Microscopical and chemical surface characterization of CAD/CAM zircona abutments after different cleaning procedures. A qualitative analysis

Effects of sterilization, conditioning, and thermal aging on the retention of zirconia hybrid abutments: A laboratory study

OBJECTIVE

To investigate the effects of sterilization, conditioning method, and thermal aging on the retentive strength of two-piece zirconia abutments.

MATERIALS AND METHODS

In total, 128 stock zirconia abutments were divided into four groups (n = 32) according to the conditioning parameters: (A) air-abrasion using 50 μm alumina particles/1.0 bar, (B) 50 μm/2.0 bar, (C) 100 μm/1.0 bar, and (D) 100 μm/2.0 bar. All abutments were bonded onto titanium bases using DTK adhesive resin and stored in water bath (37°C) for 72 h. Each group was subdivided into two subgroups (n = 16), group 1 was disinfected, whereas group 2 followed disinfection and autoclave sterilization. Half of the specimens of each subgroup (n = 8) was directly subjected to the axial retention test (groups N), while the other half was first subjected to 150 days of thermocycling followed by retention test (groups T). Statistical analysis was performed with three-way ANOVA, additional statistical analysis was performed by using separate one-way ANOVAs followed by the Tukey's post-hoc test for post hoc pairwise comparisons among groups.

RESULTS

The highest median retention strength was recorded for group B2N (1390 N), whereas the lowest strength was recorded for group C1T (688 N). No significant interaction (p ≥ 0.05) was detected between the different variables; conditioning method, sterilization, and the thermal cycling regarding the effect on the resulting retention. However, the sterilization always showed a positive effect. Thermocycling presented an adversely significant effect only in the absence of sterilization (p < 0.05), with the exception of subgroups A. For the sterilized groups, thermocycling had no statistically significant effect on the retention.

CONCLUSION

Steam autoclaving increased the retention of hybrid zirconia abutments. DTK adhesive resin for two-piece zirconia abutments performed well after sterilization and thermocycling.

Impact of CAD/CAM burs lifetime on surface properties of dental zirconia: Implications for biocompatibility of custom abutments

OBJECTIVE

To evaluate the effect of the deterioration of computer aided design/computer aided manufacturing (CAD/CAM) burs during zirconia milling, on surface roughness, contact angle, and fibroblast viability.

MATERIALS AND METHODS

Ceramic blocks were milled and 75 ceramic disks (8 × 1.5 mm) made and allocated into three groups (n = 25): G1-brand new 2L and 1L burs, G2-2L bur at the end of lifetime and brand new 1L bur and G3-both burs at the end of their lifetimes. Roughness (Ra, Rq, and Rz) was evaluated using a 3D optical profilometer, the contact angle by the sessile drop method and the cell viability of the mouse NIH/3T3 fibroblast, using the Alamar Blue assay at intervals of 24, 48, and 72 h (ISO 10993-5). Data were analyzed by one-way ANOVA and Kruskal-Wallis tests (p ≤ 0.05).

RESULTS

Roughness increased as the burs deteriorated and G3 (0.27 ± 0.04) presented a higher value for Ra (p < 0.001). The highest contact angle was observed in G3 (86.2 ± 2.66) when compared with G1 (63.7 ± 12.49) and G2 (75.3 ± 6.36) (p < 0.001). Alamar Blue indicated an increase in cell proliferation, with no significant differences among the groups at 24 and 72 h (p > 0.05).

CONCLUSIONS

The deterioration of the burs increased the surface roughness and decreased the wettability, but did not interfere in cell viability and proliferation.

CLINICAL SIGNIFICANCE

The use of custom zirconia abutments represents an effective strategy for single crowns restorations. Our findings suggest that these abutments can be efficiently milled using CAD/CAM burs within their recommended lifetime.

The integration of peri-implant soft tissues around zirconia abutments: Challenges and strategies

Stable soft tissue integration around the implant abutment attenuates pathogen penetration, protects underlying bone tissue, prevents peri-implantitis and is essential in maintaining long-term implant stability. The desire for "metal free" and "aesthetic restoration" has favored zirconia over titanium abutments, especially for implant restorations in the anterior region and for patients with thin gingival biotype. Soft tissue attachment to the zirconia abutment surface remains a challenge. A comprehensive review of advances in zirconia surface treatment (micro-design) and structural design (macro-design) affecting soft tissue attachment is presented and strategies and research directions are discussed. Soft tissue models for abutment research are described. Guidelines for development of zirconia abutment surfaces that promote soft tissue integration and evidence-based references to inform clinical choice of abutment structure and postoperative maintenance are presented.

