Today we are going to talk about the local dental factors . This slide is very imp., it indicate that the malocclusion is multifactorial. So local factors are: 1-abnormalities in tooth size, number and form. 2-premature loss of primary teeth. 3-loss of permanent teeth. 4-prelonged retention of primary teeth. 5- abnormal development in position of tooth germs. 6-sucking habit. 7- large persistent labial frenum. We talked about sucking habit and large persistent labial frenum. So lets start with :

abnormalities of both size, number and form: small teeth which called microdontia result in spacing , because its small. Large teeth on the opposite way may result in crowding. Supernumerary teeth: an extra teeth which account about 1%, have many complications we will talk about them later. Missing teeth or congenitally missing teeth, called hypodontia which account for 6%, it may result in spacing if left missing ,however if the space grow prematurely it will not result in space. Abnormal forms: 1-dense in dentin 2-dilaceration 3-gemination

A-supernumerary teeth: account about 1%, males have supernumerary teeth more than females. The etiology : extra teeth is excessive dental activity however its organized growth of the dental lamina. Types of supernumerary teeth: 1- conical 2-tuberculate 3-supplemental 4-Odontomes

1-conical or mesiodens: usually its inverted and often found in middline, formed early and may erupt causing displacement. You will see a radiographs with supernumerary teeth mesiodens erupted. 2-tuberculate: formed late and usually it does prevent the eruption of upper incisors, usually its in pairs. 3-supplemental: identical and often found at end of the series. Identical: its similar to the adjacent tooth, to the last teeth in the series, Lateral incisor is the most common supplemental tooth. Lateral incisor is the end of incisor series, and you may found a supplemental lateral incisor which identical to lateral incisor, however its extra so instead of 4 incisors :2 centrals and 2 laterals you may found 5,

one extra lateral incisor in one side, of course its cause crowding bec there is extra tooth. 4-odontomes: which either complex or compound. What is the difference between complex and compound odontom? [Ans: compound odontoma: An odontoma in which the odontogenic tissues are organized and bear a superficial resemblance to teeth , but complex odontoma:in which the various odontogenic tissues appear in a haphazard arrangement that bears no resemblance to teeth. Dr ans. :tooth form or non tooth form.

Why supernumerary teeth are considered as etiological factors of malocclusion? Can you see this mesiodense? Its erupting, in this case the mesiodense prevent central upper incisor from erupting. So the consequences of supernumerary teeth may result in: 1-midline diastema like first 2 photos.2-crowding. 3-delayed eruption of central incisors. 4-malposition of central incisors. 5-root resorbtion of central incisors. 6-cystic formation.

B-hypodontia or congenitally missing teeth.

it accounts for 6%, at order: 1-3rd molars, usually its the most common missing tooth. 2-mandibular 2nd premolar. 3-lateral incisor. 4-maxillary 2nd premolar. 5-mandibular central incisor. So missing teeth may result in spacing.

A)lateral incisor: the case in(p.5 slide1),on the right. Its more unilateral than bilateral. It can affect the path of eruption of the canine, usually if lateral incisor is missing there is a great risk that the adjacent canine on that side will be palataly impacted, its 2.5 more times than normal patient without missing lateral incisor , why? Because one of the theories behind the palatal impaction of maxillary canine is the guidance theory which states that the distal side of the lateral incisor root will act as a guide of canine eruption, if this guide is no more available then canine eruption may be affected. Repeat : one of the theories called maxillary canine impaction is the guidance theory which states that dental aspect of the lateral incisor root acts as a guide for the canine eruption, if there is no guidance anymore the eruption will be affected.

b)missing mandibular 2nd premolar : it may result in 1- spacing (like p.5 slide2). 2-over eruption of opposing tooth So if you need to put prosthesis you may need to protrude this tooth, in this case its not so sever, but there are many cases with severe over eruption of the opposing teeth. In retained deciduous 2nd molar :in this case upper E still retain and it submerge or intra occluded.

C) variation or abnormalities of tooth form:

Like gemination or fusion. What is fusion and what is gemination? The key point is the number. In case of gemination you will find extra tooth geminated with its adjacent tooth. In fusion its the same number with fused 2 teeth, if you will considered the fused 2 teeth as one tooth its less than one. (p.6 slide 1), in this case its gemination because this is the central and this is the lateral and there are 2 teeth geminated together. So one tooth bud divide into 2 teeth, the result is one big tooth so this is gemination, if you count the tooth adjacent to the tooth you will found that the central is there and lateral is there , however there are 2 centrals geminated together. In case of fusion you may found that the 2 centrals fused together, so this is the difference between germination and fusion.

Student asked: what about the roots? Gemination: maybe one root but there is identication indicates that there are 2 roots

,like the crown. geminated together, one root Most likely to affect upper or lower incisor, the effect is crowding and esthetic complication.

B)Premature loss of primary teeth: Why its serious problem to have premature loss of primary teeth? Usually the most commonly loss teeth are the molars: 1-primary 2nd molars 2-primary 1st molars 3- canine For the primary 2nd molar and primary 1st molar the most common cause for premature loss is : dental caries. However for the canine the most common cause is: root resorbtion from the adjacent crowded lateral incisors.

1- 2nd primary molar : if its lost before eruption of 6s, 6s will erupt in amore ant. Position, so there will be a loss of space and this will result in crowding or may result in impaction of the adjacent 5, because 5 have no space to erupt in. so either it erupts palataly in a crowded position or it will not erupt and stay impacted tooth. If after eruption of 6s there will be a mesial tipping of lower 6s and mesial rotation of upper 6s. why rotation in the upper and tipping in the lower ? bec of the morphology of the roots: In upper: the upper 6 has big palatal root, so the movement around that axis in form of rotation. Repeat: mesial tipping of lower 6s and palatal rotation of upper 6s, and again it will result in space loss and crowding.

As a treatment either you close the space and extract 5 or regain the space by opening it.

2- 1st primary molars: again 6s and Es will drift mesially. Because this is the normal expected movement , post. Teeth move forward bec of occlusal forces.

result in centerline shift. mayIf unilateral In the the upper arch usually upper 4s erupt before upper 3s so if the D (1st primary molar ) is lost prematurely this may enhance the upper 4s to erupt. If this happen and the space lost by the mesial drifting of the post. teeth the upper canine will be shortage of space so either it will erupt buccally in a crowded position or it will be impacted. In the lower arch usually 3s erupt before 4s, so if the Ds is lost this may enhance the canine to erupt first and to relieve the ant. Crowding however 4s will be crowded or impacted.

3-primary canines: we Saied the most common cause for pre mature loss is root resorbtion from the adjacent lateral incisor. Not all lat. Incisors cause root

resorbtion but crowded lateral incisors may cause it. root Why? Because usually lat. Incisors develop palatal. So mostly as a result of root resorbtion by crowded lateral incisors may result in canine crowding, yes bec if they lost prematurely, space loss and canine crowding or impaction, if unilateral it will affect the midline or the center line. The more ant the tooththe more the effect on the midline. Thats why before a minute in the upper first primary molar I put question mark may have effect on the center line.

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