Income-related inequalities in inadequate dentition over time in Australia, Brazil and USA adults

Do people with shortened dentalarches have worse oral health-related quality of life than thosewith more natural teeth? Apopulation-based study

Tan H, Peres KG, Peres MA. Do people with shortened dental arches haveworse oral health-related quality of life than those with more natural teeth? Apopulation-based study. Community Dent Oral Epidemiol 2014. © 2014 JohnWiley & Sons A/S. Published by John Wiley & Sons Ltd.

Abstract – Objective: To test whether people with shortened dental arches(SDA) have impaired oral health-related quality of life than those with morenatural teeth. Method: We analysed data from the 2004–2006 AustralianNational Survey of Adult Oral Health (including telephone interview, oralepidemiological examinations and mailed questionnaire). Participants aged ≥15years and with intact anterior teeth were eligible in this study. We usedmultivariable negative binomial regression analyses to test the association ofSDA, according to two alternative definition (1. having intact teeth and 3-5natural occlusal units; 2. having intact anterior teeth and four natural occlusalunits), with OHIP-14 severity and extent, adjusting for potential confounders,including demographic variables (age and sex), socioeconomic variables(income and education), behaviour characteristics (time since last visit, reasonfor the last dental visit, difficult in paying $100 dental bill and dental insurancepossession), and dental outcomes (coronal and root caries, and periodontaldisease). Result: We analysed on 2,750 dentate participants that were eligible forthe study. When SDA was classified as intact anterior teeth, four occlusal unitsand no dental prosthesis, no statistical difference in OHIP-14 severity or extentwas identified compared with those with intact anterior teeth, over fourocclusal units and no dental prosthesis. Participants who presented intactanterior teeth, 3-5 occlusal units and no prosthesis showed 50% higher rates ofOHIP-14 severity than those with intact anterior teeth, over five occlusal unitsand no prosthesis while their OHIP-14 extent was similar to that of thereference group. Conclusion: SDA is not associated with negative impacts onquality of life, according to both OHIP-14 severity and extent, when SDA isdefined as four occlusal units and no dental prosthesis. When SDA is defined as3-5 occlusal units and no dental prosthesis, it is only associated with OHIP-14severity, but not OHIP-14 extent.

Haiping Tan, Karen G. Peres and

Marco A. Peres

Australian Research Centre for Population

Oral Health, School of Dentistry, The

University of Adelaide, Adelaide, SA,

Australia

Key words: dental health survey(s); dentalpublic health; epidemiology; oralrehabilitation; quality of life

Haiping Tan, Australian Research Centre forPopulation Oral Health, School of Dentistry,The University of Adelaide, Level 1, 122Frome Street, Adelaide, Adelaide, SA 5000,AustraliaTel: +61 8 8313 4044Fax: +61 8 8313 3070e-mail: [email protected]

Submitted 13 February 2014;accepted 28 July 2014

It has been recognized that tooth loss can affect oral

health-related quality of life (OHRQoL) (1). The

traditional approach to restorative dentistry stres-

ses the use of idealized morphological criteria and

mechanically oriented concepts. For example, one

textbook in prosthodontics emphasizes that a full

doi: 10.1111/cdoe.12124 1

Community Dent Oral EpidemiolAll rights reserved

� 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

complement of teeth is a prerequisite for a healthy

masticatory system and satisfactory oral function

(2). Indeed, an important issue in prosthodontic

treatment of broken-down dentitions is the deci-

sion on which, if any missing teeth, should be

replaced to maintain OHRQoL. Literature to date

has provided conflicting evidence with regard to

the effect of dentures on OHRQoL (3–7).At present, the principle aim of dental care may

be considered to be maintenance of a natural func-

tional dentition throughout life, including all the

social and biological functions, such as self-esteem,

aesthetics, speech, chewing, taste and oral comfort

(8). The current criteria for a healthy or physiologi-

cal occlusion, as developed by Ramfjord and Ash

(9), reflected this shift: (i) the absence of pathologic

manifestations; (ii) satisfactory function (aesthetics,

chewing, etc); (iii) variability in form and function;

and (iv) adaptive capacity to changing situations.

Variability in form and function means that the

number of teeth may vary, and thus, the number

may be less than 28. Keeping a certain number of

teeth, depending on their position and condition,

might give more satisfaction than having the miss-

ing teeth replaced with partial dentures (10).

The concept of ‘shortened dental arches’ (SDA)

was first used by Kayser for a dentition with intact

anterior teeth and loss of posterior teeth (11). By

November 2013, when a literature search on SDA

and OHRQoL was conducted, we only found two

studies and they had small samples. One study

tested the relationship between patterns of missing

OUs and OHRQoL among SDA patients in special-

ist prosthodontic clinics (12). The other study

tested cost-effectiveness of functionally orientated

treatment based on the SDA concept, compared

with a partial removable dental prosthesis, with

the treatment effect measured as OHRQoL (13). It

is unknown whether at a population-level people

with SDA have worse OHRQoL, compared with

those with more natural OUs or those with fixed or

removable prosthesis. A population-based study to

investigate the association between OHRQoL and

the presence of SDA may provide evidence for pol-

icy makers to better understand where resources

should be allocated in terms of denture treatment

to improve OHRQoL.

This study aimed to compare the OHRQoL by

dentition status among the Australian population

aged ≥15, using two alternative definitions of den-

tition status. The null hypothesis to be tested is that

individuals with SDA have no worse OHRQoL

compared with those with more natural teeth.

Methods

Data were from the 2004–2006 Australian National

Survey of Adult Oral Health (NSAOH) (14). People

aged ≥15 were selected randomly from the popula-

tion from all six states and two territories by a

stratified, clustered, random sampling procedure.

Telephonic interviews of potential participants

established eligibility and collected sociodemo-

graphic and dental care information. Dentate

participants were invited to an oral epidemiologi-

cal examination, after the completion of which they

received a questionnaire by mail. The target sam-

ple size was calculated to address different survey

aims, namely 80% power with 5% type-I error in

detecting reductions of 10% in age group-specific

mean DMFT since the 1987–1988 national survey.

