Restoration of Oligodontia with a Long Span Bar Supported Fixed Dental Prosthesis

Introduction

The treatment options for partially edentulous patients with missing single or multiple teeth include provisional removable partial denture, a definitive cast partial denture, a resin bonded prosthesis, fixed partial denture or implant prosthesis.¹ Prosthesis design is based on prosthodontic criteria of support, stability, and retention. A properly designed prosthesis that results in favourable biomechanical stress distribution, esthetics, phonetics, comfort, and hygiene is of prime importance.^1,2 Clinical decision for making any kind of prosthesis is dependent on the status of abutment teeth and its periodontal condition. Therefore, meticulous evaluation of abutments is necessary for longevity of prosthesis.

Fixed Dental Prosthesis (FDP), in contrast to partial removable dental prosthesis generally offers a higher degree of satisfaction for the patient as they have greater resemblance to natural teeth with regard to function and comfort.³ Forces on the FDP are transmitted to the abutment teeth through the pontic, connector and retainers. Longevity of prosthesis and its abutment depends on occlusion, span length, bone loss, and quality of periodontium.^2,3 Biomechanical factors such as overload, leverage, torque, and flexing induce abnormal stress concentration in a FDP.

Depending on the present condition of the remaining dentition and number of abutments, fixed restoration may be done with a long span fixed dental prosthesis that is not meeting Ante’s law. The law states, “the combined pericemental area of the abutment teeth should be greater than or equal to pericemental area of the tooth or teeth to be replaced.”^4,5 Nonetheless, many controversial  discussions have been done on this topic in the past and the knowledge on it still remains sparse. Loss of retention, endodontic and prosthodontic problems have been the major complications associated with long span FDP.^5-7 Clinicians equipped with knowledge about the complications associated with fixed prosthodontics can be more careful in diagnosis and treatment plan and can explain how far the treatment can fulfil patient’s expectations.^8-10

Polymethyl methacrylate (PMMA) is one of the most widely used polymers in dentistry. It has varied uses and is polymerised by different mechanisms. Heat cure PMMA has better mechanical properties when compared to other forms of PMMA, but overall, it is not considered a dental material of choice where excessive strength is required.¹⁰ This article describes a case report of a long span fixed dental prosthesis incorporating the bar and heat cure acrylic pontics to reduce the occlusal load on the abutment and also to reduce the weight of the prosthesis.

Case Report

A 27-year-old female patient reported to the Department of Prosthodontics and Crown & Bridge with a chief complaint of unesthetic appearance due to missing teeth.

She underwent extraction of few teeth and visited a dental surgeon for the fixed prosthesis. All her remaining teeth were prepared to receive the bridge. However, she did not continue with the treatment as she was dissatisfied with the outcome.

The patient had no past medical history and the general heath was good. After a thorough examination and evaluation, treatment options were planned and discussed with the patient. CBCT investigation was done to evaluate bone for implant placement. The reports did not show favourable condition as there was decreased bone width and height in the edentulous span. Endosseous implants were therefore not possible and patient could not afford bone implants due to high treatment cost. Fixed removable prosthesis with attachments was also suggested but patient was non-compliant with that option.

Due to her young age and concern for esthetics and function, fixed treatment option was planned. Thus, a bar supported long span fixed dental prosthesis was planned with heat cure acrylic pontics.

Diagnostic impressions were made with irreversible hydrocolloid, followed by diagnostic mounting and mock up. Treatment planning was done (Figure 1). To correct the aesthetics, a metal post was placed in 11 and 21 each, and tooth preparation was done (Figure 2). Final impressions of both the arches were made using silicone impression material (Figure 3). Face bow record was made and transferred to the articulator. Jaw relation was done (Figure 4). Temporaries were adjusted and delivered to the patient (Figure 5). Wax pattern of the copings were fabricated for crowns and a bar was made of inlay wax connecting the terminal abutments (Figure 6). The entire prosthesis was made in four segments for each quadrant. Coping try in was done to check the marginal fit (Figure 7). Porcelain layering was done and Porcelain-fused-to-metal (PFM) prosthesis was completed with a bar (Figure 8). Mock up wax was used to design pontics around the bar (Figure 9). Each segment was invested in dental plaster in a flask and dewaxing was done (Figure 10). Tooth coloured heat cure PMMA was used for packing and was cured. Different shades were mixed and matched to porcelain. Finishing and polishing of heat cure acrylic pontics was done. Occlusal adjustments were done (Figure 11). Final PFM prosthesis with heat cure acrylic PMMA pontics in four segments was cemented using GIC (Figure 12).

Discussion

According to Schillingburg et al., every restoration must be able to withstand the constant functional and parafunctional forces to which it is subjected.^8,11,12 Thus, when designing and fabricating FPD, we should consider the mechanical, biological and esthetic considerations.^13-15

In the present case, the patient presented with a prepared tooth. As already discussed, implants were not possible due to lack of bone availability and patient did not have time for bone augmentation. Fixed removable prosthesis with attachment was suggested to the patient; however, she was not compliant with this treatment option. Therefore, a long span FPD had to be planned in four sections for each quadrant. Patient had been informed about the longevity and associated consequences. The heat cure PMMA pontics were planned to decrease the weight of the prosthesis when compared to conventional PFM. 

The major limitation of heat cure PMMA is its rigidity and fracture toughness which is not sufficient to withstand masticatory forces. Also, due to weak mechanical properties and abrasion resistance, it is more commonly used for temporary crowns and bridges.^16,17 In this case, heat cure PMMA has been used for making pontics as the opposing teeth were also missing. Thus, the masticatory load was not heavy. Pontic design chosen was modified sanitary so as to maintain the hygiene. Patient was also advised to use water flosser for good oral hygiene maintenance. Occlusion scheme chosen was Group function.

Follow up

Patient was recalled for follow up at 15 days, 1 month, 3 months and 6 months intervals. Patient was happy and satisfied with the outcome. No tissue changes have been observed in any follow up visits and radiographic examination verified healthy periodontal state of all the abutments. Slight discolouration with food stains can be seen in the heat cure acrylic pontics in comparison to retainers made of porcelain.

Long span FDP survival has always been questionable. Therefore, it is often avoided in clinical practice. However, in situation where number of teeth present are less and distant to each other, and there is lack of bone availability or financial constraints for implants, a long span FDP can be given. A bar supported prosthesis with heat cure PMMA pontics can be a good innovative idea to decrease the weight of prosthesis and decrease the load on abutments. One disadvantage which remains is slight discolouration of the heat cure PMMA pontics with time due to its composition.

Conflict of Interest

All authors declare that they have no conflict of interest directly or indirectly in the information or products listed in the paper.