Abstract
Objectives
With a decreased number of teeth, a reduction in chewing function can contribute to changes in food choices and ultimately impact on overall nutritional status. This study compared the impact of two tooth replacement strategies for partially dentate older patients on masticatory performance and nutritional status.
Methods
Patients aged 65 years and older were randomly allocated to two different treatment groups. For the RPDP-group (removable partial dental prostheses) each participant was restored to complete dental arches with cobalt-chromium removable prostheses. For the SDA-group (shortened dental arch), participants were restored to 10 occluding pairs of natural and replacement teeth using adhesive bridgework. Masticatory performance was assessed with a colour-mixing ability test. Each patient provided haematological samples that were screened for biochemical markers of nutritional status. Patients were also assessed using the Mini Nutritional Assessment (MNA).
Results
Eighty-nine patients completed the test for masticatory performance and provided blood samples and MNA scores at baseline (BL) and after 12 months (12 m). Masticatory performance (p < 0.001) and MNA (p < 0.05) increased significantly in both groups, but no significant between group differences were noted. A mixed picture was observed for nutrition biomarkers. Mixed-effect linear regression models did not demonstrate that nutritional status could be predicted from masticatory performance.
Conclusions
These results indicate that prosthodontic rehabilitation according to the principles of the SDA is equivalent to RPDPs in terms of restoration of chewing capacity for partially dentate older patients. However, masticatory performance may only have minor associations with nutritional status for this patient group.
Clinical significance
Replacing teeth with either RPDPs or SDA provides a prerequisite for efficient chewing. Further research is required to determine the impact of oral rehabilitation coupled with nutritional counselling for this patient population.
1
Introduction
As preventative strategies continue to advance, more and more older adults are now retaining natural teeth into old age. This trend can be seen throughout most of the western world and has resulted in an increasing proportion of partially dentate older patents. Consequently, the prevalence of edentulism is becoming an increasingly scarce condition in high-income households in countries such as North America . Projections suggest that in future, edentulousness will be seen almost exclusively within the older, economically deprived population. Whilst natural tooth retention is a very positive development, natural teeth are at significant risk from chronic dental diseases particularly when coupled with hyposalivation . Age-related systemic diseases can make it extremely difficult to clean remaining natural teeth and removable dental prostheses, therefore the maintenance burden is very high. In a review, Gonda et al. state that removable partial dental prostheses (RPDP) may be a significant factor for further multiple tooth loss and have the potential to contribute to oral disease .
In older people, it has been shown that the perceived ability to chew foods is closely associated with the number of natural teeth remaining, as well as the number of occluding pairs of teeth . There are many factors that can potentially influence food choice, such as socio-economic status, cultural beliefs and personal preference. However the physical ability to bite and chew is also very important . There is evidence to suggest that a reduction in the number of natural teeth can subsequently reduce chewing ability, with edentate patients demonstrating poorer chewing ability compared to patients who are dentate . This has been shown to result in changes in food choice behaviour, as well as a decreased enjoyment of food . Further, a reduced, unrestored dentition is associated with increased mortality risk . When fewer natural teeth are present, older adults tend to develop food choice habits based around foods that are softer and easier to chew. Further, for example, serum 25-hydroxyvitamin D was inversely associated with incidence of tooth loss and might be a protective factor for tooth loss . However, these soft foods are often low in nutrients and fibre but high in calories and complex carbohydrates . Some of the possible reasons for this are thought to be difficulty in chewing hard foods such as certain raw vegetables and fruits, and a diminished sense of taste.
Chewing is a complex function of the oro-facial system. The ultimate goal is to break down and lubricate foodstuffs, and thus form a cohesive bolus that is safe to swallow . This process involves numerous structures including muscles, mucosa, salivary glands, central and peripheral nerves as well as cortical and basal structures and receptors . However, the most important predictor for masticatory function is the number and distribution of natural teeth and dental prostheses . Loss of occluding tooth pairs can result in reduced chewing efficiency and may in turn influence nutritional status. . Chewing efficiency with a reduced dentition may result in a reduction in masticatory performance by up to 40% and RPDPs may only partially compensate this functional deficit . Prosthodontic rehabilitation has previously been demonstrated to provide mixed results in improving masticatory ability in partially dentate older patients .
The aim of this study was to compare the chewing efficiency of partially dentate older patients with RPDP with those restored to a SDA. The study also aimed to investigate if an improvement in masticatory function was associated with an improvement in overall nutritional status.
