Introduction
Orthodontic-aided closed eruption of impacted second premolars often fails in patients with cleidocranial dysplasia (CCD). This study aims to evaluate the 3-dimensional position and root morphology of impacted second premolars and identify factors affecting the success of orthodontic-guided closed eruption in CCD patients.
Methods
Cone-beam computed tomography images from CCD patients with impacted second premolars were selected and evaluated. The original cone-beam computed tomography data were reconstructed using Dolphin Imaging software (Dolphin Imaging and Management Solutions, Chatsworth, Calif), and the 3-dimensional position, root morphology of impacted second premolars, along with factors associated with closed-eruption success, were analyzed.
Results
Eleven patients (37 impacted second premolars) with CCD, comprising 7 males and 4 females, were included. The average duration of the closed-eruption treatment was 29.00 ± 6.84 months, yielding a success rate of 89.29%. In the 37 impacted second premolars, vertical impaction was the most common (23 [62.16%]), followed by palatal (10 [27.03%]) and buccal (4 [10.81%]). Moreover, 9 of the 37 impacted second premolars failed to erupt, of which 6 were in the low palatal position with a completed root apex. Chi-square tests revealed that the impacted second premolars in the coronal and axial positions, and Nolla’s stages were significantly associated with closed-eruption failure ( P <0.05).
Conclusions
Most impacted second premolars with failed eruption were at the mandibular palatal side and in Nolla’s stages 9 and 10. Closed-eruption treatment in patients with CCD is primarily influenced by coronal and axial positions and Nolla’s stage.
Highlights
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This study analyzed 3-dimensional positions of impacted premolars in cleidocranial dysplasia using CBCT.
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The closed-eruption success rate was 89.29%, with vertical impaction dominant.
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Premolars in Nolla’s stages 9-10 showed the highest rate of eruption failure.
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Coronal and axial positions affected the treatment outcome, especially palatally.
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Findings offer new insights for improving cleidocranial dysplasia premolar eruption treatment.
Cleidocranial dysplasia (CCD; OMIM 119600 ) is a rare autosomal dominant inheritance disorder, which is mainly associated with mutations of the runt-related transcription factor 2 ( RUNX2 ) gene, which is an essential transcription factor for coding osteoblasts and osteoclasts differentiation, as well as bone remodeling. The disease prevalence is estimated to be 1/1000000 inhabitants, with no ethnic or sex-associated predisposition. Some patients might be underdiagnosed because of relatively mild symptoms.
Mutations of RUNX2, causing CCD, negatively affect osteogenesis and the osteoclastic ability of dental follicles, resulting in abnormal tooth genesis and tooth eruption. The main dental abnormalities include supernumerary tooth formation, early uncovering of primary teeth, and suspended or unsuccessful eruption of permanent teeth. Patients with CCD usually present themselves at the orthodontics department on their own initiative, requesting advice and help for multiple retained primary teeth and the delayed eruption of permanent teeth. Approximately 70% of patients are diagnosed during childhood or adolescence, mostly because of dental complications. The main challenge in the orthodontic treatment of these patients is facilitating the eruption of multiple impacted teeth into proper dentition.
Approximately 25 years ago, Jensen and Kreiborg proposed a dental treatment strategy for patients with CCD, focusing on the significance of early treatment that involved the promotion of spontaneous eruption of permanent teeth through primary teeth extraction, surgical removal of supernumerary teeth, and removal of the bone covering the first formed permanent teeth when their root formation has reached half or two-thirds of their final length. Compared with the other recommended treatment protocols, this approach remains valid and is suggested to reduce the burden of care for the patient. Currently, closed orthodontic traction after extracting supernumerary and retained primary teeth for the traction of impacted permanent teeth is a common treatment strategy for patients with CCD. Previous research has indicated that the closed-eruption technique for impacted teeth in patients with CCD has a 93.9% success rate, with eruption failure observed in some permanent teeth in different patients. In particular, the closed-traction therapy for the second premolars requires a longer duration and is more prone to eruption failure; however, the reasons for eruption failure after traction treatment are still unclear.
A few studies have shown that closed-traction treatment for impacted teeth is affected by their 3-dimensional (3D) position and root morphology, , and may be related to factors associated with orthodontic treatment, including age. , Moreover, the comparatively posterior tooth germ of the second premolar results in its late eruption in the permanent dentition, with its eruption also being potentially influenced by its 3D position. Cone-beam computed tomography (CBCT) has been widely employed to diagnose and describe the 3D position of impacted teeth, including the orientation of their crowns and roots. In addition, such CBCT data can be used to generate 3D reconstructions using relevant software, thereby assisting in determining the relative positions of the adjacent teeth and detecting the closure of the apical foramen.
