Winter 1999 Presentation Summary:

Prior to the 1980s, orthodontics was primarily concerned about occlusion and the alignment of teeth in children and adolescents. By the start of that decade, however, adults were appearing as patients in significant numbers. Sometimes they were referred by their dentists for a specific purpose, other times they came on their own to see about improving their appearances. Restorative options and complications were a common issue that differentiated these patients from the younger patients the orthodontist usually treated.

At the same time, the pace of change in the dental profession accelerated and the dental knowledge of the average orthodontist became outdated. Neither the orthodontist nor his dentist colleague had a good understanding of the other’s field. The need for interdisciplinary exchange was ripe. In 1984, Dr. Kokich and a group of colleagues in Tacoma, Washington, started meeting at frequent intervals to exchange knowledge and improve their understanding of dentistry’s broad spectrum. The subject matter of this presentation grew out of this continuing endeavor.

Dentistry has far more to offer in esthetic solutions to common problems than it did 20 or 30 years ago. Most of the issues in Dr. Kokich’s discussion were not even recognized at that time, since there were no viable solutions. Today’s goal is more than a beautiful alignment of teeth.

About a half dozen topics are to be considered. The small or missing lateral incisor needs an optimal amount of space. How much space and where should the small lateral incisor be placed within that space? What is the proper amount of tooth and gingival display for an attractive smile? What can be done about an asymmetric smile? What factors influence the errant dental mid-line? What considerations should the dental team give to crown length? Finally, what solutions exist for the dark triangular void that results when the gingival papilla does not fill the space between adjacent teeth?

The Undersized Maxillary Lateral Incisor

A number of issues need to be considered when dealing with the missing and diminutive maxillary lateral incisor. First is the proportion of the lateral relative to the central. The former is generally two-thirds the width of the latter, or close to it. Given adequate space, the lateral needs to be closer to the central incisor than it is to the cuspid. This is related to incisor morphology. Both are flatter on the mesial, more convex on the distal. For this reason, the restorative dentist will want the lateral placed a third closer to the central than to the cuspid to provide the optimal emergence angle.

Palatal-labial position of the small lateral depends on the nature of its anomaly. If the tooth has a discernible incisal edge, it will most likely be restored with a veneer or composite build up. In this case, there will be no reduction of the cingulum. The cingula of the central, lateral, and cuspid should be even and in contact with their mandibular antagonists. This will permit optimal color depth as well. If, however, the lateral is cone shaped, it will eventually require restoration with a crown and its cingulum is best-positioned labial to the adjacent teeth.

Dr. Kokich recommends restorative augmentation of these teeth prior to the end of orthodontic treatment so that the dentist has a chance to refine and polish the restoration in the presence of excess space which can be closed in the final stage of orthodontics. When both lateral incisors are anomalous, establish ideal dimensions by placing the posterior teeth in ideal interdigitation, slightly over sizing the laterals which are then reduced as ideal over bite and over jet are established. In general, the dimension will be close to two-thirds of the central, but refinements help to reduce the incidence of crowding or spacing in retention.

To avoid restorative complications or compromises later, it is important to consider root angulation. Proper emergence profiles are difficult or impossible to establish when the tooth is not in a proper axial inclination. Occasionally this trap is deceptively easy to fall into if the orthodontist does not recognize that a tooth has been previously repaired in a less than optimal position. It is far better to realize this at the inception of orthodontic treatment, have the tooth restored to its proper morphologic shape, and bracket it in the usual manner. Ideal position of the root is easily established with out guesswork.

To establish ideal space for implants the rule of two-thirds the size of the central applies. This will usually provide adequate space for the optimal 4mm implant. In the instance where the centrals are unusually small however, it is possible to avoid using a 3mm implant by slightly reducing the enamel surfaces of adjacent teeth. This will leave enough space for sound restorative principles and avoid compromising the integrity of the papilla.

Dental mid-lines are often deceptive. Research has determined that this can be off by as much as 4mm without being detected by the lay public. If, however, the incisors are tilted relative to the incisal plane, mid-line discrepancies as little as 2mm are readily noticed. We can conclude that if mid-line discrepancy is unavoidable, be sure the angulation of incisors is vertical and you will most likely get away with it.

