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Dentistry > Orthodontics > Flashcards

Orthodontics Flashcards

(42 cards)

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1
Q

OverJet

A

The horizontal distance from the labial surface of the lower incisors to the palatal surface of the upper incisors.

Normal is 2-4mm

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2
Q

Overbite

A

The vertical distance from the incisal edges of the upper and lower central incisors.

Normal value: 2-4mm

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3
Q

Crowding - classification of severity

A

Mild <4mm
Moderate 5-9mm
Severe >9mm

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4
Q

Common developmentally absent teeth

A

Combined : 2% in caucasians

Lower Second Premolar
Upper Lateral Incisor
Upper second premolar
3 molars

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5
Q

Types of Supernumaries

A

Conical
Tuberculate
Supplemental
Odontome

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6
Q

Porion

A

Upper margin of boney external auditory meatus

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7
Q

Pogonion

A

Most anterior point of mandible/bony chin

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8
Q

Sella

A

Midpoint of the sella turcica i.e. the pituitary fossa (on lateral ceph)

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9
Q

Nasion

A

The intersection of the frontal bone and the nasal bones

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10
Q

Holdaway Line

A

A line drawn from the anterior soft tissue chin up through the upper and lower lips

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11
Q

Rickett’s E plane

A

A line drawn through the soft tissue chin up through the tip of the nose

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12
Q

Menton

A

Most inferior point of the anterior mandible at the symphysis

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13
Q

Gonion

A

The lowest point on the curvature of the angle of the mandible where the body of the mandible meets the ramus

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14
Q

ANS

A

Anterior Nasal Spine

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15
Q

PNS

A

Posterior Nasal Spine

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16
Q

A Point (sub-spinale)

A

Deepest point of the curvature of the anterior maxilla (between the ANS and the alveolar crest of the upper central incisor)

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17
Q

B Point (sub-mentale)

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A

The deepest point on the curvature of the anterior mandible (between the pogonion and the alveolar crest of the lower central incisors)

18
Q

Maxillary Plane

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A

A plane from the ANS to the PNS

19
Q

Mandibular Plane

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A

Gonion to Menton

20
Q

Functional Occlusal Plane (FOP)

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A

A line passing through the occlusion of the premolars (or Es) and the permanent molars

*Used in WITS analysis

21
Q

Frankfort Plane

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A

A line drawn from the porion (most superior part of the boney EAM) to the orbitale (the most inferior portion of the orbital rim)

22
Q

ANB angle

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A

The angle from point A to the Nasion to point B

Calculated by determining the difference between the SNA and the SNB

2-4 degrees = skeletal base I
>4 degrees = skeletal base II
<2 degrees = skeletal base III

23
Q

SNA/SNB compensation for sella or nasion abnormality

The Eastman Correction

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A

First ensure the position of the sella is normal:
Measure angle SN to maxillary plane which should be 8deg +/- 3deg

SNA normal value is 81 degrees (caucasian)

