Oral Anatomy & Histology (Review: Outcome 5 & 6) Flashcards
What are the 3 dentition periods?
- Primary
- Mixed
- Permanent
Primary Dentition
- 20 primary teeth
- Also referred to “baby teeth” or “deciduous dentition”
- 10 Maxillary teeth
- 10 Mandibular teeth
- Includes: Incisors, canines, molars
- FDI: 5 to 8 (quadrants)
Mixed Dentition
- Occurs between ages 6 to 12 years
- Both primary and permanent teeth are present
- Period begins with eruption of the 1st PERMANENT tooth (PERMANENT MANDIBULAR FIRST MOLAR)
- Period ends with shedding of the last primary tooth
Permanent Dentiton
- Final or adult dentition
- Period begins with shedding of last primary tooth
- Growth of jawbones slows and eventually stops (puberty has passed)
Primary Teeth Eruption
The actual dates are not as important as the eruption sequence because there can be variation in the actual dates of eruption
- Sequence tends to be uniform
Eruption sequence > actual dates
How long does primary teeth take to develop completely?
Completed between 2 and 3 years
Compare the Primary and Permanent Dentition
Primary:
- Crown of any tooth is short in relation to its total length; also narrower at CEJ, making them appear bulbous
- Smaller overall
- Roots are narrower and longer than crown length
- Crown-to-root ratio is smaller than permanent
- Enamel is thinner
- Pulp chambers and pulp horns are relatively larger than permanent
- Whiter in colour; permanent is yellower
Primate Spaces
Spaces between:
- primary maxillary lateral incisors & canine
- primary mandibular canine and first molar
Leeway Space
Spaces between first and second primary molars
- Allow an extra margin of space for the eruption of permanent cuspid, first and second bicuspid
Clinical Considerations with Primary Teeth & Why they are important
- Primary teeth hold the eruption space for the permanent tooth
- because enamel and dentin are thinner in primary teeth, decay can travel quickly through the enamel to the pulp, possibly causing loss of the tooth
- Early dental health education and dental care are essential in keeping the primary dentition
Which primary tooth is the first to erupt?
Mandibular central incisor
How do primary incisors differ from their permanent successors?
Primary incisors have no mamelons
Characteristics of Permanent Anterior Teeth
- 12 anterior teeth, 6 in each arch
- Central incisors, Lateral incisors, canines
- ALL anterior teeth are succedaneous, replacing primary teeth of the same type
- ALL anterior teeth have: cingulum, marginal ridges, and some have a fossa
Permanent Incisors
- 8 permanent incisors
- 4 Maxillary, 4 Mandibular
- These teeth completement each other in form and function
- Central incisors erupt about a year or so before lateral incisors
Maxillary Central Incisors
- Larger in all dimensions, especially mesiodistally than mandibular central incisors
- Root is short compared with the other maxillary teeth
- Lingual surface features (marginal ridges, lingual fossa, cingulum) more prominent on maxillary than mandibular central incisors
- Newly erupted - incisors have 3 mamelons (undergo attrition after eruption)
Maxillary Lateral Incisors
- Smaller than central incisors in all dimensions except root length
- Erupt after Max. central incisors
- Crown has single root - relatively smooth and straight, but may curve slightly distally
Diastema
Open contacts (spaces between teeth)
- Often occur in Maxillary lateral incisors because of variations in tooth size and position in arch
Canine eminence
The large root that is externally manifested by the bony vertical ridge
Clinical considerations with canines
- Maxillary canines may erupt labially or lingually in relation to the surrounding teeth
- Maxillary canines maay also fail to erupt fully and may remain impacted
- This occurs because they erupt after the max. incisors and possibly after premolars and their arch spaces have closed
What are the differences Between Second
and First Maxillary Premolars?
- The cusps are closer in length on the second premolar
- The lingual cusp is slightly shorter, but not as short as
the cusp on the maxillary first premolar - The mesiobuccal cusp slope is shorter than the
distobuccal cusp slope on the second premolar - The cusps of the secondary premolar are not as sharp as those of the maxillary first premolar
- The second premolar has only one root and one root
canal - The second premolar is wider buccolingually than
mesiodistally
Clinical considerations with premolars
- The maxillary and mandibular premolars work
with the molars in the chewing of food - The first premolars help the canines in shearing or
cutting bits of food - The premolars also support the corners of the
mouth and cheeks
Clinical Considerations with Maxillary Molars
- The roots may penetrate the maxillary sinus as a result of accidental trauma or during an extraction
- The third molars may fail to erupt and may remain impacted within the alveolar bone
- If the maxillary first molar is lost, the second molar
can tip and drift into the open space, causing
difficulty in chewing and furthering periodontal
disease
Clinical Considerations with Mandibular Molars
- The lingual inclination of the crowns of the
mandibular molars can make it difficult to position
the oral evacuator - The lingual inclination of the molar teeth can also
pose problems in oral hygiene for patients, who
may miss the lingual gingiva with the toothbrush
Occlusion
Relationship between maxillary an mandibular teeth when upper and lower jaws are fully closed and relationship between teeth in the same arch
Malocclusion
Abnormal or malposition relationships of maxillary teeth to mandibular teeth when they are in centric occlusion
Centric Occlusion (CO)
The voluntary position of the dentition that allows the maximum contact when the teeth occlude
- Each tooth of one arch is in occlusion with two others in the opposing arch, except for mandibular central incisors and max. 3rd molars
Centric Relation (CR)
The end point of closure of the mandible; the mandible is in the most retruded position to which it can be carried by the musculature and ligaments
- Ideally, when mandible is in CR, the dentition should be in CO (CR = CO) –> but it’s not
- Independent of tooth contact
Curve of Spee
When the maxillary and mandibular teeth come into CO, they align along anteroposterior and lateral curves.
