Comparison of dental arch relationship and craniofacial characteristics during mixed dentition in patients with complete unilateral cleft lip and palate treated with one-stage versus early two-stage palatoplasty

INTRODUCTION

Dentoalveolar development and craniofacial characteristics in patients with oral clefts are influenced by various intrinsic and extrinsic factors, including timing of palatal repair.^[1-3] Although delayed hard palate repair during mixed dentition age was shown to improve maxillary growth,^[2,4] the debate over the most optimal timing of palatal repair remains inconclusive. Hence, both clinicians and researchers continue their endeavors to find a balance between favorable maxillary growth and normal speech development.

The concept of early two-stage repair with staged soft and hard palate closures was proposed by Rohrich and Byrd in 1990.^[5] Their approach closed the soft and hard palate at approximately 3–6 months and 18 months, respectively. This was performed to reduce the risk of articulation disorder caused by a prolonged residual cleft in the hard palate. Their longitudinal study demonstrated that the approach resulted in significantly better speech outcomes compared to the late surgery at 4 years of age, with no differences in facial growth.^[6] These findings suggested that a short delay between soft and hard palate repair could improve speech development. However, the extent of delay that optimizes not only speech but also dentoalveolar and craniofacial development has yet to be determined.

Nollet et al. found that patients who underwent a delayed two-stage palatoplasty (hard palate closure at 9 years) exhibited dental arch relationship, evaluated using the GOSLON Yardstick, comparable to those from Eurocleft centers with favorable outcomes.^[7] A meta-analysis concluded that delaying palatal closure until after the age of three resulted in a better dental arch relationship than earlier repairs.^[8] Kato et al. reported comparable dental arch relationships during primary dentition between Japanese patients who underwent hard palate surgery as early as 18 months and those at an older age (5–8 years old).^[9] Nishio et al. also found that Japanese patients who underwent the two-stage palatoplasty (soft palate repaired at 12 months and hard palate at 18 months) demonstrated more favorable dental occlusion in primary dentition compared to those with the one-stage palatoplasty at 12 months.^[10] These results suggested that it might be unnecessary to delay hard palate closure until after 18 months of age to optimize dentoalveolar development. However, a recent randomized controlled trial also found no difference in GOSLON scores between patients with 12-month versus 36-month hard palate repair.^[11] Due to the lack of consistent results, a definitive conclusion regarding the most optimal time to perform a hard palate repair is still not possible.

To the best of our knowledge, previous studies advocating for hard palate repair at 18 months were conducted exclusively in Japanese patients.^[9,10,12] No published study compared the dental arch relationship and craniofacial morphology during mixed dentition between the one-stage palatoplasty versus the early two-stage repair (hard palate repair at 18 months) in non-Asian samples. Therefore, this study aimed to compare dental arch relationship and craniofacial characteristics between these two different protocols in patients with nonsyndromic complete unilateral cleft lip and palate (CUCLP) with the GOSLON rating as the primary outcome, and cephalometric parameters as the secondary outcomes.

MATERIAL AND METHODS

This retrospective study was performed in accordance with the Declaration of Helsinki regarding research in human subjects. Ethical approval was granted by the Faculty of Dentistry/Pharmacy, Mahidol University Review Board (CoA no. MU-DT/PY-IRB 2020/070.0611).

Dental arch relationship

Dental impressions were taken before any orthodontic treatment. They were processed by a commercial laboratory (OrthoCad, Cadent, Carlstadt, NJ) to create digital dental models. A photogallery of a digital dental model was generated using a PowerPoint slide (Microsoft Corporate, Redmond, WA) to display six different static views: frontal, tilted frontal in the direction to show either positive or negative overjet, upper and lower occlusal, right and left lateral with teeth in occlusion, for the GOSLON ratings^[14] [Figure 1a]. The GOSLON yardstick assigns dental models into five categories from most to least favorable dentoalveolar outcomes (1–5).^[15] It is the most widely utilized index for evaluating dental arch relationships in cleft patients during mixed dentition.^[15-17] Previous studies successfully validated the use of a photogallery of digital dental models for the GOSLON rating.^[18,19]

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Figure 1:

A photogallery of digital dental model for GOSLON rating and cephalometric analyses performed in this study. (a) A PowerPoint slide displaying six static views of a 3D dental model for the GOSLON rating. (b) Cephalometric analyses and landmarks: Ba (basion) = the most anteroinferior point on the margin of the foramen magnum; N (nasion) = the most anterior point of the fronto-nasal suture; S (sella) = the geometric center of sella turcica; A = The deepest point on the anterior contour of the maxillary alveolar process; anterior nasal spine (ANS) = the tip of the osseous ANS; posterior nasal spine = the tip of the posterior spine of the palatal bone; B = the deepest point on the anterior contour of the mandibular alveolar process; Co (condylion) = the most posterosuperior point on the head of the mandibular condyle; Gn (gnathion) = the most anteroinferior point on the outline of the chin; Go (gonion) = The most posteroinferior point on the angle of the mandible; Me (menton) = the most inferior point on the outline of the chin; Pg (pogonion) = the most anterior point on the outline of the chin; LIA (lower incisor apex) = the apex of the most labially placed mandibular central incisor; LIT ( lower incisor tip) = the incisal tip of the most labially placed mandibular central incisor; UIA (upper incisor apex) = the apex of the most labially placed maxillary central incisor; UIT (upper incisor tip) = the incisal tip of the most labially placed maxillary central incisor; A’ (soft-tissue subspinale) = the point of greatest concavity or convexity in the midline of the upper lip; B’ (soft-tissue supramentale) = the point of greatest concavity in the midline of the lower lip; G’(soft-tissue glabella) = the most prominent point on the soft tissue drape of the forehead; Gn’ (soft-tissue gnathion) = the most anteroinferior point on the soft-tissue outline of the chin; Me’ (soft-tissue menton) = the soft-tissue point overlying menton; N’ (soft-tissue nasion) the deepest point of the frontonasal curvature; Pg’ (soft tissue Pg) = the most anterior point on the soft-tissue outline of the chin; and Sn (subnasale) = the point where the base of the columella of the nose meets the upper lip.

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All slides were anonymized and presented in a random order. They were rated twice with a 2-week interval to reduce potential memory bias. The slides were also re-randomized in the second rating session. Three experienced orthodontists were calibrated before the rating sessions. Each set of models received six scores in total. The average was tabulated from the six GOSLON scores and further utilized for the statistical comparisons between the two groups. Although individual GOSLON rating is recorded on a 5-point scale, the scores reflect an underlying continuum of severity. Therefore, intra- and inter-reliability were determined using intraclass correlation coefficients (ICC).^[20]

RESULTS

Thirty-two patients, born between 1997 and 2006, with pre-orthodontic dental models and lateral cephalograms, were identified. The patients were of Caucasian or Hispanic descent. They were divided into two groups dependent on their palatal surgery protocol. The one-stage group consisted of 10 patients (6 males and 4 females). The two-stage group comprised 22 patients (16 males and 6 females). The timing of hard palate repair for the one-stage and two-stage groups is 12.9 ± 1.8 months and 18.6 ± 3.1 months, respectively. The ages that pre-orthodontic records were taken showed no significant difference between the two groups (one-stage group = 8.26 ± 0.93 years vs. two-stage group = 7.96 ± 0.97 years; P = 0.345).

Comparison of dental arch relationships between the one-stage and two-stage palatoplasty

The two-stage group demonstrated significantly more favorable GOSLON ratings compared to the one-stage. See [Table 2] for detailed results. The GOSLON scores distribution showed a significant difference between the 2 groups (P < 0.001). The two-stage group showed a higher proportion of the favorable ratings (GOSLON score 1–2), and a lower of unfavorable outcomes (GOSLON score 4–5). See further details in [Figure 2].

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Figure 2:

Distributions of GOSLON scores (Y-axis) from 1 (excellent) to 5 (very poor) for the one-stage and two-stage palatoplasty groups. The GOSLON scores distribution differed significantly two groups (P < 0.001) between the two palatoplasty protocols (X-axis). The two-stage group showed a higher proportion of favorable ratings and lower unfavorable outcomes.

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Table 2: Mean, standard deviation, median and quartile of the GOSLON scores and the cephalometric measurements. The Mann–Whitney U-test showed a significantly lower median GOSLON scores for the two-stage palatoplasty group (P<0.05).

