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Authors: Dr. Kamleshwar Singh, Dr. Kaushal Kishor Agrawal, Dr. Priyanka Mall.

Abstract:
Flabby ridges develop when hyperplasic soft tissue replaces the alveolar bone and is a common finding in long term denture wearers. They can be managed by surgical removal of fibrous tissue, implant retained prosthesis or conventional prosthodontics without surgical intervention. This article describes a technique for making definitive impression for highly displaceable residual ridges. The choice of impression material as well as design of the tray, stresses on preventing distortion of residual alveolar ridge during impression making.

Introduction:
Flabby tissue means ‘excessively mobile tissue’. 1 Occurrence of flabby ridges is 24% in edentate maxillae and 5% in edentate mandible. 2,3 Flabby ridges present in anterior maxilla is a feature of combination syndrome. 4,5 This arises because of unplanned dental extractions that result in maxillary complete dentures opposing mandibular anterior natural teeth.
Histologically flabby tissue is composed of mature, dense, fibrous connective tissue. It has dense bundles of collagen fibres, with relatively few cellular elements, with very few inflammatory cells. The overlying epithelium shows some evidence of hyperplasia.6
Ridge resorption as well as flabby ridges that are a sequlae of long term denture wearing influence denture retention and stability. The denture over the flabby ridge lacks support, so it gets displaced because of recoil of the tissue during function and thus retention and stability are compromised. So our treatment should aim at reducing the capacity for movement of flabby tissue during function. Careful attention should be paid to the recording of the impression surface details.
A variety of techniques have been suggested to overcome the difficulties of making a denture rest on the flabby tissues. Flabby tissues provide poor retention for a denture but it is still better than the no bone that results from the surgical excision.
Liddlelow used two different materials in one custom tray i.e. plaster of paris over the flabby tissues and zinc oxide and eugenol over the normal tissues. 7 Two separate impression trays and impression materials were used to record ‘flabby’ and ‘normal tissues’ separately and then were related intraorally by Osborne. 8 ‘Window’ impression technique was described by Watson.9 He made a custom tray with an opening over the flabby tissues. Normal tissues were recorded by mucocompressive technique by using zinc oxide and eugenol. Once set it was removed and reseated in mouth and plaster of paris was painted over the flabby tissues through the window. Watt and Mc Gregor used impression compound over a modified custom tray which was then manipulated to compress the normal tissues while avoiding the displacement of flabby tissues with the same material.10 Over this manipulated impression compound a zinc oxide and eugenol wash impression was made.

Case description:
A 63 year old male patient was referred to the Department of Prosthodontics for specialist treatment regarding his prosthodontic rehabilitation. The patient had changed two dentures within a period of three years and still had a complaint of loose lower dentures. On examination completely edentulous maxillary and mandibular arches were seen with extensively mobile tissue in the mandibular anterior region (Figure 1-2). The patient was not willing to undergo any surgical intervention. So it was decided to make a new set of dentures with appropriate impression technique.
An alternative method of making a final impression for mandibular edentulous arches with displaceable tissues, using zinc oxide eugenol impression paste and impression plaster is described.

Fig1 Fig2

Figure 1 : Edentulous maxillary ridge

Figure 2 : Extensively mobile tissue in the mandibular anterior region

Technique:
  1. Make a preliminary impression of the edentulous arch using impression compound (DPI pinnacle, Mumbai) in a metal stock tray.
  2. Pour the impression in Type III dental stone.
  3. Fabricate a custom impression tray on the preliminary cast using auto-polymerized acrylic resin (Rapid Repair, Gurgaon, Dentsply India). Adjust the border extension of the tray to be at least 2 mm short of the vestibules on the preliminary cast.
  4. Evaluate and adjust the extension of the tray in the mouth, if necessary.
  5. Border mold the tray with modelling plastic impression compound (DPI Tracing Sticks, Mumbai, India)
  6. Make a zinc oxide eugenol (DPI Impression paste, Mumbai)
  7. Mark the extensions of the displaceable tissues with an indelible pencil in mouth and transfer the extensions on the final impression.
  8. Trim the tray over the crest of the residual ridge and create a window opening above the displaceable residual alveolar ridge (Figure 3).
  9. Impression plaster is mixed with an anti-expansion solution (containing 4% potassium sulphate and 0.4% borax) in the ratio of 100g to 50-60 ml to produce a smooth paste, free of air bubbles.
  10. Paint this solution of impression plaster over the displaceable tissue and place the zinc oxide eugenol final impression over it.
  11. Remove the impression after setting of the impression plaster (Figure 4).
  12. The impression plaster is then coated with a thin layer of separating medium and poured with dental stone and subsequently denture was fabricated (Figure 5).

