The present results showed the primary reasons and pattern for tooth extraction in Guangzhou and reveled that extraction reasons were different in ages, genders and tooth types. It was proposed for the first time that preventive extraction of third molar was the main reason for extraction. Our results suggest that dental health institutions should pay more attention on early intervening in disease progression, reminding people of the harmfulness and consequences of the oral disease, and eventually, raising people's awareness of dental health and promoting their change of oral health habits consciously.
Related studies have been conducted in Hong Kong and Taiwan [13, 23] and studies in mainland China focused on the frequency of a certain cause and the important role of this cause[7, 33, 34]. Previous investigations did not conduct a detailed classification and criteria of all the possible causes of tooth extraction as our study.
More than half patients extracted teeth in the age of 20 to 39 (52.9%), while patients below 20 had the smallest proportion (5.20%). These may be due to the fact that caries was thought to be easily found at a young people [21] and most patients who received orthodontic treatment and extracted third molars were concentrated in the age of 20–39 years [24, 26]. We also found patients below 20 years extracted teeth mainly because of retained primary tooth and orthodontic treatment. Children could extract primary teeth in the department of pediatric dentistry in such a specialized hospital. Thus, fewer children visited our department led to fewer patients below 20 years were recorded in our study. The average number of teeth extracted increased with age among patients over 30. This was because that, there were more teeth loss because of periodontal disease in older patients, and on the other, teeth were extracted for a better prosthetic restoration in old age.
It was observed that reasons for tooth loss was varied from age groups. Caries was the leading reason in the 30–59 age groups. Some studies presented a declining prevalence as age increased [6, 8, 9, 15, 18, 25]. In contrast, our results presented an increasing trend in patients under 60 years. The proportion of e periodontal disease markedly increased in patients over 40 years and peaked in the age of 60–69. This finding was in accord with studies which concluded that the main reason for tooth loss in older patients was periodontal disease [9, 15, 21–24, 29]. It could be explained that caries was a disease of the young and many patients extracted because of caries before they suffered from periodontal disease [21]. Furthermore, with the development of crown preservation and root canal therapy, patients preferred to restoration rather than extraction, and then patients postpone their extractions to an older age of which teeth were easier to suffer periodontal disease [24].
Our results indicated that dental caries was a main reason for tooth extraction among patients presenting at a hospital of stomatology in Guangzhou, accounted for 25.4%. This finding was consistent with the majority of similar investigations in other countries [13, 17, 21–24, 27, 28, 35]. Dental caries and periodontal disease have been believed to be the more preponderant reasons. Studies in Singapore and Italy showed that both of them was equally important [8, 9], surveys in Canada and Germany stated that periodontal disease was more dominant [11, 29]. However, our data suggested that the proportion of teeth extracted as a result of preventive extraction of third molar was only second to dental caries. This preliminary result was quite inconsistent with the previous studies and it may be attributing to a higher level of dental awareness among young patients.
It was worthy of note that preventive extraction of third molar became a dominant reason for tooth loss. In contrast with patients extracted teeth for caries in all age and periodontal disease in age over 40, majority of patients undertook preventive extraction in the age of under-40. What lead people presenting at a specialized hospital to remove their third molar for preventive reason at a young age was because that, first of all, there are more than 40 colleges and universities in Guangzhou with a large number of young students. With the strengthening of the publicity of oral health care, young people have a certain understanding of the potential danger of asymptomatic wisdom teeth. Second, the age of 20–39 is the age at which woman should prepare for pregnancy. Moreover, skills and experience were required for extraction, people were more willing to go to a specialized hospital for a treatment.
