- Email: [email protected]
Evaluation of sleep bruxism with a novel designed occlusal splint
JPOR 382 No. of Pages 11
journal of prosthodontic research xxx (2017) xxx –xxx
Available online at www.sciencedirect.com
Journal of Prosthodontic Research journal homepage: www.elsevier.com/locate/jpor
Original article
Evaluation of sleep bruxism with a novel designed occlusal splint Kentaro Hirai DDS, Tomoko Ikawa DDS, PhD, Yuko Shigeta DDS, PhD, Shuji Shigemoto DDS, PhD * , Takumi Ogawa DDS, PhD Department of Fixed Prosthodontics, School of Dental Medicine, Tsurumi University, Yokohama, Japan
article info
abstract
Article history:
Purpose: This report presents our evaluation system that assesses sleep bruxism. The
Received 28 October 2016
characteristics and fabrication process of our novel designed splint, and the analysis process
Received in revised form
of our system are presented.
5 December 2016
Methods: The subjects were 17 volunteers. The splint was fabricated with a self-curing resin
Accepted 19 December 2016
compounded with an amino-acid powder for easy wear on the semi-adjustable articulator,
Available online xxx
and adjusted for a full-balanced occlusion. An impression of the splint, located on the cast, was taken before and after it was worn. The analytical casts were made and scanned via a
Keywords: Sleep bruxism Occlusal splint Occlusal wear
dental 3D scanner. The datasets were superimposed using two kinds of regions of interest (palate and occlusal surface). The differences between the two datasets were quantitatively presented with pseudo-color mapping. The maximum differences in coronal and apical directions were calculated on the selected area in the occlusal surface when the occlusal surface was used as a region of interest for registration. The relationship between the EMG activities and the change of occlusal surface of the splint were investigated. Results: In all subjects, deformation and wear facets on the splint were observed. The differences in the apical direction, which indicate wear depth, were correlated with the maximum muscle activity during sleep (p=0.036). Conclusion: From our results, it is suggested that we are not able to eliminate the influence of parafunction for the prosthesis only by designing the surface of occlusal splint using the semi-adjustable articulator. Our splint may have the potential to detect specific facets due to parafunctions as nocturnal bruxism. © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.
1.
Introduction
Occlusal overload during sleep bruxism is a significant negative factor that affects prosthetic treatment plans,
maintenance of teeth, and the longevity of dental prostheses [1–3]. Clinically, the grinding contact of the upper and lower teeth in powerful bruxism is quite important because post occlusal reconstruction stability depends upon the effect of cranio-mandibular function, such as parafunctional activity.
* Corresponding author at: Department of Fixed Prosthodontics, School of Dental Medicine, Tsurumi University, 2-1-3 Tsurumi, Tsurumiku, Yokohama, Japan. Fax: +81 45 573 9599. E-mail address: [email protected] (S. Shigemoto). http://dx.doi.org/10.1016/j.jpor.2016.12.007 1883-1958/© 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
2
journal of prosthodontic research xxx (2017) xxx –xxx
Therefore, it is extremely important to reconstruct occlusion based on strong grinding movement [3]. Furthermore, after prosthodontic treatment, the occlusal splint should be applied to avoid overloading of the abutment teeth and the prosthesis. After wearing an occlusal splint, the bruxism pattern is reflected on the surface of the occlusal splint as wear facets. A splint can be an important diagnostic tool to determine wear patterns, bruxism severity, and temporomandibular disorder status. Examination of the grinding pattern during bruxism is necessary and should be incorporated in the diagnosis of occlusion in order to make a proper treatment plan for each patient [3]. Commonly, the grinding pattern is evaluated by observing wear facets on the occlusal splint [3,4]. Information gained from wear patterns on the splints helps determine occlusal configurations, material choice, cusp heights and shapes, guidance angulations, axial loads, and the envelope of function [5]. However, it is difficult in a dental setting to accurately diagnose sleep bruxism and to objectively assess the severity, frequency or natural history of this condition in an individual patient [6]. We proposed an evaluation system of wear facets on the surface of the occlusal splint. This system includes a novel designed occlusal splint that can show grinding patterns, and an analysis technique using a 3D scanner with dedicated software. The system can analyze the location and direction of wear facets and surface loss of an occlusal splint created by the grinding of the teeth during sleep. The pattern of wear facets depends on the adjusting method and the prearranged occlusal guidance of the splint. A previous study reported that the range of mandibular movements with nocturnal bruxism extended beyond functional movements during daytime [7]. In addition, complications from long-term use (more than four to six weeks) of splints can be severe and irreversible [8]. For this reason, the occlusal splint employed in our system is a full-coverage type with fullbalanced occlusion, and designed to be easily worn in shortterm use. In this report, we introduce our evaluation system that assesses sleep bruxism. The characteristics and fabrication process of our novel designed splint, and the analysis process of our system are also presented.
2.
Materials and methods
2.1.
Participants
In this current report, the subjects were 17 volunteers (male: 6, female: 11, 46.414.2 years). The dentulous adults, with all teeth existing except their second and third molars, were recruited. The experiment procedures were explained to all participants before obtaining consent. This research was approved by the Ethical Committee at Tsurumi University Dental Hospital (Approval No. 1416).
2.2.
Fabrication of the occlusal splint
The impressions of upper and lower dentitions were taken using ready-made trays and an alginate impression material.
The casts were made by a high strength dental stone (GC FUJIROCK, GC, Tokyo, Japan). These casts were mounted on a semi-adjustable articulator with a face-bow (ProArch III, Shofu Inc., Kyoto, Japan). In addition, the condylar path angles were adjusted with protrusion and lateral check-bites, and a custom-fabricated incisal table. After mounting, the interocclusal space was set approximately 2mm in the molar region for fabrication of the occlusal splint. To obtain an adequate retentive force, and avoid a severe deformation of the splint, a polyester sheet with a 0.75mm thickness (DURAN, Scheu Dental Technology, Iserlohn, Germany) was chosen as a base material (Hereinafter referred to as base splint). The design of the base splint followed that of the cap clasp [9], where the undercut at the buccal side was utilized. However, if there was no available undercut on the buccal side, the undercut at the palatal side was utilized. The undercut was set at 0.25 mm. The sheet was pressed to the upper cast via a pressure molding machine (Ministar S, Great Lakes Orthodontics, LTD, NY, USA), and trimmed along the design line mentioned above. This base splint was located on the mounted upper cast on the articulator. The incisal guide pin of the articulator was adjusted to secure a clearance of at least 1mm in the molar region for a self-curing resin (Facet resin, GC, Tokyo, Japan). The self-curing resin, which compounded with an aminoacid powder (airflow powder, Shofu Inc., Kyoto, Japan) for easy wearing, was built-up on the occlusal surface of the base splint (resin powder: amino-acid powder =1:1). The upper cast was moved through the right, left, and protrusive movement while the soft resin was setting. Finally, the occlusal guidance of the splint was adjusted for a fullbalanced occlusion. Therefore, the subject’s mandibular movement was impressed on the occlusal surface of our splint. Fig. 1 shows our adjusted splint. The occlusal surface was not as flat as the stabilization splint, and presents an individual subject’s functionally-generated pathway which was simulated on the articulator. Occlusal guidance of each subject resulted in different characteristics.
2.3.