Biocompatibility, Surface Morphology, and Bacterial Load of Dental Implant Abutments following Decontamination Protocols: An In-Vitro Study

The long-term success of dental implant rehabilitation depends significantly on proper peri-implant soft tissue integration. Therefore, decontamination of abutments prior to their connection to the implant is beneficial to enhance soft tissue attachment and to aid in maintaining marginal bone around the implant. Consequently, different implant abutment decontamination protocols were evaluated regarding biocompatibility, surface morphology, and bacterial load. The protocols evaluated were autoclave sterilization, ultrasonic washing, steam cleaning, chlorhexidine chemical decontamination, and sodium hypochlorite chemical decontamination. The control groups included: (1) implant abutments prepared and polished in a dental lab without decontamination and (2) unprepared implant abutments obtained directly from the company. Surface analysis was performed using scanning electron microscopy (SEM). Biocompatibility was evaluated using XTT cell viability and proliferation assays. Biofilm biomass and viable counts (CFU/mL) (n = 5 for each test) were used for surface bacterial load evaluation. Surface analysis revealed areas of debris and accumulation of materials, such as iron, cobalt, chromium, and other metals, in all abutments prepared by the lab and with all decontamination protocols. Steam cleaning was the most efficient method for reducing contamination. Chlorhexidine and sodium hypochlorite left residual materials on the abutments. XTT results showed that the chlorhexidine group (M = 0.7005, SD = 0.2995) had the lowest values (p < 0.001) (autoclave: M = 3.6354, SD = 0.1510; ultrasonic: M = 3.4077, SD = 0.3730; steam: M = 3.2903, SD = 0.2172; NaOCl: M = 3.5377, SD = 0.0927; prep non-decont.: M = 3.4815, SD = 0.2326; factory: M = 3.6173, SD = 0.0392). Bacterial growth (CFU/mL) was high in the abutments treated with steam cleaning and ultrasonic bath: 2.93 × 10⁹, SD = 1.68 × 10¹² and 1.83 × 10⁹, SD = 3.95 × 10¹⁰, respectively. Abutments treated with chlorhexidine showed higher toxicity to cells, while all other samples showed similar effects to the control. In conclusion, steam cleaning seemed to be the most efficient method for reducing debris and metallic contamination. Bacterial load can be reduced using autoclaving, chlorhexidine, and NaOCl.

Monolithic hybrid abutment crowns (screw-retained) versus monolithic hybrid abutments with adhesively cemented monolithic crowns

OBJECTIVES

The objective of this study is to compare monolithic hybrid abutment crowns (screw-retained) versus monolithic hybrid abutments with adhesively cemented monolithic single-tooth crowns.

MATERIALS AND METHODS

Twenty subjects in need of an implant-borne restoration were randomly assigned to receive either a cement-retained (CRR) or a screw-retained (SRR) implant-supported monolithic lithium disilicate (LS₂ ) reconstruction. Each patient received a titanium implant with in internal conic connection. After osseointegration and second-stage surgery, healing abutments were placed for about 10 days. The type of restoration (CRR vs. SRR) was randomly assigned, and the restorations were manufactured of monolithic LS₂ . Both types of restorations, CRR and SRR, were based on a titanium component (Ti-base) that was bonded to the abutment (CRR) or the crown (SRR). The follow-up period for all restoration was 36 months. Clinical outcome was evaluated according to Functional Implant Prosthetic Score (FIPS). Quality of live (OHIP) and patient's satisfaction were assessed using patient-reported outcome measures (PROMs). Primary endpoint was loss of restoration for any reason. Kaplan-Meier curves were constructed and log-rank testing was performed (p < .05).

RESULTS

One restoration of group CRR failed after 6 months due to loss of adhesion between Ti-base and individual abutment. No further biological or technical failures occurred. Kaplan-Meier analysis showed no significant difference between both treatment options (p = .317). There was no statistically significant difference between both types of restoration, neither for FIPS, OHIP, treatment time nor patient satisfaction (p > .05).

