The use of Korat-modified nasoalveolar molding devices in patients with unilateral complete cleft lip and palate with a 5-year follow-up

Active obturator

Patients are first assessed for the need to wear an active obturator before Korat- NAM I. If a cleft size is more than 10 mm, the patient is prescribed an active obturator with a retraction screw to align the alveolar segments and decrease the cleft size. Patients with a large cleft may need two obturators for the stepwise reduction of the alveolar cleft. It is used with micropore surgical tape across the cheeks to reduce the cleft size on the upper lip.

Korat-NAM I

There are two components of the Korat-NAM I [Figure 2a]. The first component is a passive obturator. The second component is the nasal part that projects into the nostrils.

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Figure 2:

(a) Components of the Korat-NAM I (a1) are a passive obturator with acrylic bite block on both sides, (a2) extending arm on the cleft side with a coil that allows additional activation, (a3) extending arm on the non-cleft side, (a4) nasal acrylic piece on the cleft side, and (a5) nasal acrylic piece on the non-cleft side. (b) The acrylic nasal piece is 11–15 mm long with 6–8 mm inside the nostril. When the patient wears the Korat-NAM I, a thread is used to reinforce appliance retention and guide the appliance insertion and removal. (c, arrow) Both legs of the thread are wrapped around the extending wire on the cleft side and end toward the medial side. (d) The two extending arms (arrowhead) help maintain the nipple in place and squeeze the milk out during feeding. NAM: Nasoalveolar molding.

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If the cleft size is more than 4 mm but <10 mm, a set-up model is required to align the alveolar segment when fabricating the obturator part of Korat-NAM I. With a cleft size <4 mm, a set-up model is not required. In this obturator part, there is an acrylic bite block [Figure 2a-1], which is a bite registration fabricated from an impression of the opposing alveolar ridge of the posterior teeth region at the physiologic rest position (2–3 mm apart). This bite block is placed for stabilizing the appliance when the patient bites and sucks on the bottle, increasing appliance retention.

The nasal part consists of two 0.8-mm spring-hard stainless-steel arms extending from the plate to the nostril on the cleft and non-cleft sides.

Primary correction (cheiloplasty with primary rhinoplasty)

At our center, we use a combination of surgical techniques modified based on Millard’s rotation advancement method^[8,9] with the goals of creating equal distance from the oral commissure to the cupid bow on both sides, a faint white roll line, an appropriate vermillion thickness, and an elongated and lifted columella base on the cleft side. An additional flap similar to Fisher’s cheiloplasty^[10] method and a lateral V Noordhoff flap^[11] are performed. Based on the paradigm of treating the lip and nose as one unit, we perform a primary rhinoplasty at the time of cheiloplasty. Following Tajima’s method,^[12] the reverse-U incision is performed. Thereafter, we maintain the nostril shape with the customized nasal conformer that is fabricated from an endotracheal tube. The conformer is sutured and held with the nasal septum behind the columella for 3 weeks. In addition, we transfix the mucosa of the lateral nasal wall and the alar base with the dermis using one suture each to reduce hematoma and swelling. At 3 weeks post-surgery, we remove the customized nasal conformer and continue with the Korat-NAM II to maintain the nostril and alar rim and prevent relapse.

Korat-NAM II

Before primary correction, an impression is taken for fabricating the Korat-NAM II to replace Korat-NAM I which begins to wear down by this time. Three weeks after primary correction [Figure 3a], the customized nasal conformer is removed, the nostril is cleaned, and the Korat-NAM II is inserted. The Korat-NAM II is similar to the Korat-NAM I, except that there is no coil on the extending arm on the cleft side since it is mainly used as a nostril shape retainer (less activation is needed than the Korat-NAM I) [Figure 3b-1]. Moreover, without a coil on the cleft side, the extension arm can curve upward smoothly to avoid pressing on the lip after surgery. In addition, denture adhesive is required to retain the appliance with the upper arch. The alveolar ridge of the anterior teeth area part of the acrylic plate is removed to accommodate the erupting primary teeth during monthly follow-up visits. The Korat-NAM II is used to maintain the nose morphology after primary correction until before the palatoplasty [Figure 3c and d].

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Figure 3:

(a) The customized nasal conformer before removal from the repaired nose on the cleft side. (b) The Korat-NAM II is different from the Korat-NAM I because there is no coil on the extending arm on the cleft side (b-1). (c) The Korat-NAM II in place at frontal view and (d) submentovertex view. (d-1) Notice the stretching force by the extending arm on the cleft side (d-2) while the extending arm on the non-cleft side only supports the columella and nostril. NAM: Nasoalveolar molding.

