Tooth eruption is a localised event whereby the signals for eruption for a given tooth are synthesised in the dental follicle of that tooth with a possible cross talk of signals coming from the adjacent stellate reticulum. The eruption process requires alveolar bone resorption that is primarily regulated by the dental follicle. This is reflected by the fact that failures of eruption often can be traced to either osteoclast deficiencies or to dental follicle abnormalities. Recent advances in application of molecular techniques to animal models allowed for better understanding of gene regulatory events involved in the physiology of tooth eruption. This article attempts to consolidate and organise the facts that offshoot from animal studies.
Tooth Eruption ; Dental Sac ; Molecular Biology

OBJECTIVE: To evaluate the clinical efficacy of clear aligner therapy in patients with severe periodontitis accompanied by pathological tooth displacement in the anterior region. METHODS: This retrospective study analyzed patients diagnosed with severe periodontitis and pathological displacement in the anterior region, who visited both the Periodontics and Orthodontics Departments at Peking University School and Hospital of Stomatology between 2019 and 2022. A total of 26 eligible cases were included in this study. All the patients underwent regular periodontal maintenance throughout the treatment process, and clear aligners were used for orthodontic treatment. Intraoral scans were analyzed by dedicated software to measure and compare occlusal distribution and proximal contact scores before and after orthodontic treatment. Periodontal clinical indicators were assessed at three key time points: before periodontal treatment (T0), before orthodontic treatment (T1), and after orthodontic treatment (T2). All the cases were treated with clear aligner. RESULTS: A total of 217 pathologically displaced anterior teeth from 26 patients were analyzed. Among these, 105 teeth exhibited periodontal pockets [probing depth (PD) ≥5 mm] before periodontal treatment. After clear aligner therapy, the occlusal score improved significantly from 10.35±8.61 to 23.62±9.73 (P < 0.001), and the proximal contact score increased from 13.62±4.73 to 31.62±10.37 (P < 0.001). The median PD decreased significantly from 3.33 mm [interquartile range (IQR)=0.92] at T0 to 2.50 mm (IQR=0.67, P < 0.001) at T1 and remained stable at 2.50 mm (IQR=0.50) after treatment (T2). A significant reduction in PD was observed between T0 and T2 (P < 0.001), but no significant difference was found between T1 and T2 (P=0.948). CONCLUSION Clear aligner therapy demonstrates favorable clinical efficacy in patients with severe periodontitis and pathological anterior tooth displacement. It effectively improves occlusal distribution and proximal contact while maintaining periodontal health in these patients. However, further large-scale prospective controlled studies are needed to verify its long-term clinical outcomes.
Humans ; Retrospective Studies ; Periodontitis/therapy* ; Female ; Male ; Adult ; Tooth Migration/therapy* ; Tooth Movement Techniques/methods* ; Treatment Outcome ; Middle Aged ; Young Adult ; Orthodontic Appliances, Removable

