American Journal of Orthodontics and Dentofacial Orthopedics最新文献

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 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.

Introduction: Orthodontic tooth movement occurs within a functional craniofacial complex that includes the masticatory muscles. Clear aligners cover the dental occlusion and may alter muscle function and patient perception. This study evaluated changes in masticatory muscle activity with aligner use and the associated impact on oral health-related quality of life.

Methods: Twenty-four adult patients (5 males and 19 females; mean age 38.2 ± 13.4 years) undergoing clear aligner treatment were assessed in a cross-sectional study. Surface electromyography (EMG) of the masseter and anterior temporalis muscles was recorded under 2 conditions: with and without the aligners in place. EMG indexes of overall muscle effort (impact) and intensity were analyzed, along with the distribution of bite forces among the 4 muscles. Each patient's EMG signals were normalized against a maximal clench on cotton rolls. Participants also completed the 14-item Oral Health Impact Profile questionnaire. Paired statistical comparisons, correlation analyses, and 1-sample tests for muscle balance were performed (α = 0.05).

Results: Aligner use was associated with a significant increase in EMG activity. The impact index was 27.6% higher with aligners than without (P <0.001), and the EMG intensity was modestly but significantly elevated with aligners (4.1%, P = 0.007). Aligner wear produced a more balanced distribution of muscle activity: with aligners, no significant deviation from an equal 25% contribution per muscle was observed, whereas without aligners, the muscle contributions were uneven (P <0.001 for imbalance in each muscle). The 14-item Oral Health Impact Profile scores were low (median 4.5 on a 0-56 scale) and did not correlate with muscle activity (P = 0.806). No significant differences in muscle indexes were found between sexes, and longer duration of aligner use showed no significant correlation with muscle activity levels.

Conclusions: Aligners tended to distribute occlusal forces more evenly across muscles, potentially reducing localized overload. These findings suggest that clinicians should anticipate a period of adaptation in which masticatory muscles respond to the altered occlusion.