Tooth loss in Sri Lankan adults

Abstract

Aim: To determine the prevalence and correlates of tooth loss in Sri Lankan adults. Design: A descriptive cross sectional study. Setting: Colombo district of Sri Lanka. Participants: Adults aged 20 years and above. Methods: Data were collected by means of an interviewer administered questionnaire and an oral examination. Results: The overall prevalence of tooth loss was 81.6% while 1.9% of the sample was edentulous. The prevalence rates of tooth loss in the 20–39, 40–59 and ≥60-year-old were 71%, 93% and 96%, respectively, while 0%, 1.5% and 11.4% were edentulous in the three groups. Age (OR = 1.10; 95% CI = 1.08–1.11), having received 11 or more years of education (OR = 0.38; 95% CI = 0.15–0.97), use of fluoride toothpaste (OR = 0.44; 95% CI = 0.30–0.66), brushing frequency (OR = 0.62; 95% CI = 0.43–0.89) and use of dental services (OR = 2.08; 95% CI = 1.12–3.84) were significantly associated with having more than 12 missing teeth. Conclusions: The overall prevalence of tooth loss is high among Sri Lankan adults.

It is common knowledge that oral health is greatly influenced by having healthy teeth. Tooth loss is the ultimate consequence of oral disease and hence is considered as an important indicator of oral health status. One of the global goals for oral health set by the FDI/WHO for year 2000 was to maintain a natural dentition of not <20 teeth throughout life¹. Moreover, Hobdell et al.² have considered the reduction of tooth loss as one of the targets for achieving global goals for oral health for 2020.

Tooth loss occurs due to mechanical or pathological reasons. Extraction by a dental health care provider is the most common cause while spontaneous loss could occur due to advanced periodontal conditions and trauma. Tooth loss could have an impact on the oral health related quality of life of an individual by affecting the ability to chew, speak, appearance and general performance3., 4.. In recent times researchers have shown an interest in assessing the effect of tooth loss on general health status. Studies have shown that tooth loss is associated with the onset of disability and early mortality in old age⁵.

As prevention of tooth loss is an important goal in dentistry, there is a need for data on tooth loss. Studies on tooth loss have been conducted extensively throughout the world and evidence indicates that tooth loss and edentulism are declining in some countries⁶. With regards to Sri Lanka, the National Oral Health surveys as well as a few other studies provide some useful information on tooth loss and related issues for the Sri Lankan population. However these studies have their limitations in that they have been restricted to specific ethnic groups⁷, age groups⁸ or dentate subjects⁹. Thus there is a need to assess tooth loss across a wider population involving adults of all ages, social and ethnic groups to obtain in depth knowledge on the topic. Moreover information obtained from such studies will be helpful for planning and implementation of interventions to reduce tooth loss. Considering the aforementioned factors the aim of the present study was to determine the prevalence and correlates of tooth loss in Sri Lankan adults.

METHODS

The data for the present paper were obtained from a comprehensive study on tooth loss and its effects on the well-being of an adult population from the Colombo district. Only data pertaining to the prevalence and correlates of tooth loss will be presented here.

This cross-sectional study was conducted among free living adults aged 20 years and above who had been residing in the Colombo district for at least 3 years. Persons living in business premises, prisons, hostels and religious institutions, invalids and those with intellectual disabilities were excluded. As previous studies have shown that tooth loss increases with age, it was decided to consider three age groups; 20–39, 40–59 and ≥60-year-old and the sample size for each age group was calculated separately. The formula for estimating a population proportion with absolute precision was used to determine the sample size. For calculating the sample size for each group, the prevalence rates of tooth loss reported in the National Oral Health survey¹⁰ for 15 (20%), 35–44 (80%) and 65–74-year-old (90%) were used.

Considering the above prevalence rates, a confidence interval of 95% and a margin of error of 5% for the first two age groups and a margin of error of 4% for the ≥60-year-old group, the sample size required for the three groups were 246, 246 and 216. Since it was decided to use the cluster sampling technique it was necessary to make allowance for the design effect which was considered as 1.5. Therefore after adjusting for the design effect, the size of the samples required for the three age groups were 369, 369 and 324. These were further increased by 10%, 20% and 40% to make allowance for non-respondents which gave a sample size of 406, 443 and 454 for the 20–39, 40–59 and ≥60-year-old age groups respectively. When a cluster sampling method is used, in order to obtain valid data at least 30 clusters have to be included in a study¹¹. As the study population is large and distributed over a wide geographical area, it was decided to include 60 clusters from each age group to ensure validity. Hence the sample size derived for each age group was increased to the nearest multiple of 60. The final sample size considered for the three age groups were 420, 480 and 480 while it was necessary to select 7 (420/60) 20–39-year-old, 8 (480/60) 40–59-year-old and 8 (480/60) ≥60-year-old individuals from each cluster.

