Journal of

Oral Rehabilitation

Journal of Oral Rehabilitation 2014 41; 177--183

Effect of complete and partial removable dentures on chewing movements T. M. S. V. GONC ßALVES, L. S. R. VILANOVA, L. M. GONC ßALVES & R . C . M . R O D R I G U E S G A R C I A Department of Prosthodontics and Periodontology, Piracicaba

Dental School,

University of Campinas, Piracicaba, Brazil

Partial or complete edentulism impairs mastication. However, it is unclear how the chewing cycle is affected by prosthetics. We evaluated the chewing movements of patients fitted with complete (CD) or removable partial denture (RPD). A total of 29 subjects were kinesiographically evaluated during chewing of peanuts and Optocal portions in a random sequence. The subjects were divided into two groups according to prosthesis type. Group RPD was composed of 14 partially edentulous patients using a lower distal extension RPD (mean age 61  8 years), and group CD contained 15 completely edentulous patients using CD (mean age 65
9  7
9 years) in both jaws. Opening, closing, occlusal and masticatory cycle times, movement angle (opening and closing), maximum velocity (opening and closing), total area and chewing cycle amplitudes were evaluated. The SUMMARY

Background The main goal of mastication is to break food into smaller particles, increasing the surface area of the food and to facilitate the digestive process (1). However, the loss of natural teeth impairs the comminution process, and prosthetic treatments are not able to completely restore masticatory function, particularly in complete denture wearers (2). Mastication is an intermittent rhythmic act in which the tongue, facial and jaw muscles act in coordination to position the food between the teeth, cut it and prepare it for swallowing (1, 3). In humans, the © 2013 John Wiley & Sons Ltd

results were subjected to ANOVA and Tukey’s HSD test at a significance level of 5%. The RPD group exhibited shorter opening and closing phases and masticatory cycle time (P < 0
05). Maximum velocities were also higher in the RPD group, irrespective of the test material (P < 0
05). The area and amplitude of the chewing envelope was smaller in the CD group (P < 0
0001). The test material did not influence chewing cycles in any of the parameters evaluated (P > 0
05). RPD wearers use a faster chewing sequence with greater vertical and lateral jaw excursions compared with CD wearers. KEYWORDS: removable partial denture, complete denture, applied kinesiology, mastication, eating, jaw motion Accepted for publication 29 November 2013

mastication sequence may be readily elucidated using electromyography and jaw tracking devices (1, 4). Kinesiographic studies (3, 5, 6) have greatly advanced our knowledge of the normal physiology of mastication, providing useful parameters for objectively evaluating chewing function. The rhythmic chewing pattern consisting of opening and closing jaw movements is maintained under brain stem control, and the periodontal mechanoreceptors play a central role in encoding relevant aspects of the chewing process (3, 6). The sensorimotor control modifies the direction and magnitude of the bite forces, regulating the intensity of the applied doi: 10.1111/joor.12125

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T. M. S. V. GONC ß A L V E S et al. force and continuously providing spatial information concerning jaw action (3, 7). Chewing motion may be modified by factors such as food type and consistency, size of the food bolus, gender, age, dental status, occlusion and prosthetic appliances (1, 3, 8, 9). As sensorimotor inputs are important for fine regulation of mastication (3), it has been suggested that partially edentulous patients who maintain periodontal mechanoreceptors present better jaw control and smother chewing patterns than completely edentulous patients. In contrast, denture wearers who no longer possess this peripheral sensitivity have developed strategies to overcome problems with chewing by choosing softer and easier-to-chew foods and by preparing and chewing their food differently (10). Moreover, denture wearers have difficulties in centring and comminuting the food bolus, probably due to the lower retention of the mandibular denture, which allows the displacement of the denture into the soft tissue (4, 11). Thus, an extra function of the tongue and cheeks is required to stabilise the prosthesis while positioning the food bolus among artificial teeth, contributing to the lower masticatory performance found in those patients (2, 11). The remarkable differences in chewing between partially and completely edentulous patients could possibly lead to irregularities in chewing movements (4), but it is unclear how the masticatory cycle pattern is affected by the presence of a few teeth and how prosthetic treatments influence the chewing pattern. Previous studies (4, 5, 12) have revealed that posterior occlusion plays a key role in coordinating mandibular movement patterns. Partially edentulous patients with missing post-canine teeth tend to chew the bolus in the anterior region (5). On the other hand, completely edentulous patients wearing full dentures apparently use chopping movements to keep the dentures more stable during chewing (4). Thus, it is reasonable to hypothesise that chewing movements could be affected by the type of prosthesis used. The aim of the current study was to evaluate, by means of a kinesiographic instrument, the mandibular movements during chewing of complete (CD) and removable partial denture (RPD) wearers. In addition, we surveyed the influence of two test materials on chewing movements: one natural (peanuts) and one

