Mechanics Sequence for Class II Div 2BIOPROGRESSIVE THERAPY

Prepared by Bilal A. M.

Supervised by prof.Maher Fouda

Faculty of dentistry-Mansoura university - Egypt

The principles of the Bioprogressive Therapy continue to be of extreme importance in the treatment of Class II, Division 2 malocclusions.

In general, there are three treatment possibilities in a Class II, Division 2 malocclusion:1. Distalizing the upper arch.2. Advancing the lower arch.3. A reciprocal movement, advancing the lower arch and distalizing the upper arch at the same time.

Division 2 malocclusions are frequently present in brachyfacial patterns with resulting strong musculature. They generally have moderate to minimum convexity, but occasionally do have a higher convexity with

resulting orthopedic problems .

The lower facial height and mandibular arc are below normal range. Therefore, the teeth are deep in basal bone.

Many investigators have reported on the proportion of upper or lower facial height to total facial height. (Coben 1955, Goldsman 1958, Opdebeeck 1978,) According to Wylie, upper facial height (N-ANS) should be 45 percent of total facial height (N-Me), and lower facial height should be 55 percent of the total height in a well-balanced face.

TFH

Teeth in high alveolar processes seem to supply less anchorage. Teeth deep in basal bone provide more anchorage. This is the situation in most Class II, Division 2 malocclusions and these factors result in strong natural anchorage .

These facial patterns usually have excessively strong posterior vertical chain of muscles, anterior vertical chain of muscles, horizontal chain of muscles, and perioral musculature.

Ricketts has described the ten functional abnormalities of the soft tissue and musculature of the face. Sublabial contraction and upper proversion of the lips are two of the more important of these in evaluating the perioral musculature in Class II, Division 2 malocclusions.

Upper Proversion

Undesirable fullness of the upper lip, which Is closer to the E plane than the lower lip. The lower lip

is good in its relation to the E plane. The imbalance In the lips is due to the forward version of the

upper lip. This is typical of Class II. Division 2 lip relation.

Sublabial Contraction

In contrast to lip-sucking, sublabial contraction occurs at a lower level than the tip of the lip and is

commonly associated with a thick, hypertrophied band of muscle crossing the midline. The lower lip

may exhibit forward roll, but a deep sublabial furrow is evident and sometimes chronic ischemic

dermatitis is present. This is not a mentalis habit condition but may be confused with one.

There are six functions necessary in treating Class II, Division 2 malocclusions, which are general considerations for evaluating the mechanics sequence:

1 .Advancement, torque control, and intrusion of the upper incisors.2 .Intrusion of the lower incisors and cuspids.

3 .Alignment of the buccal segments and Class II correction.4 .Consolidation of the upper incisors.

5 .Idealizing the arches.6 .Finishing.

The Bioprogressive Therapy principles of progressively unlocking the malocclusion to establish normal function. The Quad-Helix or "W" appliance (Ricketts) is one of the auxiliary appliances that is most effective in the unlocking of any Class II malocclusion, in either the mixed or permanent dentition.

In many Class II, Division 2 malocclusions there is a reaction of expansionin the mandibular arch due to the functional change of the dentition and musculature. In most Class II, Division 2 malocclusions the maxillary denture is protruded and constrained by anterior facial musculature. The upper denture becomes constricted and, therefore, constricts the lower denture. Arch form development of the maxillary denture will create arch form changes reciprocally in the mandibular arch.

At the same time Quad-Helix is unlocking the denture, the maxillary incisors are being advanced with a utility arch to continue the unlocking process. Essentially, after the advancement of the upper incisors, the mechanics are basically the same as Class II ,Division 1 nonextraction mechanics, except that there is a concentration on the orthodontic change versus the orthopedic change. More Class II elastics, less headgear are used.

Advancement, Torque Control, and Intrusion of the Upper Incisors

There are four basic factors in upper incisor intrusion:1 .The direction of force.

2 .The amount of pressure.3 .The stabilization of the molars.

4 .Torque control and the timing of torque control in relation to growth factors.