The survey was approved by the University of

Adelaide’s Human Research Ethics Committee and

Australian Institute of Health and Welfare, and

participants gave written informed consent. This

manuscript is structured to address STROBE

guidelines (15).

Telephonic interview surveyParticipants were asked questions about their sex,

age (15–24, 25–34, 35–44, 45–54 or ≥55), yearly

household income ($80,000+, $40,000 �<80,000 or

<$40,000), educational attainment being classified

as having ≤year 10, year 11 or 12 or year 13 or

higher formal education, time since last dental visit

(<1 year, 1–<2 years or ≥2 years), reason for last

visit (check-up or problem) and smoking status

(never, former or current smoker). Private dental

insurance status (yes or no) and difficulty in pay-

ing $100 dental bill (hardly any, a little or a lot of

difficulty) were used for indicators of dental care

affordability.

Oral epidemiological examinationThirty trained and calibrated dentist examiners

conducted examinations in local dental clinics.

They used mirrors, compressed air and periodontal

probes but not radiographs to evaluate all the teeth

present in each participant. Examiners recorded

dental caries experience for coronal surfaces by

visual criteria and root surfaces by visual and tac-

tile criteria on each tooth (14). Measurements of

periodontal pocket depth and clinical attachment

loss were recorded at three sites of all teeth in peo-

ple with no medical contraindications to probing.

Each participant’s periodontal status was classified

as healthy, moderate or severe periodontitis (16).

2

Tan et al.

Each examined person received a written report of

findings. Intraclass correlation coefficients of reli-

ability were 1.00 on the number of teeth present

per person, 0.85 on decayed, missing or filled sta-

tus at the tooth level and 0.98 at the person-level

and 0.59 on millimetres of clinical attachment loss

per site and 0.54 on millimetres of probing pocket

depth per site among examiners, compared with

the study reference examiner in masked, replicated

examinations of 157 study participants (14).

Self-completed Mailed QuestionnaireThe questionnaire asked about alcohol consump-

tion (yes or no) and frequency of toothbrushing

(≥14 or <14) in the week before the survey. The 14-

item oral health impact profile questionnaire

(OHIP-14) (17) asked about adverse impacts of the

teeth, mouth or dentures on daily life during the

preceding year. Responses were ‘very often’, ‘fairly

often’, ‘sometimes’, ‘hardly ever’ or ‘never’, coded

4, 3, 2, 1 and 0, respectively. Twenty returned ques-

tionnaires were missing ≥3 OHIP item responses

and were omitted from analysis. For 59 people

with missing values for ≤2 OHIP items, item

responses were imputed by the use of the mean

value of the item from among nonmissing values.

Dentition status – main exposureThere are two definitions of SDA: (i) having intact

anterior teeth and 3–5 natural OUs (18) and (ii)

having intact anterior teeth and four natural

OUs (19). According to the first definition, we

categorized participants aged ≥15 and with intact

anterior teeth into the following five groups –‘dentition status 1’ groups: (1) people with >5OUs and no prosthesis; (2) people with >5 natural

OUs with prosthesis; (3) people with 3–5 OUs and

no prosthesis (SDA); (4) people with <3 OUs and

no prosthesis; and (5) people with ≤5 natural OUs

with prosthesis. According to the second defini-

tion, we categorized the same participants into

the following five groups – ‘dentition status 2’

groups: (1) people with >4 natural OUs and no

prosthesis; (2) people with >4 natural OUs with

prosthesis; (3) people with 4 natural OUs and no

prosthesis (SDA); (4) people with <4 OUs and no

prosthesis; and (5) people with ≤ 4 natural OUs

with prosthesis.

Statistical analysesFirstly, we described the studied sample character-

istics according to the two outcomes – OHIP-14

severity and OHIP-14 extent (20), using STATA

commands for complex sampling (cluster and

weights). Extent refers to the number of items

reported ‘fairly often’ or ‘very often’. Severity is

the sum of ordinal responses. Given that both out-

comes are count variables and presented skewness

and over dispersion distribution, we assessed the

association of sample characteristics describing

outcomes means, 95% confidence intervals

and median. Secondly, we performed unadjusted

and multivariable negative binomial regression

models for each outcome and for each dentition

status – the main exposures (dentition status 1 and

2) – separately which allowed the estimation of

count ratio (CR) and its 95% confidence intervals.

Statistical modelling followed a sequential analysis

from distal to proximate determinants of OHIP-14.

We presented count ratio (CR) for dentition status

1 and 2 in each model (21). Model 1 included

demographic variables (age and sex); model 2 was

similar in composition to model 1 with the addition

of socioeconomic variables (income and educa-

tion); model 3 was similar in composition to model

2 with behaviour characteristics added (time since

last visit, reason for the last dental visit, difficult in

paying $100 dental bill and card insurance posses-

sion); and finally, model 4 was similar in composi-

tion to model 3 plus dental status (coronal and root

caries, and periodontal disease). Variables with

unadjusted or adjusted P-values higher than 0.20

(i.e. alcohol consumption and frequency of tooth-

brushing) were not included in the multivariable

models.

Results

Of 28,812 selected people aged ≥15, 14,123 (49.0%)

completed a telephonic interview. The 12,606 den-

tate interviewees were asked to undergo an oral

epidemiological examination, and 5,505 (43.7%) of

them did so. Of those, 3,724 (67.6%) had complete

data from the examination and from a question-

naire completed after the examination.

