The composite resin dowel and core Gerald J. Stahl, D.D.S., and Robert B. O'Neai, D.D.S. General Leonard Wood Army Hospital, Fort Leonard Wood, Mo.
T o d a y ' s elnphasis on the maintenance and preservation of the natural dentition, combined with the success of endodontically treated teeth, has resulted in a variety of procedures to restore pulpless teeth. Unfortunately, the exact minimal mechanical and physical properties required for a dowel and core have not yet been defined. Until controlled clinical investigations provide suet1 guidelines, many materials must be tried and evaluated. Alternatives to the cast gold dowel and core include prefabricated steel dowels and numerous techniques employing pins, amalgam, and resin. ~j Although pins have been popular in recent years, they have only been shown to increase retention. They do not increase the compressive strength of a material and actually decrease tensile strength. '~ Since pins tend to weaken the remaining tooth structure, they may result in further damage to the tooth. The purpose of this study was to determine, through clinical and laboratory studies, the possibility of utilizing composite resin in the construction of dowels and cores. The technique, which will be described, requires only one visit for the patient, few instruments, and no aid from a dental laboratory. MATERIALS Composite resins were introduced in late 1965 and are superior to conventional acrylic resins with respect to compressive strength, tensile strength, modulus of elasticity, hardness, resistance to abrasion, polymerization shrinkage, and thermal expansion. c' The composite resin used in this study was Adaptic, ~ which has been shown to have properties comparable or superior to those of other brands, r' s The physical properties of Adaptic compare favorably with those of (1) other composite resins, (2) tooth structure, and (3) amalgam, as shown in Table I. This table also illustrates that Adaptic is superior to acrylic resin and silicate in ahnost every respect. It does not contract away from the cavity wall when inserted in a single increment." Because of its wetting and spreading qualities, Adaptic has been shown to exhibit a closer #Johnson & Johnson, New Brunswick, N. J.
642
Composite resin dowel and core
voL,,:,~ 33 Nmnber 6
643
Table I
•_- Material Tooth Ada ptic Composite resin Acrylic resin Amalgam Silicate Gold (Type ll) Gold (Type I1I)
[
Compressive strength (p.s.i.) 33,000 to 44,000o 33,0007 to 38,000s 18,000to 34,000° 10,7008 57,000° 23,000° NA NA
l
Tensile strength (p.s.i.) 1,500 to 7,500° 6, 1007to 7,1308 3,400 to 5,000° 4,000° 8,500° 440 to 1,0009 23,000 to 38,000* 38,500 to 46,500*
[ strength
expansion[
[
(ppm/°C.) I hardness
(p.s.i.) 14,000~ 8,700° 8,700" ~ ~ 5,1009 NA NA
11° 22~ 20 to 50~ 127~ 259 88 NA NA
Knoop 3009 70 to 80° 70 to 80° 16~. 90~ 709 113 to 153t 134 to 247J"
~NationaI Bureau of Standards. ~'The J. M. Ney Company.
m a r g i n a l a n d cavity a d a p t a t i o n than has been seen in the other composite resins and amalgam. This has been verified with isotope studies, a°
METHODS Clinical method. Before any nonvital tooth is restored, a complete pulpal, periodontal, and periapical diagnosis should be made. If it is determined t h a t the tooth can be restored, then endodontic therapy can be initiated. T h e tooth t h a t is to receive a dowel and core should have its canal filled with g u t t a - p e r c h a or a twist-off silver cone.
