McNamara C, McNamara TG. Mandibular premolar impaction: 2 case reports. J Can Dent Assoc. 2005; 71:859-863
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Sarica I, Derindag G, Kurtuldu E A retrospective study: do all impacted teeth cause pathology?. Niger J Clin Pract. 2019; 22:527-533 https://doi.org/10.4103/njcp.njcp_563_18
Laganà G, Venza N, Borzabadi-Farahani A Dental anomalies: prevalence and associations between them in a large sample of non-orthodontic subjects, a cross-sectional study. BMC Oral Health. 2017; 17 https://doi.org/10.1186/s12903-017-0352-y
Bass TB. Observations on the misplaced upper canine tooth. Dent Pract Dent Rec. 1967; 18:25-33
Mortazavi H, Baharvand M. Jaw lesions associated with impacted tooth: a radiographic diagnostic guide. Imaging Sci Dent. 2016; 46:147-157 https://doi.org/10.5624/isd.2016.46.3.147
Guerrero ME, Shahbazian M, Elsiena Bekkering G The diagnostic efficacy of cone beam CT for impacted teeth and associated features: a systematic review. J Oral Rehabil. 2011; 38:208-216 https://doi.org/10.1111/j.1365-2842.2010.02141.x
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This case presents a rare example of self-correction of a deeply impacted mandibular second premolar (LR5) in a medically fit 14-year-old male patient, referred in 2017 regarding a retained deciduous lower right second molar (LRe). CBCT imaging highlighted that the origin of the ID canal was in direct contact with the inferior buccal aspect of the LR5 root apex. The decision was made to monitor the patient in 2 years. In the meantime, the dentist extracted the retained LRe as it was seen to be erupting on routine bitewing imaging. At his review appointment, the LR5 had spontaneously erupted.
CPD/Clinical Relevance: To highlight the potential benefit of monitoring eruption in the event that high-risk surgery is the alternative option and involving the patient in the decision making.
Article
Glenda Aruede
This case presents a rare example of self-correction of a deep and disto-angularly positioned impacted mandibular second premolar. A 14-year-old male patient was referred by his dentist to the Oral and Maxillofacial department in Prince Charles Hospital, South Wales, regarding a retained deciduous lower right second molar (LRe) and an impacted lower right second premolar (LR5). He was medically fit and well with no known allergies. He had good oral hygiene and was a regular attender at his dentist, with no history of previous trauma or orthodontic treatment.
He attended his referral appointment in 2017. He presented with a Class I malocclusion on a skeletal Class I base with increased lower anterior facial height. He had both an average Frankfort mandibular plane angle and nasolabial angle, with no asymmetry. His lips were competent at rest and 90% of his upper incisal surfaces showed on smiling. There were no abnormalities detected with his temporomandibular joint.
Intra-orally, he presented in the late mixed dentition, with a retained LRe. Unerupted teeth included all the third molars and the impacted LR5. In the lower arch there was mild malalignment, mild spacing in the lower left quadrant, and mild rotations of the lower left first and second premolar. There was a retained LRe. In the upper arch there was also mild malalignment and mild rotations of the upper left first and second premolars. The incisor relationship was Class I, with an average overbite and overjet. Dental centrelines were non-coincident to each other with the lower aligned with the facial midline and the upper shifted 1 mm to the left.
An orthopantomogram (OPT) was taken to assess the position of the LR5 (Figure 1). This showed the retained LRe and the LR5, which appeared to be horizontally impacted with the crown abutting the mesial root of the lower right first molar (LR6) and the root apex close to the mental foramen.
Figure 1. A Grade 1 OPT of the 14-year-old male patient.
Appreciating that the OPT was a two-dimensional representation, a cone-beam computed tomograph (CBCT) was requested and completed to provide more detailed information and aid the decision for either monitoring or surgical intervention (Figures 2 and 3). The report stated that the LR5 was disto-angularly impacted into the mesial root of the LR6, which had no root resorption present. The origin of the ID canal was in direct contact with the inferior buccal aspect of the LR5 root apex.
Figure 2. CBCT of the lower right canine to the lower right second molar (buccal view).Figure 3. CBCT of the lower right canine to the lower right second molar (lingual view).
