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Tweed-Merrifield Sequential Directional Force Nonpremolar Extraction Treatment: A Case Report Sylvie Lamarque

The treatment of a Class II, Division 1 malocclusion without the extraction of premolars is, in many situations, the best solution for the patient. Nonpremo- lar extraction diagnosis followed by mechanotherapy with a nontorqued, nonangulated .022 edgewise appliance and the "Twelve-Two" System of Sequential Directional Force application is described. (Semin Orthod 1996;2: 268-272.) Copyright © 1996 by W.B. Saunders Company

F or the pat ient with a hypodivergent skeletal pat tern who has no mandibula r crowding,

nonp remola r extraction t rea tment is often indi- cated. Orthodontics , however, is a space manage- men t procedure , so for malocclusion correction, teeth must be moved. Space for tooth movemen t must be already available, or it must be made available with extractions.

Differential diagnosis of a hypodivergent pa- tient 's malocclusion can lead the clinician to several extraction combinat ions other than four premolars: (1) maxillary premolar, mandibula r third molar extractions; (2) maxillary second molar, mandibular third molar extractions; or (3) extraction of all third molars. Removal of third molars is a diagnostic decision, therefore, "non-extraction" means no teeth, not even third molars are removed. Rarely can a patient's malocclu- sion be treated "non-extraction." The treatment of a patient whose diagnosis and treatment required the removal of all four third molars is described.

lsabelle, a 10-year-old thumb-sucker, pre- sented with a Class II Division 1 malocclusion. Facial pho tographs (Fig 1) show a protrusion of the uppe r lip and eversion of the lower lip. The slightly retrognathic soft tissue chin is somewhat "long, clubby, and knobby" as described by Noffel. 1 The p re t rea tment casts (Fig 2) conf i rm a Class II buccal segment relationship with a 10 m m oveIjet. The mandibula r teeth are well

Dr Lamarque is in private practice. Address correspondence to Sylvie Lama~Tue, DrCJ), DUO, 94A

Route Nationale, 13240 Septemes Les Vallons, France. Copyright © 1996 by W.B. Saunders Company 1073-8746/96/0204-000655.00/0

aligned, and the curve of Spee is moderate . All teeth are present on the p re t r ea tmen t pan- oramic radiograph (Fig 3). The pre t rea tment cephalogram (Fig 4_A) and its tracing (Fig 4B) reflect a skeletal Class II relationship with an

ANB of 8 °. The ratio of poster ior facial height to anter ior facial height is 0.76 and the Frankfort mandibular plane angle (FMA) is 21°; both are indicators of a hypodivergent skeletal tendency. The Frankfort mandibular incisor angle (FMIA) of 66 ° confirms good positioning of the mandibu- lar incisors. The Z angle 2 of 72 ° is quantifiable evidence of a balanced facial profile. Although soft tissue chin thickness was 6 m m greater than uppe r lip thickness, a soft tissue modification was not calculated because mandibular incisor posi- tion did not require compensat ion and the Z angle value needed n o adjustment.

The Differential Diagnostic Analysis System 3 revealed that the pr imary tooth arch deficit was in the poster ior denti t ion area, hence the diag- nostic decision to extract the four third molars was made. Mandibular p remola r extraction was contraindicated due to the hypodivergent skel- etal pat tern, the p re t r ea tmen t mandibular inci- sor position, and the p re t rea tment facial bal- ance. The pat ient and paren t were in formed of the necessity for excellent cooperat ion dur ing active mechano the rapy because the maxillary teeth had to be distalized without proclination of the mandibular teeth.

T r e a t m e n t

An ant i - thumb-sucking appliance was placed in the maxillary arch, and the maxillary first molars

268 Seminars in Orthodontics, Vol 2, No 4 (December), 1996: pp 268-272

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Figure 1. Pretreatment facial photographs. The pho- tographs illustrate maxillary lip protrusion, lower lip eversion, and a slightly retrognathic soft tissue chin.

were stabilized with a high-pull face-bow head- gear. The pat ient s topped sucking he r t h u m b immediately, and the t h u m b appl iance was re- moved 6 mon ths later.

After the t h u m b appl iance was r emoved the pat ient ' s dent i t ion was sequential ly b a n d e d and b o n d e d with an .022 edgewise appliance. Rectan-

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Figure 3. Pretreatment panoramic radiograph. All the teeth are present and healthy.

gular maxil lary and mand ibu l a r archwires were inserted. To level the mand ibu l a r arch wi thout incisor procl inat ion, a h igh-pu l l J -hook headgea r was a t tached to hooks so ldered to the mand ibu- lar archwire distal to the mand ibu la r lateral incisors. At the same time the leveling o f the

Figure 2. Pretreatment casts. The casts exhibit a Class II buccal relationship with a 10 mm overjet.