2
Material and methods
2.1
Study design
A randomised controlled clinical trial (RCT) was conducted to compare the two treatment modalities (Trial Registration no. ISRCTN26302774). The inclusion criteria for patients involved in the study were: aged 65 years and older; minimum of six remaining sound natural teeth in either arch, seeking replacement for missing natural teeth; ability to accept routine dental care in a dental chair ; no medical conditions which could prevent routine dental treatment. Two centres were used for patient recruitment; Cork University Dental Hospital (CUDH) and St Finbarr’s Geriatric Day Hospital (SFDH) in Cork, Ireland. Patients recruited from SFDH represented an older and more systemically unwell cohort. Before treatment commenced, written information regarding the proposed treatment was provided for each patient involved in the study, and each patient also completed a written consent form prior to treatment. The Cork Teaching Hospitals Ethics Committee granted full ethical approval for the study (ref: ECM 5 (9) 05/02/08).
2.2
Randomisation
In this study patients were randomly allocated to one of two treatment groups; the RPDP treatment group, or the SDA treatment group. A computer-generated schedule in SAS© was utilised to perform the randomization remote from the clinical setting. The randomisation was stratified according to gender and age, and was carried out in blocks of varying length. For both the CUDH and SFDH recruitment sites a separate schedule for the randomisation was produced. Both the RPDP and SDA treatment groups contained patients recruited from both recruitment sites, and these were randomised independently. The randomisation procedure was performed by a research assistant, and the allocation of treatment groups was carried out by the clinical operator who was blinded to the allocation. For the duration of the study patients were assessed using an intention to treat analysis; patients were analysed according to the initial treatment intent (determined by the randomisation process), and not the treatment eventually administered.
2.3
Operative care
For the patients to be involved in the study they were required to be dentally fit. Prior to treatment onset they received standardised dental care which included extraction of unrestorable teeth, restoration of caries and replacement of defective direct restorations, extensive oral hygiene instruction and non-surgical periodontal treatment. The patients within the RPDP group had complete arch restoration; with missing teeth replaced using cobalt-chromium frameworks. For the SDA group patients, adhesive resin bonded bridgework (RBB) was carried out according to a standardised protocol throughout the arch to restore patients to a premolar occlusion of 10 occluding pairs of natural and replacement teeth. Posterior teeth distal to the SDA were left unopposed. Minimal tooth preparation within enamel only was carried out to produce retentive forms and increase the surface area for bonding. For the purpose of this study the RPDP and RBB used were constructed by the same dental laboratory and all operative treatment was conducted by a single clinician with postgraduate training in prosthodontics.
2.4
Data collection
The primary outcome measure for this RCT was oral health related quality of life (OHRQoL), which was measured using OHIP-14 . Masticatory performance was included as a secondary outcome measure.
2.4.1
Masticatory performance
Masticatory performance was assessed with a previously validated colour-mixing ability, i.e. bolus-kneading, test . A two-coloured chewing gum (Vivident Fruitswing “Karpuz/Asai Üzümü”, Perfetti van Melle, Turkey) was used. The gum contained a green and dark violet layer with the dimensions 43 × 12 × 3 mm. The gum was relatively soft (Shore hardness OO: green side: mean depth of indentation 0.8 ± 0.08 mm, mean Durometer 67.4, violet side: mean depth of indentation 1.1 ± 0.08 mm, mean Durometer 58.4) and did not adhere to denture resin, artificial teeth or to cast metal frameworks.
The chewing gum was placed in each patient’s mouth and they were asked to chew normally, with the operator counting the chewing strokes. After 20 chewing cycles, the gum was retrieved from the oral cavity and placed in a transparent plastic bag. The gum was then flattened to a 1 mm thick wafer. Both sides of the wafer were scanned with a standard flatbed scanner (Epson Perfection V37, Epson Deutschland GmbH, Kloten, Switzerland) at a resolution of 300dpi and saved in *jpg format. Both images were then jointly imported into the ViewGum © (www.dhal.com) software. The software transformed the images in the HIS (hue, intensity, saturation) colour space and separated semi-automatically the gum from the background. The hue component in this colour space showed two well-separated peaks, when the colours were not mixed. Those peaks gradually merged as the mixing of the colours increased. The variance of hue (VOH) was therefore considered as the measure of mixing . VOH is significantly associated with the number of chewing cycles and correlates to the comminution test . It was therefore used as the measure for masticatory performance in this bolus-kneading test.
2.4.2
Nutritional status
To assess nutritional status, the mini nutritional assessment (MNA) was administered by a research nurse at baseline (pre-treatment) and 12 months post-treatment intervention. The research nurse was blinded to the treatment group allocation of all participants involved. Haematological samples were provided by participants and screened in Cork University Hospital for biochemical markers of nutritional status including serum albumin, serum cholesterol, ferritin, folate, vitamin B12 and 25-hydroxycholecalciferol (vitamin D) according to standard hospital protocols. Haematological samples were collected from each participant at baseline and 12 months post-treatment intervention, by a research nurse blinded to the treatment group allocation.
