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Multiple handpiece delivery system for tooth preparation
Multiple handpiece delivery system for tooth preparation William
McGrannahan,
D.D.S.*
University of Missouri, School of Dentistry, Kansas City, MO.
T
he air-turbine handpiece has provided practitioners in the dental profession with the ability to prepare tooth structure with ease and precision, while decreasing the stress to the patient and dentist. Another benefit of the development is the revolution in the design of dental operatories. Since the traditional belt and pully apparatus is no longer necessary, handpieces may be installed wherever convenient. There are three principal locations in the dental operatory for handpiece delivery systems: (1) across the patient, (2) behind the patient, and (3) beside the operator, usually on a mobile cart. Preferences for handpiece positions vary; however, it is difficult to duplicate the versatility of the cart with other systems. For example, the utility center or junction box that attaches to the umbilical cord of the cart can be installed under the dental chair just forward of the base. This allows the cart to be moved to either side of the chair so the operatory can be used by either a rightor left-handed dentist. This article describes how a modified standard cart for the dental operatory can be customized for individual requirements. A sequence of tooth preparation is presented to illustrate the improvements. MODIFICATION
OF STANDARD
CART
The newer dental carts are equipped to carry three handpieces, but this modification allows the cart to deliver six handpieces. Two basic items are necessary for the accommodation of an air-turbine handpiece within a dental unit. First, an air/water control block must occupy some space within the cabinet. Second, a handpiece holder must be conveniently located on the outside of the cabinet. The cart shown in Fig. 1 was altered as follows. The air/water syringe has been moved from the front to the unit’s right side. Two handpiece holders (automatic shut-off type) have been added to the front bar of the *Faculty, Department of Continuing Education.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
Fig. 1. Modified cart is equipped with six handpieces and air/water syringe.
Fig. 2. A No. 169L carbide bur is used for initial separation. unit. The two knobs on the far left have been added to control water flow to the handpieces. A slow-speed handpiece holder is mounted on the unit’s left side. This holder is controlled manually by a toggle switch adjacent to the hanger. A method for crown preparation is included in this article for demonstration purposes. The dentist can
73
McGRANNAHAN
Fig. 3. Wheel-shaped occlusal reduction.
diamond
stone is used for
Fig. 4. Barrel-shaped diamond stone is used for initial occlusal shaping.
Fig. 5. Flame-shaped diamond stone is used. A, Preliminary shaping of the axial surfaces. B, Refining axial surfaces. C, Beveling occlusoaxial line angles. develop his own routines for a variety of prosthetic and operative procedures. The sequence of buts and/or stones can be designated for the assistants responsible for preoperative preparation of the dental cart.
CROWN PREPARATION The preparation of a mandibular right first molar to receive a ceramometal full crown is presented. An assistant will place the burs and stones in a designated sequence in the six handpieces immediately prior to seating the patient. 74
Interproximal
reduction (Fig. 2)
The initial separation between the operated and nonoperated teeth is made with a smooth cutting No. 169L carbide bur. This surface will be further shaped later with a tapered diamond stone.
Occlusal reduction (Fig. 3) A wheel-shaped diamond stone is used to reduce the occlusal surface. If a 1 mm thick stone is used, the 2 mm reduction advised by many clinicians is facilitated.?’ JULY 1984
VOLUME
52
NUMBER
1
MULTIPLE
Initial
HANDPIECE
SYSTEM
occlusal shaping (Fig. 4)
A V-shaped cut is made me&distally with a barrelshaped diamond stone. The contour of this surface will be further refined, shaped, and canted similar to the method described by Turner,4 and Tjan and Miller.s
Axial reduction (Fig. 5) A flame-shaped diamond stone is used for bulk reduction and preliminary shaping of the axial surfaces (Fig. 5, A). Refining of axial surfaces is shown in Fig. 5, B, and beveling or canting of the occlusoaxial line angles is shown in Fig. 5, C. A slim, tapered, diamond stone is introduced into the gingival sulcus for preparation of a margin. The buccal and lingual grooves are accentuated to add stability and retentiveness to the crown. The grooves are joined across the occlusal surface. The buccal and lingual occlusal third of the axial surface is canted to allow the proper thickness of the ceramometal crown.5 If esthetics permit, a metal collar is preferable on all margins of molar crowns. This allows the use of a knife-edge gingival finish line, which provides a more suitable marginal seal62’
Finishing
and polishing
(Fig. 6)
Because sharp angles on stone dies are vulnerable to damage in the laboratory, the angles are rounded on the prepared tooth with a flame-shaped aluminum oxide stone (Centra, San Diego, Calif.).
