Clinical management of highly resorbed mandibular ridge without fibrous tissue.

Alveolar ridge atrophy poses a clinical challenge toward the fabrication of successful prosthesis. Resorption of mandibular denture bearing areas results in unstable non-retentive dentures associated with pain and discomfort. This article describes rehabilitation procedure of a patient with resorbed ridge with maximal areas of coverage to improve support and neutral zone arrangement of teeth to improve stability of denture.

Complete denture therapy is undoubtedly among the age-old forms of dental treatment used to rehabilitate an edentulous patient.

The key to successful denture therapy lies in precise execution of the treatment plan formulated by evaluation of a complete comprehensive history and through examination. Such a treatment is based on Devan's principles of preservation of what already exists than the mere replacement of what is missing.[1]

Case Report

A 55-year-old female patient, Mrs. Latha, was referred to the Department of Prosthodontics at VDCW with the complaints of not being able to masticate, loosening of upper and lower denture, and poor esthetics for the past 3 years. She also had the complaint that the denture was moving during normal activities like swallowing and speaking. After the examination of the patient, it was clearly understood that mandibular ridge was fully compromised and the general palpation revealed there was no hypermobile tissue [Figure 1]. So, the patient was informed of all the options available for the treatment, and treatment chosen was esthetically and functionally viable for her. This article describes a simple clinical approach for fabrication of denture, which had good retention, stability, and esthetics for the patient.

Figure 1

Resorbed ridge

Techniques

Technique I: To improve the support

Support[2] is defined as resistance to vertical component of mastication in maxillary and mandibular bones.

Maximal extension of the denture base

Maximal area of contact between mucosa membrane and denture base

Intimate contact of the denture base and its basal seat.

Retromolar pad is a soft elevation of mucosa that lies distal to third molar. It consists of loose connective tissue with aggregation of mucous glands. It is covered by smoother, less cornified epithelium. Pear-shaped pad was the term coined by Craddock and refers to an area formed by residual scar of 3rd molar and the retromolar papilla. The mandibular denture should terminate over the distal edge of the pear-shaped pad. If the ridge is poor, the support is difficult. It may be advantageous to bead the denture just distal to the pear-shaped pad and cover the retromolar pad.

Technique II: Improved retention

Retention[3] is defined as the quality inherent in dental prosthesis with the ability to resist forces of dislodgment along path of withdrawal.

First, primary impression was made with impression compound and over it an wash impression was taken using alginate [Figure 2]. Cast was poured in dental stone. Over the cast, special tray was constructed of autopolymerizing resin. The tray was trimmed 2 mm short of margin, checked in the mouth, and border molding was done.

Figure 2

Primary impression

A properly formed denture base outline develops a seal that can be maintained during most normal oral functions. The labial flange extends from one buccal frenum to the other. The buccal flange extends from buccal frenum to retromolar pad. Posterior border extends to completely cover the retromolar pad. The lingual vestibule is divided into three areas: Anterior lingual vestibule (sublingual crescent area), middle vestibule (mylohyoid area), and distolingual vestibule (lateral throat form, retromylohyoid curtain).

Sublingual crescent area recording custom acrylic tray was trimmed 2 mm short of floor of the mouth and tracing compound was added to the border. The tracing compound was softened to a flowing consistency and the tray is placed into her mouth. The tongue should be in the normal rest position with the tip lightly touching the lingual surfaces of the mandibular anterior ridge.

Procedure

A custom tracing tray was trimmed 2 mm short of floor of the mouth and tracing compound was added to the border. The lateral throat form area was recorded by asking the patient to protrude the tongue. This action activates the superior constrictor muscles which support the retromylohyoid curtain. The dentist then applied downward force on the impression tray while asking the patient to close the mouth. This records the action of medical pterygoid muscle on the retromolar curtain. Secondary impression was made in zinc oxide eugenol and the cast was poured in dental stone.

Techniques for Improving Stability

Resistance offered by the prosthesis[4] in the horizontal direction:

Occlusal plane

Teeth arranged – Neutral zone

Using non-anatomical teeth

Neutral Zone

Potential space[5] between lips and cheeks on one side and tongue on other side (or) the area or position where the forces between the tongue and cheeks or lips are equal.

Materials – Recording Neutral Zone

Modeling plastic,[6] impression compound, soft wax, silicone, tissue conditioners, resilient lining materials

According to technique I, primary impressions of the upper and lower jaws are taken using the impression compound and model is poured. On this model, upper wax rims and lower special tray are constructed.[7] The special tray is a plate of acrylic adapted to the lower ridge without a handle.

The upper wax rim is adjusted as in normal registration for a complete denture. The lower special tray is placed in the mouth. Two occlusal pillars are then built in low fusing compound. These pillars are molded and adjusted to the correct height so as to give the usual 3-mm freeway space.[8]

A thick mix of viscogel is then placed around the rest of the lower special tray distally and mesially to the occlusal pillars. The patient is then asked to talk and swallow, and drink some water. After 5–10 minutes, the set impression is removed from the mouth and cleaned. The viscogel material would have been molded by the patient's musculature into a position of balance [Figure 3].[9]

Figure 3

Occlusal pillars with jaw relation

Indices are then constructed is the lab by surrounding the impression with plaster. When the viscogel and tray are removed, a gutter corresponding to the neutral zone is left behind. The teeth may then be placed into the neutral zone [Figure 4].

Figure 4

Netural zone

Discussion

The residual alveolar ridge[8] consists of denture-bearing mucosa, submucosa, periosteum, and underlying alveolar bone. Residual bone is that part of alveolar ridge which remains after the teeth have been lost. After the loss of tooth, the alveoli that contained root are filled with new bone. This alveolar process becomes the residual ridge which is the foundation for the denture. The mean denture-bearing area of mandible is 12.25 cm2. We use the following clinical techniques to improve support, retention, and stability of the lower denture. We used the maximal contact between mucosa membrane and denture base and intimate contact of denture base and basal seat area. Retention was improved by using lateral throat form. Stability[10] can be improved by using different jaw relation techniques. Neutral zone was recorded by means of tissue conditioner and tooth was set exactly in the neutral zone [Figures 5 and 6]. After the wax trail was completed, it was seen whether the patient's tongue was at par with the lingual cusp of the lower posterior teeth. Denture was processed in heat-cure acrylic resin and inserted in the patient. The patient was then recalled after 6 months and she was quite satisfied with retention stability and esthetics of the new set of denture.

Figure 5

Neutral zone in tissue conditioner

Figure 6

Wax trail in neutral zone

Conclusion

Success of complete lower dentures has been a challenge for dentists and patients alike. In particular, a flat lower ridge is associated with difficulties in providing successful dentures. A proper understanding of the factors involved in stabilizing a lower denture is necessary. A lower denture which covers the entire supporting area available to it with its flange intensions in harmony with the surrounding musculature will certainly show improved stability retention and support [Figure 7].

Figure 7

Retention stability improved denture