Bar Retained Overdenture – A Case Report

INTRODUCTION

Treating older patients may be a demanding challenge. Success is dependent on carefully planned treatment and patient cooperation so that the patient is able to make full use of the completed restoration. If a patient is planned for an overdenture, and the roots of some remaining teeth are supported in healthy alveolar bone, then a conventional over denture is a viable consideration. Natural teeth, sound residual dental roots or implants may be utilized to support an over denture. Such an appliance is more stable than a complete denture and affords better comfort, function and aesthetics.

This paper presents a situation where an over dentures were planned for both maxillary and mandibular arches and for additional retention in mandibular denture, a nylon clip in removable over denture fitting on a connective bar between canines was prepared which would ward off social stigmatization in a patient.

CASE REPORT

A male patient aged 46 years reported with a complaint of missing teeth to be replaced (Fig.1). Medical examination showed that he was a known diabetic since 4yrs and was under medication. He had a history of wearing conventional removable partial denture for both maxillary and mandibular arches since 2 years and had got his mandibular incisors and maxillary right premolars due to periodontal reasons 8 months back. Examination revealed that 16, 26, 33and 43 were the only remaining natural teeth. The vertical dimension of existing condition was acceptable. After clinical and radiographic examination treatment plan included over dentures for maxillary arch with metal copings on 16 and 26 and for mandibular arch with metal copings on 33 and 43 connected by bar on which a removable over denture with clip would be placed.

Preliminary impressions using irreversible hydrocolloid (Zelgan, DENTSPLY) for both arches were made to obtain diagnostic casts and to prepare custom tray with full spacer and with extra relief in the teeth areas.

All the abutment teeth were endodontically treated and tooth preparation was done to achieve dome shaped surface of 3mm coronal height and chamfer finish line was made on the abutment teeth.(Fig-2) Preparations should be tapered toward the incisal and occlusal surface. This will permit development of coping contours which terminate in a rounded occlusal surface as advocated by Miller. Chamfer-type margins should extent just beneath the gingival margin and should be definite enough to permit accurate carving of the wax pattern.¹

Single set border molding and final impressions were made using addition silicone material (Aquasil Ultra DECA™ Monophase Regular Set) and master cast were retrieved pouring type IV die stone (kalabhai).

A die hardener (BASE COAT) was applied over the finish line on die and die spacer of 25µ-40µm was applied over rest of the surface. Once the spacer got dried, a die lubricant (TRUE RELEASE™) was sprayed on the surface of the die, later wax pattern was made using inlay wax (GC) with the help of PKT instruments. 

Thickness of the pattern was maintained 1 mm all over using wax caliper and margins were refined with care using cervical wax (DFS) to ensure proper adaptation of the pattern to the die margin. Sprue wax of 2.5mm gauge was used for connecting bar for mandibular copings. The pattern for connecting bar was made flat on tissue side and kept 'U' shaped on occlusion side, which runs straight form one coping to other not following the contour of anterior ridge for better retention.* Sprue was attached to the patterns (wax copings on 16, 26 and on 33 and 43 with a connecting bar of sprue wax) and they were carefully removed from the die to position on the crucible former base. Debubblizer (Silikon-Wachs Entspanner) was sprayed over the patterns to reduce the surface tension so that investment comes in closer contact. Ringless casting system (Thermofix 2000) was used to allow sufficient expansion of the investment material (HERAVEST® Universal N). After investing the ring was kept aside for setting the investing material. Later burn out and induction casting was done using (Kulzer (Ni-Cr) alloy.

The castings so obtained were divested and sprues were removed. They were then cleaned by sandblasting, trimmed and finished to be placed on their respective dies on master cast. Cementation of castings were done using GIC cement (GC gold label) on prepared teeth (fig.3a).and (fig 3b) Occlusion rims on denture base were prepared using self cure acrylic resin on master cast with castings for Jaw relation. Teeth arrangement and try in were done to patient's satisfaction. The waxed up over dentures were then flasked, dewaxed, packed with heat cure resin, cured and deflasked to achieve processed over dentures. The over dentures were then trimmed and polished.

Approximately 1mm of tissue surface of lower denture was reduced for nylon clip and wetted with monomer, and repair self cure resin (DPI) in dough stage was placed in it. Then clip was placed on the connective bar in the patient's mouth and mandibular over denture with unset resin placed on it, to pick up the clip when the resin cures.( Fig-4)

DISCUSSION

Overdentures are usually indicated for a mandible when a patient have the resorbed alveolar ridge to hold the lower denture in place. Even if the patient has sufficient alveolar ridge, the flexible nature of the mandibular bone could cause the lower denture to dislodge often from its position while seated in the mouth. This necessitates the need for a prescription of an overdenture. If a patient has at least four usable roots and/or implants around the canines and first bicuspids, an Overdenture can be made.

As with a full denture, an overdenture is also a removable dental appliance. Additionally, it has some precision dental attachments embedded in the denture base. Typically, the nylon male parts of the precision attachments are embedded in the denture's base and the metal female counterparts are implanted into the tooth roots or modified existing implants to hold the overdenture in place. Therefore, the remaining tooth roots or implants have to be prepared by the dentist to provide a stable support for the overdenture. Endodontic treatment must be done on the remaining natural tooth roots prior to installing the precision attachments.

Advantages of a conventional over-denture

Feels more like having teeth

More retentive in many cases

Helps reduce shrinkage of surrounding bone

Reduces pressure to portions of the alveolar ridge

Positive psychological advantage of still having teeth

Disadvantages of a conventional over-denture

Scrupulous oral hygiene is essential in order prevent decay and gum disease.

The over-denture may feel bulkier than a conventional denture.

Generally this is a more expensive approach than a conventional denture. 

Frequent maintenance examinations are necessary.^{2, 3, 4, 5, 6, 7}

The obvious need to preserve alveolar bone for complete dentures has led to the overdenture concept. Retaining teeth permit the stresses of occlusion to be borne partially by the teeth, thus reducing the abuse, which the alveolar process and the mucoperiosteum undergo when dentures are worn. By reducing the trauma to the mucosal tissues, it is reasonable to expect that resorption of the alveolar process will be lessened.

CONCLUSION

Metal copings on abutment teeth used to retain overdentures provide numerous advantages, including enhanced esthetics, phonetics, as well as ease of maintenance and simplified hygiene. This type of prosthesis is primarily tissue-borne with the few teeth providing retention and stability. Therefore, successful treatment begins with conforming to standard denture fabrication principles. This includes ideal border adaptation, extension and full denture occlusion, with an ideal tooth set-up and try-in, to allow evaluation of esthetics, phonetics and support.