Impact of midface and upper face fracture on bite force, mandibular mobility, and electromyographic activity

Abstract

This study evaluated the bite force, electromyographic activity, and mandibular mobility in patients undergoing surgery for facial fracture treatment that required a coronal approach. Ten men were divided into two groups: group I, coronal approach with pre-auricular extension ( n = 4, average age 34.5 years); group II, coronal approach ( n = 6, average age 24.8 years). The maximum bite force was measured using a dynamometer and mandibular mobility using a calliper. The electromyographic activity of the right masseter (RM), left masseter (LM), right temporal (RT), and left temporal (LT) muscles was evaluated using a Myosystem-Br1 apparatus. Patients were evaluated at 1, 2, 3, and 6 months after surgery. Data were analysed using the repeated measures test (SPSS 21.0; P ≤ 0.05). Statistically significant differences were found for electromyographic activity at rest (group II: LM P = 0.00), left laterality (group I: RT P = 0.02; group II: RT P = 0.04), and maximum voluntary contraction (group I: RM P = 0.04 and RT P = 0.04; group II: RM P = 0.05, LM P = 0.00, and LT P = 0.01 and for maximum molar bite force in the right (group I, P = 0.00; group II, P = 0.01) and left (group II, P = 0.01) molar regions. The subjects regained electromyographic activity, maximum bite force, and mandibular mobility throughout the period evaluated.

The effects of traumatic forces to the facial bones are varied. The management and surgical treatment of facial fracture remains a mainstay of the maxillofacial surgery speciality and can present challenges for the surgeon.

The craniofacial skeleton has an important role in the functions of chewing, speech, sight, smell, breathing, and aesthetics and is fundamental in interpersonal recognition and the perception of self-image. Various factors influence chewing efficiency, such as bite force, dental occlusion, mandibular movements, and tongue and saliva activity. Skeletal muscles are able to change their morphology as a result of functional demands; therefore all tissues that form part of the stomatognathic system influence the functional demands of the masticatory muscles – the supporting skeletal geometry, soft tissue attachments, and muscle fascia. Thus, when damaged, there is an adaptation to new functional demands, which could be reflected in the contraction speed and maximum power generated by the muscles.

The trauma and repair processes modify facial muscle activity. Analysing the trauma caused by surgical treatment using internal fixation is of great value in terms of understanding the changes in the stomatognathic system, thus showing how the human body undergoes the necessary adjustments in the stomatognathic system to adapt to fractures and treatment. This, in turn contributes to improving surgical techniques and materials used for the fixation of facial fractures.

The aim of this research was to evaluate the functional recovery of the stomatognathic system over time (at 1, 2, 3, and 6 months after surgery) in patients affected by midface and upper face fractures treated with stable internal fixation and for whom the coronal approach with or without pre-auricular extension was required.

Patients and methods

This study was approved by the ethics committee of the college of dentistry in São Paulo. All patients were informed about the study procedures and signed the informed consent form. The sample selection period was from July 2014 to September 2015.

Sample

Thirteen healthy patients aged between 18 and 40 years participated in this study. All subjects were male, had a normal occlusion and all of their teeth (except third molars), had no comorbidities, and did not present extensive excoriations or lacerations of the face that would prevent the fixation of surface electrodes. They had no median or paramedian fractures of the maxilla, no Le Fort I type fractures, mandibular fractures, or dentoalveolar injuries. All of the patients included in the sample were conscious on arrival at the hospital and did not have skull base fractures or neurological injuries. However, three patients did not attend the pre-established study follow-up appointments (1, 2, 3, and 6 months). Therefore, the final sample included 10 men.

The study patients were divided into two groups: group I comprised men (average age 34.5 years) with Le Fort III type fractures ( n = 3) and left zygomatic orbital fractures ( n = 1) treated surgically using the coronal approach with pre-auricular extension, as described by Ellis and Zide ; group II comprised men (average age 24.8 years) with frontal bone fractures ( n = 3) and naso-orbito-ethmoid fractures associated with Le Fort II type fractures ( n = 3) treated surgically using the coronal approach, as described by Ellis and Zide.

