dental, cephalometrics, orthognathic surgery, TMJ Flashcards
1
Q
Define apertognathia
A
Anterior open bite
2
Q
define centric occlusion
A
maximal intercuspation of maxillary and mandibular teeth
3
Q
Define centric relation
A
- the position of the mandible when the condyles are seated in their most posterosuperior unrestrained position in the glenoid fossa
4
Q
what is the first ADULT tooth to erupt?
A
1st mandibular molar
defines angle classification
5
Q
What is angle classification
A
- normal occlusion - mesiobuccal cust of 1st maxillary molar sits in the buccal groove of the 1st mandibular molar
- mesiobuccal cust of 1st maxillary molar sits mesial to bucchal groove of 1st mandibular molar
- mesiobuccal cusp of 1st maxillary molar sits distal to bucchal groove of 1st mandibular molar
6
Q
Define overjet & overbite
A
- overjet is the degree of anterior projection (horizontal plane) of the maxillary incisors relative to the mandibular incisors; normal is 2mm
- overbite is the degree of inferior overlap (vertical plane) of the maxillary incisors relative to the mandibular incisors with the mouth closed; normal is 2mm
7
Q
define prognathic
A
forward position of mandible relative to cranial base
8
Q
Define the following cephalometric landmarks:
- Frankfurt Horizontal
- Mandibular plane & angle
- Porion
- “S” point
- “A” point
- “B” point
- “N” point
A
- Frankfurt horiztonal is plane between the porion (below) and the orbitale (inferior orbital rim)
- Mandibular plane runs in the plane from the line between Menton (most inferior point of mandible) and Gonion (the curvature [angle of Md] between ramus & body)
- Mandibular angle is angle formed by intersection of FH and MP
- Porion - superior point of EAM
- “S” point is centre of pituitary fossa
- “A” point is subspinale - most inferior part of anterior maxilla just inferior to anterior nasal spine
- “B” point is supramentale - most inferior point of anterior mandble between infradentale and pogonion
- “N” point is nasion - most anterior point of NF suture in midsagittal plane
9
Q
What is a steep or shallow mandibular plane associated with?
A
- steep - class II, anterior open bite, short mandible
- shallow - class III, long mandible
10
Q
What does SNA and SNB represent?
A
- SNA demonstrates the anterior-posterior relationship of the maxilla to the cranial base
- measured by measuring angle from sella to nasion to “A” point
- normal 82’
- SNB demonstrates the anterior-posterior relationship of the mandible to the cranial base
measured by measuring angle from sella to nasion to “B” point
- normal 80’
11
Q
What are physical findings associated w/ vertical maxillary excess?
A
- excessive tooth or gingival show
- mentalis strain
- lip incompetence
12
Q
What is mandibular autorotation?
A
- mandible rotation that occurs to maintain occlusion with maxilla, after lefort 1 osteotomy
- with lefort 1 impaction, autorotation of mandible to more anterior position
- with lefort 1 inferior inferior displacement, autorotation of mandible to more posterior position
13
Q
What is the blood supply to the tooth bearing alveolar segment after a lefort 1?
A
- ascending paryngeal (palatine branch; from ECA)
- ascending palatine (from facial)
14
Q
Name the artery most likely to be accidentally injured during lefort 1 osteotomy and it’s location
A
descending palatine
posterormedial maxillary sinus
15
Q
which orthognathic movements are considered stable?
A
- maxillary impaction
- mandibular advancement
16
Q
what are orthognathic movements associated w/ intermediate stability
A
- maxillary impaction wiht mandibular advancement
- maxillary advancement with mandibular setback
- correction of mandibular asymmetry
17
Q
What are characteristically unstable orthognathic movements
A
- posterior positioning of mandible
- inferior position of maxilla
- transverse expansion of maxilla (lease stable)
18
Q
A
19
Q
draw a tooth
A
20
Q
List the stages of tooth development, embryologically
A
- IPHMAC
- Initiation - 6 wks
- Proliferation - focal proliferation of ectoderm (enamel) & mesoderm (dentin, cementin, pulp)
- Histodifferentiation - ameloblasts make enamel (ae), odontoblasts make dentin (OD)
- Morphodifferentiation - tooth takes shape of crown, root; local tissues form
- Appositional growth - dentin and enamel grow thicker (increase in layers) via appositional growth
- Calcification - tooth mineralizes
21
Q
What is the curve of spee? What is the curve of wilson?
