Fracture nonvital
durability premolar
of restored teeth
functional
cusps on maxillary
Nuran Ulusoy, DDS,* Arun Nayyar, DMD, MS,b Charles F. Morris, DDS,C and Carl W. Fairhurst, PhDd Dicle University, School of Dentistry, Diyarbakir, Turkey, and Medical Collegeof Georgia,School of Dentistry, Augusta, Ga. Paiatal cusps of nonvital maxillary premolar teeth were restored with a coronalradicular restoration of posterior composite resin (Occlusin), amalgam (Tytin), or cermet (Chelon-Silver). Mean fracture strength values were: 370 lb for intact premolar teeth, 266 lb for amalgam, 215 lb for posterior composite resin, and 132 lb for cermet. From this in vitro study it can be suggested that for selected endodontically treated maxillary premolar teeth, the dentist can use acid-etchretained posterior composite resin or pin-retained high copper amalgam material for a definitive coronal-radicular restoration. The use of cermet for this purpose is contraindicated. (J PROSTHET DENT 1991;66:330-5.)
E
ndodontically treated teeth are susceptible to fracture because of removal of supportive dentin from within the crown of the tooth. To prevent the remaining tooth structure from splitting, it has been hypothesized that the remaining cusps should be protected with an overlay of a cast restoration.’ A common method of restoring a tooth with a fractured cusp is endodontic treatment, a coronal-radicular buildup, and a subsequent cast restoration.2 However, when a large quantity of intact tooth structure is present, a conservative restorative technique may be applied. The use of amalgam, composite, or cermet as a coronal-radicular buildup material has been reported.3p4 Preservation of tooth structure is of primary importance to the dentist. This investigation measured the fracture durability of functional cusps of maxillary nonvital premolar teeth restored with high-copper amalgam, posterior composite resin, or cermet. This researchwas supported by the Scientific and Technical ResearchCouncil of Turkey and the grant wasawardedto Dr. Ulusoy for completing her work at the Medical Collegeof Georgia. *Associate Professor and Chairman of Conservative Dentistry and Endodontics, Dicle University, School of Dentistry; Visiting research faculty, Department of Restorative Dentistry, Medical College of Georgia,School of Dentistry. bAssociate Professor and Director, Section of Fixed Prosthodontics, Department of Restorative Dentistry, Medical College of Georgia, School of Dentistry. CProfessor and Chairman, Department of Restorative Dentistry, Medical College of Georgia, School of Dentistry. dProfessor and Coordinator, Dental Material Sciences, Department of Restorative Dentistry, Medical College of Georgia, School of Dentistry. 10/l/28105
330
Fig. 1. Prepared premolar tooth ready for placement of restorative material. MATERIAL
AND
METHODS
Sixty intact human maxillary premolar teeth were obtained and were stored in 10% formalin. A Ney surveyor (J.M. Ney Co., Hartford, Conn.) was used to orient each tooth along an axis 90 degrees to the horizontal. The root segment was embedded in quick-set acrylic resin (Quikmount, Fulton Metallurgical Products, Sexonburg, Pa.) to a depth approximately 2 mm apical to the cementoenamel junction.
SEPTEMBER1991
VOLUME66
NUMBER3
DCRABILITY
OF HE!:TOHED
SONVITAL
ClJSPS
Fig. 3. Example of completed coronal--radicular replacement final restoration.
and cusp
Fig. 2. Endodol:.tic access opening enlarged 2 mm wide and 3 mm deep. Completed pr:paration ready for coronalr,adicular final restoration. space and the remaining cavity. ‘i’he amalgam was burnished and tooth anatomy was carved iFig 3). The 60 test specimens were randomly divided into four groups, each consisting of 15 teeth. The palatal cusps of 45 teeth were sectioned with a diamond disk (Brassier USA, Savannah, Cu.). The tirst cut was made vertically through the central groove and extended to within 2 mm of the cennentoenamel junction. The second cut was made horizontally to meet the vertical cut and the palatal cusp was separated (Fig. I). Endodontic access opening was completed and radicular space :i mm deep and 2 mm wide was estab1:ished according to the method of Nayyar3 (Fig. 2). Unsupported enamel rods on the mesial and distal walls of the facial cusp were removed. Fifteen test specimen were prepared for the four experimental groups.