The Direction of ForceOne of the principles of the Bioprogressive Therapy is to correct the overbite before the overjet. In Class II, Division 2 malocclusion, this is generally not true. Due to the original lingual version of the upper incisors, if these teeth are intruded initially, they will be forced into labial cortical bone, thereby limiting intrusion. It is, therefore, necessary to create overjet first and then correct the overbite. To do so, think in terms of several distinct functions advancement of the upper incisors, torque control of the upper incisors, and intrusion of the upper incisors.

The archwire used to carry out these functions is the maxillary utility arch, which is generally constructed of .016 × .022 blue Elgiloy (CHROME-COBALT) or Nitinol wire. The maxillary utility arch has three activations in the molar section:

1 .Tipback of 45°.2 .Distolingual rotation of 10-20°.

3 .Expansion of approximately 1 cm on each side.

Maxillary Utility Arch (A) activated for 45° tipback (B) ,

10-20° distolingual rotation (C), and expansion of approximately 1cm on each side (D).

The expansion is placed in the maxillary utility arch only when it is being used for anchorage. In the nonextraction Class II sequence, where we are distalizing the upper buccal sections, expansion is not placed in the maxillary utility arch. The tipback has a distal tipping effect on the molar and an intrusion effect on the incisors. The distolingual rotation helps in establishing our occlusal objectives. The anterior section of the basic maxillary utility arch has no torque in the wire. In the Bioprogressive Therapy, the central brackets have 22° torque and the lateral brackets 14° torque.

In cases where the laterals are in labioversion, it may be necessary to band/bond the laterals with the cuspid brackets (7° torque) to detorque the lateral incisors. It is essential that the posterior vertical step of the utility arch be against the molar buccal tube and that there be an anterior deflection of 5mm or more of the anterior section.

In cases with upper laterals in labioversion, utility arch is placed with posterior step against molar tube and with an anterior deflection of 5mm or more.

Many Class II, Division 2 malocclusions have the upper central incisors in lingual version locked behind the lateral incisors. To accomplish this, the anterior section of the utility arch must be well contoured and advanced. It may help to think of a "V" shape to the wire to obtain the necessary contour in the anterior arch form to advance the incisors. Only the mesial wings of the siamese brackets should be tied. This will help unlock the central incisors.

Guide to shaping anterior arch contour to unlock upper central incisors in linguoversion.

In the development of the Class II malocclusion, the upper molar is guided by the incline relationship of the lower molar. The molar has a mesial inclination and is rotated mesiolingually.

The Amount of Pressure

It takes approximately double the force to intrude the upper incisors, compared to the lower incisors (125 to 160 grams). This is one of the reasons for using the .016 × .022 blue Eligiloy or Nitinol maxillary utility arch in the initial phase of treatment. The second reason is that the span between the upper molars and the incisors is a greater distance and, therefore, decreases the force delivered to the maxillary incisors.

Stabilizing section to stabilize molars during incisor intrusion.

The Stabilization of the MolarsThe use of the .016 × .022 utility arch in order to create the added force needed to intrude the maxillary incisors has an adverse tipping effect on the maxillary molars. It, therefore, becomes necessary to stabilize the molars. The use of Quad-Helix, Lingual Arch, or Tranpalatal Bar will help stabilize the maxillary molars. The best way is to band/bond the bicuspids and cuspids and place a stabilizing leveling sectional arch in the occlusal molar tube, which will avoid excess tipping of the upper molars.

This will, in effect, pit the entire upper buccal segments (and therefore muscle function) against the intrusion of the upper incisors. The stabilizingsection is .016 × .016 or .016 × .022 with a tip-forward (down) bend in the molar section. This bend will keep the molar upright and, therefore, help in the Class II correction.

Torque ControlIn order to individualize maxillary incisor position in relation to facial type, the long axis of the upper incisors should be parallel to the facial axis. Due to the fact that many Class II, Division 2 patterns are brachyfacial and, therefore, have a high facial axis angle and resulting horizontal growth, by putting the upper incisors parallel to the facial axis (by torque) you are decreasing the interincisal angle which will help to maintain the overbite correction experienced in many Division 2 cases. There should be early torque control in the maxillary denture in all cases.

