Kenji Fueki

Effect of implant-supported or retained dentures on masticatory performance: a systematic review.

STATEMENT OF PROBLEM While subjective patient-based measures have been increasingly recognized as critical outcomes for prosthodontic treatment, there continues to be a need to validate for patients what changes in masticatory function can be expected with the provision of new implant-supported or retained dentures. PURPOSE The purpose of this review was to evaluate the critical factors impacting change in masticatory performance following the provision of new implant-supported or retained dentures. MATERIAL AND METHODS Information retrieval followed a systematic approach using PubMed and the Cochrane Library. English articles published from 1966 to June 2007, in which the masticatory performance of subjects with implant-supported or retained dentures was assessed by objective methods and compared to performance with conventional dentures, were included. Ratings of the evidence provided in each article followed United States Agency for Healthcare Research and Quality recommendations. RESULTS From 281 articles identified, 18 peer-reviewed articles met prespecified criteria for inclusion. Specific outcomes of significance identified by these articles rated as level II are: (1) fixed implant-supported partial dentures do not provide significant improvement in masticatory performance compared to conventional removable partial dentures for Kennedy Class I and II partially edentulous mandibles; (2) the combination of a mandibular implant-supported or retained overdenture (IOD) and maxillary conventional complete denture (CD) provides significant improvement in masticatory performance compared to CDs in both the mandible and maxilla for a limited population having persistent functional problems with an existing mandibular CD due to severely resorbed mandible; and (3) the type of implant and attachment system for mandibular IODs has a limited impact. Specific outcomes of significance identified by articles rated as having a moderate level of evidence (level III) are: (1) mandibular fixed implant-supported complete dentures provide significant improvement in masticatory performance compared to mandibular CDs in subjects dissatisfied with their CDs; and (2) implant-supported mandibular resection dentures have an advantage over conventional dentures in masticatory performance on the defect side of the mouth. CONCLUSIONS Objective benefits in masticatory performance of implant-supported or retained dentures compared to conventional dentures are limited to a mandibular IOD in edentulous patients with a resorbed mandible and/or difficulty adapting to CDs.

Comparisons between a mixing ability test and masticatory performance tests using a brittle or an elastic test food.

A variety of chewing tests and test items have been utilized to evaluate masticatory function. The purpose of this study was to compare a mixing ability test with masticatory performance tests using peanuts or gummy jelly as test foods. Thirty-two completely dentate subjects (Dentate group, mean age: 25.1 years) and 40 removable partial denture wearers (RPD group, mean age: 65.5 years) participated in this study. The subjects were asked to chew a two-coloured paraffin wax cube as a test item for 10 strokes. Mixing Ability Index (MAI) was determined from the colour mixture and shape of the chewed cube. Subjects were asked to chew 3 g portions of peanuts and a piece of gummy jelly for 20 strokes, respectively. Median particle size of chewed peanuts was determined using a multiple-sieving method. Concentration of dissolved glucose from the surface of the chewed gummy jelly was measured using a blood glucose meter. Pearsons correlation coefficient was used to test the relationships between the MAI, median particle size and the concentration of dissolved glucose. Mixing Ability Index was significantly related to median particle size (Dentate group: r = -0.56, P < 0.001, RPD group: r = -0.70, P < 0.001), but not significantly related to glucose concentration (Dentate group: r = 0.12, RPD group: r = 0.21, P > 0.05). It seems that ability of mixing the bolus is more strongly related to the ability of comminuting brittle food than elastic food.

Clinical application of removable partial dentures using thermoplastic resin. Part II: Material properties and clinical features of non-metal clasp dentures

This position paper reviews physical and mechanical properties of thermoplastic resin used for non-metal clasp dentures, and describes feature of each thermoplastic resin in clinical application of non-metal clasp dentures and complications based on clinical experience of expert panels. Since products of thermoplastic resin have great variability in physical and mechanical properties, clinicians should utilize them with careful consideration of the specific properties of each product. In general, thermoplastic resin has lower color-stability and higher risk for fracture than polymethyl methacrylate. Additionally, the surface of thermoplastic resin becomes roughened more easily than polymethyl methacrylate. Studies related to material properties of thermoplastic resin, treatment efficacy and follow-up are insufficient to provide definitive conclusions at this time. Therefore, this position paper should be revised based on future studies and a clinical guideline should be provided.

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.

Factors related to prosthetic restoration in patients with shortened dental arches: a multicentre study

The aim of this study was to identify the factors related to prosthetic restoration in patients with shortened dental arches (SDA). SDA patients with 2-12 missing occlusal units were consecutively enrolled from seven university-based dental hospitals in Japan. Of the 145 subjects (mean age; 63·4 years), 41% chose no treatment and 59% sought to replace their edentulous spaces with removable partial dentures or implant-supported fixed partial dentures. Restoration decisions were related to tooth loss patterns. Only 3% of subjects missing just second molar(s) sought to receive prosthetic treatment, while the percentage increased to 58% in subjects who were missing first and second molars and 93% in subjects missing premolar(s). Logistic regression analyses found that young age, increased number of missing occlusal units, asymmetric arch and presence of chewing complaint were significant predictors for prosthetic restoration (P<0·05). Increased number of missing occlusal units and asymmetric arch were significant predictors for the presence of chewing complaint (P<0·05). These results suggest that perceived impairment of chewing ability owing to missing occlusal units is a critical factor for prosthetic restoration in SDA patients.

