Bruksizam je ponavljajuća ritmička aktivnost žvačnih mišića karakterizirana stiskanjem ili škripanjem zubi i/ili potiskivanjem donje čeljusti. Može biti dnevni ili noćni ovisno o periodu pojavljivanja. Prevalencija noćnog bruksizma je između 8,6% i 13,7% kod odraslih, dok se kod djece povećava između 20% i 49%. Terapija bruksizma je kompleksna zbog nejasne i multifaktorske etiologije te se sastoji od intraoralnih naprava, farmakoterapije, bihevioralne terapije i fizikalne terapije. Cilj istraživanja bio je utvrditi utjecaj nošenja relaksacijske udlage izrađene standardiziranim postupkom na granične kretnje donje čeljusti i kretnje
kondila kod ispitanika s bruksizmom te ispitati položaj kondila kod ispitanika s bruksizmom i usporediti ga s položajem kondila kontrolne, asimptomatske skupine. U istraživanje je bilo uključeno 40 ispitanika s dijagnosticiranim bruksizmom koji su svrstani u ispitnu skupinu i 40 asimptomatskih ispitanika koji su svrstani u kontrolnu skupinu. Za sve ispitanike ispitne i kontrolne skupine izrađena je relaksacijska okluzijska udlaga standardiziranim postupkom koju su nosili 12 tjedana. Za to su vrijeme izvršena, uz inicijalno, još četiri mjerenja (nakon 2, 4, 8 i 12 tjedana) koristeći Arcus Digma II (Kavo) ultrazvučni uređaj za snimanje kretnji
donje čeljusti. Vrijednosti za incizalno otvaranje (IO), položaj lijevog kondila kod otvaranja (OLK), položaj desnog kondila kod otvaranja (ODK), položaj kondila pri lijevoj laterotruziji (LLI) i položaj kondila pri desnoj laterotruziji (LDI) povećane su nakon 12-tjednog nošenja udlage te je najveće povećanje od 14,6% zabilježeno kod OLK-a, dok je statistički značajna razlika između inicijalnog i završnog mjerenja (p<0,05) potvrđena kod LLI-ja te kod LDI-ja. Pomak kondila pri protruziji bio je veći u odnosu na pomak kondila pri laterotruzijama, a najmanji je bio kod CR-a. Promjena položaja kondila u sve tri ravnine bila je veća kod
ispitanika s bruksizmom u odnosu na kontrolnu skupinu, no bez statistički značajne razlike.
|Abstract (english)|| |
Definitions and classifications of bruxism have varied and changed throughout history until 2013, as an international consensus was reached and bruxism was defined as repetitive rhythmic masticatory muscle activity characterized by tooth clenching or grinding and/or pushing of the lower jaw. It can be diurnal or nocturnal, depending on the time of its
occurrence. The new definition aims to emphasize that bruxism is not a disorder but a behavior, which can be a risk factor if associated with one or more negative health conditions. It can also be a protective factor if associated with one or more positive health conditions, as well as a sign of other disorders. It is difficult to assess the prevalence of bruxism due to subjective characteristics, limitations of diagnostic techniques and variations over time. Most epidemiological studies report a prevalence of nocturnal bruxism between 8.6% and 13.7% in adults, while it is higher in children and amounts between 20% and 49%. The etiology of bruxism is complex and multifactorial, and it is continuously a subject of research in various fields, from dental medicine and neurology to sleep disorders. The presence of bruxism can be determined both by non-instrumental and instrumental methods. Specific questionnaires and clinical examinations are non-instrumental methods that can diagnose nocturnal and diurnal bruxism, while instrumental diagnostics of nocturnal and diurnal bruxism includes electromyography (EMG) and polysomnomyography (PSG). In the review of the present literature, for clinical and scientific purposes bruxism can be confirmed in one of the following ways: (i) by a validated questionnaire, (ii) by clinical analysis i.e.