Administration of health services in the Colombo district is carried out by two authorities: Ministry of Health and the Colombo Municipal Council (CMC). The regions under the purview of these two authorities are further divided into Public Health Inspector areas (PHI). The 60 clusters were allocated to the two regions based on the population proportions: 17 to the CMC area and 43 to the rest of the district. A PHI area was considered as a cluster unit and the required number of clusters was identified from the two regions based on the probability proportionate to size technique. Then individuals who satisfied the inclusion criteria were selected by visiting households in each cluster. Only one person from a given age category was selected from a household. Data were collected by means of a pre-tested interviewer administered questionnaire and an oral examination. The questionnaire was intended to obtain information on socio-demographic data, oral health behaviours including dental utilisation, and the medical history. The oral examination and the administration of the questionnaire were done by the first author while the subject was seated on an ordinary chair under natural light. Teeth present, number of occluding natural pairs of teeth and number of occluding pairs of teeth were noted.

Data were analysed using SPSS 13.0 software (SPSS Inc., Chicago, IL, USA). As the sample sizes were calculated for the three age groups separately, the data were weighted according to population age proportions of the district in the analysis. It was assumed that an individual would have 32 teeth by the age of 20 years. Chi-squared test was used to determine the associations between categorical variables. As the distribution of the number of missing teeth was highly skewed, a multiple logistic regression analysis was used to determine the independent associations between the dependent variable-missing teeth (dichotomised as 0 if 1–12 missing teeth and 1 if 13–32 missing teeth) and the explanatory variables. Age was added to the model as a continuous variable.

RESULTS

Of the 1,380 selected to be included in the sample, 1,314 responded giving a response rate of 95.2%. There was a female preponderance (55%) and according to the ethnic distribution 82%, 13% and 5% were Sinhala, Tamils and Moors respectively. A majority (84%) had received 6–10 years of education.

The overall prevalence of tooth loss was 81.6% while 1.9% of the sample was edentulous. The prevalence rates of tooth loss in the 20–39, 40–59 and ≥60-year-old were 71%, 93% and 96%, respectively, while 0%, 1.5% and 11.4% were edentulous in the three groups. Nearly 85% of the sample had 20 or more teeth. The mean number of missing teeth was 6.5 ± 7.6 (Table 1).

Table 1.

Tooth loss in the study population (weighted data)

Tooth loss
Prevalence of tooth loss* (%)	81.6
20–39-year-old	71.1
40–59-year-old	92.9
≥60-year-old	96.2
Prevalence of edentulousness* (%)	1.9
20–39-year-old	0.0
40–59-year-old	1.5
≥60-year-old	11.4
Percentage with 20 or more teeth* (%)	84.5
20–39-year-old	98.2
40–59-year-old	76.8
≥60-year-old	45.6
Mean number of missing teeth*	6.5 ± 7.6
20–39-year-old	2.9 ± 3.3
40–59-year-old	8.9 ± 7.7
≥60-year-old	15.9 ± 9.9

^*Total sample.

The associations between socio-demographic variables, behavioural variables and tooth loss are shown in Table 2. Of the socio-demographic variables, age, gender and level of education were associated with tooth loss. Moreover tooth loss was also associated with all behavioural variables considered namely brushing frequency, use of fluoride toothpaste, smoking status and use of dental services. Table 3 shows the multiple logistic regression analysis for tooth loss. Age was significantly associated with tooth loss. The odds of having >12 missing teeth was 1.69 times higher in females compared to males while it was 0.38 lower in those who had ≥11 years of education compared to those who had up to 5 years of education. Use of fluoride toothpaste (OR = 0.44; 95% CI = 0.30–0.66), brushing frequency (OR = 0.62; 95% CI = 0.43–0.89) and use of dental services (OR = 2.08; 95% CI = 1.12–3.84) were significantly associated with having >12 missing teeth.

Table 2.