artificial (Optocal). Both materials are commonly used in masticatory function analysis.

Material and methods Experimental design This cross-sectional study was designed to evaluate the chewing movements of removable prosthesis wearers and was composed of patients who received a CD or distal extension RPD from the dental clinic in the Piracicaba Dental School, University of Campinas. A full explanation of the clinical trial was given to each subject, and a written informed consent document was read and signed prior to enrolment. The Ethics Committee of the Piracicaba Dental School, University of Campinas (Piracicaba, Brazil), approved the research (protocol # 094/2011). Chewing movements were recorded during two sequences of 20 masticatory cycles for each test material, being the mean values of both sequences used for analysis. All evaluations were performed by a trained researcher during a single appointment. Sample selection The study participants were divided into two groups based on their dental state. The first group was composed of 15 completely edentulous patients wearing CDs, while the second group consisted of 14 partially edentulous subjects provided with maxillary CD and mandibular distal extension RPD. Inclusion criteria included the continuous use of a new and well-fitted prosthesis for at least 3 months, no complaints, discomfort or pain during chewing, bilateral contact with Angle Class I occlusal relationship in artificial teeth and the presence of residual edentulous ridges with normal volume and mucosal resilience. Subjects describing a history or symptoms of temporomandibular disorders, advanced periodontal disease, mucosal trauma induced by the denture resin base, fixed prosthetic treatments or systemic or debilitating diseases that could interfere with muscle control such as Parkinson’s or central nervous system diseases were excluded from the study. The number, gender and age distribution of each test group enrolled in the study were also provided in Table 1.

© 2013 John Wiley & Sons Ltd

JAW MOTION AND REMOVABLE DENTURES Table 1. Subjects profile according to the testing groups Subjects Testing groups

n

Male

Female

Age (mean, max–min)

CD Removable partial denture Total

15 14 29

8 4 12

7 10 17

65
9 (51–78) 61 (48–79) 63
5 (48–79)

Chewing movement measurement The chewing movements were recorded using a kinesiographic device (*) connected to a computer system. Subjects were seated comfortably in a dental chair with the Frankfort plane parallel to the floor. In the CD group, a magnet was temporarily attached to the lower denture at the artificial incisor teeth, while in the RPD group, the magnet was adhered to the lower incisor teeth with an adhesive strip according to the manufacturer’s instructions. In both cases, the magnet was positioned so that it did not interfere with normal occlusion. A magnetic sensor device was placed on the subject’s head in accordance with the instructions of the manufacturer. Jaw movements were tracked during chewing and displayed and recorded in a computer program as 3-D spatial coordinates on the vertical, anteroposterior and lateral axes. The chewing movements were evaluated using two test materials administered in a random sequence, being each of them evaluated twice. A natural (peanuts) and an artificial (Optocal) test materials were selected because both are comparable in texture and consistency, but presenting different advantages (2). For example, natural foods such as peanuts are normally consumed by subjects in their habitual masticatory action (2), while artificial test materials such as Optocal permit the control of several rheological food properties, enabling standardised masticatory function analysis (2). A portion (approximately 3
7 g) of peanuts or Optocal was given to subjects to chew in their habitual way for 20 cycles. They were instructed to place the test material on their tongue and to keep their teeth together in the maximum intercuspal position until the start signal was given by the researcher. The chewing cycles were counted in silence by the single

