Factors determining the retentiveness of luting agents used with metal- and ceramic-based implant components

A Systematic Review of Cementation Techniques to Minimize Cement Excess in Cement-Retained Implant Restorations

Background: The most used types of retention of implant-supported prostheses are screw-retained or cement-retained restorations. The advantages and disadvantages of both have been identified by various authors over the years. However, cement-retained implant crowns and fixed partial dentures are among the most used types of restorations in implant prostheses, due to their aesthetic and clinical advantages. When cemented prostheses are made on implants, the problem of cement residues is important and often associated with biological implant pathologies. The objective of this research was to establish to what extent the techniques to reduce excess cement really affect the volume of cement residues. Materials and Methods: This review was written following the PRISMA statement; a detailed search was carried out in three different electronic databases—PubMed, Scopus, and Cochrane Library. The inclusion criteria were prospective clinical studies, with at least 10 participants per group, and with at least 6 months of the follow-up period. Results: There have been many proposals for techniques supposed to reduce the amount of excess cement in the peri-implant sulcus and on the prosthetic components, but of these, which are exceptional in their in vitro capabilities, very few have been clinically validated, and this represents the real limitation and a great lack of knowledge regarding this topic. Three articles met the inclusion criteria, which were analyzed and compared, to obtain the information necessary for the purposes of the systematic review. Discussion: Extraoral cementation can reduce the excess cement, which, after a normal excess removal procedure, is, nevertheless, of such size that it does not affect the possibility of peri-implant pathologies developing. All these studies concluded that a small amount of cement residue is found in the gingival sulcus, and using eugenol-free oxide cements, the residues were only deposited on the metal surfaces, with a better peri-implant tissues health. Conclusion: Despite the limitations of this study, it was possible to carefully analyze these characteristics and obtain valuable suggestions for daily clinical practice. Resinous cements are considered, due to the free monomers present in them, toxic for the soft tissues. The provisional zinc-oxide cements, also eugenol-free, represent the ideal choice. The different grades of retentive forces provided by these cements do not seem to have clinical effects on the decementation of restorations.

Retention of different temporary cements tested on zirconia crowns and titanium abutments in vitro

Purpose

The aim of the present study was to examine the retention force of monolithic zirconia copings cemented with various temporary cements on implant abutments in vitro.

Methods

Sixty exercise implants with pre-screwed implant abutments were embedded in resin. Subsequently, 60 CAD/CAM manufactured zirconia copings were divided into three main groups [Harvard Implant Semi-permanent (HAV), implantlink semi Forte (IMP), Temp Bond NE (TBNE)]. The zirconia copings were cemented on the implant abutments and loaded with 35 N. Specimens were stored in distilled water (37 °C) for 24 h. Half of the test specimens of each group were subjected to a thermocycling (TC) process. Retention force was measured in a universal testing machine. Using magnifying glasses, the fracture mode was determined. Statistical analysis was performed applying the Kruskal-Wallis test, the post hoc test according to Dunn-Bonferroni and a chi-square test of independence.

Results

Without TC, IMP showed the highest retention of the three temporary luting agents (100.5 ± 39.14 N). The measured retention forces of IMP were higher than those of HAV (45.78 ± 15.66 N) and TBNE (61.16 ± 20.19 N). After TC, retention was reduced. IMP showed the greatest retentive strength (21.69 ± 13.61 N, three fail outs). HAV and TBNE showed pull-off forces of similar magnitude (17.38 ± 12.77 N and 16.97 ± 12.36 N, two fail outs). The fracture mode analysis showed different results regarding the tested cements before and after TC (facture type before/after TC): IMP (III+II/III), HAV (I/II) and TBNE (III/III). There were clear differences of the fracture modes regarding the examination before and after TC.

Conclusions

Within the limits of this study, IMP showed the highest pull-off forces under the chosen test conditions. All three temporary luting agents showed lower retention forces after TC. Retention values in the individual cement classes were very heterogeneous. Easy cement removal in the crown lumen favours the dominance of adhesive cement fractures on the abutment and adhesive/cohesive cement fractures on the abutment with HAV appears advantageous in case of recementation of the superstructure.

