• The Journal of Korean Academy of Prosthodontics
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• v.44 no.1
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• pp.103-111
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• 2006

Statement of problem: The previous unilateral bite force recorder has several limitations for taking long time for measuring and causing discomfort to subjects. Because of these reasons, it could not use widely for epidemiological researches. However, 'Dental Prescale System' which is new equipment for measuring bite force, is more convenient for measuring bite force than previous unilateral recorder. Purpose: The purpose of this study was to compare a new technique(Dental Prescale System) using pressure sensitive foils for recording of maximal jaw closing force with conventional measurement using unilateral bite force recorder Material and method: This studies included 22 healthy dental students in college of dentistry Yonsei university in Rep of Korea. Mean age was 23.9 years. All subjects had continuous dental arches and no significant malocclusion or signs from the teeth and craniomandibular system. The Dental Prescale System (Fuji Film, Tokyo, Japan) consists of a horseshoe-shaped pressure sensitive sheet (50H, R type) and a computerized scanning system.(FPD705) We also used unilateral bite force recorder(Denbotics Co. Seoul, Rep.Korea) for comparing with Dental Prescale. Results and conclusion: The total bite force recorded with Dental Prescale System (1423 N) was systematically higher than that recorded by unilateral bite force recorder. (256 N) However, the maximum bite force values measured in the two ways were significantly correlated (r=0.46, p<0.05). The Dental Prescale bite force calculated for first molar (208 N) was lower than that recorded by unilateral bite force recorder. (256 N) The two values were also very significantly correlated. (r=0.66. p<0.001) There were significantly different in bite force between two measurement methods. The reasons were first, unilateral bite force recorder measured only the bite force of a part of teeth, and Dental Prescale measured the total teeth force. Second, in measurement, a difference in muscle contraction appeared by an extent of mouth-opening. Third, unilateral bite force recorder has the reducing effect of the bite force by protective tape. Fourth, Dental Prescale has limitations during the computer scanning procedure. Therefore, Dental Prescale System is considered to be a very promising alternative to be conventional bite force recording methods.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.498-510
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• 2005

Purpose: The purpose of this study was to compare the maximum occlusal force implant prostheses to natural teeth. Material and Method: Fifty nine patients treated either with $Br{\aa}anemark$ implants and ITI implants during the recent ten years were involved in this study. The maximum occlusal force were measured with unilateral bite force recorder and dental prescale system. Results: 1. The maximum occlusal forces of the implant prostheses and natural teeth were not significantly different where measured with unilateral bite force recorder and dental prescale system. 2. The maximum occlusal forces were not significantly different between $Br{\aa}nemark$ implant and ITI implant prostheses. 3. The maximum occlusal forces of the implant prostheses had lower when compared with natural teeth during 1-6 months functional periods when measured with the unilareral bite force recorder(P<0.05) and 1-12 months functional periods when measured with the dental prescale system(P<0.05). After these periods there was not statistical significant difference between the implant prostheses and natural teeth. 4. The maximum occlusal forces of the wide diameter implant prostheses were higher than the maximum occlusal forces of the regular diameter implant prostheses when measured with dental prescale system(P<0.05), but there was no significant difference between the wide diameter and the regular diameter implant prostheses when measured with unilateral bite force recorder. 5. The maximum occlusal forces of the single implant prostheses were not significantly different with the splinting implants prostheses. 6. The maximum occlusal forces of the implant prostheses were not significantly different by age and sex. 7. There was significantly different between maximum occlusal forces measured with unilateral bite force recorder and dental prescale system(P<0.0001) but there was positive correlation(r=0.52. P<0.05). Conclusion: The maximum occlusal forces of the implant prostheses were not significantly different to natural teeth during clenching and unilateral maximum biting.

• Journal of Oral Medicine and Pain
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• v.31 no.4
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• pp.347-354
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• 2006

Most patients suffering from TMD appear to have unsatisfactory masticatory function and compromised values of bite force. The purposes of this study were to investigate and compare bite force between affected and unaffected sides of patients with unilateral TMD and to evaluate its relation with duration of TMD. 42 patients with unilateral TMD, from Department of Oral Medicine, Dankook University Dental Hospital, were selected for this study. The ratio of men to women was 9:33 and their mean age of $27.2{\pm}10.4$ years. The bite forces were measured over both canines (for anterior bite force) and $1^{st}$ molars (for posterior bite force) using a bite force recorder while all the subjects were asked to clench successively for 3 seconds not until pain was felt. They were compared with those measured from bilateral TMD patients(N=6, M:F=1:5, mean age: $23.0{\pm}27.3$ years). The unilateral TMD patients were divided into time groups according to duration of TMD on the basis of 1 and 6 months, respectively. Paired and unpaired t-tests were used for statistical analysis. Unilateral TMD patients in this study showed that the affected sides had significantly lower bite force than the unaffected sides(force difference of about 7-8 kgf, p<0.05) while there was no significant sides difference in the bilateral patients. Nor did bite force on the affected sides reveal significant difference between unilateral and bilateral TMD patients. With regards to TMD duration, there was significant difference between the patients with TMD < 6 months and $\geq$ 6 months (p<0.05) while no significant difference existed between < 1 month and $\geq$ 1 month. The results of this study indicated that unilateral TMD patients can exhibit more reduced bite force on the affected sides compared with that on the unaffected sides and that bite force on the unaffected sides might be deteriorated more as longer did TMD last.