Parameters	One-stage		Two-stage		P-value
	Mean±SD	Median (IQR)	Mean±SD	Median (IQR)
GOSLON	3.78±0.32	4 (3.71, 4.21)	3.07±0.22	3 (2.33, 4)	0.031*
SNA (°)	74.53±0.93	73.73 (72.4, 76.45)	76.19±0.89	76.60 (72.84, 80.00)	0.296
Ba-N-ANS (°)	62.10±0.68	62.07 (60.61, 63.35)	63.37±0.67	63.40 (61.01, 65.75)	0.155
SNB (°)	72.10±1.06	71.63 (68.45, 75.44)	72.32±0.87	72.94 (69.51, 74.63)	0.954
Ba-N-Pog (°)	55.25±1.05	55.48 (51.7, 57.53)	55.39±0.74	54.87 (53.12, 58.27)	0.893
ANB (°)	2.42±0.76	2.88 (1.74, 3.82)	3.87±0.50	3.82 (2.30, 5.49)	0.123
ANS-N-Pog (°)	6.91±0.83	7.32 (4.97, 9.57)	7.99±0.68	8.25 (5.91, 9.49)	0.363
SNPg (°)	72.82±1.03	72.48 (70.15, 75.72)	72.97±0.90	73.13 (70.36, 74.98)	0.984
Maxillary inclination (SN/ANS-PNS) (°)	12.38±0.47	12.40 (11.40, 13.42)	12.99±0.63	13.11 (11.30, 14.74)	0.550
Mandibular plane angle (SN-GoGn) (°)	39.33±1.75	37.82 (34.76, 44.01)	38.13±1.31	38.74 (35.41, 42.60)	1.000
Mandibular axis angle (BaN-CoGn) (°)	79.48±1.37	79.52 (75.48, 84.60)	78.77±0.97	79.69 (74.56, 82.25)	0.832
Lower face height ratio (ANS-Me/N-Me) (%)	67.81±0.66	67.44 (66.11, 68.80)	67.73±0.36	67.53 (66.38, 68.92)	0.686
Facial proportion (N-ANS/N-Gn) (%)	46.28±0.37	46.11 (45.14, 47.54)	50.76±3.70	47.17 (45.80, 48.65)	0.324
U1-ANS-PNS (°)	99.02±3.35	97.69 (92.59, 103.15)	95.52±1.40	96.84 (88.80, 100.42)	0.603
L1-GoGn (°)	87.08±1.86	86.10 (84.91, 89.49)	85.50±1.39	84.65 (82.99, 89.46)	0.287
Interincisal angle (U1-L1) (°)	144.53±4.36	146.21 (139.45, 153.79)	151.66±1.96	149.98 (146.25, 159.35)	0.253
Soft tissue convexity (G’-Sn-Pg’) (°)	173.05±0.96	172.50 (170.92, 175.74)	169.80±1.36	170.07 (164.68, 177.15)	0.193
Sagittal jaw relationship (A’NB’) (°)	4.05±0.61	3.58 (2.49, 5.66)	5.44±0.58	5.32 (3.51, 7.31)	0.123
Sagittal jaw relationship (A’NPg’) (°)	3.29±0.59	3.35 (1.35, 5.20)	4.88±0.68	5.30 (1.85, 7.05)	0.287
Soft-tissue facial height ratio (N’-Sn/Sn-Me’) (%)	74.73±1.56	73.44 (70.45, 78.66)	74.57±1.49	75.59 (69.92, 80.64)	0.954
Soft-tissue vertical proportions (N’-Sn/N’-Gn’) (%)	46.35±0.54	45.95 (45.33, 47.04)	46.36±0.54	47.05 (45.20, 48.12)	0.714

*P<0.05. SD: Standard deviation, IQR: Interquartile range

DISCUSSION

Our results demonstrated that the two-stage palatal repair yielded a significantly more favorable dental arch relationship during mixed dentition. These results are congruent with existing literature.^[10,12] Otsuki and coworkers found that two-stage palatoplasty with hard palate repair at 18 months exhibited a more favorable GOSLON rating compared to the one-stage palatoplasty at 15 months.^[12] Similarly, Nishio et al. demonstrated that Japanese patients treated with two-stage palatoplasty (hard palate repair at 18 months) exhibited less frequency of dental crossbites in primary dentition than those who underwent one-stage palatoplasty at 12 months.^[10] These findings supported the early two-stage palatoplasty with only a short interval between the soft and hard palate repair.

The distribution of the GOSLON scores differed significantly between the two groups [Figure 2]. The two-stage group exhibited a higher proportion of favorable GOSLON scores and a lower of unfavorable outcomes (GOSLON scores 4 and 5). The GOSLON Yardstick was validated as a reliable tool that depicts the dental arch relationship in mixed dentition.^[26] It also reflects the treatment complexity^[16-18] and predicts dentoalveolar outcomes after facial growth completion.^[26] Our findings suggested that the early two-stage protocol could reduce the number of patients requiring a more complex orthodontic treatment or orthognathic surgery.^[27]

