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SUMMARIES ANNUAL SESSION Guidelines for Building Facial Harmony and Stability Presented by Wick Alexander, DDS, MSD, at the PCSO Annual Session, October 24, 2009. Summarized by Dr. Bruce P. Hawley, PCSO Bulletin Northern Region Editor. A ccording to Dr. Wick Alexander, this is a difficult subject, particularly on account of the stability criterion. He believes that there are certain guidelines which, when followed, allow us to put these two goals together and provide the best care for the patient. There are six guidelines to building facial harmony and producing excellent final orthodontic results: anterior torque control, skeletal control, transverse control, occlusion, proper surrounding tissues, and soft tissue profile and smile. ANTERIOR TORQUE CONTROL Strive to keep IMPA within 3° of the original position; exceeding this amount increases the likelihood of instability. Exceptions would include convex and concave profiles, along with deep overbite cases. Dr. Alexander finds the use of -5° degree torque on lower incisor brackets with .018 slot to be helpful, along with using an initial flexible rectangular wire (e.g., .017x.025 Cu Niti), even with Class III elastics as needed. Interproximal enamel reduction is also an option. Upper incisor to SN is optimally in the range of 101° to 105°. He uses a pre-torqued upper incisor bracket with .017x.025 SS archwire in a .018 slot. Exceptions could include a vertical skeletal pattern, and high and low angle cases. Finally, maintaining an interincisal angle between 130° to 135° is also a key established norm. SKELETAL CONTROL Control vertical relationships by keeping SN-MP within 3° of the original value. Use high pull headgear on high angle cases, and squeezing exercises as appropriate. In the sagittal dimension, control between 1° to 3°. Headgears hold the maxilla while the mandible grows forward, for both maxillary protrusive and mandibular retrusive Class II cases. Dr. Alexander believes that the facebow headgear is the best Class II orthopedic appliance, generally used in his hands for eight to nine hours per night for six to twelve months in growing Class II patients. Lower incisor inclination changes tend to be insignificant. The exceptions to the use of headgear are no growth or compliance—then it simply won’t work! The 28 only real modality for the correction of Class III cases is face mask therapy. TRANSVERSE CONTROL Maintain the original mandibular intercanine width within 1mm, in both nonextraction and extraction cases. All of the research supports the avoidance of excessive expansion of lower 3-3 width for long-term stability. An exception would include lingually erupted lower canines, which can be expanded. Control lower intercanine width with your final archwire, which you can superimpose over the original study model in order to verify. Maxillary intermolar width between 34mm to 38mm is another important criterion. You can use expanded maxillary archwires, expanded headgear face bow, or RPE as needed. While the lower intercanine width should not be significantly expanded, one can expand maxillary intercanine width along with upper and lower premolar and first molar widths (see TABLE). AMOUNT OF STABLE EXPANSION (MM) MAX. MAND. 3-3 2.65 0.49 4-4 4.01 3.73 5-5 4.57 1.85 6-6 3.88 2.57 The final arch form should be ovoid, with every arch form similar yet individual and most within one standard deviation. Maxillary intermolar width and mandibular intercanine widths will, of course, be contributing factors to the arch form. Dr. Alexander likes to start with the maxillary arch and contour the maxillary archwire to fit the untreated mandibular arch as a template. He then expands at the molars to give the correct molar overjet. Expand or constrict the mandibular posterior archwire as needed (there are no exceptions to this). PCSO BULLETIN • WINTER 2009 ANNUAL SESSION OCCLUSION Both maxillary and mandibular incisor roots need to diverge, with the lower lateral incisor roots nearly parallel to the roots of the lower canines, without exception. Roots in the extraction sites should, of course, be parallel. Upright mandibular first molars in both normal and deep bite cases. This helps level the lower arch and maintain the overbite. He uses a -6 degree tip routinely except in open bite cases. The mean long-term lower first molar tip is 4.55°. Level the mandibular arch with a reverse curve of Spee, tied back. This tends to extrude the bicuspids 2-4mm with a slight (around 0.5mm) intrusion of lower incisors. Extrusion of the bicuspids is our desire and slight extrusion of lower molars with 6° tip back is acceptable. He heat treats his archwires and strives to keep the mandibular anterior teeth as close as possible to their original positions. A good final occlusion results from proper bracket placement and archwire sequencing, orthopedic appliances, and elastics. Dr. Alexander likes to attach a Class II elastic to the maxillary lateral incisors rather than maxillary cuspids in order to have a more horizontal force vector. He uses vertical zig zag finishing elastics (3/4 inch, 2 ½ oz being the heaviest) on every case, centered in the bicuspid regions. PERIODONTAL AND TMJ HEALTH SUMMARIES the tip of the nose. For a nice smile, the facial and dental midlines should be symmetrical (use dental floss to verify). The smile line should be such that the upper lip is at the gingival line, +/- 2mm while the patient is smiling broadly. Dental display helps determine in a deep bite case whether to put an upper accentuated curve of Spee in the maxillary archwire or a reverse curve of Spee in the lower archwire. The smile arc refers to the lower lip being parallel to the maxillary incisal edges in smiling. This is achieved orthodontically from proper bracket placement, finishing, enamoplasty, and the use of anterior boxed elastics. The buccal corridor should display teeth, not dark spaces. Achieve this by reaching proper maxillary intermolar width (34mm to 38mm), adequate rotation of upper first molars, proper tips and torques, and ovoid arch forms. This seems to work well most of the time. In the final analysis, Dr. Alexander likes to keep the mandibular intercanine dimension as close as possible to the original, and he builds the rest of the of the occlusion around this. By following these guidelines, we can provide the utmost in harmonious faces and maximize the stability of our final orthodontic results. Poor oral hygiene tends to cancel long-term stability; the roots and periodontal soft tissues need to be healthy. With respect to the TMJ, have canine and anterior guidance (good bracket placement helps), treat to CR, and work in the last six months of treatment to attain maximum interdigitaition. BALANCED SOFT TISSUE PROFILE AND SMILE In the ideal profile, the lips should be touching while relaxed. The esthetic (E-) line touches the chin and lips and bisects the nose. A proper diagnosis to determine whether to extract or go nonextraction is critical in order to position the teeth so that the lips will be relaxed in repose. In the Asian population, the E- line contacts WINTER 2009 • PCSO BULLETIN 29