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1.
Neurocase ; 18(6): 450-6, 2012.
Article in English | MEDLINE | ID: mdl-22150361

ABSTRACT

Insular degeneration has been linked to symptoms of frontotemporal dementia (FTD). Presented in this case is a patient exhibiting semantic variant primary progressive aphasia, behavioral disturbance. Upon autopsy, he was found to have severe insular atrophy. In addition, selective serotonin reuptake inhibitors were ineffective in reducing symptoms of obsessive-compulsive behaviors or emotional blunting. This case suggests that Seeley et al.'s (2007 , Alzheimer Disease & Associated Disorders, 21, S50) hypothesis that von Economo neurons and fork cell-rich brain regions, particularly in the insula, are targeted in additional subtypes of FTD beyond the behavioral variant.


Subject(s)
Aphasia, Primary Progressive/pathology , Cerebral Cortex/pathology , Frontotemporal Dementia/pathology , Aphasia, Primary Progressive/physiopathology , Aphasia, Primary Progressive/psychology , Atrophy , Autopsy , Behavioral Symptoms , Cerebral Cortex/physiopathology , Compulsive Behavior/pathology , Frontotemporal Dementia/physiopathology , Frontotemporal Dementia/psychology , Humans , Male , Middle Aged , Neuropsychological Tests , Semantics
2.
Dement Geriatr Cogn Disord ; 31(5): 371-8, 2011.
Article in English | MEDLINE | ID: mdl-21625137

ABSTRACT

BACKGROUND/AIMS: Automated, volumetrically defined atrophy in the left anterior cingulate (LAC) and anterior temporal regions (LAT) on MRI can be used to distinguish most patients with frontotemporal dementia (FTD) from controls. FTD and Alzheimer's disease (AD) can differ in the degree of anterior temporal atrophy. We explored whether clinicians can visually detect this atrophy pattern and whether they can use it to classify the 2 groups of dementia patients with the same accuracy. METHODS: Four neurologists rated atrophy in the LAC and LAT regions on MRI slices from 21 FTD, 21 controls, and 14 AD participants. Inter-rater reliability and diagnostic accuracy were assessed. RESULTS: All 4 raters agreed on the presence of clinically significant atrophy, and their atrophy scoring correlated with the volumes, but without translation into high inter-rater diagnostic agreement. CONCLUSIONS: Volumetric analyses are difficult to translate into routine clinical practice.


Subject(s)
Frontotemporal Dementia/diagnosis , Frontotemporal Dementia/pathology , Aged , Aged, 80 and over , Alzheimer Disease/diagnosis , Alzheimer Disease/pathology , Atrophy , Autopsy , Diagnosis, Differential , Female , Gyrus Cinguli/pathology , Humans , Image Processing, Computer-Assisted , Magnetic Resonance Imaging , Male , Middle Aged , Observer Variation , Reproducibility of Results , Socioeconomic Factors , Temporal Lobe/pathology
3.
Article in English | MEDLINE | ID: mdl-21365040

ABSTRACT

PURPOSE: The aim of this study was to compare the relative accuracy of the ridge-mapping method against that of standard computed tomography (CT). MATERIALS AND METHODS: Consecutive partially edentulous subjects requiring dental implants were recruited for this prospective study. Vacuum-formed radiographic templates with reference points were used for the ridge-mapping procedure and CT scanning. Ridge-mapping measurements were translated onto study models, which were subjected to CT scanning with the templates in place. CT images of the study models obtained from the ridge-mapping method were compared with CT images of the subjects. The data were analyzed with the Wilcoxon signed-rank test. Differences were considered significant if P < .05. RESULTS: Fourteen subjects were recruited and a total of 21 implant sites were evaluated. The ridge dimensions measured by the bone-mapping method and CT scanning were significantly different (P < .05). The mean difference ranged from 0.3 to 0.5 mm, and large variations were found in the sulcus region. CONCLUSION: Measurements of the alveolar bone dimension using the ridge-mapping method are different from CT scanning, with a mean difference of about 0.4 mm.


