- Email: [email protected]
Modified single and short-span restorations supported by osseointegrated fixtures in the partially edentulous jaw
Modified single and short-span restorations supported by osseointegrated fixtures in the partially edentulous jaw T. Jemt, D.D.S., Ph.D.* University of Gijteborg, Faculty of Odontology, GGteborg, Sweden
R
ecent longitudinal studies, have shown predictable long-term function of osseointegrated fixtures supporting fixed prostheses in the edentulous jaw.‘,’ The clinical technique, consisting of a two-stage surgical procedure3 followed by the final prosthetic treatment: has been proved successful in restoring oral function as well as the psychologic status in completely edentulous patients.5-‘3 However, the obvious improvement of oral function should always be considered in conjunction with esthetic appearance, which occasionally may be compromised, especially in the maxillae. These problems are mainly due to unfavorable jaw relation and visible titanium abutments supporting the maxillary fixed prostheses. For edentulous patients, treatment with overdentures supported by fixtures could be an alternative to the maxillary fixed partial denture to improve esthetics as well as oral function. Loss of a single anterior tooth presents esthetic problems that may be successfully treated with conventional fixed prostheses supported by abutment teeth. However, a single tooth or short arch restoration supported by osseointegrated fixtures may be indicated in some clinical situations; for example, in patients with an intact remaining dentition, or where a generally spaced dentition will complicate conventional fixed prosthetic treatment. When fixtures are used to support restorations in anterior edentulous spaces, esthetics must be optimal and no visible titanium can be tolerated. Conventional treatment alternatives are usually much better in partially edentulous jaws compared with the completely edentulous condition. Therefore, several modifications have been tried to optimize the esthetics of the anchorage unit. I3 The objective of this article is to present a clinical protocol for short-span restorations supported by osseointegrated fixtures and modified abutment components.
COMPONENTS Conventional fixture and abutment components are installed in the edentulous tooth space, following general surgical principles described in detail elsewhere.3
*Department THE JOURNAL
of Prosthetic
Dentistry.
OF PROSTHETIC
DENTISTRY
A modified abutment for single tooth replacement is used to support the final restoration after proper healing time following the abutment connection. The new abutment was designed to enable (1) maximal area of titanium facing soft tissue, thereby maintaining an optimal biologic situation; (2) final curing of an acrylic resin crown directly onto the abutment, thereby optimizing the junction between the veneering material and the titanium abutment cylinder; (3) individual placement of the acrylic resin/titanium junction 1 mm below soft tissue margin, thereby eliminating visible titanium; and (4) placing all metal components in pure titanium, thereby eliminating theoretic problems due to corrosion. The single tooth abutment is manufactured with a smooth titanium cylinder in different heights (Fig. 1). A 1 mm wide shelf above the titanium collar ensures sufficient space for the acrylic resin material, which is cured to the part of the abutment cylinder provided with undercuts for additional retention. A measuring device is also made to determine the distress between the shelf (veneer-titanium junction) and the soft tissue margin (1 mm) (Figs. 1 to 3).
CLINICAL
PROCEDURE
The final prosthetic treatment is performed in two appointments, the first to select a suitable special single tooth abutment to be used as a transfer coping during the impression and the second for insertion of the completed artificial crown. It is favorable to wait at least 2 weeks after abutment connection for the first prosthetic appointment, by which time the gingival margin surrounding the conventional abutment should be healed. This enables a correct assessment of the position of the junction between the smooth titanium cylinder and the acrylic resin tooth, situated about 1 mm below the gingival margin. The prosthetic treatment starts after the surgical pack, healing cap, and conventional abutment have been cautiously removed. An optimal special single tooth abutment is then selected by mounting the special abutment on the measuring device, which indicates, by a 1 line, the point 1 mm above the smooth titanium cylinder (Fig. 2). 243
Fig. 1. Single tooth abutments fabricated with smooth titanium collars with different heights. A 1 mm wide shelf above collar provides sufficient dimension for heat-cured acrylic resin to form the artificial tooth. Abutment is mounted with a modified abutment screw in titanium. A special acrylic resin measuring device and abutment guide pins arc also used during prosthetic treatment. Fig. 2. Conventional abutment is cautiously removed and a modified abutment is mounted on measuring device. Notice red line on the measuring device indicating 1 mm to titanium collar. Fig. 3. Abutment is placed onto fixture. Red line on measuring device should coincide with gingival margin, here indicating that a somewhat shorter titanium collar should be used. Fig. 4. Abutment of choice is mounted on fixture with a long guidepin. Fig. 5. A dot of autopolymerizing acrylic resin enhances position of abutment in impression material after setting. Fig. 6. Abutment collar placed in impression after setting. A fixture dummy is mounted onto abutment, cautiously secured with guide pin. 244