System description
The splint, located on the cast, was taken an impression with a duplicating silicone (Duplicone, Shofu Inc., Kyoto, Japan) before and after it was worn by the participant. The analytical casts were made of a high strength dental stone (New FUJIROCK, GC, Tokyo, Japan) and were scanned via a dental 3D scanner (D900, 3Shape, Denmark). The scanned data was analyzed via 3D image analysis software (Rapidform 2006, INUS Technology, Korea). The location and direction of the wear facets, and the surface loss of the occlusal splint created by teeth grinding during sleep were investigated. Surface EMG of the masseter muscle was also recorded for 14 nights with a portable EMG recorder with a sampling rate of 10Hz and 10 bit resolution (Chewing recorder BR-1000, Nishizawa Electric Meters Manufacturing Co., Nagano, Japan). Disposable bipolar self-adhesive pre-gelled surface Ag/AgCl electrodes (RectLoad, Nishizawa Electric Meters Manufacturing Co., Nagano, Japan) were applied over the thickest portion of the right masseter muscle belly. A reference electrode was placed on the center of the forehead. Recorded EMG signals
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
journal of prosthodontic research xxx (2017) xxx –xxx
3
Fig. 1 – Occlusal splint after adjusting the occlusal guidance.
were amplified, and band-pass filtered (100–1000Hz) and stored within an internal memory. The signals were then analyzed using dedicated software that calculated the total sleep time (h:min:s), maximum muscle activity during sleep (% MVC), number of bruxism events (times), and total duration of bruxism events (s). The total sleep time was almost equal to the total splint wearing time.
2.4. Accuracy verification in our evaluation system for occlusal facet First, our evaluation system for the occlusal facet was verified. Two analytical casts were made. For the first analytical cast, an impression of the splint, located on the upper dentition model, was taken with a duplicating silicone. Then, the splint was removed from the dentition model and put back in its original position on the model. An impression once again was taken for the second analytical cast. The analytical casts were made of a high strength dental stone. These casts were scanned via a dental 3D scanner. The first cast was scanned two times for verifying the registration accuracy. The data was analyzed via 3D image analysis software. Two scan datasets of the first cast were imported into the software. Then the datasets were superimposed to verify the registration error with Iterative Closest Point algorithm [10] and two kinds of regions of interest for image registration were the palate and the occlusal surface of splint (Fig. 2). The scan datasets of the first and the second models were analyzed to verify the registration repeatability of our evaluation system with same method. The differences between the two datasets were quantitatively presented with pseudo-color mapping. In addition, the maximum differences in coronal and apical directions were calculated on the selected area of the occlusal surface when the occlusal surface was used as a region of interest (ROI) for registration. Coronal and apical directions indicated that the original surface of the occlusal splint was warped
upward and had wear facets created by sleep bruxism respectively.
2.5.
Assessment of the occlusal surface change
On the first visit to our clinic, the impressions of the subject’s upper and lower dentitions were taken for fabrication of an occlusal splint. On the second visit, this splint was applied to the subject after a slight intraoral adjustment. The splint located on the cast was taken an impression for the first analysis model (Model1). Participants were carefully instructed on how to use the EMG recorder and told to wear the occlusal splint while sleeping for 14 nights. After a 14-day recording, the participant came to the clinic where the recorded EMG data and the occlusal splint were collected. The EMG data was transferred to a personal computer and analyzed by dedicated software. Nocturnal masseter EMG events decreased significantly only one week after the insertion of the stabilization splint [11]. Therefore, in this study, analytical EMG data was selected from the one recording day when strong masseter muscle activities occurred most frequently in the second week. The EMG parameters were calculated. The splint used for 14 days was located on the cast and then an impression was taken for the second analysis model (Model2). The maximum differences in coronal and apical direction on the surface of the occlusal splint were calculated. We investigated the relationship between the EMG activities during sleep and the change of occlusal surface of the splint after 14 days of wear.
2.6.
Statistical analysis
Statistical analysis was carried out through the SPSS 22.0 (SPSS Inc., Chicago, USA). We investigated the linear relationships between variables with the Spearman’s test and linear regression. The linear
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
4
journal of prosthodontic research xxx (2017) xxx –xxx
Fig. 2 – Region of interest (blue). Left: palate, right: occlusal surface of splint.
Fig. 3 – Results of registration on two datasets of the scanned first model. Region of interest (blue); left: palate, right: occlusal surface of splint.
regression assumptions of linearity, homoscedasticity, and normality of the residuals were successfully evaluated.
differences within 40 mm were defined as “No difference” in using our evaluation system.
3.2.
3.
Results
3.1.
Accuracy verification in our evaluation system
Fig. 3 shows the results of registration using two scan datasets of the first model. The coronal and apical direction values represent plus and minus, respectively. The differences between two datasets after registration were less than 20 mm regardless of ROI. Differences in coronal and apical direction are indicated in red and blue, respectively. Fig. 4 shows the results of registration using the scan datasets of the first and the second models. The differences between the two datasets after registration were less than 40 mm regardless of ROI. As a result of the verification test,
Assessment of the occlusal surface change
Table 1 shows the characteristics of all participants (gender, age, and condylar path angles) and characteristics of sleep bruxism (total sleep time, maximum muscle activity during sleep, events (over 30% maximum voluntary contraction), and total clenching time). Table 2 shows the maximum differences on the occlusal surface of the splint and sleep bruxism types. The differences in the apical direction, which indicate wear depth, were correlated with the maximum muscle activity during sleep (Spearman’s test; r= 0.512, p=0.036). On the other hand, the differences in the coronal direction, which indicated deformation of the splint, were not correlated with any EMG parameters.
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
5
journal of prosthodontic research xxx (2017) xxx –xxx
Fig. 4 – Results of registration using the datasets of the first and the second models. Region of interest (blue); upper: palate, lower: occlusal surface of splint.
Table 1 – Characteristic of subjects and sleep bruxism. Case
Gender
Age (year-old)
M: male F: female 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
F F M M F F M F M F F F M F M F F
35 49 51 77 33 60 28 35 28 45 63 39 46 30 57 60 53
Condylar angle (degrees) Right, left 29, 12, 30, 17, 12, 10, 30, 30, 28, 25, 25, 20, 35, 27, 16, 23, 35,
Total sleep time (h:min:s)
Maximum muscle activity during sleep (%MVC)
Events
Total clenching time (s)
6:26:48 7:54:50 4:05:05 9:24:48 5:51:51 8:59:16 6:10:33 4:10:46 6:05:50 6:09:21 4:46:41 6:48:46 4:31:04 4:45:45 6:45:56 5:51:41 4:03:03
88 95 254 155 186 82 81 103 161 160 121 135 108 106 115 102 112
40 2 97 238 10 31 3 57 25 204 50 28 80 15 74 19 27
84 6 265 450 29 70 7 171 73 800 124 113 205 52 246 32 63
31 29 39 11 14 11 36 29 32 25 31 33 35 53 25 10 38
The variables %MVC, number of events, and total clenching time explains 84.0% of the variance in the wearing depth (p<0.001) (Table 3). Sleep bruxism types were classified into following four types; bilateral grinding, unilateral grinding, protrusive grinding, and clenching type, based on features of occlusal surface change using occlusal surface region as ROI. As a result of registration, we found that the wear facets in two subjects were created by bilateral mandibular excursions (bilateral grinding type), and in seven subjects by unilateral excursions (unilateral grinding type), and in two subjects by protrusive movements (protrusive grinding type). In the remaining six subjects, the facets were created by isometric clenching with very small lateral movements (clenching type). Five representative cases are shown in the following.
3.2.1.
