Research Spotlight

Li, L., W. Saiyin, H. Zhang, S. Wang, Q. Xu, C. Qin and Y. Lu (2019). “FAM20A is essential for amelogenesis, but is dispensable for dentinogenesis.” J Mol Histol Oct 30. [Epub ahead of print].

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Mutations in the gene encoding family with sequence similarity 20, member A (FAM20A) caused amelogenesis imperfecta (AI), in humans. However, the roles of FAM20A in amelogenesis and dentinogenesis are poorly understood. In this study, we generated a Fam20a knockout (Sox2-Cre;Fam20a(fl/fl)) mouse model by crossing Fam20a(fl/fl) mice with Sox2-Cre transgenic mice, in which Fam20a was ablated in both dental epithelium and dental mesenchyme. We found that these mice developed an enamel phenotype that resembles human AI associated with FAM20A mutations, but did not have apparent dentin defects. The secretory stage ameloblasts in the mandibular incisors from the Sox2-Cre;Fam20a(fl/fl) mice were shorter and detached from the enamel matrix, and subsequently lost their polarity, became disorganized and formed numerous spherical extracellular matrices in place of normal enamel. At the molecular level, the Sox2-Cre;Fam20a(fl/fl) mice displayed dramatically reduced expression levels of the genes encoding the enamel matrix proteins, but unaltered levels of the genes encoding the dentin matrix proteins. Moreover, Fam20a ablation resulted in a great decrease in FAM20C protein level, but it did not alter the intracellular localization of FAM20C protein in ameloblasts and odontoblasts. These results indicate that FAM20A is essential for amelogenesis, but is dispensable for dentinogenesis.

“Impact of HPV Immunization Training on Dental Hygiene Students’ Attitudes and Confidence Regarding HPV Preventive Education.” J Dent Educ Oct 14. pii: JDE.019.164. [Epub ahead of print].

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Human Papilloma Virus (HPV)-related oropharyngeal cancers (OPC) have increased significantly despite availability of the HPV vaccine. HPV-positive oropharyngeal cancer is becoming more prevalent than tobacco-related OPC. Dental professionals screen for OPC and risk factors, but many are not prepared to address HPV immunization and prevention with patients. The aim of this study was to implement and assess a training module on HPV to increase dental providers’ knowledge, promote confidence in their ability to provide effective prevention interventions, and instill a positive attitude about recommending HPV immunization to their patients. The study used a pretest-posttest design. Participants were dental hygiene students in one U.S. dental hygiene program in 2017. The students completed the pretest, then viewed the online training module, and completed the posttest one week later. Of the 40 students who participated in the module, 37 completed both pretest and posttest, for a response rate of 93%. From pretest to posttest, the respondents showed a significant increase (CI=0.5, p<0.001) in knowledge of HPV prevention with mean scores increasing from 8.75 to 13.32 on a 15-point scale. The students demonstrated an increase (p<0.05) in confidence and comfort in providing HPV immunization counseling on the posttest, as well as an increase (p<0.05) in positive attitudes about recommending HPV immunization. This study found that the participants' knowledge and confidence regarding HPV, HPV-related OPC, and HPV immunization increased after the module, suggesting that effective education and preparation for HPV counseling can be accomplished through modular-based education. This education would be beneficial in an institutional or professional setting.

Chen, H., J. Zhang, Y. Wang, K. Y. Cheuk, A. L. H. Hung, T. P. Lam, Y. Qiu, J. Q. Feng, W. Y. W. Lee and J. C. Y. Cheng (2019). “Abnormal lacuno-canalicular network and negative correlation between serum osteocalcin and Cobb angle indicate abnormal osteocyte function in adolescent idiopathic scoliosis.” Faseb j Oct 18:fj201901227R. [Epub ahead of print].

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Adolescent idiopathic scoliosis (AIS) is a prevalent spinal deformity occurring during peripubertal growth period that affects 1-4% of adolescents globally without clear etiopathogenetic mechanism. Low bone mineral density is an independent and significant prognostic factor for curve progression. Currently, the cause underlying low bone mass in AIS remains elusive. Osteocytes play an important role in bone metabolism and mineral homeostasis, but its role in AIS has not been studied. In the present study, iliac bone tissues were harvested from 21 patients with AIS (mean age of 14.3 +/- 2.20 yr old) with a mean Cobb angle of 55.6 degrees +/- 10.61 degrees and 13 non-AIS controls (mean age of 16.5 +/- 4.79 yr old) intraoperatively. Acid-etched scanning electron microscopy (SEM) images of AIS demonstrated abnormal osteocytes that were more rounded and cobblestone-like in shape and were aligned in irregular clusters with shorter and disorganized canaliculi. Further quantitative analysis with FITC-Imaris technique showed a significant reduction in the canalicular number and length as well as an increase in lacunar volume and area in AIS. SEM with energy-dispersive X-ray spectroscopy analysis demonstrated a lower calcium-to-phosphorus ratio at the perilacunar/canalicular region. Moreover, microindentaion results revealed lower values of Vickers hardness and elastic modulus in AIS when compared with controls. In addition, in the parallel study of 99 AIS (27 with severe Cobb angle of 65.8 degrees +/- 14.1 degrees and 72 with mild Cobb angle of 26.6 degrees +/- 9.1 degrees ) with different curve severity, the serum osteocalcin level was found to be significantly and negatively associated with the Cobb angle. In summary, the findings in this series of studies demonstrated the potential link of abnormal osteocyte lacuno-canalicular network structure and function to the observed abnormal bone mineralization in AIS, which may shed light on etiopathogenesis of AIS.

Azarpazhooh, A., A. R. Diogenes, A. F. Fouad, G. N. Glickman, M. K. Kang, A. Kishen, L. Levin, R. S. Roda, C. M. Sedgley, F. R. Tay and K. M. Hargreaves (2019). “Insights into the November 2019 Issue of the Journal of Endodontics.” J Endod 45(11): 1277-1278.

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Welcome to the November 2019 issue of the Journal of Endodontics ( JOE ). Here, we share some of our favorite articles that were published in this issue of the journal. We hope you look forward to reading these and other articles in JOE. [Excerpt from Article].

Asiri, S. N., L. P. Tadlock and P. H. Buschang (2019). “The prevalence of clinically meaningful malocclusion among US adults.” Orthod Craniofac Res 22(4): 321-328.

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OBJECTIVE: The primary purpose of this study was to statistically evaluate age, ethnic and sex differences in the prevalence of clinically meaningful malocclusions among adults. SETTING AND SAMPLE POPULATION: A random sample of 8804 untreated US adults between 17 and 46 years of age was selected from the Third National Health and Nutrition Examination Survey data. MATERIALS & METHODS: Three ethnic (non-Hispanic White, non-Hispanic Black and Mexican Americans) and three age (17-26, 27-36 and 37-46 years) groups were evaluated. Subjects with and without clinically meaningful malocclusions were categorized based on the established cut-off values. Chi-square analyses were performed to determine differences in prevalence. RESULTS: The prevalence of clinically meaningful mandibular incisor irregularity, overjet and overbite increased significantly (P < 0.05) with age, while posterior crossbite decreased. There were statistically significant ethnic differences in the prevalence of incisor irregularity, overbite, overjet, open bite and reverse overjet. Males had a significantly higher prevalence of clinically meaningful mandibular incisor irregularity, overbite, open bite and reverse overjet than females. One-third of US adults exhibited no clinically meaningful malocclusions. CONCLUSIONS: There are age, ethnic and sex differences in the prevalence of clinically meaningful malocclusions that characterize approximately two-thirds of untreated US adults.