Mid-root fractures are rare injuries in young permanent teeth and tend to have poor prognoses. This study presents a case of oblique root fracture of both maxillary immature central incisors in the middle third accompanied by delayed dental visit and severe caries of all primary teeth. After restoring all the primary and permanent teeth that needed stabilization, the coronal fragments were repositioned and stabilized with a flexible splint consisting of orthodontic wire and composite resin. A comprehensive and sequential dental treatment for other oral diseases and oral hygiene instructions were provided. A 16-month follow-up revealed that the two injured young permanent incisors were healed, surrounded by hard tissues and continued to grow both in length of the root and thickness of the root canal wall, with significant improvement in oral hygiene. Based on the outcome of this case, initial stabilization without endodontic therapy could be considered a successful treatment modality for young permanent teeth with oblique root fracture due to the growth of fractured teeth with vital pulp and the maintenance of natural dentition.

In orthodontic treatment of patients during the mixed dentition period, arch expansion and opening deep overbite are one of the objectives to achieve proper alignment of the teeth and correction of sagittal and vertical discrepancies. However, the expected outcomes of most therapeutic regimens are not clear, making it impossible to standardize early treatment effects. Therefore, this study was designed to evaluate the impact of the Invisalign® First System on the dental arch circumference and incisor inclination in patients during the mixed dentition period. A total of 21 children during the mixed dentition period (10 females and 11 males, with an average age of 8.76 years) were included in this study. The patients received non-extraction treatment through Invisalign® First System clear aligners, and no other auxiliary devices were used except Invisalign® accessories. Subsequently, the cooperation degree of patients during treatment and the oral measurement parameters at the beginning (T1) and the end (T2) of treatment were collected. All patients showed moderate/good cooperation degree during treatment. Besides, horizontal width of the maxillary first molar increased significantly; the designed arch expansion was 4.1 mm (±1.4 mm), while the actual arch expansion was 3.0 mm (±1.7 mm). Furthermore, the torque expression rate of upper anterior teeth reached 56.53%. Invisalign® First System clear aligners can effectively correct the teeth of patients during the mixed dentition period, widen the circumference of dental arch, and control the torque of incisors.

OBJECTIVE: To study the effect of slow maxillary expansion(SME) appliance on the development of premolar tooth germ, primary molar and alveolar crest in the central segment of maxilla in the mixed dentition.
METHODS: According to the inclusion and exclusion criteria, 17 children (average age 7.41±0.80 years old ) with maxillary transverse deficiency were selected for SME. Before and after treatment, based on cone-beam CT(CBCT) and Dolphin Imaging software, the position of maxillary premolar tooth germ, the position of maxillary primary molar, the shape of maxillary alveolar crest in the central segment were analyzed. SPSS 21.0 software package was used for data analysis.
RESULTS: There was no significant change in the buccal-lingual movement and inclination of the tooth germs of the maxillary first and second premolars relative to the maxillary alveolar bone cortex after expansion(P＞0.05).After expansion, the maxillary alveolar crest in the central segment had an obvious expansion effect(P＜0.05). There was an arch expansion effect in the alveolar crest bottom of the maxillary second primary molar(P＜0.05), but there was no significant difference in the alveolar crest bottom of the maxillary first primary molar before and after treatment. Buccal cusp width of maxillary first and second primary molars increased after arch expansion (P＜0.05) without inclination of alveolar crest(P＞0.05).
CONCLUSIONS: SME in the mixed dentition did not affect the position of premolar tooth germ in alveolar bone. SME can expand and buccally tilt central alveolar crest and dental arch, and buccal inclination is greater than that of skeletal expansion and buccal inclination. The closer tooth site is to the first molar, the greater the skeletal effect of arch expansion is at this site. SME is an effective treatment for early maxillary expansion in the clinic.