Case 1 (35-year female)
For approximately six and half hours sleep, the strong muscle activities were observed 40 times. Fig. 5 shows the color mapping for indication of differences between two models in Case 1 (before and after applying the splint). When a palate was used as ROI for registration, the red areas indicate the over 200 mm differences (deformed upward regions after applying splint) in both molar regions. It is considered that the splint was not put back to the original position on the cast because of the deformation of splint. In addition, when occlusal surface was used as region of interest (ROI) for registration, maximum differences in the coronal and apical direction were 298 and 198 mm, respectively, and the blue areas indicate reduced regions after applying the splint on the inner slope correspond to the
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
6
journal of prosthodontic research xxx (2017) xxx –xxx
Table 2 – Maximum differences on the occlusal surface of splint and sleep bruxism type. Maximum differences on the occlusal surface of splint Coronal direction (mm) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Sleep bruxism type
Apical direction (mm)
298 105 453 307 170 373 576 341 220 149 206 274 173 171 150 408 177
198 116 279 481 291 138 155 140 264 160 148 142 169 166 123 180 194
Unilateral grinding Clenching Unilateral grinding Clenching Unilateral grinding Clenching Protrusion Bilateral grinding Unilateral grinding Bilateral grinding Clenching Clenching Unilateral grinding Unilateral grinding Clenching Unilateral grinding Protrusion
Table 3 – Change in wearing depth per unit of %MVC, number of events, and total clenching time. Dependent variable
A:
B:
C:
Change per increase %MVC
Change per increase number of events (events)
Change per increase total clenching time (s)
Wearing depth (mm)
1 (0.002)
2 (<0.001)
balancing (left) facet of the functional cusps. From these findings, it is suggested that the strong EMG activities occur at the eccentric jaw position during right lateral excursion. Consequently, the sleep bruxism type was classified as the unilateral grinding type.
3.2.2.
Case 2 (49-year female)
For approximately eight hours sleep, the short muscle activities were observed two times. Regardless of the ROI, there were few differences in the color changes. The color changes in the model are less than those in Case 1 (Fig. 6). Therefore, it is considered that the deformation of splint was less. When occlusal surface was used as ROI for registration, maximum differences in the coronal and apical direction were 105 and 116 mm, respectively, and there were blue spots on the deepest region on the occlusal surface of splint. From this finding, it was considered that she had evidence of clenching near by the intercuspal position with weak muscle activities. Consequently, the sleep bruxism type was classified as the clenching type.
3.2.3.
Case 3 (51-year male)
For approximately four hours sleep, the strong muscle activities were observed 97 times. The maximum muscle activity was 254%MVC. When occlusal surface was used as ROI for registration, maximum differences in the coronal and apical direction were 453 and 279 mm, respectively, and in the right molar region, the red areas indicate over 200 mm differences (deformed
1 (<0.001)
R2
F-ANOVA test p-value
0.840
<0.001
upward regions after applying splint) (Fig. 7). The occlusal surface was remarkably worn in the right incisors, canine, premolars, and first molar region. Blue areas are seen on the protrusive occlusal facet. In addition, there are blue spots in the deepest region on the left side. From these results, it was considered that he had evidence of clenching near by the intercuspal position and grinding to right side. Consequently, the sleep bruxism type was classified as the unilateral grinding type. However, on the balancing facets in the left dentition, there were no remarkable findings of wear. The acute condylar path angle in the left side might contribute to this finding (condylar path angle, right: 30 , left: 39 ).
3.2.4.
Case 4 (77-year male)
For approximately nine and half hours sleep, the strong muscle activities were observed 238 times. The maximum muscle activity was 155%MVC. When occlusal surface was used as ROI for registration, maximum differences in the coronal and apical direction were 307 and 481 mm, respectively, and the red areas on the inner slope of buccal cusp regions were shown on both sides, and the blue spots on the palatal cusp regions (Fig. 8). From these findings, it is suggested that he had the strong clenching or the short range grinding near by the intercuspal position. Consequently, the sleep bruxism type was classified as the clenching type. In addition, due to these excessive loading, the splint is remarkably deformed. The outside border of occlusal surface is warped upward.
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
journal of prosthodontic research xxx (2017) xxx –xxx
7
Fig. 5 – Color mapping for indication of differences between two models in the Case 1. Blue: reduced regions after applying, red: extruded regions after applying (Upper left: registration using palate, upper right and lower: registration using occlusal surface).
Fig. 6 – Findings on the splint in the Case 2.
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
8
journal of prosthodontic research xxx (2017) xxx –xxx
Fig. 7 – Findings on the splint in the Case 3.
Fig. 8 – Findings on the splint in the Case 4.
3.2.5.
Case 5 (33-year female)
For approximately six hours sleep, the strong muscle activities were observed ten times. The maximum muscle activity was 186%MVC.
When occlusal surface was used as ROI for registration, maximum differences in the coronal and apical direction were 170 and 291 mm, respectively, and the wear facets were observed at the left marginal region of the occlusal splint
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
journal of prosthodontic research xxx (2017) xxx –xxx
9
Fig. 9 – Findings on the splint in the Case 5.
(Fig. 9). It was suggested that there were excessive lateral movements past the left canine edge-to-edge position with strong muscle activities. Consequently, the sleep bruxism type was classified as the unilateral type.
4.
Discussions
4.1.
Accuracy verification in our evaluation system
From our results, it was revealed that our system can detect over 40 mm differences. In this current study, the occlusal surface of the splint was composed of self-curing resin, which was compounded with an amino-acid powder for easy wear. Therefore, in all subjects, the wear facets could be detected on the occlusal surface of splint after only two weeks of use, due to high detection capability and the use of the soft resin.
4.2. Relation between wearing/deformed splint and EMG parameters Occlusal splints may reduce muscle activity associated with sleep bruxism. In this study, to avoid as much as possible both of the reduction of sleep bruxism activities and the risk, side effects, and complications from long-term occlusal splint use, the recording period was limited to 14 days. The wearing depth on the occlusal surface was correlated with the maximum muscle activity during sleep. In addition, it was suggested that the wearing depth was increased with the increase of %MVC, the number of events, and the decrease of total clenching time.
From this result, it was suggested that the more severe and more frequent events influences occlusal wear. However, in this current study, the portable EMG recorder, which could export only a few EMG parameters, was used. To truly verify the above phenomenon, it was necessary to analyze all recorded EMG data and to investigate the pattern of each EMG event. In future studies, this issue should be further investigated.