Subject(s)
Alveolar Process/diagnostic imaging , Cone-Beam Computed Tomography , Dental Implantation, Endosseous , Patient Care Planning , Adult , Cephalometry/instrumentation , Cone-Beam Computed Tomography/instrumentation , Contrast Media , Dental Implantation, Endosseous/instrumentation , Dental Materials/chemistry , Female , Humans , Jaw, Edentulous, Partially/diagnostic imaging , Jaw, Edentulous, Partially/pathology , Male , Mandible/diagnostic imaging , Maxilla/diagnostic imaging , Middle Aged , Models, Dental , Periodontium/pathology , Prospective Studies , Young Adult
4.
Can J Neurol Sci ; 37(5): 601-7, 2010 Sep.
Article in English | MEDLINE | ID: mdl-21059505

ABSTRACT

OBJECTIVE: Primitive reflexes and parkinsonian signs are used by clinicians to differentiate among dementias. We reviewed our clinical sample to determine whether primitive reflexes were more prevalent in frontally-based dementias and whether parkinsonian signs were more common in dementia with Lewy bodies (DLB) than in other types of dementia. DESIGN: We retrospectively reviewed charts from 204 patients with dementia who presented for consultation at Baycrest's Ross Memory Clinic between April, 2003, to December, 2007. RESULTS: A greater proportion of subjects with DLB and dementia of the Alzheimer type with cardiovascular disease had primitive reflexes than subjects with frontotemporal dementia (FTD). Primitive reflexes were not positively predictive of FTD or vascular dementia (VaD). Dementia with Lewy bodies subjects were more likely to have parkinsonian signs than the other dementias, and bradykinesia and rigidity were positively predictive of FTD. The palmomental reflex was the most common primitive reflex in the sample, and cogwheeling was the most common parkinsonian sign. There was no significant difference between early- and late-stage groups in presence of primitive reflexes or parkinsonian signs. CONCLUSIONS: Primitive reflexes appear not to be clinically discriminative of frontally-based dementias such as FTD and VaD.


Subject(s)
Gait Disorders, Neurologic/epidemiology , Parkinsonian Disorders/epidemiology , Reflex, Abnormal/physiology , Aged , Aged, 80 and over , Analysis of Variance , Dementia/complications , Dementia/epidemiology , Female , Gait Disorders, Neurologic/etiology , Humans , Logistic Models , Male , Middle Aged , Models, Biological , Parkinsonian Disorders/etiology , Prevalence , Severity of Illness Index
5.
Dent Mater ; 26(9): e211-9, 2010 Sep.
Article in English | MEDLINE | ID: mdl-20542552

ABSTRACT

OBJECTIVE: This project studies the effect of high-performance polyethylene (HPPE) fibers on stress distributions in a maxillary denture and the influence of fiber position on improving denture performance. METHODS: A denture was scanned with a 3D Advanced Topometric Sensor digitizing system. The measuring system converted the images into a 3D digital model. A 3D reverse engineering technology then produced a numerical model which was then refined with Rapidform software. The underlying mucosa and bone were constructed using a freeform system integrated with a PHANTOM haptic device. A fiber lamella reinforcement was incorporated into the denture at different positions (fitting side, mid-palatal plane, polished side) with SolidWorks software. Boundary conditions were constrained at the top of the basal bone while bite force of 230 N was applied to the posterior teeth on both sides. The denture models were analyzed with ABAQUS software. RESULTS: Stress concentrations were found at the incisal notch and at the anterior and posterior palatal surfaces of the unreinforced denture. The incorporated reinforcement effectively reduced the stress concentrations at these surfaces. Placement of the fibers at polished side was the best position in reducing stress concentrations. SIGNIFICANCE: 3D FEM usefully provides a non-laboratory means to reveal the weak areas in the maxillary complete denture, and exhibit the effectiveness of HPPE reinforcement together with fiber positions on enhancement of denture strength.


Subject(s)
Acrylic Resins/chemistry , Dental Stress Analysis/methods , Denture Design , Denture, Complete, Upper , Bite Force , Finite Element Analysis , Humans , Models, Theoretical , Polyethylenes , Shear Strength
6.
Singapore Med J ; 49(4): 290-6, 2008 Apr.
Article in English | MEDLINE | ID: mdl-18418520

