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An injection impression technique for palatal defects
MAXILLOFACIAL PROSTHETICS TEMPOROMANDIBULAR JOINT 9 DENTAL IMPLANTS SECTION EDITORS
L KENNETH ADISMAN
RONALD P. DESJARDINS
An injection impression technique for palatal defects I. C. Benington, B.D.S., F.D.S., R.C.S.,* and T. Clifford, B.D.S., F.D.S., R.C.P.S.** Royal Victoria Hospital, School of Dentistry, Belfast, N o r t h e r n Ireland
I t is difficult to secure satisfactory retention of prostheses for edentulous patients with congenital or acquired defects of the palate (Fig. 1). One method
Presented before the British Society for the Study of Prosthetic Dentistry, Birmingham University, Birmingham, England. *Head, Prosthetics Department. **Senior Registrar, Prosthetics Department.
of overcoming this problem is to provide mechanical retention by engaging undercuts around the borders of the defect with an extension of the denture base. To provide satisfactory retention, the undercuts should be engaged by flexible extensions of the denture base or movable rigid extensions operated by a simple lever system. Flexible extensions, such as latex obturators with a replaceable stud attachment described by Watt,' and a material described by Walter'-' have been used effectively. The use of Molloplast ( K ~ t n e r & Co., Oberursel, Germany) to form flexible extensions to retain obturators has been described by Benington et al? CLINICAL PROBLEM
Fig. 1. Surgical defect of palate.
With the advent of rubber base impression materials, the recording of undercut areas has become simpler since rubber base impression materials have excellent qualities of elasticity and strength, whereas other materials such as irreversible hydrocolloid (alginate) tear when withdrawn from deep undercuts, making reproduction difficult. It may be difficult to direct the flow of the rubber base impression material above the palatal shelves. The injection
Fig. 2. Gutta percha obturator for surgical defect of palate.
414
APRIL 1982
VOLUME 47
NUMBER 4
0022-3913/82/040414 + 05500.50/0@ 1982 The G. V, Mosby Co.
INJECTION IMPRESSION TECHNIQUE
Fig. 3. Individual impression tray with palatal aperture to accommodate syringe nozzle.
impression technique was developed to secure accurate reproduction of undercut areas. Patients with acquired defects of the palate are usually rehabilitated with an immediate surgical obturator prosthesis (Fig. 2). The prosthesis is worn until sufficient healing has taken place to allow impressions to be made without undue discomfort to the patient. The definitive obturator prosthesis which is constructed with a conventional impression technique may be inclined to drop in the anterior region during function. This may occur because the prosthesis is retained posteriorly only by engagement of the undercut created by the remnant of the soft palate with a flexible extension of resilient material. No anterior retention has been achieved to oppose the posterior undercut due to an inadequate impression of the anterior region. Therefore, the obturator prosthesis lacks retention and the patient is unable to wear it satisfactorily. To overcome this problem, the impression material has to be delivered above the anterior palatal shelf on either side of the anterior residual nasal septum. Since rubber base impression material will not remain in position if placed in the nasal cavity prior to the impression tray being positioned, the impression tray should first be seated firmly in position, and additional rubber base materials should then be
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 4. Channels formed using articulator retainer pins.
injected using a syringe through preformed channels in the impression tray for delivery to the appropriate region. IMPRESSION TECHNIQUE A preliminary impression is made of the normal denture-bearing area and the defect. The palatal defect is blocked out with plasticine on the preliminary cast, and a custom impression tray is constructed of acrylic resin using one thickness of wax spacer. The tray is not extended into the defect because later in the impression procedure impression material will be injected through a hole in the palate of the tray to record undercuts in the defect. At the secondary impression stage, the impression tray is used to record an impression of the defect using modeling compound. The material should be
415
BENINGTONAND CLIFFORD
Fig. 5. Prepared impression tray with adhesive and syringe.