4.3. Differences from conventional methods and performance of our system In 1993, Holmgren et al. [7] observed the active shine facets on a splint with the naked eye. In our system, the facets were evaluated using a digital technique. Therefore, our system has the potential for quantitative evaluation of occlusal facets. However, our splint ended up being deformed, not only because of wear on the occlusal surface of the splint but also due to the excessive load during sleep. Therefore, attention needs to be paid in selecting the ROI for registration. There may be a possibility that the base splint is not thick enough to avoid a severe deformation of the splint. Our two-layered splint was fabricated with the base splint and soft resin, with approximately thickness of 2mm in the molar region. In order to ensure interocclusal thickness of more than 1mm for the soft resin, the base material with 0.75mm thickness was selected. However, it is suggested that our splint has a potential to detect degree of occlusal forces applied during sleep bruxism. In the previous study [4], to assess the occlusal wear on the splint, only the splint was scanned. On the other hand, in this
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
10
journal of prosthodontic research xxx (2017) xxx –xxx
current study we scanned the splint located on the cast. When the palate was used as ROI for registration, there were red areas which indicate over 200 mm differences in the coronal direction on the occlusal surfaces of the splint as could be seen in the Cases 1, 3, and 4. This phenomenon may provide a way to detect the deformation of splints due to the overload during sleep. In addition, the characteristics of splint deformation appeared to vary with bruxism types. In the previous studies, the deformation of splints was not considered. Because of this, our method has advantages over the previous studies. The Bruxcore Bruxism-Monitoring Device is an intra-oral appliance to measure sleep bruxism activity objectively [12]. The Bruxcore plate evaluates bruxism activity by counting the number of abraded microdots on the surface and by scoring the volumetric magnitude of abrasion. The number of missing microdots is counted to assess the abraded area. The number of layers uncovered represents the depth parameter. Pierce and Gale [13] did not find any significant correlation between the duration of bruxism analyzed with the EMG data and that with the bruxcore plate scores. On the other hand, the deformation of splint and the worn facets could be observed as could be seen in Cases 1, 3, and 4 which the strong EMG events were observed more frequently. However, the relationship between wear and muscle activity is still questionable [14]. Covering the occlusal surfaces of the teeth with an occlusal splint protects those teeth from the loading of sleep bruxism. The previous studies have shown that providing an occlusal splint therapy decreases the hyperactivity of masticatory muscles [15–17]. In addition, therapeutic occlusion of occlusal splint was defined as multiple, bilateral posterior teeth contact with the mandibular condyles physiologically seated and immediate separation of the posterior teeth by the anterior teeth in all excursive movements [18,19]. Anterior teeth contact with posterior teeth disclusion decreases elevator muscle activity, and prevents posterior teeth wear [20]. On the other hand, our splint has full-balanced occlusion to detect the wear facets due to parafunction. Conventional type splints have a flat occlusal surface. Their occlusal guidance was adjusted in the chair side. On the other hand, our splint was adjusted on the semi-adjustable articulator. The subject’s mandibular movement was reflected on the occlusal surface of our splint. In other words, the occlusal surface of our splint presents a functionally-generated pathway which was simulated on the articulator. Therefore, our splint, which was adjusted on the semi-adjustable articulator to remove the interference, may have the potential to detect specific facets due to parafunctions such as nocturnal bruxism. In our subjects, occlusal facets were observed on the splint after two weeks of use. From this result, it was suggested we are not able to remove influence of parafunction for the prosthesis only by using the semi-adjustable articulator. It was discovered that the range of mandibular movements with nocturnal bruxism extended than functional movements during daytime [7,21]. The cuspal interference, during parafunction, contributes to failed prosthodontic treatment. When the prostheses are fabricated, the clinician should consider the harmonization of the occlusal configuration and jaw
movement at nocturnal bruxism, not only for daytime function. Our method has a potential to solve this issue.
4.4.
Study limitation
The final goal of this study is to develop the clinical procedure using digital imaging techniques to accurately diagnose sleep bruxism and to objectively assess its severity. In this study, the occlusal splint before and after wearing were scanned using the dental 3D scanner, and the scanned datasets were objectively compared to analyze the location and direction of wear facets and the surface loss of the splint caused by sleep bruxism. Our system has the potential to objectively evaluate the distance, area, volume, inclination, and direction of the surface change of the splint. However, we could observe not only the surface loss but also the warp deformation of the splint, contrary to our expectation. Due to technical limitations, the maximum differences in the cranial-apical direction were only evaluated in this study. We are now considering the idea of investigating this point in a future study. In 2012, Kurt et al. [22] investigated the wear resistance of four different types of occlusal splint materials based on twobody wear simulations under wet and dry conditions. In this current study, we used an original compound resin which is easily worn in short-term use. However, the wear resistance was not investigated. A material science investigation for the resin may contribute to a more quantitative evaluation for sleep bruxism.
5.
Conclusion
In this current report, we propose an evaluation system for sleep bruxism with novel occlusal splint. From our results, it is suggested that we are not able to eliminate the influence of parafunction for the prosthesis only by designing the surface of occlusal splint using the semi-adjustable articulator. When the prostheses are fabricated, the clinician should consider the harmonization of the occlusal configuration and jaw movement at nocturnal bruxism, not only for daytime function. Our method has a potential to solve this issue.
Sources of funding None.
IRB approval The patients gave written consent to participate in this study. This study was approved by the Ethics Committee at Tsurumi university dental hospital. REFERENCES
[1] Johansson A, Omar R, Carlsson GE. Bruxism and prosthetic treatment: a critical review. J Prosthodont Res 2011;55:127–36.
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
journal of prosthodontic research xxx (2017) xxx –xxx
[2] Kato T, Yamaguchi T, Okura K, Abe S, Lavigne GJ. Sleep less and bite more: sleep disorders associated with occlusal loads during sleep. J Prosthodont Res 2013;57:69–81. [3] Onodera K, Kawagoe T, Sasaguri K, Protacio-Quismundo C, Sato S. The use of a BruxChecker in the evaluation of different grinding patterns during sleep bruxism. Cranio 2006;24:292–9. [4] Korioth TW, Bohlig KG, Anderson GC. Digital assessment of occlusal wear patterns on occlusal stabilization splints: a pilot study. J Prosthet Dent 1998;80:209–13. [5] Dylina TJ. A common-sense approach to splint therapy. J Prosthet Dent 2001;86:539–45. [6] Mcauliffe P, Kim JH, Diamond D, Lau KT, O’Connell BC. A sleep bruxism detection system based on sensors in a splint—pilot clinical data. J Oral Rehabil 2015;42:34–9. [7] Holmgren K, Sheikholeslam A, Riise C. Effect of a full-arch maxillary occlusal splint on parafunctional activity during sleep in patients with nocturnal bruxism and signs and symptoms of craniomandibular disorders. J Prosthet Dent 1993;69:293–7. [8] Widmalm SE. Use and abuse of bite splints. Compend Contin Educ Dent 1999;20:249–60. [9] Ohshima A. A fundamental study on retentive force of titanium cap clasp. Tsurumi Univ Dent J 2004;30:41–51. [10] Zhang X, Li Z, Lu P, Wang Y. Registration algorithms of dental cast based on 3D point-cloud. Info comput appl 2011; 244:233–40. [11] Matsumoto H, Tsukiyama Y, Kuwatsuru R, Koyano K. The effect of intermittent use of occlusal splint devices on sleep bruxism: a 4-week observation with a portable electromyographic recording device. J Oral Rehabil 2015;42:251–8.
11
[12] Forgione A. A simple but effective method of quantifying bruxing behavior. J Dent Res 1974;53:127. [13] Pierce CJ, Gale EN. Methodological considerations concerning the use of bruxcore plates to evaluate nocturnal bruxism. J Dent Res 1989;68:1110–4. [14] Lobbezoo F, Van Der Zaag J, Van Selms MKA, Hamburger HL, Naeije M. Principles for the management of bruxism. J Oral Rehabil 2008;35:509–23. [15] Barker DK. Occlusal interferences and temporomandibular dysfunction. Gen Dent 2004;52:56–61. [16] Roark AL, Glaros AG, O’Mahony AM. Effects of interocclusal appliances on EMG activity during parafunctional tooth contact. J Oral Rehabil 2003;30:573–7. [17] Kotani H, Abekura H, Hamada T. Objective evaluation for bite plate therapy in patients with myofascial pain dysfunction syndrome. J Oral Rehabil 1994;21:241–5. [18] Okeson JP. Management of temporomandibular disorders and occlusion. 4th ed. St Louis, MO: CV Mosby Co.; 1998. p. 124–5. [19] Dawson PE. Determining the determinants of occlusion. Int J Periodontics Restorative Dent 1983;3:8–21. [20] Becker I, Tarantola G, Zambrano J, Spitzer S, Oquendo D. Effect of a prefabricated anterior bite stop on electromyographic activity of masticatory muscles. J Prosthet Dent 1999; 82:22–6. [21] Okura K, Shigemoto S, Suzuki Y, Noguchi N, Omoto K, Abe S, et al. Mandibular movement during sleep bruxism associated with current tooth attrition. J Prosthodont Res 2016 (in press). [22] Kurt H, Erdelt KJ, Cilingir A, Mumcu E, Sülün T, Tuncer N, et al. Two-body wear of occlusal splint materials. J Oral Rehabil 2012;39:584–90.