ABSTRACT

INTRODUCTION: The aim of this study was to investigate the prevalence of malnutrition, and its associated risk factors, in stroke patients residing in an infirmary in Hong Kong. METHODS: A cross-sectional retrospective study of 61 stroke patients residing in an infirmary was conducted. Baseline demographic data, including age, gender, smoking habit, and alcohol consumption, were obtained on admission. Nutritional status was assessed according to anthropometric parameters. Malnutrition was defined as having a body mass index (BMI) of below 18.5 kg per square metres for both gender and a serum albumin level of less than 35 g/L. 12 risk factors associated with malnutrition were evaluated according to established protocols. RESULTS: 61 of the 93 patients assessed had a history of cardiovascular accident and gave consent to participate in the study. Among them were 28 (46 percent) women and 33 (54 percent) men. The mean length of stay of these patients was 850 days (or 28 months). The mean age of these patients was 76 (standard deviation 12.8) years. Among the patients, five (8.2 percent) were malnourished and 56 (91.8 percent) were adequately nourished. There were no significant differences in the distribution of eight risk factors between the malnourished and nourished groups. These risk factors were a previous history of alcohol consumption, comorbidities (five or more), polypharmacy (five or more), diabetes mellitus, impaired functional status of daily living, impaired mobility (wheelchair- or bed-bound), tube-feeding, and edentulism. Insufficient data was available to assess the effects of two risk factors: depressed mood and impaired cognitive function. The distribution of another two risks factors (previous history of smoking and dysphagia) was significantly different between the malnourished and nourished groups. Odds ratios of smoking and dysphagia associated with malnourishment were approximately 3.3 and 2.6, respectively. CONCLUSION: Five of 61 (8.2 percent) stroke patients residing in an infirmary were malnourished. Two risk factors significantly associated with malnutrition were previous history of smoking and dysphagia. It is recommended that smoking history be elicited during routine history-taking of all stroke patients and particular nutritional attention be given to these at-risk patients. It is also emphasised that the management of dysphagia should follow a standardised protocol and form an integral element of patient care.


Subject(s)
Homes for the Aged/statistics & numerical data , Malnutrition/complications , Nursing Homes/statistics & numerical data , Stroke/complications , Aged , Aged, 80 and over , Cross-Sectional Studies , Deglutition Disorders , Female , Hong Kong/epidemiology , Humans , Male , Malnutrition/epidemiology , Middle Aged , Retrospective Studies , Risk Factors , Smoking , Stroke Rehabilitation
7.
Neurology ; 66(4): 517-22, 2006 Feb 28.
Article in English | MEDLINE | ID: mdl-16505304

ABSTRACT

OBJECTIVE: To characterize the presenting clinical features for frontotemporal dementia (FTD) and contrast them with the degree of frontal and temporal hypoperfusion on SPECT imaging. METHODS: The authors evaluated 74 patients who eventually met Consensus Criteria for the FTD form of frontotemporal lobar degeneration (excluding primary progressive aphasia and semantic dementia) on 2-year follow-up. On first presentation, these patients had undergone both an FTD Inventory for 12 features based on core and supportive Consensus Criteria and SPECT imaging. The initial clinical diagnostic features were contrasted with variations in regional SPECT hypoperfusion. RESULTS: The patients with FTD had more hypoperfusion in the right frontal lobe than in other regions; the subgroup of 25 patients who met Consensus Criteria from the first presentation had the most right frontal hypoperfusion. Frontal lobe involvement was associated with significant apathy, whereas temporal lobe involvement was associated with hypomania-like behavior. Right frontal lobe hypoperfusion further predicted loss of insight, environmental dependency, and stereotyped behaviors. Other associations included left frontal hypoperfusion with a decline in personal hygiene and left temporal hypoperfusion with compulsions and mental rigidity. CONCLUSIONS: On first presentation, frontotemporal dementia (FTD) is disproportionately a right frontal disease evident on behavioral measures and on SPECT. Nonetheless, patients with FTD can initially present with further regional differences in clinical diagnostic features, such as apathy with bifrontal hypoperfusion and hypomania-like behaviors with anterior temporal involvement.


Subject(s)
Brain Mapping/methods , Brain/diagnostic imaging , Dementia/diagnostic imaging , Tomography, Emission-Computed, Single-Photon , Follow-Up Studies , Frontal Lobe/diagnostic imaging , Humans
8.
J Oral Rehabil ; 32(10): 759-65, 2005 Oct.
Article in English | MEDLINE | ID: mdl-16159355

