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A custom impression tray made with the aid of an existing prosthesis: A clinical technique
A custom impression tray made with the aid of an existing prosthesis: A clinical technique Joseph R. Cain, DDS, MSa College of Dentistry, University of Oklahoma, Oklahoma City, Okla. Prostheses for patients with intraoral defects usually have complex contours. The replacement of a successful prosthesis is more readily accomplished with the aid of a custom impression tray that reproduces the contours of the existing prosthesis. In the technique presented, an irreversible hydrocolloid impression is made of the intaglio surface of the prosthesis to be replaced. Autopolymerizing acrylic resin tray material is poured into the impression, creating a custom impression tray. This procedure can simplify the impression process and reduce the need for multistep impression techniques. (J Prosthet Dent 2001;86:382-5.)
A
n intraoral prosthesis requires replacement when the effects of oral tissue change or the teeth or denture base becomes worn or damaged, resulting in a prosthesis that no longer meets the patient’s needs. Prostheses for patients with congenital, acquired, or traumatic intraoral defects usually have complex contours (Fig. 1). The fabrication of these prostheses often requires the use of complex impression techniques to capture the relevant anatomic contours. Preliminary impressions made with stock impression trays may fail to capture the detail necessary for fabrication of an adequate custom impression tray. The use of a custom impression tray that duplicates the tissue surface of an existing prosthesis can facilitate the impression-making process. The use of an existing conventional dental prosthesis to aid in the fabrication of a custom impression tray has been well documented. One technique involves using the existing prosthesis to fabricate a plaster cast of the intaglio surface.1-3 A custom impression tray can be constructed on this cast. A second technique involves fabricating a custom impression tray directly on an irreversible hydrocolloid impression made of the entire prosthesis. This technique reproduces both the intaglio and polished surfaces of the prosthesis.4-6 A variation of the second technique involves fabricating a custom impression tray directly on an irreversible hydrocolloid impression of only the intaglio surface of the prosthesis.7-9 The accuracy of a master cast is dependent on the use of a dimensionally stable impression tray. The volumetric shrinkage of autopolymerizing acrylic resin is 6% with a polymer/monomer ratio of 3:1 by volume.10 Decreasing the polymer/monomer ratio
Presented as a poster at the joint meeting of the American Academy of Maxillofacial Prosthetics and the International Congress of Maxillofacial Prosthetics, Kauai, Hawaii, November 11, 2000. aProfessor and Director of Maxillofacial Prosthetics. 382 THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 1. Cleft lip/cleft palate overdenture prosthesis with speech bulb to be remade.
to make the acrylic resin tray material more pourable increases the volumetric shrinkage. A custom impression tray used immediately after fabrication may produce an inaccurate impression because of distortion. Pagniano et al11 recommended waiting 9 hours or boiling the tray for 5 minutes before use. Fehling et al12 demonstrated that, whereas an aged tray was preferable, significant linear changes were observed for only 40 minutes from the initiation of tray fabrication. This article presents a procedure for the fabrication of a custom impression tray made with the aid of an existing complex prosthesis. VOLUME 86 NUMBER 4
CAIN
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 3. Autopolymerizing acrylic resin being poured into irreversible hydrocolloid impression of intaglio surface of prosthesis.
Fig. 2. Intaglio surface of overdenture prosthesis duplicated in irreversible hydrocolloid.
TECHNIQUE 1. Place the prosthesis to be reproduced on a sheet of plastic. Form a boxing medium such as paper tape or boxing wax around the prosthesis, leaving a 10-mm space. A plastic denture cup reduced to a height of 30 mm can serve as a boxing form for smaller prostheses. 2. Prepare sufficient irreversible hydrocolloid impression material (Jeltrate Plus, Dentsply Caulk, Milford, Del.) to fill the container three fourths full. 3. Place impression material on the intaglio surface of the prosthesis to be reproduced. Place the prosthesis into the impression material, and depress the prosthesis until the borders are submerged (Fig. 2). 4. Remove the prosthesis from the impression material when set. Sticky wax (Kerr Corp, Romulus, Mich.) can be used to fill any voids that may be present in the impression. 5. Pour autopolymerizing acrylic resin tray material (Fastray, Henry J. Bosworth, Skokie, Ill.), which has a low viscosity upon immediate mixing, into the irreversible hydrocolloid impression. Be careful not to trap air bubbles in the deeper recesses, such as the prosthesis borders (Fig. 3). 6. Upon polymerization, remove the impression tray from the impression material, and trim the tray to remove excess acrylic resin. Relieve excessive OCTOBER 2001
Fig. 4. Impression tray trimmed to remove excess acrylic resin after polymerization.
undercuts in the impression tray to facilitate fabrication of the impression (Fig. 4). 7. Separation of the impression tray from the new master cast will likely require sectioning the tray in the defect area. Precut grooves into the thick sections of the impression tray to expedite this process (Fig. 5). 8. Modify the impression tray to capture the complex anatomic contours with modeling plastic 383
THE JOURNAL OF PROSTHETIC DENTISTRY
CAIN
Fig. 5. Precut grooves in thick sections of impression tray expedite separation from master cast.
