No significant difference was found between the first and second scorers for DDE score or DDE extents for each index tooth, indicating intra-scorer reliability (p > 0.75). For affected subjects with permanent maxillary central incisors, no significant differences in age (p = 0.664) or gender (p = 0.803) were found between the affected (n = 22) and control (n = 45) groups (). The prevalence of severe enamel defects in the teeth of affected subjects was significantly higher when compared with controls, for both diffuse opacities (p < 0.0001) and for hypoplasia (p < 0.0001). The prevalence of the number of subjects who had at least one tooth with a severe enamel defect, of at least a diffuse opacity, was significantly higher in the affected group than controls (p = 0.010). The extents of the defects were also significantly greater in the affected group when compared with the control group (p < 0.0001, ).
Enamel defect prevalence between affected and control groups.
An analysis of the enamel defects in teeth between various complementation types for affected patients with permanent index teeth (n=22) showed no significant association between the specific metabolic defect and type of enamel defect. All the metabolic subtypes examined demonstrated severe enamel defects (diffuse opacities or hypoplasia) on teeth with a significantly higher prevalence when compared to controls (p < 0.0001). However, the prevalence of the number of subjects who had at least one tooth with a severe enamel defect, of at least a diffuse opacity, was significantly higher only in the mut MMA subgroup when compared with the control group (p = 0.021).
shows a clinical photo of the teeth of a control subject with normal enamel and several affected subjects with a spectrum of severe enamel defects, demonstrating diffuse opacities and enamel pitting.
Figure 2 Control patient (row A) with normal enamel. Affected patients (row B – row E) showing Developmental Defects of Enamel (right panel shows detail of the enamel defects of left panel with arrows pointing to specific diffuse opacities and arrowheads (more ...)
For subjects with permanent index teeth (n=22), those who demonstrated severe enamel defects (diffuse opacities or enamel hypoplasia, n = 12) had significantly higher serum methylmalonic acid levels than those without (n=10) (1467.33 ± 1662.78 vs. 150.42 ± 209.28 μmol/L, p=0.022). Within the mut MMA subgroup (n=15), where serum methylmalonate levels can be expected to be elevated, the subjects who had severe enamel defects (n = 8, 5 transplant subjects (62%), 2050.50 ± 620.48 μmol/L) had significantly higher serum levels of methylmalonic acid than those without (n = 7, 2 transplant subjects (29%), 209.57 ± 86.24 μmol/L, p = 0.017) (). This association of DDE scores with serum levels of methymalonic acid remains significant, even when adjusted for transplant status (p = 0.040). No trend towards congenitally missing or supernumerary teeth was found in the affected group.
Figure 3 Affected patients with mut type MMA and severe enamel defects, , have significantly* higher serum levels of methylmalonic acid than those with normal enamel, .
For subjects with primary maxillary central incisors, no significant differences in age (p = 0.075) or gender (p = 0.656) were found between the affected (n = 10) and control (n = 10) groups (). The prevalence of severe enamel defects in the teeth of affected subjects were significantly higher when compared with controls (p = 0.044), wholly due to two cblC subjects who exhibited very severe enamel defects of generalized missing enamel (). For this cblC subgroup, the prevalence of the number of subjects who had at least one tooth with a severe enamel defect, here severe enamel hypoplasia, was significantly higher than the control group (p = 0.038). shows a control subject with primary teeth covered with normal enamel and the two cblC affected subjects with cone-shaped, severely dysmorphic primary teeth and radiographic evidence of enamel hypoplasia.
Primary teeth from control subject and radiograph (row A). Severely dysmorphic, cone shaped primary teeth and radiographic evidence of enamel hypoplasia in two affected patient with cblC disorders (row B and C).
Both primary teeth provided by the affected subjects for microstructural analysis were grossly normal morphologically (). Microstructurally, the tooth sample from the mut patient (molar) was found to have normal enamel thickness and regular crystalline structure. In contrast, the tooth sample from the cblC patient (incisor) was found to have normal enamel thickness but markedly altered microstructure. As seen by light microscopy of thin sections, the incisor sample had altered enamel opacity indicative of increased porosity as compared with the molar sample (). Also, when viewed with SEM, the incisor enamel showed flat, plate-like crystallites that were intermixed with the more classically normal appearing hexagonal enamel crystal that were seen throughout in the normal appearing molar sample ().
Figure 5 Structural analyses of two affected patient's primary teeth. Tooth picture A, light microscopy section C, and SEM picture E is of a primary molar donated by a mut type MMA patient. Tooth picture B, light microscopy section D, and SEM picture F is of primary (more ...)
Salivary levels of methylmalonic acid were massively elevated in the two mut patients whose saliva was tested (21,904 ± 1438 nmol/L) when compared to two control salivary concentrations (427 ± 142 nmol/L, p=0.002). This finding parallels the difference in the serum levels of MMA in the patients (191,887 ± 103,538 nmol/L) and controls (121 ± 18 nmol/L, p=0.120).