ABSTRACT

To evaluate the cumulative survival (CS) rates of fixed partial dentures (FPDs) retained by full-veneer retainers, and those of resin-bonded FPDs provided by graduating dental students for the replacement of a single missing tooth. In 168 patients, 61 3-unit fixed-fixed FPDs and 25 2-unit cantilevered FPDs retained by full-veneer retainers, and 77 3-unit fixed-fixed resin-bonded FPDs and 47 2-unit cantilevered resin-bonded FPDs, were examined for their retention and integrity. The periodontal health, endodontic status and coronal tissues of all abutment teeth were also evaluated. The survival rates of these various designs were analysed with the Kaplan-Meier method. The mean age of all FPDs was 31 months. At 48 months after their insertion, 3-unit FPDs retained by full-veneer retainers had a CS rate of 82%, followed by 2-unit resin-bonded FPDs at 81%, 2-unit FPDs retained by full-veneer retainers at 77%, and 3-unit resin-bonded FPDs at 63%. No significant difference was found between the four designs (P>0.05). Up to both 48 and 60 months, the most common causes of failure were endodontic for FPDs retained by full-veneer retainers, and dislodgement for resin-bonded FPDs. The 3-unit fixed-fixed FPDs retained by full-veneer retainers had the most favourable prognosis after 48 months for replacing a single missing tooth, but the difference between designs was not statistically significant.


Subject(s)
Denture, Partial, Fixed/standards , Bicuspid , Cuspid , Dental Prosthesis Design , Dental Restoration Failure , Dental Veneers , Denture Design , Denture, Partial, Fixed, Resin-Bonded , Humans , Incisor , Molar , Retrospective Studies , Students, Dental , Survival Analysis , Tooth Preparation, Prosthodontic/methods , Tooth Preparation, Prosthodontic/standards
9.
Hong Kong Med J ; 11(4): 234-42, 2005 Aug.
Article in English | MEDLINE | ID: mdl-16085939

ABSTRACT

OBJECTIVES: To investigate the prevalence and risk factors of malnutrition in geriatric patients admitted to a convalescent and rehabilitation hospital. DESIGN: Cross-sectional study. SETTING: Regional hospital, Hong Kong. PATIENTS: A total of 120 patients (aged 60 years or older) referred to Tung Wah Eastern Hospital. MAIN OUTCOME MEASURES: Anthropometric, biochemical, and haematological parameters were measured for nutritional assessment. Malnutrition was defined as a body mass index of lower than 18.5 kg/m(2) and serum albumin level of lower than 35 g/L. The clinical outcomes of patients were also recorded. The predictive value of the Chinese Mini Nutritional Assessment as a nutritional screening tool was assessed. Potential risk factors associated with malnutrition were evaluated according to established protocols. RESULTS: The mean age of patients was 80.3 years (standard deviation, 7.4 years), and the mean body mass index was 21.9 kg/m(2) (standard deviation, 4.4 kg/m(2)). The prevalence of malnutrition was 16.7%. The age distribution of malnourished patients (mean, 86.2 years; standard deviation, 7.0 years; n=20) was significantly different to those nourished (mean, 79.1 years; standard deviation, 6.9 years; n=100) [P=0.0001]. Mortality was also higher in malnourished patients (25%) than nourished patients (4%) [P=0.001]. Based on the Chinese Mini Nutritional Assessment, 16.9% of patients were classified as malnourished (cut-off value, 18.5). The Chinese Mini Nutritional Assessment was useful as a screening tool to exclude patients who were not malnourished, ie it had a high negative predictive value (95%). Being totally dependent for the performance of activities of daily living, living in a home for the elderly, and being chair- or bed-bound posed a significantly increased risk of malnutrition. The presence of mental depression (geriatric depression scale score of 8 or higher), moderately or severely impaired cognitive function (abbreviated mental test score of lower than 7), or polypharmacy (five medications or more) did not significantly affect risk of malnutrition. CONCLUSIONS: Malnutrition was common in the geriatric patients studied and was associated with an increased mortality. The Chinese Mini Nutritional Assessment was a useful screening tool to exclude malnutrition. Significant risk factors of malnutrition were total dependence, living in a home for the elderly, and being chair- or bed-bound.


