Practice Mgmt_Crown lengthening & important anatomy Flashcards
What are the biologic width studies?
Gargiulo ‘61:
CT layer is 0.97
JE is 1.07
Total biologic width is 2.04mm
Vacek ‘94:
CT layer is 0.77
JE is 1.14
Total biologic width is 1.91 mm
What studies recommend crown margins at or only slightly below the gingival margin?
Newcomb ‘74: The least inflammation is observed when subgingival crown margins are placed at the gingival crest or just into the gingival crevice.
Carnivale ‘90: Retrospective study. A gingival or slightly sub-gingival crown margin in patients with adequate plaque control + personalized maintenance recall program is no harm to gingival health.
Schatzle ‘01: Longitudinal study of 26 years. Subgingival margins are detrimental to periodontal health. Recession, over time, will bring the subgingival margins to a supragingival level.
How do restoration overhangs affect the periodontal tissues?
Jeffcoat & Howell ‘80:
Classified overhangs:
Small: <20% of interproximal space
Medium: 20-50% of interproximal space
Large: >51% of interproximal space.
Small overhangs did not affect alveolar bone levels, but medium and large overhangs had bone loss.
Rodriguez-Ferrer ‘80: Overhanging margins should be removed in the nonsurgical phase of treatment to remove the plaque accumulation areas.
How much distance should be created from the bone to the restorative margin in functional crown lengthening?
Ingber ‘77 , Bragger ‘92: Minimum of 3 mm to restoration margins
Rosenberg ‘80: 3.5 - 4 mm to the fracture line of the tooth
Wagenberg ‘89: 5 - 5.25 mm from remaining tooth structure to bone
How much is a minimum ferrule?
1.5 - 2 mm
What are the optimum and minimum crown-root ratios?
Optimum: Crown:root is 2:3
Minimum: Crown:root is 1:1
What study compared the “desired” versus “actual” bone removal in crown lengthening procedures?
Herrero ‘95:
Faculty reduced an average of 1.1 mm bone (instead of the “ideal” of 3mm). Residents and dental students reduced even less
How much bone is lost during the remodeling phase after crown lengthening?
Wilderman ‘70: 0.8mm loss after 1 year. (Initial bone loss is 1.2mm at 3 weeks postop; then 0.4 mm bone is gained over time)
How long does the increased mobility after crown lengthening last?
Selipsky ‘76: It takes 1 year for tooth mobility to return to baseline
For esthetic crown lengthening cases, how long after surgery should we wait until the final restoration?
Bragger ‘92: 6 months.
The free gingival margin can change +/- 1 mm from 6weeks to 6 months after surgery.
How long can teeth last after functional crown lengthening?
Ashnagar ‘18 - Retrospective study. Long-term survival depends on the patient’s caries and fracture risk.
5 year survival: 88%
10 year survival: 78.4%
15 year survival: 68.1%
What esthetic area has the greatest buccal concavity?
Chung ‘17: Study of 11 cadavers. Maxillary laterals have the greatest buccal concavity (about 15 mm high and 3 mm deep).
CBCT underestimates this by 0.2 - 0.6 mm
Which study discussed nasopalatine canal deflation and dental implant placement?
de Mello ‘07: Systematic review. Success was about 84.5%.
Most common complication is nerve sensory issues
How likely is sinus membrane perforation with different sinus wall angles?
Cho ‘01: When looking at the angle of the medial and lateral walls coming up from the sinus floor, narrower angles have higher risk:
≤30 degrees: 37.5% were perforated
31-60 degrees: 28.6% perforated.
≥61 degrees: 0% perforated
Chan ‘13: When looking at the palatonasal recess (the angle between the medial wall and sinus floor):
<90 degrees and >15mm from the floor has a high risk of perforation.
Premolar area usually has higher perforation risk than the 1st and 2nd molar areas.
The ENT be consulted when the sinus membrane is how thick?
Testori = 4mm
What study looked at sinus septum prevalences and locations?
Pommer ‘12:
Almost 9,000 sinuses were examined.
Overall septum Prevalence: 28.4%
Premolars: 24.4%
Molars: 54.6%
Retromolars: 21%
Average Septum Height: 7.5mm
Transverse: 87.6%
Sagittal: 11.1%
Horizontal: 1.3%
Complete septa: 0.3%
How far from the teeth is the greater palatine artery?
Tavelli ‘19: Systematic review & meta-analysis.
Greater palatine foramen: 57% are located at the mid palatal of the 3rd molar. 21% are between the 2nd and 3rd molars.
The average distances of the greater palatine artery to the CEJ’s are:
2nd molar: 13.9mm
1st molar: 13mm
2nd premolar: 13.8mm
1st premolar: 11.8 mm
Canine: 9.9mm
(Can remember 14-13-14-12-10)
The safety zone is about 4 mm from these. (10-9-10-8-5)
What are the 3 categories of palatal vaults?
Reiser ‘96:
Measured from the CEJ of the 2nd premolar to the level of the greater palatine foramen.
High: 17mm
Average: 12mm
Shallow: 7mm
What studies described the location of the mental foramen?
Fishel ‘76:
* Between premolars: 70%
* Apical to the 2nd premolar: 19%
* Superior to root apices: 46%
* Inferior to root apices: 38.6%
So, it is usually between the premolars and superior to the root apices.
Neiva ‘04: 22 Caucasian skulls.
* Mental foramen to CEJ: about 15.5 mm
Extent of the anterior loop had a wide range (1-11 mm ) with a mean length 4.13 +/- 2.04mm
Conclusion:
Most common location of Mental foramen: Between the 1st and 2nd Mandibular Premolar 58 % of the time, followed by apical to the second mandibular premolar with 42 %.
Who classified the location of the IAN nerve in the mandible?
Carter & Keen ‘71:
* Type 1 nerve: close to root apices.
* Type 2: Mid-mandible
* Type 3: Near the inferior cortical plate.
Obviously, the Type 1 nerve was most commonly injured.
How far is the lingual nerve from the teeth?
Chan -
75% of the lingual nerves course towards the tongue at the 1st and 2nd molars.
CEJ to nerve:
* 2nd molar: 9.6mm
* 1st molar: 13mm
* 2nd premolar: 14.8mm
(Can remember 10-13-15)
What are the lingual flap zones and how do you handle them?
Urban ‘17:
Zone 1: Retromolar pad. Reflect flap with periosteal elevator.
Zone 2: Posterior mylohyoid region. Flap is attached to the mylohyoid. Gently push the soft tissue superior to the muscle with a blunt instrument.
Zone 3: Premolar region. Use a semi-blunt instrument to dissect the periosteal fibers with a sweeping motion. Don’t reflect deeper than Zone 2.
Who classified the mandibular lingual undercuts?
Chan ‘10:
* C type: Convex
* P type: Parallel
* U type: Undercut
* Most common type: The U type (66% at 1st molars).
Mnemonic: “Chan Prefers Ultrasound” and what’s his favorite? “Ultrasound”
discrepancy between Pontoreiro and Bragger about the crown margin
discrepancy between Pontoreiro and Bragger about the crown margin