CONCLUSION

Monolithic hybrid abutment crowns (screw-retained) and monolithic hybrid abutment with adhesively cemented monolithic crowns using lithium disilicate showed no statistically significant difference for implant-based reconstructions in this pilot RCT setting.

Microbiological cleaning and disinfection efficacy of a three-stage ultrasonic processing protocol for CAD-CAM implant abutments

PURPOSE

Computer-aided design and manufacturing (CAD-CAM) of implant abutments has been shown to result in surface contamination from site-specific milling and fabrication processes. If not removed, these contaminants can have a potentially adverse effect and may trigger inflammatory responses of the peri-implant tissues. The aim of the present study was to evaluate the bacterial disinfection and cleaning efficacy of ultrasonic reprocessing in approved disinfectants to reduce the microbial load of CAD-CAM abutments.

MATERIALS AND METHODS

Four different types of custom implant abutments (total N = 32) with eight specimens in each test group (type I to IV) were CAD-CAM manufactured. In two separate contamination experiments, specimens were contaminated with heparinized sheep blood alone and with heparinized sheep blood and the test bacterium Enterococcus faecium. Abutments in the test group were processed according to a three-stage ultrasonic protocol and assessed qualitatively and quantitatively by determination of residual protein. Ultrasonicated specimens contaminated with sheep blood and E. faecium were additionally eluted and the dilutions were incubated on agar plates for seven days. The determined bacterial counts were expressed as colony-forming units (CFU).

RESULTS

Ultrasonic reprocessing resulted in a substantial decrease in residual bacterial protein to less than 80 µg and a reduction in microbiota of more than 7 log levels of CFU for all abutment types, exceeding the effect required for disinfection.

CONCLUSION

A three-stage ultrasonic cleaning and disinfection protocol results in effective bacterial decontamination. The procedure is reproducible and complies with the standardized reprocessing and disinfection specifications for one- or two-piece CAD-CAM implant abutments.

Factors Influencing Marginal Bone Loss around Dental Implants: A Narrative Review

Implant supported dental prostheses are increasingly used in dental practice. The aim of this narrative review is to present the influence of transmucosal surface of prosthetic abutment and implant on peri-implant tissue. The article describes causes of bone loss around the dental implant. Moreover, properties of different materials are compared and discussed. The advantages, disadvantages, and biomechanical concept of different implant-abutment connections are presented. The location of connections in relation to the bone level and the influence of microgap between the abutment and implant are described. Additionally, the implant abutments for cemented and screwed prosthetic restorations are compared. The influence of implant and abutment surface at the transmucosal level on peri-implant soft tissue is discussed. Finally, the biological aspect of abutment-implant connection is analyzed.

Evaluating the efficiency of three methods to clean and disinfect screw- and cement-retained prostheses

STATEMENT OF PROBLEM

Screw- and cement-retained prostheses (SCRPs) may be contaminated during fabrication in a dental laboratory, leading to mechanical and biological complications related to the implant treatment. Studies that explored methods to efficiently and conveniently clean and disinfect SCRPs are sparse.

PURPOSE

The purpose of this clinical study was to compare the efficiency of 3 methods to remove contaminants and microorganisms present on the surface of an SCRP.

MATERIAL AND METHODS

Forty-eight 1-unit SCRPs fabricated in a dental laboratory were randomly divided into 3 groups: wiping, soaking, or ultrasonic cleaning. The presence of contaminants was determined by scanning electron microscopy, and microbial cells were cultured before and after treatment. Bacterial colony-forming units (CFUs) on the surface of the SCRPs and contamination density at the implant-abutment interface and emergence profile area were assessed. Statistical tests including ANCOVA were used to compare the efficiency of different methods before and after treatment (α=.05).

RESULTS

Significant differences in contamination density were noted during the treatment at the implant-abutment interface and at the emergence profile area in the 3 groups (P<.05), but no significant differences were observed in the number of CFUs (P>.05). There were significant differences among the 3 methods for cleaning efficiency both at the implant-abutment interface (P=.023) and the emergence profile area (P=.038). At the implant-abutment interface, the contamination density after treatment was lower in the ultrasonic cleaning group than that in the soaking group (P=.007), whereas at the emergence profile area, the contamination density after treatment was lower in the ultrasonic cleaning group than that in the wiping group (P=.019) and the soaking group (P=.048).

