Inside the jaw, region by region: bone density in Hounsfield units.

What it shows

Three kinds of information, kept apart

The jaw map colours eight areas of the maxilla and mandible by CT density ranges reported in 2001, reproduced in 2012. Those are historical ranges for a region: they are not measurements of a patient, and the 3D model itself carries no density values. The cross sections are teaching models built in 3D by Periospot for five regions, drawn to illustrate the differences between sites reported in micro-CT studies rather than taken from those specimens. Blood supply and bone formation are explained in their own panels and drawn as optional layers, because how dense bone looks on a scan does not tell you how well it is supplied, and only loosely how one site will heal.

Reading the map

What the four density bands mean

Hounsfield units (HU) are the scale a CT scanner reports X-ray attenuation on. A higher number means more of the beam was absorbed.

These ranges are attributed to Norton and Gamble (2001) and are taken from the later reproduction by Reeves, Mah and McDavid (2012). Norton's original table has not been read directly. The grey values of an ordinary dental CBCT are not calibrated Hounsfield units, so a CBCT reading cannot be placed on this scale as it stands.

Who opens it

How people use it

Expectations

What this is, and what it is not

The text, the sources and the regional interpretation were clinically reviewed in September 2026; the 3D model geometry was not independently verified. Norton's original table has still not been read directly; the bands come from the Reeves 2012 reproduction, and the drawn sections remain teaching models.

Questions

Questions people ask about bone density

What are Hounsfield units (HU)?

Hounsfield units are the scale a CT scanner uses to report X-ray attenuation. A higher number means more of the beam was absorbed by the tissue. The Bone Quality Atlas shows the HU bands one 2001 study proposed for regions of the jaw; it does not measure HU on its own 3D model.

What is the bone density of the anterior mandible compared with the posterior maxilla?

In the regional CT density bands proposed by Norton and Gamble in 2001, as reproduced by Reeves, Mah and McDavid (2012): anterior mandible above 850 HU; posterior mandible and anterior maxilla 500 to 850 HU; posterior maxilla 0 to 500 HU; tuberosity below 0 HU. These are historical ranges for a region, not a value for a given patient or site, and the below 0 HU tuberosity figure is the one band no other published CT series we found reports, so treat it as Norton and Gamble's own observation. On the Hounsfield scale water reads 0 and air about -1000, so a value below 0 describes low attenuation, not absent or non-vital bone. Other CT series agree on the order but not the numbers: the anterior mandible averaged 945 HU in one series of 131 sites and 530 HU in another of 154 (Turkyilmaz et al. 2007; Fuh et al. 2010).

Are CBCT grey values the same as Hounsfield units?

No. In a study of ten cadaver mandibles (Parsa et al. 2012), cone beam CT grey values ran higher than medical CT Hounsfield units even though the two correlated closely. A CBCT reading cannot be placed on the HU scale as it stands.

What is the Norton and Gamble bone classification?

A 2001 study in Clinical Oral Implants Research (12(1):79-84) that proposed an objective bone density scale from CT Hounsfield values and reported a correlation between density, the subjective quality score and the region of the mouth. The four regional ranges shown on this page are the ones credited to it by Reeves et al. 2012; the original table has not been read directly. They also related the scale to the Lekholm and Zarb types, strongly for types 1 and 4, and proposed merging types 2 and 3 (as reported by Hiasa et al. 2011).

How does this relate to the Lekholm and Zarb or Misch classifications?

Lekholm and Zarb (1985) grade bone quality as types 1 to 4, assigned subjectively from the radiographic appearance of the cortex and the trabecular pattern, often with the drilling sensation at surgery, rather than from a number. Norton and Gamble related their CT values to those types: the correlation was strong for types 1 and 4, and they proposed merging types 2 and 3 (as reported by Hiasa et al. 2011). Misch's D1 to D4 scale is quoted with its own HU cut-offs (D1 above 1250 HU, D4 150 to 350 HU, as reproduced by Reeves et al. 2012), which differ from the regional bands on this page, so the colours cannot be read as D classes. Two of the atlas sources link the types to outcomes: Jaffin and Berman 1991 lost 35 of every 100 turned-surface implants placed in type IV bone against 3 of every 100 in types I to III, a historical figure rather than today's rate, and a 2017 meta-analysis of 94 studies (Chrcanovic, Albrektsson and Wennerberg) found type 4 bone still failed more often, while modern surfaces reduced the failure difference between type 1 and types 2 and 3, but not for type 4. A regional colour on the map is not a site's bone type.

Does the atlas predict implant stability or tell me how to drill?

No. It provides no bone volume fraction, no HU measurement of the model, no prediction of insertion torque, ISQ or healing, and no drilling sequence. The cross sections are drawn teaching models, not micro-CT, histology or a patient scan. A regional illustration cannot predict an individual site.