Effect of prosthetic restoration on masticatory function in patients with shortened dental arches: a multicentre study.

The aim of this multicentre study was to investigate the effect of prosthetic restoration for missing posterior teeth on mastication in patients with shortened dental arches (SDAs). Partially dentate patients who had an intact teeth in anterior region and missed distal molar(s) (2-12 missing occlusal units) classified as Kennedy Class I or Class II were recruited from seven university-based dental hospitals in Japan. Of the 125 subjects who underwent baseline (pre-treatment) and follow-up/post-treatment evaluation, 53 chose no replacement of missing teeth and 72 chose treatment with removable partial dentures (n = 53) or implant-supported fixed partial dentures (n = 19). Objective masticatory performance (MP) was evaluated using a gummy jelly test. Perception of chewing ability (CA) was rated using a food intake questionnaire. In the no-treatment group, mean MP and CA scores at baseline were similar to those at follow-up evaluation (P > 0·05). In the treatment group, mean MP after treatment was significantly greater than the pre-treatment mean MP (P < 0·05). However, the mean perceived CA in the treatment groups was similar at pre- and post-treatment (P > 0·05). In a subgroup analysis of subjects in the treatment group, subjects with lower pre-treatment CA showed a significant CA increase after treatment (P = 0·004), but those with higher pre-treatment CA showed a significant decrease in CA (P = 0·001). These results suggest that prosthetic restoration for SDAs may benefit objective masticatory performance in patients needing replacement of missing posterior teeth, but the benefit in subjective chewing ability seems to be limited in subjects with perceived impairment in chewing ability before treatment.

Detection of carotid artery calcification on the panoramic images of post-menopausal females is significantly associated with severe abdominal aortic calcification: a risk indicator of future adverse vascular events.

OBJECTIVES: Outcome studies among post-menopausal females with calcified carotid artery plaque (CCAP) on their panoramic images have not been previously undertaken. We sought to compare the extent of abdominal aortic calcification (AAC) on lateral lumbar spine radiographs (LLSRs), among groups of females with (CCAP+) and without (CCAP-) carotid lesions on their panoramic images. "Severe" levels of AAC have previously been validated as a risk indicator of future adverse cardiovascular events. METHODS: This cross-sectional case-control study included a "CCAP+ group" consisting of females more than 50 years of age having the carotid lesion diagnosed by their dentists and an atherogenic risk factor (age, body mass index, hypertension, diabetes and dyslipidaemia)-matched "CCAP- group". A physician radiologist, using the Framingham index, evaluated the LLSRs for the magnitude of AAC. Summary statistics for key variables were computed and conditional logistic regression techniques were considered. RESULTS: Members of the CCAP+ group were significantly (p=0.038) more likely to demonstrate "severe" levels of AAC on their LLSRs than members of the CCAP group. CONCLUSIONS: This is the first published study demonstrating that CCAP on panoramic images of post-menopausal females is significantly associated with "severe" levels of AACs on LLSRs independent of traditional risk factors. Given that these levels of AAC are a validated risk indicator of future myocardial infarction and stroke, dentists must evaluate the panoramic images of post-menopausal females for the presence of CCAP. Patients with carotid atheromas should be referred to their physicians for further evaluation given the systemic implications.

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.

Prevalence of calcified carotid artery atheromas on panoramic images of individuals with primary hyperparathyroidism.

OBJECTIVES: Primary hyperparathyroidism (PHPT), affecting 1% of the population, is associated with increased cardiovascular morbidity and mortality. The presence of calcified carotid artery plaque (CCAP) on panoramic images is a validated risk indicator of future adverse cardiovascular events. We hypothesized that military veterans aged 50 years or older diagnosed with PHPT by increased parathyroid hormone and calcium levels would frequently have CCAP on their images. METHODS: We determined the prevalence rates of CCAP on the images of patients diagnosed with PHPT and evaluated their atherogenic risk profiles, including hypertension, dyslipidaemia, diabetes and obesity. Comparisons of atherogenic risk factors were made between subjects with and without observed CCAP on their panoramic images. RESULTS: Of the 60 patients (86.7% males and 13.3% females, mean age 73.2 ± 11.3 years) with PHPT, 40% had atheromas. There were no significant differences between CCAP+ and CCAP- groups in gender or race (p > 0.05). The atherogenic profile (age, body mass index, hypertension, diabetes, hyperlipidaemia) in the CCAP+ and CCAP- groups was not significantly different (p > 0.05). CONCLUSIONS: Calcified carotid artery atheromas are often seen on the panoramic images of patients with PHPT. Thus, dentists must be uniquely vigilant for these lesions when evaluating these studies.