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Palatoplasty

We use a standard two-flap palatoplasty in conjunction with Furlow’s double opposing Z-plasty^[13] and perform a gingivoperiosteoplasty to close the alveolar cleft with a one-layer mucoperiosteal flap (nasal side). The procedure is considered successful if there is a complete separation between the oral and nasal cavity. In addition, the soft palate and pharyngeal muscle can function normally. After palatoplasty, the patient is instructed to wear the Korat-NM III for maintaining the nostril and alar contour for at least 2 years.

Korat-NM III

The Korat-NM III is an extraoral appliance in a head strap design, unlike the Korat-NAM I and II. Before palatoplasty, an impression of the patient’s forehead is taken. A 1-mm spring-hard stainless steel wire is bent to fit the forehead. The width between the two legs is approximately the width of the widest part of the columella. Each leg is curved to be slightly in front, of the nose, and turned 90° at the same level of the upper edge of the nostril on the cleft side, and 2 mm below the upper edge of the nostril on the non-cleft side to form a 4-mm coil on both sides [Figure 4a]. The end of each leg then projects into the nostril with kidney-shaped acrylic on both sides. The shorter leg on the cleft side [Figure 4a-1] pulls the nostril upward, while the other leg [Figure 4a-2] only passively supports the columella [Figure 4b]. The forehead wire part is sewn on an elastic head strap. The appliance is adjusted every 3 months since the wires become loose from repetitive removal and wearing and to compensate for nasal morphology changes. Adjustments were made to maintain nasal morphology with no active force. The adjustment visits last at least 2 years after the palatoplasty.

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Figure 4:

(a) The Korat-NM III is an extra-oral appliance connected with an elastic head strap. Each wire leg is curved slightly to be in front of the nose with the coil that allows adjustment to accommodate the patient’s facial growth. Notice the slightly shorter leg on the cleft side (a-1) than the non-cleft side (a-2) to pull up the nostril (b) on the cleft side slightly. NM: Nasal molding.

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Korat modification of NAM appliance

The original NAM appliance mainly consists of acrylic that has to be thick enough to achieve adequate strength. Our Korat-NAM replaces the acrylic extension arms with wires that reduce the bulkiness of this part of the appliance for patients’ acceptance and comfort. In addition, these wires extend from the occlusal surface of the plate instead of the labial surface like other previously modified NAM appliances.^[14] This is possible because the thickness of the acrylic bite block, which is a unique design of Korat-NAM, allows freeway space. This wire position also helps with feeding by locking the nipple in place and squeezing out the milk. The force during sucking and biting could be transferred from the plate to the extending arms toward the acrylic nostril part that can stretch the nostril, especially on the cleft side. In addition, it could also stretch the upper lip forward that may reduce the compression force on the maxilla and allow forward maxillary growth (forward displacement of the maxilla).^[15] However, these effects require further studies to validate these hypotheses.

For patients with initial cleft size larger than 10 mm, we used an active obturator with retraction screw before prescribing the Korat-NAM I, while for patients with initial cleft size between 4 and 10 mm, we used a set-up model to align the alveolar segments during Korat-NAM I wearing. This set-up model reduces the chair time for appliance adjustment visits, since the addition and removal of acrylic is not required like other NAMs.

Another modification that could be an advantage is that the Korat-NAM also has an extending arm that goes into the non-cleft side nostril to support the columella, unlike other NAMs. It supports columella with no active push force. We experienced that without this supporting arm on the non-cleft side, the columella tended to collapse to the non-cleft side when stretching the nostril on the cleft side. Therefore, this could reduce the asymmetry between the cleft and non-cleft sides due to relapse and tension. In addition, the thread ends in the Korat-NAM I that projects towards the medial side could pull the nostril on the cleft side medially, which may counteract the tension force direction from relapse. Furthermore, having two extended arms increases appliance retention and helps lock the nipple during feeding.

We use traditional acrylic without soft acrylic for fabricating the Korat-NAM to achieve high strength, improve its hygiene, and eliminate chair-side adjustments. In terms of overall cost per appliance, our Korat-NAM is cheaper because no soft denture liner (soft acrylic) is required, unlike the conventional NAM appliance. However, a small amount of denture adhesive is required in the Korat-NAM II.

In addition to maintaining nasal morphology after primary correction, Korat NAM II serves as an obturator while the patient is waiting for palatoplasty that also improves tongue position and function,^[16] unlike other kinds of nasal conformer.

Clinical chair time is decreased with our Korat-NAM because the nasal acrylic part is prefabricated and the appliance is quite easy for doctors and parents to insert. Therefore, the Korat-NAM can be delivered on the same day to reduce the number of clinic visits. However, an extensive amount of laboratory work is still required. Therefore, the laboratory technician is a key person in fabricating this appliance. Although digital NAM is becoming more popular nowadays,^[17,18] we experience that not all hospitals can afford the cost of an intraoral scanner and a 3D printer. Therefore, the conventional way of fabricating NAM is still essential.

