Three-dimensional assessment of maxillary arch changes in infants with bilateral cleft lip and palate using vacuum-formed nasoalveolar molding with active screw versus conventional nasoalveolar molding appliances: a randomized clinical trial

Abstract

Objectives

This study aimed to compare the 3D changes of maxillary arches in infants with bilateral cleft lip and palate (BCLP) undergoing vacuum formed nasoalveolar molding appliance with active screw (VF-NAM) to those who received conventional Grayson (G-NAM).

Methods

A total of 24 BCLP infants were randomly allocated into, group 1 (n = 12) who received V-NAM and Group 2 (n = 12) underwent G-NAM appliances. In the V-NAM group, all infants received 1- 2 vacuum formed maxillary plates incorporated with active retraction screw. In the G-NAM group, Grayson’s NAM technique was followed. The nasal stents were added to the maxillary plates in both groups in the same manner to mold the deformed nasal cartilages. Sixteen items in the digital maxillary models were analyzed at T1 (pre-NAM therapy) and T2 (post-NAM therapy) using 3D software. Parametric data were analyzed using a repeated measures ANOVA test to compare between groups and assess changes within each group by time, while non-parametric data were analyzed using the Mann–Whitney U test to compare between groups and the Wilcoxon signed-rank test to assess changes within each group by time.

Results

By the end of this study, both groups showed no statistically significant differences in all variables associated with changes in the transverse and vertical arch dimensions except the mid-arch width in which the VF-NAM group exhibited a significantly greater change compared to the G-NAM group, with an effect size of 0.953 (CI 95%: -0.03 − 2.46). In the sagittal dimensions, A more significant decrease in the right and left alveolar cleft widths was observed in the VF-NAM group relative to the G-NAM group with effect sizes of 0.89 (CI 95%: -3.73–0.11). and 0.85 (CI 95%: -3.82 − 0.14), respectively (P < 0.05). Conversely, the G-NAM group demonstrated a significantly greater increase in the premaxillary rotation angle compared to the VF-NAM group, with an effect size of 0.875(CI 95%: -3.06 − 13.56) (P < 0.05).

Conclusion

Both VF-NAM and G-NAM effectively reduced alveolar cleft gaps, retracted the premaxillary segment, and normalized alveolar contour. However, VF-NAM resulted in greater reductions in cleft width and mid-arch width expansion. Conversely, G-NAM was more effective in improving premaxillary rotation. These findings may contribute to clinical decision-making in the early cleft management by guiding the selection of appliances based on individual anatomical characteristics. The use of a VF-NAM or G-NAM appliance could strategically optimize pre-surgical outcomes and enhance treatment planning in infants with BCLP.

Trial registration

NCT04966572 -July 8th 2021.

Introduction

Orofacial clefts (OFCs) are the most common type of craniofacial defects, occurring in approximately 1:700 live births [1]. Although cleft lip and palate is not a fatal disorder, patients with such a condition usually suffer from dental, functional, and aesthetic issues, as well as additional complications such as hearing, respiratory, and nutritional problems [2].

A BCLP condition is considered one of the most severe clinical forms of cleft lip and palate cases. It is characterized by displacement of the premaxilla, abnormality in nasal cartilage morphology, and columellar deficiency, which can make the achievement of functional and cosmetic outcomes challenging for the surgeon [3]. Although advances in plastic surgery have been improved in attempts to repair clefts of the lip, alveolus, and palate, surgery alone cannot correct all aspects of the cleft deformity. The persistence of severe scarring and problems associated with nasal deformities had given rise to the use of presurgical infant orthopedics in cleft-treatment protocols [4].

The concept of nasoalveolar molding (NAM) was introduced by Grayson and Cutting 1993 based on the ear cartilage molding techniques described by Matsuo et al. (1984), which improved the nasal esthetics through nasal molding and presurgical columella lengthening allowing the surgeon to perform a one-stage repair of the lip, nose, and alveolus [5].

In the current literature, most studies reported fabrication of nasoalveolar molding by acrylic resin [6, 7]. As a modification to the original NAM technique, Batra et al. (2020) [8] and Al Khateeb et al. (2021) [9] fabricated a series of preadjusted vacuum formed nasoalveolar Molding aligners VF (NAM) using clear thermoplastic material instead of acrylic and evaluated the short-term effect of these appliances on the morphology of nose, lip, and maxillary arch in infants with unilateral cleft lip and palate (UCLP). The results proved the effectiveness of VF-NAM in reducing the nasoalabial deformities associated with infants with UCLP and improving the alveolar morphology and nasal symmetry. Furthermore, Batra et al. (2022) conducted a prospective cohort study comparing the modified Grayson’s technique and clear aligners in 30 patients with complete unilateral cleft lip and palate. Both approaches resulted in similar improvements in nasal asymmetry. However, the clear aligner group required significantly fewer visits than the group that received modified Grayson’s technique [10]. Additionally, vacuum-thermoformed appliances were observed to offer advantages such as the absence of residual monomer, uniform thickness, and superior finishing quality [11]. To the best of our knowledge, no study in the literature has evaluated the effect of VF-NAM appliances on infants with BCLP.

Furthermore, several studies in the literature have reported on the use of active screwed acrylic-formed NAM appliances in infants with bilateral cleft lip and palate (BCLP). These appliances deliver more predictable and quantified forces to retract the protruded premaxilla, which may lead to improved alveolar arch form and a potential reduction in the frequency of follow-up visits [12–17]. Most of these studies were case reports and case series. However, limited randomized clinical trials are available in the current literature to compare the efficacy of these appliances with the conventional Grayson NAM appliances.

In the present study, and in an attempt to help clinicians optimize treatment efficacy when planning presurgical infant orthopedics, a modified VF-NAM appliance with incorporated active retraction screw to retract the protruded premaxilla was compared with conventional Grayson acrylic formed nasoalveolar molding group as regards the morphological changes in the maxillary arch form. The current study hypothesized that using active screwed VF-NAM appliance in infants with BCLP could improve the clinical outcomes by repositioning the protruded premaxilla, reshaping the nasal cartilages, and facilitating subsequent surgical treatments and improving overall cosmetic and functional outcomes in the same manner as in conventional Grayson acrylic formed nasoalveolar molding appliance.

Material and methods

The Consolidated Standards of Reporting Trials guidelines for reporting Randomized Controlled Trials (CONSORT) were followed throughout the current study (Schulz et al. 2010) [18].

Trial design

This trial was a randomized, parallel-group, single-blinded, prospective, comparative clinical trial with allocation ratio 1:1. The PICO format for the trial is as follows: (P) patients with complete bilateral cleft lip and palate, (I) Active screwed vacuum formed NAM appliance (VF-NAM), (C) Conventional Grayson nasoalveolar molding (G-NAM) and (O): 3D change in maxillary arch form and duration of NAM therapy. The trial was registered on ClinicalTrials.gov with registration number: (NCT04966572) on July 8th 2021. The study protocol was registered and approved by the Research Ethics Committee at the Faculty of Dentistry, Cairo University.

Participants, eligibility criteria, and settings

The participants were recruited from the Outpatient Clinic at the Department of Pediatric Surgery (Abu El Reesh Hospital), Faculty of Medicine, Cairo University. The sample consisted of 24 infants with complete BCLP. Eligibility criteria were as follows: (1) non-syndromic infants with complete BCLP, (2) infants younger than 1 month of age, (3) both male and female participants, and (4) infants whose parents provided written consent for the study. Patients with unilateral cleft lip, incomplete cleft lip, a history of any previous surgical lip repair, or other congenital malformations were excluded. Subsequently, written informed consent was obtained from all participants'parents. The steps of infant orthopedic treatment and follow-up visits were carried out by the principal operator (K.A.A.) at the Orthodontic Outpatient Clinic, Faculty of Dentistry, Cairo University. Upon completion of NAM therapy, all surgical lip repairs were performed at Abu El Reesh Pediatric Hospital by a single surgeon (W.M.).

