Validation of a new, specific, complete, and short OHRQoL scale (QoLFAST-10) for wearers of implant overdentures and fixed-detachable hybrid prostheses

Abstract

Objectives

To validate a new index for assessing the whole concept of oral health-related quality of life (OHRQoL) of implant-prosthesis wearers.

Methods

113 patients who were not requesting dental treatment were assigned to: Group 1 (CD; n = 38): complete denture users (control); Group 2 (IO; n = 38): implant overdenture wearers; and Group 3 (HP; n = 37): hybrid implant prosthesis users. Patients answered the newly-designed ‘Quality of Life related to Function, Aesthetics, Socialization, and Thoughts about health-behavioural habits’ (QoLFAST-10) and the Oral Health Impact Profile (OHIP-20sp) questionnaires. Information on global oral satisfaction, socio-demographic, clinical, and prosthetic-related data were gathered. The QoLFAST-10 was investigated for reliability and validity. The Spearman’s test determined the correlations between both indices’ scores. Descriptive and non-parametric probes were run to assess the influence of the study variables on the OHRQoL (α = 0.05).

Results

The QoLFAST-10 confirmed its psychometric capacity. HP wearers reported significantly better global and functional satisfaction than did IO wearers. The latter revealed significantly less consciousness about the importance of health-behavioural habits than did CD and HP groups. The level of education , complaints about the mouth, and the global oral satisfaction measures significantly modulated the QoLFAST-10 scores.

Conclusions

Implant overdentures supplied lower functional and global satisfaction than did hybrid prostheses, and represent the least predictable option concerning the maintenance of the restoration.

Clinical significance

The QoLFAST-10 may help in estimating the impact of implant restorations on patients’ well-being. In this regard, hybrid prostheses seem to be the implant treatment of choice when compared with overdentures.

Introduction

Different scales using a variety of methodological approaches have been designed in previous years to assess the personal self-perception of the oral status . The effect of ‘function’ and ‘comfort’ of total rehabilitations on OHRQoL may be objectified, among others, with the Oral Health Impact Profile (OHIP-20), which is the most widely used instrument in case of edentulism . The recently-introduced Quality of Life with Implant-Prostheses (QoLIP-10) questionnaire has specifically demonstrated its psychometric adequacy for all types of dental implant restorations, and includes items about ‘function’, ‘comfort’ and ‘aesthetics’ . Nevertheless, to date, there is no questionnaire with items related to ‘health-behavioural habits’, which might be relevant for motivating the patients to shift practice toward preventive care , health promotion, and conservation of the oral tissues , and may also depend on the prosthesis design .

On the one hand, implant overdentures have demonstrated significantly higher retention, stability, and functional efficiency, than muco-supported complete dentures . As the latter stay in place with natural suction without implant retention, their mobility may be considered inconvenient . However, the use of conventional complete dentures avoids surgical risks and other difficulties and costs that are inherent in implant therapy .

On the other hand, fixed-detachable hybrid implant prostheses are cantilevered restorations that are screwed onto premaxillary or interforaminal implants (or abutments). They are recommended in absence of osteomucosal support, and are composed of a metallic CAD/CAM framework covered with heat-polymerised resin and prosthetic teeth . Despite being fixed for the patients, which provides many functional and psychological advantages , they are not exempt from other drawbacks such as plaque accumulation, peri -implant inflammatory problems, and/or fracture of the acrylic supraestructure .

This cross-sectional investigation is the first to compare the OHRQoL of patients rehabilitated with implant overdentures and hybrid implant prostheses through the use of a new customised index (‘QoLFAST-10′) that includes all of the possible areas through which the QoL (Quality of Life) concept may be defined . These areas of evaluation are represented in the name of the scale (function, aesthetics, socialization, and thoughts about health behavioural habits). The initials of these key words form the acronym ‘FAST’, remarking that it is a short, and, then, a more applicable and effective questionnaire .

Given the lack of complete indicators for measuring the impact of implant prostheses on daily life, the aim of this paper is to develop and validate an effective, short, and specific scale for assessing the OHRQoL of implant overdenture and hybrid prosthesis wearers considering the possible influence of different variables, and to analyse the factorial construct of the well-being associated to these types of implant restorations. A control group of subjects with muco-supported complete dentures allowed estimation of the benefits of using implants for supporting the abovementioned removable and semi-removable acrylic oral rehabilitations.

