TREATMENT OF ANTERIOR OPENBITE AND DEEP OVERBITE MALOCCLUSIONS WITH THE MULTILOOP EDGEWISE ARCH-WIRE (MEAW) THERAPY
Dr. Young H. Kim
I FEEL EXTREMELY HONORED TO HAVE BEEN INVITED FOR THE SECOND CONSECUTIVE YEAR TO DISCUSS THE MANAGEMENT OF VERTICAL COMPONENT PROBLEMS. (The description of the bio mechanics of the MEAW appliance and the treatment of open bite malocclusion with MEAW therapy, including several case reports, and presented in the previous Craniofacial Growth Series volume, “Growth Modification: What Works, What Doesn’t, and Why”; Kim, 1999).
Case Report 1
The first patient is a boy 12 years, 5 months of age with a severe malocclusion, in-cluding an 8mm shifting of the mandible to the left that caused a marked clicking of the left joint whenever he opened his mouth. His profile was severely prognathic (Fig. 1A, B). The cephalometric and the pantomographic analysis revealed an Overbite Depth Indicator (ODI; Kim, 1974; Wardlow et al., 1992) of 59.5 degrees, indicating a marked Class III open bite skeletal pattern (Fig. 1C, D). He had been examined previously by two other orthodontists who had recommended orthognathic surgery to correct this malocclusion. I also suggested surgical correction, primarily to improve the patient’s facial appearance. However, the patient’s family lacked financial resources or insurance, and thus requested treatment without surgery. They hoped that the occlusion could be improved enough so that their son could chew food normally.
This basic objective was achieved, although there was no noticeable improvement in the patient’s prognathisc profile. After 16 months of active treatment, the upper and the lower arches were aligned and MEAW therapy was applied (Fig. 1E, F). After a month of MEAW therapy with one short Class 11 3/16 inch, 6 oz. elastic on the left and two short Class III 3/16 inch. 6 oz. elastics on the right, the midline was corrected (Fig. 1G, H). At that time, short Class III elastics were placed bilaterally. By then, TM joint clicking symptoms had subsided. Usually, 3/16 inch, 6 oz. elastics are used for MEAW therapy.) Five months later, the occlusion had turned in a Class II anterior open bite; at that point Class III elastics were discontinued and anterior vertical elastics were applied (Fig. 1I,J). The elastics were continued for another six months, and a satisfactory occlusion was obtained. The occlusion actually turned out better than had been predicted, and even the profile appeared to have improved somewhat (Fig. 1K, L). The cephalogram and the panoramic radiograph showed a well-uprighted dentition (Fig. 1M, N). Superimposition of the tracings revealed that the maxilla had grown forward and downward considerably, whereas the mandible had grown mostly downward (Fig. 1O, P). The small upper lateral incisors were enlarged by means of esthetic bonding to take up the spaces. No extractions were required in this patient, but the third molars were removed a year after appliance removal. The total treatment took twenty-eight months.
A 24-month post-treatment examination showed a midline shifting of 3mm to the left (Fig 1Q.R). Interview of the patient revealed that he had a habit of sleeping on his stomach, always with right side of his face on the pillow. He was advised instead to sleep with the left side of his face downward. The next follow-up examination is scheduled to take place 36 months following appliance removal.
LOAD DEFLECTION RATES
The load deflection rate (LDR) of various wires is discussed in my chapter in the earlier Craniofacial Growth Series volume (Kim, 1999(. The relative LDR of the MEAW, compared to a stainless steel wire without the loops, is 40%, 32% for TMA, 28% for Sentalloy, and 20% for Nitinol. While that study result was based on the entire arch, the characteristic feature of the MEAW is the L-shaped loops incorporated between each tooth from the lateral incisor to the second molar. The LDT at various tooth regions thus would vary. To test this hypothesis, Dr. B. Kim of Seoul National University conducted a study of the regional LDR of MEAW, using an Instron unit, and found the following results (Kim, 1999):
1. In the maxilla, the average ratios of the load deflection rates of the MEAW to the L loop are 2.48 for NiTi, 3.46 for TMA, and 5.34 for stainless steel.
2. In the mandible, the average ratios of LDR compared to the L loop are 1.86 for NiTi, 2.50 for TMA, and 3.96 for stainless steel.
3. The load of force of MEAW in each interbracket span showed 994.9 gm/mm at the incisor region without the loop, and 107.68 gm/mm at the first and the second molar regions with the loop.
In summarizing this study, it can be stated that:
1. The LDR of a MEAW is high in the entire arch, but low in the interdental
span.
2. The MEAW makes all the teeth move independently and simultaneously
toward their final positions.
3. The MEAW produces an effective transmission of orthodontic force
with elastics and tip-back activations.
4. The L. loop serves as a stress breaker between two adjacent teeth.
In conclusion, I would like to repeat the statement from my chapter in the previous Craniofacial Growth Series volume (Kim, 1999 (by saying, this presentation has shown that many severe malocclusions can be corrected without surgical intervention. Mere insertion of the MEAW, however, does not guarantee the success of treatment. One must be cognizant of the biological nature of the tooth movement and the skeletal pattern of each patient. The MEAW mechanism can move teeth so rapidly that one must be aware of every little detail of the wire before it is inserted into the dentition. It seems so magical to many people, but it really isn’t. Try it, you will like it.