The Tostado Take: The Waiting Years by Dr. Julia Tostado

What happens between Phase I and Phase II

by Dr. Julia Tostado

The Tostado Take is written by Dr. Julia Tostado with AI assistance and developed under her direction to ensure it reflects her authentic voice and expertise.

Phase I gets a lot of attention. We talk about expansion, crossbite correction, growth modification, space management, habits, ectopic eruption, and all the reasons why intervening early can sometimes make a meaningful difference.

Then Phase I ends. The appliance comes out, the patient and parents are happy, and everyone takes a celebratory photo. And then comes one of the strangest instructions in orthodontics: Now we wait.

For families, this can be confusing. They just spent months coming to appointments, turning expanders, wearing appliances, keeping things clean, and asking whether that loose tooth is supposed to look like that. Suddenly, the active phase is finished, but orthodontic care is not necessarily done. Welcome to the waiting years.

The period between Phase I and Phase II is sometimes treated like an intermission, but clinically, it is a period of observation in which permanent teeth erupt, the jaw continues to grow, the occlusion evolves, and the orthodontist gets to see what early treatment accomplished and, equally important, what biology decides to do next.

The American Academy of Pediatric Dentistry (AAPD) emphasizes that management of the developing dentition requires ongoing assessment of eruption, arch length, crossbites, ectopic eruption, skeletal relationships, habits, and other developing abnormalities. Treatment timing should be based on the individual patient’s diagnosis and stage of dental development rather than age alone.¹

So perhaps a better name for it is the watching period.

Phase I was never supposed to finish everything
One of the biggest communication challenges with two-phase treatment is explaining what Phase I is actually designed to accomplish. Parents understandably hear “orthodontic treatment” and imagine the final result: straight teeth, a perfect bite, retainers, and a graduation photo.

But interceptive treatment usually has a more focused objective. We may have corrected a posterior crossbite and eliminated a functional shift, created space for developing permanent teeth, reduced a severe overjet, improved a developing Class III relationship, or addressed an eruption problem before it became a more complicated impaction. The 8-year-old will not necessarily leave Phase I with the occlusion we expect from a 15-year-old completing comprehensive treatment, and that distinction matters.

For example, evidence regarding early Class II treatment provides a useful reality check. A randomized clinical trial found that early treatment can produce changes during the initial phase, but many of those advantages do not translate into major differences in the final comprehensive treatment outcome compared with treatment started later.² A Cochrane review similarly found that two-phase treatment for prominent upper incisors reduced the incidence of incisor trauma, but otherwise showed no clear advantage over a single phase of treatment during adolescence for most final outcomes.³

Early treatment still has value, but that value depends on the problem we are trying to solve. That is an important conversation to have before Phase I begins and again when it ends.

I like to think of it this way: Phase I is not always about avoiding Phase II. Sometimes it is about giving Phase II a better starting point.

What exactly are we waiting for?
Usually, teeth and growth. Unfortunately, neither seems particularly interested in our schedule.

The permanent canines do not check the practice calendar before erupting. Premolars have their own plans. Second molars occasionally appear to have received completely different instructions. This is why chronological age alone is a poor way to decide when comprehensive treatment should begin.

During the observation period, we are watching the transition from mixed dentition toward permanent dentition. We are evaluating whether teeth are erupting along favorable paths, whether previously created space is being maintained, whether transverse correction remains stable, and how the skeletal pattern is developing. Current AAPD guidance specifically emphasizes monitoring eruption disturbances, arch length discrepancies, space maintenance, crossbites, and Class II and Class III relationships throughout development.¹

The goal is to start Phase II when the patient is developmentally ready and comprehensive treatment can be performed efficiently, not the moment enough permanent teeth appear to make bonding technically possible.

The six-month observation visit is still an orthodontic appointment
A parent may look at an observation appointment and think, “We drove across town for the orthodontist to count teeth.” Sometimes, from the outside, that is exactly what it looks like. But we are counting very important teeth.

These visits allow us to monitor eruption sequence, available space, midlines, transverse relationships, overjet, overbite, developing crowding, skeletal growth, and the position of teeth that may not be erupting as expected.

One of the most important examples is the maxillary canine. Palatally displaced permanent canines are a classic reminder of why observation is active clinical care. Evidence suggests that selected interceptive procedures can improve the likelihood of spontaneous eruption in appropriately diagnosed cases. A systematic review found that extraction of the primary canine facilitated eruption of palatally displaced permanent canines, although outcomes varied and patient selection remained important.⁴ Another systematic review found that rapid maxillary expansion may also improve eruption outcomes in selected patients with palatally displaced canines.⁵

“Let’s check again in six months” does not mean nothing is happening. It means we are giving biology time while making sure it is heading in the right direction.

