Crown Lengthening
Crown Lengthening to Facilitate Restorative Treatment in the Presence
of Incomplete Passive Eruption
Timothy J. Hempton, DDS, and Finn Esrason, DMD
Copyright 2000 Journal of the California Dental Association.
Dr. Hempton will
present "The Interrelationship Between Periodontal and Restorative Treatment
of the Natural Dentition" at the CDA Scientific Session in Anaheim. His
presentation will be from 9 to 11:30 a.m. on Friday, April 14, in Room
California D of the Anaheim Hilton and Towers. He will also present "Crown
Lengthening Workshop" from 9 to 11:30 a.m. on Saturday, April 15, in Room
212A of the Anaheim Convention Center.
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Crown-lengthening surgery can be utilized to expose subgingival caries. In this clinical case, a patient presented with incomplete passive eruption in the maxillary anterior sextant. This case illustrates that when incomplete passive eruption is present and restorative treatment is necessary in the maxillary anterior sextant, crown-lengthening surgery not only provides exposure of subgingival caries but can also result in a more esthetic therapeutic outcome.
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Originally printed in the Winter 1999 issue of the Journal of
the Massachusetts Dental Society. Reprinted with permission.
The periodontal-restorative interrelationship involves the utilization
of periodontal therapy to facilitate restorative treatment. Subgingival
caries or fractures can be properly restored with surgical crown lengthening.
Osseous recontouring is indicated if intraosseous defects are present
or if the fracture or caries is within close proximity to the osseous
crest. In the maxillary anterior sextant, periodontal surgery for the
treatment of osseous deformities, for crown lengthening, or for a combination
of both therapies, may effect an esthetic compromise. A complicating result
of this treatment is root exposure and loss of interdental tissue.1,2
A prosthetic solution to this postsurgical dilemma would involve fabricating
porcelain-fused-to-metal cast restorations, which extend apically involving
preparation of the exposed root. In addition, the restorations are wider
mesiodistally to close the unesthetic gingival embrasure areas, which
appear as black triangles.3,4
The anatomical crown extends from the cementoenamel junction to
the incisal edge. The clinical crown extends from the free gingival margin
to the incisal edge. Healthy gingival tissues normally present with the
free gingival margin located slightly coronal to the cementoenamel junction.
However, the free gingival margin can extend coronally to cover one-third
to one-half of the enamel, resulting in excess gingival display. When
this occurs, the length of the clinical crown is significantly shorter
than the anatomic crown. When excess gingival display (also referred to
as incomplete passive eruption) is present in the maxillary anterior sextant,
crown lengthening for surgical management of subgingival fractures or
caries does not necessarily effect an esthetic compromise. By contrast,
exposing enamel previously covered with excess gingiva not only provides
the periodontal solution to the restorative problem but can also improve
the esthetic appearance of the maxillary anterior dentition.5,6
Incomplete Passive Eruption
The Dentogingival Junction
The dentogingival junction refers to the combined average occlusoapical
measurements of two supracrestal periodontal structures. These structures
include the junctional epithelium and the supracrestal connective tissue
attachment. Gargiulo and colleagues studied the dimensions of the dentogingival
junction in humans.7 He noted the following: the length of
the junctional epithelium attachment averaged 0.97 mm, and the connective
tissue attachment averaged 1.07 mm. The combined average was 2.04 mm.
The study also included a measurement of the average dimension of a healthy
sulcus. This value was 0.69 mm. To review, the sulcus extends from the
most coronal aspect of the junctional epithelium to the free gingival
margin. The junctional epithelium and the connective tissue attachment
located apical to the junctional epithelium function as the supracrestal
attachment apparatus. Each component averages 1 mm.
Dental Eruption, Active and Passive
The apical migration of the structures of the dentogingival junction relate
to dental eruption. Eruption of teeth can be divided into two phases,
active and passive. Active eruption terminates when the tooth makes contact
against the opposing arch. Passive eruption involves the apical movement
of structures of the dentogingival junction without any vertical movement
of the tooth. As the dentogingival junction migrates apically exposing
enamel, the dentition appears longer. Completion of this process occurs
when the dentogingival junction approximates the level of the cementoenamel
junction. When the sulcular and junctional epithelium still remain significantly
coronal to the cementoenamel junction, passive eruption is delayed or
referred to as incomplete passive eruption.
