MYOFUNCTIONAL APPLIANCES

FORM follows FUNCTION
INTRODUCTION-

• Myofunctional Appliances-Removable or fixed orthodontic appliances which use forces generated by the stretching muscle,fascia and/or periodontium to alter skeletal and dental relationships.
• They are passive appliances.
• How they work-These appliances use the natural forces generated by the stretched muscles.The increased muscle activity act as a stimulus for mandibular growth.
• All functional appliances are made up of following components-

1. BITE PLANES
2. SHIELDS
3. WORKING BITE
4. WIRE COMPONENTS

• BITE PLANES- 

*Types- Anterior/Posterior
              Flat/Inclined

*Anterior Bite block are helpful in opening of bite.They cause selective eruption of                                                        posterior segment of teeth.They can also be used to cease the supra eruption of anteriors.They can also be used to tip the anteriors.

*Posterior Bite Block are helpful in correcting anterior cross bite cases as they lift the bite up and eliminates the hindrance caused by mandibular teeth in the growth of maxilla and maxillary incisors.

*Anterior Inclined planes can be used to give a guiding plane for the labio lingual eruption of incisors or bucco lingual deflection of molars.

• SHIELDS-Vestibular shields/oral screens/lip pads are important in eliminating the undesired muscular forces (Like that of cheeks,lips etc),that impede the growth of jaws and causes favorable forces to act on jaws that can add to there growth .

        Shield also stretches the muscles causes underlying periosteal pull,which in turn causes bone growth in     desired direction.

These shield can also be used to prohibit various oral habits like mouth breathing,thumb sucking etc.

•  WORKING BITE-All functional Appliances are Constructed to a Construction or working bite registration.This registration is the one which is desired by the dentist or which is said to be the perfect occlusion for the patient.

       Construction Bites are taken at a Vertical Dimension.For a vertical grower the vertical dimension of construction Bite is kept more and for a horizontal grower its kept less.

• Some Important Points- 

1. Myofunctional Appliances can only be used only in growing patients.
2. Myofunctional Appliances are most favorably used in cases of Class II div 1 cases,having retrognathic mandible.
3. An ideal case for functional appliances is the one which is devoid of gross irregularities like crowding,rotations etc.
4. Most functional appliances causes upper anteriors to tip palatally and lower anteriors to tip bucally
5. Functional appliances causes condylar growth in upward and backward direction,leading a downward and forward growth of mandible.
6. Myofunctional Appliances also remodel condylar fossa in forward and downward direction.
7. It should be remembered that as the lower jaw grows anteriorly,the lower posteriors move mesially and occlusaly ,leading to increase in lower anterior facial height.All myofunctional appliances causes an increase in lower anterior facial height.so they should be cautiously used in patients having excessive vertical dimensions,and if used they should be used after  giving posterior bite blocks that can control the vertical eruption of molars.
8. In the transverse direction,functional appliances can bring about expansion of jaws by incorporating screws
9. Most of the functional appliances need post treatment fixed appliance therapy for detailing occlusion.

• Types Of Myofunctional Appliances-

1. ACTIVATOR
2. BIONATOR
3. FRANKEL
4. HERBST 
5. JASPER JUMPER

DEEP BITE

DEFINITION- A condition of excessive overbite, where the vertical measurement between the maxillary and mandibular incisal margins is excessive when the mandible is brought into habitual or centric occlusion’. 
Since the crown length of the lower incisors significantly varies in individual, a notation of the overbite in percentage is more descriptive and desirable . When the teeth are brought into habitual or centric occlusion. Usually normal overbite is 2-3mm or 30% percent or 1/3 rd the clinical crown height of the mandibular incisors.
Deep bite (or deep overbite) is present when the mandibular incisors' occlusal edges occlude apical to the cingulum of the maxillary incisors.
This may be due to overeruption of either the maxillary or mandibular anteriors or due to infraocclusion of molars.
*Closed Bite-condition of excessive overbite, where the vertical measurement between the maxillary and mandibular incisal margins is excessive when the mandible brought into habitual or centric occlusion. Closed bite is excessive overbite resulting from loss of posterior teeth. It is rarely seen in young children, must not be confused with deep bite. Excessive overbite is most prevalent in the mixed dentition and is a self correcting transient malocclusion.
CLASSIFICATION- 