calibrated researcher, who informed the subjects when to stop chewing. Remaining food particles were removed by repeated rinses with 200 mL of regular water mouthwashes to remove all food particles, not interfering on the chewing of the next test material. The first masticatory cycle of each chewing test was discarded because it involved the initial positioning of the test material over the teeth (13). The chewing traces were evaluated using the BioPack software (BioResearch) (14), which provided parameters including opening, closing and occlusal-phase duration (s), total masticatory cycle time (s), opening and closing angle (frontal plane) and opening and closing maximum velocity (mm s 1)(14, 15). These parameters were obtained promptly in the Biopack (BioResearch) program. A graphic image of each of the two sequences of 20 masticatory cycles provided the following parameters: total area (mm2) in frontal and sagittal planes, vertical and lateral amplitudes (mm) in the frontal plane, and anteroposterior amplitude in sagittal planes (Fig. 1). These graphic images were exported to the IMAGE TOOL software (‡) (14–17), and values of the parameters assessed were obtained for each sequence. A mean value was calculated for each parameter considering both sequences. The reproducibility of the chewing parameters was verified in a previous study (18) in which intra-class correlation coefficients ranged from 0
7 to 0
9, which was considered excellent. Statistical analysis The results were statistically analysed using the SAS/ LAB software package (§) with a significance level of 5%. Assumptions of the equality of variances and the normal distribution of errors were checked. The data sets were transformed as suggested by the software. The chewing movement parameters of opening, closing and occlusal time, masticatory cycle duration, angle of opening and closing movement, opening and closing maximum velocity, and total area and amplitudes of the chewing cycle were analysed using twoway ANOVA followed by Tukey’s HSD test, considering the denture type and the test material as study factors.

‡

University of Texas Health Science Center, San Antonio, TX, USA.

*JT-3D; BioResearch, Milwaukee, WI, USA. © 2013 John Wiley & Sons Ltd

§

SAS Software, version 9.0; SAS Institute Inc., Cary, NC, USA.

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T. M. S. V. GONC ß A L V E S et al. RPD group compared with the CD group (P < 0
05) when peanuts were chewed. Similar results were noted only for the maximum open velocity when Optocal was used as the test material (P < 0
05) (Table 3). Table 4 contains mean values for the area (mm2) and amplitude (mm) of the masticatory cycles measured in the frontal and sagittal planes. Irrespective of test material, the RPD group exhibited greater area and vertical and lateral amplitudes in the frontal plane (P < 0
0001). No difference was observed in the sagittal area and the anteroposterior measurement of the amplitude on the sagittal plane considering groups and test materials (P > 0
05).

Discussion

Fig. 1. Image of the peanut chewing envelope after a sequence of 20 masticatory cycles regarding removable partial denture. The red line represents the opening movement, while the blue line characterises the closing movement. The white line is a reference, representing a regular chewing movement.

Results Irrespective of the test material, the RPD group experienced faster chewing cycles with reduced opening, closing and total cycle times when compared to the CD group (P < 0
05) (Table 2). There was no significant difference in the duration of the occlusal phase between groups or test materials (P > 0
05). There were no differences between groups in the opening and closing angles for both test materials (P > 0
05) (Table 3). In contrast, higher maximum opening and closing velocities were observed in the

Prior studies (3, 19) have demonstrated the importance of remaining teeth and consequently the periodontal mechanoreceptors on the spatial control of jaw movement during the chewing process. Signals from periodontal receptors are responsible for the fine motor control of jaw actions associated with biting, intra-oral manipulation and the chewing of food (3). It is clear from studies on partial and complete edentulous patients that important sensory-motor functions are lost or impaired when these receptors are removed during tooth extraction (3, 20). However, few researchers (4, 5) have examined the effect of prosthetic treatments on chewing movements, even though this could help to better understand why the masticatory function is so impaired in subjects using dentures. The current study evaluated several parameters of mastication performed by removable denture wearers, revealing significant differences in chewing mechanics between CD wearers and free-end RPD wearers.