Subject(s)
Malnutrition/epidemiology , Nutritional Status , Age Factors , Aged , Aged, 80 and over , Body Mass Index , Cohort Studies , Cross-Sectional Studies , Depression/complications , Female , Hong Kong/epidemiology , Humans , Inpatients/statistics & numerical data , Male , Malnutrition/complications , Memory Disorders/complications , Prevalence , Rehabilitation Centers/statistics & numerical data , Risk Factors
10.
J Oral Rehabil ; 32(5): 341-5, 2005 May.
Article in English | MEDLINE | ID: mdl-15842242

ABSTRACT

Alveloar ridges of limited dimensions could preclude the placement of dental implants of the regular dimension. Smaller diameter implants - narrow platform (NP) implants were commercially available to address this issue. The aim of the study was to determine the 5-year clinical performance of 3.3 mm diameter NP implants. Twenty-three machined screw-shaped NP implants were placed in nine patients (six males; three females) between 18 and 70 years of age. Clinical and radiographic examinations were performed annually for 5 years. Recognized implant success criteria was used. The criteria were based on the mean marginal alveolar bone loss, the placement of prosthesis of satisfactory appearance, and the absence of implant mobility, peri-implant radiolucency, pain, discomfort or infection. One implant failed at abutment connection. The remaining 22 implants were restored and functioned successfully according to the criteria. The mean marginal alveolar bone loss during the first year was 0.41 +/- 0.17 mm. The mean marginal alveolar bone loss between the second and fifth year was 0.03 +/- 0.06 mm. The success rate of NP implants according to a well-established set of criteria was 96%.


Subject(s)
Alveolar Process/pathology , Dental Implantation, Endosseous/methods , Dental Implants , Tooth Loss/surgery , Adult , Aged , Dental Restoration Failure , Dentures , Female , Humans , Male , Mandible , Maxilla , Middle Aged , Prospective Studies
11.
J Dent ; 32(6): 423-9, 2004 Aug.
Article in English | MEDLINE | ID: mdl-15240060

ABSTRACT

OBJECTIVES: The objective of this study was to investigate the corrosion resistance of the prototype iron-platinum (FePt) magnets and non-encapsulated neodymium-iron-boron (NdFeB) magnets in three different pH environments. METHODS: The corrosion resistance of the magnets was studied using a corrosion indicator, the breakaway force. The breakaway forces of the magnets after immersion in three media, namely 1% lactic acid solution (pH=2.7), 0.1% sodium sulphide solution (pH=12) and adjusted artificial saliva (pH=6.8) were compared after 28 and 60-day periods. RESULTS: By day 7, all NdFeB magnets dissolved completely in the acid medium, and they showed significantly lower breakaway forces at day 28 and day 60 in artificial saliva (90%, 69%) and in alkaline medium (67%, 42%). In contrast, the FePt magnets did not show a drop in the breakaway forces after immersion in acid or artificial saliva, although approximately half of the original breakaway forces were recorded at day 28 and day 60 after immersion in strong alkali. CONCLUSIONS: The new iron-platinum magnets, which require no yoke assembly or protective casing, has good corrosion resistance for the oral environment. If its retentive force can be improved without increasing its thickness (0.3 mm), then it will have distinct advantages for clinical use.


Subject(s)
Denture Retention/instrumentation , Magnetics/instrumentation , Boron , Corrosion , Dental Stress Analysis , Hydrogen-Ion Concentration , Iron , Lactic Acid , Materials Testing , Neodymium , Platinum , Saliva, Artificial , Sulfides
12.
Am J Alzheimers Dis Other Demen ; 19(3): 161-5, 2004.
Article in English | MEDLINE | ID: mdl-15214202

ABSTRACT

Subjects enrolled in the Autopsy Program at the University of Southern California Alzheimer's Disease Research Center may receive clinical diagnoses from primary care providers in the community or from specialists in neurology. We reviewed the autopsy concordance rates for 463 subjects for diagnoses made by both groups of clinicians. Seventy-seven percent of the sample met neuropathological criteria for Alzheimer's disease (AD). The overall diagnostic accuracy for this sample was 81 percent. Neurologists assessed 200 of the subjects (43 percent). The diagnostic accuracy for any clinical diagnosis among the non-neurologists was 84 percent, and 78 percent (p = 0.07) among neurologists. For AD, non-neurologists had a diagnostic concordance rate of 91 percent and neurologists 87 percent. Where neuropathological AD was missed, non-neurologists had failed to detect any cognitive impairment; neurologists had diagnosed Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS). Erroneous clinical diagnoses of AD missed dementia with Lewy bodies (DLB) or AD concurrent with Parkinson's disease (PD). Our findings identify specific foci for improving clinical diagnosis of dementia among all physicians managing dementia.


