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EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

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In summary, the variance in tongue and lip pressures seen in “normal”<br />

individuals indicates that a wide range of maximum intraoral pressures occurs in<br />

the general population, making broad predictions about the effects of the<br />

perioral musculature difficult at best.<br />

Weinstein et al. (1963) reported that the opposing forces and pressures<br />

exerted on the dentition from, principally, the tongue, cheeks, and lips can be self<br />

negating, such that a system of equilibrium between hard and soft tissues exists.<br />

Further conclusion were: (1) forces exerted on the teeth by the surrounding soft<br />

tissue may cause tooth movement much like orthodontic appliances, (2) each<br />

tooth may have more than one position of stable equilibrium within the system<br />

composed of the oral environment, and (3) differential forces, even of small<br />

magnitude, if applied over a considerable period of time, can cause changes in<br />

tooth position.<br />

Proffit (1978) extended the work of Weinstein et al. (1963) by presenting an<br />

additional review of the subject of equilibrium. The results of Proffit’s research<br />

identified four primary factors that create equilibrium between the dentition and<br />

the surrounding tissues:<br />

1. intrinsic forces by tongue and lips,<br />

2. extrinsic forces: habits, orthodontic appliances,<br />

3. forces from dental occlusion, and<br />

4. forces from the periodontal membrane.<br />

Teeth characteristically exist in a state of equilibrium with the<br />

surrounding soft tissues. For posttreatment results to maintain stability, the<br />

resting pressures of the soft tissues will determine the final tooth positions.<br />

Riedel (1976) acknowledged the importance of considering muscle balance<br />

when positioning teeth to gain lasting stability, but contended that establishing a<br />

harmonious muscle balance is almost impossible to do until growth and<br />

development have been completed. “The orthodontist moves the teeth into the<br />

relationships which he considers correct, but Nature eventually repositions them<br />

where they can best serve the patient” (Huckaba 1952, p349).<br />

Continued Physiologic Growth and Development<br />

About 1900, retention consisted of holding teeth in position until<br />

believed stable. This philosophy of stability changed when the Huning case<br />

of Dr. Angle demonstrated that anterior teeth can change axial inclinations<br />

during and after retention. This was the beginning of the realization that<br />

18

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