Chapter 10: Growth and Development/Management of the Developing Occlusion Flashcards
Two types of bone formation
Endochondral
Intramembranous
Endochondral bone formation
Bony replacement of cartilaginous precursors
Cranial bse and condyle of the mandible
Less modifiable in context of dentofacial orthopedics
Intramembranous bone formation
Secretion of bone matrix without cartilaginous precursors
Facial bones (maxilla, body of mandible)
More modifiable in context of dentofacial orthopedics
Does bone apposition occur in osteogenic areas under pressure or under tension?
Under tension
Growth of the Cranial Vault
Formed by intramembranous ossification
Apposition of new bone primarily at sutures
Remodeling on inner and outer surfaces of bones to allow for changes in contour
Growth of the Cranial Base
Formed by endochondral ossification
Bony replacement primarily at synchondroses
Spheno-occipital considered principal growth cartilage of cranial base and only one remaining active in childhood growth period
Growth of the Maxilla
Formed by intramembranous ossification
Apposition in superior and posterior sutures of maxilla
Resorption on anterior surface of maxilla
Balanced apposition and resorption
Appositional growth occurs up and back against cranial base with growth expressed down and forward
Growth of the Mandible
Formed by endochonral ossification at condyle, intramembranous at body
Endochondral replacement at fibrocartilage of condyle
Appositional growth predominates along posterior border of ramus, remodeling along anterior border
Appositional growth occurs up and back against glenoid fossa, with growth expressed downward and forward
How much sooner do females reach skeletal maturity compared to males?
2 years earlier on average
Female growth spurt
Starts at approximately 10.5-11 years
Peaks 14-18 months later (12-13 years)
Complete by about 13.5-14 years of age
Male growth spurt
Starts at approximately 12.5-13.5 years
Peaks in 18-24 months (14-16 years)
Complete by about 17-18 years of age
Hypodivergent/brachyfacial facial form
Posterior face height proportionately greater than anterior face height
Flat mandibular plane, pronounced overbite
Hyperdivergent/dolichofacial
Anterior vertical facial growth greater than posterior condylar growth
Steep mandibular plane with open bite tendency
Vertical dimension growth
Nasion-menton
70% complete by age 3; 90% by adolescent growth spurt
Transverse dimension growth (facial width)
The least amount of change of any facial dimension
Upper face width increases during childhood and adolescence with greatest rate observed between 2-6 years
Lower face width 85% complete by time first molars erupt
Anteroposterior dimension growth (facial depth)
Longest growing facial dimension
Greater mandibular increments allow profile to change from convex in childhood to straighter adult profile
Airway compromise/mouthbreathing impact on growth
May compromise facial growth
Increase vertical orientation
Similar occlusion changes as with extraoral habits
Management of mouthbreathing
Distinguish from extraoral habits
If airway related, refer to ENT assessment for allergy management, tonsillectomy/adenoidectomy followed by palatal expansion
Is there a recognized or specific standard for what type of diagnostic records are necessary for orthodontic problems?
No
General agreement that proper assessment includes questionnaire of patient, examination, as well as diagnostic records
2016 AAO list of pretreatment unaltered diagnostic records needed for comprehensive orthodontic treatment
Intra and extraoral images
Dental models of maxillary and mandibular arch
Intraoral and/or panoramic radiographs
Cephalometric radiographs, with CBCT used as alternative when necessary
Periodic radiographic assessment, such as panoramic, is recommended at what intervals during ortho treatment?
6-12 months
Recommended due to major problems such s external apical root resorption
Ceph: Maxilla to cranium
SNA
A point to Nasion
Ceph: Mandible to cranium
SNB
Pogonion to Nasion
Ceph: Maxilla to mandible
ANB
Mx-Mn length difference
Ceph: incisor position
Upper incisor to cranial base (Frankfort horizontal, S-N)
Lower incisor to mandibular plane (IMPA)
Upper and lower incisors to facial lines (NA, NB)
Ceph: growth direction
Mandibular plane angle (FMA)
Y-axis to cranial base
Lower face height
Ceph: soft tissue profile
Angle of facial convexity
Lip profile to E-line
Nasolabial fullness
Evaluating a Ceph
Head orientation: Frankfort horizontal plane should be perpendicular to vertical edge of film
Chin position: nasion to pogonion line (facial plane) should be parallel with vertical edge of film after growth is complete
Maxilla position: NA line should be parallel with vertical edge of film
Mandibular plane: Go-Gn should intersect with cranial outline at occiput
Maxillary incisor position: long axis should be tangent with orbitale
Mandibular incisor position: long axis should show proclination
Facial height: Upper face height (N-ANS) should be equal to lower face height (ANS-Me)
Eruption sequence of primary teeth
A-B-D-C-E
Both arches are this way
Primary teeth eruption timing (broad)
Erupt from 8 months (lower central incisors) to 30 months (upper second primary molars), S.D. of 3 months
By what age is primary dentition occlusal relationship established?
