Departments
MICROSURGERY
Nov/Dec 2008 —
Vol. 2,
Iss. 5
Periodontal Plastic Surgery II: Esthetic Crown Lengthening
Michael Sonick, DMD; and Debby Hwang, DMD
The dramatic appeal of a face, especially caught in a
smile or laugh, lies in the interplay between
the lips, teeth, and periodontium. Any
deviation from the ideal form alters perceived attractiveness,
particularly if the change involves an overexuberant gingival display. Indeed, a well-known survey discovered that laypeople found a show of 3 mm to 4 mm of gingiva
above the dental margin upon smiling to be less
esthetic than 0 mm.1,2 Symmetry, specific anatomic
positions, and harmonious proportions matter.
THE IDEAL ARCHITECTURE
What is normal? There are no unwavering guidelines,
but in general, the dental profession
establishes the following relationships
and dimensions as standard, based on observational studies and expert opinion.
Lip Line
The position of the lip at rest and upon smiling
determines the amount of dental and periodontal display. Highly
inconsistent labial movement from rest to full smile averages 7 mm to 8 mm,
though it ranges from 2 mm to 12 mm.3 As studied by Tjan and colleagues in dental and hygiene
students, three smile line classifications exist, based on the
location of the upper lip relative to the upper anterior teeth (Table 1).4
The analysis appraised only patients up to age
30. With time, the lips become less everted and less elastic. In other
words, the lip line changes. Older patients
show less of the maxillary teeth and more of the mandibular. Fifteen-year-old subjects reveal 10
mm of maxillary
central incisal length during smiling and 5 mm at rest.5 Vig and Brundo confirmed age-correlated changes and discovered
that women tended to exhibit twice as much maxillary
incisor length compared to men (Table 2).6 Notice that with time, the
total level of tooth exposure at rest drops from 5 mm at age 15 years to 3
mm starting at age 40.
Tooth Morphology
Teeth fall into one of three shapes: square, ovoid,
and triangular.7 The widest of all, a square tooth, possesses the longest
proximal contact and leaves the least room
in the interdental area, which creates short, blunt papilla. The triangular
tooth, in contrast, presents the shortest
contact area and widest interdental space,
allowing for a tapered and long papilla. Papillary morphology mimics that
of the underlying interproximal bone.
The maxillary central incisors are key to symmetry; if
they match, the observer is able to accept
small irregularities in adjacent teeth.
Contralateral teeth should be equivalent in length and width on either side of the midline. In theory, the length of the maxillary central incisors should exceed that of the
lateral incisors but equal that of the
canines.8 The cusp tips of maxillary centrals
and canines also must be at the same level. The incisal edge of the lateral incisor is 1 mm coronal to the canine tip.
As useful to the practitioner is the width-to-length
ratio of the anterior teeth. The restoration of proper crown proportions is
a major part of esthetic dentistry. These ratios remain more or less
constant from person to person; knowledge of one measurement may be used to
predict the other. The width-to-length ratio of
maxillary central incisors is 0.8 mm and those of other anterior teeth lies between 0.7 and 0.8 mm.9 The width and length of
incisors and canines were greater in men than women, but the canine width-to-length ratio in women surpassed that
of men.9
Furthermore, the mean incisors diameter of African-Americans exceeds those of Caucasians.10
Gingival Margin and Contour
Recall that a person with an average smile line
demonstrates no soft tissue above the maxillary central incisors and
canines. The gingival margins of these teeth
exist at the same level. On the other hand, the
margin of the lateral incisor falls 1 mm coronal to its adjacent
counterparts.11
In a similar vein, the heights of contour of maxillary
central incisors and canines match and peak at
the distal line angle, as they follow the curve
of the cementoenamel junction (CEJ); the lateral incisor’s height of
contour, alternatively, exists at the mesiodistal center (Figure 1 View Figure).8 The degree of this
gingival scallop relies on tooth morphology as
well as tissue thickness. A flatter contour, considered more masculine, stems from thick—and thus less
pliable—gingiva and a square-shaped
tooth. A highly scalloped margin appears feminine and occurs with a thin tissue and a triangular dental
form.7
CORRECTION OF THE IMPERFECT: THE GUMMY SMILE
In the end, objective beauty fails to exist. Dentists,
however, should not underestimate the utility
of the lip–tooth–gingiva relationships
outlined above. These rules, applied broadly, help to equilibrate uneven smiles. It is important to remark that the periodontal drape influences the shape of teeth. Excessive
marginal or papillary soft tissue because of
inflammation, altered passive eruption,
and a myriad of other pathologies distorts dental
silhouettes. Modification of the gingiva, then, instead of tooth structure, often resolves cosmetic deformities.