Fig. 7. Final impression.
Fig. 6. Impression tray modified with material of choice to capture complex anatomic contours.
impression compound (Iso Functional, GC Corp, Tokyo, Japan) (Fig. 6). Make the final impression with the material of choice (Aquasil LV, Dentsply Caulk) (Fig. 7). 9. Box and pour the master impression in the usual fashion. Separation of the impression from the master cast may require sectioning of the impression tray to avoid damage to the master cast (Fig. 8).
DISCUSSION Intraoral dental prostheses for patients with congenital, acquired, or traumatic intraoral defects usually have complex contours. For patients with palatal defects, preliminary impressions made with stock impression trays often fail to capture the detail necessary for fabrication of an adequate custom impression tray. Inadequate trays 384
Fig. 8. Master impression boxed and poured in usual manner. Separation of impression from master cast may require sectioning of impression tray to avoid damage to master cast.
may require impression techniques that involve a substantial amount of thermoplastic modeling plastic impression compound. Moreover, impressions made VOLUME 86 NUMBER 4
CAIN
with poor-quality or underextended impression trays often require an altered cast impression to capture the correct relation of mobile and nonmobile tissues. A custom impression tray that duplicates the tissue surface of an existing complex prosthesis can facilitate the impression-making process. The primary advantage of such a tray is that it simplifies the impression technique, resulting in a more accurate cast for the fabrication of the prosthesis. Several methods for duplicating the intaglio surface of an existing complete denture have been described. In the literature, these techniques have been applied to conventional complete dentures, but not to more complex maxillofacial prostheses. The advantages of duplicating a complex prosthesis in irreversible hydrocolloid include the ability to (1) retrieve the prosthesis from the impression without damage and (2) record prosthesis extension and borders that extend into soft tissue undercuts. Traditional impression techniques capture areas of undercut with thermoplastic modeling plastic impression compound and impression material. One advantage of these techniques is that separation of the impression from the master cast is accomplished with the addition of heat, which softens the modeling plastic impression compound. However, adequate impression extension into a maxillofacial defect can involve large quantities of modeling plastic impression compound, which can be difficult to form and support when soft. One disadvantage of an impression tray with little modeling plastic impression compound (and thus with rigid undercut borders) is that the tray must be sectioned before it can be separated from the master cast. This is a minor inconvenience to capture undercuts vital for retention of a complex maxillofacial prosthesis.
THE JOURNAL OF PROSTHETIC DENTISTRY
REFERENCES 1. LaVere AM, Freda AL. An individualized impression tray utilizing the patient’s existing denture. J Prosthet Dent 1976;36:334-6. 2. McArthur DR. Individualized impression trays from existing complete dentures. J Prosthet Dent 1980;44:577-81. 3. Vig RG. Taking advantage of existing dentures. J Prosthet Dent 1971;26:247-50. 4. Wagner AG. Making duplicate dentures for use as final impression trays. J Prosthet Dent 1970;24:111-3. 5. Wilson LG, Anderson GA. A denture tray technique for remake dentures. J Prosthet Dent 1975;34:81-5. 6. Singer IL. The “zipper” technique for duplicating dentures: final impressions, replica dentures, and a complete denture splint. J Prosthet Dent 1975;33:582-90. 7. Render PJ. Fabrication of custom trays from existing dentures. J Prosthet Dent 1980;43:693-4. 8. Kirk GA, Holt JE. Final impression trays from existing dentures. J Prosthet Dent 1985;53:443. 9. Graser SD. Custom denture impression trays from existing dentures. Gen Dent 1991;39:204. 10. Anusavice KJ. Phillips’ science of dental materials. 10th ed. Philadelphia: WB Saunders Co; 1996. p. 242. 11. Pagniano RP, Scheid RC, Clowson RL, Dagefoerde RO, Zardiackas LD. Linear dimensional change of acrylic resins used in the fabrication of custom trays. J Prosthet Dent 1982;47:279-83. 12. Fehling AW, Hesby RA, Pelleu GB Jr. Dimensional stability of autopolymerizing acrylic resin impression trays. J Prosthet Dent 1986;55:592-7. Reprint requests to: DR JOSEPH R. CAIN COLLEGE OF DENTISTRY UNIVERSITY OF OKLAHOMA PO BOX 26901 OKLAHOMA CITY, OK 73190 FAX: (405)271-4181 E-MAIL: [email protected] Copyright @2001 by The Editorial Council of The Journal of Prosthetic Dentistry. 0022-3913/2001/$35.00 + 0. 10/1/118873
SUMMARY The fabrication of a custom impression tray from an existing prosthesis has been described. This technique is particularly valuable for complex maxillofacial prostheses.
