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1.
Sci Rep ; 5: 11341, 2015 Jun 22.
Article in English | MEDLINE | ID: mdl-26095146

ABSTRACT

We predict a giant field-like spin torque, T[symbol in text], in spin-filter (SF) barrier tunnel junctions in sharp contrast to existing junctions based on nonmagnetic passive barriers. We demonstrate that has linear bias behavior, is independent of the SF thickness, and has odd parity with respect to the SF's exchange splitting. Thus, it can be selectively controlled via external bias or external magnetic field which gives rise to sign reversal of T[symbol in text] via magnetic field switching. The underlying mechanism is the interlayer exchange coupling between the noncollinear magnetizations of the SF and free ferromagnetic electrode via the nonmagnetic insulating (I) spacer giving rise to giant spin-dependent reflection at the SF/I interface. These findings suggest that the proposed field-like-spin-torque MRAM may provide promising dual functionalities for both 'reading' and 'writing' processes which require lower critical current densities and faster writing and reading speeds.

2.
HPB (Oxford) ; 10(6): 388-95, 2008.
Article in English | MEDLINE | ID: mdl-19088923

ABSTRACT

AIM: A total of 329 patients with hepatocellular carcinoma have been treated at our unit since 1990. Following the randomized controlled trial in Hong Kong by Lau et al. in 1999, patients have been offered adjuvant lipiodol I-131. The aim of this study was to determine the effectiveness of adjuvant lipiodol I-131, following potentially curative surgery with resection and/or ablation, on overall and disease-free survival rates. MATERIAL AND METHODS: The prospectively updated hepatocellular carcinoma database was analysed retrospectively. A total of 34 patients were identified to have received adjuvant lipiodol I-131 post-curative treatment with surgical resection and/or ablation. Patient demographics, clinical, surgical, pathology, and survival data were collected and analysed. RESULTS: Three patients received ablation alone, 24 resection, and 7 resection and ablation. Of the 34 patients treated, there were 2 possible cases of treatment-related fatality (pneumonitis and liver failure). Potential prognostic factors studied for effect on survival included age, gender, serum AFP concentration, Child-Pugh score, cirrhosis, tumor size, portal vein tumor thrombus, tumor rupture, and vascular and margin involvement. The median follow-up duration was 23.3 months. The overall median survival was 40.1 months, while the overall survival rates at 1, 2, 3, and 4 years were 87.1%, 71.7%, 60.7%, and 49.6%, respectively. Median duration to recurrence was 22.3 months. CONCLUSION: Administration of adjuvant lipiodol I-131 is associated with good overall survival.

3.
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
4.
J Med Microbiol ; 56(Pt 10): 1393-1398, 2007 Oct.
Article in English | MEDLINE | ID: mdl-17893179

ABSTRACT

The aim of this study was to biotype and characterize phospholipase, proteinase and haemolytic activities of oral Candida albicans isolates from 210 Chinese patients with type 2 diabetes mellitus (DM) and 210 age- and sex-matched healthy controls. Seventy-six and 50 C. albicans isolates were obtained from type 2 DM patients and controls, respectively, using the oral rinse technique. The isolates were characterized with a biotyping system based on enzyme profiles, carbohydrate assimilation patterns and boric acid resistance of the yeasts, and the isolates were further tested for in vitro phospholipase, proteinase and haemolytic activities. The major biotypes of C. albicans isolates from the type 2 DM and control groups were A1R (42.1 %) and J1R (36.0 %), respectively. Significantly higher proteinase and haemolytic activities were found in the isolates from the type 2 DM group (P<0.05). Proteinase activity was higher in isolates from patients with > or =10 years of DM history than those with <10 years (P<0.05). Haemolytic activity was significantly higher in isolates from female DM patients than in those from male counterparts (P<0.05). These data provide evidence of increased extracellular enzyme activity in Candida isolates taken from DM patients.


