A systematic review of the survival and complication rates of inlay-retained fixed dental prostheses

Abstract

Objectives

The aim of this systematic review was to investigate the survival and complication rates of inlay-retainer fixed dental prostheses (IRFDPs).

Data/Sources

A systematic search was conducted in the PubMed, EMBASE, and Cochrane Library databases in English and time filters (articles published from 1960) were used.

Study selection

Randomized controlled trails (RCTs), controlled clinical trials (CCTs) and prospective cohort studies on IRFDPs with a mean follow-up period of at least 2 years were included. Among 501 screened articles, one RCT and ten prospective cohort studies were included in this study. Of the included studies, information on failure and complications was independently extracted by two reviewers in duplicate. The failure and complication rates of IRFDPs were pooled with a random effect model and Poisson regression was applied to further investigate the influence of framework materials. The estimated 3- and 5-year survival rates of IRFDPs were 92.6% (95% CI: 85.8–97.6%) and 87.9% (95% CI: 77.4–96.1%), respectively. Debonding, fracture, dentine hypersensitivity and secondary caries were primary complications. The estimated 5-year rates of debonding, veneer fracture and secondary caries were 5.3%, 15.2% and 2.7%, respectively. Additionally, fiber-reinforced composite IRFDPs exhibited a lower incidence of debonding and caries with a higher rate of veneer fracture compared with metal-based and all-ceramic IRFDPs (p < 0.05).

Conclusions

Compared with conventional fixed dental prostheses (FDPs) and implant-supported single crowns (ISCs), IRFDPs exhibited an acceptable 3-year survival rate but higher complication rates of debonding and veneer fracture.

Clinical significance

IRFDPs can be recommended as viable short- or middle-term minimally invasive alternatives to short-span conventional FDPs and ISCs, while the clinical outcome of IRFDPs as long-term definitive restorations still calls for further research. The indications of IRFDPs should be strictly controlled and monitored.

Introduction

Implant-supported single crowns and conventional fixed dental prostheses (FDPs) have been considered to be traditional treatments for replacing single missing tooth because of the advantages of good strength, superior wear resistance and long-term reliability. However, implant treatment requires a surgical procedure and may suffer from anatomical or economic limitations of patients . With respect to conventional FDPs, 67.5%–75.6% of the sound coronal tooth structure has to be removed during the preparation of full crowns , which may lead to the risk of a pulp reaction . Currently, since minimally invasive dentistry has been considered to be a rational approach in the current diagnostic and treatment planning regimen, resin-bonded FDPs (RBFDPs) may be a promising treatment modality for partial edentulous conditions.

RBFDPs were first introduced by Rochette in the 1970s , and a recent systematic review on RBFDPs with conservative lingually/palatally tooth preparation designs exhibited a 5-year survival rate of 87.7% , which were mainly placed in anterior region. With regard to the replacement of posterior missing teeth, resin-bonded inlay-retained FDPs (IRFDPs) can be recommended as a conservative treatment modality . Originally, IRFDPs made of metal alloys were first introduced in the 1960s and suffered from frequent complications, such as loss of retention and secondary caries. In 1996, the first encouraging attempt to use inlays as retainers for posterior RBFDPs was reported by Stokholm and Isidor , demonstrating acceptable prognostic results via different metal treatment techniques.

The survival rate of IRFDPs in the literature varies widely from 38% to 95.8% because of the diverse framework materials, tooth preparation designs, cement bonding techniques and systems. For instance, apart from the initial metal-based IRFDPs, IRFDPs made from metal-free materials such as fiber-reinforced composite (FRC) resins and all-ceramic materials are becoming more prevalent, which can meet the increased aesthetic demands of patients. Additionally, various designs of inlay retainers have been used to acquire sufficient retention and resistance of IRFDPs. Specifically, a box-shaped inlay retainer can achieve superior resistance and can often make use of pre-existing fillings ; a tub-shaped inlay retainer is a conservative design that can prevent irritation of the pulp of tipped teeth ; and short retainer-wings at the buccal and lingual sides of abutment teeth have been suggested to minimize tensile and torsion forces . Furthermore, although IRFDPs offers a more conservative preparation of abutment teeth, this treatment modality is more technique sensitive and requires careful bonding procedures .

It should be noted that a complex of important factors, such as meticulous case selection, reasonable framework design, precise tooth preparation, as well as careful adhesive luting procedure can determine the clinical success of IRFDPs. To the best of our knowledge, the clinical performances of IRFDPs have not been sufficiently summarized by an evidence-based method. Therefore, the aim of this study was to systematically review existing literatures and to evaluate the survival and complication rates of IRFDPs.

