Fabrication of Hollow Denture Using Glycerine Soap:Advantages, Precautions and Limitations:Case Report

Successful rehabilitation of edentulous patients with complete denture prosthesis bank on the principles of retention, stability, and support. Effectuating these principles in severely resorbed ridges foist challenges to the clinicians due to decreased supporting area. As Resorption progresses it results in increased inter-ridge distance. Rehabilitation using conventional complete dentures in such cases often results in a heavy prosthesis; this further compromises the retention and stability of the prosthesis.¹ Reducing the weight of a prosthesis during fabrication aids in improved retention and a better prognosis.² Historically, weight reduction approaches have been achieved using dental stone, cellophane-wrapped asbestos, silicone putty, modeling clay, or salt during laboratory processing to exclude denture base material from the planned hollow cavity of the prosthesis.^2,3 Salt failed to sustain pressures produced during flask closure resulting inadequate hollow cavity inside the prosthesis. The other techniques demand tedious retrieval of the three- dimensional spacer especially from the anterior region of the prosthesis between the canines due to the curvature of the arch.⁴

This case report describes an innovative and simplified technique for the fabrication of a hollow maxillary complete denture for rehabilitating a patient with severely resorbed ridges and increased inter-ridge distance using glycerine soap.

CASE REPORT:

A 55-year male patient presented to the Department of Prosthodontics, with the chief complaint of missing teeth. He reported the loss of teeth due to mobility and is edentulous for eight years. He also presented old worn-off and ill-fitting dentures. The patient gave no relevant medical history. Intra-oral examination revealed a completely edentulous maxillary and mandibular ridge with Atwood’s order V and Atwood’s order VI respectively.

Treatment options were planned and discussed with patients which included:

1) Implant-supported Fixed prosthesis

2) Implant-supported Overdenture

3) Pre-prosthetic surgery i.e. vestibuloplasty followed by conventional complete denture

4) Conventional complete dentures using the neutral zone technique.

The patient opted for the option of conventional complete denture prosthesis due to the cost and the surgical procedure involved in pre-prosthetic surgery and an implant- supported prosthesis.

Steps:

1.Phase I: 1st Clinical Appointment

Case History Recording and Primary Impression

A thorough case history was recorded and the primary impression was made using Impression Compound for the maxillary arch and Admixed compound for the mandibular arch.

2.Phase II: 1st Laboratory Procedure:

Impression was poured in dental plaster and the custom trays were fabricated using a Modified Boucher spacer design for the maxillary arch and without a spacer for the mandibular arch.

3.Phase III: 2nd Clinical Appointment

Border molding and final impression Maxillary arch: Border molding was done using low fusing compound and the final impression was made using Zinc oxide Eugenol impression paste Mandibular arch: Impression was recorded using All green technique

4.Phase IV: 2nd Laboratory Procedure:

Impression was Poured in Type IV Dental stone and the denture base and rims were fabricated. Two denture bases were fabricated for mandibular denture and in one of the denture bases, stapler pins were attached for retention of the admixed compound while recording the neutral zone impression and rims on another for jaw relation.

5.Phase V: 3rd Clinical Appointment

Maxillo-mandibular relation was recorded and mounted on a mean value articulator. The admixed compound was attached to the denture base with stapler pins and was adjusted at the recorded vertical dimension. The patient was then asked to make the movements to record the neutral zone.

6.Phase VI: 3rd Laboratory Procedure:

Teeth arrangement was done for the maxillary and mandibular arch. In the mandibular arch, the teeth were arranged in the recorded neutral zone area.

7.Phase VII: 4th Clinical Appointment

Try in

During the try-in, esthetics and phonetics were evaluated. Due to the increase in interarch space, the trial dentures demanded an increase in the height of the rims that in turn would increase the weight of the final prosthesis. To reduce the weight of the prosthesis, it was decided to rehabilitate the patient with hollow dentures.

