Normal and Abnormal Occlusion for General practitioners

1. 1 bnormal O Occlusion For For G General practitioners eneral practitioners Normal and Normal and A Abnormal cclusion Prepared by Prepared by Dr. M Dr. Mohammed ohammed Alruby Alruby Normal and Abnormal Occlusion Normal and Abnormal Occlusion f for G.P or G.P Dr. Mohammed Alruby Dr. Mohammed Alruby

2. 2 Normal occlusion it is the usual or accepted relationship for species of teeth in the same jaw and those in the opposing jaw when the teeth are approximated in terminal occlusion and mandibular condyles are in centric position in the glenoid fossa Normal occlusion in deciduous dentition 1= except the deciduous molars all other teeth are spaced and this spacing is rule or at least not abnormal. 2= curve of spee is less marked than the permanent teeth because: = Short arch length anteroposterior. = The cusps of posterior teeth are short and occlusal plane is flat. 3= the buccal cusps of maxillary deciduous molars and the incisal edge of maxillary deciduous incisors overlaps the mandibular one but the degree of overlaps differ because of short cusps. 4= the maxillary incisors and canines are larger than the mandibular one and the mandibular molars are larger than the maxillary one. 5= the long axis of the teeth are nearly parallel to each other. 6= the midline rule and arch symmetry similar to the permanent dentition. deciduous molars oc all the maxillary teeth except 2 = 7 Occlusal relationship of primary molars: 1= flush terminal plane: occurs where the primary erupt in an end to end fashion 2= A mesial step: is where the distal surface of the mandibular second primary molars is mesial to the distal surface of the second primary maxillary molar, that leads to Class I molars relationship 3= A Distal step: is where the distal surface of the mandibular second primary molar is distal to the distal surface of the second primary maxillary molars leads to class II molar relationship nd clude with two opposing teeth Figure (1): flush terminal plane figure (2) mesial step figure (3) distal step Characteristics of normal o 1= each arch is regular with the teeth at ideal mesiodistal and buccolingual inclination and the correct proximal contact relationship at each interdental contact area. 2= All teeth must be angulated mesially. cclusion in permanent dentition : Normal and Abnormal Occlusion Normal and Abnormal Occlusion f for G.P or G.P Dr. Mohammed Alruby Dr. Mohammed Alruby

3. 3 3- The buccal surfaces of incisors are labially inclined, but from the canines posteriorly, the buccal surfaces are progressively more lingually inclined. 4=the dental arch relationships are such that: = each lower tooth except central incisors contact the corresponding upper tooth and tooth anterior to it. = the upper arch overlaps the lower arch anteriorly and laterally : Six keys to normal occlusion (1)Molar relationship: *- The mesiobuccal cusp of the upper 1st permanent molar falls within the groove between the mesial and middle cusps of the 1st permanent molar. *- The mesiopalatal cusp of the upper 1st permanent molar seat in the central fossa of the lower 1st permanent molar. *- The distal surface of the distal marginal ridge of the upper 1st permanent molar contact and occlude with the mesial surface of the mesial marginal ridge of the lower second molar. (2)Crown angulations: ( mesio- distal tip): In normally occluded teeth, the gingival portion of the long axis of each crown is distal to the occlusal portion of that axis. The degree of the tip varies with each tooth type. ingual or bucco l - Crown inclination: labio ) 3 ( Is the angle between a line 90 degree to the occlusal plane and a line tangent to the middle of the labial or buccal surface of the clinical crown. : Rotation ) 4 ( *- Teeth must be free of undesirable rotation that affect contact area and occupy space different than normal *- Rotation of premolar teeth are occupying more space than normal *- Rotation of anterior teeth is occupying space less than normal - Rotation of teeth leads to loss of contact which leads to instability of treatment results * : Tight contact ) 5 ) Contact point must be tight; the teeth in either arch are aligned into tight contact, which maintained through: 1- Periodontal force (transeptal fibers) 2-anterior component of force 3- Physiologic mesial drifting ** newly erupted teeth have pointed contact, which later on transformed into an area of contact due to interproximal wear Significance of interproximal contact: 1- Stabilize the teeth against separating forces 2- Distribution of masticatory force and forces of occlusion between the adjacent teeth 3- Prevent food impaction and traumatization of interdental tissues. 4- Maintain the integrity of periodontium. 5- Together with the interdental embrasure form a spell way for food deflection, thus prevent undue frictional trauma and allow a proper gingival massage. - lingual torque : Normal and Abnormal Occlusion Normal and Abnormal Occlusion f for G.P or G.P Dr. Mohammed Alruby Dr. Mohammed Alruby

