Oral Health Group
Feature

Replacement of a Congenitally Missing Upper Lateral

April 1, 2013
by Richard Rapoport, DDS


An upper lateral incisor is one of the most common teeth to be congenitally missing.1

Studies have estimated that between one and two per cent of the population are missing either one or both lateral incisors,2 and the agenesis of both laterals being more common than the agenesis of just one.3

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When the permanent lateral incisor is not present it is possible for the cuspid to erupt into the lateral position as there is no tooth to prevent the mesial migration of the developing cuspid. It is not uncommon to see the deciduous cuspid remain in place once the permanent cuspid erupts into the lateral position. Leaving the cuspid in the lateral position often results in a carnivorous appearance and a loss of function and harmony of the arch.2,4,5

There are many treatment options available. This paper will discuss the orthodontic treatment for an ectopically erupted canine and the prosthetic replacement of a congenitally missing lateral incisor using an implant-supported crown. This is the author’s preferred method of treatment for a congenitally missing upper lateral incisor.

Historically the cuspid was often maintained or orthodontically positioned into the lateral position and reshaped by a combination of enamelplasty and bonding to make it appear more like a lateral incisor.6,7 The main problem with this approach is that the size, contour, colour and soft tissue profile of the cuspid did not provide an acceptable aesthetic solution. A second concern with this approach is the lack of cuspid guidance. Today, there is a general preference in the profession to favour canine guidance.8

Additionally, in the past it was not uncommon for the dentist to replace the missing lateral with a fixed prosthetic restoration. A common restoration was to crown the cuspid and to place a cantilever pontic for the lateral. For the young adult, this seriously compromised the long term health of the abutment tooth by putting the pulp at risk of injury and the tooth at risk for caries. In time, there would be changes to the soft tissues around the restoration or adjacent teeth and this would necessitate a replacement of the prosthesis to maintain the aesthetic result.

Therefore, in situations where the cuspid has either erupted into its proper position or has been orthodontically placed into a Class 1 occlusion, the missing lateral incisor requires a prosthetic solution. Several options exist that are non invasive to the dentition and this is an important consideration due to the patient’s young age. A removable prosthesis or a bonded pontic are two viable options, especially for a young patient that is still developing. Girls can continue to have downward and forward development of the maxilla until the age of 17 or 18, and for boys it is not uncommon to have continued development until the age of 25 years.9

Placing an implant before the total cessation of growth will interfere with the normal growth and development of the alveolar processes. The reason for this is that the osseointegrated implant does not follow the spontaneous and continuous eruption of the natural dentition.9 For this reason, placing an implant supported restoration before the end of craniofacial/skeletal growth is not recommended.9

Today with the predictability and aesthetic possibilities of dental implants, an implant supported crown is the ideal solution to replace a congenitally missing upper lateral incisor. This will maintain the health and integrity of the patient’s teeth,10 while providing the ideal aesthetic and functional solution.

CASE STUDY
A young female patient was diagnosed at age eight with a congenitally missing upper left lateral incisor. The contralateral incisor was present but was slightly undersized. Her occlusion on the right side was Class 1. On the left side her molar was in Class 1 but her upper left cuspid had erupted into the lateral position and the upper left deciduous cuspid was retained.

The treatment plan was to wait until the end of the mixed dentition phase of development and then initiate orthodontic treatment. The plan was to extract the deciduous cuspid and orthodontically move the left cuspid into an ideal Class 1 position. The missing lateral was then to be replaced with an implant supported crown. Every effort was made to provide optimal aesthetics both in terms of the appearance of the restoration and the surrounding soft tissues.

