Impact Of Asymptomatic Visible Third Molars On The Health Of Their Adjacent Second Molars: A Cross-sectional Study

Third molars(M3s)are associated with many oral problems,including caries,periodontal pathologies,food impaction,cysts or tumors in related tissues[1-7].Although some retained M3 s can lose their symptoms over time,the disease or pathology may remain[4,8].Due to the importance of second molars(M2s)in oral health and masticatory function,the effect of M3 s on the healthy status of their adjacent second molars(A-M2s)has attracted extensive attention in recent years.Numerous studies have used various methods to investigate the association between the presence of M3 s and the periodontal pathology in their A-M2s[9-12].These studies have established M3 s as a major risk for M2 periodontal damage from the aspects of clinical examination,radiological data and periodontal pathogens detection.In addition,more and more dentists and scholars paid high attention to the rise of caries prevalence on M2 s caused by adjacent M3 s.According to various investigations,the proportion of M2 s with caries is about 12.6%-52.6% when their adjacent M3 s exist[1,7,12-14].A recent study reported that even normally erupted M3 s,which had been ignored by both dentists and patients,would negatively affect the healthy condition of their adjacent teeth[12].Although the damage of M3 s has been acknowledged,the treatment of asymptomatic M3 s remains controversial[15,16].Some authors thought that it would prevent relevant pathologies or complications resulted from extracting M3 s in old age to prophylactic remove M3 s early[17-20].However,other authors held a different idea,they argued that there wasn't sufficient evidence to support or refute the prophylactic extraction of M3s[15,16],and regular oral monitoring might be more appropriate compared with removing M3 s directly[21].There are many studies investigating the detriments of M3 s,but due to the diversity of region,race,economic,culture,living habit,and other factors like experimental methods,age and gender structure of sample,the results of different studies vary greatly.However,there are few investigations about the influence of M3 s on the healthy condition of their A-M2 s in China.On the other hand,both clinicians and patients are confused about whether to prophylactic extract M3 s and when to remove them because of the lack of uniform standards and norms to provide basis on the treatment of M3 s in clinic.To explore these questions,we designed and conducted this study.In this study,we investigated oral outpatients' perception about M3 s and assessed the prevalence of V-M3 s of this population by interviewing them to finish a structural questionnaire and viewing their medical cases;we collected and analyzed patients' clinical data to evaluate the effect of V-M3 s on several common found pathologies occurred in their A-M2 s,and to assess the influence of M3 s of different clinical status on A-M2s' periodontal condition.In addition,we also examined and described the healthy situation of V-M3 s.We hope our study can bring some inspiration for clinicians,especially supply more evidence to develop treatment plans for asymptomatic M3 s in clinical practice.Aims:To investigate subjects' perception of M3 s and the prevalence of V-M3 s by analyzing the data of their questionnaire and medical cases;to assess the impact of V-M3 s on the healthy condition of their A-M2 s by comparing the prevalence of several pathologies on M2 s with or without adjacent V-M3 s respectively;to evaluate the effect of various status of V-M3 s on the periodontal situation of their A-M2 s by comparing periodontal related parameters of M2 s adjacent to different status of V-M3 s.Methods:1 A sample survey of oral outpatients' perception about M3 s.This sample survey was conducted in the Department of Periodontology,Stomatological Hospital,Fourth Military Medical University,China from July,2015 to June,2016.Subjects who matched the inclusion criteria were asked or interviewed to finish a structural questionnaire focused on their sociodemographic information and the knowledge about M3 s.In addition,we also asked subjects for permission to access their dental records to obtain the number of each subject's V-M3 s.By analyzing the data collected,we assessed the investigated subjects' perception of M3 s and the prevalence of V-M3 s in this population.2 The pathologies occurred in asymptomatic V-M3 s and the impact of asymptomatic V-M3 s on the healthy condition of their adjacent teeth.On the basic of experiment one,we conducted oral examinations for quadrants with intact first and second molars meanwhile in the qualified patients according to the inclusion and exclusion criteria.The presence of at least one site of probing pocket depth equal to or greater than 5 mm(PPD5+),at least 3 sites of bleeding on probing(BOP ? 