Restorative Collaboration - Crown Lengthening_05092022

Question 1

Crown Lengthening definition (AAP Glossary)

Answer 1

Surgical procedure to increase the length of supragingival tooth structure for restorative purposes by:

• Apically positioning the gingival margin
• With or without removal of supporting bone

Question 2

Supracrestal tissue attachment:

• Composition and boundaries
• Dimensions (Gargiulo and Vacek)

Answer 2

• Supracrestal tissue attachment replaced the term BW (2017 WW - Jepsen 2018).
• Composed of connective tissue and epithelial attachment and extends from the crest of bone to the most apical extent of the pocket of sulcus.
• Dimensions:

Gagiulo (1961) –> defined it as “Physiologic dentogingival unit”

• JE = 0.97
• CT = 1.07
• JE + CT = 2.04

Vacek (1994)

• JE = 1.14
• CT = 0.77
• JE + CT = 1.91

CT is the most consistent measurement

Question 3

Signs of supracrestal tissue attachment violation?

Answer 3

• Gingival inflammation, hyperplasia and recession
• BOP
• Pocket formation
• CALoss
• Bone Loss

Due to destructive inflam. response to microbial plaque located at deeply placed restorative margins.

Question 4

Padbury, Eber and Wang:

Deep subG margins result in: ill-fitted restorations that violate the STA and compromise Perio health

Answer 4

CLP is indicated to :

• Re-establish STA (Carnevale 1983)
• Expose greater amount of tooth structure to support future restorations (Allen 1993).

Question 5

A study about the relationship betw. SubG crown margins and gingival inflammation

Answer 5

Newcomb 1974:

Compared Ging. inflammation (Loe and Silness GI) in 66 crowned anterior teeth with contralateral uncrowned controls. 15 months FU.

Divided into 4 groups based on distance from CM to crevice base (BC):

• Group 1: CM-BC = 0.25 mm
• Group 4: CM-BC = 1 mm

There was a strong negative correlation between the CM-BC distance and the degree of gingival inflammation.

Question 6

Study comparing Perio status (PI and GI) between crowned and natural teeth

Answer 6

Carnevale 1990

Retrospective Study comparing Perio status (PI and GI) between crowned and natural teeth (510 teeth each)

90% of the patients were on a recall schedule that required prophylaxis once every 3 months; 8% returned every 6 months and 2% once a month.

Results:

• NSSD in GI and PI between the crowned and natural teeth
• Gingival status of the crowned teeth was good, irrespective of the position of the crown margin (subG, at GM or supraG).

Question 7

Influence of restorative margins on periodontal tissues over 26 years (Longitudinal study)

Answer 7

Schatzle 2001

• CAL loss could be detected clinically 1-3 years after fabrication of subG restorations.
• GI scores at restorations improved with time –> SubG margins become supraG due to recession.
• A subsequent “burn-out” effect was suggested

Question 8

A study about the relationship between overhang size and bone loss

Answer 8

Jeffcoat and Howell 1980:

Patient records (PA and BW radiographs) were checked to detect overhanging amalgam restorations.

100 teeth with overhangs and 100 teeth without

Overhangs were classified into:

• Small: occupy < 20% of IP space
• Medium: occupy 20-50% of IP space
• Large: occupy > 51% of IP space
• Severity of bone loss increased with the size of overhang
• Greater bone loss around teeth with large overhangs
• Small overhangs did not cause SS increased AB loss (unlike large and medium ones)

Question 9

Study about the benefit of overhang removal?

Answer 9

Rodriguez-Ferrer 1980

Question 10

Furcation Arrows: Sensitivity and specificity?

Answer 10

Deas 2006

Sensitivity: 38.7%

Specificity: 92.2%

Question 11

Study clarifying the relationship between amalgam restorations with subgingival overhanging margins and gingival health

Answer 11

Rodriguez-Ferrer 1980

• Overhanging amalgam margin was the sole variable parameter
• 26 defective premolar and molar amalgams were paired with similarly defective restorations in the same mouths, test and control being allocated randomly.

Test: Overhang removal , Control: Overhang left, OH and professional care were the same

PI, GI and PD were recorded at different time points (0, 4, 8 & 12 weeks):

• BL: NSSD betw. test and Ctrl
• Other timepoints: SSD (Greatest at 4 weeks)

Conclusions:

• Overhangs may be the only clinically sig. feature of amalgam related to pathogenesis of Perio disease
• Corrective of defective resto. should be part of the initial phase of Perio therapy
• Other time points:

Question 12

Smile line, Gummy smile and golden proportion

Answer 12

Smile Line

• High (20%): < 20% of clinical crown is displayed
• Average (69%): 69% of clinical crown is displayed
• Low (11%): 2 mm of ging. is displayed

Gummy Smile

(12% prevalence)

• ≥ 4 mm ging to lip distance is considered unattractive smile

Golden proportion

Width ratio of an anterior tooth in relation to adj. tooth should be 1: 0.618

Question 13

Active vs. Passive Eruption?

