|Year : 2017 | Volume
| Issue : 1 | Page : 20-27
The effect of two different occlusal concepts on the masseter muscle activity in implant retained mandibular overdentures
Ahmed M Abdelhamid1, Kenda Ibrahim Hisham Hanno1, Mohamed H Imam2
1 Department of Prosthodontics, Faculty of Dentistry, Alexandria University, Alexandria, Egypt
2 Department of Physical Medicine, Rheumatology and Rehabilitation, Faculty of Medicine, Alexandria University, Alexandria, Egypt
|Date of Web Publication||13-Feb-2018|
Mrs. Kenda Ibrahim Hisham Hanno
1, Dinokrate Street, Azarita, Alexandria
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aims: The purpose of this study was to evaluate the effect of bilateral balanced occlusion (BBO) and canine guidance occlusion (CGO) on the masseter muscle activity using implant-retained mandibular overdentures.
Subjects and Methods: Cone beam computed tomography evaluation of twelve edentulous patients was completed. Mucoperiosteal flaps were reflected and two implants were placed in the interforaminal region for each of the twelve patients. After a healing period of 3 months, acrylic resin maxillary complete dentures and mandibular overdentures were fabricated with BBO for six patients and CGO for the other six patients. Positioner attachments were used. Electromyographic evaluation of the masseter muscles, during clenching on a silicon index and chewing peanuts and cake, was conducted on the patients after using their dentures for 4 weeks. Each occlusion concept was then converted into the other concept using the same dentures and the procedure of evaluation was repeated after 4 weeks. The recordings were analyzed statistically using Wilcoxon signed ranks test. The value of P < 0.05 was considered statistically significant.
Statistical Analysis Used: Kruskal–Wallis test and Mann–Whitney U-test were applied. Significance of the obtained results was judged at the 5% level. A P < 0.05 was considered statistically significant.
Results: The highest electromyographic activity of the masseter muscles was recorded during clenching on a preformed silicon index followed by chewing peanut then cake for both occlusal concepts. The recordings of the masseter muscle associated with CGO were higher than BBO but with no statistically significant difference.
Conclusions: The results show that by applying CGO, muscle activities similar to bilaterally balanced occlusion were obtained.
Keywords: Balanced occlusion, canine guidance, electromyography, implant-retained overdentures, muscle activity
|How to cite this article:|
Abdelhamid AM, Hisham Hanno KI, Imam MH. The effect of two different occlusal concepts on the masseter muscle activity in implant retained mandibular overdentures. J Dent Implant 2017;7:20-7
|How to cite this URL:|
Abdelhamid AM, Hisham Hanno KI, Imam MH. The effect of two different occlusal concepts on the masseter muscle activity in implant retained mandibular overdentures. J Dent Implant [serial online] 2017 [cited 2018 May 23];7:20-7. Available from: http://www.jdionline.org/text.asp?2017/7/1/20/225403
| Introduction|| |
Treatment of edentulous patients using a conventional complete removable denture was a common clinical undertaking. However, those patients experienced problems which include pain during mastication, reduced masticatory ability, as well as insufficient stability and retention of the mandibular denture.
The introduction of dental implants and subsequently implant-supported mandibular overdentures has improved the quality of life for edentulous patients. It has been established that the survival of root form titanium implants was very high in the anterior mandible and that the incidence of surgical complications was very low. This makes implant supported dentures a very feasible option that aids in the establishment of stability and retention to the mandibular denture. Implant-retained overdentures have gained significant acceptance because of their relative simplicity, minimal invasiveness, affordability, ease of usage and minimizing, or eliminating movement of the mandibular overdenture.
The selection of the interforaminal area of the mandible, where two implants were placed, was based on the recommendation by Hong et al., as the bone in this area was of good quality. Implants are demonstrated to have fewer micro-movements, increased initial stability and reduced stress concentration in high quality bone.,, The use of radiographic or surgical guide allows implant placement along planned prosthetic axes during implant surgery and ensures good visual access.
Many authors,,, emphasized the role of occlusion as a key factor in implant success. Balanced occlusion concept has been recommended in removable implant overdentures, especially for patients with complete maxillary denture and mandibular implant-retained over dentures to distribute the loads., Bilateral balanced occlusion (BBO) is present when there is equilibrium on both sides of the denture due to simultaneous contact of the teeth in centric and eccentric occlusion. It requires a minimum of three contacts for establishing a plane of equilibrium. The more contacts, the more assured the equilibrium. Such contacts will provide stabilizing forces to the denture bases on their basal seat.
The chewing forces are applied to the working and balancing sides simultaneously and over all of the surfaces of the edentulous ridge, resulting in the decrease in pressure on the edentulous jaw and preventing residual ridge reduction. BBO reduces the stresses to the supporting tissues as reported in a study by Ohguri et al. It enhances patient adaptation in the early phase of denture insertion as reported by Rehmann et al.
