|Year : 2021 | Volume
| Issue : 1 | Page : 20-24
Comparative evaluation of masseter and buccinator muscle activity using electromyography in denture wearer and nondenture wearer by fabricating dentures with neutral zone technique – An In vivo study
Anagha Dafade, Mithilesh Dhamande, Seema Sathe, Anjali Bhoyar Borle, Dipak Shinde, Tanvi Balwani
Department of Prosthodontics Crown and Bridge, Sharad Pawar Dental College, Datta Meghe Institute of Medical Sciences (Deemed to be University), Wardha, Maharashtra, India
|Date of Submission||19-Jan-2020|
|Date of Decision||18-Nov-2020|
|Date of Acceptance||30-Nov-2020|
|Date of Web Publication||29-Jul-2021|
Dr. Anagha Dafade
Department of Prosthodontics Crown and Bridge, Sharad Pawar Dental College, Wardha, Maharashtra
Source of Support: None, Conflict of Interest: None
Introduction: The objective of this study was to analyze buccinator and masseter muscle activity in previous denture wearer and nondenture wearer wherein dentures were constructed with neutral zone technique; however, complete dentures for patients with no history of previous dentures can be made with a neutral zone technique for improved stability. Methodology: A total of 50 patients were included in this study among which, Group A consisted of a total of 25 patients, who were old denture wearer and for whom a new denture was fabricated with the neutral zone technique. Group B consisted of 25 patients who were first-time denture wearer for whom a new denture was fabricated with a neutral zone technique. Results: The muscle activity does not significantly differ in previous denture and nondenture wearers. However, complete dentures for patient with no history of previous dentures can be made with a neutral zone technique for improved stability. Conclusions: Buccinator and masseter muscle activities significantly differ due to morphological changes that occurred in denture wearers and nondenture wearers.
Keywords: Buccinator, denture, electromyography, masseter, muscle, neutral zone
|How to cite this article:|
Dafade A, Dhamande M, Sathe S, Borle AB, Shinde D, Balwani T. Comparative evaluation of masseter and buccinator muscle activity using electromyography in denture wearer and nondenture wearer by fabricating dentures with neutral zone technique – An In vivo study. J Datta Meghe Inst Med Sci Univ 2021;16:20-4
|How to cite this URL:|
Dafade A, Dhamande M, Sathe S, Borle AB, Shinde D, Balwani T. Comparative evaluation of masseter and buccinator muscle activity using electromyography in denture wearer and nondenture wearer by fabricating dentures with neutral zone technique – An In vivo study. J Datta Meghe Inst Med Sci Univ [serial online] 2021 [cited 2021 Sep 16];16:20-4. Available from: http://www.journaldmims.com/text.asp?2021/16/1/20/322598
| Introduction|| |
The dimension of bone is under the influence of numerous systemic and local factors, Among these local factors are of direct concern to a prosthodontist in the design of both complete and partial dentures. Many elderly patients present with severe alveolar resorption and their oral tissues may demonstrate severe age changes.
Because of the progressive changes that accompany edentulism, the functional dynamics that define the oral cavity, the loss of the patient's capability to adapt, and increased life expectancy, have posed a challenge for the dentist when restoring and rehabilitating the oral cavity. In edentulous patients, support to the lips and the cheeks is no longer available and they tend to collapse into the oral cavity. Simultaneously, the tongue will try to expand into space. When all-natural teeth have been lost, there exists within the oral cavity a void, which is the potential denture space.
A neutral zone is that area in the potential denture space where the forces of the tongue pressing outward are neutralized by the forces of the cheeks and lips pressing inward. According to the glossary of prosthodontic Terms-9, the neutral zone is “the potential space between the lips and cheeks on one side and the tongue on the other; that area or position where the forces between the tongue and cheeks or lips are equal.”
Neutral zone philosophy is based on the concept that for each individual patient, there exists within the denture space a specific area where the function of the musculature will not unseat the denture and where forces generated by the tongue are neutralized by the forces generated by the lips and cheeks. The musculature of the denture space is divided into two groups as,
- Those muscles which primarily dislocate the denture during activity. (masseter, mentalis, incisive, medial pterygoid, and palatoglossus)
- Those muscles that fix the denture by muscular pressure on its secondary supporting surfaces. (buccinator, orbicularis oris, and genioglossus).,
Any complete denture that interferes with the actions of the surrounding muscles will, therefore, lack stability. In such situations, it can be assumed that the muscle activity will differ in patients when wearing unsatisfactory conventional complete dentures as compared with satisfactory dentures fabricated using the neutral zone techniques.
