Mutations in C4orf26, encoding a peptide with in vitro hydroxyapatite crystal nucleation and growth activity, cause amelogenesis imperfecta.

Autozygosity mapping and clonal sequencing of an Omani family identified mutations in the uncharacterized gene, C4orf26, as a cause of recessive hypomineralized amelogenesis imperfecta (AI), a disease in which the formation of tooth enamel fails. Screening of a panel of 57 autosomal-recessive AI-affected families identified eight further families with loss-of-function mutations in C4orf26. C4orf26 encodes a putative extracellular matrix acidic phosphoprotein expressed in the enamel organ. A mineral nucleation assay showed that the protein's phosphorylated C terminus has the capacity to promote nucleation of hydroxyapatite, suggesting a possible function in enamel mineralization during amelogenesis.

The role of amelogenin during enamel-crystallite growth and organization in vivo.

Amelogenin is critical for enamel formation, and human amelogenin gene (AMELX) mutations cause hypoplastic and/or hypomaturation enamel phenotypes. The Amelx null (AKO) mouse has a severe hypoplastic phenotype. This study evaluated the effect of amelogenin loss on enamel formation and crystallite morphology. Enamel from AKO and wild-type (WT) mice was used. The AKO mice were mated with transgenic mice expressing the most abundant known amelogenin isoform, TgM180-87, to rescue (KOM180-87) the enamel crystallite phenotype. Molar enamel was embedded, sectioned with a diamond microtome, and images were obtained by transmission electron microscopy. The crystallite sizes from multiple sections were measured using Image J. The mean thicknesses (WT = 26 nm, AKO = 16 nm, and KOM180-87 = 25 nm) and the mean widths (WT = 96 nm, AKO = 59 nm, KOM180-87 = 85 nm) of crystallites were measured. Despite a complete loss of amelogenin in AKO mice, a mineralized enamel layer with well-defined and organized crystallites is formed. In the absence of amelogenin, enamel crystallites were reduced in thickness and width. For the first time we show that introduction of the m180 amelogenin isoform into the AKO mouse through cross-breeding rescues the crystallite phenotype. We conclude that amelogenin is essential for the development of normal crystallite size.

Influences on dentists' adoption of nonsurgical caries management techniques: A qualitative study.

BACKGROUND: Nonsurgical caries management techniques (NSCMT) offer a simple, conservative approach to treating caries. Despite evidence supporting and potential advantages of NSCMT, dentists can be reluctant to adopt these techniques. To better understand this phenomenon, the authors interviewed dentists who primarily treat children regarding their thoughts, attitudes, and adoption of 3 NSCMT. METHODS: The 3 NSCMT were fluoride varnish, silver diamine fluoride, and Hall stainless steel crowns. The authors interviewed dentists in North Carolina whose practices were restricted mostly to children. A nonprobabilistic maximum-variation design was used in the sampling. Using a semistructured interview guide, the authors recorded the interviews digitally and analyzed them thematically. The authors stratified the analysis according to years of practice, geographic location, and type of practice. Reporting was based on emerging and recurring themes and insightful quotes. RESULTS: Factors most likely to promote the adoption of NSCMT were related to clinical practice, family preference, patient safety, and provider philosophy. Barriers to adoption included previous practitioner negative experiences using the techniques, high-risk caries population, and perceived likelihood of negative outcomes. Characteristics of the practice environment, patient population, communication with families, and financial considerations were influential in the clinician's determination as to whether to use these techniques. CONCLUSIONS: These findings provide valuable insight into practitioners' influences, motivations, and clinical decision making in the adoption and use of management and treatment approaches for carious lesions in the pediatric population. PRACTICE IMPLICATIONS: The primary factors and barriers identified in this study are possible targets for education and quality improvement programs aimed at increasing NSCMT use.