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Author: DR. Mithun Upadhya, Dr. Blessy Susan Bangera

ABSTRACT

Conventional denture systems have existed in the field of dentistry since time immemorial. The materials used and the techniques in practice have very well been documented and executed. As dentistry has progressed, new light has been thrown at Complete Denture Prosthodontics with the introduction of the Biofunctional Prosthetic System(BPS). The Biofunctional Prosthetic System(BPS) system of complete dentures is a sophisticated system designed using contractually defined core products. This article discusses the guidelines and execution of the system with a clinical case report. Keywords: Biofunctional prosthetic system, complete dentures, functional impressions.

INTRODUCTION

The BPS system of complete dentures, as the name implies, is specially designed to work harmoniously optimizing oral function, comfort and superior esthetics. This method of complete denture making differs considerably as compared to the conventional procedures. The BPS complete denture is a product of strict technical protocols based around a modular system. The standard guidelines are relatively simple to understand and provide consistent results. The lack of sufficient literature with regard to this major development, makes the system worthy of precise learning and implementation.1 The use of specialized impression materials, face bow transfers, articulators, teeth and denture base materials makes this system a sought after technique in the field of Complete Denture Prosthodontics. The involvement of team effort with specialized instrumentation is a prerequisite in this system. The following case report illustrates the use of the BPS system in fabrication of complete dentures for a completely edentulous patient.

CASE REPORT:

A male patient reported to the Department of Prosthodontics with a complaint of completely edentulous upper and lower arches that required prosthodontic rehabilitation. Intra oral examination revealed resorbed maxillary and mandibular ridges with mild masticatory dysfunction. The patient was suggested a variety of treatment options. He declined from any invasive dental treatment and opted for the BPS complete denture.

PROCEDURE:

1. Initial impression:
The Preliminary impressions were recorded using the irreversible hydrocolloid impression material Accu-Dent 1, consisting of materials with two different viscosities. Low-density hydrocolloid impression material System 1 syringe Accu Gel was syringed into the maxillary vestibular area. The impression tray was loaded with high-density hydrocolloid System 1 Tray Accu Gel to support the syringed material. Once set, the impression was checked for accuracy. Similarly, the mandibular impression was recorded (Fig.1).

2. Preliminary jaw registration with the Centric Tray:
Two points were marked on the patient’s chin and tip of the nose respectively for measurement of vertical dimension at rest and vertical dimension at occlusion. The vertical dimension at rest (VDR) was measured by asking the patient to gently hum the sound “m” and the distance between the two points was recorded using measuring callipers. The vertical dimension of occlusion (VDO) was derived by deducting the value of free way space (2mm) from the VDR (Fig.2). The centric tray was then loaded with a thick mix of irreversible hydrocolloid impression material Algitex and placed inside the mouth at the set vertical dimension and the patient was guided to centric relation position. The centric record was hence made in the irreversible hydrocolloid impression material using the centric tray. Using the centric tray, a face bow record was made and the preliminary casts were mounted on the Semi adjustable Stratos200 articulator (Fig.3). Custom trays were separately fabricated on the primary casts using light polymerised acrylic resin. To these custom trays the intra oral tracer ie, the Gnathometer M tracing device was attached (Fig.4).

3. Definitive impressions/ Gothic arch tracing:


A. Functional impression with the Gnathometer “M”: Border moulding and final impressions were made in the ‘closed mouth’ position using the vinyl polysiloxane impression material (Virtual Heavy Body and Virtual Light Body) (Fig.5). Once the functional impressions were made, the vertical maxillomandibular record was confirmed.

B. Intra Oral Tracing: The intra oral arrow point tracings were obtained using the tracing device(Fig.6). The centric and protrusive records were made using the silicone registration paste Virtual CAD Bite. Once set, the tracings were retrieved, the facebow transfer was made using the UTS 3D Transfer bow (Fig.7) and the casts were articulated on the Stratos200 articulator. Using the protrusive record, the articulator was programmed.

4. Denture fabrication and insertion :
Teeth arrangement:
The articulated master casts were used for the fabrication of trial dentures. The Facial Meter and Living Mould Guide were used for tooth selection.
The positioning of the teeth was based on anatomical landmarks of the patient that comprised of centre line, canine line, smile line, occlusal plane, anterior tooth size and shape and posterior tooth size and shape. Semi anatomic artificial teeth SR Phonares NHC were arranged on the trial base using hard wax to obtain bilateral balanced occlusion.

Stage 1 – Maxillary Anteriors The maxillary central incisors were positioned in relation to the incisive papilla. The incisive papilla was taken as the reference point and was sectioned sagitally and transversely. The saggital section was used as midline reference and the tranverse line was used to position the palatal aspect of the central incisors (Fig.8). The intervestibular distance was measured and halved. This would serve as an anterior reference point. A pair of the most prominent palatal rugae was selected and a tranverse line was marked across them. This was used to position the distal aspect of the canine. The two dimensional template was used to align and place the anterior teeth (Fig.9).

