Crown Lengthening Flashcards
what are the indications for functional crown lengthening
- subgingival restorative margins
- tooth fracture
- endodontic perforations
- cervical root resorption
what are the indications for esthetic crown lengthening
- excessive gingival display
- gingival overgrowth (from medications)
- altered passive eruption
what is the supracrestal attachment number
2.04mm
what is the supracrestal attachment made of
- CT: average of 1.07mm
- junctional epithelium: 0.97mm
which part of the supracrestal attachment is more variable
the JE
what are the indications for crown lengthening
- to allow for restoration of tooth (caries removal, clamp placement)
- increasing crown length for retention of restoration (adequate ferrule)
- restoration of tooth in harmony with supracrestal attached tissue (biologic width)
- esthetics via alteration of the gingival labial profile
what is a ferrule
the vertical axial wall that surrounds the tooth
when is the ferrule needed
every time a crown is fabricated to help resist fracture and/or crown displacement
how much ferrule do you need
at least 2mm of ferrule (natural tooth structure) circumferentially, beyond the core
what are the considerations and limitations for crown lengthening
- is the tooth restorable
- is the tooth strategically important
- prognosis
what is considered in if the tooth is restorable
caries removal is done
what is considered in “is the tooth strategically important”
- opposing tooth
- position in the arch
what is considered in the prognosis of crown lengthening
- amount of tooth remaining in supporting bone
- furcations
- mobility
- esthetic concerns
- thick or thin phenotype
when are the caries removed and when is the provisional crown done in relation to crown lengthening
before surgery
when is the final restoration placed after crown lengthening
variations between 6 weeks and 6 months but not sooner than that
if you are in doubt how long should you provisionalize the tooth after crown lengthening
3-6 months
in health the CEJ should be _____ from osseous crest
2mm
in health the gingival margin should be _____ coronal to the CEJ
0.5-2mm
describe active eruption
- as the tooth breaks through the gingiva it erupts until it meets its antagonist and occlusion
- eruption then ceases or slows
- eruption potential continues throughout life
what is passive eruption
apical shift of the dentogingival junction
- occurs during and after active eruption
- tooth does not move, gingiva does (apically)
what are the stages of passive eruption
- junctional epithelium rests on enamel surface
- JE rests on enamel and cemental surface apical to CEJ
- epithelial attachment rests on cementum
- epithelial attachment migrates apically
when does passive eruption conclude
when sulcus base is at level of the CEJ placing the gingival margin 1-2mm coronal to the CEJ
what is altered active eruption and what is it exacerbated by
- morphological variant where CEJ is less than 2mm from osseous crest
- can be exacerbated by orthodontic brackets
what is altered passive eruption and what is it exacerbated by
- morphological variant where gingiva is more than 2mm coronal to the CEJ
- can be exacerbated by inflammation and medications
what is altered passive eruption
when eruption does not progress past stage 1 or stage 2
what is the frequency of altered passive eruption in adults
12%
normal passive eruption may continue throughout:
the teen age years
why may gingiva be present on the crown of the tooth in adolescents
because the dentogingival unit has not fully receded to its final position
when do anterior teeth typically undergo passive eruption
in the early teen years
the posterior teeth can continue to undergo passive eruption into:
a patient’s 20’s
does everyone have the same supracrestal attachment
no
what are the 3 categories of supracrestal tissue attachment and their prevalence
- normal crest- 85% of the time
- high crest: 2% of the time
- low crest: 13% of the time
what are the 2 categories of low crest
stable and unstable
describe the normal crest
- bone sounding 3mm from gingival crest to alveolar crest midfacial
- 3-4.5mm from gingival crest to alveolar crest at line angles
describe the high crest
- bone sounding less than 3mm from gingival crest to alveolar crest midfacial
- less than 3mm from gingival crest to alveolar crest at line angles
describe the low crest
- bone sounding greater than 3mm from gingival crest to alveolar crest midfacial
- greater than 4.5mm from gingival crest to alveolar crest at line angles
- sulcus must be probed in order to determine sulcus depth in addition to bone sounding
describe the unstable low crest
- normal attachment apparatus (2mm)
- greater than normal sulcus depth
- prone to recession due to the deeper sulcus depth and unsupported gingival crest
- only category in which a gingivectomy alone is successful
describe the stable low crest
- normal sulcus depth
- longer than normal attachment apparatus
- susceptible to gingival rebound after crown lengthening due to inadequate ostectomy to accomodate the longer attachment apparatus
what are the components of an appealing smile
- teeth: size, shape and position
- gingival scaffold: health and contour
- lip framework: shape, length and mobility
- skeletal profile
- eyes
what is a perfect smile clinically
- show 75-100% of crowns and interproximal gingiva
- symmetrical display and harmony between the maxillary gingival line and the upper lip
- lower lip parallel to the incisal edges of maxillary teeth and in close approximation
what creates facial harmony
parallelism between interpupillary line and commissural line creates facial harmony
what is the smile line
position of the upper lip relative to the maxillary incisors and gingiva during a natural full smile
what is the normal tooth length of the central incisor, lateral and canine
- central: 11-13
- lateral: 10
- canine: 11-13
what is the minimum tooth length for centrals, laterals and canines in order to still be considered normal
- central: 10mm
- lateral: 9mm
- canines: 10mm
what is the preferred anatomical crown width to height ratio
78%
what is the acceptable range of anatomical crown width to height ratio
66-80%
does the anatomical crown height depend on race or gender
no
central incisor width is ______ than the lateral incisor
60% wider
the lateral incisor width is ______ than the mesial portion of the canine
60% wider
if you assign the value of 1.0 to a lateral incisor then the central incisor would be _____ the width of the lateral incisor
1.6x
if you assign the value of 1.0 to a lateral incisor then the canine would be _____ the width of the lateral incisor
0.6x
what would be the indications for a gingivectomy only
thick tissue and deep pockets
when would the tissue relapse after a gingivectomy
if the bone is too overgrown too and you dont reduce the bone
what is the gingival zenith of the centrals, laterals, and canines
- centrals:1 mm distal to midline
- laterals: 0.3mm distal to midline
- canines: centered MD
describe the gingival margin of the anterior teeth
- central and canine ON SAME LINE
- lateral 0.5-1.0mm coronal to central and canine
what should you do to help determine classification and treatment
- perform detailed smile analysis
- look at amount and location of keratinized tissue
- evaluate location of supporting bone using radiographs and/or bone sounding with LA
- understand where the CEJ is located
- understand the clinical vs anatomic size of the teeth
what 2 criteria must be met to diagnose altered passive eruption
-the tooth is short by measurement
- the CEJ cannot be detected in the sulcus with the tip of the exploreer
what are the treatment goals for an esthetic smile
- thin and move the alveolar bone 2mm apical to the CEJ from facial line angle to facial line angle
- position the gingival crest 3mm coronal to the new alveolar crest position
- level the tissue at the new position
what is the surgical technique to do an ostectomy
- sulcular incisions
- extend incisions to mesial of second molar (most of the time)
- thin the papilla
- apically position the flap (instead of removal of a collar of tissue)
- create the ostectomy with parallel sides that are positioned toward the interproximal areas
what are the post operative instructions after osteoctomy
- do not do anything to activate the lower lip such as sucking through a straw, kissing or pulling the lip up to look at the surgical site
- no brushing anywhere for 4 days
- no brushing of the maxillary arch for 2 weeks
- rinse twice daily with an antimicrobial rinse for 2 weeks