Electromyography (EMG) is a practical and efficient method for the study of muscle function and activity, thus serving as a valuable tool in dental research. EMG is the study of muscle function through the analysis of the electrical signals emanated during muscular contractions.,
The objective of this study was to evaluate and compare electromyographic (EMG) activity of masseter and buccinator muscles in previous denture wearer to that of nondenture wearer wherein dentures are constructed with neutral zone technique using the same material by asking patients to pronounce a series of words.
| Methodology|| |
Selection of patients
Edentulous patients reporting to the department of prosthodontics were included in this study. The patients were selected based on the inclusion and exclusion criteria given below.
In each group, every patient was specified by numbers as 1, 2, 3,……., etc. A total of 50 patients included in this group among which, Group A consisted of a total of 25 old denture wearer patients and for whom a new denture was fabricated with a neutral zone technique. Group B consisted of a total of 25 patients and those were first-time denture wearer for whom a new denture was fabricated with a neutral zone technique.
Before initiating the study, the purpose and design of the study were explained to the patients and informed consent was obtained from each patient.
The preliminary impressions of maxillary and mandibular arches were made using the Y-Dents impression compound and the preliminary cast was obtained. The special trays were fabricated for the final impression by the dough method. Final impressions of the maxillary and mandibular arch were made using zinc oxide eugenol (Dots Per Inches (DPI) impression paste) which were poured using type III gypsum product. Two sets of provisional denture bases were fabricated for recording jaw relation. Maxillomandibular relation was obtained using the niswonger method for vertical jaw relation and centric jaw relation was recorded using Alluwax was used as bite registration material. Admixed material consisting of medium fusing impression compound and low fusing impression compound in the ratio of 3:7 was knaded and placed following rim shape on individual record base. After loading, the patient was asked to perform actions such as swallowing and speaking to induce sufficient muscle contraction. All the actions were performed clearly and vigorously. Once the neutral zone was obtained, the maxillomandibular relationship that has been established previously was transferred to the mean value articulator. Then, the additional neutral zone records were transferred to the mounted master cast and adjusted over the articulator. Plaster indices were made around the recorded neutral zone, and wax rims were prepared corresponding to the indices. The lower posterior teeth were set in the neutral zone, and wax try-in was done.
After the wax try-in was found satisfactory, polished surfaces of the trial dentures were recorded using zinc oxide eugenol impression paste. The paste was placed on the lingual surface of the lower trial denture base with a liberal amount in the anterior region. Often, a definite shelf was created in this region, which provided a resting place for the tongue and aids considerably in retention. The trial denture was placed in the mouth, and the patient was instructed to swallow. The paste was allowed to set and then more of the paste was placed on the buccal and labial surfaces to record their contour. The impression paste was then distributed evenly over the palatal surface of the upper waxed up denture, and the patient was instructed to place the tongue against the roof of the mouth, to push, and then to swallow. The excess zinc oxide and eugenol impression material were trimmed away from the teeth, and the trial dentures were flasked and finished.
Once the denture processing was done in a conventional manner, it was finished and polished and the dentures were inserted in patients mouth and post insertion instructions were given. The routine follow-up appointments were followed.
All tests were conducted with surface electrodes. During the measurements, individuals remained seated comfortably on a chair, in an upright position, with their feet on the floor and their arms placed on their legs. Their heads were positioned with the frankfort horizontal plane parallel to the floor. A silent and partially illuminated environment was maintained, and patients were asked to remain relaxed to avoid any involuntary contractions that could affect muscle activity.
For the external location of buccinator muscle, the patients were asked to pronounce words such as “cheese,” “baby” eagerly, and vigorously which included bilabial (m, p, b), labiodental (f, v), alveolar (s, sh), and dental (th) sounds. Three landmarks were first determined in a hemiface [Figure 1]: Point A: external eye angle; Point B: labial angle; Point C: external point corresponding to the central point of the buccinator muscle. The electrodes were placed at the exact points corresponding to the external location of the muscles whose electrical activity was to be measured [Figure 2] and [Figure 3].
|Figure 1: Schematic drawing showing the three landmarks, points A, B, and C for the external location of the buccinator muscle|
Click here to view
For the external location of the masseter muscle, the patient was asked to bring his teeth in maximum intercuspation and maximal activity of the muscle was established. The activity continued for 15–30 s. Electrodes were placed 2 cm above the lower margin of mandible, halfway between the mandibular angle and anterior border of the muscles were identified after clenching.,
The highest electromyographic activity was considered as the maximum muscle activity during a given period. The peak-to-peak amplitude (μV) was automatically generated on the electromyography unit presented as electromyogram, and each patient graph was printed.