- This is produced by the curved alignment of all the teeth and is especially evident when viewing the posterior teeth from the buccal view
Overjet
When the teeth usually occlude in CO, the maxillary arch HORIZONTALLY OVERLAPS the mandibular arch
- Measured in millimeters with tip of periodontal probe once patient is in CO (accurate measurement)
- Probe placed at 90 degrees to the labial surface of Mand. incisors at the base of incisal ridge of Max. incisor
Overbite
In CO, the maxillary arch VERTICALLY OVERLAPS the mandibular arch
- The amount of vertical overlap (usually 2-5mm between anterior sextants of the 2 arches) allows contact between posterior teeth during mastication
- Usually expressed as a percentage at around 20-30% (guesstimate)
Severe Overbite (Deep overbite)
When the maxillary arch and its incisors have a more pronounced overlap with the mandibular arch and its incisors
Underbite
The mandibular arch and its incisors extends beyond the maxillary arch and its incisors
Crossbite
Occurs when a mandibular tooth or teeth are placed facially to the maxillary teeth
Openbite
Teeth do not occlude
End-to-End Bite
Teeth occlude without the maxillary teeth overlapping the mandibular teeth
Malocclusion Classification
- The Angle of classification of malocclusion DOES NOT describe normal or even ideal occlusion, ONLY MALOCCLUSION of the molars and canines
- Grouped into 3 main classes, according to the position of the permanent maxillary first molar to the mandibular first molar
- Classification system based on relationship of teeth and NOT the skeletal considerations that are due to the disproportionate size or position of the jaws
- 3 classes by Roman numerals; assume that both sides of dentition are affected equally unless specifically noted (separate defining classifications can be made depending on which side is affected)
Gnathic Index (Malocclusion)
- Each type of facial profile present can be measured by the gnathic index
- This measurement gives the degree of prominence of the maxillae as opposed to the mandible
- 3 types:
i. Mesognathic
ii. Retrognathic
iii. Prognathic
Class I Malocclusion (neutroclusion)
- Characterized by an ideal MD relationship of the jaws and dental arches
- The MB cusp of the Max. first molar occludes with the MB groove of the Mand. first molar
- Due to dental malalignments (e.g. crowding; “crooked teeth”) or irregular spacing withing the jaws
- Patients usually have a facial profile Mesognathic
Mesognathic
The facial profile in CO has slightly protruded jaws, giving the facial outline a relatively flat appearance or straight profile
Class II Malocclusion (Distoclusion)
- Characterized by the MB cusp of Max. first molar occluding (by more than width of a premolar) mesial to the MB groove of the Mand. first molar
- 2 subgroups: Division I & Division II (based on position of anterior teeth, shape of palate, & resulting facial profile)
Class II Malocclusion - Division I
- Facial profile shows a protruding upper lip or recessive mandible resulting in a convex profile
- Retrognathic (Facial profile)
Class II Malocclusion - Division II
- Facial profile is usually mesognathic profile, often with a prominent mandible
Class III Malocclusion (Mesioclusion)
- Characterized by the MB cusp of Max. first molar occludes (by more than width of premolar) distal to the MB groove of Mand. first molar
- Prognathic profile
Prognathic
Facial profile that shows a rather prominent mandible and possibly a retrusive maxillae, resulting in a concave profile
Retrognathic
Facial profile shows a protruding upper lip or recessive mandible resulting in a convex profile
Terminal Plane
The ideal molar relationship in primary dentition when in CO.
Flush Terminal Plane
Primary maxillary and mandibular second molars are in an end-to-end relationship
Mesial Step
The primary mandibular second molar is mesial to the maxillary second molar
- Individuals with mesial step less than 2mm, Angle Class I molar relationship will result
Distal Step
- Primary mandibular second molar is distal to the maxillary second molar
- Not an ideal molar relationship in primary dentition & thus is not a type of terminal plane relationship