A total of 2,750 participants aged ≥15, with ≤2OHIP items missing and with intact anterior teeth,

were eligible in this study. Table 1 displays the

main characteristics of the studied sample and

OHIP-14 severity and extent according to demo-

graphic, socioeconomic, behaviours and dental dis-

eases. The sample had a similar distribution

according to age bracket and insurance status, a

slightly higher proportion of females and people

brushing their teeth more frequently, higher

3

Shortened dental arches and quality of life

Table 1. Sample distribution of people with intact anterior teeth and OHIP-14 severity and extent by explanatoryvariables

n %a

OHIP-14 severityOHIP-14 extentb

Meana (95% CI) Mediana Meana (95% CI)

Total 2,750 100 6.55 (6.01–7.09) 4.00 0.40 (0.32–0.48)Demographic variablesAge group P = 0.163c P = 0.175c

15–24 236 21.9 7.07 (5.50–8.63) 4.00 0.44 (0.19–0.69)25–34 385 23.0 6.36 (5.04–7.68) 4.00 0.43 (0.25–0.61)35–44 556 18.5 6.68 (5.80–7.56) 4.00 0.42 (0.27–0.56)45–54 595 17.0 7.39 (6.44–8.33) 5.00 0.50 (0.33–0.67)≥55 978 19.6 5.35 (4.83–5.87) 3.00 0.23 (0.17–0.29)Sex P = 0.006c P = 0.005c

Male 1,019 49.9 5.82 (5.08–6.56) 4.00 0.27 (0.16–0.38)Female 1,731 50.1 7.28 (6.54–8.01) 4.00 0.54 (0.42–0.66)

SESYearly household income P = 0.001c P = 0.004c

$80k+ 685 33.8 5.41 (4.41–6.41) 3.00 0.27 (0.15–0.40)$40–<80k 907 37.1 6.24 (5.54–6.93) 4.00 0.30 (0.21–0.38)<$40k 962 29.1 8.19 (6.99–9.39) 5.00 0.65 (0.42–0.88)Education P = 0.058c P = 0.029c

Year 13 or higher 1,659 65.9 6.21 (5.51–6.91) 4.00 0.35 (0.26–0.44)Year 11 or 12 836 25.8 7.11 (6.13–8.09) 4.00 0.48 (0.30–0.67)≤Year 10 252 8.3 7.56 (5.92–9.19) 5.00 0.60 (0.32–0.88)

Behaviour and visitTime since last visit P = 0.991c P = 0.835c

<1 year 1,767 59.2 6.53 (5.90–7.16) 4.00 0.39 (0.30–0.57)1–<2 years 456 17.8 6.72 (5.41–8.02) 4.00 0.47 (0.21–0.72)≥2 years 525 23.0 6.48 (5.21–7.76) 4.00 0.39 (0.30–0.47)Reason for last visit P < 0.001c P < 0.001c

Check-up 1,711 62.3 5.07 (4.58–5.56) 3.00 0.22 (0.16–0.28)Problem 1,028 37.7 9.05 (8.02–10.07) 6.00 0.70 (0.52–0.88)Difficulty in paying $100dental bill

P < 0.001c P < 0.001c

No 1,249 45.7 4.84 (4.32–5.37) 3.00 0.21 (0.15–0.27)Hardly any/a little 1,074 39.6 7.01 (6.07–7.94) 5.00 0.37 (0.26–0.47)A lot of difficulty 418 14.7 10.59 (8.92–12.25) 7.00 1.10 (0.70–1.50)Dental insured P = 0.014c P = 0.022c

Yes 1,442 49.9 5.98 (5.28–6.69) 4.00 0.31 (0.23–0.40)No 1,286 50.1 7.25 (6.45–8.04) 4.00 0.50 (0.36–0.63)Toothbrushing frequencylast week

P = 0.254c P = 0.983c

≥14 1,703 55.6 6.27 (5.71–6.82) 4.00 0.40 (0.31–0.50)<14 1,038 44.4 6.90 (5.92–7.89) 4.00 0.40 (0.26–0.54)Smoking P = 0.049c P = 0.133c

Never smoker 1,552 59.9 6.21 (5.59–6.84) 4.00 0.38 (0.27–0.50)Former smoker 825 26.0 6.64 (5.44–7.84) 4.00 0.32 (0.19–0.45)Current smoker 373 14.1 7.83 (6.47–9.19) 5.00 0.64 (0.44–0.84)Alcohol consumption P = 0.060c P = 0.187c

No 458 16.8 7.67 (6.42–8.92) 4.00 0.53 (0.31–0.74)Yes 2,235 83.2 6.37 (5.75–6.99) 4.00 0.38 (0.29–0.47)

Dental diseasesNo. of teeth with coronalcaries

P < 0.001c P < 0.001c

0 2,188 77.2 5.71 (5.23–6.19) 4.00 0.31 (0.24–0.38)1 302 10.9 8.75 (7.01–10.50) 6.00 0.54 (0.31–0.76)2+ 260 11.9 9.99(7.58–12.40) 7.00 0.86 (0.43–1.29)No. of teeth with root caries P < 0.001c P = 0.017c

0 2,586 95.8 6.40 (5.85–6.95) 4.00 0.39 (0.31–0.47)1 108 3.0 9.13 (6.91–11.35) 6.00 0.70 (0.26–1.13)2+ 56 1.2 12.30 (8.33–16.28) 11.0 0.86 (0.33–1.39)

4

Tan et al.

proportions of well-educated people, short-term

dental visiting, never smokers, alcohol drinkers,

root caries free and without periodontal disease.

Only 11.4% and 2.5% of the sample had short den-

tal arches according to dentition status 1 and 2 clas-

sifications, respectively. Overall, the medians of

OHIP-14 severity and extent were 4 and 0, respec-

tively. Females, the poorest, those with ≤year 10

education, those who visited a dentist for problem,

who reported difficulty in paying $100 dental bill,

nondental insured people, who had dental diseases

and with fewer number of OUs, had higher values

of both OHIP-14 severity and extent.

Participants who presented between three to five

OUs (dentition status 1) and no prosthesis showed

a 50% higher rate of OHIP-14 severity than those

with over five OUs and no prosthesis, after adjust-

ment for potential confounders. However, when

SDA was classified adopting four OUs and no den-

tal prosthesis as a cut-off point, no statistical differ-

ence in OHIP-14 severity was identified compared

with those with over four OUs and no dental pros-

thesis (Table 2).