Subject(s)
Community Health Services/classification , Dementia/diagnosis , Adult , Aged , Aged, 80 and over , Alzheimer Disease/diagnosis , Alzheimer Disease/epidemiology , Dementia/epidemiology , Diagnosis, Differential , Diagnostic Errors/statistics & numerical data , Female , Humans , Lewy Body Disease/diagnosis , Lewy Body Disease/epidemiology , Male , Middle Aged , Parkinson Disease/diagnosis , Parkinson Disease/epidemiology , Workforce
13.
Dent Update ; 31(1): 6-7, 2004.
Article in English | MEDLINE | ID: mdl-15000002

ABSTRACT

A new Specialty in dentistry, Family Dentistry, has been established to provide a structured, co-ordinated training for general dental practitioners who are the major oral health service providers. The training emphasizes the importance of continuing and comprehensive care, the interface between primary and secondary care, the relationship between the patient and his/her family and the community, and a holistic approach in treatment planning and delivery.


Subject(s)
General Practice, Dental , Specialties, Dental , Comprehensive Dental Care , Continuity of Patient Care , Delivery of Health Care , General Practice, Dental/education , Holistic Health , Humans , Patient Care Planning , Primary Health Care , Specialties, Dental/education , United Kingdom
14.
Implant Dent ; 12(1): 35-40, 2003.
Article in English | MEDLINE | ID: mdl-12704954

ABSTRACT

Preoperative radiographic assessment is mandatory for the meticulous treatment planning and successful placement of implants. The precise topographical evaluation of selected implant sites, apart from the most straightforward cases, requires tomographic examination with the use of diagnostic radiographic templates. The incorporation of various radiopaque materials such as barium sulphate and lead foil as radiographic markers had not been entirely satisfactory. A new contrast medium, Lipiodol ethiodized oil (Laboratoire Guerbet, Paris, France), can easily be mixed with the monomer of autopolymerizing acrylic resin. The resultant acrylic template has several advantages. The tomographic images (Scanora; Soredex Orion Corporation, Helsinki, Finland) are radiographically homogenous and show the contour of the future prosthesis, the angulation of the planned implant, and the thickness of the soft tissue. In addition, the radiopaque template is optically transparent (with a slight yellow tint), which facilitates good visibility of surgical sites when the template is modified to become the surgical guide for implant placement. This transparent template can be further modified for implant position registration at the time of surgery. Because this multipurpose template is simple to construct and inexpensive, it can be recommended for routine use in implant dentistry.


Subject(s)
Contrast Media , Dental Implantation, Endosseous/instrumentation , Dental Implants , Iodized Oil , Radiography, Dental, Digital , Acrylic Resins , Adult , Dental Prosthesis Design , Equipment Design , Humans , Jaw, Edentulous, Partially/rehabilitation , Jaw, Edentulous, Partially/surgery , Male , Maxilla/surgery , Patient Care Planning , Radiography, Dental, Digital/instrumentation , Tomography, X-Ray/instrumentation
15.
Eur J Prosthodont Restor Dent ; 11(1): 29-31, 2003 Mar.
Article in English | MEDLINE | ID: mdl-12705036

ABSTRACT

Recordings of temperature and pressure in the mould have raised questions concerning the flow of poly(methylmethacrylate) during heat processing. Three simple experiments investigated flow of polymerised and partly polymerised poly(methylmethacrylate). Flow was not observed at normal processing temperatures. These results, combined with the results of previous work, suggest that as the mould heats up, thermal expansion of the dough exceeds polymerisation contraction, causing increase in pressure rather than flow. Maximum pressure occurs at maximum temperature. Thereafter, thermal expansion is reduced, polymerisation contraction increases and pressure in the mould drops. When the lowest pressure is reached the poly(methylmethacrylate) is polymerised.


Subject(s)
Denture Bases , Polymethyl Methacrylate , Differential Thermal Analysis , Hot Temperature , Humans , Models, Dental , Polymethyl Methacrylate/chemistry , Pressure , Rheology , Technology, Dental , Viscosity
16.
Gen Dent ; 51(4): 322-4, 2003.
Article in English | MEDLINE | ID: mdl-15055607

ABSTRACT

The increased emphasis on physical appearance in contemporary society has increased the demand for esthetic dental restorations. Although the success of implant dentistry has expanded the scope of esthetic fixed prostheses, many patients demand a removable partial denture (RPD) for health, anatomic, psychological, or financial reasons. Fabricating an esthetically pleasing RPD while avoiding the unsightly display associated with conventional clasp assemblies often presents a challenge to dentists. This article examines using lingual clasps, proximal undercuts (also known as rotational path insertion), and acetal resin clasps as simple and effective means of improving RPD esthetics.


