Hisashi Taniguchi

Comparison of food mixing ability among mandibulectomy patients

Many papers have been published on surgical mandibulectomy and reconstruction. However, only a few reports refer to masticatory function after prosthodontic treatment in mandibulectomy patients. The aim of this study was to investigate the masticatory function of mandibulectomy patients. Twenty-three subjects (10 males and 13 females, with an average age of 63 years) participated in this study: 11 subjects who had undergone unilateral marginal mandibulectomy, six subjects with unilateral segmental mandibulectomy with reconstruction and six subjects with hemimandibulectomy without reconstruction. Mixing Ability Index (MAI) was used to measure masticatory function on the non-defect side and on the defect side with a prosthesis installed. Comparisons were carried out among the marginal, segmental and hemimandibular groups and between the non-defect side and the defect side. Consequently, our study indicates these results. On the non-defect side, a significant difference was found between the marginal and the segmental groups, and between the marginal and the hemimandibular groups. In the marginal and the segmental groups, a significant difference was found between the non-defect and the defect sides. In conclusion, our study suggests that MAI is an adequate tool to study the masticatory function in mandibulectomy patients, the masticatory function of the mandibulectomy patients is more impaired than that of the ordinary removable partial denture patients, and that surgical intervention affects the masticatory function on not only the defect side but also the non-defect side in mandibulectomy patients.

Investigation of factor affecting health-related quality of life in head and neck cancer patients

OBJECTIVES Head and neck cancer (HNC) patients have profound illness of physical, social and psychological factors that affects quality of life (QOL). The purpose of this study is to investigate the factors affecting HRQL in patients with intra-oral prostheses. BACKGROUND Some cross-sectional studies have been performed to investigate HRQL in patients with HNC, but these studies did not report in detail how factors affect the HRQL of maxillectomy and mandibulectomy and/or glossectomy patients. MATERIALS AND METHODS The University of Washington Quality of Life version 4 questionnaires (Japanese version) was administered to 50 maxillectomy and 50 mandibulectomy and/or glossectomy patients with intra-oral prostheses who were selected according to inclusion and exclusion criteria. Gathered data were statistically analyzed to investigate how a number of factors, namely, age, sex, pathologic diagnosis, neck dissection, resection size, radiotherapy and dental condition affect HRQL. RESULTS In the maxillectomy patients, there were no significant differences between malignant and benign tumor in pathological diagnosis or between dentate and edentulous in dental condition. Age, sex, neck dissection and radiotherapy affected HRQL. In the mandibulectomy and/or glossectomy patients, there was no significant difference between dentate and edentulous in dental condition. Age, sex, glossectomy, neck dissection and radiotherapy affected HRQL. CONCLUSIONS The factors affecting HRQL in the maxillectomy patients were different from those in the mandibulectomy and/or glossectomy patients. Though they wore stable prostheses; we were still able to show that resection size, radiotherapy and neck dissection affected HRQL.

Modulation of H reflex of pretibial and soleus muscles during mastication in humans

A previous study in our laboratory demonstrated that the soleus H reflex was facilitated during mastication in humans. In the present study, we investigated whether there was any modulation of the magnitude of the pretibial H reflex during mastication in five healthy adult volunteers. The pretibial H reflex was significantly facilitated during mastication, and there was no significant difference in the facilitation between jaw‐closing and jaw‐opening phases; that is, the gain of the H reflex was modulated tonically but not in a phase‐dependent manner during mastication. Furthermore, in the same subjects, we confirmed that the soleus H reflex was facilitated during mastication. Based on our findings, we conclude that the H reflexes in both the pretibial and soleus muscles undergo a nonreciprocal facilitation during mastication. It is suggested that mastication contributes to stabilization of postural stance in humans.