A
- curve of spee is AP curve of mandibular occlusal surface of teeth during intercuspation
- curve of wilson is the anatomic curvature that contacts the buccal and lingual cusps of the molars in the coronal plane
22
Q
list indications and contraindications to osseointegrated implants
A
- indications
- good quality bone stock (can be augmented w/ autogenous bone graft ~ 6 mos prior if required)
- medically fit for multiple procedures
- good oral hygeine
- contraindications
- medically or psychologically unfit
- poor quality bone stock
- poor oral hygeine
- bone condition like fibrous dysplasia, osteoporosis, rickets, hyper PTH
- risk factors for poor wound healing (dm, smoking)
23
Q
list advantages and disadvantages to osseointegrated dental implants
A
- advantages
- best cosmesis
- best option for prothestic teeth
- does not rely on adjacent teeth for support/integration and does not downgrade status of adjacent teeth
- transmission of occlusal forces and therefore is not associated w/ disuse atrophy of mandible
- disadvantages
- very expensive
- success relies on excellent oral hygeine
- requires multiple stages
- failure rate of 1-2%
24
Q
list stages of osseointegrated implants
A
- pre-stage - autogenous cancellous bone graft 6 mos prior
- stage 1: elevate gingeval flap, drill bone canal, insert stem, cover w/ plug, close gingeva
- stage 2: confirm bone ingrowth; switch plug for temporary abutment with adjacent gingeva closed around
- stage 3: temporary abutment removed, permanent abutment placed & tooth fixed
25
Q
A
26
Q
list indications for orthognathic surgery
A
- occlusal deformity, impaired mastication
- dentofacial abnormality causing psychosocial distress
- osa
- tmj dysfucntion/pain
27
Q
patient presents for assessment for dentofacial abnormality and consideration of orthognathic surgery - what do you want to know on history?
A
- specific complaint, goals
- dental - extractions, treatments, hygeine
- trauma
- infections
- temporality to complaint? change over time?
- sleep - snoring, bruxism, osa
- speech/phonation
- previous surgical treatments to craniofacial
- PMHx (JRA, osteoporosis, etc)
- FHx
28
Q
What are the goals of orthognathic surgery?
A
- make the correct diagnosis: dental, skeletal, soft tissue
- multi-disciplinary approach to restore functional relationship between maxilla and mandible
- establish functional occlusion
- establish aesthetic balance of face including skeleton and soft tissue
29
Q
define the following soft tissue cephalometric landmarks:
A
- trichion - point of hairline in middle for forehead
- glabella - most projecting point of forehead in mid-sagittal plane
- nasion - most convex point forehead and nose
- subnasale - junction of columella and upper lip in mid-sagittal plane
- gnathion - mid point between menton and pogonion
- menton - most inferior point of anterior mandble in mid-sagittal plane
- pogonion - most projecting point of mandible in mid-sagittal plane
- gonion - most lateral part of angle of mandible
- note: many of these soft tissue landmarks have similar but distinct skeletal landmarks of same name (soft tissue landmarks are denoted usually with a prime in their sympbol)
30
Q
what is a cephalogram and what is its purpose?
A
- xray of craniofacial skeleton; AP and lateral specialized views; taken 60” from person and film tray 6” from patient (to get 10% increase in size)
- purpose is to take measurements that related the maxilla and mandible to the skull base and to each other
- relates or compares the underlying craniofacial form to overlying skin/subcutaneous tissue form
- helps to make correct diagnosis and treatment plan for dentofacial disproportion
- comparison to population standardized normals
- comparison over time
31
Q
what are the phases of orthognathic surgery?
A
- pre-orthodontics
- dental hygeine, management of endodontal/periodontal disease
- pre-surgical orthodontics
- dental decompensation (align teeth w/ basal bone)
- extractions for space or palatal expansion (if sutures not fused can be done w/ appliance, otherwise need to consider:
- SARPE - surgically assisted rapid palatal expansion (essentially sagittal osteotomy, application of external distraction, distraction osteogenesis)
- extractions of 3rd molar 6-12 months before BSSO
- surgery
- maxilla - lefort 1: impaction/lenthening; setback/advancement; segmentalization
- mandible: BSSO, VRO, inverted L, vertical body, step, anterior subapical osteotomy
- generally advancement or retrusion
- chin: implant, genioplasty
- post-operative orthodontics
- splint removal, ROM
- finish establish dental occlusion
- prosthedontic
- implants, dental restoration, final dental aesthetics
32
Q
define the following cephalometric landmarks
- glabella - most projecting point of forhead (in midsagittal plane)
- nasion - most concave part of nasofrontal suture
- orbitale - most inferior part of infraorbital rim
- pogonion - most projecting part of anterior mandible in mid-sagittal plane
- gnathion - most anterior-inferior part of mandibular symphysis
- menton - lowest point of mandible at symphysis
- gonion - junction of ramus and inferior border of mandible (~ angle)
*
A
33
Q
Discuss timing for orthognathic surgery
A
- aim for surgery at skeletal maturity
- ~ 16 F; 18M
- serial cephalograms
- hand XR and assessment of growth plate
- Why: bc surgery can impair craniofacial growth; bc ongoing growth may alter final result
- reasons to consider surgery before skeletal maturity
- severe speech pathology
- airway obstruction
34
Q
what are complications to lefort 1 osteotomy?