1. According to its origin;
   1. Dental deep bites (Simple).
   2. Skeletal deep bite (Complex).
2. According to functional classification;
   1. True deep bite.
   2. Pseudo deep bite.
3. Depending on the extent of deep bite
   1. incomplete over bite
   2. complete over bite

Dental deep bite- 

• localized to the teeth and alveolar processes.
•  Dental deep bites occur due to over-eruption of anteriors or infra-occlusion of molars. 
• The result may be labial version of the upper incisors and impingement of the lowers into the palatal mucosa. 
• In the mandibular dentition, it may manifest as a deep curve of Spee or a reverse curve of Spee in the maxillary dentition.

Skeletal deep bite-

• deep bite associated with basic skeletal features with which the alveolar process cannot cope.
• A skeletal type of overbite may be due either to malrelationship of alveolar bones and/or underlying mandibular or maxillary bones or to an overgrowth or undergrowth of one or more alveolar segments. 
• It occurs due to convergence of maxilla and mandible towards each other
• The dimished anterior vertical height of the face is also an important criterion for diagnosis of skeletal deep overbites. Facial height doesn't vary in case of dental deep bite.
• frequently associated with class II div 2 and occasionally with Class III.

True deep bite-

• This is caused by  infraocclusion of the posterior  segments ie..molars
• Seen in class II div II
• It is often the result of a lateral tongue posture of tongue thrust. The interposition of tongue prevents the eruption of the posterior teeth. It can also occur due to premature loss of posterior teeth
• These patients have near flat curve of spee.
• There is  a large interocclusal clearance

Pseudo deep bite-

• is caused by  overeruption of the anterior teeth  that already has normal eruption of the posterior segment teeth
• Seen in class II div I malocclusions
• It is the result  of overeruption of the incisors. Due to the presence of the increased overjet, the lower incisors to over-erupt until they meet the palatal mucosa.
• These patients hence exhibit an excessive curve of Spee
• The inter-occlusal clearance is usually normal or small as the molars are fully erupted.

Incomplete & complete deep bite- Incomplete over bite is an incisor relationship in which the lower incisors fail to occlude with either the upper incisors or the mucous of the palate when the teeth are occluded. Complete over bite on the other hand is a relationship in which the lower incisors contact the palatal surface of the upper incisors or the palatal tissue when the teeth are in centric occlusion.
ETIOLOGY-The etiology of deep overbite is a complex problem and may include one or more of the following;

1. Hereditary and may follow a genetic pattern or familial condition
2. Skeletal: 
   1. An overgrowth or undergrowth of one or more alveolar segments.
   2. An excess of growth of the ramus and posterior cranial base permits the mandible to rotate upward. Thus Long ramus and short body with decreased gonial angle is characterstic feature.
   3. Convergent upper and lower jaw bases 
   4. Horizontal growth pattern or forward rotation or anticlock wise rotation of the of the lower jaw.The four planes of the face (inraorbital ( FH Plane), palatal, occlusal, and mandibular) as seen from lateral roentgenograms are horizontal and nearly parallel to each other.
3. Dental:
   1. Loss and/or mesial tipping of posterior teeth. In other words diminished posterior dental height
   2. Early loss of teeth and lingual collapse of the anterior teeth
   3. Overeruption of the incisor teeth, infraocclusion of the buccal segment or a combination of both.
   4. Overbite may because or accentuated by an aberration in the tooth morphology.
   5. Periodontal disease. Bite may deepen if the posterior tooth drift mesially during the pathological migration and worsen the existing condition
   6. When the teeth are reduced in size and number, the dental arches oppose less resistance against mandibular closure.
4. Muscular: The posterior vertical chain of muscles (masseter, internal pterygoid, temporal) is strong and attached anteriorly on the mandible and stretches in nearly a straight line vertically. The molars are directly under the impact of the masticatory forces of this chain. When the posterior vertical chain of muscles is strong and anteriorly positioned, a greater depressive action is transmitted to the dentition
5. Habits:
   1. lateral Tongue thrust swallow
   2. Finger sucking,
   3. Lip sucking

