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Retention of posts with resin, glass ionomer and hybrid cements
Journal of Dentistry Journal of Dentistry 26 (1998) 599–602
Retention of posts with resin, glass ionomer and hybrid cements R.M. Love*, D.G. Purton Department of Restorative Dentistry, University of Otago School of Dentistry, PO Box 647, Dunedin, New Zealand Accepted 14 July 1997
Abstract Objectives: To measure and compare the retention of serrated root canal posts cemented with glass ionomer, resin and resin-modified glass ionomer (hybrid) cements. Methods: Fifty single-rooted human teeth were decoronated, treated endodontically and then embedded in resin blocks. Standard postholes, 10 mm long, were prepared to receive 1.5 mm serrated stainless steel posts. Five equal-sized groups of roots had posts cemented using either a glass ionomer cement, one of two resin cements or one of two resin-modified glass ionomer luting cements. The cements were prepared and used according to the manufacturers’ instructions. The tensile force required to dislodge the cemented posts in a testing machine was recorded. Statistical analysis was performed using Student’s t-test and Mann–Whitney U-tests at the 99.9% confidence level. Results: Statistical analysis revealed that posts cemented with resin A were significantly better retained (340.06 N 6 23.13 N) than those cemented with resin B (212.56 N 6 67.62 N), or either of the two resin-modified glass ionomer cements (53.90 N 6 28.42 N, 25.97 N 6 14.70 N), but not statistically better than posts cemented with the glass ionomer cement (286.16 N 6 38.71 N). The retention of posts cemented with either resin B or the glass ionomer cement was significantly better than with either hybrid cement. There was no significant difference in retention between the hybrid cements. Conclusion: The performance of the resin-modified glass ionomer cements was significantly below that of alternative cements in this study. Possible explanations for this finding are discussed. Dentists should be cautious in adopting this new cementing regime. q 1998 Elsevier Science Ltd. All rights reserved. Keywords: Post retention; Resin; Glass ionomer; Cement
1. Introduction The decision to use a post when restoring a root-filled tooth should primarily be based on the retention requirements of the coronal restoration. The retention of a post in a root is critical for a successful post-retained coronal restoration and is partly determined by the design of the post and the luting agent used. Standlee et al. demonstrated that a serrated parallel-sided post that is passively cemented into an oversized post hole is the post design of choice, as adequate retention can be achieved with minimal undesirable stress on the root structure [1]. However, early studies found no significant differences in post retention with zinc phosphate, polycarboxylate, glass ionomer or epoxy cement [1,2]. Recent years have seen many developments in cement composition, with adhesion to dentine being a prime goal. Many clinicians today favour the use of adhesive cements, although results of independent evaluation may be lacking in the literature. The purpose of this study was to investigate * Corresponding author. Fax: 64 3 479 7113
0300-5712/98/$19.00 q 1998 Elsevier Science Ltd. All rights reserved. PII: S0 30 0 -5 7 12 ( 97 ) 00 0 43 - 2
the retention of serrated parallel-sided stainless steel posts cemented with various newly released cements.
