Screw- versus cement-retained implant prostheses: a systematic review of prosthodontic maintenance and complications.

Screw- Versus Cement-Retained Implant Prostheses: A Systematic Review of Prosthodontic Maintenance and Complications Sunyoung Ma, BDS, DClinDenta/Aaron Fenton, DDS, MSb Purpose: This systematic review aimed to identify different prosthodontic outcomes between screw- and cement-retained implant prostheses. Materials and Methods: The relevant articles were retrieved from the following electronic databases: MEDLINE, EMBASE, PubMed (using medical subject headings), and the Cochrane Central Register of Controlled Trials (CENTRAL). The search was performed up to December 31, 2013, and was restricted to studies on human subjects reported in English. A further search was conducted through the reference lists of the articles found as well as from early online articles. Reviewed studies were those on fixed implant prostheses using different retention mechanisms such as screws or cement. Information on types of screws and mechanisms of preloading, as well as different luting cements, was collected in correlation with prosthodontic maintenance/complication issues seen in the clinical studies. Results: Sixty-two papers met the review criteria. There were only six randomized controlled trials and none of them included an equivalent number of screw- and cement-retained single implant crowns for comparison. Studies used different types of screws and only a few reported the preloading procedure for the prosthetic screws. Other studies involving cement-retained implant prostheses used a range of dental cements; however, some did not specify the type used. Studies reported various prosthodontic maintenance/complication issues such as screw loosening, porcelain fracture, loss of retention, and esthetic concerns. Five studies did not report any prosthodontic maintenance issues during their observation periods. More recent studies also did not report any incidence of screw loosening. Only two studies stated the standardized criteria for reporting their prosthodontic maintenance/ complication issues. Conclusions: With inadequate information and various study designs, it was difficult to compare the prosthodontic outcomes between screwand cement-retained fixed implant prostheses. Both retention mechanisms showed prosthodontic maintenance/complication issues that must be considered and this review showed that the introduction of newer implant components may assist in minimizing these issues. It is also recommended that standardized criteria be used when reporting prosthodontic maintenance/complication issues to allow better comparison of data. Int J Prosthodont 2015;28:127–145. doi: 10.11607/ijp.3947

I

mplant prostheses are frequently used to rehabilitate partially and completely edentulous patients. Published data endorse high and long-term successful treatment outcomes and excellent patient acceptance.1–3 Although successful clinical outcomes

aSenior

Lecturer in Prosthodontics, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand. bEmeritus Professor of Prosthodontics, University of Toronto, Toronto, Ontario, Canada. Correspondence to: Dr Sunyoung Ma, Sir John Walsh Research Institute, Faculty of Dentistry, University of Otago, Dunedin, New Zealand. Fax: +64 3 479 5079. Email: [email protected] ©2015 by Quintessence Publishing Co Inc.

depend on an optimal biologic response, the amount of prosthodontic interventions to address maintenance/complication requirements needs to be kept to a minimum.3–5 Implant dentistry has experienced ample development in producing more esthetically pleasing and mechanically stronger materials. This ongoing improvement of the manufacturing process and better understanding of biologic outcomes will no doubt contribute to even longer-term clinical outcomes. Scrupulous treatment planning is crucial in implant dentistry. Although different treatment methodologies are employed to achieve presumed ideal patient outcomes, specific concerns about esthetics, function, and biologic and prosthodontic prognoses must be addressed.6,7 Different types of retention mechanisms also may influence these outcomes as the mechanical

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Screw- Versus Cement-Retained Implant Prostheses: Review of Maintenance and Complications

stability of prostheses relies on the engineering of implant-abutment interfaces. Two main types of retention mechanisms have been employed in securing the prosthetic superstructure: screws and cement. Although there are several reports on the mechanical procedures involved in these two retention mechanisms, there is a lack of evidence-based guidelines to assist the dentist.8 It appears that the choice of retention in implant prostheses still mainly depends on the individual’s preference and experience.9–11 Clinical criteria such as prosthesis retrievability and maintenance, esthetics, occlusion, ease of fabrication, and cost may influence the retention mechanism decision of fixed implant prostheses. Implant positioning also can influence the choice of retention mechanism because non-ideal implant angulation may affect the final esthetic result if the screw access opening is visible. Retrievability is one of the major advantages of screw-retained implant prostheses because it allows for easy access to carry out prosthodontic maintenance issues such as tightening loose prosthetic screws or repairing chipped porcelain.12 However, there is anecdotal support for the notion that screw retention may result in more of these types of maintenance issues and that retrievability is not crucial when using cement retention. It is clear that there are insufficient guidelines based on evidence-based clinical data to recommend a certain type of retention mechanism when restoring fixed implant prostheses.13 Therefore, this systematic review assessed published clinical data on prosthodontic outcomes of screw- and cement-retained fixed implant prostheses.

Materials and Methods The systematic review was conducted using a population, intervention, comparison, and outcome (PICO) format14 to identify the objectives and the inclusion criteria. The essential four elements were summarized as below: 1. Population: patients that require fixed implant prostheses 2. Intervention: screw-retained fixed implant prostheses 3. Comparison: cement-retained fixed implant prostheses 4. Outcome: prosthodontic outcomes Inclusion Criteria Inclusion criteria included •• Human subjects

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•• Clinical studies on fixed implant prostheses •• Randomized controlled trials, controlled trials, prospective trials, and retrospective trials •• Clinical studies reporting prosthodontic outcomes involving definitive restorations •• Observation period of at least 12 months •• English language only Exclusion Criteria Exclusion criteria included •• •• •• ••

In vitro studies Animal studies Case series and case reports Clinical trials that did not clearly define clinical parameters to assess prosthodontic outcomes and/or failed to report the type of implant prostheses and retention mechanism •• One-piece implants or mini-implants Search Strategy The relevant articles were retrieved from the following electronic databases: MEDLINE, EMBASE, and The Cochrane Central Register of Controlled Trials (CENTRAL). The search was performed up to December 31, 2013. The search was restricted to studies on human subjects reported in English. An appropriate combination of the following medical subject heading (MeSH) terms were used: “dental implants,” “dental prosthesis, implant-supported,” “dental implants, single-tooth,” “dental implant-abutment design,” “prosthesis retention,” “dental prosthesis retention,” and “dental prosthesis repair.” The bibliographies of potentially selected papers were scrutinized for additional material. A manual search of the following journals’ most recent 10 years also was conducted: Clinical Oral Implants Research, Implant Dentistry, International Journal of Periodontics & Restorative Dentistry, International Journal of Prosthodontics, Journal of Oral Implantology, Journal of Oral Rehabilitation, Journal of Prosthetic Dentistry, and Journal of Prosthodontics. Two reviewers (SM and AF) performed the search independently, in duplicate, and any disagreement was solved by consensus. Data Collection The following information was retrieved from the selected studies: (1) publication details, (2) type of study, (3) participant details, (4) areas where the oral implants were placed, (5) observation period, (5) oral implant/prosthesis details, (6) retention mechanism, and (7) prosthodontic outcomes.

