American Journal of Orthodontics and Dentofacial Orthopedics最新文献

Introduction: Adult orthodontic patients are often exposed to various stressors, which can affect orthodontic treatment. Therefore, this study investigated the effects of chronic restraint stress on orthodontic tooth movement and alveolar bone remodeling in vivo.

Methods: Ten 8-week-old male Wistar rats were randomly divided into sham-stress orthodontic (CO) and stress orthodontic (SO) groups. Restraint stress was applied for 21 days. The orthodontic intervention involved mesial traction of the maxillary first molar from days 8 to 21. Serum inflammatory cytokine levels were measured, and micro-computed tomography scanning was performed to analyze tooth movement and alveolar bone parameters of the first molar. Osteogenic and osteoclastic activities and macrophage polarization in periodontal tissues were assessed by histological and immunohistochemical staining.

Results: Tooth movement was significantly greater in the SO group than in the CO group, as were the serum interleukin-1β and -10 levels. The SO group had increased trabecular spacing, reduced bone density, and wider periodontal ligament spaces on the force-applied side of the alveolar bone. Enhanced osteogenic and osteoclastic activities were observed in both groups under orthodontic force, but significantly more osteoclasts were observed in the SO group than in the CO group. The inducible nitric oxide synthase to arginase 1 expression ratio was also significantly higher in the SO group than in the CO group.

Conclusions: Restraint stress may exacerbate orthodontic tooth movement and alveolar bone resorption, potentially mediated by systemic inflammatory responses, as well as enhance classically activated macrophage polarization in the alveolar bone.

Introduction: This study aimed to compare the 3-dimensional (3D) variability of mandibular morphology across different age groups and skeletal classes.

Methods: A retrospective analysis was conducted on cone-beam computed tomography scans from 282 patients aged 9-50 years. The participants were stratified into 6 age groups using random stratified sampling: group (G)1 (n = 51), G2 (n = 51), G3 (n = 52), G4 (n = 56), G5 (n = 41), and G6 (n = 31). Each patient was categorized according to the skeletal classification (I, II, and III). The 3D mandibular models were created using specialized software, with 32 anatomic landmarks placed on each model. Landmark configurations were aligned through generalized Procrustes analysis. Shape variation was evaluated using principal component analysis, permutational multivariate analysis of variance, and canonical variate analysis, followed by pairwise comparisons.

Results: Significant differences in mandibular shape were found among age groups, especially in younger patients, whereas skeletal class showed no significant effect. The most notable differences were observed in canonical variables 1 and 2, particularly between younger groups (G1 and G2) and older groups (P <0.001). These differences involved changes in the basal mandibular contour, bicondylar width, and bigonial width. Skeletal class had no significant impact on mandibular morphology.

Conclusions: The 3D modeling revealed significant age-related changes in mandibular basal contour, transverse expansion, chin projection, ramus height and thickness, gonial angle, and anterior body curvature. This highlights the value of 3D models for precise analysis of changes in mandibular shape across ages.

Introduction: Cleidocranial dysplasia (CCD) often results in supernumerary teeth, impacted teeth, and malocclusions. Treatment options include orthodontics to erupt the impacted dentition in the oral cavity or prosthodontic replacement of impacted teeth. This study assesses whether patients with CCD who have certain malocclusion traits have worse oral health-related quality of life (OHRQoL) than those without these malocclusions, and whether patients with CCD who received orthodontic treatment have better OHRQoL than those treated with prosthodontics.

Methods: Patients with CCD aged 15 years and older underwent an oral examination and completed the oral health impact profile-14 survey. Independent-samples t tests were performed to compare the oral health impact profile-14 scores among patients with and without specific oral findings.

Results: Sixty-one patients participated in this study. Those with posterior crossbites experienced significantly worse OHRQoL in the domain of physical pain (P = 0.015; 95% confidence interval [CI] = 0.316-2.750). For those with anterior open bites, a significantly worse OHRQoL was observed in the domain of handicap (P = 0.046; 95% CI, 0.027-2.919). Anterior crossbites resulted in statistically significantly worse OHRQoL in the functional limitation domain (P = 0.027; 95% CI, 0.149-2.373). Lastly, patients who received prosthodontic treatment reported significantly worse OHRQoL (P = 0.037; 95% CI, 0.685-21.015) and higher scores in physical pain (P = 0.038; 95% CI, 0.114-3.981), physical disability (P = 0.005; 95% CI, 0.872-4.543), and social disability (P = 0.020; 95% CI, 0.091-3.398).