Subject(s)
Candida albicans/enzymology , Candidiasis/microbiology , Diabetes Mellitus, Type 2/complications , Hemolysin Proteins/biosynthesis , Mouth/microbiology , Peptide Hydrolases/biosynthesis , Phospholipases/biosynthesis , Adult , Aged , Candida albicans/isolation & purification , Case-Control Studies , China , Female , Humans , Male , Middle Aged , Mycological Typing Techniques
5.
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
6.
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
7.
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
8.
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
9.
Hong Kong Med J ; 9(3): 158-63, 2003 Jun.
Article in English | MEDLINE | ID: mdl-12777649

ABSTRACT

OBJECTIVES: To investigate the prevalence and pattern of impacted teeth and associated pathologies in the Hong Kong Chinese population. SETTING: The Reception and Primary Care Clinic, Prince Philip Dental Hospital, Hong Kong. DESIGN: Retrospective study. SUBJECTS AND METHODS: The records of 7486 patients were examined to determine whether the chief complaints were related to impacted teeth and associated pathologies, which were investigated using panoramic radiographs. RESULTS: A total of 2115 (28.3%) patients presented with at least one impacted tooth. Among the 3853 impacted teeth, mandibular third molars were the most common (82.5%), followed by maxillary third molars (15.6%), and maxillary canines (0.8%). Approximately 8% of mandibular second molars associated with impacted third molars had periodontal bone loss of more than 5 mm on their distal surfaces. Caries were also found on the same surfaces in approximately 7% of the second molars. Approximately 30% of patients with dental impaction had symptoms, and 75% had complaints limited to one side of the mouth. CONCLUSIONS: The prevalence of impacted teeth was high, and there was a predilection for impacted third molars in the mandible. More than 50% of maxillary third molars had erupted, creating potential trauma of the pericoronal tissues of the partially erupted mandibular third molars. Caries and periodontal diseases were commonly seen in relation to the impacted third molars, whereas cystic pathology and root resorption were rarely observed.


Subject(s)
Tooth, Impacted/epidemiology , Adolescent , Adult , Aged , Female , Hong Kong/epidemiology , Humans , Male , Middle Aged , Prevalence , Radiography , Retrospective Studies , Tooth, Impacted/complications , Tooth, Impacted/diagnostic imaging
10.
Oral Microbiol Immunol ; 18(1): 37-44, 2003 Feb.
Article in English | MEDLINE | ID: mdl-12588457

ABSTRACT

Renal transplant patients undergoing immunosuppressive therapy may experience periodontal side-effects such as gingival overgrowth. This study evaluated the subgingival microbiota of renal transplant recipients with or without periodontal tissue destruction who may have concurrent gingival enlargement. Subgingival paper point samples taken from the deepest probing sites of 38 subjects (one per patient) were examined using direct microscopy and culture techniques. A complex microflora comprising gram-positive and gram-negative cocci, rods and filaments, fusiforms, curved rods and spirochetes was observed using microscopy. Yeasts were occasionally detected. Significantly higher proportions of gram-positive morphotypes, including gram-positive cocci, were observed in samples from periodontally healthy patients. The predominant cultivable microflora from anaerobic culture comprised several species of facultative and obligate anaerobes. Colonization of the subgingival sites by 'foreign' microbes that are normally dermal, intestinal or vaginal flora was detected in up to 50% of the samples. High mean proportions of lost or unidentified species were also occasionally noted. The results showed that the subgingival biofilm of renal transplant recipients with chronic periodontitis comprised mainly gram-negative rods and spirochetes. Besides the usual predominant cultivable subgingival microbiota associated with periodontitis, the high prevalence of unidentified and 'foreign' microbes indicates the possibility of subgingival microbial alteration in renal transplant patients.


Subject(s)
Dental Plaque/microbiology , Kidney Transplantation , Periodontitis/microbiology , Adult , Aged , Bacteria, Anaerobic/isolation & purification , Colony Count, Microbial , Female , Gingival Overgrowth/chemically induced , Gingival Overgrowth/complications , Gingival Overgrowth/microbiology , Humans , Immunosuppressive Agents/adverse effects , Male , Middle Aged , Periodontitis/complications , Statistics, Nonparametric
11.
Br Dent J ; 191(9): 517-22, 2001 Nov 10.
Article in English | MEDLINE | ID: mdl-11726065