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
journal of prosthodontic research xxx (2017) xxx –xxx
Available online at www.sciencedirect.com
Journal of Prosthodontic Research journal homepage: www.elsevier.com/locate/jpor
Original article
Evaluation of sleep bruxism with a novel designed occlusal splint Kentaro Hirai DDS, Tomoko Ikawa DDS, PhD, Yuko Shigeta DDS, PhD, Shuji Shigemoto DDS, PhD * , Takumi Ogawa DDS, PhD Department of Fixed Prosthodontics, School of Dental Medicine, Tsurumi University, Yokohama, Japan
article info
abstract
Article history:
Purpose: This report presents our evaluation system that assesses sleep bruxism. The
Received 28 October 2016
characteristics and fabrication process of our novel designed splint, and the analysis process
Received in revised form
of our system are presented.
5 December 2016
Methods: The subjects were 17 volunteers. The splint was fabricated with a self-curing resin
Accepted 19 December 2016
compounded with an amino-acid powder for easy wear on the semi-adjustable articulator,
Available online xxx
and adjusted for a full-balanced occlusion. An impression of the splint, located on the cast, was taken before and after it was worn. The analytical casts were made and scanned via a
Keywords: Sleep bruxism Occlusal splint Occlusal wear
dental 3D scanner. The datasets were superimposed using two kinds of regions of interest (palate and occlusal surface). The differences between the two datasets were quantitatively presented with pseudo-color mapping. The maximum differences in coronal and apical directions were calculated on the selected area in the occlusal surface when the occlusal surface was used as a region of interest for registration. The relationship between the EMG activities and the change of occlusal surface of the splint were investigated. Results: In all subjects, deformation and wear facets on the splint were observed. The differences in the apical direction, which indicate wear depth, were correlated with the maximum muscle activity during sleep (p=0.036). Conclusion: From our results, it is suggested that we are not able to eliminate the influence of parafunction for the prosthesis only by designing the surface of occlusal splint using the semi-adjustable articulator. Our splint may have the potential to detect specific facets due to parafunctions as nocturnal bruxism. © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.
1.
Introduction
Occlusal overload during sleep bruxism is a significant negative factor that affects prosthetic treatment plans,
maintenance of teeth, and the longevity of dental prostheses [1–3]. Clinically, the grinding contact of the upper and lower teeth in powerful bruxism is quite important because post occlusal reconstruction stability depends upon the effect of cranio-mandibular function, such as parafunctional activity.
* Corresponding author at: Department of Fixed Prosthodontics, School of Dental Medicine, Tsurumi University, 2-1-3 Tsurumi, Tsurumiku, Yokohama, Japan. Fax: +81 45 573 9599. E-mail address: [email protected] (S. Shigemoto). http://dx.doi.org/10.1016/j.jpor.2016.12.007 1883-1958/© 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
2
journal of prosthodontic research xxx (2017) xxx –xxx
Therefore, it is extremely important to reconstruct occlusion based on strong grinding movement [3]. Furthermore, after prosthodontic treatment, the occlusal splint should be applied to avoid overloading of the abutment teeth and the prosthesis. After wearing an occlusal splint, the bruxism pattern is reflected on the surface of the occlusal splint as wear facets. A splint can be an important diagnostic tool to determine wear patterns, bruxism severity, and temporomandibular disorder status. Examination of the grinding pattern during bruxism is necessary and should be incorporated in the diagnosis of occlusion in order to make a proper treatment plan for each patient [3]. Commonly, the grinding pattern is evaluated by observing wear facets on the occlusal splint [3,4]. Information gained from wear patterns on the splints helps determine occlusal configurations, material choice, cusp heights and shapes, guidance angulations, axial loads, and the envelope of function [5]. However, it is difficult in a dental setting to accurately diagnose sleep bruxism and to objectively assess the severity, frequency or natural history of this condition in an individual patient [6]. We proposed an evaluation system of wear facets on the surface of the occlusal splint. This system includes a novel designed occlusal splint that can show grinding patterns, and an analysis technique using a 3D scanner with dedicated software. The system can analyze the location and direction of wear facets and surface loss of an occlusal splint created by the grinding of the teeth during sleep. The pattern of wear facets depends on the adjusting method and the prearranged occlusal guidance of the splint. A previous study reported that the range of mandibular movements with nocturnal bruxism extended beyond functional movements during daytime [7]. In addition, complications from long-term use (more than four to six weeks) of splints can be severe and irreversible [8]. For this reason, the occlusal splint employed in our system is a full-coverage type with fullbalanced occlusion, and designed to be easily worn in shortterm use. In this report, we introduce our evaluation system that assesses sleep bruxism. The characteristics and fabrication process of our novel designed splint, and the analysis process of our system are also presented.
2.
Materials and methods
2.1.
Participants
In this current report, the subjects were 17 volunteers (male: 6, female: 11, 46.414.2 years). The dentulous adults, with all teeth existing except their second and third molars, were recruited. The experiment procedures were explained to all participants before obtaining consent. This research was approved by the Ethical Committee at Tsurumi University Dental Hospital (Approval No. 1416).
2.2.
Fabrication of the occlusal splint
The impressions of upper and lower dentitions were taken using ready-made trays and an alginate impression material.
The casts were made by a high strength dental stone (GC FUJIROCK, GC, Tokyo, Japan). These casts were mounted on a semi-adjustable articulator with a face-bow (ProArch III, Shofu Inc., Kyoto, Japan). In addition, the condylar path angles were adjusted with protrusion and lateral check-bites, and a custom-fabricated incisal table. After mounting, the interocclusal space was set approximately 2mm in the molar region for fabrication of the occlusal splint. To obtain an adequate retentive force, and avoid a severe deformation of the splint, a polyester sheet with a 0.75mm thickness (DURAN, Scheu Dental Technology, Iserlohn, Germany) was chosen as a base material (Hereinafter referred to as base splint). The design of the base splint followed that of the cap clasp [9], where the undercut at the buccal side was utilized. However, if there was no available undercut on the buccal side, the undercut at the palatal side was utilized. The undercut was set at 0.25 mm. The sheet was pressed to the upper cast via a pressure molding machine (Ministar S, Great Lakes Orthodontics, LTD, NY, USA), and trimmed along the design line mentioned above. This base splint was located on the mounted upper cast on the articulator. The incisal guide pin of the articulator was adjusted to secure a clearance of at least 1mm in the molar region for a self-curing resin (Facet resin, GC, Tokyo, Japan). The self-curing resin, which compounded with an aminoacid powder (airflow powder, Shofu Inc., Kyoto, Japan) for easy wearing, was built-up on the occlusal surface of the base splint (resin powder: amino-acid powder =1:1). The upper cast was moved through the right, left, and protrusive movement while the soft resin was setting. Finally, the occlusal guidance of the splint was adjusted for a fullbalanced occlusion. Therefore, the subject’s mandibular movement was impressed on the occlusal surface of our splint. Fig. 1 shows our adjusted splint. The occlusal surface was not as flat as the stabilization splint, and presents an individual subject’s functionally-generated pathway which was simulated on the articulator. Occlusal guidance of each subject resulted in different characteristics.
2.3.