Longer NAM usage may accommodate cheiloplasty and minimize relapse after surgery

The NAM is usually used early when the cartilage is soft enough to be molded before primary correction. This molding is possible due to the effect of high levels of estrogen and hyaluronic acid early after birth.^[19,20] A previous study demonstrated that the NAM could be used at a later age; however, the molding result was not as good as when its use began earlier.^[21] At our center, we start using the Korat-NAM in CLP patients early after birth. However, the main difference in the Korat-NAM use is the duration. The Korat-NAM also has modifications that can be used after primary correction and palatoplasty, unlike other NAMs that are indicated to be used only before primary correction. We observed a decrease in postsurgical relapse, and improvement in symmetry between the cleft and non-cleft side in patients with a full course of Korat-NAM appliance use together with modified surgical techniques at our center (ongoing data collection and analysis).

After primary correction, some patients are prescribed a nasal conformer to maintain their nose morphology and prevent relapse due to scar tissue and muscle force. However, typically, it is maintained for a short period that may not be enough to prevent relapse after surgery, and a revision surgery is required. In addition, the nasal conformer can be easily removed by the patients because it is removable and small. Other centers recommend using a nasal conformer for a maximum of 6 months after primary correction.^[22] The Korat-NAM II is prescribed to be used after primary correction until the patients undergo palatoplasty, which is longer than 6 months. In addition, the Korat-NAM II can be worn more easily than the nasal conformer because the patients previously wore the Korat-NAM I. Furthermore, we use a customized nasal conformer for 3 weeks to effectively maintain the nasal morphology before switching to the Korat-NAM II. This customized nasal conformer is made from an endotracheal tube instead of a commercial nasal conformer, which can reduce cost. Subsequently, the KoratNM III is recommended to be used as long as the patients can tolerate it (the longest period we have observed is 10 years) to maintain nose morphology and prevent relapse. However, we instruct patients to strictly wear it at least for 2 years after surgery since the rate of relapse is high in the 1^st year after surgery.^[23] After that we experienced that most patients could not wear Korat-NM III as expected due to social activities which changed with age. Patients wanted to play outside with friends, and they no longer wanted to wear the appliance. Therefore, we designed as a head strap to be easily worn and encouraged them to wear only 2 h a day while they were home. The exact amount of wearing time to perfectly maintain the nostril shape after surgery still requires further studies.

Burden of care

In the viewpoint of the burden of care from using KoratNAM, it is the fact that we cannot avoid it in several aspects including multiple visits, patient discomfort, and financial cost.^[6] In terms of multiple visits, we found that every clinic visit for appliance adjustment, helped reinforce parents by seeing improvement in the oral hygiene of their children. As mentioned in the study by Magyar et al., social support is an essential factor for treatment outcomes.^[24] In addition, we schedule the adjustment visits so that several parents come in on the same day and help reinforce and share knowledge with each other. Moreover, with Korat-NAM, we can reduce chair time of appliance fabrication and adjustments as mentioned previously. More importantly, patients were also scheduled with other clinics on the same day, such as speech therapy and pediatric dentistry to minimize the overall hospital visits. In terms of patient discomfort, we modified the Korat-NAM appliance to a less bulky design and increased retention to minimize the use of taping that usually causes irritation. In terms of financial cost, Korat-NAM appliance costs and transportation costs to the hospital were covered by the government. Therefore, after weighing risks and benefits, we still recommend using Korat NAM in conjunction with surgery for CLP correction.

Primary correction and palatoplasty

With the Korat-NAM appliance, patients would present with well-aligned alveolar segments with a narrow gap, appropriate nose tip projection, and sufficient lip tissue that improve the esthetics and success of the primary correction. At the skin layer, we use the Millard rotation advancement technique with modification of Fisher’s technique which makes the scar line appear to be a philtrum ridge, and minimizes the scar contraction that may affect the vertical lip height. The key step in primary cleft lip and nose repair is the muscle layer repair. We release the muscle and alar base from the maxilla and nasal aperture rim and completely reconstruct the muscle from the upper to the lower part of the lip. The upper part of the orbicularis muscle is reconstructed to achieve nostril sill fullness and overcorrect the nostril sill width by approximately 20% to prevent relapse from the nasal cleft deformity.^[25] For the primary rhinoplasty, we approach using Tajima’s reverse U-incision to realign the lower lateral cartilage on the cleft side and perform suture plication with the unaffected side to achieve nasal tip projection and elongate the columella on the cleft side. This procedure is considered an overcorrection of the nostril height. The customized nasal conformer is retained for 3 weeks to temporarily support the nostril and minimize the nasal mucosa swelling. To maintain the nostril height for a longer period of time, the Korat-NAM II is suggested.

With the Korat-NAM appliance and a well-reconstructed orbicularis muscle, we experienced that patients at ~1.5 years old would present with well-aligned alveolar segments with a narrow gap that accommodates the palatoplasty.