Clinical outcomes of rigid and non-rigid telescopic double-crown-retained removable dental prostheses: An analytical review

Jeong-Gyo Seo; Jin-Hyun Cho

doi:10.4047/jap.2020.12.1.38

Journal List > J Adv Prosthodont > v.12(1) > 1142862

Go to TopGo to Top Go to BottomGo to Bottom

TOOLS

Seo and Cho: Clinical outcomes of rigid and non-rigid telescopic double-crown-retained removable dental prostheses: An analytical review

Original Article

The Journal of Advanced Prosthodontics 2020; 12(1): 38-48.

Published online: 20 February 2020

DOI: https://doi.org/10.4047/jap.2020.12.1.38

Clinical outcomes of rigid and non-rigid telescopic double-crown-retained removable dental prostheses: An analytical review

Jeong-Gyo Seo

, Jin-Hyun Cho

Department of Prosthodontics, School of Dentistry, Kyungpook National University, Daegu, Republic of Korea.

Corresponding author: Jin-Hyun Cho. Department of Prosthodontics, School of Dentistry, Kyungpook National University, 2177, Dalgubeoldae-ro, Jung-gu, Daegu 41940, Republic of Korea. Tel. +82536007651: prosth95@knu.ac.kr

Received 11 February 2019 Revised 30 January 2020 Accepted 12 February 2020

The Korean Academy of Prosthodontics

(open-access):

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

PURPOSE

The objective of this literature review was to analyze the cumulative survival rates (CSRs) of rigid and non-rigid double-crown-retained removable dental prostheses.

MATERIALS AND METHODS

Screening of the literature published from January 1995 to December 2019 was performed by using electronic data base (Pubmed) and manual search. The CSRs of rigid and non-rigid double crown removable dental prostheses were investigated.

RESULTS

A total of 403 articles were reviewed and 56 relevant articles of them were selected. Subsequently, 25 articles were included for data extraction. These articles were classified according to rigid and non-rigid type double crowns and further subdivided into teeth, implants, and teeth-implant combination types. The CSRs of rigid type double crown ranged from 68.9% to 95.1% of 5 to 10 years in tooth abutments, 94.02% to 100% over a 3-year mean observation periods in implant abutments, and 81.8% to 97.6% in tooth-implant combination. Non-rigid type double crowns had various CSR ranges from 34% to 94% maximum during 10 years observation in teeth abutment. The CSRs of non-rigid type had over 98% in implant abutments, and ranged from 85% to 100% in tooth-implant combination.

CONCLUSION

The CSRs of double crowns varies according to types. With accurate evaluation of the remaining teeth and plan of the strategic implant placement, it could be successful treatment alternatives for partially or completely edentulous patients.

Keywords: Telescopic double crown, Rigid double crown, Non-rigid telescopic crown, Cumulative survival rate, Clearance fit

INTRODUCTION

For the successful treatment of a removable partial denture (RPD), several factors, such as the occlusion of the denture, an impression for appropriate support in the edentulous area, and a retention element to prevent denture dislodgment, need to be considered. When considering the retention element, it can be classified into clasp-retained RPDs or double-crown-retained RPDs according to its mechanism. In patients with few residual teeth, designing claspretained RPD is often inadequate and difficult for clinicians.1 Various factors should be considered for the prosthetic restoration of these patients, particularly the prosthetic restoration preferences and economic aspects. In addition, clinicians should consider the number and locations of residual teeth, extraction, strategic implant placement, and type of opposite dentition according to the available prosthetic options. In such cases, double-crown-retained RPDs can be a successful treatment alternative for patients with few remaining teeth. Double-crown RPDs are characterized by the presence of fixed and removable restorations in hybrid form. The inner crown (primary crown) is the fixed restorations in the oral cavity, either in the form of crown of abutment teeth, or abutment of the implant. In contrast, an outer crown (secondary crown) is fabricated as a removable component in a RPD.2

Double-crown-retained RPDs can be classified as conical, telescopic, or hybrid telescopic crowns according to the mechanism ensuring retention of the inner crown.3 The conical double crown was first introduced by Köber in 1968.4 An inner crown made of precious metal has a slope of 6° and includes a mechanism for exerting 5 – 10 N of retention force from the end position via a wedge action between the inner and outer crowns.3 The telescopic double crown was first introduced by Bötteger in 1970 and includes a mechanism for exerting retentive force via friction generated between a noble metal crown with a 0° taper parallel to the end position of the noble metal inner crown.5 In noble metal crowns in conical and telescopic double crowns, retention forces are reduced by wearing of the inner and outer crowns.6 If the inner and outer crowns are made of non-precious metal, additional attachments (e.g., Marburg double crown system, or hybrid telescopic double crowns using additional friction pin) are needed to exert retention force with a definite end position, which is called a hybrid telescopic double crown.7 8