Conclusions: Patients with CCD who have anterior crossbites, posterior crossbites, or anterior open bites have worse OHRQoL in specific domains compared with those without these malocclusions. In addition, patients who underwent prosthodontics had worse OHRQoL than those who underwent orthodontics.

Introduction: This study develops a finite element analysis method to define the 3-dimensional (3D) zone of center of resistance (ZCR) position for maxillary central incisors and first molars and validates its applicability under different alveolar bone levels.

Methods: Cone-beam computed tomography scans from 40 patients were grouped: group 1 (maxillary central incisors, no bone loss), group 2 (maxillary central incisors, bone loss), group 3 (maxillary first molars, no bone loss), and group 4 (maxillary first molars, bone loss). The 3D models of teeth, a simulated 0.2-mm-thick PDL, and alveolar bone were reconstructed using Mimics software (Materialise, Leuven, Belgium) and imported into ANSYS Workbench (ANSYS Inc, Canonsburg, Pa) to calculate the tooth axis of rotation (resistance axis). A 5-step method defined the ZCR: (1) set the crown center as origin, (2) apply pure 3 N·mm couples at the crown center along the x-, y-, and z-axes, (3) find the resistance axes using displacement data, (4) use an algorithm to find best point filtering (1%-3%) where axes meet; fit a sphere to these points to get the ZCR center and radius, and (5) verify the accuracy by measuring rotation angles after applying forces at the center of the ZCR, and the 1 and 2 times radius in the 3 directions.

Results: Optimal filtering percentages averaged 2.23% (group 1), 2.10% (group 2), 1.33% (group 3), and 1.63% (group 4). Alveolar resorption reduced the ZCR height. The central incisors decreased from 59.17% (standard deviation [SD]: 1.01) to 45.19% (SD: 1.61), whereas first molars decreased from 53.76% (SD: 3.03) to 46.76% (SD: 2.02) of root length. The ZCR radius decreased with alveolar bone loss-central incisors (from 0.55 to 0.49 mm) and first molars (from 0.58 to 0.48 mm). Forces applied at the center of the ZCR minimized rotation angles (x/y-axis: 0.12°; z-axis: 0.09°). Rotation increased significantly when forces were applied beyond the sphere, reaching 1.92° at twice the radius.

Conclusions: The finite element analysis method accurately and efficiently defined the 3D ZCR position and extent in central incisors and first molars. Alveolar bone loss induced apical displacement and a reduction in the ZCR extent.

Introduction: This study aimed to evaluate and compare the palatal dimensional and morphologic characteristics (symmetry or asymmetry) before and after the treatment of functional posterior crossbite (FPXB) in mixed and permanent dentition.

Methods: Forty-four patients with a diagnosis of transverse maxillary deficiency and FPXB underwent maxillary expansion: 22 in mixed dentition (mixed dentition study group [MD-SG], mean age = 8.6 ± 1.3 years) and 22 in permanent dentition (permanent dentition study group [PD-SG], mean age = 13.3 ± 1.1 years). Two age-matched control groups (mixed dentition control group and permanent dentition control group) were included. Digital models at T0 (baseline) and T1 (12-18 months postexpansion) were analyzed for palatal dimensions, volume, and symmetry. Deviation analysis and percentage matching were performed between the original and the mirrored models. Statistical analyses assessed intragroup, intergroup, and intertiming differences.

Results: At T0, linear and volumetric measurements were greater at the noncrossbite side (nCBs) than the crossbite side (CBs) in patients with FPXB compared with controls (P <0.001). The CBs/nCBs volumetric difference was greater in PD-SG than MD-SG (P = 0.001), whereas surface matching was higher in MD-SG (P = 0.004). At T1, CBs/nCBs dimensional asymmetry decreased in both FPXB groups (P <0.001), and the surface matching improved (P <0.001). However, MD-SG remarkably showed greater posttreatment changes than PD-SG (volumetric data: P = 0.012; surface data: P = 0.009).

Conclusions: Patients with FPXB in permanent dentition could exhibit greater maxillary asymmetry than in mixed dentition. After reestablishment of normal occlusion, the asymmetry reduced in both MD-SG and PD-SG, though the latter group retained more residual asymmetry, potentially affecting final maxillary morphology.

Introduction: The purpose of this study was to quantitatively evaluate the infrazygomatic bone parameters (buccal bone thickness and buccal bone height) for miniscrew placement. An additional aim was to compare and contrast the infrazygomatic bone parameters in growing and nongrowing males and females with hyperdivergent, normodivergent, and hypodivergent skeletal patterns.

