Journal
of Dentistry,
4, 190-I
94
Matrices for the acid-etch composite technique Graham J. Roberts,
and
BDS
Department of Children’s Dentistrv, School of Dental Surgery, Royal Dental Hospital of London . ABSTRACT
The indications, method of construction and use of special matrices for the acid-etch and composite technique are discussed. Two case histories illustrating their use are presented.
INTRODUCTION remarkable retention of composite and unfilled resins to acid-etched enamel has led to the use of composite filling materials in a variety of situations which previously could only be restored with conventional techniques. When attempting to restore lost tooth structure, reshape malformed teeth and mask stained or hypoplastic tooth surfaces it is necessary to use a matrix. The matrices currently available are the flat plastic instrument, cellulose acetate strips and preformed cellulose acetate crown forms. Frequently situations arise where these matrices are not suitable and it is necessary to construct special matrices. This article describes three techniques for fabricating special matrices. Details of the acid-etch technique and its many applications where these matrices have been used are described elsewhere (Roberts, 1975).
THE
CONSTRUCTION MATRICES
OF SPECIAL
In its simplest form a matrix can be made by thermomoulding* a cellulose acetate sheetf on *Drufomat Pressure Moulding Machine, Dreve Dentamid, Uhna, Germany (available from Panadent, London). TDrufolit Cellulose Acetate Sheets, 120 mm diameter x O-5mm thick, Dreve Dentamid, Uhna, Germany.
to a work model. The moulded sheet is then trimmed and may be used directly in the mouth. Where multiple restorationsareplanned it may be necessary to make two or three separate matrices. The way in which the matrix is made will be determined by several factors : 1. The amount of space needed for the composite, and the manner in which this space is created. 2. Whether a single matrix covering several teeth or separate matrices for each tooth are to be created. 3. Whether the composite is to be polymerized by ultraviolet or chemical means. These considerations have resulted in three types of matrix. Type 1 With a localized discoloration, such as nonendemic mottling, the matrix is usually made to fit the existing tooth structure and, at the time of restoration, the space for the composite is created by removing the mottled enamel with an airotor. The matrix thus restores the pre-existing tooth structure. With a fractured incisor, it is necessary to restore the lost tooth structure on the work model before the matrix is made. Where the space for the composite is to be created by removing enamel at the time of operation the matrix is fabricated directly on to a work model of the patient’s mouth. It is usually advisable to trim the matrix in excess of the area to be restored as this provides stability, especially when occlusal stops are made on adjacent teeth (see Case 1). If the tooth structure is missing or it is necessary to increase the size of a given tooth
Roberts
: Acid-etch
and Composite
Technique
191
or group of teeth the matrix cannot be fabricated directly on to the patient’s study model. The procedure for dealing with such a problem is as follows: a. Using blue inlay wax, the desired crown morphology is created on the work model. This technique is suitable for small volumes such as a fractured incisal edge or a peg lateral being transformed to a normal shape and size. Where large volumes or numbers of teeth are to be restored it is sometimes easier to use plastic denture teeth, trim them to the required size and fix them to the work model with sticky wax. h. The resulting model is then duplicated, thus providing a stone work model. This is necessary as the heat used in the thermomoulding process is sufficient to melt the inlay wax or sticky wax holding the denture teeth to the model. c. The moulded acetate sheet is trimmed to a convenient size. Tn these cases there is only a small amount of contact between the matrix and the existing tooth structure, so the number and location of occlusal stops are critical. d. When the matrix is located on the original study model the amount of space created for the composite can be visualized. It should be noted that in a given situation a combination of enamel removal and addition with composite can be used to reshape a given tooth. Type 2 In the situation described above, the composite is usually applied on either the labial or the palatal surface only. This results in a flash of polymerized composite across the interdental space. The flash can be trimmed away using fine diamond burrs followed by tungsten carbide finishing burrs (Baker and Curson, 1974) and special composite finishing strips.* Where the restorations involve the mesial and distal surfaces of the teeth it is necessary to construct individual matrices completely encircling each tooth. On the conventional work model the teeth are so close together that the cellulose acetate *Composite Finishing Strips, Dental and Polishing System, 3M Dental London.
