Mastication and jaw motion of partially edentulous patients are affected by different implant‐based prostheses

The main goal of prosthetic treatment is to restore masticatory function. However, insufficient evidence supports the recommendation of one specific prosthetic intervention for partially edentulous patients. Function after the use of three different prostheses by the same partially edentulous subject. Mastication was assessed in 12 subjects (mean age 62·6 ± 7·8 years) after they had used removable partial dentures (RPDs), implant‐supported partial dentures (IRPDs) and implant‐fixed partial dentures (IFPDs). Masticatory ability (MA) was estimated by visual analogue scale questionnaire, while the mandibular chewing motion was evaluated by kinesiographic device, representing an objective measurement of masticatory function. Data were analysed by repeated‐measures anova followed by Tukey–Kramer (P < 0·05). MA improved after IRPD and IFPD use (P < 0·05). Opening, closing and total cycle time duration were reduced after both IRPD and IFPD use (P < 0·05), irrespectively the implant prosthesis type. IFPDs and IRPDs restore the masticatory function of partially edentulous patients better than RPDs.     

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.     

Oral health‐related quality of life in patients with non‐metal clasp dentures: a randomised cross‐over trial

We investigated the efficacy of non‐metal clasp dentures (NMCDs) with regard to the oral health‐related quality of life (OHRQoL) and compare the findings with those for conventional metal clasp‐retained dentures (MCDs). This single‐centre, randomised controlled, two‐phase, open label, cross‐over trial included 28 partially dentate individuals. The patients were randomised to receive MCDs followed by NMCDs, or the opposite sequence (n = 14 in each group); each denture was worn for 3 months. OHRQoL was evaluated using the Oral Health Impact Profile‐Japanese version (OHIP‐J) at entry (T‐entry; before treatment with the first denture) and at 3 months after treatment with each denture (T3). An examiner evaluated denture stability, oral appearance and surface roughness before denture delivery (T0) and at T3 and denture hygiene at T3. A total of 24 patients completed the trial. There were no complications related to the dentures, abutment teeth or denture‐bearing mucosa during the follow‐up periods for both dentures. The mean OHIP summary score was lower for NMCDs than for MCDs, and the difference (9 points) was greater than the minimal important difference (6 points), indicating the difference was clinically relevant. The effect size was medium (0·70). Statistical analyses with linear mixed models found a significant effect of the denture type on the OHIP summary score and scores for the Oro‐facial appearance, Oro‐facial pain and Psychological impact domains (NMCD < MCD; P < 0·05). The results of our study suggest that NMCDs allow for better OHRQoL compared with MCDs.     

A field survey of the partially edentate elderly: Investigation of factors related to the usage rate of removable partial dentures

Although the shortened dental arch (SDA) concept has been known to all over the world, acceptance of the SDA concept as an oral health standard can be questionable from the patients' point of view, even if it is biologically reasonable. Furthermore, because the health insurance system covers removable partial dentures (RPDs) for all citizens in Japan, SDA patients seem to prefer to receive prosthetic treatment to replace the missing teeth. However, there were few field surveys to investigate the usage rate of RPDs in Japan. The purpose of this study was to determine the usage rate of RPDs in older Japanese subjects and to investigate the factors related to the usage of RPDs. Partially edentate participants (n = 390) were included in this study. Oral examinations were conducted to record several indices. The Cochran–Armitage trend test was used to evaluate the relationship between the number of missing teeth and the usage rate of RPDs. Chi‐squared tests and logistic regression analysis were conducted to evaluate the factors related to the usage rate of RPDs. Usage of RPDs had a significantly positive association with the number of missing distal extension teeth and bilaterally missing teeth. The usage rate of RPDs increased as the number of missing distal extension teeth increased (P for trend < 0·001). The conclusion of this study was that participants with missing distal extension teeth had higher usage rates of RPDs than other participants, and the usage rate increased as the number of missing distal extension teeth increased.     

