DEVELOPMENT OF OCCLUSION
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DEFINITIONS •Occlusion Is defined as the anatomic alignment of teeth and their relationship to the rest of the masticatory system. •BSSO in 1926 defined occlusion as the relationship of the teeth in the maxilla and mandible when the jaws are closed and the condyles are at rest in the glenoid fossae • Normal occlusion This refers to an occlusion that deviates in one or more ways from ideal yet it is well adopted to that particular environment, is esthetic and shows no pathologic manifestations or dysfunction. www.indiandentalacademy.com
Periods of occlusal development: Occlusal development can be divided into following periods: Pre dental period The deciduous dentition period Mixed dentition period Permanent dentition period
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Pre dental period: Period after birth during which neonates does not have any teeth. It usually lasts for 6 months. The alveolar process at the time of birth are known as gum pads. They are horse shoe shaped and develop in two parts.
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ďƒ˜The gum pads are divided into ten segments by certain grooves called transverse grooves. ďƒ˜Each of these segments consist of one developing deciduous tooth sac. ďƒ˜The upper gum pad is both wider and longer than the mandibular gum pad.
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Relationship of gum pads: Anterior open bite is seen at rest with contact only in the molar region. Tongue protrude anteriorly through this space. There is complete overjet. Class II pattern with the maxillary gum pad being more prominent.
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The neonate is without teeth for about 6 months of life. At birth the gum pads are not sufficiently wide to accommodate the developing incisors. However teeth are found to have erupted at the time of birth. Such teeth that are present at the time of birth are called Natal teeth. Teeth that erupt during the first year if life are called Neonatal teeth. www.indiandentalacademy.com
Deciduous dentition period: The initiation of primary tooth buds occurs during the sixth week of intrauterine life. The primary teeth begins to erupt at the age of about 6 months. The primary dentition is usually established by 3 years on eruption of second deciduous molars. The sequence of eruption is A – B – D – C – E Between 3 to 6 years the dental arch is very www.indiandentalacademy.com stable and very few changes occurs.
Signs of primary dentition : Spacing is usually seen in the deciduous anteriors to accommodate larger permanent teeth in the jaws.
Primate spaces: this space is present mesial to the maxillary canine and distal to the mandibular canine. This space is used for early mesial shift.
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Occlusal relation: Flush terminal plane: The distal surfaces of the maxillary and the mandibular molars are in the same vertical plane, this is normal relationship in the deciduous dentition because mesiodistal width of mandibular molar is greater than the maxillary molar.
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When the terminal plane is straight until the eruption of permanent first molars, the latter are usually guided into an end to end relationship which is considered normal. Interproximal cavities, sucking habits or skeletal pattern may produce a step rather than a flush terminal plane. Distal step: Distal surface of the mandibular deciduous second molar is more distal than the distal surface of the maxillary deciduous second molar.
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Mesial step: Distal surface of the mandibular deciduous second molar is mesial to the distal surface of the maxillary deciduous second molar,
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www.indiandentalacademy.com Leader in continuing dental education
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