Proteomic Analyses Discern the Developmental Inclusion of Albumin in Pig Enamel: A New Model for Human Enamel Hypomineralization

Excess albumin in enamel is a characteristic of the prevalent developmental dental defect known as chalky teeth or molar hypomineralization (MH). This study uses proteomic analyses of pig teeth to discern between developmental origin and post-eruptive contamination and to assess the similarity to hypomineralized human enamel. Here, the objective is to address the urgent need for an animal model to uncover the etiology of MH and to improve treatment. Porcine enamel is chalky and soft at eruption; yet, it hardens quickly to form a hard surface and then resembles human teeth with demarcated enamel opacities. Proteomic analyses of enamel from erupted teeth, serum, and saliva from pigs aged 4 (n = 3) and 8 weeks (n = 2) and human (n = 4) molars with demarcated enamel opacities show alpha-fetoprotein (AFP). AFP expression is limited to pre- and perinatal development and its presence in enamel indicates pre- or perinatal inclusion. In contrast, albumin is expressed after birth, indicating postnatal inclusion into enamel. Peptides were extracted from enamel and analyzed by nano-liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS) after tryptic digestion. The mean total protein number was 337 in the enamel of all teeth with 13 different unique tryptic peptides of porcine AFP in all enamel samples but none in saliva samples. Similarities in the composition, micro-hardness, and microstructure underscore the usefulness of the porcine model to uncover the MH etiology, cellular mechanisms of albumin inclusion, and treatment for demarcated opacities.

Pit-and-fissure sealants on primary molars are a cost savings

BACKGROUND

In this study, the authors examine the cost-effectiveness of light-polymerized resin-based fluoride sealants on primary molars in high caries risk children younger than 6 years.

METHODS

The authors examined the cost-effectiveness of pit-and-fissure sealant (PFS) treatment on primary molars by comparing sealed and unsealed molars treated in the outpatient clinic or operating room. Using 1,884 primary molars followed over a 5-year period, the authors used a mixed-effects regression model to estimate the probability of caries development. They used restricted means to estimate years free of caries for carious molars. They used a decision tree to address uncertainty due to PFS treatment failure, predict the expected value associated with each strategy, and estimate the incremental cost-effectiveness ratio using a 3% discount rate to adjust future cost and outcomes to present value.

RESULTS

Over 5 years, the cost of care was $90 for unsealed molars and $75 for sealed molars. Unsealed molars remained caries free for 4.32 years compared with 4.85 years in sealed molars. The cost-effectiveness of PFS treatment was dominant, leading to a savings of $25 for each caries-free year gained and overall savings of $742 million for the United States dental health system over a 5-year period.

CONCLUSIONS

PFS treatment is associated with cost savings and a delay in caries development and should be considered in children with high caries risk.

PRACTICAL IMPLICATIONS

Policy makers should consider reimbursement of PFS treatment on primary molars in high caries risk children.

Use of Silver Diamine Fluoride for Dental Caries Management in Children and Adolescents, Including Those with Special Health Care Needs

BACKGROUND

This manuscript presents evidence-based guidance on the use of 38 percent silver diamine fluoride (SDF) for dental caries management in children and adolescents, including those with special health care needs. A guideline workgroup formed by the American Academy of Pediatric Dentistry developed guidance and an evidence-based recommendation regarding the application of 38 percent SDF to arrest cavitated caries lesions in primary teeth.

TYPES OF STUDIES REVIEWED

The basis of the guideline's recommendation is evidence from an existing systematic review "Clinical trials of silver diamine fluoride in arresting caries among children: A systematic review." (JDR Clin Transl Res 2016;1[3]:201-10). A systematic search was conducted in PubMed®/MEDLINE, Embase®, Cochrane Central Register of Controlled Trials, and gray literature databases to identify randomized controlled trials and systematic reviews reporting on the effect of silver diamine fluoride and address peripheral issues such as adverse effects and cost. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was used to assess the quality of the evidence and the evidence-to-decision framework was employed to formulate a recommendation.