Methods: Cone-beam computed tomography scans were obtained from 718 deidentified orthodontic patients and categorized by growth status (growing and nongrowing), sex (male and female), and skeletal pattern (hyperdivergent, hypodivergent, and normodivergent). Buccal bone thickness and buccal bone height were measured at 3 locations: 2P-1M (between the maxillary second premolar and first molar), 1M (between the mesial and distal roots of the maxillary first molar), and 1M-2M (between the maxillary first and second molars) and at 3 levels above base plane (BP): 5BP, 8BP, and 11BP, which were 5, 8, and 11 mm above the alveolar crest, respectively.

Results: Males had significantly greater buccal bone thickness than females at 5BP and 8BP (P <0.05). Males also had greater buccal bone height than females at the 1M-2M location. Buccal bone thickness increased, and buccal bone height decreased significantly as it moved posteriorly from the 2P-1M location to the 1M-2M location. Buccal bone thickness was higher in growing females and males than in nongrowing females and males. Multiple linear regression demonstrated a significant relationship between buccal bone thickness and the prediction variables: skeletal pattern and sex. Buccal bone thickness was greater in the hypodivergent skeletal pattern than in the hyperdivergent skeletal pattern at the level of 8BP in the location of 2P-1M and at the level of 11BP in the locations of 2P-1M and 1M. Buccal bone height was greater in the hyperdivergent skeletal pattern at the 2P-1M and 1M locations than in the hypodivergent and normodivergent skeletal patterns.

Conclusions: Because of adequate buccal bone thickness and acceptable buccal bone height, the 1M-2M location was considered the optimal insertion site for the placement of infrazygomatic miniscrews. Patients with a hyperdivergent skeletal pattern showed reduced buccal bone thickness and increased buccal bone height. Buccal bone thickness was significantly greater in males than in females in all skeletal patterns.

Introduction: This study evaluated how clinical use affects the surface properties and cytocompatibility of 3-dimensional (3D)-printed clear aligners by comparing them against saliva-unexposed and artificial saliva-exposed groups.

Methods: Eleven aligners were collected from 5 adult patients after 10 days of use (clinically used group). Two additional groups were established: the saliva-unexposed group (immediately after postprocessing) and the artificial saliva-exposed group (immersed in artificial saliva). All aligners underwent extraction for 1 day (day-1 extraction) and an additional 6 days (day-7 extraction). After 7 days of extraction, surface properties, including hardness (Shore D) and topography (scanning electron microscope imaging), were analyzed. Cytotoxicity to normal L929 cells was evaluated using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assays. Proinflammatory responses in lipopolysaccharide (LPS)-induced presensitized L929 cells were assessed by quantitative polymerase chain reaction, measuring interleukin-6, tumor necrosis factor-α, and nitric oxide synthase 2 expression levels.

Results: Shore D hardness did not differ among groups. Scanning electron microscope imaging revealed increased surface irregularities after salivary exposure. All groups exhibited no cytotoxicity (>70% viability) in both day-1 and day-7 extractions, with the clinically used group showing significantly higher cell viability than the saliva-unexposed group in both extractions (P <0.001). However, when LPS-induced presensitized cells were treated with day-7 extraction, only the clinically used group showed a significant increase in both interleukin-6 and tumor necrosis factor-α expression compared with LPS-only-treated cells (P <0.001).

Conclusions: Saliva-exposed 3D-printed aligners exhibited increased surface irregularities and lower cytotoxicity compared with unexposed aligners. However, clinically used 3D-printed aligners may exacerbate proinflammatory responses in presensitized cells. Depending on the initial state of the cells, cytological responses to 3D-printed aligners may vary.

Introduction: Orthodontically induced root resorption (OIRR) is a frequent yet poorly understood complication of orthodontic treatment. Emerging evidence links oxidative stress to mechanical loading. However, the regulation of redox homeostasis in periodontal tissues under varying force magnitudes remains unclear. Nuclear factor erythroid 2-related factor 2 (Nrf2), a master regulator of antioxidant defense, modulates inflammation and bone remodeling, but its force-dependent role in OIRR is undefined.

Methods: Periodontal ligament fibroblasts were subjected to graded compressive forces (0-2 g/cm²) in vitro to assess Nrf2/kelch-like ECH-associated protein 1 (Keap1)/sequestosome 1 (p62) pathway activation and downstream inflammatory and osteoclastic responses. Genetic and pharmacologic modulation of Nrf2 signaling was performed. In vivo, a murine orthodontic tooth movement model applying light (10 g) and heavy (40 g) forces was used to evaluate Nrf2 function in periodontal remodeling and root resorption.