FEBRUARY
1986
VOLUME
55
NUMBER
2
OSSEOINTEGRATED
FIXTURES
Fig. 7. Completed artificial crowns processed in heat-cured acrylic resin directly on titanium cylinder. Notice that titanium collars of different heights are used. Fig. 8. Right lateral incisor and first premolar are restored with artificial crowns supported by fixtures. Articulation is designed with a canine rise, avoiding contacts on artificial crowns in lateral movements. Fig. 9. Ceramic crowns fused to metal may occasionally be considered in stable occlusal situations. Crown is cemented onto abutment, outside mouth. Fig. 10. Two modified single abutments may be connected with a welded bar in titanium. Fig. 11. Left two premolars and first molar in the maxillae are replaced with prostheses supported by two osseointegrated fixtures. Modified abutments are splinted with a welded bar and covered with heat-cured acrylic resin. Abutments, with different heights of the smooth titanium cylinder (Fig. l), are consecutively placed on the fixture until an abutment that allows the line on the measuring device to coincide with the gingival margin is found (Fig. 3). THE JOURNAL
OF PROSTHETIC
DENTISTRY
The abutment of choice is carefully mounted on the fixture with a long guide pin before the impression is made (Fig. 4). It is recommended to place acrylic resin (Duralay, Reliance Dental Mfg. Co., Worth, Ill.) on the abutment before the impression is made (Fig. 5) to 245
ensure an accurate position of the abutment after setting of the impression material. An acrylic resin stock tray is tried and provided with an opening above the fixture site to gain access to the guide pin. The impression tray is loaded with irreversible hydrocolloid and placed in the mouth. After the material has set, the guide pin is located, unscrewed, and removed. The abutment is cautiously loosened from the fixture prior to removal of the impression by means of a tweezers (Fig. 6). A fixture dummy is mounted on the abutment and screwed into place. It is important to avoid too much tightening of the guide pin as this may jeopardize the hexagonal orientation of the fixture dummy. The impression is poured after boxing and the position of the abutment and the fixture is transferred from the mouth to the master cast for further processing in the laboratory. The conventional abutment, with healing cap and surgical pack, is replaced until the second treatment stage. A shade is recorded as well as an irreversible hydrocolloid impression of the opposing jaw. In the laboratory the retentive part of the abutment cylinder is shortened in relation to the available vertical space. A heat-cured acrylic resin crown is then processed onto the titanium abutment. The artificial crown can be provided with different heights of smooth titanium cylinders because of the thickness of the soft tissue above the fixture head (Fig. 7). The completed artificial tooth is finally mounted on the fixture and the titanium screw (Fig. 1) is tightened while counteracting torquing forces applied to the fixture by holding the crown with the fingers or with a clamp. Proximal contacts that are too tight will jeopardize a perfect seating of the crown. The screw access hole is sealed with gutta percha and autopolymerizing acrylic resin. It is important to correct the occlusion after treatment, following the principle of contacts on the crown in intercuspal position but avoiding contacts in either protrusive or lateral movements (Fig. 8). FURTHER
MODIFICATIONS
The choice of heat-cured acrylic resin is made primarily to achieve a shock-absorbing effect in occlusion. This has been shown to reduce the rate of fractures in the anchorage components, caused by fatigue, in complete edentulous restorations.” However, the present design of the modified abutment cylinder does not limit the choice of material. Rehabilitation with ceramic crowns could occasionally be considered provided that the occlusion is stable and no overeruption could be expected into the edentulous space (Fig. 9). The ceramic crown is processedin a conventional manner and finally cemented to the abutment cylinder under optimal conditions outside the mouth (Fig. 9), whereafter it finally can be secured
246
to the fixture with a titanium screw. The screw access hole should be wider near the occlusal surface so that occlusal contacts are mainly on the autopolymerizing acrylic resin that seals the access hole. By changing the internal hexagonal part of the abutment facing the fixture to an internal cylinder, it is possible to use the modified abutment also in fixed partial denture constructions. Two or several abutments can thereby be rigidly connected by a welded titanium bar (Fig. 10). The metal framework is covered with heat-cured acrylic resin and mounted onto the fixtures after final processing (Fig. 11).