Materials and methods

Review protocol

This review aimed to systematically retrieve and analyze clinical studies investigating the survival and complication rates of IRFDPs. The PICO principle was applied during the investigation. The patient cohort included patients with partial edentulism in the posterior region. The intervention was IRFDPs to replace missing teeth. No control or comparison was selected. The outcomes were the survival and complication rates of IRFDPs. Survival in this systematic review was defined as IRFDPs remaining in situ throughout the follow-up without any debonding, refabrication or framework facture. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied whenever applicable.

Search strategy

An electronic systematic literature search in PubMed, EMBASE, Cochrane Database of Systematic Reviews (CDSR), and Cochrane Central Register of Controlled Trials (CENTRAL) databases was conducted for articles in English based on clinical human studies in January 2017. Time filters (articles published from 1960/01/01) were used. The detailed search terms and strategy are presented in Table 1 . The electronic search was complemented by a manual search of bibliographies from full-text articles and related reviews.

Table 1
Search strategy (For PubMed database).
1 Search ((((Inlays [MeSH]) OR Inlay) OR Slot) OR Box) OR Tub
2 Search (((((((Denture, partial, fixed [MeSH]) OR Denture, partial, fixed, resin-bonded [MeSH]) OR Resin-bonded bridge) OR Fixed dental prostheses) OR Adhesive bridge) OR Acid-etched bridge) OR Resin-bonded fixed partial denture) OR Resin-bonded fixed dental prostheses
3 Search ((#1 and #2)) Filters: Publication date from 1960/01/01 to 2017/1/20

Study selection

Study selection was conducted by two independent reviewers (J.C, H.C) in duplicate. The initial screening of titles was performed, and studies that were not related to IRFDPs were excluded. The secondary scanning of abstracts was then conducted and studies were eliminated if they did not meet the inclusion and exclusion criteria. Then, the full texts of the qualified articles were obtained for independent assessment, and hand search was performed on the references of the full-text articles and related reviews. Any disagreement was solved in consensus via discussion or by a third reviewer (Q.W). The inclusion and exclusion criteria are presented as follows.

Inclusion criteria

1) Studies with a mean follow-up period of 2 years or more; 2) Clinical studies based on humans only including randomized-controlled clinical trials (RCTs), controlled clinical trials (CCTs) and prospective cohort studies; 3) Studies with quantitative clinical outcomes, such as survival/failure incidence, technical or biological complication incidence; 4) The patients should be examined clinically during the follow-up visits; and 5) Studies reporting details on the materials and methods such as retainer designs, tooth preparation designs, materials of framework, bonding systems and surface treatments.

Exclusion criteria

1) Retrospective cohort studies , In vitro or animal studies, case reports, and case series; 2) Studies with an observation time of less than 2 years; 3) Clinical outcomes based only on patient records, such as questionnaires or interviews; or 4) Multiple studies on the same patient cohort.

Data extraction

Of the included studies, information on failure, as well as biological and technical complications was independently extracted by two reviewers using a purpose designed data collection form (J.C, H.C) in duplicate. Disagreement regarding data extraction was resolved by consensus of a third reviewer (Q.W). Survival in this systematic review was defined as IRFDPs remaining in situ throughout the follow-up without any debonding, refabrication or framework facture. Failure was defined as IRFDPs that were lost and needed reconstruction or recementation (one or more recementations), and mild complications such as minor veneer fracture and dentine hypersensitivity might not be regarded as failure. The main biological complication was secondary caries and dentine hypersensitivity; the main technical complications included debonding and fractures.

Quality assessment

The bias and quality of the cohort studies were evaluated by the Newcastle-Ottawa scale (NOS) , and the bias of RCT was assessed based on the Cochrane Handbook for Systematic Reviews of Interventions .

Statistical analysis

For each study, the failure and complication rates of IRFDPs were calculated by dividing the event number of failures or complications in the numerator by the total exposure time of IRFDPs in the denominator, which were pooled with a random effect model after Freeman-Tukey double arcsine transformation when encountering low event rates. Between studies the heterogeneity was estimated using the χ2-based Q statistic. Heterogeneity was considered statistically significant for p < 0.1. If heterogeneity existed, data were analyzed using a random effects model; in the absence of heterogeneity, a fixed effects model was used. A statistical test with a P value less than 0.05 was considered significant. Three- and five-year survival proportions were calculated via the relationship between the event rate and survival function S, S(T) = exp(-T × event rate), by assuming constant event rates according to the protocol described by Kirkwood et al. . Moreover, Poisson regression was used to further investigate the influence of framework materials on the failure and complication rates of IRFDPs . All analyses were conducted using STATA, version 13.0 (Stata Corp., College Station, TX, USA).

