Adhesion/cementation to zirconia and other non-silicate ceramics: where are we now?

Self-adhesive resin cements were introduced to dentistry within the past decade but have gained rapidly in popularity with more than a dozen commercial brands now available. This review article explores their chemical composition and its effect on the setting reaction and adhesion to various substrates, their physical and biological properties that may help to predict their ultimate performance and their clinical performance to date and handling characteristics. The result of this review of self-adhesive resin cements would suggest that these materials may be expected to show similar clinical performance as other resin-based and non-resin based dental cements.

Self-adhesive resin cements - chemistry, properties and clinical considerations.

Air-abrasion seems to be mandatory for durable resin bonding to zirconia ceramic. Air-abrasion might compromise the ceramic strength by creating surface defects. Therefore, omitting air-abrasion or using reduced air-pressure seems desirable. We tested the null hypotheses that omitting air-abrasion or using reduced air-pressure does not affect zirconia ceramic bonding independent of using primers. Three mechanical surface conditions (polished, air-abraded at 0.05 or at 0.25 MPa) and 4 priming conditions were tested. After different surface conditioning, zirconia ceramic specimens were bonded, and tensile bond strengths were evaluated after water storage for 3 days or for 150 days with additional 37,500 thermal cyclings for artificial aging. Omitting air-abrasion resulted in debonding during artificial aging independent of using primers. The combination of air-abrasion and priming improved long-term resin bonding to zirconia ceramic significantly. With low-pressure air-abrasion, surface roughness was reduced without affecting long-term bond strength, provided that adequate adhesive primers were applied.

Surface Conditioning Influences Zirconia Ceramic Bonding

Objective: To evaluate short- and long-term shear bond strengths of 4 luting agents to zirconia following different surface treatments. Method and Materials: A total of 320 ceramic specimens fabricated from a commercial zirconium oxide ceramic (Lava) were randomly divided into 4 groups: left untreated (NOT), airborne-particle abraded (SND), Rocatec tribochemical silica/silane coated (ROC), or ground and polished (GRD). Resin composite cylinders were bonded to the zirconia specimens with resin composite luting agent RelyX ARC (ARC), universal adhesive resin composite RelyX Unicem (UNI), adhesive-phosphate-monomer-containing resin composite Panavia F (PAN), or the hybrid glass-ionomer cement RelyX Luting (LUT). Subgroups of 10 specimens were stored in distilled water (37°C) for 3 days (ST) or stored for 180 days and thermocycled for 12,000 cycles (LT/TC) before shear bond strength was tested. Statistical analyses included Kruskal-Wallis and Wilcoxon 2-sample rank sum test (a = .01). Results: Short-term shear bond strengths were higher with ROC than with SND, which were both greater than GRD or NOT. UNI revealed higher shear bond strengths than PAN, ARC, and LUT. LT / TC significantly decreased shear bond strength values. GRD and NOT produced the lowest shear bond strengths. SND and ROC significantly increased bond strength. ROC generally yielded the highest long-term shear bond strength, especially with UNI, PAN, or ARC. These were similar to SND and PAN, which revealed the highest long-term shear bond strengths. Conclusions: Surface treatment, luting agent, and storage conditions significantly influence shear bond strengths to zirconia. Artificial aging significantly reduces shear bond strengths. Airborne-particle abrasion combined with a resin composite containing adhesive phosphate monomers or tribochemical silica / silane coating combined with any of the tested resin composite luting agents provides superior long-term shear bond strength values.

Influence of surface treatment and simulated aging on bond strengths of luting agents to zirconia.

Influence of air-abrasion on zirconia ceramic bonding using an adhesive composite resin

Durability of the resin bond strength to zirconia ceramic after using different surface conditioning methods.

PURPOSE The purpose of this in vitro study was to evaluate the influence of cement type and application technique on seating discrepancies and retention forces of noble alloy castings cemented on titanium abutments. MATERIALS AND METHODS Eugenol-free zinc oxide (Freegenol), zinc phosphate (Harvard), glass ionomer (KetacCem), polycarboxylate (Durelon), and self-adhesive resin (RelyX Unicem) cements were used. The inner surfaces of the castings were either completely coated or half-coated with cement. Abutments were used as delivered with a machined surface for the first part of the study. Groups of 8 castings were cemented in both ways. For the second part of the study, the abutments were air-abraded (aluminum oxide, 50 microm particle size), and groups of 8 completely coated castings were cemented with all cements. Marginal discrepancies were measured before and immediately after cementation. Tensile tests were conducted to measure the retention forces. Statistical analysis was performed with pair-wise comparison using the Wilcoxon rank sum test modified by Bonferroni-Holm. RESULTS Change in seating discrepancies did not differ significantly among the different application techniques. The median retention forces for completely-coated castings were 177 N for eugenol-free zinc oxide, 346 N for zinc phosphate, 469 N for glass ionomer, 813 N for polycarboxylate, and 653 N for self-adhesive resin. With respect to retention force, 3 significantly different groups (P < .05) were identified: (1) zinc oxide, (2) zinc phosphate/glass ionomer, and (3) polycarboxylate/self-adhesive resin. No differences in retention between the 2 coating techniques were found for any cement. However, air abrading the abutments resulted in increased retention of the castings for some of the cements. CONCLUSIONS Half-coating of the restorations with cements did not result in reduced retention values compared to the complete coating technique, but air abrasion resulted in increased retention with some cements.

