journal of dentistry 42 (2014) 373–376
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Clinical performance of cantilevered fixed dental prostheses abutments in the shortened dental arch§ Martin Sasse a,*, Matthias Kern a, Birgit Marre´ b, Michael H. Walter b a
Department of Prosthetic Dentistry, Christian-Albrechts University of Kiel, Kiel, Germany Department of Prosthetic Dentistry, Universita¨tsZahnMedizin, Technische Universita¨t Dresden, University Hospital Carl Gustav Carus, Fetscherstraße 74, 01307 Dresden, Germany b
Objectives: This article is part of a randomized clinical trial on different treatments in the
Received 2 May 2013
shortened dental arch (SDA). It focused on the abutment tooth prognosis with cantilevered
Received in revised form
fixed dental prostheses (CFDPs).
19 December 2013
Methods: Sixty-two patients with a bilaterally SDA up to the first or second premolar in the
Accepted 21 December 2013
mandible or maxilla were evaluated. In 57 of 124 quadrants, second premolars were replaced by a CFDP (cantilever group). In the remaining 67 quadrants, a natural second premolar was present and thus no need for a CFDP was given (non-cantilever group). Patients were
recalled annually up to 5 years.
Results: The mean observation period was 56.3 months (min. 3.0, max. 76.2, SD 16.1).
Kaplan–Meier survival rates concerning tooth loss and tooth fracture were 93.9%/94.0%
in the cantilever group and 91.9%/92.8% in the non-cantilever group. Differences between
both groups were not significant. The survival rate concerning loss of retention of CFDP
Fixed dental prostheses
retainers was 92.1% in the cantilever group. Conclusion: After 5 years of clinical service, CFDPs for the replacement of the second premolar showed no negative impact on the abutment tooth prognosis. Clinical significance: Cantilevered fixed dental prostheses present a viable treatment option in the shortened dental arch without compromising the medium-term abutment tooth prognosis. # 2014 Elsevier Ltd. All rights reserved.
Back in 1981 research results already showed that oral functions (number of chewing strokes needed for swallowing §
increases) change slowly with a decreasing number of occlusal units until there are at least 4 occlusal units left in a dentition.1 Patients started to complain about their masticatory functions when the number of occlusal units was less than 4 in a symmetrically shortened arch. Based on these findings the
ISRCTN.org Identifier: ISRCTN97265367. * Corresponding author at: Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University at Kiel, Arnold-Heller Strasse 16, 24105 Kiel, Germany. Tel.: +49 431 597 2873; fax: +49 431 597 2860. E-mail address: [email protected]
(M. Sasse). 0300-5712/$ – see front matter # 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jdent.2013.12.013
journal of dentistry 42 (2014) 373–376
treatment concept of the shortened dental arch (SDA)2 with the non-replacement of molars has been widely accepted by the professional community as an adequate treatment approach whilst the benefit of removable dental prostheses (RDPs) for mere molar replacement is controversial.3,4 In some patients a RDP replacing missing molars might enhance masticatory functions and improve the patients oral health related quality of life.5 On the other hand is the improvement of the patients oral health related quality of life by a RDP not predictable and the RDP might also cause damage to the abutment teeth and supporting tissues due to higher stress levels. An increase in treatment costs, more maintenance and more frequent repair also comes along with RDP treatment. The randomized shortened dental arch study was designed to evaluate in patients with a complete loss of molars the efficacy of the treatment with RDPs for molar replacement compared to a FDP treatment not replacing any molars (SDA group).6 In cases with a missing second premolar, the principles of the SDA concept made a treatment with a cantilevered fixed dental prosthesis (CFDP) necessary. Implant supported restorations were not included in the study. Since randomized clinical trials on the outcome of CFDPs are lacking this article is presenting part of a larger multicentre study and evaluated the SDA group in order to gain information on how abutments of CFDPs perform. Different studies described inferior success and survival rates for CFDPs compared to conventional fixed dental prostheses (FDPs).7,8 Based on these findings, the hypothesis of this analysis was that the survival rate of CFDP abutments in the canine and premolar region is inferior compared to the survival rate of respective teeth without CFDPs.