Natural Natural
lteeth
teeth were kept intact as a control group.
Amalgam coronal-radieular replacement restoration
and cusp
Two Minim pins (Whaledent International, New York. N.Y.) were placed in the inner dentin wall of the buccal cusp. The pins were inserted a‘; a converging angle with the intent of cross-splinting. A Totfelmier matrix band was positioned and Tytin amalgam (Kerr Manufacturing Co.. Romulus, Mich.) was condensed into the coronal-radicular
THE
JOURNAL
OF 1’HOZ”THETIC
DENTISTRY
Posterior composite resin coronal-radicular and cusp replacement restoration Each premolar tooth was prepared as discussed previously. The enamel and dentin surfaces were etched for 60 seconds with the etchant provided by the manufacturer of a visible light-cured posterior composite resin restorative material- Occlusin (Coe-ICI., Chicago. Ill.). The etched enamel was then rinsed for 30 seconds with room temperature water and air dried. The supplied light-cured bonding agent was applied to the cavity surface and was cured for 15 seconds. The coronal-radicular space was built up with Occlusin resin and was cured for 60 seconds. A Toffelmier matrix band was positioned around t,he tooth, and the lingual cusp as well as the axial contours were restored with the posterior composite resin material and were cured for 60 seconds. The band was remosed and each surface of the restoration was cured an additronal 60 seconds.
Cermet (glass ionomer-silver) coronal-radicular and cusp replacement restoration The dentin and enamel surface 01’ each specimen was treated with 20”, diluted polvacrylic acid (Ultradent Products, Inc., Salt Lake City, 1.tab) according to the manufacturer’s directions. The tooth \vad restored with
331
ULUSOYETAL
Fig. 4. With 5 mm round bur, indentation was made on inner slope of each cusp.
Fracture
3 e
350
al
300.-
g u. 9
250
p
200~-
Durability
of
Restored
Fig. 5. Stainless steel sphere 5.5 mm in diameter is cradled in intimate contact of both inner slopes.
Non-vital
Pre-molars
--
--
150 100 50 0
L
Intact Teeth
Posterior Composite
Amalgam
Cermet
Fig. 6. Bar graph illustrates data presented in Table I. At 95 % confidence level, cermet restorations are significantly weaker than amalgam or posterior composite resin coronalradicular restorations.
Chelon-silver, a cermet material (Espe-Premier, Norristown, Pa.) and a single coat of varnish (Espe Glass Ionomer Varnish, Seefeld/Oberbay, Germany) was applied over the restoration.
332
All specimens were stored at 37” C and 100% humidity except during the experimental evaluation. A 5 mm round carbide bur (Brassler USA) was used to place an indentation on the inner slope of the buccal and palatal cusp (Fig.
SEPTEMBER
1991
VOLUME
66
NUMBER
3
DURABILITY
OF RISSTC?RED
NOW’ITAL
I. F’racture durability with definitive restorations
CUSPS
of intact teeth compared
Table
M%Ul
G:r0llp
Intact teeth Posterior composit;~ resin Amalgam Cermet
37*).X?
SD
(No.)
151.09
1.5
21 t.so
54.20
15
26f5.07
87.38 60.41
15
13z.00
IS
4). These t.wo indentations were used to seat the 5.5 mm stainless steel sphere (Fig. 5,. Vertical force was applied with an Instron testing machine (Instron Corp., Canton, Mass.) at a cross-head speed of 0.02 inch/min until catastrophic failure occurred.
RESULTS The data accu:mulated from the fractured specimens are :shown in Table I and Fig. 6. Analysis of data using the ‘Tukey-HS:D test showed no statistical difference between the mean values of posterior composite resin (214.8 i 54.2 Lb) and amalgam coronal-radicular restoration (266.07 :! #57.38lb). At the 95”( confidence level, fracture strength for both types of restorations was, significantly higher than for .the cermet restoraticsns (132 :: 60.41 lb). This analysis also -revealed that intact maxillary premolar teeth are more rezsistant to fracture (370.33 +- 151.09 lb) than teeth restored swith any of the three rest,orative materials. The following quantitative observations were made for .the four experimental groups.
