Biomedical subjects

M A Van 't Hof

Publications and source records attributed to M A Van 't Hof.

At least 19 recordsLinked to original sources

PubMed2004

Effectiveness of single-surface ART restorations in the permanent dentition: a meta-analysis.

Over the past few years, there has been an increase in the number of studies reporting on various aspects of the Atraumatic Restorative Treatment (ART) approach. Five randomized clinical trials in which ART restorations with glass ionomers were compared with amalgam restorations in permanent teeth for a maximum period of 3 yrs constituted the database. This meta-analysis divided the publications into 'early' (1987-1992) and 'late' (1995-) studies on the basis of improvements in the approach. The analysis showed that, in the 'early' studies, single-surface amalgam restorations survived statistically significantly longer than comparable ART restorations after 1, 2, and 3 yrs. This trend did not continue into the late group of studies; no statistically significant difference between the 2 types of restorations was found. Based on the available data, it appears that there is no difference in survival results between single-surface ART restorations and amalgam restorations in permanent teeth over the first 3 yrs.

Confidence Intervals↗

PubMed2003

Age effect on orthodontic tooth movement in rats.

Orthodontic procedures seem to be more time-consuming in adults than in juveniles. This might be related to delay in the initial tissue response or to a slower turnover of the bone and periodontal ligament in adults. To study this problem, we studied orthodontic tooth movement in two groups of 30 rats, aged 6 wks and 9-12 mos, respectively. At one side of the maxilla, 3 molars together were moved mesially with a standardized orthodontic appliance delivering a force of 10 cN. The other side served as a control. The results showed a faster initial tooth movement in juvenile than in adult animals. However, once tooth movement had reached the linear phase, the rate of tooth movement was the same in both groups. The results indicate that, besides a delay in the onset of tooth movement in adult animals, tooth movement could be equally efficient in adults once it had started.

Aging↗

PubMed2001

Evolution of deep venous thrombosis: a 2-year follow-up using duplex ultrasound scan and strain-gauge plethysmography.

OBJECTIVE: The development of the post-thrombotic syndrome (PTS) and recurrence of deep venous thrombosis (DVT) are not yet fully understood. The aim of the study was to identify factors that lead to the long-term complications of DVT. METHODS: In a 2-year prospective follow-up study, duplex scanning and strain-gauge plethysmography were used to evaluate DVT in relation to the development of long-term complications. Each of the 12 segments examined was assigned as a thrombosis score (TS). A total TS was calculated for each leg. Patent segments were assigned a TS = 0, noncompressible vein segments with flow TS = 1 and noncompressible vein segments without flow TS = 2. The degree of resolution of DVT and the incidence, timing, and outcome of further thrombotic events were measured during 24 months of follow-up. RESULTS: The study involved 86 legs with DVT. The 2-year follow-up was completed for 70 legs. Within 3 months, only 1% of the originally occluded proximal deep vein segments were still occluded. Between all time intervals, from month 12 to month 24, for example, thrombus regression continued in 36% of the legs and thrombus propagation continued in 27%. Multiple regression analysis revealed that an increase in age (P = .008) and proximal location of the original DVT (P = .05) was significantly related to thrombus propagation. Multiple regression analysis showed that the risk factors for clinical signs of PTS were a high venous outflow resistance after 1-month and 12-month follow-ups (P <or= .002) and a high thrombosis score in the proximal veins after 3 months (P = .008). CONCLUSIONS: In the follow-up of older patients and patients with proximal DVT, evolution was shown to be an unstable process with continuing propagation for 2 years. The risk factors for the development of PTS were a slow decrease in venous outflow resistance or a high thrombosis score of the proximal veins after 3 months.

Adolescent↗

PubMed2000

A controlled clinical trial of implant-retained mandibular overdentures; five-years' results of clinical aspects and aftercare of IMZ implants and Brånemark implants.

