Hugh Devlin

Mandibular radiomorphometric indices in the diagnosis of reduced skeletal bone mineral density

Abstract: Diagnosis of osteoporosis allows the delivery of preventive and therapeutic intervention and is usually achieved using bone densitometric techniques. One referral criterion for densitometry is osteopenia on radiographs. The aim of this study was to measure the validity of mandibular cortical indices measured on panoramic radiographs in the diagnosis of reduced skeletal bone density. Seventy-four women underwent bone densitometry of the femoral neck, lumbar spine and the forearm. Fifty-five patients (74%) were classified as having a reduced bone density (T-score ≤–1). Twenty-seven patients had a T-score of <–2.5 observed at one or more of the three measurement sites. A panoramic radiograph was taken of each patient and two observers made measurements of cortical thickness at the mental foramen (mental index, MI), antegonion (antegonial index, AI) and gonion (gonial index, GI) regions. Logistic regression and receiver operating characteristic (ROC) curve analyses were used to measure the validity of cortical indices in the diagnosis of reduced bone mineral density. Only MI contributed significantly to a diagnosis of low skeletal bone mineral density (T-score ≤–1). The 95% limits of agreement between observers in measurement of MI were 1.32 to +1.32 mm. When data for both observers were combined, the area under the ROC curve was 0.733 (SE = 0.072; 95% confidence interval = 0.618 to 0.83), indicating moderate accuracy. A diagnostic threshold for MI of 3 mm (or less) is suggested as the most appropriate threshold for referral for bone densitometry. However, the study provided only limited support for the use of panoramic radiomorphometric indices in diagnosing low skeletal bone mineral density. They might, questionably, be used as part of a method of osteoporosis risk assessment.

Expression and function of periostin-isoforms in bone.

Periostin was originally identified in MC3T3‐E1 osteoblast‐like cells. We have identified an isoform of periostin referred to as periostin‐like‐factor (PLF). It is homologous to other proteins such as fasciclin I (fas I), MPB70, βIG‐H3, and Algal‐CAMs. All of these proteins are implicated in regulating cell adhesion. PLF and the other isoforms of periostin differ in their C‐terminal sequences. PLF and periostin differ in two specific regions, between 673 and 699 amino acids (aa) and 785–812 aa. Periostin isoforms are expressed in vivo and in vitro during the stages of osteoblast differentiation and maturation. Their mRNAs are present in pre‐osteoblast cells as detected by in situ hybridization, and the proteins are between 86 and 93 kD in size as determined by Western blot analysis. Antisense oligonucleotides and antibodies directed against the isoforms of periostin were used to block the activity of these proteins. In both cases, the levels of osteoblast‐specific‐differentiation markers were markedly reduced suggesting a role for these proteins in osteoblast differentiation.

A comparison of maxillary and mandibular bone mineral densities.

STATEMENT OF PROBLEM The success rate of implant osseointegration is dependent on many factors such as bone mineral density, volume and vascularity of bone, implant design, ridge shape, and patient selection criteria among others. PURPOSE This study examined whether a technique to measure differences in bone mineral density in the maxilla and mandible might be useful to predict the likelihood of successful osseointegration. MATERIAL AND METHODS Bone densitometry of the jaws was performed with a densitometer, and bone mineral density was calculated at three regions of the maxilla and one site in the mandibular body in 39 edentulous subjects. RESULTS Significant differences were found between the mean bone mineral density of each site when compared with the three other locations. The mean bone mineral density for the mandible (mean = 1.11 g.cm-2), was twice that of the anterior maxilla (mean = 0.55 g.cm-2). Both were significantly greater than the bone mineral density of the posterior maxilla (mean = 0.31 g.cm-2; including the hard palate, mean = 0.45 g.cm-2). The bone mineral densities at the three maxillary sites were all highly correlated (r > or = 0.78, p < 0.001). CONCLUSION The dissimilarity in bone mineral density at different mandibular and maxillary sites may partly explain some variation in previously reported osseointegration rates. The posterior maxilla had the lowest bone mineral density and in certain circumstances before implant insertion, bone augmentation, or guided tissue regeneration may be advisable to improve the rate of osseointegration. Because the radiation dose is low, dual energy x-ray absorptiometry may be a useful noninvasive technique for determining the bone mineral density before implant insertion.