OBJECTIVE: This study aims to evaluate the potential impact of port wine stains on the development of permanent teeth in mixed dentition and provide insights for managing tooth abnormalities in patients with port wine stains.
METHODS: A retrospective analysis was conducted on 21 patients with mixed dentition and unilateral maxillary port wine stains. Two researchers concurrently utilized Nolla Analysis to assess the developmental stage of bilateral maxillary and permanent mandibular teeth based on panoramic radiographs. The cumulative developmental values of upper and lower permanent teeth on both sides were calculated, and a comparison was made between the developmental stages of the upper and lower jaws.
RESULTS: Port wine stains can influence the maturity of permanent upper teeth, within the unilateral maxillary port wine stains range, with an early developmental completion observed on the affected side compared to the unaffected side. While the developmental stages of the lower teeth on both sides showed similarities.
CONCLUSIONS: Port wine stains can accelerate the maturity of teeth on the affected side, leading to alterations in the order of tooth eruption and subsequent abnormal occlusion in children with mixed dentition. These findings provide a basis for developing appropriate management strategies for addressing tooth abnormalities in patients with port wine stains.

Ectopic eruption of the first permanent molars is a local eruption disturbance. The frequency of ectopically erupted first permanent molars is predominant in boys and primarily affects the maxilla. Interceptive treatment for irreversible ectopic eruptions should be initiated early to prevent space loss and the impaction of the second premolars. Herein, we report the case of a six-year-old girl with irreversible ectopic eruption of the bilateral mandibular first permanent molarstreated with a modified lingual arch. The mandibular first permanent molars were successfully distalised after six months of treatment, and one year of follow-up showed a satisfactory outcome. The modified lingual arch satisfies not only the clinical aspects of treatment but also the patient\'s well-being. However, the lingual arch may disturb tooth eruption in the mixed dentition stage.

Invisalign First System (First) is a new type of orthodontic appliance for maxillary arch expansion in mixed dentition children. Till now, few studies have evaluated the expansion effects of First versus other appliances. What\'s more, most studies of arch expansion did not include a natural group to rule out growth effects. This prospective cohort study aimed to evaluate the dental and dentoalveolar effects using First or acrylic splint rapid maxillary expander (RME) in adolescents excluding growth factors.
After screening by strict inclusion criteria and propensity score matching (PSM), fifty-one patients were included: First group (n = 17), RME group (n = 17), and natural growth (NG) group (n = 17). Nine indicators including dental arch width, dentoalveolar arch width, and inclination of the molars were measured on digital dental casts at baseline (T0) and six-month follow-up (T1). Paired t-tests were used for intra-group results, and two-sample independent t-tests were used for inter-group comparisons.
There was no significant increase in all indicators within six months in the NG group (p > 0.05). In the First group and RME group, all width indicators were significantly increased after treatment (p < 0.05). The RME group exhibited greater expansion than the First group in intercanine width, first interpremolar width, second interdeciduous molar width, first intermolar width, arch perimeter, intercanine dentoalveolar width, intermolar dentoalveolar width, and inclination of the molars (p < 0.05). Whereas, there was no significant difference in arch depth between the two treated groups.
Both First and RME can expand the maxillary arch in mixed dentition. In case of mild to moderate maxillary transverse deficiency (MTD), Invisalign First System could be a reasonable option. RME shows significant better efficiency of dental arch expansion than First, recommended for patients with severe MTD.
This prospective study was registered on ClinicalTrials.gov (01/02/2022, registration number: ChiCTR2200056220). The trial was approved by the Ethical Committee of the Hunan Xiangya Stomatological Hospital Central South University (20,200,088), and informed consent was obtained from all subjects and their legal guardian(s).

