Four Post-and-Core Combinations as Abutments Stefan Ellner, LDSa for Fixed Single Crowns: Tom Bergendal, LDS, PhDb A Prospective up to 10-Year Study Bo Bergman, LDS, PhDc

Purpose: In the present prospective study, four different post-and-core systems were evaluated over a period of up to 10 years. Materials and Methods: Fifty endodontically treated teeth in 31 patients were randomized to one of four groups for post-and-core placement: Group 1 received conventional tapered cast posts and cores (n = 14); group 2 received ParaPost system prefabricated posts with cast cores (n = 13); group 3 received ParaPost system cast posts and cores (n = 13); and group 4 received Radix-Anchor posts (n = 10). Clinical and radiologic evaluations were made. Results: One in group 2 was functioning well 58 months after placement when the patient died. No posts and cores in groups 1 or 2 had been lost or had any complications, one in group 3 had been lost because of a root fracture after 108 months, and two in group 4 had been lost after 54 and 88 months, respectively, because of loss of retention. The final treatment result for 46 of the 49 remaining posts (30 patients) was successful. The overall failure rate was 6%. There were no statistically significant differences between the four groups. Conclusion: If recommended procedures are strictly followed, posts and cores can serve as abutments for fixed single crowns with satisfactory long-term results. Int J Prosthodont 2003;16:249–254.

number of prefabricated and individually de- light-curing resins, and one used cast-metal posts Asigned posts have been developed and, in gen- and cores. Of 154 restorations, 11% failed. The au- eral, marketed with no presentation of any evidence thors found no statistically significant differences be- of their superiority or inferiority in relation to other tween the three techniques and concluded that ex- systems. To evaluate the different posts, numerous in tended periods of clinical investigation are needed to vitro studies have been performed.1 However, in determine which systems will have the best clinical vitro studies often produce conflicting results and results in the long term. thus are of little help in deciding which post-and-core The present prospective clinical study was de- system would be best in a given clinical situation. signed to evaluate the clinical outcome of four dif- In contrast with the numerous in vitro studies, ferent post-and-core combinations in a longitudinal comparatively few clinical studies have been pub- perspective. The hypothesis was that the four com- lished. Most are retrospective,2–17 but to the best of binations are comparable, provided that a 2-mm fer- the authors’ knowledge, only one prospective study rule is prepared on the tooth. has been published.18 That 3-year study compared three techniques; two used prefabricated screw posts Materials and Methods or ParaPost stainless steel posts (Whaledent) with Fifty endodontically treated teeth in 31 patients (14 aSenior Consultant and Head, Clinic for , Specialist women and 17 men aged 16 to 75 years, mean age Dental Care Center, Kalmar County, Sweden. 48 years) met the inclusion criteria. All patients gave bHead, Department of Prosthetic Dentistry, Institute for Post- their written informed consent to participate in the graduate Dental Education, Jönköping, Sweden. study. The patients were randomized to a certain cProfessor Emeritus and Former Chair, Department of Prosthetic Dentistry, Medical-Odontological Faculty, Umeå University, Sweden. type of post-and-core combination by lot. Initial prosthodontic treatment was performed between Reprint requests: Dr Stefan Ellner, PO Box 299, SE-391 23 Kalmar, September 1989 and September 1993. Sweden. Fax: + 46 480 84977. e-mail: [email protected]

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7 Group 4 6 Group 3 5 Group 2 4 Group 1 3 2 1 No. of posts and cores 0 15 14 13 12 11 21 22 23 24 25 45 44 43 33 34 35 Tooth No.

Fig 1 Distribution of posts and cores according to group (see Materials and Methods) and tooth (Fédération Dentaire Internationale tooth-numbering system).