Panoramic images of white and black post-menopausal females evidencing carotid calcifications are at high risk of comorbid osteopenia of the femoral neck.

OBJECTIVES: Femoral neck fractures in older females resulting from decreased bone mineral density (BMD; osteopenia) are associated with increased morbidity and mortality. Bone mineralization inhibition is probably controlled by proteins which also foster vascular calcification. Therefore, we evaluated the relationship between calcified carotid artery plaque (CCAP) on panoramic images and BMD on dual energy X-ray absorptiometry (DXA) bone scans. METHODS: Images and hospital records identified by dentists defined two study groups (20 white females and 24 black females) having CCAP and an incidentally obtained bone scan. Ethnically matched (age±7 years, body mass index ±3 units) control groups with panoramic images devoid of CCAP and accompanying DXA scan were likewise constituted. A physician determined the BMD on the DXA. RESULTS: Females with CCAP had significantly (p = 0.03) poorer BMD at the femoral neck than those without CCAP. Although mean femoral neck BMD was significantly lower (p = 0.009) for white than for black females, there was no significant interaction between race and CCAP (p = 0.80). CONCLUSION: We observed a significant inverse association between the CCAP on panoramic images and femoral neck BMD in post-menopausal white females.

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.

Objective and subjective hardness of a test item used for evaluating food mixing ability.

The aim of this study was to compare objective and subjective hardness of selected common foods with a wax cube used as a test item in a mixing ability test. Objective hardness was determined for 11 foods (cream cheese, boiled fish paste, boiled beef, apple, raw carrot, peanut, soft/hard rice cracker, jelly, plain chocolate and chewing gum) and the wax cube. Peak force (N) to compress each item was obtained from force-time curves generated with the Tensipresser. Perceived hardness ratings of each item were made by 30 dentate subjects (mean age 26.9 years) using a visual analogue scale (100 mm). These subjective assessments were given twice with a 1 week interval. High intraclass correlation coefficients (ICCs) for test-retest reliability were seen for all foods (ICC > 0.68; P < 0.001). One-way anova found a significant effect of food type on both the objective hardness score and the subjective hardness rating (P < 0.001). The wax cube showed significant lower objective hardness score (32.6 N) and subjective hardness rating (47.7) than peanut (45.3 N, 63.5) and raw carrot (82.5 N, 78.4) [P < 0.05; Ryan-Einot-Gabriel-Welsch (REGW)-F]. A significant semilogarithmic relationship was found between the logarithm of objective hardness scores and subjective hardness ratings across twelve test items (r = 0.90; P < 0.001). These results suggest the wax cube has a softer texture compared with test foods traditionally used for masticatory performance test, such as peanut and raw carrot. The hardness of the wax cube could be modified to simulate a range of test foods by changing mixture ratio of soft and hard paraffin wax.

Evaluation of a 3D digital photographic imaging system of the human face.

The aim of this study was to investigate the accuracy of a 3D photographic imaging system for potential application in fabrication of maxillofacial prostheses. For validity estimates, computer digitized 3D photographic images of calibrated ruler attached to a model were analysed for linear and curvilinear distances in 1 mm increments (1-50 mm from the centre of the image). Distortion was evaluated from 1 mm distances measured 20, 40 and 60 mm from the centre of the field. To estimate reliability of measurements in vivo, two raters measured the right endocanthion-subnasale distance and the distance between right and left endocathion on images of 10 subjects, repeated three times (30 images total). From the digital file for one subject, a rapid prototyping (RP) machine produced a 3D model of the mid-face. Measures from the model were compared with those of the 3D computer image to estimate error in fabrication. Mean error values for calibrated distances ranged from 0.07 to 0.26 mm for linear distances, 0.08-0.34 mm for curvilinear distances, and 0.06-0.12 mm for distortion from the centre. Intra- and interexaminer correlation ranged from 0.92 to 1.00 and 0.94-1.00 respectively. Measures of the endocanthion and subnasale distances on the RP fabricated mid-face model were within 8% of the corresponding measures on 3D computer images. The accuracy of the photographic 3D imaging system tested was sufficient for clinical description of the mid-face structures and may be potentially useful for rapid prototyping of facial prostheses.

A randomized clinical trial comparing the efficacy of mandibular implant-supported overdentures and conventional dentures in diabetic patients. Part IV: Comparisons of dietary intake.