Stage 2 - Mandibular Anteriors The mandibular anteriors were positioned on the alveolar ridge demonstrating a slight labial inclination in the incisal area. The canines being most prominent were positioned first so that their incisal tips aligned between the contact point of the upper laterals and canines. The lower incisors were positioned in the vertical direction so that the incisal tips were positioned at the point determined by halving the intervestibular distance. The first premolar was positioned according to the two dimensional template with the buccal cusp tip in line with the incisal edges of the mandibular anterior teeth.

Stage 3 – Mandibular Posteriors The anterior underside of the 2 dimensional template was positioned in contact with the premolar with its posterior underside rising steadily toward the upper third of the retromolar pads. The curvature of the template was designed in order to align itself to the occlusal plane hence compensating for the christensens’ phenomenon. The mesiolingual cusps of the molars were in contact with the template.

Stage 4 – Maxillary Posteriors The maxillary first molars were placed first followed by the premolars and lastly the second molar. A buccal and lingual overjet was incorporated to prevent cheek and tongue biting. The maxillary palatal cusps were centered on the central fossae of the mandibular molars. The functional harmony was checked to ensure elimination of all interferences in the working, balancing side and protrusive movements and trial was carried out (Fig 10). Followed by trial, the dentures were fabricated using the high impact injection moulded resin Ivocap System (Fig.11). Laboratory and clinical remount procedures was carried out to eliminate occlusal interferences (Fig 12). The dentures were trimmed, polished and delivered to the patient who expressed his satisfaction with the esthetics and functional harmony (Fig 13A, B, and C). The patient is on regular follow up since one year and is found to be doing well (Fig 14A,B).

DISCUSSION:

Complete denture making using conventional materials and techniques have been discussed in the past. A study conducted by Sato et al described the overall patient satisfaction in complete denture by assessment of several parameters. A three grade scale was used to assess 302 complete denture patients. Followed by multiple regression analysis, seven factors were assessed including speech, pain (lower), esthetics, chewing, fit of the upper denture, retention of lower denture and comfort of the maxillary denture. Based on these factors a quantitative assessment was developed for complete denture satisfaction.2 Mehra et al made a survey of post doctoral programmes of complete denture impression techniques in the US. Conclusions drawn on the basis of this study were as follows A) the most common material used for border moulding is plastic impression compound. B) Irreversible hydrocolloid impression material was the one most commonly used for making preliminary impressions and polyvinyl siloxane was most commonly used for final impressions. C) Flabby ridges when present were taken into special consideration. D) Most commonly used impression technique was the selective pressure technique Elastomeric impression materials have commonly been used in impression making because of their ease of handling, dimensional stability, sufficient working time and accurate recording of fine details.4 A cross over trial was performed comparing the efficiency of conventional dentures with biofunctional prosthetic dentures by Matsuda et al and it was concluded that the biofunctional prosthetic system (BPS) system delivered high quality dentures as satisfactory as conventionally processed dentures.1 The chief drawback of simplified conventional procedures advocated in the fabrication of complete dentures was the lack of assessment of each laboratory stage to yield the final product.5,6,7 The BPS system was designed to overcome the drawbacks of the conventional complete denture techniques. The system employed a combination of standardised impression making procedures, a unique method of recording maxillomandibular relationship, teeth arrangement and denture fabrication with minimal number of patient visits. The border moulding and impression making was governed by the patient’s functional composition, hence yielding denture bases that were extremely comfortable in use. Intra oral tracings were recorded by the patients function as opposed to the operator guided movements.1,8 The BPS preliminary impression technique using two specialised impression materials, was designed to produce accurate primary casts which enabled the making of custom trays that adapted much more accurately as compared to those fabricated by conventional denture techniques. The vertical jaw relation was confirmed using callipers at both the first and second procedures. The centric jaw relation record was also more accurate as it was primarily recorded with the centric tray and confirmed using Gothic arch tracings with the Gnathometer M tracing device.1,9 The use of injection moulding technique helped minimize the risk of increased vertical dimension and porosities post denture processing. The artificial teeth used in the BPS system closely simulated the characteristic features and complex layering patterns of natural teeth, and hence offered a wide range of naturally appearing aesthetic effects.1,8 Post denture insertion adjustments were minimised along with the number of patient visits reduced to four appointments. Patient comfort and aesthetics was enhanced as compared to conventional denture systems.5, 10

 
CONCLUSION:

Complete denture prosthodontics though an age old practice has always shown scope for improvement and interesting advances have been made in the area. The Biofunctional Prosthetic System enhanced the technique of denture making to a significant extent. Each stage has been evaluated and upgraded using enhanced materials, instrumentation and technique. Superior adaptation, comfort and aesthetics in dentures were easily achievable due to this modular system.

REFERENCES:
 
  1. Matsuda KI, Kurushima Y, Maeda Y, Enoki K, Mihara Y, Ikebe K. Crossover trial for comparing the biofunctional prosthetic system with conventional procedures. Eur J Prosthodont 2015;3:64-70.
  2. Sato Y, Hamada S, Akagawa, Tsuga K. A method for quantifying overall satisfaction of complete Denture patients. J oral rehab 2000; 27: 952–957.

 

 

 

 

 

 

 

 

 

 

 

 

 

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