presence of clinical signs, (iii) by intraoral devices, (iiii) by positive PSG or EMG. The therapy of bruxism is complex due to its unclear and multifactorial etiology, and it includes intraoral devices, pharmacotherapy, behavioral therapy and physical therapy. All the methods of treating bruxism focus on reducing symptoms and preventing further complications, since
no method has shown the ability to cure bruxism completely by now. The use of intraoral devices, i.e. occlusal splints, is the most common therapeutic method in bruxism, although the mechanisms of their action are not fully defined. It remains a topic of discussion among researchers. Advanced technology and modern devices are used in research of masticatory system functions. One of the devices with confirmed scientific and practical value and repeatability of measurement is Arcus Digma II (ADII). ADII is an ultrasonic electronic device, a kinematic face bow with six degrees of freedom, which registers movement and position of the condyle and lower jaw in real time. In the review of the literature on instrumental analysis
of the influence of occlusal splints on bruxism no research related to changes in mandibular movements in subjects with bruxism during and after splint therapy was found. While studies on the impact of occlusal splint therapy on the condylar position show increased vertical condylar displacement, the amounts of horizontal and transversal condylar displacement
show a large dispersion of the results. The aim of this study was to determine the effect of wearing relaxation occlusal splints fabricated according to a standardized procedure on mandibular border movements and condylar movements in subjects with bruxism, as well as to examine the condylar position in subjects with bruxism and to compare it with the condylar positions of the control asymptomatic group, by performing measurements without wearing the splint in the mouth.
Subjects and methods:
The study included 40 subjects with diagnosed bruxism classified in the experimental group and 40 asymptomatic subjects classified in the control group. The criteria for the subjects to be included in the study were adult, eugnathic subjects with dentoalveolar Angle class I. Subjects with prosthetic restorations, with previous or current orthodontic therapy, with
previous surgical procedures in the area of the temporomandibular joint and subjects suffering from a systemic disease were excluded from the study. After clinical examination, the subjects with symptoms and signs of bruxism completed the "Questionnaire for diagnosis of bruxism" and "Diagnostic criteria for examination of temporomandibular disorders" (DKI /
TMD) - Axis I. The subjects that were diagnosed with bruxism based on their medical history, clinical functional examination and the questionnaire results, were classified in the experimental group, while subjects diagnosed with TMD were excluded from the study. Subjects without symptoms and signs of bruxism and TMD were classified in the control group. Each subject signed an informed consent form approved by the Ethics Committee of the Faculty of Dentistry, University of Zagreb. The study was conducted in the way that occlusal splints were fabricated according to a standardized procedure for all the subjects of the experimental and control group, based on the values obtained with a three-dimensional kinematic face bow (ADII). After splint delivery, the subjects were instructed to wear them every day for at least 10 hours during 12
weeks. Measurements were performed at the very beginning of the splint delivery (0 weeks) and after 2, 4, 8 and 12 weeks of wearing the splints (check-up 1, 2, 3 and 4). Mandibular border movements were measured in the Motion Analysis (MA) module of the ADII device. After detailed explanation and practice, the subjects performed maximum mouth opening and closing, maximum left and right laterotrusion (occlusion guided movements), and Posselt's border movements in the frontal and sagittal plane. After the movements were performed, the software calculated the values (in millimeters) for the
movements of the sagittal incisal point during mouth opening/closing (OI) and laterotrusion movements (LLI, LDI) and the values of condylar movements during mouth opening/closing (OLK, ODK). The condylar position was measured in the "EPA-Electronic Position Analysis of the Mandibular Position" (EPA) module of the ADII device. Each subject's bite in maximum intercuspation (MIP) was registered on the device as the reference point. After that, the subjects performed maximum protrusion and both laterotrusions. After having performed all the movements, the subjects placed the splint in the mouth and bit into it as the centric relation position (CR) was registered. The software calculated the condylar position in
relation to the reference position (in millimeters) in the three spatial axes: x axis - anteroposterior, y axis - superoinferior, and z axis - mediolateral. For statistical analysis, STATISTICA 12.0 software package was used. The frequencies and percentages were calculated for each categorical variable. Continuous variables were described using basic statistical parameters (mean value, standard deviation, coefficient of variation, and standard error of mean, median, minimum and maximum value). Normality of the data was checked by the Shapiro-Wilks W test and Homogeneity of variance by the Levene test. In case of deviation from normality, the results were mathematically normalized. The difference between two groups of continuous, normally distributed variables was checked by the t-test and for more than two groups by the one way analysis of variance, followed by the Newman- Keuls test in case that the analysis of variance showed a significant difference. The difference between percentages was checked by the χ2 test. In all calculations the significance level was
set to p<0.05.