Participants with 3–5 OUs (dentition status 1)

and no prosthesis had a higher OHIP-14 extent

than that reference group, but their difference lost

its statistical significance when dental diseases

were included in the multivariable model. Those

with four OUs and no dental prosthesis had similar

values of OHIP-14 extent to the reference group in

the final adjusted model (Table 3).

Appendices display step by step negative bino-

mial multivariable regression modelling for OHIP-

14 severity and extent.

Discussion

Our study showed that participants with intact

anterior teeth and four OUs with no prosthesis

showed no difference in quality of life according to

OHIP-14 severity and extent to those with more

natural teeth after controlling for potential con-

founders. When SDA is defined as four OUs and

no dental prosthesis, the null hypothesis that peo-

ple with SDA have no worse OHRQoL than those

Table 1 Continued

n %a

OHIP-14 severityOHIP-14 extentb

Meana (95% CI) Mediana Meana (95% CI)

Periodontal disease P = 0.001c P = 0.003c

No 1,921 83.2 6.24 (5.67–6.82) 4.00 0.35 (0.26–0.43)Moderate periodontal disease 546 15.5 7.91 (6.58–9.24) 5.00 0.60 (0.38–0.81)Severe periodontal disease 61 1.3 10.10 (7.33–12.87) 8.00 0.86 (0.42–1.29)

Dentition status 1 P < 0.001c P = 0.026c

>5 occlusal units and noprosthesis

1,758 74.5 6.01 (5.42–6.59) 4.00 0.36 (0.26–0.45)

>5 natural occlusal unitswith prosthesis

76 2.1 5.02 (3.37–6.68) 3.00 0.31 (0.06–0.56)

3–5 occlusal units and noprosthesis (SDA)

382 11.4 8.36 (6.68–10.03) 5.00 0.47 (0.24–0.69)

<3 occlusal units and noprosthesis

442 10.4 8.37 (7.24–9.49) 6.00 0.63 (0.42–0.84)

≤5 natural occlusal unitswith prosthesis

92 1.6 9.29 (6.32–12.26) 6.00 0.73 (0.11–1.36)

Dentition status 2 P = 0.086c P = 0.047c

>4 occlusal units and noprosthesis

2,277 89.4 6.40 (5.82–7.00) 4.00 0.38 (0.29–0.46)


85 2.2 5.15 (3.53–6.77) 3.00 0.35 (0.09–0.60)

4 occlusal units and noprosthesis (SDA)

103 2.5 6.66 (5.00–8.32) 4.00 0.33 (0.11–0.54)


202 4.4 9.34 (7.34–11.33) 7.00 0.87 (0.47–1.28)


83 1.4 9.55 (6.34–12.75) 6.00 0.73 (0.05–1.40)

aWeighted data.bThe median of OHIP-14 extent by explanatory variables = 0.cP-values from negative binomial regression on weighted data.

5


with more natural teeth was supported. After con-

trolling for potential confounders, people with 3–5OUs with no prosthesis showed no difference in

OHIP-14 extent compared with those with more

natural teeth but higher OHIP-14 severity than the

latter, indicating worse quality of life.

To our knowledge, the present study is the

first population-based study testing whether peo-

ple with SDA have worse OHRQoL. Only one

study testing the relationship between patterns

of missing OUs and OHRQoL among SDA

patients in a clinic setting showed a dose–response relationship – the OHIP scale score had

a tendency to increase with increasing numbers

of missing OUs (12). Another study showed that

patients restored to a SDA using resin-bonded

bridgework showed improvement in OHRQoL

after the treatment (13). However, in both stud-

ies, OHRQoL among SDA patients was not com-

pared to people with more teeth and the sample

size was small.

The key strength of the study is that data are

from a national oral health survey with a large and

representative sample of the Australian popula-

tion. Furthermore, the dental examination followed

international standards and presented high exam-

iner reliability values (14). There was probably no

observer bias because examiners and interviewers

did not know the study hypothesis. There is varia-

tion in analysing OHIP-14, that is, using mean (20)

or median (13). In this study, as data on the OHIP-

14 severity and extent did not show a normal dis-

tribution and sample variance exceeds the sample

mean, negative binomial regression was adopted

as an appropriate method for multivariable analy-

ses. We developed models conservatively, that is,

as dental diseases might be on the causal pathway

of SDA and QoL, model 4 included dental diseases

and model 3. However, we found that there was

no considerable difference in parameters between

models 3 and 4.

This study is not free of limitations. For example,

a secondary analysis of data from the 2004–2006Australian NSAOH was performed. Although the

data were collected around 7 years ago, this

national oral health survey was the most recent

Table 2. Association between OHIP-14 severity and dentition status by negative binomial multivariable analyses

Unadjusted countratioa (95% CI) Model 1 Model 2 Model 3 Model 4

Dentition status 1>5 occlusal units and noprosthesis

Ref. Ref. Ref. Ref. Ref.


0.84 (0.60–1.17) 1.03 (0.74–1.42) 0.99 (0.71–1.37) 0.98 (0.69–1.39) 0.98 (0.67–1.44)

3–5 occlusal units and noprosthesis (SDA)

1.39 (1.12–1.73) 1.62 (1.32–1.98) 1.58 (1.26–1.97) 1.50 (1.22–1.84) 1.50 (1.21–1.87)


1.39 (1.19–1.63) 1.70 (1.47–1.97) 1.62 (1.37–1.91) 1.52 (1.28–1.82) 1.42 (1.20–1.68)


1.55 (1.11–2.15) 2.03 (1.55–2.65) 2.04 (1.52–2.75) 1.88 (1.48–2.38) 1.88 (1.45–2.44)

Dentition status 2>4 occlusal units and noprosthesis



0.81 (0.58–1.11) 0.90 (0.66–1.23) 0.86 (0.63–1.17) 0.88 (0.63–1.22) 0.88 (0.62–1.26)

4 occlusal units and noprosthesis (SDA)

1.04 (0.81–1.34) 1.20 (0.95–1.51) 1.22 (0.95–1.56) 1.06 (0.80–1.41) 1.06 (0.78–1.43)