• Journal of Oral Medicine and Pain
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• v.32 no.2
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• pp.211-218
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• 2007

The purpose of this study was to compare the maximum bite forces between pre- and post-treatment related to specific diagnostic groups of TMD including masticatory muscle disorder (MMD), disc derangement (DD), joint inflammation (JI) and osteoarthritis (OA). Bite force between pre- and post-treatment was compared in 36 patients with unilateral TMD, successfully-managed in the Department of Oral Medicine, Dankook University Dental Hospital, for this study. The ratio of men to women was 7:29 and their mean age of $28.1{\pm}13.7$ years. The patients were categorized, through clinical and radiographic examination, into aforementioned 4 groups; MMD (N=18), DD (N=6), JI (N=5) and OA (N=7). The maximum bite force measurements were done at the antagonizing canines and 1st molars using a bite force recorder. Paired t-test, ANOVA, Multiple Comparison t-tests were used for statistical analysis. The results of this study showed that the maximum bite force before treatment increased after TMD treatment, which was noticeable at the canines (p=0.001 and p=0.000 for the affected and unaffected sides, respectively). In comparison related to the diagnostic groups of TMD, patients with osteoarthritis of TMJ exhibited the lowest strength while those with inflammatory disorder of TMJ had the highest strength on the affected sides. Increase of bite force after treatment was also found in each group. Significant difference between pre- and post-treatment was found at canines on the affected sides in MMD (p=0.045) and DD groups (p=0.009) while on the unaffected sides in OA group (p=0.003). Conclusively, the reduced bite force due to TMD could be recovered by conservative TMD treatment and that the difference of bite forces between pre- and post-treatment was noticeable at the canines.

• Journal of Oral Medicine and Pain
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• v.32 no.3
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• pp.337-346
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• 2007

This study aimed to evaluate a relation of bruxism with clinical effects of botulinum toxin type A(BTX-A) injection. 5 bruxers and 5 nonbruxers with bilateral masseter hypertrophy were participated in this study. After injecting 25 unit of BTX-A(Allergen Inc, $Botox^{(R)}$) into each masseter muscle, the thickness of masseter(Mm) and anterior temporalis(Ta) muscles was measured by ultrasonography and the maximum bite force was evaluated during a 9-month period. Self-estimation on the recovery of occlusal force during mastication was done as well. Regardless of presence of bruxsim, all subjects showed significantly reduced Ms thickness(p<0.001) and maximum bite force at $1^{st}$ molars(p=0.027) with their peak at 3 months after injection, which then started to return. No significant difference was observed in Ta thickness and the bite force at the central incisors. While self-estimated occlusal force was the least at 2 weeks after injection and then rapidly returned to the baseline level with full recovery at the time of 6 to 9 months after injection, the maximum bite force measured by bite force recorder did not recover the original value, particularly in the nonbruxer group. It is assumed that nocturnal bruxism can influence recovery of atrophic masseter and decreased occlusal force due to BTX-A injection. These findings suggest a need of occlusal appliance to control bruxism or clenching habit for longer clinical effect of BTX-A injection.

• Journal of Oral Medicine and Pain
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• v.33 no.1
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• pp.85-95
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• 2008

The purpose of this study was to evaluate the effects of oral habits on the muscles of mastication and facial expression by means of two parameters: muscle stiffness and elasticity. 10 healthy, fully-dentate male subjects in their twenties were selected for this study; all had normal Class I occlusal relationships. Muscle stiffness and elasticity were measured with a tactile sensor(Venustron, Axiom Co., JAPAN) while subjects were asked to relax and perform various parafunctional activities such unilateral clenching(biting the bite force recorder with a force of 50kg on each subject's preferred side), jaw thrusting and lip bracing. The following muscles were examined: temporalis anterior(Ta), masseter(Mm), frontalis(Fr), inferior orbicularis oculi(OOci), zygomaticus major(Zm), superior and inferior orbularis oris(OOrs and OOri) and mentalis(Mn). Paired t-test, Correlation Coefficients, ANOVA and Multiple Comparison t-tests were used for statistical analysis. Unilateral clenching was highly correlated with bilateral stiffness and elasticity of all the muscles tested. Mm was affected by all three oral habits; Ta was affected by unilateral clenching(p<0.05); Zm was affected by unilateral clenching and OOrs, OOri and Mn were most affected by lip bracing(p<0.05). This study indicates that not only the masticatory muscles but also the muscles of facial expression, mainly circumoral muscles, can be significantly influenced by parafunctional activities such as unilateral clenching and lip bracing.