T h e preparation of the root canal for the dowel can be instituted after a thorough study of the radiographs. T h e p r e p a r a t i o n of the canal has been traditionally equal to tile length of the clinical crown or one half of the root length. In this study, this rule was adhered to, not with retention as the objective b u t with the distribution of forces in mind. Retention of the composite resin dowel and core is not d e p e n d e n t on length, but r a t h e r on multiple undercuts placed in the canal with a No. ~ r o u n d bur and on the natural irregularity of the canal. T h e dowel must be of sufficient length and a design to distribute the forces of leverage and torque t h r o u g h o u t the remaining portion of the t o o t h . " T h e desired length is verified by radiographs. Preparation of the canal is simple. :\ g u t t a - p e r c h a root canal filling may be removed to the desired depth witl~ reamers. T h e twist-off silver cone is readily removed. T h e sealer m a y be removed with reamers. T h e orifice of the canal is enlarged with a No. 8 round bur. This increases the bulk of material at the junction of the dowel a n d core and thus increases resistance to shearing and tensile stresses. A dovetail is placed in the area of the greatest bulk of tooth structure, usually lingually, to resist rotational forces (Fig. 1). With preparation of the canal and coronal structure complete, a polycarbonate crown can now be selected to fit the tooth. T h e crown is tried on and adjusted until all margins a p p r o x h n a t e tooth structure. T h e internal surface of the crown is then lubricated. This crown will be used as a matrix to carry the core portion of the composite resin and later can serve as a t e m p o r a r y restoration. T h e gingival sulcus is
644
Stahl and O'Neal
J. Prosthet. Dent. June, 1975
Fig. 1. These three teeth were fractured as a result of trauma. The canals a,nd cervical portions were prepared after endodontic therapy to receive composite resin dowels and cores. Fig. 2. The composite resin is injected into the canal and overflowed. packed with retraction cord to reduce contaminants that might interfere with adaptation of the composite resin to the prepared tooth. In addition, the retraction cord prevents flash from accumulating in the gingival sulcus and prevents injury to the gingiva during crown preparation. The canal is now air dried and ready for the dowel and core construction. A Clev-Dent C-R syringe ~' is used to insert the composite resin into the canal. These syringes are supplied with disposable plastic tips. The tips must be shortened about 2 to 3 ram. to allow for a larger orifice and facilitate the flow of the material from the syringe. After clipping off the 2 to 3 ram. segment, an explorer should be inseried in the tip to insure free passage. In order to simulate conditions found in dental practice, the universal and catalyst components of tile composite resin were not weighed. The pastes were mixed for 30 seconds with the spatula provided by the manufacturer. The plastic tip was loaded by repeatedly pressing the tip down on the pad, forcing the material into the tip. The rubber plunger was inserted into the tip which was placed into the syringe. The tip was inserted into the prepared canal as far apically-as possible, and the material ejected. The back pressure will force the syringe out of the canal. The entire canal was filled and excess material permitted to flow over the coronal preparation (Fig. 2). While the dentist was inserting the dowel material, an assistant loaded the core material from the same mix into the previously prepared polycarbonate crown. The loaded crown was placed on the tooth and joined to the dowel material (Fig. 3). The total time for insertion was one and one-half minutes. When the material became stiff but not completely set, the flash was removed with an explorer. The crown was left in place for eight minutes and then removed. The core was then ready for preparation (Fig. 4). The finish line of the preparation was placed on at least 1 mm. of sound tooth structure, not on composite resin. This precaution is important, because during mastication, the final restoration exerts more force on the cervical portion of tt~e preparation than on the incisal part. 1~ With the preparation complete (Fig. 5), the gingiva is retracted, and an impression is made immediately. The polycarbonate *Clev-Dent Div., Cavitron Corp., Cleveland, Ohio.
Voh.,,~ 33 Nttmber 6
Composite resin dowel and core
645
Fig. 3. The polycarbonate crowns carrying the core portion of the material are in place. Fig. 4. The cores are ready to be prepared.
Fig. 5. The preparations are completed for porcelain-fused-to-gold crowns. Fig. 6. The crowns cemented in place.
crown now becomes the temporary restoration. The impression is poured and sent to the laboratory for fabrication of the final restoration (Fig. 6). Over a period of six months, 36 teeth were treated using the above procedure. Of the teeth treated, 18 were central incisors, seven were lateral incisors, five were cuspids, four were premolars, and two were molars. All teeth treated were in the maxillary arch except one molar. Laboratory investigation. The laboratory portion of this study was directed toward verifying the clinical technique. We did not consider it necessary to test the physical characteristics of the material, since these have been well documented by previous studies, v, J~, 1~ Tile objective in the laboratory was to determine if our technique of material placement was consistent and void free. One-hundred recently extracted, anterior and premolar, maxillary and mandibular teeth were utilized in this part of tlae stud),. They were stored in physiologic saline until used. All teeth were prepared in a manner similar to the described clinical technique, including endodontic preparation. The teeth were divided into four groups. In Group I (30 teeth), the composite resin was inserted with the same C-R syringe that was used clinically. In Group II (30 teeth), the composite resin was condensed into the prepared canal with a nonserrated amalgam condenser. In Group III, the
646
Stahl and O'Neal
j. l'rom,,,t. June,Dent. 1975
Fig. 7. Sectioned teeth representative of those in Group IV, Note the absence of voids and the intimate relatioaship between the composite resin and the tooth structure.