In addition to the design and validation of the new index, the null hypothesis tested was that conventional complete dentures, implant overdentures, and fixed-detachable hybrid implant prostheses provide comparable levels of OHRQoL regardless of the socio-demographic, clinical, and/or prosthetic-related characteristics of the patients.

Materials and methods

Development of the Quality of life related to function, aesthetics, socialization, and thoughts about health-behavioural habits (QoLFAST-10) questionnaire

Following the EUROHIS guidelines for the development of a universal quality of life (QoL) indicator, an extensive literature review was accomplished in order to establish a theoretical framework about the preliminary structure and content of the scale. A team of five specialists in prosthodontics and an oral and maxillofacial surgeon (each with demonstrated research experience in QoL), selected the most relevant items in OHRQoL for consideration in patients wearing implant overdentures and hybrid prostheses. The development of the new questionnaire was therefore supported by previously published papers and based on existing instruments in the areas of patient satisfaction, oral symptoms, oral function, self-image/aesthetics, self-esteem, and socialization . As a novelty, the authors decided to include items asking about the patients’ thoughts about health behavioural habits, given their importance on the maintenance of the OHRQoL.

The research group interviewed 28 subjects who were rehabilitated at the Department of Buccofacial Prostheses (Stomatology I) of the Faculty of Dentistry of the Complutense University of Madrid (U.C.M., Spain). Patients attended an in-depth, face-to-face interview in order to explore the areas of OHRQoL that might be affected by the presence of implant restorations. The volunteers were also distributed in group discussions (focus discussions). The purpose was to identify what they regarded as most important requirements related to OHRQoL. The experts selected and summarised the most prevalent issues. At this stage, redundant or inappropriate items were deleted .

Finally, the committee of experts decided on a 10-item questionnaire. The items on the designed index: ‘Quality of Life related to Function, Aesthetics, Social, and Thoughts about health-behavioural habits’, hereafter called QoLFAST-10, were the following: Item 1 (Social repercussion of oral pain), Item 2 (Social repercussion of eating well), Item 3 (Speaking well), Item 4 (Satisfaction with the size, shape, and colour of the prosthetic teeth), Item 5 (Self-confidence when smiling), Item 6 (Development of daily activities), Item 7 (Feeling socially comfortable), Item 8 (Importance of dental revisions), Item 9 (Importance of daily habits of oral hygiene), and Item 10 (Oral hygiene difficulties). Ten items tried to cover four important areas of OHRQoL that may be assessed when the patient is wearing an implant restoration: function, aesthetics, socialization, and thoughts about health behavioural habits. This reason explains the name of the questionnaire, and the names of the dimensions obtained after the correspondent statistical analysis.

The questionnaire may be easily adapted to a global scale format to be applied in future assessments ( i.e., patients could be asked: ‘ Do you think that the following aspects have improved, worsened or remained the same after the prosthetic treatment ?’) .

The 10-item QoLFAST-10 indicator was designed to be intuitively self-completed as the items’ responses were expressed in a Likert-type scale with proportional codes for the impact degrees. The items evaluated as ‘<0’ on the Likert scale were considered as having negative impact, while values of ‘+1’ and ‘+2’ represented the positive side of each item (absence of negative effect). The possible responses to the items were the following: ‘strongly disagree’ (score −2), ‘disagree’ (score −1), ‘indecisive’/‘indifferent’/‘neutral’ (score 0), ‘agree’ (score +1), and ‘strongly agree’ (score +2).

The total score of the questionnaire was calculated by means of the additive scoring method (ADD) by adding the different item scores . Both negative and positive impacts contributed to the total score in such way that the higher the total score is, the higher the satisfaction of the patient is (meaning that negative or low positive scores indicate poorer self-perceived OHRQoL). Hence, the total score of the QoLFAST-10 ranges between ‘–2 × no. of items’ (−20) and ‘ + 2 × no. of items’ (+20). Similarly, the dimensional scores are the sum of the item scores that are included in each domain (ADD method) .

