Mandibular Distraction Osteogenesis in Children and Adolescents: A Clinical and Radiographic Research Using Cone-Beam Computed Tomography.

AIM: The aim of this cross-sectional study was to evaluate, via cone-beam computed tomography, the long-term postoperative outcome in children treated with mandibular distraction osteogenesis. MATERIALS AND METHODS: All young patients treated with mandibular distraction osteogenesis (MDO), during a 16-year period, at the University Department of Oral and Maxillofacial Surgery of a Pediatric Hospital, were recalled, and various clinical and radiographic parameters were recorded. RESULTS: Eleven patients were included: 5 with hemifacial microsomia (HFM) and 6 with mandibular micrognathia. In all cases, MDO had been successful in regular follow-up and decannulation, soon after MDO, was achieved in all tracheostomy cases. The long-term result in cases of HFM was found stable, functionally and esthetically accepted, although less satisfactory than in regular follow-up; in micrognathia patients, relapse of different degrees was registered in 4 of 6 cases, without any need for tracheostomy though. Detailed and accurate information was obtained by cone-beam computed tomography (CBCT). The shape of the regenerated bone was irregular in HFM cases and relatively normal in the micrognathia cases. Quality of the regenerated bone was normal in all patients. The irregular shape registered in HFM cases did not compromise a safe orthognathic operation. CONCLUSIONS: Distraction osteogenesis remains an early treatment choice in cases of mandibular deformities. Long-term findings showed that there is a degree of relapse with growth, which was more obvious in mandibular micrognathia cases. Computed tomography contributes to detailed evaluation of changes at the distraction site.

Radiologic findings of osteonecrosis, osteoradionecrosis, osteomyelitis and jaw metastatic disease with cone beam CT.

PURPOSE: The purpose of this study was to assess CBCT scans of patients with medication related osteonecrosis of the jaws (MRONJ), osteoradionecrosis (ORN), osteomyelitis (OM) and jaw metastatic disease (JM), evaluate the presence and extent of radiologic findings, identify radiologic parameters that may distinguish the four entities and last, introduce a new modified radiographic index (CRIm), in order to contribute to the diagnosis of these conditions. METHODS: Τwo major databases were retrospectively searched for fully documented and diagnosed CBCT scans of MRONJ, ORN, OM and JM from 2006 to 2019. 335 CBCT scans met the inclusion criteria and were assessed under standardized viewing conditions blindly by 2 observers. The CRIm index proposed in this study evaluates: lytic changes, sclerosis, periosteal bone formation, sequestration, non-healing extraction sockets and other findings which included: sinus implication, inferior alveolar canal implication and jaw fracture. Lytic changes, sclerosis, periosteal bone formation, sequestration and non-healing extraction sockets were scored as: absent (0), localized/single (1) and extensive/multiple (2). Each one of other findings were scored individually as: absent (0) and present (1). For statistical analysis t-test, Pearson's r correlation coefficient, one-way ANOVA and Bonferonni were performed. RESULTS: Extensive lytic changes were the most common finding, especially for ORN, where it occurred in all CBCT scans (100%). The mean value of the CRIm index differs significantly between CBCT scans with MRONJ and JM, as well as between those with OM and JM (Bonferroni p < 0.001). CONCLUSIONS: The new modified Composite Radiographic Index introduced in this study, appears to have improved an objective approach to the previously used Composite Radiographic Index by means of cumulative radiologic features. Τhe predominance of certain radiologic features in one or more of these entities may lead the diagnostician towards the correct diagnosis.

Morphological Assessment of Nasopalatine Canal Using Cone Beam Computed Tomography: A Retrospective Study of 124 Consecutive Patients.

This study aimed to assess and analyze the morphology and dimensions of the nasopalatine canal (NPC), as well as the adjacent buccal osseous plate (BOP), and to investigate the effect of gender, edentulism, NPC types, absence of maxillary central incisors (ACI) and age on the NPC and BOP, using cone beam computed tomography (CBCT). A total of 124 CBCT examinations (67 female and 57 male patients) were retrospectively included and evaluated. The assessment of the dimensions of the NPC, as well as the dimensions of the adjacent BOP, was performed by three Oral and Maxillofacial Radiologists on reconstructed sagittal and coronal CBCT sections under standardized conditions. Regarding the dimensions of the NPC and the adjacent BOP, the mean values were significantly higher among males than females. Furthermore, edentulous patients showed a significant reduction in BOP dimensions. Additionally, NPC types showed a significant effect on the length of the NPC, and the ACI had a significant effect on reducing BOP dimensions. Age had a significant effect on the diameter of the incisive foramen, with the mean values generally increasing with an increasing age. CBCT imaging of this anatomical structure contributes significantly to its full assessment.

