Introduction
The routine surgical removal of asymptomatic third molars has almost become a rite of passage in many countries. On the other hand, alignment of the remaining dentition has been addressed with special emphasis on the ‘social six’ upper anterior teeth [1]. The reasons for these trends are varied and complex but likely have an historical basis since medical complications emanating from partially-erupted and/or impacted third molars were first reported over century ago [2]. In fact, impacted third molars have a prevalence of approx. 18-32% in modern humans, which makes assessment of their eruptive prognosis mandatory [3] because of complications associated with them. Recently, Malanchuk et al. [4] confirmed local pathologic processes, which precede caries as well as inflammation of the soft tissues and the adjacent alveolar bone, to justify surgical attenuation of the (lower) third molars. A systematic review [5] had also reported that pathologies related to third molar retention include caries, periodontal diseases, second molar root resorption, and pericoronitis. In addition, Cederhag et al. [6] evaluated the anatomic relations of the lower third molars with respect to the inferior alveolar nerve using panoramic radiographs. They reported that their roots were located above the inferior alveolar nerve in about half (52%) of the cases examined. However, while panoramic radiography is extensively used for diagnosis and preoperative treatment planning, the predictive value of this data remains ambiguous. In this regard, Vranckx et al. [7] assessed radiologic risk indicators and postoperative morbidity in patients undergoing upper and/or lower third molar exodontia. They noted that severe impactions were associated with postoperative pain, trismus and swelling with a need for pain medication. However, when the ability to identify the risk of third molar non-eruption using panoramic radiographic analysis was evaluated, Libdy et al. [8] found that both orthodontists and oral maxillofacial surgeons were unable to predict which third molars would become impacted; both groups of specialists indicated extractions in approx. 50% of cases, being unable to distinguish those in which the third molars would erupt normally.
To prevent future dental pathology of adjacent teeth, the prophylactic extraction of asymptomatic third molars is commonly advocated. However, in a series of three cases [9] periodontal attachment loss and serious damage of the adjoining second molar was reported, while a third patient suffered post-operative osteomyelitis and fracture of the angle of the mandible during prophylactic exodontia. In addition, the extraction procedure is sometimes associated with damage of the inferior alveolar nerve when the tooth roots are anatomically adjacent to it, resulting in sensory dysfunction, such as paresthesia. Repass [10] was one of the first to describe the inferior dental nerves passing through the roots of impacted mandibular third molars. Furthermore, mandibular fractures are also a relatively common risk and represent a serious post-operative complication. Beret et al. [11] evaluated mandibular fracture complications of impacted lower third molars, which included post-operative malocclusion, mouth opening limitation, inferior alveolar nerve paresthesia, infection, delayed bony union, and loosening of surgically-placed hardware. To avoid the risks of post-operative morbidity and injury, coronectomy has become more common. However, one of the sequelae of coronectomy is eruption of the retained root, and Steinberg et al. [12] described a case in which the retained root displaced the inferior alveolar nerve, resulting in neurologic symptoms. Thus, as unerupted third molars rarely remain pathology-free, new approaches are needed to address their clinical management. Therefore, the aim of this study is to describe a series of cases treated by a general dentist using the DNA appliance (Vivos Therapeutics, Inc., USA) that putatively increases midfacial bone volume [13] as an alternative technique in the clinical management of unerupted third molars.