Oral health‐related quality of life of removable partial denture wearers and related factors

This study aims to investigate the oral health‐related quality of life (OHRQoL) in a group of removable partial denture (RPD) wearers in Shiraz (Iran), using the Persian version of the Oral Health Impact Profile (OHIP‐14). Two hundred removable partial denture wearers had completed a questionnaire regarding patients' demographic characteristics and denture‐related factors. In addition, the OHIP‐14 questionnaire was filled out by interviewing the patients. Two measures of interpreting the OHIP‐14 scales were utilised: OHIP‐14 sum and OHIP‐14 prevalence. The relationship of the patients' demographic characteristics and denture‐related factors, with their OHRQoL was investigated. The mean OHIP‐14 sum and OHIP‐14 prevalence of RPD wearers were 13·80 (±10·08) and 44·5%, respectively. The most problematic aspects of OHIP‐14 were physical disability and physical pain. Twenty‐seven percentage and 24% of participants had reported meal interruption and eating discomfort, respectively. OHIP‐14 prevalence and OHIP‐14 sum were found to be significantly associated with factors representing RPD wearer's oral health such as self‐reported oral health and frequency of denture cleaning. Furthermore, OHIP‐14 prevalence and OHIP‐14 sum were significantly associated with factors related to frequency of denture use such as hours of wearing the denture during the day and wearing the denture while eating and sleeping. Therefore, it can be concluded that the OHRQoL of the patients of the study was generally not optimal and found to be strongly associated with oral health.     

Oral health-related quality of life in patients treated by implant-supported fixed dentures and removable partial dentures

Objectives: This study investigated the association between denture status [implant‐supported fixed dentures (IDs) and removable partial dentures (RPDs)] and oral health‐related quality of life (OHRQoL). Materials and methods: Consecutive patients with IDs and RPDs were recruited from the Prosthodontics Departments at Showa University and Tokyo Medical and Dental University. The Japanese version of the Oral Health Impact Profile (OHIP‐J‐49) was administered to each subject. For each OHIP‐J‐49 question, the subjects were asked to indicate the frequency with which they had experienced a dental problem during the last month. Responses were recorded on a 5 point Likert rating scale, with 0 being never and 4, very often. Summary scores were calculated and regression analyses conducted to investigate the association between denture status and OHIP‐J‐49 summary score. Results: In total 79 ID subjects (mean age±SD of 51.7±12.4 years, 44.3% men) and 109 RPD subjects (mean age of 66.5±8.6 years, 30% men) participated after giving informed consent. The regression analysis between the type of treatment and the OHIP‐J‐49 summary score revealed a significant association with a coefficient of 17.0 (Confidence interval, CI: 10.9–23.1). When age and duration of denture usage, which had significant associations with OHIP‐J‐49, were included in this model, the regression coefficient remained virtually unchanged at 17.4 (CI: 9.75–25.0), thus indicating little potential confounding by them. Conclusions: OHRQoL in patients with implant‐supported fixed dentures is generally less impaired than it is in those patients with RPDs. To cite this article :
Furuyama C, Takaba M, Inukai M, Mulligan R, Igarashi Y, Baba K. Oral health‐related quality of life in patients treated by implant‐supported fixed dentures and removable partial dentures.
Clin. Oral Impl. Res. 23 , 2012; 958–962
doi: 10.1111/j.1600‐0501.2011.02247.x     

Shortened dental arch and prosthetic effect on oral health‐related quality of life: a systematic review and meta‐analysis

