Primary cilia function as critical sensory organelles that mediate multiple signaling pathways, including the Hedgehog (Hh) pathway, which is essential for organ patterning and morphogenesis. Disruptions in Hh signaling have been implicated in supernumerary tooth formation and molar fusion in mutant mice. Cilk1, a highly conserved serine/threonine-protein kinase localized within primary cilia, plays a critical role in ciliary transport. Loss of Cilk1 results in severe ciliopathy phenotypes, including polydactyly, edema, and cleft palate. However, the role of Cilk1 in tooth development remains unexplored. In this study, we investigated the role of Cilk1 in tooth development. Cilk1 was found to be expressed in both the epithelial and mesenchymal compartments of developing molars. Cilk1 deficiency resulted in altered ciliary dynamics, characterized by reduced frequency and increased length, accompanied by downregulation of Hh target genes, such as Ptch1 and Sostdc1, leading to the formation of diastemal supernumerary teeth. Furthermore, in Cilk1^-/-;PCS1-MRCS1^△/△ mice, which exhibit a compounded suppression of Hh signaling, we uncovered a novel phenomenon: diastemal supernumerary teeth can be larger than first molars. Based on these findings, we propose a progressive model linking Hh signaling levels to sequential changes in tooth patterning: initially inducing diastemal supernumerary teeth, then enlarging them, and ultimately leading to molar fusion. This study reveals a previously unrecognized role of Cilk1 in controlling tooth morphology via Hh signaling and highlights how Hh signaling levels shape tooth patterning in a gradient-dependent manner.
Animals ; Hedgehog Proteins/physiology* ; Mice ; Signal Transduction/physiology* ; Tooth, Supernumerary ; Molar ; Cilia/physiology* ; Odontogenesis/physiology* ; Patched-1 Receptor ; Protein Serine-Threonine Kinases/physiology* ; Mice, Knockout ; Adaptor Proteins, Signal Transducing

OBJECTIVES: This study aimed to investigate the clinical characteristics of deciduous fused teeth and their inherited permanent-tooth performance type by using panoramic radiographs. METHODS: A total of 14 404 panoramic radiographs of 3- to 6-year-old children with deciduous dentition were collected from January 2023 to July 2024. The incidence of deciduous fused teeth was observed, and the abnormality of permanent teeth was recorded. SPSS 24.0 software was used for statistical analysis. RESULTS: The incidence of deciduous fused teeth was 3.06% (441/14 404). The order of dental position was as follows: mandibular deciduous incisors and cusp teeth fused (58.18%) > mandibular deciduous central and lateral incisors fused (30.91%) > maxillary deciduous central and lateral incisors fused (8.89%) > deciduous incisors and supernumerary teeth fused (2.02%). Deciduous fused teeth were found in 226 boys and 215 girls, with no significant difference between the sexes (P>0.05). We observed one pair (87.76%, 387/441) and two pairs (12.24%, 54/441) of fused teeth (54/441), respectively. A total of 287 pairs of fusion teeth on the right side more than 208 pairs on the left side, and the difference between them was statistically significant (P<0.01). More fusion teeth existed in mandibular deciduous teeth (443 pairs) than in maxillary ones (54 pairs), and the difference between them was statistically significant (P<0.01). More unilateral deciduous teeth (387 subjects) were found than bilateral ones (54 subjects), and the difference between them was statistically significant (P<0.01). Three types of deciduous fused teeth with inherited permanent teeth were observed as follows: 1) 49.49% (245/495) of inherited permanent teeth was absent, 2) 46.67% (231/495) of inherited permanent teeth was not absent, and 3) the number of fused permanent teeth accounted for 3.84% (19/495). CONCLUSIONS The incidence of deciduous fused teeth was 3.06%, mostly occurring in the lower anterior teeth region, with no gender difference. One pair of fused teeth is commonly observed, more often on the right than the left. These fusions occur more frequently in the mandible than the maxillary, and unilateral cases are more common than bilateral ones. Deciduous fused teeth had a certain impact on inherited permanent teeth. Pediatric dentists should pay attention to and closely observe whether any abnormality exists in the permanent dentition for early detection to prevent the harm caused by deciduous fused teeth.
Humans ; Tooth, Deciduous/abnormalities* ; Male ; Child ; Female ; Child, Preschool ; Dentition, Permanent ; Radiography, Panoramic ; Fused Teeth/diagnostic imaging* ; Incisor/diagnostic imaging* ; Tooth, Supernumerary/diagnostic imaging* ; Incidence ; Mandible