2. Materials and method Fifty single-rooted permanent anterior and premolar human teeth, free of defects or restorations in the roots and having narrow unfilled root canal spaces were selected for study. The teeth were sectioned horizontally 1 mm above the labial cemento-enamel junction and the root canals were prepared using the step-down method with sodium hypochlorite irrigation. The canals were filled with laterally condensed gutta-percha and AH26 sealer (Dentsply DeTrey Division, Dentsply Ltd, Weybridge, UK). The roots were then grooved horizontally using a diamond bur in a high-speed handpiece, embedded in individual acrylic blocks and stored in water until required. Post-holes were prepared to a depth of 10 mm by removing gutta-percha with Gates–Glidden drills and preparing the root canal with a 1.5 mm Para-post drill. The post-holes
600
R.M. Love, D.G. Purton/Journal of Dentistry 26 (1998) 599–602
were irrigated with water and dried with paper points. The roots were then randomly assigned to five groups of equal size and 1.5 mm Para-posts were cemented into the postholes with one of five different cements. 2.1. Group A Ketac-Cem (ESPE, Dental-Medizin GmbH and Co. KG, Seefeld, Germany), a capsulated polymaleinate glass ionomer cement was used as the control. 2.2. Group B Vitremer luting cement (3M Dental Products, St Paul, MN, USA), a resin-modified glass ionomer cement. 2.3. Group C Fuji DUET (GC Corp, Tokyo, Japan), a reinforced glass ionomer cement. 2.4. Group D Scotchbond Resin Cement (3M Dental Products), a methacrylate-based dual cure resin cement. 2.5. Group E Panavia 21 (Kuraray Co., Ltd, Osaka, Japan) chemical cure resin cement. In all cases the dispensing, mixing and handling of components were undertaken according to manufacturer instructions for use. The posts were coated with the cements and seated to full depth using finger pressure. Excess cement was cleared from the root face and the posts were held in position for 15 min. The roots were stored in water for 6 weeks before testing. They were then placed into a retention device mounted in a universal testing machine (Instron, High Wycombe, UK), the portion of the post extending from the root was grasped in the vise of the machine and a tensile force was applied at a cross-head speed of 5 mm/min. The tensile force (N) required to remove the post from the root was recorded and the results for the groups were compared using Student’s t-tests and Mann–Whitney U-tests at the 99.9% confidence level. Visual inspection of the dislodged posts using a stereomicroscope at 12 3 magnification was undertaken to attempt to ascertain the mode of failure.
3. Results Table 1 presents the mean force (N) required to dislodge the posts from the root canals. Statistical analysis is displayed in Table 2 and revealed that posts cemented with Scotchbond Resin Cement were significantly better retained
Table 1 Mean tensile force, and standard deviation, required to dislodge a 1.5 mm serrated post from the root canal Group
Cement
Force (N)
D A E B C
Scotchbond Ketac-Cem Panavia 21 Vitremer Fuji DUET
340.06 286.16 212.56 53.90 25.97
s.d. (N) 23.13 38.71 67.62 28.42 14.70
than posts cemented with Panavia 21, Vitremer or Fuji DUET, and that there were no statistical differences relative to posts cemented with Ketac-Cem. The force required to dislodge posts cemented with Ketac-Cem was significantly higher than with Vitremer or Fuji DUET but not significantly different to the Panavia 21 group. Posts cemented with Panavia 21 were better retained than posts cemented with Vitremer or Fuji DUET. There was no significant difference between Vitremer and Fuji DUET in the force required to remove the posts. Visual inspection of the groups (Fig. 1) suggested that posts cemented with Scotchbond Resin Cement were generally devoid of cement remnants, implying adhesive failure at the cement–post interface. Posts cemented with KetacCem had more cement retained on the post compared to Scotchbond Resin Cement but areas were free of cement, suggesting that the mode of failure was a combination of adhesive failure at the cement–post interface and cohesive cement failure. Posts cemented with Panavia 21 retained a large amount of cement, implying adhesive failure at the cement–dentine interface. Posts cemented with either Fuji DUET or Vitremer retained a thin layer of cement especially within the serrations of the post. This pattern was suggestive of cohesive cement failure. 4. Discussion In vitro bond strength tests are a rather coarse method of estimating clinical efficacy. Shear bond strengths recorded Table 2 Paired comparisons of the tensile force required to remove posts cemented with various cements. Significance level , 0.001 p value Cement
Cement
Scotchbond Scotchbond Scotchbond Scotchbond Ketac-Cem Ketac-Cem Ketac-Cem Panavia 21 Panavia 21 Vitremer
Panavia 21 Vitremer DUET Ketac-Cem Vitremer DUET Panavia 21 Vitremer DUET DUET
Student’s t-test 0.001 0.000 0.000 0.002 0.000 0.000 0.024 0.000 0.000 0.011
Mann–Whitney U-test 0.0002 0.0002 0.0002 0.0025 0.0002 0.0002 0.0065 0.0003 0.0002 1.0000
R.M. Love, D.G. Purton/Journal of Dentistry 26 (1998) 599–602
Fig. 1. Sites of cement failure of representative posts cemented with various cements. 1, Ketac-Cem. 2, Fuji DUET. 3, Panavia 21. 4, Scotchbond. 5, Vitremer.