System description
The splint, located on the cast, was taken an impression with a duplicating silicone (Duplicone, Shofu Inc., Kyoto, Japan) before and after it was worn by the participant. The analytical casts were made of a high strength dental stone (New FUJIROCK, GC, Tokyo, Japan) and were scanned via a dental 3D scanner (D900, 3Shape, Denmark). The scanned data was analyzed via 3D image analysis software (Rapidform 2006, INUS Technology, Korea). The location and direction of the wear facets, and the surface loss of the occlusal splint created by teeth grinding during sleep were investigated. Surface EMG of the masseter muscle was also recorded for 14 nights with a portable EMG recorder with a sampling rate of 10Hz and 10 bit resolution (Chewing recorder BR-1000, Nishizawa Electric Meters Manufacturing Co., Nagano, Japan). Disposable bipolar self-adhesive pre-gelled surface Ag/AgCl electrodes (RectLoad, Nishizawa Electric Meters Manufacturing Co., Nagano, Japan) were applied over the thickest portion of the right masseter muscle belly. A reference electrode was placed on the center of the forehead. Recorded EMG signals
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
journal of prosthodontic research xxx (2017) xxx –xxx
3
Fig. 1 – Occlusal splint after adjusting the occlusal guidance.
were amplified, and band-pass filtered (100–1000Hz) and stored within an internal memory. The signals were then analyzed using dedicated software that calculated the total sleep time (h:min:s), maximum muscle activity during sleep (% MVC), number of bruxism events (times), and total duration of bruxism events (s). The total sleep time was almost equal to the total splint wearing time.
2.4. Accuracy verification in our evaluation system for occlusal facet First, our evaluation system for the occlusal facet was verified. Two analytical casts were made. For the first analytical cast, an impression of the splint, located on the upper dentition model, was taken with a duplicating silicone. Then, the splint was removed from the dentition model and put back in its original position on the model. An impression once again was taken for the second analytical cast. The analytical casts were made of a high strength dental stone. These casts were scanned via a dental 3D scanner. The first cast was scanned two times for verifying the registration accuracy. The data was analyzed via 3D image analysis software. Two scan datasets of the first cast were imported into the software. Then the datasets were superimposed to verify the registration error with Iterative Closest Point algorithm [10] and two kinds of regions of interest for image registration were the palate and the occlusal surface of splint (Fig. 2). The scan datasets of the first and the second models were analyzed to verify the registration repeatability of our evaluation system with same method. The differences between the two datasets were quantitatively presented with pseudo-color mapping. In addition, the maximum differences in coronal and apical directions were calculated on the selected area of the occlusal surface when the occlusal surface was used as a region of interest (ROI) for registration. Coronal and apical directions indicated that the original surface of the occlusal splint was warped
upward and had wear facets created by sleep bruxism respectively.
2.5.
Assessment of the occlusal surface change
On the first visit to our clinic, the impressions of the subject’s upper and lower dentitions were taken for fabrication of an occlusal splint. On the second visit, this splint was applied to the subject after a slight intraoral adjustment. The splint located on the cast was taken an impression for the first analysis model (Model1). Participants were carefully instructed on how to use the EMG recorder and told to wear the occlusal splint while sleeping for 14 nights. After a 14-day recording, the participant came to the clinic where the recorded EMG data and the occlusal splint were collected. The EMG data was transferred to a personal computer and analyzed by dedicated software. Nocturnal masseter EMG events decreased significantly only one week after the insertion of the stabilization splint [11]. Therefore, in this study, analytical EMG data was selected from the one recording day when strong masseter muscle activities occurred most frequently in the second week. The EMG parameters were calculated. The splint used for 14 days was located on the cast and then an impression was taken for the second analysis model (Model2). The maximum differences in coronal and apical direction on the surface of the occlusal splint were calculated. We investigated the relationship between the EMG activities during sleep and the change of occlusal surface of the splint after 14 days of wear.
2.6.
Statistical analysis
Statistical analysis was carried out through the SPSS 22.0 (SPSS Inc., Chicago, USA). We investigated the linear relationships between variables with the Spearman’s test and linear regression. The linear
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
4
journal of prosthodontic research xxx (2017) xxx –xxx
Fig. 2 – Region of interest (blue). Left: palate, right: occlusal surface of splint.
Fig. 3 – Results of registration on two datasets of the scanned first model. Region of interest (blue); left: palate, right: occlusal surface of splint.
regression assumptions of linearity, homoscedasticity, and normality of the residuals were successfully evaluated.
differences within 40 mm were defined as “No difference” in using our evaluation system.
3.2.
3.
Results
3.1.
Accuracy verification in our evaluation system
Fig. 3 shows the results of registration using two scan datasets of the first model. The coronal and apical direction values represent plus and minus, respectively. The differences between two datasets after registration were less than 20 mm regardless of ROI. Differences in coronal and apical direction are indicated in red and blue, respectively. Fig. 4 shows the results of registration using the scan datasets of the first and the second models. The differences between the two datasets after registration were less than 40 mm regardless of ROI. As a result of the verification test,
Assessment of the occlusal surface change
Table 1 shows the characteristics of all participants (gender, age, and condylar path angles) and characteristics of sleep bruxism (total sleep time, maximum muscle activity during sleep, events (over 30% maximum voluntary contraction), and total clenching time). Table 2 shows the maximum differences on the occlusal surface of the splint and sleep bruxism types. The differences in the apical direction, which indicate wear depth, were correlated with the maximum muscle activity during sleep (Spearman’s test; r= 0.512, p=0.036). On the other hand, the differences in the coronal direction, which indicated deformation of the splint, were not correlated with any EMG parameters.
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
5
journal of prosthodontic research xxx (2017) xxx –xxx
Fig. 4 – Results of registration using the datasets of the first and the second models. Region of interest (blue); upper: palate, lower: occlusal surface of splint.
Table 1 – Characteristic of subjects and sleep bruxism. Case
Gender
Age (year-old)
M: male F: female 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
F F M M F F M F M F F F M F M F F
35 49 51 77 33 60 28 35 28 45 63 39 46 30 57 60 53
Condylar angle (degrees) Right, left 29, 12, 30, 17, 12, 10, 30, 30, 28, 25, 25, 20, 35, 27, 16, 23, 35,
Total sleep time (h:min:s)
Maximum muscle activity during sleep (%MVC)
Events
Total clenching time (s)
6:26:48 7:54:50 4:05:05 9:24:48 5:51:51 8:59:16 6:10:33 4:10:46 6:05:50 6:09:21 4:46:41 6:48:46 4:31:04 4:45:45 6:45:56 5:51:41 4:03:03
88 95 254 155 186 82 81 103 161 160 121 135 108 106 115 102 112
40 2 97 238 10 31 3 57 25 204 50 28 80 15 74 19 27
84 6 265 450 29 70 7 171 73 800 124 113 205 52 246 32 63
31 29 39 11 14 11 36 29 32 25 31 33 35 53 25 10 38
The variables %MVC, number of events, and total clenching time explains 84.0% of the variance in the wearing depth (p<0.001) (Table 3). Sleep bruxism types were classified into following four types; bilateral grinding, unilateral grinding, protrusive grinding, and clenching type, based on features of occlusal surface change using occlusal surface region as ROI. As a result of registration, we found that the wear facets in two subjects were created by bilateral mandibular excursions (bilateral grinding type), and in seven subjects by unilateral excursions (unilateral grinding type), and in two subjects by protrusive movements (protrusive grinding type). In the remaining six subjects, the facets were created by isometric clenching with very small lateral movements (clenching type). Five representative cases are shown in the following.
3.2.1.