Bond Integrity of Titanium Surface to Resin Cement After Conditioning with Different Photobiomodulataion Therapy (PBT)

The aim of the present study was to evaluate the efficacy of interfacial bonding between resin cement and titanium alloy conditioned with different Photobiomodulataion Therapy (PBT) in comparison with conventional regimes. Seventy-five samples of titanium bar were segmented polished; and based on conditioning regime divided into five groups (15 each specimens). Group 1: No treatment (control), Group 2: Sand blasting with 120 µm Al2O3, Group 3: Er,Cr:YSGG (ECL), Group 4: Er:YAG laser (EYL), Group 5: Nd:YAG laser (NYL). After different conditioning regimes, resin cement was mixed and applied. All specimens were thermocycled for 500 cycles and positioned on universal testing machine for shear bond strength testing. Modes of failure was assessed by a single examiner using stereomicroscope at 40× magnification. Three pairs of specimens in each group were sputter coated and scanning electron microscope (SEM) images were taken at 1000× magnification using 20 Kv. The highest SBS values were observed in group 2 (14.25±2.29 MPa) and the lowest bond values were displayed in group 1 (6.98 ±0.59 MPa). Titanium alloy abutments conditioned with different laser prototypes ECL (11.22±1.40 MPa), EYL (9.29±1.22 MPa) and NYL (9.12 ±1.84 MPa) exhibited comparable SBS (p > 0.05). Adhesive failures were primarily dominant among all experimental groups. Photo-biomodulation in the form of ECL lasers has the potential to be used as a supplement to sandblasting procedure in conditioning of cement retained titanium alloy implant abutments.

A new design of a multifunctional abutment to morse taper implant connection: Experimental mechanical analysis

The objective of this study was to evaluate a new design of multifunctional abutment for Morse taper implant connections, relative to the retentive stability after the application of cyclic loads in cemented and screwed crowns. Multifunctional abutments with two different angulations in the seating portion of the crown were tested, forming 2 groups (n = 30 samples per group): Group Abut11, where Smart abutments with an angle of 11.42° were used; Group Abut5, where Ideale abutments with an angle of 5° were used. Fifteen samples from each group received cemented crowns (CC) and another fifteen screwed crowns (SC). All crown samples were subjected to the mechanical cycling test at 360,000 cycles at a frequency of 4 Hz and 150 N of the load. The samples with CC were subjected to the tensile test to remove the crowns, while in the samples with SC, the detorque value of the fastening crown screws was measured. The mean tensile strength value of CC in the Abut11 group was 131.9 ± 13.5 N and, in the Abut5 group was 230.9 ± 11.3 N; while the detorque mean value in samples with SC 5.8 ± 1.8 N for the Abut11 group and, 7.6 ± 1.1 N for Abut5 group. Significant statistical differences were found between the two groups in both situations tested (p < 0.05). The multifunctional abutments, presenting a lesser angulation of the crown-seating portion, showed higher values of retention of the CC and a lesser screw loosening of torque of the fixing screws in the SC after the application of cyclic loads when compared to the abutments with more angulation in the crown-seating portion.

Retention of zirconia crowns to Ti-base abutments: effect of luting protocol, abutment treatment and autoclave sterilization

PURPOSE

To evaluate the influence of resin cement type, surface pretreatment and autoclave sterilization on the retention of Y-TZP crowns to Ti-base abutments.

METHODS

Y-TZP crowns were designed and milled to fit Ti-base abutments. Crowns were cemented using either a conventional resin cement (conventional) with a universal adhesive or a self-adhesive resin cement (self-adhesive), both following no surface pretreatment (No) or Ti-base abutment sandblasting (SB) (n=20/group). Half of the cemented samples were subjected to in-office autoclave sterilization. Pullout testing was performed in a universal testing machine at a speed of 1 mm/min until crown displacement. Data were statistically evaluated through a linear mixed model following post hoc comparisons by LSD test.