Open Bite

INTRODUCTION-Open bite is a malocclusion that occurs in the vertical plane, characterized by lack of vertical overlap between the maxillary and Mandibular dentition. The anterior open bites particularly skeletal open bites are called as “stigmata of malocclusion”.
Openbites are easy to diagnose but difficult to retain.
CLASSIFICATION - Open bites can be: anterior or posterior
                                                         Skeletal or dental
                                                         Unilateral or bilateral
ANTERIOR OPEN BITE-
ETIOLOGY-Many potential etiologic factors are implicated as causes of open bite including heredity, unfavorable growth patterns, digit-sucking habits, tongue and orofacial muscle abnormal function, orofacial functional matrices and their interaction with the skeletal components , imbalances between jaw posture, occlusal and eruptive forces and head position.

1. Heredity with genetic disposition: Inherited factors such as increased tongue size, and abnormal skeletal size and growth pattern of the maxilla and mandible can also be responsible for open bite malocclusion.
2. Habits: The effect of habits on dentofacial structures is discussed in detail in the chapter of ‘Habits’.
   1. Prolonged thumb-sucking habit is one of the chief etiological factors of open bite. The posture of thumb positioning, the intensity, and the frequency of sucking, all have an influence on the nature and severity of the open bite.
   2. Tongue thrusting is also implicated for some cases of open bite. Tongue thrusting may develop as a complication of thumb sucking habit. Some times tongue thrusting develops as a compensatory mechanism for existing openbite. Thus whether chick comes first or egg is a matter of controversy.
   3. Nasopharyngeal airway obstruction and associated mouth breathing may also result in openbite
3. Skeletal 
   1. An overgrowth or undergrowth of one or more alveolar segments. In anterior openbites there is undergrowth of the anterior segment with excessive growth posterior alveolar portion. In posterior openbites there is undergrowth of the posterior alveolar segment .
   2. Increased anterior and decreased posterior facial height. The posterior face height (Sella -Gonion) and Anterior face height (Nasion –Menton ) are measured on lateral cephalogram with teeth in habitual occlusion to estimate growth directions according to recommendations of JARBAK(JARBAK RATIO). A ratio of less than 62 percent expresses vertical growth pattern and open bite tendency whereas a ratio of more than 65 percent increases the likelihood for horizontal vector and deep bite tendency .
   3. Vertical growth pattern or backward rotation or clock wise rotation of the of the lower jaw
   4. Anticlock wise rotation of the maxillary base.
   5. Divergent jaw bases
   6. Short ramus with long or short body and Increased gonial angle( articulare—gonian –menton )
4. Dental: When there is only dental and dentoalveolar involvement, there is predominance of environmental causes such as thumb or dummy sucking habits, mouth breathing, and tongue or lip thrusting in addition to some local factors such as tooth ankylosis and eruption disturbances that result from over eruption of the posterior teeth or under eruption of the anterior teeth. The periodontal breakdown of anterior teeth may also give rise to anterior openbites with flaring of teeth.

Features of skeletal anterior open bite

 The problem is related to the skeletal bases. A patient having a skeletal anterior open bite is characterized by the following

1. The patient often has a long and narrow face with marked convex profile. A patient with underlying skeletal class III bases may have concave profile.
   1. The patient may have a short upper lip with excessive maxillary incisor exposure
   2. Increase lower anterior facial height and decreased upper anterior facial height
   3. A steep mandibular plane angle( High angle). Thus the angle FMA is increased. There is clock wise rotation or backward rotation of the mandible with increased lower anterior facial height .
   4. Small mandibular body and ramus
   5. Divergent jaw bases 
   6. There is upward rotation of maxillary jaw base

The patient may have a narrow maxillary arch due to lowered tongue posture due to a habit.