Telescopic double crowns also could be classified as either rigid or non-rigid according to the clearance fit.9 Rigid double-crown-retained RPDs are defined as having no clearance fit between the inner and outer crowns. It uses friction or a wedging effect between the inner and outer crowns for exerting the retention forces and therefore does not allow vertical movement when loading is applied.10 The rigid type includes frictional type double crowns, RPDs using galvanoformed (same as electroformed) secondary crowns, or conically prefabricated copings. By contrast, non-rigid double-crown-retained RPDs have clearance fit between the inner and outer crowns.11

Both precious and non-noble metals can belong to this type. If noble metal alloy inner and outer crowns are fabricated with the clearance fit, it can be the non-rigid double crown. In non-precious metal alloys, the oxide slag of the cast inner crown is removed after a polishing procedure, resulting in minor dimensional changes of the fit between the inner and outer crowns.8 Hence, no retentive force exists between them and an additional retention attachment is needed, such as the Marburg double crown and hybrid telescopic double crown with a friction pin. The Marburg double-crown-retained RPD has 0.3 – 0.5 mm of clearance fit on the occlusal surface and an additional attachment called the TK-SNAP (Si-tec, GmbH, Herdecke, Germany) for retention.11 Furthermore, a hybrid telescopic crown with a friction pin has a retention pin fabricated through spark erosion between the inner and outer crowns.8 When functional loading is applied to the denture, the non-rigid type allows additional vertical movement by the clearance fit and distributes the force to the edentulous ridge.10

Recently, several review articles have reported that double-crown-retained dentures led to the successful clinical outcomes. In a systematic review reported by Koller et al., the cumulative survival rate of the abutment in seven studies was 68% – 95.3% during 4 to 10 years of follow-up and the implant survival rates in three studies was 97% – 100%.10 According to Verma et al., the survival rate of abutment teeth during a 6-year observation period was 96.5%, and the survival rate of implants was 97.9% – 100% and 100% for telescopic-retained removable dental prostheses with two mandibular implants after 10.4 years.12 However, many previous studies have not clearly defined rigid and non-rigid type, and little is known about the survival rates of abutments according to this classification. Therefore, the objective of this article review was to investigate the cumulative survival rates of abutments in rigid and non-rigid double-crown-retained RPDs.

MATERIALS AND METHODS

i. Search strategy

A PubMed search was conducted for identifying articles published in the dental literature from January 1995 to December 2019 using the following search terms as shown below:

“telescopic crown”, “telescopic double crown”, “rigid telescopic crown”, “resilient telescopic crown”, “non rigid telescopic crown”, “Marburg double crown”, “implant supported double crown”, and “tooth supported double crown”. The bibliographies of all full-text articles and related reviews selected from the electronic search were also screened. Table 1 lists the journals that were manually searched.

1) Inclusion criteria

Articles published in English with randomized clinical trials (RCTs), prospective and retrospective cohort studies of double-crown RPDs were included. The specific inclusion criteria were as follows:

① Studies on double-crown RPDs supported by teeth, implants, or combination of teeth-implants
② Human clinical studies with at least 10 patients in each group
③ Studies with clinical examinations performed at the follow-up visits
④ At least 3 years of mean observation period
⑤ Studies that presented the information about the rigid and non-rigid types
⑥ Studies that reported cumulative survival rates of abutments

2) Exclusion criteria

① In vitro studies
② Studies about questionnaires, records, reviews, clinical reports, case series, surveys, and interviews
③ Multiple studies with identical patient groups
④ Studies on zygomatic implants, transmandibular implants, and blade vent implant systems

ii. Definitions

1) Rigid double-crown-retained RPDs

Rigid double-crown-retained RPDs are defined as those with no clearance fit between inner and outer crowns. The RPDs use friction or a wedging effect between crowns for exerting retentive forces. These included conically prefabricated copings with wedging effect, frictional telescopic crown, and galvanoformed (electroformed) secondary crowns (Fig. 1).

2) Non-rigid double-crown-retained RPDs

Non-rigid types have a clearance fit between the inner and outer crowns at the terminal position of denture. There is no retentive force between crowns due to the clearance fit. An additional attachment for retention is needed, including the TK-SNAP in Marburg double crown and friction pin in hybrid telescopic crown (Fig. 2).

3) Survival

Survival of tooth and implant was defined as the reconstruction remaining in situ at the follow-up examination visit irrespective of its condition. Denture survival was defined as a condition that can be repaired by minor complications such as denture base fracture, artificial tooth fracture, and relining.