Clinical Appearance of Incomplete Passive Eruption
Clinically, incomplete passive eruption can be described as an anatomical
condition where the free gingival margin is located greater than 2 mm
coronal to the cementoenamel junction. Volchefsky and Cleaton-Jones noted
a 12 percent incidence of incomplete passive eruption occurring in the
population they observed.8 They discussed the possibility that
incomplete passive eruption could be a risk factor for necrotizing ulcerative
gingivitis.
In general, incomplete passive eruption is nonpathologic and can be described
as an anatomical aberration. The crown of the tooth is not completely
exposed, resulting in an appearance of short teeth. Evian described this
entity as having the appearance of drug-induced gingival hyperplasia.9
Viewing the position of the cementoenamel junction on the radiographs
can facilitate diagnosis of this condition. If the clinical crown length
is less than the crown length measured on the radiograph (i.e., the anatomical
crown), then incomplete passive eruption is present. The exact etiology
of this condition is unknown. Intrusion induced by orthodontic treatment
may be a factor in the development of this relationship between the cementoenamel
junction and the free gingival margin.
Incomplete Passive Eruption and Restorative Interactions
Dello Russo presented concerns about subgingival placement of crown margins
in the presence of incomplete passive eruption.10 Subgingival
crown margins are potentially plaque-retentive and can increase the risk
for the development of gingival inflammation and subsequent attachment
loss.11 The gingival tissues apical to the crown margin are
adjacent to enamel and therefore are not attached by connective tissue.
The inflammatory response initiated by the presence of plaque could result
in the disassociation of the junctional epithelium from the enamel. The
junctional epithelial attachment is not as strong as a connective tissue
attachment, and pocket formation may ensue.
Malament noted that this condition can confound proper fixed prosthetic
therapy.12 Short teeth can lead to inadequate retention and
resistance form when full cast restorations are planned. Proper embrasure
space development is also complicated in the presence of excess gingival
tissues. Moreover, esthetics are less than ideal when teeth have a short
appearance. It gives the appearance of significant wear due to bruxing
or attrition. When this condition is present in the maxillary anterior
sextant, esthetics play a critical role in treatment-planning.
A Review of Crown Lengthening Modification of the Osseous Tissues,
Osseous Resection
A crown-lengthening procedure refers to the surgical alteration of the
periodontium to facilitate definitive exposure of the dentition.
This treatment often involves modification of the investing osseous structures.
To better understand this process, several terms will be reviewed. Osseous
resection refers to the removal of bone with rotary and hand instrumentation.
Osteoplasty refers to removal of nonsupporting bone (i.e., bone which
is not directly attached to the root via the periodontal ligament). Ostectomy
is the removal of supporting bone.
Employment of a crown-lengthening procedure to expose subgingival caries
involves a three-dimensional analysis of the problem. The three parameters
include the occlusal apical dimension, the mesiodistal dimension, and
the buccolingual dimension. This analysis facilitates flap design and
determines the extent of osseous resection.
Occlusal Apical Dimension: The Biologic Width
The first dimension is the occlusal apical dimension, and involves the
"biologic width." Ingbar discussed the dentogingival junction from a periodontal
and restorative perspective.13 He described the average measurement
of the dentogingival junction (2.04 mm) as the biologic width. He recommended
that restorative treatment should not violate the biologic width (i.e.,
tooth preparation should not damage the junctional epithelium attachment
or the connective tissue attachment). Moreover, he advised placement of
supragingival margins and recommended that a minimum dimension of 3 mm
coronal to the alveolar crest is necessary to permit healing and proper
restoration of a tooth. Nevins and Skurow proposed that the biologic width
should be considered 3 mm in length, measured coronally from the alveolar
crest.14 This would allow for restorations to be placed at
least 1 mm away from the attachment apparatus within the gingival sulcus.
Presently, a 3 mm measurement is generally agreed upon as the desired
distance between the restorative margin and the osseous crest. These 3
mm account for the sulcus (1 mm), the junctional epithelium (1 mm), and
the connective tissue attachment (1 mm). Flap elevation is necessary to
observe the location of the osseous crest relative to the proposed restorative
margin. To facilitate this, surgical flap elevation is necessary to view
the osseous tissue. Moreover, osseous recontouring cannot be accomplished
with a gingivectomy procedure, as a gingivectomy procedure will not afford
adequate access.