The relationship between mandibular bone mineral density and panoramic radiographic measurements

OBJECTIVES To compare densitometric and linear measurements (mandibular cortical thickness, MCT; panoramic mandibular index, PMI) made from dental panoramic tomograms (DPTs) with bone mineral density (BMD) values obtained using dual energy X-ray absorptiometry (DXA) of the mandible and to determine whether measurements from DPTs have validity in predicting BMD. METHODS Forty edentulous female patients were examined by a DPT incorporating a nickel step wedge and by DXA of the mandible. In each case the equivalent nickel thickness of sites in the mandibular body, MCT and PMI values were calculated and their relationship with DXA measurements assessed. RESULTS Densitometric measurements of DPTs did not correlate with mandibular BMD. MCT significantly correlated with mandibular BMD (r = 0.50, P = 0.001 and r = 0.36, P = 0.021 for repeated measurements) as did PMI (r = 0.37, P = 0.019 and r = 0.38, P = 0.016 for repeated measurements). All three measurements from DPTs had limited repeatability. MCT and PMI had moderate sensitivity and specificity for diagnosis of low mandibular BMD. Using ROC analysis, MCT and PMI measurements of one observer were significantly more valid than densitometry for diagnosis of low mandibular BMD. CONCLUSIONS It may be feasible to use MCT and PMI as diagnostic indicators of mandibular BMD, but further work is required to overcome problems with repeatability and to provide a larger patient sample.

Current perspectives in residual ridge remodeling and its clinical implications: A review

PURPOSE This article reviews the current understanding of the biology of tooth extraction wound healing and residual ridge remodeling. METHODS The review of the biology of tooth extraction wound healing involves a discussion of the different cells populating the tooth extraction wound, the matrix formation, and the control of the repair process in the short-term. Defects in socket matrix formation or cellular activity will lead to stalled healing. The review of residual ridge remodeling describes the long-term result of tooth extraction and formation of residual ridges, in which the quantity of bone tissue continuously decreases. This may suggest that any potential regulatory factors of residual ridge resorption should have an adverse effect either on the increased catabolic activity by osteoclasts or on the decreased anabolic activity by osteoblasts. Both short-term tooth extraction healing and long-term residual ridge remodeling processes are interdependent. Furthermore, any potential genetic and environmental regulatory factors can affect the quality and quantity of bone by altering the gene expression events taking place in bone cells. RESULTS The intent of this article was to review the current progresses of biologic research on residual ridge remodeling and to relate the changes at molecular, cellular, and tissue levels. The understanding of residual ridge remodeling may provide a sound scientific basis for improved restorative and therapeutic treatments of the edentulous population.

Detecting patients with low skeletal bone mass

OBJECTIVES The object of this study was to determine the relative usefulness of clinical and radiographic indices in the diagnosis of patients with low skeletal bone mass amongst 135 healthy perimenopausal women, aged 45-55 years, attending for routine dental treatment. METHODS Bone mineral density was measured for the spine and femoral neck, using dual energy X-ray absorptiometry. Each patients osteoporosis status was calculated according to the WHO criteria for Caucasian women. Each patient received a dental panoramic tomogram, and the width of the inferior mandibular cortex (mental index, (MI)) was measured. The body mass index (BMI) and simple calculated osteoporosis risk estimation (SCORE) indices were calculated. RESULTS The SCORE index was a significant factor in predicting low bone mass, but with the weight of the patient being the only significant constituent factor. MI, BMI and SCORE indices were significantly correlated with skeletal bone density. When the logistic regression model included MI, BMI and SCORE indices, all three variables were significant predictors of low skeletal bone mass. CONCLUSIONS A thinning of the mandibular cortices (MI<3mm) in a normal perimenopausal female is associated with low skeletal bone mass. If, in addition, the patient is underweight (BMI is below 20kg/m(2)) or has a high SCORE index (> or =6) then this increases their risk of osteoporosis.