Fig. 7. Unprepared natural teeth fractured mesiodistally, splitting
the tooth.
YNatural teeth In 11 teeth the fracture line extended mesiodistally through the crown, propagated into the root, and split the tooth into two hslves (Fig. 7). In two teeth the fracture line extended faciolirlgually, and the root split along this axis. The buccal and lingual cusps of two teeth fractured without splitting the root,.
;High-copper
amalgam
In 14 teeth restored with high-copper amalgam, failure of the restoration was observed (Fig. 8). Only in one spec. imen did t.he amalgam remain intact while the buccal enamel cusp fractured. Additionally, a variety of fracture characteristics were observed. In eight specimens the fracture extended mesiodistally and split the root. In four specimens, only the amalgam restoration fractured. The buccal cusp and the amalgam fractured in three premolar teeth. Also, in only two specimens did one of the pins separate from the tooth
Posterior
composite
resins
For all 15 posterior composite resin specimens, a longitudinal fracture occurred at the composite resin-enamel
THE
JOURNAL
OF IPROSTHETIC
EmENTISTRY
Fig. 8. For palatal cusps restored with amalgam, fracture occurred within amalgam. Also, the root split, leaving facial enamel intact in all but three of the samples.
interface. The fracture propagated along the long axis of the tooth (Fig. 9). Three of these specimens also had a longitudinal fracture of the facial enamel that extended occlusogingivally (Fig. I;)).
333
ULUSOY
Fig. 9. Most posterior composite resin restorations fractured.
ET AL
Fig. 11. Cermet coronal-radicular restoration fragmented under applied load. Restoration failed, leaving tooth structure intact.
DISCUSSION
Fig. 10. One of three composite resin restorations that had additional fracture on facial surface of enamel.
Cermet Each of the 15 cermet restorations failed, leaving the natural tooth structure intact. Failure occurred because of fragmentation of the restorative material (Fig. 11).
334
According to Helkimo and Ingervall,5 occlusal forces in the mouth are reported to be 40 to 180 lb. The load required to fracture human premolar teeth has been variously reported to be 530 lb,6 387.2 lb,7 219.1 lb,8 and 251.46 lb.g In the present study, the mean value of the load required to fracture human maxillary premolar teeth was 370.33 lb. Variations in loading apparatus (a spherical ball, a single rod, or two rods) could possibly influence the reported fracture values. Although the use of cermet material has been recommended for coronal-radicular buildups under cast restoration, its use as the final restorative material for cusp replacement of an endodontically treated premolar tooth is contraindicated. This is due to the material’s low fracture resistance and observed tendency to crush under an applied load less than the mean biting force in humans.5 Large and moderately sized posterior composite resin (Occlusin) restorations in a 5-year clinical studylo were reported to have a relatively low failure rate (14%). Also, the clinical use of posterior composite resins as a cusp replacement restoration for vital teeth has been proposed.ll Since it has been reported12 that acid-etch composite resin restorations strengthen the remaining tooth structure in vital teeth, a similar hypothesis can be applied in restoring endodontically treated premolar teeth with a large quantity of intact enamel remaining on all margins of the restoration. The successful use of amalgam as a functional cusp replacement restorative material for vital teeth is well doc-
SEPTEMBER
1991
VOLUME
66
NUMBER
3
DURABILIT’i
OF R EST(sRED
: healthy remaining tooth structure.
CLINIC.AL
2.
.i.
TMF’LICATIONS
When a large qalantity of intact tooth structure is present, the dentist can consider an alternative to a casting as the final restoration. The use of acid-etch-retained posterior composite resin or a pin-retained amalgam as a definitive coronal-radicular restoration is indicated. This conservative approach may prove to be the most appropriate final restoration I or replacing missing tooth structure of many endodonticall : treated premolar teeth.
x.
9.
II).
li.
CONCLIJSION From this in vitro study it can be suggested that when the lingual cusp on an fsndodontically treated maxillary pre” molar is missing, the dentist may consider a definitive (coronal-radicular restoration with acid-etch posterior com.posite resin or high-copper amalgam restorative material. ‘The use of currentl;S: available cermet material as a final :restoration is cont,raindicatec’.
12.
1:;.
14.