in tests of the present type may relate to the absolute strength of a material rather than to the strength of bonds to dentine, since failure may be cohesive in nature. Clinically, however, the loss of retention of a post is equally catastrophic regardless of the mode of failure and dentists need to have some guidelines on performance before they adopt new products. Due to the small sample size of each group in this study, a demanding confidence level of 99.9% was set as being significant. In addition, analysis was done by a parametric and a non-parametric statistical method to verify results. Except for the Scotchbond/Panavia 21 comparison, all comparisons were similar with the two statistical methods. For the Scotchbond/Panavia 21 comparison, the result of the Student’s t-test ( p ¼ 0.001) was strengthened by the Mann–Whitney U-test ( p ¼ 0.0002). The bonds between dentine and conventional glass ionomer cement are known to be dynamic in nature and durable in a wet environment. The cohesive strength of the set cement is probably the limiting factor in its performance in a test of the present type, and the visual suggestion of partly cohesive failure with Ketac-Cem-retained posts would support this; although, one must be cautious in placing too much credibility on the visual examination results until further study has been carried out examining the fractured surfaces under scanning electron microscopy. The values recorded in the present experiment for the Scotchbond Resin Cement are very similar to those recorded by the authors with a different brand of adhesive resin cement used on etched dentine in a previous post-retention study [3]. Adhesive resin cements have been shown to produce long resin tags in etched non-vital dentine, especially near the pulp space [4]. This, together with the high inherent strength of the composite resin, could account for the high values recorded for the Scotchbond group. Visual inspection of this group would support this theory as adhesive failure at the cement–post interface was suggested. However, the mode of failure of Panavia 21-cemented posts appeared to be adhesive at the cement–dentine interface. This may
601
imply poor dentine adhesion; however, the force required to dislodge the posts would suggest that clinically acceptable dentine adhesion occurred. The force required to remove a post cemented with Ketac-Cem or Panavia cement in this study is similar to other reported values [5]. The nature of the bonds between dentine and resinmodified glass ionomer cements is less well understood. A number of studies of light cured resin-modified glass ionomer restorative materials and bases are reported and these show the tensile and shear strengths to fall between those of conventional glass ionomer cements and adhesive resin restorative materials [6–8]. In contrast, studies of resin-modified glass ionomer luting cements have not appeared in the literature. The relatively low retention provided by the resinmodified glass ionomer cements in the present study is difficult to explain. The cement mixing procedures used were exactly in accordance with the manufacturers’ instructions, though potential exists for inconsistent or inaccurate powder to liquid ratios with the scoop and drop system of dispensing the components. Another possibility is that in producing materials of a suitable consistency for luting the manufacturers have lowered the powder to liquid ratios to levels such that the shear bond strengths are diminished in comparison with the relatively viscous restorative materials. The pattern of cement retained on the posts for Fuji DUET and Vitremer strongly suggests that cohesive failure occurred in the cement, supporting this hypothesis. Mount (1994) hypothesised that in resin-modified glass ionomer cements a reduction in powder content would inevitably mean an increase in the proportion of HEMA with the consequent potential for greater water uptake by this hydrophilic resin [9]. The samples in the present experiment were stored in water for 6 weeks prior to testing and this may have some bearing on the results. Applying the cement to the posts only and not into the post spaces could have produced air voids, which would affect the results, although it would be unlikely that it would significantly affect one group over another. The manufacturer of one of the resin cements specifically recommends not placing cement in the canal because of the risk of setting before post placement. In view of this, and to standardise methodology, the decision was made to apply cement only to the posts in all groups. The importance of surface pre-treatment has not been investigated for resin-modified glass ionomer luting cements and it is of interest that the instructions with one of the products (Fuji DUET) used in the present study recommend acid pre-treatment of dentine while only washing and drying is recommended for the other (Vitremer). Resin-modified glass ionomer cements offer considerable promise in dentistry. They appear to have found favour as restorative materials and bases in selected cases. Their future role as luting agents is less clear and on the basis of the present study they could not be recommended for use in the cementation of root canal posts.
