One of the challenges in periodontics, and dentistry
at large, is the management of maxillary anterior spacing. When this
spacing is found in adults, periodontal causes, drifting from tooth loss,
and habits are added to the genetic reasons that cause spacing to be
present. These spacing problems often require a multidisciplined
approach between periodontics, orthodontics and restorative
dentistry. In this newsletter we would like to identify different
causes of spacing, discuss spacing assessment and the impact of
periodontal disease on anterior spacing.
In the beginning we need to say that some spacing
has its origin in developmental difficulties unrelated to periodontal
disease influences. First, narrower than normal maxillary anterior
teeth results in spacing, often bilaterally symmetrical. This
condition is resolved best by fixed orthodontics to equalize the spaces
across the maxillary anterior segment followed by restorations to enlarge
the undersized teeth. To determine whether your clinical observation
of spacing is related to tooth size inadequacy, take the widths of the
lower 6 anteriors and multiply their total width by 1.3. The
resulting number should be the width of the six maxillary anteriors.
Narrower than normal maxillary anterior teeth must be retained as is or
treated as noted above.
A second non-periodontal related adult deformity
which can produce spacing is skeletal deep overbite. The clinical
findings to look for are lower incisors which are significantly coronal to
the plane of the posterior mandible, producing a bowed occlusal line when
the occlusal plane is viewed from a lateral perspective. Deep
overbite of skeletal origin needs to be distinguished from deep overbites
resulting from posterior bite collapse or lower anterior supraeruption. One of the best confirmations of the skeletal deep
overbite comes from observing the alveolar process surrounding the lower
anterior teeth and its relationship to the upper anterior teeth.
When the incisal edge of the upper anterior teeth covers the free gingival
margin of the lower incisors, skeletal causes are likely. The deeper
the maxillary incisors cover the mandibular process the more likely the
skeletal origins of the overbite-related spacing. With the patient
in occlusion it should be evident that the lower incisors approach the
palatal gingiva and the maxillary incisors are laterally or facially
displaced without much supraeruption. Orthodontic/orthognathic
consultation should be sought for these cases following screening for
periodontal disease.
Once skeletal considerations have been addressed,
the periodontal and occlusal origins of anterior spacing remain.
Proffet, a widely published authority in orthodontics, has noted in his
texts that the tooth's position is a balance of extra-oral and intra-oral
forces. Forces from the tongue and occlusion act against the
extra-oral lip posture, the resiliency of the periodontal ligament and
it's surface area. Many years ago, Bien established that occlusal
and muscular forces on the teeth were dissipated by a fluid mechanism
within the ligament of the tooth. Upon compression of the tooth,
fluid in the ligament space is squeezed into small holes in the cribiform
plate surrounding the tooth providing a hemodynamic dampening of tooth
movement. When hemodynamic forces are exceeded, the ligament becomes
disorganized and the periodontal ligament space widens through bone
resorption. Mobility then develops. This widening is a
function of not just the intensity of the force, but also
repetition. This mechanism helps us understand why some teeth with
reduced support are stable. Loading in these teeth is not
repetitious or the magnitude doesn't exceed the resistance of fluid
dampening. We would also be quick to note that proximal contact
enlists the aid of multiple periodontal ligaments in dampening loads.
Pathologic migration results from alterations in the
intensity, duration and direction of forces on the tooth. Clinical
conditions which require evaluation and control to stabilize tooth
position included habit patterns (increased intensity, duration and
direction of pressures on the periodontal ligament), posterior bite
collapse (altered direction and loss of resistance to force provided by
enlistment of adjacent tooth periodontal ligaments) and pathologic
migration (reduced area of periodontal ligament from periodontal disease
and continuous inflammatory pressure).
Although pathologic migration can result from pipe
chewing, nail biting and other dysfunctional uses of the teeth, the major
parafunctional habit patterns include bruxing and clenching. It is
very common to find patients with extensive tooth wear who have not
experienced any pathologic migration and resultant anterior spaces. Severe
wear occurs from a centric occlusion position well onto the cusp tips in
lateral excursion. Obviously high forces of a repetitive nature do
occur but the force is being distributed throughout the periodontal
ligament without inducing widening of the periodontal ligament.
When clenching is evident, we often see mobility as
well with tooth contacts opening. Clenching forces appear to be
repetitive and more focused in specific areas of the ligament space.
When combined with periodontal attachment loss, migration is likely to
result. Open contacts with distal drifting of second molars should
alert the clinician to closely scrutinize the periodontal and occlusal
status of the teeth adjoining the space.
A second source of anterior spacing is posterior
bite collapse. The untimely loss of several posterior teeth may have
two impacts on the anterior teeth of the maxilla. The first is to
increase the load during closure because the mandible shifts anteriorly
with posterior deflecting contacts not supporting the original vertical
dimension. The second is to move the forces on the anterior teeth
closer to the rotational axis of the tooth. When periodontal disease
reduces the bone height around the tooth, the forces are magnified and
facial tilting causes loss of contact and facial drifting. With
facial anterior motion, the lower anteriors begin erupting to maintain
contact. Once the maxillary anteriors have moved labial to the lower
lip, the spacing can accelerate as lip postures no longer act with the
periodontal ligament to resist lingual forces. Effective treatment
of this situation depends upon stabilization of the posterior vertical
dimension, treatment of the periodontal disease, and repositioning of the
upper and lower anterior teeth. Often, long-term retention is needed
when periodontal attachment loss is severe.
The third source of anterior spacing is periodontal
inflammation and attachment loss. As periodontal disease begins, the
normally tightly adapted gingival tissues lose their tonicity and swelling
produces a continuous light load on the tooth surface. With loss of
the attachment apparatus and increased area of inflammatory change the
tooth migrates away from the pocket, except for facial pocketing where
occlusal forces will collapse the tooth into the defect area and
accelerated labial tilting and mandibular supraeruption will result.
Once the supraeruption process begins, treatment rapidly becomes complex
as intrusion or incisal reduction become necessary to allow room for
repositioning the now malposed anterior teeth. Restorative
correction is possible when migration has limited proximal contact
separation to less than two millimeters, within the ability of the
clinician to maintain esthetic tooth proportions while closing the
spaces. In the same way, pathologic migration which elongates the
upper anterior tooth to a point where it cannot be shortened to the
occlusal plane (or adjoining teeth elongated) without compromising
esthetics or phonetics must be treated orthodontically to be
retained.
In advanced cases of periodontal disease, pathologic
migration is usually a combination of the above conditions.
Periodontal treatment is central to determining the long-term
stabilization required for effective treatment. Zachrisson now
recommends in a most recent text that periodontal treatment be fully
completed prior to the orthodontic phase of treatment for anterior
spacing.
We would be happy to assist you in diagnosing
the origins and therapeutic approaches to pathologic migration. As a
part of the management team of generalist, orthodontist and periodontist
we can help patients retain teeth with optimal function and
esthetics. We appreciate the chance to serve them and you.