Results: Nrf2 displayed threshold-dependent regulation. Moderate force (≤1.5 g/cm²) activated the Nrf2/HO-1 pathway, preserving redox balance and limiting inflammation, whereas excessive force (2 g/cm²) led to Nrf2 saturation, resulting in ROS accumulation, amplified inflammation, and enhanced osteoclastogenesis. Keap1 knockdown restored antioxidant capacity and reduced inflammation, whereas p62 knockdown impaired Nrf2 activation and aggravated tissue injury. In vivo, heavy force induced sustained interleukin-1β expression and severe root resorption, intensified by Nrf2 inhibition.

Conclusions: Force-dependent saturation of the Nrf2/Keap1/p62 pathway acts as a molecular switch linking oxidative stress and inflammation in OIRR. Nrf2 serves as a mechanosensitive regulator of periodontal homeostasis and a potential therapeutic target to prevent root resorption.

Introduction: The objective of the present study was to compare the optical properties and color stability of direct 3-dimensional (3D)-printed and thermoformed clear aligners, after intraoral wear.

Methods: Twenty-four participants with mild crowding (<5 mm) were randomly allocated into 2 groups (group 1: 3D-printed aligner, TC85; group 2: thermoformed aligner, polyethylene terephthalate glycol). Optical properties (transmittance and absorbance) and color stability (ΔE) were evaluated at baseline (T1) and after 14 days of intraoral wear (T2) using a spectrophotometer and VITA Easyshade V. Intragroup and intergroup comparisons were performed using t test (P <0.05).

Results: At T1, 3D-printed aligners showed significantly higher absorbance (maxillary: 1.50 ± 0.76, P = 0.006; mandibular: 1.52 ± 0.52, P = 0.024) and less transmittance (maxillary: 5.71 ± 3.8; mandibular: 4.37 ± 2.24) than thermoformed aligners (absorbance: maxillary, 0.83 ± 0.24; mandibular, 0.76 ± 0.18; transmittance: maxillary, 17.63 ± 11.44; mandibular, 18.81 ± 7.97). At T2, significant increase in absorbance (group 1: maxillary, 0.47 ± 0.46; mandibular, 0.37 ± 0.47 [P = 0.001]; group 2: maxillary, 0.24 ± 0.18; mandibular, 0.23 ± 0.13 [P = 0.001]) and decrease in transmittance (group 1: maxillary, -0.66 ± 5.54; mandibular: -1.59 ± 1.62 [P = 0.001]; group 2: maxillary, -8.39 ± 9.94; mandibular, -7.17 ± 6.62 [P = 0.001]) was noted in both groups. The difference was significantly greater for 3D printed aligners (P <0.05). Thermoformed aligners showed better color stability (ΔE <3.7), though the difference was not statistically significant (P >0.05).

Conclusions: The 3D-printed aligners exhibited higher absorbance, lower transmittance, and more color change compared with the thermoformed aligner.

Introduction: The combination of mechanical and chemical cleaning methods is an effective way to remove biofilms from retainers. This study aimed to evaluate the effectiveness of household ultrasonic cleaning with chlorhexidine (CHX) in reducing microbial contamination on Essix ACE orthodontic retainers; in addition, its effects on color stability, surface roughness, and microhardness were examined.

Methods: This prospective crossover study comprised 11 orthodontic patients (3 males and 8 females), each of whom sequentially wore 4 maxillary Essix ACE retainers, with each retainer subjected to a different cleaning method: brushing with fluoride toothpaste, brushing with 1% CHX gluconate, ultrasonic cleaning with 0.12% CHX mouthwash, and ultrasonic cleaning with water. Each method was used at night for 14 days, with a new retainer introduced at each phase. Microbial contamination was assessed using ATP bioluminescence and expressed in relative light units. The properties of the retainers were evaluated by measuring the color change, surface roughness, and microhardness. Data were analyzed using the Friedman test followed by Dunn's post-hoc analysis with Bonferroni adjustment.

Results: Ultrasonic cleaning with CHX mouthwash exhibited the lowest microbial contamination, followed by brushing with CHX, brushing with toothpaste, and ultrasonic cleaning with water. Significant differences were observed among the methods (P <0.001): ultrasonic cleaning using water differed from all others, whereas brushing with toothpaste differed from ultrasonic cleaning with CHX. No significant differences were observed in color change, surface roughness, or microhardness across all methods (P >0.05).

Conclusions: This study is the first to demonstrate that using household ultrasonic cleaning with CHX mouthwash is effective for maintaining Essix retainer hygiene without compromising the properties of the material.