Guido Sterzenbach

Is Adhesive Cementation of Endodontic Posts Necessary

Recently, the appropriate, durable bond of adhesive systems and composite resin cements to retain endodontic posts was challenged. The question arises whether it would be possible to place glass fiber posts in a less technique sensitive conventional nonadhesive approach. The influence of nonadhesive, self-adhesive, and etch-and-rinse systems on load capability of postendodontic restorations was studied. Human maxillary central incisors were divided into 4 groups (n = 10). Teeth were endodontically treated and restored by using glass fiber posts luted with different cements/composite resin combinations: (1) RelyX Unicem (3M ESPE, Seefeld, Germany)/Clearfil Core (Kuraray Europe, Duesseldorf, Germany), (2) RelyX Unicem/LuxaCore, (3) zinc phosphate cement/Clearfil, and (4) LuxaCore (DMG, Hamburg, Germany)/Clearfil. A 2 mm-ferrule preparation was performed. All specimens received adhesively luted all-ceramic crowns and were exposed to thermal cycling and mechanical loading before subsequent static loading. Significant differences between the experimental groups regarding load capability and fracture patterns were observed. The conventional non-adhesive post cementation is less reliable to withstand simulated functional forces compared to adhesive approaches.

Rigid versus Flexible Dentine-like Endodontic Posts—Clinical Testing of a Biomechanical Concept: Seven-year Results of a Randomized Controlled Clinical Pilot Trial on Endodontically Treated Abutment Teeth with Severe Hard Tissue Loss

INTRODUCTION This is the first clinical long-term pilot study that tested the biomimetic concept of using more flexible, dentine-like (low Young modulus) glass fiber-reinforced epoxy resin posts (GFREPs) compared with rather rigid, stiff (higher Young modulus) titanium posts (TPs) in order to improve the survival rate of severely damaged endodontically treated teeth. METHODS Ninety-one subjects in need of postendodontic restorations in teeth with 2 or less remaining cavity walls were randomly assigned to receive either a tapered TP (n = 46) or a tapered GFREP (n = 45). The posts were adhesively luted using self-adhesive resin cement. The composite core build-ups were prepared ensuring a circumferential 2-mm ferrule. The primary endpoint was a loss of restoration for any reason. To study group differences, the log-rank test was calculated (P < .05). Hazard plots were constructed. RESULTS After 84 months of observation (mean = 71.2 months), 7 restorations failed (ie, 4 GFREPs and 3 TPs). The failure modes were as follows: GFREP:root fracture (n = 3), core fracture (n = 1) and TP:endodontic failure (n = 3). No statistical difference was found between the survival rates (GFREPs = 90.2%, TPs = 93.5%, P = .642). The probability of no failure was comparable for both post materials (risk ratio; 95% confidence interval, 0.965-0.851/1.095). CONCLUSIONS When using self-adhesive luted prefabricated posts in severely destroyed abutment teeth with 2 or less cavity walls and a 2-mm ferrule, postendodontic restorations achieved high long-term survival rates irrespective of the post material used (ie, glass fiber vs titanium).

Various irrigation protocols for final rinse to improve bond strengths of fiber posts inside the root canal

Irrigation after post space preparation and its effects on the bond strength of different adhesive strategies are still an issue of interest. The aim of the present study was to investigate the effects of various irrigation protocols (IPs) on the push-out bond strengths of fiber posts. One-hundred and fifty extracted human anterior teeth were divided into three groups (n = 50 each) and endodontically treated. The post space was irrigated before post placement using the following five IPs in each group: IP1 (control): 5 ml of distilled water; IP2: 5.25% sodium hypochlorite (NaOCl) applied with passive ultrasonic irrigation (PUI); IP3: 1% NaOCl applied with PUI; IP4: 18% ethylenediaminetetracetic acid (EDTA) followed by 5.25% NaOCl; and IP5: 2% chlorhexidine (CHX). Fiber posts placement in each group was performed using three different adhesive strategies. A self-etch adhesive system revealed higher bond strength (16.2 ± 6.9 MPa) compared with an etch-and-rinse adhesive (8.5 ± 4.2 MPa) and a self-adhesive resin cement (9.2 ± 4.7 MPa). The use of 18% EDTA/5.25% NaOCl increased the bond strength of the self-adhesive resin cement. Conversely, this IP decreased the bond strength for the etch-and-rinse adhesive system, whilst 1% NaOCl enhanced the bond strength for the same system. Consequently, each adhesive strategy may need to be adapted to a specific IP.