Table 2. Mean and standard deviation values of the duration (s) of the masticatory cycle according to the group and the chewing test material Group

Material

Opening time

CD

Optocal Peanuts Optocal Peanuts

231 212
7 192
2 174
4

Removable partial denture

   

34
6 Aa 48
6 Aa 36
3 Ab 37
2 Ab

Closing time 305
7 306
8 244
7 221
4

   

60
1 Aa 75
4 Aa 46
7 Ab 48
3 Ab

Occlusal time 152
2 173
5 136
3 141
3

   

38
9 41
7 46
9 48
6

Cycle time Aa Aa Aa Aa

673
1 677
4 573
4 534
8

   

111
5 Aa 137
2 Aa 100
4 Ab 113
5 Ab

Upper letters indicate differences between test materials. Lower letters indicate differences between groups. Proc Mixed, Tukey’s HSD, P < 0
05. © 2013 John Wiley & Sons Ltd

JAW MOTION AND REMOVABLE DENTURES Table 3. Mean and standard deviation values of angles and maximum velocity (mm s 1) according to the group and the chewing test material Groups

Material

Opening angle

CD

Optocal Peanuts Optocal Peanuts

83
9 82
4 91
2 81
5

Removable partial denture

   

19
8 21
7 23
8 21
7

Aa Aa Aa Aa

Closing angle 84
9 81
4 90
1 65
6

   

27
7 38
6 39
9 23
5

Aa Aa Aa Aa

Maximum open velocity

Maximum close velocity

128
2  43 Aa 112  44 Aa 157
4  35 Ab 156
8  32
1 Aa

92
8 77
1 132 132
2

   

26
7 Aa 31
3 Aa 21
1 Ab 37
5 Ab

Upper letters indicate differences between test materials. Lower letters indicate differences between groups. Proc Mixed, Tukey’s HSD, P < 0
05. Table 4. Mean and standard deviation values of area (mm2) and amplitudes (mm) according to the plane, group and chewing test material Amplitude Area

Frontal plane

Group

Material

Frontal plane

CD

Optocal Peanuts Optocal Peanuts

65 58
5 159
2 160
6

Removable partial denture

   

19
5 Aa 32
5 Aa 66
3 Ab 52 Ab

Sagittal plane 12
5 12
5 12
5 17
5

   

5 Aa 2
5 Aa 5 Aa 7
5 Aa

Vertical 25 23 37 38

   

6 Aa 5 Aa 4 Ab 4 Ab

Sagittal plane Lateral 14 14 29 29

   

3 Aa 2 Aa 5 Ab 4 Ab

Anteroposterior 3 2 1 2

   

1 1 1 1

Aa Aa Aa Aa

Upper letters indicate differences between test materials. Lower letters indicate differences between groups. Proc Mixed, Tukey’s HSD, P < 0
05.

The opening and closing phases of the masticatory cycle and the total length of the chewing cycle were significantly shorter in the RPD group (Table 2). Studies evaluating masticatory movements are difficult to compare due to variations in methodology and analysis. In spite of this, the findings of the present study are in agreement with previous study (21), which revealed reductions in masticatory cycle duration following replacement of conventional CD with implantsupported prostheses (21). Only few workers (4, 5) evaluated chewing movements in partially edentulous patients. Jemt et al. (5) compared the chewing cycle length between partially edentulous patients with and without distal extension RPDs and found no differences related to RPD use. These results (5) in combination with our findings support the premise that the presence of teeth and sensory input from mechanoreceptors present in the periodontal ligament of the remaining teeth play a key role in the control of jaw motion, even when posterior contacts are missing. It is important to highlight that subjects in the CD group may have experienced different problems during chewing related to denture instability (11). The majority of CD wearers complain about denture © 2013 John Wiley & Sons Ltd

