|Year : 2017 | Volume
| Issue : 3 | Page : 204-208
A modified physiologic impression technique for atrophic mandibular ridges
Smitha Daniel, Angleena Y Daniel, Nirmal Kurian
Department of Prosthodontics and Crown and Bridge, Christian Dental College, Ludhiana, Punjab, India
|Date of Web Publication||13-Jul-2017|
Department of Prosthodontics and Crown and Bridge, Christian Dental College, Ludhiana - 141 008, Punjab
Source of Support: None, Conflict of Interest: None
Restoration of comfort, esthetics and masticatory function in severely resorbed atrophic ridges is challenging to the clinician. Extreme resorption of the maxillary and mandibular denture bearing areas results in unstable and nonretentive dentures with associated pain and discomfort. These problems are more pronounced in mandible due to lesser denture bearing area and other anatomical limitations. This article attempts to present a modified physiologic impression technique using contemporary materials and suitable spacer design for atrophic mandible.
Keywords: Atrophic ridge, physiologic impression, spacer design
|How to cite this article:|
Daniel S, Daniel AY, Kurian N. A modified physiologic impression technique for atrophic mandibular ridges. CHRISMED J Health Res 2017;4:204-8
|How to cite this URL:|
Daniel S, Daniel AY, Kurian N. A modified physiologic impression technique for atrophic mandibular ridges. CHRISMED J Health Res [serial online] 2017 [cited 2020 Jan 28];4:204-8. Available from: http://www.cjhr.org/text.asp?2017/4/3/204/210475
| Introduction|| |
Restoration of masticatory function, comfort and esthetics are the functional goals of complete denture treatment. Often accomplishment of these goals is challenging to the clinician in severely resorbed atrophic ridges. The principal functional problem arises from the inability of the residual ridge and its overlying tissues to withstand masticatory forces. The mucosa is sandwiched between the denture base and the underlying bone so that all the forces exerted during function are transmitted through this atrophic tissue. Extreme resorption of the maxillary and mandibular denture bearing areas results in unstable and nonretentive dentures with associated pain and discomfort. These problems are more pronounced in mandible due to lesser denture bearing area and other anatomical limitations.
Atrophic mandibular ridges are categorized under the American College of Prosthodontics Class IV classification. This type of edentulous mandible has residual vertical bone height of about 10 mm or less measured at the least vertical height of the mandible on a panoramic radiograph. The residual ridge offers no resistance to horizontal or vertical movement. Attached mucosal base is either seen only in the posterior lingual region or is completely detached. Class IV edentulism can have Class I, II, or III maxillamandibular relationships. These atrophic ridges demand complex preprosthetic surgery to aid in implant placement and augmentation of implant sites, surgical correction of dentofacial deformities, hard tissue augmentation, and major soft tissue revision such as vestibular extensions with or without soft tissue grafting. There can be a history of paresthesia or dysesthesia with insufficient interarch space requiring surgical correction. Another feature that can add to the complexity in clinical steps and in denture usage is hyperactivity and hypertrophy of tongue. Depicting the most debilitated edentulous condition, surgical reconstruction is almost always indicated in this classification level, but when a surgical revision is not an option, prosthodontic techniques of a specialized nature must be used to achieve an adequate treatment outcome.
In the management of atrophic ridges, modifications of conventional impression making techniques such as admixed, functional, and green all compound techniques  have been proposed to provide functionally acceptable complete denture prosthesis. Admixed technique may have the disadvantage of discomfort produced by the heat used for manipulation. Handling characteristics and its use in undercut areas might possibly limit the use of fluid waxes and zinc oxide eugenol impression materials in functional and modified green all compound techniques, respectively., This article attempts to present an alternative physiologic impression technique using contemporary materials for Class IV mandible.
| Case Reports|| |
A 75-year-old male patient reported to the Department of Prosthodontics and Crown and Bridge, Christian Dental College with the chief complaint of loose lower complete denture. The patient was edentulous for the past 15 years and was wearing a set of complete denture prosthesis since then. The existing dentures were ill-fitting causing pain and discomfort to the patient. Detailed examination revealed an atrophic mandibular ridge and moderately resorbed maxillary ridge [Figure 1].
