|Year : 2016 | Volume
| Issue : 1 | Page : 24-28
Fabrication and relining of dentures with permanent silicone soft liner: A novel way to increase retention in grossly resorbed ridge and minimize trauma of knife edge and severe undercuts ridges
Kunwarjeet Singh1, Nidhi Gupta2
1 Department of Prosthodontics, Dental Materials and Implantology, Institute of Dental Studies and Technologies, Modinagar, Ghaziabad, Uttar Pradesh, India
2 Department of Pedodontics and Preventive Dentistry, Institute of Dental Studies and Technologies, Modinagar, Ghaziabad, Uttar Pradesh, India
|Date of Web Publication||15-Dec-2015|
Department of Prosthodontics, Dental Materials and Implantology, Institute of Dental Studies and Technologies, Modinagar, Ghaziabad, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
The aim of this study is to suggest a technique to improve the retention of the prosthesis in grossly resorbed ridge and minimize the trauma of thin, atrophic knife edge ridge with severe undercuts. Significant numbers of patients seek treatment for edentulism throughout the world. In the current scenario, implant retained/supported prostheses have been considered a standard of care for rehabilitation of completely edentulous patients, but still this treatment modality is out of reach of many patients due to economic factor. In such patients, conventional removable complete dentures are considered for functional rehabilitation. However, in some of the patients with grossly resorbed ridges and knife edge ridges or ridges with severe undercuts, these prostheses have compromised retention and also continuously causes trauma to knife edge ridges and mucosa covering the undercuts during insertion and removal of the prosthesis thereby reducing the compliance of the patient. By incorporating, a layer of resilient permanent silicone soft liner on the tissue surface of a new or old denture is a novel way to reduce the trauma of thin and severe undercut ridges and also improve the retention of the prosthesis. This study described the successful functional rehabilitation of three completely edentulous patients with grossly resorbed, thin knife edge, and severe undercut mandibular ridges with permanent silicone soft liner. Permanent silicone soft liner act as a shock absorber, helps in equal dissipation of occlusal stresses, maintains an intimate contact with the underlying tissues and compressed during function thereby increasing retention and minimizing trauma by preventing a direct contact of hard denture base with compromised tissues.
Keywords: Knife edge ridge, Molloplast B, permanent soft liner, severe undercuts ridges
|How to cite this article:|
Singh K, Gupta N. Fabrication and relining of dentures with permanent silicone soft liner: A novel way to increase retention in grossly resorbed ridge and minimize trauma of knife edge and severe undercuts ridges. Dent Med Res 2016;4:24-8
|How to cite this URL:|
Singh K, Gupta N. Fabrication and relining of dentures with permanent silicone soft liner: A novel way to increase retention in grossly resorbed ridge and minimize trauma of knife edge and severe undercuts ridges. Dent Med Res [serial online] 2016 [cited 2021 Apr 11];4:24-8. Available from: https://www.dmrjournal.org/text.asp?2016/4/1/24/171922
| Introduction|| |
Edentulous patients often seek treatment for replacement of their missing teeth for improvements in esthetics, function, and speech. Conventional removable complete dentures fabricated by heat cure acrylic resins are most commonly used for prosthodontic rehabilitation of completely edentulous patients. However, some patients are maladaptive in their ability to tolerate conventional removable prosthodontic treatment and may require more advanced treatments.  The implant-supported prostheses have vastly improved the outcome related to treating edentulous patients. 
However, this treatment modality might not be possible in all completely edentulous patients due to financial reasons, inadequate bone quantity and quality, unwillingness of the patient to undergo different surgical protocols. In some circumstances, osseointegrated implants in augmented jaws when compared to the results with newly fabricated conventional complete dentures do not always lead to a superior patient-perceived improvement over complete denture wear.  Therefore, the use of conventional denture treatment is the mainstay of treatment for many of these patients.
Conventional removable complete dentures fabricated by heat cure acrylic resins are most commonly used for prosthodontic rehabilitation of completely edentulous patients, but in some of the patients with grossly resorbed flat ridges and thin, sharp knife edge ridges or ridges with severe undercuts, these prostheses have compromised retention and also continuously causes trauma to knife edge ridges and mucosa covering the undercuts during insertion and removal of the prosthesis thereby reducing the compliance of the patient.