ABSTRACT

The conceptual difference between a competency-based education and an education based upon a conventional dental curriculum is, perhaps, the starting point for the development of new curricula. The two systems are not, in themselves, exclusive. There is common ground to be found, and the concept of combining instruction with competency-based learning experiences is emerging in recent publications. This paper describes a competency-based approach applied to a clinical course in conservative dentistry. The learning outcomes of the fourth-year dental students in the new course were assessed using methods that included continuous clinical assessments, student presentations and peer-group reflective evaluations, patient management reviews, a clinical progress examination, the range and amount of work completed, and a written examination and viva voce. Different weightings were given to various elements of the assessment. A formal student assessment of the course rated it as being satisfactory.


Subject(s)
Competency-Based Education , Dentistry, Operative/education , Education, Dental , Clinical Competence , Competency-Based Education/methods , Competency-Based Education/standards , Curriculum , Dental Audit , Dental Records , Educational Measurement/methods , Humans , Learning , Peer Group , Peer Review , Personal Satisfaction , Program Evaluation , Self-Evaluation Programs , Students, Dental
12.
Int J Prosthodont ; 14(3): 260-4, 2001.
Article in English | MEDLINE | ID: mdl-11484575

ABSTRACT

PURPOSE: Because of existing controversy, the present study investigated the individual and combined effects of endodontic treatment and porcelain veneer restoration on the fracture behavior of human mandibular incisors. MATERIALS AND METHODS: Forty extracted intact human mandibular incisors were assigned to four groups of ten with a similar range of labiolingual widths at the cementoenamel junctions. Group A consisted of intact teeth; group B consisted of endodontically treated teeth; group C teeth were restored with labial porcelain veneers; and those of group D were endodontically treated and had labial porcelain veneers. All teeth were subjected to a slow continuous loading test at 30 degrees to the long axis of the teeth and 1 mm below the incisal edge on the labial side. RESULTS: Fracture forces were 415 +/- 220 N, 370 +/- 89 N, 420 +/- 128 N, and 448 +/- 156 N for groups A, B, C, and D, respectively. Root fracture was the most common mode of failure. There were no statistically significant differences between the groups in terms of fracture forces and modes of failure. CONCLUSION: Human mandibular incisors with endodontic treatment and/or porcelain veneer restorations were able to withstand the same magnitude of oblique loading as intact teeth. Endodontic treatment and/or porcelain veneer restoration did not affect the mode of failure of mandibular incisors.


Subject(s)
Dental Porcelain , Dental Veneers , Incisor/physiopathology , Root Canal Therapy , Tooth Fractures/physiopathology , Acid Etching, Dental , Analysis of Variance , Composite Resins , Dental Cements , Dentin-Bonding Agents , Gutta-Percha , Humans , Incisor/anatomy & histology , Mandible , Normal Distribution , Root Canal Filling Materials , Root Canal Preparation , Silanes , Stress, Mechanical , Tooth Cervix/anatomy & histology , Tooth Preparation , Tooth Root/injuries , Tooth Root/physiopathology
13.
Gen Dent ; 49(3): 282-7; quiz 288-9, 2001.
Article in English | MEDLINE | ID: mdl-12004728

ABSTRACT

In mixed and early permanent dentitions, median diastema can be a major esthetic concern for patients and/or their parents. The space can be transient or created by developmental, pathological, or iatrogenic factors. Different treatment techniques have been proposed to manage the situation. This paper reviews the common causes of median diastema and presents four cases to illustrate a range of restorative and orthodontic options.


