Tooth types

Within several of the species there is significant interindividual variation (Table 6.2). This is due, in large part, to a lack of control for tooth type. Several recent studies (Bryant et al. 1996 Fricke and O Neil 1996 Stuart-Williams and... 

Purchase NG, Fergusson JE. 1986. Lead in teeth The influence of the tooth type and the sample within a tooth on lead levels. Sci Total Environ 52 239-250. 

The importance of P0 in PNS myelin has been clearly demonstrated. In P0 gene knockout experiments in mice [40], severe hypomyelination and a virtual absence of compact myelin in the PNS is observed. In humans, there are two disease states associated with mutations in the P0 gene Charcot-Marie-Tooth type I disease (see Ch. 38) and Dejerine-Sottas disease, both dysmyelinating diseases that exhibit a spectrum of severity depending on the particular mutation. 

Detmer, S. A., Vande Velde, C., Cleveland, D. W. and Chan, D. C. (2008) Hindlimb gait defects due to motor axon loss and reduced distal muscles in a transgenic mouse model of Charcot-Marie-Tooth type 2A. Hum Mol Genet 17, 367-375. 

Vigo T, Nobbio L, Hummelen PV, Abbruzzese M, Mancardi G, Verpoorten N, et al. Experimental charcot-marie-tooth type 1A A cDNA microarrays analysis. Mol Cell Neurosci 2005 28(4) 703-714. 

Tooth type and position are often noted with a combination of numbers and letters, depending on the species. Each tooth has a lingual side, adjacent to the tongue, and a labial surface, which is closest to the lips (if there are any). The posterior teeth are at the back of the mouth, and the anterior to the front. The occlusal surface is the area where opposing teeth meet during chewing or biting. 

The caps are slotted around the lower periphery and can be anchored to the plate with teeth touching the plate or suspended to permit a so-called skirt clearance between the plate and the cap. Slots can be of a saw-tooth type or in the form of punched holes, usually rectangular or triangular. In common practice, a skirt clearance in the range of 0.5 to 1.5 in. is recommended to prevent plugging of the slots by residue buildup. Since the purpose of the slots is to disperse the gas into the liquid in the form of small bubbles, sufficient slot area should be provided in order that no gas may pass through the skirt clearance. 

Species Tooth type Overall shape and size Shape X-section Longitudinal section Cementum X-section Dentine X-section... 

Deviation from the mid-plane during delamination propagation in the cross-ply lay-up, specifically jumping from one adjacent unidirectional layer to that on the other side (symmetric) at regular delamination length intervals, resulting in a saw-tooth -type of fracture surface (Fig. 1). 

Fig. 1 Regular saw-tooth -type fracture surface during delamination propagation in (left) non-symmetric lay-up [0°/90°]i2 and (right) symmetric lay-up [0790°]6s, (top row) low and (bottom row) high amount of fibre-bridging (photographs courtesy of D.D.R. Cartie).

Nobbio L, Gherardi G, Vigo T, Passalacqua M, Melloni E, Abbruzz-ese M, Mancardi G, Nave KA, Schenone A (2006) Axonal damage and demyelination in long-term dorsal root ganglia cultures from a rat model of Charcot-Marie-Tooth type lA disease. Eur J Neurosci 23 1445-1452. 

Leonard DGB. Improved method for diagnosis of Charcot-Marie-Tooth type lA patent pending Clin Chem 2001 47 807-8. 

Pentao L, Wise CA, Chinault AC, Patel PI, Lupski JR. Charcot-Marie-Tooth type lA duplication appears to arise from recombination at repeat sequences flank-... 

Stronach EA, Clark C, BeU C, Lofgren A, McKay NG, Timmerman V, et al. Novel PCR-based diagnostic tools for Charcot-Marie-Tooth type lA and hereditary neuropathy with liability to pressure palsies. J Peripher Nerv Syst 1999 4 117-22. 

Sturtz FG, Latour P, Mocquard Y, Cruz S, FenoU D, LeFur JM, et al. Clinical and electrophysiological phenotype of a homozygously duplicated Charcot-Marie-Tooth (type lA) disease. Europ Neurol 1997 38 26-30. 

Delague V, Jacquier A, Hamadouche T et al (2007) Mutations in fgd4 encoding the rho gdp/gtp exchange factor frabin cause autosomal recessive charcot-marie-tooth type 4 h. Am J Hum Genet 81 1-16... 