Study Criteria Endodontic Treatment

Clinical inclusion criteria were: If the root filling of the tooth to undergo post-and-core buildup had a radiologically detectable poor seal, was • One or more single-rooted teeth in need of a sin- less than 3 mm from the radiologic apex, or had an api- gle crown and not intended for use in the support cal radiolucency near the tooth, the tooth was en- of a removable partial denture (Fig 1). dodontically retreated. All root canals had been filled • No marked signs of bruxism, expressed as heavy with gutta percha. The gutta percha was removed with attrition. A limited number of wear facets on the a Gates reamer (Hager & Meisinger). The periapical remaining teeth were accepted. conditions were classified according to Petersson et al19: • At least 2 mm of remaining vertical marginal tooth substance available for ferrule preparation. • Normal = Apical periodontal ligament space not more than double the width of the other parts of Some of the teeth had a screw post retaining an the root; appearance of the surrounding osseous crown; none of these posts had been structure is normal. placed more than 5 years before the tooth was in- • Bone destruction = Periapical radiolucency ob- cluded in the study, and the screw post was re- served; bone destruction ≤ 5 mm and > 5 mm moved. were registered separately. At the initial examination, the following general • Periapical conditions not evaluable = Poor radi- clinical and radiologic factors were evaluated: ographic quality; periapical structures impossible to evaluate. • Clinical and radiologic caries for all teeth. • Sagittal, transverse, and vertical maxilloman- Post-and-Core Designs dibular relationships. • , including intercuspal contact on teeth • Group 1 = Conventional tapered posts and cores with posts and cores (stable/unstable). Any oc- cast in a type III gold alloy according to Zarb et clusal interference was noted and adjusted. al20 (n = 14) •Occlusion in lateral excursions (balanced/unbal- •Group 2 = ParaPost system with prefabricated anced). Canine-protected articulation was regis- posts in nonoxidizing gold alloy and cast cores in tered separately. a type III gold alloy (n = 13) • Plaque at four surfaces: mesial, buccal, distal, • Group 3 = ParaPost system with cast posts and and lingual, after use of a dye solution (yes/no). cores in a type III gold alloy after the use of pre- • Pocket depth at six surfaces: mesiobuccal, buccal, fabricated burnout posts (n = 13) distobuccal, distolingual, lingual, and mesiolin- • Group 4 = Radix-Anchor (Maillefer) threaded ti- gual. tanium posts with cores in chemically cured resin • Bleeding on probing of pocket depths (yes/no). composite (n = 10) •Gingival retractions, gingival swelling, cracks, and so on, around the experimental tooth. The type III gold alloys used were JS C-guld (JS Sjöding) • Periapical conditions. Intraoral radiographs were and Protor (Cendres & Métaux). Concise (3M) and made using the long-cone parallel technique. Adaptic (Dentsply) were the resin composites used.

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20 18 16 14 12 10 8

No. of posts 6 4 2 0 678910111213 Post length (mm)

Fig 2 Number of posts according to post length as measured on the working cast; light gray bars = lost posts and cores.

The first 40 teeth were randomly assigned to one of 4, the reamers provided by the manufacturers were the above groups. Radix-Anchor was excluded from used. The transition between the post and the core in the randomization of the last 10 teeth, since there were all systems was conical, and the shape of the holes for indications that the system was not suitable for use in the posts was oval to prevent rotation, except in the all situations. During preparation of the core buildup Radix-Anchor system. Care was taken to prepare the on incisors with a large angulation between the crown outer surfaces of the root parallel at least 2 mm to cre- and the root, a large portion of the core-retention part ate a ferrule effect. The finishing line was accomplished of the Radix-Anchor post had to be removed. This cre- as a shallow chamfer preparation. A polyvinyl siloxane ated a problem, as the teeth in the study had been ran- material, President (Coltène/Whaledent), was used for domized, which made it mandatory to treat the se- impression taking. Before cementation of the post and lected tooth with the randomized post-and-core core, the inner surface of the was gently combination. To preserve the random design of the coarsened with a medium-grit diamond on a low-speed study as much as possible, group 4 was excluded contra-angle handpiece to create surface roughness. from the randomization process and teeth were only The root canal was thoroughly cleaned with 3% hy- assigned to groups 1, 2, or 3 (Fig 1). drogen peroxide, Tubulucid (an ethylenediaminete- traacetic acid [EDTA]–containing cleaner; Dental Clinical Preparation Therapeutics), and 96% alcohol using a rotating brush. All posts and cores were cemented with zinc-phosphate Five experienced performed the initial cement (Dentsply/DeTrey). The crowns—metal ce- prosthodontic treatment. Two clinicians placed one ramic or type III gold alloy with acrylic resin facing— post and core each, one placed four posts and cores, were placed using the same luting cement. and another placed five. The remaining 39 posts and The patients were re-examined regularly until 1999. cores were inserted by one of the authors. The place- The final examination took place after between 72 and ment of all posts and cores followed, if available, the 122 months (median 109 months). At the follow-up, manufacturers’ recommendations concerning prepa- the cariologic and periodontal parameters were as- ration, design, cementation, and choice of super- sessed for the experimental tooth and its contralat- structure (acrylic resin–veneered gold alloy crowns or eral. If the latter was missing or included in the study, metal-ceramic crowns). an adjacent tooth was used. The treatment was judged Post space was prepared to accommodate a post of as successful if the post and core was still in place, with at least 8 mm (Fig 2). Other objectives were that the no loss of retention after crown placement; exhibited length of the post should equal the height of the artifi- no radiologic signs of fractures or sudden loss of bone cial crown and that the apical part of the tooth should along the root surface indicating fracture or perforation; contain at least 4 mm of gutta percha.21 In some cases, and exhibited no clinical signs of fracture such as pain, these objectives were in conflict. The amount of gutta localized increased pocket depth, or fistulation. percha was considered to be the most important fac- tor. The diameters of the posts were at least 1.25 mm, Statistical Methods with the exception of one Radix-Anchor size No. 1, di- ameter 1.0 mm. A Davis reamer (JS Sjöding) was used The chi-square test was used to test whether differ- to prepare the canals in group 1; the diameter of the post ences between the four groups of posts and cores was measured in the coronal half. In groups 2, 3, and could be explained by mere chance or represented