Protect what Phase I accomplished
Another important job during the waiting years is preserving the correction we worked so hard to obtain. Expansion is an obvious example.

Once the transverse discrepancy has been corrected, the orthodontist has to consider retention, eruption, growth, and stability rather than simply removing the expander and declaring victory. Long-term evidence suggests that both rapid and slow maxillary expansion can demonstrate meaningful stability, although treatment protocols, retention, growth, and patient characteristics all influence outcomes.⁶

Space management deserves the same attention. If Phase I created or preserved space for permanent teeth, premature loss of primary teeth or unexpected eruption patterns can alter the situation. Evidence shows that premature loss of primary molars can produce measurable space changes, although the clinical significance varies substantially among patients.⁷

This is why automatic rules can be dangerous: Not every lost primary tooth needs a space maintainer, not every millimeter of crowding needs immediate treatment, and not every small change represents relapse. The question should always be: Does this change threaten the objective we achieved during Phase I or complicate what we expect to do in Phase II? That keeps observation purposeful rather than reactive.

Growth has not read our treatment plan
Perhaps nowhere is this more obvious than in Class III treatment. Early maxillary protraction can produce meaningful short-term skeletal and dental improvements. Systematic review evidence supports favorable short-term effects of facemask therapy, although the certainty regarding long-term outcomes has historically been more limited.⁸

Follow-up studies have shown that favorable changes can persist in many patients. At the same time, continued mandibular growth can alter the relationship years after a successful early correction.⁹

That is one of the hardest concepts to communicate to families: We can influence growth, but we cannot guarantee it. A child may finish Phase I with positive overjet and a greatly improved profile, then continue growing in a direction that changes the prognosis. That does not necessarily mean Phase I “failed.” It means the patient kept growing.

This is why I am careful with words such as “fixed,” “permanent,” and “done” when talking to parents of growing patients. Instead, I prefer something like: “We corrected the problem we wanted to address at this stage. Now we need to watch how the permanent teeth and jaws develop before deciding what comes next.” That sentence saves a surprising number of future conversations.

Did Phase I actually work?
This is the question we should ask before automatically moving into Phase II. And the answer should not simply be, “The teeth look straighter.” Return to the original diagnosis.

If we treated a functional posterior crossbite, is the functional shift gone? If we expanded to improve arch relationships and eruption, did we accomplish that? If we intervened because of a severe overjet and trauma risk, was the overjet meaningfully reduced? If we were managing ectopic eruption, did the permanent tooth improve its path? If we performed early Class III treatment, what happened to the sagittal relationship as growth continued?

The success of Phase I should be measured against the reason Phase I was recommended in the first place. That sounds obvious, but it is easy to lose sight of when the patient returns two years later with four new teeth, crowding, a deeper bite, and a parent asking, “Didn’t we already fix this?” The answer may be yes: We fixed that problem, and now we are looking at this one.

The parent communication problem
The biology of the waiting period may actually be easier than the communication. Parents tend to have three questions: Why are we waiting? Why does my child still need braces? Didn’t Phase I already fix this?

If these questions surprise us, we probably did not explain Phase I clearly enough at the beginning. Families should understand from Day One that Phase I is typically targeted treatment during a developing stage of dentition. Depending on the original malocclusion and how the patient develops, comprehensive treatment may still be recommended later.

I also avoid promising that early treatment will make Phase II “short and easy.” Sometimes it simplifies later treatment substantially, and sometimes growth and eruption introduce completely new challenges.

Randomized evidence in Class II patients illustrates why those promises should be made cautiously. Early treatment can produce favorable initial skeletal changes, but individual responses vary considerably, and final outcomes after comprehensive treatment may be similar to those achieved with later single-phase treatment.² Parents generally understand uncertainty when we explain it before it becomes their problem.

Do not start Phase II just because everyone is tired of waiting
There is also pressure in the opposite direction. The patient is 11. Friends have braces. Mom is ready. The lateral incisors are in. A canine cusp is visible. Everyone starts looking at the orthodontist. “Can we start now?”

Maybe. But comprehensive treatment should not begin simply because the family has reached its emotional eruption date. Sometimes the best orthodontic appliance is patience. That is not always an easy treatment plan to sell, especially when the family is enthusiastic and the schedule has an opening at 3:30 p.m. Tuesday. But efficiency matters. Our goal is to begin comprehensive treatment when we can make meaningful progress toward the final result, not to maximize the number of months a child spends wearing braces.