For every degree > 81deg subtract 0.5deg from SNB

For every degree < 81deg add 0.5deg to SNB

24
Q

The Eastman Analysis

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A

SNA and SNB
Determine ANB

Apply Eastman Correction

Draw mandibular plane (Go-Menton)
Draw maxillary plane (ANS to PNS)
Angle between them is MMPA
Measure the lower face height
Assess angulation of Incisors
Measure inter-incisal angle
25
Maxillary-Mandibular Plane
27deg +/- 4 If this angle is significantly >32 deg then lower facial height is increased If this angle is < 23 then the anterior lower facial height is reduced
26
Lower face height percentage
Should be 55% Lower third should be 33% or equal to midface
27
Angulation of Incisors
Measured by drawing a line through the long axis of the tooth and the respective alveolar plane Upper incisors = 109deg Lower incisors = 93 deg If the angles are reduced then the teeth and retroclined vs increased and they are proclined N.B. The lower incisal angle is inversely proportional to the MMPA i.e. is 93 deg where the MMPA is 27deg
28
Inter-incisal angle
Intersection of the long axes of the upper and lower incisors = 133-135 deg
29
SNA
Gives the AP position of the maxilla Normal value is 81deg
30
SNB
Gives the AP position of the mandible Normal value is 78 deg
31
African Variation in Eastman Analysis
SNA - 85 SNB - 80 ANB - 5 MMPA - 28 Upper incisal angle 118 Lower incisal angle 96
32
Chinese variation in Eastman Analysis
SNA- 83 SNB- 80 ANB- 3 MMPA- 28 Upper incisal angle- 113 Lower incisal angle- 96
33
Ballard’s Conversion Tracing
The Lines are drawn as for measuring incisal angles The upper incisor is then tipped to it’s ideal 109deg about a point 1/3 from it’s root apex The lower incisor angle and the MMPA need to equal 120deg This new ideal position of the lower incisor is drawn and projected until it meets the upper incisor This will represent the angles incisor classification and removes any dental compensation
34
WITS analysis
1. Uses the FOP 2. A perpendicular line drawn from A point to the FOP 3. A perpendicular line drawn from B point to the FOP 4. Measure the difference between where these lines meet the FOP Within 1mm = skeletal I If A-FOP is >1mm ahead of B-FOP = skeletal II If B-FOP is >1mm ahead of A-FOP = skeletal III
35
Index of Orthodontic Treatment Need (IOTN)
To determine need for orthodontic treatment 2 elements: ``` Dental component (1-5) Aesthetic component (1-10) ```
36
IOTN dental component grading
Grade 2-5 Increased over jet (lip competence) Grade 2-4 ``` Reverse overjet (S&M difficulties) Overbite (ST trauma) Crossbite Open bite Displacement ``` ``` Grade 4 Reverse overjet with S&M difficulty Lingual crossbite Impacted partially erupted teeth Uncomplicated Supernumerary teeth ``` Grade 4 and 5 Hypodontia Grade 5 Impeded eruption of teeth Submerged deciduous teeth Cleft lip and palate
38
IOTN grade 1 No treatment need
Extremely minor malocclusion including displacements of <1mm
39
IOTN Grade 2 Minimal need for treatment
Increased overjet 3.5mm to 6mm with competent lips Reverse Overjet 0-1mm Anterior or posterior crossbite of <1mm Anterior or posterior open bite 1-2mm Increased overbite >3.5mm (no gingival contact) Displacement of teeth 1-2mm *uncomplicated pre or postnormal occlusions
40
IOTN grade 3 Borderline need for treatment
Increased overjet 3.5mm to 6mm but with incompetent lips Reverse overjet 1-3.5mm Anterior or posterior crossbites 1-2mm Lateral or anterior open bite 2-4mm Increased and incomplete overbite without gingival trauma Displacement of 2-4mm
41
IOTN 4 Treatment required
Increased over jet >6mm (but <9mm) Reverse overjet 1-3.5mm (with S&M issues) Reverse overjet >3.5mm (with no S&M issues) Anterior or posterior crossbites >2mm Lateral or anterior open bites >4mm Posterior lingual cross bite (with no functional buccal contact) Increased and complete overbite with ST trauma Displacement of >4mm Mild to mod hypodontia (less than one tooth in each quadrant) Partially erupted teeth, tipped and impacted against other teeth Existing supernumerary teeth
42
Leeway space
Surplus space for the permanent successors (3,4 & 5) left by the discrepancy in width with the deciduous predecessors (c, d & e) 1-1.5mm in the maxilla 2-2.5 in the mandible
43
IOTN 5 Treatment Required
Increased overjet >9mm Reverse overjet >3.5mm With speech or masticatory difficulties Extensive hypodontia (>1 tooth missing per quadrant) Impeded eruption of any teeth for any cause (except 3rd molars) Submerged deciduous teeth Cleft lip and palate

Dentistry (1 decks)

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