Purpose: The purpose of this study was to clarify the effect of different chewing rates on salivary cortisol levels as a stress indicator. Methods: The subject group consisted of 16 healthy males. They were required to rest for 30 min, and then given arithmetic calculations to perform for 30 min as stress loading. Immediately after, the first set of saliva specimens (S1) was collected over a period of 1 min to measure cortisol levels. Next, they were asked to chew a tasteless gum base for 10 min, and the second set of saliva specimens (S2) was collected in the same manner. They were then required to rest for 10 min, after which the third set of saliva specimens (S3) was collected. Chewing rates were set to slow, habitual, and fast in time with a metronome. Salivary cortisol levels were analyzed by radioimmunoassay. Changes in salivary cortisol levels comparing S1 with S2, and S1 with S3 were determined. Results: Changes in salivary cortisol levels between S1 and S2 showed a reduction of 4.7%, 14.6%, and 16.2% with slow, habitual, and fast chewing, respectively. A significant difference was observed between slow and fast chewing. Changes in salivary cortisol levels between S1 and S3 showed a reduction of 14.4%, 22.2%, and 25.8% with slow, habitual, and fast chewing, respectively. A significant difference was observed between slow and fast chewing. Conclusion: This study showed that differences in chewing rate affected salivary cortisol levels as a stress indicator, and suggested that the effect on stress release with fast chewing is greater than that with slow chewing.
Purpose: The purpose of this study was to investigate the influence of mandibular residual ridge shape on the masticatory ability in complete denture wearers. Methods: The subject group consisted of 199 complete denture wearers. The mandibular residual ridge of each subject was evaluated using a replica of the ridge which was obtained with heavy-body silicone impression material. The basal area of each replica was measured with a digitizer. The volume and the height of each replica were also calculated. The masticatory ability of each subject was evaluated using a-25-item food intake questionnaire method by authors. The masticatory score of each subject was calculated to represent the masticatory ability. Furthermore, all subjects were divided into three groups (S, M, L group) according to the value of the basal area. Results: There were statistically significant correlations between the basal area of the residual ridge and the masticatory score (r = 0.366, p < 0.01), and also the volume of the residual ridge and the masticatory score (r = 0.314, p < 0.01). The basal area of the residual ridge, the volume of the residual ridge, and the masticatory score of the L group (29 persons) were statistically larger than those of the M group (136 persons) and the S group (34 persons) (p < 0.05), and those values in the M group were statistically larger than those of the S group (p < 0.05). Conclusion: It was confirmed that the basal area of denture foundation of the mandible had an influence on the masticatory ability in complete denture wearers.
Purpose: Neck pain is one of the main symptoms of temporomandibular disorder. Muscle activity of the sternocleidomastoid muscle during occlusion has been clarified in recent years. We reported that when healthy individuals were instructed to chew rapidly, the activity of the sternocleidomastoid muscle responded to activity of the masseter muscle, however, during voluntary jaw opening, activity of the sternocleidomastoid muscle did not respond, but worked actively due to motor programming. The objective of the present study was to investigate the learning effects of repetitive training, that is, changes in activity mode of the neuromuscular system. Materials and Methods: The sternocleidomastoid and the anterior belly of digastric muscles in 8 healthy male adults were analyzed. In response to acoustic stimulation, each subject was instructed to open their mouth as quickly and widely as possible a total of 30 times with a break between measurements. EMG-reaction times (RT) of the sternocleidomastoid and anterior belly of digastric muscles were measured, and the length of time from the start of EMG activity of agonist to the start of actual movement was measured. Results: In all subjects, at first measurement, EMG-RT of the sternocleidomastoid muscle did not precede that of the anterior belly of digastric muscle. With each measurement, the difference in EMG-RT between the sternocleidomastoid and the anterior belly of digastric muscles decreased, and in 6 of the 8 subjects, EMG-RT of the sternocleidomastoid muscle preceded that of the anterior belly of digastric muscle. Conclusion: Repetitive task movement alters the start times of muscular activities, and from the perspective of EMG kinesiology, motor learning effects were confirmed with maximum ballistic voluntary jaw opening.