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Table 1 No. of Teeth Failed and Failure Rate for real differences. The following levels of significance Each Group Based on All Teeth were used: P ≤ .01 significant; .01 < P ≤ .05 almost significant; and P > .05 not significant. No. of teeth No. of teeth Failure Group* total failed rate (%) Results 11400 21318 31300The overall failure rate was 6% (Table 1). If group 4 410220(Radix-Anchor) is excluded—since the use of this All 50 3 6 type of post and core was discontinued after the 1, 2, and 3 40 1 3 placement of the first 40—the overall failure rate was *Group 1 = conventional cast tapered post and core, type III gold alloy; 3% at the final examination. It should be empha- group 2 = ParaPost prefabricated post, No-Ox alloy, cast core type III gold alloy; group 3 = ParaPost cast post and core, type III gold alloy; sized that until the first failure, 54 months after inser- group 4 = Radix-Anchor post, composite resin core. tion, all 50 original posts and cores had functioned sat- isfactorily. One patient in group 2 died 58 months after place- ment of a post and core; the restoration was func- Table 2 Actual and Mean Functional Times (mo) for Still-Functional and Failed Posts and Cores at Final tioning well at that time. Two posts and cores in Examination group 4, 9 mm long and placed on the maxillary left central incisor and second premolar, were lost after Function Mean 54 and 79 months, respectively, because of loss of Posts and cores* time time retention. One post and core in group 3, 8 mm long Group 1 and placed on the maxillary left canine, was lost be- Posts still in place 81Ð122 101 cause of root fracture after 108 months. One patient Group 2 Posts still in place 72Ð122 100 in group 1 was ill at the time of the final examination Deceased patient 58 and could not attend, but reported that the post and Group 3 core was in place and that there were no problems Posts still in place 77Ð123 110 Root fracture 108 with it. Consequently, among the 30 patients who Group 4 completed the study, 46 of 49 posts (94%) were still Posts still in place 90Ð119 101 in place after a mean of 103 months. Loss of retention 54, 79 At the final registration, there were no statistically *See Table 1 for explantions of groups. significant differences between the four groups. No differences in function times between the four groups were found at the final examination (Table 2). A de- tailed analysis of the three failures did not indicate any connection with factors such as maxillo- mandibular relationships, occlusal interferences, un- d e f balanced occlusion in lateral excursions or canine- protected articulation, caries, or periodontal affections. The conflicting objectives regarding post length resulted in a post:crown ratio (c:d; Fig 3) of < 1 for 34 of the 50 posts. At the beginning of the study, periapical radiolu- cencies were found around 10 roots. Three were still a b c radiolucent at the final registration. Two of these roots had a small radiolucency around excess gutta percha material, and one root had a destruction 3 mm in diameter. None of these defects changed in size during the study period. Another three sites with no signs of radiolucency at baseline had developed the defect at the final registration. However, none of these defects was larger than 1 mm in diameter or had other symptoms that indicated a need for endodon- Fig 3 Reference points for measurements: a = distance from tic retreatment or apical surgical therapy. The intra- apex to marginal bone ridge; b = length of post protruding from crown; c = total length of post; d = length of crown; e = length of oral radiographs of the other roots revealed no ab- post and crown; f = total length of tooth. normal signs.