(Failure of dentures is defined as a condition that requires remake due to fracture of denture frame work, extraction of all abutment teeth, etc.)

iii. Data extraction

The outcome variables included the survival data of telescopic double-crown-retained RPDs, abutment teeth, and/or implants.

The following data were extracted:

1) Study information: authors, years of study, study design. number of patients, mean observation period
2) Types of double crown: rigid and non-rigid double crowns according to the definitions
3) Details of abutments: number of teeth and implants, CSRs of abutments and dentures

RESULTS

Of the 403 studies identified in the search, two reviewers (Cho and Seo) selected 56 articles for full-text review based on the information given in the abstracts (Fig. 3). From these 56 articles, 25 were chosen for data extraction with 12 studies derived from the PubMed search and 2 studies derived from the manual search (Table 2). The included papers were grouped according to the types of double crown, and each type was subdivided into tooth, implant, or tooth-implant combination support (Table 3). Excluded articles were excluded for the reasons listed below (Table 4).

1) Rigid type, tooth supported double crowns

Total 4 articles were included as shown below (Table 5). The RCTs, performed by Stober et al.,30 reported CSRs (6-year observation period) of the prostheses supported by either electroplated (EP-RPDs) or cast double crowns (C-RPDs). The CSRs of abutment were 85% for EP-RPDs and 91% for C-RPDs, and those of dentures were 77% and 97%, respectively. Overall CSRs of teeth and dentures were reported 88% and 87%.

The three retrospective studies were reported. Wöstmann et al.23 reported CSRs of abutment as 95.3%, and denture as 95.1% after 5-year observation period according to the Kaplan-Meier survival curve. Szenpètery et al.24 assessed 74 patients (mean age, 66 years) with frictional telescopic crowns, and the CSR was 90.4% after 5 years of follow-up. Zierden et al.32 has reported that 5-year CSRs of tooth and denture were 92.0% and 96.1%, and 10-year of those were 68.9% and 84% each.

2) Rigid type, implant supported double crowns

Seven papers were selected (Table 6), three of which were prospective studies and the others were retrospective studies. In prospective studies, Zou et al.26 reported 100 % of CSR for 3 years in the group treated with four implants per patient and electroformed double crown, and Weigl et al.31 and Krennmair et al.17 also reported 98.91% and 100% of CSR for 3 years, respectively. In four retrospective studies, Rinke et al.20 and Romanos et al.37 studies showed CSR of 98.8% and 94.02%, respectively. The remaining two studies showed a high overall score of 100% regardless of the mean observation period.

3) Rigid type, tooth-implant combination double crowns

Total four studies were involved (Table 7). Guarnieri and Ippoliti28 reported that CSRs of tooth was 91.8% and that of implant was 96.4%. Kern et al.29 also performed prospective studies that the CSRs were 81.8% for tooth, and 97.6% for implant with 11.3 years mean observation period. Fobbe et al. presented that CSR of tooth and implant was 97.2%, 96% for 5 years, respectively. Romanos et al.36 involved the immediate loading of mandibular telescopic RPDs, and the CSRs of tooth and implant were reported 88% and 97.27%.

4) Non-rigid type, tooth supported double crowns

Three retrospective studies were included (Table 8). Wenz et al.13 treated with Marburg double-crown-retained RPDs; the CSR was 94% after 5 years and 82% after 10 years, and that of RPDs was 100%. Rinke et al. reported relatively low CSR of tooth and RPDs on less than four abutments of telescopic crowns. The CSR of tooth and RPD was 55% and 62% after 5 year, 34% and 38% after 8 years. Widbom et al. reported that the CSR of tooth was 93% with snap attachment called Ipso-clip system (Ipso-clip, Cendres et Métaux).

5) Non-rigid type, implant supported double crowns

One prospective study and two retrospective studies were searched (Table 9). These three studies all used Marburg systems. Frisch et al.14 the CSR of implant recoreded 98.9% in 14.1 years. In another study by the same author, the CSR was 98.75% during the mean observation period of 5.64 years. A prospective study of Krennmair et al.18 showed 100% of CSR in two mandibular interforaminal implants treatment with double-crown-retained prostheses.

6) Non-rigid tooth-implant combination telescopic double crowns

A total of four studies were included and all studies used Marburg double crown system (Table 10). Frisch et al.16 reported the CSR of tooth was 86.36%, and those of implant and RPD were 98.63% and 100%, respectively. Rinke et al.21 reported that the CSR of tooth was 85.19% and that of both implant and RPD was 100% during 5.84 years mean observation period. In a study by Krennmair et al.19, the CSRs of tooth and implant were both 100%. In a study by Mengel et al.51, the CSR was reported 100% for both tooth and implant.

