LEC 2 Orthodontic Definitions PDF

LEC.2 9-10-2017 ORTHODONTIC DEFINITIONS ‫ثامر هاني الصفار‬.‫د‬ Incisal overjet The overjet is the horizontal distance between the upper and the lower incisors in occlusion, measured at the tip of the upper incisors. It is dependent on the inclination...

LEC.2 9-10-2017 ORTHODONTIC DEFINITIONS ‫ثامر هاني الصفار‬.‫د‬ Incisal overjet The overjet is the horizontal distance between the upper and the lower incisors in occlusion, measured at the tip of the upper incisors. It is dependent on the inclination of the incisor teeth and the antero-posterior relationship of the arches. In most people there is a positive overjet , i.e. the upper incisor is in front of the lower incisor in occlusion ( normally 2-4 mm), but it may be reversed or edge to edge. Incisal overbite The overbite is the vertical distance between the tips of the upper and the lower incisors in occlusion. It is governed by the degree of vertical development of the anterior dento- alveolar segments. Ideally the lower incisors contact the middle third of the palatal surface of the upper incisors in occlusion (2-4mm), but there may be excessive overbite (deep bite), or there may be no incisal contact , in which case the overbite is described as incomplete when the lower incisors are above the level of upper incisal edges , or anterior open bite ,when the lower incisors are below the level of the upper incisal edges in occlusion. open bite ( negative overbite): inherited ,developmental or acquired malocclusion whereby no vertical overlap exists between maxillary and mandibular anterior teeth( anterior open bite) , or no vertical contact is exhibited between maxillary and mandibular posterior teeth (posterior open bite). Subdivided Dental open bite : A localized open bite that involves only a few teeth due to a digit sucking or other local factors. Skeletal open bite : Caused by divergence of the skeletal mandibular or / and maxillary planes leading to increased facial height as in case of posterior rotational growth of the mandible. Deep bite (excessive overbite): type of malocclusion in which the vertical overlap of the anterior teeth is increased beyond the ideal relationship (more than normal 2- 4mm) ;frequently associated with decreased vertical dimensions. subdivided into ; 1-Non traumatic deepbite : in which the deepbite still associated with teeth-teeth relation. 2-Traumatic deepbite : in which the deepbite associated with impingement of the mandibular incisors in the mucosa palatal to maxillary incisors commonly is seen malocclusions with extremely deep bite as in sever Class II malocclusion. 3-Bitraumatic deepbite: usually seen in some Class II ,division ii malocclusions with minimal overjet, the retroclined maxillary incisors may impinge the keratinized tissues labial to the mandibular incisors , causing gingival recession at the same time there is a trauma to the palatal mucosa caused by the mandibular incisors. Buccal overjet:  The distance between the buccal surfaces of the maxillary posterior teeth and the buccal surfaces of their mandibular antagonists. An unofficial term sometimes used to indicate whether or not there is tendency for a posterior cross bite. Crossbite An abnormal relationship of one or more teeth to one or more teeth of the opposing arch, in the buccolingual or labiolingual direction. A crossbite can be dental or skeletal in etiology. [Note : The appropriate type of crossbite can be specified by the teeth or the jaws that deviate the most from their ideal position (e.g. when crossbite mainly due to narrow maxillary arch the correct term is" maxillary posterior lingual crossbite" as apposed to "mandibular posterior buccal crossbite "which indicates wider mandibular arch). Anterior crossbite: if one or more of the lower incisors are in front of the upper incisors , the condition is called reverse overjet or anterior crossbite. Buccal crossbite: A crossbite due to buccal displacement of the affected posterior tooth (or group of teeth) from its (their) ideal position relative to its (their) antagonist(s). subdivided into: 1- Unilateral posterior: affect only one side of the dental arch, and can be either ; a- True unilateral posterior crossbite : caused by asymmetry present in the dental arch and usually does not associated with deviation of the mandible. b- False unilateral posterior crossbite : caused by narrowing of the maxilla or widening of the mandible leading to cusp-cusp relation then the patient try to get maximum intercuspation by deviation of the mandible to one side leading to unilateral crossbite. 2- Bilateral posterior crossbite : caused by sever maxillary collapse or/ and mandibular widening , there is no mandibular deviation during closure. Scissors-bite: Situation in which several adjacent posterior teeth overlap vertically in habitual occlusion with their antagonists, without contact of their occlusal surfaces. The deviation of the affected teeth from their ideal position could occur either in a buccal or in a lingual direction. Spacing of the dentition: A dental arch with spacing of more than accepted range (2mm or more), it is either : a-Localized : localized in one position like Median Diastema that caused by abnormal frenal attachment. b-Generalized : Affect the whole dental arch mostly caused abnormal soft tissue function like tongue thrust. Crowding of the dentition: A dental arch with crowding of more than accepted range (2mm or more ) , either caused by local factor like early extraction of deciduous teeth or general factor like collapsed maxillary arch that lead to crowding of the whole arch. Imbrication: The overlapping of incisors and canines in the same arch usually due to crowding. Midline shift (deviation) : Occur when the upper and the lower midline are not coincide and subdivided into : 1. Associated with mandibular deviation during closure as in case of premature occlusal contact. 2. Not Associated with mandibular deviation during closure as in case of unilateral missing of the teeth or crowding.  Midline shift may be due to shift of upper or lower teeth or sometime may be both of them and it is very important to determine that during diagnosis and treatment planning specially to choose a tooth or teeth to be extracted , in addition to that it is important to differentiate between midline shift of the dentition and the face because we may see one of them or some time both of them. Midline of the face mostly caused by abnormal skeletal factor ( like unilateral hyperplasia of the mandible )or deviation of the nose. Midline of the dentition mostly associated unilateral (extraction or congenital missing or impaction ) of a tooth. Infraposition ( infra occlusion): A situation in which a tooth or group of teeth is positioned below the occlusal plane; commonly due to a deleterious habit or to ankylosis. Overeruption (supraeruption ,supraposition ,supraocclusion): The situation whereby an unopposed or non –occluding tooth extends beyond the occlusal plane. Dental retrusion: Posterior position of a tooth or group of teeth but keeping their long axis with normal inclination. Dental retroclination: Posterior positioning of a tooth or group of teeth their long axis are tipped labio-ligually. [Note: A tooth can be retrusive without being retroclined , if it is positioned too far posteriorly but has a normal inclination.] Dental proclination: Anterior positioning of a tooth or group of teeth but their long axis are tipped labially. Dental protrusion: Anterior positioning of a tooth or group of teeth but keeping their long axis with normal inclination. Impaction of teeth : Occurs when eruption is completely blocked by other teeth due to crowding , it tends to affect last teeth to erupt in each segment(as in case of upper canines). Rotation of teeth: A type of malocclusion in which there is a rotation of a tooth about its long axis ,most evident when viewing the tooth from an occlusal perspective mostly , caused by crowding and subdivided into: 1-Mild (less than 90°):can be treated easily by removable orthodontic appliance using couple force system. 2-Sever (more than 90°): must be treated by fixed orthodontic appliance only. Displacement of tooth: Abnormal position of the tooth ( crown and root) in the dental arch. Overlapping of teeth: Abnormal position of the crown of the tooth in the dental arch while there is normal position of the root in the arch.