Case 1 (35-year female)
For approximately six and half hours sleep, the strong muscle activities were observed 40 times. Fig. 5 shows the color mapping for indication of differences between two models in Case 1 (before and after applying the splint). When a palate was used as ROI for registration, the red areas indicate the over 200 mm differences (deformed upward regions after applying splint) in both molar regions. It is considered that the splint was not put back to the original position on the cast because of the deformation of splint. In addition, when occlusal surface was used as region of interest (ROI) for registration, maximum differences in the coronal and apical direction were 298 and 198 mm, respectively, and the blue areas indicate reduced regions after applying the splint on the inner slope correspond to the
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
6
journal of prosthodontic research xxx (2017) xxx –xxx
Table 2 – Maximum differences on the occlusal surface of splint and sleep bruxism type. Maximum differences on the occlusal surface of splint Coronal direction (mm) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Sleep bruxism type
Apical direction (mm)
298 105 453 307 170 373 576 341 220 149 206 274 173 171 150 408 177
198 116 279 481 291 138 155 140 264 160 148 142 169 166 123 180 194
Unilateral grinding Clenching Unilateral grinding Clenching Unilateral grinding Clenching Protrusion Bilateral grinding Unilateral grinding Bilateral grinding Clenching Clenching Unilateral grinding Unilateral grinding Clenching Unilateral grinding Protrusion
Table 3 – Change in wearing depth per unit of %MVC, number of events, and total clenching time. Dependent variable
A:
B:
C:
Change per increase %MVC
Change per increase number of events (events)
Change per increase total clenching time (s)
Wearing depth (mm)
1 (0.002)
2 (<0.001)
balancing (left) facet of the functional cusps. From these findings, it is suggested that the strong EMG activities occur at the eccentric jaw position during right lateral excursion. Consequently, the sleep bruxism type was classified as the unilateral grinding type.
3.2.2.
Case 2 (49-year female)
For approximately eight hours sleep, the short muscle activities were observed two times. Regardless of the ROI, there were few differences in the color changes. The color changes in the model are less than those in Case 1 (Fig. 6). Therefore, it is considered that the deformation of splint was less. When occlusal surface was used as ROI for registration, maximum differences in the coronal and apical direction were 105 and 116 mm, respectively, and there were blue spots on the deepest region on the occlusal surface of splint. From this finding, it was considered that she had evidence of clenching near by the intercuspal position with weak muscle activities. Consequently, the sleep bruxism type was classified as the clenching type.
3.2.3.
Case 3 (51-year male)
For approximately four hours sleep, the strong muscle activities were observed 97 times. The maximum muscle activity was 254%MVC. When occlusal surface was used as ROI for registration, maximum differences in the coronal and apical direction were 453 and 279 mm, respectively, and in the right molar region, the red areas indicate over 200 mm differences (deformed
1 (<0.001)
R2
F-ANOVA test p-value
0.840
<0.001
upward regions after applying splint) (Fig. 7). The occlusal surface was remarkably worn in the right incisors, canine, premolars, and first molar region. Blue areas are seen on the protrusive occlusal facet. In addition, there are blue spots in the deepest region on the left side. From these results, it was considered that he had evidence of clenching near by the intercuspal position and grinding to right side. Consequently, the sleep bruxism type was classified as the unilateral grinding type. However, on the balancing facets in the left dentition, there were no remarkable findings of wear. The acute condylar path angle in the left side might contribute to this finding (condylar path angle, right: 30 , left: 39 ).
3.2.4.
Case 4 (77-year male)
For approximately nine and half hours sleep, the strong muscle activities were observed 238 times. The maximum muscle activity was 155%MVC. When occlusal surface was used as ROI for registration, maximum differences in the coronal and apical direction were 307 and 481 mm, respectively, and the red areas on the inner slope of buccal cusp regions were shown on both sides, and the blue spots on the palatal cusp regions (Fig. 8). From these findings, it is suggested that he had the strong clenching or the short range grinding near by the intercuspal position. Consequently, the sleep bruxism type was classified as the clenching type. In addition, due to these excessive loading, the splint is remarkably deformed. The outside border of occlusal surface is warped upward.
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
journal of prosthodontic research xxx (2017) xxx –xxx
7
Fig. 5 – Color mapping for indication of differences between two models in the Case 1. Blue: reduced regions after applying, red: extruded regions after applying (Upper left: registration using palate, upper right and lower: registration using occlusal surface).
Fig. 6 – Findings on the splint in the Case 2.
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
8
journal of prosthodontic research xxx (2017) xxx –xxx
Fig. 7 – Findings on the splint in the Case 3.
Fig. 8 – Findings on the splint in the Case 4.
3.2.5.
Case 5 (33-year female)
For approximately six hours sleep, the strong muscle activities were observed ten times. The maximum muscle activity was 186%MVC.
When occlusal surface was used as ROI for registration, maximum differences in the coronal and apical direction were 170 and 291 mm, respectively, and the wear facets were observed at the left marginal region of the occlusal splint
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
journal of prosthodontic research xxx (2017) xxx –xxx
9
Fig. 9 – Findings on the splint in the Case 5.
(Fig. 9). It was suggested that there were excessive lateral movements past the left canine edge-to-edge position with strong muscle activities. Consequently, the sleep bruxism type was classified as the unilateral type.
4.
Discussions
4.1.
Accuracy verification in our evaluation system
From our results, it was revealed that our system can detect over 40 mm differences. In this current study, the occlusal surface of the splint was composed of self-curing resin, which was compounded with an amino-acid powder for easy wear. Therefore, in all subjects, the wear facets could be detected on the occlusal surface of splint after only two weeks of use, due to high detection capability and the use of the soft resin.
4.2. Relation between wearing/deformed splint and EMG parameters Occlusal splints may reduce muscle activity associated with sleep bruxism. In this study, to avoid as much as possible both of the reduction of sleep bruxism activities and the risk, side effects, and complications from long-term occlusal splint use, the recording period was limited to 14 days. The wearing depth on the occlusal surface was correlated with the maximum muscle activity during sleep. In addition, it was suggested that the wearing depth was increased with the increase of %MVC, the number of events, and the decrease of total clenching time.
From this result, it was suggested that the more severe and more frequent events influences occlusal wear. However, in this current study, the portable EMG recorder, which could export only a few EMG parameters, was used. To truly verify the above phenomenon, it was necessary to analyze all recorded EMG data and to investigate the pattern of each EMG event. In future studies, this issue should be further investigated.
4.3. Differences from conventional methods and performance of our system In 1993, Holmgren et al. [7] observed the active shine facets on a splint with the naked eye. In our system, the facets were evaluated using a digital technique. Therefore, our system has the potential for quantitative evaluation of occlusal facets. However, our splint ended up being deformed, not only because of wear on the occlusal surface of the splint but also due to the excessive load during sleep. Therefore, attention needs to be paid in selecting the ROI for registration. There may be a possibility that the base splint is not thick enough to avoid a severe deformation of the splint. Our two-layered splint was fabricated with the base splint and soft resin, with approximately thickness of 2mm in the molar region. In order to ensure interocclusal thickness of more than 1mm for the soft resin, the base material with 0.75mm thickness was selected. However, it is suggested that our splint has a potential to detect degree of occlusal forces applied during sleep bruxism. In the previous study [4], to assess the occlusal wear on the splint, only the splint was scanned. On the other hand, in this
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
10
journal of prosthodontic research xxx (2017) xxx –xxx
current study we scanned the splint located on the cast. When the palate was used as ROI for registration, there were red areas which indicate over 200 mm differences in the coronal direction on the occlusal surfaces of the splint as could be seen in the Cases 1, 3, and 4. This phenomenon may provide a way to detect the deformation of splints due to the overload during sleep. In addition, the characteristics of splint deformation appeared to vary with bruxism types. In the previous studies, the deformation of splints was not considered. Because of this, our method has advantages over the previous studies. The Bruxcore Bruxism-Monitoring Device is an intra-oral appliance to measure sleep bruxism activity objectively [12]. The Bruxcore plate evaluates bruxism activity by counting the number of abraded microdots on the surface and by scoring the volumetric magnitude of abrasion. The number of missing microdots is counted to assess the abraded area. The number of layers uncovered represents the depth parameter. Pierce and Gale [13] did not find any significant correlation between the duration of bruxism analyzed with the EMG data and that with the bruxcore plate scores. On the other hand, the deformation of splint and the worn facets could be observed as could be seen in Cases 1, 3, and 4 which the strong EMG events were observed more frequently. However, the relationship between wear and muscle activity is still questionable [14]. Covering the occlusal surfaces of the teeth with an occlusal splint protects those teeth from the loading of sleep bruxism. The previous studies have shown that providing an occlusal splint therapy decreases the hyperactivity of masticatory muscles [15–17]. In addition, therapeutic occlusion of occlusal splint was defined as multiple, bilateral posterior teeth contact with the mandibular condyles physiologically seated and immediate separation of the posterior teeth by the anterior teeth in all excursive movements [18,19]. Anterior teeth contact with posterior teeth disclusion decreases elevator muscle activity, and prevents posterior teeth wear [20]. On the other hand, our splint has full-balanced occlusion to detect the wear facets due to parafunction. Conventional type splints have a flat occlusal surface. Their occlusal guidance was adjusted in the chair side. On the other hand, our splint was adjusted on the semi-adjustable articulator. The subject’s mandibular movement was reflected on the occlusal surface of our splint. In other words, the occlusal surface of our splint presents a functionally-generated pathway which was simulated on the articulator. Therefore, our splint, which was adjusted on the semi-adjustable articulator to remove the interference, may have the potential to detect specific facets due to parafunctions such as nocturnal bruxism. In our subjects, occlusal facets were observed on the splint after two weeks of use. From this result, it was suggested we are not able to remove influence of parafunction for the prosthesis only by using the semi-adjustable articulator. It was discovered that the range of mandibular movements with nocturnal bruxism extended than functional movements during daytime [7,21]. The cuspal interference, during parafunction, contributes to failed prosthodontic treatment. When the prostheses are fabricated, the clinician should consider the harmonization of the occlusal configuration and jaw
movement at nocturnal bruxism, not only for daytime function. Our method has a potential to solve this issue.