DISCUSSION

When a clinician encounters a patient with only a few teeth in the arch, the double crown system can be an excellent treatment alternative, given the cost and technical difficulty. In this case, the prognosis of RPD can be successfully guided by assessing the number of teeth remaining, the distribution, the degree of periodontal support, and additional implant placement. Recent reports support that double-crown-retained RPDs have similar clinical performance compared to clasp-retained RPDs. According to Ishida et al.,66 the CSR of double-crown-retained RPDs and claspretained RPDs for 5 years were 100% and 94.5%, respectively. The 5-year cumulative survival rate of abutment teeth was 96.8% in double-crown-retained RPDs and 91.5% in clasp-retained RPDs. Saito et al.62 reported that the incidence of loss of abutment was 11.4% in telescopic crown dentures with an average wearing period of 8.1 years and 5.2% in ordinary clasp-retained dentures with an average wearing period 5.3 years.

The CSR of tooth tends to decrease over time in double-crown-retained RPDs, regardless of types. Study of Rinke et al.22 recorded excessively low CSR of tooth in non-rigid type. The author suggested that non-rigid type itself has no beneficial effects on clinical performance comparing to rigid type, but the number of abutment has an effect on the CSR. Considering reporting of Rinke et al.,22 the CSR of abutment is relatively low in both non-rigid and rigid types. This suggests that it is recommended to evaluate the number, distribution, and periodontal support of remaining teeth at the beginning of the treatment and to increase the CSR through additional implant placement. Regardless of the types, strategic implant placement should lead to a therapeutic approach to increase the survival rate of abutments and prostheses. This is in line with the result that the CSR of abutment in the tooth-implant combination is more than 80% in both types for maximal 10-year observation period. Higher CSR in the implant-only or tooth-implant combination, rather than the tooth-only form, does not mean that the implant itself is better for survival than natural teeth, but its additional placement has a positive effect on survival. Implants located at strategic positions additionally contribute to the distribution of occlusal forces applied to the alveolar bone and supporting tissue through the placement of the RPD. When the secondary splinting effect is applied to natural teeth and implants in double crown dentures, osseointegrated implants can distribute stress to the surrounding cortical region.67 68 69 Hence, stress around abutment teeth and their supportive tissue is reduced so that the implants in tooth and tooth-implant combination double-crown-retained RPDs can protect the teeth and their periodontal support tissues by relieving functional loading during mastication.70

These are closely related to complications that affect the survival and success of abutments and implants. A number of articles reported that the main factors affecting abutment tooth loss have also biological and technical complications (progression of periodontal disease, secondary caries and tooth fractures, etc.).12 Widbom et al.35 reported that the most common complication was cement loss and abutment tooth fracture (only 10% of abutment teeth had caries and 20% had a periodontal pocket depth of over 4 mm). Stober et al. reported that the risk of failure was higher for non-vital teeth than for vital teeth.30 Technical complications also occurred frequently in the following order: decementation of primary crowns (37% in Mock et al.71, 34.2% in Schwindling et al.38), failure of the veneer of secondary crowns (26.9% in Wöstmann et al.23 11.1% in Schwindling et al.38), fracture of denture base, and need for relining.

Decementation more frequently occurs in rigid type double crown RPDs. Behr et al.40 reported the frequency of decementation according to the type of double crown RPDs (frictional fit, conical fit and clearance fit). After 10 years of observation, decementation occurred in 32% of friction fit and 53.2% of conical fit, whereas it occurred in 21.3% of the clearance fit. Retentive forces from the rigid type largely depend on mechanical factors such as length and taper of the crown. In addition to that, ductility and malleability of the noble metal alloy makes retention force adjustment be difficult. Excessive retentive force is often needed just after denture delivery. However, non-rigid type uses an additional attachment, allowing control of retentive force.

Complications that affect the CSR of implant are mainly categorized as biologic and mechanical factors. Factors affecting implant loss have also been suggested to be biologic complications such as peri-mucositis and peri-implantitis, which are related to the perio-parameters such as bleeding on probing and the modified Quigley-Hein Index. In a systematic review by Lian et al.,46 the estimated incidences of mucositis and peri-implantitis were reported 5.89/100 implants/year and 0.12/100 implants/year, respectively. They lead to the marginal bone loss of implants ranged from 1.33 mm to 1.62 mm. Most studies on implant double-crown-retained dentures have reported that the main technical complications are loosening and fracture of primary abutment screws.14 15 17 18 20 For maintenance, screw retightening or replacement of abutment could be performed. It is similar to re-cementation of primary crown of tooth abutment.