Associations between socio-demographic, behavioural variables and tooth loss (weighted data; n = 1,314)

Variable	Missing teeth, n (%)				P-value
	0	1–12	13–31	32
Age group (years)
20–39 (706)	204 (28.9)	489 (69.3)	13 (1.8)	0 (0.0)	<0.001
40–59 (450)	32 (7.1)	313 (69.6)	98 (21.8)	7 (1.5)
≥60 (158)	6 (3.8)	66 (41.8)	68 (43.0)	18 (11.4)
Gender
Male (589)	122 (20.7)	398 (67.6)	59 (10.0)	10 (1.7)	0.003
Female (725)	120 (16.6)	470 (64.8)	120 (16.6)	15 (2.1)
Ethnicity
Sinhala (1,087)	204 (18.7)	702 (64.5)	158 (14.5)	23 (2.1)	0.06
Tamil (165)	31 (18.8)	118 (71.5)	16 (9.7)	0 (0.0)
Moor (62)	7 (11.3)	48 (77.4)	5 (8.1)	2 (3.2)
Education (years)
Up to 5 (140)	22 (15.7)	66 (47.1)	41 (29.3)	11 (7.9)	<0.001
6–10 (1,100)	199 (18.1)	755 (68.6)	132 (12.0)	14 (1.3)
≥11 (74)	22 (29.7)	47 (63.5)	5 (6.8)	0 (0.0)
Brushing frequency
≤once/day (229)	22 (9.6)	147 (64.2)	42 (18.3)	18 (7.9)	<0.001
>once/day (1,085)	220 (20.3)	721 (66.5)	137 (12.6)	7 (0.6)
Use of fluoride toothpaste
No (164)	18 (11.0)	90 (54.9)	39 (23.8)	17 (10.3)	<0.001
Yes (1,150)	224 (19.5)	778 (67.7)	140 (12.1)	8 (0.7)
Smoking status
Never (1,000)	185 (18.5)	653 (65.3)	146 (14.6)	16 (1.6)	0.006
Current (275)	55 (20.0)	190 (69.1)	23 (8.4)	7 (2.5)
Former (39)	2 (5.1)	25 (64.1)	10 (25.7)	2 (5.1)
Use of dental services
No (212)	118 (55.7)	84 (39.6)	9 (4.2)	1 (0.5)	<0.001
Yes (1,102)	124 (11.3)	785 (71.2)	170 (15.4)	23 (2.1)

Table 3.

Multiple regression analysis of tooth loss (n = 1,152)

Variable	Odds ratio	95% CI	P-value
Age	1.10	1.08–1.11	<0.001
Gender
Male	1.00
Female	1.69	1.11–2.59	0.014
Education (years)
Up to 5	1.00
6–10	0.76	0.51–1.13	0.18
≥11	0.38	0.15–0.97	0.04
Use of fluoride toothpaste
No	1.00
Yes	0.44	0.30–0.66	<0.001
Brushing frequency
≤once/day	1.00
>once/day	0.62	0.43–0.89	0.01
Smoking status
Never	1.00
Former	0.62	0.37–1.05	0.07
Current	1.30	0.67–2.53	0.43
Use of dental services
No	1.00
Yes	2.08	1.12–3.84	0.02

Tooth loss dichotomized 0 if 1–12 missing teeth and 1 if >12 missing teeth.

R²: Cox & Snell = 30.0%; Nagelkerke = 42.0%.

DISCUSSION

This study was the first comprehensive study to assess the prevalence and correlates of tooth loss in an adult population in Sri Lanka. Having reviewed the literature for studies on tooth loss, it was evident that there were only a very few studies that had assessed tooth loss in the adult population as a whole while most have been limited either to the elderly or specific age groups. Therefore the results of this study had to be compared mainly with the latter group of studies. The overall prevalence of tooth loss was 81% while the prevalence rates were 71%, 93% and 96% for the ≥20–39, 40–59 and ≥60-year-old respectively. The third National Oral Health Survey of Sri Lanka¹² indicated that the prevalence rates for the 35–44 and 65–74-year-old were 81% and 96% respectively. In a Brazilian study it has been reported that 94% of urban adults aged 30 years and above had experienced tooth loss while the prevalence was 100% among those ≥60 years¹³. Kida et al.¹⁴ in their study on over 50-year-old Tanzanians found that 84% had lost one or more teeth. In an analysis of data from two national surveys Ojima et al.¹⁵ found that the prevalence of tooth loss was 31% among 20–39-year-old Japanese, a much lower figure than what was found for the same age group in the present study. The overall prevalence of edentulousness in this study was 1.9% while 1.6% and 11.4% in the 40–59 and ≥60-year-old were edentulous. According to the third National Oral Health Survey of Sri Lanka¹², 0.1% and 21.8% of 35–44 and 65–74-year-old had lost all their teeth. However higher rates of edentulousness have been reported in Mexican¹⁶ (6.3%) and Hungarian¹⁷ (0.6–39%) national surveys conducted among adults over the age of 18 years. The variations in tooth loss observed between the present study and those reported in the literature may be due to several reasons. Firstly the levels of dental caries and periodontal disease in the populations under study may have been different. Tooth loss is the ultimate outcome of these two conditions. Secondly, as tooth loss occurs mainly due to extractions by oral health care providers, differences in the availability and accessibility to oral health services as well as dentists’ treatment decisions may have also contributed to the observed variations between populations. Thirdly, individuals’ perceptions about the value of teeth, attitudes to dental extractions and dental utilisation behaviours may have differed between populations studied.