A literature review on the treatment of impacted teeth in patients with CCD demonstrated that most were case reports and reviews, , only a few original research studies analyzing abnormal dental phenotypes in this specific population. , Furthermore, only 1 study used CBCT data to characterize the distribution of impacted supernumerary teeth in patients with CCD. However, the influence of the 3D position and other factors related to orthodontic treatment on the eruption of second premolars in patients with CCD has not been comprehensively investigated. Therefore, this retrospective study aimed to analyze the clinical features and 3D position of impacted second premolars in patients with CCD and to determine the influence of root morphology and additional orthodontic treatment-related factors on the closed-eruption technique. We hope these findings will help improve the diagnosis and clinical treatment of the patient group.
Material and methods
This retrospective study was approved by the Research Ethics Committee of the School and Hospital of Stomatology, China Medical University (No. k2021005) and was conducted in accordance with the Declaration of Helsinki on medical protocol and ethics. The purpose, procedure, and possible complications of the treatment were explained to all patients, and signed consent forms were obtained from all participating patients.
The patients were consecutively treated by the corresponding author (Z.J.Z), in the department of Department of Orthodontics and the First Dental Clinic of the School and Hospital of Stomatology, China Medical University, between January 2014 and June 2024. All participants were selected by 2 resident doctors (J.L.C. and L.N.Y.) and finally evaluated by the corresponding author (Z.J.Z.). The diagnosis of CCD was established in an individual with typical clinical and radiographic findings, and/or a heterozygous pathogenic variant in RUNX2 identified by molecular genetic testing. The typical clinical features included short stature, sloping shoulders that can be opposed at the midline, delayed eruption of permanent teeth, and failure to shed the primary teeth. The radiographic features included open fontanelles, clavicular hypoplasia/aplasia, impacted permanent teeth, and supernumerary teeth. After the establishment of the tentative diagnosis, the family history was checked, and genetic analysis was performed. Patient inclusion criteria were as follows: (1) diagnosed with CCD, (2) impacted teeth were treated with the closed-eruption technique and orthodontic traction, and (3) availability of clear lateral cephalometric films, panoramic radiographs, and CBCT images. Patients were excluded based on the following exclusion criteria: (1) multiple impacted teeth and supernumerary teeth without characteristic CCD features, clavicular dysplasia, or maxillofacial deformity; (2) other severe oral, maxillofacial, or systemic diseases; and (3) removal of impacted second premolars before closed-eruption treatment because of their identification as being unable to erupt (inverted impaction or root curvature of >90°). After applying the inclusion and exclusion criteria, 11 patients with 37 impacted second premolars were finally included. In this study, 11 Chinese Han subjects from Northeast China (male, 7; female, 4; aged 15.71 ± 5.42 years) were included ( Table I ). In each patient, sex, age at the time of CBCT, systemic findings (anterior fontanel patency, clavicular hypoplasia, and ascending ramus), hereditary characteristics, and the total number of impacted permanent teeth and supernumerary teeth were listed ( Table I ).
Table I
Characteristics of the 11 subjects with CCD included in this study
| Case | Sex | Age | Abnormal suture | Abnormal clavicle | Abnormal mandible | Hereditary characteristics | No. of impacted permanent teeth | No. of supernumerary teeth |
|---|---|---|---|---|---|---|---|---|
| 1 | M | 12 y 0 mo | (+) | (+) | (+) | Sporadic | 14 | 5 |
| 2 | F | 12 y 0 mo | (−) | (+) | (+) | Sporadic | 14 | 2 |
| 3 | M | 11 y 9 mo | (+) | (+) | (+) | Sporadic | 15 | 6 |
| 4 | M | 11 y 5 mo | (+) | (+) | (+) | Familial | 13 | 9 |
| 5 | F | 11 y 9 mo | (−) | (+) | (+) | Sporadic | 15 | 4 |
| 6 | F | 13 y 7 mo | (−) | (+) | (+) | Sporadic | 11 | 3 |
| 7 | M | 16 y 1 mo | (−) | (+) | (+) | Familial | 17 | 3 |
| 8 | M | 19 y 9 mo | (−) | (+) | (+) | Sporadic | 13 | 1 |
| 9 | M | 28 y 4 mo | (−) | (+) | (+) | Familial | 5 | 5 |
| 10 | F | 21 y 9 mo | (−) | (+) | (+) | Familial | 16 | 0 |
| 11 | M | 14 y 5 mo | (−) | (+) | (+) | Sporadic | 15 | 4 |
Age , time of CBCT scan; Abnormal suture , open or delayed closure of suture; Abnormal clavicle , hypoplastic or aplastic clavicles; Abnormal mandibular , abnormal shape of ascending ramus in mandible; F , female; M , male.