Tooth loss and osteoporosis: the OSTEODENT Study

AIM To determine the cross-sectional association of the osteoporotic status of patients with the number of their teeth, with and without taking into account age and/or smoking. MATERIAL & METHODS At four centres, the study recruited 665 females aged 45-70 years and the number of teeth was counted for 651 subjects. Bone density was measured at the total hip, femoral neck and lumbar spine. RESULTS The mean number of teeth in the osteoporotic subjects was 3.3 fewer than normal subjects and 2.1 fewer if those with no teeth were excluded. The association between osteoporosis and having <6 or having <28 teeth remained significant after adjusting for age, smoking and centre with p-values of 0.016 and 0.011, respectively. A single regression model for tooth count with normal errors would not fit all the data. By fitting mixture regression models to subjects with tooth count >0, three clusters were identified corresponding to different degrees of tooth loss. The overall effect of osteoporosis was as follows: -1.8 teeth before and after adjusting for smoking, -1.2 teeth after adjusting for age, and -1.1 teeth after adjusting for both age and smoking. CONCLUSIONS We have established a significant association between osteoporosis and tooth loss after adjusting the effect for age and smoking.

Clinical bone densitometric study of mandibular atrophy using dental panoramic tomography

Using the dental panoramic tomogram (DPT) and a nickel stepwedge, the prevalence of mandibular osteoporosis in 99 elderly, edentulous individuals was investigated densitometrically. A site was chosen on each DPT adjacent to the mandibular mental foramen and the optical density measured using a digital densitometer. Each DPT was then independently examined by a radiologist and the patients grouped into those exhibiting osteoporosis and those not. Twenty-seven of the patients exhibited qualitative evidence of osteoporosis on the DPT, using established radiological criteria. A large majority of this group was female (25 individuals, 93 per cent). Of the remaining 72 non-osteoporotic patients, only 32 (44 per cent) were female. There was a significant difference in the quantitative, densitometrically derived measurements of mandibular bone density between the osteoporotic and non-osteoporotic groups. The osteoporotic group had a mean optical density at the mandibular measurement site (mean D = -0.773, s.d. = 0.2) which was significantly different from that of the non-osteoporotic group (mean D = -0.888, s.d. = 0.21), t = 2.432, P less than 0.02. This previously diagnosed difference supports the validity of the densitometric technique. When all 99 patients were studied, the difference between the mean mandibular, equivalent nickel thickness of the males and females was significant (t = 2.32, P = 0.022). This sex difference could not be entirely accounted for by differences in the period of edentulousness or age of males and females.

The effect of ovariectomy on the healing tooth socket of the rat

Under general anaesthesia, 35-day-old female rats were ovariectomized and the right maxillary molar teeth removed. Dynamic measures of alveolar bone formation were determined at 10 days after surgery, using the fluorochrome labelling technique, and compared with control animals. Ovariectomy significantly increased buccal resorption and palatal bone formation. In a second experiment, ovariectomized rats had the right maxillary molar teeth extracted and were killed at either 5 or 14 days after surgery. The mean mineralizing surface of the alveolar bone (percentage of surfaces occupied by a double fluorescent label) was significantly lower in rats killed at either 5 or 10 days than at 14 days after ovariectomy and tooth extraction. The mean appositional rate was significantly greater at 5 days after ovariectomy and tooth extraction than at 10 or 14 days. Oestrogen deficiency can therefore affect alveolar bone turnover following tooth extraction.

A radiographic investigation into bone resorption of mandibular alveolar bone in elderly edentulous adults

Clinical experience suggests that severe alveolar bone resorption can limit the success of complete denture wearing. The loss of bone mineral with age occurs throughout the skeleton, which contributes to the high incidence of bone fractures later in life. Women are more commonly affected by some of these fractures. The decline in serum oestrogen concentration following the menopause has been implicated in the aetiology of these fractures. We have found that age is important in determining the bone resorption observed in females but not in males.