Histological evaluations and inflammatory responses of different dental implant abutment materials: A human histology pilot study

Evaluation of a platform-switched Morse taper connection for all-on-four or six treatment in edentulous or terminal dentition treatment: A retrospective study with 1-8 years of follow-up

BACKGROUND

The survival rate, marginal bone loss and soft tissue health of the Ankylos implants and the balanced base abutments in all-on-four or six implant restoration of edentulous or terminal dentition patients has not been reported in the clinical research.

PURPOSE

This retrospective study aimed to evaluate the Ankylos implants and the balanced base abutments in all-on-four or six implant restoration of edentulous or terminal dentition patients after 1-8 years of follow-up.

MATERIALS AND METHODS

A retrospective study was conducted based on the medical records of 33 patients who received all-on-four or six treatments from April 2014 to May 2020. Four radiographic examinations [immediate postoperative (T0), definitive restorations (T1), 1-3 years after prosthetic restorations (T2), and more than 3 years after prosthetic restorations (T3)] were obtained to evaluate vertical bone height (VBH). We also calculated the survival rate and examined the condition of soft tissue with this implant system in edentulous or terminal dentition patients. Three-level linear model analyses were used to explore potential risk factors for VBH changes on the mesial and distal sides. The generalized linear model was used to analyze the influencing factors of BOP and plaque.

RESULTS

A total of 218 implants were included in this study. The cumulative survival rate of the implants was 97.25% before the definitive prosthesis, 96.33% within 3 years of follow-up and 95.32% after more than 3 years of follow-up. The mean ± standard deviation (SD) bone losses of the VBH were 0.27 ± 0.05 mm (T1-T3) on the mesial side and 0.49 ± 0.06 mm (T1-T3) on the distal side. During 1-8 years of follow-up, the height and angle of the abutment (p < 0.001), the mandible implant site (p < 0.001), the length of the implant (p = 0.014 < 0.05) and age (p = 0.029 < 0.05) showed statistically significant effects on vertical mesial bone height (VMBH) and vertical distal bone height (VDBH). The risk of BOP among participants who brushed three times a day was lower than those who brushed less than three times. The plaque risk of short abutment height was higher than the long abutment.

CONCLUSION

The current study showed that the Ankylos implants with the balanced base abutments in all-on-four or six implants treatment is a viable and predictable option with a high survival rate and low marginal bone loss in edentulous or terminal dentition patients. VBH around the implants was strongly associated with the mandible implant site, abutment height and angle, the length of the implant and age. Moreover, teeth-brushing times and abutment height significantly affect soft tissue health.

Contour Analysis of Three-Dimensional Peri-Implant Mucosal Model as an Endpoint Analysis of Photofunctionalization Effects on Implant Abutment Materials

INTRODUCTION

The objective of this study was to examine the effect of photofunctionalization on the soft-tissue contour formed at the interface of various abutment materials using end-point analyses obtained from the three-dimensional oral mucosal model (3D-OMMs).

METHODS

Commercially pure titanium (CPTi), alumina-toughened zirconia (ATZ), and yttria-stabilized zirconia (YSZ) made into discs shapes were classified into two groups: UV-treated (PTx) and non-treated (NTx). The materials in PTx groups were exposed to UV light for 12 min. Human gingival fibroblasts and TR146 epithelial cell lines co-cultured on the acellular dermal membrane were used to construct the 3D-OMM. After 4 days of culture, the discs were inserted into the holes prepared within the membrane of 3D-OMMs. The contour formed by the tissue was evaluated after 14 days of culture.

RESULTS

The UV treatment of abutment materials resulted in the formation of more non-pocket-tissue types among the PTx group (p = 0.002). Of all materials tested, soft tissue contour around YSZ showed higher scores for the non-pocket type in both non- and UV-treated groups.

CONCLUSIONS

The non-pocket type of tissue attachment was frequently found in all surfaces modified by photofunctionalization, particularly zirconia. The 3D-OMM can be used to evaluate the biological endpoints of implant surface modifications.