The International Journal of Prosthodontics


Ma/Fenton

Results A total of 1,432 studies were identified from the databases and, of these, 103 studies were eligible for fulltext evaluation. Of these, 49 papers were excluded and 54 papers15–68 were included in the systematic review. Manual searching provided 8 additional studies.69–76 The data were divided according to the type of retention mechanisms. The characteristics of the included studies are summarized in Tables 1 to 3. There were six randomized controlled trials,57,61–63,67,71 of which only two studies57,71 included both screw- and cement-retained single implant crowns. However, these studies did not have the equivalent number of participants with each retention mechanism to be able to compare the prosthodontic outcomes between screw- and cement-retained single implant crowns. The remaining studies were either prospective,15,20–24,26,28,33,36,42–44,46,49,50,59,60,66,68,75,76 retrospective,16,25,30,32,34,55,58,69,72–74 or longitudinal.41,70 The majority of studies included only one retention mechanism for the single implant crowns and emphasized implant survival and biologic outcomes. Only one study32 used different types of screw retention mechanism, including cross-pinning and traditional vertical screws. There were five studies involving both single implant crowns and fixed partial prostheses.19,37,39,47,52 They were either retrospective or prospective studies. Four studies used a cement-retained mechanism and only one study37 compared the different retention mechanisms. Eighteen studies analyzed the prosthodontic outcomes of full-arch fixed implant prostheses and none of them were randomized controlled trials. Most studies used only one type of retention mechanism except one study,64 which investigated the outcomes of allceramic crowns cemented onto a titanium framework compared to screw-retained zirconia copings with ceramic veneering. The number of participants and implants varied among the studies, ranging from 12 participants with 24 single implant crowns to 471 participants with 671 single implant crowns. The largest cohort was from a retrospective, multicenter study.34 Some studies focused on specific regions such as maxillary anterior sites20,61,63 or maxillary and mandibular molar sites.16,34 Observation Period The observation period of studies involving single implant crowns ranged from 1 to 10 years. One study44 with the longest observation period included an implant system that is no longer commercially available.

There were several studies that used Brånemark implants with the external hex connection, many of which were restored using CeraOne abutments and cement-retained crowns. Studies involving single implant crowns as well as fixed partial prostheses had a shorter observation period of up to 8 years. On the other hand, studies analyzing full-arch implant prostheses had the longest observation period of up to 23 years.38 Types of Prostheses There was a mixture of different types of crowns such as all-ceramic, all-metal, gold-acrylic, and porcelainfused-to-metal crowns. Only two older studies25,26 used gold-acrylic crowns as part of their rehabilitation method. Three studies16,34,41 did not specify the type of crown used but did report on the type of retention mechanisms. All fixed partial prostheses were made of porcelain-fused-to-metal except one study,52 which did not state the material. Studies involving full-arch fixed implant prostheses included various framework materials such as type III gold alloy, silver-palladium alloy, and titanium, which were fabricated according to different methods. Veneering materials included acrylic resin teeth and ceramic. One study64 used zirconia copings with Nobel Rondo zirconia ceramic and pink acrylic resin. Retention Mechanism Twenty-one studies used screw-retained single implant crowns. Seven studies16,22,25,33,43,49,58 specified the type of screws used and seven studies22,41,43,49,57,68,71,73 subsequently identified the mechanism of screw tightening. One study41 followed a manual hand tightening procedure for securing the prosthetic screws. However, the authors subsequently used a torque driver for any implant crowns that suffered screw loosening. An earlier study16 reported a high incidence of screw loosening over 2 years (38% of implants) with screw-retained implant crowns. Recent studies60,61,66 with shorter observation periods showed no incidence of screw loosening regardless of retention mechanism for the single implant crowns. Two studies37,39 involving both single implant crowns and partial prostheses followed the screwretained method. None of the studies included the information on the type of screws used. The majority of studies (14 out of 16) investigating full-arch fixed implant prostheses used the screw-retained mechanism; however, only two studies17,53 specified the type of screws used.


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Table 1 C linical Studies Reporting Prosthodontic Maintenance/Complication Issues Involving Screw-Retained Prostheses

Study

Type of study

Original number of participants; implants

Region

Observation period

Type of implant and connection

Single implant crowns Jemt et al15 (1991)

Prospective

92; 107

Maxilla and mandible

1y

Becker and Becker16 (1995)

Retrospective

22; 24

Deporter et al22 (1998)

Prospective

20; 20

Maxilla and mandible (molar sites only) Maxilla

2y (mean) 1y

NS (NobelPharma); external hex Endopore (Innova)

Levine et al69 (1999)†

Retrospective, multicenter

110; 157


40.1 mo (mean)

ITI (Straumann)

Scholander25 (1999)†

Retrospective

135; 259


1–9 y

Brånemark

Wannfors and Smedberg26 (1999)†

Prospective

69; 80


3y

Brånemark

Andersson et al28 (2001)*

Prospective, multicenter

75; 89


1–3 y

Brånemark

Mericske-Stern et al70 (2001)*

Longitudinal

72; 109


4.2 y (mean)

ITI (Straumann)

Gibbard and Zarb33 (2002)† Krennmair et al32 (2002)†

Prospective Retrospective

42; 49 112; 146

Maxilla and mandible Maxilla and mandible

5y 7y

Brånemark Frialit-2 (Friatec)



