Dentists are treating what seems to be a rising number of patients having a missing lateral incisor. It has been reported that there is an incidence of congenitally missing laterals in just under 2 % of the population (1). The absence of both maxillary laterals occurs more often than the absence of only one and when unilateral the remaining lateral is found to be a microdont in 57 % of patients. (Fig 1A, B).

Recognition at an early age is critical in order to coordinate a treatment sequence to be able to restore natural looking aesthetics and function (2). (Fig 2A, B) It is imperative to take a panoramic X-ray to determine if any teeth are missing or are not erupting normally.

Treatment of congenitally missing lateral incisors is an orthodontic and a restorative issue. The aesthetic/restorative challenge is based on a tooth to arch size discrepancy. Robertson et al (3) did a retrospective study of orthodontic space closure vs. restoratively replacing the missing laterals. Other articles discuss moving canines mesially (4) or question whether or not to open or close the space. (5)

Fig 1A, B: 17 year old with a single tooth implant replacing a congenitally missing lateral and the other lateral being a microdont and discolored.
Fig 2 A, B: Recognition of congenitally missing teeth and early treatment planning are essential to a natural looking result.

I believe that too often orthodontists move canines into the lateral position and create an aesthetic nightmare (Fig 3A, B, C, D, E). They are taking a wide tooth and moving it into a position designed to accommodate a narrow tooth. The canines are usually one half to a full shade darker than the laterals and their color appears strange when it is not in their normal position. As well, the gingival levels of canines and laterals are different resulting in visual disharmony.

“Beautiful teeth are in!” All one has to do is look at fashion magazines, television and billboard advertising to realize that people want to look like other people (not like dogs).

The orthodontists really believed that they were helping their patients. They spent considerable time and energy in order to move the canines into the lateral position and were proud of their achievement. But what about their patients?

It wasn’t their fault that they had congenitally missing laterals. They undertook orthodontic treatment in order to correct the problem with expectations that they would look like everyone else once treatment was completed. Now they must either accept the way they look, hide their faces in shame or completely redo the orthodontic treatment in order to move the canines into their natural position and then replace the laterals with prostheses.

Even in situations where the canines are small and can be moved into the lateral position (Fig 4A, B) eventually the patient may become dissatisfied and would have been better off if the canines were left where nature intended them to be. Moving the canines mesially into the lateral position may take years to achieve, yet yield a result that is neither functionally nor aesthetically satisfying.

Fig 3 A, B: Was the orthodontist really helping the patient?

Fig 3 C, D, E: A missing lateral incisor was treated by moving the canine into the lateral position resulting in asymmetry and a unilaterally collapsed profil

There are numerous potential problems associated with moving a canine into the lateral position:

• Occlusion and articulation are inefficient because there is no cuspid guidance as a result of the mesial positioning of the maxillary canines preventing the upper and lower canines from working together (6)
• There is an increase in the amount of wear to all the teeth because they do not benefit from being protected by cuspid guidance.
• There is an increase in abfraction and microfractures in the posterior teeth because the occlusion is usually in premolar rise. Premolars are not canines and abfractions will occur as the teeth will flex under stress causing enamel to sheer off at the gingival level. Over time, periodontal and sensitivity problems may result.
• Retention of the canine in the lateral position after orthodontics may be difficult because the canine is not in a physiologically stable position. Long-term wear of an orthodontic retainer is often required.
• Patient’s often display temporomandibular joint (TMJ) symptoms, muscle tension, tooth grinding and headaches because of a lack of cuspid guided occlusion. The facial muscles are not responding in the manner in which they were meant to.
• The labial tissue and boney eminence associated with the canines does not look natural adjacent to the central incisor(7). Not having the canine protuberance where it belongs does not offer adequate facial support with a resulting dished in face and narrow buccal corridors. As the patient ages, this tends to be aesthetically displeasing as fewer teeth become visible when smiling. By the age of 50, patients often resort to having full aesthetic rehabilitation to enable their teeth to be lengthened and their buccal corridors expanded.
• On a daily basis we are consulted by patients wishing to improve a dished in face created by previous orthodontic treatment. Treatment alternatives involving maxillofacial surgery and redoing orthodontics are difficult, invasive and non-predictable. Patients usually opt for full mouth reconstruction involving opening their vertical dimension and expanding their dental arches.
• The canine itself has aesthetic limitations in the lateral position. The gingival level is different. It is darker in colour than a lateral incisor. Its rounded labial contour does not resemble that of the flat lateral incisor. The canine is a pointed tooth resulting in incisal embrasures that are too open yielding a fang like appearance.(8)