The Effect of UV Treatment on Surface Contact Angle, Fibroblast Cytotoxicity, and Proliferation with Two Types of Zirconia-Based Ceramics

UV photofunctionalization of Zirconia-based materials for abutment fabrication is a promising approach that might influence the formation of a sound peri-implant seal, thus promoting long-term soft and hard tissue implant integration. This study aimed to evaluate the effect of UV treatment of test specimens made by two different ZnO₂-based ceramic materials on the hydrophilicity, cell cytotoxicity, and proliferation of human gingival fibroblasts (HGFs). Two Zirconia-based materials, high-translucent and ultra-translucent multi-layered Zirconia (Katana, Kuraray Noritake, Japan), were used to prepare a total of 40 specimens distributed in two equally sized groups based on the material (n = 20). The same surface finishing protocol was applied for all specimens, as suggested by the manufacturer. Half the specimens from each group were treated with UV-C light for 48 h. Water contact angle (WCA), fibroblast cytotoxicity, and proliferation were investigated. The WCA values for the high-translucent Zirconia ranged from 69.9° ± 6.4° to 73.7° ± 13.9° for the treated/non-treated specimens and from 79.5° ± 12.8° to 83.4° ± 11.4° for the ultra-translucent multi-layered Zirconia, respectively. However, the difference was insignificant (F(16) = 3.50, p = 0.292). No significant difference was observed for the fibroblast cytotoxicity test. The results for proliferation revealed a significant difference, which was material-dependent (F(8) = 9.58, p = 0.005). We found that UV surface photofunctionalization of ZrO₂-based materials alters the human gingival fibroblast cell viability, which might produce favourable results for cell proliferation.

Comparison of the Clinical Outcomes of Titanium and Zirconia Implant Abutments: A Systematic Review of Systematic Reviews

Background: Dental implants are widely used and in order to answer to esthetic demands, zirconia has been introduced as an abutment material as an alternative to titanium. Several studies have been published on this topic, but the results have been often inconsistent. The objective of the present study is to systematically analyze the existing literature comparing clinical outcomes of titanium and zirconia implant abutments. The study was designed as a systematic review of systematic reviews. Methods: This systematic review is in accordance with the Transparent Reporting of Systematic Reviews and Meta-analyses. A MEDLINE/PubMed, Cochrane Database of Systematic Reviews and SCOPUS literature search was performed up to and including June 2021. Data were extracted independently by two reviewers and tAMSTAR2 was used to assess the quality of the systematic reviews. Results: The electronic search identified 1146 papers, and 175 duplicates were removed. After manual screening, 954 studies were excluded and the final analysis was conducted on 11 papers. Both mechanical and esthetic outcomes and biological complications were analyzed. Conclusions: It can be concluded that titanium abutments have a better mechanical resistance than zirconia ones. Plaque accumulation is reported to be slightly higher on titanium but without any significant inflammatory process. The esthetic outcomes seem to be more related to the thickness (>3 mm) of the soft tissues than to the abutment material.

Histologic Evaluation of Soft Tissues around Dental Implant Abutments: A Narrative Review

The basis for dental implant success comes not only with the titanium implant osseointegration but also depends on other factors such as the development of a soft tissue barrier, which protects the peri-implant bone from the oral environment. The characteristics of surfaces in contact with peri-implant soft tissues may affect the capacity of peri-implant mucosal cells to create a tight seal around the implant, thus influencing long-term implant success. Many histological studies on animals have been conducted on different materials to better understand their influence on peri-implant soft tissues, with the limitation that results from animal studies cannot be fully translated in humans. The aim of this review paper was to analyze the literature focusing on histological clinical studies in humans which have examined different materials or different surface treatments and their effects on peri-implant soft tissues. The research was conducted according to the following PICO question: “Do different implant/abutment materials affect peri-implant soft tissues adhesion and health?”. Nine articles were analyzed in this review. The results of this review show the influence of different abutment materials on the peri-implant soft tissues, and the need of further research regarding the effect that abutment materials, surface treatments, and surface properties have on soft tissues.