Fiber post placement with core build-up materials or resin cements—An evaluation of different adhesive approaches

Abstract Objective. To compare push-out bond strength of fiber-posts luted with different adhesive approaches to root canal dentin. Materials and methods. Forty maxillary first incisors were decoronated and endodontically treated. Specimens were randomly distributed into five groups (n = 8) and fiber-posts (DentinPost coated, Komet) were inserted using five different luting materials: etch-and-rinse adhesive systems and corresponding core-and-post material in groups 1 (DentinBond/DentinBuild, Komet) and 2 (XP Bond + SCA/Core-X flow, Densply), self-adhesive resin cements in groups 3 (RelyX Unicem, 3M Espe) and 4 (SmartCem 2, Dentsply) and a self-etch adhesive/resin cement in group 5 (ED-Primer II/Panavia F 2.0, Kuraray). The roots were sectioned into eight 1 mm thick serial slices and within 48 h push-out bond strength was investigated. Statistical analyses were performed using non-parametrical Kruskal-Wallis H-test and Mann-Whitney U-test for differences between experimental groups at p < 0.05. The failure modes were analyzed using Chi square test. Results. The bond strength [MPa] (mean/min–max) for groups 3 (12.35/3.60–32.44), 4 (13.52/4.48–30.69) and 2 (11.15/5.23–35.58) were significantly higher (p < 0.001) compared to groups 1 (6.66/2.34–24.89) and 5 (7.41/0.28–34.18). Adhesive failure between dentin and luting agent was the most frequent failure mode. Conclusions. Bond strength of fiber-posts adhesively luted to root canal dentin was significantly higher when self-adhesive resin cements were used. One (group 2) of the tested core-and-post materials/etch-and-rinse adhesive achieved comparable bond strength values.

Self-adhesive cements as core build-ups for one-stage post-endodontic restorations?

AIM To investigate the load capability of root filled teeth restored with glass fibre posts when the same self-adhesive composite resin cement was used as post cement and core build-up material. METHODOLOGY Human maxillary central incisors were divided into four groups (n=10). Teeth were root filled, decoronated and restored using glass fibre posts luted with different cements and composite resins for core build-up (i) RelyX Unicem/Clearfil Core (RXU/CC), (ii) RelyX Unicem/ RelyX Unicem (RXU/RXU), (iii) RelyX Unicem/LuxaCore-Dual (RXU/LCD) and (iv) LuxaCore-Dual/Clearfil (LCD/CC). A 2-mm ferrule crown preparation was always performed. All specimens were restored with adhesively luted all-ceramic crowns and were exposed to thermal cycling and mechanical loading (TCML) and subsequently statically loaded. For analysis of cycles-to-failure during TCML, log-rank statistics were calculated. The nonparametric Kruskal-Wallis test was applied to study group mean differences. Differences in the frequency of the failure modes between the groups were evaluated by Fishers exact test. All tests were two-sided (α=0.05). RESULTS Three specimens of RXU/LCD and two of RXU/RXU and LCD/CC, respectively, failed during TCML (P=0.379). For these specimens, the load capability value was set at 0 N. The median fracture load values (min/max) in (N) were RXU/CC=294 (209/445), RXU/RXU = 166 (0/726), RXU/LCD=241 (0/289) and LCD/CC=200 (0/371) (P=0.091). The RXU/CC had the highest (80%) and RXU/LCD the lowest (20%) percentage of restorable failures (P=0.028). CONCLUSIONS These results imply that self-adhesive composite achieved similar load capabilities when used as core build-up materials in root filled teeth restored with glass fibre posts and all-ceramic crowns.

