Supernumerary nines: Rare after all? an overview and case series

Supernumerary teeth, a form of hyperdontia, are defined as an odontostomatological anomaly where teeth, or tooth substance, are in excess of the usual configuration of 20 deciduous and 32 permanent teeth.^1,2,3,4 Supernumerary teeth are classified according to their position in the dental arch or their morphological form. Conversely, supplemental teeth are a type of hyperdontia without anatomical differences. These developmental abnormalities arise due to a combination of genetic and environmental factors.^3,4

A supernumerary molar is defined by position as a paramolar, distomolar or parapremolar. Paramolars are small and rudimentary, often found buccally or palatally to maxillary molars.^1,4,5 A distomolar is a fourth permanent molar, which is usually placed either directly distal or distolingual to the third molar.⁴ Finally, parapremolars commonly occur interproximally and buccally to the upper first and second premolars.^1,3,4

This article discusses the prevalence, management and morbidity of supernumerary nines through case studies and a literature review. Demographic data enable improved diagnosis of supernumerary molar teeth. Early detection allows for measures against complications and improved therapy.² As reports are rare in the literature, this article highlights case management to aid treatment of future cases.

Literature review

A literature search using ‘supernumerary molar’ and/or ‘paramolar’ with ‘prevalence’, ‘comorbidities’, ‘management’ and ‘recommendations’ was undertaken by one of the present authors (VP) using Pubmed with no limitations on date or language of publications. After review of the 24 articles that were found, 11 matched the criteria.

Prevalence

Most supernumerary teeth are impacted and asymptomatic,^3,6 usually discovered by chance during radiographic examination with no associated complications.^4,7

Supernumerary molars rarely occur as reported in dental literature.^4,8,9,10 The first published article describing supernumerary molars was Shimizu et al's 2007 case study, in which only primary supernumerary teeth in the anterior region were reported.¹⁰ Our review found that prevalence ranged from 0.06% to 0.96% in the permanent dentition.^1,2,3,8 In the study by Kara et al, distomolars (62.9%) were more common than paramolars.² Nayak found the prevalence of supernumerary molars to range from 0.3% to 0.6% in the deciduous dentition.⁴ An ex vitro case study of the prevalence of supernumerary molar teeth in the skull collection of the Zimbabwe Museum of Human Sciences, found a low occurrence of 0.76% of supernumerary molars in 153 maxillae and 112 mandibles.⁹ In is unclear how gender how affects the incidence of supernumerary molars. Açikgöz et al and Shimizu et al found a greater frequence in males (mean age 23.1 years)^8,10 while Kara et al found a greater frequency in females (56.4%).²

Supernumeraries (anatomically abnormal) are more frequent than supplemental (anatomically normal) teeth.¹ Kara et al and Shimizu et al found supernumeraries usually occur in the maxilla (87.7%).^2,10 They occur anteriorly in the maxilla and occur infrequently in the primary dentition.¹ Supernumerary molars tend to have conical morphology (45.7%), be impacted (81.1%) and in a vertical position (52.1%).² Impaction rates range from 21.6%⁸ to 33%.²

The four morphological variantsof supernumerary teeth are:

• Conical: small, peg-shaped and the most common;²
• Tuberculated: multi-cusped, barrel-shaped, rudimentary root;^2,4
• Supplemental: eumorphic, resembling a tooth of the normal series, usually deciduous dentition;
• Odontomes: no regular shape, hamartomatous malformation, complex composite of diffuse mass, disorganized, or compound composite odontome of superficially normal anatomy.⁴

Aetiology

Hyperdontia is the overarching term for teeth in excess number. Thought to be a disorder of multifactorial inheritance (from hyperactivity of dental lamina and remnants persisting as ‘rests of Serres’ within the jaw), the exact aetiology of a supernumerary tooth is not completely understood.^1,4 Theories include the ‘phylogenetic theory’ (atavism: return/reappearance of ancestral type), the ‘dichotomy theory’ (from splitting of developing tooth bud) and a hyperactive dental lamina (proliferation of epithelial remnants of the dental lamina, induced by pressure or ‘induction factors’ of the complete dentition), the latter being the most accepted cause. However, a combination of genetic and environmental factors is the most accredited aetiology. This is further explained by occasional presence of supernumerary teeth in case subject's relatives.^1,4

Comorbidities

Some studies reported finding higher percentages of comorbidity than expected,⁹ such as:

• Mechanical–obstructive pathology: preventing/delaying eruption of adjacent permanent teeth (28.9%⁴);³
• Retention or eruption of the ectopic tooth;^3,4
• Malocclusion: crowding and associated malocclusion/traumatic bite that can also interfere with orthodontic treatment.⁴ There is an associated risk of plaque retention in inaccessible areas and soft tissues irritation,² with gingival inflammation and localized periodontitis in the surrounding soft tissues;⁴
• Affected development of adjacent permanent teeth: dilaceration, delay or abnormal root development, displacing or rotating of position;^4,8
• Enlargement of the follicular sack by over 3 mm (16.2%³) or to a cyst;⁴
• Neoplasm;⁴
• Trigeminal neuralgia from paramolar compression of adjacent nerve;⁴
• Pulp necrosis or root resorption of adjacent tooth;^4,6
• Non-syndromic adjacent dentigerous cysts associated with a mandibular supernumerary molar.⁶

It is important to note that additional pathology is not found in every supernumerary case.⁸

Supernumerary teeth may erupt normally, remain impacted, appear inverted, or assume an abnormal path of eruption. Of all permanent and primary supernumerary teeth, 13–34% and 73%, respectively, erupt normally, with the rest remaining unerupted and risking complications.⁴

McCrea first reported the association of dentigerous cysts with supernumerary molars, finding 5% around supernumerary molars.⁶ These cysts are the second most common odontogenic cyst (after radicular cysts), accounting for 24% of all true jaw cysts and are the most common developmental jaw cyst. Odontogenic cysts are slow-growing cysts, often expanding the outer cortex of the mandible and occurring mostly around unerupted mandibular third molars. They are typically diagnosed in patients aged 30–40 years, usually as incidental findings resulting from radiographic or dental examination. Signs include: a missing tooth swelling; facial asymmetry; ‘possible’ pathological fracture; and pain or discomfort is most often absent. Multiple dentigerous cysts are rare, and most often occur in association with a developmental syndrome. Lesions that mimic a dentigerous cyst include radicular cysts, odontogenic keratocysts, ameloblastomas, and squamous cell carcinomas. Malignant lesions can mimic the imaging appearance of dentigerous cysts, therefore histopathological examination should be carried out. Most dentigerous cysts are solitary.⁶

Supernumerary molars can cause problems if they occur ectopically. Saleem et al reported a supernumerary molar presenting in the maxillary antrum with recurrent haemoptysis.⁷ Associated symptoms and risks when in the sinus include chronic or recurrent sinusitis, sepsis, nasolacrimal duct obstruction, headaches, ostiomeatal complex disease and facial numbness. Recommendations include removal with 10 days of post-operative co-amoxiclav, based on the successful resolution of symptoms.

Case reports

Five cases of supernumerary molars presented to the oral and maxillofacial surgery teams at Addenbrooke's Hospital, Cambridge and Norfolk and Norwich University Hospital, Norfolk in 2022.

Case 1

A 39-year-old female was referred by her GDP for removal of both her lower right wisdom tooth (LR8) and lower right supernumerary molar (LR9), which was found on an oral panoramic tomograph (OPG/OPT) (Figure 1). She reported a history of pain, swelling, discomfort and food packing at the distal to LR7, which resolved with improved oral hygiene. She reported no other symptoms.

Dental examination found a deep pocket distal to LR7, with plaque, food packing and gingival inflammation seen. A partially erupted molar appeared distally to the LR7. The UR8 was also over-erupted with traumatic occlusion identified. Figure 1 shows a partially erupted and horizontally impacted supernumerary nine (LR9) lying superior to an additionally horizontally impacted LR8.

With risk of decay to LR7 indicated by these findings, treatment options were discussed including: no treatment; removal of LR9 and UR8 under local anaesthetic (LA); coronectomy of LR8 with removal of LR9 and UR8 under general anaesthetic (GA); and removal of LR89 and UR8 under GA.

The patient opted to have the LR9 removed only, which was performed without complication as a simple extraction under LA. At the 1-year review, there were no complications and the patient was discharged.

Case 2

A 61-year-old male patient was referred by his GDP for extraction of the UL7 in hospital owing to his complex medical history of haemophilia type A, hypertension, and aortic and mitral valve repairs. The patient's medical history necessitated Factor VIII pre- and post-operatively, as well as chemoprophylaxis. The procedure requested was the extraction of UL7, which was acutely painful, tender to percussion, heavily restored and with subgingival caries.