CONCLUSION Short-term experience indicates the possibility of restoring single-tooth and short edentulous space by using osseointegrated fixtures as support for the artificial teeth. Diverse designs have been used to optimize esthetic and hygienic conditions.
REFERENCES I
?
3
4
5
0
,\drll R Long-term trralmcnt results. In Br&mark P-I, Zarb G. Alhrektsson ‘I‘. Tissue-integraled Prostheses. Chseoinrcgra,~on in (Xniwl I)emislry. London. 1985. Qu~n~esscnte Publish,111:(:I) Iw. .\dell R, I.ekholm U. Rockier B. Brinemark P-l: I5 Years studv IBCvsseointrgrawd implants in trwrment of thr edrnrulous jaw. Inr J Oral Surq 6~387. 1981 ;\delI R. Lekholm U. Brinemark P-1: Surgical procedures. fn l%rAwmark P-I, Zarb C, Albrektsson T. ediwrs ‘Tissue-inte
_)
R
‘1.
IO.
I I.
I.undgrrn
D, Laurel1
L, Bergendahl
FEBRUARY
1986
T: Owlusal
VOLUME
foru
55
paucrn
NUMBER
in
2
OSSEOINTEGRATED
FIXTURES
dentitions restored with mandibular bridges supported on osseointegrated implants. Swed Dent J [Suppl]28:107, 1985. 12. Blomberg S, Lindquist LW: Psychological reactions to edentulousness and treatment with jawbone-anchored bridges. Acta Psychiatr Stand 68:251, 1983. 13. Brinemark P-I, Zarb G, Albrektsson T, editors: Tissue-integrated Prostheses. Osseointegration in Clinical Dentistry. London, 1985, Quintessence Publishing Co. Inc.
Reprint requesis to: DR T. JEMT UNIVERSITY OF G~TEBORG FACULTY OF ODONTOL~GY FACK S-400 33 G~TEBORC 33 SWEDEN
A versatile and easily fabricated mouthstick Richard A. Olsen, D.D.S.,8 Edwin M. Prentice,** and Donna B. Olsen, D.D.S.*** University of Chicago, Chicago, Ill., Cleveland Metropolitan Veteran’s Administration Hospital, Chicago, Ill.
General/Highland
View Hospital, Cleveland, Ohio, and
D
entists have a long-standing history of providing care for the handicapped. ‘32 Mouthsticks are often made for quadraplegics to help them perform a few tasks by using a dowel held between the teeth (Fig. 1).3-6 This article describes a simple procedure for fabrication of a mouthstick with parts available at many retail outlets (Table I). This mouthstick was designed to (1) conform to established criteria,’ (2) be inexpensive, (3) be lightweight, (4) be easy to produce, and (5) be used for multiple tasks by use of several tips that can be changed without assistance.
TECHNIQUE Gather and assemble the parts described below (Fig. 2). 1. Cut the brass tubing into 4-inch sections. 2. Slide the smaller tubing into the larger tubing. Double the wall thickness to increase its strength. 3. Silver solder the piece of 2-inch shim stock onto the end of the tubing, creating a 90-degree relationship. 4. To form a spring clip, bend one end of the 2?&nch brass shim stock to form a W with ?&inch sides. 5. Grind a ?AX ?&inch slot through the tubing 2% inches from the attached shim stock. 6. Place the V section of the spring clip into the slot
*Assistant Professor and Head, Section of General Dentistry, Zoller Memorial Dental Clinic, University of Cdicago. **Rehablitation Engineer, Department of Clinical Engineering, Cleveland Metropolitan General/Highland View Hospital. ***General Practice Resident, Department of Dentistry, Veteran’s Administration Hospital.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
Fig. 1. Mouths&k design allows individuals form different tasks by changing tip.