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270 Sylvie Lamarque

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Figure 4. (A) Pretreatment cephalogram. The cepha- logram confirms a poor skeletal relationship of the maxilla to the mandible, maxillary anterior overjet and excessive posterior facial height. (B) Pretreat- ment cephalometric tracing: The tracing exhibits an ANB of 8 °, a low Frankfort mandibular plane angle of 21 °, and an FMIA of 66 °. The 72 ° Z-angle reflects a balanced facial profile.

maxillary arch was started with a high-pull J-hook headgear placed against the maxillary canines.

During the denture correction step of treat- ment, the patient was instructed to attach the maxillary high-pull headgear to hooks soldered to the maxillary archwire distal to the central incisors. The maxillary incisors were then re- tracted as mandibular anchorage was prepared.

Mandibular anchorage was prepared by using Merrifield's sequential anchorage system. .6 The patient wore a J-hook headgear attached to hooks soldered distal to the maxillary central incisors. Anterior vertical elastics were worn from these maxillary hooks to hooks soldered to the mandibular archwire distal to the central incisors. These anterior vertical elastics sup- ported the mandibular arch during mandibular anchorage preparation, so the need for a man- dibular headgear was eliminated.

After mandibular anchorage preparation, dis- tal movement of the maxillary teeth for Class II correction was initiated. It was accomplished with a maxillary bulbous loop archwire, Class II elastics, anterior vertical elastics, and a maxillary high-pull J-hook headgear attached to the hooks soldered to the maxillary archwire distal to the central incisors. After distal movement of the maxillary teeth, occlusal interdigitation was en- hanced with up and down elastics worn in the premolar areas. Total treatment time was 30 months. Mandibular Hawley retainers were used for retention.

Results Achieved

Facial esthetics (Fig 5) was improved. The face has better balance and lip posture. The posttreat- ment casts (Fig 6) exhibit a Class I occlusal relationship as well as an ideal overjet/overbite relationship. The posttreatment panoramic radio-

Figure 5. Posttreatment fa- cial photographs. Facial es- thetics has been improved. The face has good balance and lip posture.

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Figure 6. Posttreatment casts. The casts exhibit a Class I occlusal interdigitation and an ideal overbite and overjet relationship.

graph is shown in Fig 7. The four third molars have been removed. The pos t t rea tment cephalo- gram (Fig 8A) and its tracing (Fig 8B) conf i rm a decrease in the ANB angle, main tenance of the occlusal plane relationship, and an increase of the hypodivergent skeletal tendency of the pa- tient. The superimposit ions of the tracings (Fig 9) show downward and forward growth with vertical control during treatment.

Conclusion

This pat ient 's records have been presented to illustrate the application of sequential direc- tional force technology for hypodivergent maloc- clusion correction. These malocclusions can be treated to an op t imum esthetic result because

Figure 7. Posttreatment panoramic radiograph (7 months after debanding). The third molars have been removed.

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272 Sylvie Lamarque

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FMA 20 m" ~ ' ~ J / / ) FMIA 63 ~ ~ I MPA 97 A N B 5 o p ~ ZA PFH 54 AFH 6"-6 0,81

Figure 8. (A) Posttreatment cephalogram. The cephalogram illustrates correction of the maxillary protrusion and an increase in the hypodivergent tendency. (B) Posttreatment cephalometric tracing: The tracing confirms maxillary incisor retraction, a decrease in the ANB angle, and maintenance of the occlusal plane relationship.

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Figure 9. (A) Pretreatment and posttreatment cephalometric tracings superimposed on SN registered at S. The pretreatment/post treatment superimpositions tracings show downward and forward growth/displacement with vertical control during treatment. (B) Maxillary, mandibular superimpositions: Note upward and backward movement of the maxillary incisors.

the use o f the Mer r i f i e ld Force System allows the

o r t h o d o n t i s t to t rea t the p r o b l e m with p rec i s ion

and cont ro l . Di f fe ren t ia l diagnosis is the crit ical

first step on the road to t r e a t m e n t success.

A c k n o w l e d g m e n t

The patient's treatment was rendered by the author and her associate, Marie Christine Videau.

References

1. Noffel ES. Danger signs of the occlusion face. J Charles Tweed Foundation 1986;14:50-96.

2. Merrifield LL. The profile line as an aid in critically evaluating facial esthetics. Am J Orthod Dentofacial Or- thop 1966;52:804-822.

3. Merrifield LL, Klontz HA, Vaden JL. Differential diagnostic analysis systems. AmJ Orthod Orthop 1994;106:641-648.

4. Merrifield LL. The systems of directional force. J Charles Tweed Foundation 1982;10:15-29.

5. Merrifield LL. Edgewise sequential directional force tech- nology.J Charles Tweed Foundation 1986;14:22-37.

6. Vaden JL, Dale JG, Klontz HA. The Tweed-Merrifield Edgewise Appliance: Philosophy, diagnosis, and treat- ment. Orthodontics--Current Principles and Techniques (ed 2). St Louis, MO: Mosby, 1994:627-684.