OBJECTIVE: To analyze the factors related to spontaneous re-eruption after intruded injury in permanent anterior teeth in children and adolescents. METHODS: Clinical data from 5- to 17-year-old patients who sustained intrusive luxation of permanent anterior teeth and treated in the Department of Pedia-tric Dentistry of Peking University School and Hospital of Stomatology from June 2015 to August 2024 were reviewed. Information of age, gender, degree of intrusion, direction of intrusion, tooth development, concomitant injuries, luxation and post-osteoclastic eruption of the adjacent teeth were recorded. The patients were divided into two groups based on whether they showed spontaneous re-eruption during advised observation after intrusion. Univariate and multifactor analysis were performed using Logistic regression. RESULTS: Data from 170 teeth in 139 patients whose age ranging from 5.3-16.3 years [mean age (9.0± 2.1) years] were examined. A gender disparity was observed among the patients, with 84 being male and 55 being female. Among the 170 teeth, 112 were categorized as successfully spontaneous re-eruption during advised observation after intrusion, while 58 were not. In terms of the degree of intrusion, 45 teeth (26.47%) had intrusion less than 3 mm, 102 teeth (60.00%) experienced intrusion between 3-7 mm, and 23 teeth (13.53%) were faced with intrusion exceeding 7 mm. As for the direction of intrusion, 117 teeth (68.82%) were straight intrusion while mesial-distal and buccal-lingual intrusion respectively accounting for 17 (10.00%) and 23 (13.53%). Multivariate Logistic regression analysis showed that mesial-distal intrusion (OR=0.167, 95%CI: 0.031-0.9048, P=0.038), intrusion of >7 mm (OR=0.065, 95%CI: 0.014-0.299, P < 0.001) and luxation of adjacent teeth (OR=0.369, 95%CI: 0.144-0.944, P=0.037) were independent risk factors for spontaneous re-eruption of traumatically intruded permanent anterior teeth in children and adolescents during advised observation after intrusion, while intrusion of < 3 mm (OR=9.860, 95%CI: 2.430-40.009, P=0.001) and post-osteoclastic eruption of adjacent teeth (OR=4.712, 95%CI: 1.528-14.531, P=0.007) were independent protective factors. The possibility of spontaneous re-eruption in permanent anterior teeth during advised observation after intrusion was decreased by 61.1% with the increase of root development using Cvek' s classification (OR=0.611, 95%CI: 0.408-0.914, P=0.017). Age (OR=1.077, 95%CI: 0.763-1.521, P=0.673) and laceration of gingival (OR=0.865, 95%CI: 0.290-2.578, P=0.794) didn't significantly affect the spontaneous re-eruption during advised observation after intrusion. CONCLUSION In this study, mesial-distal intrusion, intrusion of >7 mm and luxation of adjacent teeth were independent risk factors for spontaneous re-eruption of traumatically intruded permanent anterior teeth in children and adolescents during advised observation, while intrusion of < 3 mm and post-osteoclastic eruption of adjacent teeth were served as independent protective factors.
Humans ; Adolescent ; Child ; Female ; Male ; Tooth Eruption/physiology* ; Child, Preschool ; Tooth Avulsion/therapy* ; Dentition, Permanent ; Incisor/injuries* ; Remission, Spontaneous

OBJECTIVE: To measure and analyze the occlusal force and contact in children with mixed dentition, and to preliminarily provide baseline data on the occlusion of individual normal occlusion children with mixed dentition. METHODS: A cross-sectional study was conducted, including 20 children with mixed dentition and individual normal occlusion, consisting of 12 boys and 8 girls, aged 6.5-9.8 years. The Dental Prescale Ⅱ occlusal analysis system was used to measure the occlusal force and contact at the intercuspal position, including the maximum occlusal force (N) and the occlusal contact area (mm²) of the entire dentition, and the left and right sides, average occlusal pressure (MPa), maximum occlusal pressure (MPa), and to determine the position of the center of occlusal force. The gender differences in maximum occlusal force, average occlusal pressure, and occlusal contact area were analyzed, the bilateral symmetry of occlusion in children with mixed dentition and individual normal occlusion was compared, and the correlation between occlusal data and age, height, weight, and body mass index (BMI) was analyzed. RESULTS: (1) The average maximum occlusal force of the entire dentition in the 20 children with mixed dentition at the intercuspal position was (869.18±106.64) N, the average occlusal contact area was (25.19±2.89) mm², the average occlusal pressure was (34.37±5.98) MPa, and the maximum occlusal pressure M(P₂₅, P₇₅) was 120 (120, 120) MPa; (2) There was no statistically significant difference in the maximum occlusal force, average occlusal pressure, maximum occlusal pressure, and occlusal contact area between the left and right sides (P>0.05); (3) At the intercuspal position, the average occlusal contact area for 12 boys and 8 girls was (26.71±3.91) mm² and (21.62±3.08) mm² respectively, and the average maximum occlusal force was (911.92±145.05) N and (769.47±116.45) N respectively, with statistically significant differences (P < 0.05), while there was no statistically significant difference in the average occlusal pressure between boys and girls (P>0.05); (4) The maximum occlusal force at the intercuspal position was weakly correlated with age (r=0.219, P=0.046), and strongly positively correlated with the occlusal contact area (r=0.949, P < 0.001), while the average occlusal pressure, maximum occlusal pressure, and occlusal contact area were not correlated with age, height, weight, or BMI; (5) The center of occlusal force in the 20 children with mixed dentition and individual normal occlusion was located in the molar region, with 7 children having the maximum occlusal pressure point only in the first permanent molar region, 10 children having it in both the deciduous molar region and the first permanent molar region, and 3 children having it only in the deciduous molar region. CONCLUSION In children with mixed dentition and individual normal occlusion, the maximum occlusal force, occlusal contact area, average occlusal pressure, and maximum occlusal pressure at the intercuspal position show good bilateral symmetry; there are gender differences in the maximum occlusal force and occlusal contact area, with boys having greater values than girls; the maximum occlusal force is positively correlated with the occlusal contact area.
Humans ; Child ; Male ; Bite Force ; Female ; Dentition, Mixed ; Cross-Sectional Studies ; Dental Occlusion