Materials and methods

Review protocol

This review aimed to systematically retrieve and analyze clinical studies investigating the survival and complication rates of IRFDPs. The PICO principle was applied during the investigation. The patient cohort included patients with partial edentulism in the posterior region. The intervention was IRFDPs to replace missing teeth. No control or comparison was selected. The outcomes were the survival and complication rates of IRFDPs. Survival in this systematic review was defined as IRFDPs remaining in situ throughout the follow-up without any debonding, refabrication or framework facture. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied whenever applicable.

Search strategy

An electronic systematic literature search in PubMed, EMBASE, Cochrane Database of Systematic Reviews (CDSR), and Cochrane Central Register of Controlled Trials (CENTRAL) databases was conducted for articles in English based on clinical human studies in January 2017. Time filters (articles published from 1960/01/01) were used. The detailed search terms and strategy are presented in Table 1 . The electronic search was complemented by a manual search of bibliographies from full-text articles and related reviews.

Table 1
Search strategy (For PubMed database).
1 Search ((((Inlays [MeSH]) OR Inlay) OR Slot) OR Box) OR Tub
2 Search (((((((Denture, partial, fixed [MeSH]) OR Denture, partial, fixed, resin-bonded [MeSH]) OR Resin-bonded bridge) OR Fixed dental prostheses) OR Adhesive bridge) OR Acid-etched bridge) OR Resin-bonded fixed partial denture) OR Resin-bonded fixed dental prostheses
3 Search ((#1 and #2)) Filters: Publication date from 1960/01/01 to 2017/1/20

Study selection

Study selection was conducted by two independent reviewers (J.C, H.C) in duplicate. The initial screening of titles was performed, and studies that were not related to IRFDPs were excluded. The secondary scanning of abstracts was then conducted and studies were eliminated if they did not meet the inclusion and exclusion criteria. Then, the full texts of the qualified articles were obtained for independent assessment, and hand search was performed on the references of the full-text articles and related reviews. Any disagreement was solved in consensus via discussion or by a third reviewer (Q.W). The inclusion and exclusion criteria are presented as follows.

Inclusion criteria

1) Studies with a mean follow-up period of 2 years or more; 2) Clinical studies based on humans only including randomized-controlled clinical trials (RCTs), controlled clinical trials (CCTs) and prospective cohort studies; 3) Studies with quantitative clinical outcomes, such as survival/failure incidence, technical or biological complication incidence; 4) The patients should be examined clinically during the follow-up visits; and 5) Studies reporting details on the materials and methods such as retainer designs, tooth preparation designs, materials of framework, bonding systems and surface treatments.

Exclusion criteria

1) Retrospective cohort studies , In vitro or animal studies, case reports, and case series; 2) Studies with an observation time of less than 2 years; 3) Clinical outcomes based only on patient records, such as questionnaires or interviews; or 4) Multiple studies on the same patient cohort.

Data extraction

Of the included studies, information on failure, as well as biological and technical complications was independently extracted by two reviewers using a purpose designed data collection form (J.C, H.C) in duplicate. Disagreement regarding data extraction was resolved by consensus of a third reviewer (Q.W). Survival in this systematic review was defined as IRFDPs remaining in situ throughout the follow-up without any debonding, refabrication or framework facture. Failure was defined as IRFDPs that were lost and needed reconstruction or recementation (one or more recementations), and mild complications such as minor veneer fracture and dentine hypersensitivity might not be regarded as failure. The main biological complication was secondary caries and dentine hypersensitivity; the main technical complications included debonding and fractures.

Quality assessment

The bias and quality of the cohort studies were evaluated by the Newcastle-Ottawa scale (NOS) , and the bias of RCT was assessed based on the Cochrane Handbook for Systematic Reviews of Interventions .