In this review, failure rates or abutments per year could not be calculated because of the lack of detailed information provided in the original articles. The Marburg double crown system was mainly included in non-rigid telescopic double crowns, and data about other attachment system were insufficient. Various follow-up studies are needed for non-rigid systems with different types of attachment. In addition, it is necessary to increase the homogeneity of the included literature so that quantitative analysis of clinical outcomes can be achieved through well-designed studies.

CONCLUSION

The CSR of double crowns varies according to the rigid, or non-rigid type. Regardless of its types, the CSRs of tooth supported groups were low and decreased over time. In implant supported double crowns, CSRs were reported above 94% for both rigid and non-rigid types. For both rigid and non-rigid types, CSRs of tooth-implant combination double crowns ranged over 80% in both teeth and implants. Subsequent studies should increase the homogeneity of articles to enable quantitative statistical analysis of cumulative survival rates.

Figures and Tables

Fig. 1

Schematic diagrams of a rigid type double crown system. (A) Conical double crown with wedging effect, (B) Telescopic double crown with friction fit, (C) Galvanoformed (electroformed) double crown.

Fig. 2

Schematic diagrams of a non-rigid type double crown system. (A) Telescopic double crown with clearance fit, (B) Hybrid telescopic double crown with friction pin (cross sectional view), (C) Hybrid telescopic double crown with friction pin (occlusal view), (D) Marburg double crown and TK-SNAP (during insertion), (E) Marburg double crown and TK-SNAP (terminal position).

Fig. 3

Search strategy and results.

Table 1

Journal list of manual searching

Table 2

Results of the literature search

Table 3

Classification of included articles

Table 4

Reasons for exclusion

Table 5

Studies of rigid type with tooth supported double crowns

RCT^*: randomized clinical trial, RS^†: retrospective study, RPD^‡: removable partial denture

Table 6

Studies of rigid type with implant supported double crowns

PS^*: prospective study, RS^†: retrospective study, RPD^‡: removable partial denture, a: mean observation period was calculated from the article

Table 7

Studies of rigid type, tooth-implant combination double crowns

PS^*: prospective study, RS^†: retrospective study, RPD^‡: removable partial denture

Table 8

Studies of non-rigid type, tooth supported double crowns

^*RS: retrospective study, RPD^†: removable partial denture

Table 9

Studies of non-rigid type, implant supported double crowns

RS^*: retrospective study, PS^†: prospective study, RPD^‡: removable partial denture

Table 10

Studies of non-rigid type, tooth-implant combination double crowns

RS^*: retrospective study, PS^†: prospective study, RPD^‡: removable partial denture, a: mean observation period was calculated from the article

References

1. Weaver JD. Telescopic copings in restorative dentistry. J Prosthet Dent. 1989; 61:429–433.

2. Isaacson GO. Telescope crown retainers for removable partial dentures. J Prosthet Dent. 1969; 22:436–448.

3. Körber KH. Conus crowns: the rational telescope system introduction to clinics and technology [in German]. 5th ed. Heidelberg: Dr. Alfred Hüthig Verlag GmbH;1988. p. 81–86.

4. Körber KH. Cone crowns-a physically defined telescopic system. German Dent J. 1968; 23:619–630.

5. Böttger H, Engelhardt JP. Telescopic system in dental practice [in German]. Quintessenz. 1970; 21:69–72.

6. Engels J, Schubert O, Güth JF, Hoffmann M, Jauernig C, Erdelt K, Stimmelmayr M, Beuer F. Wear behavior of different double-crown systems. Clin Oral Investig. 2013; 17:503–510.

7. Lehmann KM, Gente M. Double crowns used to support removable partial dentures [in German]. German Dent Cal. 1988; 47:106–112.

8. Weber H, Frank G. Spark erosion procedure: a method for extensive combined fixed and removable prosthodontic care. J Prosthet Dent. 1993; 69:222–227.

9. Langer A. Telescope retainers and their clinical application. J Prosthet Dent. 1980; 44:516–522.

10. Koller B, Att W, Strub JR. Survival rates of teeth, implants, and double crown-retained removable dental prostheses: a systematic literature review. Int J Prosthodont. 2011; 24:109–117.

11. Wenz HJ, Lehmann KM. A telescopic crown concept for the restoration of the partially edentulous arch: the Marburg double crown system. Int J Prosthodont. 1998; 11:541–550.

12. Verma R, Joda T, Brägger U, Wittneben JG. A systematic review of the clinical performance of tooth-retained and implant-retained double crown prostheses with a follow-up of ≥ 3 years. J Prosthodont. 2013; 22:2–12.

13. Wenz HJ, Hertrampf K, Lehmann KM. Clinical longevity of removable partial dentures retained by telescopic crowns: outcome of the double crown with clearance fit. Int J Prosthodont. 2001; 14:207–213.