Finishing Products,
sheet cannot be thermomoulded to encircle each tooth. To overcome this it is necessary to construct a work model where the individual teeth can be separated sufficiently to allow the thermomoulded matrices to encircle each tooth. This can be achieved by constructing the work model using similar techniques to those for constructing work models for crown and bridgework. Both the ‘boat’ technique and the dowel technique (Ney, 1964) have been found to be satisfactory. Both techniques involve sawing the model through the interproximal space. If the space for the composite is to be created by removing enamel, the matrices are made directly on to the separated models of individual teeth. Where the space is to be created on the work model, the individual teeth are modified with inlay wax as in the single matrix technique. The individual modelled teeth are then duplicated and the individual matrices constructed on the duplicates.When the matrices are replaced on the original work model the space created for the composite can be seen.
Type
3
If an ultraviolet-light-polymerized composite is to be used it is necessary for the matrix to allow the transmission of ultraviolet light to the unpolymerized composite. The cellulose acetate is sufficiently transparent to allow ultraviolet light to pass through it and bring about complete polymerization of the composite, provided that the composite layer is not more than 1.0-1.5 mm thick. In the incisal edge region, where the light can be applied palatally as well as labially, the thickness can increase to 2.0-3.0 mm. Because of the unlimited working time afforded by ultraviolet light polymerization, great care and time can be used when seating the matrix and compacting the composite. In these circumstances the cellulose acetate matrices are strong enough on their own, especially when the compaction pressure is reduced. by vent holes pierced in the incisal edges and corners. When a chemically polymerized composite is used the cellulose acetate matrices are usually
Fig. I.-Case
of incremental
I. Discoloration lines.
and accentuation
I. 3211123 after partial removal of labial face enamel. Note the accessible margins.
Fig. Z.-Case
Fig. J.-Case
1. Custom-made matrix on q with occlusal stops on 411. Polymerized composite (Nuva-Fil) with flashprior to trimming on _. II23
Fig. I.-Case
sufficiently rigid to allow full seating of the matrix and composite for one or two teeth. However, where the volume of composite is large and several teeth are involved, the working time is too short for adequate seating of the matrix without distorting or even splitting the matrices. This can be overcome as follows: the cellulose acetate matrices are constructed as described for types 1 and 2 and placed on the original study models, and a supporting matrix or blanket of dental composition is made by warming dental composition and moulding it around the matrices. The dental composition provides sufficient support for the cellulose acetate matrices so that when the composite is being carried to the teeth being restored, sufficient pressure can be applied to ensure complete seating of the matrices. Because of the bulk of the composition it is more difficult to drill vent holes, and
so to avoid trapping air bubbles in the composite greater care must be taken when loading the matrices. The 2 cases presented here illustrate special matrices of types 1 and 2. Matrix type 3 is not illustrated as it is either type 1 or 2 supported by dental composition.
I. Completed restorations on -7 3211123 trimmed and glazed.
CASE REPORTS Case 1 The patient was a 13-year-old girl with severe tetracycline staining of all her teeth. Her Class II division 1 malocclusion had been treated using fixed appliances and she was now out of retention. Eventually porcelain jacket crowns are to be made, but because of the risk of pulpal damage at this early age these restorations are not to be attempted until the patient is at least 18 years old. The appearance of the teeth was unsightly, and at the request of the parents and child an attempt to
Roberts:
Acid-etch
and Composite
Technique
2. 32123well-aligned and stable, but the size and shape of these teeth make them unsightly.
Fig. 5.-Case
improve their aesthetics with interim restorations was carried out. A matrix of type I was constructed to fit 3211123. -Fig. I shows the teeth to be restored at the time of making the study models. A layer of enamel of 1.0-1.5 mm was removed from the labial surface of 3211123.Care was taken to keep all the margins of the preparation accessible (Fig. 2). In Fig. 3 the composite (Nuva-Fil*) has been applied to lg but the flash has not been trimmed away. The custom-made matrix with occlusal stops on If and 41 has been inserted to check for proper seating. The completed restorations, trimmed and glazed, are shown in Fig. 4. Case 2 The patient was a 15year-old boy in whom @ had been severely fractured. As space was needed to correct a malocclusion these teeth were extracted and 212 and 313 moved mesially with a fixed appliancrAs in?u.re 1, porcelain jacket crowns are planned but for the same reason are to be delayed until the patient is 18 years old. Composite crowns retained by the acid-etched enamel were constructed. Because of the need to place the composite between the teeth as well as labially and palatally it was decided to use separate matrices of type 2. The shape of 32123 was such that some enamel had to be removed from the tips as well as from the most bulbous part of the buccal surfaces of the canines (Fig. 5). This enamel is usually removed before the impression for the study model is made. *Nuva System, Caulk Division, Amalgamated Dental, London. ?Alphafil, Amalgamated Dental, London.