471; 671

Maxilla and mandible (molar sites only)

21.3 mo (mean)

Cho et al41 (2004)

Longitudinal

NS; 39


3–7 y

3i, Implant Innovations

Vigolo et al43 (2004)†

Prospective

12; 24

4y


Brägger et al44 (2005)†

Prospective

48; 69

NS

10 y

Schropp et al71 (2005)†

RCT

43; 43


2y

Kreissl et al49 (2007)

Prospective

NS; 46

NS

5y

ITI Bonefit (ITI Straumann) OsseoTite (3i, Implant Innovations) OsseoTite (3i, Implant Innovations)

Jemt55 (2009)† Sailer et al57 (2009)†

Retrospective RCT

35; 41 22; 40

10 y 1y

Brown and Payne60 (2011)

Prospective

25; 26

Maxilla Maxilla and mandible (canine, premolar, and molar sites only) Maxilla (anterior region only, including second premolars)

1y

Brånemark

Solid-screw ITI, (Straumann); internal connection

Brånemark Brånemark (Nobel Biocare); external hex Co-Axis 12d (Southern Implants); external hex

RCT = randomized controlled trial; NS = not specified; AC = all ceramic; AM = all metal; PFM = porcelain fused to metal; Ti = titanium; × = number of event(s); (pts) = number of patients affected by the maintenance issues; Au = gold; (C) = control group; (T) = test group; comp resin = composite resin; CNC = computer numeric controlled. *Data combined with other retention mechanism. †Data separated from other retention mechanism.

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Ma/Fenton

Type of crown

Retention mechanism (screw-retained)

Prosthodontic outcomes

Veneering material: Acrylic resin (35/106) Porcelain (61/106) Comp resin (10/106) NS

NS

Abutment screw loosening: 29/106 Prosthetic screw loosening: 34× Crown repair/remake: 6×

Gold screws

Screw loosening: 16× (38% of implants)

PFM

Ti alloy, “maximum” tightening with a manual wrench NS (81)

None

NS

Abutment screw (Octa abutment) loosening: 1× Prosthetic screw loosening: 18× None

AC (175) PFM (79) Gold-acrylic (4) AC (9) Gold-acrylic (36) PFM (35)

Gold screw (2) NS (44)

Abutment screw loosening: 13× New abutment screws: 2× Esthetics: 12× New crowns: 12× Porcelain fracture: 1× Loss of screw access material: 1×

AC (15) using CerAdapt abutment

NS (15)

Abutment fracture during preparation/placement: 5× Abutment fracture (after loading): 2× Porcelain fracture: 2×

PFM

NS (102)

NS AC (27) PFM (119) NS

Gold screw (47) NS (22)

Prosthetic screw loosening: 19× Porcelain fracture: 1× Abutment fracture: 3×(Octa abutment, now withdrawn from the market) Screw loosening: 13%

NS (71)

Screw loosening: 16.9% (1× occasion) Screw loosening: 1.4% (multiple occasions) Abutment screw loosening: 1.4%

NS

NS Hand-tightened, torque driver only in the case of screw loosening GoldTite (3i, Implant Innovation) (12); torque at 30 Ncm NS (2)

Screw loosening: 4×

GoldTite screw (2); torque at 32 Ncm Gold-coated square head screws; torque at 32 Ncm

None

PFM PFM PFM PFM

PFM AC (19) PFM (21)

NS (18) NS (2); torque at 32 Ncm

AC

NS

Porcelain/crown fracture: 1×

None None

Screw loosening: 6(9)/36 Screw fracture: 2/36 Porcelain fracture: 2/36 Event-free survival: 77.6% Abutment screw loosening: 2/18 None

Porcelain fracture: 2× Abutment fracture: 2× (zirconia) Esthetics: 10× (Walton75 [1998])


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Table 1 (continued) Clinical Studies Reporting Prosthodontic Maintenance/Complication Issues Involving Screw-Retained Prostheses

Study Gallucci et al61 (2011) Atieh et al68 (2013)

Fixed dental prostheses (partial) Wennerberg and Jemt73 (1999)

Type of study RCT

Original number of participants; implants 20; 20

Prospective

Retrospective

24; 24

133; 422

Region Maxilla (anterior region only) Mandible (molar region only)

Observation Type of implant period and connection 2y Standard Plus (Straumann) 1y MAX (Southern Implants)

Maxilla

5y

Brånemark

Duncan et al37 (2003)†

Prospective

32; 83

NS

3y

ITI (Straumann)

Jemt et al76 (2003)


42; 170


5y

Brånemark

Astrand et al39 (2004)

Prospective

28; 150

Maxilla

3y

Brånemark or ITI

156; 579


10 y

Brånemark

Fixed dental prostheses (complete) Brånemark et al17 (1995) Retrospective Lindquist et al18 (1996)

Prospective

Group 1 (G1): 26; 150

Mandible

Group 2 (G2): 21; 123

G1: 15 y

Brånemark; external hex

G2: 12 y

Friberg et al27 (2000)

Retrospective

Zitzmann and Marinello74 (2000)

Prospective

10; 84

Maxilla

Hellem et al29 (2001)

28; NS

Mandible

5y

ITI hollow-screw

Tinsley et al31 (2001)

Prospective, longitudinal Prospective

21; 104

Mandible

4–6 y

Calcitek Integral

Murphy et al35 (2002)

Prospective

26; 131

Mandible

5y

Astra Tech

Duncan et al37 (2003)

Prospective

9; 103

Mandible

3y

ITI (Straumann)

45

Mandible

8 y (mean)

Brånemark

39 mo (mean)

Brånemark


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Ma/Fenton

Type of crown AC (10) PFM (10) AC

Retention mechanism (screw-retained) NS (20)

Prosthodontic outcomes Porcelain fracture: 2× (AC)

NS; torque at 20 Ncm

Porcelain fracture: 6× Screw loosening: 1× (Walton75 [1998]); Payne et al76 [2001])

Multiple: Cast-gold alloy framework with resin (74%) or PFM (23%) Ti framework with resin

