By Menachem Roth, DMD, MMSc
We’ve all been there before. It’s the end of a busy day, and the 4 PM new-patient exam and consult is late. When the new patient arrives at 4:30, your treatment coordinator corners you to give you an update: The new patient is a 13-year-old girl with a concern regarding some mild crowding that the dentist has been watching, and "Mom would prefer no x-rays." The TC goes on to explain that Mom is in a bit of a rush and really just wants to get an idea of cost. You’re hoping this will be straightforward. Of course it’s not.
Clinical evaluation shows that the molar occlusion is half-cusp Class II. The laterals have worn incisal edges and look a whole lot like deciduous teeth. You know it’s likely that the laterals are missing, and you have a mom in the room who not only has no idea her daughter is missing two teeth, but who seems to be under the impression that the orthodontic needs are limited. We know this is anything but a quick consultation to get an idea of price, and while mom is in a bit of a rush, what everyone actually needs for a successful experience is time.
This is a difficult situation. In adolescent cases with missing lateral incisors, there are two typical treatment options: 1) open space for a replacement tooth, likely an implant; or 2) close the remaining space with canine substitution. As orthodontists, we are very used to these ideas, but for our patient’s family and possibly for their dentist, these topics are likely not standard fare. The key to working with the family is good communication at that initial consult, followed by communication that includes the general dentist in the treatment-planning decisions.
It’s easy to sit down with your records in a vacuum and formulate a treatment plan that is orthodontically sound, but cases with missing anterior teeth are more complex than just us as orthodontists figuring how to get a Class I or Class II molar relationship. Treatment from end to end often lasts 7 to 10 years before completion, and everyone should be happy with the results.
Types of Canine Substitution Cases
For the remainder of this discussion of missing lateral incisors, let’s eliminate obvious cases on both sides of the treatment-planning spectrum. As a general rule, cases that lend themselves to canine substitution would be those with a reasonable Class I or mild Class II profile, a Class II dental relationship, and minimal lower arch crowding; or a Class I dental relationship with crowding in the lower arch that requires premolar extraction or dentoalveolar protrusion.1-2 A typical space-opening implant case has one or both maxillary lateral incisors are missing, an acceptable profile, Class I occlusion, and spacing or minimal crowding with the spaces for the lateral incisors intact. Only a limited number of patients fall into these more clear-cut categories.
More frequently, what we see are cases with the molar half-cusp Class II, the first premolars forward due to the reduced tooth mass in the anterior, and the maxillary canines erupting somewhere between where they should ideally be and in the space occupied by or previously occupied by the deciduous lateral incisors. These cases require an extra level of communication with the general dentist and then the family to help not only treatment plan the goals but create a time line for completion and set the expectations.
Expectations should be set not only for the end orthodontic result—straight teeth and a good bite—but also for what will happen following the removal of orthodontic appliances. If we have chosen canine substitution, then we need to talk to the parent/patient about the steps for reshaping the canine, as well as any planned restorative or gingival procedures. If we have chosen an implant restoration, then we should review steps related to retention and space maintenance. Setting these expectations early on helps to avoid confusion as orthodontic treatment begins to wind down.
In the case I discussed above, after hearing the two typical treatment options, Mom responds that she would like to think it over and bring Dad back for another discussion, but that she really prefers to close the space from the missing teeth, because she had a friend with an implant who had a terrible experience. When I speak to the general dentist on the phone, he lets me know that he likes to treat these types of cases with implants and really isn’t a fan of canine substitution. So where does this leave me as the orthodontist? In these situations, it is helpful to have a checklist of the main factors to consider in deciding which direction to take. The checklist aids our treatment planning and is also helpful in framing the discussions with patients and their dentists in order to resolve differences in opinion regarding the treatment plan.
Kokich and Kinzer2 have elegantly described some of the key treatment-planning considerations, including the following:
1) Profile Evaluation: A harmonious and balanced profile is a goal that we generally want to achieve for our patients. A critical evaluation of the profile will therefore have a major impact on our treatment-planning decisions. When the skeleton is Class I, it is easier to either opening space or close it. When the skeleton is significantly Class II with a retrusive mandible, space closure may provide adequate dental correction but may have negative consequences for the profile. We need to teach patients and parents about this, because it can influence their decision-making. For Class III growth situations, maxillary space closure should be avoided or at least delayed until enough growth has taken place to ensure that a negative overjet will not develop, although Zachrisson does present it as a viable treatment option under the right conditions.3
2) Lip position: Lip position is a factor in treatment-planning for missing anterior teeth in both the horizontal and vertical planes of space. In the horizontal plane, the lip position is supported by the position of the maxillary incisors. Change in the position of the incisors will affect the lip position over time. Over-retraction of the maxillary incisors for the purpose of space closure can accentuate the appearance of lip-thinning at a younger age, which has a negative aesthetic impact in the long term. In the vertical plane, the lip position at rest and (more importantly) in a full smile influences how much gingival tissue is displayed. The more display, the more important the correct architecture is. Gingival procedures that may be needed following treatment should be discussed in general terms with patients prior to beginning orthodontic treatment, rather than at the end when they are unhappy with the result.