Interventions

Before the commencement of NAM therapy, an impression of the infant’s maxillary arch was taken using a condensation silicone elastomeric impression material (putty viscosity). The procedure involved a customized acrylic tray and was conducted with the infant fully awake, positioned almost upright, and securely held by one of the parents in a clinical setting. The impression should record accurately all the maxillary arch extending to the labial vestibule anteriorly and to the maxillary tuberosity posteriorly. It was poured within 1 h with a hard dental stone to fabricate accurate plaster models. This model was scanned by a 3D desktop scanner to obtain the digital 3D model, which was used to evaluate the changes in the maxillary arch using the 3shape Ortho Analyzer. Then, the same plaster model was utilized for the fabrication of NAM appliances.

Active Screwed Vacuum Formed NAM appliance (VF- NAM)

All the infants in the VF-NAM group received 1–2 VF-NAM aligners incorporated with active retraction screw to retract the premaxillary segment. Firstly, any undercut areas were blocked with stone to facilitate the removal of the appliance without damaging the working cast. Also, a hard stone was added to the occlusal and lateral surfaces of the posterior alveolar segments, along with the occlusal surface of the premaxillary segment, to maintain the vertical and transverse dimensions during growth. In cases with collapsed posterior lateral segments, the working model was modified by selective grinding of the palatal surfaces of the posterior alveolar segments and the addition of contrasting colored stone on the buccal surfaces before the fabrication of the intraoral portion of the VF-NAM aligner. Then, the VF-NAM was activated using a one-way retraction screw (RS) (One-way Leone standard expansion screw, Italy). The proper size of RS was selected based on the distance needed to retract the premaxillary segment. Before positioning on the modified working model, the retraction screw was fully opened (pre-activated) to allow for a maximum retraction of 6 mm or 9 mm, depending on the screw size (Fig. 1). The screw closure activation technique involved a quarter turn (0.25 mm) on alternating days, resulting in approximately 1 mm of retraction per week and 4 mm per month. If additional premaxilla retrusion was deemed necessary, a new maxillary arch impression was taken to fabricate a new VF-NAM aligner with a retraction screw.

Fig. 1.

Pre-activation of the retraction screw using a special key

The intraoral portion of the VF-NAM appliance was fabricated using a 2 mm vacuum thermoplastic sheet (Thermoplastic sheet, Ultrafit Plastic, DENTSPLY Raintree Essix, USA) on a modified working model with the retraction screw secured in place. The vacuum forming process involved adapting the heat-softened plastic sheet to the model using a vacuum machine that applied negative pressure. The retraction screw (RS) was attached to the inner surface of the vacuum-formed intraoral plate with a small amount of self-cure clear acrylic resin (Fig. 2- A).

Fig. 2.

A Active screwed VF- NAM aligner with attached acrylic buttons. B Frontal photographic view shows the retention of the VF-NAM aligner using extra-oral orthodontic elastic secured to the cheek with surgical tape. C Addition of the nasal stents to the VF-NAM aligner. D Lateral photographic view shows proper positioning of the nasal stents inside the nasal cavities

The retentive acrylic buttons were fabricated using a rubber base template that was constructed from two previous ready-made buttons. The position of the two acrylic buttons on the labial flange of the intra-oral plate was at the junction of the upper and lower lips at rest position, with an angle of 45° to the occlusal plane. After that, a small amount of cold-cured acrylic resin was used to secure the buttons on the plate. The appliance was fabricated and delivered within one week. Extra-oral orthodontic elastic bands were utilized to secure the appliance to the cheeks. Protective tape was applied to each cheek to reduce tissue irritation caused by surgical tapes, and the tape was replaced every 2 to 3 days. Furthermore, a horizontal surgical tape measuring 6 mm × 100 mm was placed across the base of the nose, extending from one cheek to the other, starting from the first visit (Fig. 2- B).

Two nasal stents were introduced two weeks after the initiation of VF-NAM therapy. The lower part of the nasal stents extended from the anterior flange of the intraoral molding plate, while the upper part was positioned within the nostrils to adequately elevate the deformed nasal cartilages. The nasal stents pushed the nasal tip upward, while horizontal lip taping applied downward pressure on the columella base (Fig. 2- C, D). Parents were instructed to change the protective and surgical tapes every 2 days by wetting them thoroughly with water before carefully removing the tapes, and hydration cream should be applied to the cheeks to prevent skin irritation. In cases with collapsed posterior lateral segments or deviated premaxillary segment, the infants’ parents were instructed to postpone the activation of the retraction screw for 7–10 days, allowing the VF-NAM appliance to expand the collapsed lateral alveolar segments or upright the deviated premaxillary part before starting the activation of the retraction screw. The completion of VF-NAM therapy was determined by total alveolar cleft gap approximation and/or when reached time of surgical lip closure which was 5–6 months, and then all patients were referred to Abu EL Reesh hospital for surgical lip closure to be performed by a single surgeon.

Conventional Grayson nasoalveolar molding (G-NAM) group

The steps for fabricating the conventional Grayson NAM appliance followed the technique described by Grayson and Cutting (1993) for correcting the nose, lip, and alveolus in infants born with bilateral clefts using a presurgical nasoalveolar orthopedic molding appliance [5].

Initially, the working model was prepared by blocking out all undercut areas with dental wax. Wax was also added to guide alveolar growth in specific regions, including the lateral, anterior, and occlusal surfaces of the posterior lateral alveolar segments and the palatal side of the premaxilla. An intraoral molding plate was then fabricated on the prepared working model using cold-cured acrylic resin (Fig. 3- A). Two retentive acrylic buttons were attached to the molding plate in a manner similar to that used in the VF-NAM group. Retention of the appliance in the G-NAM group was achieved in the same way as in the VF-NAM group; medium elastic bands (1/3-inch, 4.5 oz) were looped around each button and secured to the cheeks with surgical tape. The elastic bands were stretched to twice their passive diameter to ensure proper force activation and retention. Protective tape was applied to the cheeks to minimize tissue irritation from the surgical tapes and was replaced every 2 to 3 days. Additionally, a horizontal lip tape measuring 6 mm × 100 mm was applied across the base of the nose, extending from one cheek to the other, starting from the first visit (Fig. 3- B). The appliance was constructed and delivered within one week, and detailed instructions for its use were provided to the parents.

Fig. 3.

A modifications performed in conventional Grayson NAM molding plate through selective grinding of the palatal and occlusal surfaces of the premaxilla and lateral and occlusal surfaces of posterior alveolar segments (Blue), and addition of soft acrylic resin on the labial surface of premaxilla and palatal surfaces of the posterior lateral segments (Yellow). B Frontal photographic view shows the retention of the G-NAM intraoral plate using extra-oral orthodontic elastic secured to the cheek with surgical tape. C Addition of the nasal stents to the G-NAM appliance. D Lateral photographic view shows proper positioning of the nasal stents inside the nasal cavities

The patients were followed up biweekly for appliance activation. Activation of the appliance was performed through selective grinding of the fitting surface and the addition of soft acrylic resin to guide alveolar growth and align the alveolar segments. Specifically, soft acrylic was applied to the labial side of the premaxilla segment and the palatal sides of the two lateral alveolar processes. Selective grinding was done to promote anterior growth of the lateral alveolar segments and vertical growth of the premaxilla and lateral segments. For cases involving a deviated or rotated premaxilla, selective grinding and the addition of soft acrylic resin were carried out in a targeted manner to align and centralize the premaxilla. When the alveolar gap was reduced to 5 mm or less, nasal stents were introduced and adjusted biweekly to apply gentle molding forces to the lower lateral cartilages and nasal tip (Fig. 3- C, D).