Purpose: The purpose of this study was to investigate the ion release from titanium casts in solutions of mixed organic acids and to reconsider the possibility of allergic reactions to titanium. Methods: Cast specimens were made from commercially pure titanium. For the immersion solutions, we prepared two types of organic acid solutions, one mixed with organic acids contained in whole stimulated saliva at two different dilutions, and the other, a lactic acid solution. Following immersion, the amounts of dissolved titanium ions, weight loss of the casts, and micrographs of the specimen surfaces were examined. Results: There were significantly larger amounts of dissolved titanium ions in the mixed organic acid solutions than in the lactic acid solution. There was also a significant difference in the weight loss values between the immersion solutions (p < 0.0001), but the significance level was different from that of the difference in the quantity of ion elution. Conclusion: The results suggested that a much larger quantity of ions is released from titanium casts attached in the oral cavity than has been reported previously, and that it is necessary to consider the possibility of allergic reactions to titanium casts.
Purpose: The purpose of this study was to establish an evaluation method using a Nasometer, with several monosyllabic test words, to reveal the level of air leakage in maxillectomy patients without limitations due to language or ability to read. Methods: 20 normal Japanese (Group 1) and 20 international adults (Group 2), were asked to read 7 monosyllables, (5 vowels and 2 combined vowels, /a/, /i/, /u/, /e/, /o/, /am/, /aj/), 6 times each and 12 Japanese maxillectomy patients (Group 3) were asked to read only 3 monosyllables (/a/, /am/, /aj/) 6 times each. The “Nasalance Score” was calculated using a Nasometer (Nasometer II, model 6400 KayPentax, Lincoln Park, NJ, USA). Results: Coefficient of variations (CVs) of three monosyllables /a/, /am/, /aj/ of Group 1 and Group 2 showed less than 0.33. There is significant difference in all pairs of three monosyllables between Group 1 and Group 3 (p < 0.05). Conclusion: Using a Nasometer, these three monosyllables, /a/, /am/ and /aj/, could be used as standard test words and could reveal the level of air leakage in maxillectomy patients.
Purpose: This study evaluated the masticatory side as well as which side was the habitual chewing side by the use of wax cubes and a bite force measuring system in normal dentate subjects (ND) and complete denture wearers (CD). Methods: Forty two ND subjects (29 males, 13 females; mean age, 24.8 ± 2.4 years), and 11 CD subjects (4 males, 7 females; mean age, 72.8 ± 7.0 years) participated in the study. The test food used in this study was wax cubes to determine the masticatory side. The difference in the occlusal contact area and occlusal force between the masticatory side and the opposite side was investigated using Dental Prescale®. ND was classified into 2 groups: those whose agreement on the masticatory part was high (ND-H) or low (ND-L). The distribution of the center of the occlusal balance was analyzed by Dental Prescale® in ND-H, ND-L, and CD. Results: The occlusal contact area and occlusal force of the masticatory side was greater than the opposite one, and the center of the occlusal balance was wide in ND-H. In ND-L and CD, the occlusal contact area and occlusal force did not differ between the masticatory side and the opposite one, and the center of the occlusal balance developed a tendency to gather in the center. Conclusion: The results of this study suggested that the evaluation of the masticatory side and the use of Dental Prescale were helpful in determining the habitual chewing side.
Purpose: Hard resins for crowns and bridges are widely used for esthetic restorations. The objective of this study was to evaluate the mechanical properties of new commercial hard resins and to compare the results with those of the other hard resins previously investigated. Methods: Dentin and enamel made with two new hard resins (Epricord®: EP, Kuraray, Co., Ltd., Osaka, Japan and Prossimo®: PR, GC, Co., Ltd., Tokyo, Japan) were used in this study. Regarding the fundamental characteristics, the thermal expansion/shrinkage coefficient, the filler content, the polymerization shrinkage, and the wear were examined. Regarding the strength of resin, the bending strength, hardness, compression strength, elastic modulus, and fracture strength of a jacket crown were measured. Results: These resins showed comparatively lower levels than the other hard resins regarding the bending strength, hardness, compression strength, and fracture strength of the jacket crown. The total filler content rate and wear amount of these resins exhibited similar values to those of the other resins. The thermal expansion/shrinkage coefficients of these resins exhibited higher values than those of the other resins. EP showed a different tendency from PR about the compression strength, elastic modulus, and polymerization shrinkage. Conclusions: PR and EP did not show dramatically better physical properties. However, the results of each examination in this study may be acceptable clinically. The results of each investigation changed according to the products used, and proper use for each case and application was suggested.