Subject(s)
Diastema/therapy , Adolescent , Adult , Composite Resins , Dental Porcelain , Dental Restoration, Permanent , Dental Veneers , Dentition, Mixed , Denture, Partial, Fixed, Resin-Bonded , Diastema/etiology , Female , Humans , Iatrogenic Disease , Incisor , Male , Orthodontic Appliances, Removable , Palatal Expansion Technique/adverse effects , Patient Care Planning , Periodontal Diseases/complications , Periodontal Diseases/therapy , Tooth Eruption/physiology , Tooth Movement Techniques , Tooth, Supernumerary/complications
14.
SADJ ; 56(10): 476-80, 2001 Oct.
Article in English | MEDLINE | ID: mdl-11763616

ABSTRACT

OBJECTIVE: To review the effectiveness of computer-assisted learning (CAL) in undergraduate clinical dentistry. METHODS: A review of dental and related medical literature was conducted using a selective MEDLINE search and by manual search. RESULTS: An attempt was made to evaluate the results of computer-based teaching methods in clinical dentistry, and the future. Analysis of several controlled studies showed equivocal learning improvements for CAL when compared with other teaching methods in clinical dentistry. However, CAL technology and appreciation of the standards required for effective learning programmes have changed considerably since these early studies were published. CONCLUSIONS: There is considerable potential for effective computer-based education in undergraduate clinical dental programmes, and the Internet can provide better access to such material. However, using newer technologies, further controlled studies of the learning effectiveness and cost-effectiveness of CAL in clinical dentistry are required.


Subject(s)
Computer-Assisted Instruction , Education, Dental/methods , Humans , Internet
15.
J Pediatr Ophthalmol Strabismus ; 38(6): 327-30; quiz 354-5, 2001.
Article in English | MEDLINE | ID: mdl-11759769

ABSTRACT

PURPOSE: The type of horizontal strabismus from loss or impairment of vision is thought to depend on patient age at the time of vision loss. Association between the age at onset of vision loss and development of esotropia vs exotropia will be determined. METHODS: Patients with a diagnosis of sensory strabismus and visual acuity of 20/40 or poorer were reviewed as well as patients with diagnoses consistent with the development of sensory strabismus. Parameters considered were age at onset of vision loss and type of strabismus. Patients were excluded if the age at onset was not clear. RESULTS: Of 123 patients with sensory strabismus reviewed: 82 (67%) had unilateral vision loss; 41 (33%) had bilateral vision loss; 75 (61%) had congenital vision loss; 50 (67%) developed esotropia; 25 (33%) developed exotropia; 48 (39%) had acquired vision loss; 5 (10%) developed esotropia; and 43 (90%) developed exotropia. A significant difference was noted between age at onset and type of horizontal strabismus (X2= 37.44; P <.0001). CONCLUSION: Of patients with congenital vision loss, 67% developed sensory esotropia and 33% developed sensory exotropia. Of those with acquired vision loss, 10% developed sensory esotropia and 90% developed sensory exotropia. Patients with congenital vision loss are significantly more likely to develop esotropia, P <.005, and those with acquired vision loss are significantly more likely to develop exotropia, P <.001.


Subject(s)
Esotropia/epidemiology , Exotropia/epidemiology , Age of Onset , Esotropia/etiology , Exotropia/etiology , Humans , Infant , Infant, Newborn , Retrospective Studies , Vision Disorders/etiology , Visual Acuity
16.
Spec Care Dentist ; 21(6): 216-21, 2001.
Article in English | MEDLINE | ID: mdl-11885670

ABSTRACT

The atraumatic restorative treatment (ART) technique or approach for the restoration of primary and permanent teeth has been widely adopted in, but not limited to, developing countries. However, the requirement for the placement of the restorative materials under often less-than-ideal conditions imposes significant restrictions on their selection; and there have been very few randomized clinical trials or reports comparing different types of restorative materials and treatments. Although conventional glass-ionomer cements (GICs) have relatively poor mechanical and adhesive strengths, their satisfactory biological features, ease of use, and low costs are distinct advantages. Most of the published reports of the clinical performance of the newer, high-strength esthetic conventional GICs specifically marketed for the ART approach have been from short-term studies. Satisfactory clinical performance has been demonstrated for single-surface posterior restorations only, over three years. Findings indicate that further improvements in restorative materials are still required for their use with the ART approach, together with further clinical investigations of the remineralization of shallow open caries lesions, as an alternative to placing definitive restorations.


