Search PubMed⌕ Search

Biomedical subjects

W Kalk

Publications and source records attributed to W Kalk.

At least 55 records · Page 3Linked to original sources
PubMed1994

Comminution of food with mandibular implant-retained overdentures.

When complete-denture wearers are treated with from four to six implants and mandibular implant-borne prostheses, masticatory performance improves. No significant improvement has been observed with two implants and implant-mucosa-borne overdentures, suggesting that the masticatory performance of edentulous subjects depends on the degree of support for their mandibular prostheses by implants or alveolar mucosa. To verify this hypothesis, we studied, in a randomized clinical trial, the comminution of an artificial test food during mastication. The trial involved the provision of a new maxillary denture and either a new conventional mandibular denture, a mandibular overdenture retained by two permucosal cylindric implants through a single bar-clip attachment, or a mandibular overdenture retained by a transmandibular implant through five clips on a triple-bar construction with cantilever extensions. In comparison with the subjects wearing mandibular implant-retained overdentures, the subjects with conventional complete dentures needed between 1.5 and 3.6 times more chewing strokes to achieve an equivalent reduction in particle size. No differences in masticatory performance and efficiency were found between the subjects who had received two permucosal cylindric implants and those who had received a transmandibular implant. The results suggest that the increased retention and stability of the mandibular denture, rather than the degree of support by implants or alveolar mucosa, determine the wearer's ability to comminute food during mastication.

Adult↗
PubMed1994

[Guidelines for occlusions and articulation. Part 2. Crown and bridgework on dental implants].

It is generally accepted that one should minimize horizontal forces or horizontal components of more vertically directed forces when loading dental implants. This has its implications for the choice of the occlusion concept. In this article various occlusal concepts aimed at different types of fixed prostheses on dental implants are discussed. When possible canine guided articulation or group function must be strived for. It is stressed that detailed pre-implantological diagnostics and treatment planning are essential to achieve high treatment standards.

Biomechanical Phenomena↗
PubMed1994

[Guidelines on occlusion and articulation. Part 1. Overdentures on implants in the edentulous lower jaw].

When loading dental implants it is generally accepted that one should minimize horizontal forces. This has its implications for the choice of the occlusal concept that is to be used for overdentures on implants. In this article various occlusal concepts for overdentures on dental implants in the lower jaw opposing different types of dental arch mutilation in the upper jaw are discussed. Apart from number, length and position of the implants, the condition of the opposite dental arch and the intermaxillary relationship play a role when choosing an occlusal concept. This article discusses the type of overdenture and the occlusal concepts for the edentulous lower jaw. A distinction is made between mucosally borne, mucosally-implant borne and implant borne overdentures on dental implants.

Biomechanical Phenomena↗
PubMed1993

Measurement of mandibular bone density ex vivo and in vivo by dual-energy X-ray absorptiometry.

Severe bone resorption is a vexing clinical problem, especially in patients without teeth. To study resorption in vivo, measurements of bone mineral density (BMD) of the mandible of both patients with and without teeth are needed. Using a Hologic QDR-1000 bone densitometer designed to measure lumbar spine and hips, ex vivo and in vivo measurements were made in selected areas of the mandible. The mandible was positioned such that the X-ray beam was perpendicular to its sagittal plane. In this way the beam hits first one half of the mandible and then the other. The reproducibility--expressed as coefficient of variation--of the ex vivo measurements was 0.5%. For in vivo measurements this coefficient was 3%. The method used for mandibular BMD would make it possible to define an average BMD in several categories of the normal population and of patients, and to compare bone density in the mandible with that in the axial and perpendicular skeleton. Improvement may be obtained by repeating the measurement. The entrance dose per scan is low, equalling that of one bitewing/radiograph.

Absorptiometry, Photon↗
PubMed1993

Five-year study of all-porcelain veneer fixed partial dentures.

Improvements in enamel-dentinal bonding systems combined with the introduction of new ceramics have encouraged replacement of missing anterior teeth in specific patients with porcelain veneer fixed partial dentures. Metal substructures are not needed, and more natural tooth structure can be preserved because the preparation of abutments is conservative. Twelve porcelain veneer fixed partial dentures were monitored for 5 years, and fractures attributed to degradation of the gingival margins occurred in the veneer surface of the fixed partial dentures. The success rate of 75% was dependent on rigid patient selection criteria, strength of the major connectors, and precise adjustment of occlusion to prevent overloading. The failing margins were attributed to the degeneration, attrition, and deterioration of the composite resin cements. Despite these limitations, patients were extremely satisfied with the esthetics. Improvement in the mechanical properties of composite resin cement will ameliorate the prognosis with this approach.

Composite Resins↗
PubMed1993

Oral health care for nursing home residents in The Netherlands--a national survey.