4. 4 Curve of spee It is imaginary curve in the horizontal dimension passing through the condyle and buccal cusps of the teeth ending at the incisal edge of the mandibular central incisors. It is measured from the most prominent cusp of the lower second molar to the incisal edge of the most prominent central incisors. Normal curve of spee lead to stability of the dental arch which decrease tendency to relapse 6 ) : Figure (4) molar relationship Figure (5) crown angulations Figure (6) crown inclination Normal and Abnormal Occlusion Normal and Abnormal Occlusion f for G.P or G.P Dr. Mohammed Alruby Dr. Mohammed Alruby

5. 5 Figure (7) tooth rotation Figure (8) curve of spee Centric relation and centric occlusion: Centric relation is the relation of the mandible to the maxilla when the mandibular condyles are in the most superior and retruded position in their glenoid fossa with the articular disc properly interposed. At centric relation both the condyles are simultaneously seated most superiorly in their glenoid fossa. Centric occlusion is that position of the mandibular condyle when the teeth are in maximum intercuspation. Centric relation and centric occlusion should coincide in order to have perfect harmony between the teeth, the teporomandibular joint and the neuromuscular system. **- definition of classification: it is the description of dentofacial deviations according to a common characteristic or norm. **- purpose of classification: 1-for the traditional reasons and for ease of reference. 2-for purposes of comparisons and for ease in self-communication 3-it indicates the proper procedures in treatment. 4-it facilitates more accurate conclusions about the etiology, progress, retention and presentation of malocclusion. Types of malocclusion: Malocclusion can be broadly divided into: a)Intra -arch malocclusions that include variations in individual tooth position and malocclusion affecting a group of teeth within the arch. b)Inter – arch malocclusion that comprise of mal-relation of dental arches to one another upon a skeletal bony bases, which may themselves be normally related. Normal and Abnormal Occlusion Normal and Abnormal Occlusion f for G.P or G.P Dr. Mohammed Alruby Dr. Mohammed Alruby

6. 6 c)Skeletal malocclusions that involve the underlying bony bases. a)Intra arch malocclusion: A tooth can be abnormally related to its neighboring teeth. Such abnormal variations are called individual tooth malposition. Some commonly seen individual teeth malposition’s are: *- Distal inclination or distal tipping: this refers to a condition where the crown of the tooth is tilted or inclined distally. *- Mesial inclination or mesial tipping: this is a condition where the crown of the tooth is tilted or inclined mesially. *- Lingual inclination or lingual tipping: this is an abnormal lingual or palatal tilting of the tooth. This condition is also called retroclination. *- Buccal inclination or buccal tipping: this refers to labial (in case of anterior) or buccal (in case of posterior) tilting of the tooth. This condition is also called proclination. *- Mesial displacement: this refers to a tooth that is bodily moved in a mesial direction toward the midline. *- Distal displacement: this refers to a tooth that is bodily moved in a distal direction away from the midline. *- Lingual displacement: This condition where the entire tooth is displaced in lingual direction. *- Buccal displacement: this describes a condition where the tooth is displaced bodily in a labial or buccal direction. *- Infra occlusion or infraversion: this refers to a tooth that has not erupted enough compared to the other teeth in the arch. *- Supra version or supra occlusion: this refers to a tooth that has over-erupted as compared to other teeth in the arch. *- Rotation: referred to a tooth moved around its long axis. *- Disto- lingual or mesio- buccal rotation: this described a tooth that has moved around its long axis so that the distal aspect is more lingually placed. *- Mesio- lingual or disto buccal rotation: this described a tooth that has moved around its long axis so that the mesial aspect is more lingually placed. *- Transposition: this term describes a condition where two teeth have exchanged places. B) Inter- arch malocclusions: 1- Sagittal plane malocclusion: this includes conditions where the upper and lower arches are abnormally related to each other in a sagittal plane. *- Pre-normal occlusion: this term refers to a condition where the lower arch is more forwardly placed when the patients bites in centric occlusion. *- Post- normal occlusion: this is a condition where the lower arch is more distally placed when the patient bites in centric occlusion. 2- Vertical plane malocclusion: This malocclusion includes deep bite and open bite where an abnormal vertical relation exists between the teeth of the upper and lower arch. *- deep bite or increased over bite: it is a condition where there is excessive vertical overlap between the upper and lower anterior. *- open bite: this is a condition where there is no vertical overlap between the upper and lower teeth. Thus a space may exist between the upper and lower teeth when the patient bites in centric occlusion. The open bite can be in the anterior or posterior region. Normal and Abnormal Occlusion Normal and Abnormal Occlusion f for G.P or G.P Dr. Mohammed Alruby Dr. Mohammed Alruby