to per-
and align the remaining portion over the tubing with the long end tdward the shim stock. 7. With a No. 50 drill bit, make two holes approximately *S inch apart through the spring clip and into the tubing. Enlarge the holes to %z inch, and screw the spring clip to place. 8. Place the fiberglass rod into the tubing until it contacts the screws. 9. Mark the location of the spring clip slot on the fiberglass rod. Remove it, and cut a circumferential groove into the rod at that point. The clip will snap into the groove and retain the rod. 10. Make accukate casts of the maxillary and mandibular arches and mqunt them in centric occlusion on a semiadjustable articulator. Increase the interocclusal
247
R
ecent longitudinal studies, have shown predictable long-term function of osseointegrated fixtures supporting fixed prostheses in the edentulous jaw.‘,’ The clinical technique, consisting of a two-stage surgical procedure3 followed by the final prosthetic treatment: has been proved successful in restoring oral function as well as the psychologic status in completely edentulous patients.5-‘3 However, the obvious improvement of oral function should always be considered in conjunction with esthetic appearance, which occasionally may be compromised, especially in the maxillae. These problems are mainly due to unfavorable jaw relation and visible titanium abutments supporting the maxillary fixed prostheses. For edentulous patients, treatment with overdentures supported by fixtures could be an alternative to the maxillary fixed partial denture to improve esthetics as well as oral function. Loss of a single anterior tooth presents esthetic problems that may be successfully treated with conventional fixed prostheses supported by abutment teeth. However, a single tooth or short arch restoration supported by osseointegrated fixtures may be indicated in some clinical situations; for example, in patients with an intact remaining dentition, or where a generally spaced dentition will complicate conventional fixed prosthetic treatment. When fixtures are used to support restorations in anterior edentulous spaces, esthetics must be optimal and no visible titanium can be tolerated. Conventional treatment alternatives are usually much better in partially edentulous jaws compared with the completely edentulous condition. Therefore, several modifications have been tried to optimize the esthetics of the anchorage unit. I3 The objective of this article is to present a clinical protocol for short-span restorations supported by osseointegrated fixtures and modified abutment components.
COMPONENTS Conventional fixture and abutment components are installed in the edentulous tooth space, following general surgical principles described in detail elsewhere.3
*Department THE JOURNAL
of Prosthetic
Dentistry.
OF PROSTHETIC
DENTISTRY
A modified abutment for single tooth replacement is used to support the final restoration after proper healing time following the abutment connection. The new abutment was designed to enable (1) maximal area of titanium facing soft tissue, thereby maintaining an optimal biologic situation; (2) final curing of an acrylic resin crown directly onto the abutment, thereby optimizing the junction between the veneering material and the titanium abutment cylinder; (3) individual placement of the acrylic resin/titanium junction 1 mm below soft tissue margin, thereby eliminating visible titanium; and (4) placing all metal components in pure titanium, thereby eliminating theoretic problems due to corrosion. The single tooth abutment is manufactured with a smooth titanium cylinder in different heights (Fig. 1). A 1 mm wide shelf above the titanium collar ensures sufficient space for the acrylic resin material, which is cured to the part of the abutment cylinder provided with undercuts for additional retention. A measuring device is also made to determine the distress between the shelf (veneer-titanium junction) and the soft tissue margin (1 mm) (Figs. 1 to 3).
CLINICAL
PROCEDURE
The final prosthetic treatment is performed in two appointments, the first to select a suitable special single tooth abutment to be used as a transfer coping during the impression and the second for insertion of the completed artificial crown. It is favorable to wait at least 2 weeks after abutment connection for the first prosthetic appointment, by which time the gingival margin surrounding the conventional abutment should be healed. This enables a correct assessment of the position of the junction between the smooth titanium cylinder and the acrylic resin tooth, situated about 1 mm below the gingival margin. The prosthetic treatment starts after the surgical pack, healing cap, and conventional abutment have been cautiously removed. An optimal special single tooth abutment is then selected by mounting the special abutment on the measuring device, which indicates, by a 1 line, the point 1 mm above the smooth titanium cylinder (Fig. 2). 243