DISCUSSION The parts and materials necessary to effect the alterations to the dental cart are not costly. The time involved is probably no more than 2 hours, and the modification can be performed in the office with available hand tools. A major investment is required for the additional handpieces, especially if more than one operatory is so equipped. However, breakdowns that require factory service of the handpieces are reduced proportionately. It is suggested that the handpiece hangers and the handpiece tubings be color coded to prevent confusion. Plastic electric tape is commonly used.
Fig. 6. Flame-shaped aluminum oxide stone is used to round angles on prepared tooth.
and one low-speed air-driven handpieces. This relatively simple dental unit is versatile and can be adapted to a variety of tooth preparation techniques. The product of organization is efficiency, which encourages optimum results with an economy of actions and a reduction of stress. REFERENCES 1. Goldstein, R. E.: Esthetics in Dentistry. Philadelphia, 1976. J. B. Lippincott Co., p 75. 2. Preston, J. D.: Tooth preparation for ceramo-metal restorations. Den Clin North Am !21:692, 1977. 3. Wrisgold, A. S., and Feder, M.: Tooth preparation in fixed prosthesis. Compendium of Continuing Education 1:375, 1980. 4. Turner, C. H.: Bevels and slots in full crown preparations. Dent Update 4~161, 1977. 5. Tjan, A. H., and Miller, G. D.: Common er.-ors in tooth preparation, J Acad Gen Dent 28~20, 1980. 6. Fusayama, T., Kimiko, I., and Hiroyasu, H.: Relief of resistance of cement of full cast restorations. J PROSTHET DENT 3 1495, 1964. 7. Gavelis, J. R., Morency, J. D., Riley, E. D., and Sozio, R. B.: The effect of various finish line preparations on the marginal seal and occlusal seat of full crown preparations. J PROSTHET DENT 45:138, 1981. Kqbrtnt requests to: DR. WILLIAM MCGRANNAHAN 411 NICHOLS RD. STE. 200 KANSAS CITY, MO 64112
SUMMARY A cart-type handpiece delivery system has been modified to provide the operator with five high-speed
THE JOURNAL
OF PROSTHETIC
DENTISTRY
75
McGrannahan,
D.D.S.*
University of Missouri, School of Dentistry, Kansas City, MO.
T
he air-turbine handpiece has provided practitioners in the dental profession with the ability to prepare tooth structure with ease and precision, while decreasing the stress to the patient and dentist. Another benefit of the development is the revolution in the design of dental operatories. Since the traditional belt and pully apparatus is no longer necessary, handpieces may be installed wherever convenient. There are three principal locations in the dental operatory for handpiece delivery systems: (1) across the patient, (2) behind the patient, and (3) beside the operator, usually on a mobile cart. Preferences for handpiece positions vary; however, it is difficult to duplicate the versatility of the cart with other systems. For example, the utility center or junction box that attaches to the umbilical cord of the cart can be installed under the dental chair just forward of the base. This allows the cart to be moved to either side of the chair so the operatory can be used by either a rightor left-handed dentist. This article describes how a modified standard cart for the dental operatory can be customized for individual requirements. A sequence of tooth preparation is presented to illustrate the improvements. MODIFICATION
OF STANDARD
CART
The newer dental carts are equipped to carry three handpieces, but this modification allows the cart to deliver six handpieces. Two basic items are necessary for the accommodation of an air-turbine handpiece within a dental unit. First, an air/water control block must occupy some space within the cabinet. Second, a handpiece holder must be conveniently located on the outside of the cabinet. The cart shown in Fig. 1 was altered as follows. The air/water syringe has been moved from the front to the unit’s right side. Two handpiece holders (automatic shut-off type) have been added to the front bar of the *Faculty, Department of Continuing Education.
THE JOURNAL
OF PROSTHETIC
DENTISTRY
Fig. 1. Modified cart is equipped with six handpieces and air/water syringe.
Fig. 2. A No. 169L carbide bur is used for initial separation. unit. The two knobs on the far left have been added to control water flow to the handpieces. A slow-speed handpiece holder is mounted on the unit’s left side. This holder is controlled manually by a toggle switch adjacent to the hanger. A method for crown preparation is included in this article for demonstration purposes. The dentist can
73
McGRANNAHAN
Fig. 3. Wheel-shaped occlusal reduction.
diamond
stone is used for
Fig. 4. Barrel-shaped diamond stone is used for initial occlusal shaping.