material was spiralled into the canal with a motor-driven rotary instrument. After attempting this on 10 teeth, the technique was abandoned due to the inability to force the material into the canal. In Group IV (30 teeth), the canal was filled by inserting the dowel material with the syringe, and in addition, the core was placed with previously adapted polycarbonate crowns. In each group, half of the teeth were prepared and treated hy each author. This was clone to determine any variation in results due to the individual method of each investigator. All specimens were sectioned at the periphery and the center of the dowels in the long axis of the tooth. Half of the specimens were sectioned buccolingually and half mesiodistally (Fig. 7). All specimens were mounted on glass slides and examined at 28x for voids in the material. A binocular, compound stereomicroscope with a direct light source, a horsehair ocular, and a calibrated stage capable of measurement to 0.1 ram. was used. RESULTS
Of the 36 clinically treated teeth, 33 are still stable, sound, and functional as verified by three-, six-, and 12 month postoperative clinical and radiographic examinations. The three failures resulted from traumatic injury. Although the injury was severe enough to require hospitalization, there were no root fractures of the involved teeth. These maxillary anterior teeth were retreated and are again functioning satisfactorily. In Group I of the laboratory tested teeth, all 30 teeth (100 per cent) treated by use of the syringe technique were free of voids. In Group II, 28 of the 30 teeth (94 per cent) filled by the condensation technique had one or more voids varying in size from 0.5 to 1.9ram. in diameter. Group III was excluded from the study. In Group IV, all 30 teeth were void free in the dowel portion, but eight teeth (26 per cent)
V,,h,,,,, a:~ Ii
Number
Composite resin dowel and core
647
exhibited voids in the core~ortion ranging in size from 0.6 to 1.0 mm. However, there were no voids at the junction of the dowel and the core, where they could prodace a weakness, iI1 any of the specimens. All the voids were in the core and would be eliminated during preparation of the crown. DISCUSSION
The composite resin dowel and core is a practical alternative to the cast gold dowel and core. Although it does not have the tensile or compressive strength of gold, preliminary studies have shown that it is strong enough to withstand normal masticatory forces. ~t The composite resin dowel and core appears to be more retentive than the gold dowel and core. This was verified in the previously mentioned case of the patient sustaining the traumatic injury. Although all three crowns and underlying cores were completely fra,.,tured, the dowel portion remained in each canal. The composite resin will fracture before it will dislodge, thus protecting the remaining root against injury when encountering traumatic forces. Because retention is achieved primarily by undercuts, the length of the dowel preparation need not be equal to that for gold, reducing the possibility of perforation. The technique presented eliminates considerable time and expense for both the dentist andlth.e~patient. It requires only one visit for the patient, and the dentist can fill the root canal, construct the dowel and core, make the crown preparation, and take the final impression in one appointment. The composite resin dowel and core is ideally suited for teeth with irregular root canals, because it does not require a conyerging path of insertion. It is also indicated in other conditions in which the cast gold dowel and core is not (i.e., multirooted, tilted, and short-rooted teeth). Because of its translucency, composite resin appears to be superior to cast gold under a complete porcelain-veneer crown. The laboratory results verified that our clinical technique produced void-free dowels. The insertion techniques showed that it is desirable to use the syringe for placement of the dowel material. Clinically, all the dowels and cores have been functioning for one ),ear. Excluding the,-three lost through trauma, there have been no postoperative problems. There have been no patient complaints, and clinical and radiographic examinations have revealed no complications. SUMMARY AND CONCLUSIONS
Utilizing composite resin, a new technique was introduced for the construction of dowels and cores. The results presented were drawn from a I2 month clinical and laboratory study. Although more time may be needed for further evaluation, preliminary results indicate that the composite resin dowel and core, along with the final restoration, fulfills the objectives of restoring the pulpless tooth to health, function, and esthetics. References 1. Watson, R. J.: The Amalgam Core, J. PROSTItET. DENT. 19: 500-505, 1968. 2. Waxman, H. N.: A One Visit Gore Procedure for Non-Vital Teeth, Worcester Med. News 34: '..)4-26, 1970. 3. Sehuhnan, L. S.: Plastic Pin Cores, Dent. Dig. 76: 429-430, 1970.