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Discussion the measurements described in Fig 3 were made and used in the following calculations: The results of two of the systems (groups 1 and 3) were excellent—no failures. One of 13 failed in group 2, 1. c/d = length of post divided by length of crown and two of 10 failed in group 4, but the differences be- 2. c/f = length of post divided by length of tooth tween the four post-and-core systems were statistically 3. b/e = length of post protruding out of the crown nonsignificant. The success rates exceeded (groups 1 divided by length of post and crown and 3) or were comparable with (groups 2 and 4) those 4. a – (f – e) = length of post under bone margin in previous retrospective studies. However, it should be noted that the number of posts and cores in each No correlations between any of these calculations for of the groups in the present study was comparatively the entire material and the calculations of the failed small. Furthermore, during the collection of the pre- posts and cores could be found. sent material, clinical experience indicated that the One special post-and-core system is sometimes Radix-Anchor system seemed unsuitable for use on all touted as being superior to all others. The present teeth; its use was therefore discontinued after the first prospective long-term clinical study, covering up to 40 posts and cores had been placed. The compara- 10 years and comparing different systems, does not tively negative results obtained with Radix-Anchor support such a dogmatic view. On the contrary, it can should therefore be judged in this light. The reason for be concluded that—provided the procedures used in discontinuing use of the system was a fear of problems this study are strictly followed—the use of post-and- with the retention of the core composite buildup. core buildups and abutments for single crowns has an However, the reason for the two failures in group 4 excellent prognosis in the medium-term perspective. was a loss of cement retention between the root and the post. The crown had become loose in situ but did References not fall off, as the post and core was retained by the threads of the post. 1. Fernandes AS, Dessai GS. Factors affecting the fracture resistance A pilot study covering a mean follow-up period of of post-core reconstructed teeth: A review. Int J Prosthodont 2001; 7.9 years16 analyzed the outcome of 112 post-and- 14:355–363. 2. Bergman B, Lundquist P, Sjögren U, Sundquist G. Restorative and core buildups of a prefabricated metal post—Dentatus endodontic results after treatment with cast posts and cores. J (Dentatus), Unimetric (Mailleter), or Radix-Anchor— Prosthet Dent 1989;61:10–15. in combination with a composite core. The mean 3. Sorensen JA, Martinoff JT. Endodontically treated teeth as abut- failure rate was 12.5%; Dentatus had the highest ments. J Prosthet Dent 1985;53:631–636. (30%; n = 7), Radix-Anchor had the next highest 4. Grieve AR, McAndrew R. A radiographic study of post-retained crowns in patients attending a dental hospital. Br Dent J 1993;174: (13%; n = 6), and Unimetric had the lowest (2%; n = 197–201. 1). The mean follow-up times differed between the 5. Roberts DH. The failure of retainers in prostheses—An three systems; the follow-up time for Dentatus was the analysis of 2000 retainers. Br Dent J 1970;128:117–124. longest. Furthermore, teeth with a poor initial prog- 6. Palmqvist S, Swartz B. Artificial crowns and fixed partial nosis had been included in the material. These short- 18 to 23 years after placement. Int J Prosthodont 1993;6:279–285. 7. Molin M, Bergman B, Ericson Å. A clinical evaluation of coni- comings complicate a fair comparison between the cal crown retained dentures. J Prosthet Dent 1993;70:251–256. three post-and-core systems, and the authors them- 8. Randow K, Glantz PO, Zöger B. Technical failures and some re- selves underlined the need for controlled clinical tri- lated clinical complications in extensive . An als to verify the findings. For Radix-Anchor, the main epidemiological study of long-term clinical quality. Acta Odontol cause of failure was dislodgment, and the authors Scand 1986;44:241–255. 9. Laurell L, Lundgren D, Falk H, Hugoson A. Long-term progno- recommended that this post be provided with an an- sis of extensive polyunit cantilevered fixed partial dentures. J tirotation pin after insertion. It is interesting to note the Prosthet Dent 1991;66:545–552. similarity in the mode of failure in this study and the 10. Lewis R, Smith B. A clinical survey of failed post retained crowns. previous one.16 The Radix-Anchor post is cylindric Br Dent J 1988;165:95–97. with one sharp thread, whose purpose is both to 11. Weine FS, Wax AH, Wenckus CS. Retrospective study of tapered, smooth post systems in place for 10 years or more. J Endod 1991; thread the root before luting and act as a retention el- 17:293–297. ement after the luting procedure. The post is also 12. Mentink AGB, Meeuwissen R, Käyser AF, Mulder J. Survival rate highly polished, possibly making retention of the ce- and failure characteristics of the all metal post and core restora- ment more difficult. tion. J Oral Rehabil 1993;20:455–461. Several guidelines have been proposed to opti- 13. Torbjörner A, Karlsson S, Ödman PA. Survival rate and failure char- 20–24 acteristics for two post designs. J Prosthet Dent 1995;73:439–444. mize the success of a post, such as the length of 14. Sundh B, Ödman P. A study of fixed prosthodontics performed at the post in absolute numbers and as related to tooth a university clinic 18 years after insertion. Int J Prosthodont 1997; length, crown length, and so on. In the present study, 10:513–519.