602
R.M. Love, D.G. Purton/Journal of Dentistry 26 (1998) 599–602
References [1] Standlee JP, Caputo AA, Hanson EC Retention of endodontic dowels: effects of cement, dowel length, diameter and design. Journal of Prosthetic Dentistry, 1978;39:401–405. [2] Krupp JD, Caputo AA, Trabert KC, Standlee JP Dowel retention with glass-ionomer cement. Journal of Prosthetic Dentistry, 1979;41:163– 166. [3] Love RM, Purton DG The effect of serrations on carbon fibre posts— retention within the root canal, core retention, and post rigidity. International Journal of Prosthodontics, 1996;9:484–488. [4] Blair F, Whitworth J, Wassell RW Impregnation by dentine bonding agents into instrumented root-face dentine. Journal of Dentistry, 1995;23:289–294.
[5] Mendoza DB, Eakle WS Retention of posts cemented with various dentinal bonding cements. Journal of Prosthetic Dentistry, 1994;72:591–594. [6] Friedl K-H, Powers JM, Hiller K-A Influence of different factors on bond strength of hybrid ionomers. Operative Dentistry, 1995;20:74– 80. [7] Fritz UB, Finger WJ, Uno S Resin modified glass ionomer cements: bonding to enamel and dentine. Dental Materials, 1996;12:161–166. [8] Burgess JO, Nasser B, Chan DCN, Hummert T A comparative study of three glass ionomer base materials. American Journal of Dentistry, 1993;6:137–141. [9] Mount GJ Glass-ionomer cements: past, present and future. Operative Dentistry, 1994;19:82–90.
Retention of posts with resin, glass ionomer and hybrid cements R.M. Love*, D.G. Purton Department of Restorative Dentistry, University of Otago School of Dentistry, PO Box 647, Dunedin, New Zealand Accepted 14 July 1997
Abstract Objectives: To measure and compare the retention of serrated root canal posts cemented with glass ionomer, resin and resin-modified glass ionomer (hybrid) cements. Methods: Fifty single-rooted human teeth were decoronated, treated endodontically and then embedded in resin blocks. Standard postholes, 10 mm long, were prepared to receive 1.5 mm serrated stainless steel posts. Five equal-sized groups of roots had posts cemented using either a glass ionomer cement, one of two resin cements or one of two resin-modified glass ionomer luting cements. The cements were prepared and used according to the manufacturers’ instructions. The tensile force required to dislodge the cemented posts in a testing machine was recorded. Statistical analysis was performed using Student’s t-test and Mann–Whitney U-tests at the 99.9% confidence level. Results: Statistical analysis revealed that posts cemented with resin A were significantly better retained (340.06 N 6 23.13 N) than those cemented with resin B (212.56 N 6 67.62 N), or either of the two resin-modified glass ionomer cements (53.90 N 6 28.42 N, 25.97 N 6 14.70 N), but not statistically better than posts cemented with the glass ionomer cement (286.16 N 6 38.71 N). The retention of posts cemented with either resin B or the glass ionomer cement was significantly better than with either hybrid cement. There was no significant difference in retention between the hybrid cements. Conclusion: The performance of the resin-modified glass ionomer cements was significantly below that of alternative cements in this study. Possible explanations for this finding are discussed. Dentists should be cautious in adopting this new cementing regime. q 1998 Elsevier Science Ltd. All rights reserved. Keywords: Post retention; Resin; Glass ionomer; Cement
1. Introduction The decision to use a post when restoring a root-filled tooth should primarily be based on the retention requirements of the coronal restoration. The retention of a post in a root is critical for a successful post-retained coronal restoration and is partly determined by the design of the post and the luting agent used. Standlee et al. demonstrated that a serrated parallel-sided post that is passively cemented into an oversized post hole is the post design of choice, as adequate retention can be achieved with minimal undesirable stress on the root structure [1]. However, early studies found no significant differences in post retention with zinc phosphate, polycarboxylate, glass ionomer or epoxy cement [1,2]. Recent years have seen many developments in cement composition, with adhesion to dentine being a prime goal. Many clinicians today favour the use of adhesive cements, although results of independent evaluation may be lacking in the literature. The purpose of this study was to investigate * Corresponding author. Fax: 64 3 479 7113
0300-5712/98/$19.00 q 1998 Elsevier Science Ltd. All rights reserved. PII: S0 30 0 -5 7 12 ( 97 ) 00 0 43 - 2
the retention of serrated parallel-sided stainless steel posts cemented with various newly released cements.