RESULTS

The panel made a conditional recommendation regarding the use of 38 percent SDF for the arrest of cavitated caries lesions in primary teeth as part of a comprehensive caries management program. After taking into consideration the low cost of the treatment and the disease burden of caries, panel members were confident that the benefits of SDF application in the target populations outweigh its possible undesirable effects. Per GRADE, this is a conditional recommendation based on low-quality evidence. Conclusions and practical implications: The guideline intends to inform the clinical practices involving the application of 38 percent SDF to enhance dental caries management outcomes in children and adolescents, including those with special health care needs. These recommended practices are based upon the best available evidence to-date. A 38 percent SDF protocol is included in Appendix II.

The collection of NFATc1-dependent transcripts in the osteoclast includes numerous genes non-essential to physiologic bone resorption

Osteoclasts are specialized secretory cells of the myeloid lineage important for normal skeletal homeostasis as well as pathologic conditions of bone including osteoporosis, inflammatory arthritis and cancer metastasis. Differentiation of these multinucleated giant cells from precursors is controlled by the cytokine RANKL, which through its receptor RANK initiates a signaling cascade culminating in the activation of transcriptional regulators which induce the expression of the bone degradation machinery. The transcription factor nuclear factor of activated T-cells c1 (NFATc1) is the master regulator of this process and in its absence osteoclast differentiation is aborted both in vitro and in vivo. Differential mRNA expression analysis by microarray is used to identify genes of potential physiologic relevance across nearly all biologic systems. We compared the gene expression profile of murine wild-type and NFATc1-deficient osteoclast precursors stimulated with RANKL and identified that the majority of the known genes important for osteoclastic bone resorption require NFATc1 for induction. Here, five novel RANKL-induced, NFATc1-dependent transcripts in the osteoclast are described: Nhedc2, Rhoc, Serpind1, Adcy3 and Rab38. Despite reasonable hypotheses for the importance of these molecules in the bone resorption pathway and their dramatic induction during differentiation, the analysis of mice with mutations in these genes failed to reveal a function in osteoclast biology. Compared to littermate controls, none of these mutants demonstrated a skeletal phenotype in vivo or alterations in osteoclast differentiation or function in vitro. These data highlight the need for rigorous validation studies to complement expression profiling results before functional importance can be assigned to highly regulated genes in any biologic process.

NFATc1 in mice represses osteoprotegerin during osteoclastogenesis and dissociates systemic osteopenia from inflammation in cherubism

Osteoporosis results from an imbalance in skeletal remodeling that favors bone resorption over bone formation. Bone matrix is degraded by osteoclasts, which differentiate from myeloid precursors in response to the cytokine RANKL. To gain insight into the transcriptional regulation of bone resorption during growth and disease, we generated a conditional knockout of the transcription factor nuclear factor of activated T cells c1 (Nfatc1). Deletion of Nfatc1 in young mice resulted in osteopetrosis and inhibition of osteoclastogenesis in vivo and in vitro. Transcriptional profiling revealed NFATc1 as a master regulator of the osteoclast transcriptome, promoting the expression of numerous genes needed for bone resorption. In addition, NFATc1 directly repressed osteoclast progenitor expression of osteoprotegerin, a decoy receptor for RANKL previously thought to be an osteoblast-derived inhibitor of bone resorption. "Cherubism mice", which carry a gain-of-function mutation in SH3-domain binding protein 2 (Sh3bp2), develop osteoporosis and widespread inflammation dependent on the proinflammatory cytokine, TNF-alpha. Interestingly, deletion of Nfatc1 protected cherubism mice from systemic bone loss but did not inhibit inflammation. Taken together, our study demonstrates that NFATc1 is required for remodeling of the growing and adult skeleton and suggests that NFATc1 may be an effective therapeutic target for osteoporosis associated with inflammatory states.