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15. Ottl P, Laucer CH. Success rates for two different post and cores. 20. Zarb GA, Bergman B, Clayton JA, Mackay HF. The buildup of J Oral Rehabil 1998;25:752–758. individual teeth. In: Prosthodontic Treatment for Partially 16. Mentink AGB, Creugers NHJ, Meeuwissen R, Leempoel PJB, Edentulous Patients. St Louis: Mosby, 1978:130–139. Käyser A. Clinical performance of different post and core sys- 21. Morgano SM, Milot P. Clinical success of cast metal posts and tems—Results of a pilot study. J Oral Rehabil 1993;20:577–584. cores. J Prosthet Dent 1993;70:11–16. 17. Lindhe LA. The use of composites as core material in root-filled 22. Glantz PO, Nilner K. Root canal posts—Some prosthodontic as- teeth. II. Clinical investigation. Swed Dent J 1984;8:209–216. pects. Endod Dent Traumatol 1986;2:231–236. 18. Hatzikyriakos AH, Reisis GI, Tsingos N. A 3-year postoperative 23. Torbjörner A. Treatment management. Posts and cores. In: clinical evaluation of posts and cores beneath existing crowns. Karlsson S, Nilner K, Dahl BL (eds). A Textbook of Fixed J Prosthet Dent 1992;67:454–458. Prosthodontics. Stockholm: Gothia, 2000:173–186. 19. Petersson K, Petersson A, Olsson B, Håkansson J, Wennberg A. 24. Zmener O. Adaptation of threaded dowels to dentin. J Prosthet Technical quality of root fillings in an adult Swedish population. Dent 1980;43:530–535. Endod Dent Traumatol 1986;2:99–102.

Literature Abstract

Comparative evaluation of casting retention using the ITI Solid abutment with six cements.

This study tested the retention of metal copings cemented on ITI Solid titanium abutments using six different cements: zinc oxide (non-eugenol; Temp Bond NE); zinc oxide eugenol (IRM); zinc phosphate (HY-Bond); resin-modified glass-ionomer (Protec Cem); zinc polycarboxylate (Durelon); and resin cement (Panavia 21). Ten prefabricated burnout caps with wax loops at- tached to the occlusal surface were cast with a noble alloy. The metal copings were cemented onto solid titanium abutments connected to hollow-screw 3.8-mm ITI implants with a torque of 35 Ncm. A pullout test was carried out using a universal testing machine at a cross-head speed of 0.5 mm/min until decementation. The same 10 castings were used to test the six cements. Based on the results, the retentive ability of the various cements was ranked in the following as- cending order: Temp Bond, IRM, HY-Bond, Protec Cem, Durelon, and Panavia 21. The mean loads at failure ranged from 3.18 kg (Temp Bond) to 36.53 kg (Panavia 21). The retentive value of Temp Bond was not significantly different from IRM. HY-Bond and IRM provided statistically similar retention values. Protec Cem and Durelon were not statistically different. Panavia 21 showed significantly higher retention than the other cements. The ability of the cements to retain the castings differed from values obtained in studies where the same cements were used on nat- ural teeth. The authors explained that this difference is likely due to the material and surface characteristics of the implant abutment. Therefore, cement retention values reported in studies that use teeth as abutments may not apply to cement-retained implant-supported restorations.

Mansour A, Ercoli C, Graser G, Tallents R, Moss M. Clin Oral Implants Res 2002;13:343Ð348. References: 24. Reprints: Dr Carlo Ercoli, Division of Prosthodontics, University of Rochester Eastman, Department of Dentistry, 625 Elmwood Avenue, Rochester, New York 14620. e-mail: [email protected]—Swee-Chian Tan, Iowa City, Iowa

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