The aim of this prospective randomized controlled clinical trial was to evaluate a set of clinical items and prosthetic aftercare of edentulous patients with a mandibular overdenture retained by 2 IMZ implants or 2 Brånemark implants during a 5-years' period. Patients were allocated to the IMZ group (n = 29) or the Brånemark group (n = 32) by a computerized balancing method. In the IMZ group 4 implants were lost during the 5-years' follow-up (survival rate: 93%). In the Brånemark group 9 implants were lost (survival rate: 86%). All patients were re-operated successfully. Multiple prosthetic revisions were necessary in both groups, especially the precision attachment system in the overdenture was subject to frequent fracture or loosening. From this study can be concluded that there is no difference in clinical state, radiographical state, survival rate and clinical implant performance between the IMZ implant system and the Brånemark implant system supporting an overdenture on 2 implants after 5 years of follow-up.

Chi-Square Distribution↗

PubMed2000

No increased mortality in patients with rheumatoid arthritis: up to 10 years of follow up from disease onset.

OBJECTIVE: To investigate mortality, functional capacity, and prognostic factors for mortality in an inception cohort of patients with recently diagnosed RA followed up for up to 10 years. METHODS: The observed mortality of this inception cohort with recently diagnosed RA, was analysed in relation to the expected mortality, calculated with the aid of life tables of the general population of the Netherlands (matched for age and sex). Functional capacity was measured by the Health Assessment Questionnaire. Prognostic factors for mortality were analysed multivariately by the Cox proportional hazards model. RESULTS: Between January 1985 and April 1997, 622 patients entered the study, and were included in the analysis of mortality. The death rate in the first 10 years of the disease was not significantly different from that of the general population. Fifty five patients from the study group died (16% up to 10 years of follow up). The most commonly reported causes of death were of cardiovascular and respiratory origin. The other causes of death could be classified into cancer, sepsis, amyloidosis, leukaemia, renal insufficiency of unknown cause, perforation of the oesophagus, probably related to the treatment with non-steroidal anti-inflammatory drugs, and pancytopenia during aurothioglucose treatment. Functional capacity improved significantly during the first six years compared with the value at start. Statistically significant predictors for death were age at the start and male sex. CONCLUSIONS: In contrast with earlier studies performed, no excess mortality in the first 10 years of an inception cohort of patients with RA was seen. In addition, the functional capacity was relatively constant during the first six years after an initial improvement from baseline. Age at start and male sex were the only statistically significant predictors for death.

Adolescent↗

PubMed1998

Assessment of dental and facial aesthetics in adolescents.

The Index of Orthodontic Treatment Need (IOTN) is currently widely used for clinical, as well as epidemiological purposes. The Aesthetic Component (AC) of this index focuses on dental aesthetics and does not include facial aesthetics. The aim of the present study was to evaluate whether dental aesthetics as measured by the AC of the IOTN correlates with facial aesthetics. Facial attractiveness of 69 males and 75 females was scored on facial photographs at two different ages (11-13 years and 14-16 years). Scoring of the AC of the IOTN was undertaken on the dental casts. Increments between the observations at the two ages were calculated. To assess the association between scores of dental and facial aesthetics, correlation coefficients were calculated. There was a highly significant influence of orthodontic treatment on facial and dental aesthetic scores in the group which was not treated orthodontically at the first observation, but was treated orthodontically at the second observation. No correlation, however, was found between the increments in the facial aesthetic score and those in the dental aesthetic score. The results indicate that facial and dental aesthetics are influenced by different factors, and both should be evaluated when judging dentofacial aesthetics.

Adolescent↗

PubMed1994

A Dutch version of the functional index for ankylosing spondylitis: development and validation in a long-term study.

A Dutch Functional Index (DFI) for AS has been developed, containing 37 questions in essence this is a modification of a French index with additional questions. Internal consistency, reproducibility, criterion and construct validity and sensitivity to change were studied in different groups of AS patients. In a group of 149 patients the questionnaire was completed and internal consistency calculated (Cronbach's alpha = 0.94) after exclusion of three items. Reproducibility was studied in 39 patients with stable disease; Pearson correlation was 0.94. Criterion validity, against a 'gold standard' i.e. experts' observation of 25 items, was studied in 19 patients; r = 0.85. In a 48-week NSAID study patients were enrolled after a washout period: DFI scores before and after treatment showed significant improvement (P < 0.02). There were 187 DFI with corresponding clinical measurements, correlations varied from -0.30 to 0.68. Estimated measurement-remeasurement correlation was 0.87. The DFI is, thus, a potentially useful instrument, which is valid, reliable and sensitive to the effects of NSAID treatment.

