The effect of denture factors on masticatory performance. V. Food platform area and metal inserts

Influence of food platform width of mandibular removable partial denture on food mixing ability

The aim of this study was to clarify the influence of food platform width on food mixing ability in patients with mandibular removable partial dentures (RPDs). Twelve subjects (six males and six females, mean age 56.8 years) with intact dentition except for unilaterally missing mandibular first and second molars participated in the study. The food platforms of their RPDs were made of light polymerized composite and three platform conditions were evaluated. A food platform (Control condition) had 7 mm width with a central focus on the top of the residual ridge. Narrowed platforms (5 mm) were created by trimming a lingual portion (Buccally oriented occlusion, Buccal condition) or a buccal portion (Lingually oriented occlusion, Lingual condition) from the control. Subjects chewed a standardized wax cube which provided an estimate of food mixing ability [Mixing Ability Index (MAI)] for each of the three platforms. A significant effect (P < 0.001) on the MAI was found for food platform type (repeated measures one-way analysis of variance). Tukey multiple comparisons found significant differences of MAI between Control condition (1.05 +/- 0.26) and Buccal condition (0.86 +/- 0.23) (P = 0.032), and between Control and Lingual condition (0.54 +/- 0.37) (P < 0.001). Furthermore, MAI with Lingual condition was significantly smaller than that with Buccal condition (P < 0.001). These results suggest that reduction in the width of the food platform may impair masticatory function and the buccal portion of mandibular food platform of RPD is more critical for food mixing than the lingual portion of the platform.

Evidence-based considerations for removable prosthodontic and dental implant occlusion: A literature review

The dental literature is filled with discussions of dental occlusion, occlusal schemes, philosophies, and methods to correct and restore the diseased, worn, or damaged occlusion. Traditionally, these discussions have been empirical in nature and not based on scientific evidence. Due to the empirical nature of the literature, the study of occlusion has been extremely complex and troublesome to both pre- and post-doctoral students. The introduction of osseointegrated implants has further complicated the situation. Dentists may apply the principles of occlusion for the natural dentition directly to implant-supported and retained restorations. Although this may be successful, this rationale may result in overly complex or simplified treatment protocols and outcomes. There is an emerging body of scientific literature related to dental implant therapy that may be useful in formulating treatment protocols and prosthesis designs for implant-supported restorations. This review focuses on some of the "classic" removable prosthodontic literature and the currently available scientific literature involving removable prosthodontic occlusion and dental implant occlusion. The authors reviewed the English peer-reviewed literature prior to 1996 in as comprehensive manner as possible, and material after 1996 was reviewed electronically using MEDLINE. Electronic searches of the literature were performed in MEDLINE using key words-animal studies, case series, clinical trials, cohort studies, complete denture occlusion, dental implant function, dental implant occlusion, dental implant occlusion research, dental implant functional loading, dental implants, dental occlusion, dental occlusion research, denture function, denture occlusion, dentures, implant function, implant functional loading, implant occlusion, occlusion, and removable partial denture occlusion-in various combinations to obtain potential references for review. A total of 5447 English language titles were obtained, many of which were duplicates due to multiple searches. Manual hand searching of the MEDLINE reference list was performed to identify any articles missed in the original search.

Treating the modern complete denture patient: a review of the literature

This article reviews the physical and mental compromises of today's patients, techniques, materials, occlusion, impressions, and soft liners and makes recommendations as to managing these compromises when fabricating complete dentures. References used were primarily from the "classical literature," and an effort was made to ascertain whether these treatment recommendations are appropriate for today's more difficult patients. An effort was made to incorporate recent recommendations where appropriate.

Can dentures improve the quality of life of those who have experienced considerable tooth loss?

OBJECTIVES

The aim of this study was to identify variations in the impact of oral health on quality of life (OHQOL) among UK residents in relation to self-reported number of teeth possessed and denture status. In addition, to determine whether recourse to a removable prosthesis for those who claimed that they had experienced considerable tooth loss (having <20 teeth) was associated with quality of life.

