Treating mixed dentition cases with clear aligner therapy and low pulsatile forces

mixed dentitionJasmine Gorton and Sona Bekmezian discuss a viable treatment option for mixed dentition cases.

Mixed dentition treatment can be important and effective. It can ensure that patients have healthy, beautiful smiles as they grow and develop. It also lays the foundation for any ensuing orthodontic treatment experience they may have in their lifetime.

Mixed dentition treatment is also known as phase one treatment or interceptive therapy. It seeks to correct focused clinical conditions while the child is still actively growing. The American Association of Orthodontists urges orthodontic screening of children at age seven. Perceived benefits of phase one include (Suresh et al 2015).

  • Growth modification
  • Prevention of dental trauma/wear
  • Improved patient self-esteem and parental satisfaction
  • Prevention of permanent tooth impaction
  • Stability
  • Less extensive subsequent treatment.

The goal of this article is to present a novel approach to mixed dentition treatment. Through the combination of technologies usually thought to be reserved for older patients.

Protocol for mixed dentition cases

This practice was one of 54 orthodontic offices worldwide that was asked by Invisalign (Align Technology) to develop a protocol for using clear aligners for expansion in young children.

Typically, patients in this category are between the ages of seven and 10.

The traditional treatment process for these cases involves separators and metal expanders. In most situations, the patient would also receive braces on the upper and/or lower front teeth to address alignment.

From sour-tasting glue, to tissue impingement, and speech and swallowing interference. These methods involve inconvenience and discomfort (Gecgelen et al 2012).

Clear aligner therapy

Clear aligner therapy is hygienic, comfortable and convenient. It is also a single simultaneous appliance, providing expansion, alignment and upper and lower arch coordination, and thus obviating the need for fixed appliances in conjunction with expanders and/or functional appliances.

As a result, in many cases, we have been able to complete phase one treatments within six months.

In contrast to expanders and brackets, there are no dietary restrictions in clear aligner therapy and no barriers to oral hygiene.

Since the aligners are removable, patients have unrestricted access to brush their teeth, floss, and receive professional prophylaxis. However, as such, clear aligners are a 100% compliance-dependent appliance.

Invisalign and Acceledent

The practice uses Invisalign First clear aligner therapy in conjunction with the Acceledent Optima (Orthoaccel Technologies, Inc, Bellaire, Texas) vibratory device.

Acceledent Optima is an FDA-cleared class II medical device that applies precisely calibrated micropulses, which transmit through the roots of teeth to stimulate the surrounding bone and, as a result, increase cellular activity (Pavlin et al 2015).

Our practice has found that regular use of the Acceledent Optima improves the predictability of mixed dentition cases, provides relief from the discomfort of tooth movement, and provides greater assurance that the aligners are tracking according to the programmed movements.

Mixed dentition patients are instructed to wear their aligners 20 to 22 hours per day, use the Acceledent Optima for 20 minutes daily (or more, as needed for pain relief), and change aligners twice weekly (every three to four days).

The practice also recommends the frequent use of aligner Chewies for proper aligner seating and provides Clinpro 5000 (3M) sodium fluoride anti-cavity toothpaste for this age group.

Our patients are able to comply with all of these instructions without the help of an adult. However, as many of our patients are unable/unwilling to brush/floss their teeth regularly following meals and snacks at school, we suggest a thorough swishing with water before replacing the aligners.

Clinpro 5000 toothpaste is provided to help alleviate the risk of enamel decalcification given the likely increased plaque load. Brushing and flossing after meals and snacks is encouraged prior to aligner replacement at home.

Aligner delivery is scheduled three weeks after the initial record gathering and scanning appointment to minimise eruptive changes that could compromise aligner fit.

Following delivery, monitoring appointments are scheduled at six-week intervals.

Diagnosis and treatment planning

An important part of our practice’s diagnosis and treatment planning for mixed dentition cases is evaluating craniofacial morphology and dental development with cone beam computed tomography (CBCT) (Scarfe et al 2017). We also confirm that the airway morphology is within normal limits for the patient’s age (Alwadei et al 2018).

Patients and parents have a choice of treatment modality. As long as they present with normal airway findings on the pretreatment CBCT and do not report symptoms of sleep-disordered breathing, for which fixed rapid maxillary expansion is prescribed.