Retention forces and seating discrepancies of implant-retained castings after cementation.

Objectives: The purpose of this study was to assess the retrievability of cemented implant crowns using two different removal devices. The influence of five cement types and two cement application techniques was evaluated.

Methods: Forty copings were cast from a CoCr alloy for 40 tapered titanium abutments (5° taper, 4.3 mm diameter, 6 mm height, Camlog, Germany). Twenty copings were modeled as single crowns, whereas 20 copings were modeled with an extension to simulate fixed partial dentures (FPDs). Before cementation, the inner surfaces of the copings were air-abraded (50 μm Al2O3 particles at 2.5 bars), while the abutments were used as delivered with machined surfaces. Copings were cemented with eugenol-free zinc oxide (Freegenol), zinc phosphate (Harvard), glass ionomer (Ketac Cem), polycarboxylate (Durelon) and so-called self-adhesive resin (RelyX Unicem) cement. Cement was applied in a thin film band of 1 or 3 mm to the cervical margin of the inner surface of the copings, respectively. After cementation, specimens were stored in saline solution for 24 h. The Coronaflex and a standardized custom-made removal device were used to remove the copings from the abutments.

Results: Using the same cement, no statistically significant influence with regard to the type of restoration (crown/FDP), cement application mode and device was detected (P>0.05). Therefore, data of specimens cemented with the same cement were pooled. Median attempts to remove the copings were: zinc oxide: 3, self-adhesive resin: 3, zinc phosphate: 5, glass ionomer: 16 and polycarboxylate: 58. Four levels of significance (P<0.0001) were found: (1) zinc oxide/self-adhesive resin; (2) zinc phosphate; (3) glass ionomer; and (4) polycarboxylate.

Conclusions: Zinc phosphate and glass ionomer cement might be suitable for a so-called ‘semipermanent’ (=retrievable) cementation, while polycarboxylate seems to provide the most durable cementation.

Retrievability of implant-retained crowns following cementation.

Purpose The aim of this study was to evaluate whether there is a need to develop a new questionnaire measuring dental appearance or if this is already covered by the Oral Health Impact Profile (OHIP-49). Materials and methods Based on internationally accepted guidelines about dental esthetics, a questionnaire was developed to measure dental appearance (QDA). Eleven items defined a QDA sum score (0 = absolutely satisfied, 44 = absolutely dissatisfied). Furthermore, oral health-related quality of life was evaluated using the German version of the OHIP-49 and the OHIP-esthetic. Thirty patients (14 women, 16 men; mean age 59 +/- 10 years) were included in the study. All patients received a complete oral rehabilitation including the anterior teeth of the maxilla. Questionnaires were completed before and after treatment. Results The median values were 16 and 1.5 for the QDA sum score, 46 and 16 for the OHIP sum score, and 14.5 and 2 for the OHIP-esthetic before and after rehabilitation, respectively. The improvement after treatment was significant for all questionnaires (P .05). Between the QDA sum score and the OHIP-esthetic, a significant correlation could be found before treatment (r = 0.505, P = .004) but not after treatment (P > .05). Conclusions If the OHIP-49 is used in clinical studies and a profound evaluation of dental appearance is desired, it is reasonable to use an additional esthetic modulus.

Does the Oral Health Impact Profile questionnaire measure dental appearance

Objective
One aim of this prospective clinical study was to measure the effects of strategicimplant placement under removable partial dental prostheses (RPDPs) and among removable complete dental prostheses (RCDPs) on oral health-related quality of life (OHRQoL).

Materials and methods
Twenty-three patients participated in this study restored with RCDPs (n = 12) or RPDPs retained by telescopic crowns with 1–2 abutment teeth (n = 11). The total number of abutments was increased to 5–6 (maxilla) or to 4 (mandible) by placing implants in strategically advantageous regions. Ball attachments were attached to the implants and integrated in the existing denture. The Oral Health Impact Profile (49 questions) was completed by patients before implant placement, at baseline (integration of ball attachments), and during 12- and 24-month follow-up visits.

Results
There were marked reductions of impacts in both groups when comparing pre-treatment scores and scores at baseline (P   0.05).

Conclusion
It can be concluded that a strategic placement of implants under the existing dental prostheses improves OHRQoL in both treatment groups.

Mona Wolfart

Papers

Durability of the resin bond strength to zirconia ceramic after using different surface conditioning methods.

Retention forces and seating discrepancies of implant-retained castings after cementation.

Retrievability of implant-retained crowns following cementation.

Does the Oral Health Impact Profile questionnaire measure dental appearance

Implant placement under existing removable dental prostheses and its effect on oral health-related quality of life.