Subject(s)
Denture Design , Denture, Partial, Removable , Esthetics, Dental , Adult , Dental Clasps , Denture Retention/instrumentation , Denture Retention/methods , Female , Humans , Male , Middle Aged , Tooth Preparation, Prosthodontic
17.
Dent Mater ; 18(8): 622-9, 2002 Dec.
Article in English | MEDLINE | ID: mdl-12385904

ABSTRACT

OBJECTIVES: The aims of this study were to measure the pressure and temperature changes of acrylic resin during processing, to record the highest temperature reached when fast cured in boiling water and to determine the elevated boiling point of monomer under high pressure. METHODS: A subminiature pressure transducer (temperature compensated to 94 degrees C) and a thermocouple were placed on the palate of a standardized maxillary complete denture base. A heat-cured resin (Trevalon C) was polymerized by a long heating cycle (72 degrees C for 6.5 h and 92 degrees C for 1.5 h). Recordings of pressure and temperature (n=6) were made at initial clamping of denture flasks and throughout the processing cycles of resin. The temperature of the resin was also monitored during a fast cycle, which was accomplished by placing the flask directly into boiling water for 40 min. RESULTS: The pressure of acrylic dough inside the clamped flask was initially 11.5 atm (SD=3.2) and reached a peak of 22.0 atm (SD=3.5) during the long heating cycle. The elevated boiling point of monomer at increased pressure was calculated to be about 193 degrees C (at 11.5 atm) and 228 degrees C (at 22.0 atm). These elevated boiling points are higher than the maximum temperature 131 degrees C (SD=6.6) reached during the fast curing cycle. No porosity was observed even in the denture bases heat-cured by the fast cycle. SIGNIFICANCE: The highest temperature reached by heating of resin during processing is well below the elevated boiling point of monomer. Monomer therefore does not boil in clamped denture flasks under sufficient pressure. Thus adequate clamp pressure prevents gaseous porosity irrespective of curing cycle used.


Subject(s)
Acrylic Resins , Denture Bases , Acrylic Resins/chemistry , Chemical Phenomena , Chemistry, Physical , Differential Thermal Analysis , Materials Testing , Methylmethacrylates/chemistry , Polymers/chemistry , Porosity , Pressure , Temperature
18.
Int J Artif Organs ; 25(6): 549-55, 2002 Jun.
Article in English | MEDLINE | ID: mdl-12117295

ABSTRACT

UNLABELLED: Platelets are consumed during cardiopulmonary bypass (CPB) and mechanical ventricular assistance, at least partly as a result of the formation of platelet microaggregates in the blood pump. There is no commonly accepted method currently available to detect platelet microaggregates during the use of CPB or left ventricular assist devices (LVAD). The purpose of this study was to develop a flow cytometric method for the quantification of platelet microaggregates generated in blood pumps, and to evaluate the effect of cellular fragments from hemolyzed erythrocytes on the perioperative assessment of platelet counts during CPB. METHOD: Fresh human anticoagulated blood (1IU heparin/mL, activated clotting time 250+/-24 sec.) was circulated for 120 minutes in an artificial circulatory system, containing either a centrifugal pump (CP) or roller pump (RP). Whole blood was used to quantify platelet consumption and to detect circulating platelet microaggregates in a flow cytometer. Platelet consumption was additionally analyzed using an automated "Coulter" blood cell counter. Hemolysis was analyzed by measurement of plasma free hemoglobin (fHb), as well a by flow cytometric detection of red blood cell (RBC) fragments. RESULTS: Flow cytometric analysis demonstrated significantly more circulating platelet aggregates and platelet consumption in the RP than in the CP (p<0.01). Quantification of RBC fragments and plasma free hemoglobin (fHb) levels also indicated significantly increased hemolysis in the RP than in the CP (p<0.01). In contrast, the Coulter count data indicated less platelet consumption in the PP compared to the CP. CONCLUSION: Fragments from hemolyzed erythrocytes have the same size distribution as intact platelets and the number of RBC fragments correlates with the extent of pump-induced hemolysis during CPB. Our data suggest that assessment of platelets by "Coulter counting" cannot distinguish platelets from RBC fragments and may underestimate platelet consumption in the presence of hemolysis during CPB. We conclude that flow cytometry is more accurate in the perioperative assessment of platelet count and platelet aggregation during CPB and LVAD support.