2. Materials and method Fifty single-rooted permanent anterior and premolar human teeth, free of defects or restorations in the roots and having narrow unfilled root canal spaces were selected for study. The teeth were sectioned horizontally 1 mm above the labial cemento-enamel junction and the root canals were prepared using the step-down method with sodium hypochlorite irrigation. The canals were filled with laterally condensed gutta-percha and AH26 sealer (Dentsply DeTrey Division, Dentsply Ltd, Weybridge, UK). The roots were then grooved horizontally using a diamond bur in a high-speed handpiece, embedded in individual acrylic blocks and stored in water until required. Post-holes were prepared to a depth of 10 mm by removing gutta-percha with Gates–Glidden drills and preparing the root canal with a 1.5 mm Para-post drill. The post-holes
600
R.M. Love, D.G. Purton/Journal of Dentistry 26 (1998) 599–602
were irrigated with water and dried with paper points. The roots were then randomly assigned to five groups of equal size and 1.5 mm Para-posts were cemented into the postholes with one of five different cements. 2.1. Group A Ketac-Cem (ESPE, Dental-Medizin GmbH and Co. KG, Seefeld, Germany), a capsulated polymaleinate glass ionomer cement was used as the control. 2.2. Group B Vitremer luting cement (3M Dental Products, St Paul, MN, USA), a resin-modified glass ionomer cement. 2.3. Group C Fuji DUET (GC Corp, Tokyo, Japan), a reinforced glass ionomer cement. 2.4. Group D Scotchbond Resin Cement (3M Dental Products), a methacrylate-based dual cure resin cement. 2.5. Group E Panavia 21 (Kuraray Co., Ltd, Osaka, Japan) chemical cure resin cement. In all cases the dispensing, mixing and handling of components were undertaken according to manufacturer instructions for use. The posts were coated with the cements and seated to full depth using finger pressure. Excess cement was cleared from the root face and the posts were held in position for 15 min. The roots were stored in water for 6 weeks before testing. They were then placed into a retention device mounted in a universal testing machine (Instron, High Wycombe, UK), the portion of the post extending from the root was grasped in the vise of the machine and a tensile force was applied at a cross-head speed of 5 mm/min. The tensile force (N) required to remove the post from the root was recorded and the results for the groups were compared using Student’s t-tests and Mann–Whitney U-tests at the 99.9% confidence level. Visual inspection of the dislodged posts using a stereomicroscope at 12 3 magnification was undertaken to attempt to ascertain the mode of failure.
