1. Introduction to Oral & Dental Anatomy and Morphology 13
Dr Jamal Naim
PhD in Orthodontics
Introduction to Oral & Dental Anatomy and Morphology 13

2. Occlusion

3. Definition Occlusion is an act and state.
J. Naim-Faculty of Dentistry-University of Palestine
Definition
Occlusion is an act and state.
Act: The bringing of the opposing surfaces of the teeth of the two jaws into contact;
State: The relation between the maxillary and mandibular teeth surfaces when in contact.

4. Ideal Occlusion versus Malocclusion
J. Naim-Faculty of Dentistry-University of Palestine
Ideal Occlusion versus Malocclusion
Ideal occlusion is the harmonious static and dynamic relationship of teeth and jaws guarantying good form and function.
Malocclusion, the deviation of ideal occlusion, can be due to an improper alignment of teeth, disharmony of jaws that prevents teeth from occluding ideally.

5. Development of occlusion
J. Naim-Faculty of Dentistry-University of Palestine
Development of occlusion
Human oral functions that are acquired or modified during the natural progression from birth through infancy to adulthood are in part related to the development of occlusion, both of the deciduous and permanent teeth.

6. Development of occlusion
J. Naim-Faculty of Dentistry-University of Palestine
Development of occlusion
Breast feeding versus bottle feeding.
Habits during infancy and childhood: thumb and lip sucking, tongue thrusting, mouth breathing etc.
Habits in adulthood: bruxism, clenching, mouth breathing etc.

7. Development of occlusion
J. Naim-Faculty of Dentistry-University of Palestine
Development of occlusion
The learning of mastication may be highly dependent on the stage of development of the occlusion (type and number of teeth present), maturation of the neuromuscular system, and factors such as diet.

8. J. Naim-Faculty of Dentistry-University of Palestine
Primary occlusion
An outline following the labial and buccal surfaces of the maxillary teeth describes the segment of an ellipse and is larger than the segment following the same surfaces on the mandibular teeth.

9. J. Naim-Faculty of Dentistry-University of Palestine
Primary occlusion

10. J. Naim-Faculty of Dentistry-University of Palestine
Primary occlusion
The relation between the maxillary and mandibular primary teeth when in occlusion is such that each tooth occludes with two teeth of the opposing jaw.
The exceptions are the mandibular central incisor and the maxillary second molar.

12. J. Naim-Faculty of Dentistry-University of Palestine
Primary occlusion
The primary teeth should be in normal alignment and occlusion shortly after the age of 2, with all the roots fully formed by the time the child is 3 years old.

13. J. Naim-Faculty of Dentistry-University of Palestine
Primary occlusion
A year or so after the teeth have fully erupted and have assumed their respective positions in the arches, the rapid development of the jaws is sufficient to create an interdental space, or diastemata, between some of them:
Diastema
Primate spaces

14. J. Naim-Faculty of Dentistry-University of Palestine
Primary occlusion
The canines and molars are supposed to keep their positive contact relation during all the jaw growth keeping the jaws in good relationship.
Around 6 years the occlusion is supported by the eruption and occlusion of the first permanent molars.

15. J. Naim-Faculty of Dentistry-University of Palestine
Contact relations
A number of factors affect the development of contact relations, including:
the position of the tooth germ,
presence of permanent teeth,
development of the condyles,
cuspal inclines, and
neuromuscular influences.

16. J. Naim-Faculty of Dentistry-University of Palestine
Interdental spacing
The size of the primary teeth and the spacing between them has a relationship to the size of the dental arches.
One of the indicators of future sufficiency of space in the dental arches for the permanent teeth is the presence or absence of spacing between the teeth of the primary dentition.