Data collection and outcome measures

The primary outcome was to compare between active screwed VF-NAM and conventional Grayson (G-NAM) appliances regarding the three dimensionally change in maxillary arch: anteroposterior, transverse, and vertical. The secondary outcome included the duration of treatment needed to complete NAM therapy. The changes in maxillary arch were assessed via the digital models acquired at two-time intervals: before NAM therapy and 4-5 months after the start of either intervention modality (VF-NAM and G-NAM). The analysis used in the current study was modified from a previously reported study done by Gong et al. 2017 [19] and Tankittiwat et al. 2021 [20]. The models were digitized using a 3D desktop scanner, and the data were analyzed using the 3shape Ortho-Analyzer software. Three-dimensional arch analysis was performed by identifying fifteen landmarks and five constructed points on each digitized model in 3 dimensions (Fig. 4 -A, B, C, and Table 1). Landmarks on either side of the maxillary arch were referred to by R and L letters to indicate the side with the right and the left cleft gap respectively. In this study, the linear and angular measurements were divided into 3 dimensions: Transverse measurements were recorded as follows: premaxillary width (P-P´), anterior arch width (L-L´), inter-canine arch width (C-C´), lateral sulcus width (Q-Q´), mid-arch width (M-M´), and posterior arch width (T-T') (Fig. 4-D and Table 1). Sagittal measurements were performed in this dimension, which included the right cleft width (RPX), left cleft width (LP´X´), right alveolar length (RLT), left alveolar length (LL´T´), premaxilla protrusion (I-Y), arch depth (I-Z), premaxillary deviation angle (Z I G°), and premaxillary rotation angle (Rot°) (Fig. 4 -E, F, G, H, and Table 1). In vertical dimension, the horizontal plane was used for the assessment of vertical positions of two landmarks identified on the scanned model (right alveolar height CD and left alveolar height C´D´) (Fig. 4 -I, and Table 1).

Fig. 4.

A Landmarks used for analysis of digital models. B, C Constructed points used for analysis of digital models. D Transverse measurements; (P-P´): Premaxillary width, (L- L´): Anterior arch width, (C- C´): Inter- canine arch width, (Q- Q´): Lateral sulcus width, (M- M´): Mid- arch width, (T- T´): Posterior arch width. E, F, G, H Anteroposterior measurements; (RPX): Right cleft width, (LP´X´): Left cleft width, (RLT): Right alveolar length, (LL´T´): Left alveolar length, (I- Y): Premaxilla protrusion, (I- Z): Arch depth, (Z I G°): Premaxillary deviation angle, (Rot °): Premaxillary rotation angle. I Vertical measurements; (CD): Right alveolar height, (C´D´): Left alveolar height

Table 1.

Description of landmarks, constructed points, lines, plane and 3D measurements used for analysis of digital models

Landmarks	Abbreviations	Description
landmarks used for analysis of digital models
Incisal point	I	The point on the alveolar crest where the incisive papilla and labial frenum meet.
Premaxilla right margin point	P	The lateral right end of premaxilla at its widest dimension.
Premaxilla left margin point	P´	The lateral left end of premaxilla at its widest dimension.
Lateral segment margin point at right cleft side	L	The most anterior point of the alveolar crest of the lateral segment (right).
Lateral segment margin point at left cleft side	L´	The most anterior point of the alveolar crest of the lateral segment (left).
Canine point of right lateral segment	C	Point of intersection between the alveolar ridge crest and lateral right sulcus.
Canine point of left lateral segment	C´	Point of intersection between the alveolar ridge crest and lateral left sulcus.
Middle arch point at right cleft side	M	Most lateral point on the widest curve of the lateral segment on right cleft side.
Middle arch point at left cleft side	M´	Most lateral point on the widest curve of the lateral segment on left cleft side.
Gingival groove point (R)	Q	The point of intersection between the lateral sulcus and gingival groove on the right cleft side.
Gingival groove point (L)	Q´	The point of intersection between the lateral sulcus and gingival groove on the left cleft side.
Tuberosity point (R)	T	The most posterior point in the maxillary tuberosity the right cleft side.
Tuberosity point (L)	T´	The most posterior point in the maxillary tuberosity on the right cleft side.
Canine palatal point of right lateral segment	D	The deepest point of the right cleft at the same level as CC´.
Canine palatal point of left lateral segment	D´	The deepest point of the left cleft at the same level as CC´.
Lines and plane used for analysis of digital models
Posterior transverse line	T-T´	Line connecting between T and T´ points
Anterior transverse line	L- L´	Line connecting between L and L´ points
Horizontal plane	HP	Horizontal plane constructed by connecting C, C´, and I point.
Constructed points used for analysis of digital models.
Point X	Intersection of the transverse line from point L (parallel to the T-T´) with the perpendicular from the T-T´ to point P.
Point X´	Intersection of the transverse line from point L´ (parallel to the T-T´) with the perpendicular from the T-T´ to point P´.
Point G	Mid-point on T-T´ line.
Point Y	The point of intersection of perpendicular line from point I to L-L´ line.
Point Z	The point of intersection of perpendicular line from point I to T-T´ line.
Measurementsfor three-dimensional arch analysis
Measurements in transverse dimension
Premaxillary width	P-P´	Distance between left and right lateral edges of premaxilla.
Anterior arch width	L- L´	Distance between the most anterior point of the alveolar crest of left and right lateral segments.
Inter-canine arch width	C- C´	Distance between the left and right canine points.
Lateral sulcus width	Q- Q´	Distance between the left and right lateral sulcus and the gingival groove points of intersection.
Mid- arch width	M- M´	Distance between the left and right middle arch points.
Posterior arch width	T- T´	Distance between the left- and right-most posterior point in the maxillary tuberosity.
Measurements in anteroposterior dimension
Right cleft width	RPX	Distance between the lateral end point of the premaxilla (P) and the most anterior, constructed point of lateral segment (X) on the right cleft side
Left cleft width	LP´X´	Distance between the lateral end point of the premaxilla (P´) and the most anterior, constructed point of lateral segment (X´) on the left cleft side
Right alveolar length	RLT	Distance from the most anterior point of the lateral segment (L) to the most posterior point in the maxillary tuberosity (T) on the right cleft side
Left alveolar length	LL´T´	Distance from the most anterior point of the lateral segment (L´) to the most posterior point in the maxillary tuberosity (T´) on the left cleft side
Premaxilla protrusion	I- Y	Distance between the incisal point perpendicular to the anterior arch width (Y).
Arch depth	I- Z	Distance between the incisal point perpendicular to the posterior arch width (Z).
Premaxillary deviation angle	Z I G °	Degree between the incisal point (I) perpendicular to the posterior arch width (Z) and the middle point of the posterior arch width (G).
Premaxillary rotation angle	Rot °	Degree between the incisal point perpendicular to the posterior arch width and PP´
Measurements in vertical dimension
Right alveolar height	CD	Distance to deepest point in right cleft perpendicular to the horizontal plane
Left alveolar height	C´D´	Distance to deepest point in left cleft perpendicular to the horizontal plane

Additionally, the duration of treatment needed to complete NAM therapy for each group was recorded in months.

