Mushroom-ShapedResilient Retainer forMaxillary Obturator

Prostheses

Shogo Minägi, DDS, PbO'

Itsuaki Nagäre, DDS"

Masamichi Salo, DDS"

Takashi Sato, DDS, PhD'"

Department of Removable ProsfhodonticsOkayama University Denfai SchoolOkayaina City, ¡apan

A new type of highly re5ilient retainer for maxillary obturatorprosthesei is described. The obturator component iscomposed of an acrylic resin connector and a roundresilient wing, with the combined shape resembling amushroom. The retainer is designed to absorb mechanicalstresses, which are transmitted from the denture portion tonasal soft tissues through the obturator extension, and touse tissue undercuts more effectively than do conventionalhollow extension prostheses. Renewability of the retainerpart is another advantage of this retainer. From theseproperties, the retainer seems to have many indications forthe prosthodontic treatment of maxillary defects, intjProsthodont 1991,-4:473-476,

A n ideal prosthesis tor treating patients afterthey have undergone a partial maxillectomy

has long been sought by many dentists. Since Nidif-fer and Shipmon' reported on hollow, light-weightobturators, several modifications have beenmade.^ Chalian and Barnett^ described a one-piecehollow obturator, and Obyama et ah modified theobturator using a resilient layer of siiicone. Asstated by Habn,= hard acrylic resin created prob-lems with tbe nasal tissues tbrougb irritation of thefragile mucosa lining the turbinâtes and sinuses,Poly(vinyl siloxane) or other sucb resilient materialsrecently have been used for tbe obturator pros-thesis.^ However, it appears tbat additional modi-fication or improvement in structure or materialsis still needed to prevent tissue irritation, provideadditional retention, reduce the weigbt, andimprove the cleanliness of tbe obturator prosthesis.

This paper presents a new type of highly resilientretainer for a maxillary obturator prosthesis and dis-

'Assistant Professor."Research Associate.

"'Professor and Chairman.

Correspondence to: Dr Shogo Minagi, Department of Kemov-ahle Prosthodontics, Okayama University Dentai Schooi, 2-5-I, Shikata-cho, Okayama City 700, Japan.

cusses the indications and characteristics of thisretainer compared to conventional hollow exten-sion prostheses.

Procedure

A schematic diagram of the new obturator pros-thesis retainer is shown in Fig 1. The resilient

Fig 1 Schematic cross-section of a completed maxillaryprosthesis with mushroom-shaped resilient retaining obtur-ator. Note the part overhanging [a] the tisstje edge of theresected maxilia, which is designed not to irritate the tissueedge, s, connector; d. denture prosthesis; r. resilient portion.

4, Number 5, 1991 473 The International Journal of Proillioriontii

Mii5hroom-Sliapeil Resilient Relaine Minagi e l .

Figs 2a to 2c Obturator prosthesis using the mushroom-shaped resiiient retainer. Top: Frontal view of the prosthesis.Center: Posterior view of the prosthesis. Bottom: Patient'smaxillary detect.

retainer is attacbed to tbe denture prosthesis withtbe connector at the center of the retainer. Figures2a to 2c show the resilient retainer obturator pros-thesis made for a patient who had undergone amaxillectomy. To construct the obturator pros-thesis, the resilient retainer with the connector isprocessed first, then the retainer is connected tothe denture prosthesis intraorally using autopolym-erizing acrylic resin.

Fabrication procedures are as follows:1. Make a final impression using an individual

tray and irreversible hydrocolloid impressionmaterial.

2. Block out the relief areas on the working castwith wax (Fig 3a], The edge of the resectedmaxilla should be elongated with wax as apreparation for making the extension of theresilient portion. Make an impression of thecast to produce the modified cast (Fig 3b) forprocessing the mushroom-shaped retainer.

3. Using paraffin wax, wax the pattern of theretainer on the modified cast. Although theproper thickness of the wax depends on thetype of resilient material used, it is approxi-mately 3 mm when the soft material subse-quently described is used. After waxing,reduce tbe border of the modified cast (Fig3b¡ to make an entrance hole for packing theresilient material, then embed one end of thepreprocessed acrylic resin connector. Theconnector is approximately 5 mm in diameterand the embedded end is widened to be con-nected with the resilient portion. If necessary,a metal rod can be contained in the resin con-nector, as shown in Fig 4.

4. Flask the wax pattern of the retainer on thecast with the acrylic resin connector (Fig 4).

5. After wax elimination, pack and process theresilient material for the mushroom-shapedretainer. A soft resin of polyfluoroethylenecopolymers for denture base lining (KurepeetDough, Kureha Co, Tokyo, japan) is usuallyused as the resilient material in the authors'laboratory. The processed retainer is shown inFig 5.