OCTOBER 2001
doi:10.1067/mpr.2001.118873
385
A
n intraoral prosthesis requires replacement when the effects of oral tissue change or the teeth or denture base becomes worn or damaged, resulting in a prosthesis that no longer meets the patient’s needs. Prostheses for patients with congenital, acquired, or traumatic intraoral defects usually have complex contours (Fig. 1). The fabrication of these prostheses often requires the use of complex impression techniques to capture the relevant anatomic contours. Preliminary impressions made with stock impression trays may fail to capture the detail necessary for fabrication of an adequate custom impression tray. The use of a custom impression tray that duplicates the tissue surface of an existing prosthesis can facilitate the impression-making process. The use of an existing conventional dental prosthesis to aid in the fabrication of a custom impression tray has been well documented. One technique involves using the existing prosthesis to fabricate a plaster cast of the intaglio surface.1-3 A custom impression tray can be constructed on this cast. A second technique involves fabricating a custom impression tray directly on an irreversible hydrocolloid impression made of the entire prosthesis. This technique reproduces both the intaglio and polished surfaces of the prosthesis.4-6 A variation of the second technique involves fabricating a custom impression tray directly on an irreversible hydrocolloid impression of only the intaglio surface of the prosthesis.7-9 The accuracy of a master cast is dependent on the use of a dimensionally stable impression tray. The volumetric shrinkage of autopolymerizing acrylic resin is 6% with a polymer/monomer ratio of 3:1 by volume.10 Decreasing the polymer/monomer ratio
Presented as a poster at the joint meeting of the American Academy of Maxillofacial Prosthetics and the International Congress of Maxillofacial Prosthetics, Kauai, Hawaii, November 11, 2000. aProfessor and Director of Maxillofacial Prosthetics. 382 THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 1. Cleft lip/cleft palate overdenture prosthesis with speech bulb to be remade.
to make the acrylic resin tray material more pourable increases the volumetric shrinkage. A custom impression tray used immediately after fabrication may produce an inaccurate impression because of distortion. Pagniano et al11 recommended waiting 9 hours or boiling the tray for 5 minutes before use. Fehling et al12 demonstrated that, whereas an aged tray was preferable, significant linear changes were observed for only 40 minutes from the initiation of tray fabrication. This article presents a procedure for the fabrication of a custom impression tray made with the aid of an existing complex prosthesis. VOLUME 86 NUMBER 4
CAIN
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 3. Autopolymerizing acrylic resin being poured into irreversible hydrocolloid impression of intaglio surface of prosthesis.
Fig. 2. Intaglio surface of overdenture prosthesis duplicated in irreversible hydrocolloid.
TECHNIQUE 1. Place the prosthesis to be reproduced on a sheet of plastic. Form a boxing medium such as paper tape or boxing wax around the prosthesis, leaving a 10-mm space. A plastic denture cup reduced to a height of 30 mm can serve as a boxing form for smaller prostheses. 2. Prepare sufficient irreversible hydrocolloid impression material (Jeltrate Plus, Dentsply Caulk, Milford, Del.) to fill the container three fourths full. 3. Place impression material on the intaglio surface of the prosthesis to be reproduced. Place the prosthesis into the impression material, and depress the prosthesis until the borders are submerged (Fig. 2). 4. Remove the prosthesis from the impression material when set. Sticky wax (Kerr Corp, Romulus, Mich.) can be used to fill any voids that may be present in the impression. 5. Pour autopolymerizing acrylic resin tray material (Fastray, Henry J. Bosworth, Skokie, Ill.), which has a low viscosity upon immediate mixing, into the irreversible hydrocolloid impression. Be careful not to trap air bubbles in the deeper recesses, such as the prosthesis borders (Fig. 3). 6. Upon polymerization, remove the impression tray from the impression material, and trim the tray to remove excess acrylic resin. Relieve excessive OCTOBER 2001
Fig. 4. Impression tray trimmed to remove excess acrylic resin after polymerization.
undercuts in the impression tray to facilitate fabrication of the impression (Fig. 4). 7. Separation of the impression tray from the new master cast will likely require sectioning the tray in the defect area. Precut grooves into the thick sections of the impression tray to expedite this process (Fig. 5). 8. Modify the impression tray to capture the complex anatomic contours with modeling plastic 383
THE JOURNAL OF PROSTHETIC DENTISTRY
CAIN
Fig. 5. Precut grooves in thick sections of impression tray expedite separation from master cast.
