Evaluation of Permanent First Molar Tooth Loss in Young Population from North Turkey

SUMMARY Background/Aim: Rate of missing permanent teeth in a population is important for oral health indicators. The aim of this retrospective study was to evaluate the prevalence of previously missing permanent first molar (PMF) teeth in a young population. Material and Methods: 1204 healthy patients who received panoramic radiographs were selected randomly at their first visiting to Samsun Ondokuz Mayis University Faculty of Dentistry. The patients’ age ranges were 7 to 17. Information about extracted permanent first molar teeth, missing regions, patients’ ages, and genders was recorded. The data were statistically analyzed using chi-square tests. Results: 1,204 patients, of these, 608 (51%) were female, and 596 (49%) were male. 4,816 PFM teeth were evaluated in this study, and 128 of them (2.66%) had extracted from 97 different patients. There were statistically differences between groups in terms of age and gender (p<0.05). It was observed that mandibular teeth were more frequently extracted than maxillary ones, and lower left permanent first molar teeth had more extracted than the others. Conclusions: The first permanent molar teeth could be extracted different reasons. However, these teeth should be protected by both dentists and patients.


Introduction
Oral health care is part of general health, and it is considered essential to an individual's quality of life. Therefore, tooth loss is considered a public health problem 1,2 . Dental health programs are aimed to decrease dental plaque, tooth decay, periodontal disease and loss of teeth 3 . Although many alternative practices have been developed to protect oral health, early tooth loss is still a big problem 4 .
Permanent first molar (PFM) teeth are the first developing permanent teeth in posterior region. However, permanent first molar teeth have been characterized as most caries-prone teeth in the mixed dentition 5 . Additionally, 10-19% of PFM teeth were hypomineralization 5,6 . Consequently, PFM teeth may be lost at an early age. Other reasons for PFM teeth loss were poor prognosis, caries, orthodontic reasons and periodontal diseases 7 .
Early extraction of PFM teeth may cause undesirable rotation and mesial drifting of secondary permanent molars 8 . PFM teeth play an important role in balanced and normal occlusion 9 . Because of this, early extraction of PFM may affect whole occlusion and development of both jaws. Additionally, asymmetry and temporomandibular joint problems may be observed 8,10 . For making a decision about extraction of PFM, dental pain, excessive material loss, parental attitudes and toleration of dental treatment may affect indication. All conditions, in the developing dentition, should be assessed before extraction of PFM teeth 11 .

Material and Methods
This study was performed in the north region of Turkey (Middle Black Sea Region). Ethics approval was obtained from the Ethics Committee of Medical Research of Ondokuz Mayis University, Samsun, Turkey (2015/02). This study was performed in Ondokuz Mayis University, Faculty of Dentistry, and included 1,204 healthy patients (608 females and 596 males) who were admitted for the first time to Pediatric Dentistry Clinic for a routine dental control at first quarter of 2012. The patients' age ranges were 7 to 17, and they had received panoramic radiographs. Patients with edentulism due to a systemic disease were excluded from the study. Demographic information was recorded, including age and gender. Extracted PFM teeth, jaws, right or left side of the oral cavity were determined from panoramic radiographs. Extraction required teeth were not recorded. The data were collected retrospectively by the same physician.
Statistical analyses were performed using SPSS version 22.0 (SPSS Inc., Chicago, IL, U.S.A.). All data were evaluated as frequency and percentage. Chisquare tests were used to compare relative differences in extracted PFM, gender, age and jaws. P<0.05 was accepted as statistically significant in comparisons.