3. Results Table 1 presents the mean force (N) required to dislodge the posts from the root canals. Statistical analysis is displayed in Table 2 and revealed that posts cemented with Scotchbond Resin Cement were significantly better retained
Table 1 Mean tensile force, and standard deviation, required to dislodge a 1.5 mm serrated post from the root canal Group
Cement
Force (N)
D A E B C
Scotchbond Ketac-Cem Panavia 21 Vitremer Fuji DUET
340.06 286.16 212.56 53.90 25.97
s.d. (N) 23.13 38.71 67.62 28.42 14.70
than posts cemented with Panavia 21, Vitremer or Fuji DUET, and that there were no statistical differences relative to posts cemented with Ketac-Cem. The force required to dislodge posts cemented with Ketac-Cem was significantly higher than with Vitremer or Fuji DUET but not significantly different to the Panavia 21 group. Posts cemented with Panavia 21 were better retained than posts cemented with Vitremer or Fuji DUET. There was no significant difference between Vitremer and Fuji DUET in the force required to remove the posts. Visual inspection of the groups (Fig. 1) suggested that posts cemented with Scotchbond Resin Cement were generally devoid of cement remnants, implying adhesive failure at the cement–post interface. Posts cemented with KetacCem had more cement retained on the post compared to Scotchbond Resin Cement but areas were free of cement, suggesting that the mode of failure was a combination of adhesive failure at the cement–post interface and cohesive cement failure. Posts cemented with Panavia 21 retained a large amount of cement, implying adhesive failure at the cement–dentine interface. Posts cemented with either Fuji DUET or Vitremer retained a thin layer of cement especially within the serrations of the post. This pattern was suggestive of cohesive cement failure. 4. Discussion In vitro bond strength tests are a rather coarse method of estimating clinical efficacy. Shear bond strengths recorded Table 2 Paired comparisons of the tensile force required to remove posts cemented with various cements. Significance level , 0.001 p value Cement
Cement
Scotchbond Scotchbond Scotchbond Scotchbond Ketac-Cem Ketac-Cem Ketac-Cem Panavia 21 Panavia 21 Vitremer
Panavia 21 Vitremer DUET Ketac-Cem Vitremer DUET Panavia 21 Vitremer DUET DUET
Student’s t-test 0.001 0.000 0.000 0.002 0.000 0.000 0.024 0.000 0.000 0.011
Mann–Whitney U-test 0.0002 0.0002 0.0002 0.0025 0.0002 0.0002 0.0065 0.0003 0.0002 1.0000
R.M. Love, D.G. Purton/Journal of Dentistry 26 (1998) 599–602
Fig. 1. Sites of cement failure of representative posts cemented with various cements. 1, Ketac-Cem. 2, Fuji DUET. 3, Panavia 21. 4, Scotchbond. 5, Vitremer.
in tests of the present type may relate to the absolute strength of a material rather than to the strength of bonds to dentine, since failure may be cohesive in nature. Clinically, however, the loss of retention of a post is equally catastrophic regardless of the mode of failure and dentists need to have some guidelines on performance before they adopt new products. Due to the small sample size of each group in this study, a demanding confidence level of 99.9% was set as being significant. In addition, analysis was done by a parametric and a non-parametric statistical method to verify results. Except for the Scotchbond/Panavia 21 comparison, all comparisons were similar with the two statistical methods. For the Scotchbond/Panavia 21 comparison, the result of the Student’s t-test ( p ¼ 0.001) was strengthened by the Mann–Whitney U-test ( p ¼ 0.0002). The bonds between dentine and conventional glass ionomer cement are known to be dynamic in nature and durable in a wet environment. The cohesive strength of the set cement is probably the limiting factor in its performance in a test of the present type, and the visual suggestion of partly cohesive failure with Ketac-Cem-retained posts would support this; although, one must be cautious in placing too much credibility on the visual examination results until further study has been carried out examining the fractured surfaces under scanning electron microscopy. The values recorded in the present experiment for the Scotchbond Resin Cement are very similar to those recorded by the authors with a different brand of adhesive resin cement used on etched dentine in a previous post-retention study [3]. Adhesive resin cements have been shown to produce long resin tags in etched non-vital dentine, especially near the pulp space [4]. This, together with the high inherent strength of the composite resin, could account for the high values recorded for the Scotchbond group. Visual inspection of this group would support this theory as adhesive failure at the cement–post interface was suggested. However, the mode of failure of Panavia 21-cemented posts appeared to be adhesive at the cement–dentine interface. This may