The orthodontic treatment which started when the patient was 14y9m took approximately 20 months to complete. It was very important to achieve bodily movement of the cuspid and not just tip its crown distal. Doing so would have left the root of the cuspid in the path of the planned implant. Ideally the width of the crown of the lateral incisor is 75% of the width of the central incisor.5,11 In this case the central incisor measured 8.5mm. It was calculated that the lateral incisor would measure approximately 6.5mm. It is also recommended to maintain a minimum of 1.5mm distance between the planned implant and the adjacent teeth.12 That means with a 3.25mm diameter implant one requires a minimum of 6.25mm of arch length. This does not leave much “wiggle” room. As a measure of precaution the roots of the adjacent teeth were tipped away from the surgical site to provide a zone of safety before placing the implant. Once the implant was placed, the roots could them be moved back into their proper position.

The presurgical planning included a CBCT scan. All implant sites must be scanned as part of the normal surgical protocol. Furthermore, CBCT site scanning is recommended by the 2012 position statement of the American Academy of Oral and Maxillofacial Radiology.13 It is only by using the scan that it is possible to properly plan the surgical strategy.

In order to maintain the stability of the labial and palatal soft tissues a minimum of 1.5mm and ideally 2mm7 of buccal and palatal bone must surround the implant.14 Without this volume of bone there is a risk of bone loss after surgery with the accompanying soft tissue recession.13,14 The planned restoration was to be a screw retained crown. The implant placement was planned so that the access to the screw would be in the cingulum of the crown.

At the time of the implant surgery, a bone allograft was placed between the flap and the labial cortical bone to fill in the labial soft tissue concavity. This could have been accomplished with a connective tissue graft but that would involve an additional surgical site.

The orthodontic appliances were maintained during the healing phase for two reasons. First, it was necessary to realign the roots as they were tipped out of the surgical site. Second, the orthodontic appliances provided support for the temporary pontic.

After five months the implant was exposed and a screw retained provisional was secured to the implant. This is a very important part of the procedure and will make all the difference in the final aesthetic outcome. The provisional has to be shaped with the correct contours to support the soft tissues and to encourage the development of the interdental papillae. After proper implant placement this is the second most critical aspect to achieving optimal aesthetics.15,16

Once the provisional was in place, the orthodontic appliances where removed to allow the case to settle in and to give time for the soft tissues to mature around the implant.

At the age of 17y5m and after having the provisional in function for seven months, a final impression was taken with an open tray technique. To provide a most accurate distortion-free impression of the matured soft tissues, a flowable resin was immediately placed once the impression coping was seated. The resin supported the soft tissues during the impression and provided the technician with an accurate index to use in the fabrication of the working model and crown.

The final restoration was a one-piece porcelain fused to gold screw retained crown. It is the preference of the author to use screw reta
ined crowns whenever possible, especially in aesthetic cases. The big advantage is that one can seat a crown and have no concerns about inadvertently leaving cement subgingival. As well, moisture control is not an issue. Another big advantage of a screw retained anterior restoration is retrievability. In the years to come this crown can be removed and the temporary can be replaced if adjustments to the crown are needed.OH


Dr. Richard Rapaport is in private practice in Westmount, Quebec. Mastership Academy of General Dentistry, Associated Fellow American Academy of Implant Dentistry, Fellow of the Misch International Implant Institute, Active Member of the International Association for Orthodontics.

Oral Health welcomes this original article.

REFERENCES

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3. Stamatiou J, Symons A L Agenisis of the permanent lateral incisor: distribution, number and sites. Journal of Cliical Pediatric Dentistry 15: 244-246, 1991

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7. Zachrisson B, Thilander B. Treatment of dento-alveolar anomalies. In Thilander B, Ronning O (eds) Introduction to orthodontics. Tandlakarforlaget, Stockholm, pp 166-168, 1985

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11. Bolton W A: Disharmony in tooth size and its relation to the analysis and treatment of malocclusion. Angle ortho 28 no 3: 113-128, 1958

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15. Tarnow DP,Magner AW, Fletcher P. The effect of the distance from the contact point to the crest of bone on the presence of the interdental papillae. J Periodontol. 1992;63 12:995

16. Buser D,Martin W,Belser U. Optimizing esthetics for implant restorations in the anterior maxilla:anatomic and surgical considerations. Int J Oral Maxillofac Implants 2004;16 Suppl: 43-61