Agents Within a Developmental Complex Adaptive System: Intrauterine Male Hormones and Dental Arch Size in Humans

Abstract

Oral development is a complex adaptive system influenced by genetic, epigenetic and environmental factors. The dental arch develops from 6 weeks in utero until adult life, forming an accessible record to study general growth and development. Increased tooth size in female dizygotic opposite-sex (DZOS) twins compared with female dizygotic same-sex (DZSS) twins provides evidence for the masculinisation of females gestated with a male co-twin, possibly due to the intrauterine influence of male sex hormones: the "Twin Testosterone Transfer" (TTT) hypothesis. This study aimed to investigate the potential influence of intrauterine male hormones on dental arch size of female DZOS twins. Serial dental models of the primary and permanent dentitions of 69 female DZOS and DZSS twins were examined. Intercanine width, intermolar width, arch length and arch circumference were measured using a customised 2D image analysis system. Unpaired t-tests showed significant differences for mandibular intercanine width (p = 0.03; effect size = 0.6) and borderline differences for mandibular intermolar width and arch circumference (p = 0.05; effect size = 0.5). No significant differences were found in the permanent dentition. These findings provide support for the TTT hypothesis with some arch dimensions being larger in female DZOS twins. We have developed a model of assessing the effects of intrauterine male hormones on the epigenetic changes that last into postnatal life. Our evidence suggests that this is a moderate effect possibly interacting with numerous other environmental factors that may influence arch size.

Inter-Operator Reliability of Dental Morphometric Measurements

“…3 Teeth and dental arches were analyzed with the help of a previously validated bidimensional image analysis method. 4,5 Increased correlation coeffi cients were found, in several studies, for the bidimensional image analysis method, with small errors of method for all parameters. [5][6][7] A previous study showed excellent coefficients of reliability for dental morphometric measurements.…”

“…4,5 Increased correlation coeffi cients were found, in several studies, for the bidimensional image analysis method, with small errors of method for all parameters. [5][6][7] A previous study showed excellent coefficients of reliability for dental morphometric measurements. The intra-operator reliability of these measurements was found to be in the Excellent category.…”

Korelasi Panjang Gigi Insisif Sentral Maksila Dengan Tinggi Badan pada Subras Deutromelayu

“…Proses kalsifikasi gigi insisif sentral maksila permanen dimulai pada usia 3-4 bulan setelah kelahiran dan kalsifikasi mahkota gigi umumnya selesai sekitar 3-4 tahun seteleh gigi erupsi. 9,10 Waktu erupsi gigi insisif sentral sekitar usia 6-7 tahun.Pembentukan akar pada umumnya selesai pada usia 10 tahun ditandai dengan foramen apikal yang telah tertutup sempurna dan menunjukkan bahwa pertumbuhan panjang gigi telah selesai. 10 Pertumbuhan manusia dipengaruhi oleh banyak faktor seperti genetik, hormon, jenis kelamin, nutrisi, ras, dan lingkungan.…”