Sample size

G*Power software was used to calculate the sample size by a specialized statistician. Mean differences and standard deviations were estimated according to Aslan et al. 2018 [7], who evaluated the efficacy of nasoalveolar molding (NAM) therapy on bilateral (BCLP) and unilateral (UCLP) cleft lip and palate. The sample size calculation was based on the maxillary arch dimensions (inter-canine width CC'), with a mean difference of 4 mm and a standard deviation of 2.79 for the control group. The results showed that a total sample size of 18 participants was adequate to detect a mean difference between study groups with a power of 80% and a 2-sided significance level of 0.05, with equal allocation to two arms (9 patients in each group). In this study, the total sample size was raised to 24 infants with complete bilateral cleft lip and palate to avoid attrition bias.

Randomization

Patients were randomly assigned to either the VF-NAM or G-NAM group. A computer random sequence table was generated using a Microsoft Excel sheet by a person who was not involved in the clinical trial. The randomization numbers were written on opaque white paper, folded three times into sealed envelopes, and kept securely in a box at the secretary’s office. Upon patient recruitment and after obtaining informed consent, the patient’s parent was asked to select an envelope. Then, the parent handed the envelope to the implementer, who opened it to reveal the participant’s group assignment. The implementer informed the investigator whether the participant was assigned to the VF-NAM or G-NAM group.

Blinding

All study contributors, except the implementer, were blinded to the randomization list. Due to the nature of the study, the operator and patients’ parents could not be blinded. However, the outcome assessors, responsible for digital model analysis, and the statistician were completely blinded. All parameters were measured by two independent, blinded assessors, who were trained to accurately place all landmarks on the digital models before taking measurements. To ensure reliability, the first assessor repeated 20% of the measurements after two weeks to evaluate intra-observer reliability, while the second assessor repeated the same 20% of the measurements to assess inter-observer reliability.

Controlling for confounding variables

In an attempt to minimize the influence of potential confounding variables, including the age of infants at the initiation of NAM therapy and cleft severity. The participants were randomly allocated to treatment groups using a computer-generated random sequence. This method was designed to ensure an equal distribution of these variables between the VF-NAM and G-NAM groups. Additionally, inclusion criteria were standardized to reduce variability, restricting assignment to infants aged less than one month with complete bilateral cleft lip and palate. Furthermore, baseline characteristics were evaluated and found to be statistically comparable between groups, confirming the effectiveness of randomization.

Statistical methods

Statistical analysis was performed with IBM SPSS Statistics for Windows, Version 23.0. Armonk, NY: IBM Corp. Data were presented as mean, standard deviation (SD), median and range values. The data for the transverse, anteroposterior, and vertical maxillary arch changes were explored for normality by checking the distribution of data using tests of normality (Kolmogorov–Smirnov and Shapiro–Wilk tests). All data showed normal (parametric) distribution except for pre-maxillary deviation angle as well as all amounts of change in different measurements, which showed non-normal (non-parametric) distribution. For parametric data, a repeated measures ANOVA test was used to compare the two groups and to study the changes by time within each group. Bonferroni’s post-hoc test was used for pair-wise comparisons when the ANOVA test is significant. For non-parametric data, the Mann–Whitney U test was used to compare the two groups. The Wilcoxon signed-rank test was used to study the changes by time within each group (T1 vs. T2). The treatment duration (in months) was analyzed using Student’s t-test to compare the two groups. The baseline characteristics of the two groups were presented as frequencies (n), percentages (%), means, and standard deviations (SD), and were analyzed using Student’s t-test and Fisher’s Exact test. Inter-observer agreement was assessed using Cronbach’s alpha reliability coefficient and Intra-Class Correlation Coefficient (ICC). Closer values of these coefficients to one indicate better agreement. The significance level was set at P ≤ 0.05.

Results

Clinical results

Twenty-four infants diagnosed with bilateral cleft lip and palate (BCLP) were enrolled in the study, comprising 16 males and 8 females. In the VF-NAM group, 7 males (58.3%) and 5 females (41.7%) participated, while the G-NAM group included 9 males (75%) and 3 females (25%). The mean age at T1 (pre-NAM records) was 20.8 ± 5.4 days for the VF-NAM group and 18.3 ± 6.4 days for the G-NAM group. As for the post-NAM records (T2), the mean age was 5.1 ± 1.1 months for the VF-NAM group and 5.7 ± 1.1 months for the G-NAM group. All 24 participants completed the study without dropouts. Clinical findings showed that both active screwed V- NAM and G- NAM appliances were effective in producing significant improvements. These included reductions in the right and left alveolar cleft gaps, diminished premaxillary protrusion, and decreased arch depth, as illustrated in Fig. 5.

Fig. 5.

Intraoral occlusal photographs illustrate the changes in the maxillary arch for an infant with BCLP before and after NAM therapy. A, B (above): Clinical findings of an infant before and after using the active screwed VF-NAM appliance. C, D (below): Clinical findings of an infant before and after using the conventional Grayson G-NAM appliance

Statistical results

Baseline data

At baseline, data on gender, age at the initiation and completion of NAM therapy were recorded in Table 2. The baseline characteristics of the active screwed VF-NAM and conventional G-NAM groups showed comparable average values for all variables. Inter and intra-observer reliability tests demonstrated good to very good reliability for all measurements, with Cronbach’s alpha ranging from 0.712 to 0.939 and 0.712 to 0.947, respectively, in the VF-NAM group, and from 0.708 to 0.931 and 0.702 to 0.941, respectively, in the G-NAM group.

Table 2.

Frequencies (n), percentages (%), mean, standard deviation (SD), and results of Student’s t-test and Fisher’s Exact tests for comparisons of baseline characteristics in the two groups

Baseline characteristics	VF-NAM (n = 12)	G-NAM (n = 12)	P value
Gender [n, (%)]
Male	7 (58.3%)	9 (75%)	0.386
Female	5 (41.7%)	3 (25%)
Age on starting treatment in days [Mean, (SD)]	20.8 (5.4)	18.3 (6.4)	0.310
Age after NAM therapy in months [Mean, (SD)]	5.1 (1.1)	5.7 (1.1)	0.236
Age after surgery in months [Mean, (SD)]	20 (4.6)	18.4 (5.1)	0.451
Cleft severity at initiation of NAM therapy:
Pre-maxillary protrusion (mm) [Mean, (SD)]	12.12 (1.56)	12.03 (1.89)	0.907
Right cleft width (mm) [Mean, (SD)]	10.08 (1.48)	9.45 (2.93)	0.513
Left cleft width (mm) [Mean, (SD)]	10.12 (2.3)	10.54 (2.17)	0.646

*Significant at P ≤ 0.05

Active screwed VF- NAM group

In the transverse dimension analysis, a significant increase was observed in the mid-arch width (M-M´) and posterior arch width (T-T´), with mean differences of 1.04 ± 1.29 mm (CI 95%: 0.31 − 1.77) and 1.01 ± 1.08 mm (CI 95%: 0.39 − 1.62), respectively. Conversely, the lateral sulcus width (Q-Q´) demonstrated a significant decrease by a mean difference of 1.52 ± 1.54 mm (CI 95%: −2.39 − −0.64). Changes in the premaxillary width (P-P´), anterior arch width (L-L´), and inter-canine arch width (C–C´) were not statistically significant (Table 3). For the anteroposterior assessment, a significant reduction was observed in the right and left cleft widths (RPX and LP´X´), premaxilla protrusion (I-Y), arch depth (I-Z), and premaxillary deviation angle (ZIG°) with mean differences of 7.52 ± 1.93 mm (CI 95%: −8.61 − −6.42), 7.74 ± 2.26 mm (CI 95%: −8.01 − −5.46), 8.51 ± 2.23 mm (CI 95%: −9.77 − −7.24), 5.59 ± 2.91 mm (CI 95%: −7.23 − −3.94), and 5.73° ± 9.23° (CI 95%: −10.95 − −0.50), respectively (Table 3). Meanwhile, the right and left alveolar lengths (RLT and LL´T´) increased significantly by mean differences of 3.33 ± 1.99 mm (CI 95%: 2.20 − 4.45) and 3.23 ± 1.27 mm (CI 95%: 2.51–3.94), respectively. However, no significant changes were observed in the premaxillary rotation angle (Rot°) (Table 3). In the vertical dimension, significant increases were identified in right and left alveolar heights (CD and C´D´) by 3.08 ± 1.64 mm (CI 95%: 2.15 − 4.0) and 2.27 ± 1.55 mm (CI 95%: 1.39 − 3.14), respectively (Table 3).