For more than a 100 years, textbooks and undergraduate teaching have stated that canine guided dentures should be avoided, since they would result in denture instability and impaired muscle function; however, recent research has shown that conventional complete dentures can function successfully without balanced occlusion.
Canine guidance disengaged the posterior teeth during excursive mandibular movements by vertically and horizontally overlapping the canines. Grubwieser et al., stated that canine guidance occlusion (CGO) can be used successfully in complete dentures as it improves mandibular denture retention, esthetic appearance, and masticatory ability. They also observed that CGO reduced muscle activity during lateral movement and protrusion when compared with BBO. Canine guidance was easier and faster to be provided. It seemed to be rational to recommend this occlusal concept for the excursive movements of the mandible in complete dentures wearers until future research can solve this question.,
The type of opposing occlusion is a critical factor that influences the magnitude of forces transmitted to the implant bone interface. Occlusion may alter muscle activity and related jaw movements in mastication. Muscle activity, which is a reflection of masticatory function of the patient, can be objectively evaluated using surface electromyography (EMG).,,,, The electrical output of a muscle, measured by EMG, is proportional to the energy consumed to produce contractions. Different types of food can be used to represent soft and hard food and to study the effect on muscle activity during function. In the literature, there are only a few studies concerning the EMG of implant restorations., The choice of an occlusal design or configuration for implant-retained prosthesis is broad and often controversial. To date, there is no evidence to recommend a specific occlusal design for implant-retained overdentures. No sufficient scientific evidence was found on applying canine guidance in implant-retained overdentures. Therefore, this study was conducted to investigate the effect of balanced occlusion and CGO on masseter muscle activity in implant-retained mandibular overdentures.
| Subjects and Methods|| |
This research has been conducted in full accordance with ethical principles, including the World Medical Association Declaration of Helsinki. This study protocol was approved by the Research Ethics Committee of the Faculty of Dentistry, Alexandria University, Egypt.
All the patients signed an informed consent form before participation in this study.
Twelve edentulous patients aged 45–65 years with sufficient inter-ridge space (>20 mm) and with no previous denture experience (edentulous for 3–5 years) were selected for this study. According to the PDI classification, the patients were selected with Class II mandibular bone height, Type A maxillary ridge morphology, Type A mandibular muscle attachments and Class I maxilla-mandibular relationship. Complete maxillary and mandibular dentures were fabricated for each patient while applying the concept of BBO.
A mucoperiosteal flap was reflected exposing the mandibular interforaminal region for optimal implant placement. The previously fabricated denture was duplicated in clear acrylic resin and used as a radiographic surgical guide using gutta percha as radiopaque markers.
Each patient was evaluated radiographically using cone beam computed tomography (CBCT). The radiographic surgical template was inserted inside the patient mouth and evaluated through CBCT to examine the condition of the bone height and bone quality through coronal (frontal views), cross-sectional (sagittal views), in addition to the original transverse (axial views). Analysis of CBCT was performed by OnDemand3D software. The gutta-percha rods were visible for determining the three-dimensional position of the implant [Figure 1]. CBCT showed mandibular bone height of 18 mm or greater and with sufficient inter-ridge space (>20 mm). The bone quality was either Type 1 or Type 2 according to Lekholm and Zarb classification.
|Figure 1: Cone beam computed tomography showing the selected implant size and position with the gutta percha markers|
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Two implants were screwed in position. The length of the implants was 10 mm and the diameter was 3.6mm (Dentium Co. Ltd., Dentium Superline Implants, Korea).
After a healing period of 3 months, acrylic resin maxillary and mandibular overdentures were fabricated with BBO for all patients. Six patients used their dentures with BBO for 4 weeks then were evaluated by EMG. Following evaluation, it was converted into CGO using the same denture. This was achieved clinically by remounting using the semi-adjustable articulator.
Light-cured composite resin was added in the mandibular canines on the articulator to provide an interarch disocclusion space of 2 mm during eccentric movements.
For the other six patients, CGO was applied first in the try-in stage through application of light-cure composite resin on the mandibular canines [Figure 2].
The patients used their dentures for 4 weeks then were evaluated using EMG. After evaluation, CGO was converted into BBO by removal of the composite resin from the mandibular canines [Figure 3]. The positioner attachments were placed on the implants and attached to the dentures by direct pickup method [Figure 4] and [Figure 5].
|Figure 4: The white block-out spacers in place with the locator caps on top|
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Recording the electromyographic activity
Evaluation of muscle activity was performed by measuring activity of the masseter muscles on both sides for both occlusal concepts at the end of the 2 weeks using EMG (Nicolet VikingQuest version 11, USA) with three types of test foods.