Gold screws

Single (22) or multiple (19): Porcelain-fused to metal Cast Au alloy framework with porcelain or laser-welded Ti framework with low-fusing porcelain

NS (14)

Veneering fracture: 55× Abutment screw fracture: 16× Abutment/prosthetic screw loosening: 22× Framework fracture: 1× Prosthetic screw fracture: 1× Peri-implant mucosal complications: 17× Esthetics: 12× Phonetics: 3× Stomatognathic: 5× Screw loosening and loss of screw access plug (comp resin): 5/14 (pts)

Multiple: gold-ceramic

NS

Gold with acrylic veneering

Gold screws

Type III gold alloy with resin teeth and bilateral posterior cantilever units

NS

Fixed prostheses

NS

Screw fracture: 2×

Acrylic (5)/porcelain (5) veneering

NS

Gold-acrylic

NS

Abutment screw loosening: 1× Porcelain fracture: 2× Acrylic resin veneering fracture: 3× Acrylic resin veneering fracture

Fixed prostheses

NS

(a) Chicago IV gold alloy superstructures and acrylic resin teeth or (b) Palliag M silver-palladium alloy superstructures and acrylic resin teeth NS

NS

NS

NS

Abutment screw fracture: 2× (Ti) Framework fracture: 1× (Ti) Porcelain fracture: 3× (Au); 15× (Ti) Abutment screw loosening: 1× (Au); 2× (Ti) Prosthetic screw loosening: 2× (Au); 4× (Ti) Soft tissue complication: 1× (Au); 3× (Ti) Screw loosening Porcelain fracture Acrylic resin veneering fracture Screw loosening/fracture G1 15/26; G2 8/21: screw loosening G1 3/26: screw fracture G1 2/26: remake G1 1/26; G2 2/21: replacement of acrylic teeth G1 2/26; G2 3/21: fracture of acrylic tooth G1 14/26; G2 18/21: loss of acrylic in screw access

Loss of screw access plug (Fermit): 9/21 Remake: 5/21 Opposing complete denture: Repair: 3/21 Reline: 7/21 Remake: 6/21 Screw fracture: 2/26 (pts) Abutment fracture: (b) 1/13 (pts) Screw loosening: (a) 11×, (b) 13× Fracture of acrylic teeth: 4/26 (pts)

Screw loosening: 2× Fracture of opposing complete denture: 5× Fracture of denture teeth (either opposing complete denture or mandibular implant prosthesis): 22×


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Table 1 (continued) Clinical Studies Reporting Prosthodontic Maintenance/Complication Issues Involving Screw-Retained Prostheses

Study Ekelund et al38 (2003)

Type of study Prospective


Region Mandible

Observation Type of implant period and connection 20–23 y Brånemark

Attard and Zarb40 (2004)

Prospective

45; 265


20 y (mean)

Rasmusson et al45 (2005) Astrand et al51 (2008)

Prospective Prospective

36; 199 48; 111

Maxilla and mandible Maxilla and mandible

10 y 20 y

Purcell et al53 (2008)

Retrospective

46; 233

Mandible

7.9 y (mean)

Gallucci et al54 (2009)


45; 237

Mandible

5y

Straumann

Örtorp and Jemt56 (2009)

Retrospective

155; 1,099

Mandible

15 y

Brånemark

Maló et al64 (2012)†

Prospective

108; 634


Up to 10 y

Brånemark (Nobel Speedy)

Örtorp and Jemt65 (2012)

Prospective

126; 728


10 y

Brånemark

Brånemark

TiOblast (Astra Tech) Brånemark

Steri-Oss; external hex


Studies reported various types of luting cement, such as temporary cement (Temp Bond, Kerr; Dycal, LD Caulk Division), IRM, zinc phosphate cement,

134

glass-ionomer cement, and resin cement (Panavia, Kuraray; RelyX, 3M ESPE) for cement-retained implant crowns. The most common type of temporary



Ma/Fenton

Type of crown Type III gold alloy with resin teeth and bilateral cantilever units

Retention mechanism (screw-retained) NS

Metal alloy and acrylic resin denture teeth

NS

NS Gold alloy framework and acrylic resin teeth

NS NS

Framework: (a) Type III or IV gold alloy (b) Gold-palladium alloy (c) High palladium alloy (d) Silver-palladium alloy

Ti alloy

Veneering: acrylic resin denture teeth

Prosthodontic outcomes New prosthesis: 2/47 Screw loosening: 2/47 Loss of screw access plug: 1/4 1/47 Tissue hyperplasia/inflammation: 47× Fractured gold screw: 78× Fractured abutment screw: 25× Fractured acrylic denture teeth: 22× Reline of opposing complete denture: 5× Fractured framework: 16× Remake of prosthesis: 57× Remake of opposing complete denture: 27× Porcelain fractures: 1/36 Screw loosening (abutment/prosthetic): 3/48 New prosthesis: 1/48 Replacement of acrylic resin teeth: 4/48 Abutment screw loosening: 5× Abutment screw fracture: 2× Retaining screw loosening: 13× Retaining screw fracture: 8× Stripped screws: 8× Fractured acrylic resin teeth: 28× Replacement of acrylic resin teeth: 24× Fractured acrylic resin: 5×

Hybrid-type with distal cantilever Acrylic base and prosthetic teeth mounted on a metallic framework (41/45) Metal-ceramic (4/45)

NS

Screw loosening: 2× Screw fracture: 5× Fractured acrylic resin tooth or denture base: 20× Porcelain fracture: 1× Fracture opposing complete denture: 12× Inflammation under opposing complete denture: 2× Framework fracture: 2× Loss of screw access plug: 4× (comp resin) Esthetics, remake: 1×

(C) Cast gold alloy frameworks and acrylic resin teeth

NS

New prosthesis: 4× (C); 7× (T) Framework fracture: 17× (C); 23× (T) Implant component fracture: 6× (T) Screw loosening: 3× (T) Acrylic resin veneer fracture: 12× (C); 41× (T) New acrylic resin veneers due to wear: 7× (T) Loss of screw access plug: 11× (C); 27× (T) Crown fracture: 14/59 Abutment screw loosening: 1/56 (pts) Abutment replacement: 1/56 (pts)