In-vitro simulation of tooth mobility for static and dynamic load tests: A pilot study

Abstract Objective. Simulation of tooth mobility in vitro with or without reduced bone support is an aspect of particular interest from the clinical perspective. To elucidate adequate simulation of the periodontal ligament in terms of tooth mobility, three materials were investigated. Methods. Human lower sound premolars were selected and randomly assigned to six groups (n = 5) and stored at 37°C in a 0.5%-chloramine solution. For tooth mobility simulation, roots were covered with a thin layer of three types of material: (i) polyurethane elastomeric material, (ii) polyether impression material and (iii) A-polysiloxane soft cushion material. Teeth were embedded in an acrylic resin block simulating no and 50% bone loss, respectively. Specimens were statically subjected up to a maximum load of 30 N perpendicular to tooth axis (crosshead speed = 1 mm/min) in a universal material testing machine. Load-deflexion curves and periotest values were recorded. Statistical analysis was performed using 2-way Anova and post-hoc Bonferroni Test (p = 0.05). The Pearsons correlation coefficient between deflexion and periotest values was calculated. Results. Median horizontal deflexion values (μm) of specimen crowns with no bone loss were significant higher for polysiloxane (210) compared to polyurethan (24) (p < 0.001). The tooth deflexion, e.g. tooth mobility, increased significantly as the bone level decreased only when specimens were embedded in polysiloxane (iii) (1150) (p = 0.045). All specimens with reduced bone support layered with polyether were dislocated. Deflexion was significantly positive correlated with periotest values (p = 0.01). Conclusion. Using A-polysiloxane soft cushion material combined with autopolymerizing acrylic resin may be suitable to simulate increased tooth mobility in vitro.

A flood tide of systematic reviews on endodontic posts: methodological assessment using of R-AMSTAR

ObjectivesTo help the dental practitioner solve a specific clinical problem, systematic reviews (SRs) are seen as the best guide. In addition to the unmanageable quantity of SRs, however, one should be aware of their variable quality. The present review describes the methodological quality of SRs on postendodontic restorations to work out the value of these reviews for the dental practitioner.MethodologySRs were searched in April 2012, independently and in triplicate. Post survival was used as measure of outcome. The methodological quality of included SRs was assessed with the Revised Assessment of Multiple Systematic Reviews (R-AMSTAR) checklist. Kappa statistics were used to assess reviewer agreement.ResultsThree hundred sixty-three papers were retrieved from the initial search. Ten SRs were included. One SR achieved a high R-AMSTAR score, whereas the other nine SRs achieved scores that indicate a substantial lack of methodological quality. Especially the items “grey literature,” “combination of findings,” “likelihood of publication bias,” and conflict of interest” showed low R-AMSTAR scores. The three reviews with the highest R-AMSTAR scores tended to conclude that fewer failures occurred when using nonmetal posts. The reviewer agreement was excellent (kappa ranged from 0.79 to 0.85) in the R-AMSTAR classification.ConclusionThe approach presented revealed a lack of SRs with high methodological quality. Thus, no decisive conclusion can be drawn with respect to this topic. It appears that there is a trend for the superiority of fiber-reinforced posts.Clinical relevanceSRs must be of high methodological quality. This can be achieved by taking into consideration the results of this review. Improved methodological quality would make SRs more supportive for the general practitioner.

In vitro performance of self-adhesive resin cements for post-and-core build-ups: Influence of chewing simulation or 1-year storage in 0.5% chloramine solution

The aim of this investigation was to test the in vitro performance of a self-adhesive resin composite core build-up in comparison with two typical conventional etch-and-rinse composite core build-up materials, before and after 1year of storage in 0.5% chloramine solution (LTS). Sixty human maxillary central incisors were divided into three groups. Teeth were root filled and decoronated. Specimens were restored using glass fiber posts cemented with a self-adhesive resin cement. Core build-ups were made with a self-adhesive (U) and two core build-up materials (C and L) applied with their corresponding bonding systems. All specimens received adhesively luted lithium disilicate crowns. Ten specimens of each group were exposed to LTS and examined monthly for cracks or other alterations. All specimens were thermocycled, mechanically loaded (TCML) and finally loaded until failure occurred. There was no statistical significant difference in regard to the number of failures during TCML without and with LTS (log rank: p = 0.225 and 0.609, respectively). The median fracture load values after static loading without LTS and with LTS did not differ significantly (Kruskal-Wallis test: p = 0.057 and 0.106, respectively), though the fracture patterns between the groups without (p = 0.024) and with LTS (p = 0.027) did. Self-adhesive cements used for core build-up have no significantly higher risk of failure compared to conventional core build-up materials in both LTS and TCML test scenarios.

