Impacted first mandibular molar: a rare enigma

The phenomenon in which a tooth that is fully or partially non-eruptive is positioned against another tooth, bone, or soft tissue such that its re-eruption is unlikely, as described by its anatomical position, is known as impact. [1]. Permanent tooth impaction is not very uncommon. Impaction of third molars is the most common, followed by maxillary canines, mandibular premolars, mandibular canines, maxillary premolars, maxillary central incisors and mandibular second molars [1].

The incidence of dental impaction ranges from 5.6 to 18.8% of the population. Failure of the eruption of the first permanent molar is rare; the prevalence is 0.01% in the case of the first permanent molar [2]. However, impaction of the mandibular first molar (prevalence of 0.01%) and of the maxillary first and second molars (prevalence of 0.02%) is quite rare. [3]. Permanent molars are particularly important in providing sufficient occlusal support and coordinating facial growth [2]. Impactions of these teeth can lead to various complications. Early diagnosis and treatment are essential because delayed treatment will lead to various problems such as decreased spontaneous eruptive strength, longer duration of treatment and increased complications. Due to the importance of permanent molars, eruptive guidance before the extraction of impacted teeth is necessary [4].

Excessive bone removal may be required to extract deeply impacted molars, leading to complications such as inferior alveolar nerve damage and iatrogenic mandibular fractures. A modified surgical approach may be warranted in such a challenging scenario [5].

A 21-year-old, systemically healthy patient was referred to the oral surgery department for extraction of an impacted first molar. The condition was identified by chance radiologically before orthodontic treatment (Figure 1).

Figure
1: Cone beam computed tomography (CBCT) image of impacted mandibular first molar

After a thorough intraoral and radiological examination, it was decided that the affected tooth should be extracted with a conventional technique. The biggest challenge in this case was to preserve as much bone as possible for orthodontic movement while minimizing damage to an adjacent tooth because less space was available, while avoiding nerve damage. All risks were explained to the patient and a consent was signed. Under local anesthesia, a crevicular incision was made from the distal aspect of the mandibular right first premolar to the distal part of the mandibular right second molar, and a revitalizing incision was made mesial to the first premolar, which actually an envelope flap design. The full-thickness mucoperiosteal flap was lifted, and the mental nerve was identified and preserved. Irrigation was done with normal saline to reduce heat and remove debris. Oral and occlusal bone splints and shaves were performed to expose the tooth up to the cement-enamel junction. The odontectomy was started with a micromotor and a number eight round bur under abundant irrigation with normal saline solution. To reduce patient cost, a micromotor was used for tooth sectioning. First, the crown and the root were separated by a horizontal cut, then the crown was divided into two parts by a vertical cut and delivered vestibularly without damaging the adjacent tooth. Subsequently, the root was split into two parts and delivered coronally and buccally (Figure 2).

Figure
2: Extraction of the impacted mandibular first molar in sections

After inspecting the socket for debris and pieces of bone, a thorough cleaning of the socket was performed using normal saline and betadine solution. The previously lifted flap was closed primarily with 3-0 vicryl sutures (Figure 3).

Figure
3: Closure of a previously lifted mucoperiosteal flap

To relieve pain after surgery, a combination of aceclofenac (100 mg), paracetamol (325 mg) and serratiopeptidase (15 mg) was given twice daily. With the exception of temporary inferior alveolar nerve paresthesia, which was confirmed by a two-point discrimination test, recovery was almost uneventful. Vitamin B complex tablets with B12 twice a day have been advised for 30 days. The paresthesia was resolved in six months (Figure 4).

Figure
4: Complete mandibular arch at six months follow-up.

Impaction results from a physical obstruction and lack of space, which can cause the second and third molar follicles to collide. Impaction can also occur if there is excess space between the first and second molars as they grow, likely because the distal root of the first molar is needed for proper eruption of the tooth. crown of the second molar. Physical, clinical, and radiological examinations should be used to rule out all probable reasons if mandibular molars are not erupting when expected or if others have already done so.

Ectopic location, obstructions in the eruption pathway, and failures of the eruption process are the three main factors that Andreasen et al. identified for eruptive disturbances [3]. For diagnostic purposes, Raghoebar et al. divided tooth eruption disturbances into the following three groups: impaction, primary retention and secondary retention [6]. A variety of local and systemic factors are related to tooth eruption failure. One of the etiological factors is heredity [3]. Recently, some familial cases of primary eruption failure have shown mutations in parathyroid hormone receptor 1 [3]. Malocclusion, temporary dentition problems, positioning of adjacent teeth, lack of space in the dental arch, idiopathic factors, supernumerary teeth, odontomas or cysts are some local causes of eruptive failure. Unfortunately, it was difficult to establish a firm differential diagnosis for these atypical rash patterns clinically or radiographically before starting treatment. Impaction of the first molar is caused primarily by ectopic eruption, while impaction of the second molar is caused primarily by deficiency of arch length. [6].

The term “primary eruption failure” has been used to describe a rare disorder that has been linked to non-eruptive teeth, most commonly molars. It is described by Profitt and Vig as a condition in which the eruption mechanism is unable to function normally, resulting in the failure of eruption of non-ankylosed teeth. Infraocclusion, large posterior open bite, non-syndromic eruptive failure without mechanical obstruction, and inability to orthodontically move impacted teeth are some of the features. Because they are difficult to make, most diagnoses are made by exclusion [7].

The surgeon faces difficulties when trying to remove an impacted mandibular first molar without adequate preoperative preparation. The difficulty of extracting an impacted tooth depends on its depth. Deeply impacted molars can be surgically removed using a variety of methods, including the extra-oral approach, lingual splitting, and buccal osteotomy. In all cases, conventional extraction of impacted teeth causes lingual nerve paresthesia in 0.9% to 11% of cases and inferior alveolar nerve (IAN) paresthesia in 1.6% to 3.3% of cases. . [8]. The extra-oral technique endangers the mandibular marginal branch of the facial nerve and can lead to nerve damage.

Surgical management of these rare conditions has always been difficult and requires step-by-step repair. For this case, we opted for a combined surgery-orthodontic approach. Our goal was to cause minimal damage to adjacent teeth while preserving as much bone as possible for orthodontic tooth movement. Before beginning the procedure, an appropriate sequence of surgical procedures for the desired results should be established. Therefore, it is clear that no specific processing algorithm can be developed for the defects presented in the present case. Each case is unique and requires a tailored treatment plan.