Dental trauma is a common oral condition in children. For single-type trauma to young permanent teeth, timely treatment often results in a high survival rate for both the teeth and the pulp. However, in cases of complex dental trauma or when supernumerary teeth are impacted near the apex of the injured tooth, the prognosis is less predictable. This article reports a case of root fracture in an immature maxillary permanent central incisor combined with impacted supernumerary tooth in the apical region. After supernumerary tooth extraction and pulp revascularization therapy, the case demonstrated a good treatment outcome over a nearly 10-year follow-up period.
Child ; Humans ; Incisor/injuries* ; Maxilla ; Tooth Extraction ; Tooth Fractures/complications* ; Tooth Root/injuries* ; Tooth, Impacted/surgery* ; Tooth, Supernumerary/surgery*

OBJECTIVES: This study aimed to investigate the clinical characteristics of congenital deciduous teeth absence and its permanent teeth performance type by using panoramic radiographs. METHODS: A total of 15 749 panora-mic radiographs of 3-6-year-old children with deciduous dentition were collected from January 2020 to December 2021. The incidence of congenital deciduous teeth absence was observed, and the abnormality of permanent teeth was recor-ded. SPSS 24.0 software was used for statistical analysis. RESULTS: The incidence of congenital deciduous teeth absence was 2.54% (400/15 749), which was found in 217 girls and 183 boys, and the difference between the genders was statistically significant (P=0.003). The absence of one and two deciduous teeth accounted for 99.75% (399/400) of the subjects. In addition, 92.63% (490/529) of mandibular deciduous lateral incisor was congenitally absent, 44.80% (237/529) of deciduous teeth was absent in the left jaw, and less than 55.20% (292/529) was absent in the right; the difference between them was statistically significant (P=0.017). The absence of 96.41% (510/529) deciduous teeth in the mandibular was significantly more than that of 3.59% (19/529) in the maxillary, and the difference between was statistically significant (P=0.000). Furthermore, 68.00% (272/400) and 32.00% (128/400) of deciduous teeth were absent in unilateral and bilateral, respectively, and the difference was statistically significant (P=0.000). Four types of congenital deciduous teeth absence with permanent teeth were observed as follows: 1) 73.91% (391/529) of permanent teeth was absent; 2) 20.60% (109/529) of permanent teeth was not absent; 3) the number of fused permanent teeth accounted for 4.91% (26/529); 4) the number of supernumerary teeth was 0.57% (3/529). CONCLUSIONS Although the absence of congenital deciduous teeth is less common than that of permanent teeth, it affects deciduous and permanent teeth to some extent. Dentists should pay attention to trace and observe whether abnormalities are present in the permanent teeth and take timely measures to maintain children's oral health.
Male ; Female ; Humans ; Tooth, Deciduous ; Dentition, Permanent ; Tooth, Supernumerary/epidemiology* ; Anodontia/etiology* ; Tooth Abnormalities/complications* ; Fused Teeth/epidemiology*

