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To the Editor: Although tooth loss among elderly patients is known to be influenced by environmental factors, the role of genetic factors is largely unknown. A study of US patients, for instance, found some genetic contribution to the height of alveolar bone that supports the teeth.¹ It is likely that the estrogen-receptor (ER) gene could be associated with tooth loss in women because recent studies^2-3 suggest that the long-term estrogen replacement therapy (ERT) may protect against tooth loss in elderly women. We investigated the effect of ER genotype on tooth loss and alveolar height in Japanese women.

Methods
Of 531 women who visited our clinic for bone mineral density assessment between 1996 to 2001, 132 postmenopausal women (mean [SD] age, 55.3 [7.3] years) were randomly recruited for this study. Sixteen of the patients had received ERT for 6 months or less, and 1 had received it for 4 years. No patients had other medications affecting bone metabolism, and none had a history of tobacco use. Forty-eight patients had normal spinal bone mineral density (T score >-1.0), 52 were osteopenic (T score of -1.0 to -2.5), and 32 were osteoporotic (T score <-2.5) without spinal fracture. Patients' DNA was amplified with the polymerase chain reaction and the Pvu II and Xba I restriction enzymes were used to analyze ER gene alleles. Patients who were homozygous for the absence of these restriction sites were designated as genotypes pp and xx, respectively. The number of teeth was counted on dental panoramic radiograph, and the ratio of the mandibular total bone height (TBH) to basal bone height (BBH) was calculated to assess the alveolar bone loss.

Results
Analysis of covariance adjusting for age, body mass index, years since menopause, and estrogen use showed significant associations between number of teeth and Pvu II genotypes (P = .02), and between TBH/BBH ratio and Xba I genotypes (P<.001) (Table 1). Adjustment for history of hysterectomy and oophorectomy did not significantly change these associations. Exploration of the results revealed that the patients with the pp genotype had fewer teeth than those with a P (either PP or Pp) allele (20.9 [95% confidence interval {CI}, 19.0-22.8] vs 23.8 [95% CI, 22.5-25.1]; P = .02). Patients with an X (either XX or Xx) allele had lower TBH/BBH ratio (indicating more alveolar bone loss) than those with the xx genotype (2.13 [95% CI, 2.04-2.22] vs 2.25 [95% CI, 2.19-2.31]; P = .03).

View this table: [in this window] [in a new window] Table. Relationship Between Number of Remaining Teeth, TBH/BBH Ratio, and 2 Estrogen-Receptor Genotypes*

Comment
An association between number of teeth and Pvu II genotypes, but no association between TBH/BBH ratio and Pvu II genotypes, imply that these genes might not influence alveolar bone loss but rather alveolar bone fragility. There were no subjects with both an X allele and pp genotype in our study (as well as a previous Japanese study⁴) so it was not possible to examine the interaction of these genotypes on tooth loss. Nonetheless, our results suggest that ER gene analysis may help identify women with a high risk of tooth loss.

AUTHOR INFORMATION
Acknowledgment: We thank Elizabeth Krall, PhD, MPH, for her help in statistical analysis.

Akira Taguchi, DDS, PhD; Junya Kobayashi, PhD; Yoshikazu Suei, DDS, PhD; Masahiko Ohtsuka, BS; Keiji Tanimoto, DDS, PhD
Department of Oral and Maxillofacial Radiology
Hiroshima University Faculty of Dentistry

Mitsuhiro Sanada, MD, PhD; Koso Ohama, MD, PhD
Department of Obstetrics and Gynecology
Hiroshima University Faculty of Medicine
Hiroshima, Japan

1. Michalowicz BS, Aeppli DP, Kuba RK, et al. A twin study of genetic variation in proportional radiographic alveolar bone height. J Dent Res. 1991;70:1431-1435. FREE FULL TEXT 2. Paganini-Hill A. The benefits of estrogen replacement therapy on oral health. Arch Intern Med. 1995;27:2325-2329. 3. Grodstein F, Colditz GA, Stampfer ML. Post-menopausal hormone use and tooth loss: a prospective study. J Am Dent Assoc. 1996;127:370-377. FREE FULL TEXT 4. Kobayashi S, Inoue S, Hosoi T, Ouchi Y, Shiraki M, Orimo H. Association of bone mineral density with polymorphism of the estrogen receptor gene. J Bone Miner Res. 1996;11:306-311. ISI | PUBMED

Letters Section Editors: Stephen J. Lurie, MD, PhD, Senior Editor; Jody W. Zylke, MD, Contributing Editor.

JAMA. 2001;286:2234-2235.

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