14. Frisch E, Ziebolz D, Rinke S. Long-term results of implant-supported over-dentures retained by double crowns: a practice-based retrospective study after minimally 10 years follow-up. Clin Oral Implants Res. 2013; 24:1281–1287.

15. Frisch E, Ziebolz D, Ratka-Krüger P, Rinke S. Double crown-retained maxillary overdentures: 5-year follow-up. Clin Implant Dent Relat Res. 2015; 17:22–31.

16. Frisch E, Ratka-Krüger P, Wenz HJ. Unsplinted implants and teeth supporting maxillary removable partial dentures retained by telescopic crowns: a retrospective study with >6 years of follow-up. Clin Oral Implants Res. 2015; 26:1091–1097.

17. Krennmair G, Sütö D, Seemann R, Piehslinger E. Removable four implant-supported mandibular overdentures rigidly retained with telescopic crowns or milled bars: a 3-year prospective study. Clin Oral Implants Res. 2012; 23:481–488.

18. Krennmair G, Seemann R, Weinländer M, Piehslinger E. Comparison of ball and telescopic crown attachments in implant-retained mandibular overdentures: a 5-year prospective study. Int J Oral Maxillofac Implants. 2011; 26:598–606.

19. Krennmair G, Krainhöfner M, Waldenberger O, Piehslinger E. Dental implants as strategic supplementary abutments for implant-tooth-supported telescopic crown-retained maxillary dentures: a retrospective follow-up study for up to 9 years. Int J Prosthodont. 2007; 20:617–622.

20. Rinke S, Ziebolz D, Ratka-Krüger P, Frisch E. Clinical outcome of double crown-retained mandibular removable dentures supported by a combination of residual teeth and strategic implants. J Prosthodont. 2015; 24:358–365.

21. Rinke S, Buergers R, Ziebolz D, Roediger M. Clinical outcome of double crown-retained implant overdentures with zirconia primary crowns. J Adv Prosthodont. 2015; 7:329–337.

22. Rinke S, Schneider L, Schulz X, Wiedemann V, Bürgers R, Rödiger M. Overdentures borne on less than four abutments with telescopic crowns: 5-year results of a retrospective clinical study. Clin Oral Investig. 2019; 23:3153–3160.

23. Wöstmann B, Balkenhol M, Weber A, Ferger P, Rehmann P. Long-term analysis of telescopic crown retained removable partial dentures: survival and need for maintenance. J Dent. 2007; 35:939–945.

24. Szentpétery V, Lautenschlager C, Setz JM. Frictional telescopic crowns in severely reduced dentitions: a 5-year clinical outcome study. Int J Prosthodont. 2012; 25:217–220.

25. Zou D, Wu Y, Huang W, Zhang Z, Zhang Z. A 5- to 8-year retrospective study comparing the clinical results of implantsupported telescopic crown versus bar overdentures in patients with edentulous maxillae. Int J Oral Maxillofac Implants. 2013; 28:1322–1330.

26. Zou D, Wu Y, Huang W, Wang F, Wang S, Zhang Z, Zhang Z. A 3-year prospective clinical study of telescopic crown, bar, and locator attachments for removable four implant-supported maxillary overdentures. Int J Prosthodont. 2013; 26:566–573.

27. Zou D, Wang F, Wu Y, Huang W, Zhang C, Zhang Z. Implant-supported telescopic crown-retained overdentures for oral rehabilitation of patients with severe bony defects: A 5-year retrospective study. Int J Oral Maxillofac Implants. 2015; 30:937–944.

28. Guarnieri R, Ippoliti S. Restoration of periodontally compromised dentitions using telescopic full-arch retrievable prosthesis supported by tooth-implant combination: A long-term retrospective study. Int J Periodontics Restorative Dent. 2018; 38:217–224.

29. Kern JS, Hanisch O, Hammächer C, Yildirim M, Wolfart S. Telescopic crowns on implants and teeth: Evaluation of a clinical study after 8 to 12 years. Int J Oral Maxillofac Implants. 2019; 34:977–986.

30. Stober T, Bermejo JL, Séché AC, Lehmann F, Rammelsberg P, Bömicke W. Electroplated and cast double crown-retained removable dental prostheses: 6-year results from a randomized clinical trial. Clin Oral Investig. 2015; 19:1129–1136.

31. Weigl P, Trimpou G, Lorenz J, Nentwig GH, Lauer HC. Prefabricated taper crowns for the retention of implant superstructures: Three-year results of a prospective clinical trial. J Prosthet Dent. 2019; 121:618–622.