RESULTS

Pullout data as a function of cement type demonstrated higher retention for conventional relative to self-adhesive cement (p < 0.001). Ti-base sandblasting (SB) favored crown retentiveness over No pretreatment (p < 0.001). Sterilized crowns exhibited higher pullout values than non-sterile (p=0.036). All the two- and three-factor interaction analyses corroborated with the superior adhesive strength of conventional compared to self-adhesive cement (all, p < 0.011), as well as, SB relative to No pretreatment (all, p < 0.024). While autoclave sterilization maximized bond strength when self-adhesive cement (data collapsed over surface pretreatment, p < 0.050) and No pretreatment were evaluated (data collapsed over surface pretreatment, p < 0.013), no significant difference was observed for conventional resin cement (p=0.280) and SB (p=0.878) groups.

CONCLUSIONS

Conventional resin cement and/or Ti-base sandblasting increased Y-TZP crown retentiveness, with no significant influence of autoclave sterilization. Autoclaving increased retentiveness when self-adhesive cement and/or no Ti-base pretreatment were used.

In Vitro Simulation of Dental Implant Bridges Removal: Influence of Luting Agent and Abutments Geometry on Retrievability

Implant fixed dental prostheses are widely used for the treatment of edentulism, often preferred over the screw-retained ones. However, one of the main features of an implant-supported prosthesis is retrievability, which could be necessary in the case of implant complications. In this study, the retrievability of implant-fixed dental prostheses was investigated considering two of the main factors dental practitioners have to deal with: the abutments geometry and the luting agent. Impulsive forces were applied to dental bridge models to simulate crowns’ retrievability in clinical conditions. The number of impulses and the impulsive force delivered during each test were recorded and used as retrievability indexes. One-hundred-and-five tests were conducted on 21 combinations of bridges and luting agents, and a Kruskal-Wallis test was performed on the results. The abutment geometry significantly influenced the number of impulses needed for retrieval (p < 0.05), and a cement-dependent trend was observed as well. On the other hand, the forces measured during tests showed no clear correlation with bridge retrievability. The best retrievability was obtained with long, slightly tapered abutments and a temporary luting agent.

In Vitro Impact Testing to Simulate Implant-Supported Prosthesis Retrievability in Clinical Practice: Influence of Cement and Abutment Geometry

Cement-retained implant-supported prosthetics are gaining popularity compared to the alternative screw-retained type, a rise that serves to highlight the importance of retrievability. The aim of the present investigation is to determine the influence of luting agent, abutment height and taper angle on the retrievability of abutment–coping cementations. Abutments with different heights and tapers were screwed onto an implant and their cobalt-chrome copings were cemented on the abutments using three different luting agents. The removals were performed by means of Coronaflex^®. The number of impulses and the forces were recorded and analyzed with a Kruskal–Wallis test. Harvard cement needed the highest number of impulses for retrieval, followed by Telio CS and Temp Bond. However, abutment height and taper showed a greater influence on the cap’s retrievability (p < 0.05). Long and tapered abutments provided the highest percentage of good retrievability. The influence of the luting agent and the abutment geometry on the cap’s retrieval performed by Coronaflex^® reflects data from literature about the influence of the same factor on the maximum force reached during uniaxial tensile tests. The impulse force was slightly affected by the same factors.

Implant-abutment fit influences the mechanical performance of single-crown prostheses

OBJECTIVES

To evaluate the three-dimensional fit of abutments fabricated by the industry to those either milled or cast by a commercial laboratory and to correlate the implant-abutment connection fit with stress at fatigue failure of prostheses. Probability of survival (reliability) and fractography to characterize failure modes were also performed for cemented and screw-retained prostheses.

METHODS

One-hundred and twenty-six maxillary central incisor crowns were milled to restore implants and divided in 3 cemented and 3 screwed-retained groups (n = 21/each), as follows: [Digital-Sc]: milled one-piece monolithic abutment/crown; [TiB-Sc]: milled crowns cemented onto Ti-base abutments; [UCLA]: screw-retained crown using UCLA abutments; [Digital-Ce]: milled two-piece assembly comprised by screwed monolithic abutment and a cemented crown; [TiB-Ce]: milled coping cemented onto Ti-base abutments to receive a cemented crown; [UCLA-Ce]: UCLA abutments that received an overcast coping and a cemented crown. Implant-abutment volume misfit was assessed by micro-computed tomography using the silicone replica technique. Implant/crown systems were subjected to step-stress accelerated life testing (SSALT) in water. The use-level probability Weibull curves and reliability for a mission of 50,000 cycles at calculated stress at failure of 2,300, 3300 and 4300 MPa were plotted. Fractographic analysis was performed with scanning electron microscopy. Internal misfit was analyzed through one-way ANOVA following post-hoc comparisons by Tukey test (p < 0.05). Correlation between misfit volume and the stress at fatigue failure was assessed by Pearson test.