Fig. 6. R u b b e r b a s e impression material being injected through hole in impression tray.
placed in the nasal cavity at the height of the palatal shelves around the periphery of the defect. If the impression tray is lowered anteriorly first on removal, the anterior nasal undercut will be obliterated by deformation of the impression material, but the
416
Fig. 7. A, Impression made by conventional technique. B, Impression made by syringe technique. posterior undercut above the remnant of the soft palate will be well recorded, since that part of the impression is undistorted as the impression tray is removed in a downward and forward direction. The composition extension must be reduced around its diameter to allow space for the final rubber base impression material to flow freely. The location of the difficult area to record is assessed, and the impression tray and composition are modified as follows: 1. Gut an opening in the vault of the palate large enough to allow the nozzle of a 20 ml syringe to fit accurately (Fig. 3). This may be facilitated by orienting the aperture down and forward so that the syringe nozzle engages it readily at a convenient angle when the impression tray is in place in the mouth. 2. Using a hot retainer pin from an articulator as a skewer, extend the hole in the tray into a channel of a similar diameter as the hole so that it opens out at the anterosuperior limit of the modeling compound (Fig. 4). Form a similar channel on the other side so that the superior opening is adjacent to the anterior nasal shelves and on either side of the anterior remnant of the nasal septum. Clear the channels of
APRIL 1982
VOLUME 47
NUMBER 4
INJECTION IMPRESSION TECHNIQUE
Fig. 8. A, Stone cast with anterior undercut. B, Stone cast without anterior undercut.
debris prior to recording the impression. Apply adhesive to the tray in the normal manner, taking care not to obstruct the channels (Fig. 5). 3. Prepare mixes of regular and light-bodied rubber base impression material (Permalastic, Kerr Mfg. Co., Romulus, Mich.), spatulating the regular material slightly in advance of the light-bodied material. Apply the regular material to the impression tray and over the composition so that it does not coverthe superior exits of the channels. 4. Place the impression tray upward and posterior to engage the posterior palatal shelf. Seat normally. Place approximately 10 cc of light-bodied rubber base impression material in the 20 ml syringe, injecting it carefully through the hole in the impression tray as soon as the tray is in position, so that the two mixes of rubber base impression material may fuse and harden (Fig. 6). 5. Allow the impression tray to remain in position for approximately 8 minutes, and then remove it carefully from the mouth. If too great a quantity of light-bodied material has been injected the tray may be difficult to remove; however, with experience the correct amount, approximately 10 cc, may be used to record the appropriate undercut region and the impression tray m a y be removed without any difficulty. An impression made without injecting material with a syringe is compared to one made with the injection technique in Fig. 7. 6. Record varying dimensions of the defect undercut by altering the quantity of light-bodied rubber base impression material injected. A comparison of
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 9. Anterior and posterior Molloplast extensions on obturator prosthesis.
the master casts indicates that no anterior retention was available in the original cast and that the new cast has ample undercut for retention (Fig. 8). 7. Pour the casts in artificial stone, a n d duplicate if possible in case of accidents or failures with the flexible base. Block out the roof of the nasal cavity on the cast with plaster of Paris so that the superior surface of the obturator prosthesis does not impinge on sensitive nasal mucosa and to permit an adequate airway for nasal breathing. SUMMARY A master cast suitable for fabricating a retentive flexible base using any of the materials and tech-
417
BENINGTON AND CLIFFORD
niques previously mentioned is provided. The flexible extension fits snugly into the defect laterally and extends above the remnants of the soft palate posteriorly and into the nasal floor anteriorly on either side of the remnants of the nasal septum (Fig. 9). The use of a thin flexible extension such as Molloplast will provide a good chemical bond to the acrylic resin of the denture base, allows for easy cleaning, and will maintain flexibility for several years. Prostheses constructed with this technique are retained well. The technique described will provide increased mechanical retention of prostheses for defects of the palate by engaging undercuts around the borders of the defect with a flexible material. The impression is made by injecting an elastic impression material with a syringe through a hole prepared in the palate of the impression tray. This technique may not always be required, but is recommended where a retention problem is anticipated and there is difficulty in obtaining a satisfactory flow of the impression material to the appro-
418
priate undercut. A correct impression can be secured the first time, overcoming further discomfort and inconvenience to the patient. We would like to thank Dr. Eric Scher, School of Dentistry, Royal Victoria Hospital, Belfast, for his help with the photography, and the Department of Medical Illustration, Royal Victoria Hospital, Belfast.
REFERENCES 1. Watt, D. M.: Cleft palate in edentulous patients. Br Dent J 102:253, 1957. 2. Waher, J. D.: A material for retentive obturators. Dent Pract 20:208, 1970. 3. Benington, I. C., Watson, I. B., Jenkins, W. M. M., and Allan, G. R. J.: Restorative Treatment of the Cleft Palate Patient. London, 1979, T h e British Dental Association, pp 25-27.