Fig3 Fig4 Fig5

Figure 3: Trimming of the tray to create a window

Figure 4: Final impression

Figure 5: Post-operative view

Discussion:
Other treatment modalities for the scenario described in this article include surgical ‘debulking’ or excision of the flabby tissues, and the use of dental implants. Surgical ‘debulking’ of flabby tissues is mainly a historical concept nowadays. The rationale behind its use was that removal of flabby tissues would result in a ‘normal’ compressible denture bearing area on which a mucocompressive impression technique could be used. Some of the difficulties caused by this approach include the fact that many complete denture patients are elderly or have complex medical histories, for which any form of surgery is contraindicated. Furthermore, the excision of flabby tissues and resultant ‘shallow’ ridge may provide little retention or resistance to lateral forces on the resultant denture. One is reminded of the concept that prosthodontic therapy should be concerned with the ‘conservation of what remains, rather than the meticulous replacement of what has been lost’. The use of dental implants in this scenario is also not without difficulty. It is clear that if there has been excessive bone resorption and replacement by flabby tissues, then there will be little bone remaining into which dental implants can be placed. While it would be technically possible to augment the remaining ridge with bone grafts, the prognosis of such treatment would be questionable. Furthermore, there are a group of patients who for a variety of clinical or medical reasons are unsuited for dental implant treatment. There are also some patients who do not wish to have surgically invasive procedures such as placement of dental implants. It is worth noting two further items from the technique described. Firstly, after completion of the master impression, it is crucial to ensure that the occlusal plane is properly orientated, and that a suitable occlusal scheme with proper balancing contacts in excursive movements is achieved. The use of a face-bow transfer and arrangement of the teeth on a semiadjustable articulator can facilitate this. It is important to realize that an incorrectly oriented occlusal plane, or incorporation of displacing occlusal contacts, will further destabilize a denture that is relying on poor quality denture-bearing tissues. The efforts to secure an adequate impression will have been wasted. Secondly, the use of a transparent acrylic heat-cured base permits rapid assessment of the accuracy of the impression technique. Using a transparent base allows rapid visualisation of the adaptation of the base to the underlying denture bearing areas. Ingress of air can be rapidly noticed, and movement of the base can be observed in association with specific movements.

Summary:
Final impression technique using both zinc-oxide eugenol and impression plaster for displaceable mandibular residual ridges is described. Impression plaster is chosen because it reproduces good surface details, has excellent dimensional stability and rate of the setting reaction can be controlled by the clinician.

References:
  1. The glossary of prosthodontic terms J Prosthet Dent 2005;94:39
  2. Carlsson GE. Clinical morbidity and sequelae of treatment with complete dentures. J Prosthet Dent 1998; 79: 17-23.
  3. Xie Q, Nähri TO, Nevalainen JM et al. Oral status and prosthetic factors related to residual ridge resorption in elderly subjects. Int J Prosthodont 1997; 55: 306- 313.
  4. Kelly E. Changes caused by a mandibular removable partial denture opposing a maxillary complete denture. J Prosthet Dent 1972; 27: 210-215.
  5. Lynch CD, Allen PF. The ‘combination syndrome’ revisited. Dent Update 2004; 31: 410-420.
  6. Ellisworth Kelly.Changes caused by aremovable partial Denture opposing a maxillary complete denture. J Prosthet Dent 2003;90:213-219
  7. Liddelow KP. The prosthetic treatment of the elderly. Br Dent J 1964; 117: 307-315.
  8. Osborne J. Two impression methods for mobile fibrous ridges. Br Dent J 1964; 117: 392-394.
  9. Watson RM. Impression technique for maxillary fibrous ridge. Br Dent J 1970; 128: 552.
  10. Watt DM, MacGregor AR. Designing complete dentures. 2nd edn. Bristol: IOP Publishing Ltd, 1986

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