This systematic review aimed to compare oral health‐related quality of life (OHRQoL) between two tooth replacement strategies – the shortened dental arch (SDA) concept and conventional treatment with removable partial dental prosthesis (RPDP) or implant‐supported fixed partial dental prosthesis (IFPDP) – for distal extension of edentulous space in the posterior area. We retrieved eligible randomised controlled trials (RCTs) and non‐RCTs published between 1980 and November 2016 retrieved from MEDLINE and the Cochrane Central Register of Controlled Trials. The primary outcome was OHRQoL evaluated using validated questionnaires. Two reviewers independently screened and selected the articles, evaluated the risk of bias and determined the standardised weighted mean difference (SWMD) in OHRQoL scores between the two strategies using a random effects model. Two RCTs and one non‐RCT involving 516 participants were included in this review. All studies employed the oral health impact profile (OHIP) for evaluation of OHRQoL. There was no statistically significant difference in OHIP summary scores between SDA and RPDP at 6 (SWMD = 0·24) or 12 (SWMD = 0·40) months post‐treatment. Only one non‐RCT had reported higher OHRQoL with IFPDP than with SDA; however, because of the small sample size, there was no significant difference in OHIP summary scores between the two strategies at 6 (SWMD = ?0·59) or 12 (SWMD = ?0·67) months post‐treatment. In terms of OHRQoL in partially dentate patients, the SDA concept appears to be as feasible as RPDP restoration. Further clinical trials are required to clarify the effect of IFPDP restoration on OHRQoL.     

General population norms of the Swedish short forms of Oral Health Impact Profile

We reported the development and psychometric evaluation of a Swedish 14‐item and a five‐item short form of the Oral Health Impact Profile. The 14‐item version was derived from the English‐language short form developed by Slade in1997. The five‐item version was derived from the German‐language short form developed by John et al. in 2006. Validity, reliability and normative values for the two short form summary scores were determined in a random sample of the adult Swedish population (response rate: 46%, N = 1366 subjects). Subjects with sufficient OHRQoL information to calculate a summary score (N = 1309) were on average 50·1 ± 17·4 years old, and 54% were women. Short form summary scores correlated highly with the 49‐item OHIP‐S (r ≥ 0·97 for OHIP‐S14, r ≥ 0·92 for OHIP‐S5) and with self‐report of oral health (r ≥ 0·41). Reliability, measured with Cronbach's alpha (0·91 for OHIP‐S14, 0·77 for OHIP‐S5), was sufficient. In the general population, 50% of the subjects had ≥2 OHIP‐S14 score points and 10% had ≥11 points, respectively. Among subjects with their own teeth only and/or fixed dental prostheses and with partial removable dental prostheses, 50% of the population had ≥2 OHIP‐S14 score points, and 10% had ≥11 points. For subjects with complete dentures, the corresponding figures were 3 and 24 points. OHIP‐S5 medians for subjects in the three population groups were 1, 1 and 2 points. Swedish 14‐item and 5‐item short forms of the OHIP have sufficient psychometric properties and provide a detailed overview about impaired OHRQoL in Sweden. The norms will serve as reference values for future studies.     

A systematic review of prosthetic restoration in patients with shortened dental arches

The literature regarding the effect of prosthetic restoration in patients having distal extension edentulous space in posterior area (shortened dental arch: SDA) is reviewed in the following article. Information retrieval followed a systematic approach using PubMed. Articles in English published between 1966 and March 2011 describing the outcome of treatment with various prostheses were evaluated. From the search results of 98 articles, 21 articles met the inclusion criteria. Treatment with removable partial dentures (RPDs) improved masticatory function, patient satisfaction and oral health-related quality of life (OHRQoL). However, no significant difference was found in the outcomes between patients with RPDs and with cantilever fixed partial dentures (CFPDs). Caries developed more frequently after treatment with RPDs than CFPDs. The time to survival for CFPDs was not longer than that for RPDs, while more visits to maintain RPDs were required than for CFPDs. No significant difference was found in masticatory function, OHRQoL, and occlusal stability between patients with RPDs and those without restoration of missing molars. Consequently, treatment with RPDs for SDA seems to be less advantageous than CFPDs or no restoration for missing molars. Further research is required to validate treatment with implant-supported fixed partial dentures for SDA.     