Discussion
For a long time, extraction of PFM has been subject to debate. The extraction of PFM should be planned with an orthodontist before the eruption of second and third permanent molars. In recent years, orthodontists have favored extraction and also have given indications for extraction of PFM 12,13 . Pediatric dentists have to perform complicated fillings that result in excessive material loss in children who have dental anxiety and behaviormanagement problems 14,15 . Also, these molar teeth must be kept in the mouth for preventive reasons. Sometimes, orthodontists may want to preserve these teeth because of orthodontic procedure 13 . Consequently, it is difficult the rate of missing maxillary first molar teeth was 10%. Barbato and Peres 20 showed that most missing teeth in jaws were mandibular first molars. Demirbuga et al. 18 reported that rates of missing permanent first molar teeth in mandibula were 2.77% (438) and 1.17% (185) teeth in maxilla. In the present study, the number of extracted PFM teeth in the lower arch was 87 and in the upper arch was 41. This situation can be explained by several factors. One of them is that more nutrients remain in the lower jaw than upper. Others are early eruption of mandibular teeth, caries, increased hypomineralization level, different effects of saliva and different anatomical structures of the teeth.
In the literature, there is limited information about early missing teeth on the left and right sides of the oral cavity in pediatric patients 18 . It was claimed that hand selection when tooth brushing may affect ra tes of extraction on left or right sides of the oral cavity 18 . Similarly, chewing and cleaning habits and the residence time of food in the mouth may play important roles in ra tes of extraction on the left or right sides of the jaws. In contrast, Bhat et al. 21 found no significant difference between ra tes of extraction on the left and right sides of the oral cavity. Demirbuga et al. 18 reported that right side missing teeth numbered 302 (1.91%) and left side missing teeth amount to 321 (2.03%), and they did not find statistical differences between the right and left sides of jaws. Similar to previous studies, this study's results showed that the numbers of formerly extracted PFM teeth were 60 in the right side and 68 in the left side and showed no statistical differences.
The ideal time for extraction of a PFM is at a chronological age of 8-10 years 11 . Gill et al. 23 claimed that extraction of PFM with poor prognosis in this time interval should facilitate mesial movement of the permanent second molar into the PFM area. Otherwise, extraction at a later age may result in unsatisfactory and inadequate space closure, condylar problems and orthodontic malocclusion 24 . In the present study, according to age, the rate of missing teeth was 5.5% in 8-10 age and 57% in 13-15 age, but the time of extraction of the missing teeth was not known exactly.
Nowadays, dental materials and treatment choices have rapidly evolved. Direct/indirect pulp capping, root canal treatment, post-core, inlays/onlays, porcelain and ceramic crowns are good alternative treatments 25 . The results of the study showed that a large number of teeth had extracted between the ages of 11-16. Preventive treatments should be increased for preservation of natural dentition, especially, in females.

Conclusions
In this retrospective study, mandibular first molar teeth were more frequently missing than maxillary teeth, to decide about PFM tooth extraction. Therefore, in the present study, only the frequency of extracted PFM teeth was investigated.
Despite the researches, early tooth loss is still a big problem, especially since the early loss of permanent first molars plays a key role in the asymmetry of dentition 4,8,10 . Therefore, determination of the number of patients with early loss of permanent first molars in the community will be beneficial. In the present study, although many cases required tooth extraction etiologically, only extracted first molar teeth were investigated. In this study, the number of previously extracted permanent first molars was 128 (2.66%) of 4,816 PFM teeth in 97 (8%) of 1,204 patients. The data were compared with previous studies [16][17][18] .
Alves et al. 16 performed a study among 12-yearold schoolchildren from South Brazil. The researchers observed that tooth loss rate in 1,528 patients were 5.81%. This rate was lower than in this study (8%) because they included only patients who were 12 years of age. George et al. 17 reported that rates of all missing permanent teeth in children and young people of 6, 12 and 15 ages were 5.7% 22% and 28.3%, respectively. These rates were higher than in this study because they had included all permanent teeth. Atieh 19 reported that the rate of teeth loss in 484 patients aged 14-19 were 40.9% (198 patients). This rate was higher than in this study because they had included all permanent teeth. Demirbuga et al. 18 performed a study on 31,580 permanent first molar teeth from 7,895 patients' panoramic radiography, and reported that missing teeth rates from 19,488 teeth in 6-11 age groups were 0.47% (122) and in 12-16 age groups from 12,092 teeth were 4.14% (501). These results were very similar to the results in this study.
Several studies 17,18,20 determined that gender may influence tooth loss, which agrees with findings of present study. Demirbuga et al. 18 reported that of the 15,008 teeth examined in the boys' group, 1.84% (276) were missing, and in the girls' group, of 16,572 teeth, 347 (2.09%) teeth were missing. George et al. 17 determined that tooth loss rates in males (42.9%) were lower than in the females (47.9%). Barbato and Peres 20 claimed that this finding could be explained by the fact that females use more dental services due to their deeper health or aesthetic concerns, which may lead to overtreatment. On the contrary, Bhat et al. 21 reported that the percentages of extracted teeth in males were 53.1% and in fe males were 46.9%. Jafarian and Etebarian 7 assessed that males comprised 48.7% of patients, but they had more extracted teeth (56.1%) than females (43.9%). On the other hand, Susin et al. 22 claimed that tooth loss was affected more by the age factor than by gender. They stated that the prevalence of tooth loss increased markedly with age from 26% to 60% in the age groups 14-19 and 25-29 years, respectively 22 .
Some studies stated that most missing teeth were in the mandibular 20,21 . Bhat et al. 21 determined that the rate of missing mandibular first molar teeth was 21%, while