Sandwiching a layer of resilient permanent silicone soft liner within denture base improves retention in atrophic flat ridges with inadequate vestibular depth by intimate contact with underlying tissues and also reduce the traumatic impact to residual ridges by distributing masticatory load. The resilient layer acts as a shock absorber or stress distributor by absorbing some of the load and equal distribution of remaining stress during function, so that the hard basal seat of the denture receive less impact force. Being elastic in character, it stretched during insertion and removal of prosthesis over bony prominences without traumatizing the tissues and spring back into close contact with the undercut area thereby improving the retention.
Permanent silicone soft liner Molloplast B, (Molloplast B, Regneri GmbH and Co. KG Karlsruhe, West Germany) a heat-polymerized silicone rubber, is supplied as a one-paste system activated by heat (boiling water for 2 h). It consists of a polymer (polydimethylsiloxane), cross-linking agent (acryloxy alkylsilane), and catalyst (heat and benzoyl peroxide). An adhesive (Y-methacryloxy propyl trimethoxysilane) which is a silicone polymer in is supplied as a solvent to aid bonding to the denture base. Molloplast B retains viscoelasticity and softness for longer periods and does not harden due to lack of plasticizer.
| Case Reports|| |
A 52-year-old female reported to our dental center with chief complaint of difficulty in chewing due to loose ill-fitting dentures and continues trauma of underlying tissues. She had 3 sets of dentures but was not satisfied with any of them. She had the habit of using a cotton roll under the mandibular denture. She desired a denture with good retention and no trauma of denture-supporting tissues during function. Clinical examination revealed grossly resorbed mandibular ridge and poorly designed complete dentures.
A 56-year-old female reported to us with chief complaint of difficulty as well as trauma of the tissues during insertion and removal of the mandibular denture. Her oral examination revealed severe bony undercut in mandibular anterior region [Figure 1]a and well-fabricated complete dentures.
|Figure 1: (a) Mandibular ridge with severe anterior undercuts. (b) Silicone adhesive applied to tissue surface of the mandibular denture. (c) Separating media applied to the master cast. (d) Silicone soft liner placed over tissue surface of the denture. (e) Trial closure with cellophane sheet. (f) Permanent silicone soft liner relined denture. (g) Definitive prosthesis|
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A 60-year-old female patient reported to our dental centre chief complaint of trauma of mandibular denture bearing tissues. Clinical examination revealed thin knife edge mandibular posterior ridge [Figure 2]a-d and well-designed complete dentures with proper vertical dimension and centric relation coinciding with centric occlusion.
|Figure 2: (a) Grossly resorbed mandibular knife edge ridge. (b) Final impression with light body. (c) Soft liner relined mandibular denture. (d) Definitive polished mandibular denture|
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In case 1, new complete dentures were by combination of heat cure acrylic resin and permanent silicone soft liner and in case 2 and 3, previous dentures were well designed with proper vertical dimension and centric relation so only relining of mandibular dentures were done with permanent soft liner.
Procedure for fabrication of new dentures with permanent silicone soft liner
After try-in, the flasking and dewaxing of the completed trial dentures were done [Figure 3]a; the modeling wax about 1.5 mm thick was adapted on the casts [Figure 3]b to create space for the permanent soft liner [Figure 3]c. The thickness of spacer should be 1-2 mm and it can be fabricated from modeling wax, thermoplastic resin sheet (1.5 mm), or cold curing acrylic resin trimmed to the required thickness (1-2 mm). The separating media were then applied on the mold, except the teeth, and on the master cast.
