Biomedical subjects

Hugh Devlin

Publications and source records attributed to Hugh Devlin.

9 recordsLinked to original sources

PubMed2006

A mathematical model for simulating the bone remodeling process under mechanical stimulus.

OBJECTIVES: Among the current mathematical models for bone remodeling, few can consider bone resorption due to overload. The objective of this paper is to develop a new bone remodeling model which can simulate both underload and overload resorptions that often occur in dental implant treatments. METHODS: Based on the traditional model, a new mathematical equation relating the density change rate with mechanical stimulus has been developed. The new equation contains an additional quadratic term which can produce reduction in bone density at high load levels. In addition, to fully exploit the characteristics of this model, a range of different bone remodeling behaviors were studied under the load cases with both constant and varying stress magnitudes. Finally, the model was applied in conjunction with the finite element method to a practical case of dental implant treatment. RESULTS: The FE analysis results showed that bone resorption at the neck of the implant occurred due to occlusal overload but then resorption stopped after some time before reaching the coarse threads. Meanwhile, the density of the bone deeper into the mandible increased slightly due to the additional mechanical stimulus provided by the occlusal load. This phenomenon is observable in some clinical situations. SIGNIFICANCE: The new model can describe the bone overload resorption, a feature which is absent in most of the current models. And by simulating the dental implant treatment using FE method, the ability of the new mathematical model to simulate overload bone resorption has been clearly demonstrated.

Biomechanical Phenomena↗

PubMed2006

Mandibular morphological changes in low bone mass edentulous females: evaluation of panoramic radiographs.

OBJECTIVE: The objective of this study was to evaluate morphological changes of the mandible in osteopenic and osteoporotic edentulous females. STUDY DESIGN: Fifty-two female edentulous patients underwent panoramic radiography and dual-energy x-ray absorptiometry of the lumbar spine and femoral neck. Measurements of the gonial angle, antegonial angle, antegonial depth, antegonial index (AI), and mental index (MI) were performed. Patients were classified as normal (T-score > -1.0), osteopenic (T-score of -1.0 to 0 -2.5), or osteoporotic (T-score < -2.5). RESULTS: The gonial angle did not show differences among the three categories of skeletal bone status (P > .05). The antegonial angle was significantly smaller in individuals with low bone mass (P < .05). The antegonial depth was significantly greater in osteoporotic (P < .05) and osteopenic individuals (P < .05). The AI and MI were significantly smaller in individuals with low bone mass (P < .05); however, after age adjustment there were no differences among the groups (P > .05). CONCLUSIONS: Edentulous females with low bone mass have a deeper antegonial region. The thickness of the cortical mandibular bone is highly influenced by age.

Absorptiometry, Photon↗

PubMed2005

Radiomorphometric indices and their relation to gender, age, and dental status.

OBJECTIVES: To evaluate the antegonial index (AI) and the mental index (MI) in edentulous and dentate patients, in different age groups and between genders. STUDY DESIGN: We evaluated 312 panoramic radiographs and grouped them into 4 10-year age groups. Gender, dentition status and age were recorded. The measurements were performed by 2 researchers independently. RESULTS: The AI and MI were significantly smaller in older females, whereas they were greater for older males (P < 0.01). Edentulous individuals had a lower AI than dentate and partially dentate individuals (P < 0.01). CONCLUSIONS: There is a continuous remodelling in the mandibular cortex with age and this is influenced by dental status and gender. The difficulty of measuring the AI in a reproducible manner, its interaction with dental status and low correlation with MI in younger patients should discourage its use in detecting patients at risk of osteoporosis.

Adult↗

PubMed2005

The effect of water absorption on acrylic surface properties.

