occlusion. www.indiandentalacademy.com

If the resultant (c) of the arch wire expansion force (a) and the vertical component of the Class II elastic force (b) passed directly through CR, the lower molar would be likely to move occlusally and buccally (A). Molar extrusion without buccal movement (B) is probably accounted for by force b being considerably greater than a. Bone anatomy and muscle are also involved.www.indiandentalacademy.com

Forces on a lower molar produced by a Class II elastic hooked on the distal end of the arch wire (a) and a mesial hook (b) . The moment arm, and hence the moment tending to tip the molar mesially, may be much greater with distal elastic attachment. www.indiandentalacademy.com

Incorrect (A) and correct (B) molar tube designs. The mesial hook, optional, is for intramaxillary elastics only. www.indiandentalacademy.com

Consistently correct mesiogingival angulation of molar tubes is achieved easily by making a scratch mark on the band parallel to the occlusal surface at the desired height and then welding the tube diagonally across the scratch so that the mesio-occlusal and distogingival points of the tube ends are on the line. This method automatically determines the correct position for the tube, no matter what the inclination of the molar in the malocclusion may be.www.indiandentalacademy.com

With short, horizontally oriented molar tubes (top), when arch wires are pinned into incisor brackets (broken lines), the anchor bends are so placed as to be very likely to be deformed by mastication. This is not the case with long, mesiogingivally angulated tubes (bottom). In both ,the arch wires are activated through the same range and thus deliver the same force to molars and incisors, but the degree of anchor bend in the top illustration is twice as great as that in the bottom one. www.indiandentalacademy.com

Maxillary molar tube having its distal end offset from the buccal surface facilitates control of molar rotation.


"check elastic"www.indiandentalacademy.com

SUMMARY• 1. Retraction of maxillary incisors deserves careful

force system analysis and application, particularly in the many cases in which intrusion is desirable.

• 2. Anchor bends, as commonly used in the conventional Begg technique, are not likely to have a significant effect on maxillary incisor movement.

• 3. Slight bite-opening bends mesial and distal to the canines in all arch wires can help ensure that intrusive force is delivered primarily to incisors, and maintain level arches.

• 4. Vertical intrusive force on mandibular incisors may cause proclination unless accompanied by some distal force.


• 5. There are many reasons for routinely cinching almost all arch wires at the distal ends of the buccal tubes throughout treatment.

• 6. Positioning intermaxillary elastics at the posterior ends of arch wires, using long buccal tubes, and angulating all tubes mesiogingivally are important factors in efficient reduction of overbite.

• 7. The use of maxillary molar tubes whose distal ends are set out from the buccal surface and arch wires with ''toe-in'' throughout treatment aids correction and control of maxillary molar rotations.


• 8. ''Check elastics'' can provide a potent mechanism for overbite reduction, causing extrusion of maxillary and mandibular molars and counteracting the tendency of the anchor bends to tip the molars distally, thus aiding incisor intrusion.

• 9. A conventional Begg Stage III appliance tends to rotate the occlusal plane, and especially the maxillary arch, down in front and up in back and to deepen the overbite.

• 10. The above tendency can be counteracted by routine use of check elastics in most cases. Cervical headgear to maxillary molars or anterior high-pull headgear may be preferable in a few cases of specific types.


Maxillary anterior intrusive forces generated by Begg Stage I appliances

Charles B. Thornton, Robert J. Nikolai, Ph.D.

• The capability of Begg mechanotherapy to produce intrusion of the maxillary anterior teeth, particularly the incisors, has been questioned. Although the Stage I appliance opens the bite, this can be the result of one or a combination of several occlusogingival displacements, and the manner of bite opening continues to be a subject of discussion. Support in favor of anterior maxillary intrusion exists, at least in part, because of the potential for extrusion of these teeth during Stage III.

• The purpose of this experimental study was to quantify and compare the intrusion potentials of maxillary appliances


Significant results of the investigation may be summarized as follows:

• 1. Appliance configurations generated initial mean values of intrusive force, distributed (although nonuniformly) over the four- or six-tooth segment, of approximately 40 grams.

• 2. Anchor-bend size and Class II elastic-force magnitude were most influential in increasing and decreasing, respectively, anterior intrusive force.

• 3. Within the 0.016-inch-wire sample, addition or deletion of a gable bend quantitatively affected intrusive force almost independently of the magnitude of Class II elastic force.

• 4. Variation in the location of the anchor bend, up to 5 mm. mesial to the buccal tube, had a very small influence on the intrusive-force size.

• 5. Increasing the wire diameter 25 percent, from 0.016 to 0.020 inch, resulted in dramatically raised intrusive-force values generated by the appliances. www.indiandentalacademy.com

The results of this study apparently warrant the following conclusions:• 1. The commonly used maxillary appliances of Begg Stage I

mechanotherapy produce initially light but continuous force against the anterior segment. With no torque potential in the appliance, the teeth may seek the intrusive path of least resistance.

• 2. Increasing (decreasing) the sizes of the anchor and/or gable bends may be equivalent to decreasing (increasing) the Class II elastic force with regard to the effect on intrusive potential. Not to be overlooked, however, is the fact that alterations in the elastic force also affect the horizontal action of the appliance, whereas the bends do not.

• 3. In fabricating the appliances studied, with their common over-all design, the approximate magnitude of intrusive force desired should be approached from the low side through an appropriate combination of anchor-bend size and Class II elastic-force magnitude

• 4. Because of long moment arms, even a light force against the anterior segment will result in sizable tipping moments against the molars. Accordingly, molar positions must be monitored while the appliance is active, and if unwanted displacements occur, anchorage reinforcement may be necessary.www.indiandentalacademy.com

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Begg Mechanics ORTHO / orthodontic courses by Indian dental academy

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