During all recordings, the patients were seated with their head unsupported and were asked to maintain a naturally erect position. The masseteric myoelectric activity of both sides (right and left) were recorded by means of disposable bipolar electrodes positioned on the bellies of the muscles parallel to the fiber orientation (Natus Medical Incorporated, Nicolet VikingQuest version 11, Middleton, USA) [Figure 6].
Electro-conductive gel was used on the electrodes before contacting the skin and the recording electrodes were positioned approximately 20 mm apart. The patient was grounded by grounding electrode by fixing the third electrode on the palm of the patient's hand.
Each patient was instructed to clench with a preformed silicon index made by using vinyl polysiloxane material (putty) of standardized size positioned at the premolar region for 30 s to measure the muscle activity during clenching. Then, the patients were instructed to chew on one peanut of similar size and diameter and the EMG was recorded. Then, the patients were instructed to chew on a piece of cake of standardized size (2 cm × 2 cm) and the EMG was recorded. The patients chewed the test samples on the right and left sides at 10 s intervals using their arbitrary chewing frequency until they are ready to swallow before the EMG was recorded.
At the end of the record and before removing the surface electrodes, the positions of the electrodes were marked to be used as a guide for accurate reproducibility. The previous tasks were separated by a recovery rest period of 2 min. The computerized data showed the root mean square (RMS) of the EMG signals.
Data were fed to the computer and analyzed using IBM SPSS software package version 20.0. Quantitative data were described using range (minimum and maximum), mean, standard deviation and median. Kruskal–Wallis test and Mann–Whitney U-test were applied. Significance of the obtained results was judged at the 5% level. A P< 0.05 was considered statistically significant.
| Results|| |
Analysis of the root mean square values of the electromyography signals of the masseter muscle
[Table 1] shows the range (minimum and maximum), mean, standard deviation and median values of RMS values of EMG signals of the masseter muscle (right and left), with two different occlusal concepts, BBO and CGO, during clenching with a preformed silicon index, chewing peanut, and chewing cake.
|Table 1: Comparison between bilateral balanced occlusion and canine guidance occlusion according to electromyography signals (root mean square values) of the masseter muscle|
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In the right masseter muscle, BBO has shown lower RMS values on clenching with the silicon index, chewing peanut and chewing cake than the RMS values of CGO.
However, the table shows no statistically significant difference between the two occlusal concepts for the right masseter muscle. The difference was statistically significant only during clenching on a silicon index (P = 0.042).
In the left masseter muscle, BBO has shown lower RMS values on clenching with the silicon index, chewing peanut, and chewing cake than the RMS values of CGO. The table shows no statistically significant difference between the two occlusal concepts for the left masseter muscle.
Analysis of the root mean square values of the electromyography signals of the masseter muscle in bilateral balanced occlusion
[Table 2] shows the range (minimum and maximum), mean, standard deviation, and median values of RMS values of EMG signals of the right and left masseter muscles with BBO during clenching with a preformed silicon index, chewing peanut, and chewing cake.
|Table 2: Comparison between the different test foods according to root mean square values of the electromyography signals of right and left masseter muscles in bilateral balanced occlusion|
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In the right masseter muscle, clenching on silicon index showed the highest RMS values followed by chewing peanut and the least RMS value was for chewing cake. The results showed a statistical significant difference between them (P = 0.006).
In the left masseter muscle, clenching on silicon index showed the highest RMS values followed by chewing peanut and the least RMS value was for chewing cake. The results showed no statistical significant difference between them (P = 0.082).
There was a statistical significant difference between clenching on silicon index and chewing cake (P1 =0.037).
Analysis of the root mean square values of the electromyography signals of the masseter muscle in canine guidance occlusion
[Table 3] shows the range (minimum and maximum), mean, standard deviation and median values of RMS values of EMG signals of the right and left masseter muscles with CGO during clenching with a preformed silicon index chewing peanut and chewing cake.
|Table 3: Comparison between the different test foods according to root mean square values of the electromyography signals of right and left masseter muscles in canine guidance occlusion|
Click here to view
In the right masseter muscle, clenching on silicon index showed the highest RMS values followed by chewing peanut and the least RMS value was for chewing cake. The results showed no statistical significant difference between them (P = 0.778).
In the left masseter muscle, clenching on silicon index showed the highest RMS values followed by chewing peanut and the least RMS value was for chewing cake. The results should no statistical significant difference between them (P = 0.344).
| Discussion|| |
In this study, twelve completely edentulous patients were selected. Since the type of opposing occlusion is a critical factor that influences the magnitude of forces transmitted to the implant bone interface, the opposing occlusion was selected to be mucosa-supported complete denture. This was done to standardize and control the amount of occlusal forces applied to the abutments since complete dentures were proved to exert less amount of force compared to the natural teeth.