1.46 (1.16–1.83) 1.68 (1.37–2.05) 1.54 (1.26–1.89) 1.49 (1.18–1.90) 1.28 (1.00–1.65)


1.49 (1.06–2.11) 1.79 (1.35–2.39) 1.83 (1.33–2.52) 1.68 (1.31–2.15) 1.68 (1.28–2.22)

Negative binominal regression (those with P > 0.20 in the unadjusted or adjusted analysis are not included in the multi-variable model).Model 1: adjusted for demographic variables (age and sex).Model 2: adjusted for model 1+ socioeconomic variables (yearly household income and education).Model 3: adjusted for model 2+ behaviour characteristics (reason for last visit and difficulty in paying $100 dental bill).Model 4: adjusted for model 3+ dental outcomes (coronal caries, root caries and periodontal disease).aCount ratio reflects change in the ratio of OHIP-14 severity for a unit change in the corresponding ‘Dentition Status’groups.

6

Tan et al.

one in Australia. The response rates for telephonic

interview and oral epidemiology examinations

were about 50%, and it was unknown about the

difference in the oral health status and self-

reported information between the participants and

nonrespondents.

There are two definitions of SDA in the literature.

By November 2013, by searching for the citations

via ‘Web of Knowledge’ (apps.webofknowl-

edge.com), we found that the original definition of

SDA as having intact anterior teeth and 3–5 natural

OUs (18) has been cited by 71 papers, while the

recent definition of SDA as having intact anterior

teeth and four natural OUs (19) has been cited by

56 papers. The latter one seemed to be more com-

monly adopted recently. We still conservatively

adopted two definitions of SDA and found that

people with four OUs have equivalent OHRQoL to

those with more natural teeth, while the result was

not consistent when 3–5 OUs were used as a cut-off

point for SDA. Thus, we supported that a SDA with

four OUs was the criteria for maintaining a good

OHRQoL.

In the 2004–2006 Australian NSAOH, 14.9% of

adult population wear dentures and there was a

threefold relative difference in the frequency of

denture wearing among people eligible for public

dental care (30.1%) compared with ineligible peo-

ple (10.4%), which might be attributed to the sub-

sidy of denture treatments by the dental public

health system (14). Considering the high impact of

denture treatments on the health system, especially

within the public sector, it is necessary to consider

a threshold for indication towards denture treat-

ment to fairly allocate resources and potentially

improve OHRQoL for the population.

The existing literature indicates that the progno-

sis of free-end saddle removable partial dentures

may not be predictable and may even be problem-

atic, and its contribution to oral functions in

patients with SDA is considered to be dubious (22).

The current population-based study finding has

important implications for oral health care at a

population level. Given the evidence that the OHR-

QoL among people with four OUs is not inferior to

that of people with more natural teeth, the treat-

Table 3. Association between OHIP-14 extent and dentition status by negative binomial multivariable analyses


Dentition status 1>5 occlusal units andno prosthesis


>5 natural occlusalunits with prosthesis

0.88 (0.38–2.04) 1.57 (0.70–3.51) 1.48 (0.59–3.70) 1.19 (0.43–3.25) 1.10 (0.30–4.10)

3–5 occlusal units andno prosthesis (SDA)

1.31 (0.76–2.24) 2.25 (1.28–3.96) 2.09 (1.25–3.50) 1.97 (1.13–3.43) 1.63 (0.86–3.08)

<3 occlusal units andno prosthesis

1.76 (1.15–2.70) 3.47 (2.27–5.31) 3.18 (1.99–5.07) 3.13 (1.80–5.42) 2.91 (1.65–5.14)

≤5 natural occlusalunits with prosthesis

2.06 (0.84–5.06) 3.89 (1.96–7.72) 4.68 (2.13–10.23) 3.96 (1.95–8.04) 5.09 (2.43–10.66)




0.92 (0.43–1.99) 1.16 (0.55–2.44) 1.20 (0.53–2.70) 1.05 (0.44–2.53) 1.14 (0.39–3.28)

4 occlusal units andno prosthesis (SDA)

0.86 (0.42–1.76) 1.26 (0.64–2.45) 1.87 (0.80–4.38) 1.25 (0.43–3.59) 1.69 (0.59–4.87)


2.31 (1.40–3.85) 3.58 (2.18–5.89) 3.63 (2.17–6.06) 4.03 (2.13–7.63) 3.68 (1.89–7.15)


1.92 (0.73–5.04) 2.84 (1.39–5.81) 3.87 (1.72–8.67) 3.24 (1.59–6.61) 4.58 (2.13–9.83)

Negative binominal regression (those with P > 0.20 in the unadjusted or adjusted analysis are not included in the multi-variable model).Model 1: adjusted for demographic variables (age and sex).Model 2: adjusted for model 1+ socioeconomic variables (yearly household income and education).Model 3: adjusted for model 2+ behaviour characteristics (reason for last visit, difficulty in paying $100 dental bill,insured or not and smoking status).Model 4: adjusted for model 3+ dental outcomes (coronal caries and periodontal disease).aCount ratio reflects change in the ratio of OHIP-14 extent for a unit change in the corresponding ‘Dentition Status’groups.

7


ment goals should be changed from the preserva-

tion of complete dental arches towards the preser-

vation of a reduced natural, functional dentition

such as SDA. Accordingly, the complex treatment

plan involving removable prosthodontic treatment

should move towards preventive and restorative

treatments concentrating on the functionally strate-

gic and sustainable parts of the existing dentition

to maintain a SDA. The latter also has the advanta-

ges of being less time-consuming and less expen-

sive (18).

Although there were only 2.5% of people with

four OUs in this study, the sample size was big

enough for comparison of OHIP-14 among differ-

ent dentition groups. The study findings are appli-

cable for, for example, around 434 092 people aged

≥15 [about 2.5% of the 17 363 689 Australian popu-

lation aged ≥15 (23)], which indicates maintaining

a SDA, with the adoption of the definition as four

OUs and no prosthesis, should be considered as an

important oral healthcare policy, especially in the

public health system.

