Pacific Coast Society of Orthodontists Bulletin Spring 2015 - (Page 40)

SUMMARY ANNUAL SESSION CLASS III TREATMENT: TIMING AND PROTOCOL Presented by Dr. Peter Ngan at PCSO Annual Session, October 4, 2014. Summarized by Dr. Shahram Nabipour, PCSO Bulletin Central Region Editor. Dr. Ngan provided some very useful guidelines in the treatment of Class III patients. He explained a few options for the treatment of the young patient who presents with an anteroposterior (AP) discrepancy: challenging cases is a Class III without a functional shift and with a high mandibular plane angle. Dr. Ngan suggests orthodontists just wait and treat these patients surgically. If the patient's growth pattern can't be readily determined, take a lateral cephalose a facemask (FM) or chin cup. gram; recall the patient in six months to one If skeletal AP discrepancy is mild, year, and do a superimposition. Look at both treatment can be delayed until the magnitude and direction of growth on growth is complete; the discrepancy superimpositions. As for cephalometric indican then be corrected with camouflage cators, a European study found that the Wits Dr. Ngan treatment. If the AP discrepancy is large, analysis is predictive as to whether or not a treatment can also be delayed until growth patient will need surgery. This study was subsequently is completed; the discrepancy can then be corrected with repeated at West Virginia University. The findings were orthognathic surgery. as follows: As part of the initial assessment, take careful note of The average Wits appraisal that can be camouflaged the patient's profile, molar relationship, overjet, and safely with a good periodontal result is -7 mm to -4 mm. overbite. Check for a functional shift on closure. If there A Wits appraisal of between -10 mm to -13 mm indicates is no functional shift, the case is a true Class III discrepthat surgical correction is necessary. ancy, and will therefore be harder to treat. When making your assessment, also look at the growth patterns. Dr. Use a bonded RPE if possible; it is easier in Class III paNgan takes into account not just the patient's mandibutients because you can jump the crossbite. Using an RPE lar plane angle, but also the occlusal plane angle. in conjunction with a facemask will bring forward the TIMING OF TREATMENT: PHASE 1 OR NOT? maxilla about 2.1mm on average. U If the patient has a functional Class III malocclusion, then the objective of Phase 1 treatment would be to eliminate the functional shift. (This would be from age 5 to 10 years.) How long would this treatment last? If using a chin cup, it would take about four years. Facemask without the use of an rapid palatal expander (RPE) to loosen the sutures would take about a year; facemask with an RPE treatment can last about seven to eight months. Once the anterior cross bite is corrected, a waiting period is observed until (primarily vertical) growth is completed. In general, vertical growth is completed in girls by age 14; in boys, by 17. At that time, a final decision is made: will the clinician treat with orthodontics alone and do camouflage treatment or wait for completion of growth and perform surgery. One of the most 40 Dr. Ngan presented the Growth Treatment Response Vector (GTRV) analysis: GTRV = Horizontal growth of point A/Horizontal growth of point B This ratio can be used to determine which patients can be successfully camouflaged and which need surgical correction. The normal GTRV for an 8-year-old patient is 0.77 (mandible outgrowing maxilla by about 23%). The mean GTRV for patients who can be camouflaged successfully is 0.49 (range of 0.33 to 0.88). The mean GTRV for patients who will need surgery is 0.22 (range of 0.06 to 0.33). About 80% of Class III patients who undergo orthognathic surgery have a mandibular asymmetry. This needs to PCSO BULLETIN * SPRING 2015

Table of Contents for the Digital Edition of Pacific Coast Society of Orthodontists Bulletin Spring 2015

The Whole is Greater Than Its Parts
The Land of Opportunity
Donated Orthodontic Services Program — AAO-DOS
Trustee Report
AAO Council on Scientific Affairs (COSA) Report
Component Reports
AAOF Report
AAO Leaders Complete Terms in San Francisco: The End of an Era for PCSO
Preparing for the Unexpected: Your Emotional SOS Plan Part I
Resident Spotlight: Dr. Mona Afrand, Orthodontic Resident, University of Alberta Department of Orthodontics; Younger Member Spotlight: Dr. Mostafa Altalibi, Calgary, Canada
PCSO At A Glance
The AEODO Research Data Portal: Restructuring Workflow
The Aveolar Bone Housing — The Orthodontist’s World
Case Report Pre-Treatment
Smile and Appliance Esthetics — New Understandings
How to Remember Names and Places: A Dale Carnegie Program
The Latest Trends in Orthodontic Treatment: Part I
Training and Giving Feedback to The Clinical Staff to Ensure a Well-Tuned Team
Treatment Possibilities with Invisalign®
Class III Treatment: Timing and Protocol
Orthodontics: The Key to Successful Interdisciplinary Treatment
CBCT: Assessment of Anatomical Boundary Conditions Important to Orthodontists
Case Report Post-Treatment
Sectional Mechanics for Class II Correction
Dr. Donald Poulton

Pacific Coast Society of Orthodontists Bulletin Spring 2015