|Figure 3: (a) Mold with acrylic teeth after dewaxing. (b) Modeling wax spacer for the soft liner. (c) Permanent silicone soft liner (Molloplast B) with adhesive. (d) Heat cure acrylic resin packed into the mold. (e) After trial closure. (f) Permanent soft liner placed over heat cure acrylic resin. (g) Silicone liner with acrylic resin after trial closure. (h) Processed denture with silicone liner. (i) Definitive polished prostheses|
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The heat cure acrylic resin (Lucitone 199 denture base material, Dentsply, Germany) was mixed according to manufacturer instruction and packed in dough stage into a lukewarm flask [Figure 3]d. Prior to pressing, a polyethylene (PE) foil was placed between acrylic and spacer for easy separation of flask parts at trial closure. The flask was pressed for 10-15 min at 100 kp under hydraulic press to allow acrylic resin to gain adequate stiffness to avoid deformation by the permanent soft liner (Molloplast B, Detax GmbH and Co, Germany) material during pressing. Then the flask was removed from the clamp and opened carefully. The PE foil, excess acrylic resin, and spacer were removed [Figure 3]e.
Molloplast B needs no mixing. It is available in the form of dough-like consistency in a jar. The required amount of material was dispensed with a clean spatula from the jar and packed onto the prepressed acrylic in the flask [Figure 3]f. A new PE foil was placed between the permanent soft liner and counter of the flask. The flask was closed and prepressed in intervals at 100 kp. The flask was opened, and PE foil and excess soft liner were removed [Figure 3]g. The flask was again closed and pressed for approximately 10-15 min at 100 kp. The flask was then placed in the clamp, and the whole assembly was placed in cold water and heated slowly to 100°C. The polymerization was done in boiling water at 100°C for approximately 2 h. The flask was cool down slowly. After opening the flask, the prosthesis was retrieved, finished, and polished [Figure 3]h and i. The polishing of acrylic was done by normal procedures. The excess soft liner was cut with scissors, and polishing was done over rough areas with polishing disc. After occlusal adjustments, prosthesis was delivered to the patient. During 1 year follow-up, patient was quite satisfied with the prosthesis.
Relining of dentures with permanent silicone soft liner
The intaglio surface of the existing complete denture was trimmed about 1.5-2 mm with carbide bur. Tray adhesive (caulk tray adhesive, Dentsply, Germany) was applied to the intaglio surface including the borders of the denture and allowed to dry for 10 min. Final impression [Figure 2]b was made with light body polyvinyl siloxane (Aquasil LV, Dentsply, Germany). While setting of the impression, patient was instructed to close in centric occlusion with light contact to minimize the changes in the vertical dimension. The definitive cast [Figure 1]c was poured in type IV dental stone (Ultrarock, Kalabhai Karson Pvt. Ltd.).
After flasking and dewaxing, the impression material was removed from the tissue surface of the denture. The tissue surface was properly cleaned after trimming and adhesive (primo adhesive) was applied [Figure 1]b 1-2 times with brush onto the entire tissue surface to achieve optimum bonding between denture base and permanent silicone soft liner (Molloplast B, Detax GmbH and Co, Germany). The adhesive should be allowed to air dry for 60-90 min before applying Molloplast B. After proper drying of the adhesive, Molloplast B was taken with a clean spatula from the jar and applied onto the tissue surface of the prosthesis [Figure 1]d. Before closing the flask, a PE sheet was covered over the soft line for the trial closure. The closed flask was placed under hydraulic press for 6-10 min, after which flask was opened [Figure 1]e, PE sheet and excess soft liner were removed. The flask was again closed and placed under hydraulic press for 15 min at 100 psi. The flask was then placed in clamp and tightened and then placed in heat curing pot for heat polymerization. The flask was placed in cold water and heated slowly up to 100°C. The polymerization in boiling water at 100°C was done for approximately for 2 h. The flask was opened after allowing to cool to room temperature and relined prosthesis was retrieved, finished, and polished [Figure 1]f and [Figure 2]c. Mechanical polishing of Molloplast B relined prosthesis is not possible. To achieve high gloss polishing, Lustrol gloss varnish applied on the entire surface and at the borders along the junction of soft liner and acrylic base and prosthesis finally delivered to the patient [Figure 1]g. It was applied with a brush in a thin layer and allowed to set for 10-15 min.