Fig. 1. Single tooth abutments fabricated with smooth titanium collars with different heights. A 1 mm wide shelf above collar provides sufficient dimension for heat-cured acrylic resin to form the artificial tooth. Abutment is mounted with a modified abutment screw in titanium. A special acrylic resin measuring device and abutment guide pins arc also used during prosthetic treatment. Fig. 2. Conventional abutment is cautiously removed and a modified abutment is mounted on measuring device. Notice red line on the measuring device indicating 1 mm to titanium collar. Fig. 3. Abutment is placed onto fixture. Red line on measuring device should coincide with gingival margin, here indicating that a somewhat shorter titanium collar should be used. Fig. 4. Abutment of choice is mounted on fixture with a long guidepin. Fig. 5. A dot of autopolymerizing acrylic resin enhances position of abutment in impression material after setting. Fig. 6. Abutment collar placed in impression after setting. A fixture dummy is mounted onto abutment, cautiously secured with guide pin. 244
FEBRUARY
1986
VOLUME
55
NUMBER
2
OSSEOINTEGRATED
FIXTURES
Fig. 7. Completed artificial crowns processed in heat-cured acrylic resin directly on titanium cylinder. Notice that titanium collars of different heights are used. Fig. 8. Right lateral incisor and first premolar are restored with artificial crowns supported by fixtures. Articulation is designed with a canine rise, avoiding contacts on artificial crowns in lateral movements. Fig. 9. Ceramic crowns fused to metal may occasionally be considered in stable occlusal situations. Crown is cemented onto abutment, outside mouth. Fig. 10. Two modified single abutments may be connected with a welded bar in titanium. Fig. 11. Left two premolars and first molar in the maxillae are replaced with prostheses supported by two osseointegrated fixtures. Modified abutments are splinted with a welded bar and covered with heat-cured acrylic resin. Abutments, with different heights of the smooth titanium cylinder (Fig. l), are consecutively placed on the fixture until an abutment that allows the line on the measuring device to coincide with the gingival margin is found (Fig. 3). THE JOURNAL
OF PROSTHETIC
DENTISTRY
The abutment of choice is carefully mounted on the fixture with a long guide pin before the impression is made (Fig. 4). It is recommended to place acrylic resin (Duralay, Reliance Dental Mfg. Co., Worth, Ill.) on the abutment before the impression is made (Fig. 5) to 245
ensure an accurate position of the abutment after setting of the impression material. An acrylic resin stock tray is tried and provided with an opening above the fixture site to gain access to the guide pin. The impression tray is loaded with irreversible hydrocolloid and placed in the mouth. After the material has set, the guide pin is located, unscrewed, and removed. The abutment is cautiously loosened from the fixture prior to removal of the impression by means of a tweezers (Fig. 6). A fixture dummy is mounted on the abutment and screwed into place. It is important to avoid too much tightening of the guide pin as this may jeopardize the hexagonal orientation of the fixture dummy. The impression is poured after boxing and the position of the abutment and the fixture is transferred from the mouth to the master cast for further processing in the laboratory. The conventional abutment, with healing cap and surgical pack, is replaced until the second treatment stage. A shade is recorded as well as an irreversible hydrocolloid impression of the opposing jaw. In the laboratory the retentive part of the abutment cylinder is shortened in relation to the available vertical space. A heat-cured acrylic resin crown is then processed onto the titanium abutment. The artificial crown can be provided with different heights of smooth titanium cylinders because of the thickness of the soft tissue above the fixture head (Fig. 7). The completed artificial tooth is finally mounted on the fixture and the titanium screw (Fig. 1) is tightened while counteracting torquing forces applied to the fixture by holding the crown with the fingers or with a clamp. Proximal contacts that are too tight will jeopardize a perfect seating of the crown. The screw access hole is sealed with gutta percha and autopolymerizing acrylic resin. It is important to correct the occlusion after treatment, following the principle of contacts on the crown in intercuspal position but avoiding contacts in either protrusive or lateral movements (Fig. 8). FURTHER
MODIFICATIONS
The choice of heat-cured acrylic resin is made primarily to achieve a shock-absorbing effect in occlusion. This has been shown to reduce the rate of fractures in the anchorage components, caused by fatigue, in complete edentulous restorations.” However, the present design of the modified abutment cylinder does not limit the choice of material. Rehabilitation with ceramic crowns could occasionally be considered provided that the occlusion is stable and no overeruption could be expected into the edentulous space (Fig. 9). The ceramic crown is processedin a conventional manner and finally cemented to the abutment cylinder under optimal conditions outside the mouth (Fig. 9), whereafter it finally can be secured
246
to the fixture with a titanium screw. The screw access hole should be wider near the occlusal surface so that occlusal contacts are mainly on the autopolymerizing acrylic resin that seals the access hole. By changing the internal hexagonal part of the abutment facing the fixture to an internal cylinder, it is possible to use the modified abutment also in fixed partial denture constructions. Two or several abutments can thereby be rigidly connected by a welded titanium bar (Fig. 10). The metal framework is covered with heat-cured acrylic resin and mounted onto the fixtures after final processing (Fig. 11).