Fig. 7. Final impression.
Fig. 6. Impression tray modified with material of choice to capture complex anatomic contours.
impression compound (Iso Functional, GC Corp, Tokyo, Japan) (Fig. 6). Make the final impression with the material of choice (Aquasil LV, Dentsply Caulk) (Fig. 7). 9. Box and pour the master impression in the usual fashion. Separation of the impression from the master cast may require sectioning of the impression tray to avoid damage to the master cast (Fig. 8).
DISCUSSION Intraoral dental prostheses for patients with congenital, acquired, or traumatic intraoral defects usually have complex contours. For patients with palatal defects, preliminary impressions made with stock impression trays often fail to capture the detail necessary for fabrication of an adequate custom impression tray. Inadequate trays 384
Fig. 8. Master impression boxed and poured in usual manner. Separation of impression from master cast may require sectioning of impression tray to avoid damage to master cast.
may require impression techniques that involve a substantial amount of thermoplastic modeling plastic impression compound. Moreover, impressions made VOLUME 86 NUMBER 4
CAIN
with poor-quality or underextended impression trays often require an altered cast impression to capture the correct relation of mobile and nonmobile tissues. A custom impression tray that duplicates the tissue surface of an existing complex prosthesis can facilitate the impression-making process. The primary advantage of such a tray is that it simplifies the impression technique, resulting in a more accurate cast for the fabrication of the prosthesis. Several methods for duplicating the intaglio surface of an existing complete denture have been described. In the literature, these techniques have been applied to conventional complete dentures, but not to more complex maxillofacial prostheses. The advantages of duplicating a complex prosthesis in irreversible hydrocolloid include the ability to (1) retrieve the prosthesis from the impression without damage and (2) record prosthesis extension and borders that extend into soft tissue undercuts. Traditional impression techniques capture areas of undercut with thermoplastic modeling plastic impression compound and impression material. One advantage of these techniques is that separation of the impression from the master cast is accomplished with the addition of heat, which softens the modeling plastic impression compound. However, adequate impression extension into a maxillofacial defect can involve large quantities of modeling plastic impression compound, which can be difficult to form and support when soft. One disadvantage of an impression tray with little modeling plastic impression compound (and thus with rigid undercut borders) is that the tray must be sectioned before it can be separated from the master cast. This is a minor inconvenience to capture undercuts vital for retention of a complex maxillofacial prosthesis.
THE JOURNAL OF PROSTHETIC DENTISTRY
REFERENCES 1. LaVere AM, Freda AL. An individualized impression tray utilizing the patient’s existing denture. J Prosthet Dent 1976;36:334-6. 2. McArthur DR. Individualized impression trays from existing complete dentures. J Prosthet Dent 1980;44:577-81. 3. Vig RG. Taking advantage of existing dentures. J Prosthet Dent 1971;26:247-50. 4. Wagner AG. Making duplicate dentures for use as final impression trays. J Prosthet Dent 1970;24:111-3. 5. Wilson LG, Anderson GA. A denture tray technique for remake dentures. J Prosthet Dent 1975;34:81-5. 6. Singer IL. The “zipper” technique for duplicating dentures: final impressions, replica dentures, and a complete denture splint. J Prosthet Dent 1975;33:582-90. 7. Render PJ. Fabrication of custom trays from existing dentures. J Prosthet Dent 1980;43:693-4. 8. Kirk GA, Holt JE. Final impression trays from existing dentures. J Prosthet Dent 1985;53:443. 9. Graser SD. Custom denture impression trays from existing dentures. Gen Dent 1991;39:204. 10. Anusavice KJ. Phillips’ science of dental materials. 10th ed. Philadelphia: WB Saunders Co; 1996. p. 242. 11. Pagniano RP, Scheid RC, Clowson RL, Dagefoerde RO, Zardiackas LD. Linear dimensional change of acrylic resins used in the fabrication of custom trays. J Prosthet Dent 1982;47:279-83. 12. Fehling AW, Hesby RA, Pelleu GB Jr. Dimensional stability of autopolymerizing acrylic resin impression trays. J Prosthet Dent 1986;55:592-7. Reprint requests to: DR JOSEPH R. CAIN COLLEGE OF DENTISTRY UNIVERSITY OF OKLAHOMA PO BOX 26901 OKLAHOMA CITY, OK 73190 FAX: (405)271-4181 E-MAIL: [email protected] Copyright @2001 by The Editorial Council of The Journal of Prosthetic Dentistry. 0022-3913/2001/$35.00 + 0. 10/1/118873
SUMMARY The fabrication of a custom impression tray from an existing prosthesis has been described. This technique is particularly valuable for complex maxillofacial prostheses.
OCTOBER 2001
doi:10.1067/mpr.2001.118873
385