The Presence of Impacted Teeth (Except for Wisdom Teeth) in Orthodontic Patients in Israel

Abstract

The research objectives were to determine the prevalence of impacted teeth in orthodontic patients in Israel, examining the epidemiological and genetic linkage. Methods: Data was collected from the cohort of patients treated in Tel-Aviv University between 2010–2017. Forty-five patients treated for impacted teeth were randomly selected, compared to 45 control patients, paired by age and sex. Collected data included: week of birth, type of birth, medical history, dental anomalies, treatment referee, chief complaint, treatment modalities and treatment duration. Results: The periodic prevalence of impacted teeth was 11.9%. There was a statistical tendency in the week of birth and type of birth (earlier birth week and more caesarean sections in the study group). Statistical significance was found for systemic disease, chief complaint, referee for treatment and treatment duration. Dental anomalies for the patient or first-degree relatives found odds ratio for the presence of an impacted tooth up to 6 times higher. Conclusions: There is epidemiological data related to impacted teeth, such as preterm births and caesarean sections, with the need for further research.

1. Introduction

Impacted tooth refers to a situation in which a tooth will probably not erupt spontaneously into the oral cavity at the estimated time according to dental age, without the aid of surgical intervention and/or orthodontic treatment [1]. The incidence of impacted teeth is 0.8–3.6% of the total population [2], with the most common teeth being, in descending order, wisdom teeth, maxillary canines, mandibular second premolars and maxillary lateral incisions [2]. Among patients with impacted canines, in about 8% of patients, the condition is bilateral [3]. Most studies reported no gender predilection, whereas some studies reported a higher incidence in women compared to men: for example, with impacted canines, a ratio of up to three times greater in women was reported [4,5].

The causes for impacted teeth are multifactorial and can be divided into three groups: systemic factors, local factors and genetic factors. Endocrine deficiencies and radiation therapy are examples of systemic factors. Local factors include various causes such as problems related to deciduous teeth (over-retained, early extractions), excess number of teeth, dental crowding, and local pathology (such as dentigerous cyst, odontoma, or other pathology), thick mucosa, dental trauma and abnormal position of the tooth. Genetic factors may include amelogenesis imperfecta, alveolar cleft and Cleidocranial dysostosis [3,4,5,6].

Previous studies found a link between genetics and impacted teeth, with higher correlation with other dental anomalies such as peg-shaped/small lateral incisors, infra-occlusion of deciduous molars, small sized maxillary teeth, enamel hypoplasia, and wisdom tooth malformation [7,8,9,10,11,12]. There are cases of multiple impacted teeth, which are usually associated with rare genetic syndromes such as Cleidocranial dysplasia, Gardener’s syndrome and Noonan’s syndrome. However, in rare cases, multiple impacted teeth may be found without any known syndrome [13]. It has been reported that premature birth indicates higher incidence of impacted teeth compared to control group [14].

Clinical features raising suspicion for an impacted tooth may include delay in normal eruption time, crowding with lack of space for eruption, tilted adjacent tooth and over-retained deciduous tooth [8]. The diagnosis is made through clinical examination concomitant with X-ray imaging, to diagnose and assess the location, angulation, and adjacent anatomical landmarks of the tooth [8]. Early diagnosis is crucial for successful treatment [7].

Treatment options should be tailored to the specific patient and may include follow-up, extraction of the deciduous tooth, forced orthodontic eruption (with the help of orthodontic appliances and surgical exposure of the impacted tooth), and extraction of the impacted tooth. Traction of the tooth into the oral cavity is a common treatment option [1,15]. The two common methods used for surgical exposure of impacted tooth are open exposure (removing the buccal/palatal mucosa and the bone covering the tooth crown leaving the tooth exposed to the oral cavity) and closed exposure (with flap elevation to expose the impacted tooth followed by suturing the flap back to its place after the exposure) [16].

The choice of surgical type depends on several considerations and factors, which include the location of the impacted tooth (buccal or palatal), the depth of the impacted tooth within the bone and the presence of the orthodontist at the time of surgery [1]. Previous studies comparing the two methods have found no significant difference in terms of postoperative pain, but better periodontal condition in the closed method [17,18].

The purposes of this study were to determine the presence of impacted teeth (except wisdom teeth) in orthodontic patients in Israel and to examine possible epidemiological link and family genetics to impacted teeth. The data were also used to examine the surgical intervention for the treatment of impacted teeth (duration of orthodontic treatment, the surgical method of treatment and the relationship between the patient’s age and the surgical treatment performed).

