The brass wire ligature is an efficient method to correct a moderately mesially impacted mandibular second molar (MM2). The aim of this prospective clinical pilot study was to evaluate the influence of mandibular third molar (MM3) germectomy on the treatment time for this procedure and to determine its impact on oral health-related quality of life (OHRQoL) using the short-form Oral Health Impact Profile (OHIP-14). The STROBE guidelines were followed. Impacted MM2 were assigned randomly to receive brass wire ligature treatment either with germectomy (group A) or without germectomy (group B). Descriptive statistics and the Student t -test were used in the statistical analysis; significance was set at P ≤ 0.05. One thousand and thirty patients were assessed. Fourteen subjects with 20 mesially angulated (range 25–40°) impacted MM2 were identified. Paired comparisons of groups A and B showed no statistically significant difference in treatment time (171 days for group A and 174 days for group B; P = 0.440), but a statistically significant difference in OHIP-14 values at the 3- ( P = 0.017) and 7-day ( P = 0.002) follow-up. The brass wire technique can be used effectively in moderately impacted MM2, but the combined use of MM3 germectomy does not influence the treatment time and shows a negative impact on OHRQoL.
Mandibular second molar (MM2) impaction is relatively rare, with a reported prevalence of 0–2.3% . However an increase in prevalence has been observed over the years , probably due to the reduction of extractive orthodontic treatments performed in recent years .
A relationship between the presence of the mandibular third molar (MM3) and MM2 impaction can be hypothesized, although crowding has been cited as a common cause of MM2 impaction . In a recent study, the distance between the mandibular first molar (MM1) and the ramus was found to be smaller in patients with MM2 impaction compared to a control group, with the difference being statistically significant . These data confirm the results of Kaplan, who suggested that MM2 impaction can be related to a problem of arch length deficiency that may be associated with an MM3 impaction .
As occurs in cases of MM3 impaction, it is likely that any biomechanical approach that prevents mesialization of MM1 will determine an MM2 impaction . MM2 impaction has been described in terms of three forms of angulation: mesial, vertical, and distal . Mesial angulation is the most common form (88%) , and an initial MM2 inclination of greater than 20°/24° or 30° has been significantly associated with a high risk of impaction . Unilateral impaction is more common than bilateral impaction, males are more affected than females, and the frequency is higher on the right side than on the left side .
The treatment of MM2 impaction is often interdisciplinary and very challenging for the orthodontist. An early diagnosis of a disturbance in the eruption process of MM2 is imperative, because this might reduce the risk of impaction or the difficulty of treatment. The best time to treat an impacted MM2 is between 11 and 14 years of age, when development of the MM2 roots is still incomplete . The choice of treatment will depend on the degree of tooth inclination, as well as the required tooth movement. The position of a slightly tipped molar can be corrected by placing a brass wire separator between the teeth . A more severe inclination requires surgical or orthodontically assisted eruption .
No agreed classification exists to categorize the degree of mesial inclination of the impacted MM2, although the terms mild, moderate, and severe are frequently used in the literature . Furthermore, there is little information in the literature regarding the degree of mesial inclination that can be treated using a brass wire.
In addition, results are conflicting with regard to the extraction of the MM3 germ to facilitate MM2 uprighting. According to some authors, the position of the MM3 germ may represent an obstacle to the distal movement of the impacted MM2, indicating the need for extraction . According to others, it is sometimes better to leave the MM3 bud to facilitate MM2 rotation .
The primary objective of this clinical pilot study was to evaluate the influence of MM3 germectomy on the duration of treatment for MM2 impaction. The impact of germectomy on oral health-related quality of life (OHRQoL) was also evaluated.
It was hypothesized that MM3 germectomy would reduce the treatment time for MM2 uprighting using the brass wire technique. It was also hypothesized that MM3 germectomy would not have a statistically significant impact on OHRQoL.
Materials and methods
This prospective clinical pilot study was conducted at the Department of Orthodontics of the School of Dentistry, “Sapienza” University of Rome, Italy, between November 2014 and November 2015. The STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines for prospective case–control studies were followed.
The MM2 was considered impacted if its complete eruption to occlusal height was prevented by abnormal contact with another tooth in the same arch, or when it remained unerupted beyond the time at which it should normally have erupted . The diagnosis of impaction and the site of impaction were determined on the basis of clinical examinations and panoramic radiographs.
This clinical investigation was conducted in accordance with the ethical principles of the World Medical Association Declaration of Helsinki. The clinical investigation was undertaken after informing the parents or guardians of the content, risks, and benefits of the study and after obtaining written consent. The investigation was independently reviewed and approved by the local ethics committee.
Eligibility criteria were the following: (1) Caucasian child over 12 years of age; (2) no previous orthodontic treatment; (3) no systemic syndrome involved; (4) absence of dental caries; (5) good oral hygiene; (6) MM2 impaction with mesial inclination between 25° and 40° (the angle of inclination of the MM2 was measured as described by Evans ); (7) MM2 with a depth of impaction between 4 mm and 10 mm (the depth of impaction was measured as described by Fu et al. ); (8) unilateral or bilateral MM2 impaction; (9) presence of the MM3 bud distal to the impacted MM2; (10) availability of pre-treatment panoramic radiographs with a magnification ratio of 1:1.
The impacted MM2 teeth were assigned randomly to receive brass wire treatment either with MM3 germectomy (group A) or without MM3 germectomy (group B) ( Figs 1 and 2 ). A randomization sequence was created using Clinstat statistical software (Martin Bland, York, UK) for the treatment allocation.