6. Fabricate the denture prosthesis separatelyusing conventional metbods.

7. Place a bole in the palatal portion of tbe den-ture prosthesis tbrough which the connectorof the retainer can be passed. Insert theretainer into the maxillary defect (Fig 6a) andplace the denture in the mouth over theretainer (Fig 6b). Attach the connector of theretainer directly to the denture prosthesisintraorally using autopolymerizing acrylicresin. Remove the excess portion of the con-nector and finish the prosthesis.

Discussion

Resilient materials such as soft silicone havebeen used in the fabricat ion of obturatorprostheses to gain adequate retention whiie notmechanically irritating nasal soft tissues."^ Althougb

The Internaficnal lournal of Prosthodontii 474 Volume 4, Number 5, 1991

Minagi et ai Mushroom Shaped Resriient Rétame

Figs 3a and 3b Sctiematic cross-section ot the working cast (leñ) and Ihe modified cast for wax up of the mushroom-shapedretainer (rigbt), a, area that should be biocked out with paraffin wax before making the impression for the modified cast; b,elongation of the edge of the resected maxillae with wax, in preparation for making the overhang of the resilient portion; c,portion that would be removed before fiasking to provide an entrance hoie for pacKmg Ihe resiiient materiai.

Fig 4 Schematic diagram of the flasked wax pattern anfl themodified cast, s, preprocessed acrylic resin retainer; c, mod-ified cast; w. wax pattern; m, metai rod.

Fig 5 Finished mushroom-shaped acrylic resin retainer.

Fig 6 Mushroom-shaped retainer placed in the maxiilary defect (ieft) and denture prosthesis placed in the mouth over theretainer (rigfit). Note that ttie support of the retainer exits from the hole in the denture and is ready to be attached usingautopolymeriiing acryiic resin in the mouth.

Volumes, Numbers. 1991 nternational lournai of Prosthoclonticî

M ushroorr-Shaped Resilient Reta i ne Minagi eE ai

the soft obturator reported by Hahn^ seems to haveovercome many of the disadvantages of the con-ventional hollow obturator, it still appears to bedifficult for the obturator to absorb functionalmechanical stresses transmitted from the dentureportion to nasal soft tissues through the obturatorextension. It is, therefore, still necessary to have aneffective stress absorber in the obturator pros-thesis, especially in situations where the ability ofthe nasal soft tissues to bear the mechanicalstresses is poor. The mushroom-shaped retainerpresented here is designed not only to gain ade-quate retention and stability, but also to play a roleas an effective absorber of mechanical stresses. Themushroom design enables the quantity and exten-sion of the resilient material between the connec-tor and the tissue undercuts to be suitable forabsorbing the mechanical stresses.

Morphologic change of the maxillary defect isanother important problem for prognosis of theobturator prosthesis, especially when the pros-thesis is made shortly after surgery. However,unlike the conventional hollow extension obtura-tors, the mushroom-shaped retainer can bereplaced with a new one and the denture portioncan continue to be used. When a new retainer isneeded, only an impression of the defect isneeded. The new retainer can be attached to thedenture using autopolymerizing resin. From theseproperties, the mushroom-shaped resilient retainerseems to have many indications for the treatmentof a maxillary defect.

The mushroom-shaped resilient retainer hasbeen used by the authors for 1 year, and theretainer was applied for all nine patients who pre-sented to the authors' department with a maxillarydefect. All of these patients have adapted well totheir prostheses. One retainer is to be replacedbecause of a morphologic change of the maxillary

defect. The soff material has retained its resilienceand no degradation of the material has been clin-ically observed. Also, although it is only an empir-ical observation without corroborating data,microbiologie colonies are rarely observed on thesoff material of polyfluoroethylene copolymers,unlike the conventional silicon soff materials.

Summary

A new type of highly resilient retainer for max-illary obturator prostheses has been described. Thismushroom-shaped retainer is designed to absorbmechanical stresses transmitted from the dentureportion to the nasal soft tissues through the obtur-ator extension and to be able to engage tissueundercuts more effectively than the conventionalhollow extension. The retainer presented here canbe applied to many types of maxillary defects andappears to be especially effective for those situa-tions in which the ability of the nasal soft tissuesto bear mechanical stresses is poor.

References

1. Nidifier T|, Shipmon TH: The holiow buib obturator foracquired palatal openings. J Prosi/ie/DenM9S7;7:1 26-134.

2. Mahdy AS: Processing a hollow obturator. / Prosthet Dent1969:22:682-686.

3. Chalian VA, Barnett MO: A new technique for constructinga one-piece hollow obturator after partial maxillectomy. jProsthet Dent 1972:28:449-453.

4. Ohyama T, Gold HO, Pruzansky S: Maxillary obturatorwithsil icone-lined hollow extension. / Prosthet Deni1975;34:336-341.

5. Hahn GW: A comfortable silicone bulb obturator with orwithout dentures./ Prosthet Dent 1972,28:448-453.

6. Gardner LK, ParrGR, Rahn AO: Combination nasal supportbreathing flange with hoilow obturator prostheses. A clin-ical report ; Prosthet Dent 1990,63:497-501.

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