2. Materials and Methods

The study included the cohort of patients in the departments of orthodontics and oral and maxillofacial surgery treated at the School of Dentistry in Tel-Aviv University between the years 2010–2017. Full IRB approval from Tel-Aviv University was provided for the research. The data collected included the total number of patients who sought treatment in the Department of Orthodontics at Tel-Aviv University, as well as the number of patients who sought orthodontic treatment suffering from impacted teeth (other than wisdom teeth). For the purpose of the study, 45 patients with impacted teeth were randomly selected from the impacted teeth cohort and 45 patients selected for the control group (without impacted teeth) paired by age and sex. Inclusion criteria for the study group included impacted teeth that required surgical intervention, without syndromes associated with the impacted teeth, with full documentation regarding their treatment.

Data collected included sex, date of birth, chief complaint (missing teeth/aesthetics/other) and past medical history. Other variables collected regarding the birth details: week of birth, type of child delivery (natural or cesarean), complications during birth, first-degree relatives with impacted teeth and number of impacted teeth in a specific patient. More data included referee for treatment, treatment time (from the beginning of treatment until tooth exposure and until the end of the treatment) and surgical treatment (open/closed exposure vs. extraction of impacted tooth).

The missing details in the files, such as details regarding family genetics, were collected in a telephone conversation with the patients. All patients had pre-treatment panoramic X-ray—in which counting the dental germs of third molars was performed.

Statistical analysis was performed using SPSS software (IBM SPSS Statistics for Windows, version 24.0. Armonk, NY, USA: IBM Corp). Analysis of possible risk factors for the presence of impacted teeth was performed using a t-test for continuous variables, chi-square or Fisher’s exact test for dichotomous variables, and a logistic regression model for risk factors affecting the presence of impacted teeth.

3. Results

Between the years 2010–2017, 1654 patients were treated in the Department of Orthodontics at Tel-Aviv University, of whom 197 were patients with impacted teeth, with periodic prevalence for impacted teeth being 11.9% (95% confidence interval: 10.35–13.47%). Age and sex distribution in the research group (impacted teeth) and the control group are presented in

Table 1. Demographic data of the research group and the control group.

		Research Group (Impacted Teeth)	Control Group	p-Value
Age (Mean ± Std.)		15.71 ± 6.71	16.38 ± 6.30	0.627
Sex	Female	26 (57.8%)	26 (57.8%)	0.584
	Male	19 (42.2%)	19 (42.2%)

.

Table 2. Comparative variables between the research group and the control group.

		Research Group	Control Group	p-Value
Birth week (Mean ± Std.)		38.69 ± 2.009	39.36 ± 1.35	0.068
Labor	Natural	34 (75.6%)	40 (88.88%)	0.087
	Cesarean	11 (24.4%)	5 (11.11%)
Complication during labor	Yes	5 (11.1%)	2 (4.4%)	0.434
	No	40 (88.9%)	43 (95.6%)
Systemic disease	Yes	8 (17.8%)	0 (0.0%)	0.006
	No	37 (82.2%)	45 (100.0%)
Other teeth anomalies	Yes	15 (33.3%)	3 (6.7%)	0.003
	No	30 (66.7%)	42 (93.3%)
Relatives’ teeth anomalies	Yes	11 (24.4%)	2 (4.4%)	0.014
	No	34 (75.6%)	43 (95.6%)
No. of wisdom teeth/germ	None	15 (33.3%)	10 (2.2%)	0.347
	1/2/3/4	30 (66.7%)	35 (77.8%)
Chief complaint	None	1 (2.2%)	1 (2.2%)	0.000
	Esthetics	25 (55.6%)	43 (95.6%)
	Missing teeth	19 (42.2%)	1 (2.2%)
Who referred for treatment	Self	7 (15.6%)	18 (40.0%)	0.027
	Pedodontics	4 (8.9%)	2 (4.4%)
	General dentist	31 (68.9%)	25 (55.6%)
	Other	3 (6.7%)	0 (0.0%)
Duration of treatment in years (Mean ± Std.)		4.24 ± 1.87	2.43 ± 0.87	0.000

presents the epidemiological data. There was a tendency for statistical significance in the research group compared to the control group both in the average birth week (38.7 vs. 39.4 weeks respectively, p = 0.068) and the type of birth (natural/cesarean section: 24.4% vs. 9.1%, respectively, p = 0.087). There was no statistical difference regarding complications during childbirth.