STATEMENT OF PROBLEM: It is unclear whether the replacement of conventional mandibular dentures with implant-supported overdentures alters the diet and thus improves the nutritional intake of edentulous persons. PURPOSE: The purpose of this study was to compare the pretreatment and posttreatment diets of edentulous diabetic patients who received new dentures with either a conventional complete mandibular denture (CD) or a mandibular implant-supported overdenture (IOD). MATERIAL AND METHODS: New dentures were made for 89 edentulous diabetic patients with acceptable metabolic control without insulin (NIT) or with insulin (IT). A randomized approach was used to assign 37 patients a mandibular CD and 52 patients a mandibular IOD supported by 2 cylindrical implants. Of the 89 patients, 58 submitted a dietary log for 7 consecutive days before treatment (PT) and 6 months after treatment completion (PTC). An average daily intake of 28 essential nutrients was determined for each patient at each time interval. Separate 2 x 2 x 2 repeated analysis of variance (ANOVA) tests were performed for each nutrient to compare the means of the 2 denture groups (CD and IOD), 2 diabetic groups (NIT and IT), and 2 time intervals (PT and PTC). The intakes were also compared with the recommended daily allowance (RDA). RESULTS: ANOVAs for all 28 nutritional variables showed no main effect for either denture type or diabetic treatment. Time effects were seen for magnesium, potassium, copper, and monounsaturated fats. The PTC mean intake of the total sample (N = 58) decreased for all 3 minerals and increased for monounsaturated fats with study dentures. Post hoc tests showed the differences between PT and PTC means to be statistically significant for only magnesium (P=.043) and potassium (P=.015). The percentage of patients with PT intake 25% or more below the RDA ranged from 33% to 85% in the CD group and from 24% to 100% in the IOD group for the same 11 nutrients. PTC fiber intake deficiency was noted in almost all participants. Carbohydrate consumption was markedly lower than that recommended by the American Diabetic Association. CONCLUSION: As is often the case with elderly groups, this group of edentulous diabetic patients showed highly comprised nutritional intakes of fiber, vitamins, and minerals. The replacement of old dentures with new dentures that included either a mandibular CD or IOD did not alter patient diets such that the patients improved their nutritional intakes of essential micronutrients and macronutrients.

Randomized clinical trial comparing the efficacy of mandibular implant-supported overdentures and conventional dentures in diabetic patients. Part III: comparisons of patient satisfaction.

STATEMENT OF PROBLEM: There is insufficient evidence to indicate the functional superiority of mandibular implant-supported overdentures to justify their use in edentulous patients. PURPOSE: This study compared the benefits perceived by patients who received a new maxillary denture and a mandibular conventional denture (CD) and an implant-supported overdenture (IOD). METHOD: New maxillary and mandibular dentures were delivered to 89 diabetic denture wearers with clinically acceptable metabolic control who treated their diabetes either with insulin (IT) or without insulin (NIT). Of the 89 patients, 37 received maxillary and mandibular CDs and 52 received a maxillary CD and an IOD. Two questionnaires with categorical responses were used; the first contained 13 questions to ascertain a patient's absolute assessments of original dentures at entry and study dentures at 6- and 24-months after treatment completion; the second questionnaire had 11 questions that assessed the relative change perceived by patients with study dentures. Of the 78 patients who completed the posttreatment (PT) assessments at 6 months, 68 patients provided longitudinal data for questionnaire I and cross-sectional data for questionnaire II. In addition, 46 patients (18 CD and 28 IOD) also provided PT assessments at 24 months. RESULTS: Both mean scores and percentage distributions of longitudinal data for questionnaire I showed perceptual improvements with both types of study dentures. Improvements were higher in the IOD than in the CD group. Mean scores failed to show any significant differences between the 2 treatment groups. The only significant difference was found in the change in percentage distributions for perceptual chewing ability in favor of the IOD group. Even this advantage was lost at 24 months. With the comparative questionnaire, a higher percentage of patients in the IOD group than in the CD group perceived improvements with study dentures from their original dentures in chewing ability, chewing comfort, and denture security. However, mean differences were statistically significant in favor of the IOD group only for chewing ability and less difficulty to chew hard foods. CONCLUSION: The mandibular implant-supported overdenture offers same advantage in terms of perceived chewing function over the conventional denture.

A randomized clinical trial comparing the efficacy of mandibular implant-supported overdentures and conventional dentures in diabetic patients. Part II. Comparisons of masticatory performance.