Following the recommendations of Streiner and Norman , the face and content validity of the QoLFAST-10 scale was empirically checked in a pilot trial that was conducted on a representative sample of patients ( n = 28) from the same source population, which constituted 23.33% of the main study sample ( n = 120). Although ten (or even fewer) patients have proven to be sufficient to assess the clarity of instructions, item wording, acceptability of formatting, and ease of administration of a questionnaire; given the population variability in this study , approximately 10 patients per treatment group were selected for the pilot trial. Thus, they wore complete dentures ( n = 10; 35.8% of the sample for the pilot trial), implant overdentures ( n = 9, 32.1%), and hybrid implant prostheses ( n = 9; 32.1%), and met selection criteria that were similar to those of the patients in the main study . The comprehensiveness of the QoLFAST-10 index was evaluated by asking the participants specific questions about possible difficulties in understanding the items in order to make the instrument more clear. This allowed optimising its face and content validity for the main cross-sectional research .

Study protocol

Study sample

The reference population included 120 subjects from 40 to 90 years-old and who were treated with at least one conventional complete denture, one implant overdenture, or one hybrid implant prosthesis; at the Department of Buccofacial Prostheses of the Complutense University of Madrid between 2000 and 2014. The patients were recruited by chronology of past treatment.

To standardise the inclusion criteria, patients with complete dentures, implant overdentures fitted over 4 implants in the maxilla and/or over 2–4 implants in the mandible, and hybrid implant prostheses screwed to 4–6 maxillary and/or interforaminally implants defined the reference population. The subjects were invited to take part in the study between January and March of 2014. The exclusion criteria were: patients rehabilitated with an implant overdenture and a hybrid implant prosthesis (to avoid misinterpretation of the findings), patients seeking dental treatment, and patients with cognitive impairment, motility disorders, implant loss, and/or serious illness .

The 113 final volunteers were scheduled for appointments that were to take place in April 2014. The subjects were assigned to three groups, depending on the type of implant restoration worn by each patient: Group 1 (CD; n = 38): muco-supported complete denture wearers (control); Group 2 (IO; n = 38): patients wearing implant overdentures and Group 3 (HP; n = 37): subjects with hybrid implant prosthesis.

This work was conducted in full accordance with the World Medical Association Declaration of Helsinki ( www.wma.net ) and the Spanish Law 14/2007 of July 3rd for Biomedical Research ( www.boe.es ) . All of the participants were briefed about the purpose and process of the study. The experiment was undertaken with the written consent of each subject and according to the abovementioned principles. The approval of the Ethics Committee of the San Carlos University Hospital of Madrid (C.I. 12/240-E, and 12/241-E) was obtained after the ethical board of the Spanish Hospital completed an independent review of the study protocol. The subjects’ anonymity was preserved, and their rights were protected in all cases.

Data gathering

Patients completed the QoLFAST-10 questionnaire aided by a trained interviewer, who formulated the questions. Participants also completed the 20-item Oral Health Impact Profile (OHIP-20sp) form, which had been previously validated in the Spanish population and has been described in detail elsewhere . Answering the OHIP-20sp, patients scored in terms of the frequency of appearance, 20 situations of impact that were conceptually divided into seven ‘domains’ or ‘dimensions’ (i.e., Functional limitation, Physical pain, Psychological discomfort, Physical disability, Psychological disability, Social disability and Handicap) . Frequency in the OHIP was codified using a classic Likert-type scale with five options . The possible impact responses were: ‘hardly ever’ (score +1), ‘occasionally’ (score +2), ‘fairly often’ (score +3), and ‘very often’ (score +4). The ‘never’ response (score 0) revealed the absence of impact. The OHIP-20sp outcome variable ranged from 0 to 80. With this index, the higher the total score is, the higher the level of negative impact on oral well-being and quality of life is, and, therefore, the lower the satisfaction of the patient is .

The volunteers were also asked about their overall satisfaction with their mouths, which comprised individual assessments of the satisfaction with their oral aesthetics, functionality, and comfort with their prostheses . A visual analogue scale (VAS) was used for each of the abovementioned areas, so that these perceptions were quantified in a continuous range from 0 to 10 . Subjects could thereby declare themselves to be ‘dissatisfied’, ‘neutral’, or ‘satisfied’, offering values situated left to the midpoint of a 100-mm long line, on the midpoint, or to the right of the midpoint, respectively .