Are endodontically treated incisors reliable abutments for zirconia-based fixed partial dentures in the esthetic zone?

INTRODUCTION This ex vivo pilot study tested the influence of defect extension and quartz-fiber post placement (QFP) on the ex vivo survival rate and fracture resistance of root-treated upper central incisors served as abutments for zirconia 2-unit cantilever fixed partial dentures (2U-FPDs) exposed to 10 years of simulated clinical function. METHODS Human maxillary central incisors were endodontically treated and divided into the following 5 groups (n = 8): (1) access cavity filled with core build-up composite, (2) biproximal class III cavities filled as in group 1, (3) specimens restored as in group 2 with QFP placed, (4) specimens decoronated and core buildup as in group 1, and (5) specimens restored as in group 4 but with QFP as in group 3. On all specimens, 2U-FPDs were placed with dual-curing resin cement. In order to simulate 10 years of clinical function, specimens were exposed to thermal cycling and mechanical loading with subsequent loading to failure. Kaplan-Meier curves were constructed, and log-rank tests were performed. Fracture force and patterns were compared by means of Kruskal-Wallis, Mann-Whitney U (post hoc), and Fisher exact tests, respectively (P = .05). RESULTS For specimens only with an access cavity, it was observed that 25% had catastrophic tooth fractures and the lowest load-to-fracture values. In all other groups, chipping combined with or without debonding occurred. Groups did not differ significantly regarding the survival rate (P = .603) and fracture patterns (P = .633), but they did for fracture load including technical failures (P = .017). CONCLUSIONS After 10 years of simulated clinical function, both defect extension and placement of QFP had no significant influence on survival of root-treated upper central incisors as abutments restored with zirconia-based 2U-FPDs.

Are self-adhesive resin cements suitable as core build-up materials? Analyses of maximum load capability, margin integrity, and physical properties

ObjectivesThe aim of the present study was to test a self-adhesive resin cement used as core build-up material in comparison to two commercially available core build-up materials.Materials and methodsForty human anterior teeth were endodontically treated and fiber post insertion (RelyX Fiber posts) and core build-ups were performed using two core build-up materials applied with an etch-and-rinse adhesive approach (Luxacore Dual-LC and Clearfil Core-CC) and an experimental self-adhesive resin cement (SAR) in two application modes (SAR Handmix and SAR Automix). Samples were subjected to thermo-mechanical loading. Margin integrity was determined using scanning electron microscopy (SEM), and maximum load capability (Fmax) was evaluated. Physical properties of the tested materials were also examined.ResultsFmax was significantly affected by the core build-up material (p < 0.0005; one-way ANOVA). CC [481 (158) N] revealed significantly higher Fmax compared to LC [226 (80) N], SAR Hand [205 (115), and SAR Automix [197 (134) N] (p < 0.05; Tukey-B). The percentage of margin quality “continuous margin” in enamel after thermo-mechanical loading (TML) differed significantly among groups (p < 0.0005; Kruskal-Wallis); CC demonstrated a significantly higher percentage of margin quality “continuous margin” compared to the other groups. Physical properties were significantly affected by the different core materials (p < 0.0005; ANOVA); CC and LC demonstrated significantly higher flexural strength compared to both SAR groups as well as significantly higher water sorption of both SAR groups compared to CC and LC.ConclusionWithin the limitations of the present in vitro study, we conclude that the investigated experimental self-adhesive resin cement is not suitable as a core build-up material due to the lower maximum load capability, low margin quality, and the data of the mechanical properties.Clinical relevanceThe investigated experimental self-adhesive resin cement cannot be recommended as a core build-up material.