Investigation of predictors affecting food mixing ability in mandibulectomy and/or glossectomy patients

PURPOSE Several previous reports have described factors that affect masticatory function. However, there are no known predictors that affect the food mixing ability of the masticatory function, and it has been impossible to predict masticatory function in mandibulectomy and/or glossectomy patients. The purpose of the present study was to develop a numerical formula that could predict the food mixing ability of the masticatory function among mandibulectomy and/or glossectomy patients. The null hypothesis of the study was that five predictors, namely mandibulectomy, mandibular continuity, number of residual mandibular teeth, occlusal units and tongue movement score, were unable to account for the mixing ability index (MAI) in mandibulectomy and/or glossectomy patients. METHODS The subjects were 20 patients who had undergone mandibulectomy and/or glossectomy. The above-described five predictors were assessed. Tongue movement was evaluated with a tongue movement test and the MAI was evaluated with a mixing ability test. Multiple regression analysis was used to examine whether the five predictors affected the MAI after prosthetic treatment. RESULTS A regression equation was determined for the five predictors (R(2)=0.83; adjusted R(2)=0.77; p<0.001). CONCLUSION The obtained regression equation could successfully account for the MAI in mandibulectomy and/or glossectomy patients.

Standardization of Thresholding for Binary Conversion of Vocal Tract Modeling in Computed Tomography

Postoperative head and neck cancer patients suffer from speech disorders, which are the result of changes in their vocal tracts. Making a solid vocal tract model and measuring its transmission characteristics will provide one of the most useful tools to resolve the problem. In binary conversion of X-ray computed tomographic (CT) images for vocal tract reconstruction, nonobjective methods have been used by many researchers. We hypothesized that a standardized vocal tract model could be reconstructed by adopting the Hounsfield number of fat tissue as a criterion for thresholding of binary conversion, because its Hounsfield number is the nearest to air in the human body. The purpose of this study was to establish a new standardized method for binary conversion in reconstructing three-dimensional (3-D) vocal tract models. CT images for postoperative diagnosis were secondarily obtained from a CT scanner. Each patients minimum settings of Hounsfield number for the buccal fat-pad regions were measured. Thresholds were set every 50 Hounsfield units (HU) from the bottom line of the buccal fat-pad region to -1024 HU, the images were converted into binary values, and were evaluated according to the three-grade system based on anatomically defined criteria. The optimal threshold between tissue and air was determined by nonlinear multiple regression analyses. Each patients minimum settings of the buccal fat-pad regions were obtained. The optimal threshold was determined to be -165 HU from each patients minimum settings of the Hounsfield number for the buccal fat-pad regions. To conclude, a method of 3-D standardized vocal tract modeling was established.

Prosthodontic abutment in four patients with unilateral cleft lip and palate

An examination of the relation between the number of teeth used as the abutment of a fixed prosthesis and the increase of the functional loading capacity of the upper jaw was conducted in four male patients with unilateral cleft lip and palate (age range, 19 to 21 years). This was measured at the maximum biting force at each two teeth adjacent to the cleft under various splint extension conditions and compared with that in the nonsplint condition. In all subjects, the maximum biting force under every splinted condition was significantly increased compared with the nonsplint condition. The increase was proportional to the number of teeth included in the splinting. Results indicated that two teeth should be used in each segment in the abutment of the splint across the cleft in order to increase the functional loading capability of the upper jaw comparable to that of the lower jaw. The results also indicated that inclusion of more than two teeth has no further advantageous effect on the functional loading capability.

A new simple evaluation method of the monosyllable /sa/ using a psychoacoustic system in maxillectomy patients

PURPOSE An objective assessment of speech would benefit the prosthetic rehabilitation of maxillectomy patients. This study aimed to establish a simple, objective evaluation of monosyllable /sa/ utterances in maxillectomy patients by using a psychoacoustic system typically used in industry. MATERIALS AND METHODS This study comprised two experiments. Experiment 1 involved analysis of the psychoacoustic parameters (loudness, sharpness and roughness) in monosyllable /sa/ utterances by 18 healthy subjects (9 males, 9 females). The utterances were recorded in a sound-treated room. The coefficient of variation (CV) for each parameter was compared to identify the most suitable parameter for objective evaluation of speech. Experiment 2 involved analysis of /sa/ utterances by 18 maxillectomy patients (9 males, 9 females) with and without prosthesis, and comparisons of the psychoacoustic data between the healthy subjects and maxillectomy patients without prosthesis, between the maxillectomy patients with and without prosthesis, and between the healthy subjects and maxillectomy patients with prosthesis. RESULTS The CV for sharpness was the lowest among the three psychoacoustic parameters in both the healthy males and females. There were significant differences in the sharpness of /sa/ between the healthy subjects and the maxillectomy patients without prosthesis (but not with prosthesis), and between the maxillectomy patients with and without prosthesis. CONCLUSION We found that the psychoacoustic parameters typically adopted in industrial research could also be applied to evaluate the psychoacoustics of the monosyllable /sa/ utterance, and distinguished the monosyllable /sa/ in maxillectomy patients with an obturator from that without an obturator using the system.