Fig. 5. Flame-shaped diamond stone is used. A, Preliminary shaping of the axial surfaces. B, Refining axial surfaces. C, Beveling occlusoaxial line angles. develop his own routines for a variety of prosthetic and operative procedures. The sequence of buts and/or stones can be designated for the assistants responsible for preoperative preparation of the dental cart.
CROWN PREPARATION The preparation of a mandibular right first molar to receive a ceramometal full crown is presented. An assistant will place the burs and stones in a designated sequence in the six handpieces immediately prior to seating the patient. 74
Interproximal
reduction (Fig. 2)
The initial separation between the operated and nonoperated teeth is made with a smooth cutting No. 169L carbide bur. This surface will be further shaped later with a tapered diamond stone.
Occlusal reduction (Fig. 3) A wheel-shaped diamond stone is used to reduce the occlusal surface. If a 1 mm thick stone is used, the 2 mm reduction advised by many clinicians is facilitated.?’ JULY 1984
VOLUME
52
NUMBER
1
MULTIPLE
Initial
HANDPIECE
SYSTEM
occlusal shaping (Fig. 4)
A V-shaped cut is made me&distally with a barrelshaped diamond stone. The contour of this surface will be further refined, shaped, and canted similar to the method described by Turner,4 and Tjan and Miller.s
Axial reduction (Fig. 5) A flame-shaped diamond stone is used for bulk reduction and preliminary shaping of the axial surfaces (Fig. 5, A). Refining of axial surfaces is shown in Fig. 5, B, and beveling or canting of the occlusoaxial line angles is shown in Fig. 5, C. A slim, tapered, diamond stone is introduced into the gingival sulcus for preparation of a margin. The buccal and lingual grooves are accentuated to add stability and retentiveness to the crown. The grooves are joined across the occlusal surface. The buccal and lingual occlusal third of the axial surface is canted to allow the proper thickness of the ceramometal crown.5 If esthetics permit, a metal collar is preferable on all margins of molar crowns. This allows the use of a knife-edge gingival finish line, which provides a more suitable marginal seal62’
Finishing
and polishing
(Fig. 6)
Because sharp angles on stone dies are vulnerable to damage in the laboratory, the angles are rounded on the prepared tooth with a flame-shaped aluminum oxide stone (Centra, San Diego, Calif.).
DISCUSSION The parts and materials necessary to effect the alterations to the dental cart are not costly. The time involved is probably no more than 2 hours, and the modification can be performed in the office with available hand tools. A major investment is required for the additional handpieces, especially if more than one operatory is so equipped. However, breakdowns that require factory service of the handpieces are reduced proportionately. It is suggested that the handpiece hangers and the handpiece tubings be color coded to prevent confusion. Plastic electric tape is commonly used.
Fig. 6. Flame-shaped aluminum oxide stone is used to round angles on prepared tooth.
and one low-speed air-driven handpieces. This relatively simple dental unit is versatile and can be adapted to a variety of tooth preparation techniques. The product of organization is efficiency, which encourages optimum results with an economy of actions and a reduction of stress. REFERENCES 1. Goldstein, R. E.: Esthetics in Dentistry. Philadelphia, 1976. J. B. Lippincott Co., p 75. 2. Preston, J. D.: Tooth preparation for ceramo-metal restorations. Den Clin North Am !21:692, 1977. 3. Wrisgold, A. S., and Feder, M.: Tooth preparation in fixed prosthesis. Compendium of Continuing Education 1:375, 1980. 4. Turner, C. H.: Bevels and slots in full crown preparations. Dent Update 4~161, 1977. 5. Tjan, A. H., and Miller, G. D.: Common er.-ors in tooth preparation, J Acad Gen Dent 28~20, 1980. 6. Fusayama, T., Kimiko, I., and Hiroyasu, H.: Relief of resistance of cement of full cast restorations. J PROSTHET DENT 3 1495, 1964. 7. Gavelis, J. R., Morency, J. D., Riley, E. D., and Sozio, R. B.: The effect of various finish line preparations on the marginal seal and occlusal seat of full crown preparations. J PROSTHET DENT 45:138, 1981. Kqbrtnt requests to: DR. WILLIAM MCGRANNAHAN 411 NICHOLS RD. STE. 200 KANSAS CITY, MO 64112
SUMMARY A cart-type handpiece delivery system has been modified to provide the operator with five high-speed
THE JOURNAL
OF PROSTHETIC
DENTISTRY
75