Purpose: The aim of this study was to develop a means of coordinating helical computed tomography (CT)—based morphological data in 3 dimensions (3-D) with that pertaining to jaw movement as recorded by a device that measures jaw movement in six-degrees-of-freedom (6-DOF), thus producing multi-point movement analysis of the condyle. Methods: The study sample was two volunteers. One of the subjects had erosive bony changes in both condyles, while the other had healthy condyles. We employed a customized facebow, which enabled us to coordinate jaw movement data and morphological volume data from CT. Total uncertainty of the coordination was computed, according to International Organization for Standardization (ISO). In order to demonstrate the effects of multi-point analysis for complex condylar movement, we tried to visualize the trajectory of the working condyle in lateral excursion. Results: The overall uncertainty at a condylar center chosen as an example to illustrate the method was 0.38 mm, 0.19 mm, and 0.50 mm in antero-posterior, latero-medial, and supero-inferior directions, respectively, in terms of 95% coverage as defined by the ISO. Conclusion: We developed facebow-based X-ray markers with high clinical operability, which could correlate the helical CT's coordinate system with our 6-DOF jaw movement measuring system for precise analysis of 3-D condylar movements. In motion analysis of rotational condyle, even a small amount of measurement error cannot necessarily be neglected. Then, a multi-point approach such as that realized by our system presents the best option.
Purpose: The aim of this study was to investigate the relationship between medicine and stimulated saliva and oral moisture. Methods: Fourteen patients with subjective oral dryness and 13 healthy adults were enrolled in this study. Disease, medicine, and medicines that had a side effect of oral dryness were investigated. The Saxon test was performed by chewing a piece of gauze sponge for 2 min. Oral moisture was measured at the lingual and buccal mucosa using an oral moisture checking device. Statistical analysis was performed by the Mann-Whitney U-test and Student t-test. Results: Stimulated saliva and oral moisture did not differ according to the number of diseases. Oral moisture at lingual mucosa was different between a minor medicine group (0-2 types of medicine) (31.3 ± 1.9%) and a major medicine group (≥3 types of medicine) (29.5 ± 2.2%) (p = 0.05). Oral moisture differed between a group not taking any medicine that had a side effect of oral dryness (31.2 ± 1.8% at lingual mucosa and 33.8 ± 1.4% at buccal mucosa) and a group taking such medicine (29.3 ± 2.3% at lingual mucosa and 32.4 ± 1.8% at buccal mucosa) (p < 0.05). Conclusion: The results of this study showed that oral moisture tended to decrease in the subjects who took many types of medicine or who took medicine that had a side effect of oral dryness. The medicine did not influence the amount of stimulated saliva. Therefore, it was suggested that medicine could influence the moisture of the oral mucosa.
Purpose: The aim of this study was to investigate the factors influencing the outcome of prostheses on speech rehabilitation of mandibulectomy patients. Methods: Eleven patients (6 males and 5 females) who underwent mandibulectomy without glossectomy because of a tumor participated in the study. A Speech Intelligibility (SI) test was applied without and with a prosthesis to evaluate their speech ability. The type of resection, whether soft tissue grafting was undertaken or not, the continuity of mandibular bone, and the number of remaining teeth related to the stability of the prosthesis were determined from the medical records. The some of acoustic features, Formant 1 and Formant 2 range, were investigated to evaluate objectively the limitation of tongue movement. Five questionnaires were sent out to evaluate subjectively the difference in sense of discomfort while speaking with and without the prosthesis. These eleven items were entered into stepwise multiple regression models to determine the predictors of the differences in SI score without and with a prosthesis. Results: Three variables, the ease of tongue movements, whether soft tissue grafting was undertaken or not, and whether the mandibular bone was continuous or not, contributed to the recovery of speech ability with prosthodontic treatment. Conclusion: The ease of tongue movement, no soft tissue grafting, and the continuity of mandibular bone contribute to the recovery of speech ability with prosthodontic treatment.