Materials and methods
Patients over 35 years of age with all molars missing in one jaw and with at least both canines and one premolar left on each side were eligible to enter this 14-centre randomized controlled trial. The study design was approved by the Institutional Review Board (TU Dresden, EK 260399). All patients gave written informed consent before entering the study. In the SDA group, tooth-borne metal-ceramic FDPs were used for replacement of missing teeth. Any missing second premolar was replaced with a CFDP. No prosthetic treatment was performed if the shortened dental arch was complete up to the second premolar. Clinical and laboratory procedures were standardized according to a detailed study protocol.6 Overall, 215 patients were enrolled in the main trial. One hundred and six patients were assigned to the SDA group. The primary outcome measure in the main trial was tooth loss. The secondary outcome measures included clinical, technical and subjective variables amounting to a total of 21 variables described in detail in the study design and protocol publication.6 The main trial sample size was determined by calculating to reach a power of 75% at a two sided .05 significance level. The expected tooth loss was presumed to reach 20% with RDP treatment and 5% with SDA treatment. With a scheduled twoyear recruitment period and a five-year follow-up period the calculated number of patients required, therefore amounted
to a total of 70 patients per treatment group. Further details concerning presumptions and sample size calculation as well as details on the randomization have already been published.6 The randomization took place centrally at the biometrical centre of the University of Mu¨nster. Regarding this article, the total available sample size (n = 124) was determined by the main trial and the calculated power to be reached with this sample size was 1 b = 0.80 with a = 0.05 and effect size d = 0.1 at an estimated control group event rate of 5%. CFDP abutments received a chamfer preparation whilst the frameworks were made of high noble alloys. Feldspathic porcelain materials were used for veneering of the frameworks and to achieve an ovate pontic form on the basal aspect. Out of the 106 randomized patients in the SDA group, 69 patients actually underwent the respective treatment in the upper or lower jaw. Only canines and premolars were included in the analysis. Quadrants were regarded separately. Five patients who received wide span CFDPs extending to the contralateral side and two patients who switched treatment within the first year after insertion were excluded. Therefore, a total number of 124 quadrants in 62 patients could be evaluated. Of these 124 quadrants, 57 were restored with a CFDP (cantilever group) whereas 67 quadrants did not receive a cantilevered restoration (non-cantilever group). In the cantilever group, the canine and the first premolar were abutment teeth. In the non-cantilever group, in 8 quadrants the missing first premolar was replaced by an FDP extending from the canine to the second premolar. In 59 quadrants, the canine and both premolars were present. In 14 of these 59 quadrants, none of these teeth were crowned. The primary outcome measure within the conducted analysis was tooth loss. Secondary outcome measure variables in this particular part of the larger study were reduced as compared to the main trial to tooth fracture and loss of retention of CFDP retainers. These secondary outcome measure variables were, amongst others, part of the main trials secondary outcome measures. Fractures were defined as the coronal part of a tooth being fractured off the root at gingival level. Statistical analysis encompassed Kaplan–Meier survival analyses9 and Mantel–Cox log-rank tests (SPSS 16 Software, SPSS Inc., Chicago, USA)10 for comparisons.
The mean observation period amounted to 56.3 months (min. 3.0, max. 76.2, SD 16.1). Eight tooth losses, 7 tooth fractures and 4 losses of retention occurred. Of the 8 tooth losses, 3 occurred in the cantilever group (5.3% of the respective quadrants) and 5 losses (7.5%) occurred in the non-cantilever group. The eight teeth lost were extracted either because of fracture (n = 5, 62.5%) or because of caries or periodontal problems (n = 3, 37.5%). Three fractures were found in the cantilever group (5.3%) two of which lead to tooth loss. Four fractures were found in the non-cantilever group (6.0%) three of which lead to tooth loss. All the mentioned tooth fractures were not repairable except for the two cases in which a cast post and core was made and the tooth could be saved. The reason for the teeth to fracture could not be determined for sure. Fracture causes
cantilever no cantilever 60
Survival Rate (%)
journal of dentistry 42 (2014) 373–376
Observation Time (Years) Fig. 1 – Kaplan–Meier analysis. Cumulative survival regarding tooth loss.