As mentioned earlier, the typical patient may not
judge his or her smile as gummy until at least
3 mm to 4 mm of soft tissue shows above the
tooth margins. The level of discernment, of course,
varies, and a patient may complain about an unsightly smile but be unable to pinpoint the features that make it so. The
role of the dentist is to address these grievances by identification of non-ideal situations, such as a gummy smile. Correction
of gingival excess enhances appearance, often
radically.
Definition of a Gummy Smile
The dental profession considers more than 2 mm of
gingival display above the tooth margin upon smiling to be excessive.12 Any band of
gingiva, other than the papillary tips, that appears at rest is unnecessary in the adult. A patient may grumble about “short teeth” or “too much gum
showing.” The papilla may be bulbous and misshapen.
Etiology
A number of scenarios manifest in gingival excess.
Proper treatment tackles these underlying problems.
Excessive Maxillary
Growth. In patients with vertical maxillary excess, ones observes longer facial heights, shorter or
hypermobile lips, maxillary anterior
supra-eruption, or large alveolar processes.12,13 In an ideal
situation, the face may be divided into three equal proportions from
the hairline to the eyebrow, from the eyebrow to the base of the nose, and
from the base of the nose to the chin. If the lower third appears
longer than the other segments and if the
maxillary lip is of regular vertical length (18
mm to 21 mm), the patient requires
orthognathic surgery.11
According to Garber and Salama, bilateral excessive
gingival display of roughly 8 mm in a patient with coincident incisal and
posterior occlusal planes designates the need for a LeFort I procedure.14 In the case of a
4-mm to 8-mm surplus, orthognathic treatment may be indicated if
traditional periodontal crown lengthening unacceptably elevates the
crown-to-root ratio or exposes so much radicular structure that it impedes
prosthetic achievement of a natural-looking emergence profile.14
Tooth Malposition. Orthodontic movement corrects gummy smiles caused by malpositioned teeth. In this scenario, there is usually an excessive display of 2 mm to 4 mm.14 Specifically, if there is a step between the incisal and occlusal
planes, a deep overbite exists, resulting in
excessive gingival display.12 Here, in the presence of
shallow probing depths, orthodontic intrusion alone of the maxillary incisors moves the gingival margins
apically. Deep probing depths call for additional gingival resection.
When incisor supra-eruption occurs in response to
protrusive bruxism, a gummy smile with short, abraded incisors develops.
Again, treatment entails orthodontic intrusion with restoration
of the incisal edges.
Gingival Enlargement. Inflammation (ie, periodontal disease), hereditary gingivofibromatosis, and certain medications
cause enlarged gingiva. Treatment for
inflammation involves oral hygiene instruction, scaling and root
planing, and/or periodontal surgery. If poor plaque control in the presence
of orthodontic appliances triggers enlargement, therapy may include the
removal of brackets and bands.
Treatment of gingival overgrowth caused by drugs (ie,
anticonvulsants, immunosuppressants, and antihypertensives) and
gingivofibromatosis requires not only plaque control and dosage
modifications but possibly resective periodontal surgery.
Altered Passive
Eruption. As teeth erupt from their crypts, the
gingival margin migrates apically to a level at or 1 mm coronal to the
CEJ.11
This is passive eruption. The four stages of passive eruption concern the
relationship between the junctional epithelium
and the CEJ. In stage 1, the epithelial attachment rests on the enamel surface. In stage 2, the attachment lies on
the enamel and cemental surface apical to the CEJ. In stage 3, the
junctional epithelium is completely on cementum. Stage 4 occurs
pathologically—inflammation causes the attachment to migrate
further apically.
Roughly 12% of patients fail to progress past
stage 1 or 2, and they appear to have short
clinical crowns and gingival surplus (Figure
2 View Figure). This is known as altered passive eruption. Such patients may or may not have a high osseous crest. Boyle and coworkers measured the radiographic interproximal bone
levels in a wide age range of subjects (ages 11 to 70).15 They saw that the
distance from the CEJ to the osseous crest increased as patients aged and
insinuated that the crest position was not static.
Coslet and associates proposed a classification system for adult delayed passive eruption based on amount of
gingiva and level crestal bone (Table 3A and Table 3B).16
Altered passive eruption treatment always
involves some kind of periodontal resection (ie, crown lengthening), at
least of gingiva if not also of underlying bone.