The effect of nano-hydroxyapatite/chitosan scaffolds on rat calvarial defects for bone regeneration.

BACKGROUND: This study aims at determining the biological effect of 75/25 w/w nano-hydroxyapatite/chitosan (nHAp/CS) scaffolds on bone regeneration, in terms of fraction of bone regeneration (FBR), total number of osteocytes (Ost), and osteocyte cell density (CD), as well as its biodegradability. METHODS: Two critical-size defects (CSDs) were bilaterally trephined in the parietal bone of 36 adult Sprague-Dawley rats (18 males and 18 females); the left remained empty (group A), while the right CSD was filled with nHAp/CS scaffold (group B). Two female rats died postoperatively. Twelve, 11, and 11 rats were euthanized at 2, 4, and 8 weeks post-surgery, respectively. Subsequently, 34 specimens were resected containing both CSDs. Histological and histomorphometric analyses were performed to determine the FBR, calculated as [the sum of areas of newly formed bone in lateral and central regions of interest (ROIs)]/area of the original defect, as well as the Ost and the CD (Ost/mm2) in each ROI of both groups (A and B). Moreover, biodegradability of the nHAp/CS scaffolds was estimated via the surface area of the biomaterial (BmA) in the 2nd, 4th, and 8th week post-surgery. RESULTS: The FBR of group B increased significantly from 2nd to 8th week compared to group A (P = 0.009). Both the mean CD and the mean Ost values of group B increased compared to group A (P = 0.004 and P < 0.05 respectively). Moreover, the mean value of BmA decreased from 2nd to 8th week (P = 0.001). CONCLUSIONS: Based on histological and histomorphometric results, we support that 75/25 w/w nHAp/CS scaffolds provide an effective space for new bone formation.

A novel success scale for evaluating alveolar cleft repair using cone-beam computed tomography.

PURPOSE: Radiographic scales, based on plain radiographs, for the evaluation of alveolar cleft repair, have certain weaknesses and are thought to overestimate to some degree the success of the surgical intervention. The aim of this study was the presentation of a novel success scale for evaluating alveolar cleft repair using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Patients treated with secondary osteoplasty for unilateral or bilateral alveolar cleft were evaluated using the Bergland and Enemark scales, as well as the novel success scale, which measures the bone height, the bone width and the level of the nasal floor. RESULTS: A total of 44 patients with a total of 53 alveolar cleft sites were included. According to the new scale, 60% of the cases were defined as successful, with moderate (kappa = 0.511) or substantial (kappa = 0.718) agreement, between the new scale and the Bergland or Enemark scale, respectively. Statistically significant correlation was reported between the new success scale and the closure of space of the lateral incisor, the patient's age at surgery, the graft revision and the presence of residual fistula. CONCLUSIONS: The novel success scale for evaluating alveolar cleft repair using CBCT takes into consideration all dimensions of the bony bridge. Future application is necessary for validation of its potential value.

Alveolar bone histological necrosis observed prior to extractions in patients, who received bone-targeting agents.

OBJECTIVE: We reported the alveolar bone histology prior to dental extractions in cancer patients, who received bone-targeting agents (BTA). SUBJECTS AND METHODS: Fifty-four patients were included. Patients underwent extractions, and bone biopsies were taken. RESULTS: Extractions were performed due to pain, swelling, purulence, fistula, and numbness, not responding to treatment, in 40 patients (group A); extractions due to asymptomatic, non-restorable teeth, were performed in 14 patients (group B). Complete alveolar jaw bone histological necrosis was observed in 28 of 40 (70%) patients of group A and none of group B (p < .001). The development of clinical osteonecrosis (MRON) was assessed in 44 patients; 10 patients, who were also treated with Low Level Laser Treatments-LLLT, were excluded from this analysis, as the alternative therapies were a confounding factor. Twelve patients, with alveolar bone histological necrosis prior to extraction, developed medication-related osteonecrosis of the jaw (MRONJ) compared with two patients with vital or mixed vital/non-vital bone (p < .0007). BTAs >1 year and concurrent targeted therapy were also significantly associated with MRONJ (p = .016 and p = .050). CONCLUSION: Pain, swelling, purulence, fistula, and numbness were significantly associated with complete bone histological necrosis prior to extractions and increased MRONJ development. Research is justified to explore whether histological necrosis represents an early stage of osteonecrosis.