(T) Laser-welded Ti frameworks and acrylic resin teeth

Alumina copings (Procera) with Allceram ceramics cemented onto a Ti framework (Procera) with pink ceramic Zirconia copings with Nobel Rondo zirconia ceramic and pink acrylic (C): Au alloy frameworks and acrylic resin teeth (T): CNC-milled grade 2 Ti frameworks with acrylic resin teeth

NS

NS

Screw loosening: 1× (C) Implant component fracture: 1× (C), 2× (T) Framework fracture: 2× (C) Veneer fracture (uncomplicated): 9× (C), 7× (T); (severe): 37× (C), 26× (T) Wear of acrylic resin teeth 3× (C), 2× (T) Loss of screw access plug: 25× (C), 5× (T)

cement was Temp Bond. There was no mention of mixing the temporary cement with petroleum jelly. The studies failed to identify the rationale behind the

choice of luting cement. There was no report on the explanation of procedures involving placing the luting cement and removing the excess material.


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Table 2 C linical Studies Reporting Prosthodontic Maintenance/Complication Issues Involving Cement-Retained Prostheses

Study

Type of study


Region

Observation period


Single implant crowns Palmer et al20 (1997)

Prospective

15; 15

Maxilla (anterior sites only)

2y

Astra Tech

Andersson et al21 (1998)

Prospective

57; 62


5y

Nobel Biocare

Scheller et al23 (1998)


82; 99


5y

Brånemark



110; 157


40.1 mo (mean)

Polizzi et al24 (1999)

Prospective

21; 30

Maxilla and mandible (incisor sites only)

3–7 y

Brånemark

Scholander25 (1999)†

Retrospective

135; 259


1–9 y

Brånemark

Wannfors and Smedberg26 (1999)†

Prospective

69; 80


3y

Brånemark

Andersson et al28 (2001)*


75; 89


1–3 y

Brånemark

Mangano and Bartolucci30 (2001)

Retrospective

69; 80

NS

3.5 y (mean)

MAC System (Carbon)

Mericske-Stern et al70 (2001)*

Longitudinal

72; 109


4.2 y (mean)

ITI

Gibbard and Zarb33 (2002)†

Prospective

42; 49


5y

Brånemark

Krennmair et al32 (2002)†

Retrospective

112; 146


7y

Frialit-2 (Friatec)



471; 671

Maxilla and mandible (molar sites only)

21.3 mo (mean)

Drago36 (2003)

Prospective

73; 110


1y

Osseotite (3i, Implant Innovations)

Gotfredsen42 (2004)

Prospective

20; 20

Maxilla (anterior region)

5y

Astra Tech ST (Astra Tech)

Vigolo et al43 (2004)†

Prospective

12; 24

4y


Bragger et al44 (2005)†

Prospective

48; 69

NS

10 y

ITI Bonefit (ITI Straumann)

Schropp et al71 (2005)†

RCT

43; 43


2y

Osseotite (3i, Implant Innovations)

Wennström et al46 (2005)

Prospective

40; 45


5y

Astra ST-implants, Astra Tech

ITI (Straumann)

Solid-screw ITI (Straumann); internal connection

RCT = randomized controlled trial; NS= not specified; AC = all ceramic, AM = all metal; PFM = porcelain fused to metal; Ti = titanium; × = number of event(s); (pts) = number of patients affected by the maintenance issues; Au = gold; (C) = control group; (T) = test group; comp resin = composite resin; CNC = computer numeric controlled. *Data combined with other retention mechanism. †Data separated from the other retention mechanism.

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Ma/Fenton

Retention mechanism (cement-retained)

Type of crown


PFM

Temporary cement (Temp Bond, Kerr)

Cement loss: 1× Porcelain fracture: 1×

AC (n = 62) PFM (n = 3)

NS

Abutment screw loosening: 1×

AC (81) PFM (16)

Zinc phosphate (69) Glass-ionomer (5) Temporary cement (22) NS (1)

Crown fracture: 7× Esthetics: 1× Abutment screw loosening: 4× Cement loss: 3×

NS

NS (76)

Abutment screw (solid conical abutment) loosening: 4×

PFM

NS

Cement loss: 1×

AC (175) PFM (79) Gold-acrylic (4)

Zinc phosphate (160) Temporary cement (73) Glass-ionomer (23)

Loose abutment screws: 10× Cement loss: 4× Crown fracture: 3× Porcelain fracture: 1× Remake: 8×

AC (9) Gold-acrylic (36) PFM (35)

Zinc phosphate (36)

Abutment screw loosening: 1× Esthetics: 2× Porcelain fracture: 1×

AC (70)

Zinc phosphate (54) Glass-ionomer (7) Zinc oxide eugenol (6) Resin (3)

Abutment fracture during preparation/ placement: 5× Abutment fracture (after loading): 2× Porcelain fracture: 2× Crown fracture: 1×

AC

Temporary cement

Crown fracture: 2× Abutment screw loosening: 1×

PFM

NS (7)

Cement loss: 1× Porcelain fracture: 1× Abutment fracture: 3× (Octa abutment, withdrawn from the market)

NS

NS (2)

Screw loosening: 13%

AC (27) PFM (119)

Temporary cement (Temp Bond, Kerr) (93)

Cement loss: 9× Abutment screw loosening: 4× Porcelain/crown fracture: 2×

NS

NS (600)

Abutment screw loosening: 0.3% Abutment fracture: 0.5% Cement loss: 0.6% Porcelain fracture: 0.2%

AM PFM

Temporary cement (Dycal, LD Caulk Division)


PFM

NS

Abutment screw loosening: 2× Porcelain fracture: 2× Cement loss: 2×

PFM

Temporary cement (Temp Bond NE, Kerr) (12)

None

PFM

Zinc phosphate (67)

Prosthetic screw loosening: 1× Abutment screw loosening: 2× Porcelain fracture: 3×

PFM

NS (41)

Cement loss: 5×

PFM

Zinc phosphate



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Table 2 (continued) Clinical Studies Reporting Prosthodontic Maintenance/Complication Issues Involving Cement-Retained Prostheses