In order to be able to develop adequate oral health care programs for nursing home residents in The Netherlands, currently available arrangements and problems experienced by dentists participating in this field of dentistry were evaluated in a national survey. One questionnaire was mailed to the managements of all nursing homes and a second to all dentists known to be involved in nursing home dentistry. The response rates were very high. The study indicated that, in almost every nursing home, dental care for residents was available, at least in cases of dental emergency. On average the dentists were spending only limited time on nursing home dentistry. The majority of dentists examined or treated the residents only when either the patients or others experienced or discovered an oral health problem. In delivering this kind of care the dentists experienced a lot of problems. These findings suggest that the oral health care for nursing home residents in The Netherlands must be evolved by research, special training of dentists, and through development of special care programs.

Aged↗
PubMed1993

Factors connected with alveolar bone resorption among institutionalized elderly people.

In this socio-dental investigation among 175 institutionalized somatically disabled edentulous elderly people correlations are described between the test subjects' degree of alveolar bone resorption, their gender and age, their duration of edentulousness, and the number of complete dentures worn. All test subjects were interviewed by dental students and clinically examined by dentists. The mandibular alveolar bone resorption was significantly stronger in women than in men and stronger in people who had been edentulous longer. The longer the test subjects had been edentulous and the greater their degree of mandibular alveolar bone resorption was, the more mandibular dentures they had worn. This study among institutionalized elderly people provides for the most part the same results as a previously presented study among much younger people. Obviously, in these respects there are no differences between these groups.

Age Factors↗
PubMed1993

The effectiveness of oral hygiene programmes for elderly people--a review.

Comprehensive oral health care is an essential feature of quality of life. In the near future, a greater number of elderly people will retain more natural teeth, whether or not supplemented by prosthetic provisions, and/or may be provided with implants. As a consequence, oral self-care will be much more demanding. Prevention must reduce the greater risk of oral disease for elderly people. Effective early intervention strategies are: promotion of over-all general health, obviation of stereotypes, education by dental hygienists, instruction and demonstration combined with systematic evaluation, use of a fluoride containing dentifrice, and regular professional support and use of chlorhexidine rinses for less well and confused elderly.

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

[Jawbone reduction in immediate prostheses. A comparison between overdentures and complete dentures].

In a randomized controlled clinical trial 74 patients who required immediate dentures were randomly treated with immediate overdentures on 2 lower canines or immediate complete dentures. Mandibular bone reduction was measured using oblique lateral cephalometric radiographs made at base-line 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 0.75 in the immediate overdenture group and 1.90 mm in the immediate complete denture group. In the posterior parts of the mandible the bone reduction was respectively 0.77 and 1.77 mm. The differences were statistically significant in all measured regions. The differences in the first two years were significant in all regions except the molar region. 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 region of the mandible.

Alveolar Bone Loss↗
PubMed1993

Preventive goals in oral implantology.

Preventive dentistry is mainly concerned with caries and periodontal disease and little or no attention is paid to the prevention of alveolar bone loss. An overdenture contributes to the preservation of alveolar bone and offers a number of advantages in comparison to a conventional complete denture. After tooth extraction the atrophy of edentulous lower jaws can be prevented or delayed by using implants supporting an overdenture or a fixed mandibular prosthesis. Hydroxyapatite implants have been studied as submerged tooth root substitutes and have proven to be able to preserve the bulk of the alveolar ridge. A drawback of this submucosal implant is that the ridge maintenance depends solely on the physical presence of the hydroxyapatite implants. If implants support an overdenture or a fixed prosthesis they also play a role in maintaining the function of the bone in the different stages of reduction of the mandible. In this paper a classification for the different resorption stages of the mandible is presented and is used to determine the correct moment for preventive implantology. In addition the use of a lingualised occlusion is discussed as a contribution to the preventive goals in oral implantology.

Alveolar Bone Loss↗
PubMed1993

Anatomic consideration for preventive implantation.

The aim of preventive implant therapy is to prevent or delay loss of alveolar ridge bone mass. For use in an anatomic study of 60 mandibles, resorption of the alveolar ridge was classified into four preventive stages: (1) after extraction of teeth; (2) after initial resorption; (3) when the ridge has atrophied to a knife-edge shape; and (4) when only basal bone remains. Implantation in stage 3 necessitates removal of the knife-edge ridge to create space for cylindrical implants. Therefore, implantation in stage 2 is advocated to prevent the development of stage 3. The aim of implantation in stage 4 is to prevent total loss of function of the atrophic mandible.

Alveolar Bone Loss↗
PubMed1993

Needs for tooth replacement.

The prime objective of dental care is maintaining a natural functional dentition for life. It is expected that a growing group of adults will keep their dentition into old age. Although routine prosthodontic care will still be important in the future the treatment strategy for older adults and elderly people with a reduced dentition does require a different approach. The traditional approach in prosthetic therapy was guided primarily by morphological criteria aimed at preservation of complete dental arches, which resulted in emphasis on quantity in dental care. Nowadays requirements such as aesthetics and functional comfort are considered more important and more easily achieved. In the presented principles for treatment planning the importance of a thorough preliminary treatment is stressed. Furthermore, needs for tooth replacement are discussed and guidelines are given for a preventive prosthodontic treatment approach in severely broken-down dentitions and edentulous patients.

Dental Prosthesis↗