STATEMENT OF PROBLEM: Convincing evidence is lacking to demonstrate the functional superiority of mandibular implant-supported overdentures over conventional dentures. PURPOSE: This randomized clinical trial was conducted to compare masticatory functional effectiveness of mandibular implant-supported overdentures and conventional dentures in diabetic denture wearers with clinically acceptable metabolic control. METHODS: A total of 102 edentulous diabetic patients, treated with or without insulin, were randomized to receive a new maxillary and either a mandibular conventional denture or an implant-supported overdenture. Treatment was completed in 89 patients, 37 with conventional dentures and 52 with Hader bar-clip attachment overdentures supported by two IMZ implants. Besides data from medical and dental histories, oromaxillofacial examinations, and questionnaires, masticatory tests were performed by patients before and at 6 and 24 months after treatment completion. Although 78 patients (28 in the conventional, 50 in the overdenture group) performed tests at 6 months after treatment, 68 (25 in the conventional, 43 in the overdenture) had performance data for both entry and 6-month posttreatment intervals. RESULTS: The two treatment groups were highly comparable in terms of general characteristics, quality of original dentures, tissue support, and past denture experience. No significant differences were found between patients treated for diabetes with or without insulin. All four masticatory performance scores with original dentures were higher in the conventional denture group than the overdenture group. The posttreatment performance scores for the two treatment groups became similar because of the higher gains in the overdenture group. Patients with low initial performance scores showed greater posttreatment gains with both conventional dentures and overdentures. CONCLUSIONS: The implant-supported overdenture showed no significant advantage over the conventional denture for improving the ability to comminute food in this group of diabetic patients with higher than average initial functional levels observed for other groups of denture wearers in previous studies.

A randomized clinical trial comparing the efficacy of mandibular implant-supported overdentures and conventional dentures in diabetic patients. Part I: Methodology and clinical outcomes.

STATEMENT OF PROBLEM: Scientific evidence is lacking to support the general application of implant-supported mandibular overdentures. PURPOSE: This randomized clinical trial was undertaken to compare the efficacy of conventional mandibular and implant-supported overdentures in diabetic edentulous patients with clinically acceptable metabolic control. METHOD: A total of 102 diabetic patients, treated with or without insulin, were randomized to receive a new maxillary denture and either a conventional or an implant-supported removable mandibular overdenture. Treatment was completed for 89 patients, 37 with the conventional and 52 with implant-supported dentures. Detailed examinations, tests, and questionnaires were given before and at 6- and 24-months after treatment completion. Comparisons between the two treatment groups were made for treatment failures based on prespecifed criteria and the type and amount of maintenance care provided. RESULTS: The insulin and noninsulin treated groups were collapsed because of the lack of significant differences at entry. The conventional denture and implant-supported overdenture groups were similar in terms of general demographics, medical status, quality of their original dentures and denture support, several functional measures, and patient satisfaction. Treatment was judged to be successful in 56.9% of patients with conventional dentures and 72.1% with overdentures. This difference in success rate was not statistically significant (p > 0.05). Patients with treatment failures in both groups required excessive maintenance care. Those with conventional dentures needed frequent denture base adjustments and relines, whereas those with overdentures required frequent clip replacements and repairs. Although significant improvements were seen with both treatment modalities, a higher percentage of patients with implant-supported overdentures than those with conventional dentures reported improvements in chewing comfort and moderate-to-complete overall satisfaction.

A randomized clinical trial of two basic removable partial denture designs. Part II: Comparisons of masticatory scores.

STATEMENT OF PROBLEM: There is no known data on the functional efficacy of different removable partial denture designs. PURPOSE: This randomized clinical trial compared the masticatory performance of two commonly used designs in 118 patients who needed a unilateral or bilateral mandibular partial denture. MATERIAL AND METHODS: One half of the patients received a partial denture with distal occlusal rests and cast circumferential clasps and the other half a partial denture with mesial rests and I-bar cast clasps. The left side, right side, and swallowing threshold masticatory tests were made with peanuts and carrots before treatment and 16 weeks after the prosthesis insertion (baseline) and thereafter at 6, 18, 36, and 60 months. RESULTS: Masticatory scores at entry were higher in the circumferential design group, but the only significant (p < 0.05) difference was found in the right side carrot performance. Both groups realized significant improvements (p < 0.001) in all performance scores with partial dentures. Mean improvements of 24.7 with peanuts and 35.8 with carrots in the right side performance scores and 19.0 in the swallowing threshold score with peanuts in the bar design group were significantly higher (p = 0.017) than the respective mean improvements of 15.9, 21.4, and 5.6 in the circumferential design group. However, no significant differences were found between the two groups for any of the 10 performance scores at baseline. CONCLUSIONS: Despite some performance differences at entry, the mean performance scores for the two groups became similar at baseline and at subsequent intervals.

