So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

https://www.semortho.com/article/S1073-8746(05)00021-6/pdf

The Cervical Vertebral Maturation (CVM) Method for the Assessment of Optimal Treatment Timing in Dentofacial Orthopedics

A link between oral health and cardiovascular disease has been proposed for more than a century. Recently, concern about possible links between periodontal disease (PD) and atherosclerotic vascular disease (ASVD) has intensified and is driving an active field of investigation into possible association and causality. The 2 disorders share several common risk factors, including cigarette smoking, age, and diabetes mellitus. Patients and providers are increasingly presented with claims that PD treatment strategies offer ASVD protection; these claims are often endorsed by professional and industrial stakeholders. The focus of this review is to assess whether available data support an independent association between ASVD and PD and whether PD treatment might modify ASVD risks or outcomes. It also presents mechanistic details of both PD and ASVD relevant to this topic. The correlation of PD with ASVD outcomes and surrogate markers is discussed, as well as the correlation of response to PD therapy with ASVD event rates. Methodological issues that complicate studies of this association are outlined, with an emphasis on the terms and metrics that would be applicable in future studies. Observational studies to date support an association between PD and ASVD independent of known confounders. They do not, however, support a causative relationship. Although periodontal interventions result in a reduction in systemic inflammation and endothelial dysfunction in short-term studies, there is no evidence that they prevent ASVD or modify its outcomes.

/pdf/periodontal-disease-and-atherosclerotic-vascular-disease-5dzvnap7v8.pdf

Periodontal Disease and Atherosclerotic Vascular Disease: Does the Evidence Support an Independent Association? A Scientific Statement From the American Heart Association

Objectives: Cone beam computed tomography (CBCT), which provides a lower dose, lower cost alternative to conventional CT, is being used with increasing frequency in the practice of oral and maxillofacial radiology. This study provides comparative measurements of effective dose for three commercially available, large (12″) field-of-view (FOV), CBCT units: CB Mercuray, NewTom 3G and i-CAT. Methods: Thermoluminescent dosemeters (TLDs) were placed at 24 sites throughout the layers of the head and neck of a tissue-equivalent human skull RANDO phantom. Depending on availability, the 12″ FOV and smaller FOV scanning modes were used with similar phantom positioning geometry for each CBCT unit. Radiation weighted doses to individual organs were summed using 1990 (E1990) and proposed 2005 (E2005 draft) ICRP tissue weighting factors to calculate two measures of whole-body effective dose. Dose as a multiple of a representative panoramic radiography dose was also calculated. Results: For repeated runs dosimetry was ge...

/pdf/dosimetry-of-3-cbct-devices-for-oral-and-maxillofacial-3pq1k8mr17.pdf

Dosimetry of 3 CBCT devices for oral and maxillofacial radiology: CB Mercuray, NewTom 3G and i-CAT

Objectives This study compares 2 measures of effective dose, E1990 and E2007, for 8 dentoalveolar and maxillofacial cone-beam computerized tomography (CBCT) units and a 64-slice multidetector CT (MDCT) unit. Study design Average tissue-absorbed dose, equivalent dose, and effective dose were calculated using thermoluminescent dosimeter chips in a radiation analog dosimetry phantom. Effective doses were derived using 1990 and the superseding 2007 International Commission on Radiological Protection (ICRP) recommendations. Results Large-field of view (FOV) CBCT E2007 ranged from 68 to 1,073 μSv. Medium-FOV CBCT E2007 ranged from 69 to 560 μSv, whereas a similar-FOV MDCT produced 860 μSv. The E2007 calculations were 23% to 224% greater than E1990. Conclusions The 2007 recommendations of the ICRP, which include salivary glands, extrathoracic region, and oral mucosa in the calculation of effective dose, result in an upward reassessment of fatal cancer risk from oral and maxillofacial radiographic examinations. Dental CBCT can be recommended as a dose-sparing technique in comparison with alternative medical CT scans for common oral and maxillofacial radiographic imaging tasks.

/pdf/comparative-dosimetry-of-dental-cbct-devices-and-64-slice-ct-omz4if0pfp.pdf

Comparative dosimetry of dental CBCT devices and 64-slice CT for oral and maxillofacial radiology

Cone-beam computed tomography (CBCT) systems have been designed for imaging hard tissues of the maxillofacial region. CBCT is capable of providing sub-millimetre resolution in images of high diagnostic quality, with short scanning times (10-70 seconds) and radiation dosages reportedly up to 15 times lower than those of conventional CT scans. Increasing availability of this technology provides the dental clinician with an imaging modality capable of providing a 3-dimensional representation of the maxillofacial skeleton with minimal distortion. This article provides an overview of currently available maxillofacial CBCT systems and reviews the specific application of various CBCT display modes to clinical dental practice.

/pdf/clinical-applications-of-cone-beam-computed-tomography-in-4kp8tgr2p7.pdf

Clinical applications of cone-beam computed tomography in dental practice.

What is Cone-Beam CT and How Does it Work?

Skeletal maturation evaluation using cervical vertebrae

Cone Beam Computed Tomography (CBCT) is a diagnostic imaging modality that provides high-quality, accurate three-dimensional (3D) representations of the osseous elements of the maxillofacial skeleton. CBCT systems are available that provide small field of view images at low dose with sufficient spatial resolution for applications in endodontic diagnosis, treatment guidance, and posttreatment evaluation. This article provides a literature review and pictorial demonstration of CBCT as an imaging adjunct for endodontics.

/pdf/use-of-cone-beam-computed-tomography-in-endodontics-2nwthzi1d8.pdf

Use of Cone Beam Computed Tomography in Endodontics

Objective: To compare accuracy of linear measurements made on cone beam computed tomographic (CBCT) derived 3-dimensional (3D) surface rendered volumetric images to direct measurements made on human skulls. Materials and Methods: Twenty orthodontic linear measurements between anatomical landmarks on 23 human skulls were measured by observers using a digital caliper. The skulls were imaged with CBCT and Dolphin 3D (version 2.3) software used to generate 3D volumetric reconstructions (3DCBCT). The linear measurements between landmarks were computed by a single observer three times and compared to anatomic dimensions using Student's t-test (P ≤ .05). The intraclass correlation coefficient (ICC) and absolute linear and percentage error were calculated. Results: The ICC for 3DCBCT (0.975 ± 0.016) was significantly less than for skull (0.996 ± 0.007) measurements. Mean percentage measurement error for 3DCBCT (2.31% ± 2.11%) was significantly higher than replicate skull measurements (0.63% ± 0.51%). Sta...

Allan G. Farman

Papers

Clinical applications of cone-beam computed tomography in dental practice.

What is Cone-Beam CT and How Does it Work?

Skeletal maturation evaluation using cervical vertebrae

Use of Cone Beam Computed Tomography in Endodontics

Linear accuracy and reliability of cone beam CT derived 3-dimensional images constructed using an orthodontic volumetric rendering program.