CONCLUSIONS

All 3 treatment methods reduced contaminants on the SCRP surface, but ultrasonic cleaning yielded the most favorable results. However, none of the methods provided additional disinfection for SCRPs previously disinfected by ozone and UV in a dental laboratory.

The Effect of Different Cleaning Protocols of Polymer-Based Prosthetic Materials on the Behavior of Human Gingival Fibroblasts

Dental implant abutment and prosthetic materials, their surface treatment, and cleaning modalities are important factors for the formation of a peri-implant soft tissue seal and long-term stability of bone around the implant. This study aimed to investigate the influence of a polymeric material surface cleaning method on the surface roughness, water contact angle, and human gingival fibroblasts (HGF) proliferation. Polymeric materials tested: two types of milled polymethylmethacrylate (PMMA-Ker and PMMA-Bre), three-dimensionally (3D) printed polymethylmethacrylate (PMMA-3D), polyetheretherketone (PEEK), and polyetherketoneketone (PEKK). Titanium (Ti) and zirconia oxide ceramics (ZrO-HT) were used as positive controls. A conventional surface cleaning protocol (CCP) was compared to a multi-step research cleaning method (RCP). Application of the RCP method allowed to reduce S_a values in all groups from 0.14-0.28 µm to 0.08-0.17 µm (p < 0.05 in PMMA-Ker and PEEK groups). Moreover, the water contact angle increased in all groups from 74-91° to 83-101° (p < 0.05 in the PEKK group), except ZrO-HT-it was reduced from 98.7 ± 4.5° to 69.9 ± 6.4° (p < 0.05). CCP resulted in higher variability of HGF viability after 48 and 72 h. RCP application led to higher HGF viability in PMMA-3D and PEKK groups after 48 h, but lower for the PMMA-Ker group (p < 0.05). After 72 h, no significant differences in HGF viability between both cleaning methods were observed. It can be concluded that the cleaning method of the polymeric materials affected surface roughness, contact angle, and HGF viability at 48 h.

Qualitative and Semi-Quantitative Assessment of Processing-Related Surface Contamination of One- and Two-Piece CAD/CAM Abutments before and after Ultrasonic Cleaning

Manufacturing processes of custom implant abutments may contaminate their surfaces with micro wear deposits and generic pollutants. Such particulate debris, if not removed, might be detrimental and provoke inflammatory reactions in peri-implant tissues. Although regulatory guidelines for adequate cleaning, disinfection, or sterilization exist, there does not appear to be a consistent application and data on the amount and extent of such contaminants is lacking. The aim of the present in vitro study was to evaluate the quality and quantity of processing-related surface contamination of computer-aided design/computer-aided manufacturing (CAD/CAM) abutments in the state of delivery and after ultrasonic cleaning. A total of 28 CAD/CAM monotype and hybrid abutments were cleaned and disinfected applying a three-stage ultrasonic protocol (Finevo protocol). Before and after cleaning, the chemical composition and the contamination of the abutments were assessed using scanning electron microscopy (SEM), dispersive X-ray spectroscopy (EDX), and computer-aided planimetric measurement (CAPM). In the delivery condition, monotype abutments showed a significantly higher amount of debris compared to hybrid abutments (4.86 ± 6.10% vs. 0.03 ± 0.03%, p < 0.001). The polishing process applied in the laboratory after bonding the hybrid abutment components reduces the surface roughness and thus contributes substantially to their purity. The extent of contamination caused by computer-aided manufacturing of custom abutments can be substantially minimized using a three-stage ultrasonic protocol.

