© 2006 - The Charles H. Tweed International Foundation

Two Phase Treatment for Deep Bite PatientsIsabelle Thiers-Jegou, DCD, CECSMOMontfort l’Amaury, FranceAs the faces Mona Lisa and Napoléon-Bonaparte exhibit, (Fig 1a/1b), “low angle” patients present similar faces:a short or decreased anterior facial height, a prononced chin, thin lips, a straight or concave profile with an increasedvalue of the Z angle and a poor smile. Very few teeth are visible in the smile. Diagnostic decisions must pay attention tothis type of face and how it will look in the future.What about the dental component of themalocclusion? Most of the time, there is minorcrowding and a mild curve of Spee. The upperincisor is well positioned in the profile and in thesmile. As there is no significant pathology in thelower arch, one can often decide not to consider achange in lower incisor position. Because muscleinsertions are perpendicular to the occlusalplane, occlusal forces make any individual toothmovement difficult. So, premolar extraction isgenerally contraindicated in the lower arch.The last but not least problem is how tocorrect the skeletal “class II” without unfavorablyimpacting the concave face. This problembecomes more critical in the class II patient whenFig. 1a/1b. Historical Low angle personalitiesthe mandibule is retrognatic and the maxilla is wellbalanced. All these variables have to be factored into an equation to find the best treatment plan that will not accentuatethe low angle characteristics.Our treatment goals are:• To maintain or even to increase the lower vertical dimension to harmonize the profile.• To respect the upper incisor position as a guide• To keep the lower incisor in its pretreatment position (IMPA)• To correct the class II relationship by “stimulating” mandibular growth without retracting the maxilla while keepingin mind the Tweed- Merrifield dental principles.How do we do this?• No premolar extractions in order to avoid any alveolo-dental contraction that might decrease the vertical dimension.Use the freeway space which is really excessive in hypodivergent patients.• Promote an increase in anterior face heightSome ideas:• Management in mixed dentition to prevent the worsening of the malocclusion.• Facilitate the opportunity for mandibular growth to express itself.• Consider two phase treatment.• Use functional and orthopedic forces in young patients in the late mixed dentition• Finalize treatment with a nonextraction Tweed-Merrifield approach before second molar eruption.The following patient record will illustrate this approach. This young boy presents with a class II malocclusion inthe late mixed dentition. The pretreatment photographs (Fig. 2) show the upper lip protrusion, an accentuated chin anda hypodivergent face. The smile is “well placed” in the face. The pretreatment cephalometric tracing (Fig. 3) confirmsa skeletal class II pattern with mandibular retrusion. The SNB angle of 76° and the ANB of 6°confirm the Class IIproblem. The vertical values confirm a hypodivergent patient: FMA is 23° and the vertical index is .81. The occlusalplane is 6°. The Z angle of 66° confirms an unbalanced face which is based on a retrognathic chin. The crano-facialdifficulty of 56 is mainly due to the horizontal deficit. The pretreatment casts (Fig. 4) show a full class II relationshipon both sides, a large overbite and an overjet of 12 mm. There is no crowding. The curve of Spee is mild. Arch formsare different because of an old habit of thumb sucking FMIA is 59° and IMPA is 98°. The objective is to keep the42