A different researcher conducted each questionnaire. To ensure that the clinic staff had no access to the patients’ responses, the completed forms were placed in sealed envelopes. The QoLIP-10 (original version) , the OHIP-20sp, and the VAS evaluations were then linked by means of a unique identification code for each participant .

To capture the clinical modulating factors, subjects were examined by a single investigator using the diagnostic methodology published by the World Health Organization .

The study variables were grouped as follows: Group 1: Socio-demographic variables (gender, age, marital status, and level of education/schooling); Group 2: Clinical variables (presence of oral candidiasis, and mucosal lesions); Group 3: Variables related to the prosthetic rehabilitation (location, type of antagonist, status of the prosthesis, and retention system in case of overdentures); and Group 4: Self-perceived satisfaction with the mouth (complaints about the mouth, and perception of needing dental treatment).

Data analysis

The additive method (-ADD) was used for both the QoLFAST-10 and the OHIP-20sp analyses by adding the item codes at the appropriate frequency . The dimensional scores of each questionnaire were obtained in a similar fashion. All of the data collected were processed according to well-established statistical methods used in related research .

Descriptive statistics and percentages for qualitative and categorical variables were calculated .

The main psychometric characteristics of the QoLFAST-10 questionnaire (reliability and validity) were investigated. On the one hand, as each item measured different aspects of the same attribute, the reliability was assessed by examining the internal consistency of the scales through the use of the Cronbach’s α value, the α value if an item was deleted, the inter-item correlation, and the item-total correlation . On the other hand, different types of validity were tested:

  • (a)

    The face and content validity (which refers to the extent to which a measure represents all facets of a given construct) were verified in the pilot trial because the patients reported no difficulties in understanding the items and did not mention any situation of impact that had not been included in the questionnaire .

  • (b)

    The construct validity of the QoLFAST-10 (or the extent to which the OHRQoL was actually recorded with this scale) was examined using the factor analysis (a data reduction technique that allows homogeneous subgroups of variables to be found), and the convergent validity of the scale (which measures how closely the new scale is related to other variables and measures of the same construct to which it should be associated) .

Concerning the factor analysis, the principal components’ analysis (PCA) was applied together with the rotation method: the Varimax plus Kaiser normalization was selected to extract the underlying domains of the prosthetic construct . Afterwards, the Bartlett’s Sphericity and the Kaiser-Meyer-Olkin (KMO) tests, which are measures of sampling adequacy, were run to detect the factorial structure of the QoLFAST-10. Factors with an eigenvalue of less than one were disregarded to avoid distortion . The items were assigned to the rotated factors (or dimensions) when they had a loading of 0.5 or greater in a single factor .

To establish the degree of convergent validity, the QoLFAST-10 total and sub-scale scores were correlated to the total score of the OHIP-20sp with the Spearman’s rank test .

  • (c)

    The criterion validity of the QoLFAST-10 indicator (which measures how well the test predicts the OHRQoL based on information obtained from other variables) was analysed by contrasting the total QoLFAST-10 and OHIP-20sp scores with the VAS punctuations using non-parametric probes, since the Kolmogorov-Smirnov test did not assume a normal distribution of the QoLFAST-10 outcome variable in the treatment groups. The Kruskal-Wallis test was applied for variables with three or more categories, while the Mann-Whitney U test was run for variables with two categories, and for pair-wise comparisons .

  • (d)

    In order to investigate the discriminant validity, the total and dimensional scores of the QoLFAST-10 were compared with the total score of the OHIP-20sp (and vice versa ) among the prosthodontic groups. The Kruskal-Wallis test was used to assess the differences among the three prosthodontic groups, and the Mann-Whitney U test was chosen for post-hoc comparisons .

After evaluating the psychometric characteristics of the new questionnaire, the possible modulating effect of the study variables on the QoLFAST-10 impact scores were examined with the Kruskal-Wallis and the Mann-Whitney U tests .

Data were processed using the Statistical Package for the Social Sciences (software v.22) (SPSS/PC+, Inc.; Chicago, IL, USA) taking in advance the cut-off level for statistical significance at α = 0.05 .