Decontamination of Titanium Surface Using Different Methods: An In Vitro Study

Contamination of implants is inevitable during different steps of production as well as during the clinical use. We devised a new implant cleaning strategy to restore the bioactivities on dental implant surfaces. We evaluated the efficiency of the Finevo cleaning system, and Ultraviolet and Plasma treatments to decontaminate hydrocarbon-contaminated titanium disks. The surfaces of the contaminated titanium disks cleaned using the Finevo cleaning system were similar to those of the uncontaminated titanium disks in scanning electron microscopy and X-ray photoelectron spectroscopy analysis, but no obvious change in the roughness was observed in the scanning probe microscopy analysis. The rat bone marrow mesenchymal stem cells (rBMMSCs) cultured on the treated titanium disks attached to and covered the surfaces of disks cleaned with the Finevo cleaning system. The alkaline phosphatase activity, calcium deposition, and osteogenesis-related gene expression in rBMMSCs on disks cleaned using the Finevo cleaning system were higher compared to those in the ultraviolet and plasma treatments, displaying better cell functionality. Thus, the Finevo cleaning system can enhance the attachment, differentiation, and mineralization of rBMMSCs on treated titanium disk surfaces. This research provides a new strategy for cleaning the surface of contaminated titanium dental implants and for restoration of their biological functions.

Biofunctionalization of zirconia with cell-adhesion peptides via polydopamine crosslinking for soft tissue engineering: effects on the biological behaviors of human gingival fibroblasts and oral bacteria

Rapid soft tissue integration is essential for long-term dental implant success. Zirconia is increasingly used as an abutment material owing to its excellent aesthetic properties and biocompatibility; however, it is bioinert, and tissue integration is poor. We developed a feasible surface modification method, exploiting the reactivity of polydopamine (PDA) films to immobilize cell-adhesion peptides (Arg-Gly-Asp, RGD) onto zirconia abutment surfaces. Further, we evaluated the effect thereof on human gingival fibroblast (HGF) behavior and oral bacterial adhesion, which influence the peri-implant soft tissue seal. HGF responses to linear KGGRGDSP and cyclic RGDfK sequences were compared. PDA deposition and covalent coupling of RGD were verified by X-ray photoelectron spectroscopy and fluorescence microscopy. The biological behaviors of HGFs on the modified zirconia; i.e., adhesion, spreading, proliferation, gene and protein expression, were elucidated. Biofunctionalization of zirconia with the adhesion peptides significantly enhanced the biological activities of HGFs. Cyclic RGD induced slightly improved cell attachment, spreading, and proliferation, but similar cell differentiation when compared to linear RGD peptides. To assess their antimicrobial properties, the different substrates were exposed to cultures of the early colonizer Streptococcus mutans or the periodontal pathogen Porphyromonas gingivalis, and bacterial adhesion was evaluated by scanning electron microscopy and live/dead staining. PDA and PDA-RGD coatings decreased zirconia surface colonization by both bacterial species to similar extents. Thus, PDA-RGD-functionalized zirconia modulates specific HGF responses, while maintaining the antimicrobial activity of the PDA coating. The selective bio-interaction pattern of this surface modification holds great promise for improving soft-tissue integration around zirconia abutments in clinical applications.

Biofunctionalization of zirconia with cell-adhesion peptides via polydopamine and its effect on HGFs/bacterial adhesion for enhanced soft tissue seal.

Influence of margin location and luting material on the amount of undetected cement excess on CAD/CAM implant abutments and cement-retained zirconia crowns: an in-vitro study

Background

The flexibility in designing the submucosal part of CAD/CAM customized implant abutments and the individual positioning of its shoulder line has been suggested to reduce the risk of leaving undetected cement residues, thus preventing adverse effects on peri-implant tissues. A high correlation between excess cement left in the soft tissues and the occurrence of increased biofilm accumulation with sulcular bleeding and/ or suppuration has been reported. This in turn may cause peri-implant inflammation and peri-implant marginal bone loss. The aim of this study was to assess the frequency of cement remnants after the luting of zirconia crowns on CAD/CAM custom molar abutments with different margin levels and to evaluate the impact of the luting material.