The Mesiodistal Dimension: A Scalloped Osseous Morphology
The second dimension is the mesiodistal dimension. If caries extends toward
the interproximal area, re-establishment of positive osseous architecture
must be accomplished to facilitate proper wound healing. Positive osseous
architecture refers to the normal position of the osseous crest relative
to the cementoenamel junction. In health, the osseous crest is usually
located 1.5 to 2 mm apical to the cementoenamel junction. The cementoenamel
junction on the proximal surfaces of the dentition is coronal to the level
of the cementoenamel junction on the facial and lingual surfaces. The
osseous crest reflects the location of the cementoenamel junction, resulting
in a scalloped or parabolic appearance. The measured difference between
the level of the cementoenamel junction on the proximal surface and the
cementoenamel junction on the approximal surface is greater in the anterior
sextants. This results in a more scalloped appearance of the crestal osseous
morphology. In the posterior sextants the scalloping is not as extensive,
resulting in a relatively flat appearance. Rosenberg recommended re-creating
the scalloped appearance at a more apical level during crown lengthening
procedures.15 He was, in effect, referring to altering the
osseous morphology in the mesiodistal dimension as the caries or fracture
approaches the interproximal areas.
The Buccolingual Dimension, Osseous Ledging, Osseous Torri
The third dimension is the buccal lingual dimension. An osseous topography
consisting of bony ledges that are wide in the buccolingual dimension
will present with concomitant excess gingival display in an occlusal apical
dimension. Failure to reduce the thickness of the osseous ledging will
affect the healing of the overlying gingiva. The maximum reduction of
the occlusal apical postoperative gingival height will not be achieved.
A reduction of the osseous ledges in conjunction with treatment of the
occlusal apical and, if needed, the mesiodistal dimension will affect
the optimal position of the free gingival margin postoperatively.
A clinical situation could present with significant osseous ledging with
the osseous crest located 3 mm apical to the proposed restorative margin.
In this case, reduction of the buccolingual dimension without osseous
resection in the occlusal apical dimension will result in the optimal
occlusal apical position of the gingival tissue without removal of the
supporting bone (ostectomy). If there is thick bone and ledges are not
reduced, the underlying osseous topography will influence the overlying
gingival tissues as they heal. By thinning the bone in a buccolingual
dimension, the overlying gingival tissues will heal at a more apical level.
In cases of incomplete passive eruption, the osseous crest may be located
at or within close proximity to the cementoenamel junction.16
Removal of supporting bone will not significantly affect the stability
of the invested dentition.
In the case of the maxillary anterior sextant, removal of bone in the
interproximal area is a concern, as it can result in a black triangle
in the gingival embrasure area. In cases where caries is limited to the
facial aspects of the maxillary anterior dentition, a flap can be elevated
on the facial aspect only. The interdental bone and overlying soft tissues
(the papillae) can be left intact. If caries does extend to the proximal
surfaces or onto the palatal surface, elevation of a palatal flap and
interdental denudation will need to be performed. In addition, removal
of bone in the interdental will also have to be done. Under these circumstances,
recession or loss of papilla will occur in the interdental area. To compensate
for these anatomical changes, the crowns placed in the area may have to
be fabricated with contours modified to eliminate or reduce the black
triangle.
Case Report
The patient was a 21-year-old white male in good health. He presented
for an initial consultation in September of 1997. At that time, class
V carious lesions were noted on teeth Nos. 6, 7, 8, 9 and 11. These lesions
extended subgingivally (Figure 1). The gingival tissues were only
slightly inflamed. The overall tone of the gingival tissue was fibrotic
in nature. Some loss of the interdental papillae can be seen between teeth
Nos. 8 and 9. The maxillary anterior dentition appeared short. Minimal
wear patterns were noted on the incisal edges of these teeth.
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Figure 1. A 21-year-old male patient with incomplete passive eruption in the maxillary anterior sextant resulting in short clinical crowns. Class V carious lesions extending subgingivally were noted on teeth Nos. 6, 7, 8, 9, and 11. Moderate loss of interdental tissue between teeth Nos. 8 and 9 is evident. |
Periapical radiographs indicated that enamel was present apical to the carious lesions (Figure 2). The length of the clinical crowns measured on the radiographs was 2 to 3 mm longer than the clinical crowns. A periodontal probe placed apical to the free gingival margin detected the topography of the cementoenamel junction, which was apical to the caries.
