McNamara Analysis

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San Francisco native James A. McNamara Jr. is most widely known for his development of the McNamara Analysis, one of the most popular methods of cephalometric analyses. Circa 1983, McNamara’s research focused mainly on clinical modification of the growth of face and jaw.

He introduced this cephalometric analysis because there was a need for a method of cephalometric analysis that is sensitive to not only the position of one’s teeth within a given bone, but also to the relationship of one’s jaw elements and cranial base structures and how they relate to one another. Since, the McNamara analysis has become one of the most important tools of clinical and research orthodontics.

This analysis is one of the more recent additions to the contemporary textbooks on cephalometry. The textbook contains a list of the most well known cephalometric analyses including 23 analyses between the years 1946 and 1985 i.e. Wits Analysis, and Rickett’s Analysis. The majority of these analyses use references from small samples of Caucasians.

The McNamara analysis combines the anterior reference plane, the plane that runs perpendicularly to the Frankfurt horizontal through the nasion) with a description of the length of the patient’s jaw and the relationship between them. McNamara’s approach is the most suitable for diagnosis, treatment planning, and treatment evaluation. This goes for patients with skeletal discrepancies who may be candidates for dentofacial orthopedics and orthognathic surgery.

McNamara Analysis Advantages

The McNamara analysis relates several variables: teeth to teeth; teeth to jaws; each jaw to the other; and jaws to the cranial base. The analysis is a combination of elements of the Ricketts and Harvold approaches, using original measurements to create a more precise definition of jaw and tooth positions. According to this method, the anatomic Frankfort plane as well as the basion-nasion line are used as reference planes.

There are three main advantages of the McNamara analysis. Firstly it depends largely on linear measurements rather than angles. It analyzes the interarch relationship in the vertical plane as well as sagittal making them into one single integrated unit. Lastly, it helps to diagnose external conditions in the airway.

Skeletal Study

According to McNamara, the skeletal and dental components of the face are composed of the following planes and measurements used for skeletal study: Nasion perpendiculars (aka McNamara’s Vertical), linear distance from point A to nasion perpendicular, linear distance from point pog to nasion perpendicular, maxillary length, mandibular length, and lower anterior facial height. The planes and measurements used for the analysis of the airways are upper pharynx diameter and the lower pharynx diameter.

Analysis of Airways

The upper pharyngeal width is the smallest distance from the posterior pharyngeal wall to anterior half of the small plate outline. The normal for an adult is 17 +/- 4. The measurement marked with a decrease is only used as an indicator for possible upper airway impairment. For a more accurate diagnosis you’ll have to see a clinical otorhinolaryngologist for a clinical exam.

The lower pharyngeal width is measured on the mandibular plane from the posterior tongue to posterior pharyngeal wall. The norm for an adult women is 11.3 +/- 4, while the norm for an adult male is 13.5 +/- 4. Values that are less than 15 millimeters suggest that the anterior positioning of the tongue is either postural or there’s an enlargement of the tonsils.

All of these components and measurements can be easily recorded and stored through CephX’s cloud based platform for cephalometric analyses. In cephalometrics, the landmarks, or points of measurement, often demonstrate the relationship of the maxillary teeth and mandibular teeth, the jaws to the teeth and the jaws to one another, and the jaws to the cranial base. By drawing a complex series of angle and plane values, doctors are able to create values to compare for each measurement series.

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