 

Treatment philosophy

Education

In 2006, the standards of dental treatment changed significantly. In the

1970’s dentistry focused on health and function. Today’s dentist tries to envision the complete picture striving for health, function, muscle balance and preserving a youthful appearance.

Our pursuit of knowledge is pushing the boundaries and the standards of dental care. Research and continuing dental education have increased our knowledge of dental health, aesthetics, gingival form and the importance and role of the TMJ and facial musculature.

In the 1960’s and 70’s, we relied on specialists to lead the way. Whatever they said usually dictated treatment.

Often dentist are stuck in a rut because their level of education does not coincide with that of the specialists they deal with. Egos and the resistance to change interfere with our ability to improve. Today’s dentistry should leave egos at the door. We must develop a strong dental team. The patient is the one who will benefit.

 

Patient Expectations

People today are living longer. The average life span of a male in North America is 72 years and 79 years for a female. It is not uncommon to see 60 year olds on a motorcycle or 40-something’s like Madonna modeling jeans.

Fig 4 A, B: At 44 years old, this female patient wanted a wider more radiant smile and wishes to undo the orthodontic treatment she had as a child.

Fig 5 A, B: Should not the patient and his parents be given the option of arch expansion, distalising the canines and replacing the laterals?

People take pride in their appearance. So why would a dentist move a canine into the lateral position? Here are few possible reasons.

• They like the challenge and are proud of the achievement. They are able to close their eyes and erase the mental image of the typodont model they were given as a first year dental student.
• They assume that the parents of the child are not interested in replacing the lateral incisor(s) and do not offer the option. Dentists should explain to parents the long-term effects of compromised treatment. (Fig 5A, B)
• The dentist may not realize how long the life of the patient may be and how long they will have to suffer with the aesthetic and functional compromise they have been left with.
• On some occasions the patient may have a very small mouth, too many teeth and narrow arches. In this case, the canine is suitable to be moved into the lateral position, reshaped, bonded, or veneered. The crowded pre-molars and molars can be expanded to fill out the buccal corridors. (Fig 5C, D, E)

Fig 5C: Missing laterals, bonded centrals and canines	Fig 5D: Removal of the bonding	Fig 5E: The canines flattened and narrowed to be able to be moved into the lateral position

 

Case 1

Figures (6A, B, C ) illustrate how teeth added to an orthodontic retainer and appliance can look quite appropriate in the mouth of a teenager to allow time for growing to end and the placement of a more permanent restoration. This is an inexpensive and non-invasive solution and often forces the adolescent to wear a retainer that otherwise would be left in their drawer and cause rebound to their orthodontic treatment.

Fig 6A, B, C: Teeth have been added to an appliance after orthodontic treatment
Fig 6D: Implants centered in the lateral root position	Fig 6E: Sculpted gingiva and temporary placement to recreate interdental papilla	Fig 6F: The implant in the cingulum position surrounded by ideal gingival architecture

Once growing was completed the patient requested a more permanent solution and she was given all the possible treatment options.

She chose to have individual implants to replace her missing teeth. If the alveolar ridge allows placement of the implants in the cingulum position, I have found that the ideal restoration is one that is screwed directly into the implant. This enables us to have a porcelain restoration recreating root form and emergence profile.

Fig 6G: Papillary form recreated	Fig 6H: Crowns screwed directly to the implant
Fig 6I, J: A beautiful smile

Zimmer (3.7 x 13) implants (Carlsbad, CA, USA) were placed using a surgical stent into the cingulum position of each missing lateral. After six months of osseointegration, the implants were exposed (Fig 6D). Temporary crowns replacing the laterals were then placed on temporary abutments and the gingiva sculpted using a diode laser recreating papillary form and removing the frenum pull (Fig 6 E), healing resulted in an ideally placed implant (Fig 6F) with ideal papillary form. (Fig 6G)

Porcelain fused to gold crowns were fabricated and screwed directly to the implant (Fig 6H) yielding a most satisfying result (Fig 6I, J).