REFERENCES
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
335
durability premolar
of restored teeth
functional
cusps on maxillary
Nuran Ulusoy, DDS,* Arun Nayyar, DMD, MS,b Charles F. Morris, DDS,C and Carl W. Fairhurst, PhDd Dicle University, School of Dentistry, Diyarbakir, Turkey, and Medical Collegeof Georgia,School of Dentistry, Augusta, Ga. Paiatal cusps of nonvital maxillary premolar teeth were restored with a coronalradicular restoration of posterior composite resin (Occlusin), amalgam (Tytin), or cermet (Chelon-Silver). Mean fracture strength values were: 370 lb for intact premolar teeth, 266 lb for amalgam, 215 lb for posterior composite resin, and 132 lb for cermet. From this in vitro study it can be suggested that for selected endodontically treated maxillary premolar teeth, the dentist can use acid-etchretained posterior composite resin or pin-retained high copper amalgam material for a definitive coronal-radicular restoration. The use of cermet for this purpose is contraindicated. (J PROSTHET DENT 1991;66:330-5.)
E
ndodontically treated teeth are susceptible to fracture because of removal of supportive dentin from within the crown of the tooth. To prevent the remaining tooth structure from splitting, it has been hypothesized that the remaining cusps should be protected with an overlay of a cast restoration.’ A common method of restoring a tooth with a fractured cusp is endodontic treatment, a coronal-radicular buildup, and a subsequent cast restoration.2 However, when a large quantity of intact tooth structure is present, a conservative restorative technique may be applied. The use of amalgam, composite, or cermet as a coronal-radicular buildup material has been reported.3p4 Preservation of tooth structure is of primary importance to the dentist. This investigation measured the fracture durability of functional cusps of maxillary nonvital premolar teeth restored with high-copper amalgam, posterior composite resin, or cermet. This researchwas supported by the Scientific and Technical ResearchCouncil of Turkey and the grant wasawardedto Dr. Ulusoy for completing her work at the Medical Collegeof Georgia. *Associate Professor and Chairman of Conservative Dentistry and Endodontics, Dicle University, School of Dentistry; Visiting research faculty, Department of Restorative Dentistry, Medical College of Georgia,School of Dentistry. bAssociate Professor and Director, Section of Fixed Prosthodontics, Department of Restorative Dentistry, Medical College of Georgia, School of Dentistry. CProfessor and Chairman, Department of Restorative Dentistry, Medical College of Georgia, School of Dentistry. dProfessor and Coordinator, Dental Material Sciences, Department of Restorative Dentistry, Medical College of Georgia, School of Dentistry. 10/l/28105
330
Fig. 1. Prepared premolar tooth ready for placement of restorative material. MATERIAL
AND
METHODS
Sixty intact human maxillary premolar teeth were obtained and were stored in 10% formalin. A Ney surveyor (J.M. Ney Co., Hartford, Conn.) was used to orient each tooth along an axis 90 degrees to the horizontal. The root segment was embedded in quick-set acrylic resin (Quikmount, Fulton Metallurgical Products, Sexonburg, Pa.) to a depth approximately 2 mm apical to the cementoenamel junction.
SEPTEMBER1991
VOLUME66
NUMBER3
DCRABILITY
OF HE!:TOHED
SONVITAL
ClJSPS
Fig. 3. Example of completed coronal--radicular replacement final restoration.
and cusp
Fig. 2. Endodol:.tic access opening enlarged 2 mm wide and 3 mm deep. Completed pr:paration ready for coronalr,adicular final restoration. space and the remaining cavity. ‘i’he amalgam was burnished and tooth anatomy was carved iFig 3). The 60 test specimens were randomly divided into four groups, each consisting of 15 teeth. The palatal cusps of 45 teeth were sectioned with a diamond disk (Brassier USA, Savannah, Cu.). The tirst cut was made vertically through the central groove and extended to within 2 mm of the cennentoenamel junction. The second cut was made horizontally to meet the vertical cut and the palatal cusp was separated (Fig. I). Endodontic access opening was completed and radicular space :i mm deep and 2 mm wide was estab1:ished according to the method of Nayyar3 (Fig. 2). Unsupported enamel rods on the mesial and distal walls of the facial cusp were removed. Fifteen test specimen were prepared for the four experimental groups.