When the waiting years end
Eventually, something changes. The permanent dentition reaches an appropriate stage. The eruption path becomes clearer. Growth provides enough information to refine the treatment plan. The objectives become comprehensive rather than interceptive. Now we reassess, and I mean truly reassess rather than simply continue the treatment plan we wrote three years ago.

The child who returns for Phase II is not the same patient who began Phase I. There are new teeth, new skeletal relationships, new periodontal considerations, and new levels of cooperation. Sometimes there are new habits, new restorations, new trauma, or new expectations. Take updated records when indicated. Reevaluate the diagnosis. Look at the face again. Look at the smile. Evaluate the occlusion and growth. Ask whether the extraction decision has changed. Ask whether the original Phase II plan still makes sense.

Phase II should be a new diagnostic decision built on what Phase I accomplished, not an automatic second installment.

Waiting is part of treatment
Perhaps the biggest misconception about the period between Phase I and Phase II is that nothing is happening. In reality, permanent teeth are erupting, roots are developing, alveolar processes are changing, jaws are growing, and the occlusion is reorganizing itself. The corrections we created are being tested by growth and function.

Our job is to know when to intervene and, just as importantly, when not to. That may be one of the harder lessons in orthodontics. We are trained to move teeth. Sometimes excellent orthodontic care means watching them.

Phase I can create an opportunity. The waiting years tell us what the patient does with it. Then Phase II, when necessary, takes the result of growth, eruption, and early intervention and turns it into a comprehensive treatment plan.

So perhaps there really is no “break” between Phase I and Phase II. There is active treatment and careful observation. The appliance may be gone, but the orthodontist is still very much at work.

How do you manage the years between Phase I and Phase II, and what clinical sign tells you that it is finally time to stop watching and start comprehensive treatment?

References

1. American Academy of Pediatric Dentistry. Management of the developing dentition and occlusion in pediatric dentistry. The Reference Manual of Pediatric Dentistry. Chicago, IL: American Academy of Pediatric Dentistry; 2024:475–493.

2. Tulloch JFC, Proffit WR, Phillips C. Outcomes in a 2-phase randomized clinical trial of early Class II treatment. American Journal of Orthodontics and Dentofacial Orthopedics. 2004;125(6):657–667. doi:10.1016/j.ajodo.2004.02.008

3. Batista KBSL, Thiruvenkatachari B, Harrison JE, O’Brien KD. Orthodontic treatment for prominent upper front teeth (Class II malocclusion) in children and adolescents. Cochrane Database of Systematic Reviews. 2018;3(3):CD003452. doi:10.1002/14651858.CD003452.pub4

4. Almasoud NN. Extraction of primary canines for interceptive orthodontic treatment of palatally displaced permanent canines: A systematic review. The Angle Orthodontist. 2017;87(6):878–885. doi:10.2319/021417-105.1

5. De Stefani A, Bruno G, Visentin S, Lucchi P, Gracco A. Rapid maxillary expansion for interceptive orthodontic treatment of palatally displaced canine: A systematic review. European Journal of Paediatric Dentistry. 2021;22(2):139–143. doi:10.23804/ejpd.2021.22.02.10

6. Srivastava SC, Mahida K, Agarwal C, Chavda RM, Patel HA. Longitudinal stability of rapid and slow maxillary expansion: A systematic review. Journal of Contemporary Dental Practice. 2020;21(9):1068–1072.

7. Tunison W, Flores-Mir C, ElBadrawy H, Nassar U, El-Bialy T. Dental arch space changes following premature loss of primary first molars: A systematic review. Pediatric Dentistry. 2008;30(4):297–302.

8. Woon SC, Thiruvenkatachari B. Early orthodontic treatment for Class III malocclusion: A systematic review and meta-analysis. American Journal of Orthodontics and Dentofacial Orthopedics. 2017;151(1):28–52. doi:10.1016/j.ajodo.2016.07.017

9. Kakali L, Christopoulou I, Tsolakis IA, et al. Mid-term follow-up effectiveness of facemask treatment in Class III malocclusion: A systematic review. International Orthodontics. 2021;19(3):365–376. doi:10.1016/j.ortho.2021.07.003

Dr. Julia Tostado earned her DDS from Universidad Autónoma de Nuevo León and completed her Master of Science in orthodontics at Centro de Estudios Superiores de Ortodoncia. She currently practices at the family-owned clinic Tostado Ortodoncia and shares insights with the orthodontic community through her contributions on Orthotown’s social media.