A clear acrylic resin radiographic/surgical mandibular template including gutta-percha radiopaque indicators which were located in the canine- first premolar region was duplicated from the mandibular conventional denture; to be worn by the patient during preoperative radiographic scanning. As a radiographic guide, it allows selection of optimal implant sites regarding the bone width, height and their relation with anatomical landmarks such as mental foramen while meeting prosthetic and anatomical requirements.
BBO and CGO were chosen for evaluation in this study. Both include simultaneous contact in centric occlusion but differ in eccentric movements. BBO is considered by many authors as fundamental for treatment success, as it provided greater retention and stability than canine guidance by centralizing the forces on the residual alveolar ridge. However, there is no sufficient scientific evidence to support BBO as the ideal occlusal concept for conventional complete dentures and implant-retained overdentures.
Since the procedures in construction of dentures with BBO are much more complex and time-consuming, other authors recommended and preferred the use of canine guidance in complete dentures. They concluded that it can be used successfully in complete denture treatment as it provides better mandibular denture retention, esthetic appearance, and chewing ability. However, no scientific evidence was available for the application of canine guidance in implant-retained overdentures.
EMG has also been used to assess the masticatory function of mandibular implant-retained overdentures. The masseter and anterior temporalis muscles on both sides were evaluated because they are the largest and strongest of the masticatory muscles, the most superficial and are accessible to surface EMG examination. The surface EMG recordings provided a safe, easy, and noninvasive method that allowed objective quantification of the energy of the muscle.
Standard amounts and sizes of cake and peanuts were used to reduce patient variability. These test foods were an example of soft and hard food respectively and they gave an idea about the effect of different types of food on muscle activity during function. Preformed silicon index was used to measure the muscle activity during clenching.
Many authors stated that BBO promotes better masticatory efficiency by bringing a larger amount of grinding surfaces into contact at each movement., The results of the current study did not show a significant difference for muscle function by EMG between the studied occlusal concepts. This finding coincides with El-Okel who compared masticatory efficiency through evaluation of electromyographic activity between BBO, CGO, lingualized and monoplane occlusion schemes and found no significant difference. The results also coincide with Grunert et al., who found no difference in muscle activity between BBO and CGO in complete dentures. These results were also similar to Farias Neto et al., who stated that BBO did not improve masticatory efficiency when compared with canine guidance. Abd Elmonem evaluated masticatory efficiency in complete denture wearers with BBO and canine guidance using the colorimetric method and also found no statistical significant difference between them.
Despite the insignificant difference between EMG activity of the masseter muscles in BBO and CGO, the mean EMG activity was higher in canine guidance compared to BBO. This could be due to larger amount of grinding surfaces brought into contact at each movement in balanced occlusion resulting in less effort needed by the muscles during chewing. This could also be due to BBO facilitating adaptation to the new denture as stated by Rehmann et al. These results are in contrast with Grubwieser et al., and Miralles et al., who found that CGO reduced masseter muscle activity in complete denture wearers. They stated that neuromuscular function in edentulous subjects is similar to that found in dentate people and that canine guided dentures prevent parafunctional habits.,
The results of this study showed that the EMG activity of the masseter muscles during clenching on a preformed silicon index was significantly higher than during chewing peanut and chewing cake. This finding is in line with Miralles et al., who pointed out that the increased EMG activity may be due to increased vertical dimension leading to increased muscle activity during maximum voluntary clenching. This finding is also in line with Darwish et al. The results also show higher mean EMG activity when chewing peanut than when chewing cake in this study. This coincides with van der Bilt et al., who stated that harder food consistency required higher muscle activity levels due to higher muscle force needed to comminute hard food. The results are also in agreement with Karkazis, who found that harder foods required higher chewing rates, higher electrical activity of the masseter muscle, and higher relative contraction periods, accompanied by shorter cycle durations.
| Conclusions|| |
Within the limitations of this study of short follow-up periods of mandibular implant-retained over denture and maxillary complete denture, the results lead to that both BBO and CGO can be used successfully in implant-retained overdentures without affecting masticatory function. However, the procedures involved in construction of dentures with BBO are more complex and time consuming. Greater muscle activity of both muscles is shown when chewing hard food due to higher muscle force needed to comminute hard food compared to soft food.
Consent for publication
All the patients who participated in the study provided consent to publish the data obtained from them during the study.
I would like to express my sincere gratitude to my father, Dr. Ibrahim Hisham Hanno (pedodontist) who supplied all the materials used for the research and funded the research. I would also like to express my deepest gratitude to my mother, Dr. Mervat M. Ghoneim (prosthodontist) for her continuous support and revision of both the prosthodontic clinical steps and intellectual content of the article.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3]