|Figure 1: Case 1 - Pretreatment photograph showing mandibular atrophy. The patient had a chief complaint of loose lower dentures and has been a denture wearer for the past 15 years|
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Another 72-year-old male patient reported to the Department of Prosthodontics and Crown and Bridge, Christian Dental College with the chief complaint of difficulty in chewing. He gave a history of denture wearing for more than 12 years during which he had used two sets of dentures for 6 years each. On clinical examination, inflammation of mucosa was observed along with thin, resorbed mandibular ridge indicating atrophic ridge [Figure 2]. Medical history revealed that he is diabetic since 15 years and was on regular medication.
|Figure 2: Case 2 - Pretreatment photograph showing thin resorbed mandibular ridge. The patient was a denture wearer for the past 12 years|
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After the complete evaluation of patient's history, radiographs, and existing clinical condition, various treatment options were discussed with both the patients. This included preprosthetic surgeries such as bone augmentation and vestibuloplasty for implant supported overdenture and conventional complete denture. However, the patients were not interested in any surgical intervention and opted for a new conventional complete denture. Moreover, diabetic patients are prone to chronic infections and inflammations of denture bearing area which have long lasting effects on the mucosa and the bone. Thus, a need for physiologic impression technique was presented to the clinician to exert uniform pressure on the denture bearing surface for prevention of sandwiching of the mucosa between the denture base and the mandibular bone and to retard resorption of bone. It is also mandatory to educate and motivate diabetic patients toward maintenance of oral hygiene and regular review biannually.
The physiologic impression technique utilized was the same for both cases that is described as follows:
Preliminary impression was made with admixed technique. Impression compound (DPI Pinnacle, Bombay Burmah Trading Corporation, Mumbai, India) and low fusing impression compound (DPI Pinnacle Tracing Sticks, Bombay Burmah Trading Corporation, Mumbai, India) in the ratio of 3:7 parts by weight are placed in a bowl of water at 60°C and kneaded to a homogeneous mass that provides a working time of about 90 s. This homogenous mass is loaded, and the patient is made to do various tongue movements [Figure 3] and [Figure 4].
Spacer of 2 mm thickness was maintained using baseplate wax (Y Dents Modelling Wax, MDM Corporation, Kacha Pandit, New Delhi, India) and the design included crest of the atrophied mandibular ridge with tissue stops of 3 mm × 3 mm in canine and molar regions. Custom tray was fabricated using cold cure acrylic material (DPI Rapid Repair, Bombay Burmah Trading Corporation, Mumbai, India) and was shortened up to 2 mm from the limiting border of preliminary cast. After checking the custom tray extension in the mouth, it was border molded using low fusing impression compound.
Following border molding, incremental loading of softened low fusing impression compound on the anterior, middle and posterior third of the impression surface of custom tray was done. It was then seated onto the denture bearing area, labial and buccal borders were molded and the patients were asked to perform various tongue movements to mold the lingual flange. Any excess low fusing impression compound on the periphery was trimmed with a Bard-Parker Blade No. 15 [Figure 5] and [Figure 6].
|Figure 5: Case 1 - Incremental impression made with low fusing impression compound|
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|Figure 6: Case 2 - Incremental impression made with low fusing impression compound|
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Relief area was trimmed and the intaglio surface was roughened by making grooves for mechanical retention of light bodied elastomeric impression material (Express™ Light Body, 3M ESPE, Seefeld, Germany) [Figure 7] and [Figure 8]. Adhesive (VPS Tray Adhesive, 3M ESPE, Seefeld, Germany) was applied on the intaglio surface and allowed to dry. Light bodied elastomeric impression material was loaded, and final wash impression was obtained by performing lip, cheek movements, and tongue movements [Figure 9] and [Figure 10]. The impression is washed and disinfected by immersing in 2% glutaraldehyde (CIDEX Johnson & Johnson Company, India) for 10 min and the cast poured. Later, the denture is fabricated following the standard procedure.
|Figure 10: Case 2 - Final impression with light body impression material|
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| Discussion|| |
Management of resorbed ridges is a cumbersome and difficult task especially in mandible because of smaller denture bearing area than maxillary ridge and other anatomical limitations. Surgical management requires patient cooperation and may not be feasible at all times. Alternatively, prosthetic management of such severely resorbed ridges involves special impression techniques mainly to achieve stability.