648
Stahl and O'Neal
J. Prosthet. Dent. Juuc, 1975
4. Baraban, D. J.: A Simplified Method for Making Posts and Cores, J. PROSTHET. DENT. 24: 287-297, 1970. 5. Going, R. E., Moffa, J. P., lNostrant, G. W., et al.: The Str,mgth of Dental Amalg/am as Influenced by Pins, J. Am. Dent. Assoc. 77: 1331-1334, 1968. 6. Stanford, J. W.: The Current Status of Restor;xtive Resins, Dent. Clin. North A~n. 15: 57-66, 1971. 7. Phillips, R. W., Swartz, M. L., and Norman, R. D.: Materials for the Practicing Dentist, St. Louis, 1969, The C. V. Mosby Company, p. 185. 8. Hollenback, G. M.: A Further Report on the Physical Properties of Five Composite Resins, Part II, J. Am. Dent. Assoc. 55: 17-33, 1971. 9. Phillips, R. W.: Composite Restorative Resins, J. Am. Dent. Assoc. 80: 357-358, 1970. 10. Lee, H. L., and Swartz, M. L.: Scanning Electron Microscope Study of Composite Restorative Materials, J. Dent. Res. 49: 149-158, 1970. 1 I. Sheets, C. E.: Dowel and Core Foundations, J. PROSTHET. DENT. 23: 58-65, 1970. I2. Dooley, B. S.: Preparz~tion and Construction of Post-Retention Crowns for Anterior Teeth, Aust. Dent. J. 12: 54~-550, 1967. 13. Lee, H. L., Swartz, M. L., and Smith, F. F.: Physical Properties of Four Thermosetting Dental Restorative Resins, J. Dent. Res. 48: 526-535, 1969. 14. Phillips, R. W., Avery, D. R., Mikra, R., et al.: One-Year Observations on a Composite Resin for Class II Restorations, J. PROSTHET. DENT. 26: 68-77, 1971. DR. STAHL 3415 HERITAGE RD. COLUMBUS, IND. 47201 DR. O'NEAL 279TJ:t STATION HOSPITAL BERLIN~ GERMANY
APO N~w YORK 09742
T o d a y ' s elnphasis on the maintenance and preservation of the natural dentition, combined with the success of endodontically treated teeth, has resulted in a variety of procedures to restore pulpless teeth. Unfortunately, the exact minimal mechanical and physical properties required for a dowel and core have not yet been defined. Until controlled clinical investigations provide suet1 guidelines, many materials must be tried and evaluated. Alternatives to the cast gold dowel and core include prefabricated steel dowels and numerous techniques employing pins, amalgam, and resin. ~j Although pins have been popular in recent years, they have only been shown to increase retention. They do not increase the compressive strength of a material and actually decrease tensile strength. '~ Since pins tend to weaken the remaining tooth structure, they may result in further damage to the tooth. The purpose of this study was to determine, through clinical and laboratory studies, the possibility of utilizing composite resin in the construction of dowels and cores. The technique, which will be described, requires only one visit for the patient, few instruments, and no aid from a dental laboratory. MATERIALS Composite resins were introduced in late 1965 and are superior to conventional acrylic resins with respect to compressive strength, tensile strength, modulus of elasticity, hardness, resistance to abrasion, polymerization shrinkage, and thermal expansion. c' The composite resin used in this study was Adaptic, ~ which has been shown to have properties comparable or superior to those of other brands, r' s The physical properties of Adaptic compare favorably with those of (1) other composite resins, (2) tooth structure, and (3) amalgam, as shown in Table I. This table also illustrates that Adaptic is superior to acrylic resin and silicate in ahnost every respect. It does not contract away from the cavity wall when inserted in a single increment." Because of its wetting and spreading qualities, Adaptic has been shown to exhibit a closer #Johnson & Johnson, New Brunswick, N. J.