Soft tissue response to different abutment materials: A controlled and randomized human study using an experimental model

OBJECTIVES

Aim of this study was to compare the soft-tissue response to implant abutments made of titanium, zirconia, zirconia veneered with feldspar ceramics and PEEK by various clinical, histological, microbiological and molecular biological markers in an experimental model.

MATERIALS AND METHODS

40 experimental one-piece healing abutments of four different materials were mounted on bone-level implants in 20 volunteering patients (split-mouth design). After a three months period of open healing, clinical parameters at the abutments were assessed and adjacent mucosa was sampled for inflammatory cytokine mRNA-concentrations and histological analysis by a novel method. In addition, PISF-samples were obtained for the analysis of periodonto-pathogenic bacteria counts and active MMP-8 levels. Marginal bone level change was measured by intra oral radiographs.

RESULTS

Abutments of the different materials did not exhibit significant differences regarding clinical parameters, pathogenic bacteria counts or pro-inflammatory cytokine concentrations. Likewise, no significant differences were detected regarding soft tissue morphology or bone level change. Compared to titanium abutments, significantly less mononuclear inflammatory cells were detected in the mucosa at abutments made of zirconia veneered with feldspar ceramics.

CONCLUSIONS

All examined abutment materials exhibited a similar soft tissue response compared to titanium and histological data did not reveal early signs of elevated inflammation caused by PEEK- and feldspar-veneered zirconia abutments. Due to the short observation period and the small sample size, a final conclusion on the long term suitability of those abutment materials cannot be drawn. However, based on the presented data, we consider further studies on that subject as appropriate.

Integration of collagen fibers in connective tissue with dental implant in the transmucosal region

Dental implants have been widely accepted as an ideal therapy to replace the missing teeth for its good performance in aspects of mechanical properties and aesthetic outcomes. Its restorative success is contributed by not only the successful osseointegration of the implant but also the tight soft tissue integration, especially the collagen fibers, in the transmucosal region. Soft tissue attaching to the dental implant/abutment is overall similar, but in some aspects distinct with that seen around natural teeth and soft tissue integration can be enhanced via several surface modification methods. This review is going to focus on the current knowledge of the transmucosal zone around the dental implants (compared with natural teeth), and latest strategies in use to fine-tune the collagen fibers assembly in the connective tissue, in an attempt to enhance soft tissue integration.

Early soft tissue response to zirconium oxide and titanium healing abutments in vivo: a study in dogs

Background

This study aimed to investigate the clinical characteristics and early soft tissue response to zirconium oxide (Zr) and titanium (Ti) healing abutments in dogs.

Methods

Eight implants (four at each hemi-mandible) were inserted after bilateral mandibular third and fourth premolars and first molar extraction in dogs. Then, two Zr and two Ti healing abutments were connected to each unilateral mandible eight weeks later. The ligation method was used to create a peri-implant mucositis model and the 24 abutments were divided into four groups: Zr or Ti healing abutments with ligation (ZrL, TiL) or non-ligation (ZrN, TiN). The clinical indices, peri-implant crevicular fluid (PICF), and inflammatory cytokines (TNF-α and IL-1β) were measured and analyzed on days 0 and 28. The dogs were then sacrificed on day 28, soft tissues around the implants were harvested, and inflammation infiltration was tested by immunohistochemistry. Normal distribution test and two-way analysis of variance was used to analyze the data.

Results

The results showed that the clinical indices were similar for Zr and Ti healing abutments. There was significantly more PICF in the ZrL and TiL groups compared to in the ZrN and TiN groups. The TNF-α levels in PICF were significantly different between ZrL and ZrN groups on day 28. And the TNF-α levels in PICF were significantly higher in TiL group on day 28 than that on day 0. However, the number of inflammatory cells was not significantly different between the groups as measured by immunohistochemistry.

Conclusions

These data indicate that soft tissue responses to Zr healing abutments with peri-implant mucositis were comparable to those of Ti healing abutments in vivo, providing a theoretical foundation for the clinical application of Zr abutments.