Study Norton72 (2006)

Levine et al73 (2007)

Type of study Retrospective


Region Maxilla and mandible

Observation period 3y (mean)

Maxilla and mandible (molar sites only) Maxilla

23 mo (mean) 4y

Type of implant and connection Astra Tech

410; 499

Turkyilmaz et al50 (2007)

Retrospective, multicenter Prospective

Jemt55 (2009)† Sailer et al57 (2009)†

Retrospective RCT

35; 41 22; 40

Maxilla Maxilla and mandible (canine, premolar, and molar sites only)

10 y 1y

Brånemark Brånemark (Nobel Biocare); external hex

Krennmair et al58 (2010)

Retrospective

NS; 112


5y

Camlog

Mangano et al59 (2010)

Prospective

295; 307


4y

Hosseini et al62 (2011)

RCT

36; 75

Maxilla and mandible (premolar region only)

1y

Leone Implant System (Inta) Astra Tech

Visser et al63 (2011)

RCT

93; 92

5y

Oyama et al66 (2012)

Prospective

13; 17

Maxilla (anterior region) Maxilla and mandible (incisor region only)

Vigolo et al67 (2012)

RCT

18; 18

Maxilla (canine and premolar region) and mandible (premolar and molar region)

10 y

Singer and Serfaty19 (1996)

Retrospective

70; 225


Up to 3 y

Spectra System, Integral, Integral-Omniloc

Duncan et al37 (2003)†

Prospective

32; 83

NS

3y

ITI implants (Straumann)

Nedir et al47 (2006)

Prospective

NS; 383

Maxilla and mandible (posterior region only)

Up to 8 y

Straumann

Khraisat et al52 (2008)


49; 87

Minimum 1y

Solid-screw implants (Straumann)

Crespi et al48 (2007)

Prospective

27; 160

Maxilla and mandible (anterior region including first premolars) Maxilla and mandible

29; 59

1y

Straumann MK III TiUnite (Nobel Biocare); external hex

ITI-Esthetic Plus (ITI Straumann) Xive S (Dentsply)

3i, Implant Innovations; external hex

Fixed dental prostheses (partial)

18 mo

Outlink, Sweden & Martina; internal hex

Fixed dental prostheses (complete) RCT = randomized controlled trial; NS= not specified; AC = all ceramic, AM = all metal; PFM = porcelain fused to metal; Ti = titanium; × = number of event(s); (pts) = number of patients affected by the maintenance issues; Au = gold; (C) = control group; (T) = test group; comp resin = composite resin; CNC = computer numeric controlled. *Data combined with other retention mechanism. †Data separated from the other retention mechanism.

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Ma/Fenton

Type of crown NS

NS PFM

PFM AC (19) PFM (21)

AC PFM AC (65) PFM (42) AC (38) PFM (37)

Retention mechanism (cement-retained) Temporary cement (Temp Bond, Kerr) Solid abutment torqued to 35 Ncm with a torque wrench Temporary cement (Temp Bond NE, Kerr) CeraOne abutments (Nobel Biocare) NS (23) Resin cement (Panavia or RelyX) Glass-ionomer (Ketac Cem) (38) Temporary cement (Temp Bond, Kerr) NS

Prosthodontic outcomes Cement loss: 32× Porcelain fracture: 13× Abutment screw loosening: 4× Cement loss: 2× Porcelain fracture: 3×

Abutment screw loosening: 3/23 Porcelain fracture: 2× PFM

Screw loosening: 5/112 Cement loss: 11/112 Porcelain fracture: 5/112 Abutment screw loosening: 0.66%

Zinc phosphate (35 AC, 36 PFM) Resin cement (Panavia, Kuraray) (3 AC, 1 PFM) NS

Porcelain fracture: 1× PFM Cement loss: 1× PFM

Temporary cement (Temp Bond, Kerr); Type IV gold customized abutment Temporary cement (Temp Bond NE, Kerr)

None

Single or multiple: PFM

Temp Bond or IRM

Single (22) or multiple (19): PFM Multiple: PFM

Zinc phosphate (18)

Out of 92 arches Cement loss: 0.02% Porcelain fracture: 0.02% Abutment screw loosening: 0.02% None

Zinc phosphate

Out of 265 prostheses Abutment screw loosening: 0.0075% Abutment fracture: 0.0038% Cement loss: 0.011% Porcelain fracture: 0.023% (minor), 0.045% (major) Prosthesis remake: 0.034%

Single or multiple (2 units)

Polycarboxylate

Cement loss: 3×

Metal-ceramic

NS

None

AC PFM

PFM

Remake: 11/93

None


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Table 2 (continued) Clinical Studies Reporting Prosthodontic Maintenance/Complication Issues Involving Cement-Retained Prostheses

Study Maló et al64 (2012)†

Type of study Prospective


Region Maxilla and mandible

Observation period Up to 10 y

Type of implant and connection Brånemark, Nobel Speedy

RCT = randomized controlled trial; NS= not specified; AC = all ceramic, AM = all metal; PFM = porcelain fused to metal; Ti = titanium; × = number of event(s); (pts) = number of patients affected by the maintenance issues; Au = gold; (C) = control group; (T) = test group; comp resin = composite resin; CNC = computer numeric controlled. *Data combined with other retention mechanism. †Data separated from the other retention mechanism.

Table 3 C linical Studies Reporting Prosthodontic Maintenance/Complication Issues Involving Horizontal Screw-Retained Prostheses

Study

Type of study


Region

Observation period


Type of crown

Retention mechanism


Single implant crowns Krennmair et al32 (2002)*

Retrospective

112; 146


7y

Frialit-2 (Friatec)

AC (27) PFM (119)

Horizontal screw (31)

Screw (horizontal) loosening: 3× Abutment screw loosening: 1× Porcelain/crown fracture*: 1×

AC = all ceramic; PFM = porcelain fused to metal; × = number of event(s). *Data combined with other retention mechanism.