The conventional technique of impressing edentulous ridges involve custom tray with relief/spacer wax covering secondary stress bearing and relief areas, but in cases, with severe resorption, such a custom tray design would involve the entire edentulous ridge as proper demarcation between stress bearing, relief areas, and limiting structures are not easily achievable. Border molding with conventional techniques is inefficient owing to obscurity in identifying limiting structures making impression making more technique sensitive. Modified impression technique described here is an alternative attempt taking into consideration the above-mentioned limitations associated with conventional technique to achieve better denture support from the compromised denture bearing area.
In this technique, the primary impression was recorded using admixed technique due to its lower compressibility and better flow characteristics. Spacer design covered crest of residual ridge to minimize stresses on them leaving the buccal shelf area. Custom tray so prepared was used to record functional form of the primary stress-bearing area and anatomic form of the area that cannot withstand functional loading. Low fusing impression compound was used to selectively exert pressure, by restricting the flow of impression material in the stress bearing area and scraping out the material from nonstress bearing areas. Tray was held by placing two fingers on the tray in the buccal shelf area and the thumb supporting the chin without exerting pressure on any part of tray. Incremental loading was done for the ease of molding all borders perfectly. Reheating of the intaglio surface was avoided to ensure that there is no differential loading of tissues caused by the flow of the material.
All the movements of lips, cheeks, and tongue aid in functional recording of edentulous mandible resulting in physiologic impression. Final impression was made using light body polyvinyl siloxane impression material. In a study conducted by Al-Ahmad et al., it was found that low viscosity polyvinyl siloxane material exhibited least pressure and provided an excellent record of minute details of the residual ridge in its passive form. This technique is comparable to the physiologic impression technique except in its preliminary impression which was made using admixed technique and its spacer design that conforms with Boucher's design for mandibular ridge.
The goal of this technique is to provide maximum stability covering maximum denture bearing area selectively distributing the pressure over the entire denture bearing area. This is attributed to various steps contributing to impression making. First, the intimate contact of custom tray helps in distributing maximum forces to the buccal shelf area. This is achieved by the spacer design. Second, the viscosity of the low fusing impression compound removes any soft tissue folds and smoothens them over the mandibular bone, thus reducing the potential for discomfort arising from the “atrophic sandwich” of the mucosa between the denture and the bone. The sequencing of the clinical steps in this modified physiologic impression technique was done considering the principles of “Green all compound technique” by Tunkiwala and Ram  and “Admixed technique” by McCord and Tyson.
The primary advantage of this impression technique is that the spacer design, functional molding, and the impression materials used in the fabrication of mandibular denture minimize the forces transmitted to the denture-bearing area. Thus, this technique prevents sandwich of mucosa, maintains the health and integrity of overlying mucosa and residual ridge and renders comfort to the patient during denture usage. It has an advantage over the admixed technique in that it allows incremental molding of the intaglio surface of the custom tray. Another merit as compared to green all compound technique is that this technique recommends the use of spacer which allows the distribution of forces to the buccal shelf, the primary stress bearing area. Further, contemporary and readily available impression materials are used in this technique.
The drawbacks of this technique include discomfort due to heat used during functional molding with green stick impression compound. Furthermore, the brittleness of the material during scraping is also a disadvantage. Besides, its usefulness as a new technique needs to be evaluated.
| Conclusion|| |
The presented technique describes an alternative method to impress the Class IV mandibular ridge using a modified special tray and elastomeric impression materials. This technique incorporates theoretical principles to impress such tissues and concurrently overcomes the practical difficulties commonly encountered during such procedures.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10]