Patients who had zygomatic, naso-orbito-ethmoid, and Le Fort fractures required additional surgical incisions, such as subciliary and intraoral buccal incisions. A single surgeon performed the fracture surgery. There was no difference in the anchorage system used for the fractures (1.5-mm plates and screws system, Tóride; Tóride Implantes Ind. Com. Ltda, Mogi Mirim, SP, Brazil). All patients received preoperative cephalexin 2 g at 1 h before surgery and took 1 g every 8 h while hospitalized; after discharge they took cephalexin 500 mg every 6 h for 7 days, ketoprofen 100 mg every 8 h for 3 days, and dipyrone as a painkiller in the case of pain in the first week.

All fractures were middle and upper third, caused by a high-energy trauma. The most prevalent aetiology of the fractures was traffic accidents; however physical aggression and falls were also among the causes. One patient in group 1 and one patient in group 2 had transient neuropraxia of the frontal branch of the facial nerve for 15 days after the surgery. No patient included in the study had a postoperative infection, or wound dehiscence or bruising that could interfere with the study. The average duration of hospitalization was 3 ± 2 days.

The control group comprised healthy subjects with a normal occlusion and no temporomandibular dysfunction. These subjects were matched to the study group subjects by age, sex, height, and weight. They had electromyographic (EMG) data, molar bite force, and jaw mobility values within the normal range.

Bite force

A digital dynamometer (model IDDK; Kratos, Cotía, SP, Brazil) was used to analyse the bite force in the first molar region on both sides. The patients were instructed to bite the dynamometer with maximum force three times (2-min rest interval). The maximum molar bite force (the largest number) was obtained.

Electromyographic data

Muscular activity was evaluated using EMG recordings of the masseter and temporalis muscles in the following conditions: rest (5 s), teeth clenching in maximum voluntary contraction (MVC) (4 s), maximum right (5 s) and left (5 s) laterality with dental contact (canine guidance), and maximum protrusion with dental contact in anterior guidance (5 s), presenting the Christensen phenomenon.

EMG activity was evaluated using a Myosystem-Br1 apparatus (DataHominis Tecnologia Ltda, Uberlândia, MG, Brazil). The EMG analysis was performed by one trained professional. The electrodes were placed on the masticatory muscles in the intermediate region between the centre of the innervation zone (motor point) and the muscle tendon, aligned longitudinally and parallel to the direction of the muscle fibres, as this was considered the most suitable place. To ensure precise location of the muscles, specific palpation manoeuvres in MVC were carried out. To avoid cross-talking, a reference electrode was placed in a region distant from the muscles to be tested. The EMG analysis was performed by one trained professional.

Mandibular mobility

A digital pachymeter (Mitutoyo, Santo Amaro, São Paulo, Brazil) was used to measure mandibular mobility, considering the maximum standards for mouth opening, as well as right and left lateral movement and protrusion. The necessary instructions and explanations were given, and the patient was always asked to remain as calm as possible and to breathe slowly. The mandibular mobility benchmarks were the dental midlines. The calliper was positioned in the incisal and mesial region of the maxillary right central incisor and the incisal and medial region of the lower right central incisor.

Statistical analysis

The raw electromyographic signal was used to derive electromyographic amplitude values obtained by calculating the root mean square (RMS). The EMG, bite force, and mandibular mobility data were tabulated and submitted to statistical analysis using the repeated measures test (IBM SPSS Statistics version 21.0; IBM Corp., Armonk, NY, USA). A 95% level of significance was adopted ( P ≤ 0.05).

Results

Table 1 shows the results of the maximum molar bite force (right and left) for group I and group II. There were statistically significant differences ( P ≤ 0.05) for the right molar bite force ( P = 0.00) and left molar bite force ( P = 0.01) for group I, and for left molar bite force ( P = 0.01) for group II over the 6-month period.

