A novel method for fabricating nasoalveolar molding appliances for infants with cleft lip and palate using 3-dimensional workflow and clear aligners

Introduction

Nasoalveolar molding (NAM) was introduced over 20 years ago as adjunctive therapy for the correction of cleft lip and palate. In the current study, we propose a new approach using a digital workflow and 3-dimensional printing to fabricate clear aligner NAM devices.

Methods

A polyvinyl siloxane (PVS) impression of an infant with a unilateral complete cleft lip and palate (UCLP) is acquired and poured, and the stone model is scanned with an intraoral scanner. The stereolithography file is digitized, and the alveolar segments are digitally segmented and moved to the desired final position. The total distance moved is divided into a sequence of 1-1.5 mm increments, creating a series of digital models. The models are 3-dimensionally printed along with button templates to allow free form positioning of the button on each model. A Vacuform machine (Taglus, Mumbai, India) was used to fabricate a 0.040-in aligner for each stage.

Results

We present 1 case that was treated successfully with this approach. Appointments for the NAM adjustments were primarily to monitor progress and counseling with less time spent adjusting the appliance. The appointment length was reduced by over 30 minutes. Benefits of the aligner are improved fit, more precise increments of activation, reduced chairside time, and potentially minimized number of visits.

Conclusions

NAM custom aligners may provide similar benefits to the traditional approach while reducing the burden of care by reducing the number of visits and appointment duration. Further studies with a sample and longitudinal observations are needed to investigate the benefits of the proposed digital approach.

Graphical abstract

Highlights

  • Nasoalveolar molding (NAM) appliances can be used in neonates with cleft lip and palate.

  • A novel method is presented for fabricating NAM appliances from clear aligners.

  • The method uses computer-aided design and computer-aided manufacturing.

  • NAM aligners are a promising approach for reducing the burden of care.

Cleft lip and/or palate is the most common craniofacial condition, with an incidence rate of about 1 in 700 births in the United States. Presurgical Infant Orthopedics (PSIO) appliances have been used since the 1950s as an adjunctive neonatal therapy for the correction of cleft lip and palate. The objective of these therapies is to help approximate the segments, with the goal of reducing the defect size, and simplifying the surgical procedure and minimize scarring. The biologic basis for the efficacy of PSIO is based on the high degree of plasticity in the cartilage of neonates because of transient high levels of estrogen and hyaluronic acid. Since their introduction, many PSIO techniques have been described in the literature. , , In the early 1990s, Grayson introduced nasoalveolar molding (NAM) therapy. Traditionally, NAM appliances are made of a removable alveolar molding plate, to which a nasal stent is added, that is worn in conjunction with lip taping. The nasal stent and the molding plate are adjusted weekly for 10-16 weeks to gradually correct the nasal and alveolar deformities until the infant is ready for surgical repair. The objectives of NAM are to approximate the lips and alveolar segments, improve the symmetry of the nasal cartilages and provide a nonsurgical elongation of the columella. ,

A recent study showed that nearly 50% of cleft centers in the United States offer NAM therapy. Despite the advantages of NAM therapy, a major concern is the considerable burden of care associated with the number of visits required, distance traveled for adjustments, visit duration, and the cost of treatment, which may reduce the likelihood of adhering to the treatment protocol.

Over the last decade, digital imaging technology, such as computer-aided design (CAD), computer-aided manufacturing (CAM), and 3-dimensional (3D) printing, has gained wide popularity in the medical field, with reports of a wide range of clinical applications that were shown to facilitate and improve clinical outcomes. , More recently, investigators have reported successful usage of 3D technologies to aid with the fabrication of NAM appliances.

In the current manuscript, we propose a novel method for using CAD and/or CAM technologies to simulate the desired movements, 3D print the models, and then fabricate a series of NAM appliances using thermoplastic clear aligners in a single step. Our goal was to reduce the burden of care, minimize clinician chair time, and facilitate the process for the clinician and the infant’s family.