Treatment Considerations for the Gummy Smile
Elimination of a gummy smile rests on appropriate
diagnosis of its etiology. Gingival
surgery alone is not a panacea. It must be realized
that the monotherapeutic use of crown lengthening does not succeed in all
circumstances. Periodontal surgery in some
instances functions as an adjunct to orthognathic, orthodontic, or
prosthetic treatment. For example, orthodontic intrusion ideally moves the
dentogingival complex apically, but use of more
forceful mechanics leaves the attachment apparatus at its original position, which results in a short clinical crown,
a low crown-to-root ratio, and an even
“gummier” appearance.17-19 Gingival and osseous
resection easily remedies this issue.
To maintain periodontal stability around teeth with
cosmetic veneer and full-coverage
reconstructions, there must be no biologic-width
invasion. Otherwise, inflammation, attachment loss, and recession initiate.20-22 Inflamed gingiva, of course, contributes
to a gummy smile. The prosthetic margin should lie at least 3 mm from the
alveolar crest, as the junctional epithelial and connective tissue
attachment averages 2 mm and the sulcus comprises 1 mm.23-25 Osseous
crown lengthening resolves both restorative and esthetic concerns.
As alluded to before, relative contraindications
to crown lengthening exist and include patients with:
- vertical maxillary
excess;
- malpositioned teeth
with shallow probing depths;
- an anticipated poor
crown-to-root ratio postsurgery;
- an anticipated poor
restorative emergence profile postsurgery;
- active
inflammation; and
- unrestorable teeth.
Barring these limiting factors, the operator
may employ esthetic crown lengthening to
treat cases with approximately 2 mm to 7 mm of
gingival excess (seen upon full smile); if excess tissue ranges from 2 mm to 4 mm, crown lengthening alone may be the solution.
ESTHETIC CROWN-LENGTHENING METHODS
Once the clinician selects periodontal resection as his or her treatment-of-choice, the Coslet system allows the dentist to determine the most suitable crown-lengthening approach for each patient. Not every scenario necessitates the removal of
soft tissue; this holds true for osseous
resection as well. Two major factors govern the surgical design: width of
the attached gingiva and the level of the alveolar crest in relation to the
CEJ (Figure 3 View Figure).16 Excessive gingiva calls for resection, as does a
too-coronally positioned alveolar crest, one at the level of the CEJ or
less than 3 mm from an existing or expected restorative margin (ie, Coslet
Subgroup A altered passive eruption or biologic width invasion,
respectively).
Secondary factors influence resection as well (Figure
3 View Figure). Some patients desire to lessen gingival
pigmentation, whether racial, tattooed, or from
another cause. For them, an externally beveled gingivectomy removes the
undesired color and creates pink tissue upon
initial healing. The clinician must extend the incision
along the entire anterior esthetic zone to avoid color mismatch upon smiling. The hue change is not always permanent, however, and pigment may return in a few months. If a patient decides to maintain pigment, an internally beveled
gingivectomy will suffice.
Large quantities of bone and redundant mucosa require
flap surgery, as thick tissue rebounds. When more than 4 mm of tissue is
removed in a gingivectomy, healing proceeds at a slower pace, associated
with undue discomfort and potential regrowth. In comparison, a flap
approach may produce fewer complications in the long term.
Essentially, a crown lengthening encompasses
one or a combination of the following:
- gingival
repositioning (ie, apically positioned flap);
- gingival resection;
and/or
- osseous resection.
The clinician must systematically determine the
best surgical design in accordance with the Coslet classification
(Figure 4 View Figure). The type of altered
passive eruption, overgrowth, or other situation seen dictates the
crown-lengthening strategy. The clinician must
first assess the amount of attached gingiva. If soft tissue resection would lead to deficient attached
mucosa, then an apically positioned flap
is the plan of choice, as it preserves keratinized gingiva. Deep pocket
depths (ie, greater than 3 mm) do not mandate a resective technique,
as apically positioned flaps reduce pocketing as well. Likewise, shallow
pocket depths do not compel any particular
surgical design. Deep probing, however,
may indicate periodontitis, and the patient must receive
infection control before cosmetic work.
Next, analyze the level where the alveolar crest takes
place. Customarily, the interproximal bone
lies 1 mm to 2 mm away from the CEJ
radiographically, and the distance from the contact point to the alveolar
crest is roughly 4 mm to 4.5 mm.26-28 Facially, the dentogingival complex—measured from the
gingival margin to the bone—probes 3 mm.29 If a normal bony relationship exists and if there is no
expectation of biologic width compromise
by future prostheses, then ostectomy is unwarranted.
Bone removal occurs in some types of altered passive eruption, in which the
crest lies coronally to the norm, and for restorative purposes (biologic
width health and retention). Exostoses should be excised.