CONCLUSION Short-term experience indicates the possibility of restoring single-tooth and short edentulous space by using osseointegrated fixtures as support for the artificial teeth. Diverse designs have been used to optimize esthetic and hygienic conditions.
REFERENCES I
?
3
4
5
0
,\drll R Long-term trralmcnt results. In Br&mark P-I, Zarb G. Alhrektsson ‘I‘. Tissue-integraled Prostheses. Chseoinrcgra,~on in (Xniwl I)emislry. London. 1985. Qu~n~esscnte Publish,111:(:I) Iw. .\dell R, I.ekholm U. Rockier B. Brinemark P-l: I5 Years studv IBCvsseointrgrawd implants in trwrment of thr edrnrulous jaw. Inr J Oral Surq 6~387. 1981 ;\delI R. Lekholm U. Brinemark P-1: Surgical procedures. fn l%rAwmark P-I, Zarb C, Albrektsson T. ediwrs ‘Tissue-inte
_)
R
‘1.
IO.
I I.
I.undgrrn
D, Laurel1
L, Bergendahl
FEBRUARY
1986
T: Owlusal
VOLUME
foru
55
paucrn
NUMBER
in
2
OSSEOINTEGRATED
FIXTURES
dentitions restored with mandibular bridges supported on osseointegrated implants. Swed Dent J [Suppl]28:107, 1985. 12. Blomberg S, Lindquist LW: Psychological reactions to edentulousness and treatment with jawbone-anchored bridges. Acta Psychiatr Stand 68:251, 1983. 13. Brinemark P-I, Zarb G, Albrektsson T, editors: Tissue-integrated Prostheses. Osseointegration in Clinical Dentistry. London, 1985, Quintessence Publishing Co. Inc.
Reprint requesis to: DR T. JEMT UNIVERSITY OF G~TEBORG FACULTY OF ODONTOL~GY FACK S-400 33 G~TEBORC 33 SWEDEN
A versatile and easily fabricated mouthstick Richard A. Olsen, D.D.S.,8 Edwin M. Prentice,** and Donna B. Olsen, D.D.S.*** University of Chicago, Chicago, Ill., Cleveland Metropolitan Veteran’s Administration Hospital, Chicago, Ill.
General/Highland
View Hospital, Cleveland, Ohio, and
D
entists have a long-standing history of providing care for the handicapped. ‘32 Mouthsticks are often made for quadraplegics to help them perform a few tasks by using a dowel held between the teeth (Fig. 1).3-6 This article describes a simple procedure for fabrication of a mouthstick with parts available at many retail outlets (Table I). This mouthstick was designed to (1) conform to established criteria,’ (2) be inexpensive, (3) be lightweight, (4) be easy to produce, and (5) be used for multiple tasks by use of several tips that can be changed without assistance.
TECHNIQUE Gather and assemble the parts described below (Fig. 2). 1. Cut the brass tubing into 4-inch sections. 2. Slide the smaller tubing into the larger tubing. Double the wall thickness to increase its strength. 3. Silver solder the piece of 2-inch shim stock onto the end of the tubing, creating a 90-degree relationship. 4. To form a spring clip, bend one end of the 2?&nch brass shim stock to form a W with ?&inch sides. 5. Grind a ?AX ?&inch slot through the tubing 2% inches from the attached shim stock. 6. Place the V section of the spring clip into the slot
*Assistant Professor and Head, Section of General Dentistry, Zoller Memorial Dental Clinic, University of Cdicago. **Rehablitation Engineer, Department of Clinical Engineering, Cleveland Metropolitan General/Highland View Hospital. ***General Practice Resident, Department of Dentistry, Veteran’s Administration Hospital.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
Fig. 1. Mouths&k design allows individuals form different tasks by changing tip.
to per-
and align the remaining portion over the tubing with the long end tdward the shim stock. 7. With a No. 50 drill bit, make two holes approximately *S inch apart through the spring clip and into the tubing. Enlarge the holes to %z inch, and screw the spring clip to place. 8. Place the fiberglass rod into the tubing until it contacts the screws. 9. Mark the location of the spring clip slot on the fiberglass rod. Remove it, and cut a circumferential groove into the rod at that point. The clip will snap into the groove and retain the rod. 10. Make accukate casts of the maxillary and mandibular arches and mqunt them in centric occlusion on a semiadjustable articulator. Increase the interocclusal
247