RESULTS

Similar misfit volumes were observed for TiB-Sc (0.458 mm³), TiB-Ce (0.461 mm³), UCLA (0.471 mm³) and UCLA-Ce (0.480 mm³), which were significantly lower than Digital-Sc (0.676 mm³) and Digital-Ce (0.633 mm³). The mean β values were: 1.68, 1.39, 1.48, 2.41, 2.27 and 0.71 for Digital-Sc, TiB-Sc, UCLA, Digital-Ce, TiB-Ce and UCLA-Ce, respectively, indicating that fatigue was an accelerating factor for failure of all groups. Higher stress at failure decreased the reliability of all groups, more significantly for screw compared to cement-retained groups, especially for Digital-Sc that demonstrated the lowest reliability. The failure mode was restricted to abutment screw fracture. A negative correlation was observed between misfit values and stress at failure (r = -0.302, p = 0.01).

CONCLUSIONS

Abutments milled by a commercial lab presented higher misfit compared to those provided by the industry and a moderate correlation was observed between higher misfit and lower stress at failure during fatigue. Probability of survival decreased at higher stress, especially for screw compared to cement-retained groups, and failures were confined to abutment screws.

Digital versus conventional techniques for pattern fabrication of implant-supported frameworks

Objective

The aim of this experimental study was to compare retention of frameworks cast from wax patterns fabricated by three different methods.

Materials and Methods

Thirty-six implant analogs connected to one-piece abutments were divided randomly into three groups according to the wax pattern fabrication method (n = 12). Computer-aided design/computer-aided manufacturing (CAD/CAM) milling machine, three-dimensional printer, and conventional technique were used for fabrication of waxing patterns. All laboratory procedures were performed by an expert-reliable technician to eliminate intra-operator bias. The wax patterns were cast, finished, and seated on related abutment analogs. The number of adjustment times was recorded and analyzed by Kruskal-Wallis test. Frameworks were cemented on the corresponding analogs with zinc phosphate cement and tensile resistance test was used to measure retention value.

Statistical Analysis Used

One-way analysis of variance (ANOVA) and post hoc Tukey tests were used for statistical analysis. Level of significance was set at P < 0.05.

Results

The mean retentive values of 680.36 ± 21.93 N, 440.48 ± 85.98 N, and 407.23 ± 67.48 N were recorded for CAD/CAM, rapid prototyping, and conventional group, respectively. One-way ANOVA test revealed significant differences among the three groups (P < 0.001). The post hoc Tukey test showed significantly higher retention for CAD/CAM group (P < 0.001), while there was no significant difference between the two other groups (P = 0.54). CAD/CAM group required significantly more adjustments (P < 0.001).

Conclusions

CAD/CAM-fabricated wax patterns showed significantly higher retention for implant-supported cement-retained frameworks; this could be a valuable help when there are limitations in the retention of single-unit implant restorations.

What is the Best Available Luting Agent for Implant Prosthesis?

Cement-retention is a viable option in restoring dental implants. A wide range of dental cements with different properties are commercially available for use in the cementation of implant prostheses. The selection of a dental cement for proper clinical application can be challenging. This article overviews the commercially available dental cements used in cement-retained implant-supported prostheses. Guidelines for cement selection are presented according to abutment and prosthetic material. Cementation techniques to reduce excess cement in peri-implant tissues are also mentioned.

Effect of CAD/CAM Abutment Height and Cement Type on the Retention of Zirconia Crowns

PURPOSE

To evaluate Ti-Base abutment height and cement type on the retentiveness of zirconia-based restorations.

MATERIAL AND METHODS

Four millimeter (tall) and 2.5-mm-height (short) abutments along with temporary (provisional), glass ionomer (Meron), self-adhesive (U200), and conventional resin cement (Ultimate) were evaluated using pull-out testing (n = 10 crowns/group).