Fig. 6.-Case
2. Custom-made matrices tried in place on 212 only; the space created for the composite can be visualized.
Fig. 7.-Case 2. Completed fil), trimmed and glazed.
When mouth needed pleted glazed,
restorations
(Alpha-
completed, the matrices were tried in the to estimate the amount of composite (Fig. 6 shows matrices on 212). The comrestorations of Alphafil,t%immed and are shown in Fig. 7.
CONCLUSIONS The matrix techniques described here have been found to be satisfactory in the hands of operators of both limited and wide experience. It has been found that the chairside time necessary for the type of restorations described is greatly reduced by using special matrices. The amount of flash at the margins of the restorations is usually much less and consequently it is easier and quicker to finish the restorations. The excellent surface finish of the restorations rarely needs to be disturbed.
194
Acknowledgements I wish to thank Mr Malcolm Pratt for carrying out the technical work and Mr H. S. Orton for allowing publication of case records of patients who were under his care. REFERENCES BAKER D. L. and CURSONI. (1974) A high speed method for finishing cavity margins. Br. Dent. J. 137, 391-396.
Journal
of Dentistry,
Vol. ~/NO.
4
NEY (1964) Ney Z&J and Crown Manual. J. M. Ney Co., Hartford, Connecticut, USA, pp. 1617. ROBERTSG. J. (1975) The acid etch technique in dentistry for children and adolescents. J. Znt. Assoc. Dent. Child. 6, 29-37.
of Dentistry,
4, 190-I
94
Matrices for the acid-etch composite technique Graham J. Roberts,
and
BDS
Department of Children’s Dentistrv, School of Dental Surgery, Royal Dental Hospital of London . ABSTRACT
The indications, method of construction and use of special matrices for the acid-etch and composite technique are discussed. Two case histories illustrating their use are presented.
INTRODUCTION remarkable retention of composite and unfilled resins to acid-etched enamel has led to the use of composite filling materials in a variety of situations which previously could only be restored with conventional techniques. When attempting to restore lost tooth structure, reshape malformed teeth and mask stained or hypoplastic tooth surfaces it is necessary to use a matrix. The matrices currently available are the flat plastic instrument, cellulose acetate strips and preformed cellulose acetate crown forms. Frequently situations arise where these matrices are not suitable and it is necessary to construct special matrices. This article describes three techniques for fabricating special matrices. Details of the acid-etch technique and its many applications where these matrices have been used are described elsewhere (Roberts, 1975).
THE
CONSTRUCTION MATRICES
OF SPECIAL
In its simplest form a matrix can be made by thermomoulding* a cellulose acetate sheetf on *Drufomat Pressure Moulding Machine, Dreve Dentamid, Uhna, Germany (available from Panadent, London). TDrufolit Cellulose Acetate Sheets, 120 mm diameter x O-5mm thick, Dreve Dentamid, Uhna, Germany.