Occlusal rehabilitation is an effective means of treating tooth wear, edentulous jaws and other oral diseases. Among them, full-mouth fixed occlusal reconstruction can effectively restore aesthetics and function, but the complexity of the clinical process, the high sensitivity of the technique, and the high incidence of various complications have always drawn much attention. With the application and development of digital technology in occlusal rehabilitation, the treatment outcome has been improved compared with traditional treatment. However, there are many kinds of digital technology with different efficacy, how to build an efficiently standardized digital clinical technical solution is a current difficulty. Therefore, combined with the long-term work of the department of prosthodontics in our hospital, in this paper, the minimum (occlusal perception of thickness) and maximum (centric relation) geometric quantities which should be paid attention to during reconstruction are put forward. We systematically organized the clinical procedure of digital full-mouth fixed occlusal rehabilitation used in our department for a long time. In conclusion, a 5-stage 19-step or n-step solution (5-19N for short) characterized by "from large to small" restorative space splitting logic is proposed. It has a certain reference value for the future use of digital technology to deal with complex occlusal rehabilitation cases.
Humans ; Dental Occlusion ; Computer-Aided Design ; Mouth, Edentulous/rehabilitation*

OBJECTIVES: This study aimed to investigate the incidence, imaging characteristics, and clinical manifestations of the eruption failure of deciduous molars using panoramic radiographs to provide a foundation for diagnosis and treatment in this population. METHODS: This study retrospectively reviewed panoramic radiographs of children aged 4-8 years obtained from Stomatology Hospital, Zhejiang University School of Medicine between January 2021 and December 2023. A total of 31 331 subjects were included for the radiographic assessment of the tooth eruption failure of deciduous molars. Incidence, radiographic characteristics, and associated complications were documented. Statistical analysis was performed using SPSS 26.0. RESULTS: The incidence of the eruption failure of deciduous molars among children aged 4-8 years was 0.94% (296/31 331). The rate was 1.55 times higher in females than in males, demonstrating a significant gender difference (P<0.001). Among the affected deciduous molars, mandibular first deciduous molars accounted for 76.4%, followed by the mandibular second deciduous molars (13.8%), and the maxillary deciduous molars collectively comprised 9.8%. The severity of eruption disorders was significantly associated with the mesial and distal tilting of adjacent teeth and elongation of the antagonist (P<0.001). CONCLUSIONS The incidence of the eruption failure of deciduous molars in children aged 4-8 years was 0.94%, with a high prevalence in females and a predilection for the mandible, particularly the mandibular first deciduous molar. For deciduous molars with severe eruption failure, early intervention is crucial to mitigate complications such as malocclusion and space loss.
Humans ; Child ; Child, Preschool ; Tooth, Deciduous/diagnostic imaging* ; Female ; Molar/physiopathology* ; Male ; Retrospective Studies ; Tooth Eruption ; Radiography, Panoramic ; Incidence

