Patients with congenitally missing maxillary lateral incisors often need a challenging interdisciplinary treatment, whether canine substitution, single implants, or tooth-supported restorations are chosen. Currently, it would be inappropriate to remove enamel and dentin to place crowns on adjacent teeth in patients with dental agenesis, mainly if these individuals have no restorations or wear of their existing teeth.⁸ In case of unilateral agenesis of the maxillary lateral incisor, space closure should not be used, except in exceptional cases, because of subsequent esthetical and functional problems.⁷

If the treatment plan calls for opening of the edentulous spaces, implants would be an ideal alternative for replacing the missing teeth. Research has shown that the success rate of implants is very high. However, maxillary lateral incisor implants are challenging aesthetically. The amount of space is often small, the alveolar ridge may be deficient, the papillae are occasionally short, the adjacent roots could be too close, the gingival levels may be uneven, and the patient could be too young. Any of these issues could compromise the aesthetic outcome of even the finest surgical implant placement.⁹

In this approach, orthodontic treatment combines:

Working with aligners, the functional placement of the canine requires the use of attachments to properly control the movement of the root in the three dimensions. A good option to obtain predictable movements is always represented by their sequentialization. If the canine requires distalization, mesiodistal root tipping, and torque control, then a good suggestion is to plan distalization steps of 2 mm, application of mesial root tipping of at least 2 degrees every 2 mm of distalization, and (only once distalization and mesiodistal root tipping have been completed) planning the root torque information.¹⁰ The control of all those movements can be achieved with the use of rectangular and vertical attachments.

If a patient is congenitally missing one maxillary lateral incisor, the amount of space to accommodate a cosmetic replacement is determined by opposite lateral incisor. However, in some patients the contralateral incisor could be peg shaped. If this is the case, management of spaces should be performed on the basis of surrounding teeth and tissue esthetics and function. The same approach should be used when both lateral incisors are congenitally missing.

The fundamental criteria for esthetic analysis should include facial, dentogingival, and dental esthetics.¹¹ In recent years, several computer software programs for digital smile design (DSD) have been introduced to clinical practice and research. They are multiuse conceptual tools that can strengthen diagnostic vision, improve communication, and enhance treatment predictability by permitting careful analysis of the patient’s facial and dental characteristics that may have been overlooked by clinical, photographic, or diagnostic cast-based evaluation procedures.¹²

With today’s implant technology, assuming a 3.25-mm lateral incisor implant, most surgeons would probably be comfortable placing a maxillary lateral incisor implant in a patient with an interradicular space greater than 5.5 mm, leaving at least 1 mm of alveolar bone on either side of the implant. If the interradicular space were less than 4 mm, many surgeons would suggest orthodontic retreatment. Therefore, speaking specifically to minimizing the risk of root movement during retention that would impede implant placement, Olsen and Kokich¹³ recommend leaving extra space for the surgeon (i.e., a minimum of 6.3 mm between the crowns and 5.7 mm between the roots). This correlates well with the space traditionally suggested for implant placement of 1 mm on either side of the implant.

A 27-year-old female presented with the chief complaint of an unaesthetic lateral profile due to protruded upper teeth, in addition to lower dental crowding. She had a short face, an acute nasolabial angle, a mildly convex profile, and lip incompetence, with class I canine and molar relationships and significant overjet and overbite (Fig. 14.1). Furthermore multiple restorations were present. The panoramic radiograph confirmed that 1.2 was missing (Fig. 14.2).

This patient did not wish to change her facial esthetics but to merely improve the appearance of her anterior teeth. Therefore the goals of esthetic interdisciplinary treatment were to reduce the protrusive profile and obtain a class I canine occlusion, with normal overjet and overbite, by means of orthodontic treatment; enhance dental esthetics and the smile line with orthodontics and prosthetic restorations; and replace the upper right lateral incisor with an implant.

Prior to clear aligner treatment, the dental bridge from the upper right canine to the upper left lateral incisor was sectioned and polyvinyl siloxane (PVS) impressions were taken. Clear aligner treatment in the upper arch was designed to intrude and retract the anterior teeth, supported by class II elastics to bonded buttons on the upper canines and lower first molars. In the lower arch, intrusion and proclination of the anterior teeth were planned. A temporary resin pontic replaced the missing upper right lateral incisor during aligner treatment (Figs. 14.3, 14.4, and 14.5). At the conclusion of 19 months of aligner treatment, the severe overjet and overbite were improved, and the original vertical dimension was unaltered. An upper right lateral incisor implant was placed, followed by final esthetic restorations (Figs. 14.6, 14.7, and 14.8).

The mesial tipping of mandibular second molars is a frequent source of request for orthodontic intervention by restorative dentists. Inadequate mandibular arch length, excessive teeth size, loss of the adjacent first molar, premature eruption of the mandibular third molar, and unusually mesial eruption pathway of the second molar can also cause its partial or total impaction.¹⁴ Zachrisson¹⁵ stated that in case of severe mesial tipping of lower second molars, periodontal status can be aggravated, with angular bone loss, and an apparent pocket at the mesial surface of a tipped mandibular molar. In excessive inclination cases, overeruption of the antagonist molar with subsequent premature contacts and occlusal interferences hamper prosthetic intervention.

Repositioning of the second molar eliminates pathologic condition and facilitates the placement of a prosthetic restoration. Among the limitations of aligners, severely tipped teeth (>45 degrees) were included.¹⁶ Uprighting a severe mesial tipped molar using aligners could be quite risky since the fitting loss could produce a worsening of the mesial tipping. As well described by Brezniak,¹⁷ if the tooth is not performing the desired movement, the aligner will surrender to the stiffer teeth and become distorted. Its gingival edges move away from the teeth, and no force can be exerted in the gingival area while the force is concentrated only in the occlusal part. This distortion prevents any possible couple to be developed, and no bodily movement of the tooth is possible. This occlusal force encourages intrusion that, for a severe mesial tipped molar, means worsening of its tipping. Therefore when planning, uprighting of molars with aligners is preferable to reduce the velocity of the angular movement and to accurately control the fitting of aligners at every appointment (Figs. 14.9 through 14.20). The intrusion effect and thus the worsening of the mesial tipping could be accelerated if a large attachment has been displayed on the buccal surface of the molar and if the aligner is losing fitting. Attachments are helpful especially in those cases with rounded shape teeth but close controls in the office are required. To increase the efficiency of the uprighting mechanics and to increase the stiffness of the aligner, pontics mesially to the tipped teeth should be avoided. Pontics are equivalent to loops bent on an archwire. They increase elasticity and then a potential undesired distortion of the aligner if it is going to lose fitting.

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