Effect of prosthetic restoration on oral health‐related quality of life in patients with shortened dental arches: a multicentre study

The aim of this multicentre prospective study was to investigate the effect of prosthetic restoration for missing posterior teeth in patients with shortened dental arches (SDAs). SDA patients with 2-12 missing occlusal units (a pair of occluding premolars corresponds to one unit, and a pair of occluding molars corresponds to two units) were consecutively recruited from seven university-based dental hospitals in Japan. Patients chose no replacement of missing teeth or prosthetic treatment with removable partial dentures (RPDs) or implant-supported fixed partial dentures (IFPDs). Oral health-related quality of life (OHRQoL) was measured using the oral health impact profile (Japanese version - OHIP-J) at baseline and follow-up/post-treatment evaluation. Of the 169 subjects who completed baseline evaluation, 125 subjects (mean age; 63.0 years) received follow-up/post-treatment evaluation. No-treatment was chosen by 42% (53/125) of the subjects, and 58% (72/125) chose treatment with a RPD (n = 53) or an IFPD (n = 19). In the no-treatment (NT) group, the mean OHIP summary score at baseline was similar to that at follow-up evaluation (P = 0.69). In the treatment (TRT) group, the mean OHIP summary score decreased significantly after the RPD treatment (P = 0.002), and it tended to decrease, though not statistically significant (P = 0.18), after the IFPD treatment. The restoration of one occlusal unit was associated with a 1.2-point decrease in OHIP summary score (P = 0.034). These results suggest that the replacement of missing posterior teeth with RPDs or IFPDs improved OHRQoL. Prosthetic restoration for SDAs may benefit OHRQoL in patients needing replacement of missing posterior teeth.

Association between food mixing ability and electromyographic activity of jaw‐closing muscles during chewing of a wax cube

The purpose of this study was to clarify association between food mixing ability and activity of jaw-closing muscles during chewing of a wax cube. Twenty subjects with complete dentitions (mean age 24.1 years) were directed to chew a two-coloured paraffin wax cube for 10 strokes on preferred chewing side. Surface electromyograms (EMG) were recorded from the right and left masseter and anterior temporalis muscles during chewing of the wax cube. Maximum voltage, duration and muscle work for burst of each chewing cycle were measured on integrated EMG in each muscle. Food mixing ability was estimated as mixing ability index determined from the colour mixture and shape of the chewed wax cube. Some EMG parameters of all muscles except for masseter muscle on non-chewing side showed significant positive correlations with the mixing ability index (r = 0.45-0.56, P < 0.05). However, most of the EMG parameters correlated with one another. As a result, only muscle work of masseter muscle on the chewing side was identified as a significant predictor accounting for 28% interindividual variation in the mixing ability index (P < 0.01). These results suggest that activity of jaw-closing muscles during chewing the wax cube seems to be weakly related to food mixing ability.

A structural equation model to investigate the impact of missing occlusal units on objective masticatory function in patients with shortened dental arches

The aim of this study was to investigate the impact of missing occlusal units (MOUs) on objective masticatory function with respect to food comminuting and mixing ability. Sixty partially dentate patients (mean age, 64·1 years) with shortened dental arches participated in the study. Food comminuting ability was assessed using a masticatory performance test with peanuts as a test food. Food mixing ability was assessed using a mixing ability test with a two-coloured wax cube. Maximum bite force (MBF) was measured using a pressure-sensitive film as a mediator for food comminuting and mixing ability. A structural equation model was constructed based on a hypothesis that MOUs would be associated with reduced MBF and impairment of food comminuting and mixing ability. Structural equation modelling analysis found significant direct effects of MOU on median particle size and mixing ability index (MAI) (P < 0·001). In addition, MOU had significant indirect effects on median particle size and MAI with MBF as a mediator (P < 0·05). These results suggest that decrease in occlusal platform area and reduced MBF because of MOUs are associated with the impairment of food comminution and mixing in patients with shortened dental arches.

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.

Microbiological risk for periodontitis of abutment teeth in patients with removable partial dentures

Tannerella forsythia, Porphyromonas gingivalis and Treponema denticola are identified as the red complex which exists in high proportions in periodontally diseased patients. The aim of this study was to assess the microbiological risk for periodontitis of abutment teeth in subjects wearing removable partial dentures (RPDs) by measuring the red complex using BANA-ZymeTM test. Thirty-eight subjects (mean age: 62.2 years) with Kennedy Class II partially edentulous arch participated in this study. The red complex and clinical parameters, such as plaque index, gingival index, probing depth and tooth mobility were recorded at abutment teeth in contact with the direct retainer of unilaterally designed RPDs and the corresponding non-abutment teeth on the opposite side. Mean scores for the red complex, plaque index, gingival index and tooth mobility of the abutment teeth were significantly greater than those of the non-abutment teeth (P < 0.01). No significant mean difference in pocket depth was found between the abutment and non-abutment teeth. Logistic regression analysis revealed that abutment teeth, high scores of plaque index and a maintenance interval longer than 6 months were significant predictors for positive red complex scores (P < 0.05). These results suggest that the microbiological risk for periodontitis of abutment teeth is greater than that for non-abutment teeth in RPD wearers.