Adolescent↗

PubMed1993

A prospective analysis of risk factors for the discontinuation of second-line antirheumatic drugs.

Clinical and laboratory factors influencing the discontinuation of second-line antirheumatic drugs were prospectively studied using survival analysis in a consecutive series of 245 patients with recently diagnosed rheumatoid arthritis. A statistically significant influence of age, sex, serum IgA and HLA-DR3 on the discontinuation rate of chrysotherapy because of toxicity was observed. The discontinuation of sulfasalazine was increased by advanced age and high rank order of prescription. With respect to efficacy, high initial disease activity appeared to predispose to treatment termination of hydroxychloroquine, sulfasalazine and penicillamine. Furthermore, an influence of the rank order of prescription on discontinuation of sulfasalazine therapy because of lack of efficacy was found. Of interest is that discontinuation of hydroxychloroquine therapy because of lack of efficacy occurred less frequently in HLA-DR3-positive than in HLA-DR3-negative patients. Although these prognostic factors are of secondary importance in clinical practice, they may be of significance in the interpretation and comparison of clinical trials.

Aged↗

PubMed1993

Differences two years after tooth extraction in mandibular bone reduction in patients treated with immediate overdentures or with immediate complete dentures.

In a randomized controlled clinical trial, 74 patients who required immediate dentures were randomly treated with immediate overdentures on two lower canines or with immediate complete dentures. Mandibular bone reduction was measured by use of oblique lateral cephalometric radiographs made at baseline and the results compared with those of one year and two years after denture treatment. Analysis of the data showed that the average bone reduction in the lower canine regions in the first year was 0.9 mm in the immediate-overdenture group and 1.8 mm in the immediate complete-denture group. In the posterior parts of the mandible, the bone reductions were, respectively, 0.7 mm and 1.9 mm. The differences were statistically significant in all measured regions. During the second year, no significant differences in bone reduction were found. The sums of differences in the first two years were significant in all regions except the molar region, preserving the initial difference. Retention of roots of canines beneath a mandibular denture in immediate denture patients, even when they were in poor condition, reduced the collapse of the alveolar processes in all regions of the mandible.

Alveolar Bone Loss↗

PubMed1993

Prevalence in the Dutch adult population and a meta-analysis of signs and symptoms of temporomandibular disorder.

A nationwide survey of oral conditions, treatment needs, and attitudes toward dental health care in Dutch adults was carried out in 1986. One of the aims of the study was to assess the prevalence of signs and symptoms of temporomandibular disorder (TMD). A sample of 6577 persons (from 15 to 74 yr of age), stratified for gender, age, region, and socio-economic status, was contacted. Of this sample, 4496 persons participated in the behavioral part of the study, of whom 3526 were examined clinically. The TMD prevalence was based on (1) perceived signs and symptoms of TMD and (2) clinical examination of joint sounds, deviation, and pain on mandibular movements. A total of 21.5% of the Dutch adult population perceived some dysfunction, and 44.4% showed clinically assessed signs and symptoms of TMD. In nearly all age groups, the signs and symptoms of TMD appeared more in women than in men. Agreement between the results of the clinical examination and the anamnestic dysfunction index was significant (p < 0.0001); however, the Pearson's correlation coefficient was low (r = 0.29). The odds-value (risk-ratio) that subjects who perceived signs and symptoms of TMD would present with clinically assessed signs and symptoms of TMD was 2.3. The results of the survey were compared with results of a meta-analysis performed on 51 TMD prevalence studies. The analysis revealed (1) a perceived dysfunction rate of 30% and (2) a clinically assessed dysfunction of 44%, both based on compound samples of, respectively, over 15,000 (23 studies) and over 16,000 (22 studies) randomly selected subjects.