Subject(s)
Cardiopulmonary Bypass , Centrifugation , Erythrocytes/physiology , Flow Cytometry/methods , Heart-Assist Devices , Hemolysis/physiology , Platelet Aggregation , Humans , In Vitro Techniques , Platelet Count/methods , Sensitivity and Specificity , Time Factors
19.
J Oral Rehabil ; 29(2): 127-32, 2002 Feb.
Article in English | MEDLINE | ID: mdl-11856390

ABSTRACT

The aim of this study was to describe the usage of cobalt-chromium (Co-Cr) removable partial dentures (RPDs) by patients 5-6 years after denture insertion and to find out the factors that affected their denture usage. A random sample of patients provided with Co-Cr RPDs from a dental teaching hospital in Hong Kong was selected. Patients were interviewed using a structured questionnaire concerning their assessment and use of the dentures. Those who had been constantly wearing their original RPDs were examined by one calibrated examiner under optimal clinical conditions. The response rate of the patients who could be contacted was 98%. The results from 189 patient interviews showed that usage of the RPDs declined with time and that half of the dentures had been discarded or replaced 5-6 years after insertion. These discarded RPDs had been in use for an average of 19.5 months. The main reason given by the patients for not using the RPDs was general dissatisfaction with the dentures in various combinations of comfort, fit and chewing ability and, less importantly, with food trapping and appearance. No statistically significant association between denture usage and their respective Kennedy classification was found. The status of the Co-Cr RPDs that had been constantly used for 5-6 years was generally good. The majority of these RPDs demonstrated fair to good cleanliness, stability and retention and had no defect of any sort.


Subject(s)
Chromium Alloys , Denture, Partial, Removable/statistics & numerical data , Adult , Aged , Aged, 80 and over , Dental Restoration Failure , Denture Retention , Hong Kong , Humans , Longitudinal Studies , Middle Aged , Patient Satisfaction , Retrospective Studies , Surveys and Questionnaires , Time Factors
20.
Int J Geriatr Psychiatry ; 17(1): 22-8, 2002 Jan.
Article in English | MEDLINE | ID: mdl-11802226

ABSTRACT

BACKGROUND: The prevalence of Alzheimer's disease is similar across ethnic groups. To our knowledge, no comparison of behavioral symptoms has been addressed. OBJECTIVE: This cross-sectional, retrospective, descriptive study compares neuropsychiatric symptoms of Chinese subjects with Alzheimer's disease (AD) at tertiary care centers in Taiwan and Hong Kong against Caucasian subjects in Los Angeles, California. We compared the frequency and severity of symptoms and caregiver responses to neuropsychiatric symptoms of AD using the Neuropsychiatric Inventory (NPI). We hypothesized that Chinese patients do not seek care unless they have high severity of neuropsychiatric symptoms and that Caucasian Americans do not wait for behavioral disturbances to develop before coming to medical attention. RESULTS: The Caucasian sample had the highest mean educational level and mildest Clinical Dementia Rating (CDR) scale distributions of all four groups. Older age and lower educational levels contributed to higher CDR scale scores, which in turn correlated with higher total NPI scores. Only one of the Chinese samples had a higher frequency of severe neuropsychiatric symptoms than the Caucasian sample. Chinese caregivers reported anxiety and delusions more frequently (58.1%) than Caucasians (37.3% and 39.6%; chi(2), p < 0.01 and p < 0.05, respectively). Caucasians reported appetite changes (47.3%) and apathy (59.2%) more frequently than the Chinese samples (chi(2), p < 0.05 and p < 0.01, respectively). Caregivers at all four centers were distressed by behaviors qualified as severe. CONCLUSION: We found support for our hypothesis, in that Chinese subjects presented during a more severe stage of dementia than American subjects, but the delay in seeking care could not be correlated with significant differences in neuropsychiatric profiles of the demented subjects. Other barriers to dementia care warrant investigation.


Subject(s)
Alzheimer Disease/ethnology , Asian People , Cross-Cultural Comparison , Aged , Aged, 80 and over , Alzheimer Disease/diagnosis , Alzheimer Disease/psychology , Female , Hong Kong , Humans , Los Angeles , Male , Neuropsychological Tests , Patient Acceptance of Health Care/ethnology , Taiwan
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