7. 7 3- Transverse plane malocclusions: it is inter-arch malocclusions include various types of cross bites. The term cross bite refers to abnormal transverse relationship between the upper and the lower arches. Figure (8) Diagrammatic representation of the possible skeletal relationship in the transverse plane Angle's system of classification: Angle's classification was based on the mesio-distal relation of the teeth, dental arches and the molar is the key to occlusion. He considered these jaws. According to Angle the maxillary 1 teeth as fixed anatomical points within the jaws. Based on the relation of the lower 1 molar to the upper one, he classified malocclusion into three main classes designated by the Roman numeral, I, II, III. : Angle's class I The mandibular dental arch and the body of the mandible are in normal relation to the maxillary dental arch, with the mesio anteroposterior buccal groove ermanent molar occludes in the p permanent molar occludes in the occlusal fossa, when the jaws are palatal cusp of the upper 1 at rest and the teeth are approximated in centric occlusion. Malocclusion in Class I is localized anterior to the first molars and fall one of the following: 1-lacal abnormalities: *- crowding of anterior teeth. *- labial inclination of upper anterior teeth. *- anterior cross bite. *-impaction of premolars or canines. *- deep over bite. *- anterior or posterior open bite. st st permanent st buccal cusp of the upper 1 permanent molar, and the mesio the lower 1 - st of - st Normal and Abnormal Occlusion Normal and Abnormal Occlusion f for G.P or G.P Dr. Mohammed Alruby Dr. Mohammed Alruby

8. 8 *- local abnormalities due to premature loss of deciduous molars and forward tilting of permanent molars with loss of space in the premolar region. 2- Disproportion in size between the teeth and basal bone resulting in crowding or spacing of teeth. Figure (9) Class I occlusion Angle's Class II The mandibular dental arch and the body of the mandible are in distal relation to the maxillary permanent molar or mesio arch by half width of the 1 permanent molar occlude in the space between mesio buccal buccal cusp of the maxillary 1 permanent molar and the distal aspect of buccal cusp of 2 cusp of the mandibular 1 permanent molar occludes mesial to the mesio lingual e mesio palatal cusp of maxillary 1 Th . Class II malocclusion divided into molar cusp of the mandibular 1 : st - distal width of a premolar. The mesio st st nd premolar. st st : - * Class II division 1: 1- Maxillary incisors are in labio- version. 2- Excessive over jet and deep bite. 3-V shaped upper arch. 4-Short upper lip with failure of anterior lip seal. 5- Mandible may be deficient and the chin under developed. 6- Normal path of closure. 7- Increased mentalis and buccinators activity. that characterized by the following : - * Class II division 2: 1- Maxillary lateral incisors may over-lap the central incisors which are in lingo version. 2- Deep over bite. 3- Normal upper lip with normal lip seal and deep mental groove. 4- Mandible is of good size. 5- Upper arch usually broad. 6- Backward path of closure. 7- Decreased lower facial height. 8- Normal muscle activity of mentalis and buccinator. that characterized by the following : Normal and Abnormal Occlusion Normal and Abnormal Occlusion f for G.P or G.P Dr. Mohammed Alruby Dr. Mohammed Alruby