| Discussion|| |
Residual ridge resorption is inevitable, continuous process which might get aggravated by many local and systematic factors resulting in excessive resorption with compromised retention of the prosthesis and trauma of underlying soft tissues due to occlusal problems, underlying bony irregularities, reduced keratinization of the epithelium with increasing age, and atrophic changes in postmenopausal women. Incorporation of a resilient liner beneath a rigid denture base can improve retention, masticatory efficiency, and oral comfort for patients presenting with a reduced thickness or lessened resilience of the oral mucoperiosteum. The intimate contact of the liner with tissues improves the retention particular in patients with grossly resorbed ridge and in xerostomic patients (salivary flow is decreased). Adequate saliva required both for lubrication and to aid retention and its absence can result in loose denture since the forces of adhesion, cohesion, and negative atmospheric pressure is lacking. Being elastic in character, it stretched during insertion and removal of prosthesis over bony prominences without traumatizing the tissues and spring back into close contact with the undercut area thereby improving the retention.
Soft denture lining materials lead to a more uniform distribution of stress at the mucosa/lining interface.  They reduce the traumatic effect that a denture may have on patients with thin atrophic mucosa, ridge atrophy or resorption, deep anatomical undercuts, bruxism tendencies or where the oral mucosa exhibits a reduced tolerance to the load applied by a denture, and in congenital and acquired oral defects requiring obturation.  Currently, two types of soft denture lining material are available; silicone elastomers and soft acrylic compounds. , In the clinical situation, the silicone materials are preferred because they remain more stable, while the acrylic materials undergo a more marked loss of cushioning effect over time. , The silicone materials are also available in both autopolymerizing and heat-curing forms.
Over the years, many modifications have been done in the designing of the complete dentures, but still a hard rigid denture base remain in contact with the soft tissues covering the residual ridges which might be subjected to trauma in compromised cases. Parker  reduced the effect of traumatic impact over the edentulous ridge by sandwiching a resilient liner layer within in denture base. This soft liner layer acts as "shock absorber" and "stress distributor." Molloplast B has excellent shock absorber property which is directly related to the thickness of the layer of the liner.  Plotnick  had found 20% reduction in force for 0.25 mm thick silicone soft liner layer which was further reduced to 60% for the thickness of 4 mm silicone layer.
| Conclusion|| |
Fabrication of new dentures and relining of new or old dentures with permanent silicone soft liner is a novel way to minimize the trauma of compromised underlying denture-supporting tissues and thin mucous membrane over prominent bony prominence and to improve the retention of the prosthesis by maintaining intimate contact with the tissues.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Zarb GA, Schmitt A. The longitudinal clinical effectiveness of osseointegrated dental implants: The Toronto Study. Part II: The prosthetic results. J Prosthet Dent 1990;64:53-61.
Adell R, Lekholm U, Rockler B, Brånemark PI. A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg 1981;10:387-416.
Kimoto K, Garrett NR. Effect of mandibular ridge height on patients' perceptions with mandibular conventional and implant-assisted overdentures. Int J Oral Maxillofac Implants 2005;20:762-8.
Braden M, Wright PS, Parker S. Soft lining materials - A review. Eur J Prosthodont Restor Dent 1995;3:163-74.
Lammie GA, Storer R. A preliminary report on resilient denture plastics. J Prosthet Dent 1958;8:411-24.
Qudah S, Harrison A, Huggett R. Soft lining materials in prosthetic dentistry: A review. Int J Prosthodont 1990;3:477-83.
Polyzois GL, Frangou MJ. Influence of curing method, sealer, and water storage on the hardness of a soft lining material over time. J Prosthodont 2001;10:42-5.
Murata H, Taguchi N, Hamada T, Kawamura M, McCabe JF. Dynamic viscoelasticity of soft liners and masticatory function. J Dent Res 2002;81:123-8.
Murat H, Taguchi N, Hamada T, McCabe JF. Dynamic viscoelastic properties and the age changes of long-term soft denture liners. Biomaterials 2000;21:1421-7.
Parker HM. Impact reduction in complete and partial dentures, a pilot study. J Prosthet Dent 1966;16:227-45.
Kawano F, Kon M, Koran A, Matsumoto N. Shock-absorbing behavior of four processed soft denture liners. J Prosthet Dent 1994;72:599-605.
Plotnick IJ. Stress regulator for complete and partial dentures. J Prosthet Dent 1967;17:166-71.
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