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