Table 3.

Results of repeated measures ANOVA test for the changes in measurements in transverse, anteroposterior, and vertical dimensions within each group

Measurement (mm)	Group		95% CI for mean difference		P-value	Effect size (Partial Eta Squared)
		Mean difference (T2-T1) ± SD	Lower limit	Upper limit
Premaxillary width (mm)	VF-NAM	0.78 ± 1.73	−0.199	1.759	0.130	0.101
	G-NAM	1.45 ± 1.68	0.499	2.401	0.007*	0.283
Anterior arch width (mm)	VF-NAM	−1.34 ± 2.45	−2.726	0.0462	0.136	0.098
	G-NAM	0.31 ± 3.47	−1.653	2.273	0.726	0.006
Inter-canine arch width (mm)	VF-NAM	−0.08 ± 2.5	−1.494	1.334	0.900	0.001
	G-NAM	−1.43 ± 2	−2.562	−0.298	0.039*	0.179
Lateral sulcus width (mm)	VF-NAM	−1.52 ± 1.54	−2.391	−0.649	0.006*	0.301
	G-NAM	−1.45 ± 1.87	−2.508	−0.392	0.008*	0.281
Mid-arch width (mm)	VF-NAM	1.04 ± 1.29	0.310	1.770	0.023*	0.215
	G-NAM	−0.17 ± 1.64	−1.098	0.758	0.694	0.007
Posterior arch width (mm)	VF-NAM	1.01 ± 1.08	0.399	1.621	0.007*	0.284
	G-NAM	1.3 ± 1.27	0.581	2.019	0.001*	0.397
Right cleft width (mm)	VF-NAM	−7.52 ± 1.93	−8.612	−6.428	< 0.001*	0.857
	G-NAM	−5.7 ± 2.56	−7.148	−4.252	< 0.001*	0.775
Left cleft width (mm)	VF-NAM	−6.74 ± 2.26	−8.019	−5.461	< 0.001*	0.832
	G-NAM	−7.22 ± 2.21	−8.470	−5.970	< 0.001*	0.850
Right alveolar length (mm)	VF-NAM	3.33 ± 1.99	2.204	4.456	< 0.001*	0.633
	G-NAM	2.33 ± 1.74	1.346	3.314	< 0.001*	0.459
Left alveolar length (mm)	VF-NAM	3.23 ± 1.27	2.511	3.949	< 0.001*	0.703
	G-NAM	2.82 ± 1.79	1.807	3.833	< 0.001*	0.643
Pre-maxilla protrusion (mm)	VF-NAM	−8.51 ± 2.23	−9.772	−7.248	< 0.001*	0.870
	G-NAM	−6.95 ± 2.62	−8.432	−5.468	< 0.001*	0.816
Arch depth (mm)	VF-NAM	−5.59 ± 2.91	−7.236	−3.944	< 0.001*	0.688
	G-NAM	−4.25 ± 2.64	−5.744	−2.756	< 0.001*	0.561
Pre-maxillary rotation angle (º)	VF-NAM	−2.93 ± 6.99	−6.885	1.025	0.264	0.056
	G-NAM	5.33 ± 10.41	−0.560	11.220	0.049*	0.164
Pre-maxillary deviation angle (º)	VF-NAM	−5.73 ± 9.23	−10.952	−0.508	0.043*	0.906
	G-NAM	−2.73 ± 9.04	−7.845	2.385	0.355	0.384
Right alveolar height (mm)	VF-NAM	3.08 ± 1.64	2.152	4.008	< 0.001*	0.676
	G-NAM	1.94 ± 1.5	1.091	2.789	< 0.001*	0.453
Left alveolar height (mm)	VF-NAM	2.27 ± 1.55	1.393	3.147	< 0.001*	0.572
	G-NAM	2.1 ± 1.35	1.336	2.864	< 0.001*	0.533

Conventional G-NAM group

In the transverse assessment, the premaxillary width (P-P´) and posterior arch width (T-T´) significantly increased by mean differences of 1.45 ± 1.68 mm (CI 95%: 0.49 − 2.40) and 1.3 ± 1.27 mm (CI 95%: 0.58 − 2.01), respectively (Table 3). However, significant decreases were observed in the inter-canine arch width (C–C´) and lateral sulcus width (Q-Q´), with mean differences of 1.43 ± 2 mm (CI 95%: −2.56 − −0.29) and 1.45 ± 1.87 mm (CI 95%: −2.50 − −0.39), respectively. Nonsignificant increases were observed in the anterior arch width (L-L´) and mid-arch width (M-M´) (Table 3). For the anteroposterior analysis, the alveolar cleft widths (RPX and LP´X´) exhibited statistically significant reductions of 5.7 ± 2.56 mm (CI 95%: −7.14 − −4.25) and 6.22 ± 2.21 mm (CI 95%: −8.47 − −5.97), respectively (Table 3). Similarly, the premaxilla protrusion (I-Y) and arch depth (I-Z) showed significant decreases of 6.95 ± 2.62 mm (CI 95%: −8.43 − −5.46) and 4.25 ± 2.64 mm (CI 95%: −5.74 − −2.75), respectively (Table 3). A statistically significant increase was also detected in right and left alveolar lengths (RLT and LL´T´) and the premaxillary rotation angle (Rot°), with mean differences of 2.33 ± 1.74 mm (CI 95%: 1.34 − 3.31), 3.23 ± 1.27 mm (CI 95%: 1.80 − 3.83), and 5.33 ± 10.41° (CI 95%: −0.56 − 11.22), respectively. However, no significant change was found in the premaxillary deviation angle (ZIG°) (Table 2). In the vertical assessment, the right and left alveolar heights (CD and C´D´) significantly increased by 1.94 ± 1.5 mm (CI 95%: 1.09 − 2.78) and 2.1 ± 1.35 mm (CI 95%: 1.33 − 2.86), respectively (Table 3).

Active screwed VF- NAM versus Conventional G-NAM

The comparison of treatment outcomes between the active screwed VF-NAM and conventional G-NAM groups revealed no statistically significant differences in most variables associated with changes in the transverse and vertical arch dimensions. These variables included premaxillary width, anterior arch width, inter-canine arch width, lateral sulcus width, posterior arch width, and the right and left alveolar heights. However, a notable exception was observed in the mid-arch width, where the VF-NAM group exhibited a significantly greater change compared to the G-NAM group, with an effect size of 0.953 (CI 95%: −0.03 − 2.46; P < 0.05; Table 4). For the anteroposterior dimension, a significant difference was found between both groups (VF- NAM and G-NAM) in the mean change observed for the right and left alveolar cleft widths, and the pre-maxillary rotation angle. A more significant decrease in the right and left alveolar cleft widths was observed in the VF- NAM group relative to the G-NAM group with effect sizes of 0.89 (CI 95%: −3.73 − 0.11) and 0.85 (CI 95%: −3.82 − 0.14), respectively (P < 0.05; Table 4). Conversely, the G-NAM group demonstrated a significantly greater increase in the premaxillary rotation angle compared to the VF-NAM group, with an effect size of 0.875 (CI 95%: −3.06 − 13.56; P < 0.05; Table 4). However, there was no statistically significant difference between the two groups in terms of changes in the premaxillary deviation angle.