3) Tooth size, shape, and color: Certain canines look more natural as lateral incisors than others. Canines with a narrow mesial-distal and buccal-lingual width and flat buccal contours will lend themselves to reshaping more than those that are wide and bulbous. Radiographically, it is sometimes possible to get a sense of the size and shape of erupting canines, but in cases where a parent is considering the option of space closure, it makes sense to delay the start of active orthodontics as much as possible to allow the canine to erupt.4 Once the canine has fully erupted, you can do a wax-up to allow the restorative dentist to see how much enameloplasty needs to be done to get an ideal aesthetic result. There comes a point where, if too much enamel needs to be reduced to get the appropriate size, other treatment options may be more appropriate.
4) Complexity of orthodontic movements: The last thing anyone wants to do is finish an orthodontic case with an implant site and have the restorative dentist or specialist tell the patient at the pre-debanding appointment that there is not enough room for the implant to be placed. Certainly, this does happen, and the reason is often that the mechanics were difficult. Obviously, with the use of TADs, things are possible that were not before, but it still takes time. Patients as well as dentists should be educated as much as possible regarding the treatment time it takes to achieve certain goals. This information can then be used to help determine which treatment plan is ideal.
When thinking about these considerations, it is clear that the decision is more than just "is there enough space for an implant?"
The following are two cases where the above considerations not only guided my treatment plan but opened communication with the patients and referring dentists, ultimately modifying the treatment plan from the patient’s or dentist’s initial inclination.
This patient began orthodontics elsewhere in the country with a treatment plan involving restoration of the missing maxillary lateral incisors with implants. The patient was 23 years old, and for aesthetic reasons, she requested implants at the start of treatment. Conversations with her family dentist had supported this. When she transferred into our office, examination of the lateral ceph showed severely proclined incisors. Clinical evaluation of the soft tissue revealed muscle and lip strain both in repose and lip closure.
Even though we could have made space for the implants, I felt that the poor occlusal scheme (lack of anterior guidance/coupling) and profile considerations outweighed the aesthetic benefits that implants could provide. I recommended extraction of lower premolars along with maxillary space closure to allow for a better occlusion and profile.
This 11-year-old female with a Class II occlusion and agenesis of both maxillary lateral incisors had a mom who was very motivated to close the space with canine substitution but did not want to accept an "average aesthetic result." So rather than beginning treatment early to facilitate space closure, we waited until the maxillary canines had erupted to determine their suitability as lateral incisors.
When they did erupt, I requested a consult at the prosthodonitst (who would have done the modifications rather than her pediatric dentist) to evaluate the aesthetic outcome of canine substitution. Obviously, these are bulbous teeth with a triangulated shape and sharp contours. A wax-up showed that too much enameloplasty would have been needed to achieve an ideal result. This information allowed the family to make the decision to proceed with orthodontics to open space for implants.
Unquestionably, there is a lot to consider when making a decision regarding the management of missing anterior teeth. Sometimes we can find ourselves balancing the requests of our patients, the requests of our referring dentists, and our own ideas. The above points have helped me communicate with both dentists and patients in a way that gets us all on the same page when treatment-planning for missing anterior teeth.
Menachem Roth, DMD, MMSc, maintains private practices in Newton, Northboro, and Marlboro, Mass. He is on the board of the Massachusetts Association of orthodontists. He can be reached at DrR@bracesonline.com.
1. Rosa M, Zachrisson BU. Integrating esthetic dentistry and space closure in patients with missing maxillary lateral incisors. J Clin Orthod. 2001;35(4):221-234.
2. Kochich VO Jr, Kinzer GA. Managing congenitally missing lateral incisors Part 1: Canine substitution. J Esthet Restor Dent. 2005;17(1):5-10.
3. Rosa M, Zachrisson BU. Integrating space closure and esthetic dentistry in patients with missing maxillary lateral incisors. J Clin Orthod. 2007;41(9):563-573.
4. Graber TM, Vanarsdall Jr RL, Vig KW. Orthodontics: Current Principles and Techniques. 3rd ed. Philadelphia: Mosby; 2000.