Evaluation of articulation simulation system using artificial maxillectomy models.

Acoustic evaluation is valuable for guiding the treatment of maxillofacial defects and determining the effectiveness of rehabilitation with an obturator prosthesis. Model simulations are important in terms of pre-surgical planning and pre- and post-operative speech function. This study aimed to evaluate the acoustic characteristics of voice generated by an articulation simulation system using a vocal tract model with or without artificial maxillectomy defects. More specifically, we aimed to establish a speech simulation system for maxillectomy defect models that both surgeons and maxillofacial prosthodontists can use in guiding treatment planning. Artificially simulated maxillectomy defects were prepared according to Aramanys classification (Classes I-VI) in a three-dimensional vocal tract plaster model of a subject uttering the vowel /a/. Formant and nasalance acoustic data were analysed using Computerized Speech Lab and the Nasometer, respectively. Formants and nasalance of simulated /a/ sounds were successfully detected and analysed. Values of Formants 1 and 2 for the non-defect model were 675.43 and 976.64 Hz, respectively. Median values of Formants 1 and 2 for the defect models were 634.36 and 1026.84 Hz, respectively. Nasalance was 11% in the non-defect model, whereas median nasalance was 28% in the defect models. The results suggest that an articulation simulation system can be used to help surgeons and maxillofacial prosthodontists to plan post-surgical defects that will be facilitate maxillofacial rehabilitation.

Relationships between perceived chewing ability, objective masticatory function and oral health-related quality of life in mandibulectomy or glossectomy patients with a dento-maxillary prosthesis

PURPOSE This preliminary study examined whether the type of surgery performed for head and neck lesion was associated perceived chewing ability, objective masticatory function, and oral health-related quality of life (OHRQoL) in patients who required a dento-maxillary prosthesis postoperatively. METHODS Thirty-eight patients with a dento-maxillary prosthesis were divided into three groups according to the type of surgery received: marginal mandibulectomy, segmental mandibulectomy with bony reconstruction, or glossectomy. Perceived chewing ability, objective mixing ability, and OHRQoL were evaluated using a food intake questionnaire, color-changeable chewing gum, and the Geriatric Oral Health Assessment Index (GOHAI), respectively. Differences in the scores obtained by the three measures were compared between the surgical groups using the Kruskal-Wallis test, and associations between the scores in each group were analyzed by Spearmans rank correlation analysis. RESULTS Objective mixing ability was found to be significantly low only in patients who underwent glossectomy. No other measures differed significantly between the surgical groups. Perceived chewing ability and objective mixing ability were significantly associated in the marginal mandibulectomy and glossectomy groups but not in the segmental mandibulectomy group. Furthermore, GOHAI score was significantly associated with perceived chewing ability and objective mixing ability in the marginal mandibulectomy group. CONCLUSIONS Within the limitations of this study, the present findings suggest that the type of surgery received might influence food mixing ability. Associations among food mixing ability, perceived chewing and OHRQoL are not accountable depending on the type of surgery received, indicating the presence of other contributing factors to be considered.

Measurement of Voice Onset Time in Maxillectomy Patients

Objective speech evaluation using acoustic measurement is needed for the proper rehabilitation of maxillectomy patients. For digital evaluation of consonants, measurement of voice onset time is one option. However, voice onset time has not been measured in maxillectomy patients as their consonant sound spectra exhibit unique characteristics that make the measurement of voice onset time challenging. In this study, we established criteria for measuring voice onset time in maxillectomy patients for objective speech evaluation. We examined voice onset time for /ka/ and /ta/ in 13 maxillectomy patients by calculating the number of valid measurements of voice onset time out of three trials for each syllable. Wilcoxons signed rank test showed that voice onset time measurements were more successful for /ka/ and /ta/ when a prosthesis was used (Z = −2.232, P = 0.026 and Z = −2.401, P = 0.016, resp.) than when a prosthesis was not used. These results indicate a prosthesis affected voice onset measurement in these patients. Although more research in this area is needed, measurement of voice onset time has the potential to be used to evaluate consonant production in maxillectomy patients wearing a prosthesis.