Journal of Oral Rehabilitation, 1991, Volume 18, pages 413-420
Swallow thresholds using dentures made on different types of articulator F. MOWLANA and M. R. HEATH* Department of Prosthetic Dentistry, Faculty of Dental Sciences, University of Peradeniya, Sri Lanka, and *Depm?ment of Prosthetic Denhtry, The London Hospiial Medical College, London, U.K .
summary The purpose of this study was to determine whether edentate subjects achieved different performance when using dentures constructed on different articulators. A cross-over experimental design was employed to evaluate these swallow thresholds using complete dentures constructed on the hinge and free plane articulators. Seven subjects completed the study. Swallow threshold tests were performed 3 months after the insertion of dentures. The overall particle size distribution achieved with the dentures constructed on free plane articulators was significantly better at the end of the 3-month period (P < 0.01 to P < O~OOOl),but significantly more strokes were used to achieve this success rate (P< 0.04). A questionnaire revealed that the subjects had a preference for the denture constructed on the free plane articulator. It is concluded that patients performed better with dentures constructed on the free plane articulator. Introduction A wide variety of articulators is available, with different principles of design and a wide range of adjustability. However, few studies have compared dentures constructed with different articulators. Wesley et al. (1984) studied the masticatory performance of dentures constructed by means of ‘standard‘ and ‘complex’ techniques. Evaluation involved a single sieve method without a cross-over design, which did not discriminate the performance sensitively; although statistical analysis revealed changes over a 5-year period, no significant difference was found between the groups. f i e only other available report, that of Hickey et al. (1969), described the response of tissues to dentures constructed by the ‘standard’ and ‘complex’ techniques, but did not study masticatory performance. The ability to masticate with dentures was studied by Christianssen in 1922, who developed a method for assessment of masticatory efficiency in full denture wearers (reported by Dahlberg in 1 M ) . Since then, swallow thresholds have been measured by multi-sieve methods, with modifications by Dahlberg (1946), Yurkstas (1%5), Helkimo, Carlsson and Helkimo (1978), Jiffry (1981, 1983), Lucas .and Luke (1983a), Lucas et al. (1986a) and Olthoff et al. (1984). A single sieve method was developed by Manly and Braley (1950). This was followed by several studies on natural and artificial dentitions, by Manly and Vinton
Correspondence: Dr Fawziya Mowlana, Department of Prosthetic Dentistry, The London Hospital Medical’College, Dental School, Turner Street, London, U.K.
413
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F. Mowlana and M . R. Heath
(1951), Yurkstas (1951), Manly (1951), and Kapur and Soman (1964). Although the single sieve method is simpler, there is inevitable difficulty in the choice of sieve size; Dahlberg (1942) and Manly and Braley (1950) used 1.8mm mesh, but Gelman (1933) used a 2.4mm mesh, whilst Wesley et al. (1984) used 2.0mm mesh. The multi-sieve method yields more data, although at greater cost. Since 1900 a range of natural test foods has been used in chewing experiments, the aim being to obtain a food that can be fractured by almost all individuals, but that still allows discriminationbetween the performance of different individuals. In an evaluation of 33 test foods, Kapur er al. (1964) found that nuts and carrots presented an appropriate degree of difficulty in mastication for discrimination between denture wearers. Many later studies have employed peanuts; some have used other nuts such as almonds, soya beans and brazil nuts (Helkimo et al., 1978; Jiffry, 1981; Lucas & Luke, 1986). Because of the problems posed by natural foods, several authors have used artificial foods for chewing experiments. Dahlberg (1942), Gunne et al. (1982) and Gunne & Wall (1985) used formaline-hardened gelatine, Heath (1982) used chewing gum, while Edlund & Lamm (1980) and Olthoff et al. (1984) selected a silicone impression rubber. The combination of baked soya bean and a multi-sieve technique has shown discrimination between dentate subjects and denture wearers (Jiffry, 1983). The complete denture wearers were found to prepare a swallow threshold with a mode of > 3 mm. However, it is open to speculation whether this poor swallow threshold was a consequence of the occlusions created on a hinge articulator. The aim of this study was to determine whether better articulation has an effect on the swallow thresholds, by comparing the performance of dentures constructed on free plane and hinge articulators. Materials and methods Twenty edentulous subjects with previous denture experience were selected, who had no temporomandibular problems, no pathology of the oral mucous membrane, and no systemic disease. A hinge articulator and a simple free plane articulator were used in this study (Figs
~~
-
Fig. 1. Hinge articulator.
Different types of articulator
415
Fig. 2. Free plane articulator.