METHODS

The vehicle for this was the Office for National Statistics Omnibus survey in Great Britain. A random probability sample of 2667 addresses was selected in a multistage sampling process. Participants were interviewed about their oral health status. The impact of oral health on quality of life was measured utilising the OHQoL-UK(W) measure.

RESULTS

The response rate was 68%. Variations in OHQoL-UK(W) scores were apparent in relation to self-reported number of teeth possessed (P < 0.001) and denture status (P < 0.001). Moreover, disparities in OHQOL were apparent among those who experienced considerable tooth loss who didn't have recourse to a denture (P < 0.001). In regression analysis, those who claimed that they had <20 natural teeth but had no recourse to a denture were less than half as likely to enjoy enhanced oral health related quality of life compared to others in the population (OR = 0.46, 95% Cl 0.30, 0.71), controlling for socio-demographic factors.

CONCLUSIONS

Experience of considerable tooth loss without recourse to a removable dental prosthesis is an important predictor of oral health related quality of life, as captured by OHQoL-UK(W), and associated with reduced quality of life.

A procedure for constructing dentures with interchangeable teeth

Studies that compare different types of complete denture teeth have repeatedly emphasized the importance of standardizing all denture factors, except the type of teeth. Within-subject comparisons have also been recommended to avoid personal differences between patients. For optimum results, one denture should be constructed for each patient with interchangeable teeth. This article describes a simple and accurate procedure for constructing dentures with interchangeable posterior teeth.

Effects of improvements of poorly fitting dentures and new dentures on masticatory performance

The effect of four modifications to improve the fit and maxillomandibular relationships of poorly fitting dentures and the insertion of new dentures on masticatory performance was assessed in 21 denture wearers. A 2-week adaptation period was allowed for each of the four modifications and 3 weeks and 12 weeks of adaptation for new dentures. The preferred side masticatory performances were not appreciably affected by either the modifications to improve the fit of the original dentures or the new dentures. In most instances there was a slight decline in performance. Three denture modifications caused significant declines in the carrot-swallowing threshold performances and the new dentures in the peanut-swallowing threshold performance. In other words, the denture wearers had a greater percentage of coarse particles in their bolus ready for ingestion when they chewed with altered or new dentures compared with original dentures. However, they chewed faster and applied fewer chewing strokes with their modified and new dentures. A steady but gradual improvement in the mean performance score with carrots was noted with time after the insertion of new dentures. Dentists and patients need to understand that adaptation to new or modified old dentures may be a long, drawn-out process for some patients.

Masseter muscle activity in denture wearers with superior and poor masticatory performance

A cross-sectional study tested the hypothesis that denture wearers with superior and poor chewing ability use similar masseter muscle effort and biting forces during mastication. Masticatory performance tests on the preferred chewing side and swallowing threshold tests were conducted with peanuts and carrots in 70 denture wearers, 35 with superior (SP) (mean 46.3%) and 35 with poor (PP) (mean 30.7%) masticatory performance. Right and left masseter muscle electromyographic (EMG) activity was recorded during the masticatory tests and peak bite force during chewing was estimated from the bite force--EMG ratios on guided maximal biting trials. Bite force under maximal pressure did not differ significantly between the two groups. Neither the total mean EMG activity of the preferred and nonpreferred side masseter muscles nor the mean peak biting forces exerted by the two groups differed significantly (p > 0.05). This was true when denture wearers restricted chewing to their preferred side for a given number of strokes or chewed the test food freely until ready to swallow. The only significant differences (p < 0.05) were evident in the ratios of the preferred to nonpreferred side masseter EMG activity during chewing. The ratios were 1.2 for peanuts and 1.3 for carrots in the SP group compared to 1.8 for both foods in the PP group. Similar patterns of bilateral activity in the SP group and unilateral activity in the PP group were evident for the swallowing threshold tests. The results indicated that application of more equivalent force by the right and left masseter muscles during unilateral chewing is consistent with improved chewing ability in denture wearers.

