Flangeless horseshoe maxillary complete denture: a prosthodontic solution to maxillary tori

Prosthodontic options in the presence of tori

Avoidance of the tori where possible, such as the approach undertaken in this presented case, may be advisable. Cases requiring full palatal coverage, such as conventional edentulous maxillae, may need to specifically account for the torus. This may involve prescribing relief by applying tin-foil over the torus on the master cast, to act as a spacer to minimize friction between torus and connector.⁶

Alternatively, implant-retained restorations that do not primarily rely on anatomical coverage for their retention, and can therefore be designed giving a wide berth to the torus. A high ridge profile with limited resorption, however, such as with this case, may actually complicate implant placement instead, and mandate prior surgery.

In any case, impressions of the arch must be taken using an appropriate material at a time when the torus is untraumatized (‘stable’). Adequate assessment and full recording of desirable anatomical features, such as the maxillary tuberosities and buccal peripheries, is essential for success, as in this case.

Surgical approach

Removal or reduction of tori, involving flap retraction and osteotomy, naturally poses surgical risks and complications, which depending on torus location and dimension may traumatize the surrounding anatomy, such as the greater palatine neurovascular bundle in the maxillary arch and the lingual nerve in the mandibular arch.⁷ Surgery has been reported to manage ridge discrepancies and facilitate removable prosthetic rehabilitation.⁸ Referral to an appropriate OMFS/OS unit for consultation, following initial efforts to manage the torus conservatively, would be required.

Surgery may be indicated in cases where the torus is too large (such as it hampering adequate denture connector thickness or being traumatized by opposing natural dentition) and/or situated at an important prosthetic landmark, for example at the vibrating line.⁹ Tori may indeed be harvested as a source of autogenous bone for grafting purposes.^10,11

Case report

A 63-year-old woman presented to the prosthetics department at Birmingham Dental Hospital with difficulties wearing a complete maxillary denture, which had been provided some months before by her GDP, owing to its poor stability. The design was horseshoe-shaped as per the patient's wish, citing difficulties tolerating full palatal coverage and extension. The patient had also requested a flangeless anterior design of the denture, as the lip support offered by the present conventional design was considered unnecessary bulky. The patient wished for a new maxillary denture to wear for functional and aesthetic reasons, having been only wearing the current denture when away from home. The patient also wore a mandibular partial acrylic denture that was clinically satisfactory.

The patient's medical history was unremarkable with respect to prosthetic rehabilitation. Social history revealed the patient was a district nurse, drank alcohol socially and used to smoke 10 cigarettes a day for 40 years.

On examination, extra-orally no abnormalities were detected. Intra-oral examination revealed a 30-mm diameter, 15-mm raised midline bilobed torus palatinus. The erythema visible in the presented images was due to the recently experienced mechanical trauma according to the patient (Figures 1 and 2). This was reviewed at future appointments where traumatic features had resolved.

The maxillary arch was edentulous with prominent tuberosities, minimal resorption and the presence of both posterior and anterior soft-tissue buccal undercuts. This would qualify as an Atwood Ridge Classification 3¹² or as a Birmingham Ridge Type 2 owing to its bulky nature.¹³ Lip support from the ridge proved satisfactory without a prosthesis. The patient's gag reflex was hypersensitive on palpation at the vibrating line. The mandibular arch was partially dentate with fair plaque control and no caries visible. Evidence of now-stable periodontitis was appreciated given no increase in periodontal probing depths clinically.

The currently worn maxillary denture was poorly retentive, and was generally underextended. The anterior labial flange provided excessive lip support.

Prior to examination, discussion with regards to the merits of full palatal coverage and peripheral extensions to maximize border seal (and, therefore, retention and stability of the denture base) were discussed with the patient; the patient accepted a potentially compromised result with this denture design and the probable need to use denture fixative with the prosthesis.

The benefit that a prosthesis with full palatal coverage would have in terms of improved peripheral seal, while also protecting the torus from further mucosal trauma during function, was explained to the patient. The potentially compromised retention and peripheral seal with a flangeless prosthesis was also explained. Finally, referral for surgical reduction of the torus was also discussed if provision of a removable prosthesis was not effective in the first instance.

The patient declined referral for surgical consultation and insisted on an anterior flangeless, horseshoe-shaped denture to start with, fully accepting a potentially compromised treatment outcome.

The final plan was, therefore, to provide a conventional maxillary complete denture incorporating features that the patient wished, and a conventional mucosal-borne mandibular partial acrylic denture in accordance with the new occlusal scheme, as the patient expressed aversion to clasps given previous experience.

Preliminary impressions were taken in red impression compound (Kerr, Orange, CA, USA), ensuring total anatomical recording. The master impression was then taken using greenstick compound (Kerr, Orange, CA, USA) and light-bodied silicone wash (Aquasil Ultra+, Dentsply, Milford, DE, USA) in a full-coverage 1-mm spaced special tray. Registration was completed using a wax-base block. Completing registration was challenging owing to the lack of retention of the wax-wire base and the reduced palatal coverage. Try-in confirmed satisfactory vertical dimensions, balanced occlusion, stability and comfort of the base, satisfactory speech and acceptable denture aesthetic. High-impact acrylic was prescribed for fabrication of the denture.

On insertion, the denture was retentive in spite of under extension towards the vibrating line and the omission of the anterior flange, and was improved when the patient ensured her mouth was sufficiently hydrated. No adjustment was required to the peripheries of the denture or the occlusal surfaces of the denture teeth. The denture was resistant to rotational forces and did not trigger the hypersensitive gag reflex. The patient reported no issues on review, and reported occasional use of fixative. The patient was content with the treatment provided (Figures 3–5).

Discussion

In this case, tuberosity coverage, adequate palatal seal and the presence of a minimally resorbed ridge with adequate soft tissue undercut allowed for a horseshoe shaped design to succeed in spite of its unconventionality.

Admittedly, the importance of capturing the relevant anatomy as well as possible to maximize the potential of the final prosthesis was underestimated by both practitioner and patient. The excellent result achieved for this patient may not be possible for all patients with a large torus, for example cases where the ridge profile is resorbed and buccal undercuts are non-existent etc. Therefore the recognition of Ridge Type 2 as a separate entity is fundamental in appropriate case selection.¹³

The aesthetics of the flangeless denture was very good. The horseshoe shaped design of the denture made it weaker relative to conventional full-coverage designs. The prescribed wire mesh provided further mechanical strength where natural mandibular incisors occlude against the connector. A metal baseplate could have been prescribed instead of using the high-impact acrylic alone, to provide extra strength foro the connector,¹⁴ albeit at the expense of the superior retention that can be gained from a purely acrylic baseplate, given previously reported incidences of denture fracture.

Tori vary in their profile. This case presented a torus that impacted conventional practice, but was not significantly detrimental to our provision of the prosthesis. Other cases may involve tori of different shapes and positions, which would therefore require alternative management.

Conclusion

Fixed prosthetics, in spite of their availability and efficacy, may not be possible in every case. This case highlights the importance of appreciating and adapting the removable denture design to the anatomy for maximal benefit.

A denture with a horseshoe connector and a flangeless anterior tooth set-up was successful in this case owing to a number of factors: the presence of a minimally resorbed alveolar Type 2 ridge,¹³ close adaptation of the prosthesis to the denture bearing area, use of buccal undercut, prescription of a pin dam and maximal coverage over the tuberosities in order to optimise peripheral seal.

The unconventional design of the denture was initially provided primarily because of the patient's specified wishes. This treatment modality could, however, be routinely suggested for patients with similar anatomy, following proper case selection.