2-Facial axis angleRead as the inferio-anterior angle between the PTM-Gn line (facial axis) and N-Ba line.Similar to Y-axis angle of Downs analysis as it indicates the degree of downward and forward position of the chin in relation to upper face thus indicates the growth pattern of the mandible.

Averages: 90 + 3.5Less than normal a more vertical pattern of growth as in severe class II division 1Normal range equal downward and forward growth pattern.Larger than normal a more horizontal pattern of growth as in a class II division 2

CC–Point where the basion-nasion plane and the facial axisintersect.

In Class I occlusions, denture balance is maintained through normal growth of molars down the facial axis and incisors on their polar axis (A). In Class II, Division 2 malocclusions, the same pattern results in jamming upper incisors against lower incisors by the labial musculature (B).

Summery The treatment of class II div. 2 include the following steps-:

1 -Unlocking the malocclusion to establish normal function by using-:

A- Quad-Helix or "W" appliance (Ricketts) that can be used in cases with constricted upper arch or in mixed dentition.B- utility arch with an anterior deflection of 5mm or more of the anterior section.

2 .torque control, and intrusion of the upper incisors.3 .Intrusion of the lower incisors and cuspids.

4 .Alignment of the buccal segments and Class II correction.5 .Consolidation of the upper incisors.

6 .Idealizing the arches.7 .Finishing.

intrusion of the upper incisors-:four basic factors in upper incisor intrusion:

1 .The direction of force . advance the incisors (increase the over jet) before

staring the intrusion due to the original lingual version of the upper incisors, if these teeth are intruded initially, they will be forced into labial cortical bone that will limit the intrusion .

The archwire used (.016 × .022 blue Elgiloy) (CHROME-COBALT) or Nitinol wire with activations in the molar section:

a. Tipback of 45°. b. Distolingual rotation of 10-20° .

2 .The amount of pressure (125 to 160 grams).

3 .The stabilization of the molars.- Quad-Helix, Lingual Arch, or Tranpalatal Bar may be used to

stabilize the maxillary molars. -The best way is to stabilize the maxillary molarsis to bond the

bicuspids and cuspids and place a stabilizing leveling sectional arch in the occlusal molar tube. The stabilizing section is .016 × .016 or .016 × .022 .

Intrusion of the Lower Incisors and Cuspids

Checking the VTO tells us the movements that will be necessary in the mandibular denture:

1 .To intrude the lower incisors and cuspids.2 .To advance the lower incisors.

3 .To upright or distalize the lower molars.4 .And/or advance the lower denture.

The lower incisors and molars are banded/bonded and a utility arch placed (.016 × .016 blue Eligiloy or Nitinol). The mandibular utility arch is activated to give approximately 60-75 grams of force to intrude the lower incisors. Usually, the lower molars are allowed to upright with minimum buccal root torque and anchorage preparation.

Cuspid intrusion by tying elastic ligature from cuspid bracket to utility arch bridge section.

After the lower incisors have been intruded, we band/bond the lower cuspids. In many cases, the cuspids need to be intruded. There are two ways of accomplishing this:

1 .Using an .016 × .022 stabilizing utility arch and tying the elastic ligature lightly from the cuspid bracket to the utility arch in the bridge section.

2 .The second possibility after the intrusion of the lower incisors is to place an .016 × .016 utility arch with a 45° tipback at the molar and allow the anterior section, when it is placed in the molar bracket,

to extend down into the mucobuccal fold (this will give approximately 60-75 grams of force); then tie the elastic ligature from the cuspid bracket to a notch bent into the

utility arch bridge section and elevate the anterior section, by tightening the elastic ligature, until it is level with the incisor brackets .