Subject(s)
Dental Restoration, Permanent/methods , Glass Ionomer Cements , Cariostatic Agents/administration & dosage , Cariostatic Agents/chemistry , Dental Bonding , Dental Caries/prevention & control , Dental Caries/therapy , Dental Restoration Wear , Fluorides/administration & dosage , Fluorides/chemistry , Follow-Up Studies , Glass Ionomer Cements/chemistry , Glass Ionomer Cements/classification , Glass Ionomer Cements/standards , Humans , Randomized Controlled Trials as Topic , Resin Cements/chemistry , Stress, Mechanical , Surface Properties , Tooth Remineralization , Treatment Outcome
17.
J Prosthet Dent ; 83(6): 644-7, 2000 Jun.
Article in English | MEDLINE | ID: mdl-10842131

ABSTRACT

STATEMENT OF PROBLEM: Although bonding to all-ceramic restorations is desirable, there is little information on the use of resin cements containing a phosphate monomer, and the importance of different surface treatments on their adhesion to high-strength core materials. PURPOSE: This study attempted to determine the shear bond strength values between Panavia 21 resin cement (Kuraray) and an alumina core material (In-Ceram) after 3 surface treatments and the application of a silane coupling agent. MATERIAL AND METHODS: Forty-five In-Ceram cylindrical rods were fabricated and assigned to 3 groups. Group I specimens were treated with a 9.5% hydrofluoric (HF) acid, group II with a 5% HF acid, and group III were sandblasted. All specimens were coated with a silane coupling agent (Cavex Clearfil Photobond and Activator) before cementation with Panavia 21 to sandblasted nickel-chromium rods. As a control, group IV consisted of 8 porcelain (Vitadur Alpha) rods treated with a 5% HF acid and silane. All specimens were subjected to a load of 1.2 kg during cementation, then stored under water for 36 hours. A jig mounted on a Hounsfield Universal Testing machine was used at a crosshead speed of 0.5 mm/min to test the shear bond strengths. RESULTS: The results were 14.65 +/- 4.64 MPa for group I, 18.03 +/- 6.13 MPa for group II, and 22.35 +/- 5.98 MPa for group III In-Ceram specimens; and 18.05 +/- 8.46 MPa for control (group IV). CONCLUSION: The use of Panavia 21 resin cement and a silane coupling agent can achieve a successful bond between either sandblasted or 5% HF acid-etched In-Ceram core material.


Subject(s)
Aluminum Oxide/chemistry , Dental Bonding , Dental Porcelain/chemistry , Phosphates/chemistry , Resin Cements/chemistry , Analysis of Variance , Chromium Alloys/chemistry , Dental Bonding/statistics & numerical data , Humans , In Vitro Techniques , Materials Testing/instrumentation , Materials Testing/methods , Materials Testing/statistics & numerical data , Post and Core Technique , Silanes/chemistry , Surface Properties , Tensile Strength
18.
Aust N Z J Surg ; 70(6): 428-30, 2000 Jun.
Article in English | MEDLINE | ID: mdl-10843398

ABSTRACT

BACKGROUND: We reviewed our data of laparoscopic cholecystectomies between 1990 and 1997 with reference to gangrenous cholecystitis. METHODS: In a consecutive series of 1304 patients having laparoscopic cholecystectomies, prospective data collection has permitted analysis of the relationship between gangrenous cholecystitis (GC), acute (non-gangrenous) cholecystitis (AC) and non-acute cholecystectomies (NAC). RESULTS: Twenty-five patients had gangrenous cholecystitis and 238 had acute cholecystitis. We found that patients with GC were significantly older (65.4 years vs 56.1 years (AC) and 52.7 years (NAC), P < 0.05) and had a higher M: F ratio (1.5:1 vs 1:2.6 (AC) and 1:2.8 (NAC), P < 0.05). Cardiac disease was found to be a significant factor but not diabetes. Preoperative ultrasonography correctly identified only 17 patients with acute inflammatory changes. Seven patients had an absent sonographic Murphy's sign. The gall bladder wall was generally thicker (4.11 mm vs 3.8 mm (AC) and 2.7 mm (NAC), P < 0.05) but there was marked overlap between the three groups. The common bile duct (CBD) was more dilated (6.1 mm vs 4.8 mm (AC) and 4.6 mm (NAC), P < 0.006) and there was increased incidence of CBD stones in the GC group. Our conversion rate was 8.7% with minimal complications and no operative mortality. CONCLUSION: Patients with GC were generally older, more likely to be male and had increased incidence of cardiovascular disease. Preoperative ultrasound cannot accurately identify those patients with gangrenous cholecystitis, but with conversion rates of 8.7% and no operative mortality, they can generally be managed safely with laparoscopic surgical techniques.