Significant results (p = 0.006) were obtained regarding the medical condition of the patients: eight patients in the study group (17.8%) suffered from a systemic disease (7 suffered from respiratory disease and one patient with thrombophilia) compared to 0 patients in the control group. Regarding the genetics and dental condition of the patients and their families, the existence of other dental anomalies (peg shaped lateral/excess tooth/missing tooth) was statistically significant among the study group and among their family members compared to the control (p = 0.003, and p = 0.014, respectively). No significant difference was found comparing the number of existing wisdom teeth.

Comparing the reason for seeking orthodontic treatment, in the study group the most common referring doctor was a general practitioner (31 patients, 68.9%), compared to a general practitioner (25 patients, 55.6%) and self-referral (18 patients, 40%) in the control group, with statistical significance (p = 0.027). The chief complaint was also significant (p < 0.0001) with aesthetic complaint in the control group at 95.6% compared to 55.6% in the study group. The overall duration of orthodontic treatment was 4.2 years in the study group compared to 2.4 years in the control (p < 0.0001).

Table 3. The distribution of the impacted teeth in the study group.

		Number of Patients
Jaw	Maxilla	38 (84.4%)
	Mandible	4 (8.9%)
	Both	3 (6.7%)
Side	Right	17 (37.8%)
	Left	12 (26.7%)
	Bilateral	16 (35.5%)
Type	Maxillary central Incisor	8 (11.1%)
	Maxillary lateral Incisor	1 (1.4%)
	Mandibular lateral Incisor	1 (1.4%)
	Maxillary canine	44 (61.1%)
	Mandibular canine	5 (6.9%)
	Maxillary 1st premolar	3 (4.2%)
	Maxillary 2nd premolar	3 (4.2%)
	Mandibular 2nd premolar	2 (2.8%)
	Maxillary 1st molar	1 (1.4%)
	Mandibular 1st molar	1 (1.4%)
	Maxillary 2nd molar	2 (2.8%)
	Mandibular 2nd molar	1 (1.4%)
Number of impacted teeth	1	25 (55.6%)
	2	15 (33.3%)
	3	4 (8.9%)
	4	0 (0%)
	5	1 (2.2%)

shows the distribution of impacted teeth. Most of the impacted teeth were in the maxilla (84.4%); no difference was found between right and left or bilateral impaction. The most commonly impacted teeth in descending order were: maxillary canine, maxillary incisor, mandibular canine, premolars and molars. A total of 55.6% of the patients had one impacted tooth, while the other 44.4% had more than one impacted tooth.

Analyzing the impacted teeth group separately, most patients underwent open or closed exposure (14 and 21, respectively), 5 underwent tooth extraction, and the remaining five underwent no surgical procedure at all (two patients underwent rapid palatal expansion—RPE, and in three patients the tooth erupted spontaneously after orthodontic space opening). In addition, there was no correlation between the type of surgical procedure and the patient’s age. Of all patients who underwent surgical procedures for the exposure of impacted tooth, 8 (18.2%) patients underwent an additional surgical procedure (recurrent exposure/extraction).

The logistic regression model found that the factors influencing the presence of an impacted tooth were only the presence of other dental anomalies (in the specific patient) and the presence of dental anomalies in their family members, with an odds ratio 6 times higher and 5.7 times higher, respectively (p = 0.009 and p = 0.034), while the other variables were not found to affect risk (week of birth, type of birth, medical condition, etc.).

4. Discussion

In this study, we examined data on the presence and distribution of impacted teeth in orthodontic patients in Israel. It was found that the prevalence of impacted teeth in orthodontic patients is 11.9% (95% confidence interval: 10.35–13.47%). This prevalence is higher than reported in other studies, being up to 6.15% of the population [2,19]. It probably represents the population of patients referred for treatment within a university/hospital setting and is less suitable for describing the general population, since in many cases the complex cases fall within the university framework.