Soft Tissue Interface with Various Kinds of Implant Abutment Materials

Various materials, such as titanium, zirconia and platinum-gold (Pt-Au) alloy, have been utilized for dental implant trans-mucosal parts. However, biological understanding of soft tissue reaction toward these materials is limited. The aim of this study was to compare the response of cell lines and soft tissue to titanium, zirconia and Pt-Au substrata. The surface hydroxyl groups and protein adsorption capacities of the substrata were measured. Next, gingival epithelial-like cells (Sa3) and fibroblastic cells (NIH3T3) were cultured on the materials, and initial cell attachment was measured. Immuno-fluorescent staining of cell adhesion molecules and cytoskeletal proteins was also performed. In the rat model, experimental implants constructed from various materials were inserted into the maxillary tooth extraction socket and the soft tissue was examined histologically and immunohistochemically. No significant differences among the materials were observed regarding the amount of surface hydroxyl groups and protein adsorption capacity. Significantly fewer cells of Sa3 and NIH3T3 adhered to the Pt-Au alloy compared to the other materials. The expression of cell adhesion molecules and a well-developed cytoskeleton was observed, both Sa3 and NIH3T3 on each material. In an animal model, soft tissue with supracrestal tissue attachment was observed around each material. Laminin-5 immuno-reactivity was seen in epithelia on both titanium and zirconia, but only in the bottom of epithelia on Pt-Au alloy. In conclusion, both titanium and zirconia, but not Pt-Au alloy, displayed excellent cell adhesion properties.

The effect of zirconia and titanium surfaces on biofilm formation and on host-derived immunological parameters

The aim of this study was to analyse the effect of zirconia and titanium surfaces on biofilm formation and host-derived parameters. Studies comparing zirconia and titanium surfaces were selected up to September 1, 2019. The outcome measures were surface roughness, contact angle, bacterial count, bacterial adherence, biofilm thickness, bacterial distribution, and specifically investigated biofilm and specific host-derived immunological parameters. Random-effects meta-analyses of in vitro and in vivo studies were conducted. A total of 39 studies were included for data extraction. In the systematic review data, 10 studies stated that zirconia accumulated less initial oral biofilm parameters, 16 investigations showed negligible inter-material differences, and only one study showed that zirconia attracted the most biofilm. However, in the meta-analysis, the bacterial coverage was found to be significantly superior for zirconia surfaces (P< 0.00001); the other outcome measures did not show any statistically significant differences between zirconia and titanium for the remaining parameters and the studies presented a substantial degree of heterogeneity. Overall, on the basis of the meta-analysis, the current data situation does not allow a clear preference for the use of zirconia or titanium.

Novel method to obtain human non-separated histological samples for the assessment of peri-implant soft tissue response: A feasibility study

OBJECTIVES

To introduce a standardized and less invasive clinical model that provides histological information on the abutment-mucosa interface in humans.

MATERIALS AND METHODS

New experimental healing abutments were left in an open healing position on bone-level implants in the interforaminal region of the mandibles in six edentulous patients. The one-piece abutments were hollow cylinder-shaped with two lateral openings that allow for ingrowth of the peri-implant mucosa into the central abutment cavity. After three months of healing, abutments and ingrown mucosa were sampled and processed for histological analysis in a non-separated resin-embedding technique. To test the validity of the new model, the ingrown tissue was compared to the peri-implant mucosa around the same samples.

RESULTS

None of the experimental abutments exhibited signs of failure, and all samples showed mucosal ingrowth to the inner-abutment cavity. Comparison of ingrown tissue and peri-implant mucosa revealed no significant differences regarding the traits: tissue morphology, quality of collagen fibers, and adherence to the abutment. Ingrown mucosa exhibited a tendency for higher leukocyte infiltration.

CONCLUSIONS

The presented model is a promising approach to reduce invasiveness during the sampling process for human non-separated abutment biopsies.

Peri-implant soft tissue integration in humans - influence of materials: A study protocol for a randomised controlled trial and a pilot study results

Background

Recently, there has been a growing interest in mucointegration as the formation of an early and long-standing soft tissue barrier seems essential for both the initial healing and long-term implant survival.