 

Case 2

In this case, 2 acrylic pontics had been acid etched and bonded into place using a nylon mesh (Splint grid, Ellman, Hewlett, NY, USA ) to replace the patient’s lateral incisors after her orthodontic treatment was completed (Fig 7A, B). This is a semi permanent solution because the teeth are fixed into place and create no damage to the adjacent natural teeth. The patient often can remain with this restoration for a long period of time. However, they do not have the psychological security of having a solid restoration.

Fig 7A, B: Acrylics pontics bonded into place
Fig 7C: Custom gold posts	Fig 7D: Restoration with porcelain fused to gold crowns

At 19 years of age, once the patient was fully grown, Zimmer (3.7 x 13) implants (Carlsbad, CA, USA) were placed into the lateral position and custom gold posts were fabricated (Fig 7C). Porcelain fused to gold crowns were placed which offered a strong long term restoration (Fig 7D)

The patient was able to bite into anything and immediately accepted the new teeth as her own.

Sometimes a patient does not want to use an implant for tooth replacement but desires a strong permanent restoration. The canines being the strongest tooth in the arch can be conservatively prepared to hold a cantilever pontic. This is a time tested restoration which can achieve pleasing aesthetics.

 

Case 3

Our 29 year old patient wore an orthodontic retainer incorporating teeth to replace her missing lateral incisors. (Fig 9A, B, C)

Fig 9A,B,C: Missing laterals incorporated into an orthodontic retainer
Fig 9D, E, F: Porcelain fused to metal restoration cantilevered off the canines

After being presented with all the treatment options and their advantages and disadvantages she opted to replace her lateral incisors by cantilevering them prosthetically from her canines.

Ovate pontic sites were created in the lateral position, the canines prepared, and porcelain to metal restorations fabricated. (Fig 9D, E, F)

 

Treatment alternatives to restore the space of a congenitaly missing lateral incisor

If we have planned orthodontic treatment to re-create the natural space to be occupied by a lateral incisor, we leave ourselves open to many prosthetic options. Optimally, we would like to place single tooth implants, which, if well treatment planned will prove to be indiscernible from the real tooth. The patient will often forget that they have an implanted tooth.

However implants are not the only option. Some patients (parents) are against placing a foreign object into one’s body, cannot afford to place the implant at the present time, or as is often the case, the child is too young after orthodontic treatment and has not finished growing to allow placement of dental implants. The premature placement of implants may result in gingival disharmony and teeth positioned at different levels if the adjacent teeth have not finished erupting. This results in a whole set of new problems.

The following examples illustrate replacement of lateral incisors by various methods. One must realize the fact that the prosthetic option can always be upgraded or changed depending on the desires of the patient. As long as we create a proper foundation, we leave the door open to many prosthetic possibilities.

 

Conclusion

Fig 10: Typodont model

Every dental student is given a typodont dental model (Kilgore International, MI,USA) In first year dental school (Fig 10) This model illustrates the way teeth are supposed to look. It is imperative that dentists never forget that this is what their patients want to look like. “People want to look like people”.

Dentists must be able to envision the end result before commencing treatment and logically explain the different treatment alternatives to the patient (and/or parents) with the advantages and disadvantages of each. They will then be able to make an informed decision.

Patients go to dentists for educated advice in order to help them keep their teeth healthy, functional and looking good. By placing the canines in the position where they belong and by replacing the laterals, we are most predictably achieving these goals.

 

Dr Elliot Mechanic

Dr. Elliot Mechanic practices aesthetic dentistry in Montreal, Canada. He received his Bachelor of Science (1975) and Doctor of Dental Surgery (1979) degrees from McGill University. Dr Mechanic is the aesthetic editor to the Oral Health Journal, Canada. A native Montrealer, he is married to Mireille and has four daughters.

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