Prosthodontics

Fahrication of a custom-made impression tray for makingpreliminary impressions of edentulous mandiblesA. M. Sofou, DDS, PhD*/I. Diakoyiatini-Mordohai. DDS, PhD^VA. L. Pissiotis, DMD, MS, PhD*/I. Emmanuel, DDS, PhD**

Severe mandibular alveolar ridge résorption is usually observed in patients with long-term edentulismand/or ill-fitnng dentures. In some of these patients, the genial tubercles project into the floor of ihemouth as a high point in the anterior area of the mandibular residual ridge. The lingual flanges ofmandibular stock impression trays usually impinge on ihe most prominent areas of the resorbed mandibu-lar edentulous ridge (ie. internal oblique lines and genial tubercles). !i is suggested that a preliminai-ycustom tray be made in such cases lo pour an initial impression so that individual custom Irays can befabricated. An efficient method for constructing such a custom impression tray from readily availablematerials is described. (Quintessence lut 1998;29;5I3-5I6)

Key words: alveolar ridge résorption, custom-made impression tray, edentulous mandible, preliminaryimpression

Clinical relevance

The clinician often has to improvise to solve a clin-ical problem. This technique allows the ciinician tofabricate an impression tray for severely resorbedmandibular edentulous ridges, when ordinary stockimpression trays cannot facilitate prehtninary im-pression making.

The achievement of maximum retention, stability,and support is the major objecfive in the philoso-

phies and techniques of cotnplete-denture construcfionthat have been introduced to the dental profession overthe years.'- Maximum coverage of the denture-support-ing tissues is a principal factor that enhances dentureretention, stability, and support.'^-" Most of the tech-niques for denture fabricafion that have been introducedinvolve an impression procedure, starting with prelimi-nary impressions, that utilizes stock trays that cover asmuch of the edentulous areas as possible.

"Assistant Proiessor, Depanment of Removable Prosthodontics. Aris-totle University, Th es Saloniki. Greece.

""Lecturer, Department of Removable Prosthodoniics, Aristotle Univer-sity, Thessaloniki, Greece.

ReprinI requests: Dr A.M. Sofou. 118 Vas. Olgas Street, 546 45 Thessa-loniki, Greece. Fax: 3O-03l-S12-9Ü<).

However, in many patients, résorption of the al-veolar ridge is such that the genial tubercles projectinto the floor of the mouth and form the highest pointin the anterior region of the mandibular residualridge.^'"This situation presents difficulties in the selec-tion of an appropriate stock impression tray hecausethe lingual flange area in the anterior region cannot beseated properly hecause of the protruding genialtubercles. This creates problems in preliminary impres-sion tnaking.

The purpose of this article is to demonstrate a tech-nique in which a custom tray is fahricated to achievesuitable coverage of the edentulous area in pafients withextreme ridge resorpfiou and thus to obtain proper pre-liminary impressions.

Technique

The method involves the fabricafion and use of a cus-tomized stock tray. The material used is a perforatedmeial mesh (Dentaurum), available in sheets with athickness of 0.6 mm (Fig 1 ).

The square mesh is cut to create an outline of animpression tray. The area representing the lingual flangeis cut so that the excess metal is folded around the ante-rior (lingual frenum) area to créale the handle of thetray. The flange areas are created by folding the metaiso as to create an impression tray. The whole metalmesh now resembles an impression tray {Fig 2).

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Fig 1 Perforated me:ai mesh (Q 5 to 0.6 mmthick)

Fig 2 Mesh cut to fabricate a mandibularimpression tray.

Fig 3 Mesh outlined with TAK iHydroplastic material, softened inhot water and border moided in the mouth.

Fig 4 Impression made with heavy-body condensation siiiconimpression material with extended working time (set in 8 minutes).

Fig 5 Wash impression made with iight-body condensation siii-con impression material.

The patient's mouth is examined to determine theavailable space in both the relaxed and functionalpositions. The customized tray is cut according to theseobservations and is tried in the mouth, TAK Hydro-plastic material (TAK Systems}, softened in hot water,is used to border mold the tray in the tnouth and toextend the tray where necessary. Material is placed overthe handle for added support (Fig 3).

A condensation silieon putty material with an ex-tended working time (Sta-Seal F. Detax Dental) isloaded. The material is extended over the border of thetray. The tray is placed in the mouth with moderatepressure, and the tissue side is adapted to the minutedetail of the oral soft tissues. The borders of the im-pression should end in soft movable tissues to provide aperipheral seal for the final denture. The labial, buccal,and lingual vestibules should be completely filled. Theretromolar pad should be covered to allow the mandibu-lar denture to end on soft movable tissues throughoutthe entire border area.

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The impression material (which can be worked for upto 8 minutes from initial inixing) is horder molded, andthe patient is asked to move the tongue according tostandard impression procedures. The tray is removedfrom the mouth, and the impre.ssion is examined (Fig 4).

