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D.U.C Faculity of Dentistry 4th Grade Orthodontic Dr. Ghufran Dhari Lec.1 Definitions Orthodontics: “Ortho” means correction of irregularity and “dontics” means teeth, so orthodontics means correction the irregularities of teeth. According to American Board of Orthodontics “Orthodontics is that specific area of dental practice that has as its responsibility the study and supervision of the growth and the development of the dentition and its related anatomical structures from birth to dental maturity, including all preventive and corrective procedures of dental irregularities requiring the repositioning of teeth by functional or mechanical means to establish normal occlusion and pleasing facial contours”. Orthodontics: is that branch of dental science concerned with genetic variation, development and growth of facial forms and the manner in which these factors affect the occlusion of teeth and the function of associated organs. Orthodontics: is that branch of dentistry concerned with prevention, interception and correction of malocclusion and other abnormalities of the dento -facial region. Occlusion The relationship of the maxillary and mandibular teeth when the jaws are - Closed in centric relation There are three types of occlusion: D.U.C Faculity of Dentistry 4th Grade Orthodontic Dr. Ghufran Dhari Lec.1 Ideal occlusion: is a hypothetical concept of an ideal arrangement of teeth based on the anatomy of teeth combined with an ideal inter-arch relationship which result in optimal esthetic, function and stability of dentition and supporting structures. It is rarely if ever found in nature. However, it provides a standard by which other occlusion can be judged. Normal occlusion: is an occlusion which includes variation in tooth position and relationship that diverge in minor way from the ideal. In general, these variations are not of esthetic or functional importance. Malocclusion: is an irregularity in the occlusion beyond the accepted range of normal. Class I Class III Class II D.U.C Faculity of Dentistry 4th Grade Orthodontic Dr. Ghufran Dhari Lec.1 The fact that an individual has a malocclusion is not itself a justification for treatment, the orthodontic treatment should be considered only: If the patient will benefit esthetically or functionally. If the patient is suitable and willing to undergo the treatment. The scope of orthodontic treatment: • • • Alteration in tooth position. Alteration in skeletal pattern. Alteration in soft tissue pattern. The objectives (aims) of orthodontic treatment: The improvement of facial & dental esthetics which lead to improvement the quality of life and Individual’s self –esteem( how positively the person feels about himself), It reflects the patient’s desire to improve their social acceptability and eliminate discrimination based on appearance, which can affect their quality of life greatly Alignment of teeth in order to reduce the stagnation area, the presence of stagnation areas makes the effective cleansing and brushing is difficult which increase the risk for the development of dental caries. Alignment of teeth in order to reduce periodontal diseases, the malocclusion may force one or more teeth to be squeezed buccally or lingually out of their investing bone reducing periodontal support and traumatic occlusion may lead to increase the loss of periodontal support. Alignment of anterior proclined teeth in order to reduce the possibility of fracture or damage to the anterior teeth due to traumatic injury or accident. Alignment of teeth in order to improve masticatory function, patients with open bites, markedly increased over jet (Class II) or reversed over jet (Class III) often complain difficulties with eating particularly incising food. The elimination of premature contacts which give rise to mandibular displacement and may cause later muscle or joint pain. D.U.C Faculity of Dentistry 4th Grade Orthodontic Dr. Ghufran Dhari Lec.1 Orthodontic treatment of certain malocclusion which is related to speech problems will result in speech improvement. (Not all cases of speech problem are caused by malocclusion, sometimes there is a normal speech associated with sever anatomic distortion). The alignment of irregular teeth prior to bridge work, crown or partial denture. The six keys of normal occlusion Six significant occlusal characteristics identified & first reported in 1972 by Lawrence F. Andrews, These six keys were found to be consistently present in a collection of 120 models of teeth with natural excellent occlusion. The criteria of the models included in this study: Teeth of selected models never had orthodontic treatment Teeth of selected models were straight and pleasing in appearance Had a bite which looked generally correct 1. Class I Molar relationship (inter-arch relationship) The mesiobuccal cusp of the upper first molar should occlude in the groove between the mesial and middle buccal cusp of the lower first molar. The distal surface of the distobuccal cusp of the upper first permanent molar made contact and occluded with the mesial surface of the mesiobuccal cusp of the lower second molar. The mesiopalatal cusp of the upper first molar should occlude in the central fossa of the lower first molar. The premolars enjoy a cusp-embrasure relationship buccally, and a cusp fossa relationship lingually. Maxillary canine has a cusp-embrasure relationship with mandibular canine & 1st premolar. D.U.C Faculity of Dentistry 4th Grade 2. Orthodontic Dr. Ghufran Dhari Lec.1 Crown angulation (Mesio-distal crown angulation) Crown angulation refers to angulation (or tip) of the facial long axis of the crown. The degree of crown tip is the angle formed by the facial long axis of the crown and a line perpendicular to the occlusal plane. A “+ reading" when the gingival portion of the facial long axis of the crown is distal to the incisal portion. A “- reading" when the gingival portion of the facial long axis of the crown is mesial to the incisal portion. For normal occlusion, the crown angulation