Verhoeven K, De Jonghe P, Coen K, Verpoorten N, Auer-Grumbach M, et al. 2003. Mutations in the small GTP-ase late endosomal protein RAB7 cause Charcot-Marie-Tooth type 2B neuropathy Am J Hum Genet 72 722-727. 

Bolino A, MugUa M, Conforti FL et al (2000) Charcot-Marie-Tooth type 4B is caused by mutations in the gene encoding myotubularin-related protein-2. Nat Genet 25 17-19... 

In performing tooth lead analysis, it has to be considered that the lead concentrations vary among different tooth types (when analyzing whole teeth) as well as, within one tooth, between different tooth tissues (Ewers et al., 1990 Grandjean et al., 1984, 1986). In deciduous teeth the lead concentration tends to decrease from the medial incisors to the premolars. Whether there is a similar variation in permanent teeth of adults has not yet been evaluated. Thus, when comparing analytical data on lead concentrations in whole teeth, it should be stated what type of tooth was analyzed. 

Grandjean. P., Lyngbye, T., Hansen, O.N. (1986). Lead concentration in deciduous teeth Variation related to tooth type and analytical technique. J. Toxicol. Environ. Health. 19. 437-445. 

Utilized a miniature punch shear apparatus to determine shear strength and toughness perpendicular to the direction of dentinal tubules. Dentin harvested from the cemento-enamel junction to one-third the distance to the root apex. Strengths novel measurements, precise measurements, defined specimen location, defined orientation of testing. Limitations tooth type not defined for constrained tests, teeth stored in mineral oil prior to testing. 

Antagonistic interactions between FGF and BMP signals have been invoked as one possible mechanism for positioning tooth sites (Neubiiser et al. 1997), while the function of Bgf-8 as an inducer of known markers in the rostral mesenchyme (Tucker et al. 1999) may be involved in tooth type specification at the earlier stages. The latter experiments demonstrated that, at least, localised signal expression in the epithelium directs rostro-caudal patterning within the mandibular arch, rather than putative prespecification of cranial neural crest cells (Tucker et al. 1999). 

MUling cutters vary widely in type and size and are broadly classified as peripheral mills, face mills, end mills, and special mills. Cutters can be of the solid, tipped, or inserted tooth types and have the same materials as single-point tools. Large cutters commonly have teeth of expensive material that are inserted and locked in place in a sofl steel or cast iron body. AU cutters should be ground and mounted to make sure etll teeth are cutting the same amount of material. Typical tool geometries are shown in Tables 6, 7, and 8. 

Although marked differences in lead content across types of dentition have been recognized, there is also the question of how much variance exists in the measure within dentition type for tooth exfoliation in children, e.g., the two upper central incisors. Using central and lateral incisor crowns. Delves et al (1982) noted that the extent to which lead values in central-central, lateral-lateral, or central-lateral pairs of shed incisors from a group of children exceeded relative analytical variance was 23, 35, and 54%, respectively. Subsequently, the same group found that the differences are maximized with differing jaw position, i.e., upper versus lower (Smith et al, 1983). Variance within the jaw was considerably less. By contrast, variation within-tooth-type lead level appeared to be rather modest in the studies of Pinchin et al (1978) and Ewers et al (1982). However, a close comparison of these three studies is not readily made. 

The relevance of the results of Delves et al (1982) for some of the major surveys of the effects of lead exposure in children, employing tooth lead analysis, remains unclear. For example, in the study of Needleman et al (1979), dentine zone analysis was carried out using concordance criteria for acceptability of replicate measurements. The relative impact of variation in lead level within tooth type may be increased at very low levels of concentration and decreased with higher concentration. There is no evidence to indicate that the relative biological variance of the type seen by Delves et al persists with increasing concentration. As Delves et al have acknowledged, their mean and median lead levels are lower than those noted elsewhere in... 

Figure 1 Full-scale IQ and tooth lead concentration (adjusted for tooth type) in 402 London schoolchildren...

Grandjean, P., Nielsen, O.V. and Shapiro, I.M. (1979) Lead retention in ancient Nubian and contemporary populations. ]. Environ. Pathol. Toxicol, 2, 781-787 Grandjean, P., Hansen, O.N. and Lyngbye, K. (1984) Analysis of lead in circumpulpal dentin of deciduous teeth. Ann. Clin. Lab. Sci., 14, 270-275 Grandjean, P., Lyngbye, T. and Hansen, O.N. (1986) Lead concentration in deciduous teeth variation related to tooth type and analytical technique. ]. Toxicol Environ. Health, 19, 437-445... 

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