Effect of dietary counselling with prosthetic restoration on fruit and vegetable intake in partially dentate patients: A prospective study

The aim of this study was to investigate the effects of a counselling‐based dietary intervention on nutritional status in partially dentate patients receiving removable partial dentures (RPDs). Thirty‐eight patients [mean age (standard deviation): 73.2 (7.7) years] who were scheduled to receive RPDs at a dental hospital and were currently eating <350 g of vegetables per day were included in the study. A dentist provided basic dietary counselling aimed at increasing dietary fruit and vegetable intake and improving dietary habits. Patients received dietary counselling directly after treatment with new RPDs and at 1 week after a 1‐month follow‐up evaluation (T1). Food intake was assessed via a validated brief‐type self‐administered diet history questionnaire, and carotenoids and vitamin C in 6‐hour fasting blood samples were measured before RPD administration, and at 1 (T1) and 3 months (T3) thereafter. Vegetable but not the fruit intake increased significantly at T1 and T3 compared to before treatment. Alpha carotene significantly increased at T3 while β significantly increased both at T1 and T3 compared to before treatment (P < .05). The number of occlusal units on natural teeth was significantly positively associated with increased vegetable and β‐carotene intake (P < .05). Serum carotenoids and vitamin C levels measured with 6‐hour fasting blood samples remained constant. These results suggest that basic dietary counselling may improve vegetable intake in partially dentate patients receiving RPD treatment, but did not lead to haematological changes. The presence of occlusion of remaining posterior teeth may be critical for improving vegetable intake.     

Oral health‐related quality of life and complications after treatment with partial removable dental prosthesis

The aims of this study were to measure and describe the oral health‐related quality of life (OHRQoL) and to identify the complications caused by partial removable dental prosthesis (RDPs) in patients 1–5 years after treatment. Complications were identified in 65 patients who were treated with 83 RDPs (48 upper, 35 lower). OHRQoL was measured using the OHIP‐49 before treatment and at the baseline (1–2 months after treatment) and follow‐up (1–5 years after treatment) examinations. The types and numbers of oral problems that were experienced were described based on OHIP items with a score of 3 and 4. A significant improvement (P < 0·05) in the total OHIP‐49 was registered from pre‐treatment (mean 42, SD ± 37) to baseline (mean 29, SD ± 27) and from pre‐treatment to 1–5 years after treatment (mean 32, SD ± 30). There was no significant difference between the baseline and 1‐ to 5‐year follow‐up examinations. Problems with eating and appearance registered at pre‐treatment were improved at baseline and after 1–5 years. Problems with dentures that had been registered pre‐treatment were improved at baseline but reoccurred after 1–5 years. The two most frequent complications were ill‐fitting RDPs and inflammation of the oral mucosa, followed less frequently by fractures of the clasps. Treatment with RDPs improved OHRQoL, but denture‐related problems partly remained, and new problems related to RDPs occurred 1–5 years after treatment. The two most frequent complications were ill‐fitting RDPs and inflammation of the oral mucosa.     

The effect of implant placement in patients with either Kennedy class II and III on oral health‐related quality of life: a prospective clinical trial

There is little evidence of the effect of implants restored with fixed partial dentures on oral health‐related quality of life (OHRQoL) in partially edentulous Kennedy class II and III patients. The aim of this study was to determine the change in OHRQoL in Kennedy classification II and III patients treated with a two‐implant‐supported fixed dental prosthesis (FDP). Kennedy class II and III patients received dental implants and an FDP. Oral health‐related quality of life was measured by administration of the Oral Health Impact Profile‐14 (OHIP‐14NL) questionnaire at intake (T1), 2 weeks after surgery (T2) and after 1 year of loading (T3). The mean OHIP score at T1 was 6·5 ± 1·2, 2·4 ± 1·0 at T2, and 0·9 ± 0·3 at T3. There was a statistically significant difference between T1 and T2 (P = 0·002) and T1 and T3 (P < 0·001) but not between T2 and T3 (P = 0·407). The OHIP score in Kennedy II patients decreased from 4·8 ± 3·2 at T1 to 1·5 ± 2·0 at T2 and 1·1 ± 1·8 at T3, and that in Kennedy III patients decreased from 8·9 ± 9·6 at T1 to 3·6 ± 8·9 at T2 and 0·8 ± 2·2 at T3. There were no statistically significant differences in the reductions in Kennedy II and III patients. Oral health‐related quality of life changed positively in patients treated with implants and an FDP in both groups. There was no change in OHRQoL between the times of implant placement and FDP placement.     