Imaging of nano-hydroxyapatite/chitosan scaffolds using a cone beam computed tomography device on rat calvarial defects with histological verification.

OBJECTIVES: Τhis study aims at determining the ability of cone beam computed tomography (CBCT) to visualize critical-size defects (CSD) created at rat calvaria and filled with 75/25 w/w nano-hydroxyapatite/chitosan (nHAp/CS) scaffolds, prior to their histological investigation. MATERIALS AND METHODS: Thirty adult Sprague Dawley rats, 15 males and 15 females, were used. Two CSD, 5 mm in diameter, were bilaterally trephined in the parietal bone. The right CSD was filled with nHAp/CS scaffold, while the left CSD remained empty, as the control group. Two female rats died post-operatively. Rats were euthanized at 2, 4, and 8 weeks post-surgery. Twenty-eight specimens (15 × 2 × 10 mm) were resected-containing both CSDs-and then scanned using a NewTom VGi CBCT imaging unit (Verona, Italy). The manufacturer's software trace region profile tool (NNT v6.2, Verona, Italy) was used in selected axial slices. The greyscale value (in VGiHU) and the traced/selected region of interest (ROI, in mm2) of those areas were automatically calculated. Subsequently, all specimens were histologically examined. RESULTS: An increased VGiHU (P = 0.000), was observed in the experimental group relative to the control group. The ROI of CSD (in mm2) was significantly reduced (P = 0.001) from the fourth to the eighth week in both groups. No statistically significant difference between male and female rats (P = 0.188) was observed with respect to VGiHU. CONCLUSIONS: The nHAp/CS scaffolds are easily visualized using a particular high-resolution CBCT device. CLINICAL RELEVANCE: Both the CBCT measurements and also the histological results suggest that the nHAp/CS scaffold presence contributes to new bone formation in rat calvarial CSD.

Recurrence in a patient with a 10-year history of sinonasal mucosal melanoma manifesting as facial swelling.

Sinonasal mucosal melanoma is a rare tumor that develops slowly and may manifest with non specific signs and symptoms, causing significant delay in diagnosis. Local recurrence is common and usually occurs within the first two years after the initial treatment. Prognosis of recurrent lesions is poor and 5-year survival ranges between 10-47%. We report the clinical, radiographic, histopathological and immunohistochemical findings of a recurrent sinonasal mucosal melanoma which was diagnosed 10 years after the initial treatment, in a patient who presented with unilateral facial swelling and one-sided difficulty in breathing of two years duration. We discuss the causes of late diagnosis and review the negative predictive factors for recurrence and survival. As early diagnosis is of paramount importance for prognosis, we emphasize the signs and symptoms of patients with a history of sinonasal mucosal melanoma which should raise the suspicion for recurrence, in spite of a long time interval since diagnosis. Key words: Mucosal melanoma, nasal cavity, sinus, recurrence.

The presence of calcifications along the course of internal carotid artery in Greek and Brazilian populations: a comparative and retrospective cone beam CT data analysis.