Esthetic crown-lengthening procedures relocate or
remove buccal tissue only, as palatal contours
are not noticeable. On the other hand, a
treatment plan that includes full-coverage restorations may call for surgery on the lingual as well, depending on the available tooth structure and
margin-to-alveolar crest proximity.
The decision tree outlined in Figure 5 ( View Figure) summarizes this
methodical approach to operative design.
SURGICAL HOW-TO GUIDE: THE TWO-STAGE TECHNIQUE
Again, it is imperative to measure the following
parameters before surgery to identify the right
crown-lengthening tactic: probing depths, width
of the attached gingiva, CEJ location, and bone levels. Bone sounding
with a probe under local anesthesia aids in assessment.
A major component of the diagnostic workup consists of
surgical guide fabrication. Use of a template relieves operative guesswork and allows for better reproducibility of the
desired lip–teeth–gingiva
proportions upon full smile. After appraisal of the patient at chairside, from photographs, radiographs, and casts, the practitioner creates a guide from a diagnostic
wax-up or model, following the tenets of ideal orofacial esthetics, listed
in a previous section. A simple vacuform appliance will suffice. He or she
must keep in mind several factors:
- gingival display at
rest and upon smiling;
- proper
width-to-length tooth ratios;
- heights of contour;
- gingival margin
level differences between teeth;
- symmetry; and
- dental crowding.
If crown lengthening fails to rectify all defects,
prosthetic work may compensate for the rest. Ultimately, most cases include
reshaping both teeth and gums.
Two-Stage Crown Lengthening
To combat gingival shifts that occur after
conventional crown lengthening and to speed the
temporization process, Sonick proposed a biphasic crown-lengthening method
in which only ostectomy occurs, without any preliminary gingival resection,
followed by gingivectomy several weeks later.30 The flap is repositioned to its original level at the first surgical
stage, and it appears as though no lengthening transpired. Four to 6 weeks
later, after initial attachment and bone healing, gingivectomy takes place.
As this short waiting period allowed for biologic-width reestablishment, which gingival removal should not
disturb, the author suggested that
provisionalization may begin 2 weeks after gingival resection. Finalization occurs at 3 to 6
months, as stated above. This two-step method
has particular use next to dental implants.
Contraindications include gingivectomy-only cases and inadequate attached gingiva pre- or postgingival
resection.
With diagnostics and guides completed and with the
exception of insufficient attached gingiva or gingivectomy-only scenarios, osseous surgery proceeds in the two-stage manner
suggested here (Table 4 and Figure 6 View Figure, 7 View Figure, 8 View Figure, 9 View Figure, 10 View Figure, 11(left) View Figure, 11(right) View Figure, 12 View Figure, 13 View Figure, 14 View Figure and 15 View Figure).
HEALING AND PROSTHETIC FINALIZATION
Gingivectomy
After gingivectomy, the gingiva returns to normal
function, including surface
epithelialization, in about 1 month (3 to 5 weeks); total remodeling of the attachment apparatus completes at
3 months (12 weeks).31,32 Any restorative finalization then may take place beginning
1 to 3 months postsurgery.33 The longer the delay, the less the tissue instability.
Osseous Crown Lengthening
Even after careful consideration of patient factors
and adequate surgical technique, it is difficult to predict where the
gingival margin will be in the long term. A number of articles on
osseous crown lengthening demonstrate a 1-mm to 3-mm coronal rebound of the free gingival margin 6 months to 1
year postsurgery.34,35 Attributed to thick tissue biotype and inadequate bone
removal, this coronal shift may be avoided by adequate gingivectomy and
ostectomy, and stable results may be detected at 3 months.36 Final prosthetic
impressions may begin at least 3 months after crown lengthening, though to
be safe, wait 6 months, when the remodeling finishes.34
Advantages of the Two-Stage Approach
In the majority of cases, the tissue level at 6 weeks
predicts the level at 6 months after osseous crown lengthening.34 Two-stage crown
lengthening lets the tissue settle and the attachment remodel
post-ostectomy, making the mucosal level post-gingivectomy more
predictable, important particularly in the esthetic area.
Remember that the gingiva follows the alveolar crest; initial
bone maturation, then, forecasts gingival maturation. Ultimately, this
two-stage approach speeds the prosthetic completion time because it
achieves marginal stability faster (Figure
13 View Figure, Figure 14 View Figure and Figure 15 View Figure). Traditional lengthening technique (ie, concomitant soft and hard tissue resection) may
require several “touch-up” procedures to attain proper
length or contour, thus slowing the restorative process. The two-stage
method precludes these unplanned touch-ups.