The largest number of extractions in patients under 20 was attributing to orthodontic reason (36.36%), which was consistent with previous studies in Italy, England, and Germany [8, 11, 36]. Young people extracted more than 90% of teeth for the orthodontic reason before 30 years old. They removed teeth in such young age were to correct malocclusion and maintain the effect of orthodontic treatment. The most important reason in those over 70 was pre-prosthetics extraction. Pre-prosthetics extraction, dental caries and periodontal disease were accounted for 93.89% of tooth extractions in patients over 70 years, consistent with results from previous studies [17, 23]. The present results may reflect a worse oral condition and more tooth loss in older people. However, in some backward countries like Afghanistan [21], Libya [25] and Iran [24], a small number of teeth were extracted because of orthodontic and prosthetics reasons. This is because financially and technically demanding were in need in these treatments and in a country like Afghanistan, people were eager to eat and live in peace rather than seeking for an improvement of appearance or restoration [21].
Gender difference was also suggested in this study. Males were reported more extractions (20.02%) because of periodontal disease than females (7.91%). Our finding confirmed most previous investigations which have indicated that more teeth were removed for periodontal disease in males than in females [20, 23, 29]. We observed that tooth was more likely extracted by caries and orthodontic reason in females, which was in accordance with previous investigations [15, 22, 24]. It can be explained that females are more willing to spend time and money than males to treat periodontal disease in order to avoid the loss of masticatory function and the effect of aesthetics caused by tooth loss. Moreover, male has been considered as a risk predictor for periodontal disease severity [15]. However, studies in Afghanistan and Iran have come to an opposite conclusion [21, 24]. These differences were possibly the result of different methodologies and population composition. Females were easier to suffer oral disease, which because of changes in habits and hormones when they were pregnant. As a result, the proportion of preventive extraction of third molar in female (24.78%) is much larger than that in male (12.79%).
Concerning tooth types, current results confirmed several previous findings that more posterior teeth were extracted than anterior teeth [21, 25, 27], and third molars were most extracted [8, 9, 11, 19, 23]. Third molar were comprising 54.64% of extractions, followed by first molar (11.11%), and canine extraction was the least common (2.67%). On the basis of our definition (Table 1), third molar was the unique tooth type extracted for prevention, pericoronitis and surgical reasons. And supernumerary tooth and primary tooth was almost extracted for other reasons. After careful consideration, we eventually decided to exclude subjects of these three reasons as well as subjects involving supernumerary tooth and primary tooth. We then found a statistically significant difference in the reasons for tooth extraction among tooth types (χ2 = 822.21, n=1871, df = 35, p༜0.05).
There were more than one third of third molars extracted because of preventive extraction. Caries was the principal reason in first molars and second molars. A few numbers of incisors and canines were loss for caries. These findings have been reported previously as well [12, 13, 21, 24, 27]. Furthermore, the number of third molar extracted for caries was more than double the number of either first molar or second molar, which was alike to that reported in Taiwan [23]. One possible explanation that has been discussed before was that posterior teeth were more important and involved in mastication and beyond that, posterior teeth particularly third molars were more difficult than anterior teeth to be brushed clean, thus they were easier to be exposed to a greater risk of caries. In contrast, anterior teeth were frequently extracted because of periodontal disease and pre-prosthetic reasons, which was in agreement with findings in Hong Kong [13]. Anterior teeth are less susceptible to caries than posterior teeth, they could remained longer and might be more exposed to the risk of periodontal disease [15, 24]. Moreover, anterior teeth are easier to undergo endodontic and complicated restoration treatment and thus extraction of these teeth could be deferred to an older age for aesthetic [21].Furthermore, orthodontic reason was important for premolar extraction[8, 21, 28, 36]. What was different from the previous results was that only first premolars mainly extracted for orthodontic reasons in present study. This might be due to the fact that few subjects of second premolars extractions was collected in our study.
However, there were some limitation of this study. For one, because of the vast area and huge population of China, we only chose a southern city as a sample to perform this survey. The hospital is the reginal medical center of Guangdong Province, indicating that the results we shown can represent the characteristics in this region. However, such a single-center study can’t stand for the whole country. We will conduct a multi-centers investigation in China and make a 5 years’ comparison with the current data in the future. For another, we discussed few factors associated with missing teeth. Some studies have shown several factors such as education, fluoride-related preventive effort, cultural background and dental attendance [23–25, 37]. Future studies should focus on establishing several predictors of tooth loss and this information could help to improve the oral health status.