OBJECTIVES: We aimed to retrospectively compare the prevalence of soft tissue calcifications (STCs) depicted incidentally along the extra- and intracranial course of the internal carotid artery (ICA) on cone beam computed tomography examinations in 2 different populations (Greeks and Brazilians). METHODS: The cohort consisted of examinations of 232 Greeks and 174 Brazilians, for a total of 406 patients. The scans were evaluated for the presence of STCs along the course of the ICA, with data analyzed in each ethnic group according to gender and age criteria. RESULTS: In total, 355 STCs were recorded; 78 (22.0% of all STCs) and 58 (16.3%) were extracranials, and 128 (36.1%) and 91 (25.6%) were intracranials for Greeks and Brazilians, respectively. The χ(2) test indicated no statistical differences between Greeks and Brazilians in the occurrence of STCs; however, their prevalence differed between genders in those populations. The presence of lesions, both extra- and intracranially, was found to increase with age (P < .05). The odds ratios were estimated at 2.23 (95% CI, 1.81-2.74) and 3.26 (95% CI, 2.56-4.16) for extracranial and intracranial lesions, respectively, with increasing age. CONCLUSIONS: We found an equal distribution for both extra- and intracranial STCs among Greeks and Brazilians. The prevalence of lesions differed between genders within both populations. Aging was found to be a risk factor for STCs, as the odds ratio increased significantly.

The frequency of non-syndromic distomolar teeth in a Greek population sample?

BACKGROUND: To investigate the frequency of non-syndromic distomolars in a Greek population sample. MATERIAL AND METHODS: The study population of this retrospective study consisted of 859 Orthopantomograms (OPGs) of 425 male and 434 female patients, attended the Department of Oral Diagnosis and Radiology, Dental School of Athens seeking for treatment. The OPGs were taken as a part of the patients treatment planning. Patients' mean age was 33.57 years. Exclusion criteria from this study was cleft lip ± palate and diseases associated with systemic conditions and syndromes (such as cleidocranial dysplasia and Gardner syndrome). OPGs were only included in the study if at least one 3rd molar was present. The data collected were the number of 3rd molars, the number of distomolars, the age and the gender of each patient, information concerning previous extraction of 3rd molars. Statistical evaluation of the data included descriptive and bivariate analyses (Chi-square test and Spearman's rho correlation coefficient). In an attempt to further estimate the correlation between the presence of upper and lower 3rd conditions we assumed that the absence of 3rd molars, the presence of 3rd molars, and the presence of distomolars was ordinal in nature and we calculated the Spearman Correlation Coefficient. RESULTS: The number of distomolars was greater in the maxilla than in the mandible. In the maxilla the distomolars were located almost equally in both left and right side. It was more possible lower left distomolars to be present in males than in females. Furthermore, males present higher prevalence of supernumerary teeth than females. CONCLUSIONS: Early radiographic diagnosis of distomolars is fundamental so as to prevent complications such malocclusion, delayed eruption or displacement root or/ and resorption of adjacent teeth, pulp necrosis, follicular cyst, pain. KEY WORDS: Non syndromic, distomolars, supernumerary molars, fourth molars.

Extra- and intra-cranial arterial calcifications in adults depicted as incidental findings on cone beam CT images.

OBJECTIVE: The aim of this study was to evaluate, retrospectively, the gender- and age-related prevalence of incidentally found calcifications, depicted within the course of the extra- and intra-cranial portion of internal carotid artery (ICA), in cone beam computed tomography (CBCT) examinations in adults, and to assess their clinical significance. MATERIALS AND METHODS: Out of a pull of 700 CBCT examinations a total of 484 CBCT scans of adult patients were finally selected according to a set of pre-defined criteria. These were evaluated for arterial calcifications presence within the ICAs course according to gender and age criteria. RESULTS: In total, 492 calcifications were detected: 211 (42.88%) extra-cranial and 281 (57.11%) intra-cranial. Those were recorded in 150 scans (30.99%) and 161 scans (33.26%), respectively. Calcifications, with either extra- or intra-cranial allocation, were found more frequent in males than in females (all p-values < 0.05); also patients who presented with positive findings were older than those without findings (all p-values < 0.05). Furthermore, calcification presence with either extra- or intra-cranial allocation increases with age (all p-values < 0.05). CONCLUSION: Significant calcification frequencies were found within the ICA's course, in CBCT scans. Moreover, an increased incidence of either extra- or intra-cranial presence of these depictions and its relation to age and gender was documented.

Estimating cancer risk from dental cone-beam CT exposures based on skin dosimetry.