32. Zierden K, Kurzrock L, Wöstmann B, Rehmann P. Nonprecious alloy vs precious alloy telescopic crown-retained removable partial dentures: Survival and maintenance needs. Int J Prosthodont. 2018; 31:459–464.

33. Fobbe H, Rammelsberg P, Lorenzo Bermejo J, Kappel S. The up-to-11-year survival and success of implants and abutment teeth under solely implant-supported and combined tooth-implant-supported double crown-retained removable dentures. Clin Oral Implants Res. 2019; 30:1134–1141.

34. Mengel R, Wendt J, Peleska B. Prosthodontic treatment outcomes in periodontally compromised patients: A 6- to 20-year long-term cohort study. Int J Prosthodont. 2019; 32:153–161.

35. Widbom T, Löfquist L, Widbom C, Söderfeldt B, Kronström M. Tooth-supported telescopic crown-retained dentures: an up to 9-year retrospective clinical follow-up study. Int J Prosthodont. 2004; 17:29–34.

36. Romanos GE, May S, May D. Immediate loading of tooth-implant-supported telescopic mandibular prostheses. Int J Oral Maxillofac Implants. 2012; 27:1534–1540.

37. Romanos GE, May S, May D. Implant-supporting telescopic maxillary prostheses and immediate loading. Clin Implant Dent Relat Res. 2014; 16:412–418.

38. Schwindling FS, Dittmann B, Rammelsberg P. Double-crown-retained removable dental prostheses: a retrospective study of survival and complications. J Prosthet Dent. 2014; 112:488–493.

39. Eitner S, Schlegel A, Emeka N, Holst S, Will J, Hamel J. Comparing bar and double-crown attachments in implant-retained prosthetic reconstruction: a follow-up investigation. Clin Oral Implants Res. 2008; 19:530–537.

40. Behr M, Kolbeck C, Lang R, Hahnel S, Dirschl L, Handel G. Clinical performance of cements as luting agents for telescopic double crown-retained removable partial and complete overdentures. Int J Prosthodont. 2009; 22:479–487.

41. Rammelsberg P, Bernhart G, Lorenzo Bermejo J, Schmitter M, Schwarz S. Prognosis of implants and abutment teeth under combined tooth-implant-supported and solely implant-supported double-crown-retained removable dental prostheses. Clin Oral Implants Res. 2014; 25:813–818.

42. Krennmair G, Weinländer M, Krainhöfner M, Piehslinger E. Implant-supported mandibular overdentures retained with ball or telescopic crown attachments: a 3-year prospective study. Int J Prosthodont. 2006; 19:164–170.

43. Marotti J, Gatzweiler B, Wolfart M, Sasse M, Kern M, Wolfart S. Implant Placement under Existing Removable Dental Prostheses and the Effect on Follow-Up and Prosthetic Maintenance. J Prosthodont. 2019; 28:e752–e763.

44. Stober T, Bermejo JL, Beck-Mussoter J, Seche AC, Lehmann F, Koob J, Rammelsberg P. Clinical performance of conical and electroplated telescopic double crown-retained partial dentures: a randomized clinical study. Int J Prosthodont. 2012; 25:209–216.

45. Szentpétery V, Lautenschläger C, Setz JM. Longevity of frictional telescopic crowns in the severely reduced dentition: 3-year results of a longitudinal prospective clinical study. Quintessence Int. 2010; 41:749–758.

46. Lian M, Zhao K, Feng Y, Yao Q. Prognosis of combining remaining teeth and implants in double-crown-retained removable dental prostheses: A systematic review and meta-analysis. Int J Oral Maxillofac Implants. 2018; 33:281–297.

47. Bernhart G, Koob A, Schmitter M, Gabbert O, Stober T, Rammelsberg P. Clinical success of implant-supported and tooth-implant-supported double crown-retained dentures. Clin Oral Investig. 2012; 16:1031–1037.

48. Heckmann SM, Schrott A, Graef F, Wichmann MG, Weber HP. Mandibular two-implant telescopic overdentures. Clin Oral Implants Res. 2004; 15:560–569.

49. Kaufmann R, Friedli M, Hug S, Mericske-Stern R. Removable dentures with implant support in strategic positions followed for up to 8 years. Int J Prosthodont. 2009; 22:233–241. discussion 242.

50. Dittmann B, Rammelsberg P. Survival of abutment teeth used for telescopic abutment retainers in removable partial dentures. Int J Prosthodont. 2008; 21:319–321.

51. Mengel R, Kreuzer G, Lehmann KM, Flores-de-Jacoby L. A telescopic crown concept for the restoration of partially edentulous patients with aggressive generalized periodontitis: a 3-year prospective longitudinal study. Int J Periodontics Restorative Dent. 2007; 27:231–239.