Table 4.

Descriptive statistics, results of repeated measures ANOVA test for comparison between measurements in transverse, anteroposterior, and vertical dimension in the two groups and Mann–Whitney U test for comparison between amounts of change in the two groups

Measurements (mm)	Time	VF-NAM (n = 12)		G-NAM (n = 12)		95% CI for mean difference		P-value	Effect size
		Mean	SD	Mean	SD	Lower limit	Upper limit
Premaxillary width	T1	17.23	1.66	17.76	2.95	−2.56	1.49	0.590	Partial Eta Squared = 0.013
	T2	18	2.07	19.21	2.36	−3.09	0.67	0.196	Partial Eta Squared = 0.075
	Change							0.298	d = 0.434
	Median (Range)	0.2 (−1.2, 3.6)		2.1 (−1.2, 3.4)		−2.12	0.77
	Mean (SD)	0.78 (1.73)		1.45 (1.68)
Anterior arch width	T1	19.34	2.8	18.05	3.57	−1.43	4	0.335	Partial Eta Squared = 0.042
	T2	18	2.38	18.36	2.08	−2.25	1.53	0.699	Partial Eta Squared = 0.007
	Change							0.083	d = 0.756
	Median (Range)	−1.01 (−5.5, 3.7)		0.85 (−7.8, 4.4)		−4.19	0.89
	Mean (SD)	−1.34 (2.45)		0.31 (3.47)
Inter-canine arch width	T1	29.55	3.47	28.98	3.13	−2.22	3.37	0.674	Partial Eta Squared = 0.008
	T2	29.47	2.79	27.54	3.1	−0.57	4.42	0.124	Partial Eta Squared = 0.104
	Change							0.141	d = 0.63
	Median (Range)	0.25 (−4.4, 4.7)		−1.25 (−4.8, 2.2)		−0.57	3.27
	Mean (SD)	−0.08 (2.5)		−1.43 (2)
Lateral sulcus width	T1	24.26	3.1	22.54	2.39	−0.62	4.06	0.141	Partial Eta Squared = 0.096
	T2	22.74	2.85	21.08	2.92	−0.79	4.1	0.175	Partial Eta Squared = 0.082
	Change							0.795	d = 0.106
	Median (Range)	−1.95 (−3.5, 1)		−1.31 (−5.2, 1.6)		−1.52	1.38
	Mean (SD)	−1.52 (1.54)		−1.45 (1.87)
Mid-arch width	T1	41.59	3.29	40.59	3.04	−1.68	3.69	0.445	Partial Eta Squared = 0.027
	T2	42.63	3.13	40.42	2.44	−0.16	4.59	0.066	Partial Eta Squared = 0.145
	Change							0.035*	d = 0.953
	Median (Range)	0.95 (−1.1, 3.2)		0 (−3.32, 3.3)		−0.03	2.46
	Mean (SD)	1.04 (1.29)		−0.17 (1.64)
Posterior arch width	T1	33.45	2.88	31.86	2.41	−0.66	3.84	0.157	Partial Eta Squared = 0.089
	T2	34.46	2.68	33.16	2.19	−0.77	3.37	0.206	Partial Eta Squared = 0.072
	Change							0.311	d = 0.422
	Median (Range)	1.1 (−0.8, 3)		1.54 (−1.41, 3.4)		−1.29	0.71
	Mean (SD)	1.01 (1.08)		1.3 (1.27)
Right cleft width (mm)	T1	10.08	1.48	9.45	2.93	−1.34	2.6	0.513	Partial Eta Squared = 0.020
	T2	2.56	1.24	3.74	1.27	−2.24	−0.12	0.030*	Partial Eta Squared = 0.196
	Change							0.046*	d = 0.89
	Median (Range)	−7.5 (−10.8, −3.9)		−5.6 (−10, −0.4)	−3.73		0.11
	Mean (SD)	−7.52 (1.93)		−5.7 (2.56)
Left cleft width (mm)	T1	10.12	2.3	10.54	2.17	−2.32	1.47	0.646	Partial Eta Squared = 0.010
	T2	2.38	1.39	4.33	1.17	−1.04	1.14	0.926	Partial Eta Squared = 0.0004
	Change							0.048*	d = 0.85
	Median (Range)	−6.5 (−12, −3.62)		−7.9 (−9.2, −1.9)		−3.82	0.14
	Mean (SD)	−7.74 (2.26)		−6.22 (2.21)
Right alveolar length (mm)	T1	21.25	1.56	21.77	2.76	−2.42	1.38	0.574	Partial Eta Squared = 0.015
	T2	24.58	1.54	24.1	2.13	−1.1	2.05	0.538	Partial Eta Squared = 0.017
	Change							0.118	d = 0.671
	Median (Range)	3.33 (−1.3, 6.7)		2.5 (−1.8, 4.7)		−0.59	2.58
	Mean (SD)	3.33 (1.99)		2.33 (1.74)
Left alveolar length (mm)	T1	21.53	1.72	21.41	2.18	−1.54	1.79	0.878	Partial Eta Squared = 0.001
	T2	24.77	1.67	24.23	1.82	−0.95	2.01	0.462	Partial Eta Squared = 0.025
	Change							0.544	d = 0.249
	Median (Range)	3.2 (0.2, 5.3)		3.05 (−1.2, 5.6)		−0.91	1.72
	Mean (SD)	3.23 (1.27)		2.82 (1.79)
Pre-maxilla protrusion (mm)	T1	12.12	1.56	12.03	1.89	−1.38	1.55	0.907	Partial Eta Squared = 0.001
	T2	3.61	1.02	5.09	1.68	−3.05	0.1	0.065	Partial Eta Squared = 0.147
	Change							0.126	d = 0.657
	Median (Range)	−7.8 (−13.2, −6.4)		−6.95 (−13, −2.8)		−3.62	0.5
	Mean (SD)	−8.51 (2.23)		−6.95 (2.62)
Arch depth (mm)	T1	32.38	1.29	32.42	3.51	−2.28	2.2	0.970	Partial Eta Squared = 0.0001
	T2	26.78	2.76	28.17	2.02	−3.43	0.67	0.176	Partial Eta Squared = 0.082
	Change							0.340	d = 0.396
	Median (Range)	−5.2 (−12, −2.2)		−3.8 (−8.5, −0.5)		−3.69	1.01
	Mean (SD)	−5.59 (2.91)		−4.25 (2.64)
Pre-maxillary rotation angle (º)	T1	89.57	7.54	86.71	13.29	−6.29	12	0.524	Partial Eta Squared = 0.019
	T2	86.63	2.99	92.03	7.85	−10.43	−0.37	0.037*	Partial Eta Squared = 0.184
	Change							0.050*	d = 0.875
	Median (Range)	−0.7 (−17.5, 7.5)		3.45 (−12.1, 22.3)		−3.06	13.56
	Mean (SD)	−2.93 (6.99)		5.33 (10.41)
Pre-maxillary deviation angle (º)		Median (Range)	Mean (SD)	Median (Range)	Mean (SD)
	T1	3.75 (0.6, 20.5)	5.3 (5.31)	7.1 (0.2, 20.1)	8.23 (7.18)	−8.27	2.42	0.355	d = 0.384
	T2	2.1 (−9.4, 6.5)	−0.43 (5.58)	4.65 (−2.4, 15)	5.5 (5.66)	−10.68	−1.17	0.043*	d = 0.906
	Change	−2.05 (−27.1, 4.5)	−5.73 (9.23)	−2 (−15.1, 11)	−2.73 (9.04)	−10.73	4.73	0.507	d = 0.274
Right alveolar height	T1	7.68	1.37	8.02	1.05	−1.38	0.69	0.500	Partial Eta Squared = 0.021
	T2	10.76	2.26	9.96	1.26	−0.75	2.35	0.297	Partial Eta Squared = 0.049
	Change							0.148	d = 0.617
	Median (Range)	2.55 (1, 6.7)		2 (−0.9, 4.3)		−0.19	2.47
	Mean (SD)	3.08 (1.64)		1.94 (1.5)
Left alveolar height	T1	8.01	1.19	8.06	1.04	−1	0.9	0.914	Partial Eta Squared = 0.001
	T2	10.28	2.21	10.16	1.33	−1.42	1.67	0.871	Partial Eta Squared = 0.001
	Change
	Median (Range)	1.83 (0.5, 5.5)		2.05 (-0.2, 4.2)		−1.06	1.4	0.931	d =0.035
	Mean (SD)	2.27 (1.55)		2.1 (1.35)