To evaluate transverse maxillomandibular discrepancy and dental compensation in first molar areas in 7- to 9-year-old children with skeletal Class III malocclusion without posterior crossbite using cone-beam computed tomography (CBCT).
The sample of this retrospective study consisted of 60 children (7 to 9 years old), who were divided into the skeletal Class III malocclusion group (study group, skeletal Class III malocclusion without posterior crossbite, N = 31) and the Class I occlusion group (control group, Class I occlusion with one or two impacted teeth, N = 30). CBCT data were obtained from the database of the Department of Radiology of Hospital of Stomatology, Shandong University. For three-dimensional reconstruction of the head, the dental arch width, basal bone width, and buccolingual inclination angle were measured using MIMICS 21.0 software. Independent-sample t tests were used to compare the two groups.
The mean age of the children was 8.18±0.83years. The width of the maxillary basal bone was significantly smaller in the skeletal Class III malocclusion group (59.75 ± 3.14 mm) than in the Class I occlusion group (62.39 ± 3.01 mm) (P < 0.01). The mandibular basal bone width was significantly larger in the skeletal Class III malocclusion group (60.00 ± 2.56 mm) than in the Class I occlusion group (58.19 ± 2.42 mm) (P < 0.01). The difference in the width of the maxillary and mandibular bases in the skeletal Class III malocclusion group (-0.25 ± 1.73 mm) was significantly different from that in the Class I occlusion group (4.20 ± 1.25 mm) (P < 0.01). However, there was no significant difference in the upper or lower dental arch width between the two groups (P > 0.05). The buccal inclination of the maxillary molars in the skeletal Class III malocclusion group (31.4° ± 8.9°) was significantly higher than that in the Class I occlusion group (17.64° ± 7.3°) (P < 0.01), as was the lingual inclination angle of mandibular molars (45.24° ± 8.3° vs. 37.96° ± 10.18°; P < 0.01).
Transverse maxillary and mandibular discrepancies in the posterior area and transverse dental compensation were found in the early mixed dentition of patients with skeletal Class III malocclusion without posterior crossbite. This suggests that even in the absence of posterior crossbite, maxillary expansion can be attempted to correct the maxillomandibular transverse discrepancy.

To compare the differences in salivary metabolites between caries-active and caries-free children in the mixed dentition, and explore their correlation with caries status.
The study involved 20 children (aged 8-9 years) in the mixed dentition, including 10 caries-active (aged 8.6 ± 0.49years) and 10 caries-free children(aged 8.5 ± 0.5years), with a male/female ratio of 1:1. The saliva samples were collected from all children. Metabolite extraction, LC-MS/MS-based untargeted metabolomics, qualitative and semi-quantitative analysis and bioinformatics analysis were performed to identify differential metabolites between the two sample groups. The differential metabolites identified were further analyzed in an attempt to find their correlations with caries status.
In the positive ion mode, a total of 1606 molecular features were detected in the samples of the two groups, 189 of which were differential metabolites when comparing the caries-active group with the caries-free group, including 104 up-regulated and 85 down-regulated metabolites. In the negative ion mode, a total of 532 molecular features were detected in the samples of two groups, 70 of which were differential metabolites when comparing the caries-active group with the caries-free group, including 37 up-regulated and 33 down-regulated metabolites. In the positive ion mode, two of the top 5 up-regulated differential metabolites were found in and annotated to specific metabolic pathways, whereas in the negative ion mode, only one of the top 5 up-regulated differential metabolites was found in and annotated to specific metabolic pathways. In both the positive and negative ion modes, the top 5 down-regulated differential metabolites were both annotated to the metabolic pathways. KEGG pathway enrichment analysis of differential metabolites showed that histamine and arachidonic acid identified in the positive ion mode, as well as succinate and L-histidine identified in the negative ion mode were enriched in the top 3 significantly altered pathways.
The enriched differential metabolites including histamine, L-histidine and succinate were correlated with the presence of dental caries, but their role in the caries process needs to be further investigated.