RESULTS

Tall and short abutments demonstrated similar retention for all within cement comparisons, except U200 (P = 0.032). Resin cements exhibited superior retentiveness than others (P < 0.01). Although no significant difference was evidenced between resin cements for short abutments, Ultimate evidenced higher retention than U200 for tall abutments (P = 0.043).

CONCLUSIONS

Although Ti-Base abutment height has not influenced zirconia superstructures' retentiveness, resin-based cements significantly evidenced higher retention than glass ionomer and temporary cements.

The Effect of CAD/CAM Crown Material and Cement Type on Retention to Implant Abutments

PURPOSE

To evaluate the pullout resistance of CAD/CAM implant-supported crowns cemented with provisional and definitive cements on Ti-base implant abutments.

MATERIALS AND METHODS

Sixty crowns were milled for use in Ti-base implant abutments and divided (n = 15/group) according to material, as follows: (a) [Pr] Temporary acrylic resin; (b) [Co-Cr] Cobalt-Chromium alloy; (c) [Zr] polycrystalline zirconia; and (d) [Ti] titanium. The cementation was performed with RelyX Temp NE (RxT) cement or RelyX U200 self-etching resin cement, under a 50 N (5 kg) load for 10 minutes. Twenty-four hours after cementation, the crowns were subjected to the pullout test in a universal test machine, at a 1.0 mm/min crosshead speed. The tests were performed first without cement to evaluate frictional resistance (Baseline), then with provisional cement (RelyX Temp NE without cement again (Baseline After RxT), and finally with resin cement (U200). The results were analyzed by ANOVA and Tukey test (p < 0.05).

RESULTS

Data evaluation as a function of cement type demonstrated the superiority of resin-based cements relative to provisional and baseline groups (p < 0.01). While Co-Cr crowns presented the highest pullout strength values, Pr showed the lowest values (data collapsed over cement) (p < 0.001). Retentiveness data as a function of both factors demonstrated similar pullout resistance between groups without cement (p < 0.001), except Zr baseline. Also, Co-Cr presented higher pullout strength compared to other materials.

CONCLUSIONS

Self-adhesive resin cement exhibited superior retention compared to temporary cement, regardless of crown material. Co-Cr and titanium presented higher levels of retention to Ti-base abutment after being cemented.

Dislodgement Resistance of Zirconia Copings Cemented onto Zirconia and Titanium Abutments

PURPOSE

To determine the effect of the cement type and abutment material on the tensile strength required to dislodge zirconia copings.

MATERIALS AND METHODS

Two experimental groups of abutments were prepared: (1) titanium abutments (n = 30) and (2) zirconia abutments (n = 30). Sixty zirconia copings (custom designed) were fabricated using 3-dimensional computer-assisted design to have a 6-mm projection above the abutment to accommodate a hole, through which a wire was inserted to attach the zirconia coping to a universal testing machine. Each abutment was placed onto an implant analog embedded in acrylic resin blocks to fit onto the universal testing machine. The zirconia copings were cemented onto the abutments with a provisional luting agent, zinc phosphate (ZP) cement, and adhesive resin cement, and after 5500 thermocycles, a tensile force was applied at a crosshead speed of 0.5 mm/min. The removal force was recorded for each specimen. Two-way analysis of variance (ANOVA) and 1-way ANOVA were used for the statistical analysis (P < 0.05).

RESULTS

The mean forces necessary to remove the zirconia copings from titanium abutments were 6.52, 83.09, and 251.18 N for temporary cement, ZP cement, and resin cement, respectively. For zirconia abutments, the required forces were 17.82, 116.41, and 248.72 N.

CONCLUSIONS

The abutment material had no effect on retention, but the cement type affected the retention of the zirconia copings.

Comparative evaluation of bonding strength of computer aided machined ceramic, pressable ceramic, and milled metal implant abutment copings and effect of surface conditioning on bonding strength: An in vitro study

Background/Purpose:

The aim of this study was to compare the shear bond strength of computer aided design/computer aided machined ceramic (CAD/CAM), pressable ceramic, and milled metal implant copings on abutment and the effect of surface conditioning on bonding strength.