Features of dental anterior open bite

Dental anterior open bites do not present with the skeletal complications mentioned above. The following are the features of dental open bite:

1. 1. Proclined upper anterior teeth.
   2. The upper and lower anteriors fail to overlap each other resulting in a mild open bite.
   3. The patient may have a narrow maxillary arch due to lowered tongue posture due to a habit.

POSTERIOR OPEN BITE-

Posterior open bite is a condition characterized by lack of contact between the posteriors when the teeth are in centric occlusion. It mostly occurs in a segment of the posterior teeth.

Causes of posterior open bite

There are two possible causes of posterior open bite:

1. Mechanical interference with eruption, either before or after the tooth emerges from the alveolar bone, or
2. Failure of the eruptive mechanism of the tooth so that the expected amount of eruption does not occur.

Mechanical interference with eruption may be caused by ankylosis of the tooth to the alveolar bone, which can occur spontaneously or as a result of trauma, or by obstacles in the path of the erupting tooth. Examples of such obstructions prior to emergence are supernumerary teeth and non resorbing deciduous tooth roots or alveolar bone. After the tooth emerges from the bone, pressure form soft tissues interposed between he teeth (cheek, tongue, finger) can be obstacles to eruption Ankylosed teeth are usually in infraocclussion and are said to be submerged.The most commonly submerged tooth is retained lower decidous second molar. The second possible cause of eruption failure is a disturbance of the eruption mechanism itself. These patients have no other recognizable disorder, and no mechanical interferences with eruption seem to exist. The condition may be the cause of posterior open-bite which does not respond to orthodontic treatment.

Angle's Class II Malocclusion

DEFINITION-Angles class II malocclusion is characterized by class II molar relation where the distobuccal cusp of upper first molar falls in the buccal groove of mandibular first molar.
CLASSIFICATION- Class II Div 1 & Class II Div 2
Angles class II malocclusion can be dental or it can be of skeletal origin.
Skeletal Features can include a prognathic maxilla or a retruded (hypoplastic) mandible or both.
CLASS II DIV 1 MALOCCLUSION-

• Its a condition exhibiting class II molar relationship along with proclined maxillary incisors.
• Increased over jet(due to protruded upper incisors)
• Convex profile(due to protruded upper incisors)
• Short hypo tonic upper lip(due to protruded upper incisors)
• Patient may place lower lip against palatal surface of upper incisors leading to lip trap
• Abnormal muscle activity  and lower tongue possition (abnormal buccinator and mentalis activity leading to constricted maxillae)
• Posterior Cross bite(due to constricted maxilla)
• Patient shows a normal path of closure for mandible

Class II div1 can again be classified depending on the lower facial height.
In class II div1 lower facial height can be found to get increased or it can be normal.
If its increased than there would be reduced overbite or mild open bite and if its normal than there would be pseudo deep bite.
Pseudo Deep bite-Due to proclined upper anterior,the lower anterior fail to make contact with the palatal surface of upper anterior.thus they are free to erupt leading to an increased overbite and excessive curve of spee.

CLASS II DIV2 MALOCCLUSION-

• The Class II div 2 malocclusion is a condition characterized by a class II molar relation with retroclined upper centrals that are overlapped by lateral incisors.
• Here the muscle activity seems to be normal and so is the maxillary arch
• Backward path of closure of mandible is seen (due to palatally tipped upper CI)
• Straight profile face

Class II div 2 are always cases of true deep bite.


Thus Class II div 1 can either show excess vertical growth or normal growth whereas Class II div 2 are always cases of horizontal growth.
HOW TO CHECK THAT WHETHER CLASS II MALOCCLUSION IS BECAUSE OF MAXILLARY PROGNATHISM OR MANDIBULAR RETROGNATHISM?
Visual treatment Objective-In this patient is asked to bring his mandible forward,if the patient's profile improve by this movement than the malocclusion is due to retrognathic mandible.and patient is an ideal candidate for myofunctional appliance therapy.(if he is meeting other requirements as well)

MANDIBULAR MOVEMENTS