Statistical analysis

For each study, the failure and complication rates of IRFDPs were calculated by dividing the event number of failures or complications in the numerator by the total exposure time of IRFDPs in the denominator, which were pooled with a random effect model after Freeman-Tukey double arcsine transformation when encountering low event rates. Between studies the heterogeneity was estimated using the χ2-based Q statistic. Heterogeneity was considered statistically significant for p < 0.1. If heterogeneity existed, data were analyzed using a random effects model; in the absence of heterogeneity, a fixed effects model was used. A statistical test with a P value less than 0.05 was considered significant. Three- and five-year survival proportions were calculated via the relationship between the event rate and survival function S, S(T) = exp(-T × event rate), by assuming constant event rates according to the protocol described by Kirkwood et al. . Moreover, Poisson regression was used to further investigate the influence of framework materials on the failure and complication rates of IRFDPs . All analyses were conducted using STATA, version 13.0 (Stata Corp., College Station, TX, USA).

Results

Included studies

Initial searches using MeSH terms and text words resulted in 501 potential studies. 435 studies were excluded according to the titles and 66 abstracts were obtained. After scanning the included abstracts, 38 full-text articles were obtained. Hand searches were performed on bibliographies of the full-text articles and related narrative reviews, which identified 5 additionally articles. Finally, 32 articles were excluded, resulting in the inclusion of 11 studies. The reasons for exclusion and the process for selecting studies are presented in Fig. 1 . The patient and methodological characteristics of the included studies are shown in Tables 2 and 3 . These included studies reported on 11 different cohorts, including 341 patients with 394 IRFDPs. Among these studies, only one was an RCT, and ten were prospective cohort studies. The included IRFDPs were reported to replace premolars or first molars. Various designs of the inlay retainer were applied in the included studies, which ranged from conservative tub-shaped inlay retainers to relatively extensive preparation styles such as box-shaped inlay retainers and short retainer-wings at the buccal and lingual sides of abutment teeth. Additionally, various adhesive cements were applied in these included studies, and dentine adhesive combined with dual-cured resin cement was most frequently used.

Fig. 1
Flow chart of the selection of studies for the systematic review of survival and complication rates of IRFDPs.

Table 2
Study and patient characteristics of the included studies.
study Year Study design Mean follow-up time (year) No. of patients Age range Mean age Drop out
Chaar et al. 2015 Prospective 5.4 30 NR 41.9 1
İzgi et al. 2013 Prospective 6.3 35 18–52 29.3 0
İzgi et al. 2011 Prospective 2.6 10 NR NR 0
Harder et al. 2010 Prospective 5.8 42 20–67 39.0 1
Monaco et al. 2006 RCT 2.0 39 NR NR 0
Ayna et al. 2005 Prospective 2.0 19 NR 21.4 0
Göhring et al. 2005 Prospective 5.2 36 19–66 40.0 6
Behr et al. 2003 Prospective 2.5 19 15–67 49.0 0
Monaco et al. 2003 Prospective 2.3 30 NR NR 0
Serdar et al. 1997 Prospective 3.1 42 18–65 28.8 0
Stokholm et al. 1996 Prospective 5.0 39 NR 39 0
NR, not reported.

Table 3
Methodological characteristics of included studies.
Study Inlay Manufacturing and clinical procedure Location
Framework materials Surface treatment Adhesive/Cement
Chaar et al. Short wings a Zirconia ceramic Air-abrasion Panavia 21 TC Premolars and molars
İzgi et al. Slot retainer Ni-Cr alloy c Sandblast Concise Fisrt molars
İzgi et al. Tub-shaped; Box-shaped Glass-FRC;
Polyethylene-FRC
None Clearfil SE Bond Premolars and molars
Harder et al. Box-shaped;
Hybrid-retained b
IPS e.max Press Silane coating Variolink II Premolars and molars
Monaco et al. Slot-shaped;
Box-shaped;
Onlay; Overlay
Glass-FRC Sandblast;
Silanation
Variolink II Premolars and molars
Ayna et al. d Slot-shaped;
Box-shaped;
Polyethylene-FRC None Clearfil AP-X Premolars and molars
Göhring et al. Box-shaped Glass-FRC Silanation Tetric Premolars and molars
Behr et al. Not reported Glass-FRC Not reported Variolink II/Syntac classic Posterior teeth
Monaco et al. Box-shaped;
Short wings a
Glass-FRC Sandblast;
Silanation
Variolink II Posterior teeth
Serdar et al. Box-shaped;
Hybrid-retained b
Cast metal alloys Sandblast Panavia EX;
ABC cement
Posterior teeth
Stokholm
et al.
Box-shaped Noble alloy c Silicoating;
Lost sugar crystal;
Tin plating
MI, Kerr Premolars and molars
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Jun 19, 2018 | Posted by in General Dentistry | Comments Off on A systematic review of the survival and complication rates of inlay-retained fixed dental prostheses
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