Materials and methods

Development of the Quality of life related to function, aesthetics, socialization, and thoughts about health-behavioural habits (QoLFAST-10) questionnaire

Following the EUROHIS guidelines for the development of a universal quality of life (QoL) indicator, an extensive literature review was accomplished in order to establish a theoretical framework about the preliminary structure and content of the scale. A team of five specialists in prosthodontics and an oral and maxillofacial surgeon (each with demonstrated research experience in QoL), selected the most relevant items in OHRQoL for consideration in patients wearing implant overdentures and hybrid prostheses. The development of the new questionnaire was therefore supported by previously published papers and based on existing instruments in the areas of patient satisfaction, oral symptoms, oral function, self-image/aesthetics, self-esteem, and socialization . As a novelty, the authors decided to include items asking about the patients’ thoughts about health behavioural habits, given their importance on the maintenance of the OHRQoL.

The research group interviewed 28 subjects who were rehabilitated at the Department of Buccofacial Prostheses (Stomatology I) of the Faculty of Dentistry of the Complutense University of Madrid (U.C.M., Spain). Patients attended an in-depth, face-to-face interview in order to explore the areas of OHRQoL that might be affected by the presence of implant restorations. The volunteers were also distributed in group discussions (focus discussions). The purpose was to identify what they regarded as most important requirements related to OHRQoL. The experts selected and summarised the most prevalent issues. At this stage, redundant or inappropriate items were deleted .

Finally, the committee of experts decided on a 10-item questionnaire. The items on the designed index: ‘Quality of Life related to Function, Aesthetics, Social, and Thoughts about health-behavioural habits’, hereafter called QoLFAST-10, were the following: Item 1 (Social repercussion of oral pain), Item 2 (Social repercussion of eating well), Item 3 (Speaking well), Item 4 (Satisfaction with the size, shape, and colour of the prosthetic teeth), Item 5 (Self-confidence when smiling), Item 6 (Development of daily activities), Item 7 (Feeling socially comfortable), Item 8 (Importance of dental revisions), Item 9 (Importance of daily habits of oral hygiene), and Item 10 (Oral hygiene difficulties). Ten items tried to cover four important areas of OHRQoL that may be assessed when the patient is wearing an implant restoration: function, aesthetics, socialization, and thoughts about health behavioural habits. This reason explains the name of the questionnaire, and the names of the dimensions obtained after the correspondent statistical analysis.

The questionnaire may be easily adapted to a global scale format to be applied in future assessments ( i.e., patients could be asked: ‘ Do you think that the following aspects have improved, worsened or remained the same after the prosthetic treatment ?’) .

The 10-item QoLFAST-10 indicator was designed to be intuitively self-completed as the items’ responses were expressed in a Likert-type scale with proportional codes for the impact degrees. The items evaluated as ‘<0’ on the Likert scale were considered as having negative impact, while values of ‘+1’ and ‘+2’ represented the positive side of each item (absence of negative effect). The possible responses to the items were the following: ‘strongly disagree’ (score −2), ‘disagree’ (score −1), ‘indecisive’/‘indifferent’/‘neutral’ (score 0), ‘agree’ (score +1), and ‘strongly agree’ (score +2).

The total score of the questionnaire was calculated by means of the additive scoring method (ADD) by adding the different item scores . Both negative and positive impacts contributed to the total score in such way that the higher the total score is, the higher the satisfaction of the patient is (meaning that negative or low positive scores indicate poorer self-perceived OHRQoL). Hence, the total score of the QoLFAST-10 ranges between ‘–2 × no. of items’ (−20) and ‘ + 2 × no. of items’ (+20). Similarly, the dimensional scores are the sum of the item scores that are included in each domain (ADD method) .