To conclude, people with SDA (when it is

defined as four OUs and no dental prosthesis) have

no worse OHRQoL compared with those with

more natural teeth, according to OHIP-14 severity

and extent.

AcknowledgementsThe NSAOH was supported by the Australian Govern-ment Health Agencies, including NHMRC Grants#299060, #349514 and #349537. Colgate Oral Care pro-vided gifts for participants. The authors gratefullyacknowledge the chief investigators of the survey, ARC-POH staff and the dental team for data collection andexpress thanks to all participants. The authors declare nopotential conflict of interest with respect to the author-ship and/or publication of this article.

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12. Baba K, Igarashi Y, Nishiyama A, John MT, Akaga-wa Y, Ikebe K et al. Patterns of missing occlusalunits and oral health-related quality of life in SDApatients. J Oral Rehabil 2008;35:621–8.

13. McKenna G, Allen F, Woods N, O’Mahony D, Cro-nin M, Damata C et al. Cost-effectiveness of toothreplacement strategies for partially dentate elderly: arandomized controlled clinical trial. CommunityDent Oral Epidemiol. 2014;42:366–74. doi: 10.1111/cdoe.12085.

14. Slade GD, Spencer AJ, Roberts-Thomson KF. Austra-lia’s dental generations: the National Survey ofAdult Oral Health 2004–06. Canberra: AustralianInstitute of Health and Welfare, 2007; AIHW cat. no.DEN 165.

15. von Elm E, Altman DG, Egger M, Pocock SJ,Gøtzsche PC, Vandenbroucke JP. The Strengthen-ing the Reporting of Observational Studies in Epi-demiology (STROBE) statement: guidelines forreporting observational studies. Epidemiology 2007;18:800–4.

16. Page RC, Eke PI. Case definitions for use in popula-tion-based surveillance of periodontitis. J Periodon-tol 2007;78(7 Suppl.):1387–99.

17. Slade GD. Derivation and validation of a short-formoral health impact profile. Community Dent Oral Ep-idemiol 1997;25:284–90.

18. Witter DJ, van Palenstein Helderman WH, CreugersNH, K€ayser AF. The shortened dental arch conceptand its implications for oral health care. CommunityDent Oral Epidemiol 1999;27:249–58.

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info:doi/10.1111/cdoe.12085

info:doi/10.1111/cdoe.12085

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23. Australian Bureau Statistics Census, 2011; www.abs.gov.au.

Table A1. Association between OHIP-14 severity and dentition status 1 by negative binomial multivariable analyses


Dentition status 1>5 occlusal unitsand no prosthesis



0.84 (0.60–1.17) 1.03 (0.74–1.42) 0.99 (0.71–1.37) 0.98 (0.69–1.39) 0.98 (0.67–1.44)


1.39 (1.12–1.73) 1.62 (1.32–1.98) 1.58 (1.26–1.97) 1.50 (1.22–1.84) 1.50 (1.21–1.87)


1.39 (1.19–1.63) 1.70 (1.47–1.97) 1.62 (1.37–1.91) 1.52 (1.28–1.82) 1.42 (1.20–1.68)


1.55 (1.11–2.15) 2.03 (1.55–2.65) 2.04 (1.52–2.75) 1.88 (1.48–2.38) 1.88 (1.45–2.44)

Demographic variablesAge group15–24 Ref. Ref. Ref. Ref. Ref.25–34 0.90 (0.67–1.22) 0.87 (0.65–1.16) 0.83 (0.59–1.14) 0.83 (0.62–1.10) 0.83 (0.62–1.11)35–44 0.95 (0.73–1.23) 0.87 (0.67–1.13) 0.84 (0.61–1.15) 0.87 (0.66–1.14) 0.86 (0.65–1.13)45–54 1.05 (0.81–1.36) 0.89 (0.69–1.15) 0.87 (0.64–1.18) 0.97 (0.75–1.25) 0.94 (0.72–1.22)55+ 0.76 (0.59–0.97) 0.58 (0.45–0.75) 0.53 (0.39–0.72) 0.67 (0.51–0.87) 0.68 (0.51–0.91)SexMale Ref. Ref. Ref. Ref. Ref.Female 1.25 (1.07–1.46) 1.29 (1.11–1.51) 1.20 (1.03–1.39) 1.12 (0.98–1.29) 1.12 (0.97–1.29)

SESYearly household income$80k+ Ref. Ref. Ref. Ref.$40–<80k 1.15 (0.95–1.40) 1.11 (0.94–1.31) 1.06 (0.90–1.24) 1.03 (0.88–1.22)<$40k 1.51 (1.20–1.92) 1.48 (1.20–1.84) 1.08 (0.88–1.33) 1.07 (0.87–1.32)EducationYear 13 or higher Ref. Ref. Ref. Ref.Year 11 or 12 1.14 (0.95–1.37) 1.11 (0.95–1.31) 1.05 (0.89–1.24) 1.07 (0.91–1.25)≤Year 10 1.22 (0.96–1.54) 1.18 (0.93–1.50) 1.04 (0.81–1.33) 1.00 (0.77–1.31)

Behaviour and visitTime since last visit≤12 months Ref.1–<2 years 1.03 (0.83–1.28)≥2 years 0.99 (0.80–1.23)Reason for last visitCheck-up Ref. Ref. Ref.Problem 1.78 (1.54–2.07) 1.68 (1.44–1.95) 1.54 (1.32–1.79)Difficulty in paying $100 dental billNo Ref. Ref. Ref.Hardly any/a little 1.45 (1.22–1.72) 1.35 (1.15–1.58) 1.35 (1.14–1.59)A lot of difficulty 2.19 (1.81–2.64) 1.77 (1.40–2.23) 1.74 (1.37–2.21)InsuredYes Ref.No 1.21 (1.04–1.41)Toothbrushing frequency last week≥14 Ref.<14 1.10 (0.93–1.30)SmokingNever smoker Ref.Former smoker 1.07 (0.88–1.30)Current smoker 1.26 (1.02–1.56)