642
Composite resin dowel and core
voL,,:,~ 33 Nmnber 6
643
Table I
•_- Material Tooth Ada ptic Composite resin Acrylic resin Amalgam Silicate Gold (Type ll) Gold (Type I1I)
[
Compressive strength (p.s.i.) 33,000 to 44,000o 33,0007 to 38,000s 18,000to 34,000° 10,7008 57,000° 23,000° NA NA
l
Tensile strength (p.s.i.) 1,500 to 7,500° 6, 1007to 7,1308 3,400 to 5,000° 4,000° 8,500° 440 to 1,0009 23,000 to 38,000* 38,500 to 46,500*
[ strength
expansion[
[
(ppm/°C.) I hardness
(p.s.i.) 14,000~ 8,700° 8,700" ~ ~ 5,1009 NA NA
11° 22~ 20 to 50~ 127~ 259 88 NA NA
Knoop 3009 70 to 80° 70 to 80° 16~. 90~ 709 113 to 153t 134 to 247J"
~NationaI Bureau of Standards. ~'The J. M. Ney Company.
m a r g i n a l a n d cavity a d a p t a t i o n than has been seen in the other composite resins and amalgam. This has been verified with isotope studies, a°
METHODS Clinical method. Before any nonvital tooth is restored, a complete pulpal, periodontal, and periapical diagnosis should be made. If it is determined t h a t the tooth can be restored, then endodontic therapy can be initiated. T h e tooth t h a t is to receive a dowel and core should have its canal filled with g u t t a - p e r c h a or a twist-off silver cone.
T h e preparation of the root canal for the dowel can be instituted after a thorough study of the radiographs. T h e p r e p a r a t i o n of the canal has been traditionally equal to tile length of the clinical crown or one half of the root length. In this study, this rule was adhered to, not with retention as the objective b u t with the distribution of forces in mind. Retention of the composite resin dowel and core is not d e p e n d e n t on length, but r a t h e r on multiple undercuts placed in the canal with a No. ~ r o u n d bur and on the natural irregularity of the canal. T h e dowel must be of sufficient length and a design to distribute the forces of leverage and torque t h r o u g h o u t the remaining portion of the t o o t h . " T h e desired length is verified by radiographs. Preparation of the canal is simple. :\ g u t t a - p e r c h a root canal filling may be removed to the desired depth witl~ reamers. T h e twist-off silver cone is readily removed. T h e sealer m a y be removed with reamers. T h e orifice of the canal is enlarged with a No. 8 round bur. This increases the bulk of material at the junction of the dowel a n d core and thus increases resistance to shearing and tensile stresses. A dovetail is placed in the area of the greatest bulk of tooth structure, usually lingually, to resist rotational forces (Fig. 1). With preparation of the canal and coronal structure complete, a polycarbonate crown can now be selected to fit the tooth. T h e crown is tried on and adjusted until all margins a p p r o x h n a t e tooth structure. T h e internal surface of the crown is then lubricated. This crown will be used as a matrix to carry the core portion of the composite resin and later can serve as a t e m p o r a r y restoration. T h e gingival sulcus is
644
Stahl and O'Neal
J. Prosthet. Dent. June, 1975
Fig. 1. These three teeth were fractured as a result of trauma. The canals a,nd cervical portions were prepared after endodontic therapy to receive composite resin dowels and cores. Fig. 2. The composite resin is injected into the canal and overflowed. packed with retraction cord to reduce contaminants that might interfere with adaptation of the composite resin to the prepared tooth. In addition, the retraction cord prevents flash from accumulating in the gingival sulcus and prevents injury to the gingiva during crown preparation. The canal is now air dried and ready for the dowel and core construction. A Clev-Dent C-R syringe ~' is used to insert the composite resin into the canal. These syringes are supplied with disposable plastic tips. The tips must be shortened about 2 to 3 ram. to allow for a larger orifice and facilitate the flow of the material from the syringe. After clipping off the 2 to 3 ram. segment, an explorer should be inseried in the tip to insure free passage. In order to simulate conditions found in dental practice, the universal and catalyst components of tile composite resin were not weighed. The pastes were mixed for 30 seconds with the spatula provided by the manufacturer. The plastic tip was loaded by repeatedly pressing the tip down on the pad, forcing the material into the tip. The rubber plunger was inserted into the tip which was placed into the syringe. The tip was inserted into the prepared canal as far apically-as possible, and the material ejected. The back pressure will force the syringe out of the canal. The entire canal was filled and excess material permitted to flow over the coronal preparation (Fig. 2). While the dentist was inserting the dowel material, an assistant loaded the core material from the same mix into the previously prepared polycarbonate crown. The loaded crown was placed on the tooth and joined to the dowel material (Fig. 3). The total time for insertion was one and one-half minutes. When the material became stiff but not completely set, the flash was removed with an explorer. The crown was left in place for eight minutes and then removed. The core was then ready for preparation (Fig. 4). The finish line of the preparation was placed on at least 1 mm. of sound tooth structure, not on composite resin. This precaution is important, because during mastication, the final restoration exerts more force on the cervical portion of tt~e preparation than on the incisal part. 1~ With the preparation complete (Fig. 5), the gingiva is retracted, and an impression is made immediately. The polycarbonate *Clev-Dent Div., Cavitron Corp., Cleveland, Ohio.