displacements during chewing, especially for chewy foods, which could require an extra function of the tongue and cheeks to retain the dentures apart from positioning the food bolus (4, 11). This limited ability to manipulate food, in addition to the longer chewing cycles presented by CD wearers, could explain why the masticatory capacity of this patients is so impaired faced up to partially edentulous and complete dentate subjects (2). Furthermore, a previous study (21) comparing the chewing movements before and after the stabilisation of conventional CD with implants revealed a shorter duration of the chewing cycle during the occlusal phase. Besides, they also found a higher mandibular velocity, greater displacement of the jaw during chewing and more rhythmical chewing pattern after the implant fixed dental prostheses. Thus, it seems that the denture retention and stability plays a crucial role in chewing motion impairments. Differences between groups were also observed with respect to maximum velocity, which was greater among RPD wearers particularly during peanuts chewing (Table 3). Similar results were reported by Jemt et al. (5), despite the different test material (hard bread) applied in the former study. In addition, it has

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T. M. S. V. GONC ß A L V E S et al. been reported (2, 9) that subjects using CD generally increase the number of chewing cycles and reduce the velocity of chewing movements. Chewing movement and masticatory performance are closely related (6, 21), and higher chewing efficiency is obtained with faster chewing cycles (6), supporting the higher chewing velocity found in the RPD group. Greater chewing movement area and amplitudes were recorded in the RPD group (Table 4). These results are in accordance with reports (4, 11) that the chewing pattern of CD wearers is characterised by smaller vertical and lateral excursions compared with subjects with natural teeth. The comminution of consistent foods such as peanuts or Optocal requires specific skills related to the selection and breakage process, which could be difficult for CD wearers (2). Thus, to keep dentures more stable during mastication, subjects wearing CD apparently used more chopping movements and avoided lateral jaw motions, explaining the results founded in the CD group. Chewing motions were evaluated using two test materials (peanuts and Optocal) in the present study. Our purpose was to verify whether natural (peanuts) and artificial food substances (Optocal) would differentially influence mandibular movements. Standardised artificial materials such as Optocal are commonly used in masticatory function evaluation due to their repeatable consistency and texture (2, 8). However, these materials are not normally consumed as are natural foods, and people may be somewhat hesitant to chew them in a normal manner, influencing the results. Thus, both analyses are important when studying chewing movements, and according to our results, chewing patterns were similar for both natural and artificial materials. The current study has a cross-sectional design and limited conclusions may be drawn with respect to the long-term influence of prosthetic treatments on the chewing process, which could be a focus of future research. Despite the limitations, remarkable differences were observed between the CD and RPD groups, demonstrating the importance of retaining natural teeth for proper masticatory function.

Conclusion Remarkable differences were found between groups, with a faster chewing sequence, higher maximum

chewing velocity and greater vertical and lateral jaw excursions observed in RPD wearers compared with CD wearers. These results were probably a consequence of the higher retention and stability of RPD, revealing the importance of the natural remaining teeth for masticatory function.

Acknowledgments The Ethics Committee of the Piracicaba Dental School, University of Campinas (Piracicaba, Brazil) approved this research (protocol # 094/2011). Authors declare no conflict of interests. This research was carried out without funding.