Prosthodontic Maintenance/Complications Various types of prosthodontic maintenance/complications were reported. The common types of maintenance/complications included screw loosening (crowns or abutments), luting cement loss, veneering or porcelain fracture, and esthetic concerns (Table 4). Several studies involving screw-retained implant prostheses, with the majority being full-arch fixed implant prostheses, mentioned the maintenance issues of losing restorative materials used as screw access plugs. Ten studies22,25,37,43,44,48,57,66,67,71 did not have any prosthodontic maintenance/complication during the observation period. Several studies that included screw-retained and cement-retained prostheses made it difficult to separate their prosthodontic maintenance/complication data according to the retention mechanism because they did not distinguish them in their studies. Only two studies60,68 specified the prosthodontic maintenance/ complication criteria77,78 used to report their prosthodontic outcomes.

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Discussion The aim of this systematic review was to analyze evidence regarding prosthodontic outcomes between screw- and cement-retained fixed implant prostheses. Although single implant crowns have been promoted as a successful rehabilitation option for partially dentate patients, it appears that this drive has been based more on the biologic outcomes than the long-term data on the prosthodontic maintenance/complications issues. On the other hand, fullarch fixed implant prostheses have well-documented long-term data because this treatment modality introduced the clinical protocol for contemporary implant dentistry. In regard to guidelines on choosing the retention mechanisms for fixed implant prostheses, this issue also has never been resolved because the choice has been based on individual preference or anecdotal evidence. Retrievability is the main advantage of screwretained implant prostheses. It is important when managing prosthodontic maintenance issues such as screw loosening or repair of superstructures. Various



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Type of crown Alumina copings (Procera) with Allceram ceramics cemented onto a titanium framework (Procera) with pink ceramic Zirconia copings with Nobel Rondo zirconia ceramic and pink acrylic

Retention mechanism (cement-retained) NS

Prosthodontic outcomes Recurrent crown fractures ➞ replaced by acrylic resin prostheses: 5/66 Crown fracture: 33/66 Abutment screw loosening: 2/29 (pts) Porcelain fracture (gingival region): 3/36

Table 4 S ummary of Commonly Reported Prosthodontic Maintenance/Complication Issues According to the Selected Prosthetic Retention Method Screw-retained

Cement-retained

1. Patient objection to visible screw access sites

1. Inadequate seating during cementation

2. Loosening of accessible crown/fixed partial denture/abutment screws

2. Subgingival cement retention causing inflammation

3. Loss of renewable screw sealant material

3. Loosening of prosthetic screws with difficult accessibility

4. Fracture of veneering material

4. Loss of retention 5. Need for recementation and cement reselection 6. Fracture of veneering material

reports of screw loosening for single implant crowns (as high as 65%) have surfaced.6,15 One older study16 using gold prosthetic screws to retain single implant crowns did not specify the tightening procedure and also reported 38% of implants being affected by screw loosening. Although frequency of this clinical mishap appears to have occurred frequently, recent ongoing changes in implant components must be taken into consideration. The mechanics of prosthetic screws have evolved enormously in regard to preload and better torque controllers.36 Application of the correct torque is translated into a preload, producing a clamping force and preventing a one-sided lift-off of the abutment.79 This positive impact on maintenance events is clearly evident in the newer studies43,60; although it may still be argued that cement retention is a viable option for single implant crowns. However, it must be considered that there are other prosthodontic maintenance issues such as repair of chipped veneering porcelain or loosening of abutments supporting the implant crowns. In order to manage these longterm prosthodontic maintenance issues, it is essential that the superstructure can be readily removed

without damage occurring to the oral implants as well as the prostheses. Temporary cements such as Temp Bond can be used to retain single implant crowns to provide “easier” retrieval of the prostheses. However, due to the close fitting between the abutment and crown, it is difficult to remove the prostheses intact. Any damages made to the restorations may result in remaking of the prostheses, which would be an additional financial burden to the patients. There have been innovative ways to achieve retrievability with cement-retained prostheses by including a palatal/ lingual screw to cause shear force that can disrupt the cement layer.80–84 Studies using screw-retained mechanisms reported loss of restorative materials in the screw access.18,26,27,31,38,54,56,65 The common material of choice was composite resin except in one study,18 which used acrylic. While this is a minor prosthodontic maintenance issue that can be easily managed, it can become a nuisance for patients and clinicians alike. Loss of retention is a major disadvantage for cement-retained prostheses because they depend on the dimension of abutments. Several


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studies20,23–25,32,34,42,58,62 in this review reported loss of retention when using cement-retained single implant crowns. However, authors did not associate this maintenance issue with the type of luting cement. While in vitro studies have shown that the convergence and height of abutments are crucial in maintaining the stability of implant prostheses,85 there are no guidelines for the selection of luting cement. Studies suggest using provisional cement such as zinc oxide eugenol for the ease of retrievability, although clinical experience has shown that with the ideal abutment dimension, it is still difficult to remove the prostheses.86 The principle of progressive cementation has been suggested for recurrent loss of retention, whereby cements with better adhesion are progressively used until adequate retention is achieved.6 Three studies19,47,52 involving either single implant crowns or fixed partial prostheses showed cement loss, whereas studies involving full-arch fixed implant prostheses using cement retention did not report any debonding of the prostheses.48,64 This is not surprising as the full-arch fixed implant prostheses can rely on multiple implants for retention and any individual debonding may not be clinically detectable. However, a recent paper85 has reported equal frequencies (16% to 17%) of repeated abutment screw loosening between screw- and cement-retained single implant crowns. Fracture of the veneering acrylic or porcelain has shown to be a common maintenance/complication issue for implant prostheses. This occurred for both all-ceramic and porcelain-fused-to-metal crowns regardless of retention mechanism. A recent retrospective study showed that a screw-retained suprastructure was the only significant risk factor when assessing for fracture of veneering material.88 Another study89 reported the differences in the incidence of porcelain chipping when comparing cement-retained single metal-ceramic to all-ceramic single implant crowns. The authors stated that because the chipping was more frequent with all-ceramic single implant crowns, these crowns should be recommended with care. The majority of studies in this systematic review indicate that the chipping was minor and thus did not require remakes of prostheses. While only two studies used cement-retained full-arch fixed implant prostheses and only one of them reported maintenance issues, this study64 did not explain the procedure involved in the repair of the veneering chipping and whether the prostheses were retrievable. This study also failed to specify the type of cement used. With the improvement of ceramic technology and better understanding of the fabrication process, the incidence of porcelain chipping may improve. Studies26,54,60 have reported esthetics as one of prosthodontic maintenance/complication issues