OBJECTIVES: Through the investigation of the microhardness and microstructure of permanent tooth enamel at various eruption stages during childhood, this research offers references for the early prevention of childhood dental caries. METHODS: Forty-five premolars extracted due to orthodontic reasons were collected and screened. These premolars were divided into three experimental groups according to the time since eruption: Group A (erupted for 0-1 year), Group B (erupted for 1-3 years), and Group C (erupted for 3-5 years). Additionally, the third molars that were extracted due to impaction and had not erupted were selected as the control group, with 15 teeth in each group. Samples were prepared, and the surface microhardness, microstructure, and elemental composition of the enamel were measured using Vickers microhardness tester, scanning electron microscope, and electron probe, respectively. RESULTS: Compared with that in the control group, the microhardness of enamel in groups A, B, and C increased with prolonged eruption time, the surface porosity structure decreased considerably, the contents of Na and Mg on the surface decreased, and that of F increased (P<0.05). CONCLUSIONS The microhardness and microstructure of enamel in permanent teeth at different stages vary. Permanent teeth are at a substantially higher risk of caries within one year after eruption, and early prevention should be emphasized.
Dental Enamel/ultrastructure* ; Humans ; Hardness ; Dental Caries/prevention & control* ; Microscopy, Electron, Scanning ; Tooth Eruption ; Bicuspid/chemistry* ; Dentition, Permanent ; Child ; Child, Preschool

Tooth resorption is the degradation of dental hard tissue due to the continuous action of odontoclasts. External cervical resorption refers to the cervical resorption of a tooth due to destruction and/or defects of the periodontal ligament or subepithelial cementum. In this paper, we report a case of maxillary central incisor with external cervical resorption after dental trauma and orthodontic treatment. The resorption site and morphology of the affected tooth were thoroughly analyzed by cone beam computed tomography prior to the operation. Dental operating microscope and layered external repair with composite resin and bioceramics ensured a perfect restoration of the resorption, and the vital pulp was preserved. The 6-year follow-up indicated a favorable treatment effect.
Humans ; Composite Resins ; Cone-Beam Computed Tomography ; Incisor/surgery* ; Maxilla ; Microsurgery/methods* ; Tooth Resorption/etiology*

Long-term dental implant stability is governed by the synergistic regulation of multiple factors, with occlusal parameters and marginal bone loss (MBL) progression being of paramount importance. Progressive MBL undermines mechanical retention, predisposing implants to micromotion and jeopardizing their long-term survival. Accumulating evidence has revealed that homeostatic occlusion imbalance, characterized by excessive occlusal loading, aberrant occlusal contacts, and dysfunctional guidance, significantly increases the incidence of peri-implant bone loss, thereby disrupting biomechanical homeostasis. Therefore, this manuscript delineates the mechanistic role of steady-state occlusal imbalance in driving peri-implant MBL and proposes a homeostatic occlusion-based strategy for preventing and controlling such bone loss, aiming to enhance the long-term stability of dental implants.
Humans ; Dental Implants ; Homeostasis ; Dental Occlusion ; Alveolar Bone Loss/prevention & control* ; Biomechanical Phenomena

Objective: To determine the effect of the impacted position of the maxillary canine on the root resorption of the adjacent incisor using Cone-beam Computed Tomography (CBCT) imaging. Methods: This was an analytic quantitative study. The research sample determined CBCT images of treatment patients at the Orthodontic Specialist Policlinic in Dental Hospital of Airlangga University over a three-year period and secondary data taken from Pramita Laboratory. CBCT photos that met the inclusion criteria, including mesially impacted canine or close to central or lateral incisors with completely formed anatomy were then analyzed. Multiple linear regression was used to determine x-axis, y-axis, z-axis position of the impacted canine on the severity of root resorption of the adjacent incisor, and the effect of impacted canines on all axes simultaneously on the severity of root resorption of the adjacent incisors. Results: The position of the impacted canine in the x-axis and z-axis planes had a significant influence on the root resorption of the adjacent incisor. Meanwhile, impacted canine from the y-axis plane showed non-significant influence on the root resorption. Conclusion The position of the impacted canine when viewed in all planes of the tooth axis has a significant effect on the severity of root resorption of the adjacent incisor
Root Resorption ; Cone-Beam Computed Tomography