References 1. Lund JP. Mastication and its control by the brain stem. Crit Rev Oral Biol Med. 1991;2:33–64. 2. Slagter AP, Bosman F, Van der Bilt A. Comminution of two artificial test foods by dentate and edentulous subjects. J Oral Rehabil. 1993;20:159–176. 3. Trulsson M. Sensory-motor function of human periodontal mechanoreceptors. J Oral Rehabil. 2006;33:262–273. 4. Tallgren A, Mizutani H, Tryde G. A two-year kinesiographic study of mandibular movement patterns in denture wearers. J Prosthet Dent. 1989;62:594–600. 5. Jemt T, Hedegard B, Wickberg K. Chewing patterns before and after treatment with complete maxillary and bilateral distal-extension mandibular removable partial dentures. J Prosthet Dent. 1983;50:566–569. 6. Yamashita S, Hatch JP, Rugh JD. Does chewing performance depend upon a specific masticatory pattern? J Oral Rehabil. 1999;26:547–553. 7. Lund JP, Kolta A, Westberg KG, Scott G. Brainstem mechanisms underlying feeding behaviors. Curr Opin Neurobiol. 1998;8:718–724. 8. van der Bilt A, Engelen L, Pereira LJ, van der Glas HW, Abbink JH. Oral physiology and mastication. Physiol Behav. 2006;89:22–27. 9. Woda A, Foster K, Mishellany A, Peyron MA. Adaptation of healthy mastication to factors pertaining to the individual or to the food. Physiol Behav. 2006;89:28–35. 10. N’Gom PI, Woda A. Influence of impaired mastication on nutrition. J Prosthet Dent. 2002;87:667–673. 11. Postic SD, Krstic MS, Teodosijevic MV. A comparative study of the chewing cycles of dentate and denture-wearing subjects. Int J Prosthodont. 1992;5:244–256. 12. Molenaar WN, Gezelle Meerburg PJ, Luraschi J, Whittle T, Schimmel M, Lobbezoo F et al. The effect of food bolus location on jaw movement smoothness and masticatory efficiency. J Oral Rehabil. 2012;39:639–647. 13. Lepley CR, Throckmorton GS, Ceen RF, Buschang PH. Relative contributions of occlusion, maximum bite force,

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JAW MOTION AND REMOVABLE DENTURES

14.

15.

16.

17.

18.

and chewing cycle kinematics to masticatory performance. Am J Orthod Dentofacial Orthop. 2011;139:606–613. Kuwahara T, Miyauchi S, Maruyama T. Clinical classification of the patterns of mandibular movements during mastication in subjects with TMJ disorders. Int J Prosthodont. 1992;5:122–129. Ohkubo C, Kobayashi M, Suzuki Y, Hosoi T. Effect of implant support on distal-extension removable partial dentures: in vivo assessment. Int J Oral Maxillofac Implants. 2008;23:1095–1101. Maruyama T, Nishio K. A new mandibular tracking device– the Sirognathograph and its analyzing computer system. Shikai Tenbo. 1984;63:1535–1546. Ogawa T, Shigeta Y, Ando E, Hirai S, Suma M, Hirabayashi R et al. Application of a jaw motion tracking device that measures six degrees of freedom using optoelectronic. Nihon Hotetsu Shika Gakkai Zasshi. 2006;50:210–218. Oliveira JA, Goncalves TM, Vilanova LSR, Ambrosano GMB, Rodrigues Garcia RCM. Female hormones fluctuation

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and chewing movement of patients with disc displacement. Revista Odonto Ciencia. 2012;27:20–25. 19. Svensson KG, Trulsson M. Impaired force control during food holding and biting in subjects with tooth- or implantsupported fixed prostheses. J Clin Periodontol. 2011; 38:1137–1146. 20. Svensson KG, Grigoriadis J, Trulsson M. Alterations in intraoral manipulation and splitting of food by subjects with tooth- or implant-supported fixed prostheses. Clin Oral Implants Res. 2013;24:549–555. 21. Karlsson S, Jemt T. Adaptive changes of masticatory movement characteristics after rehabilitation with osseointegrated fixed prostheses in the edentulous jaw: a 10-year follow-up study. Int J Oral Maxillofac Implants. 1991;6:259–263. Correspondence: Renata C. M. Rodrigues Garcia, Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas, Av. Limeira, no. 901, Bairro Arei~ ao, Piracicaba, SP, Brazil, CEP 13414-903. E-mail: [email protected]

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