A comparison of oral health related quality of life between complete and partial removable denture-wearing older adults in Korea

The purpose of this study was to compare the oral health related quality of life (OHRQoL) between older Korean adults with complete and partial removable dentures using oral health impact profile (OHIP). A pool of 4250 Korean older adults was identified by random stratification by area from the sample cohort of Korean National Survey of Oral Health in the year of 2000. Out of the potential pool, 445 subjects with removable partial dentures (RPDs) or complete dentures (CDs) agreed to be interviewed by telephone. Each question in the survey was about how frequently each event was experienced during the past 12 months. To analyse the association between OHIP scores and removable denture status, bivariable analysis and multiple linear regression analysis were used. RPD users showed higher scores on eight items than CD users. They were 'breath stale', 'food catching', 'sensitive teeth', 'toothache', 'tense', 'unable to brush teeth', 'less tolerant to family members' and 'irritable with others'. RPD users might be associated with higher scores of functional limitation, physical pain and psychological discomfort than CD users. RPD users had slight tendency to be associated with higher OHIP-49 score than CD users, but it was not statistically significant. The findings of the present study confirm that there is no general OHRQoL difference between RPD and CD users. But in the items and subscales of OHIP, RPD users might experience more impaired OHRQoL than CD users.     

Oral health‐related quality of life,oral aesthetics and oral function in head and neck cancer patients after oral rehabilitation

Head and neck cancer (HNC) is diagnosed in more than 500 000 patients every year worldwide with increasing prevalence. Oral rehabilitation is often needed after HNC treatment to regain oral function, aesthetics and oral health‐related quality of life (OHRQoL). The objectives were to evaluate OHRQoL, oral aesthetics and oral function after oral rehabilitation in HNC patients and compare it to that of non‐HNC patients. Eighteen patients treated for HNC who subsequently had oral rehabilitation (2014‐2017), and a control group of eighteen age‐ and gender‐matched non‐HNC patients treated with removable prostheses (2014‐2018) were included in a cross‐sectional study. The OHRQoL was assessed by the Oral Health Impact Profile 49 questionnaire (OHIP‐49), the oral aesthetics by the Prosthetic Esthetic Index (PEI) and the Orofacial Esthetic Scale (OES), and the oral function by the Nordic Orofacial Test‐Screening (NOT‐S). The HNC patients had worse oral function and OHRQoL than the control patients (mean NOT‐S score 4.56 vs 0.56, P < 0.01 and mean OHIP‐49 score 42.50 vs 20.94, P = 0.050). When including number of replaced teeth and type of prosthesis in the tests, no significant difference in OHRQoL was found between the groups. No difference was found in the overall aesthetic outcomes (mean PEI total score 32.28 vs 30.67, P = 0.367 and mean OES total score 48.78 vs 53.56, P = 0.321). Multiple regression analyses showed that being HNC patient compared to control patient impaired the oral function. Oral function is significantly impaired in HNC patients compared to non‐HNC patients after oral rehabilitation.     