1 and 2)*. The latter provides an example of ‘average’ condylar guidance fixed at 33”, as is commonly used even where condylar angles are adjustable. Cross-over experimental design Patients were randomly assigned to the cross-over experiment; 10 subjects were given dentures constructed on the hinge articulator first, while the rest received dentures constructed on the free plane articulator. All subjects who participated in the project were reviewed within 1 week after the insertion of dentures. At the end of the 3-month period, swallow threshold tests were performed and the first set of dentures was replaced by the second set, constructed on the other type of articulator. The first set of dentures was retained by the operator until the swallow threshold tests were completed with the second set of dentures. One technician constructed all the dentures. A questionnaire was administered at the end of each experiment with each set of dentures. Prior to inclusion in the study, the quality of all the dentures was assessed for retention, stability, base extensions, occlusal relationship and occlusal vertical height ad modum Kapur (1967). Dentures rated clinically from ‘good’ to ‘excellent’ were selected, and four subjects were therefore eliminated at this stage. Seven subjects completed the study, of whom four were male and three were female, of age range 35-68 years. Swallow threshold testing Soya beans baked at 70°C for 1-2 h were used in this study. The material was acceptable to these subjects, and as it does not dissolve in water the chewed particles can be sieved in order to analyse their sizes. The swallow threshold test developed by Jiffry (1981) was used, with some modifications. Subjects were instructed to chew a comfortable mouthful of baked soya beans
* Ash Dental Products, U.K.
416
F. Mowlana and M . R. Heath
(about 4-7g), until they felt the desire to swallow. This procedure was repeated three times. In the first instance, the patients swallowed the masticated particles; secondly, the patients expelled the chewed particles into a spitoon; finally, the masticated particles were collected in a beaker, together with the mouth washings. The number of chewing strokes used in each test was recorded by two observers. The masticated particles were filtered, using a Biichner funnel, oven-dried for 3h at 7VC, and passed through a series of 12 sieves. The particles collected on each sieve were weighed. Size distribution analysis The weight of particles on each sieve was divided by the difference in mesh size between that sieve and the one above in order to derive the particle density for unit size. Those particles on the largest sieve were therefore not analysed. For analysis, the densities are expressed as a percentage of the total value. All comparisons between data were tested for significance using a two-tailed paired r-test. ReSdtS The overall particle size distribution achieved by the subjects was observed to vary according to the type of denture. After 3 months of denture experience, the percentage of larger particles (> 1.85 mm) was significantly greater with the hinge denture (P> 0-01-PC 0-OOOl), and the percentage of smaller particles (< 1.4mm) was significantly less (P
Swallow thresholds using dentures made on different types of articulator F. MOWLANA and M. R. HEATH* Department of Prosthetic Dentistry, Faculty of Dental Sciences, University of Peradeniya, Sri Lanka, and *Depm?ment of Prosthetic Denhtry, The London Hospiial Medical College, London, U.K .
summary The purpose of this study was to determine whether edentate subjects achieved different performance when using dentures constructed on different articulators. A cross-over experimental design was employed to evaluate these swallow thresholds using complete dentures constructed on the hinge and free plane articulators. Seven subjects completed the study. Swallow threshold tests were performed 3 months after the insertion of dentures. The overall particle size distribution achieved with the dentures constructed on free plane articulators was significantly better at the end of the 3-month period (P < 0.01 to P < O~OOOl),but significantly more strokes were used to achieve this success rate (P< 0.04). A questionnaire revealed that the subjects had a preference for the denture constructed on the free plane articulator. It is concluded that patients performed better with dentures constructed on the free plane articulator. Introduction A wide variety of articulators is available, with different principles of design and a wide range of adjustability. However, few studies have compared dentures constructed with different articulators. Wesley et al. (1984) studied the masticatory performance of dentures constructed by means of ‘standard‘ and ‘complex’ techniques. Evaluation involved a single sieve method without a cross-over design, which did not discriminate the performance sensitively; although statistical analysis revealed changes over a 5-year period, no significant difference was found between the groups. f i e only other available report, that of Hickey et al. (1969), described the response of tissues to dentures constructed by the ‘standard’ and ‘complex’ techniques, but did not study masticatory performance. The ability to masticate with dentures was studied by Christianssen in 1922, who developed a method for assessment of masticatory efficiency in full denture wearers (reported by Dahlberg in 1 M ) . Since then, swallow thresholds have been measured by multi-sieve methods, with modifications by Dahlberg (1946), Yurkstas (1%5), Helkimo, Carlsson and Helkimo (1978), Jiffry (1981, 1983), Lucas .and Luke (1983a), Lucas et al. (1986a) and Olthoff et al. (1984). A single sieve method was developed by Manly and Braley (1950). This was followed by several studies on natural and artificial dentitions, by Manly and Vinton
Correspondence: Dr Fawziya Mowlana, Department of Prosthetic Dentistry, The London Hospital Medical’College, Dental School, Turner Street, London, U.K.