A discussion followed with the patient and his mother regarding the treatment options. The first was to do nothing, and continue with routine monitoring at his own dentist. This would eliminate the surgical risk of nerve damage; however, the tooth may cause resorption to the LR6. Furthermore, it could become cystic and require removal in future. In this case, no orthodontic treatment would be required. The second option was to surgically remove the LR5 as well as the LRe, orthodontic or restorative treatment could then be considered to manage the space. This would need to be completed under general anaesthesia, and the risks associated with that were included. There would also be a risk of temporary or permanent paraesthesia to the lower lip and chin.
The decision was made to leave the tooth in situ and monitor the patient 2 years later. In May 2019, the patient attended his dental practice for a routine appointment. Bitewings were taken and the LR5 was now seen to be erupting between the roots of the LRe. The dentist therefore made the decision to remove the retained LRe. In November 2019, the patient attended his 2-year review appointment at the hospital. On examination the LR5 had spontaneously erupted in the correct position in the arch (Figure 4).
Figure 4. Intra-oral photos showing spontaneous eruption of the formerly impacted lower right second premolar. (a) Front; (b) left; and (c) right.
Discussion
Impaction is defined as prevention of complete eruption into a normal functional position of one tooth by another. This can be due to development in an abnormal position, limited space within the dental arch, or obstruction by tooth, bone or fibrous tissue.1 In this case, the retained LRe caused a lack of space to allow for eruption of the LR5, and it was impacted against the LR6 root. This was complete impaction as the tooth was covered entirely by bone within the alveolus.
The prevalence of premolar impaction has been reported in the literature to range between 0.2% and 4%.2,3,4 Laganà et al conducted a large cross-sectional study of 4706 patients and examined the prevalence of dental anomalies and any identifiable associations.5 In total, 13 (0.2%) mandibular premolars were reported as impacted. A retrospective study of 1239 patients in Greece between 1991 and 1999 reviewed OPTs that had been taken to determine the presence of any impacted or supernumerary teeth. Impacted canines were the most prevalent (8.8%), followed by impacted premolars (2.2%); 9 cases (0.72%) were specifically impacted mandibular premolars.3
Some authors have further explained that the impaction should be present for more than 2 years following the expected physiological eruption time.6 The Journal of the American Dental Association highlighted that eruption of the mandibular second premolars usually takes place between the ages of 11 and 12 years.7 In this case, the patient presented to the hospital at the age of 14 years with an impacted LR5, which is 2 years beyond the expected eruption age, and therefore fits the described diagnosis.
To radiographically assess impacted teeth, the primary imaging modality is an OPT. Although it provides useful information to visualize the tooth, associated lesions and aid diagnosis, it is only a 2D representation and does not provide detailed information regarding proximity to adjacent structures and orientation.8 Use of a CBCT is the optimal imaging technique to assess impaction in three dimensions, providing precise information and aiding management. A systematic review comparing CBCT with panoramic imaging showed that more research is needed to compare both methods; however, CBCT can be justified for pre-surgical assessment of an unerupted tooth in cases where conventional radiographs do not provide adequate information.9 The diagnostic accuracy of inferior alveolar nerve exposure during third molar removal was 55% and 45%, respectively in a study looking at the position of impacted third molars in relation to the ID canal.10
Tantanapornkul et al looked at imaging for 142 mandibular third molars and found an accuracy of 80% and 64%. The sensitivity and specificity for predicting exposure were 93% and 77% for CBCT, and 70% and 63% for OPTs, respectively. This indicated that CBCT imaging is superior in diagnostic accuracy.11 Treatment methods include observation, a combination of surgical exposure and orthodontics, autotransplantation and surgical removal.12 In the mandibular premolar region, there is close proximity to the inferior dental, and in particular the mental, nerve where it emerges from the mental foramen.13 Paraesthesia is a sensory disturbance that can include any deviation from normal sensation, including numbness or burning. When surgically removing impacted mandibular premolars, this poses a risk to the mental nerve.14 If left untreated, impacted teeth can lead to inflammatory or dentigerous cyst formation with the risk of infection, and resorption of adjacent teeth.15 When considering treatment, the risk of leaving the tooth in situ compared to surgical removal should be evaluated. Periodic examination is recommended to clinically and radiographically monitor impacted teeth if there is no planned surgical treatment.13
Conclusion
In conclusion, this case highlighted that self-correction of impacted teeth is unpredictable. It can be beneficial to monitor eruption in the event that high-risk surgery is the alternative option. Orthodontic and surgical treatment was no longer required, which frees up NHS time and resources to other cases.