4.4.
Study limitation
The final goal of this study is to develop the clinical procedure using digital imaging techniques to accurately diagnose sleep bruxism and to objectively assess its severity. In this study, the occlusal splint before and after wearing were scanned using the dental 3D scanner, and the scanned datasets were objectively compared to analyze the location and direction of wear facets and the surface loss of the splint caused by sleep bruxism. Our system has the potential to objectively evaluate the distance, area, volume, inclination, and direction of the surface change of the splint. However, we could observe not only the surface loss but also the warp deformation of the splint, contrary to our expectation. Due to technical limitations, the maximum differences in the cranial-apical direction were only evaluated in this study. We are now considering the idea of investigating this point in a future study. In 2012, Kurt et al. [22] investigated the wear resistance of four different types of occlusal splint materials based on twobody wear simulations under wet and dry conditions. In this current study, we used an original compound resin which is easily worn in short-term use. However, the wear resistance was not investigated. A material science investigation for the resin may contribute to a more quantitative evaluation for sleep bruxism.
5.
Conclusion
In this current report, we propose an evaluation system for sleep bruxism with novel occlusal splint. From our results, it is suggested that we are not able to eliminate the influence of parafunction for the prosthesis only by designing the surface of occlusal splint using the semi-adjustable articulator. When the prostheses are fabricated, the clinician should consider the harmonization of the occlusal configuration and jaw movement at nocturnal bruxism, not only for daytime function. Our method has a potential to solve this issue.
Sources of funding None.
IRB approval The patients gave written consent to participate in this study. This study was approved by the Ethics Committee at Tsurumi university dental hospital. REFERENCES
[1] Johansson A, Omar R, Carlsson GE. Bruxism and prosthetic treatment: a critical review. J Prosthodont Res 2011;55:127–36.
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007
JPOR 382 No. of Pages 11
journal of prosthodontic research xxx (2017) xxx –xxx
[2] Kato T, Yamaguchi T, Okura K, Abe S, Lavigne GJ. Sleep less and bite more: sleep disorders associated with occlusal loads during sleep. J Prosthodont Res 2013;57:69–81. [3] Onodera K, Kawagoe T, Sasaguri K, Protacio-Quismundo C, Sato S. The use of a BruxChecker in the evaluation of different grinding patterns during sleep bruxism. Cranio 2006;24:292–9. [4] Korioth TW, Bohlig KG, Anderson GC. Digital assessment of occlusal wear patterns on occlusal stabilization splints: a pilot study. J Prosthet Dent 1998;80:209–13. [5] Dylina TJ. A common-sense approach to splint therapy. J Prosthet Dent 2001;86:539–45. [6] Mcauliffe P, Kim JH, Diamond D, Lau KT, O’Connell BC. A sleep bruxism detection system based on sensors in a splint—pilot clinical data. J Oral Rehabil 2015;42:34–9. [7] Holmgren K, Sheikholeslam A, Riise C. Effect of a full-arch maxillary occlusal splint on parafunctional activity during sleep in patients with nocturnal bruxism and signs and symptoms of craniomandibular disorders. J Prosthet Dent 1993;69:293–7. [8] Widmalm SE. Use and abuse of bite splints. Compend Contin Educ Dent 1999;20:249–60. [9] Ohshima A. A fundamental study on retentive force of titanium cap clasp. Tsurumi Univ Dent J 2004;30:41–51. [10] Zhang X, Li Z, Lu P, Wang Y. Registration algorithms of dental cast based on 3D point-cloud. Info comput appl 2011; 244:233–40. [11] Matsumoto H, Tsukiyama Y, Kuwatsuru R, Koyano K. The effect of intermittent use of occlusal splint devices on sleep bruxism: a 4-week observation with a portable electromyographic recording device. J Oral Rehabil 2015;42:251–8.
11
[12] Forgione A. A simple but effective method of quantifying bruxing behavior. J Dent Res 1974;53:127. [13] Pierce CJ, Gale EN. Methodological considerations concerning the use of bruxcore plates to evaluate nocturnal bruxism. J Dent Res 1989;68:1110–4. [14] Lobbezoo F, Van Der Zaag J, Van Selms MKA, Hamburger HL, Naeije M. Principles for the management of bruxism. J Oral Rehabil 2008;35:509–23. [15] Barker DK. Occlusal interferences and temporomandibular dysfunction. Gen Dent 2004;52:56–61. [16] Roark AL, Glaros AG, O’Mahony AM. Effects of interocclusal appliances on EMG activity during parafunctional tooth contact. J Oral Rehabil 2003;30:573–7. [17] Kotani H, Abekura H, Hamada T. Objective evaluation for bite plate therapy in patients with myofascial pain dysfunction syndrome. J Oral Rehabil 1994;21:241–5. [18] Okeson JP. Management of temporomandibular disorders and occlusion. 4th ed. St Louis, MO: CV Mosby Co.; 1998. p. 124–5. [19] Dawson PE. Determining the determinants of occlusion. Int J Periodontics Restorative Dent 1983;3:8–21. [20] Becker I, Tarantola G, Zambrano J, Spitzer S, Oquendo D. Effect of a prefabricated anterior bite stop on electromyographic activity of masticatory muscles. J Prosthet Dent 1999; 82:22–6. [21] Okura K, Shigemoto S, Suzuki Y, Noguchi N, Omoto K, Abe S, et al. Mandibular movement during sleep bruxism associated with current tooth attrition. J Prosthodont Res 2016 (in press). [22] Kurt H, Erdelt KJ, Cilingir A, Mumcu E, Sülün T, Tuncer N, et al. Two-body wear of occlusal splint materials. J Oral Rehabil 2012;39:584–90.
Please cite this article in press as: K. Hirai, et al., Evaluation of sleep bruxism with a novel designed occlusal splint, J Prosthodont Res (2016), http://dx.doi.org/10.1016/j.jpor.2016.12.007