Appendices


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http://www.abs.gov.au

http://www.abs.gov.au

Table A1 Continued


Alcohol drinkingNo Ref.Yes 0.83 (0.69–1.01)

Dental diseasesNo. of teeth withcoronal caries0 Ref. Ref.1 1.53 (1.24–1.89) 1.23 (0.99–1.50)2+ 1.75 (1.35–2.27) 1.31 (0.99–1.72)No. of teeth with root caries0 Ref. Ref.1 1.43 (1.11–1.84) 1.29 (0.99–1.67)2+ 1.92 (1.38–2.68) 0.99 (0.66–1.50)Periodontal diseaseNo Ref. Ref.Moderate-severedisease

1.27 (1.06–1.51) 1.19 (0.99–1.41)

Severe periodontaldisease

1.62 (1.20–2.18) 1.28 (0.98–1.69)

Negative binominal regression (Those with P > 0.20 in the unadjusted or adjusted analysis are not included in the multi-variable model).Model 1: adjusted for age and sex.Model 2: adjusted for model 1 +model 2 (yearly household income and education).Model 3: adjusted for model 1 +model 2 SES +model 3 (reason for last visit and difficulty in paying $100 dental bill).Model 4: adjusted for model 1 +model 2 +model 3 +model 4 (coronal caries, root caries and periodontal disease).aCount ratio reflects change in the ratio of OHIP-14 severity for a unit change in the corresponding “Dentition Status”groups.

Table A2. Association between OHIP-14 severity and dentition status 2 by negative binomial multivariable analyses





0.81 (0.58–1.11) 0.90 (0.66–1.23) 0.86 (0.63–1.17) 0.88 (0.63–1.22) 0.88 (0.62–1.26)


1.04 (0.81–1.34) 1.20 (0.95–1.51) 1.22 (0.95–1.56) 1.06 (0.80–1.41) 1.06 (0.78–1.43)


1.46 (1.16–1.83) 1.68 (1.37–2.05) 1.54 (1.26–1.89) 1.49 (1.18–1.90) 1.28 (1.00–1.65)


1.49 (1.06–2.11) 1.79 (1.35–2.39) 1.83 (1.33–2.52) 1.68 (1.31–2.15) 1.68 (1.28–2.22)


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Table A2 Continued



Behaviour and visitTime since last visit≤12 months Ref.1–<2 years 1.03 (0.83–1.28)≥2 years 0.99 (0.80–1.23)Reason for last visitCheck-up Ref. Ref. Ref.Problem 1.78 (1.54–2.07) 1.72 (1.48–2.01) 1.56 (1.34–1.81)Difficulty in paying $100 dental billNo Ref. Ref. Ref.Hardly any/a little 1.45 (1.22–1.72) 1.36 (1.14–1.62) 1.36 (1.14–1.62)A lot of difficulty 2.19 (1.81–2.64) 1.72 (1.36–2.18) 1.70 (1.33–2.16)InsuredYes Ref.No 1.21 (1.04–1.41)Toothbrushing frequency last week≥14 Ref.<14 1.10 (0.93–1.30)SmokingNever smoker Ref.Former smoker 1.07 (0.88–1.30)Current smoker 1.26 (1.02–1.56)Alcohol drinkingNo Ref.Yes 0.83 (0.69–1.01)

Dental diseasesNo. of teeth with coronal caries0 Ref. Ref.1 1.53 (1.24–1.89) 1.26 (0.99–1.59)2+ 1.75 (1.35–2.27) 1.30 (0.98–1.72)No. of teeth with root caries0 Ref. Ref.1 1.43 (1.11–1.84) 1.32 (1.02–1.70)2+ 1.92 (1.38–2.68) 1.06 (0.69–1.64)Periodontal diseaseNo Ref. Ref.Moderate-severe disease 1.27 (1.06–1.51) 1.24 (1.03–1.50)Severe periodontal disease 1.62 (1.20–2.18) 1.33 (1.00–1.76)

Negative binominal regression (Those with P > 0.20 in the unadjusted or adjusted analysis are not included in themultivariable model).Model 1: adjusted for age and sex.Model 2: adjusted for model 1 +model 2 (yearly household income and education).Model 3: adjusted for model 1 +model 2 SES +model 3 (reason for last visit and difficulty in paying $100 dental bill).Model 4: adjusted for model 1 +model 2 +model 3 +model 4 (coronal caries, root caries and periodontal disease).aCount ratio reflects change in the ratio of OHIP-14 severity for a unit change in the corresponding “Dentition Status”groups.

11


Table A3. Association between OHIP-14 extent and dentition status 1 by negative binomial multivariable analyses





0.88 (0.38–2.04) 1.57 (0.70–3.51) 1.48 (0.59–3.70) 1.19 (0.43–3.25) 1.10 (0.30–4.10)


1.31 (0.76–2.24) 2.25 (1.28–3.96) 2.09 (1.25–3.50) 1.97 (1.13–3.43) 1.63 (0.86–3.08)


1.76 (1.15–2.70) 3.47 (2.27–5.31) 3.18 (1.99–5.07) 3.13 (1.80–5.42) 2.91 (1.65–5.14)


2.06 (0.84–5.06) 3.89 (1.96–7.72) 4.68 (2.13–10.23) 3.96 (1.95–8.04) 5.09 (2.43–10.66)