Following the recommendations of Streiner and Norman , the face and content validity of the QoLFAST-10 scale was empirically checked in a pilot trial that was conducted on a representative sample of patients ( n = 28) from the same source population, which constituted 23.33% of the main study sample ( n = 120). Although ten (or even fewer) patients have proven to be sufficient to assess the clarity of instructions, item wording, acceptability of formatting, and ease of administration of a questionnaire; given the population variability in this study , approximately 10 patients per treatment group were selected for the pilot trial. Thus, they wore complete dentures ( n = 10; 35.8% of the sample for the pilot trial), implant overdentures ( n = 9, 32.1%), and hybrid implant prostheses ( n = 9; 32.1%), and met selection criteria that were similar to those of the patients in the main study . The comprehensiveness of the QoLFAST-10 index was evaluated by asking the participants specific questions about possible difficulties in understanding the items in order to make the instrument more clear. This allowed optimising its face and content validity for the main cross-sectional research .

Study protocol

Study sample

The reference population included 120 subjects from 40 to 90 years-old and who were treated with at least one conventional complete denture, one implant overdenture, or one hybrid implant prosthesis; at the Department of Buccofacial Prostheses of the Complutense University of Madrid between 2000 and 2014. The patients were recruited by chronology of past treatment.

To standardise the inclusion criteria, patients with complete dentures, implant overdentures fitted over 4 implants in the maxilla and/or over 2–4 implants in the mandible, and hybrid implant prostheses screwed to 4–6 maxillary and/or interforaminally implants defined the reference population. The subjects were invited to take part in the study between January and March of 2014. The exclusion criteria were: patients rehabilitated with an implant overdenture and a hybrid implant prosthesis (to avoid misinterpretation of the findings), patients seeking dental treatment, and patients with cognitive impairment, motility disorders, implant loss, and/or serious illness .

The 113 final volunteers were scheduled for appointments that were to take place in April 2014. The subjects were assigned to three groups, depending on the type of implant restoration worn by each patient: Group 1 (CD; n = 38): muco-supported complete denture wearers (control); Group 2 (IO; n = 38): patients wearing implant overdentures and Group 3 (HP; n = 37): subjects with hybrid implant prosthesis.

This work was conducted in full accordance with the World Medical Association Declaration of Helsinki ( www.wma.net ) and the Spanish Law 14/2007 of July 3rd for Biomedical Research ( www.boe.es ) . All of the participants were briefed about the purpose and process of the study. The experiment was undertaken with the written consent of each subject and according to the abovementioned principles. The approval of the Ethics Committee of the San Carlos University Hospital of Madrid (C.I. 12/240-E, and 12/241-E) was obtained after the ethical board of the Spanish Hospital completed an independent review of the study protocol. The subjects’ anonymity was preserved, and their rights were protected in all cases.

Data gathering

Patients completed the QoLFAST-10 questionnaire aided by a trained interviewer, who formulated the questions. Participants also completed the 20-item Oral Health Impact Profile (OHIP-20sp) form, which had been previously validated in the Spanish population and has been described in detail elsewhere . Answering the OHIP-20sp, patients scored in terms of the frequency of appearance, 20 situations of impact that were conceptually divided into seven ‘domains’ or ‘dimensions’ (i.e., Functional limitation, Physical pain, Psychological discomfort, Physical disability, Psychological disability, Social disability and Handicap) . Frequency in the OHIP was codified using a classic Likert-type scale with five options . The possible impact responses were: ‘hardly ever’ (score +1), ‘occasionally’ (score +2), ‘fairly often’ (score +3), and ‘very often’ (score +4). The ‘never’ response (score 0) revealed the absence of impact. The OHIP-20sp outcome variable ranged from 0 to 80. With this index, the higher the total score is, the higher the level of negative impact on oral well-being and quality of life is, and, therefore, the lower the satisfaction of the patient is .

The volunteers were also asked about their overall satisfaction with their mouths, which comprised individual assessments of the satisfaction with their oral aesthetics, functionality, and comfort with their prostheses . A visual analogue scale (VAS) was used for each of the abovementioned areas, so that these perceptions were quantified in a continuous range from 0 to 10 . Subjects could thereby declare themselves to be ‘dissatisfied’, ‘neutral’, or ‘satisfied’, offering values situated left to the midpoint of a 100-mm long line, on the midpoint, or to the right of the midpoint, respectively .

A different researcher conducted each questionnaire. To ensure that the clinic staff had no access to the patients’ responses, the completed forms were placed in sealed envelopes. The QoLIP-10 (original version) , the OHIP-20sp, and the VAS evaluations were then linked by means of a unique identification code for each participant .