9. 9 N: B: When a Class II molar exist in one side and a Class I relation on the other side, it is referred to as Class II subdivision based on it is division 1 or division 2, it can be called Class II division 1 subdivision or Class II division 2 subdivision. Figure (10) A) Class II division 1 B) division 2 Angle's Class The mandibular dental arch and the body of the mandible present in bilateral mesial relationship to the maxillary dental arch. permanent molar occludes in the interdental space The mesio buccal cusp of the maxillary 1 st l cusps of lower 1 between distal aspect of dista permanent molar. The teeth are in centric occlusion and mandibular condyles cusps of lower 2 are within the glenoid fossa. this is class III malocclusion of genetic ori true Class III: - * following causes: 1. Excessively large mandible. 2. Forwardly placed mandible. 3. Smaller than normal maxilla. 4. Retro positioned maxilla. 5. Combination of the above causes. postural pre bite of accommodation, pseudo Class III, - * The lower dental arch is postured forward in relation to the upper dental arch while the condyles are outside their normal position within the glenoid fossa. It may be the result of premature loss of both upper and lower 2 will protrude the mandible to bring lower posterior part in contact with the upper to achieve bite of comfort. This can be differentiating from true Class III by: 1. The mandible can assume a normal mesio distal relationship by manual retrusion of mandible. 2. The condyles are in forward position outside glenoid fossa with the teeth in occlusion. 3. There may be labial inclination of lower incisors due to pulling action of muscles to retrude the mandible to its original position and also this may be cause some lingual inclination of upper incisors. II: I (mesio occlusion ) st permanent molar and mesial aspect of mesial nd gin that can occur due to the - normal occlus ion : n d deciduous molars as the child Normal and Abnormal Occlusion Normal and Abnormal Occlusion f for G.P or G.P Dr. Mohammed Alruby Dr. Mohammed Alruby

10. 10 Class III subdivision other side - * : The molar relationship is Class III on one side and Class I on the Skeletal malocclusion: They are malocclusions caused due to abnormalities in the maxilla or mandible. The defect can be in size, position or relationship between the jaws. The skeletal malocclusions can also occur in the three planes of space namely sagittal, vertical, and transverse plane. In the sagittal plane, the forward placement of jaw is referred to as prognathism while retrognathism refers to a more backward placement of jaw. These sagittal abnormalities can occur in one or both the jaws and can occur in various combinations. Skeletal malocclusions in the transverse plane are usually a result of narrowing or widening of the jaws. They can be described as narrow maxilla, wide mandible etc. these transverse malocclusions are usually referred to as cross bites. In the vertical plane abnormal variations in the vertical measurements of the jaws can affect the lower facial height. Normal development of dentition and occlusion : Deciduous dentition stage Eruption of deciduous teeth beings usually at 6 to 7 months and complete between 2, 5 to 3 years. mandibular central incisors (6 : Sequence of eruption molars (15months), canines (18months), and second (8months), lateral incisors (9months), 1 molars (30months). By about 2.5 years the deciduous teeth is usually complete and in full function, the jaw of the child contain the calcifying crowns of all the permanent teeth with the . molars exception of the permanent 3 The deciduous teeth are usually spaced; the spaces in the incisor region are present to allow for the difference in size between the deciduous incisor and their permanent successors. Two distinct spaces can be observed one between the mandibular deciduous canine and the 1 molar and the other between the maxillary lateral deciduous incisor and the deciduous canine, these two spaces are termed primate spaces. With the eruption of incisor teeth, the upper incisors overlap the lower incisor teeth (deep over bite), and characterized by slight over jet. This deep overbite is reduced by the eruption o f the deciduous molars, at the age of about 5 years, the occlusal surfaces of the primary teeth wear to - 7 months), maxillary central incisors st rd st deciduous Normal and Abnormal Occlusion Normal and Abnormal Occlusion f for G.P or G.P Dr. Mohammed Alruby Dr. Mohammed Alruby

