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Outcome of single maxillary complete dentures opposing mandibular teeth: A need to introspect on the prosthodontic treatment protocol

Introduction: In the era of implant supported restorations, conventional complete denture (CD) for isolated edentulous maxilla still remains the first choice of treatment despite being its frequent mechanical failures. Statement of Problem: Edentulous maxillary arch restored with polymethyl methacrylate (PMMA) based CDs when opposed by natural and/or restored dentition is biomechanically and functionally a compromised rehabilitation. Materials and Methods: Seven patients (4 males, 3 females) in the age range of 55–75 years were treated for their frequent fracture of the single maxillary denture. They were asked to rate their prosthodontic experience on a scale of 1–10. They were further inquired about the awareness of their clinical condition and knowledge on the alternative treatment options available to them, number of different dentists they have been treated by and frequency of their re-visits to the dental office after being edentulous. Results: Removable PMMA based CD in maxilla was the first choice of treatment for all the restorative dentists who treated these patients. No attempt was ever made to treat the opposing dentition in any of the seven patients. Despite being under regular prosthodontic care for fabrication and repairs by as many as 23 dentists, none of the patients was aware of their clinical situation and the alternative treatment options available. Conclusion: It is imperative that the restorative dentist be aware of the perils of such inter-arch relationships. Appropriate treatment done on time may avert a situation where the oral conditions become incompatible for the longevity of treatment done even with the aid of dental implants.

The Journal of Indian Prosthodontic Society | Jan-Mar 2016 | Vol 16 | Issue 1 and eventually leading to frequent mechanical failures of the prosthesis.
Any factor that exacerbates the deformation of the base or alters its stress distribution may predispose the polymethyl methacrylate denture to fracture. [1] The mechanical failure of such dentures under functional masticatory forces, especially in the presence of opposing dentition, is a persistent problem and its prevention is still a challenge for the clinician. Denture fractures cause functional insufficiency, compromised esthetic and financial burden on its users for its repair or refabrication. [2][3][4] Further, the repaired denture bases become more prone to subsequent fractures if the root cause(s) is not addressed to. [5,6] Focus of prosthodontic treatment has always been on finding the antidote for the problems concurrent with respect to the rehabilitation of the edentulous mandibular arch. In addition, subjective satisfaction with maxillary denture, relatively low success rate of dental implants in maxilla, [7] lack of awareness and consent from the patients for the correction of misaligned opposing dentition worsens the situation with every passing year.
The purpose of this article is to re-emphasize the importance basic prosthodontic principle of preservation of the remaining, which is largely been, ignored in patients of the single maxillary complete denture (CD) opposing natural teeth.

Patients presentation
Seven patients (4 males, 3 females) in the age range of 55-77 years with edentulous maxillary arch and opposing mandibular natural and/or restored teeth were treated for complaints related to the their broken maxillary dentures [ Figure 1a and b]. They all presented with an overlapping history of frequent maxillary denture fracture, corresponding repairs, and subsequently multiple new dentures. All of them lost maxillary teeth due to the periodontal breakdown of the supporting structures.
Critical clinical evaluation revealed amalgamation of following factors which lead to repeated fracture of the denture base in these patients: i. Completely edentulous and resorbed maxillary alveolar ridge [ Figure 2] ii. The defective plane of occlusion either due to supraeruption, wear or defective full coverage restorations of mandibular teeth iii. Supra-erupted and labial proclination of mandibular anterior teeth creating a pseudo class III malocclusion which further lead to an inadequate thickness of denture base resin in the anterior palatal area [ Figure 3] iv. Multiple fractures and corresponding repairs of maxillary denture at various sites.

Proposed treatment
Foremost concern was to educate the patient regarding their oral conditions and factors responsible for the frequent fracture of their maxillary dentures. Emphasis was given to begin the treatment by correcting the defective mandibular plane of occlusion by modifying shape and size of existing teeth and/or restorations. Finally, rehabilitation of maxilla by implant supported prosthesis with bone augmentation procedure, if deemed necessary.