Adolescent↗

PubMed1992

Treatment times of amalgam restorations.

The aim of this study was to present information about treatment times for amalgam restorations and the factors influencing them. The study was carried out as part of a clinical trial. Following a written treatment protocol, 1044 class II restorations with two surfaces and 1433 restorations with three surfaces were made by seven operators. The statistical method consisted of an ANOVA after log. transformation of the treatment times. The mean total treatment time for two-surface restorations was 24 min and for three-surface restorations 30 min. The mean finishing and polishing time was 6.3 min. A significant effect on the treatment time was noted for: (1) operator, (2) size of the restorations, and (3) type of tooth (molar/premolar). The results of this study may be useful for cost-benefit analysis and for efficient planning in dental practice.

Analysis of Variance↗

PubMed1992

A longitudinal radiographic study of the periosteal migration along the growing rabbit mandible.

In the present study, the role of the periosteum in mandibular growth was investigated. The orientation of the superficial bony spicules of rabbit mandibles was determined on dry skulls after perfusion of the animals with an India ink solution. The spicular orientation in the ramus area appeared to be toward the condyle, rostrally toward the incisors, and caudally toward the angular region. The behavior, during growth, of the periosteum in the caudal mandibular half was studied by implantation of metal periosteal and bone markers. A series of cephalograms revealed the migration pattern of the periosteal markers, and by that the migration pattern of the periosteum. It can be concluded that both the pattern of the superficial bony spicules and the periosteal migration pattern suggest a possible influence of the periosteum on mandibular growth.

Animals↗

PubMed1992

Demand and need for treatment of craniomandibular dysfunction in the Dutch adult population.

A nationwide survey of oral conditions, treatment needs, and attitudes toward dental health care in Dutch adults was carried out in 1986. One of the aims of the study was to investigate the perceived need and demand for treatment of craniomandibular dysfunction (CMD). A sample of 6577 persons (15-74 yrs of age), stratified for gender, age, region, and socio-economic status, was contacted. Of this sample, 4496 persons participated in the behavioral part of the study, of which 3526 were examined clinically. The CMD-treatment demand was based on (1) CMD complaints in the past, (2) CMD complaints at present, and (3) an anticipated increase of the present complaints. CMD was both anamnestically and clinically assessed, independently by different examiners. A total of 21.5% of the Dutch adult population reported dysfunction, but 85% of these perceived no need for treatment. With most of the remaining 15% either seeking or intending to seek treatment (or having had it before), a figure of 3.1% can be used to summarize the actual level of treatment need for CMD in the Dutch adult population.

Adolescent↗

PubMed1991

An analysis of clinical studies on resin-bonded bridges.

Many clinical data on resin-bonded bridges (RBBs) have been published in the last ten years. The survival rates vary widely, and the conclusions are sometimes conflicting. A method of combining the results of different studies in order to draw conclusions about the effectiveness of therapeutic concepts is meta-analysis. The aims of the meta-analysis in this study were: (1) to assess an "overall" survival ratio for RBBs and (2) to explore relationships between potential success factors and reported survival times. About 60 publications with clinical data on RBBs were reviewed. Following a number of inclusion criteria (information adequate to calculate or assess survival rates, as well as adequate information about the patients, the designs, and types of RBBs), 16 different samples were used for this meta-analysis. A weighted multiple-regression analysis revealed no significant effects of "type of retention" and "location" on the survival percentages. Kaplan-Meier estimates were used to assess overall survival in a secondary analysis with the data from all 16 samples (n = 1598). The overall survivals were: one year, 89 +/- 1%; two years, 84 +/- 1%; three years, 80 +/- 1%; and four years, 74 +/- 2%.

Composite Resins↗

PubMed1991

Design, methods and participation. Euronut SENECA investigators.