Results and discussion:
For all five measured parameters of the mandibular border movements, a linear increase in movements was observed parallelly with an increase in the time of wearing relaxation splints. After 12 weeks of therapy an increase of 7.7% was observed for initial opening. An almost twofold increase (14.4%) from the initial 12.15 ± 5.48 mm to 13.82 ± 6.08 mm was found for left condyle opening. A slightly lower increase (11.5%), from the initial 12.45 ± 5.14 mm to 14.07 ± 5.52 mm, was found for right condyle opening. An increase of 10.6% was established for left laterotrusion, and 11.9% for right laterotrusion. A statistically significant difference was confirmed for laterotrusions. In this study of subjects with bruxism, the mean initial value of maximum mouth opening of 44.98 mm and the mean final value of 48.72 mm are within the range of the normal values for healthy temporomandibular joints. These results are expected because the subjects with TMD, myofascial pain, muscle spasm or some other condition that restricts jaw movement were excluded from the study. On the other hand, bruxism is not considered as a disorder and it causes only masticatory muscle hypertrophy. Initial values for left and right condyle position during opening (OLK and ODK) of 12.15 mm and 12.45 mm in subjects with bruxism are in the lower part of normal values in this study, and only one study with lower values was found. The pathways of the left and right
condyle in this study had a symmetrical and uniform wave pattern at mouth opening, which is expected in healthy persons and in accordance with previous research. Initial and final values in the range of normal values of condylar movement, correct condylar pathway during opening and a small increase with no statistically significant difference indicate that splint
therapy in subjects with bruxism has no effect on condylar movement during mouth opening. Of all mandibular border movements and condylar movements in this study, a statistically significant difference was found only in left and right laterotrusion within subjects with bruxism. The statistically significant difference was found between the initial values of left
and right laterotrusion and the final values after splint therapy. This study confirmed the positive effect of the splint on the lateral pterygoid muscle as the main muscle for laterotrusive movements often affected in bruxism. The splint therapy had the greatest effect on it and indicated the greatest differences in mandibular movements during laterotrusion. The results of this study confirmed anterior displacement of the condyle during handing in of the splint in the experimental and control group. During protrusion, the largest displacement of the condyle was in the horizontal plane (x), amounting to 0.56 mm (19.8%). The transversal shift (z) of -0.04 mm changed after splint therapy in the experimental group to 0.04. In the control group, a minimal change of 0.05 mm was also recorded, indicating that the use of splints had no effect on transversal condylar movements in protrusion. The position of the condyle during left and right laterotrusion changed in the horizontal (x) plane in the direction of a greater distance from the reference position in the experimental and control group. The initial position for the experimental and control group in right laterotrusion amounted to 0.80 mm from the reference position. At the end of therapy it changed to 1.05 mm in the experimental group and to 0.92 mm in the control group. Changes in the condylar position after splint therapy were expectedly the lowest in both the experimental and the control group in the CR position. In this study, none of the subjects in the experimental and control group showed a match between the reference position (IPK) and the CR position.
Conclusion: The scientific contribution of this study was based on providing a better understanding of the
effect of wearing a relaxation occlusal splint as a generally accepted therapeutic procedure in subjects diagnosed with bruxism, as well as on providing better insight into the impact of relaxation occlusal splint on the position and movements of condyles and mandibular movements parametres in subjects with bruxism. The effect of occlusal splints was confirmed at mandibular border movements (incisal opening, left and right laterotrusion) and condylar movements (opening of the left and right condyle), which increased during splint therapy. Occlusal splint therapy affected the change in the condylar position in all the three planes, which was higher in subjects with bruxism compared to the control group, but without a
statistically significant difference.