could not be identified and might be related to multiple causes. We assume the reason for the teeth to fracture was overloading of the remaining tooth substance. The reasons why the teeth were overloaded remain unclear and are probably a combination of multiple causes. There were 4 cases (7.0%) of loss of retention in the cantilever group. The survival rate according to Kaplan–Meier9 concerning tooth loss was 93.9% in the cantilever group and 91.9% in the non-cantilever group (Fig. 1). No statistically significant difference could be detected (p = .577). Neither could a significant difference be found (p = .841) when evaluating the survival rate concerning tooth fracture amounting to 94.0% in the cantilever group and 92.8% in the non-cantilever group (Fig. 2). The graphs of the survival functions for both groups were comparable. The survival rate concerning loss of retention of CFDP retainers was 92.1%.
cantilever no cantilever
CFDPs compared to conventional FDPs over 10 years was reported. In the same review, the difference in survival after 5 years was only 2.4% though. Therefore, it remains to be seen whether survival and performance of CFDPs in this study will differ significantly during long-term observation. In our study, cantilevered extensions were no longer than one premolar because it has been shown that longer extensions lead to high failure rates14. This might explain the comparable results for quadrants with and without CFDPs. It still has to be kept in mind that these results refer to the use of CFDPs for exclusive replacement of the second premolar only as done in the current study. An increased failure rate which might be expected due to increased stress on CFDPs15 could not be found. A possible reason for this might be a lower functional loading based on neuromuscular regulatory processes in quadrants with CFDPs. Even though the limited number of restorations involved in this study might limit the findings, the medium-term clinical outcome of cantilevered restored quadrants and non-cantilevered quadrants can be considered comparable.
After 5 years of clinical service, CFDPs showed no negative impact on the medium-term abutment tooth prognosis. CFDPs present a viable treatment option in the shortened dental arch.
Acknowledgement This trial was funded by the Deutsche Forschungsgemeinschaft (German Research Foundation, DFG WA 831/2-1, 2-2, 2-3, 2-4, 2-5, 2-6). The following colleagues have contributed materially to this paper Sandra Freitag-Wolf (Kiel, Germany), Wolfgang Gernet (Munich, Germany), Eckhard Busche (Witten, Germany), Bernd Wo¨stmann (Giessen, Germany), Wolfgang Hannak (Berlin, Germany), Andreas Chatzidakis (Berlin, Germany), Nicole Passia (Kiel, Germany), Joerg Strub (Freiburg, Germany), Stefan Wolfart (Aachen, Germany), Thomas Reiber (Leipzig, Germany), Sinsa Hartmann (Mainz, Germany), Herbert Scheller (Mainz, Germany), Guido Heydecke (Hamburg, Germany), Florentine Jahn (Jena, Germany), Wilfried Reinhardt (Jena, Germany), Ralph G. Luthardt (Ulm, Germany), Torsten Mundt (Greifswald, Germany), Rainer Biffar (Greifswald, Germany), Peter Pospiech (Dresden, Germany), Klaus Bo¨ning (Dresden, Germany), Helmut Stark (Bonn, Germany), Ernst-Ju¨rgen Richter (Wu¨rzburg, Germany), Jan Huppertz (Wu¨rzburg, Germany).
Survival Rate (%)
No significant difference in survival of CFDP abutments compared to the respective teeth in quadrants without CFDPs could be found within the evaluated 5-year period. This is in contrast to our expectations as well as to the findings reported in other studies which showed inferior survival rates of CFDPs.11–13 A systematic review12 revealed a 10 year loss of retention rate of 16.1% which seems to be in line with our 5 year rate of 7%. An important factor regarding loss of retention of CFDPs as evaluated in this article, is probably an increased pull-off force or tensile stress due to the leverage of the restoration. In another study,13 a 9% lower survival rate of
Observation Time (Years) Fig. 2 – Kaplan–Meier analysis. Cumulative survival regarding tooth fracture.
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