is mesially, the gingival part of the facial long axis of the crown must be distal to the incisal (occlusal) part of the axis, It varied with each tooth type. D.U.C Faculity of Dentistry 4th Grade 3. Orthodontic Dr. Ghufran Dhari Lec.1 Crown inclination (Labio-lingual or Bucco-lingual inclination) Crown inclination refers to the labiolingual or buccolingual inclination of the facial long axis of the crown. Crown inclination is determined by angle formed by a line perpendicular to the occlusal plane and the facial long axis of the crown (as viewed from the mesial or distal). In upper incisors, the crown inclination is labially, the gingival portion of the crown’s labial surface is lingual to the incisal portion (positive inclination) In all other crowns, including lower incisors, the crown inclination is lingually, the gingival portion of the labial or buccal surface is labial or buccal to the incisal or occlusal portion. (negative inclination) with progressively greater negative inclination exist in lower(canines, premolar and molars) when compared with upper (canines, premolar and molars). 4. Rotations. There were no rotations. D.U.C Faculity of Dentistry 4th Grade 4. Orthodontic Dr. Ghufran Dhari Lec.1 Spaces. There were no spaces; contact points were tight. 6. Occlusal plane. The plane of occlusion is measured from the most prominent cusp of the lower second molar to the lower central incisor. The occlusal plane varied from flat to a slight curve of Spee. The mandibular curve of spee should not be deeper than 1.5mm. Recently, the authors believe that the correct crown diameter (correct tooth size) represents the 7th key to normal occlusion. This key had to be present in Andrew’s non orthodontic study models. D.U.C Faculity of Dentistry 4th Grade Orthodontic Dr. Ghufran Dhari Lec.1 Overjet & Overbite Overjet: is the horizontal distance between the upper and lower incisors in occlusion, measured at the tip of upper incisor. Normally the upper incisors are in front of the lower incisors in occlusion (2-4 mm). It is dependent upon the inclination of incisors and the antero-posterior relationship of the dental arches. In most people, there is a positive overjet (2-4mm) in which the upper incisors are in front of the lower incisors in occlusion. Sometimes the overjet may be zero in case of edge-to-edge relationship, the overjet may be reversed (negative) in cases of class III. D.U.C Faculity of Dentistry 4th Grade Orthodontic Dr. Ghufran Dhari Lec.1 Edge to edge Overbite: is the vertical distance between the tips of the upper and lower incisors in occlusion. Normally, the tip of lower incisors contacts the middle third of the palatal surface of the upper incisors in occlusion (2-4mm). It is dependent upon the degree of vertical development of the anterior dento-alveolar segment. There may be excessive overbite (deep bite) more than 4 mm, or there may be no incisal contact and the lower incisor edge is above the level of the upper incisal edge in occlusion which is called incomplete overbite, or there may be no incisal contact and the lower incisor edge is below the level of the upper incisal edge in occlusion which is called anterior open bite. D.U.C Faculity of Dentistry 4th Grade Open bite Orthodontic Normal Dr. Ghufran Dhari Lec.1 Deep bite Note: Basal arches (skeletal bases) mean maxillary and mandibular bones, while dental arches mean the teeth and their investing alveolar bone. D.U.C Faculity of Dentistry 4th Grade Orthodontic Dr. Ghufran Dhari Lec.1 Skeletal bases Dental arches Malocclusion Malocclusion is an irregularity in the occlusion beyond the accepted range of normal. It could be considered in the following groups: A.Teeth: Malpositioning of individual tooh or groups of teeth in normally related dental arches and jaws. B.Dental arches: Malrelation of the dental arches to one another upon bony bases which are themeselves normally related. The malrelation of the dental arches can take place in all dimensions, antero-posteriorly, laterally and vertically. Class II Open bite D.U.C Faculity of Dentistry 4th Grade Orthodontic Dr. Ghufran Dhari Lec.1 C.Dental bases (skeletal bases): The shape and the relation of the mandible to the maxilla are unfavorable to the production of a normal occlusion. Skeletal class II Malocclusion Intra-arch problems: malpositions of individual tooth or group of teeth in the same arch. Inter-arch problems: malrelation between the upper & lower dental arches. Intra-arch problems Labioversion (buccoversion): A tooth that has assumed a position labial or buccal to the normal position. D.U.C Faculity of Dentistry 4th Grade Orthodontic Dr. Ghufran Dhari Lec.1 Lingoversion (palatoversion): A tooth that has assumed a position lingual or palatal to the normal position. Mesioversion: A tooth that has assumed a position mesial to the normal position. Distoversion: A tooth that has assumed a position distal to the normal position. Supraversion: Over-erupted above the level of occlusion. D.U.C Faculity of Dentistry 4th Grade Orthodontic Dr. Ghufran Dhari Lec.1 Infraversion: Depressed below the level of occlusion, for example, primary tooth that is submerged or ankylosed. Torsiversion: Turned or rotated tooth around its long axis, it could be: Mild: which is less than 90° Severe: which is more than 90° Transposition: interchange in the position of two adjacent teeth. D.U.C Faculity of Dentistry 4th Grade Orthodontic Dr. Ghufran Dhari Lec.1 Impaction: occur when the eruption is completely blocked by other teeth due to crowding. It tend to affect the last tooth erupt in each segment. Crowding: the irregularities of teeth due to inadequate space in the dental arch for normal alignment. Spacing: Condition where there are gaps or spaces present between the teeth. It could be either localized or generalized. D.U.C Faculity of Dentistry 4th Grade Orthodontic Dr. Ghufran Dhari Lec.1 Proclination: is term used to describe labial inclination (tilting) of anterior teeth toward the lips. Retroclination: is term used to describe lingual inclination (tilting) of anterior teeth.