Alternate method of intruding lower cuspid, using a 45° tipback bend to deflect anterior section of utility arch downward. Elastic ligature is tied from cuspid bracket to notch in utility arch bridge section (A) and tightened until anterior section of archwire is level with incisor brackets (B). The anterior section is then tied into the brackets and the ligature secured (C)

The opposite side will be down slightly, and tying the elastic ligature on the opposite side can be carried out in the same manner. When the anterior section is level with the incisor brackets, it is then tied into the brackets.

This can usually be accomplished in one appointment and will insure that there will not be an extrusion force on the incisors.

In cases in which there has been a great deal of intrusion in the lower incisors and difficulty in controlling the tipping of the lower molars, it may be necessary to band/bond the bicuspids and cuspids, and place a stabilizing section. This will control the tip of the lower molars. In today's bonding procedures, where all the teeth may be bonded at one visit, it is an advantage to use a stabilizing section in the buccal segments when initiating utility arch placement. It is possible at this stage of treatment to band/bond the upper maxillary cuspids and premolars, if not previously done, and place a traction section .

Utility arch modification using four helical loops at the corners.

The VTO will point out if you have to advance the lower incisors and/or the lower denture. If advancing the lower incisors is necessary, one of the modified utility arches may be constructed.These modifications are:

1 .The basic utility arch has four vertical loops added at the corners. The same consideration is given to the four components that can be placed in the molar section: tipback, toe-in, buccal root torque and expansion, and labial root torque in the anterior section .

Utility arch modification using tour helical loops at the corners.

The posterior vertical step must be tight against the molar buccal tube and the anterior section deflected forward 2 or 3mm from the incisor bracket so that the engagement has an advancing force. The objectives of our molar anchorage (VTO) will dictate the amount of buccal root torque and, therefore, the amount of expansion that will be necessary in the molar section for anchorage requirements.

Utility arch modification using three helical loops.

2 .The second modification for advancing is to add three vertical loops — two small ones extending occlusally and one larger one extending gingivally in the bridge section. The advancing force of the wire is then taken up in the loop system and expelled with a continuous light force. The same principles are followed as in the previous arch.

Utility arch modification using three helical loops.

Utility arch modification using coil spring.

3 .The third possibility for an advancing arch has been demonstrated by Dr. James McAndrew. An .0056 × .025 coil spring is placed around the utility archwire midway from the bridge section back though the molar section. Enough coil is left beyond the molar section for the amount of advancement desired. This wire can be soldered to the bridge section to prevent thecoil from sliding forward. All three of these arches have the possibility of allowing the lower denture to advance forward with the use of Class II mechanics if molar anchorage is removed.

The Aligning of the Buccal SegmentsThe leveling of the maxillary and mandibular buccal segments may have been accomplished in the previous steps. If so, then Class II mechanics can proceed. Depending on the anchorage requirements which have been established from the VTO, either headgear or Class II elastics or acombination of both can be initiated. If headgear were desirable in the particular case, it would most likely have been started at the beginning of treatment.

Three basic types of sections. A. The stabilizing section. B. The consolidation section. C. The tractionsection.

There are three basic types of sections:1 .The stabilizing section, which also would function in leveling (A).

2 .The consolidation section, which may be used to help close any spaces that have developed (B).

3 .The traction section for distalizing the buccal sections with Class II elastics (C). The molar section would have a horizontal helical loop and bayonet bend mesial to the molar bracket.The cuspid section would have a horizontal helical loop with a gable and tip-up bend.

If buccal segments are not yet aligned, "T" sections or Twistoflex arch may be used for leveling and stabilizing.

In bonding techniques, the use of the stabilizing sections from the beginning of treatment becomes very practical in conjunction with the utility arches to accomplish leveling. Depending on the case, the buccal section should be leveled before a traction section is placed to initiate Class II elastics. In cases in which the buccal sections are reasonably level, it is possible toinitiate traction sections at an earlier stage. If, at this

stage of treatment, the buccal sections are not aligned in the maxillary or mandibular segments ,

you may use "T" sections or Nitinol or Cable wire.

A. Maxillary torquing utility arch. Vertical helix (1 ) backed up with Class II elastics (2). B. Anterior section can be bent gingivally (at 1) to increase torquing action.