17. J. Naim-Faculty of Dentistry-University of Palestine
Interdental spacing

18. Molar relationship in primary dent.
J. Naim-Faculty of Dentistry-University of Palestine
Molar relationship in primary dent.
Primary molar relationships have been described by Moyers as the:
flush terminal plane,
mesial step, and
distal step

19. Molar relationship in primary dent.
J. Naim-Faculty of Dentistry-University of Palestine
Molar relationship in primary dent.
Normally :
the mesiolingual cusp of the maxillary 1st molar occludes in the central fossa of the deciduous 1st mandibular molar.
The mesiobuccal cusp occludes in the buccal groove of the deciduous mandibular molar

20. Details of Primary Occlusion
J. Naim-Faculty of Dentistry-University of Palestine
Details of Primary Occlusion
The normal occlusion of the primary teeth at the age of 3 years is as follows.
Mesial surfaces of maxillary and mandibular central incisors are in line
with each other at the
median line.

21. Details of Primary Occlusion
J. Naim-Faculty of Dentistry-University of Palestine
Details of Primary Occlusion
The maxillary central incisor occludes with the mandibular central incisor and the mesial third of the mandibular
lateral incisor.

22. Details of Primary Occlusion
J. Naim-Faculty of Dentistry-University of Palestine
Details of Primary Occlusion
The mandibular anterior teeth contact the maxillary anterior teeth lingually above the level of the incisal ridges.

23. Details of Primary Occlusion
J. Naim-Faculty of Dentistry-University of Palestine
Details of Primary Occlusion
The maxillary canine occludes with that portion of the mandibular canine distal to its cusp tip and the mesial third of the
mandibular first molar.

24. Details of Primary Occlusion
J. Naim-Faculty of Dentistry-University of Palestine
Details of Primary Occlusion
The maxillary first molar occludes with the distal two thirds of the mandibular first molar and the mesial portion of the
mandibular second molar.

25. Details of Primary Occlusion
J. Naim-Faculty of Dentistry-University of Palestine
Details of Primary Occlusion
The maxillary second molar occludes with the distal surface of the maxillary molar projecting slightly over the distal
portion of the mandibular
second molar.

26. Occlusion
Mixed (Transitional) stage

27. Mixed (transitional) Stage
J. Naim-Faculty of Dentistry-University of Palestine
Mixed (transitional) Stage
The transition from primary to permanent dentition begins at about 6 years of age with the emergence of the mandibular permanent central incisors or the first permanent molars at 6 to 7 years of age.

28. Mixed (transitional) Stage
J. Naim-Faculty of Dentistry-University of Palestine
Mixed (transitional) Stage
The timing of the shedding of the primary teeth has an effect on the emergence of the permanent teeth (i.e., early shedding of primary teeth advances the emergence of the permanent teeth).

29. Mixed (transitional) Stage
J. Naim-Faculty of Dentistry-University of Palestine
Mixed (transitional) Stage
The growth of the jaw provides space for the teeth to erupt and emerge into the mouth.
The anterior part of the alveolar process grows in anterior direction during the eruption of the incisors>>>>> increase in arch length

30. Mixed (transitional) Stage
J. Naim-Faculty of Dentistry-University of Palestine
Mixed (transitional) Stage
An important portion of the dental arch in the development of the occlusion of the permanent dentition is the premolar segment.
The erupting premolars are significantly smaller in mesiodistal dimension than the primary molars, which they replace.

31. Mixed (transitional) Stage
J. Naim-Faculty of Dentistry-University of Palestine
Mixed (transitional) Stage
Leeway Space: The arch circumference difference between the primary canine, first primary and second primary molars, and the permanent canine and the first and second premolars. According to Black’s means, the maxillary arch leeway space is 1.9 mm, and the mandibular arch leeway space is 3.4 mm/quadrant.

32. J. Naim-Faculty of Dentistry-University of Palestine
Leeway space

33. Mixed (transitional) Stage
J. Naim-Faculty of Dentistry-University of Palestine
Mixed (transitional) Stage
A transpalatal width increase of 2.5 to 3.0 mm occurs in untreated persons from 7 to 15 years of age.