Natural Natural
lteeth
teeth were kept intact as a control group.
Amalgam coronal-radieular replacement restoration
and cusp
Two Minim pins (Whaledent International, New York. N.Y.) were placed in the inner dentin wall of the buccal cusp. The pins were inserted a‘; a converging angle with the intent of cross-splinting. A Totfelmier matrix band was positioned and Tytin amalgam (Kerr Manufacturing Co.. Romulus, Mich.) was condensed into the coronal-radicular
THE
JOURNAL
OF 1’HOZ”THETIC
DENTISTRY
Posterior composite resin coronal-radicular and cusp replacement restoration Each premolar tooth was prepared as discussed previously. The enamel and dentin surfaces were etched for 60 seconds with the etchant provided by the manufacturer of a visible light-cured posterior composite resin restorative material- Occlusin (Coe-ICI., Chicago. Ill.). The etched enamel was then rinsed for 30 seconds with room temperature water and air dried. The supplied light-cured bonding agent was applied to the cavity surface and was cured for 15 seconds. The coronal-radicular space was built up with Occlusin resin and was cured for 60 seconds. A Toffelmier matrix band was positioned around t,he tooth, and the lingual cusp as well as the axial contours were restored with the posterior composite resin material and were cured for 60 seconds. The band was remosed and each surface of the restoration was cured an additronal 60 seconds.
Cermet (glass ionomer-silver) coronal-radicular and cusp replacement restoration The dentin and enamel surface 01’ each specimen was treated with 20”, diluted polvacrylic acid (Ultradent Products, Inc., Salt Lake City, 1.tab) according to the manufacturer’s directions. The tooth \vad restored with
331
ULUSOYETAL
Fig. 4. With 5 mm round bur, indentation was made on inner slope of each cusp.
Fracture
3 e
350
al
300.-
g u. 9
250
p
200~-
Durability
of
Restored
Fig. 5. Stainless steel sphere 5.5 mm in diameter is cradled in intimate contact of both inner slopes.
Non-vital
Pre-molars
--
--
150 100 50 0
L
Intact Teeth
Posterior Composite
Amalgam
Cermet
Fig. 6. Bar graph illustrates data presented in Table I. At 95 % confidence level, cermet restorations are significantly weaker than amalgam or posterior composite resin coronalradicular restorations.
Chelon-silver, a cermet material (Espe-Premier, Norristown, Pa.) and a single coat of varnish (Espe Glass Ionomer Varnish, Seefeld/Oberbay, Germany) was applied over the restoration.
332
All specimens were stored at 37” C and 100% humidity except during the experimental evaluation. A 5 mm round carbide bur (Brassler USA) was used to place an indentation on the inner slope of the buccal and palatal cusp (Fig.
SEPTEMBER
1991
VOLUME
66
NUMBER
3
DURABILITY
OF RISSTC?RED
NOW’ITAL
I. F’racture durability with definitive restorations
CUSPS
of intact teeth compared
Table
M%Ul
G:r0llp
Intact teeth Posterior composit;~ resin Amalgam Cermet
37*).X?
SD
(No.)
151.09
1.5
21 t.so
54.20
15
26f5.07
87.38 60.41
15
13z.00
IS
4). These t.wo indentations were used to seat the 5.5 mm stainless steel sphere (Fig. 5,. Vertical force was applied with an Instron testing machine (Instron Corp., Canton, Mass.) at a cross-head speed of 0.02 inch/min until catastrophic failure occurred.
RESULTS The data accu:mulated from the fractured specimens are :shown in Table I and Fig. 6. Analysis of data using the ‘Tukey-HS:D test showed no statistical difference between the mean values of posterior composite resin (214.8 i 54.2 Lb) and amalgam coronal-radicular restoration (266.07 :! #57.38lb). At the 95”( confidence level, fracture strength for both types of restorations was, significantly higher than for .the cermet restoraticsns (132 :: 60.41 lb). This analysis also -revealed that intact maxillary premolar teeth are more rezsistant to fracture (370.33 +- 151.09 lb) than teeth restored swith any of the three rest,orative materials. The following quantitative observations were made for .the four experimental groups.