The Consolidation of the Maxillary IncisorsIn many Class II, Division 2 malocclusions, there is a need for additional torque in the upper incisors and slight consolidation. The arch most frequently used is the maxillary torquing utility arch.

This is an .016 × .016 blue Elgiloy utility arch with a vertical helix facing occlusally (A). The anterior

section of this arch can be bent gingivally to increase its torquing action(B).

The tipback also gives you additional torque, as does the activation. The amount of activation is just enough to cross the vertical legs of the helix. The arch has intrusion, retraction, and excellent torque control of the incisor segment.

The second modification would be the maxillary contraction utility arch. The same principles follow in this arch. This would be used where additional retraction force on the incisors is needed.

Maxillary contraction utility arch (A). Before activation (B). After activation (C).

The third modification would be the double delta utility arch. It appears that the previous two arches have more torquing ability than the double delta. In all three of these arches, a maximum tipback, a distolingual rotation bend, and expansion would be placed in the molars. The expansion would be placed in the maxillary utility arch to help anchor the molars .

Double delta utility arch.

The expansion would be placed in the maxillary utility arch to help anchor the molars. At this stage of treatment, the buccal Class II correction is usually completed. It is important to leave the vertical steps, or bayonet bends, approximately mesial to the second premolar brackets to allowenough distance between the vertical step and the molar bracket for approximately three activations, pulling the arch through the gingival tube and cinching it back. All of these arches would have Class II mechanics to traction sections to help maintain molar anchorage. It is unusual in Class II, Division 2 malocclusions, but if the bite has had excessive opening with the utility arch treatment, a continuous double delta contraction arch can be placed with Class II elastics. This will have a tendency to extrude the incisors and help close the open bite.

Idealizing the ArchesAt the completion of the previous stages, before inserting the ideal arches, a maxillary and mandibular utility arch should be placed with ideal sections, or a square twist wire for one visit, to allow leveling. An .016 × .016 blue Elgiloy or an .016 × .022 blue Elgiloy ideal arch can then be placed. In the use of tractional control, a straight ideal arch with ideal arch form would be placed.

The Finishing StageIf using bands, the finishing arches are used to consolidate band spaces. The bands on the cuspids, first and second bicuspids are removed, and .018 × .022 finishing arches placed. The lower arch is activated. The upper arch is not activated, but Class II elastics are used to close the band spaces. After the spaces are closed, impressions are taken for a maxillary Ricketts retainer and a mandibular 4×4 lingual retainer. In today's direct bonding procedures, this step will be changed as there will be no necessity for band space closure. The impressions for retainers could be taken immediately .

One of the principles of the Bioprogressive Therapy is to overtreat the buccal sections and anterior overbite. It is necessary to overtreat the overbite in order to overtreat the buccal sections.This is to allow the placement of a Ricketts maxillary retainer with the buccal segments in an overcorrected position. The mesiolingual of the acrylic portion of the retainer is ground to allow muscle function to settle in the buccal occlusion. The molar portion of the retainer is ground at the distolingual to maintain molar rotation. The lower arch has a 4×4 lingual retainer placed to maintain the upright position of the first bicuspids and the slight labial position of the distal contact of the lateral with the mesial contact of the cuspids.

It is also possible to mount a case and do a positioner setup. The principle of overcorrection is still adhered to. The positioner is constructed to extend 1 or 2mm over the mandibular denture and approximately at the cervical line of the maxillary denture. It is then possible to place a lingual 4×4 retainer. The positioner will then settle in the functional occlusion.

Fig. 5 Uprighting effect of (a) simple tipback on lower first molars shows center of resistance (b) at the gingivalbase of mesial root. This allows a forward movement of the mesial root (c) and trades space in the alveolar troughfor arch length (d).

Fig. 8 The arc of intrusion from the lower molar (A) that is parallel to the long axis of the tooth (B) results in amore effective intrusion (typical of brachyfacial types). The same arc (C) applied to a labially inclined tooth (D)results in a further labial flaring and less intrusion (typical of double protrusions).