A WORD ON LASERS
A recent trend, laser-driven esthetic crown
lengthening, has risen in popularity. Is there value to such use? In
theory, lasers improve hemostasis, disinfect
tissue, lessen edema and scarring, attenuate postoperative discomfort, and hasten healing.37,38 Based on wavelength and waveform, they cut soft and/or hard tissue.
Soft Tissue Lasers
Carbon dioxide, Nd:YAG, diode, Ho:YA, Nd:YAP, and
argon lasers incise and ablate soft tissue for gingivectomy, gingivoplasty, and depigmentation, among other operations. The first three types have the most studies published on them, but
with respect to accelerated healing, none best the scalpel standard.39 In fact, some
investigations report slower initial and overall healing in laser-made
wounds, including gingivectomy and periodontal flap surgery, compared
to scalpel-formed.40-44 Lasers enhance coagulation, however, and this
boosts visualization and patient acceptance.
Hard Tissue Lasers
Er:YAG and Er,Cr:YSGG lasers cut both soft and hard
tissue and perform ostectomy and osteoplasty. Soft tissue-only
devices tend to char, melt, sequester, and delay healing of bone,
but at specific energies and pulses, the
Er:YAG and Er,Cr:YSGG incise bone with relative
safety. These instruments work on dentin
and enamel as well; in fact, some companies tout ostectomy efficacy based on evidence and settings culled from use on dentin and enamel.39 As with their soft tissue counterparts, the literature
support behind hard tissue lasers remains heavy on anecdotal observations
and light on scientific studies.45,46
Flapless Laser Crown Lengthening
Case reports cite use of the Er,Cr:YSGG to crown
lengthen teeth that require ostectomy without raising a flap.45-48 No re-entry
investigations exist to confirm or deny incision of bone vs enamel or
dentin or presence of charring, cratering, ditching, or root
gouging with this method. Because of a lack of visualization and tactile
sensation, precise ostectomy cannot be guaranteed. Cases of altered
passive eruption with coronally located bone or biologic width
concerns demand measurement accuracy. It is a characteristic not
well-documented in the flapless approach.
In short, there is a scarcity of controlled studies on
laser-guided crown lengthening. Its major advantage over traditional
scalpel methods is hemostasis. Clinical results for gingival resection
using lasers match but do not surpass those for conventional techniques.
With respect to hard tissue applications, less proof
exists. The value of laser therapy rests in its appeal to patients, who consider such treatment novel. It remains to
be seen whether novelty will shift to practicality.
A GUMMY SMILE NO LONGER
Patients who consider their smiles unattractive may
blame “gumminess.”
Skeletal deformities, labial musculature, oral pathology, periodontitis, genetic predisposition, and dental issues
contribute in varying degrees to excessive
gingival display. Scrupulous diagnosis yields
treatment that involves a multitude of specialties or perhaps just one. Sometimes a simple gingivectomy resolves
the chief complaint. More rarely, the patient
must tolerate orthognathic and facial
surgery, orthodontics as well as periodontal and restorative remedies to meet his or her standard of beauty and function. Therapeutic complexity notwithstanding, any
treatment plan that restores a person’s
dignity has merit. In this regard, one cannot
underestimate the worth of esthetic crown lengthening.
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Figure 1 Ideal gingival contour. |
Figure 2 “Gummy smile” seen in altered passive eruption. |
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Figure 3 Crown-lengthening technique determinants. |
Figure 4 Step-by-step analysis for crown-lengthening design. |
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Figure 5 Crown-lengthening design decision tree. |
Figure 6 Preoperative gingival display. |
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Figure 7 Full-thickness reflection. Note
the coronal level of the alveolar crest. |
Figure 8 Ostectomy performed. Note that
there is enough biologic width space created
for new anterior restorations. Positive
architecture is maintained. |
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Figure 9 Replacement of flap to original
position. |
Figure 10 Gingival level after 4 weeks of
healing. Minor apical pullback of tissue
occurred postostectomy, but the level still
approximates the initial presentation. |
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Figure 11 Model of diagnostic wax-up (left) and clinical recapitulation of desired tooth dimensions using calipers (right). |
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Figure 12 External bevel gingivectomy outline. |
Figure 13 Final periodontal and restorative result after two-stage
crown lengthening and porcelain veneer placement. |
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Figure 14 The patient’s smile before treatment. |
Figure 15 The patient’s smile after treatment. |
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Table 1 |
Table 2 |
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Table 3A |
Table 3B |
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Table 4 |
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