Force-deformation properties of artificial and natural foods for testing chewing efficiency

The force-deformation characteristics of two artificial test foods (Optosil and Optocal) for measurements of food comminution during mastication were investigated in a bite simulator and compared with those of carrots and peanuts. The influence of cusp geometry was evaluated by use of a flat plate and three cusp forms. The forces at the yield point were lower for Optocal than for Optosil artificial test food. The forces needed for Optocal overlapped those needed for carrots and peanuts. The natural foods showed more variation in the force and percentage of deformation at the yield point than the artificial foods. The artificial foods reflected the differences in cusp form better than did the natural foods. The use of artificial foods fulfills a need for standardization and warrants consideration in studies of mastication.

Meeting the oral health needs of institutionalized elderly

Numerous impairments cause suffering to the institutionalized elderly person. The medically compromised or severely demented patient, especially one with swallowing difficulties, presents a challenge to the dental practitioner. This paper summarizes typical geriatric dental problems that caregivers in a long-term care (LTC) facility should find recognizable. It also describes palliative and preventive treatment modalities that help improve the quality of life for such institutionalized patients.

Comparison of food particle distribution masticated by subjects wearing complete dentures and with natural teeth

The sizes of soya particles masticated by 12 complete denture wearers and 10 subjects with natural dentition were directly measured by means of a graphic digitizer and computer, following a varied number of chewing strokes. It was found that the chewed particle size frequency distributions of the two groups tended to a state of normal logarithm distribution. Compared with the dentate subjects, the mean, 20th, 50th and 80th percentile of the particle sizes chewed by complete denture wearers were increased, whilst the distribution shapes were nearly identical. The results suggest that there are no qualitative differences in the manner in which the two groups break up food. Selection and breakage functions of complete denture wearers are decreased, and this could be related to the denture conditions and the change of oral state in such individuals.

Effects of anaesthesia of human oral structures on masticatory performance and food particle size distribution

Ten persons with intact dentitions performed a series of 6 masticatory tests, employing 5, 10, 20, 40, 80 and 160 strokes to chew standard quantities of peanuts on their preferred chewing side for each of three test conditions: (1) before anaesthesia: (2) after maxillary anaesthesia; and, (3) after maxillary and mandibular anaesthesia (unilateral). A seventh test employing 20 strokes was also repeated on the non-anaesthetized contralateral side. The chewed food was sieved through 5, 10, 20, 40, 80 and 100 mesh screens. The percentage of the ratio of the volume of peanuts that passed through the sieve and the total volume of recovered food provided the performance score for the given sieve. The performance scores increased significantly with the number of stokes and dropped markedly after anaesthesia. The maximum reduction of 19.6% in the mean masticatory performance and 46% in the mean masticatory efficiency occurred after unilateral anaesthesia at 10 mesh particle size in the 20-stroke test. An average of 40 strokes was required after unilateral anaesthesia to achieve almost the same performance achieved with 20 strokes before anaesthesia. The regression slopes, derived from the 5, 10 and 20 mesh particle distributions showed that coarse particles were ground more rapidly than fine particles before anaesthesia. This preferential comminution became less evident after maxillary anaesthesia and was least evident after unilateral anaesthesia. The regression slope for the control peaked at 10 strokes as compared to 20 strokes after unilateral anaesthesia. Thus peripheral sensory impairment affects masticatory efficiency in dentate persons.

Feeding disorders research and teams: a new challenge for dentistry

Feeding disorders, which include masticatory and cerebral disabilities, present a major problem for disabled persons, but only in the last decade have health professionals shown an increased interest in the diagnosis and management of patients with such problems. Dentists are experts in the diagnosis and treatment of disorders of the oral-facial region, yet they have either worked in intradisciplinary isolation or have not demonstrated their interest in patients with feeding disorders. Consequently, those involved in the assessment and treatment of persons with feeding disorders are not aware of the contributions dentists have made to the basic and clinical data base of feeding assessment and therapy. Dentistry is simply not mentioned in rehabilitation. The opportunity now exists for dentistry to inform others of our expertise in the field from both a research and a clinical perspective. The basic and clinical base of dental therapeutics and its role in the diagnosis and treatment of disorders of the masticatory apparatus and of swallowing are reviewed here. It is hoped that this review will stimulate interest among dentists to take part in the rehabilitation of patients with feeding disorders through the use of the extensive data base within the profession.