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Figure 2. Periapical radiographs of the maxillary anterior dentition reveal that the lengths of the anatomic crowns are 2 to 3 mm longer than the lengths of the clinical crowns. Note the presence of unexposed enamel located 2 to 3 mm apical to the carious lesions. |
To provide proper exposure for adequate restorative treatment, a crown lengthening procedure was recommended. This procedure included teeth Nos. 6 through 11. Caries was not present on the palatal aspects of the maxillary anterior dentition; therefore, a palatal flap was unnecessary. Moreover, access to the facial lesions could be obtained with elevation of a facial flap, leaving the interdental papilla intact. This flap was designed to prevent loss of interdental tissue with the concomitant appearance of black triangles (Figure 3). The incision was an internally beveled scalloped incision, which extended from the mesial aspect of tooth No. 5 to the mesial aspect of tooth No. 12. One to 2 mm of marginal tissue were excised after the initial incision.
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Figure 3. An inverse bevel incision was utilized to provide access to the underlying osseous structure. A palatal flap was not elevated. |
Access to the underlying osseous structure is critical in treatment of' incomplete passive eruption (Figure 4). Often the cementoenamel junction will be located within less than 2 mm to the osseous crest. In normal osseous architecture, the osseous crest follows the cementoenamel junction and is located 2 mm away from it. This gives the osseous morphology a scalloped or parabolic appearance. At various locations it was noted, however, that the cementoenamel junction was less than 2 mm away from the osseous crest on the facial aspects of teeth No. 6 through 11. The bone was not unusually thick in the buccolingual dimension.
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Figure 4. Subsequent to elevation of the facial flap, enamel apical to the carious lesions was exposed. Moreover, the relationship between the osseous and the cementoenamel junctions could be observed. |
A hand chisel was utilized to recontour the bone on the facial aspects of teeth Nos. 6 through 11 (Figure 5.) The facial flap was positioned at the cementoenamel junctions of teeth No. 6 through 11. A 4-0 expanded polytetrafluoroethylene suture was utilized to position the facial flap. Interrupted sutures were employed and engaged the remaining interdental tissue. After 12 weeks the patient presented for an evaluation (Figure 7). All carious lesions were exposed as well as 2-3 mm of enamel that was previously subgingivally located. The patient was subsequently referred to the restorative dentist for placement of composite restorations on teeth Nos. 6, 7, 8, 9 and 10 (Figure 8).
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Figure 5. Osseous recontouring was performed around teeth Nos. 6, 7, 8, 9, 10, and 11, resulting in a minimum distance of 2 mm from the osseous crest to the cementoenamel junction. As the caries did not extend onto the proximal surfaces, the interdental tissues were left intact to preserve aesthetics. |
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Figure 6. The facial flap was positioned at the cementoenamel junction, utilizing 4-0 expanded polytetrafluoroethylene sutures. |
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Figure 7. Postoperative view at 12 weeks. The anatomic crown is completely exposed (i.e., the clinical crown length approximates the anatomic crown length). |
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Figure 8. Restorative treatment has been completed. Composite restorations were placed on teeth #6, 7, 8, 9, and 10. The diastema closed between teeth Nos. 8 and 9. |
Summary
Crown-lengthening surgery can be utilized to expose subgingival caries.
In this clinical case, a patient presented with incomplete passive eruption
in the maxillary anterior sextant. The carious lesions did not generally
extend toward the proximal surfaces to such a degree that resection of
interdental tissue was warranted. As a result, it was necessary to elevate
only a facial flap, thereby preserving interdental tissue. This case illustrates
that when incomplete passive eruption is present and restorative treatment
is necessary in the maxillary anterior sextant, crown-lengthening surgery
not only provides exposure of subgingival caries but can also result in
a more esthetic therapeutic outcome.
Acknowledgment
The authors wish to thank Dr. Sandra Cove for her help in preparing this
manuscript.
Authors
Timothy J. Hempton, DDS is an assistant clinical professor in the Department
of Periodontology at Tufts University School of Dental Medicine. His private
practice is limited to periodontology and implantology, and is located
in Dedham, Mass.
Finn Esrason, DMD, is a clinical instructor in the Department of Restorative
Dentistry at Tufts University School of Dental Medicine. His private
practice in restorative dentistry is located in Randolph, Mass.
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To request a printed copy of this article, please contact/Timothy J. Hempton,
DDS, 347 Washington St., Suite 103, Dedham, MA 02026.