For the multiple logistic regression analysis tooth loss was dichotomised into 1–12 and 13–32 missing teeth. This categorisation was based on the currently accepted norm of having a minimum of 20 teeth to maintain satisfactory oral function. It was evident from the results that several demographic factors and behavioural factors were independently associated with tooth loss. As expected and conforming with other studies18., 19. tooth loss was associated with age. Due to the cumulative nature of the two most common causes of tooth loss, dental caries and periodontal diseases, tooth loss would increase with age. The mean number of teeth lost in the 20–39, 40–59 and ≥60-year-old age groups were 2.8, 8.9 and 15.9 respectively. This shows that tooth loss increases markedly from the fourth decade of life. In addition to dental caries it may be due to periodontal disease taking a toll on the dentition in over 40-year-old.

Gender differences in tooth loss have been observed in many studies with females having more missing teeth than males13., 14.. Kida et al.¹⁴ have attributed the gender difference in tooth loss to the variations in the use of dental services between men and women. In the present study, 88% of females had used dental services compared to 79% of males and the difference was significant. However, the association between gender and tooth loss remained when adjusted for use of dental services. Thus the observed gender difference in tooth loss may be due the differences in the levels of oral disease between the males and females. However, women having fewer teeth despite better periodontal health when compared to men have been attributed to an increased bone turnover rate in women²⁰.

Consistent with findings from other studies²¹, higher levels of education were associated with less tooth loss. Moreover, tooth brushing frequency and use of fluoride toothpaste had independent effects on tooth loss. As these two oral health promoting behaviours prevent and control periodontal disease and dental caries they could reduce tooth loss as well. Kim et al.²² in their study found that those who brushed frequently were less likely to have tooth loss. Routine dental attendance is associated with better oral health including lower tooth loss²³. However it was evident from the results that the odds of having >12 missing teeth was higher in those who had visited a dentist compared to those who did not visit. Similar findings have been reported elsewhere²².

Sri Lankans are generally problem-oriented dental attendees where a visit to the dentist is made particularly for the relief of pain²⁴. Hence it is likely that many individuals may end up having extractions for their dental problems. Though smoking was associated with tooth loss in the bivariate analysis, it lost its significance when controlled for other variables in the multivariate analysis indicating that the effect of smoking on tooth loss may have been mediated by those variables. A variable that may have had a confounding effect on the smoking/tooth loss relationship is gender. In this study the habit of smoking was practiced exclusively by males. Moreover in the present study, the smoking status was categorised into three groups: a current/former smoker or never smoked. Studies indicate that the relationship between tooth loss and smoking is dose dependent15., 25.. Perhaps the results may have been different if the quantity smoked by individuals was considered. Amarasena et al.⁹ found that smoking when considered as a simple dichotomous variable (whether a smoker or not) in a multiple regression analysis, was not significantly associated with tooth loss in Sri Lankans but on the other hand the quantity of tobacco used was significant.

Similar to many other community based studies, missing teeth in the present study were determined by a clinical examination. It is possible that measurement bias may have had an influence on the results of the study. Some unerupted teeth, particularly the third molars which were likely to be impacted or yet to erupt may have been misclassified as missing teeth thus marginally over-estimating the number of missing teeth in the sample.

In conclusion, the results indicate that the overall prevalence of tooth loss is high among Sri Lankan adults and a fair percentage of over 40-year-old have less than 20 functioning teeth. With respect to tooth loss, the global goals for oral health for 2020 are to reduce tooth loss and edentulousness as well as to increase the number of individuals with a functional dentition. If Sri Lanka is to achieve these goals by 2020², it is timely that health care authorities introduce programmes to prevent and control common oral disease in the community.