Christopher L.B. Lavelle

Review of vitamin D deficiency during pregnancy: who is affected?

Abstract Objectives. Vitamin D deficiencies have been documented in several populations, including aboriginal Canadians from isolated northern communities. Such deficiencies can impact the health of both the mother and her infant. This review was performed to determine how widespread vitamin D deficiency is during pregnancy. Study design. Electronic literature search. Methods. A Medline search was conducted using the Mesh terms “pregnancy” and “vitamin D”. Those studies meeting the inclusion criteria were reviewed. Results. 35 of 76 studies reported deficient mean, or median, concentrations of 25(OH)D. Low concentrations were reported among different ethnic groups around the world. In addition, deficient concentrations were identified in 3 northern First Nations communities in Manitoba. Conclusions. Such deficiencies are of concern, as the developing fetus acquires its 25(OH)D across the placenta and may influence infant health. Future research is required to resolve the discourse surrounding ambiguous threshold values for vitamin D deficiencies and insufficiencies and to identify effective strategies to improve the vitamin D status of expectant women. Vitamin D supplementation may be necessary for many women during pregnancy, especially those in northern regions where endogenous synthesis may be constrained. (Int J Circumpolar Health 2005; 64(2):112–120)

Prenatal Vitamin D and Dental Caries in Infants

OBJECTIVES: Inadequate maternal vitamin D (assessed by using 25-hydroxyvitamin D [25OHD]) levels during pregnancy may affect tooth calcification, predisposing enamel hypoplasia and early childhood caries (ECC). The purpose of this study was to determine the relationship between prenatal 25OHD concentrations and dental caries among offspring during the first year of life. METHODS: This prospective cohort study recruited expectant mothers from an economically disadvantaged urban area. A prenatal questionnaire was completed and serum sample drawn for 25OHD. Dental examinations were completed at 1 year of age while the parent/caregiver completed a questionnaire. The examiner was blinded to mothers’ 25OHD levels. A P value ≤ .05 was considered significant. RESULTS: Overall, 207 women were enrolled (mean age: 19 ± 5 years). The mean 25OHD level was 48 ± 24 nmol/L, and 33% had deficient levels. Enamel hypoplasia was identified in 22% of infants; 23% had cavitated ECC, and 36% had ECC when white spot lesions were included in the assessment. Mothers of children with ECC had significantly lower 25OHD levels than those whose children were caries-free (41 ± 20 vs 52 ± 27 nmol/L; P = .05). Univariate Poisson regression analysis for the amount of untreated decay revealed an inverse relationship with maternal 25OHD. Logistic regression revealed that enamel hypoplasia (P < .001), infant age (P = .002), and lower prenatal 25OHD levels (P = .02) were significantly associated with ECC. CONCLUSIONS: This study found that maternal prenatal 25OHD levels may have an influence on the primary dentition and the development of ECC.

Study of tooth emergence in British blacks and whites.

The timing of tooth emergence into the oral cavity is frequently used in the assessment of dental age. There is controversy, however, relating to the criteria to be used in the assessment of tooth emergence since this comprises but one phase in the process of tooth eruption which spans from the completion of crown formation until the tooth attains its occlusal location. As a result, it is difficult to compare the data from different workers. This study was undertaken to compare the timinig of tooth emergence between two ethnic groups derived from the same socioeconomic group and living under similar environmental conditions. This was a cross-sectional study based on equal samples of 1,800 British white and black males. Withini each sample there were 200 subjects in each year of the range of this study (5 to 13 years) All subjects were derived from a 20-mile radius of Birmingham, and although the black participants were born in the United Kingdom, their parents were all immig,rants from West Africa. Each participant was examined under standardized conditions, and the presence of a tooth on the left side of the dental arch was recorded when any portion had pierced the oral mucosa (in the few instances where there had been an extraction, the tooth was regarded as erupted) . The observed probabilities of finding a given tooth erupted into the oral cavity in each age category were then transformed into probits

Preliminary study of mandibular shape after tooth loss

T he assessment of jaw size is a critical component in prosthodontic planning. There is increasing realization that traditional osteometric data are scientifically invalid, because size and shape parameters are combined rather than being dissociated.’ For example, mandibular size and shape are considered together as mandibular form rather than as separate entities. As a result, the reported reduction in mandibular ramus height and body length from Anglo-Saxon to modern times may predominantly reflect size and/or shape contrasts.” Marked changes in mandibular form have also been described after tooth extraction, although their objective metric descriptions in terms of size and shape have yet to be defined.’ Whether based on dried skulls or cephalographs, traditional osteometric studies depend on the assumption of datum point homology: a possibly dubious assumption in view of the constant skeletal remodeling that accommodates functional changes, for example, during growth or after tooth extraction.4 In addition, overall mandibular dimensions, for example body length or ramus height, provide only a cursory morphologic summary and yield scant information to relate the intervening structures. The mandible has been subdivided into a number of component skeletal units, each influenced by discrete functional matrices, such as the masticatory muscle groups.5 In fact, such skeletal subdivisions do not appear to be as discrete as originally envisaged but rather are highly correlated one with another.” There is no doubt that the mandible is a complex biologic unit affected by a variety of factors, although scientifically rigorous techniques are required for their assessment. The early classic transformation grids of Thompson,’ which are used to define morphologic shape, have thus far proved resistant to quantitative analyses.8 Fourier and biorthogonal analyses hinge on datum point homology.9, ‘” A conceptually simple technique termed medial axis transformation has proved to be a rigorous method for the definition of morphology, however, and is independent of specific datum point identification. The medial (symmetric) axis of a curved form provides a stick figure: a precisely defined middle curve equidistant from both sides.” The length of such an axis, plus an

Craniofacial growth in patients with craniosynostosis.