The aim of this study was to measure entrance skin doses on patients undergoing cone-beam computed tomography (CBCT) examinations, to establish conversion factors between skin and organ doses, and to estimate cancer risk from CBCT exposures. 266 patients (age 8-83) were included, involving three imaging centres. CBCT scans were acquired using the SCANORA 3D (Soredex, Tuusula, Finland) and NewTom 9000 (QR, Verona, Italy). Eight thermoluminescent dosimeters were attached to the patient's skin at standardized locations. Using previously published organ dose estimations on various CBCTs with an anthropomorphic phantom, correlation factors to convert skin dose to organ doses were calculated and applied to estimate patient organ doses. The BEIR VII age- and gender-dependent dose-risk model was applied to estimate the lifetime attributable cancer risk. For the SCANORA 3D, average skin doses over the eight locations varied between 484 and 1788 µGy. For the NewTom 9000 the range was between 821 and 1686 µGy for Centre 1 and between 292 and 2325 µGy for Centre 2. Entrance skin dose measurements demonstrated the combined effect of exposure and patient factors on the dose. The lifetime attributable cancer risk, expressed as the probability to develop a radiation-induced cancer, varied between 2.7 per million (age >60) and 9.8 per million (age 8-11) with an average of 6.0 per million. On average, the risk for female patients was 40% higher. The estimated radiation risk was primarily influenced by the age at exposure and the gender, pointing out the continuing need for justification and optimization of CBCT exposures, with a specific focus on children.

Quantification of metal artifacts on cone beam computed tomography images.

OBJECTIVES: To quantify metal artifacts obtained from a wide range of cone beam computed tomography (CBCT) devices and exposure protocols, to compare their tolerance to metals of different densities, and to provide insights regarding the possible implementation of metal artifact analysis into a QC protocol for CBCT. MATERIALS AND METHODS: A customized polymethyl methacrylate (PMMA) phantom, containing titanium and lead rods, was fabricated. It was scanned on 13 CBCT devices and one multi-slice computed tomography (MSCT) device, including high-dose and low-dose exposure protocols. Artifacts from the rods were assessed by two observers by measuring the standard deviation of voxel values in the vicinity of the rods, and normalizing this value to the percentage of the theoretical maximum standard deviation. RESULTS: For CBCT datasets, artifact values ranged between 6.1% and 27.4% for titanium, and between 10.% and 43.7% for lead. Most CBCT devices performed worse than MSCT for titanium artifacts, but all of them performed better for lead artifacts. In general, no clear improvement of metal artifacts was seen for high-dose protocols, although certain devices showed some artifact reduction for large FOV or high exposure protocols. CONCLUSIONS: Regions in the vicinity of the metal rods were moderately or gravely affected, particularly in the area between the rods. In practice, the CBCT user has very limited possibilities to reduce artifacts. Researchers and manufacturers need to combine their efforts in optimizing exposure factors and implementing metal artifact reduction algorithms.

Comparison of spatial and contrast resolution for cone-beam computed tomography scanners.

OBJECTIVE: The purpose was to evaluate the perceived spatial and contrast resolution for a wide range of cone-beam computed tomography (CBCT) devices. STUDY DESIGN: A customized polymethyl methacrylate (PMMA) phantom was developed. Inserts containing a line-pair and rod pattern were used. The phantom was scanned with 13 CBCT devices and 1 multislice CT (MSCT) device using a variety of scanning protocols. The images were presented to 4 observers for scoring. RESULTS: The observer scores showed excellent agreement. A wide range was seen in image quality between CBCT exposure protocols. Compared with the average CBCT scores, the MSCT protocols scored lower for the line-pair insert but higher for the rod insert. CONCLUSIONS: CBCT devices are generally suitable for the visualization of high-contrast structures. Certain exposure protocols can be used for depicting low-contrast structures or fine details. The user should be able to select appropriate exposure protocols according to varying diagnostic requirements.

Development and applicability of a quality control phantom for dental cone-beam CT.