to a work model. The moulded sheet is then trimmed and may be used directly in the mouth. Where multiple restorationsareplanned it may be necessary to make two or three separate matrices. The way in which the matrix is made will be determined by several factors : 1. The amount of space needed for the composite, and the manner in which this space is created. 2. Whether a single matrix covering several teeth or separate matrices for each tooth are to be created. 3. Whether the composite is to be polymerized by ultraviolet or chemical means. These considerations have resulted in three types of matrix. Type 1 With a localized discoloration, such as nonendemic mottling, the matrix is usually made to fit the existing tooth structure and, at the time of restoration, the space for the composite is created by removing the mottled enamel with an airotor. The matrix thus restores the pre-existing tooth structure. With a fractured incisor, it is necessary to restore the lost tooth structure on the work model before the matrix is made. Where the space for the composite is to be created by removing enamel at the time of operation the matrix is fabricated directly on to a work model of the patient’s mouth. It is usually advisable to trim the matrix in excess of the area to be restored as this provides stability, especially when occlusal stops are made on adjacent teeth (see Case 1). If the tooth structure is missing or it is necessary to increase the size of a given tooth
Roberts
: Acid-etch
and Composite
Technique
191
or group of teeth the matrix cannot be fabricated directly on to the patient’s study model. The procedure for dealing with such a problem is as follows: a. Using blue inlay wax, the desired crown morphology is created on the work model. This technique is suitable for small volumes such as a fractured incisal edge or a peg lateral being transformed to a normal shape and size. Where large volumes or numbers of teeth are to be restored it is sometimes easier to use plastic denture teeth, trim them to the required size and fix them to the work model with sticky wax. h. The resulting model is then duplicated, thus providing a stone work model. This is necessary as the heat used in the thermomoulding process is sufficient to melt the inlay wax or sticky wax holding the denture teeth to the model. c. The moulded acetate sheet is trimmed to a convenient size. Tn these cases there is only a small amount of contact between the matrix and the existing tooth structure, so the number and location of occlusal stops are critical. d. When the matrix is located on the original study model the amount of space created for the composite can be visualized. It should be noted that in a given situation a combination of enamel removal and addition with composite can be used to reshape a given tooth. Type 2 In the situation described above, the composite is usually applied on either the labial or the palatal surface only. This results in a flash of polymerized composite across the interdental space. The flash can be trimmed away using fine diamond burrs followed by tungsten carbide finishing burrs (Baker and Curson, 1974) and special composite finishing strips.* Where the restorations involve the mesial and distal surfaces of the teeth it is necessary to construct individual matrices completely encircling each tooth. On the conventional work model the teeth are so close together that the cellulose acetate *Composite Finishing Strips, Dental and Polishing System, 3M Dental London.
Finishing Products,
sheet cannot be thermomoulded to encircle each tooth. To overcome this it is necessary to construct a work model where the individual teeth can be separated sufficiently to allow the thermomoulded matrices to encircle each tooth. This can be achieved by constructing the work model using similar techniques to those for constructing work models for crown and bridgework. Both the ‘boat’ technique and the dowel technique (Ney, 1964) have been found to be satisfactory. Both techniques involve sawing the model through the interproximal space. If the space for the composite is to be created by removing enamel, the matrices are made directly on to the separated models of individual teeth. Where the space is to be created on the work model, the individual teeth are modified with inlay wax as in the single matrix technique. The individual modelled teeth are then duplicated and the individual matrices constructed on the duplicates.When the matrices are replaced on the original work model the space created for the composite can be seen.
Type
3
If an ultraviolet-light-polymerized composite is to be used it is necessary for the matrix to allow the transmission of ultraviolet light to the unpolymerized composite. The cellulose acetate is sufficiently transparent to allow ultraviolet light to pass through it and bring about complete polymerization of the composite, provided that the composite layer is not more than 1.0-1.5 mm thick. In the incisal edge region, where the light can be applied palatally as well as labially, the thickness can increase to 2.0-3.0 mm. Because of the unlimited working time afforded by ultraviolet light polymerization, great care and time can be used when seating the matrix and compacting the composite. In these circumstances the cellulose acetate matrices are strong enough on their own, especially when the compaction pressure is reduced. by vent holes pierced in the incisal edges and corners. When a chemically polymerized composite is used the cellulose acetate matrices are usually
