Immunohistochemical analysis of soft tissue response to polyetheretherketone (PEEK) and titanium healing abutments on dental implants: a randomized pilot clinical study

Clinical and biochemical assessment of the soft tissue response to titanium stock versus custom composite resin healing abutments

STATEMENT OF PROBLEM

Custom healing abutments made of flowable composite resin have gained popularity, although the soft tissue response to composite resin has not been adequately studied.

PURPOSE

The purpose of this randomized controlled clinical trial was to evaluate the soft tissue response to titanium stock healing abutments and custom composite resin healing abutments by assessing clinical indices and the level of matrix metalloproteinase-8 (MMP-8) in the peri-implant crevicular fluid (PICF).

MATERIAL AND METHODS

A randomized controlled clinical trial was performed on 42 osseointegrated implants. The implants were divided into 2 groups: a test group comprising 21 custom composite resin healing abutments that were attached to the implants at second stage surgery and a control group comprising 21 stock titanium healing abutments. Plaque index (PL), bleeding on probing (BOP), modified gingival index (MGI), and level of MMP8 were measured at the second and fourth week after second stage surgery. Peri-implant crevicular fluid was collected by paper points at each follow-up, and the level of MMP8 was measured by an enzyme-linked immunosorbent assay kit. For statistical analysis, group comparisons used the Mann-Whitney U test, and comparisons within each group at 2 and 4 weeks used the Wilcoxon Sign Rank test. Group differences were analyzed with the Fisher exact test, and the McNemar test was used to compare percentages at 2 and 4 weeks. All tests were two-tailed (α=.05).

RESULTS

For the PI, no statistically significant differences were found within groups or between groups (P>.05). Bleeding on probing was positive in 14.3% of titanium abutments versus 20% of composite resin abutments at 4 weeks, with no significant difference between groups (P>.05). Similarly, the mean MGI was 0.38 ±0.5 in the control group while it was 0.4 ±0.5 in the test group, with no significant differences between groups (P>.05). The MMP8 level at 2 weeks was 11.1 ±8.65 and 13.11 ±9.29 for the control and test groups, respectively while it was 16.35 ±8.31 and 19.80 ±8.44 at 4 weeks, showing a statistically significant increase within groups (P<.05). No significant difference between groups was detected at either follow-up time point regarding MMP8 level (P>.05).

CONCLUSIONS

The clinical and biochemical soft tissue response to composite resin healing abutments and titanium stock healing abutments were comparable, suggesting the clinical safety of custom composite resin healing abutments.

In Vivo Biocompatibility Study on Functional Nanostructures Containing Bioactive Glass and Plant Extracts for Implantology

In this paper, the in vivo behavior of orthopedic implants covered with thin films obtained by matrix-assisted pulsed laser evaporation and containing bioactive glass, a polymer, and natural plant extract was evaluated. In vivo testing was performed by carrying out a study on guinea pigs who had coated metallic screws inserted in them and also controls, following the regulations of European laws regarding the use of animals in scientific studies. After 26 weeks from implantation, the guinea pigs were subjected to X-ray analyses to observe the evolution of osteointegration over time; the guinea pigs' blood was collected for the detection of enzymatic activity and to measure values for urea, creatinine, blood glucose, alkaline phosphatase, pancreatic amylase, total protein, and glutamate pyruvate transaminase to see the extent to which the body was affected by the introduction of the implant. Moreover, a histopathological assessment of the following vital organs was carried out: heart, brain, liver, and spleen. We also assessed implanted bone with adjacent tissue. Our studies did not find significant variations in biochemical and histological results compared to the control group or significant adverse effects caused by the implant coating in terms of tissue compatibility, inflammatory reactions, and systemic effects.

Synergistic Effect of Nano Strontium Titanate Coating and Ultraviolet C Photofunctionalization on Osteogenic Performance and Soft Tissue Sealing of poly(ether-ether-ketone)

This study aimed to evaluate the bioactivity of poly(ether ether ketone) (PEEK) after surface modification by persistent photoconductive strontium titanate (SrTiO3) magnetron sputtering and ultraviolet (UV) C irradiation. According to the different modifications, the PEEK specimens were randomly divided into five groups (n = 38/group): PEEK, Sr100-PEEK, Sr200-PEEK, UV/PEEK, and UV/Sr200-PEEK. Then, the specimens of Sr100-PEEK and Sr200-PEEK groups were, respectively, coated with 100 and 200 nm thickness photocatalyst SrTiO3 on the PEEK surface by magnetron sputtering. Subsequently, UV-C light photofunctionalized the specimens of PEEK and Sr200-PEEK groups to form UV/PEEK and UV/Sr200-PEEK groups. The specimens were characterized by a step meter, scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), and a water contact angle meter. The release test of the Sr ion was performed by inductively coupled plasma mass spectrometry (ICP-MS). In vitro study, osteogenic activity (MC3T3-E1 osteoblast-like cells) and epithelial and connective tissue attachment (gingival epithelial cells GE1 and fibroblasts NIH3T3) were analyzed in five groups. Surface morphology of the specimens was changed after coating, and the Sr content on the Sr-PEEK surface was increased with increasing coating thickness. In addition, the contact angle was increased significantly after magnetron sputtering. After UV-C photofunctionalization, the content of surface elements changed and the contact angle was decreased. The release of Sr ion was sustained, and the final cumulative release amount did not exceed the safety limit. In vitro experiments showed that SrTiO3 improved the cell activity of MC3T3-E1 and UV-C irradiation further enhanced the osteogenic performance of PEEK. Besides, UV-C irradiation also significantly promoted the cell viability, development, and expression of adhesion proteins of GE1 and NIH3T3 on PEEK. The present investigation demonstrated that nano SrTiO3 coating with UV-C photofunctionalization synergistically enhanced the osteogenic properties and soft tissue sealing function of PEEK in vitro.