413
414
F. Mowlana and M . R. Heath
(1951), Yurkstas (1951), Manly (1951), and Kapur and Soman (1964). Although the single sieve method is simpler, there is inevitable difficulty in the choice of sieve size; Dahlberg (1942) and Manly and Braley (1950) used 1.8mm mesh, but Gelman (1933) used a 2.4mm mesh, whilst Wesley et al. (1984) used 2.0mm mesh. The multi-sieve method yields more data, although at greater cost. Since 1900 a range of natural test foods has been used in chewing experiments, the aim being to obtain a food that can be fractured by almost all individuals, but that still allows discriminationbetween the performance of different individuals. In an evaluation of 33 test foods, Kapur er al. (1964) found that nuts and carrots presented an appropriate degree of difficulty in mastication for discrimination between denture wearers. Many later studies have employed peanuts; some have used other nuts such as almonds, soya beans and brazil nuts (Helkimo et al., 1978; Jiffry, 1981; Lucas & Luke, 1986). Because of the problems posed by natural foods, several authors have used artificial foods for chewing experiments. Dahlberg (1942), Gunne et al. (1982) and Gunne & Wall (1985) used formaline-hardened gelatine, Heath (1982) used chewing gum, while Edlund & Lamm (1980) and Olthoff et al. (1984) selected a silicone impression rubber. The combination of baked soya bean and a multi-sieve technique has shown discrimination between dentate subjects and denture wearers (Jiffry, 1983). The complete denture wearers were found to prepare a swallow threshold with a mode of > 3 mm. However, it is open to speculation whether this poor swallow threshold was a consequence of the occlusions created on a hinge articulator. The aim of this study was to determine whether better articulation has an effect on the swallow thresholds, by comparing the performance of dentures constructed on free plane and hinge articulators. Materials and methods Twenty edentulous subjects with previous denture experience were selected, who had no temporomandibular problems, no pathology of the oral mucous membrane, and no systemic disease. A hinge articulator and a simple free plane articulator were used in this study (Figs
~~
-
Fig. 1. Hinge articulator.
Different types of articulator
415
Fig. 2. Free plane articulator.
1 and 2)*. The latter provides an example of ‘average’ condylar guidance fixed at 33”, as is commonly used even where condylar angles are adjustable. Cross-over experimental design Patients were randomly assigned to the cross-over experiment; 10 subjects were given dentures constructed on the hinge articulator first, while the rest received dentures constructed on the free plane articulator. All subjects who participated in the project were reviewed within 1 week after the insertion of dentures. At the end of the 3-month period, swallow threshold tests were performed and the first set of dentures was replaced by the second set, constructed on the other type of articulator. The first set of dentures was retained by the operator until the swallow threshold tests were completed with the second set of dentures. One technician constructed all the dentures. A questionnaire was administered at the end of each experiment with each set of dentures. Prior to inclusion in the study, the quality of all the dentures was assessed for retention, stability, base extensions, occlusal relationship and occlusal vertical height ad modum Kapur (1967). Dentures rated clinically from ‘good’ to ‘excellent’ were selected, and four subjects were therefore eliminated at this stage. Seven subjects completed the study, of whom four were male and three were female, of age range 35-68 years. Swallow threshold testing Soya beans baked at 70°C for 1-2 h were used in this study. The material was acceptable to these subjects, and as it does not dissolve in water the chewed particles can be sieved in order to analyse their sizes. The swallow threshold test developed by Jiffry (1981) was used, with some modifications. Subjects were instructed to chew a comfortable mouthful of baked soya beans
* Ash Dental Products, U.K.
416
F. Mowlana and M . R. Heath
(about 4-7g), until they felt the desire to swallow. This procedure was repeated three times. In the first instance, the patients swallowed the masticated particles; secondly, the patients expelled the chewed particles into a spitoon; finally, the masticated particles were collected in a beaker, together with the mouth washings. The number of chewing strokes used in each test was recorded by two observers. The masticated particles were filtered, using a Biichner funnel, oven-dried for 3h at 7VC, and passed through a series of 12 sieves. The particles collected on each sieve were weighed. Size distribution analysis The weight of particles on each sieve was divided by the difference in mesh size between that sieve and the one above in order to derive the particle density for unit size. Those particles on the largest sieve were therefore not analysed. For analysis, the densities are expressed as a percentage of the total value. All comparisons between data were tested for significance using a two-tailed paired r-test. ReSdtS The overall particle size distribution achieved by the subjects was observed to vary according to the type of denture. After 3 months of denture experience, the percentage of larger particles (> 1.85 mm) was significantly greater with the hinge denture (P> 0-01-PC 0-OOOl), and the percentage of smaller particles (< 1.4mm) was significantly less (P