601
imply poor dentine adhesion; however, the force required to dislodge the posts would suggest that clinically acceptable dentine adhesion occurred. The force required to remove a post cemented with Ketac-Cem or Panavia cement in this study is similar to other reported values [5]. The nature of the bonds between dentine and resinmodified glass ionomer cements is less well understood. A number of studies of light cured resin-modified glass ionomer restorative materials and bases are reported and these show the tensile and shear strengths to fall between those of conventional glass ionomer cements and adhesive resin restorative materials [6–8]. In contrast, studies of resin-modified glass ionomer luting cements have not appeared in the literature. The relatively low retention provided by the resinmodified glass ionomer cements in the present study is difficult to explain. The cement mixing procedures used were exactly in accordance with the manufacturers’ instructions, though potential exists for inconsistent or inaccurate powder to liquid ratios with the scoop and drop system of dispensing the components. Another possibility is that in producing materials of a suitable consistency for luting the manufacturers have lowered the powder to liquid ratios to levels such that the shear bond strengths are diminished in comparison with the relatively viscous restorative materials. The pattern of cement retained on the posts for Fuji DUET and Vitremer strongly suggests that cohesive failure occurred in the cement, supporting this hypothesis. Mount (1994) hypothesised that in resin-modified glass ionomer cements a reduction in powder content would inevitably mean an increase in the proportion of HEMA with the consequent potential for greater water uptake by this hydrophilic resin [9]. The samples in the present experiment were stored in water for 6 weeks prior to testing and this may have some bearing on the results. Applying the cement to the posts only and not into the post spaces could have produced air voids, which would affect the results, although it would be unlikely that it would significantly affect one group over another. The manufacturer of one of the resin cements specifically recommends not placing cement in the canal because of the risk of setting before post placement. In view of this, and to standardise methodology, the decision was made to apply cement only to the posts in all groups. The importance of surface pre-treatment has not been investigated for resin-modified glass ionomer luting cements and it is of interest that the instructions with one of the products (Fuji DUET) used in the present study recommend acid pre-treatment of dentine while only washing and drying is recommended for the other (Vitremer). Resin-modified glass ionomer cements offer considerable promise in dentistry. They appear to have found favour as restorative materials and bases in selected cases. Their future role as luting agents is less clear and on the basis of the present study they could not be recommended for use in the cementation of root canal posts.
602
R.M. Love, D.G. Purton/Journal of Dentistry 26 (1998) 599–602
References [1] Standlee JP, Caputo AA, Hanson EC Retention of endodontic dowels: effects of cement, dowel length, diameter and design. Journal of Prosthetic Dentistry, 1978;39:401–405. [2] Krupp JD, Caputo AA, Trabert KC, Standlee JP Dowel retention with glass-ionomer cement. Journal of Prosthetic Dentistry, 1979;41:163– 166. [3] Love RM, Purton DG The effect of serrations on carbon fibre posts— retention within the root canal, core retention, and post rigidity. International Journal of Prosthodontics, 1996;9:484–488. [4] Blair F, Whitworth J, Wassell RW Impregnation by dentine bonding agents into instrumented root-face dentine. Journal of Dentistry, 1995;23:289–294.
[5] Mendoza DB, Eakle WS Retention of posts cemented with various dentinal bonding cements. Journal of Prosthetic Dentistry, 1994;72:591–594. [6] Friedl K-H, Powers JM, Hiller K-A Influence of different factors on bond strength of hybrid ionomers. Operative Dentistry, 1995;20:74– 80. [7] Fritz UB, Finger WJ, Uno S Resin modified glass ionomer cements: bonding to enamel and dentine. Dental Materials, 1996;12:161–166. [8] Burgess JO, Nasser B, Chan DCN, Hummert T A comparative study of three glass ionomer base materials. American Journal of Dentistry, 1993;6:137–141. [9] Mount GJ Glass-ionomer cements: past, present and future. Operative Dentistry, 1994;19:82–90.