This study employed the Jerusalem and Belfast Hamburg approaches, involving surgical extraction of primary and supernumerary teeth under general anesthesia, bone removal to expose impacted teeth, intraoperative bonding of traction chains, and wound closure. Orthodontic traction with light force (25-35 N) was initiated 2 weeks postsurgery, using sequential nickel-titanium and stainless-steel wires, with careful traction direction control to prevent adverse movements.
The cervical vertebral maturation (CVM) stages were determined using the lateral cephalometric films. Nolla’s staging method was applied to divide tooth formation into 11 main stages, which start from the absence of a crypt and end at the completed apical root end. Patients underwent CBCT scans (i-CAT 17-19; Imaging Sciences International, Pa) using the following parameters: 37.07 mA, 120 kVp, exposure time of 26.9 seconds, voxel size of 0.25 mm, axial slice thickness of 0.25 mm, and scanning area of 16 × 13 cm. Original digital imaging data of these CBCT images were imported into the Dolphin software (version 11.9; Dolphin Imaging and Management Solutions, Chatsworth, Calif) in digital imaging and communications in medicine format using a Lenovo Xiaoxin Pro 14 laptop (AMD Ryzen 7 7735HS with Radeon Graphics CPU, 2 GB discrete graphics card, 16 GB memory, Windows 11 operating system; Lenovo, Beijing, China). Finally, 3D models were constructed, and all the maxillary and mandible impacted second premolars were observed and analyzed by 2 orthodontists (J.L.C. and L.N.Y.).
Initially, the 3D reconstructed models were used to analyze the distribution of the impacted second premolars. Subsequently, the effects of the relevant variables (such as tooth position in the alveolar bone, morphology of the impacted teeth, and factors associated with orthodontic traction) on the eruption of the impacted second premolars were evaluated. In this study, an impacted tooth was considered to have successfully erupted if it was aligned to the occlusal plane, whereas it was considered to have failed to erupt if it did not move by occlusal retraction for 3.5 years. The 3D positions and morphologic characteristics of the impacted second premolars are defined in Table II . The definition of factors associated with orthodontic traction was listed in Table III , and the descriptive statistics of qualitative variables were described in Table IV . The overview of 3D positional distribution of the impacted second premolars is detailed in Table V . The comparison of various factors associated with the eruption of impacted second premolar, including 3D positions, locations, morphologic characteristics, and other factors associated with orthodontic treatment, was listed in Table VI . The Nolla’s stage classification and root morphology of impacted second premolars are interpreted in Figure 1 . The 3D morphology and position analysis of a typical impacted tooth is illustrated in Figure 2 . The 3D relationship between the impacted mandibular second premolar and adjacent teeth, including supernumerary teeth and retained primary molars, is illustrated in Figure 3 with the lingual view shown in panel A and the buccal view in the panel B.