Fig. I.-Case
of incremental
I. Discoloration lines.
and accentuation
I. 3211123 after partial removal of labial face enamel. Note the accessible margins.
Fig. Z.-Case
Fig. J.-Case
1. Custom-made matrix on q with occlusal stops on 411. Polymerized composite (Nuva-Fil) with flashprior to trimming on _. II23
Fig. I.-Case
sufficiently rigid to allow full seating of the matrix and composite for one or two teeth. However, where the volume of composite is large and several teeth are involved, the working time is too short for adequate seating of the matrix without distorting or even splitting the matrices. This can be overcome as follows: the cellulose acetate matrices are constructed as described for types 1 and 2 and placed on the original study models, and a supporting matrix or blanket of dental composition is made by warming dental composition and moulding it around the matrices. The dental composition provides sufficient support for the cellulose acetate matrices so that when the composite is being carried to the teeth being restored, sufficient pressure can be applied to ensure complete seating of the matrices. Because of the bulk of the composition it is more difficult to drill vent holes, and
so to avoid trapping air bubbles in the composite greater care must be taken when loading the matrices. The 2 cases presented here illustrate special matrices of types 1 and 2. Matrix type 3 is not illustrated as it is either type 1 or 2 supported by dental composition.
I. Completed restorations on -7 3211123 trimmed and glazed.
CASE REPORTS Case 1 The patient was a 13-year-old girl with severe tetracycline staining of all her teeth. Her Class II division 1 malocclusion had been treated using fixed appliances and she was now out of retention. Eventually porcelain jacket crowns are to be made, but because of the risk of pulpal damage at this early age these restorations are not to be attempted until the patient is at least 18 years old. The appearance of the teeth was unsightly, and at the request of the parents and child an attempt to
Roberts:
Acid-etch
and Composite
Technique
2. 32123well-aligned and stable, but the size and shape of these teeth make them unsightly.
Fig. 5.-Case
improve their aesthetics with interim restorations was carried out. A matrix of type I was constructed to fit 3211123. -Fig. I shows the teeth to be restored at the time of making the study models. A layer of enamel of 1.0-1.5 mm was removed from the labial surface of 3211123.Care was taken to keep all the margins of the preparation accessible (Fig. 2). In Fig. 3 the composite (Nuva-Fil*) has been applied to lg but the flash has not been trimmed away. The custom-made matrix with occlusal stops on If and 41 has been inserted to check for proper seating. The completed restorations, trimmed and glazed, are shown in Fig. 4. Case 2 The patient was a 15year-old boy in whom @ had been severely fractured. As space was needed to correct a malocclusion these teeth were extracted and 212 and 313 moved mesially with a fixed appliancrAs in?u.re 1, porcelain jacket crowns are planned but for the same reason are to be delayed until the patient is 18 years old. Composite crowns retained by the acid-etched enamel were constructed. Because of the need to place the composite between the teeth as well as labially and palatally it was decided to use separate matrices of type 2. The shape of 32123 was such that some enamel had to be removed from the tips as well as from the most bulbous part of the buccal surfaces of the canines (Fig. 5). This enamel is usually removed before the impression for the study model is made. *Nuva System, Caulk Division, Amalgamated Dental, London. ?Alphafil, Amalgamated Dental, London.
Fig. 6.-Case
2. Custom-made matrices tried in place on 212 only; the space created for the composite can be visualized.
Fig. 7.-Case 2. Completed fil), trimmed and glazed.
When mouth needed pleted glazed,
restorations
(Alpha-
completed, the matrices were tried in the to estimate the amount of composite (Fig. 6 shows matrices on 212). The comrestorations of Alphafil,t%immed and are shown in Fig. 7.
CONCLUSIONS The matrix techniques described here have been found to be satisfactory in the hands of operators of both limited and wide experience. It has been found that the chairside time necessary for the type of restorations described is greatly reduced by using special matrices. The amount of flash at the margins of the restorations is usually much less and consequently it is easier and quicker to finish the restorations. The excellent surface finish of the restorations rarely needs to be disturbed.
194
Acknowledgements I wish to thank Mr Malcolm Pratt for carrying out the technical work and Mr H. S. Orton for allowing publication of case records of patients who were under his care. REFERENCES BAKER D. L. and CURSONI. (1974) A high speed method for finishing cavity margins. Br. Dent. J. 137, 391-396.
Journal
of Dentistry,
Vol. ~/NO.
4
NEY (1964) Ney Z&J and Crown Manual. J. M. Ney Co., Hartford, Connecticut, USA, pp. 1617. ROBERTSG. J. (1975) The acid etch technique in dentistry for children and adolescents. J. Znt. Assoc. Dent. Child. 6, 29-37.