Material and methods

A total of 20 titanium molar CAD/CAM implant abutments (BEGO Medical GmbH) with internal taper connection/ internal hex anti-rotation protection, and a convex emergence profile with different margin positions (0, 1, 2 and 3 mm below the mucosa), were virtually designed (Implant Studio, 3Shape) and manufactured. A master cast was scanned, duplicated by a 3D printer and individual gingival masks were produced to simulate peri-implant soft tissues. 20 corresponding zirconia crowns were designed (Cerec 3D, Dentsply Sirona), produced and cemented to the abutments with two different luting materials; a zinc oxide non-eugenol cement (Temp Bond NE) or a methacrylate cement (Panavia V5). To ensure retrievability of the crown/abutment connection, occlusal openings providing access to the abutment screws were designed. Excess cement was thoroughly removed and the crown/abutment units were unscrewed to evaluate the occurrence of cement residues. All the quadrants of each specimen were evaluated for calculation of the ratio between the cement remnant area and the total specimen area using Adobe Photoshop. Spearman analysis was performed to detect correlations between different variables. A two-sided t-test, ANOVA, Mann–Whitney, and Kruskal–Wallis tests were applied to detect differences between the groups.

Results

Cement remnants were found in every depth of the crown abutment complex and in almost every area investigated. The amount of cement residues increased as the crown-abutment margin was located more submucosally. Lingual areas were more prone to cement remnants than other surface areas (p = 0.0291). Excess cement was not only found at the margins of the crown-abutment complex, but also underneath (basal) the abutment itself, where cleaning was impossible. No statistical difference in the effect of zinc oxide non-eugenol- and methacrylate cement on the frequency of excess material at the lateral abutment surfaces could be demonstrated in vitro. The proportion of basal abutment aspects covered with cement residues was, however, significantly smaller in Panavia V5 samples with an average of 4.9 ± 3.7% compared to Temp Bond samples with an average of 8.6 ± 5.5%.

Conclusions

Given the results obtained in the present investigation the margin of CAD/CAM molar abutments should be located as coronally as possible to minimize the amount of cement remnants. If an epigingival or supragingival margin location is not feasible due to esthetic concerns, it cannot be recommended to place the margin of molar CAD/CAM abutments deeper than 1.5 mm in the proximal and oral regions.

The Influence of an Ultrasonic Cleaning Protocol for CAD/CAM Abutment Surfaces on Cell Viability and Inflammatory Response In Vitro

BACKGROUND/AIM

To evaluate the effect of an ultrasonic cleaning and disinfection method for CAD/CAM abutment surfaces on cell viability and inflammatory response in vitro.

MATERIALS AND METHODS

Untreated and manually polished surfaces of CAD/CAM generated titanium and zirconia disks were randomly assigned, either to a 3-step ultrasonic cleaning and disinfection process (test: TiUF, TiPF, ZrUF, ZrPF) or to 30 sec steam cleaning (control: TiUS, TiPS, ZrUS, ZrPS). Pre-cleaning surface analyses using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and surface profilometry were performed. Human gingival fibroblasts (HGFs) were cultured on test and control specimens and subsequently examined for cell viability and inflammatory response. Expression of acute inflammatory cytokine interleukin (IL)-6 and vascular endothelial growth factor A (VEGFA) were assessed by means of RT-qPCR.

RESULTS

Cells on all specimens exhibited a satisfactory viability, indicating firm attachment. Cells on polished zirconia samples, cleaned by means of sonication (ZrPF), exhibited significantly higher viability than cells on the same material cleaned by steam (ZrPS), p=0.019. For all other three material/ surface treatment combinations (TiU, TiP, ZrU), no such difference was observed between the cleaning methods. The messenger ribonucleic acid (mRNA) levels of IL-6 and VEGFA were between 50 and 105% of that of the control cells on the non-toxic control surface. mRNA levels of IL-6 and VEGFA correlated well with each other.

CONCLUSION

Except for higher viability of cells cultured on polished zirconia specimens, no universally applicable advantage could be found for the ultrasonic cleaning procedure for zirconia and titanium abutment surfaces regarding cell viability, IL-6 expression or VEGFA expression. The cleaning procedures did not have any negative effect either.

Effects of different surface treatments on the shear bond strength of veneering ceramic materials to zirconia

PURPOSE

To evaluate and compare the effect of different materials and techniques on the shear bond strength of veneering ceramic materials to zirconia.