52. Schwarz S, Bernhart G, Hassel AJ, Rammelsberg P. Survival of double-crown-retained dentures either tooth-implant or solely implant-supported: an 8-year retrospective study. Clin Implant Dent Relat Res. 2014; 16:618–625.

53. Rehmann P, Rudel K, Podhorsky A, Wöstmann B. Three-year analysis of fixed and removable telescopic attachment-retained implant-supported dental prostheses: Survival and need for maintenance. Int J Oral Maxillofac Implants. 2015; 30:918–924.

54. Weng D, Richter EJ. Maxillary removable prostheses retained by telescopic crowns on two implants or two canines. Int J Periodontics Restorative Dent. 2007; 27:35–41.

55. Brandt S, Brandt J, Ketabi AR, Lauer HC, Kunzmann A. Locator® versus ceramic/electroplated double-crown attachments: a prospective study on the intraindividual comparison of implant-supported mandibular prostheses. Clin Oral Investig. 2019; 23:763–770.

56. Keshk AM, Alqutaibi AY, Algabri RS, Swedan MS, Kaddah A. Prosthodontic maintenance and peri-implant tissue conditions for telescopic attachment-retained mandibular implant overdenture: Systematic review and meta-analysis of randomized clinical trials. Eur J Dent. 2017; 11:559–568.

57. Behr M, Hofmann E, Rosentritt M, Lang R, Handel G. Technical failure rates of double crown-retained removable partial dentures. Clin Oral Investig. 2000; 4:87–90.

58. Schwindling FS, Dittmann B, Rammelsberg P. Double-crown-retained removable dental prostheses: a retrospective study of survival and complications. J Prosthet Dent. 2014; 112:488–493.

59. Brandt S, Winter A, Weigl P, Brandt J, Romanos G, Lauer HC. Conical zirconia telescoping into electroformed gold: A retrospective study of prostheses supported by teeth and/or implants. Clin Implant Dent Relat Res. 2019; 21:317–323.

60. Eisenburger M, Gray G, Tschernitschek H. Long-term results of telescopic crown retained dentures-a retrospective study. Eur J Prosthodont Restor Dent. 2000; 8:87–91.

61. Coca I, Lotzmann U, Pöggeler R. Long-term experience with telescopically retained overdentures (double crown technique). Eur J Prosthodont Restor Dent. 2000; 8:33–37.

62. Saito M, Notani K, Miura Y, Kawasaki T. Complications and failures in removable partial dentures: a clinical evaluation. J Oral Rehabil. 2002; 29:627–633.

63. Bergman B, Ericson A, Molin M. Long-term clinical results after treatment with conical crown-retained dentures. Int J Prosthodont. 1996; 9:533–538.

64. Joda T. Combined tooth-implant-supported telescopic prostheses in a midterm follow-up of > 2 years. Int J Prosthodont. 2013; 26:536–540.

65. Weischer T, Mohr C. Implant-supported mandibular telescopic prostheses in oral cancer patients: an up to 9-year retrospective study. Int J Prosthodont. 2001; 14:329–334.

66. Ishida K, Nogawa T, Takayama Y, Saito M, Yokoyama A. Prognosis of double crown-retained removable dental prostheses compared with clasp-retained removable dental prostheses: A retrospective study. J Prosthodont Res. 2017; 61:268–275.

67. Lin CL, Wang JC, Chang WJ. Biomechanical interactions in tooth-implant-supported fixed partial dentures with variations in the number of splinted teeth and connector type: a finite element analysis. Clin Oral Implants Res. 2008; 19:107–117.

68. Michalakis KX, Calvani P, Hirayama H. Biomechanical considerations on tooth-implant supported fixed partial dentures. J Dent Biomech. 2012; 3:1758736012462025.

69. Koosha S, Mirhashemi FS. An Investigation of Three types of Tooth Implant Supported Fixed Prosthesis Designs with 3D Finite Element Analysis. J Dent (Tehran). 2013; 10:51–63.

70. Chen Y, Wang C, Huang Y, Feng T, Zou H, Fan Y. Biomechanical evaluation of the natural abutment teeth in combined toothimplant-supported telescopic prostheses: a three-dimensional finite element analysis. Comput Methods Biomech Biomed Engin. 2017; 20:967–979.

71. Mock F, Schrenker H, Stark HK. Success of telescopic crowns-a prospective long-term study [in German]. German Dent J. 2005; 60:148–153.

TOOLS

ORCID iDs

Jeong-Gyo Seo
https://orcid.org/0000-0003-2322-5715

Jin-Hyun Cho
https://orcid.org/0000-0002-2453-9372

Similar articles