1. Dentoalveolar Flashcards
3 most common teeth to be missing
Third molars
Second premolars
Maxillary lateral incisors
4 most common teeth to be impacted
Third molars
Maxillary canines
Mandibular premolars
Maxillary premolars
Second molars
Development of third molars:
-When are follicles first visible?
- When is crown formation done?
- When is 50% of the root formed
- When are 95% of molars in final tooth position
- Age 6-9 follicles become visible
- Crown formation done at age 14
- 50% root formation at age 16
- 95% of molars in final tooth position at age 24
Why do teeth become impacted?
- differential growth rate of roots causes over- or under-rotation leading to impaction
- arch length: impacted third molars are larger than erupted third molars
- ectopic position: abnormal germ position puts teeth in contact with denser external oblique ridge
- late mineralization: tooth growth lags behind maturation of jaws
- attrition: softer diet leads to less attrition maintaining MD space
What are two classification systems for third molars?
- Pell and Gregory based on radiographic review
- Winter’s classification (most common)
Pell & Gregory Classification
A-C based on relation to second molar occlusal plane
A: occlusal plane in line with second molar
B: occlusal plane between occlusal plane and CEJ of second molar
C: occlusal plane below cervical junction second molar
1-3 based on relation to anterior border of the ascending ramus
1. MD diameter of crown anterior to ascending ramus
2. half of crown is covered by ramus
3. Tooth is completely within ramus
Winter’s classification
Most commonly used classification system for third molars.
Angle between occlusal plane and longitudinal axis of third molar.
>0 degrees= inverted (rare)
0-30 degrees= horizontal impaction
31-60 degrees= mesioangular impaction
61-90 degrees= vertical impaction
<90 degrees= distoangular impaction
Indications for removal of third molars
- Pericoronitis (most common over age 20). Inflammation of operculum.
- Orthodontic needs (dental crowding may not be associated with third molars but can interfere with orthodontic treatment).
- Pericoronal pathology (pericoronal radiolucency >3mm is suggestive of a dentigerous cyst)
- Caries
- Fracture
- Unexplained pain
- Overlying prosthesis
- Periodontal disease
Inferior alveolar nerve injury after third molar extraction %
1%
Lingual nerve injury after third molar surgery
0.6-2.0%
Lingual nerve location in relation to third molar
2.8mm below crest and 2.5mm medial to lingual cortex
In 4.6-21%, lingual nerve is at or above crest of bone
22% reported at lingual plate of bone
Turns toward tongue at region of first and second molars
Rood’s Criteria
Describe intimacy of IAN with roots of mandibular third molar:
1. Darkening of Root
2. Deflection of Root
3. Narrowing of Root
4. Bifid Root Apex
5. Diversion of Canal
6. Narrowing of Canal
7. Interruption in white line of canal
Darkening of root
Diversion of canal
Interruption of white line
Most predictive
Theory of alveolar osteitis
Risk factors
Incidence
Timing
Symptoms
Increased fibrinolytic activity leading to breakdown of clot.
Risk factors: tobacco smoke, increased age, pericoronitis, birth control, female gender, inexperienced surgeon, inadequate irrigation.
Incidence 1-30%
Timing 3-7 days after EXT
Symptoms: referred pain to ear, eye, temple, foul odor, extreme tenderness
Treatment: eugenol on gel foam or iodoform gauze (inhibit neural transmission). Do not place eugenol on IAN. Can use topical lidocaine instead.
What is Gelfoam?
Absorbable gelatin sponge
Matrix for blood clot formation
Made from purified porcine skin
May cause excessive granuloma or fibrosis
What is Avitene?
Microfibrillar collagen
Mechanically broken down bovine collagen
Aggregates platelets onto fibrils and acts as matrix for blood clot formation
What is HemCon and ChitoFlex?
Chitosan dressing
Polysaccharide from shellfish, positively charged to attract erythrocytes. Acts as scaffold for clotting. New dental formulation dissolves in 48 hours.
What is Thrombin?
Promotes clot formation through activated bovine prothrombin. Activates factor IIA. Acts as serine protease converting fibrinogen to fibrin.
What is Surgicel?
Oxidized regenerated methylcellulose
Binds platelets
Negative pH is bacteriostatic
Precipitates fibrin
More efficient at hemostasis than gelatin sponge
Can be packed into socket to aid in pressure hemostasis
Does cause some prolonged healing
Be cautious when using in lower third molar sockets as surgicel creates an acidic milieu which can be toxic to the inferior alveolar nerve.
What is a Collaplug?
Cross linked collagen that promotes platelet aggregation
What is a Tanin?
Found in tea bag, serves as vasoconstrictor
What is aminocaproic acid mouth rinse?
Stabilizes clot by inhibiting plasmin
What is tranexamic acid 5% mouth rinse
Antifibrinolytic that inhibits conversion of plasminogen into plasmin
When to use apically positioned flap for impacted maxillary canine?
For labial impactions
Maintains keratinized gingiva
Use if less than 3mm of keratinized gingiva is expected after an open window technique
Do not use if high in alveolus (high labial impactions should be treated with closed technique).
When to use open exposure technique (window technique) for impacted maxillary canine?
Crown is uncovered and left exposed.
Ortho bracket may or may not be placed at time of surgery (tooth may spontaneously erupt or site can be packed with periodontal packing open with or without bracketing (speak to orthodontist preference). Packing is normally left for 2-3 weeks.
When to use a closed technique for impacted maxillary canine?
Used when teeth are not in a position to allow for repositioning of the flap after the crown is exposed.
Palatal impaction that is not close to the alveolar ridge.
Describe nerve anatomy (layers)
Endoneurium: connective tissue sheath that surrounds group fo fibers to form a fascicle.
Perineurium: surrounds a bundle of fascicles
Epineurium: outermost layer of a peripheral nerve, surrounding multiple fascicles and blood vessels