142

whereby the participants were not satisfied with the final esthetic outcomes and the crowns either had to be adjusted or remade. However, this was not due to the retention mechanism. Esthetics is driven by the implant position, and proper planning is essential for achieving satisfactory outcomes. The position of the screw access can dictate the esthetic outcomes, especially in the anterior maxillary region, and clinicians would prefer to mask the unfavorable screw access opening by fabricating cement-retained prostheses.90 One study offered a different technique to improve the esthetics when restoring the screw access,84 while other authors suggested cross-pinning so that the prostheses are still retrievable but avoid the direct screw access.32,80,91 There was only one study 32 from this systematic review that investigated the prosthodontic outcomes when using horizontal screws. It showed that for 31 horizontal screws over 7 years, these screws loosened three times while the abutment screw loosened only once. Only one crown that suffered porcelain chipping. This type of retention mechanism will allow for easy prosthodontic maintenance without causing any damage to the prostheses. Whether the esthetics was affected due to the retention mechanism could not be identified in this review as the studies did not provide any guidelines for how each participant was chosen for the particular retention mechanism. Maintaining an optimal occlusion is also crucial for implant prostheses. As screw-retained single implant crowns require the prosthetic screw access through the occlusal surfaces, this may actually interfere with the occlusion.6 However, the dimension of screw access depends on the size of the prosthetic screw, and, unless this increased dramatically according to the size of the implant, there would be minimal impact to the occlusion. Studies included in this systematic review did not discuss any impact of different retention mechanisms on occlusion. Cement-retained implant crowns require attention to the removal of excess cement so that any associated peri-implant complications can be avoided.67,92–96 Although delivery of cement-retained single implant crowns may be more ideal in situations involving limited mouth opening and the posterior region of the oral cavity,6 any oral implant placed too subgingivally may cause difficulties during excess cement removal and any remaining cement may cause peri-implant inflammation,93,95,96 as shown by a recent retrospective study.96 Therefore, careful planning of the abutment design must be carried out to assist in easy removal of excess cement. There is also a lack of consensus regarding the type of cement, the appropriate quantity of cement, and the placement method for cementretained implant prostheses.97



Ma/Fenton

The passive fit of implant prostheses is a controversial topic, and there have been no conclusive data on the necessity for or appropriate dimension involved in a passive fit. Non-passively fitting prostheses have been cautioned as causing undue implant stress leading to biologic and prosthetic implant failure.7 Cement retention, therefore, has been encouraged to provide passively fitting implant crowns because the cement space may compensate for a lack of passive fit and serve as a shock absorber. None of the included studies investigated the passivity of the fixed implant prostheses and its impact on the ongoing prosthodontic maintenance. There was a lack of standardized reporting protocol for prosthodontic maintenance associated with fixed implant prostheses. Only two studies60,68 specified the criteria used for their data collection, and several studies did not specify the type of screws or screw tightening procedure, while others did not state the type of cement used to retain the implant prostheses. However, recent studies, albeit with short-term prosthodontic data, suggest that more improved designs of implant components and controlled protocol of screw tightening have contributed positively to minimizing the amount of prosthodontic maintenance/ complication burden.

Conclusions The inadequacy of available information and diversity of reported study designs precluded a comparison of prosthodontic outcomes between screw- and cement-retained fixed implant prostheses. Both retention mechanisms showed prosthodontic maintenance/ complication issues that must be considered, although the introduction of newer implant components may assist in minimizing these clinical concerns. It is also recommended that standardized criteria are used when reporting prosthodontic maintenance/complication issues to permit better future data comparison.

Acknowledgments The authors would like to thank the support from the Foundation for Oral Rehabilitation. The authors reported no conflicts of interest related to this study.

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Clinical performance of screw- versus cement-retained fixed implant-supported reconstructions--a systematic review.

A systematic review of screw- versus cement-retained implant-supported fixed restorations.

Influence of prosthesis type and retention mechanism on complications with fixed implant-supported prostheses: a systematic review applying multivariate analyses.

Effect of cantilevers for implant-supported prostheses on marginal bone loss and prosthetic complications: systematic review and meta-analysis.

Evaluation of cement-retained versus screw-retained implant-supported restorations for marginal bone loss: A systematic review and meta-analysis.

Implant loading protocols for edentulous patients with fixed prostheses: a systematic review and meta-analysis.

Impact of fixed implant supported prostheses in edentulous patients: protocol for a systematic review.

Peri-implant bone loss around single and multiple prostheses: systematic review and meta-analysis.

Implant survival and prosthetic complications of mandibular metal-acrylic resin implant complete fixed dental prostheses.

Clinical outcomes and complications of a collagen meniscus implant: a systematic review.

Zirconia-Based Screw-Retained Prostheses Supported by Implants: A Retrospective Study on Technical Complications and Failures.

Prosthodontic management of implant therapy.

The effects of anti-infective preventive measures on the occurrence of biologic implant complications and implant loss: a systematic review.

Systematic review of the survival rate and incidence of biologic, technical, and esthetic complications of single implant abutments supporting fixed prostheses.

Technical and biological complications related to crown to implant ratio: a systematic review.

Complications associated with inferior alveolar nerve repositioning for dental implant placement: a systematic review.

Ologen implant versus mitomycin C for trabeculectomy: a systematic review and meta-analysis.

Pedicle screw versus hybrid instrumentation in adolescent idiopathic scoliosis: A systematic review and meta-analysis with emphasis on complications and reoperations.

Effects of Screw- and Cement-Retained Implant-Supported Prostheses on Bone: A Nonlinear 3-D Finite Element Analysis.

Reliability of four zygomatic implant-supported prostheses for the rehabilitation of the atrophic maxilla: a systematic review.

Pulmonary rehabilitation maintenance interventions: a systematic review.

Implant-assisted complete prostheses.

Predictors of surgical complications: A systematic review.

The transmandibular implant: prosthodontic treatment considerations.