MATERIALS AND METHODS
Their detailed history was recorded citing their problems and prosthodontic experience after becoming edentulous in the maxilla. The severity of their problems was scored on the scale of 1-10, with lower scores corresponding to a positive response. They were further asked to record the number of different dentists they have visited after being edentulous, number of CD they have worn during this time and number of times they revisited the dental office for the repair of the prosthesis. Their respective awareness of oral condition, treatment options available to them and their reasons for refusing implant related treatment was also ascertained.

RESULTS
All patients had a difficult prosthodontic experience and were, in general, unsatisfied with regard to their CD [ Table 1]. Except for one patient, all other patients were edentulous for over 6 years and had changed their dentists at least twice for a better prosthetic care. These patients went on numerous occasions to the dental office for denture repairs but could not recollect precisely the number and frequency of their visits. During all these years and visiting 23 dentists, they were never educated by any of the restorative dentists about their oral situation and therefore, none of them were aware of the same [ Table 2]. Implant related treatment was proposed to only one them but was never initiated.
Due to their age, time involved in overall management, need for the correction of opposing dentition, preprosthetic surgical procedures to improve upon bony foundation and economic constraints four patients did not agree to dental implant related treatment [ Table 3]. Three patients accepted implant related treatment but without any additional surgical procedures and alteration in the opposing teeth. In due course, only one patient underwent implant surgery with modification of the lower teeth. For remaining six patients, change of denture base material to cast base metal alloy was proposed and was well accepted by them.

DISCUSSION
Fracture of maxillary CD is a common complaint in the presence of mandibular teeth and is probably an acceptable problem. The mode of failure is flexural fatigue failures caused The level of awareness in patients with respect to their clinical condition and reasons for their frequent problems by cyclic deformation due to masticatory forces. The reported incidence of fracture of the maxillary CDs is twice that of the mandibular CDs and the typical fatigue failure of maxillary CDs is evidenced by its midline fracture. [8] Initiation and propagation of the cracks in a maxillary denture are relatively quick due to high tensile principal stress and a high maximum shear stress. [9] In the current scenario, when the number of implant related treatments is exponentially increasing, rehabilitation of patients with isolated maxillary edentulism with implants is rather ignored. Plausible reasons for this line of thinking seems to be a higher failure rate of implants in maxilla due to poorer bone quality in comparison to mandible, higher treatment cost as well as further expectancy of higher failure rate in patients presenting with opposing teeth. The negative effect of antagonist occlusion on the maxillary implant supported prosthesis can be gauged by only 22.2% survival rate of implant overdenture and 6 out of 8 implants failure in patients with opposing natural dentition. [10,11] These patients in concern have been edentulous for a long time and were regularly visiting their restorative dentists for denture repairs and prospects of a better treatment option. When given the alternative treatment options, patient's age, time required for rehabilitation, economic status and fear for extensive surgical procedures for improving the bony foundation and associated morbidity preclude them for giving consent for the implant supported treatment.
Despite desiring for a solution to their persistent problems, six patients were not taken up for implant related treatment. Therefore, the only option remained was to offer them a strong denture base with a harmonious occlusal relationship between both the arches. Since force factors were left unmodified, the longevity of this treatment provided also remains doubtful as the fracture of reinforced CD was also experienced [ Figure 4a and b].
Even though, this study involved less number of the patients; results do suggest a general tendency to restore the edentulous maxilla with conventional CD irrespective of the status of the mandibular arch. Considering the time involved and money spent on frequent visits for denture repairs and for achieving optimal general and oral health, this group of patients should routinely be treatment planned for fixed implant supported prosthesis unless indicated otherwise. The much needed correction of mandibular teeth should be part of treatment planning and its correction should be the foremost concern before initiating treatment for edentulous maxilla. Early initiation of the treatment will preserve the remaining hard and soft tissues and provide the patient with an appropriate prosthesis, leading to their improved oral health related quality of life.

CONCLUSION
Comprehensive treatment planning for holistic oral care and its timely execution may avert known potential complications in restoring isolated edentulous maxilla. Implant supported prosthesis should be the treatment of choice over conventional CD and in other patients, providing a strong maxillary denture base with correction of the dentition in the opposing arch seems to be a prudent solution to the frequent mechanical complexities.

Financial support and sponsorship
Nil.

Conflicts of interest
There are no conflicts of interest.