Age and gender variations in the cone-beam computed tomographic location of mandibular canal : implications for mandibular sagittal split osteotomy

Mandibular sagittal split osteotomy (MSSO) may incur unfavorable split and sensorineural injuries. Knowledge of the anatomic location of the mandibular canal (MC) and bone thickness in the region of interest for MSSO, and the possible variations by age and gender can assist in avoiding such complications. Purpose: To study the location of the MC and bone thickness in the region of MSSO by cone-beam computed tomography (CBCT) radiographs and to evaluate the possible variations by age and gender in a Jordanian population. This retrospective radio-anatomical study examined all CBCT radiographs for patients treated over three years at the University of Jordan Hospital, Amman, Jordan. Distances from the MC to the cortical external surfaces and MC diameter (MCD) were measured by a reliable observer at three predetermined regions for MSSO: region (A) [mandibular foramen area], region (B) [mandibular angle area] and region (C) [directly mesial to the second molar]. Gender and age differences in all measurements were then compared using non-parametric Mann-Whitney U test. The final study radiographs comprised a total of 202 CBCT belonged to a cohort of 202 subjects; 91 males (45.1%) and 111 (54.9%) females, with mean age (± SD) of 42.94 ± 18.54 years (range 18?90 years). Whereas only the bone thickness superior, buccal and inferior to MC in regions (B) and (C), and MCD in the three regions exhibited significant (p< 0.05) gender differences, all measured distances exhibited statistically significant (p< 0.05) differences between young and adult patients. The location of MC and bone thickness in the region of MSSO were significantly variable according to age, but exhibited sexual diamorphism only in regions (B) and (C). This fundamental knowledge should be considered during MSSO planning

FAM20A mutations can cause enamel-renal syndrome (ERS).

Enamel-renal syndrome (ERS) is an autosomal recessive disorder characterized by severe enamel hypoplasia, failed tooth eruption, intrapulpal calcifications, enlarged gingiva, and nephrocalcinosis. Recently, mutations in FAM20A were reported to cause amelogenesis imperfecta and gingival fibromatosis syndrome (AIGFS), which closely resembles ERS except for the renal calcifications. We characterized three families with AIGFS and identified, in each case, recessive FAM20A mutations: family 1 (c.992G>A; g.63853G>A; p.Gly331Asp), family 2 (c.720-2A>G; g.62232A>G; p.Gln241_Arg271del), and family 3 (c.406C>T; g.50213C>T; p.Arg136* and c.1432C>T; g.68284C>T; p.Arg478*). Significantly, a kidney ultrasound of the family 2 proband revealed nephrocalcinosis, revising the diagnosis from AIGFS to ERS. By characterizing teeth extracted from the family 3 proband, we demonstrated that FAM20A(-/-) molars lacked true enamel, showed extensive crown and root resorption, hypercementosis, and partial replacement of resorbed mineral with bone or coalesced mineral spheres. Supported by the observation of severe ectopic calcifications in the kidneys of Fam20a null mice, we conclude that FAM20A, which has a kinase homology domain and localizes to the Golgi, is a putative Golgi kinase that plays a significant role in the regulation of biomineralization processes, and that mutations in FAM20A cause both AIGFS and ERS

Scanning Electron Micrographs (SEMs) of molar (#18) occlusal surface.

<p><i>A:</i> Low magnification view of occlusal surface after partially cutting and then splitting the tooth sagitally (mesial-distal direction) for SEM analyses (bar: 1 mm). The boxes, from top to bottom, are locations of higher magnification views shown in B–E, respectively. <i>B:</i> Region showing knob-like calcifications (bar: 100 µm). <i>C:</i> Region where dentinal tubules reach the surface (bar: 10 µm); <i>D:</i> Region showing a relatively smooth surface (bar: 10 µm). <i>E:</i> Region from edge of crown (bar: 100 µm); <i>F:</i> Higher magnification of box in panel E showing no true enamel and apparent resorption lacunae (bar: 10 µm).</p

Family 2 from Jordan with <i>FAM20A</i> mutation c.720-2A>G; g.62232A>G; p.Q241_R271del.

<p><i>A:</i> Pedigree: a dot marks person who donated samples for DNA sequencing. <i>B: FAM20A</i> intron 4 DNA sequencing chromatograms. The proband's parents (IV:1 and IV:2) were both heterozygous (R = A or G) at cDNA position 720 (2 arrowheads). The proband (V:5) had the c.720-2A>G transition mutation in both alleles of <i>FAM20A</i>. This mutation is predicted to cause the skipping of exon 5, which is predicted to delete 31 amino acids (Q241-R271) from the protein without shifting the reading frame. <i>C:</i> Proband's oral photo showing enamel hypoplasia, gingival enlargement and failed eruption. <i>D:</i> Proband's panoramic radiograph. Note the enamel hypoplasia, pulp calcifications, and unerupted teeth with pericoronal radiolucencies delimited by sclerotic borders. The left mandibular second molar (#18) shows apparent crown resorption. <i>E:</i> Ultrasound of proband's right kidney, located to the right of the yellow line.</p

Family 3 from Iran with <i>FAM20A</i> nonsense mutations in exon 2 (c.406C>T; g.50213C>T; p.R136*) and in exon 11 (c.1432C>T; g.68284C>T; p.R478*).

<p><i>A:</i> Pedigree consistent with a recessive pattern of inheritance. <i>B:</i> Exon 2 (left) and exon 11 DNA sequencing chromatograms. The proband (III:16) is heterozygous for nonsense mutations in exon 2 (c.406C>T) and exon 11 (c.1432C>T). The unaffected brother (III:17) is only heterozygous for the c.406C>T mutation in exon 2. <i>C:</i> Panoramic radiograph of proband. Note the lack of enamel, pericoronal radiolucencies over the unerupted mandibular third molars (arrowheads), and apparent crown resorption of the left mandibular second molar (#18).</p