Reprint requests to: DR. IAN C. BENINGTON ROYAL VICTORIA HOSPITAL SCHOOL OF DENTISTRY GROSVENOR RD. BELFAST BT12 6BP NORTHELN IRELAND
APRIL 1982
VOLUME 47
NUMBER 4
L KENNETH ADISMAN
RONALD P. DESJARDINS
An injection impression technique for palatal defects I. C. Benington, B.D.S., F.D.S., R.C.S.,* and T. Clifford, B.D.S., F.D.S., R.C.P.S.** Royal Victoria Hospital, School of Dentistry, Belfast, N o r t h e r n Ireland
I t is difficult to secure satisfactory retention of prostheses for edentulous patients with congenital or acquired defects of the palate (Fig. 1). One method
Presented before the British Society for the Study of Prosthetic Dentistry, Birmingham University, Birmingham, England. *Head, Prosthetics Department. **Senior Registrar, Prosthetics Department.
of overcoming this problem is to provide mechanical retention by engaging undercuts around the borders of the defect with an extension of the denture base. To provide satisfactory retention, the undercuts should be engaged by flexible extensions of the denture base or movable rigid extensions operated by a simple lever system. Flexible extensions, such as latex obturators with a replaceable stud attachment described by Watt,' and a material described by Walter'-' have been used effectively. The use of Molloplast ( K ~ t n e r & Co., Oberursel, Germany) to form flexible extensions to retain obturators has been described by Benington et al? CLINICAL PROBLEM
Fig. 1. Surgical defect of palate.
With the advent of rubber base impression materials, the recording of undercut areas has become simpler since rubber base impression materials have excellent qualities of elasticity and strength, whereas other materials such as irreversible hydrocolloid (alginate) tear when withdrawn from deep undercuts, making reproduction difficult. It may be difficult to direct the flow of the rubber base impression material above the palatal shelves. The injection
Fig. 2. Gutta percha obturator for surgical defect of palate.
414
APRIL 1982
VOLUME 47
NUMBER 4
0022-3913/82/040414 + 05500.50/0@ 1982 The G. V, Mosby Co.
INJECTION IMPRESSION TECHNIQUE
Fig. 3. Individual impression tray with palatal aperture to accommodate syringe nozzle.
impression technique was developed to secure accurate reproduction of undercut areas. Patients with acquired defects of the palate are usually rehabilitated with an immediate surgical obturator prosthesis (Fig. 2). The prosthesis is worn until sufficient healing has taken place to allow impressions to be made without undue discomfort to the patient. The definitive obturator prosthesis which is constructed with a conventional impression technique may be inclined to drop in the anterior region during function. This may occur because the prosthesis is retained posteriorly only by engagement of the undercut created by the remnant of the soft palate with a flexible extension of resilient material. No anterior retention has been achieved to oppose the posterior undercut due to an inadequate impression of the anterior region. Therefore, the obturator prosthesis lacks retention and the patient is unable to wear it satisfactorily. To overcome this problem, the impression material has to be delivered above the anterior palatal shelf on either side of the anterior residual nasal septum. Since rubber base impression material will not remain in position if placed in the nasal cavity prior to the impression tray being positioned, the impression tray should first be seated firmly in position, and additional rubber base materials should then be
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 4. Channels formed using articulator retainer pins.
injected using a syringe through preformed channels in the impression tray for delivery to the appropriate region. IMPRESSION TECHNIQUE A preliminary impression is made of the normal denture-bearing area and the defect. The palatal defect is blocked out with plasticine on the preliminary cast, and a custom impression tray is constructed of acrylic resin using one thickness of wax spacer. The tray is not extended into the defect because later in the impression procedure impression material will be injected through a hole in the palate of the tray to record undercuts in the defect. At the secondary impression stage, the impression tray is used to record an impression of the defect using modeling compound. The material should be
415
BENINGTONAND CLIFFORD
Fig. 5. Prepared impression tray with adhesive and syringe.
Fig. 6. R u b b e r b a s e impression material being injected through hole in impression tray.