A
- early
- bleeding/hemorrhage (descending palatine #1; iMAX or other branches)/transfusion/transfusion reactions
- under/over resuscitation
- posterior superior alveolar nerve/infraorbital nerve injury/abnormal sensations (increase/decrease)
- pain
- unanticipated fracture or bone loss
- injury to stenson’s duct, lacrimal duct
- devitalization of teeth, injury to gingeva
- Late
- hardware: loose, palpable, painful, infected
- avn maxilla
- malreduction/malunion
- relapse
- asymmetry/undercorrection/overcorrection
- inadvertant anterior open bite
- new / ongoing malocclusion
- VPI
- nasal septum injury/buckling
35
Q
what are complications to BSSo?
A
- EARLY
- V3 paraesthesia (up to 25% have permanent changes; nearly 100% have temporary immediate post-op changes; 2-3% transection rate of IAN/MN)
- bleeding/hemorrhage/transfusion/transfusion reaction
- inadvertant fracture
- devitalization of teeth
- late
- hardware: loose, palpable, painful, infected
- malunion
- malocclusion
- avn mandible/condyle
- condylar resorption
36
Q
Describe clinical features on physical exam of maxillary deficiency
A
- vertical maxillary deficiency
- short lower 1/3 face
- no incisor show (edentulous appearance)
- retruded short upper lip
- concave profile
- acute (<90) nasolabial angle
- overclosure of mandible
37
Q
describe work up and findings for maxillary deficiency
A
- cephalometric
- ANB negative; SNA acute (< 82) SNB normal
- decrease lower facial and anterior maxillary height
- exam:
- class III malocclusion
- proclined maxillary incisors
- acute mandibular plane angle
- plus/minus protruding chin
38
Q
describe a treatment plan for maxillary deficiency
A
- primary treatment, after pre-orthodontic phase, pre-surgical orthodontic phase,
- treatment planning w/ cephs, splints
- would be to undertake a lefort 1 osteotomy and lengthen the maxilla, possibly advance maxilla, possibly use autogenous bone graft depending on size of movement
- will anticipate some mandibular autorotation
- may still need to consider mandible surgery, including genioplasty
39
Q
describe work up and findings when mandible excess
A
- lower 1/3 excess
- mandibular prognathism +- asymmetry
- class III malocclusion
- anterior cross-bite
- lower lip incompetence and strain
- anb negative, sna normal, snb acute (< 80)
- retroclined mandible incisors (+/- proclined max incisors)
40
Q
describe a treatment plan for mandibular excess
A
- cephs, splints, treatment planning, pre-op dental intervention, pre-op orthodontics
- BSSO w/ setback
- consider genioplasty alone or in concert w/ BSSO (vertical reduction)
- consider double jaw surgery with lefort 1 maxillary advancement (will decrease mand mvmt setback required)
41
Q
describe work up and physical findings w/ vertical maxillary excess
A
- vertically long midface and lower 1/3 face
- excessive tooth show, gummy smile
- lip incompetence, strain
- anterior open bite
- retrubed vertically long chin 2’ mandible autorotation
- class II
- proclined max and mand incisors
- anb/sna/snb may be abnormal (increase sna, anb) vs. normal
42
Q
discuss a treatment plan for vertical maxillary excess
A
- work up, cephs, treatment planning, pre op dentist, pre op orthodontist
- lefort 1 maxillary impaction
- anticipate mandible autorotation
- consider genioplasty, bsso
43
Q
describe work up and findings with mandibular deficiency
A
- retrognathic
- short lower 1/3
- short hypotonic upper lip and redundant lower lip
- class II occlusion
- increase anb, sna normal, snb decrease (< 80)
- proclined mandible teeth
44
Q
discuss a treatment plan for retrognathia
A
- work up, cephs, treatment planning, dentistry, pre op orthodontics
- mandible BSSO advancement
- +/- genioplasty
*
45
Q
describe a lefort 1 osteotomy
A
- Exposure: UGBS incision from first molar to first molar
- Degloving
-
Osteotomy - anterior: Mark the planned osteotomy, use a reciprocating proceeding from the lateral nasal wall across the anterior maxillary wall and through the posterior-lateral maxillary wall 5mm above most superior part of canine root
- Osteotomy – nasal: Separate the nasal septum and vomer from the maxillary crest with a septal osteotome directed downward & posterior
- Osteotomy – posterior: Use a curved osteotome to separate the pterygoid plate from the maxillary tuberosity – always direct osteotome downward parallel to the occlusal plane to avoid injuring the IMAX
- Down-fracture the maxilla, using digital pressure
- Mobilize the maxilla
- Apply splint: prefabricated occlusal splint wired to maxilla, then placed in MMF with wire or dental elastics. Centric relation.