To capture the clinical modulating factors, subjects were examined by a single investigator using the diagnostic methodology published by the World Health Organization .

The study variables were grouped as follows: Group 1: Socio-demographic variables (gender, age, marital status, and level of education/schooling); Group 2: Clinical variables (presence of oral candidiasis, and mucosal lesions); Group 3: Variables related to the prosthetic rehabilitation (location, type of antagonist, status of the prosthesis, and retention system in case of overdentures); and Group 4: Self-perceived satisfaction with the mouth (complaints about the mouth, and perception of needing dental treatment).

Data analysis

The additive method (-ADD) was used for both the QoLFAST-10 and the OHIP-20sp analyses by adding the item codes at the appropriate frequency . The dimensional scores of each questionnaire were obtained in a similar fashion. All of the data collected were processed according to well-established statistical methods used in related research .

Descriptive statistics and percentages for qualitative and categorical variables were calculated .

The main psychometric characteristics of the QoLFAST-10 questionnaire (reliability and validity) were investigated. On the one hand, as each item measured different aspects of the same attribute, the reliability was assessed by examining the internal consistency of the scales through the use of the Cronbach’s α value, the α value if an item was deleted, the inter-item correlation, and the item-total correlation . On the other hand, different types of validity were tested:

  • (a)

    The face and content validity (which refers to the extent to which a measure represents all facets of a given construct) were verified in the pilot trial because the patients reported no difficulties in understanding the items and did not mention any situation of impact that had not been included in the questionnaire .

  • (b)

    The construct validity of the QoLFAST-10 (or the extent to which the OHRQoL was actually recorded with this scale) was examined using the factor analysis (a data reduction technique that allows homogeneous subgroups of variables to be found), and the convergent validity of the scale (which measures how closely the new scale is related to other variables and measures of the same construct to which it should be associated) .

Concerning the factor analysis, the principal components’ analysis (PCA) was applied together with the rotation method: the Varimax plus Kaiser normalization was selected to extract the underlying domains of the prosthetic construct . Afterwards, the Bartlett’s Sphericity and the Kaiser-Meyer-Olkin (KMO) tests, which are measures of sampling adequacy, were run to detect the factorial structure of the QoLFAST-10. Factors with an eigenvalue of less than one were disregarded to avoid distortion . The items were assigned to the rotated factors (or dimensions) when they had a loading of 0.5 or greater in a single factor .

To establish the degree of convergent validity, the QoLFAST-10 total and sub-scale scores were correlated to the total score of the OHIP-20sp with the Spearman’s rank test .

  • (c)

    The criterion validity of the QoLFAST-10 indicator (which measures how well the test predicts the OHRQoL based on information obtained from other variables) was analysed by contrasting the total QoLFAST-10 and OHIP-20sp scores with the VAS punctuations using non-parametric probes, since the Kolmogorov-Smirnov test did not assume a normal distribution of the QoLFAST-10 outcome variable in the treatment groups. The Kruskal-Wallis test was applied for variables with three or more categories, while the Mann-Whitney U test was run for variables with two categories, and for pair-wise comparisons .

  • (d)

    In order to investigate the discriminant validity, the total and dimensional scores of the QoLFAST-10 were compared with the total score of the OHIP-20sp (and vice versa ) among the prosthodontic groups. The Kruskal-Wallis test was used to assess the differences among the three prosthodontic groups, and the Mann-Whitney U test was chosen for post-hoc comparisons .

After evaluating the psychometric characteristics of the new questionnaire, the possible modulating effect of the study variables on the QoLFAST-10 impact scores were examined with the Kruskal-Wallis and the Mann-Whitney U tests .

Data were processed using the Statistical Package for the Social Sciences (software v.22) (SPSS/PC+, Inc.; Chicago, IL, USA) taking in advance the cut-off level for statistical significance at α = 0.05 .

Results

The main findings of the study are outlined in Tables 1–5 . The description of the study sample, the analysis of the reliability and validity of the QoLFAST-10 index, and the assessment of the prosthetic well-being construct are detailed below.