Even though patients in the two-stage group showed a tendency toward more favorable maxillary position and maxillomandibular relationships, our results showed that none of the cephalometric parameters differed significantly between the two groups. Similarly, Zemann and coworkers conducted their study in Austria and reported no significant difference in cephalometric parameters between 12-month one-stage repair and two-stage protocol with 30-month hard palate surgery.^[28] It should be noted that in their two-stage group, the hard palate repair was combined with primary bone grafting which was shown to have an adverse effect on the maxillary development.^[7,27] In contrast to our findings, Otsuki et al. reported that their two-stage palatoplasty with hard palate repair at 18 months demonstrated significantly more favorable skeletal patterns compared to one-stage palatoplasty at 15 months.^[12] However, two of the three significant differences were linear cephalometric measurements which could be subjected to radiographic magnification errors. Cephalometric parameters are the secondary outcomes in this study. Moreover, the sample size calculation was based only on the difference between GOSLON scores. Hence, this study could possibly be underpowered to detect significant skeletal differences.

Intrinsic factors such as morphological characteristics and genetics could also influence the treatment outcomes.^[3] A recent study demonstrated a significant correlation between the initial cleft severity and craniofacial morphology, but not with the GOSLON score.^[29] Their results suggested that the skeletal development could be more influenced by the intrinsic factors, whereas the dental arch relationship might be more affected by the extrinsic factors, such as surgical protocol. Furthermore, Ishii et al. demonstrated that the GOSLON rating did not always correspond to the underlying skeletal morphology.^[30] These results could offer additional explanation regarding the significant differences in GOSLON scores and the absence of cephalometric parameters between the two groups observed in our study.

The length of the interval period between soft and hard palate closure should be optimized not only for maxillary growth but also for speech development. Although an early veloplasty reduces velopharyngeal insufficiency, the articulation disorders could still arise as the anterior pressure sounds are articulated behind the residual cleft in the hard palate.^[10] Previous studies reported that the residual palatal cleft width spontaneously decreased, reaching a plateau at 6–12 months after closure of the soft palates.^[7,10] This reduction may lead to a minimization of the mucoperiosteal denuded area at the time of hard palate closure which could possibly lessen surgical interference during maxillary development.^[12] As speech outcomes were not assessed, no conclusions can be drawn regarding whether the early two-stage protocol could yield speech development comparable to that of the one-stage protocol. However, Lohmander et al. found no significant difference in speech outcomes between patients who underwent one-stage palatal repair at 12 months and those who had early soft palate repair at 3–4 months followed by hard palate repair at 36 months.^[31] In addition, the rates of oronasal fistula (ONF) formation were also not evaluated in the present study. Previous literature reported that the incidence of ONF following Bardach two-flap palatoplasty and early two-stage palatoplasty was 5.6% and 8.8%, respectively.^[32,33] Future studies incorporating speech and ONF data are essential to understand the overall clinical effects of the early two-stage palatoplasty protocol.

Pre-surgical NAM, when performed with primary rhinoplasty, was shown to enhance nasolabial aesthetics but not dentoalveolar and maxillary development.^[14,34,35] Since NAM was performed in both groups, it is unlikely to have an effect on the outcomes of either group. Both treatment protocols also involved the same number of surgeries; therefore, the burden of care between the two groups should be comparable. The experience and skill of the surgeon performing primary surgeries could also contribute to the outcomes.^[7,12,26] Both craniofacial surgeons who participated in this study are highly experienced and practiced at a high-volume regional cleft-craniofacial center. Hence, the surgeon’s skills should not influence findings in this study.

This study could be the first to demonstrate that a shorter delay between soft and hard palate repairs was sufficient to optimize dental arch relationship outcomes during mixed dentition in Caucasian and Hispanic patients. One limitation is a relatively small sample size. Although the calculated sample size has adequate power to detect a GOSLON difference between the two groups, it could have been inadequate to detect significant differences for the cephalometric parameters. In addition, speech evaluation was not part of the present study. As a retrospective study is prone to several biases, it cannot definitively establish a direct cause-and-effect relationship. Therefore, future research should include a larger sample size with a more rigorous study design and evaluation of speech outcomes.

CONCLUSION

This study compared the dental arch relationship and craniofacial characteristics between patients with CUCLP who underwent one-stage palatoplasty and those who had the early two-stage palatal surgery. Our findings demonstrated significantly more favorable dental arch relationships in patients who underwent the two-stage palatoplasty. The distribution of the GOSLON scores also differed significantly between the two groups. The two-stage group exhibited a higher proportion of favorable dental arch relationships and lower unfavorable outcomes. However, all cephalometric parameters did not demonstrate a significant difference between the two groups.