The Institutional Ethics Committee of DMIMSDU has approved the Research work proposed to be carried out at Sharad Pawar Dental College & Hospital, Sawangi(M), Wardha. Date : 10th October 2016 with Reference no DMIMS(DU)/IEC/2016-17/5085.
| Results|| |
The statistical tests used for the analysis of the result were as follows:
- Two-way ANOVA
- One-way ANOVA
- Student's unpaired t-test
- Multiple comparisons: Tukey test.
Mean muscle activity of Group A (Masseter) was 471 ± 99.80, for Group A (Buccinator) was 239.80 ± 48.11, for Group B (Masseter) it was 288 ± 133.26, and for Group B (Buccinator) it was 115 ± 14.94).
On comparing muscle activity of all groups using multiple comparisons: Tukey Test statistically significant difference was found between Group A (Masseter) and Group A (buccinator) (P = 0.0001), Group A (masseter) and Group B (masseter) (P = 0.0001), Group A (masseter) and Group B (buccinator) (P = 0.0001), Group A (buccinator) and Group B (buccinator) (P = 0.0001), and Group B (masseter) and Group B (buccinator) (P = 0.0001), whereas for Group A (buccinator) and Group B (masseter) (P = 0.146) it shows no statistically significant difference.
The mean EMG activity of the buccinator was comparable among the groups, statistically significant differences observed. A statistically significant difference was observed between groups demonstrating higher activity in Group A.
| Discussion|| |
The objective of this study was to observe the electromyographic (EMG) activity of buccinator and masseter muscle with patients wearing new complete denture fabricated using the neutral zone technique. The location method proposed was based on the external anatomical facial points, accurately located in the central point of the buccinator muscle, which allows precise positioning of the electrodes for EMG analysis with a 95%° of reliability [Graph 1] and [Table 1].
Although both the neutral zone dentures were found to be clinically superior and yielded higher patient satisfaction when compared with the old ones, the mean EMG activity of the buccinator was comparable among the two groups during pronunciation of the words such as “cheese,” “baby.” To evaluate the effect of previous denture wearer on the morphology of neutral zones, it was recorded with similar material. Impression compound was used to eliminate the effect of viscosities of different materials during muscular movements.
Lingual deviation of the phonetic neutral zone in nondenture wearers on mandibular anterior buccal surfaces have resulted because of stronger contraction of inferior orbicularis oris to produce bilabial sounds. Since lingua-alveolar fricatives are/s/and/z/require the adequate spreading of the tongue for passage of air through teeth, high precision movement of the tongue and controlled jaw positioning.
These may be affected more in nondenture wearers. In the premolar segment, correlation of the denture wearing with morphologies of the neutral zone was not significant on either buccal or lingual sides. It may be because of the relative similarities among the positions of musculature. The contraction of buccinators is not affected by the presence or absence of dentures. If the dentures are constructed in accordance with the shape of buccinators, this may result in improved retention and stability.
On the buccal surfaces of the molar regions, the influence of musculature was almost similar as buccinators are active during swallowing and speech. An electromyographic study of orbicularis oris and buccinators, also shows the comparable activity of these muscles during rest, pursing, speaking, and laughing with or without neutral zone dentures.
The lower jaw develops a range of motion (lifting, lowering, protrusion, retraction, and lateralization), influenced by the muscles responsible for chewing. The jaw elevation is performed by the masseter muscle, anterior temporal muscle, and medial pterygoid muscle. The masseter muscle fibers on contraction project the jaw upward, promoting contact between the dental arches. The chewing efficiency is guaranteed by force exerted on the contraction of this muscle. Masseter muscle has no influence on the neutral zone, but it affects the distobuccal border of the denture. The jaw elevation is performed by the masseter muscle, anterior temporal muscle, and medial pterygoid muscle 14.
However, on the lingual side, there was more of buccal deviation of the neutral zone in non-denture wearers. This shows the expansion of the lingual musculature and the broadened shape of the tongue during swallowing and speech in this specific area. This may be predominant in cases where tongue after the loss of teeth was not confined in its space by a previous denture. This finding may influence the shape of the polished surface of the denture in the posterior lingual area, especially in new denture wearer.
Considering the limitations of the study, the increased sample size may give a definitive result about the influence of previous dentures over existing neutral zones.,,,,,,,,
| Conclusions|| |
The influence of the previous denture on the comparative shapes of the neutral zone may not be prominent. The muscle activity significantly differs in previous denture and nondenture wearers. However, complete dentures for patient with no history of previous dentures can be made with a neutral zone technique for improved stability.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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