Light-body condensation silicon impression material(Silasoft, Detax Dental) is loaded in the impression andinserted in the mouth. The patient is instructed to repeatthe tongue movements, more vigorously, while thelight-body impression material is horder molded alongthe huccal and labial fiange areas. After the material hasset, the impression is removed from tbe mouth (Fig 5),and preliminary casts of the edentulous mandible arepoured. A custom individual Iray is fabricated, and afinal impression can be made according to the preferredtechnique of each individual clinician.

Clinical trial

The authors used the technique in seven patientswith severe mandibular atropby wbo presented forcomplete-denture treatment in the clinic of theDepartment of Removable Prosthodontics, AristotleUniversity, Thessaloniki, Greece. In all the patients, afterinitial examination and stock tray selection procedures,stock trays failed to adequately cover the hngual flangearea because the genial tubercle protmded as the highestpoint of the mouth and did not allow the tray to he prop-erly seated on the edentulous ridge-

The custom technique was utilized, and successfulmandihular preliminar}' impressions were made for allseven patients. The patients were ultimately treated withcomplete dentures with proper lingual extension andsatisfactory support, retention, and stability.

Discussion

The success of every complete denture relies on ihe ful-fillment of the three basic properties of retention, stabil-ity, and support."^

Mandibular dentures usually present more difficultiesin achieving tbese three properties, basically because ofthe larger number of anatomic limitations that requireadded attention.

Long-term edentulism and long-term use of ill-fitting dentures usually result in severe résorption of themandible. This severe résorption changes the morpho-logic appearance of the mandibular edentulous ridge insuch a dramatic way that stock impression trays cannotbe used to make preliminary impressions in a correctmanner. The most common observation in mouths withsevere résorption is the projection of the genial tuber-cles a.s the highest point in the anterior region of the

edentulous mandible.^'" An attempt to use a stock trayin .such a mouth will result in impingement of thelingual flange of the stock tray on the genial tuhercles,preventing the tray from being seated properly. Theresulting impressions are usually short in the huccal,labial, and posterior lingual areas, creating difficultiesin the final impression procedures hecause the in-dividual custom trays will not adequately cover thedenture-.supporting areas.

The proposed method of creating a custom stock traywith low-cost materials that are readily available in adental office solves these problems. The metal mesh iseasily manipulated to provide the basic frame outhne ofan impression tray, and the TAK Hydroplastic material,heing themioplastic, provides the means for further cus-tomizing of the impression tray. The condensation siU-con putty allows for further extension to areas possihlyunsupported by the impression tray. The extended work-ing time of the suggested material is an additionaladvantage, ensuring that the clinician will have plentyof time to go over all the areas of the lingual, buccal,and labial flanges.

Finally, the light-body silicon material will captureall the minute details of the denture-supporting areas,resulting in a perfect preliminary impre.ssion. The ca.stsohtained from such an impression will enable the dentaltechnician to fabricate an accurate custom individualtray, allowing tbe clinician to acbieve an accurate finalimpression without difficulty.

Conclusion

Customized trays for making preliminary impressionscan be used in patients with severe résorption of edentu-lous mandibular tissues where available stock impres-sion trays cannot be used because they impinge on tis-sues such as the genial tubercles. It can also be used inother situations, such as in patients with limited mouthopening and in postsurgical patients with serious tissuedeficiencies.

The results are very satisfactory. Prehminary impres-sions obtained with such a tray were very close to afmal impression, although because of the use of theheavy-hody putty silicon material, it is possible to endup with a slightly overextended impression-References

1. Azaria H. Elements of Removable Prosthodoniics. CompleteDentures. Thessaloniki, Greece: Aristotle University ofThessaloniki, l972;52-62,l46-l64,271-288, 292-306.

2. Azzam MKA, Yurk.ilas AA, Kronman J. The subUnguai cre.îceniextension atid its relation to the stability and retention of mandi-bular complete dctitures. J Prosthet Dent 1992;ñ7:205-2l Ü.

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3. Bocage M, Lehrhoupt J. Lingual flange design in complete den-tures, J Prostliet Dent l977;37:499-50ñ.

4. Jacobaon TE, Krol AJ. A contemporary review of the factor.^involved in cúmplete denture retention stability and support. Pait1. Retention. J Prosthet Dent I983;49:5-15,

5. Jacobson TE, Krol AJ, A contemporary review of tlin factor-iinvolved in complete detittires. Part II, Stability. J Prosthet Dei«1983;49:165-172.

6. Jacobson TE, Krol AJ, A contemporary review of the factorsinvolved in complete denlures. Part HI. Support. J Prosthet Dent1983:49:306-313.

7. Klein IE. Goldstein BM. Physiologic determinants of primaryimpressions for complete dentures, J Proslhet Dent I9g4;5.i:611-616.

8. Lott F, Levin B. Flange technique: An anatomic and physiologicapproach to increased retention, function, comfort and appear-ance of dentures. J Prosthet Dent 1966:16:394-413.

9. Shanahan TE. Stabilizing lower denture on unfavorable ridges.J Prosthet Dent 1962; 12:420-424.

10. Pissiotis AL. The Mandibular Denture Border. An AnatomicalStudy of the Mylohyoid Muscle and Its Effects on the LingualFlange of Ihe Mandibular Denture [lhesn|. Boston: Tufts Univer-sity, 1983:21-22.

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