PURPOSE: The aim of the present study was to determine whether an increased water content during thermal cycling of hot water-treated acrylic was associated with a reduction in surface hardness and an increased opacity or whitening of the surface. MATERIALS AND METHODS: Ten acrylic samples were treated with 30 soak cycles (cycle duration, 24 hours), using warm water (40 degrees C) and an alkaline peroxide tablet (Efferdent control group); a further ten samples were treated with boiling water (100 degrees C) and one Efferdent tablet (experimental group). Indentation hardness of the acrylic specimens was measured prior to and immediately following the completion of the warm and hot water treatments, using an automated micro-indentation system. The hydrated acrylic specimens were then allowed to air dry at room temperature (20 degrees C) and were weighed weekly until they had obtained a constant dry weight. The loss in weight of the acrylic specimens represented the maximum water absorption. RESULTS: The hot water-treated specimens were much whiter than the warm water-treated specimens. The mean reduction in hardness (H(IT)) of the acrylic specimens following the treatment with hot water and alkaline peroxide tablet was 12.9%. Treatment with warm water and alkaline peroxide resulted in a slight increase in mean hardness (2.63%). There was a significant correlation between the water content of the acrylic specimens after treatment and the percentage of change in indentation hardness (r= 0.495, p= 0.026). CONCLUSIONS: The hot water treatment of the acrylic was associated with a significant reduction in hardness. We attribute the whitening and reduction in the hardness of the hot water-treated specimens to absorption of water and a disruption of the acrylic surface structure.

Absorption↗

PubMed2005

The shortened dental arch--an assessment of patients' dental health state utility values.

OBJECTIVES: The aim of this study was to determine how patients value the potential outcomes from different treatments for the shortened dental arch (SDA). METHODS: 110 partially dentate patients were interviewed and presented with illustrative models as well as a description of the process and likely outcome of six possible treatments for the shortened dental arch. The patients were asked to indicate on a standardised visual analogue scale how they would value the health of their mouth if they had received each of the treatments described. RESULTS: With a utility value of 0.0 representing the worst possible health state for a mouth and 1.0 representing the best, the mean utility value for 'no treatment' for a SDA was 0.28 (sd=0.29). For a cobalt-chromium based removable partial denture, an acrylic-resin based removable partial denture, implant treatment, a resin-bonded cantilevered bridge and a conventional cantilevered fixed bridge the utility values were 0.42 (sd=0.3), 0.49 (sd=0.31), 0.53 (sd=0.35), 0.63 (sd=0.26) and 0.64 (sd=0.28) respectively. CONCLUSIONS: The treatment outcome from a cantilevered bridge attracted the highest mean utility value. Participants did not value implant treatment as highly as fixed bridgework, but they did rate the utility of implants more highly than the utility value of removable dentures. However, the patients placed a very low value on the outcome from 'no' treatment. Thus, the appropriateness of the shortened dental arch as an oral health goal can be questioned.

Dental Arch↗

PubMed2004

The effect of ovariectomy on mandibular cortical thickness in the rat.

OBJECTIVES: The purpose of this study was to investigate the effects of long-term oestrogen deficiency on mandibular cortical thickness in ovariectomized rats. METHODS: Twelve female rats either underwent ovariectomy or received a sham-operation. One year later images of the left side of the mandible were made using a standardized radiographic protocol. Manual measurements were made of the lower mandibular cortical thickness at three locations. The mean cortical thickness was also assessed using a specially developed image analysis program by placing points at three positions, identical to those used for the manual measurements, and additionally at 20 points evenly distributed along the mandibular cortex. RESULTS: The mean mandibular cortical thickness of the ovariectomized mandibles was significantly less than that of the sham-operated rats, measured using the computer image analysis (p=0.016, 95% CI=0.125, 0.016) and measured manually (p=0.011, 95% CI=0.0218, 0.1309). When 20 computational points were used, the mean mandibular cortical width of the ovariectomized rats was significantly less than that for the control rats (p=0.016, 95% CI=0.127, 0.018). CONCLUSIONS AND CLINICAL IMPLICATIONS: Long-term oestrogen deficiency in ovariectomized rats decreased the mandibular cortical thickness. If our result is applicable to human studies, a considerable duration of oestrogen deficiency may be necessary before a reduction of mandibular cortical bone loss can be observed. Because mandibular cortical bone is resistant to resorption, the value of clinically determined mandibular cortical thickness measurements as a method of detecting patients at risk of osteoporosis may have a reduced importance in younger postmenopausal patients.

Animals↗

PubMed2004

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, betaIG-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.

Amino Acid Sequence↗

PubMed2003

Correction of the ptotic chin.

Where there is extensive stripping of the mentalis muscle from the mandible during vestibuloplasty procedures the chin tissues often become lax and droop, giving an unsightly ptotic defect. If this soft-tissue defect is combined with excessive chin tissue an excisional surgical procedure is required. This article describes a surgical procedure to produce an acceptable chin profile.

Chin↗

PubMed2002

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 patient's 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.

Absorptiometry, Photon↗