13. A case Report of the RPD with magnetic attachments applied to the partially edentulous patient without occlusal contact

M.Hideshima, M.Fukumoto, M,Toko, T.Andoh, H. Mizutani, Y. Igarashi

Section of Removable Prosthodontics, Graduate School, Tokyo Medical and Dental University, Japan

---

Introduction

It is well known that partially edentulous cases without or less occlusal contacts are severe cases because remaining dentition, supporting tissue and residual ridge are apt to be damaged and prosthodontic devices are easy to be fractured. Miyachi advocated to call these condition with such defects as "collapsed area" and recommends to apply affirmative prosthodontic intervention.

The authors applied magnetic attachments for preparatory treatment so as to decrease overloading on abutment teeth and increase retention and stability of the denture.

Case Report

A 74-year-old male patient presented partial edentia of maxillary Kennedy class sAand mandibular Kennedy classs>(Fig.1) contacting only with upper right lateral incisor(#12), canine(#13) and lower right canine(# 43) at the habitual occlusal position(Fig.2,3). The existing maxillary denture was recurrently fractured(Fig.4) and right lower canine which was only contacting at the occlusal position was with marked mobility.

Panoramic radiograph showed remarkable distorted resorption of left maxillary residual alveolar ridge and localized bone resorption around bucco-mesial root of extruding left upper second molar(#27, Fig.5). Plotting along the Dento-occlusal triangular relationship according to Miyachi's classification were located in area s@ which is calledqｭﾄollapsed area" (Fig.6) and represented unfavorable prognosis with less occlusal supports despite of multiple remaining teeth.

Treatment Planning and Procedures

Clinical examination revealed to fabricate maxillary and mandibular denture separately in order to maintain the existing occlusal height. For economical reasons of the patient, resin based dentures were selected within the limitations of permitted design in social health-insurance system. Treatment planning was as follows;

• Remove the cast crown of the left upper second molar(#27)
• Tri-section and remove bufcco-mesial root
• Root canal treatment of the remaining roots
• Deliver a cast base with a keeper of the magnetic attachment
• Fabricate a maxillary denture first with the existing occlusal height
• Remove the resin-faced crown of the lower right canine(# 43)
• Root canal treatment of # 43
• Deliver a cast base with a keeper of the magnetic attachment
• Fabricate a mandibular denture with the occlusal height with a newly deliverd maxillary denture
• Upper and lower partial dentures would be designed rigid connecting concept.

At first for the purpose of clearing the chief complain of recurrent fracture and modifying deformed occlusal plane, the full-cast crown of isolated extruding #27 was removed and poor conditioned bucco-mesial root was extracted following tri-sectional operation(Fig.7). A magnetic attachment was applied to #27 and to corresponding upper existing denture temporally(Fig.8).

Secondly a new resin based upper denture which was designed with the magnetic attachment as the direct retainer and with wrought wire clasps as the indirect retainer was fabricated. Except for retainers each component of the denture; occlusal rests, embrasure hooks, reinforcing framework was cast with cobalt-chrome alloy in one-piece because of increasing rigidity of the denture and distributing functional loads effectively to each abutment(Fig.9). The reinforcing metal frameworks were delivered with T-shaped in cross section(Fig.10) resisting against bending strength and squamous processes were added in order to prevent fractures of buccal portion of the resin base(Fig.10).

Each buccal wrought wire clasp was reinforced with cast embrasure hooks therefore stability of the denture was ensured(Fig.11).

Thirdly the resin-faced crown of #43 with marked mobility was removed. Thus mobility was diagnosed to be derived from occlusal trauma because less attachment loss was found. In order to improve crown-root ratio, the canine crown was reduced and a cast base with a keeper of the magnetic attachment was delivered(Fig.13).

Finally mandibular denture was fabricated with the occlusal height with newly set maxillary denture(Fig.14). The magnetic attachment as a direct retainer and wrought wire and cast clasps as indirect retainers were designed with one-piece cast reinforcing framework as well as the maxillary denture(Fig.15).

Comparing without and with upper/ lower dentures, occlusal contact was not attained and over closure was presented without dentures whereas favorable occlusal height at the initial visit was attained with dentures(Fig.16). Mobility of the right lower canine was reduced.

In the past 3 years after the upper/ lower dentures setting, fracture of the resin base was not occurred but wrought wire clasp of the upper denture were loosen or fractured followed by continuous adjustment. Occlusal height with upper/ lower dentures showed slightly decreased(Fig.17).

It is considered that continuous follow-up is necessary with bite-up or relining of the denture base to prevent from occlusal height reduction, as well as periodontal management and force control of the remaining dentition.

This case suggested that magnetic attachments are useful for distributing overload on abutments and for efficiently obtaining retentive force of dentures.

References

1. Miyachi T: Clinical evaluation and principle for defective dentition, 1-189, Ishiyaku Publishers Inc, Tokyo, 1998. (in Japanese)

2. Obana J, Ohyama T, Hosoi T,: Prosthodontic treatment for maxillary and mandibular teeth cross each other(Eichiner classification C1), 1-276, Ishiyaku Publishers Inc, Tokyo, 1994. (in Japanese)

Discussion Board