- Plate fixation (4x 2.0mm L-plates). the maxillary-mandibular fixation & verify occlusion in that the mandible passively closes
- ± ICBG: presence of any vertical defect 5 mm or greater.
- Fix the septum mid line & closure: and place an alar cinch suture (necessary because have stripped alar base from pyriform aperture) for wide flaring ala if necessary.
46
Q
describe a BSSO
A
·bilateral sagittal split osteotomy
Exposure: intraoral incision begins approximately 1-2 cm above the occlusal plane and continues to the region of the first molar; inferior alveolar nerve is 5mm superior to the occlusal plane
- Degloving
- Osteotomy – internal transverse unicortical osteotomy above lingual fossa, across external oblique ridge to the interval between the 1st and 2nd molar, then continue buccal vertical unicortical osteotomy to inferior margin of mandible
- Complete the osteotomies using an osteotome
- The NV bundle stays with the MESIAL segment
- MMF & fixation: seat the condyles in glenoid fossa; transbuccal trocar approach for 3 bicortical screws or L plate, but do not lag or tighten down too much so there is no displacement
47
Q
List symptoms of TMJ dysfunction
A
- bruxism
- incomplete mouth opening
- jaw pain
- clicking
48
Q
what type of joint is the TMJ
A
- ginglymoarthroidal
49
Q
describe the TMJ and it’s movement
A
- ginglymoarthroidal joint
- mandible condyle
- articular disc (attached to condyle by collateral ligs)
- glenoid fossa of temporal bone (anterior limit articular eminence; posteriorly by articular lip)
- joint capsule
- joint ligaments
- superior joint (disc to temporal bone) - sliding/translation part; utilized in wide mouth opening
- inferior joint (disc to condyle) - hinge/rotation part; utilized to initiate mouth opening
50
Q
describe history and physical exam for TMJ disorder
A
- Hx: Pain, click/pop/crepitation, limited ROM, previous trauma, previous surgery, arthritic/inflammatory systemic sx (r/o rheum etiology)
- PE: ROM, tenderness, dental/occlusal exam
- Document CN7 function
- Non-level cranial base – probable congenital etiology
- Level cranial base – probable developmental problem
51
Q
what imaging would you order for tmj disfunction?
A
- CT for bone detail - asymmetries, degeneration, arthritic changes, joint spaces
- MRI for soft tissue detail - ie disc pathology
52
Q
What is the etiology of tmj ankylosis
A
- true ankylosis: secondary to primary pathology to joint
- trauma
- hematoma
- prolonged immobilization
- infection
- JRA
- false / extra-articular ankylosis
- secondary to ZA fracture, impingment of temporalis between ZA and coronoid
53
Q
what are congenital anomalies of the condyle?
A
- condylar agenesis
- condylar hypoplasia
- For both of above:
- can be treated w/ DO or free costochondral graft (good option if growing)
- all consider (especially if late presentation / done growing) other orthodontics, revision surgery, orthognathic surgery, reconstruction of any associated defects
- condylar hyperplasia
- jaw deviating to contralateral side
- persistent growht & problematic - contined active surveillance until skeletal maturity vs. condylectomy
- done growing: orthodontics + blanacing orthognathic surgery, most likely double jaw
54
Q
what are complications of TMJ procedures?
A
- facial nerve injury
- frey’s syndrome
- parotid injury, parotiditis
- inferior alveolar nerve injury
- infection
- dural perforation
55
Q
what is frey’s syndrome?
A
Damage to the auriculotemporal nerve during parotid surgery (for facelift) may cause a misdirected re-growth that results in parasympathetic innervation of sympathetic receptors in the skin and, therefore, facial sweating and flushing with gustatory stimulation.
*
56
Q
what is first line treamtent of TMJ dysfunction?
A
nsaids
activity modification
physiotherapy
muscle relaxants
splint