Results for the duration of NAM therapy

The duration of NAM therapy, measured from initiation to completion before surgical lip repair, was evaluated for both the VF-NAM and G-NAM groups. The treatment duration is influenced by the severity of the cleft defect. Therefore, a more severe defect requires a longer treatment period. In the present study, the baseline characteristics of the cleft defect showed no statistically significant difference between the two groups. The VF-NAM group had an average treatment period of 4.5 ± 1.5 months, while the G-NAM group required 5 ± 1 months. However, the difference in treatment duration between the two groups was not statistically significant.

Discussion

Bilateral cleft lip and palate (BCLP) is considered one of the most severe craniofacial anomalies, presenting significant challenges for surgeons due to premaxillary protrusion, nasal cartilage deformities, and columellar deficiency. These anatomical complexities often compromise surgical outcomes, resulting in residual nasal deformities and scarring. To address these issues, presurgical infant orthopedics (PSIO) was introduced by McNeil in 1950 [21] to align the alveolar segments and facilitate surgical repair.

Presurgical nasoalveolar molding (NAM), developed by Grayson and Cutting in 1993, incorporated nasal molding and columellar elongation to improve nasal esthetics and enable single-stage repair of the lip, nose, and alveolus. More recently, active screw-based NAM appliances have been introduced to deliver controlled retraction forces, potentially enhancing arch alignment and reducing the frequency of follow-up visits. To the best of our knowledge, no randomized clinical trials have directly compared the efficacy of these appliances with the conventional Grayson NAM technique. In the present study, a vacuum-formed NAM appliance (VF-NAM) with an incorporated active retraction screw was compared with the conventional Grayson NAM appliance in terms of morphological changes in the maxillary arch.

In the active screwed VF-NAM group, the VF-NAM appliance was fabricated using a thermoplastic vacuum sheet called Essix. This material offers several advantages, including ease of manual construction, reduced finishing time, smooth surfaces and edges that enhance comfort for newborns, and biocompatibility with oral tissues. An active retraction screw was integrated into the VF-NAM appliance to retract the protruded premaxilla and close the labial and alveolar gaps efficiently. Parents were instructed to turn the retraction screw by a quarter turn (0.25 mm) on alternating day, allowing gradual premaxillary retraction over a short period. The activation was deliberately designed to apply mild forces to protect the fragile vomer bone and premaxillary segments from potential damage. It was assumed that activating the retraction screw by a quarter turn (0.25 mm) on alternate days would result in approximately 1 mm of retraction per week and about 4 mm per month. Patients were scheduled for regular follow-ups every three weeks. Two nasal stents were introduced two weeks after starting VF-NAM therapy, once the premaxillary segment had retracted slightly, revealing the previously obscured nostrils. The nasal stents were added earlier in the VF-NAM group than in the G-NAM group to take advantage of the high plasticity of the infant's nasal cartilage, as described by Matsuo and Hirose 1991 [22].

For the conventional Grayson NAM group, the steps for fabricating the NAM appliance followed the technique described by Grayson and Cutting 1993 [5]. The appliance activation was performed through selective grinding of the fitting surface and the addition of soft acrylic resin to guide alveolar growth and align the alveolar segments. The patients were followed up biweekly for appliance activation.

In the current study, the analysis of the maxillary arch was performed through laser-scanned 3D digital models. Sousa et al. 2012 [23] and Kuijpers et al. 2014 [24] assessed the reliability of measurements obtained from digital models. Their findings showed no statistically significant differences between measurements taken directly on cast models and those on digital models, demonstrating good reliability and validity for 3D arch assessments.

For the transverse arch analysis, some differences were observed between the VF-NAM and G-NAM groups. The VF-NAM group exhibited a significant increase in the mid-arch width and decrease in the lateral sulcus width with minimum change in the premaxillary width, and inter-canine arch width. Conversely, in the G-NAM group, a significant increase in the premaxillary width and a decrease in the inter-canine arch width, with minimum change in the mid-arch width. Both groups showed a significant increase in the posterior arch width with minimum change in the anterior arch width. Our results were consistent with the findings of Tankittiwat et al. 2021 [20] and Spengler et al. 2006 [25], who reported a significant increase in posterior arch width with insignificant change in inter-canine width. This finding implies that the active screwed VF-NAM and G- NAM appliances were designed not only to maintain the width of the maxilla, but also to compensate for the alveolar growth without a negative effect on the transverse growth of the alveolus. However, there was no significant difference between the two groups in the posterior arch width. Furthermore, both the VF-NAM and G-NAM groups showed a nonsignificant difference in the premaxillary width, anterior arch width, inter-canine arch width, lateral sulcus width. The VF-NAM group exhibited a significantly greater increase in the mid-arch width compared to the G-NAM group, this could be attributed to that the expansion of the lateral alveolar segments in the VF-NAM group was planned excessively to allow the transverse growth of lateral alveolar segments and provide an adequate space to accommodate the retracted premaxillary segment.

In terms of anteroposterior dimension, both VF-NAM and G-NAM appliances were effective in reducing the right and left alveolar cleft widths and correcting the outward rotation of the premaxillary segment. Our findings were similar to previous studies conducted by Gong et al. 2017 [19]; Tankittiwat et al. 2021 [20]; El-Ashmawi et al. 2023 [26]. However, a more significant reduction in the right and left alveolar cleft widths was observed in the VF- NAM group relative to the G-NAM group, this could be attributed to that the active screwed VF- NAM aligner was designed to apply continuous and gradual forces along the period of treatment, while the Grayson NAM appliance necessitate biweekly appointments to modify and activate the appliance.