placed in the nasal cavity at the height of the palatal shelves around the periphery of the defect. If the impression tray is lowered anteriorly first on removal, the anterior nasal undercut will be obliterated by deformation of the impression material, but the
416
Fig. 7. A, Impression made by conventional technique. B, Impression made by syringe technique. posterior undercut above the remnant of the soft palate will be well recorded, since that part of the impression is undistorted as the impression tray is removed in a downward and forward direction. The composition extension must be reduced around its diameter to allow space for the final rubber base impression material to flow freely. The location of the difficult area to record is assessed, and the impression tray and composition are modified as follows: 1. Gut an opening in the vault of the palate large enough to allow the nozzle of a 20 ml syringe to fit accurately (Fig. 3). This may be facilitated by orienting the aperture down and forward so that the syringe nozzle engages it readily at a convenient angle when the impression tray is in place in the mouth. 2. Using a hot retainer pin from an articulator as a skewer, extend the hole in the tray into a channel of a similar diameter as the hole so that it opens out at the anterosuperior limit of the modeling compound (Fig. 4). Form a similar channel on the other side so that the superior opening is adjacent to the anterior nasal shelves and on either side of the anterior remnant of the nasal septum. Clear the channels of
APRIL 1982
VOLUME 47
NUMBER 4
INJECTION IMPRESSION TECHNIQUE
Fig. 8. A, Stone cast with anterior undercut. B, Stone cast without anterior undercut.
debris prior to recording the impression. Apply adhesive to the tray in the normal manner, taking care not to obstruct the channels (Fig. 5). 3. Prepare mixes of regular and light-bodied rubber base impression material (Permalastic, Kerr Mfg. Co., Romulus, Mich.), spatulating the regular material slightly in advance of the light-bodied material. Apply the regular material to the impression tray and over the composition so that it does not coverthe superior exits of the channels. 4. Place the impression tray upward and posterior to engage the posterior palatal shelf. Seat normally. Place approximately 10 cc of light-bodied rubber base impression material in the 20 ml syringe, injecting it carefully through the hole in the impression tray as soon as the tray is in position, so that the two mixes of rubber base impression material may fuse and harden (Fig. 6). 5. Allow the impression tray to remain in position for approximately 8 minutes, and then remove it carefully from the mouth. If too great a quantity of light-bodied material has been injected the tray may be difficult to remove; however, with experience the correct amount, approximately 10 cc, may be used to record the appropriate undercut region and the impression tray m a y be removed without any difficulty. An impression made without injecting material with a syringe is compared to one made with the injection technique in Fig. 7. 6. Record varying dimensions of the defect undercut by altering the quantity of light-bodied rubber base impression material injected. A comparison of
THE JOURNAL OF PROSTHETIC DENTISTRY
Fig. 9. Anterior and posterior Molloplast extensions on obturator prosthesis.
the master casts indicates that no anterior retention was available in the original cast and that the new cast has ample undercut for retention (Fig. 8). 7. Pour the casts in artificial stone, a n d duplicate if possible in case of accidents or failures with the flexible base. Block out the roof of the nasal cavity on the cast with plaster of Paris so that the superior surface of the obturator prosthesis does not impinge on sensitive nasal mucosa and to permit an adequate airway for nasal breathing. SUMMARY A master cast suitable for fabricating a retentive flexible base using any of the materials and tech-
417
BENINGTON AND CLIFFORD
niques previously mentioned is provided. The flexible extension fits snugly into the defect laterally and extends above the remnants of the soft palate posteriorly and into the nasal floor anteriorly on either side of the remnants of the nasal septum (Fig. 9). The use of a thin flexible extension such as Molloplast will provide a good chemical bond to the acrylic resin of the denture base, allows for easy cleaning, and will maintain flexibility for several years. Prostheses constructed with this technique are retained well. The technique described will provide increased mechanical retention of prostheses for defects of the palate by engaging undercuts around the borders of the defect with a flexible material. The impression is made by injecting an elastic impression material with a syringe through a hole prepared in the palate of the impression tray. This technique may not always be required, but is recommended where a retention problem is anticipated and there is difficulty in obtaining a satisfactory flow of the impression material to the appro-
418
priate undercut. A correct impression can be secured the first time, overcoming further discomfort and inconvenience to the patient. We would like to thank Dr. Eric Scher, School of Dentistry, Royal Victoria Hospital, Belfast, for his help with the photography, and the Department of Medical Illustration, Royal Victoria Hospital, Belfast.
REFERENCES 1. Watt, D. M.: Cleft palate in edentulous patients. Br Dent J 102:253, 1957. 2. Waher, J. D.: A material for retentive obturators. Dent Pract 20:208, 1970. 3. Benington, I. C., Watson, I. B., Jenkins, W. M. M., and Allan, G. R. J.: Restorative Treatment of the Cleft Palate Patient. London, 1979, T h e British Dental Association, pp 25-27.
Reprint requests to: DR. IAN C. BENINGTON ROYAL VICTORIA HOSPITAL SCHOOL OF DENTISTRY GROSVENOR RD. BELFAST BT12 6BP NORTHELN IRELAND
APRIL 1982
VOLUME 47
NUMBER 4