Table 1
Bite force (Newtons) in the right and left molar regions in group I and group II during the 6-month period; mean ± standard error of the mean and P -values in comparison to the control group (CG).
Time Group I Group II
Right molar Left molar Right molar Left molar
1 month 153.08 ± 65.21 166.22 ± 52.36 252.12 ± 44.42 241.73 ± 60.80
2 months 232.90 ± 75.11 238.00 ± 71.78 300.18 ± 59.72 265.95 ± 55.99
3 months 174.06 ± 52.46 204.95 ± 53.15 247.32 ± 41.87 286.55 ± 32.95
6 months 446.49 ± 99.24 377.16 ± 83.35 318.12 ± 39.71 388.34 ± 45.11
P -values (CG) 0.00 a (368.92) 0.01 a (364.70) 0.28 (368.92) 0.01 a (364.70)

a Statistically significant, P < 0.05.

The EMG data for the right masseter (RM), left masseter (LM), right temporal (RT), and left temporal (LT) muscles in each condition analysed are shown in Table 2 (group I) and Table 3 (group II). There were statistically significant differences ( P ≤ 0.05) in group I for left laterality in the RT ( P = 0.02) and MVC in the RM ( P = 0.04) and RT ( P = 0.04), 6 months after the surgery. For group II, there were statistically significant differences ( P ≤ 0.05) in the mandibular rest condition for LM ( P = 0.00), left laterality for RT ( P = 0.04), and MVC for RM ( P = 0.05), LM ( P = 0.00), and LT ( P = 0.04).

Table 2
Electromyographic data (μV) for the right masseter, left masseter, right temporal, and left temporal muscles for group I during the 6-month period, at rest, maximum voluntary contraction (MVC), right laterality, left laterality, and protrusion; mean ± standard error of the mean and P -values in comparison to the control group (CG).
Clinical condition and muscle Period P -value (CG)
1 month 2 months 3 months 6 months
Rest
Right masseter 6.89 ± 0.78 6.11 ± 0.85 6.58 ± 0.21 5.93 ± 0.60 0.74 (5.38)
Left masseter 7.91 ± 1.80 5.77 ± 0.63 6.49 ± 0.52 5.95 ± 0.30 0.40 (6.23)
Right temporal 9.31 ± 1.34 6.21 ± 0.54 8.04 ± 0.58 7.15 ± 0.97 0.16 (7.93)
Left temporal 8.36 ± 1.57 5.95 ± 0.62 7.36 ± 0.19 7.72 ± 0.72 0.35 (9.11)
MVC
Right masseter 43.35 ± 8.66 97.23 ± 21.43 77.47 ± 14.73 93.62 ± 8.08 0.04 a (121.51)
Left masseter 33.11 ± 10.16 76.64 ± 26.87 53.23 ± 10.20 90.23 ± 21.96 0.06 (116.99)
Right temporal 24.65 ± 2.89 34.23 ± 7.78 49.93 ± 12.44 57.88 ± 7.81 0.04 a (144.80)
Left temporal 30.76 ± 2.23 29.75 ± 4.57 37.26 ± 4.50 43.25 ± 3.89 0.13 (157.87)
Right laterality
Right masseter 10.92 ± 3.64 7.73 ± 2.02 9.57 ± 2.98 9.97 ± 2.70 0.83 (8.69)
Left masseter 17.44 ± 3.90 17.22 ± 4.07 13.89 ± 2.67 15.75 ± 3.72 0.75 (9.79)
Right temporal 13.05 ± 1.83 9.40 ± 0.65 15.84 ± 2.69 9.54 ± 1.74 0.17 (10.73)
Left temporal 8.74 ± 1.34 6.97 ± 0.97 8.43 ± 0.94 8.53 ± 1.03 0.67 (8.43)
Left laterality
Right masseter 19.93 ± 6.00 16.94 ± 4.23 17.21 ± 2.45 17.35 ± 3.98 0.93 (8.52)
Left masseter 16.45 ± 6.74 13.20 ± 5.74 11.10 ± 1.80 9.58 ± 2.26 0.78 (6.45)
Right temporal 11.93 ± 1.34 6.05 ± 0.78 14.31 ± 2.90 6.72 ± 0.70 0.02 a (7.41)
Left temporal 12.34 ± 1.97 8.24 ± 0.51 13.02 ± 4.52 11.03 ± 1.69 0.63 (8.89)
Protrusion
Right masseter 31.75 ± 6.21 29.05 ± 1.85 25.98 ± 7.33 38.50 ± 5.15 0.41 (12.74)
Left masseter 19.30 ± 3.43 26.53 ± 8.52 17.47 ± 4.79 35.09 ± 5.32 0.06 (15.70)
Right temporal 10.94 ± 1.03 6.91 ± 0.52 14.32 ± 4.64 7.96 ± 0.63 0.22 (7.39)
Left temporal 9.87 ± 1.64 6.26 ± 0.69 7.74 ± 0.46 8.27 ± 0.68 0.16 (9.67)

a Statistically significant, P < 0.05.