In an attempt to find an epidemiological link and understand the family genetics of impacted teeth, the groups were compared with respect to a number of variables, some with significant results and some with a tendency to significant results. Examining patients’ birth data, we found that the mean week of birth in the study group (38.7 weeks) was earlier than the week of birth in the control group (39.36 weeks) and the results were almost significant, even though the clinical significance is doubtful. In addition, we found significant tendency regarding the nature of birth, with more cesarean sections in the study group compared to the control group. These results are consistent with the hypothesis that a preterm birth week can affect the presence of impacted teeth, and accordingly are consistent with other studies in which the connection between preterm births and the need for complex orthodontic treatment has been proven, including impacted teeth [13]. A possible explanation for this phenomenon may lie in the fact that infants born in the week of pregnancy earlier than normal have not yet completed their fetal development, especially when it comes to the respiratory system. Another explanation is related to iatrogenic damage that can be caused in the care of babies after birth, such as oxygen given to the baby through his nose affecting bone development [20]. A meta-analysis conducted in England examined the effects of cesarean delivery on infants and found an association between surgical birth and an increased risk of developing asthma in those children compared to children born by normal birth [20], which corresponds to the findings in the present study in which in the study group presented more systemic diseases related to the respiratory system.

There are multiple causes for impacted teeth, such as systemic factors, local factors and genetic factors [3,4,5,6]. The familial connection to impacted teeth and other dental anomalies has been investigated and proven in many studies [12], and significant results have been obtained in the present study as well. Among the study group, it was found that there were significantly more dental anomalies in the patient’s family members, including impacted teeth. In addition, the study group had more dental anomalies in the patients themselves (with the impacted teeth), findings which are consistent with reports from previous studies that showed a correlation between impacted teeth and other dental anomalies [9]. In performing the logistic regression model, risk factors for the presence of impacted teeth were the only dental anomalies in the patients and in their family members with increased odds ratios of 5.7-fold and 6-fold, respectively, for the presence of an impacted tooth, which is consistent other studies [4,5,21]. Previous studies have also reported the association between impacted teeth and lack of wisdom teeth [10,11], but in the present study we have not been able to prove this association, probably due to limited sample size.

Other differences found between the groups were related to the treatment referee and the chief complaint of the patients. In the study group, most patients were referred by a community general dentist compared to the control group where high percentages of patients came independently. This difference can be explained by the fact that most dentists refer complex patients for treatment in a university/hospital setting while the simpler cases remain in community care. This figure also explains the high prevalence of impacted teeth among patients who came to the university. Regarding the main complaint that brought the patients for treatment, most “simple cases” have aesthetic complaint, while the study group had a high percentage with a complaint about lack of teeth. This finding highlights the awareness of patients with impacted teeth to the problem that led them to seek treatment.

Regarding the treatment duration, as expected, impacted teeth treatment time was almost twice that of regular treatment (4.2 years vs. 2.4 years). Although the treatment is performed in the university setting (with residents treating most cases) in which the duration of treatment may take longer because of teaching, it is nevertheless an important fact that must be considered in the beginning of orthodontic treatment, which involves impacted teeth. Moreover, in 18.2% of the cases who had surgical exposure of the impacted tooth, there was a second surgical intervention, which also influenced the longer duration of treatment.

In examining the distribution of the impacted teeth in the study group, we obtained results that are mostly consistent with previous studies. Apart from wisdom teeth, which were excluded from the study, it was found that the most common impacted tooth is a maxillary canine, as has already been proven in previous studies, followed by incisors, pre-molars, and molars. The maxilla was more involved with impacted teeth and there was no difference in the side of the impacted tooth between right and left [1,2,6,8,22].

Examining the type of surgical procedure performed for the traction of the impacted tooth found no relationship between the patient’s age at the time of surgery and the type of surgery. The type of exposure probably depends, among other things, on the personal preferences of the operating surgeon and the orthodontist, in addition to other factors that depend on the location of the tooth and its position. The hypothesis that tooth extraction will be more common at a relatively older age, rather than tooth exposure, has not been proven in the current study. This can be also attributed to the limited sample size of the research group.

Our study found that the only factors correlated to impacted teeth were the presence of other dental anomalies in the specific patient or in their family members, with an odds ratio of up to 6 for the presence of impacted teeth. These findings, with the fact that preterm birth week can affect the presence of impacted teeth, may lead to the need for further studies with higher number of patients, in order to check the possible correlation of birth delivery and systemic disease to impacted teeth.

5. Conclusions

There may be an association between preterm births and cesarean child delivery to the presence of impacted teeth, as well as a higher presence of systemic diseases related to the respiratory system. There is a high correlation between other dental anomalies and impacted teeth (both in the patient and in their first-degree family members). The duration of treatment of impacted teeth is significantly higher than regular treatment. Further research with a larger sample size is recommended.