Materials and Methods:

A total of 90 test samples were fabricated on three titanium abutments. Among 90 test samples, 30 copings were fabricated by CAD/CAM, 30 by pressable, and 30 by milling of titanium metal. These 30 test samples in each group were further subdivided equally for surface treatment. Fifteen out of 30 test samples in each group were surface conditioned with airborne particle abrasion. All the 90 test samples were luted on abutment with glass ionomer cement. Bonding strength was evaluated for all the samples using universal testing machine at a crosshead speed of 5 mm/min. The results obtained were compared and evaluated using one-way ANOVA with post-hoc and unpaired t-test at a significance level of 0.05.

Results:

The mean difference for CAD/CAM surface conditioned subgroup was 1.28 ± 0.12, for nonconditioned subgroup was 1.20 ± 0.11. The mean difference for pressable surface conditioned subgroup was 1.18 ± 0.04, and for nonconditioned subgroup was 0.75 ± 0.28. The mean difference for milled metal surface conditioned subgroup was 2.57 ± 0.58, and for nonconditioned subgroup was 1.49 ± 0.15.

Conclusions:

On comparison of bonding strength, milled metal copings had an edge over the other two materials, and surface conditioning increased the bond strength.

Influence of abutment design on retention of metal copings cemented to implants

Objective The study evaluated the influence of abutment design on the retention of implant-cemented metal copings.

Material and methods Two abutments of the same system with the same indications, height and the total occlusal convergence, but of different designs were evaluated. Ten RN synOcta abutments (Straumann, Waltham, MA) and ten RN titanium solid abutments (Straumann, Waltham, MA) were tightened to 35 Ncm on 20 implant analogs previously placed in resin blocks. Twenty plastic burnout copings were waxed, included, cast and machined by a single operator. Coping was inspected for surface irregularities using a stereomicroscope at 10x magnification, and then, they were cemented (Temp Bond NE, Kerr, Romulus, MI) with 5 kg load for 10 min. The samples were stored for 24 h in room temperature and 100% humidity and then subjected to pull-out test at a crosshead speed of 0.5 mm/min. The load required to dislodge each coping was recorded (kgf) and and mean values for each group statistically calculated. Means and standard deviations of loads at failure were analyzed using Student’s t-test.

Results The mean load required to dislodge the copings showed by synOcta abutments (11.19 kgf) was statiscally higher than s solid abutments (10.18 kgf).

Conclusions: It was concluded that the abutment design influenced significantly the retention of metal copings.

In Vitro Fit and Cementation Resistance of Provisional Crowns for Single Implant-Supported Restorations

Abstract: This study aimed to verify marginal fit and the effect of cement film thickness standardization on retention of provisional crowns made with prefabricated acrylic cylinders on abutments, using two temporary luting agents subjected or not to mechanical cycling. Provisional crowns were made from bis-acryl (Luxatemp Fluorescence) or methyl methacrylate (Duralay) resins on acrylic cylinders and marginal fit and cement film thickness were evaluated. For retention evaluation, crowns were cemented with two temporary luting agents: non-eugenol zinc oxide (Tempbond NE) or calcium hydroxide-based (Hydcal) cements and subjected to tensile strength in a universal testing machine. After cleaning, debonded crowns were cemented again, subjected to mechanical cycling and retention was reassessed. The results of marginal fit and cement film thickness were analyzed by Student's t-test while retention of cements before and after mechanical cycling was analyzed using a mixed linear model. Methyl methacrylate crowns presented greater marginal misfit (p=0.001) and occlusal cement film thickness (p=0.003) than the bis-acryl ones. No difference was observed at axial cement film thickness (p=0.606). Resins (p=0.281) did not affect crown retention, but luting agents (p=0.029) and mechanical cycling (p=0.027) showed significant effects. The only significant interaction was mechanical cycling*luting agents, which means that luting agents were differently affected by mechanical cycling (p=0.002). In conclusion, the results showed that bis-acryl resin associated to calcium-hydroxide luting agent provided the best retention and lower cement thickness.

Clinical evaluation of an improved cementation technique for implant-supported restorations: a randomized controlled trial

BACKGROUND

Cement remnants were frequently associated with peri-implantitis. Recently, a shoulderless abutment was proposed, raising some concern about cement excess removal.