Behaviour and visitTime since last visit≤12 months Ref.1–<2 years 1.21 (0.67–2.19)≥2 years 1.01 (0.61–1.67)Reason for last visitCheck-up Ref. Ref. Ref.Problem 3.13 (2.16–4.54) 2.24 (1.51–3.32) 2.01 (1.37–2.94)Difficulty in paying $100 dental billNo Ref. Ref. Ref.Hardly any/a little 1.76 (1.18–2.62) 1.53 (1.05–2.22) 1.55 (1.04–2.31)A lot of difficulty 5.25 (3.34–8.25) 3.60 (2.06–6.29) 3.22 (1.84–5.65)InsuredYes Ref. Ref. Ref.No 1.58 (1.07–2.35) 0.75 (0.51–1.09) 0.79 (0.52–1.21)Toothbrushing frequency last week≥14 Ref.<14 1.00 (0.64–1.55)SmokingNever smoker Ref. Ref. Ref.Former smoker 0.83 (0.50–1.39) 1.13 (0.72–1.76) 1.08 (0.67–1.74)Current smoker 1.66 (1.07–2.57) 1.37 (0.86–2.18) 1.32 (0.83–2.10)Alcohol drinkingNo Ref.Yes 0.73 (0.45–1.17)

Dental diseasesNo. of teeth with coronal caries0 Ref. Ref.1 1.71 (1.06–2.77) 1.13 (0.70–1.84)2+ 2.75 (1.58–4.79) 1.65 (0.96–2.85)

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Table A3 Continued


No. of teeth with root caries0 Ref.1 1.80 (0.94–3.45)2+ 2.23 (1.16–4.31)Periodontal diseaseNo Ref. Ref.Moderate-severedisease

1.71 (1.12–2.62) 1.99 (1.30–3.04)


2.46 (1.43–4.25) 2.11 (1.12–3.95)

Negative binominal regression (Those with P > 0.20 in the unadjusted or adjusted analysis are not included in the multi-variable model).Model 1: adjusted for age and sex.Model 2: adjusted for model 1 +model 2 (yearly household income and education).Model 3: adjusted for model 1 + model 2 SES +model 3 (reason for last visit, difficulty in paying $100 dental bill, insuredor not and smoking status).Model 4: adjusted for model 1 +model 2 +model 3 +model 4 (coronal caries and periodontal disease).aCount ratio reflects change in the ratio of OHIP-14 extent for a unit change in the corresponding “Dentition Status”groups.

Table A4. Association between OHIP-14 extent and dentition status 2 by negative binomial multivariable analyses


Dentition status 2>4 occlusal unitsand no prosthesis



0.92 (0.43–1.99) 1.16 (0.55–2.44) 1.20 (0.53–2.70) 1.05 (0.44–2.53) 1.14 (0.39–3.28)


0.86 (0.42–1.76) 1.26 (0.64–2.45) 1.87 (0.80–4.38) 1.25 (0.43–3.59) 1.69 (0.59–4.87)


2.31 (1.40–3.85) 3.58 (2.18–5.89) 3.63 (2.17–6.06) 4.03 (2.13–7.63) 3.68 (1.89–7.15)


1.92 (0.73–5.04) 2.84 (1.39–5.81) 3.87 (1.72–8.67) 3.24 (1.59–6.61) 4.58 (2.13–9.83)


SESYearly household income$80k+ Ref. Ref. Ref. Ref.$40–<80k 1.08 (0.62–1.87) 1.04 (0.66–1.640 1.02 (0.62–1.68) 0.84 (0.50–1.42)<$40k 2.35 (1.33–4.16) 2.31 (1.35–3.95) 1.31 (0.78–2.21) 1.26 (0.73–2.17)EducationYear 13 or higher Ref. Ref. Ref. Ref.Year 11 or 12 1.39 (0.87–2.21) 1.67 (1.09–2.55) 1.35 (0.88–2.08) 1.41 (0.91–2.16)≤Year 10 1.72 (1.03–2.89) 3.05 (1.78–5.24) 2.44 (1.33–4.48) 2.10 (1.11–3.93)

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Table A4 Continued


Behaviour and visitTime since last visit≤12 months Ref.1–<2 years 1.21 (0.67–2.19)≥2 years 1.01 (0.61–1.67)Reason for last visitCheck-up Ref. Ref. Ref.Problem 3.13 (2.16–4.54) 2.40 (1.63–3.55) 2.07 (1.43–3.01)Difficulty in paying $100 dental billNo Ref. Ref. Ref.Hardly any/a little 1.76 (1.18–2.62) 1.45 (0.99–2.13) 1.53 (1.02–2.30)A lot of difficulty 5.25 (3.34–8.25) 3.40 (1.95–5.92) 3.14 (1.80–5.45)InsuredYes Ref. Ref. Ref.No 1.58 (1.07–2.35) 0.78 (0.54–1.12) 0.82 (0.54–1.23)Toothbrushing frequency last week≥14 Ref.<14 1.00 (0.64–1.55)SmokingNever smoker Ref. Ref. Ref.Former smoker 0.83 (0.50–1.39) 1.12 (0.72–1.72) 1.06 (0.66–1.71)Current smoker 1.66 (1.07–2.57) 1.43 (0.88–2.30)) 1.33 (0.83–2.14)Alcohol drinkingNo Ref.Yes 0.73 (0.45–1.17)

Dental diseasesNo. of teeth with coronal caries0 Ref. Ref.1 1.71 (1.06–2.77) 1.06 (0.68–1.66)2+ 2.75 (1.58–4.79) 1.69 (0.98–2.93)No. of teeth with root caries0 Ref.1 1.80 (0.94–3.45)2+ 2.23 (1.16–4.31)Periodontal diseaseNo Ref. Ref.Moderate-severedisease

1.71 (1.12–2.62) 2.05 (1.35–3.11)


2.46 (1.43–4.25) 2.60 (1.24–5.43)

Negative binominal regression (Those with P > 0.20 in the unadjusted or adjusted analysis are not included in the multi-variable model).Model 1: adjusted for age and sex.Model 2: adjusted for model 1 +model 2 (yearly household income and education).Model 3: adjusted for model 1 + model 2 SES +model 3 (reason for last visit, difficulty in paying $100 dental bill, insuredor not and smoking status).Model 4: adjusted for model 1 +model 2 +model 3 +model 4 (coronal caries and periodontal disease).aCount ratio reflects change in the ratio of OHIP-14 extent for a unit change in the corresponding “Dentition Status”groups.

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Income-related inequalities in inadequate dentition over time in Australia, Brazil and USA adults

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