MATERIALS AND METHODS

136 sintered zirconia cubes were prepared and randomly divided into four study groups according to corresponding methods of surface treatment and materials: GLN (grinding followed by laser scanning using Noritake Cerabien ZR), SLN (sandblasting followed by laser scanning using Noritake Cerabien ZR), GLV (grinding followed by laser scanning using VITA VM 9), and SLV (sandblasting followed by laser scanning using VITA VM 9). Spraying technique was performed to coat the core. Profilometer, SEM, XRD, EDS, universal testing machine, and stereomicroscope were used to record surface roughness Ra, surface morphology, phase transformation, elemental compositions, shear bond strength SBS values, and failure types, respectively. Specimens were investigated in unaged (not immersed in artificial saliva) and aged (stored in artificial saliva for a month) conditions to evaluate SBS values.

RESULTS

Grinding and GLN as first and second surface treatments provided satisfactory Ra values in both conditions (1.05 ± 0.24 µm, 1.30 ± 0.21 µm) compared to sandblasting and other groups (P<.05). The group GLN showed the highest SBS values in both conditions (30.97 ± 3.12 MPa, 29.09 ± 4.17 MPa), while group SLV recorded the lowest (23.96 ± 3.60 MPa, 22.95 ± 3.68 Mpa) (P<.05). Sandblasting showed phase transformation from t-m. Mixed failure type was the commonest among all groups.

CONCLUSION

GLN showed to be a reliable method which provided satisfactory bond strength between the veneer ceramic and zirconia. This method might preserve the integrity of fixed dental crowns.

Characteristics of Local Delivery Agents for Treating Peri-Implantitis on Dental Implant Surfaces: A Preclinical Study

Local delivery agents (LDAs) are widely used in peri-implantitis treatments. The aim of this study was to identify LDAs remaining on the dental implant surfaces and to analyze the components of these residues after applying various cleaning methods. Implants were prepared with a sand-blasted, large-grit, acid-etched surface. Four kinds of LDAs were applied on the implant surfaces: chlorhexidine gel (group 2), tetracycline solution (group 3), and 2 kinds of minocycline hydrochloride agents (groups 4 and 5). Group 1 received normal saline as a control. Two cleaning methods were applied for different durations as follows: (1) running distilled water for 10 seconds (subgroup A), 5 minutes (subgroup B), and 15 minutes (subgroup C); and (2) water spray of a dental-unit chair for 10 seconds (subgroup D) and 5 minutes (subgroup E). Scanning electron microscopy and energy-dispersive x-ray spectroscopy were used to analyze the surface morphology and residue components for all implants. The amount of LDA removed from the implant surfaces in groups 1, 2, 3, and 5 increased with the cleaning duration and pressure. However, Minocline remained coated on the implant surfaces in group 4 under all cleaning conditions. Minocline could not be cleaned off well by water due to its hydrophobicity. Therefore, directly using this agent on implant surfaces with peri-implantitis should be carefully considered. The presence of LDA residues without drug efficacies on implant surfaces might interfere with reosseointegration and act as a reservoir of microorganisms.

Influence of scaling procedures on the integrity of titanium nitride coated CAD/CAM abutments

PURPOSE

To determine the extent of treatment traces, the roughness depth, and the quantity of titanium nitride (TiN) removed from the surface of CAD/CAM abutments after treatment with various instruments.

MATERIALS AND METHODS

Twelve TiN coated CAD/CAM abutments were investigated for an in vitro study. In the test group (9), each abutment surface was subjected twice (150 g vs. 200 g pressure) to standardized treatment in a simulated prophylaxis measure with the following instruments: acrylic scaler, titanium curette, and ultrasonic scaler with steel tip. Three abutments were used as control group. Average surface roughness (Sa) and developed interfacial area ratio (Sdr) of treated and untreated surfaces were measured with a profilometer. The extent of treatment traces were analyzed by scanning electron microscopy.

RESULTS

Manipulation with ultrasonic scalers resulted in a significant increase of average surface roughness (Sa, P<.05) and developed interfacial area ratio (Sdr, P<.018). Variable contact pressure did not yield any statistically significant difference on Sa-values for all instruments (P=.8). Ultrasonic treatment resulted in pronounced surface traces and partially detachment of the TiN coating. While titanium curettes caused predominantly moderate treatment traces, no traces or detectable substance removal has been determined after manipulation with acrylic curettes.