AIM

To compare different cementation techniques for implant-supported restorations assessing the amount of cement remnants in the peri-implant sulcus. Additional aim was to compare the effect of these cementation techniques using two different abutment designs.

MATERIAL & METHODS

Forty-six patients requiring double implant-supported restoration in the posterior maxilla were randomly divided in two groups according to the cementation modality: intraoral and extraoral. According to the abutment finishing line, implants in each patient were randomly assigned to shoulderless or chamfer subgroup. In the intraoral group, crowns were directly seated onto the titanium abutment. In the extraoral group, crowns were firstly seated onto a resin abutment replica and immediately removed, then cleansed of the cement excess and finally seated on the titanium abutment. After cement setting, in both groups, cement excess was carefully tried to remove. Three months later, framework/abutment complexes were disconnected and prepared for microscopic analysis: surface occupied by exposed cement remnants and marginal gaps were measured. Additionally, crown/abutment complexes were grinded, and voids of cement were measured at abutment/crown interface. Related-samples Friedman's two-way analysis of variance by ranks was used to detect differences between groups and subgroups (P ≤ 0.5).

RESULTS

At the end of the study, a mean value of 0.45 mm² (±0.80), 0.38 mm² (±0.84), and 0.065 mm² (±0.13) and 0.07 mm² (±0.15) described surface occupied by cement remnants in shoulderless and chamfer abutment with intraoral cementation and shoulderless and chamfer abutment with extraoral cementation, respectively. A mean value of 0.40 mm² (±0.377), 0.41 mm² (±0.39) and 0.485 mm² (±0.47) and 0.477 mm² (±0.43) described cement voids at the abutment/crown interface; a mean value of 0.062 mm (±0.03), 0.064 mm (±0.35), 0.055 mm (±0.016) and 0.054 mm (±0.024) described marginal gaps. Statistics showed tendency of intraoral cementation to have significantly higher cement remnants compared with abutments with extraoral cementation groups. At the same time, the presence of voids was significantly higher in case of extraoral cementation. No significant differences between groups for the variable "gap".

CONCLUSIONS

Despite the presence of more voids, extraoral cementation reduces cement excess. However, using low adhesivity cement and careful cement removal, a very limited quantity of cement remnants was observed also in the intraoral cementation.

Evaluation of removal forces of implant-supported zirconia copings depending on abutment geometry, luting agent and cleaning method during re-cementation

PURPOSE

To evaluate the effects of different abutment geometries in combination with varying luting agents and the effectiveness of different cleaning methods (prior to re-cementation) regarding the retentiveness of zirconia copings on implants.

MATERIALS AND METHODS

Implants were embedded in resin blocks. Three groups of titanium abutments (pre-fabricated, height: 7.5 mm, taper: 5.7°; customized-long, height: 6.79 mm, taper: 4.8°; customized-short, height: 4.31 mm, taper: 4.8°) were used for luting of CAD/CAM-fabricated zirconia copings with a semi-permanent (Telio CS) and a provisional cement (TempBond NE). Retention forces were evaluated using a universal testing machine. Furthermore, the influence of cleaning methods (manually, manually in combination with ultrasonic bath or sandblasting) prior to re-cementation with a provisional cement (TempBond NE) was investigated with the pre-fabricated titanium abutments (height: 7.5 mm, taper: 5.7°) and SEM-analysis of inner surfaces of the copings was performed. Significant differences were determined via two-way ANOVA.

RESULTS

Significant interactions between abutment geometry and luting agent were observed. TempBond NE showed the highest level of retentiveness on customized-long abutments, but was negatively affected by other abutment geometries. In contrast, luting with Telio CS demonstrated consistent results irrespective of the varying abutment geometries. Manual cleaning in combination with an ultrasonic bath was the only cleaning method tested prior to re-cementation that revealed retentiveness levels not inferior to primary cementation.

CONCLUSION

No superiority for one of the two cements could be demonstrated because their influences on retentive strength are also depending on abutment geometry. Only manual cleaning in combination with an ultrasonic bath offers retentiveness levels after re-cementation comparable to those of primary luting.