Cone-beam CT (CBCT) has shown to be a useful imaging modality for various dentomaxillofacial applications. However, optimization and quality control of dental CBCT devices is hampered due to the lack of an appropriate tool for image quality assessment. To investigate the application of different image quality parameters for CBCT, a prototype polymethyl methacrylate (PMMA) cylindrical phantom with inserts for image quality analysis was developed. Applicability and reproducibility of the phantom were assessed using seven CBCT devices with different scanning protocols. Image quality parameters evaluated were: CT number correlation, contrast resolution, image homogeneity and uniformity, point spread function, and metal artifacts. Deviations of repeated measurements were between 0.0% and 3.3%. Correlation coefficients of CBCT voxel values with CT numbers ranged between 0.68 and 1.00. Contrast-to-noise ratio (CNR) values were much lower for hydroxyapatite (0 < CNR < 7.7) than for air and aluminum (5.0 < CNR < 32.8). Noise values ranged between 35 and 419. The uniformity index was between 3.3% and 11.9%. Full width at half maximum (FWHM) measurements varied between 0.43 mm and 1.07 mm. The increase of mean voxel values surrounding metal objects ranged between 6.7% and 43.0%. Results from preliminary analyses of the prototype quality control phantom showed its potential for routine quality assurance on CBCT. Large differences in image quality performance were seen between CBCT devices. Based on the initial evaluations, the phantom can be optimized and validated.

Cone beam computed tomographic findings in temporomandibular joint disorders.

Radiographic examination and imaging play an important role in the diagnosis and management of most temporomandibular joint (TMJ) disorders. Several techniques have been used for the examination of the TMJ, including conventional tomography, magnetic resonance imaging (MRI), arthrography, computed tomography (CT), and, recently, cone beam computed tomography (CBCT).

Evaluation of the visibility and the course of the mandibular incisive canal and the lingual foramen using cone-beam computed tomography.

OBJECTIVES: To assess the visibility and the course of the incisive canal and the visibility and the location of the lingual foramen using cone-beam computed tomography (CBCT). METHODS: In total, 100 CBCT examinations of patients for preoperative planning were used for this study. The examinations were taken using the NewTom 3G CBCT unit, applying a standardized exposure protocol. Image reconstruction from the raw data was performed using the NewTom software. Three experts were asked to assess the visibility of the incisive canal using a four-point rating scale. The position of the incisive canal was recorded in relation to the lower, buccal and lingual border of the mandible using the application provided by the CBCT software. RESULTS: The incisive canal was definitely visible in 83.5% of the scans and the mean endpoint was approximately 15 mm anterior to the mental foramen. The mean distance from the lower border of the mandible was 11.5 mm and its course was closer to the buccal border of the mandible in 87% of the scans. The lingual foramen was definitely visible in 81% of the scans. CONCLUSIONS: The high detection rate of the incisive canal and the lingual foramen in the anterior region of the mandible using CBCT indicates the potential high preoperative value of CBCT scan for surgical procedures in the anterior mandible.

Treatment of periodontal endosseous defects with platelet-rich plasma alone or in combination with demineralized freeze-dried bone allograft: a comparative clinical trial.

BACKGROUND: Platelet-rich plasma (PRP) alone or combined with other regenerative materials was previously studied in human periodontal endosseous defects. There are no sufficient data evaluating to what extent the addition of demineralized freeze-dried bone allograft (DFDBA) to PRP may enhance the effectiveness of PRP. The aim of this randomized, double-masked, controlled clinical trial was to compare the effectiveness of autologous PRP alone to PRP + DFDBA in periodontal endosseous defects. METHODS: Twenty-four proximal endosseous defects in 24 patients with severe chronic periodontitis were randomly treated with PRP alone or in combination with DFDBA. The final evaluation at 6 months was based on clinical and radiographic parameters. Subtraction radiography was used. The primary outcome variable was clinical attachment level (CAL). RESULTS: The two treatment groups were initially comparable (mean CAL: 8.67 +/- 2.19 mm for PRP + DFDBA and 8.25 +/- 1.96 mm for PRP). Both treatments achieved statistically significant and similar CAL gain (3.08 +/- 1.17 mm for PRP + DFDBA and 3.08 +/- 0.95 mm for PRP), probing depth, defect depth, and area surface reduction. The percentage of defect fill did not significantly differ between the two treatments. There was a non-significant trend to greater defect fill (45.42% versus 41.29%), defect depth (54.05% versus 49.52%), and area surface (58.43% versus 52.16%) reduction with the graft. In both groups, 66.66% of the defects gained > or =3 mm of CAL. CONCLUSION: Within its limits, this study demonstrates that both PRP and PRP combined with DFDBA resulted in significant clinical and radiographic improvement in human periodontal endosseous defects at 6 months, and the addition of DFDBA to PRP did not significantly enhance the treatment outcome.

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.