Purpose: The riegel and swing-lock® attachments are excellent retainers in terms of secure retention, but the former requires a great volume of abutment tooth reduction and the latter has problems with aesthetics and abrasion. In contrast, the RPI and RPA clasps have been highly appreciated as excellent retainers for abutment tooth protection, but any retentive forces are needed. Thus, the purpose of the study is to design a retainer that made the use of these merits. Methods: The form of the retainer (named Suginaka Riegel® lock retainer) for this purpose is based on the RPPA, for which a lingual arm is provided. In applying this technique, the buccal arm corresponding to the Akers-type buccal arm in the RPPA utilizes the undercut area below the survey line, ranging from the distal to the mesial corner. This buccal arm extends from the metal tooth that turns the hinge placed in the buccal denture border. The Suginaka Riegel® device placed in the denture base locks the metal tooth in place. Results: Utilizing the deeper undercut below the survey line provides secure retention while eliminating the risk of adverse forces being exerted on the abutment tooth during denture function or insertion and removal. Conclusion: This new, additional form of the Suginaka Riegel® lock denture allows the abutment tooth to provide latch effect-derived retention solely by preparation of the rest seat and guide plane. This allows use on a healthy tooth and on a tooth for which prosthodontic treatment has already been completed.
Patient: An 83-year-old woman visited the hospital for new complete dentures. A mesh type stainless palatal plate (Trutissu plate) was selected, because it enables the patient to experience the taste and temperature of food. Twenty one months after insertion, the patient returned complaining of pain on mucosa under the mandibular denture base. On clinical examination, a small swollen area was observed on the palatine rugae region of the mesh plate. By making a small hole in the swollen part, a creamy mass of dark brown color was discharged from the swollen space between the laminated structure of the Trutissu plate. Three months after the first deformation was corrected, further deformation of the Trutissu plate was observed. The patient admitted that she had not used the ultrasonic cleansing apparatus. A candidiasis-like lesion was observed on the palatal mucosa. Discussion: The formation of Candida biofilms on dentures may assist survival of fungal cells and contribute to the disease process in patients with denture stomatitis. In this case, the patient did not use ultrasonic cleaner, thus resulting in microbial accumulation and morphological change of the laminated mesh plate. However, this is rare in the clinical use of the Trutissu mesh plate, and the only case reported in 20 years. Ultrasonic cleansing was effective in removing microorganisms from the denture. Conclusion: Routine ultrasonic cleansing should be performed to avoid the possible accumulation of microorganisms in the laminated mesh structure.
Patient: A 58-year-old man with a complaint of masticatory disturbance presented. His mandibular left premolars and molars were missing, and the mandibular left canine, which was neighboring to the missing part, showed marked labial tipping. A cobalt-chromium removable partial denture was fabricated using a new magnetic attachment retainer because it seemed difficult to apply a conventional clasp for this case. This retainer is constructed from the buccal hook arm sliding bucco-lingually and the magnetic attachment which works to lock the movable part when it was closed. Six years after the delivery of this denture, both the abutment tooth and the periodontal tissue are healthy, and the denture is functioning well. Discussion: As this retainer does not use the elasticity of clasp arms, block out area can be minimized, and the maximum area of the contacting surface of the hook arm brings about very positive retention and bracing. The function of attractive force is to resist the splitting force and not to become directly involved in the retention of the denture. Therefore, the attractive force for this system does not need to be very strong. This system also provides the advantages of a sectional denture, allowing protection of the abutment tooth and the use of the abutment tooth in its original form. Conclusion: The retainer described in this report has many advantages including, no hazardous lateral force, adequate retentive force, and application to natural teeth or tipped teeth.