2.5
Sample size calculation
A power calculation was made based on summary OHIP-14 score data from the UK Adult Dental Health Survey as this was the primary outcome measure for the study.
The sample size calculation (α = 0.05, β = 0.8) indicated that 44 patients from both treatment groups were required to complete the study, however the aim was to over-recruit patients to allow for a drop-out rate of up to 30%. The sample size calculation was also checked to ensure validity for masticatory performance as a secondary outcome measure. The null hypothesis tested was that there would be no difference observed in masticatory performance between the RPDP Group and the SDA Group. Data from a previous study employing the same methodology was used . The effect size d was 1.77 for VOH between the investigated groups and it was calculated that a total sample size of 40 (n = 20 in each group) was necessary to achieve sufficient power (α = 0.0001, β = 0.90) to reject the null-hypothesis. The calculation was performed using PS Power and Sample Size Calculations Version 3.1 .
2.6
Statistical analysis
All variables recorded were summarised using appropriate descriptive statistics and graphics, and presented by time-point and treatment group. All statistical analysis was carried out using R, version 3.2.2 (The R Project for Statistical Computing, Vienna, Austria), with the additional package “lme4”. Frequency and descriptive statistics were calculated for numerical and categorical variables (mean, standard deviation, median and quantiles as appropriate). Student’s t -tests were performed to compare means and frequencies were compared using a binomial test for proportions. In order to detect associations between two quantitative variables with a normal distribution, the two variables in question were plotted against each other and a Pearson’s correlation carried out, to indicate the strength and direction of the association between the two variables. Masticatory performance (VOH) was also further analysed with linear regression; with several models being performed to find the optimal predictive structure. Linear mixed effects models were also performed for flexibility for both fixed and random effects and to allow predictors to be controlled for age or gender.
For all analyses performed the level of significance was set to 0.05.
2
Material and methods
2.1
Study design
A randomised controlled clinical trial (RCT) was conducted to compare the two treatment modalities (Trial Registration no. ISRCTN26302774). The inclusion criteria for patients involved in the study were: aged 65 years and older; minimum of six remaining sound natural teeth in either arch, seeking replacement for missing natural teeth; ability to accept routine dental care in a dental chair ; no medical conditions which could prevent routine dental treatment. Two centres were used for patient recruitment; Cork University Dental Hospital (CUDH) and St Finbarr’s Geriatric Day Hospital (SFDH) in Cork, Ireland. Patients recruited from SFDH represented an older and more systemically unwell cohort. Before treatment commenced, written information regarding the proposed treatment was provided for each patient involved in the study, and each patient also completed a written consent form prior to treatment. The Cork Teaching Hospitals Ethics Committee granted full ethical approval for the study (ref: ECM 5 (9) 05/02/08).
2.2
Randomisation
In this study patients were randomly allocated to one of two treatment groups; the RPDP treatment group, or the SDA treatment group. A computer-generated schedule in SAS© was utilised to perform the randomization remote from the clinical setting. The randomisation was stratified according to gender and age, and was carried out in blocks of varying length. For both the CUDH and SFDH recruitment sites a separate schedule for the randomisation was produced. Both the RPDP and SDA treatment groups contained patients recruited from both recruitment sites, and these were randomised independently. The randomisation procedure was performed by a research assistant, and the allocation of treatment groups was carried out by the clinical operator who was blinded to the allocation. For the duration of the study patients were assessed using an intention to treat analysis; patients were analysed according to the initial treatment intent (determined by the randomisation process), and not the treatment eventually administered.
2.3
Operative care
For the patients to be involved in the study they were required to be dentally fit. Prior to treatment onset they received standardised dental care which included extraction of unrestorable teeth, restoration of caries and replacement of defective direct restorations, extensive oral hygiene instruction and non-surgical periodontal treatment. The patients within the RPDP group had complete arch restoration; with missing teeth replaced using cobalt-chromium frameworks. For the SDA group patients, adhesive resin bonded bridgework (RBB) was carried out according to a standardised protocol throughout the arch to restore patients to a premolar occlusion of 10 occluding pairs of natural and replacement teeth. Posterior teeth distal to the SDA were left unopposed. Minimal tooth preparation within enamel only was carried out to produce retentive forms and increase the surface area for bonding. For the purpose of this study the RPDP and RBB used were constructed by the same dental laboratory and all operative treatment was conducted by a single clinician with postgraduate training in prosthodontics.