Voh.,,~ 33 Nttmber 6
Composite resin dowel and core
645
Fig. 3. The polycarbonate crowns carrying the core portion of the material are in place. Fig. 4. The cores are ready to be prepared.
Fig. 5. The preparations are completed for porcelain-fused-to-gold crowns. Fig. 6. The crowns cemented in place.
crown now becomes the temporary restoration. The impression is poured and sent to the laboratory for fabrication of the final restoration (Fig. 6). Over a period of six months, 36 teeth were treated using the above procedure. Of the teeth treated, 18 were central incisors, seven were lateral incisors, five were cuspids, four were premolars, and two were molars. All teeth treated were in the maxillary arch except one molar. Laboratory investigation. The laboratory portion of this study was directed toward verifying the clinical technique. We did not consider it necessary to test the physical characteristics of the material, since these have been well documented by previous studies, v, J~, 1~ Tile objective in the laboratory was to determine if our technique of material placement was consistent and void free. One-hundred recently extracted, anterior and premolar, maxillary and mandibular teeth were utilized in this part of tlae stud),. They were stored in physiologic saline until used. All teeth were prepared in a manner similar to the described clinical technique, including endodontic preparation. The teeth were divided into four groups. In Group I (30 teeth), the composite resin was inserted with the same C-R syringe that was used clinically. In Group II (30 teeth), the composite resin was condensed into the prepared canal with a nonserrated amalgam condenser. In Group III, the
646
Stahl and O'Neal
j. l'rom,,,t. June,Dent. 1975
Fig. 7. Sectioned teeth representative of those in Group IV, Note the absence of voids and the intimate relatioaship between the composite resin and the tooth structure.
material was spiralled into the canal with a motor-driven rotary instrument. After attempting this on 10 teeth, the technique was abandoned due to the inability to force the material into the canal. In Group IV (30 teeth), the canal was filled by inserting the dowel material with the syringe, and in addition, the core was placed with previously adapted polycarbonate crowns. In each group, half of the teeth were prepared and treated hy each author. This was clone to determine any variation in results due to the individual method of each investigator. All specimens were sectioned at the periphery and the center of the dowels in the long axis of the tooth. Half of the specimens were sectioned buccolingually and half mesiodistally (Fig. 7). All specimens were mounted on glass slides and examined at 28x for voids in the material. A binocular, compound stereomicroscope with a direct light source, a horsehair ocular, and a calibrated stage capable of measurement to 0.1 ram. was used. RESULTS
Of the 36 clinically treated teeth, 33 are still stable, sound, and functional as verified by three-, six-, and 12 month postoperative clinical and radiographic examinations. The three failures resulted from traumatic injury. Although the injury was severe enough to require hospitalization, there were no root fractures of the involved teeth. These maxillary anterior teeth were retreated and are again functioning satisfactorily. In Group I of the laboratory tested teeth, all 30 teeth (100 per cent) treated by use of the syringe technique were free of voids. In Group II, 28 of the 30 teeth (94 per cent) filled by the condensation technique had one or more voids varying in size from 0.5 to 1.9ram. in diameter. Group III was excluded from the study. In Group IV, all 30 teeth were void free in the dowel portion, but eight teeth (26 per cent)
V,,h,,,,, a:~ Ii
Number
Composite resin dowel and core
647
exhibited voids in the core~ortion ranging in size from 0.6 to 1.0 mm. However, there were no voids at the junction of the dowel and the core, where they could prodace a weakness, iI1 any of the specimens. All the voids were in the core and would be eliminated during preparation of the crown. DISCUSSION
