Small Molecules Promote the Rapid Generation of Dental Epithelial Cells from Human-Induced Pluripotent Stem Cells.

Human-induced pluripotent stem cells (hiPSCs) offer a promising source for generating dental epithelial (DE) cells. Whereas the existing differentiation protocols were time-consuming and relied heavily on growth factors, herein, we developed a three-step protocol to convert hiPSCs into DE cells in 8 days. In the first phase, hiPSCs were differentiated into non-neural ectoderm using SU5402 (an FGF signaling inhibitor). The second phase involved differentiating non-neural ectoderm into pan-placodal ectoderm and simultaneously inducing the formation of oral ectoderm (OE) using LDN193189 (a BMP signaling inhibitor) and purmorphamine (a SHH signaling activator). In the final phase, OE cells were differentiated into DE through the application of Purmorphamine, XAV939 (a WNT signaling inhibitor), and BMP4. qRT-PCR and immunostaining were performed to examine the expression of lineage-specific markers. ARS staining was performed to evaluate the formation of the mineralization nodule. The expression of PITX2, SP6, and AMBN, the emergence of mineralization nodules, and the enhanced expression of AMBN and AMELX in spheroid culture implied the generation of DE cells. This study delineates the developmental signaling pathways and uses small molecules to streamline the induction of hiPSCs into DE cells. Our findings present a simplified and quicker method for generating DE cells, contributing valuable insights for dental regeneration and dental disease research.

Combined effect of dietary calcium consumption and physical activity on dental caries in children and adolescents: a study of the NHANES database.

BACKGROUND: Calcium (Ca) is a nutritional factor that associated with dental caries. A recent study showed that in the case of adequate Ca intake, a higher level of physical activity may contribute to bone mass accumulation. However, the combined effect between Ca intake and physical activity on caries experience is unclear. Herein, we aimed to explore the above combined effect on dental caries in children and adolescents. METHODS: Data of 5,917 children and adolescents were extracted from the National Health and Nutrition Examination Surveys (NHANES) database in 2015-2020 in this cross-sectional study. The NHANES assessed the dietary Ca intake through the 24-hour dietary recalls, and the physical activity level was self-reported using the questionnaires. Also, the dental caries was diagnosed according to the Decayed, Missing and Filled Teeth/Surfaces (DMFT/S) index. Weighted univariate and multivariate logistic regression analyses were utilized to screen the covariates and to investigate the associations of dietary Ca intake and physical activity with dental caries, respectively, and assess the combined effect between dietary Ca intake and physical activity on dental caries. The evaluation indexes were odd ratios (ORs) and 95% confidence intervals (CIs). Subgroup analyses of age, obesity, and total sugar intake were also performed. RESULTS: Among the eligible participants, 2,687 had caries experience. After adjusting for the covariates, we found that children and adolescents who not reach the recommendation level of Ca intake combined with physical activity less than 7 time in 1 week seemed to have higher odds of dental caries [OR = 1.77, 95%CI: (1.38-2.27)], compared with those who reached the standards. In addition, this potential combined effect was also found in age < 12 years old [OR = 1.62, 95%CI: (1.23-2.14)], non-obesity [OR = 1.88, 95%CI: (1.49-2.35)], and total sugar intake (all P < 0.05) subgroups. CONCLUSIONS: Ca intake and physical activity had a potential combined effect on dental caries in children and adolescents, but the causal relationships between them needed further clarification.

Investigation of transient machining in the cortical bone drilling process by conventional and axial vibration-assisted drilling methods.

A temperature exceeding the safety threshold and excessive drilling force occurring during bone drilling may lead to irreversible damage to bone tissue and postoperative complications. Previous studies have shown that vibration-assisted drilling methods could have lower temperatures and drilling forces than those of the conventional drilling method; we hypothesized that the main reason for these reductions stems from the differences in the transient machining processes between conventional and vibration-assisted drilling methods. To investigate these differences, comparative experiments and two-dimensional finite element models were performed and developed. The differences in the transient machining processes were verified by experimentation and clearly exhibited by the finite element models. Compared with the steady cutting process that produced continuous-spiral chips in the conventional drilling method, transient machining in the low-frequency vibration-assisted drilling method was a periodically dynamic cutting-separation process that produced uniform petal chips with specific settings of drilling and vibration parameters. Moreover, the transient machining process in the ultrasonic vibration-assisted drilling method was transformed into a combined action with high-speed impact and negative rake angle cutting processes; this action produced a large proportion of powdery chips. Therefore, it could be concluded that the superposed axial vibration significantly changed the transient machining process and radically changed the mechanical state and thermal environment; these changes were the main reason for the apparent differences in the drilling performance levels.

Analysis of machining process and thermal conditions during vibration-assisted cortical bone drilling based on generated bone chip morphologies.