Studies of biologic parameters for denture design. Part III: Effects of occlusal adjustment, base retention, and fit on masseter muscle activity and masticatory performance

EMG recordings of ipsilateral and contralateral masseter muscles and standardized masticatory performance tests were made in 20 denture wearers before and after modifications were made to their clinically unsatisfactory dentures. The improvement of retention and stability by correction of gross occlusal prematurities and by the use of a denture adhesive or base reline with a soft tissue-conditioning material did not significantly alter the chewing performance or muscle activity during mastication in denture wearers. The results support our previous findings that the influence of denture factors on chewing ability of denture wearers is limited. To avoid variations in EMG activity caused by changes in electrode positions, all tests for a given subject were made at the same sitting. Thus the study design did not provide time to denture wearers for their neuromuscular mechanism to adapt to the modifications prior to testing masticatory function. A replication of this study that permits sufficient adaptation time after each modification is suggested to validate the findings.

Masticatory efficiency of complete denture patients. A clinical examination of potential changes at the transition from old to new denture

The masticatory efficiency was studied among 19 complete denture wearers with their old and new dentures. The test chewing material was gelatin hardened by formalin. A standardized preparation of the test chewing material and the sieve-system is described. The patients were tested on seven different occasions from the period with the old dentures until about 1.5 years after the insertion of the new dentures. The test pieces were chewed for ten seconds--a practice test--20 seconds and until ready to be swallowed. The chewed material was strained in a sieve-system and masticatory efficiency indices were calculated. The results revealed no statistical significant differences in masticatory efficiency between any of the seven testing occasions with the method used. Thus no significant difference was noticed when patients changed from old to new dentures or during the first 18 months after insertion of new dentures.

Aging and mastication: changes in performance and in the swallowing threshold with natural dentition

Few comprehensive studies of oral function have been conducted on adult populations. A "Longitudinal and Cross-Sectional Study of Oral Health in Healthy Veterans" was activated at the VA Outpatient Clinic in Boston in 1969; it included general oral and dental examinations as well as tests of masticatory performance and the swallowing threshold. The current investigation involved 863 subjects from the "Dental Study" who had either their natural teeth or a fixed replacement for missing teeth. Masticatory performance as measured by the subject's ability to reduce a test portion of cut carrot by a mandatory number of chewing stroked remained constant for persons with complete or partially compromised natural dentition. Swallowing threshold performance as measured by the particle size acceptable for swallowing remained constant for persons with complete dentition. Tooth loss significantly decreased the swallowing threshold performance and increased the particle size which the subject was willing to swallow. Older subjects increased the number of chewing strokes and the time required for this test, an observation not related to performance as measured by final particle size. Only with compromised dentition, however, did this increased effort result in increased performance.

Masticatory function - a review of the literature. III. Masticatory performance and efficiency

A review and evaluation of the literature on mastication has been undertaken. Part I discusses the form of the masticatory cycle in the natural and artificial dentitions, including the controversial question of whether tooth contact occurs during function. Part II reviews the literature concerning the speed of movement of the mandible, rate of chewing, and the forces developed in chewing. Part III describes masticatory efficiency and performance, the effect of food on masticatory function, and incorporates a summary of all these three papers.

Studies of biologic parameters for denture design. Part I. Comparison of masseter muscle activity during chewing of crisp and soggy wafers in denture and dentition groups

The motor response to two textures was studied by comparing the EMG activities of the ipsilateral muscle during 5 minute periods of eating crisp and soggy wafers in each group of subjects. In both groups, the activity of the ipsilateral muscle was significantly greater for eating crisp wafers than for eating soggy wafers. The ratio of EMG activities for crisp and soggy textures was 1.48 in the dentition group and 1.72 for the denture wearers. These differences between the activities of ipsilateral muscles for the two textures were significant in both groups (P smaller than 0.05). Thus, in terms of muscle effort, denture wearers display discrimination of textural characteristics of food during chewing similar to that shown by subjects with natural teeth.