Objective: To summarize the clinical characteristics of patients with cleidocranial dysplasia (CCD) and analyze their treatment methods. Methods: From January 2000 to December 2020, patients with CCD who completed comprehensive treatment in the Department of Orthodontics and the First Dental Clinic, School and Hospital of Stomatology, China Medical University were retrospectively analyzed. A total of 14 CCD patients [7 males and 7 females, aged (16.1±4.5) years] were collected. There were 153 impacted permanent teeth in this study. In addition to the teeth that needed to be extracted due to special conditions, 147 impacted teeth were pulled into the dentition using closed traction. Patients were divided into adolescent group (≥12 years and<18 years, 10 patients) and adult group (≥18 years, 4 patients). Failure rate of traction was compared between the two groups. Factors affecting the success rate of closed traction such as vertical position of teeth (high, middle and low) and horizontal position of the teeth (palatal, median and buccal) were analyzed. Results: The incidence of maxillary impacted teeth [69.3% (97/140)] was higher than that of mandibular impacted teeth [40% (56/140)]. The difference was statistically significant (χ²=24.22, P<0.001). The supernumerary teeth were mainly located in the premolar area 61.4% (21/44), and most of them were in the palatal region of the permanent teeth 95.5% (42/44). They were generally located at the same height or the occlusal side of the corresponding permanent teeth. The success rate of closed traction was 93.9% (138/147). The success rate in the adolescent group [98.2% (108/110)] was higher than that in the adult group [81.1% (30/37)], and the difference was significant (χ²=14.09, P<0.05). Failure after closed traction of 9 teeth was found totally, including 7 second premolars. The success rate of traction in impacted second premolars at different vertical (χ²=11.44, P<0.05) and horizontal (χ²=9.71, P<0.05) positions in alveolar bone was different significantlly. The success rates of the second premolars were high (15/16), middle (12/13), low (2/7), and lingual palatine (10/17), median (19/19), lip-buccal (0/0), respectively. Conclusions: The closed traction of impacted teeth in patients with CCD was effective, and the age was the main variable affecting the outcome. The success rate of traction in impacted second premolars located in low position vertically or in palatal position was low, which required close observation during treatment.
Adolescent ; Adult ; Bicuspid ; Child ; Cleidocranial Dysplasia/therapy* ; Female ; Humans ; Male ; Mandible ; Retrospective Studies ; Tooth, Supernumerary/surgery* ; Young Adult

OBJECTIVE: To explore the application of digital positioning guide plate in extraction of impacted supernumerary teeth and evaluate its clinical efficacy. METHODS: From March to August, 2019, 30 patients with labial impacted supernumerary teeth treated in the Department of Oral and Maxillofacial Surgery, Stomatological Hospital, Southern Medical University were enrolled in this study. Fifteen of the patients were treated with digital positioning guide plate to remove the impacted supernumerary teeth (test group). According to the CBCT data and the dentition model of the patients, the positioning guide plate was positioned by avoiding the important anatomical structure with the tooth-bone surface as the support to design the soft tissue incision line and bone tissue exposure range. The other 15 patients who were treated without the use of the guide plate for operation served as the control group. The design time, tooth searching time, operation time and complications were compared between the two groups. RESULTS: The positioning guide plate was well attached during the operation and allowed quick location of the supernumerary teeth while helping to expose the supernumerary teeth and avoid the damage of the adjacent important anatomical structures. The pre-operative design time was 50 ± 5 min in the test group and 0 min in the control group. The average time of tooth finding in the test group was 5±2 min, as compared with 10±3 min in the control group (=15.40, < 0.01); the average time of operation was significantly shorter in the test group than in the control group (25±4 min 45±6 min; =35.50, < 0.01). No intraoperative complications occurred in the test group, and slight deviation occurred in one case in the control group. CONCLUSIONS The application of digital positioning guide plate in extraction of embedded supernumerary teeth can significantly shorten the time of tooth finding, reduce the difficulty of operation, and improve the quality of operation.
Bone Plates ; Bone and Bones ; Humans ; Operative Time ; Tooth Extraction ; Tooth, Impacted ; Tooth, Supernumerary

Cleidocranial dysplasia (CCD) is an autosomal-dominant disease characterized by the delayed closure of cranial sutures, defects in clavicle formation, supernumerary teeth, and delayed tooth eruption. Defects in the Runt-related transcription factor 2 (RUNX2), a master regulator of bone formation, have been identified in CCD patients. The aim of this study was to identify the molecular genetic causes in a CCD family with delayed tooth eruption.The 23-year-old female proband and her mother underwent clinical and radiographic examinations, and all coding exons of the RUNX2 were sequenced. Mutational analysis revealed a single nucleotide deletion mutation (NM_001024630.4 : c.357delC) in exon 3 in the proband and her mother. The single C deletion would result in a frameshift in translation and introduce a premature stop codon [p.(Asn120Thrfs*24)]. This would result in the impaired function of RUNX2 protein, which may be the cause of delayed eruption of permanent teeth in the family.
Clavicle ; Cleidocranial Dysplasia ; Clinical Coding ; Codon, Nonsense ; Core Binding Factor Alpha 1 Subunit ; Cranial Sutures ; Exons ; Female ; Humans ; Molecular Biology ; Mothers ; Osteogenesis ; Sequence Deletion ; Tooth ; Tooth Eruption ; Tooth, Supernumerary ; Transcription Factors ; Young Adult