3),caries,looseness,furcation involvement and at least one of these lesions in M2 s and asymptomatic V-M3 s were recorded.After adapting patients' age,gender,education level,occupation and other related factors,we compared the healthy condition of M2 s when their adjacent V-M3 s were present or absent respectively to investigate the influence of V-M3 s on the healthy situation of their A-M2 s.Besides,the prevalence of these diseases in V-M3 s was also described.3 A cross-sectional study of the effect of asymptomatic V-M3 s on the periodontal situation of their adjacent teeth.Objectives of this study were the subjects of experiment two.All M2 s and V-M3 s in the investigated quadrants received detailed periodontal examinations and M2 s were divided into V-M3s(+)group and V-M3s(-)group according to the presence or absence of adjacent V-M3 s.We compared the periodontal parameters of M2 s of the two groups to assess the impact of asymptomatic V-M3 s on the periodontal condition of their adjacent teeth.V-M3s(+)group was further divided into N-M3 s group(M3s erupted normally)and I-M3 s group(M3s partially impacted),and V-M3s(-)group were further divided into C-M3 s group(M3s completed impacted or congenitally missing)and R-M3s(M3s being removed more than 6 months prior to the study)group by conducting clinical examination and screening medical history.The difference of periodontal condition of M2 s in different groups was analyzed to evaluate the association between V-M3 s of various clinical status and the periodontal pathology of their A-M2 s.Besides,we investigated the influence of V-M3s' periodontal condition on the periodontal pathology of their A-M2 s by dividing V-M3 s into two groups according to the presence or absence of periodontal damage on them.4 Statistical analysisData collected from questionnaire survey and clinical examinations were entered into Epi Data 3.0 software and subsequently analyzed using the SPSS 18.0 software.Mean and standard deviation was applied to describe measurement data;frequency and rate was applied to describe enumeration data.T-test and Chi-square test was used to compare the difference among groups and the significance level was set at 0.05.Multivariable logistic regression analysis was used to assess the association of the presence of V-M3 s and their different status with the healthy condition of their A-M2 s.The analysis unit was a quadrant,except for the subset analysis for subjects who had two investigated quadrants(each in the V-M3(+)group or V-M3 group(-))in the same region(maxillary or mandible)that received clinical examinations.Given there were multiple observations per subject,we adjusted patients' age,gender,occupation and education level before analyzing the data with multivariable logistic regression analysis,or applied Stata software to eliminate clustered variances within persons and then built logistic regression model to analyze the data.Results:Completely finished questionnaires of 904 oral outpatients(37.4±13.4 years;56.1% male)were gathered and analyzed,and 52.8% of them had at least one V-M3 s.Among them,the proportion of subjects with four V-M3 s was the largest.When grouping the subjects into males and females,we found that V-M3 s were more common in males.In terms of the perception of M3 s,36.7 % of the patients gave right answers to all questions we had raised,and 43.9% had not any knowledge about M3 s or wisdom teeth.When their retained M3 s had ever been present of symptoms or pathologies,almost half of the subjects didn't take any measure.Clinical data of 2070 M2 s and 1100 V-M3 s from 572 patients(36.9±12.7 years;59.3% male)were analyzed.M2 s adjacent to V-M3 s were associated with a relatively higher risk of occurring PPD5+,BOP ? 3,caries,looseness,furcation involvement and at least one of these lesions compared to those without adjacent V-M3 s with ORs of 1.93(95% CI,1.60 to 2.34),1.38(95% CI,1.16 to 1.64),1.54(95% CI,0.81 to 2.93),1.64(95% CI,1.02 to 2.62),3.51(95% CI,1.68 to 7.34),and 3.85(95% CI,3.18 to 4.66),respectively.Neverthless,there was no statistical difference with respect to the impact of V-M3 s on caries of A-M2 s.Mandibular V-M3 s influenced the healthy condition of their A-M2 s more obvious than maxillary V-M3 s except for the prevalence of caries.More than 80% of the enrolled 1100 V-M3 s suffered at least one kind of the pathologies we examined,and mandible V-M3 s were more likely to be with the diseases than maxillary V-M3 s.M2s in the V-M3(-)group were analyzed as the reference group throughout the analysis.When V-M3 s were retained,the average of probing pocket depth(PPD),plaque index(PLI)and the percentage of PPD5+,BOP ? 3 of their A-M2 s was higher.Multivariate logistic regression analysis showed that the presence of V-M3 s significantly elevated the risk of PPD5+ on their A-M2s(ORs,2.39;95% CI,1.70 to 3.37).Either N-M3 s or I-M3 s increased the risks of PPD5+ on their A-M2 s with the ORs of 1.67(95% CI,1.09 to 2.57)and 3.02(95% CI,2.14 to 4.79)respectively.Other factors associated with the increased odds of PPD5+ of M2 s were mandibular region and age older than 35 years.In terms of the periodontal condition of V-M3 s,54.5% of the enrolled V-M3 s had at least one PPD5+ site and 53.9% of them were recorded as BOP ? 3.Periodontal pathologies were more likely to occur in I-M3 s than N-M3 s.When V-M3 s were with PPD5+ or BOP ? 3,their A-M2 s would also suffer higher PPD average and greater risks of occurring PPD5+ or BOP ? 3.Conclusions:The prevalence of V-M3 s was high in the investigated population,but they were shortage of the knowledge about M3 s.The presence of V-M3 s could negatively impact the healthy condition of their A-M2s;a relatively large proportion of V-M3 s were with pathologies themselves.Either N-M3 s or I-M3 s could elevate the risks for periodontal pathologies on their A-M2s;when there existed periodontal problems in N-M3 s or I-M3 s,their A-M2 s also suffered higher risks of periodontal pathologies;the periodontal condition of M2 s would improve to some extent after their adjacent M3 s were removed.