Establishing an ideal mid-line is not always all that simple. Faces are asymmetric. Nasal deviations are not uncommon. In the speaker’s view, the best means of locating the dental mid-line is to frame it in the smile. Cupids bow is always the center of the lips, unless the patient is a burn victim or presents a labial cleft. The philtrum is a reliable measure of the dental mid-line.

Gingival display, whether related to a short upper lip or over eruption, falls into an arena that did not exist twenty to thirty years ago. Today there are orthodontic, restorative, periodontal, and surgical modalities to consider singly or in concert. If gingival exposure involves only the anterior teeth, it may well respond to an orthodontic solution. Or, it may result from delayed eruption and periodontal sounding to locate the cemento-enamel junction may indicate that tissue removal will resolve the issue.

If excessive gingival prominence involves posterior as well as anterior areas, orthodontic treatment will not rectify the problem. True vertical maxillary excess is more than likely a surgical problem. Caution must be exercised to avoid over correction. Since a millimeter or two of gingival exposure is considered desirable, the lip posture at rest is a better guide to repositioning than the high smile position. Periodontal tissue removal may also be effective in this situation, especially in the presence of significant wear when a perio-restorative solution may provide the optimal solution.

The incisal plane is another problem to be considered if one is interested in the maximum esthetic result. The most reliable indicator here is the relationship to the inter-pupillary line. This can be detected with good clinical photographs. When the slant of the incisal plane is coincident with the occlusal plane, it probably represents a skeletal asymmetry as opposed to a more dental problem. Models mounted to the inter-ocular plane as opposed to Frankfurt Horizontal may be more diagnostic. A frontal head film would be more informative. Ramus heights are likely to be unequal with compensatory facial growth and eruption.

When considering the canted incisal plane, unusual wear patterns must not be overlooked. When considering asymmetric wear, the most reliable method of detection is to examine the incisal edges. The fingerprint of wear are the incisal widths. The worn side will have wide incisal tables, while the unworn side will present thin, sharp incisal edges. Asymmetric incisal planes in the absence of posterior involvement may be amenable to orthodontic, periodontic, or restorative procedures.

Crown length is a facet of dental esthetics that the orthodontist was slow to recognize. Short crown length can result from wear or trauma. In its most readily detected manifestation, the gingival margin of the central incisors are not equal, or lower than the margin of the lateral This will catch the eye of even the most casual observer. Ideally the margins of the centrals and cuspids are higher than the laterals. If a worn tooth is to be intruded to establish the appropriate margin position followed by restoration, caution must be exercised to avoid relapse. Dr. Kokich feels that principal fiber (not circumferential) reorganization may take from six to nine months in humans.

The final item of interest in satisfying patient expectations is to insure that the papilla fills the inter-dental embrasure. In general, incisor contact extends half way up the tooth. The remaining space is occupied by the papilla. When the papilla falls short, one has to consider if the axial inclination is correct, and whether the shape of the crown is a contributory factor. If the crown is excessively triangular, contact may occur only at the incisal edge and some type of reshaping either enamel reduction or restorative augmentation may be in order. To determine which, the proportion of crown height to width needs to be appraised. Typically, width should be sixty per cent of length. If it is greater than sixty percent, enamel reduction is indicated, if less restorative enhancement is in order.

Adequacy of bone level has a considerable impact on the ability of the papilla to fill the embrasure. Periodontal enhancement of the deficient papilla, particularly in the absence of adequate bone is at best not a predictable procedure.

Gingival sufficiency in the lower anterior area is a well-known challenge, particularly in the presence of bone loss. In this area, incisal contact accounts for two-thirds of the embrasure, the papilla occupies the remaining one third. The ability to reduce inter-proximal enamel is limited by the circumference of the roots. If roots are large, only minimal crown reduction can be attempted. In this instance, veneers may be the best option to extend the contact down to the papilla.

Dr. Kokich is a leading proponent of interdisciplinary dentistry. He has been at the forefront of integrating the myriad facets of dental knowledge into a cohesive whole to provide patients with the optimal esthetic results that they and their professional team are capable of achieving.

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