36 months
Baume Type I
Spaced primary dentition
Approximately 2/3 of kids
Baume Type II
Non-spaced primary dentition
Approximately 1/3 of kids
Primate Spaces
Mesial to upper primary canines in maxilla
Distal to lower primary canines in mandible
Molar terminal plane relationships frequencies
Mesial step: 14% incidence
Flush terminal plane: 76% incidence
Distal step: 10% incidence
Incisor relationships
Overbite: 2mm (30-50% vertical overlap)
Overjet: 0-3mm
Early Mesial Shift
Closing of interdental space between molars prior to eruption of permanent molars
Occurs due to eruption path of permanent molars which guide on distal roots of primary second molars
What age does early mesial shift occur?
Approximately 4 years of age
Eruption timing of permanent teeth (broad)
Permanent teeth erupt beginning at 6 years of age and is generally complete by 12 years of age upon eruption of maxillary canines and/or second permanent molars
Permanent teeth eruption sequence
Maxilla: 6-1-2-4-5-3-7
Mandible: 6-1-2-3-4-5-7
*Permanent mandibular arch is the only one that erupts in order of position (with exception of first molar of course)
What is the buccal segment in the transitional dentition?
Primary teeth that remain (C-D-E)
Incisor liability
Permanent incisors are larger than primary incisors
- 1mm in maxilla
- 1mm in mandible
Intercanine width expansion
Upper width: mean of 3.0mm
Lower width: men of 2.4mm
More labial eruption of permanent incisors increases arch perimeter
Permanent incisor relationships
Typically 1-2mm of lower incisor “crowding”
No spacing or crowding in upper incisor segment
“Ugly duckling” stage with splayed maxillary incisors considered normal
Overjet: range 0-3mm
Overbite: range 0-5mm
Permanent molar relationships - Class I
Considered ideal
Maxillary first molar mesial cusp in mandibular molar buccal groove
Occurs when primary molars are mild mesial step
Permanent molar relationships - End On Class II
Majority of mixed dentition occlusions
Occurs when primary molars are flush terminal plane
Permanent molar relationships - Full Class II
Maxillary first molar mesial cusp forward in embrasure between lower first molar and second primary molar or second premolar
Occurs when primary molars are distal step
Permanent molar relationships - Class III
Maxillary first molar mesial cusp distal to lower first molar buccal groove
Occurs when primary molars are more severe mesial step
Must discriminate from pseudo-class III with forward shift of mandible to exaggerate discrepancy
Leeway space
Size differential between primary C-D-E segment and permanent 3-4-5 segment
Upper leeway space: 0.9-1.1mm per quadrant
Lower leeway space: 1.7-2.4mm per quadrant
Late mesial shift
Mesial shift of permanent first molars into leeway space when second primary molars exfoliate Contributes to correction of typical flush terminal plane relationship into class I
Closure of maxillary diastema
Maxillary diastemata in mixed dentition typically close on eruption of maxillary canines
Ideal primary dentition occlusion
Flush terminal plane or mesial step molar with class I canines
Generalized spacing including primate spaces
2mm overjet, 2mm overbite (30%)
How does primary spcae affect rowding outcome in mixed dentition?
Spacing 3-6mm: no transitional crowding
Spacing less than 3mm: 20% incisor crowding
No spacing: 50% incisor crowding
Crowded primary teeth: 100% incisor crowding
Mesial step indication for permanent molar relationship
68% convert to class I 19% convert to class III Usually reflecting class III skeletal malocclusion
Flush terminal plane indication for permanent molar relationship
56% shift to class I 44% stay end-on or class II 15% reflect skeletal malocclusion involving mandibular retrognathia Canines also demonstrate class II positioning with pronounced overjet of 6mm+
DIstal step indication for permanent molar relationship
Usually results in full class II Some shift to end-on class II molars
Canine relationship in primary and permanent dentitions
Best predictor of sagittal relationship into permanent dentition Mesial step canines usually result in class I Distal step/end-on usually result in class II Excessive mesial step with incisor crossbite usually results in class III