On consultation, an OPG (Figure 2) showed an incidental finding of supernumerary maxillary molars (UL9 and UR9). As both were asymptomatic, and there were no radiographic nor intra-oral signs of infection, discussion with the patient resulted in the decision to monitor the teeth.

The UL7 was extracted with forceps under local anaesthetic, following pre-operative antibiotics (co-amoxiclav 3 g), tranexamic acid and DDAVP (desmopressin – Factor VIII) from the haemophilia team prior to the procedure. The extraction was performed without complications and haemostat measures put in place. His fluid intake was restricted to 1.5 L for 24 hours, and 3 days of tranexamic acid were advised as per haematology instruction.

Case 3

A 40-year-old female presented complaining of a dull ache to the LR8 and UR3. The patient complained of a ‘bulge’ on the buccal aspect of the alveolar bone of UR3. Her medical history included carbamazepine and betamethasone.

Upon examination, her masseters were hypertrophic. Intra-orally the upper right quadrant of her dentition was tender to percussion, her UR3 was restored and discoloured, and her LL8 was partially erupted. Increased sensitivity to cold was identified. An OPG (Figure 3) and magnetic resonance image (MRI) were taken, finding the UR3 to have a deep restoration near the pulp. Additionally, both lower wisdom teeth (LR8, LL8) were near the inferior alveolar nerves (IANs). The LR8 presented with 90° angled roots, and an incidental finding of a supernumerary molar (LR9) was made.

Diagnoses of bruxism (hypertrophic masseters), reversible pulpitis of the UR3 (owing to the deep restoration), partially erupted LR8 and supernumerary LR9 was made. Treatment options were discussed regarding the LR9 including: monitoring; coronectomy of the LR8 and extraction of LR9; or extraction of both LR8 and LR9, which would risk nerve damage. She opted to monitor all the teeth in question.

Consequently, we requested the GDP to review and manage the bruxism, to monitor the UR3 regularly until the patient requested treatment or the tooth lost vitality, and meticulous oral hygiene of the LR89 region. We explained to the patient that should decay occur in the LR7, treatment of the LR8 and LR9 may need to be reconsidered.

Case 4

A 20-year-old male presented to the emergency department following an alleged assault. On examination, the patient presented with deranged occlusion, a step deformity and limited mouth opening of 15 mm. An OPG (Figure 4) identified a left parasymphyseal and right condylar fractures of the mandible, as well as incidental findings of supernumerary LR9 and LL9 teeth.

The fractures were managed routinely with open reduction internal fixation of the left paraymphysis with plates and screws and intermaxillary fixation with elastics. The patient was informed of the presence of the supernumerary teeth, and following discussion, opted to leave and monitor the teeth. The patient was followed up at routine intervals and had no complications.

Case 5

A 59-year-old male was referred by ENT to the oral and maxillofacial department regarding a 3-year history of worsening chronic left sinusitis. Following MRI (Figure 5), this was confirmed to be associated with the unerupted impacted UL8 and supernumerary UL9 within the left maxillary sinus. The patient consented for removal of the UL8 and UL9 with a Caldwell–Luc procedure to washout and debride the sinus.

Post-operatively, there was reduced sensation of the left cheek and lower left eyelid, but the surgical site healed well. In subsequent reviews, the numbness continued to improve. This case highlights the importance of careful discussion of risks when considering removal of supernumerary teeth, especially when their anatomy or positioning necessitates a more complex surgical procedure.

Discussion:

When a supernumerary molar is suspected, radiographs should be taken to enable diagnosis and management. OPGs are the most useful radiograph, and should be accompanied with occlusal or peri-apical (PA) radiographs views, with parallax technique to determine position.^3,4,11 Long cone peri-apical views should be considered where there are concerns of resorption of adjacent teeth.⁴

Treatment includes observation or extraction,^4,7 depending upon the position of the supernumerary molar and its current or potential effect on adjacent teeth and important anatomical structures.⁶

Conclusion

Additional pathology is not found in every supernumerary case. Although rarely occurring, awareness of appearance and patient complaints' matching the presence of a supernumerary can successfully enable the examination, identification and therefore management of supernumeraries.

Treatment should remain tailored to individual patient need, with observation or extraction being deemed acceptable depending on the case.