With the growing appreciation that traditional cephalographic analyses provide data of dubious scientific validity, this study was undertaken to investigate craniofacial growth using the technique of biorthogonal analysis. This specific technique for the analysis of shape change showed relatively minor contrasts between control and craniosynostotic patients between 6 and 10 years of age. By contrast, marked variation was noted within component regions of the craniofacial skeletons in both patient samples: a feature not evident from traditional cephalographic analyses.

Stress and anxiety in dental treatment

This chapter discusses the stress and anxiety related to dental treatment. Many patients who attend a dentist are frankly afraid; this fear manifests itself physiologically in a number of ways. Anxiety may be manifest by a host other signs including: sleep loss, hunger, pain, excessive analgesic consumption, sweating, palpitations, and talkativeness. The treatment of such anxious patients results in stress for the dentist and the dental team. The body reacts in a number of ways when placed in a situation interpreted as adverse or threatening. The physiological responses to emotional stimulation are autonomic and controlled by a complex system involving the limbic structures, especially the amygdala, hypothalamus, and reticular formation. The stimulation of the reticular formation induces cerebral arousal, alerting reactions, panic, and fear responses. Three of the most important hormonal and neurohormonal changes are the secretion of glucocorticoids, catecholamines, and vasopressin. Haemorrhage is a potent stimulus for cortisol release. The chapter describes both adrenocorticotropic hormone (ACTH) and ACTH-independent mechanisms.

Growth and development of the craniofacial skeleton

This chapter discusses the growth and development of the craniofacial skeleton. Craniofacial defects include cleft lip and cleft palate, jaw deformities, dental anomalies, ossification defects of the facial and cranial bones, too wide or narrow spacing between the eyes, facial asymmetry, and fetal alcohol syndrome. The comparison of neonate and adult skulls demonstrates the differential effects of development and growth. The cranial vault dominates fetal, neonatal, and early childhood skulls. The head is divisible into three regions: the upper face, the mid-face, and the lower face. These three cranial regions follow different growth patterns, and they are not discrete entities. The maldevelopment of one region variably affects that of others. This hinders evaluation of the factors influencing craniofacial form. The chapter discusses the factors influencing craniofacial development. The craniofacial development is characterized by the occlusal relationships between the maxillary and mandibular teeth. The chondrocranium also plays an important role in craniofacial development and growth.

Calcium metabolism and bone

This chapter discusses calcium and bone metabolism. Bone is a highly organized complex tissue. It is characterized by abundant extracellular matrix in which three principal bone cell families are found, each existing at a number of different stages of development and maturation. The metabolic activity of bone matrix and its component cells resides in a constant state of flux, controlled by a large number of humoral and other agents. Bone loss, associated with aging or with disease, leads to osteoporosis and fractures and reflects disturbances in the maintenance of skeletal balance. Osteoblasts synthesize the extracellular matrix components and prime the matrix for its subsequent mineralization. Osteocytes are derived from osteoblasts and lie in concentric layers in bone matrix. These cells are in contact with each other through a network of canaliculi, which also connect them to osteoblasts on the bone surface. Such intimate intercommunications facilitate the osteocytic control of mineral exchange between bone and plasma. Osteoclasts are large multinucleated cells lying on the surface of bone in varyingly shaped Howships lacunae. They are responsible for the resorption of calcified bone or cartilage.

The blood supply of the oral tissues

This chapter describes the blood supply of the oral tissues. The blood and lymph vessels that permeate most oral tissues provide essential component homeostatic mechanisms. Most of the gaseous, nutrient, and metabolic waste product exchange occurs at the microcirculatory level. The knowledge of the structure and function of the microcirculatory system is important for the subsequent understanding of the physiology and pathology of the oral tissues. The microcirculatory system comprises the terminal portions of the vessels between arterioles and venules. This is the key area of the circulatory system. It includes not only the true capillaries but also the smallest divisions of the arterioles and venules, all components being less than 100 μm in diameter. The blood flow through this microcirculatory system undergoes continuous variation in rate, volume, and direction, that is, the blood flow to the oral tissues is characterized by marked variability. Based on light and electron microscopic studies, the component microcirculatory unit can be sub-divided into a number of endothelial-lined units: arteriole, true capillary, collecting venule, and preferential channel.

Investigation of Mandibular and Neurocranial Form

In a study of mandibular form, 19 traditional linear dimensions were found to be consistently greater for macrocephalics than microcephalics. As such dimensions combine both size and shape parameters together, their interpretation proved difficult. In order to examine specifically mandibular shape only, each mandibular outline form was digitized and subjected to the technique of medial axis transformation. The data indicate that the shape contrasts between the mandibles of macrocephalics and microcephalics are more complex than traditionally envisaged and emphasize the need for further study to ascertain the effect of genetic and environmental influences on mandibular form.