Additionally, the decreases of the premaxillary protrusion, and arch depth were found in both groups, which indicated that the anteroposterior arch length decreased and the protrusion of the premaxillary segment was retracted significantly. After retraction of premaxillary segment, the shape of the alveolus was corrected without causing the alveolar segments to collapse. These findings come into agreement with Mossaad et al. 2024 [17]; Gong et al. 2017 [19]; Tankittiwat et al. 2021 [20]; Spengler et al. 2006 [25], and El-Ashmawi et al. 2023 [26]. However, the amount of premaxillary retraction observed in the active screw VF-NAM group in our study was 8.51 ± 2.23 mm, which is notably higher than the 4.22 ± 0.4 mm reported by Mossaad et al. (2024) [17]. This difference may be attributed to the use of a larger retraction screw in our protocol, capable of achieving up to 9 mm of retraction. Additionally, the duration of NAM therapy in our study (4.5 ± 1.5 months) was longer compared to the 2-month treatment period in the study by Mossaad et al. Meanwhile, the right and left alveolar lengths increased significantly in both groups, a finding that is in line with that of Tankittiwat et al. 2021 [20]. This was possibly due to the fact that, in the VF-NAM group, activation of the retraction screw exerted an inward force to retract the premaxillary segment and an outward force to advance the posterior alveolar segments. In contrast, in the Grayson group, the waxing up of alveolar cleft gaps may have facilitated the anterior growth of the posterior alveolar segments, thereby increasing alveolar length.

Regarding the premaxillary rotation angle, the G-NAM group showed a significantly greater improvement in the premaxillary rotation compared to the VF-NAM group. This could be attributed to the biweekly gradual modifications of the rigid G-NAM appliance, which may have facilitated the correction of the rotated premaxilla. In contrast, the VF-NAM aligner was designed to correct the rotation in a single visit, and the thermoplastic material used for its construction was flexible rather than rigid, making it less effective in correcting the rotated premaxilla. In terms of the premaxillary deviation angle, the VF-NAM group demonstrated significant centralization of the deviated premaxilla. This could be attributed to the early correction of the deviated premaxilla in the VF-NAM group; however, the amount of change was not statistically significant between the two groups.

In the vertical assessment, only a limited number of studies have investigated changes in the vertical dimension in BCLP, likely due to challenges associated with measurement techniques. In our study, the right and left alveolar heights significantly increased in both groups without a significant difference between them. This result could be attributed to adding a hard stone in the VF-NAM group and dental wax in the G-NAM group to the occlusal surfaces of the posterior alveolar segments to maintain the vertical dimension during growth. The result of the present study was in line with that of Tankittiwat et al. 2021 [20] and contrast to other studies conducted by Gong et al. 2017 [19] and El-Ashmawi et al. 2023 [26], who found the inhibition of vertical growth during NAM therapy was likely to result from vertical component forces of the retention tapes during the. However, the growth inhibition is temporary, and the alveolus may continue to grow vertically when the forces are removed.

Although the VF-NAM aligner shortened the duration of NAM therapy by maintaining the active phase, the Grayson NAM appliance required biweekly modifications of the intraoral maxillary plate, which extended the treatment time. However, the difference in treatment duration between the two groups was not statistically significant.

The current study was not specifically designed to evaluate gender-based differences in treatment outcomes; however, the observed predominance of males (16 males vs. 8 females) is consistent with findings in cleft epidemiology, where cleft conditions are more commonly reported in males [27]. Moreover, it has been reported that sex hormones, particularly estrogen, may influence cartilage remodeling, potentially affecting the response to nasoalveolar molding (NAM) therapy [28]. Additionally, social and cultural factors such as caregiver involvement in daily cleft management, feeding issues, and gender-specific care preferences may contribute to variations in treatment adherence and outcomes. These considerations highlight the need for future studies to evaluate the impact of both biological and sociocultural factors on gender differences in cleft treatment outcomes.

The findings of our study have important implications for clinical practice, particularly within cleft care programs and early intervention strategies. When a greater reduction in alveolar cleft width and expansion of the mid-arch width is desired, the VF-NAM appliance with active screws may be the preferred choice to enhance tissue approximation before surgical repair. Conversely, the G-NAM appliance may be more suitable in cases characterized by pronounced premaxillary rotation. Selecting nasoalveolar molding appliances based on individual anatomical characteristics may help reduce surgical complexity, improve surgical outcomes, and shorten the duration of postoperative care. From a public health perspective, promoting early screening and timely intervention using these appliances may contribute to improved long-term functional and aesthetic outcomes, decreased healthcare expenditures, and an enhanced overall quality of life for infants born with bilateral cleft lip and palate.

Limitations and future scope

Despite the current study's strengths, several limitations should be considered when interpreting the results. First, this study evaluated and compared two different NAM techniques based on changes in the maxillary arch; however, it did not assess the effects of these appliances on facial esthetics. Further studies are needed to explore their impact on nasal and facial morphology. Second, the follow-up period was confined to the post-NAM phase. Long-term outcomes, particularly the stability of alveolar and nasal changes after surgery, were not assessed. It is suggested to conduct longitudinal and interventional studies to establish causality and evaluate the persistence of treatment effects over time. Third, the sample size was relatively limited, which may affect the generalizability of the findings. Although statistically significant differences were observed, a larger multicenter trial would provide stronger evidence and allow subgroup analyses based on the age of infants at initiation of NAM therapy, cleft severity, and compliance levels of infants’ parents. Additionally, this study did not use digital intraoral scanning technologies, which could have provided a more accurate assessment of arch changes. Future studies should consider integrating advanced imaging tools for detailed morphometric analysis. Finally, this study introduced a novel active screwed vacuum-formed NAM appliance. However, comparisons were limited to conventional Grayson NAM. Future research should investigate how this innovation compares to other techniques, such as digitally designed and 3D-printed NAM systems, in terms of clinical effectiveness, parents’ satisfaction, and cost-effectiveness.

Conclusion

The assessments indicated that both VF-NAM and G-NAM appliances could effectively reduce the right and left alveolar cleft gaps, retract the premaxillary segment, centralize the deviated premaxilla, and normalize the contour of the anterior and posterior alveolar segments. However, a more significant decrease in the right and left alveolar cleft widths and an increase in the mid-arch width were observed in the VF-NAM group relative to the G-NAM group. Conversely, the G-NAM group demonstrated a significantly greater improvement in the premaxillary rotation compared to the VF-NAM group. Therefore, active screwed VF-NAM might be an addition to CLP treatment protocol to decrease the burden of follow up visits. From a clinical perspective, the present findings may support clinical decision-making in the early cleft management by guiding the selection of nasoalveolar molding appliances based on individual anatomical considerations. From a public health standpoint, the use of either VF-NAM or G-NAM appliances may contribute to optimizing presurgical outcomes, improving treatment efficiency, and enhancing the overall quality of care for infants with bilateral cleft lip and palate.

Abbreviations

3D

Three-Dimensional

BCLP

Bilateral cleft lip and palate

UCLP

Unilateral cleft lip and palate

NAM

Nasoalveolar molding appliance

VF-NAM

Vacuum formed nasoalveolar molding appliance

G-NAM

Grayson nasoalveolar molding appliance

OFCs

Orofacial clefts

CONSORT

Consolidated Standards of Reporting Trials guidelines for reporting Randomized Controlled Trials

RS

Retraction screw

Authors’ contributions

K. A. did all the clinical work and prepared the manuscript. M.A. superivised the clinical work and revised the manuscript. F. A. superivised the clinical work and revised the manuscript. W.M. the surgeon who did the lip repair surgeries. M.A. superivised and particpated in the clinical work, did the randomization and revised the manuscript.

Funding

This research had no funders.

Data availability

Data is provided within the manuscript or supplementary information files.

Declarations

Ethics approval and consent to participate

The current study was approved by the ethics committee at the school of dentistry, Cairo Univeristy, Egypt. All the included patients’ guardians signd an informed consent to participate in the study. The consent obtained form all the particpants’ guardians was informed. The current study adhered to the Declaration of Helsinki.

Consent for publication

All patients’ guardians gave written informed consent for their childern or clinical details along with any identifying images to be published in this study.

Competing interests

The authors declare no competing interests.