OBJECTIVE: To study the application of surgical locating guides based on cone beam computed tomography (CBCT) and computer-aided design/computer-aided manufacturing (CAD/CAM) technique on extraction of impacted supernumerary teeth. METHODS: This study included 15 patients with impacted supernumerary teeth in anterior maxillary. Surgical approach was determined by CBCT. Surgical locating guides of labial approach or palatal approach were designed and fabricated by CAD/CAM technique. Impacted supernumerary teeth were extracted under the location of surgical locating guides. RESULTS: Surgical locating guides were well attached in the operation. The impacted supernumerary teeth were located and exposed rapidly, and the adjacent important anatomical structures were avoided. CONCLUSIONS Surgical locating guides benefit the accurate detection and reduction of trauma in extraction of impacted supernumerary teeth.
Cone-Beam Computed Tomography ; Humans ; Maxilla ; Tooth Extraction ; Tooth, Impacted ; Tooth, Supernumerary

PURPOSE: The prevalence of supernumerary teeth has been reported to be between 0.1% and 3.8%. The aim of this study was to determine the prevalence, clinical significance, and associated pathologies of fourth molars based on a retrospective study and a literature review. MATERIALS AND METHODS: A 5-year retrospective prevalence study was conducted at the Department of Oral Diagnosis and Dentomaxillofacial Radiology of Okayama University Hospital, Okayama, Japan. The study involved extracting data from the digital records of patients from January 1, 2013 through December 31, 2017. The sampling frame included all patients who had panoramic radiographs, cone-beam computed tomography (CT), and multislice CT images during the period under review. RESULTS: A total of 26,721 cases were reviewed and 87 fourth molars were identified. The prevalence of fourth molars in the 5-year study at Okayama was calculated as 0.32%. The mean age of patients with a fourth molar was 30.43 years, and the male-to-female ratio was 1:0.98. The vast majority of cases were in the maxilla (92%) and had normal shapes (89.7%); furthermore, 82.8% of cases were unerupted. CONCLUSION: The prevalence of fourth molars in the study population was found to be 0.32%, and fourth molars occurred with approximately equal frequency in males and females. Fourth molars were more common in the maxilla and were predominantly unerupted and small.
Cone-Beam Computed Tomography ; Cross-Sectional Studies ; Diagnosis, Oral ; Female ; Humans ; Japan ; Male ; Maxilla ; Odontogenic Cysts ; Odontoma ; Pathology ; Prevalence ; Retrospective Studies ; Tooth, Supernumerary

This report describes 3 cases of cleidocranial dysplasia (CCD) and presents relevant findings on long-term follow-up radiographic images of impacted permanent teeth with delayed eruption. Radiographic images of 3 CCD patients were reviewed retrospectively. These images were mainly composed of panoramic and skull radiographs, and the follow-up periods were 3, 13, and 13 years, respectively. The distinct features revealed by the images were described, and the eruption state of impacted permanent teeth was evaluated. The features common to the 3 cases were multiple supernumerary teeth, the presence of Wormian bone, underdevelopment of the maxilla and the maxillary sinus, and clavicular hypoplasia. The eruption of impacted permanent teeth was not observed without proper dental treatment in adult CCD cases, even after long time periods had elapsed. When proper orthodontic force was applied, tooth movement was observed in a manner not significantly different from the general population.
Adult ; Cleidocranial Dysplasia ; Follow-Up Studies ; Humans ; Jaw ; Maxilla ; Maxillary Sinus ; Radiography ; Retrospective Studies ; Skull ; Tooth Movement ; Tooth ; Tooth, Supernumerary