8.Phase VIII: 4th Laboratory Procedure

Steps in Fabricating hollow denture

i. V-shaped notches were made at three sites on the land area of the maxillary cast and the waxed maxillary denture was sealed to the master cast (Figure 1). The maxillary trial denture was duplicated with irreversible hydrocolloid impression (figure 2) material and poured into Type III dental stone to obtain a working cast.

ii. A template of 1mm thick BIOPLAST transparent film was then fabricated on this working cast to obtain the external contours of a trial denture (Figure 3).

iii. The maxillary trial denture was invested and dewaxing was done conventionally.

iv. Modelling wax (2mm thick) was adapted over the master cast to ensure uniform and adequate thickness of resin all around the planned hollow cavity in the completed denture.

v. A temporary putty spacer was fabricated such that a minimum of 2 mm space is left on all the sides for heat cure resin (Figure 5), and to be ensured by the placement of thermoplastic resin.

vi. The putty spacer fabricated was poured in irreversible hydrocolloid to obtain a mold on which the glycerine soap replica was fabricated (Figure 6).

vii.A glycerine soap (Pears, Hindustan Unilever Ltd., Mumbai, India) was heat melted and poured into the mold (Figure 7) for the replica of the putty spacer and was hand carved using a Le Cron carver after it was completely set. The exact replication was ensured by measuring with Endodontic files and scale.

viii. The accuracy of the 3D spacer was evaluated from all aspects by placing it between the master cast with 2mm modeling wax adapted to it and the BIOSTAR template.

ix. After this, packing was done (Figures 8 and 9). The layer of heat cure acrylic was adapted over which the glycerine soap template was placed. After ensuring enough space available than the resin was added again over it and the flask was closed.

x. The denture was retrieved in the usual manner following the processing

xi. Openings were created in the denture base distal to the second molar and in the canine region(Figure 10) using a micromotor handpiece. The denture was then immersed in a bowl of water overnight to allow the dissolution of soap. Intermittent cleaning was done using a brush by pushing in and out through the openings to aid in the mechanical removal of the soap. Water spray was used to flush traces of soap completely.

xii. The hollow cavity was air-dried, and the openings were sealed using auto-polymerizing acrylic resin, the denture was then finished and polished.

xiii. A water test was performed to evaluate the reduced weight of the prosthesis as evidenced by the floating denture(Figure 11).

xiv. The mandibular denture was processed using a conventional technique, finished, and polished.

Phase IX: 5th Clinical Appointment

Denture Insertion

Denture insertion was done. Centric and vertical jaw relations were re-evaluated Aesthetics and phonetics were assessed. Patient satisfaction was obtained and post-insertion instructions were given.

Phase X: 6th Clinical Appointment

Follow up

The patient was recalled for follow-up after 1 week; No adjustments were needed and the patient was satisfied. The patient gave no history of unsatisfactory smell or any allergic reaction due to the use of glycerine soap.

DISCUSSION:

Fabrication of hollow dentures using glycerine soap is a simple and innovative technology that gives the best results if accurate measurements and precautions are taken.

PRECAUTIONS:

1.Measuring the putty spacer accurately leaving 2 mm of space from all the sides for acrylic resin

2.Letting the soap set completely before packing: If packing is done before glycerine soap is completely set it will get displaced with the pressure and may lead to a solid denture or exposure of palatal surface due to inadequate space available for resin

3.Ensuring by trial packing

LIMITATIONS:

1.Time-consuming

2.Technique sensitive: If the measurements for the glycerine soap spacer are inaccurate it will result in inadequate space for acrylic resin.

ADVANTAGES:

1.Better results

2.Reduces the weight of the prosthesis which in turn enhances retention.

3.The main advantage of using a glycerine soap spacer is its ability to sustain high curing temperatures (boiling point of glycerine 290°C) and also it doesn’t interfere with the polymerization of heat cure acrylic resin leaving no residues inside the hollow cavity.^[4]

4. The soap spacer is eventually removed leaving behind a clean hollow cavity, any concern regarding its biocompatibility in the oral cavity is dismissed.^[4]

In prosthodontics everything is reversible. So, even if such errors occur they could be corrected by following methods:

i.The putty spacer can be re-fabricated using the denture as a guide leaving 2 mm of space from the palatal aspect. Then, obtain the glycerine soap spacer from the putty spacer as before. Adaptation of modeling wax on the cast and dewaxing by keeping the retrieved denture in the flask. After dewaxing the layer of acrylic to be adapted over the palatal aspect and re-packing to be done.

ii .Relining of the denture.

iii. Refabrication of hollow dentures using other techniques like the lost salt technique, putty spacer technique, or thermocol denture technique.

CONCLUSION:

Fabrication of hollow dentures using glycerine soap is an easy but technique-sensitive method that ensures better results when all the steps are followed accurately.