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International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 5. Hakodate 1998 
Distribution of Bone Mineral Density(BMD) in Edentulous Mandible 
-A Measuring System of BMD Using Computed Radiography- 
Seiji TAKAOKA, Ken'ichi KOBAYASHI, Tsuguhisa KATOH*, Shunsuke MINAKUCHI, 
Toshiaki SEKITA, Masanori NAGAO and Takehito SASAKI* 
Department of Geriatric Dentistry, Faculty of Dentistry, Tokyo Medical and Dental University 
*Department of Dental Radiology and Radiation Research, Faculty of Dentistry, Tokyo Medical and Dental University 
1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8549 JAPAN 
E-mail: s.takaoka.gero @ dent.tmd.ac.jp 
Commission V, Working Group 4 
KEY WORDS: Computed Radiography, Bone Mineral Density, Mandible 
ABSTRACT 
In dental region, X-ray image provides useful information for denture or implant treatment, especially information on bone 
mineral density(BMD). The purpose of this study was to develop a in vitro measuring system for BMD using computed 
radiography(CR) and to make a distribution map of BMD in edentulous mandible with this system. 
To reduce the structural noise on imaging plate, X-ray image with no object was subtracted from object image in optimum 
exposure condition. Each image of ninety sections cut from five edentulous mandible were divided into 64 elements. The 
mean BMD of every element was calculated and the BMD distribution map was made. 
The system measured bone mineral content up to 1400mg/cm* and the detection limit was 11mg/cm?(2SD). Standard 
deviation of pixel value was reduced by factor 17 using the noise reduction technique. The accuracy of our BMD measuring 
system was 1.4%(relative error) and the reproducibility was 1.1%(CV). 
In anterior region, between the mental foramina, the BMD of inferior cancellous bone was significantly higher than that of 
the lingual and labial side(p < 0.001). In posterior region, the BMD of buccal cancellous bone was significantly higher 
than that of the lingual side(p < 0.001). Greater individual variation of BMD was observed near mental foramen, and in 
incisor lingual and inferior cancellous bone. 
Our BMD measuring system demonstrated excellent precision and reproducibility. BMD distribution varied near regions 
of muscle attachment and the mandibular canal. Deep placement of fixtures between the mental foramina in anterior 
region and placement into buccal cancellous bone within 24mm from the mental foramen in molar region may contribute 
to additional stability on endosseous implants. 
edentulous mandible did not show the coordinates of 
distribution of measuring area, and are not precise enough 
for numerical comparison for BMDs among different areas. 
1. INTRODUCTION 
Bone quality and quantity is refered in many studies in 
osteoporosis, aging and other metabolic bone diseases. BMD can be measured by 1) the scanning density of X-ray 
It is considered to be one of important factors for the photo, 2)quantitative computed tomography, 3)dual energy 
prognosis of implant and denture prosthesis. Bone mineral X-ray absorptiometry. However, BMD measured by the 
density is one of the indices of the bone quality and reflects technique 1) can be easily influenced by processing 
the degree of bone mineralization. condition. The technique 2) has problem with spatial 
resolution and precision. The technique 3) it requires 
Many edentulous jaws are found among advanced ages. specialized devices. 
Previously, complete denture was only options available 
to restore masticating function for edentulous jaw. Recent The computed radiography(CR) system(Sonoda et al., 
advances in implant dentistry made implant retained dental 1983, Ogawa et al., 1995) uses an imaging plate(IP) in 
prosthesis an alternative option. place of an usual X-ray film. The image data is obtained by 
scanning with laser beam. The image from CR is not 
For the those considering implant prosthesis, proper affected by developing condition. The signal output is in 
evaluation is necessary to determine wheater such proportion to X-ray dose. Digital radiography systems 
treatment is appropriate in individual bases. including CR are commonly characterized by a large 
dynamic range of the detector, an enough contrast with 
The relevance between bone quality and application of low dose of X-ray, and an availability of direct digital image 
implant treatment was previously reported(Bránemark et processing. The CR image of 6 * 4 inches has a high 
al., 1977, Bass et al., 1991). However, the marginal BMD spatial resolution(2510 * 2000 pixels, 0.1mm/pixel) and 8 
and its application for implant treatment is not well studied. bits gray scale. However, CR image has a noise mainly 
3-D distribution of BMD near planned implant placement resulting from scattering X-ray and from IP structural noise. 
site may be beneficial to know prior to implant placement. We are able to make a system for measuring bone mineral 
The previous studies about the BMD distribution in density using CR by controlling these noises. Therefore, 
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