2.4
Data collection
The primary outcome measure for this RCT was oral health related quality of life (OHRQoL), which was measured using OHIP-14 . Masticatory performance was included as a secondary outcome measure.
2.4.1
Masticatory performance
Masticatory performance was assessed with a previously validated colour-mixing ability, i.e. bolus-kneading, test . A two-coloured chewing gum (Vivident Fruitswing “Karpuz/Asai Üzümü”, Perfetti van Melle, Turkey) was used. The gum contained a green and dark violet layer with the dimensions 43 × 12 × 3 mm. The gum was relatively soft (Shore hardness OO: green side: mean depth of indentation 0.8 ± 0.08 mm, mean Durometer 67.4, violet side: mean depth of indentation 1.1 ± 0.08 mm, mean Durometer 58.4) and did not adhere to denture resin, artificial teeth or to cast metal frameworks.
The chewing gum was placed in each patient’s mouth and they were asked to chew normally, with the operator counting the chewing strokes. After 20 chewing cycles, the gum was retrieved from the oral cavity and placed in a transparent plastic bag. The gum was then flattened to a 1 mm thick wafer. Both sides of the wafer were scanned with a standard flatbed scanner (Epson Perfection V37, Epson Deutschland GmbH, Kloten, Switzerland) at a resolution of 300dpi and saved in *jpg format. Both images were then jointly imported into the ViewGum © (www.dhal.com) software. The software transformed the images in the HIS (hue, intensity, saturation) colour space and separated semi-automatically the gum from the background. The hue component in this colour space showed two well-separated peaks, when the colours were not mixed. Those peaks gradually merged as the mixing of the colours increased. The variance of hue (VOH) was therefore considered as the measure of mixing . VOH is significantly associated with the number of chewing cycles and correlates to the comminution test . It was therefore used as the measure for masticatory performance in this bolus-kneading test.
2.4.2
Nutritional status
To assess nutritional status, the mini nutritional assessment (MNA) was administered by a research nurse at baseline (pre-treatment) and 12 months post-treatment intervention. The research nurse was blinded to the treatment group allocation of all participants involved. Haematological samples were provided by participants and screened in Cork University Hospital for biochemical markers of nutritional status including serum albumin, serum cholesterol, ferritin, folate, vitamin B12 and 25-hydroxycholecalciferol (vitamin D) according to standard hospital protocols. Haematological samples were collected from each participant at baseline and 12 months post-treatment intervention, by a research nurse blinded to the treatment group allocation.
2.5
Sample size calculation
A power calculation was made based on summary OHIP-14 score data from the UK Adult Dental Health Survey as this was the primary outcome measure for the study.
The sample size calculation (α = 0.05, β = 0.8) indicated that 44 patients from both treatment groups were required to complete the study, however the aim was to over-recruit patients to allow for a drop-out rate of up to 30%. The sample size calculation was also checked to ensure validity for masticatory performance as a secondary outcome measure. The null hypothesis tested was that there would be no difference observed in masticatory performance between the RPDP Group and the SDA Group. Data from a previous study employing the same methodology was used . The effect size d was 1.77 for VOH between the investigated groups and it was calculated that a total sample size of 40 (n = 20 in each group) was necessary to achieve sufficient power (α = 0.0001, β = 0.90) to reject the null-hypothesis. The calculation was performed using PS Power and Sample Size Calculations Version 3.1 .
2.6
Statistical analysis
All variables recorded were summarised using appropriate descriptive statistics and graphics, and presented by time-point and treatment group. All statistical analysis was carried out using R, version 3.2.2 (The R Project for Statistical Computing, Vienna, Austria), with the additional package “lme4”. Frequency and descriptive statistics were calculated for numerical and categorical variables (mean, standard deviation, median and quantiles as appropriate). Student’s t -tests were performed to compare means and frequencies were compared using a binomial test for proportions. In order to detect associations between two quantitative variables with a normal distribution, the two variables in question were plotted against each other and a Pearson’s correlation carried out, to indicate the strength and direction of the association between the two variables. Masticatory performance (VOH) was also further analysed with linear regression; with several models being performed to find the optimal predictive structure. Linear mixed effects models were also performed for flexibility for both fixed and random effects and to allow predictors to be controlled for age or gender.
For all analyses performed the level of significance was set to 0.05.
3
Results
3.1
Characteristics of the study participants
A total of 89 participants were recruited into the study and randomly allocated to RPDP group (n = 44) and the SDA group (n = 45), respectively ( Fig. 1 ). At baseline there were no significant differences observed between the two patient groups, with regards to gender, age, number of teeth and number of occluding units (OU). Twelve months after treatment intervention, the RPDP group had a significantly higher number of OU ( Table 1 )) compared to the SDA group (p < 0.0001).