At the initiative of EC/Euronut a European Community project (SENECA) began in 1988, with 19 research groups working on the major nutritional issues affecting the growing number of elderly people in Europe. Some 2600 people born between 1913 and 1918 were studied, using strictly standardized methodology. Data have been collected on the dietary intake of these people, their nutritional status, physical activity, life-style, health and performance. It is envisaged that the SENECA project will be continued according to a mixed longitudinal design. The mean response rate in a group of 18 communities in which a non-participation study was conducted was 51%, while 60% of the non-responders were prepared to complete a non-responders' questionnaire. On the basis of the data collected from both responders and non-responders, it was found that males, non-smokers, healthy and better educated persons participated better in the SENECA study than females, smokers, persons who judged their health to be poor, and persons with comparatively poor education, respectively. Housing (having a garden), age, and marital state (single) were only of minor importance for the participation. Persons who did not eat a cooked meal daily, generally participated less, but this differed between towns. It is demonstrated how stratum-specific weighting factors can be calculated to partially remove bias due to selectivity in participation.

Aged↗

PubMed1990

Clinical performance of resin-bonded bridges: a 5-year prospective study. Part III: Failure characteristics and survival after rebonding.

A total of 203 resin-bonded bridges were inserted under controlled clinical conditions and evaluated over a period of 5 years. During the evaluation period there were 47 dislodgements and 30 pontic fractures. The majority of the failures were retreated successfully. Dislodgement was in most cases due to fracture at the resin/retainer interface. The small number of fractures at the resin/tooth interface indicate that the clinical procedures, as used in this study, were satisfactory. Dislodged and rebonded resin-bonded bridges had a lower retention than original bonded bridges, indicating that patients with a dislodged bridge are a risk group for the retention of rebonded bridges. However, possible factors that may be responsible for this higher risk could not be demonstrated. The bridges which were removed for repair of the pontics and rebonded showed an acceptable retention. There was no relationship between the failure characteristic and the retainer type or the cementation material used.

Dental Abutments↗

PubMed1990

Caries prevalence in the deciduous dentition of a Tanzanian urban and rural child population in relation to levels of fluoride in drinking water in 1984, 1986 and 1988.

A mixed-longitudinal study to determine the prevalence of caries in the deciduous dentition of a Tanzanian child population was carried out in Morogoro Region between 1984 and 1988. Since 1978 shallow wells have been constructed in the study areas which contained water in the range of the assumed optimal fluoride level in tropical countries (0.5-1.0 ppm). Three areas were distinguished, urban, rural and villages in rural areas with an average fluoride concentration of 0.5 ppm or more in all drinking water sources present. There were no fluoridated toothpaste for sale nor were organised oral health programmes implemented in the study areas. The following background parameters were studied; age, locality, socioeconomic status and sex. School children aged 7- to 9-year (= 694), 7- to 11-year (n = 652) adn 7- to 13-year (n = 555) were examined in 1984, 1986 and 1988 respectively. For all three years of investigation, children living in villages with naturally fluoridated water were found to have significantly lower mean number of dentinal lesions than those living in urban and/or rural areas. There were no restorations found. Over the three years of investigation the mean dft*-scores were low and varied between 1.67 (urban area in 1984) and 0.79 (naturally fluoridated rural areas in 1984). No SES and sex effect on the dft-condition were found. It is recommended that water samples be collected from all drinking water sources in all regions of Tanzania and to map the results of the fluoride analyses for use in prioritization setting in planning oral health services at national and regional level.

Adolescent↗

PubMed1989

Cohort effects in the prevalence of caries in child populations in Tanzania.

In 1984, a four-year mixed-longitudinal study of oral health was begun in Morogoro Town and Morogoro District, Tanzania. Its main goal was to detect a possible upward trend in prevalence of caries in child cohorts in this developing country. The sample consisted of 722 seven- to nine-year-olds in 1984, 833 seven- to 11-year-olds in 1986, and 989 seven- to 13-year-olds in 1988. Mixed-longitudinal studies provide the opportunity for application of the Age-Period-Cohort analysis. On the basis of external information, either age and/or cohort and/or period effects can thus be isolated. Apart from significant age and period effects, a cohort effect was found, indicating that the prevalence of caries has decreased in these child populations between 1984 and 1988.

Adolescent↗