CONCLUSION

Inappropriate instruments during regular plaque control may have an adverse effect on the integrity of the TiN coating of CAD/CAM abutments. To prevent defects and an increased surface roughness at the transmucosal zone of TiN abutments, only acrylic scaling instruments can be recommended for regular maintenance care.

Effects of cleaning methods for custom abutment surfaces on gene expression of human gingival fibroblasts

The aim of this study was to develop an effective method for cleaning implant abutments made by computer-aided design and computer-aided manufacturing techniques and to investigate the effect of decontamination in vitro. Briefly, a newly developed reagent (PK) and/or vacuum plasma (Plasma) were used to clean the surfaces of zirconia disks, and the effects of this decontamination were evaluated by X-ray photoelectron spectroscopy. Human gingival fibroblasts (HGFs) were cultured on sample disks for 6, 24, and 48 h. We evaluated cell attachment and gene expression of the acute inflammatory cytokines interleukin-6 and vascular endothelial growth factor A, and type 1 collagen. In the PK and PK+Plasma groups, surface contaminants were reduced by washing. In addition, HGF attachments was increased in the PK and PK+Plasma groups. Gene expressions of interleukin-6 and vascular endothelial growth factor A were lower at 6 h. Gene expression of type 1 collagen was increased at all time points after seeding. These results suggest that decontamination of implant abutment surfaces is important in initial HGF attachment and may improve the biological seal of peri-implant soft tissue.

Effect of Clinically Relevant CAD/CAM Zirconia Polishing on Gingival Fibroblast Proliferation and Focal Adhesions

Mucosal seal formation around dental abutments is critical to the successful integration of dental implants into the human oral cavity. No information exists for how clinically relevant polishing procedures for computer-aided design and computer-aided manufactured (CAD/CAM) zirconia abutments affects cellular responses important to mucosal seal formation. CAD/CAM zirconia was divided into four groups for clinically relevant polishing utilizing commercial polishing heads: control, coarse, coarse plus medium, and coarse plus medium plus fine. Surfaces were analyzed with scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical profilometry (OP). Subsequently, human gingival fibroblasts (HGFs) were seeded onto the zirconia surfaces. Proliferation was measured via a quantitative SEM technique and focal adhesion kinase (FAK) phosphorylation status was measured by an enzyme-linked immunosorbent assay (ELISA). Results showed an increase in proliferation on all polished surfaces as compared to the control. Phosphorylation of FAK at tyrosine 397 (Y397) was up-modulated on the control surfaces. The associated cell adaptation is discussed. In all cases, FAK phosphorylation was greater at 24 h than 48 h. These results suggest that clinicians should be mindful of the effects of abutment polishing methodology, as this may have an impact on early mucosal seal formation.

Biocompatibility of polymer-infiltrated-ceramic-network (PICN) materials with Human Gingival Fibroblasts (HGFs)

OBJECTIVES

Polymer-infiltrated-ceramic-network (PICN) materials constitute an innovative class of CAD-CAM materials offering promising perspectives in prosthodontics, but no data are available in the literature regarding their biological properties. The objective of the present study was to evaluate the in vitro biocompatibility of PICNs with human gingival fibroblasts (HGFs) in comparison with materials typically used for implant prostheses and abutments.

METHODS

HGF attachment, proliferation and spreading on discs made of PICN, grade V titanium (Ti), yttrium zirconia (Zi), lithium disilicate glass-ceramic (eM) and polytetrafluoroethylene (negative control), were evaluated using a specific insert-based culture system (IBS-R). Sample surface properties were characterized by XPS, contact angle measurement, profilometry and SEM.

RESULTS

Ti and Zi gave the best results regarding HGF viability, morphology, number and coverage increase with time in comparison with the negative control, while PICN and eM gave intermediate results, cell spreading being comparable for PICN, Ti, Zi and eM. Despite the presence of polymers and their related hydrophobicity, PICN exhibited comparable results to glass-ceramic materials, which could be explained by the mode of polymerization of the monomers.

SIGNIFICANCE

The results of the present study confirm that the currently employed materials, i.e. Ti and Zi, can be considered to be the gold standard of materials in terms of HGF behavior, while PICN gave intermediate results comparable to eM. The impact of the present in vitro results needs to be further investigated clinically, particularly in the view of the utilization of PICNs for prostheses on bone-level implants.