They are removable or fixed (cemented) appliances that mostly alter the posture of the mandible (designed to correct class II malocclusion, primarily by forwards posturing of the mandible in a growing child) and transmit the forces created by the resulting stretch dental and skeletal tissues to produce movement of the teeth and growth modification to the jaws and lower facial third. Clinical use of functional appliances
The ideal case for treatment with a functional appliance should have the following clinical features:
•Increased overjet and class II buccal segment relationship;
•Mild to moderate skeletal class II base;
•Average to reduced lower face height;
•Proclined maxillary incisors;
•Retroclined mandibular incisors; and
• Active growth (Favourable growth pattern).
Advantages and disadvantages of MFA
? It produce dentoalveolar and favourable growth of the jaw.
? The appliance must be worn for long hours.
? Reduce treatment time and severity
? Critical treatment time.
? Needs well cooperative patient.
? Needs fixed appliance after finishing. Theories on how functional appliances work
Functional appliances effect their changes by posturing the mandible forwards. This postural correction is fundamental to the appliances’ mode of action and influences four principal regions:
• Orofacial soft tissues; • Muscles of mastication;
• Dentition and occlusion; • Facial skeleton.
ORTHODONTICS Assist.Lec.Kasem A.
University of Babylon Faculty of Dentistry 4th stage
2
Clinical effects of functional appliances
Numerous types and designs of functional appliance have been described, each with its own treatment philosophy. In essence, all of these appliances have similar effects, with the most significant being dentoalveolar change:
• Retroclination of maxillary incisors;
• Proclination of mandibular incisors;
• Distal tipping of the maxillary dentition;
• Mesial eruption of the mandibular buccal dentition;
• Restraint of forwards maxillary development; and
• Forwards movement of the mandible due to small additional growth at the condyle and remodelling of the glenoid fossa. The treatment results depend on the following:
1) Amount of force
The force magnitude should be high or at least (400- 600 gm) per each side to make sure that only skeletal and no dental movements takes place. Such high forces produce hyalinization of the bony socket which prevents tooth and thus only orthopaedic movement is seen.
2) Duration of force
According to most authors, intrmittent forces produce skeletal changes whereas continuous forces produce dental movement. MFA should be worn for about 12- 14 hr/day to bring about the desired effect. Increasing the duration beyond the optimum range increases the dental effects. An intermittent heavy force is less harmful to the teeth and periodontium than a continuous heavy force.
3) Direction of force: The direction of force application should be such as to maximize the skeletal effect. A favourable skeletal effect is seen when a force is directed postero-superiorly through the center of resistance of maxilla.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
|