Table II
Definition of impacted second premolar 3D position and morphology characteristics
| Classification | Definition |
|---|---|
| Position | |
| Coronal | Palatal: The crown of the tooth is located in the palatal third of the alveolar bone |
| Vertical: The crown of the tooth is located in the middle third of the alveolar bone | |
| Buccal: The crown of the tooth is located in the labial third of the alveolar bone | |
| Sagittal | Mesial: In the sagittal plane, the tooth is inclined to the mesial |
| Centered: In the sagittal plane, the tooth is not inclined | |
| Distal: In the sagittal plane, the tooth is inclined to the distal | |
| Axial | Low: In the axial plane, the tooth has its tip of crown located in the apical third of the root of the ipsilateral first molar |
| Middle: In the axial plane, the tooth has its crown located in the middle third of the root of the ipsilateral first molar | |
| High: In the axial plane, the tooth has its crown located in the cervical third of the root of the ipsilateral first molar | |
| Location | Maxillary: The tooth impacted in the maxillary bone |
| Mandibular: The tooth impacted in the mandibular bone | |
| Morphology | |
| Root morphology | Upright or dilacerated |
| Crown-to-root ratio | 1:1 group: The ratio of crown length to root length is close to 1:1 |
| 1:1.5 group: The ratio of crown length to root length is close to 1:1.5 | |
| 1:2 group: The ratio of crown length to root length is close to 1:2 | |
| Nolla’s stage | Stage 7-8 group: One-third or two-thirds of the root completed |
| Stage 9-10 group: Root almost completed with open apex or root completed with closed apical foramen |
Table III
Definition of factors associated with orthodontic traction
| Factors associated with orthodontic traction | Definition |
|---|---|
| Sex | Male or female |
| Age | Age at the date of the surgical exposure |
| Adolescent group: 12 y≤ age <18 y; Adult group: age ≥18 y | |
| CVM stage | C3-C4: Pubertal stage |
| C5-C6: Postpubertal stage | |
| Skeletal classification | Class I: 0°< ANB <4°; |
| Class II: ANB ≥4° | |
| Class III: ANB ≤0° | |
| Posterior crossbite | Yes or no |
| Maxillary arch expansion | Yes or no |
| Supernumerary tooth | Occlusal: Located on the occlusal side of the second premolar |
| Palatal: Located on the palatal side of the second premolar | |
| Absent: No supernumerary tooth around the second premolar | |
| Primary second molar | Retained or exfoliated |
| Primary first molar | Retained or exfoliated |
| First premolar | Erupted or unerupted |
Table IV
Descriptive statistics of qualitative variables
| Variable | n (%) |
|---|---|
| Sex | |
| Male | 7 (63.64) |
| Female | 4 (36.36) |
| Total | 11 (100.0) |
| Age | |
| Adolescent group | 8 (72.73) |
| Adult group | 3 (27.27) |
| Total | 11 (100.00) |
| CVM stage | |
| C3-C4 | 5 (45.45) |
| C5-C6 | 6 (54.55) |
| Total | 11 (100.00) |
| Skeletal classification | |
| Class I | 2 (18.18) |
| Class II | 2 (18.18) |
| Class III | 7 (63.64) |
| Total | 11 (100.00) |
| Posterior crossbite | |
| Yes | 9 (81.82) |
| No | 22 (18.18) |
| Total | 112 (100.0) |
| Maxillary arch expansion | |
| Yes | 52 (45.45) |
| No | 62 (54.55) |
| Total | 112 (100.0) |
| Coronal position | |
| Palatal | 102 (27.03) |
| Vertical | 232 (62.16) |
| Buccal | 42 (10.81) |
| Total | 372 (100.00) |
| Sagittal position | |
| Mesial | 42 (10.81) |
| Centered | 262 (70.27) |
| Distal | 72 (18.92) |
| Total | 372 (100.00) |
| Axial position | |
| Low | 192 (51.35) |
| Middle | 82 (21.62) |
| High | 102 (27.03) |
| Total | 372 (100.00) |
| Location | |
| Maxillary | 182 (48.65) |
| Mandibular | 192 (51.35) |
| Total | 372 (100.00) |
| Root morphology | |
| Upright | 312 (83/78) |
| Dilacerated | 62 (16.22) |
| Total | 372 (100.00) |
| Crown-to-root ratio | |
| 1:1 group | 102 (27.03) |
| 1:1.5 group | 132 (18.18) |
| 1:2 group | 142 (18.18) |
| Total | 372 (100.0) |
| Nolla’s stage | |
| Stage 7-8 group | 242 (64.86) |
| Stage 9-10 group | 132 (35.14) |
| Total | 372 (100.00) |
| Supernumerary teeth | |
| Occlusal | 32 (8.11) |
| Palatal | 22 (18.18) |
| Absent | 322 (86.49) |
| Total | 372 (100.00) |
| Primary second molar | |
| Retained | 302 (81.08) |
| Exfoliated | 72 (18.92) |
| Total | 372 (100.00) |
| Primary first molar | |
| Retained | 282 (18.18) |
| Exfoliated | 92 (18.18) |
| Total | 372 (100.00) |
| First premolar | |
| Erupted | 52 (13.51) |
| Unerupted | 322 (86.49) |
| Total | 372 (100.00) |
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