Aim

To develop an experimental method to characterize the mucointegration of different transgingival materials (titanium (Ti), polyetheretherketone (PEEK), polymethylmethacrylate (PMMA), zirconia (Zi), polymer infiltrated ceramic network (PICN), cobalt-chrome (Co–Cr), and lithium disilicate (LD)) in a human model.

Methods

The study is designed as a multi-part randomized controlled clinical trial. Ninety bone level Straumann implants will randomly receive an experimental, custom-made abutment to allow for the removal of the abutment together with the surrounding soft tissues using a punch biopsy device at 8 weeks of healing (10 per material). The specimens will be further processed for non‐decalcified histology, followed by histomorphometric analysis. The same protocol will be used for additional 90 implants-abutments, but during harvesting, soft tissues will be separated from the abutment and processed for immunohistochemistry in order to study tissue inflammation and vascularization, while the abutments will undergo SEM analysis. Additionally, in vitro analyses, including SEM and profilometry, will be performed in order to characterize surface topography of all experimental materials.

Conclusion

The limited number of pilot samples presented herein indicate that the use of custom-made abutments in humans is a reproducible method to study peri-implant soft tissue integration. This further intensifies the rationale to compare different abutment materials, used as transgingival components in daily practice, under the same conditions.

Immunohistochemical assessment of the peri-implant soft tissue around different abutment materials: A human study

BACKGROUND

Soft tissue reaction to dental implant abutments influences the sustainability of restoration. Several abutment materials, such as titanium and gold alloy, have been introduced for strength and esthetic solutions. Zirconia and titanium-base abutments have also become popular in recent years due to high esthetic demands.

PURPOSE

To investigate the immune cell infiltration into the soft tissue in response to different abutment materials.

MATERIALS AND METHODS

Twenty dental implants were placed in the posterior regions of 17 patients. Titanium, zirconia, gold alloy, and titanium-base were randomly selected for each patient on the day of surgery. After 8 weeks of healing, the abutments were removed along with 1 mm of peri-implant soft tissue. Immunohistochemical assessment was performed using labeled streptavidin-biotin to identify T cells, B cells, macrophages, plasma cells, and microvascular infiltration.

RESULTS

Gold alloy demonstrated an overall higher inflammatory cell infiltration and highest number of CD3⁺ , CD20⁺ , and CD 68⁺ cells (P value <.05). The number of plasma cell and new microvascular infiltrations among abutment materials was not significantly different.

CONCLUSION

Titanium, titanium-base, and zirconia abutments showed comparable infiltration profiles; gold alloy abutments showed the highest B-cell, T cell, and macrophage infiltration. None of the abutment materials caused clinical inflammation; hence, they can be effectively used.

Titanium Porous Coating Using 3D Direct Energy Deposition (DED) Printing for Cementless TKA Implants: Does It Induce Chronic Inflammation?

Because of the recent technological advances, the cementless total knee arthroplasty (TKA) implant showed satisfactory implant survival rate. Newly developed 3D printing direct energy deposition (DED) has superior resistance to abrasion as compared to traditional methods. However, there is still concern about the mechanical stability and the risk of osteolysis by the titanium (Ti) nanoparticles. Therefore, in this work, we investigated whether DED Ti-coated cobalt-chrome (CoCr) alloys induce chronic inflammation reactions through in vitro and in vivo models. We studied three types of implant surfaces (smooth, sand-blasted, and DED Ti-coated) to compare their inflammatory reaction. We conducted the in vitro effect of specimens using the cell counting kit-8 (CCK-8) assay and an inflammatory cytokine assay. Subsequently, in vivo analysis of the immune profiling, cytokine assay, and histomorphometric evaluation using C57BL/6 mice were performed. There were no significant differences in the CCK-8 assay, the cytokine assay, and the immune profiling assay. Moreover, there were no difference for semi-quantitative histomorphometry analysis at 4 and 8 weeks among the sham, smooth, and DED Ti-coated samples. These results suggest that DED Ti-coated printing technique do not induce chronic inflammation both in vitro and in vivo. It has biocompatibility for being used as a surface coating of TKA implant.