Neutral zone or conventional mandibular complete dentures: a randomised crossover trial comparing oral health‐related quality of life

There is widespread consensus that the neutral zone (NZ) concept contributes to improved stability for mandibular complete dentures (CDs). However, little is known about its impact on oral health‐related quality of life (OHRQoL) of edentulous patients compared to conventionally (CV) manufactured dentures. In this prospective crossover trial, performed at the Oral Health Centre of the University of the Western Cape, CV and NZ mandibular dentures were made for each patient. Scores from the 20‐item oral health impact profile (OHIP‐20) for both types of dentures were compared with pre‐treatment scores using paired t‐tests. Treatment effect size (ES) was established. Associations of OHIP‐20 scores and several patient variables (age, gender, period of edentulousness, quality of the denture‐bearing tissue, denture dimensions, preference) were performed using the generalised linear model. Significance was set at P = 0·05. Records of thirty‐five participants were included in the study (mean age of 62·3 years, range 47–85 years). There were highly significant differences between pre‐treatment and both post‐treatment OHIP‐20 scores with t = 6·470 for CV and t = 6·713 for NZ. Treatment ES was large for both types of dentures (>0·8). Difference of ES between NZ and CV dentures was small (ES < 0·2). None of the patient variables showed significant associations with OHIP‐20 scores of the two types of dentures, except for preference and NZ OHIP‐20 scores. For this group of patients, both treatment methods improved OHRQoL significantly and patient‐related factors did not influence impact on OHRQoL differently for both interventions.     

A survey of treatment outcomes with removable partial dentures

The patient's satisfaction with removable partial denture (RPD) therapy has become an increasingly important factor in prosthetic treatment. This study examined patients' satisfaction with RPDs in relation to some socio-economic variables, patients' habits of wearing and cleaning RPDs, comfort of wearing RPDs and different RPDs characteristics. A questionnaire was devised for the purpose. Two hundred and five patients were required to assess satisfaction with RPDs. They graded RPDs, depending on the level of satisfaction, on scale ranging from 1 to 5. A dentist determined Kennedy classification, material and denture support, denture base shape, number of missing teeth and evaluated denture construction. Majority of the patients were satisfied with the prosthesis. The patients of a higher education level gave lower grades (P < 0.05) to aesthetics of maxillary RPDs. Almost half of the patients were wearing RPDs during the day. Most of the patients cleaned RPDs three times a day. A significant difference was found between the patients' grades for comfort of wearing mandibular RPDs and number of missing teeth and between hygiene of mandibular RPDs and habits of cleaning them. Majority of the patients treated with RPDs were satisfied with the prosthesis. Dissatisfaction was related to mastication, esthetics, number of missing teeth and maintenance of oral hygiene.     

Treatment planning for replacing missing teeth in UK general dental practice: current trends

Summary The aim of this study was to examine the confidence, barriers and attitudes towards the replacement of missing teeth by general dental practitioners (GDPs). The perceived impact of the recently introduced National Health Service (NHS) contract on the provision of prosthodontic treatments was also considered. Pre‐piloted postal questionnaires were mailed to 500 GDPs in Wales. Open‐ and closed‐ended questions were utilised to establish confidence, adequacy of training and attitudes towards treatments for replacing missing teeth. Two hundred and seventeen completed questionnaires were received (response rate = 43·4%). Many respondents described themselves as ‘confident’ or ‘very confident’ in the provision of removable partial dentures (RPDs) (acrylic = 100%, metal based = 99·5%), cantilever resin‐bonded bridges (94·4%) and conventional bridgework (98·6%). GDPs were ‘not confident’ providing fixed‐fixed resin‐bonded bridges (21·1%) or implants (81·4%). Financial barriers were identified to the provision of prosthodontic treatments, including comments such as “the new [National Health Service] contract does limit the treatments available”. Privately funded patients were more likely to be offered a fixed bridge or implant replacement of a missing upper first molar, whereas non‐privately funded patients were more likely to be offered no treatment (P < 0·01). Most respondents reported confidence at providing more routine forms of prosthodontic care such as RPDs and bridges. It appears that funding arrangements may have an impact on treatments offered to replace missing teeth, particularly under the current NHS contract.     