When the temperature during bone drilling exceeds the safety threshold, the bone tissue surrounding the drilling site can be irreversibly damaged. To investigate the influence of vibration-assisted drilling (VAD) methods on the temperature increase during bone drilling and the causes for temperature increase, drilling experiments were performed on fresh bovine femur samples. The morphology and granularity distribution of the generated bone chips were innovatively used to directly compare the machining processes and thermal conditions of conventional drilling (CD), low-frequency vibration-assisted drilling (LFVAD), and ultrasonic vibration-assisted drilling (UVAD). The experimental results indicated that LFVAD produced the lowest temperature increase of 31.4°C, whereas UVAD produced the highest temperature increase of 44.1°C with the same drilling parameters. Additionally, the morphologies and granularity distributions of the bone chips significantly differed among these methods. We concluded that the smaller temperature increase in LFVAD was mainly attributed to the improved thermal conditions resulting from the periodic cutting/separation motion and the reliable geometric chip-breaking mechanism. In contrast, the unfavourable thermal conditions of UVAD were caused by the higher applied frequency, which created a significantly larger amount of friction heat. This was the main cause for the highest observed temperature increase, resulting in bone crushing processes that generated additional heat.

Experimental investigation of the temperature elevation in bone drilling using conventional and vibration-assisted methods.

Bone drilling is widely used in orthopaedics for inserting screws and fixing prostheses. Thermal necrosis is one of the major problems that may seriously affect post-operative recovery. Accordingly, this paper mainly focuses on comparing the influences of conventional drilling (CD), ultrasonic vibration-assisted drilling (UVAD) and low-frequency vibration-assisted drilling (LFVAD) methods, and drilling parameters on the temperature elevation in bone drilling process. A full factorial experiment was performed, and the temperatures were measured using an infrared camera. The lowest temperature elevation was obtained by LFVAD compared with CD and UVAD at the same drilling conditions. Setting CD as a reference, the maximum difference between LFVAD and CD was approximately -4 °C, whereas that between UVAD and CD was approximately 16 °C. The temperature elevation increases linearly with the spindle speed and follows an inverted U-shaped curve, with the feed rate having a peak at 40 min/mm in each drilling method. The results were discussed with regard to the features of LFVAD and UVAD. It was expected that the LFVAD could achieve minimal thermal damage and attain better results in the medical bone drilling process.

Morphometry research of deer, sheep, and human lumbar spine: feasibility of using deerand sheep in spinal animal models / Investigación morfometríca de la columna vertebral lumbar de ciervos, ovejas y humanos: factibilidad del uso de ciervos y ovejas como modelos animales de columna vertebral

Deer and sheep are used as spinal animal models in clinical and basic research. In this paper, the anatomical morphology, curvature, and morphology index parameters were investigated to assess the feasibility of using deer and sheep as animal models of the human spine. Fresh adult male sheep, deer, and human spine specimens (n = 10 each) were screened and subjected to morphological analyses. The statistical software package SPSS (version 17.0) was used to analyze the statistical similarity and variability among the 3 species. Deer displayed good similarity to human in terms of the vertebral transverse diameter, radius vector, spinal canal transverse diameter, radius vector, and vertebral upper and lower endplate curvature radii. Sheep displayed good similarity to human in terms of the vertebral body height, pedicle height, vertebral mid-lever curvature radius, and vertebral positive curvature radius. Human, deer, and sheep each displayed unique morphological characteristics and trends for the lumbar spine. These findings indicate that deer and sheep are good spinal animal models of human in morphometry, but with specific advantages in different research fields: deer are more suitable when studying vertebrae and endplate structures, while sheep are more suitable when referring to structures such as the vertebral walls.

Los ciervos y las ovejas se utilizan como modelos animales para la investigación clínica y básica de columna vertebral. En este trabajo, fueron investigados parámetros de morfología anatómica, curvatura e índice morfológico para evaluar la viabilidad de la utilización de ciervos y ovejas como modelos animales de la columna vertebral humana. Fueron examinados y sometidos a análisis morfológicos, especímenes frescos de columna vertebral (n = 10 cada uno) de ovejas y ciervos machos adultos, y columnas de individuos adultos humanos, de sexo masculino. Se utilizó el programa estadístico SPSS (versión 17.0) para analizar la similitud estadística y la variabilidad entre las 3 especies. Los ciervos muestran similitud con el humano en términos del diámetro vertebral transversal, vector radio, diámetro del canal espinal transversal, vector radio, y los radios de curvatura vertebral superior e inferior de la placa terminal. Las ovejas muestran similitud con el humano en cuanto a la altura del cuerpo vertebral, altura del pedículo, curvatura de radio vertebral medio, y el radio de curvatura vertebral positiva. Los humanos, ciervos y ovejas muestran características morfológicas y direcciones de la columna vertebral únicas. Estos hallazgos indican que los ciervos y las ovejas son buenos modelos animales en la morfometría de la columna vertebral humana, pero con ventajas específicas en diferentes campos de investigación: los ciervos son más adecuados en el estudio de las vértebras y las estructuras de placa terminal, mientras que las ovejas son más adecuados cuando se refiere a estructuras como las paredes vertebrales.