Fig. 7. Unprepared natural teeth fractured mesiodistally, splitting
the tooth.
YNatural teeth In 11 teeth the fracture line extended mesiodistally through the crown, propagated into the root, and split the tooth into two hslves (Fig. 7). In two teeth the fracture line extended faciolirlgually, and the root split along this axis. The buccal and lingual cusps of two teeth fractured without splitting the root,.
;High-copper
amalgam
In 14 teeth restored with high-copper amalgam, failure of the restoration was observed (Fig. 8). Only in one spec. imen did t.he amalgam remain intact while the buccal enamel cusp fractured. Additionally, a variety of fracture characteristics were observed. In eight specimens the fracture extended mesiodistally and split the root. In four specimens, only the amalgam restoration fractured. The buccal cusp and the amalgam fractured in three premolar teeth. Also, in only two specimens did one of the pins separate from the tooth
Posterior
composite
resins
For all 15 posterior composite resin specimens, a longitudinal fracture occurred at the composite resin-enamel
THE
JOURNAL
OF IPROSTHETIC
EmENTISTRY
Fig. 8. For palatal cusps restored with amalgam, fracture occurred within amalgam. Also, the root split, leaving facial enamel intact in all but three of the samples.
interface. The fracture propagated along the long axis of the tooth (Fig. 9). Three of these specimens also had a longitudinal fracture of the facial enamel that extended occlusogingivally (Fig. I;)).
333
ULUSOY
Fig. 9. Most posterior composite resin restorations fractured.
ET AL
Fig. 11. Cermet coronal-radicular restoration fragmented under applied load. Restoration failed, leaving tooth structure intact.
DISCUSSION
Fig. 10. One of three composite resin restorations that had additional fracture on facial surface of enamel.
Cermet Each of the 15 cermet restorations failed, leaving the natural tooth structure intact. Failure occurred because of fragmentation of the restorative material (Fig. 11).
334
According to Helkimo and Ingervall,5 occlusal forces in the mouth are reported to be 40 to 180 lb. The load required to fracture human premolar teeth has been variously reported to be 530 lb,6 387.2 lb,7 219.1 lb,8 and 251.46 lb.g In the present study, the mean value of the load required to fracture human maxillary premolar teeth was 370.33 lb. Variations in loading apparatus (a spherical ball, a single rod, or two rods) could possibly influence the reported fracture values. Although the use of cermet material has been recommended for coronal-radicular buildups under cast restoration, its use as the final restorative material for cusp replacement of an endodontically treated premolar tooth is contraindicated. This is due to the material’s low fracture resistance and observed tendency to crush under an applied load less than the mean biting force in humans.5 Large and moderately sized posterior composite resin (Occlusin) restorations in a 5-year clinical studylo were reported to have a relatively low failure rate (14%). Also, the clinical use of posterior composite resins as a cusp replacement restoration for vital teeth has been proposed.ll Since it has been reported12 that acid-etch composite resin restorations strengthen the remaining tooth structure in vital teeth, a similar hypothesis can be applied in restoring endodontically treated premolar teeth with a large quantity of intact enamel remaining on all margins of the restoration. The successful use of amalgam as a functional cusp replacement restorative material for vital teeth is well doc-
SEPTEMBER
1991
VOLUME
66
NUMBER
3
DURABILIT’i
OF R EST(sRED
: healthy remaining tooth structure.
CLINIC.AL
2.
.i.
TMF’LICATIONS
When a large qalantity of intact tooth structure is present, the dentist can consider an alternative to a casting as the final restoration. The use of acid-etch-retained posterior composite resin or a pin-retained amalgam as a definitive coronal-radicular restoration is indicated. This conservative approach may prove to be the most appropriate final restoration I or replacing missing tooth structure of many endodonticall : treated premolar teeth.
x.
9.
II).
li.
CONCLIJSION From this in vitro study it can be suggested that when the lingual cusp on an fsndodontically treated maxillary pre” molar is missing, the dentist may consider a definitive (coronal-radicular restoration with acid-etch posterior com.posite resin or high-copper amalgam restorative material. ‘The use of currentl;S: available cermet material as a final :restoration is cont,raindicatec’.
12.
1:;.
14.
REFERENCES
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
335