Effect of complete and partial removable dentures on chewing movements

Partial or complete edentulism impairs mastication. However, it is unclear how the chewing cycle is affected by prosthetics. We evaluated the chewing movements of patients fitted with complete (CD) or removable partial denture (RPD). A total of 29 subjects were kinesiographically evaluated during chewing of peanuts and Optocal portions in a random sequence. The subjects were divided into two groups according to prosthesis type. Group RPD was composed of 14 partially edentulous patients using a lower distal extension RPD (mean age 61 ± 8 years), and group CD contained 15 completely edentulous patients using CD (mean age 65·9 ± 7·9 years) in both jaws. Opening, closing, occlusal and masticatory cycle times, movement angle (opening and closing), maximum velocity (opening and closing), total area and chewing cycle amplitudes were evaluated. The results were subjected to anova and Tukey's HSD test at a significance level of 5%. The RPD group exhibited shorter opening and closing phases and masticatory cycle time (P < 0·05). Maximum velocities were also higher in the RPD group, irrespective of the test material (P < 0·05). The area and amplitude of the chewing envelope was smaller in the CD group (P < 0·0001). The test material did not influence chewing cycles in any of the parameters evaluated (P > 0·05). RPD wearers use a faster chewing sequence with greater vertical and lateral jaw excursions compared with CD wearers.     

Influence of posterior dental arch length on brain activity during chewing in patients with mandibular distal extension removable partial dentures

It is well known that shortened dental arch decreases masticatory function. However, its potential to change brain activity during mastication is unknown. The present study investigates the effect of a shortened posterior dental arch with mandibular removable partial dentures (RPDs) on brain activity during gum chewing. Eleven subjects with missing mandibular molars (mean age, 66·1 years) on both sides received experimental RPDs with interchangeable artificial molars in a crossover trial design. Brain activity during gum chewing with RPDs containing (full dental arch) and lacking artificial molars (shortened dental arch) was measured using functional magnetic resonance imaging. Additionally, masticatory function was evaluated for each dental arch type. Food comminuting and mixing ability and the perceived chewing ability were significantly lower in subjects with a shortened dental arch than those with a full dental arch (P < 0·05). Brain activation during gum chewing with the full dental arch occurred in the middle frontal gyrus, primary sensorimotor cortex extending to the pre‐central gyrus, supplementary motor area, putamen, insula and cerebellum. However, middle frontal gyrus activation was not observed during gum chewing with the shortened dental arch. These results suggest that shortened dental arch affects human brain activity in the middle frontal gyrus during gum chewing, and the decreased middle frontal gyrus activation may be associated with decreased masticatory function.     

A retrospective comparative ten-year study of cumulative survival rates of remaining teeth in large edentulism treated with implant-supported fixed partial dentures or removable partial dentures

PurposeThis study aimed to compare the survival rates of remaining teeth between implant-supported fixed dentures (IFDs) and removable partial dentures (RPDs) in patients with large edentulous cases. The second goal was to assess the risk factors for remaining tooth loss.Materials and methodsThe study subjects were selected among those who received prosthodontic treatment at Okayama University Dental Hospital for their edentulous space exceeding at least four continuous missing teeth. Twenty-one patients were included in the IFD group and 82 patients were included in the RPD group. Survival rates of remaining teeth were calculated in three subcategories: (1) whole remaining teeth, (2) adjacent teeth to intended edentulous space, and (3) opposing teeth to intended edentulous space.ResultsThe ten-year cumulative survival rate of the whole remaining teeth was significantly higher in the IFD group (40.0%) than in the RPD group (24.4%). On the other hand, there was no significant difference between two groups in the survival rate of teeth adjacent or opposing to intended edentulous space. A Cox proportional hazard analysis revealed that RPD restoration and gender (male) were the significant risk factors for remaining tooth loss (whole remaining teeth).ConclusionsThese results suggest that IFD treatment can reduce the incidence of remaining tooth loss in large edentulous cases.