Table 1
Impact of the study variables on the OHRQoL (N = 113).
Patients’ features
(%, n)
Statistical significance
QoLFAST-10 total score OHIP-20sp total score
Mean (SD) p-values Mean (SD) p-values
Group 1: Socio demographic variables
Gender
Male (31.9%, n = 36) 9.50 (5.2) 0.27 NS (a) 4.6 (3.8) 0.37 NS (a)
Female (68.1%, n = 77) 10.10 (6.6) 7.0 (7.3)
Age
≤60 years (23.0%, n = 26) 8.3 (7.0) 0.13 NS (a) 6.3 (6.1) 0.90 NS (a)
>60 years (77.0%, n = 87) 10.4 (5.8) 6.2 (6.6)
Being partnered
Without partner (23.9%, n = 27) 10.78 (4.7) 0.57 NS (a) 5.6 (5.0) 0.98 NS (a)
With partner (76.1%, n = 86) 9.6 (6.5) 6.5 (6.9)
Level of education/schooling
Illiterate (17.7%, n = 20) 10.2 (5.7) 0.004 ** (b) 7.5 (8.8) 0.86 NS (b)
Non-university education (56.6%, n = 64) 11.4 (6.0) 6.1 (6.6)
University education (25.7%, n = 29) 7.6 (6.1) 5.9 (4.8)
Group 2: Clinical variables
Presence of oral candidiasis
Yes (17.7%, n = 20) 9.8 (5.9) 0.34 NS (a) 6.4 (6.8) 0.87 NS (a)
No (82.3%, n = 93) 10.5 (7.3) 5.6 (5.1)
Presence of mucosal lesions
Yes (23.9%, n = 27) 9.1 (8.0) 0.87 NS (a) 6.6 (6.7) 0.71 NS (a)
No (76.1%, n = 86) 10.1 (5.5) 6.1 (6.5)
Group 3: Variables related to the prosthetic rehabilitation
Location
Maxillary (36.3%, n = 41) 10.9 (5.2) 0.16 NS (b) 5.6 (6.0) 0.48 NS (b)
Mandibular (27.4%, n = 31) 8.0 (7.2) 7.3 (6.8)
Bimaxillary (36.3%, n = 41) 10.4 (6.0) 6.1 (6.8)
Type of antagonist
Complete denture (CD) (21.2%, n = 24) 8.4 (7.5) 0.43 NS (b) 6.3 (6.0) 0.36 NS (b)
Implant-supported FDP (49.6 %, n = 56) 10.4 (5.1) 6.7 (6.4)
Tooth-supported FDP (25.7%, n = 29) 10.5 (6.6) 5.3 (7.4)
Removable partial denture (RPD) (3.5%, n = 4) 9.7 (7.5) 6.3 (6.5)
Status of the prosthesis
Good condition (GC) (70.8%, n = 80) 10.0 (5.6) 0.27 NS (b) 5.4 (5.9) 0.17 NS (b)
Needs reparation (R) (16.8%, n = 19) 11.6 (5.3) 8.7 (8.3)
Requires to be replaced (CH) (12.4%, n = 14) 6.8 (9.0) 7.6 (6.7)
Retention system (overdentures)
Bar (84.21%, n = 32) 9.2 (7.4) 0.20 NS (b) 7.4 (5.7) 0.15 NS (b)
Balls (2.63%, n =1) 11.0 (-) 0.0 (-)
Locators (13.16%, n = 5) 3.8 (7.0) 11.6 (8.5)
Group 4: Self-perceived satisfaction with the mouth
Complaints about the mouth
Yes (18.6%, n = 21) 5.8 (8.5) 0.001** (a)
QoL:
Complaint < No complaint
11.3 (7.8) 0.001** (a)
QoL:
Complaint < No complaint
No (81.4%, n = 92) 10.8 (5.1) 5.1 (5.6)
Perception of needing dental treatment
Yes (29.2%, n = 33) 8.7 (7.6) 0.29 NS (a) 8.7 (7.5) 0.02* (a)
QoL: Perception of needing dental treatment < No perception
No (70.8%, n = 80) 10.4 (5.4) 5.2 (5.8)
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Jun 19, 2018 | Posted by in General Dentistry | Comments Off on Validation of a new, specific, complete, and short OHRQoL scale (QoLFAST-10) for wearers of implant overdentures and fixed-detachable hybrid prostheses
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