Veterans Administration Cooperative Dental Implant Study--comparisons between fixed partial dentures supported by blade-vent implants and removable partial dentures. Part V: Comparisons of pretreatment and posttreatment dietary intakes.

PROBLEM: Good scientific evidence is lacking on the impact of improvement in masticatory function after prosthodontic restoration of missing teeth. PURPOSE: This study compares 1-week dietary intakes of 218 healthy, male patients, 111 patients restored with mandibular unilateral or bilateral distal base extension removable partial dentures and 107 patients with fixed partial dentures. MATERIAL AND METHODS: Dietary logs recorded before the initiation of treatment and 6-months after the baseline period after partial denture treatment were analyzed for 30 nutritional variables of food intakes including total calories, fats, carbohydrates, proteins, fiber, and a number of vitamins and minerals. RESULTS: Both before and after treatment, intakes of various nutrients were more than 25% above or below the RDAs for approximately half of the patients in both groups. No significant differences were observed between the mean scores of the two groups for any of the 30 variables either before or after treatment. However, beneficial treatment effects were seen in subsets of patients with low and high caloric intakes at entry. Both treatments increased the intakes of calories and 27 nutrients in the low caloric group and decreased the intakes of calories and 27 nutrients in the high caloric group. The decreases in the caloric intake and eight nutrients, including total protein, fat, carbohydrates, and cholesterol, were significantly greater (p < 0.05) in the fixed partial denture group than those in the removable partial denture group. CONCLUSIONS: These beneficial effects of partial dentures, if verified by other studies, may have profound clinical implications for the undernourished and obese patients.

Effects of improvements of poorly fitting dentures and new dentures on masseter activity during chewing.

The effects of four sequential modifications to improve occlusion, vertical dimension, retention, and stability of poorly fitting dentures, and of placing new dentures, on the EMG activity were investigated in 21 denture wearers with a mean age of 67.7 years. Electromyographic recordings of right and left masseter muscles were made while the subjects performed masticatory and swallowing threshold tests and applied static guided forces were measured before and after each modification and at three intervals after the delivery of new dentures. A 2-week adaptation period was allowed for each denture modification. Three- and 12-week adaptation periods were allowed for the new dentures. No significant changes were found in guided static bite force or peak bite force during chewing following any modification or insertion of new dentures. Significant decreases (p < 0.05) from the original poorly fitting denture in preferred side and nonpreferred side muscle activity were found for the preferred side tests with both foods after both the correction of occlusion and 3 mm increase in vertical dimension. Concomitant decreases (p < 0.05) in the masseter closing burst and stroke durations were found and contributed to the reduction in masseter muscle effort. Further reductions (p < 0.01) in masseter closing bursts and stroke durations were observed with new dentures. The results revealed that new dentures or the stabilization of poorly fitting dentures through occlusal correction and restoration of occlusal vertical dimension permits patients to use less muscle effort while chewing and maintaining their initial masticatory performance.

Effects of improvements of poorly fitting dentures and new dentures on patient satisfaction.

Clinicians reline or replace dentures to improve occlusion, stability, retention and facial support. They believe that well-fitting dentures will maintain supporting tissues in good health and satisfy patients by improving oral function and self-esteem. In this study, satisfaction of 21 patients with poorly fitting dentures was assessed before and after the dentures were modified to improve occlusion, vertical dimension of occlusion, and retention and stability or the dentures were replaced with new ones. More than 55% of the patients were moderately to fully satisfied with their poorly fitting dentures. Most patients perceived improvements in chewing comfort, chewing ability, eating enjoyment, food choices, security, and speech after each denture modification and with new dentures. The relative importance of the four sequential modifications could not be determined because they were made sequentially and their effects became cumulative. Chewing ability, eating enjoyment, particles under dentures, and food choices were highly correlated with chewing comfort and overall patient satisfaction. The results support the belief of many clinicians that patients benefit from relining of poorly fitting dentures or replacement with new dentures. Improvements in chewing function were perceived by most patients despite the lack of improvement in masticatory performance or masseter muscle activity with modified or new dentures. It is likely that denture wearers perceive chewing ability in terms of chewing comfort rather than ability to comminute food, an objective measure of chewing performance. The latter is not altered markedly by the clinical excellence of dentures.