Various preformed early orthodontic appliances for correcting oral habits and training orofacial muscles have emerged on the market. However, there are few reports on the effectiveness of these appliances for orofacial myofunctional training.
This retrospective study evaluated children with lip incompetence and mixed dentition treated at the Pediatric Dentistry Department of Shanghai Ninth People\'s Hospital from 2016 to 2018. A total of 109 children (54 males, 55 females; age range: 7-10 years, mean age: 8.2 years) were selected from an overall sample of 870 patients. During the first visit, all patients were instructed to perform active lip and tongue training at home daily and were divided into two groups according to the kind of appliances worn. The first group consisted of 56 subjects (30 females; 26 males), with a mean age of 8.1 years (SD 1.1 years), treated with preformed appliances. The second group consisted of 53 subjects (25 females; 28 males), with a mean age of 8.2 years (SD 1.0 years), treated with conventional early orthodontic appliances (arch expansion devices along with \"2*4\" local fixed appliances). For each subject in the two groups, initial (pretreatment, T1) and final (posttreatment, T2) intraoral and external photos, dental casts, lateral cephalograms, and orthopantograms were taken, and lip strength was measured. SNA, SNB, ANB, APDI, FMA, U1SN, and IMPA before and after treatment were measured by The Dolphin Imaging Cephalometric Analysis Software. The hyoid bone position was also recorded. Differences between groups were identified with an independent sample t-test (P < 0.05).
In the first group, a statistically significant forward movement of the mandible was detected by an increase in SNB of - 1.06 degrees (P < 0.01) and an increase in APDI of - 2.23 degrees (P < 0.01). The increase in IMPA (- 3.21 degrees, P < 0.01) demonstrated a statistically significant protrusion of the lower incisors. Lip strength significantly increased (- 2.44, P < 0.01). The increase in HC3 (- 1 mm, P < 0.01) and HFH (- 2.95 mm, P < 0.01) implied a forward and downward movement of the hyoid bone. In the second group, a statistically significant forward movement of the mandible was also detected by an increase in APDI of -1.96 degrees (P < 0.01). Lip strength also significantly increased (- 1.24, P < 0.01). The increase in HFH (- 2.55 mm, P < 0.01) implied a downward movement of the hyoid bone. Compared with the treatment in the second group, orofacial myofunctional therapy combined with the preformed appliances led to a statistically significant lip strength increase (- 2.30, P < 0.05). Significant differences were observed in SNB and IMPA between the two groups (P < 0.05).
Orofacial myofunctional therapy effectively improved patient lip strength and was a good option for mixed dentition patients with lip incompetence. Preformed appliances could enhance the orofacial myofunctional therapy effect and result in significant improvements in lip strength and forward movement of the mandible, which can optimize the jaw relationship.

BACKGROUND: We investigated changes in the roots of maxillary incisors at different stages of root development after fixed-appliance treatment using cone-beam computed tomography.
METHODS: Data from 52 subjects receiving fixed-appliance treatment were collected retrospectively. The subjects were divided into 3 groups: mixed dentition group (aged 7-10 years; root development stage: Nolla eighth-10th; n = 16), early permanent dentition group (aged 12-18 years; root development stage: Nolla 10th; n = 20), and adult group (aged 18-35 years; root development stage: Nolla 10th; n = 16). Changes in root lengths and volume of the maxillary central incisors were measured using pretreatment and posttreatment cone-beam computed tomography.
RESULTS: The root lengths and volumes of maxillary central incisors in the mixed dentition group significantly increased after orthodontic treatment (P >0.05). No significant differences were found when comparing the final root length and volume of the mixed dentition group with the pretreatment maxillary incisor values of the early permanent dentition group (P >0.05). The early permanent dentition group showed a significant decrease in root length (P <0.05), and both the root length and volume of the adult group significantly decreased after treatment (P <0.05). The differences in root length and volume reduction between the 2 groups were not significant (P >0.05).
CONCLUSIONS: Orthodontic treatment had no significant negative impact on the continued root development of incomplete roots with two-thirds root formation. Both the early permanent dentition and adult groups exhibited root resorption after orthodontic treatment. It seemed age was not a factor that resulted in significant root resorption during routine orthodontic leveling and alignment treatment once the roots were fully developed.