Answer 13

Active eruption: process by which a tooth moves from its germinative position to its functional position in occlusion with the opposing arch

Passive eruption: Tooth exposure secondary to apical migration of the GM to a location at or slightly coronal to CEJ

Question 14

Potential causes of excessive gingival display

Answer 14

• Gingivitis induced pseudopockets
• Drug-induced ging. enlargment
• Altered passive eruption

Question 15

3 Potential risk factors for gummy smile (GS)?

Cite a study

Answer 15

Conditions that may cause (GS)

• Hypermobile upper lip (HUL)
• APE
• Vertical maxillary excess
• Other: Short UL (SUL), genetics, dental plaque, medications

Cetin 2020: found that age (OR:0.9), HUL (OR: 18.8) and APE (OR: 8.8) were sig. risk factors. Gender and SUL were not sig. factors

Question 16

Treatment options for excessive ging. display (EGD)

Answer 16

• Ortho or combined ortho + Surgical
• Orthognathic surgery: Le Fort I (long lower face, lip incompetence & excess display of max. anterior teeth)
• Perio Sx
• Cosmetic Sx: HUL –> lip repositioning and/or Botox

Question 17

Etiology and treatment modalities of EGD

Answer 17

Silberberg 2009

• Plaque-induced ging. enlarg. : Perio tx
• Drug-induced ging. enlarg.: medical consult, drug replacement and Perio plastic Sx.
• Anterior dento-alveolar excess/vertical maxillary excess: Multidisciplinary (Ortho, OS, Perio and Resto.)
• Short/hyperactive /asymetric UL: Plastic Sx, Botox and lip fillers
• APE: Crown lengthening

Question 18

APE definition

Answer 18

Delayed or retarded passive eruption occurs when the marginal gingival is positioned incisally on the anatomic crown in adulthood and does not approximate CEJ

Question 19

Passive eruption vs. APE (subtypes of each)

Answer 19

Passive eruption: occurs when active eruption is complete and may conytinue to mid 20’s. It’s a process during which dentoging. junction shifts apically

APE: When FGM fails to recede during tooth eruption to a level apical to the cervical convexity of the clinical crown

Question 20

Coslet 1977 APE classification

Answer 20

Question 21

What is the effect of the distance from contact point to bone crest on the presence/absence of ID papilla?

Answer 21

Tarnow and Fletcher 1992

Distance from contact point to ABC:

• < 5 mm ⇒ 100% papilla fill
• 5 mm ⇒ 98% papilla fill
• 6 mm ⇒ 56% papilla fill
• 6 mm ⇒ 27% papilla fill

Question 22

Ferrule effect?

Definition and amount

Answer 22

Sorensen and Engelman

“360- metal collar of the crown surrounding the parallel
dentin walls extending coronal to the shoulder of the preparation”

There should be 1.5 - 2.0 mm of sound tooth structure from the core margin to the finish line.

Crown should envelop sound tooth structure to protect the tooth from fracture after crown prep.

Question 23

If Ferrule is absent, what can be done??

Answer 23

• Place margin subG
• Functional crown lengthening (after RCT and placement of provisional)
• Ortho extrusion

Question 24

When trying to achieve adequate Ferrule, what are the concerns with using either crown lengthening or ortho extrusion?

Answer 24

Crown lengthening

Requires removal/recontouring of supporting bone on adjacent teeth, which may lead to furcation exposure.

Ortho extrusion

May expose furcation which compromise home-care and long-term survivability of the tooth

Question 25

Indications for functional crown lengthening

Answer 25

• Tooth decay or fracture below GM with sufficient periodontal support
• Excessive occlusal/incisal wear
• Insufficient interocclusal distance
• APE (Coronally positioned GM)
• To provide ferrule effect

Question 26

Contraindications for functional crown lengthening

Answer 26

• Unfavorable crown: root ratio (< 1:1)
• Periodontally involved teeth or furcation involvement
• If the adjacent teeth will be compromised
• Anatomical considerations (external oblique ridge, zygoma)
• Esthetic concerns

Question 27

Minimum and optimum CR ratio?

Answer 27

Minimum is 1:1

Optimum 2:3

Question 28

Treatment sequence for CLP?

Answer 28

Removal of defective restoration ⇒ Caries excavation ⇒ RCT ⇒ Provisional ⇒ Re-eval ⇒ CLP ⇒ 6-8 weeks eval ⇒ Final crown

Question 29

What is the minimum distance between the crown margin and ABC?

Answer 29

At least 3 mm. If less, clinician should recommend CLP to allow the crown margin to end supraG (Bragger 1992)

• 1 mm : CT attachment
• 1 mm: Epithelium
• 1 mm: Sulcus depth

This is based on Gagiulo’s 2.04 mm BW.

However, Wagenberg recommended a 5 mm of tooth structure above ABC.

Crown margin should be at most 0.5 - 1mm into the sulcus (As far from JE and as close to the GM as possible.

Alveolar bone must be removed on the teeth adjacent to the one being lengthened

Question 30

What has been shown with regards to clinician’s of varying experience performance for CLP?

Answer 30

Herrero 1995 ⇒ Showed under-reduction

clinician’s of different experience perfomed CLP, with a separate examiner doing measurements before, during and after the procedure and found a mean bone level reduction by 2.4 mm (0.6 mm less than the required 3 mm)

Recommendation ⇒ Clinicians need to be more aggressive & take measurements during Sx.

Question 31

Altereted Active Eruption vs. Altered Passive Eruption??

Answer 31

Zangrando vs. Jepsen

Question 32

Silberberg 2009

Answer 32