11. 11 the extent that, the incisor relationship end with an edge to edge bite. This edge to edge bite occurs among people whose diet includes coarse rough food. The removal of cuspal interferences permits the mandible which is growing more at this age than the maxilla to assume a forward position more easily. Two types of occlusion considered normal, one in which the canine and the posterior teeth to it are in a cusp to cusp relationship, and the other with cuspal relationship resemble that in the permanent dentition, the maxillary canine occlude distal to the mandibular canine and mesial to the deciduous first molar. The distal surfaces of the upper and lower second deciduous molars may end of the same vertical plane, mesial step, distal step. The occlusal relationship remains unchanged during development and the arches are comparatively constant from 3.5 years until beginning of eruption of the permanent teeth. : this is the distance from the distal surface of the 2 Arch length or arch circumference deciduous molar alongside to the distal surface of the 2 diminishes with age from 3 to 6 years due to mesial migration of the 2 inter-proximal attrition and inter-proximal cavities. Mixed dentition stage: This stage start from 6years of age until all the deciduous teeth have been shed, the most common sequence of eruption in the maxillary and mandibular teeth are the following: . permanent molars The mandibular 1 - 1 . permanent molars The maxillary 1 - 2 3-the mandibular central incisors. 4-The maxillary central incisors. 5-The mandibular lateral incisors. 6-The maxillary lateral incisors. . premolars The maxillary 1 - 7 8-The mandibular canines. . premolars The mandibular 1 - 9 . premolars maxillary 2 The - 10 11-The maxillary canines. . premolars The mandibular 2 - 12 premolars, the mandibular permanent teeth erupt ahead the maxillary 2 With the exception of of the maxillary teeth. There are two different mechanisms of normal occlusal adjustment as the deciduous dentition enters the mixed dentition until the permanent dentition is established. deciduous molars is distal to that of the lower 2 When the distal surface of the maxillary 2 - 1 molars erupt directly in the proper position the permanent 1 molars; deciduous position of deciduous teeth. When the distal surfaces of both upper and lower - 2 molars occlusion is affected by an early me plane, normal permanent 1 deciduous molars closing the primate space distal to the mandibular deciduous canines. Or late nd molars after 2 mesial shift of the mandibular 1 e between the sum of the mesio premolars. This because the differenc the 2 nd nd deciduous molar on the other side. It deciduous molars, inter nd - st st st st nd nd nd nd nd st altering the nd 2 deciduous molars are in the same vertical sial shift of the st st deciduous molars are shed and the eruption of nd - distal dimensions of Normal and Abnormal Occlusion Normal and Abnormal Occlusion f for G.P or G.P Dr. Mohammed Alruby Dr. Mohammed Alruby

12. 12 the deciduous canines and molars, and that of their permanent successors. The mesio-distal dimension of the deciduous is greater than that of the permanent, by about 1.9 to 1.3mm in the in the mandible. The difference is known as .7 to 3.1mm maxilla and from 1 that is most important in normal occlusal adjustment of the 1 LEE WAY SPACE . st permanent molars The permanent maxillary incisors usually erupted fanning out and with median diastema, due to roots from the developing permanent canines, this is known as the pressure on their stage. The incisor position usually improved with the eruption o UCKLING D canines. UGLY - f the permanent The permanent mandibular incisors may show crowding at the time of their eruption and the permanent lateral incisors may overlap the deciduous canines. This crowded condition can be overcome by the lee-way space thus provided in addition to the usual increase in the inter-canine width, which is active during the eruption of the permanent incisors and canines. This increase is about 2.5 to 3.5mm from the age 6 to 8 years. Permanent dentition stage: At 14 years the 2 by the forward migration of the anterior two third of the facial mass and partially by the backward growth of the posterior third of the face. The 2 premolars and the mandibular before the maxillary one shortly after the 2 nd permanent molar is erupting. Thus space for these teeth is created principally nd permanent molars usually . erupt nd At 18 years the room of the third molars is now available and takes their way toward the occlusal plane, to complete the permanent dentition. Normal and Abnormal Occlusion Normal and Abnormal Occlusion f for G.P or G.P Dr. Mohammed Alruby Dr. Mohammed Alruby