Orthodontic space opening during adolescence is a common treatment for congenitally missing maxillary lateral incisors. Because of continued facial growth and compensatory tooth eruption, several years can elapse between completion of orthodontic treatment for a teenage patient and implant placement. There are reports that, after successful orthodontic opening of the implant space, the central incisor and canine roots reapproximate during retention and prevent implant placement.
To study this phenomenon, the records of 94 patients with missing maxillary lateral incisors were collected. Periapical and panoramic radiographs were used to measure intercoronal and interradicular distances between the central incisor and the canine adjacent to the missing lateral incisor before and after orthodontic treatment and at implant placement.
Although root approximation between the adjacent central incisor and canine during retention did not occur consistently, 11% of the patients experienced relapse significant enough to prevent implant placement.
To ensure sufficient space for implant placement, we recommend at least 6.3 mm of intercoronal space and 5.7 mm of interradicular space between the adjacent central incisor and canine. A bonded wire or resin-bonded bridge will help to reduce root approximation that might occur during retention.
Orthodontists who have been in practice at least 10 years will understand the reason for this study from the University of Washington. Let’s say that, 5 years ago, you completed orthodontic treatment for a growing patient with missing maxillary lateral incisors. A retainer with 2 pontics was delivered to the patient with instructions to wear it full-time until implants could be placed. Now, the patient’s general dentist is on the phone. He is ready to place the implants, but there is not enough space between the roots of the adjacent teeth. To the orthodontist, this is difficult to understand. The roots seemed to be well aligned when the fixed appliances were removed, and now the dentist is hinting that the patient might need braces again to provide the needed space. Admit it—you’ve been there, and it’s not a nice place!
More importantly, what happened? Did the roots of adjacent teeth converge while the retainer was being worn, or were they not moved enough in the first place? Should the retainer have been bonded in place? This dilemma is frustrating for everyone involved. The purpose of this study was to evaluate postorthodontic root approximation adjacent to congenitally missing maxillary lateral incisors during retention.
The records of 94 patients with a total of 142 missing lateral incisors were gathered for this study. As much as possible, the records were evaluated at pretreatment, posttreatment, and just before implant placement. The sample was divided into those with adequate space for implant placement and those with inadequate space.
The findings of this clinical study are interesting and worth reviewing. Although root approximation was not consistent, 11% of the patients had enough relapse to prevent implant placement. To ensure sufficient space for implants, the authors recommend at least 6.3 mm of intercoronal space and 5.7 mm between the roots. A bonded wire or resin-bonded bridge will help maintain the posttreatment root alignment. The authors concluded that, generally, the space between roots of adjacent teeth remains fairly consistent.