The composite resin dowel and core is a practical alternative to the cast gold dowel and core. Although it does not have the tensile or compressive strength of gold, preliminary studies have shown that it is strong enough to withstand normal masticatory forces. ~t The composite resin dowel and core appears to be more retentive than the gold dowel and core. This was verified in the previously mentioned case of the patient sustaining the traumatic injury. Although all three crowns and underlying cores were completely fra,.,tured, the dowel portion remained in each canal. The composite resin will fracture before it will dislodge, thus protecting the remaining root against injury when encountering traumatic forces. Because retention is achieved primarily by undercuts, the length of the dowel preparation need not be equal to that for gold, reducing the possibility of perforation. The technique presented eliminates considerable time and expense for both the dentist andlth.e~patient. It requires only one visit for the patient, and the dentist can fill the root canal, construct the dowel and core, make the crown preparation, and take the final impression in one appointment. The composite resin dowel and core is ideally suited for teeth with irregular root canals, because it does not require a conyerging path of insertion. It is also indicated in other conditions in which the cast gold dowel and core is not (i.e., multirooted, tilted, and short-rooted teeth). Because of its translucency, composite resin appears to be superior to cast gold under a complete porcelain-veneer crown. The laboratory results verified that our clinical technique produced void-free dowels. The insertion techniques showed that it is desirable to use the syringe for placement of the dowel material. Clinically, all the dowels and cores have been functioning for one ),ear. Excluding the,-three lost through trauma, there have been no postoperative problems. There have been no patient complaints, and clinical and radiographic examinations have revealed no complications. SUMMARY AND CONCLUSIONS
Utilizing composite resin, a new technique was introduced for the construction of dowels and cores. The results presented were drawn from a I2 month clinical and laboratory study. Although more time may be needed for further evaluation, preliminary results indicate that the composite resin dowel and core, along with the final restoration, fulfills the objectives of restoring the pulpless tooth to health, function, and esthetics. References 1. Watson, R. J.: The Amalgam Core, J. PROSTItET. DENT. 19: 500-505, 1968. 2. Waxman, H. N.: A One Visit Gore Procedure for Non-Vital Teeth, Worcester Med. News 34: '..)4-26, 1970. 3. Sehuhnan, L. S.: Plastic Pin Cores, Dent. Dig. 76: 429-430, 1970.
648
Stahl and O'Neal
J. Prosthet. Dent. Juuc, 1975
4. Baraban, D. J.: A Simplified Method for Making Posts and Cores, J. PROSTHET. DENT. 24: 287-297, 1970. 5. Going, R. E., Moffa, J. P., lNostrant, G. W., et al.: The Str,mgth of Dental Amalg/am as Influenced by Pins, J. Am. Dent. Assoc. 77: 1331-1334, 1968. 6. Stanford, J. W.: The Current Status of Restor;xtive Resins, Dent. Clin. North A~n. 15: 57-66, 1971. 7. Phillips, R. W., Swartz, M. L., and Norman, R. D.: Materials for the Practicing Dentist, St. Louis, 1969, The C. V. Mosby Company, p. 185. 8. Hollenback, G. M.: A Further Report on the Physical Properties of Five Composite Resins, Part II, J. Am. Dent. Assoc. 55: 17-33, 1971. 9. Phillips, R. W.: Composite Restorative Resins, J. Am. Dent. Assoc. 80: 357-358, 1970. 10. Lee, H. L., and Swartz, M. L.: Scanning Electron Microscope Study of Composite Restorative Materials, J. Dent. Res. 49: 149-158, 1970. 1 I. Sheets, C. E.: Dowel and Core Foundations, J. PROSTHET. DENT. 23: 58-65, 1970. I2. Dooley, B. S.: Preparz~tion and Construction of Post-Retention Crowns for Anterior Teeth, Aust. Dent. J. 12: 54~-550, 1967. 13. Lee, H. L., Swartz, M. L., and Smith, F. F.: Physical Properties of Four Thermosetting Dental Restorative Resins, J. Dent. Res. 48: 526-535, 1969. 14. Phillips, R. W., Avery, D. R., Mikra, R., et al.: One-Year Observations on a Composite Resin for Class II Restorations, J. PROSTHET. DENT. 26: 68-77, 1971. DR. STAHL 3415 HERITAGE RD. COLUMBUS, IND. 47201 DR. O'NEAL 279TJ:t STATION HOSPITAL BERLIN~ GERMANY
APO N~w YORK 09742