Subject(s)
Cholecystectomy, Laparoscopic , Cholecystitis/pathology , Cholecystitis/surgery , Acute Disease , Aged , Female , Gangrene , Humans , Male , Middle Aged , Prospective Studies
19.
Quintessence Int ; 31(6): 385-91, 2000 Jun.
Article in English | MEDLINE | ID: mdl-11203954

ABSTRACT

Trauma to anterior teeth is relatively common among children and teenagers; it has been estimated that approximately one quarter of the population under the age of 18 years sustain traumatic injury in the form of anterior crown fracture. Reattachment of a fractured fragment to the remaining tooth can provide esthetically pleasing results provided that the fragment is available. In this report, a systematic clinical approach through evaluation of periodontal, endodontic, coronal, and occlusal aspects is presented to help dentists analyze the factors affecting selection of techniques and materials. In addition, use of adhesive materials for tooth fragment reattachment is illustrated. Modifications of the reattachment process, including placement of veneer and radicular post, are also discussed.


Subject(s)
Dental Restoration, Permanent/methods , Tooth Fractures/therapy , Acid Etching, Dental , Adhesives , Adolescent , Adult , Child , Composite Resins , Cuspid/injuries , Dental Bonding/methods , Dental Occlusion , Dental Porcelain , Dental Pulp/physiopathology , Dental Restoration, Temporary , Dental Veneers , Dentin-Bonding Agents , Esthetics, Dental , Female , Humans , Incisor/injuries , Male , Periodontium/physiopathology , Post and Core Technique , Tooth Crown/injuries , Tooth Fractures/physiopathology
20.
Int J Prosthodont ; 13(1): 66-71, 2000.
Article in English | MEDLINE | ID: mdl-11203612

ABSTRACT

PURPOSE: Because of existing controversy, the present study investigated 3 methods for reducing surface roughness and improving the strength of porcelain restorations. MATERIALS AND METHODS: Ninety laminated In-Ceram/Vitadur Alpha self-glazed porcelain disks were fabricated and randomly divided into 3 groups (n = 30 each). Group 1 consisted of 30 of the original disks. The remaining 60 disks were then polished by 6 operators according to the recommendations of the American Academy of Esthetic Dentistry; group 2 consisted of 30 of these polished disks. The remaining 30 polished disks were reglazed (group 3). Average roughness values (Ra) of the veneers were measured by a profilometer. In each group, 20 disks were subjected to a flexure test, with 10 of the In-Ceram cores and 10 of the Vitadur Alpha veneers placed in tension. RESULTS: The Ra values were 0.5 +/- 0.1 micron, 0.7 +/- 0.3 micron, and 0.4 +/- 0.1 micron for groups 1 to 3, respectively. Following one-way analysis of variance (ANOVA), Bonferroni's multiple comparison tests found that groups 1 and 3 were significantly smoother than the polished group (P < 0.001). Reglazed disks were also significantly smoother than the original self-glazed disks (P < 0.01). With the veneers in tension, the flexural strengths were 151 +/- 22 MPa, 118 +/- 22 MPa, and 172 +/- 27 MPa for group 1 to 3, respectively. Following one-way ANOVA, Bonferroni's multiple comparison tests found that groups 1 and 3 were similar and were significantly stronger than the polished samples (P < 0.05 and P < 0.001). CONCLUSION: Reglazing polished porcelain surfaces significantly improved the surface texture and flexural strength of the materials tested.


Subject(s)
Aluminum Oxide/chemistry , Dental Polishing , Dental Porcelain/chemistry , Dental Veneers , Algorithms , Analysis of Variance , Humans , Materials Testing , Microscopy, Electron, Scanning , Pliability , Post and Core Technique/instrumentation , Random Allocation , Surface Properties
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