Material and methods

We present a new method for fabricating NAM appliances using 3D planning and 3D printing, along with clear thermoplastic aligners. The first step was acquiring a traditional impression using Sil-tech (Ivoclar Vivadent, Amherst, NY) matrix putty material in a hospital setting, to allow for rapid response by an airway team in the event of an emergency. The impression is then poured, and the stone model is scanned with an intraoral scanner. The resultant stereolithography file is imported into Ortho Insight 3D software (MotionView Software, Chattanooga, Tenn) ( Fig 1 , A ). The alveolar segments are digitally segmented and moved to the desired final position ( Fig 1 , B and C ; See Video , available at www.ajodo.org ). The segmentation is done by manually placing a point on the most anterior and most posterior points of each segment, resulting in an approximate perimeter surrounding the segment, which is then manually adjusted by the operator to ensure the inclusion of the whole segment. However, depending on the case, the operator may choose to split the greater segment further into 2 segments, if more rotational control is needed for the anterior portion of the greater segment (See Video , available at www.ajodo.org ). The final position is set by the operator, and the goal is to approximate the segments to the estimated position of the midline ( Fig 1 , B and C ; See Video , available at www.ajodo.org ). The movement, as shown in the Video (See Video , available at www.ajodo.org ), can be tailored by the operator to each case. The total distance moved was divided into a sequence of 1-1.5 mm increments, allowing us to create a sequence of digital models ( Fig 1 , D ). The total movements were divided evenly among the number of stages, as the software allows us to perform the entire movement, choose the number of stages and then automatically evenly distribute the movements over the number of stages. The increments of activation were determined by the operator on the basis of previous recommendations from the literature. Subsequently, the staged models are 3D printed ( Fig 1 , E ).

Fig 1
The digital workflow for designing and fabricating NAM aligners: A, the scanned model is imported into MotionView Software (MotionView Software, Chattanooga, Tenn); B, the alveolar segments are digitally segmented; C, the alveolar segments are moved into the desired final position; D, the total distance moved was divided into a sequence of 1-2 mm increments, allowing us to create a sequence of digital models; E, the staged models are 3D printed; F, a button template is 3D printed and attached to the printed model at each stage; G, a Vacuform machine is used to fabricate an 0.040-in aligner for each stage; H, the button is retained in the aligner and easily separates from the model, after which the aligner is trimmed and smoothened for comfort; I, the nose piece is added to the aligner at the desired stage with a 0.030-in orthodontic wire and Triad is added for nasal support. Triad and Assure Plus are used to adhere the nasal support wire to the aligner, with retention holes cut out for increased retention. Done at each stage. § Done at the desired stage (in the presented example, stage 6).

We used a Fused filament fabrication (FFF) printer, Monoprice Ultimaker (Monoprice, Rancho Cucamonga, Calif), with high-temperature polylactic acid filament to allow for the fabrication of NAM aligners with thermoplastic clear aligner material. When the models are printed, a button template is also printed to allow free form positioning of the button for each patient. The button is added directly to the model and attached using light cure Triad gel (Dentsply Sirona, Charlotte, NC) ( Fig 1 , F ). Once the button is placed, a Vacuform machine is used to fabricate an 0.040-in aligner (Taglus, Mumbai, India) for each stage ( Fig 1 , G ). The button is retained in the aligner and easily separates from the model, after which the aligner is trimmed and smoothened for comfort, and the edges were polished with a polishing wheel ( Fig 1 , H ). The nose piece is added to the aligner at the desired stage with a 0.030-in orthodontic wire, and Triad is added for nasal support. Triad and Assure Plus (Reliance Orthodontic Products, Itasca, Ill) are used to adhere the nasal support wire to the aligner, with retention holes cut out for increased retention ( Fig 1 , I ).

One male infant with an 8 mm left unilateral cleft lip and palate was treated with digitally designed clear aligner NAM appliances. The patient was aged 21 days at the start of treatment ( Fig 2 ). A total of 6 aligners were fabricated, and the nose piece was added to the last stage. The appliance was fabricated, as mentioned above, with most of the movement designed to target the minor segment of the alveolus because the major segment was well-aligned ( Fig 1 ; See Video , available at www.ajodo.org ). The total number of visits was 11, and the total treatment duration was 14 weeks until the cheiloplasty was performed. The Table describes the patient and treatment process. In our study, the infant’s NAM treatment was simulated, and the appliances were constructed on the basis of the simulation, as described above. At the initial impression visit, taping with elastics was applied and reviewed with the parents ( Fig 2 ). Taping continued throughout treatment after delivery of the appliance, in which the tape and elastics were attached to the molding aligner ( Fig 3 ). The nose piece was added to the last aligner only, which was possible in this case because there was sufficient time between the last aligner stage and the lip repair surgery. Figure 3 illustrates the appliance in place at the final stage with the nose piece and the fit of the appliance intraorally.

Oct 7, 2020 | Posted by in Orthodontics | Comments Off on A novel method for fabricating nasoalveolar molding appliances for infants with cleft lip and palate using 3-dimensional workflow and clear aligners
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