During the treatment planning phase in Clincheck, we strategically programme attachments to optimise intrusion/extrusion, root control, and rotations.

Our current protocol is to place attachments on all available permanent teeth (because these teeth tend to have larger bonding surfaces) and also on the lower deciduous first molars to address hyper-eruption of the lower anterior teeth (Liu and Hu 2018).

Attachments are placed during the initial aligner delivery appointment, but in our experience are best to avoid altogether in patients with special needs or hypersensitivity.

Since Invisalign First does not currently offer a specialised retainer option for phase one cases, the practice’s retention protocol is an upper removable Hawley. The practice does not prescribe mandibular retention for phase one patients who have acceptable pretreatment alignment and arch length. However, cases with moderate pre-treatment misalignment are prescribed a bonded retainer on the lingual of the lower anterior teeth.

Cases with severe pre-treatment lower crowding are prescribed a lower lingual holding arch (Woods 2002).

Patient example

  • Figure 1: Initial photographs

An eight-year-old female presented with anterior crossbite of the lateral incisors and bilateral posterior crossbite (Figure 1). Other clinical findings included a central diastema, generalised lower spacing. Also, a V-shaped maxillary arch, anterior open bite tendency, and excess proclination of the upper and lower anterior teeth. Overjet and overbite were minimal.

Further clinical examination revealed a developmentally delayed/congenitally missing lower left second premolar and ankylosis of the lower right first deciduous molar.

Profile was flat, and an anterior tongue thrust was present. There were prominent mamelons on the upper central incisors and lower lateral incisors.

The treatment goals were correction of the anterior and posterior crossbites, space closure, and improvement in overjet and overbite.

Invisalign First clear aligner therapy was recommended to achieve treatment goals comfortably and efficiently. For her initial set, the patient was prescribed 22 aligners for the maxillary and mandibular arches.

Expansion was programmed into the upper arch to resolve the posterior crossbite, with simultaneous alignment of the anterior teeth for anterior crossbite resolution as well as space closure.

There was no interproximal reduction prescribed, and there were no auxiliaries used. Extrusion of upper central and lateral incisors was programmed with optimised extrusion attachments to improve smile arc. Attachments were placed at initial aligner delivery.

The patient was instructed to wear her aligners 20 to 22 hours per day. Use the Acceledent Optima for 20 minutes daily and change aligners twice weekly (every three to four days).

She was also instructed to use Chewies for proper aligner seating and brush with Clinpro 5000 toothpaste. Appointment intervals were every six weeks.

Refinement phase

  • Figure 2: Treatment progress photographs

There was a refinement phase of 20 aligners for the maxillary and mandibular arches (Figure 2). The refinement aligners were prescribed for increased lateral expansion. This achieves complete resolution of the posterior crossbite, continued space closure for the upper and lower incisors, and extrusion of the upper anterior teeth for increased overbite.

The patient completed active treatment in six months (Figure 3). All treatment goals were achieved, including improved axial inclination of the anterior teeth and improved interincisal angle.

The author was also pleased with the aesthetic smile line and arch coordination.

The patient was prescribed an upper Hawley retainer (with the acrylic cut away from the posterior teeth to allow for unimpeded permanent tooth eruption) for daily night time wear. A fixed lingual retainer was bonded to the lower central and lateral incisors to maintain space closure.

  • Figure 3: Final photographs

Discussion

Phase one treatment with aligners is still relatively uncommon. This case report, as well as others that are pending publication, should provide validation that this treatment approach is not only a viable treatment modality for mixed dentition cases, but also an advantageous option.

Aligners allow orthodontists to simultaneously achieve anterior alignment, posterior expansion, and arch coordination.

Aligners also provide the flexibility to regain space in the canine area if the patient has early loss of deciduous canines or a midline shift.

While the fact that these patients are constantly growing throughout treatment can present challenges, the benefit lies in their rapid biological response.

Additionally, these patients tend to have a more regimented sleep routine of 10 or more hours of sleep per night (Galland et al 2012). This longer sleep cycle allows uninterrupted aligner wear for longer stretches of time, improving total compliance. All of these factors contribute to the successful and predictable treatment of many mixed dentition patients within six months.


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