Effects of improvements of poorly fitting dentures and new dentures on masticatory performance.

The effect of four modifications to improve the fit and maxillomandibular relationships of poorly fitting dentures and the insertion of new dentures on masticatory performance was assessed in 21 denture wearers. A 2-week adaptation period was allowed for each of the four modifications and 3 weeks and 12 weeks of adaptation for new dentures. The preferred side masticatory performances were not appreciably affected by either the modifications to improve the fit of the original dentures or the new dentures. In most instances there was a slight decline in performance. Three denture modifications caused significant declines in the carrot-swallowing threshold performances and the new dentures in the peanut-swallowing threshold performance. In other words, the denture wearers had a greater percentage of coarse particles in their bolus ready for ingestion when they chewed with altered or new dentures compared with original dentures. However, they chewed faster and applied fewer chewing strokes with their modified and new dentures. A steady but gradual improvement in the mean performance score with carrots was noted with time after the insertion of new dentures. Dentists and patients need to understand that adaptation to new or modified old dentures may be a long, drawn-out process for some patients.

Masseter muscle activity in denture wearers with superior and poor masticatory performance.

A cross-sectional study tested the hypothesis that denture wearers with superior and poor chewing ability use similar masseter muscle effort and biting forces during mastication. Masticatory performance tests on the preferred chewing side and swallowing threshold tests were conducted with peanuts and carrots in 70 denture wearers, 35 with superior (SP) (mean 46.3%) and 35 with poor (PP) (mean 30.7%) masticatory performance. Right and left masseter muscle electromyographic (EMG) activity was recorded during the masticatory tests and peak bite force during chewing was estimated from the bite force--EMG ratios on guided maximal biting trials. Bite force under maximal pressure did not differ significantly between the two groups. Neither the total mean EMG activity of the preferred and nonpreferred side masseter muscles nor the mean peak biting forces exerted by the two groups differed significantly (p > 0.05). This was true when denture wearers restricted chewing to their preferred side for a given number of strokes or chewed the test food freely until ready to swallow. The only significant differences (p < 0.05) were evident in the ratios of the preferred to nonpreferred side masseter EMG activity during chewing. The ratios were 1.2 for peanuts and 1.3 for carrots in the SP group compared to 1.8 for both foods in the PP group. Similar patterns of bilateral activity in the SP group and unilateral activity in the PP group were evident for the swallowing threshold tests. The results indicated that application of more equivalent force by the right and left masseter muscles during unilateral chewing is consistent with improved chewing ability in denture wearers.

Oral stereognostic ability and masticatory performance in denture wearers.

This study examined the relationship between masticatory performance and oral stereognostic ability in 71 dentate individuals and 64 denture wearers. Stereognosis was evaluated in denture wearers with and without dentures in place. No significant differences (P > .05) were noted between the stereognostic scores of either group, with both groups correctly identifying approximately 68% of the items. This suggests that the receptors in the periodontal ligament are of minimal importance in the oral detection of shape and that the loss of teeth and placement of dentures does not diminish the perception of shape differences. Correlations between masticatory performance and stereognostic measures ranged in magnitude from 0.01 to 0.12 (P > .05). Further studies employing smaller test forms may be needed to assess the role of stereognosis on food manipulation during mastication.

Comparisons of tactile thresholds between implant-supported fixed partial dentures and removable partial dentures.

This study compared the tactile sensitivity of splinted abutment and denture teeth of 16 fixed partial dentures (FPD) supported by blade implants and 16 removable partial dentures (RPD) in patients with Kennedy Class I and Class II edentulous conditions. No significant differences were noted between the tactile thresholds of the natural abutment teeth and artificial teeth in the FPD and RPD groups. The splinted abutment teeth required 45.4 g, or 5.4 to 5.8 times higher occlusal loads than did those needed for the comparable nonsplinted teeth, to detect the stimulus. A further increase of 54% in thresholds with the FPD and over 100% with the placement of the RPD indicated the superiority of the RPD in terms of load distribution as a result of the cross-arch splinting and mucosal support. Moderate positive correlations (r = 0.37 to 0.46; P < .05) between tactile thresholds and masticatory performance were found, signifying that reduced tactile perception was not responsible for the incomplete restoration of the masticatory function with RPDs or FPDs but might be contributing to increased masticatory performance within both treatment groups.