Table 3
Electromyographic data (μV) for the right masseter, left masseter, right temporal, and left temporal muscles for group II during the 6-month period, at rest, maximum voluntary contraction (MVC), right laterality, left laterality, and protrusion; mean ± standard error of the mean and P -values in comparison to the control group (CG).
Clinical condition and muscle Period P -value (CG)
1 month 2 months 3 months 6 months
Rest
Right masseter 7.56 ± 1.12 6.83 ± 0.71 5.23 ± 0.21 7.41 ± 0.99 0.17 (5.38)
Left masseter 8.06 ± 0.80 7.28 ± 0.68 5.90 ± 0.75 7.63 ± 0.20 0.00 a (6.23)
Right temporal 7.88 ± 0.34 8.72 ± 1.17 7.30 ± 0.76 9.61 ± 0.61 0.10 (7.93)
Left temporal 7.55 ± 0.33 8.76 ± 1.01 6.47 ± 0.73 9.12 ± 0.91 0.11 (9.11)
MVC
Right masseter 92.34 ± 22.80 198.44 ± 53.88 255.38 ± 38.13 232.60 ± 51.95 0.05 a (121.51)
Left masseter 99.51 ± 29.39 180.02 ± 52.71 284.43 ± 52.29 275.98 ± 67.69 0.00 a (116.99)
Right temporal 75.70 ± 20.64 95.35 ± 19.61 96.21 ± 10.97 120.18 ± 19.27 0.08 (144.80)
Left temporal 61.85 ± 22.88 73.94 ± 16.89 90.95 ± 14.94 112.49 ± 6.28 0.01 a (157.87)
Right laterality
Right masseter 21.61 ± 6.33 16.98 ± 6.02 6.28 ± 0.15 11.14 ± 2.74 0.07 (8.69)
Left masseter 23.19 ± 7.78 26.01 ± 4.78 17.71 ± 3.77 21.21 ± 4.60 0.35 (9.79)
Right temporal 22.19 ± 6.14 12.33 ± 1.81 14.72 ± 4.57 21.39 ± 5.01 0.18 (10.73)
Left temporal 8.07 ± 0.61 9.20 ± 1.06 6.63 ± 0.80 9.23 ± 0.91 0.14 (8.43)
Left laterality
Right masseter 23.79 ± 7.41 20.22 ± 5.95 24.10 ± 6.97 13.28 ± 3.07 0.35 (8.52)
Left masseter 22.73 ± 7.13 20.48 ± 6.70 16.40 ± 6.60 14.56 ± 4.39 0.59 (6.45)
Right temporal 7.75 ± 0.60 8.08 ± 0.53 6.45 ± 0.87 9.32 ± 0.63 0.04 a (7.41)
Left temporal 15.37 ± 4.28 10.95 ± 1.09 10.33 ± 0.87 13.11 ± 2.39 0.48 (8.89)
Protrusion
Right masseter 65.31 ± 17.40 42.46 ± 13.57 92.11 ± 17.91 36.60 ± 12.77 0.07 (12.74)
Left masseter 78.83 ± 21.27 54.84 ± 14.43 91.72 ± 25.89 50.98 ± 18.10 0.28 (15.70)
Right temporal 13.55 ± 3.49 12.38 ± 2.69 7.20 ± 0.99 10.77 ± 1.16 0.18 (7.39)
Left temporal 14.46 ± 4.44 12.48 ± 2.68 7.62 ± 1.33 10.72 ± 1.63 0.19 (9.67)
Only gold members can continue reading. Log In or Register to continue

Dec 15, 2017 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Impact of midface and upper face fracture on bite force, mandibular mobility, and electromyographic activity
Premium Wordpress Themes by UFO Themes