Experimental models for contamination of titanium surfaces and disinfection protocols

Experimental models for peri-implant diseases: a narrative review

OBJECTIVES

Peri-implant diseases, being the most common implant-related complications, significantly impact the normal functioning and longevity of implants. Experimental models play a crucial role in discovering potential therapeutic approaches and elucidating the mechanisms of disease progression in peri-implant diseases. This narrative review comprehensively examines animal models and common modeling methods employed in peri-implant disease research and innovatively summarizes the in vitro models of peri-implant diseases.

MATERIALS AND METHODS

Articles published between 2015 and 2023 were retrieved from PubMed/Medline, Web of Science, and Embase. All studies focusing on experimental models of peri-implant diseases were included and carefully evaluated.

RESULTS

Various experimental models of peri-implantitis have different applications and advantages. The dog model is currently the most widely utilized animal model in peri-implant disease research, while rodent models have unique advantages in gene knockout and systemic disease induction. In vitro models of peri-implant diseases are also continuously evolving to meet different experimental purposes.

CONCLUSIONS

The utilization of experimental models helps simplify experiments, save time and resources, and promote advances in peri-implant disease research. Animal models have been proven valuable in the early stages of drug development, while technological advancements have brought about more predictive and relevant in vitro models.

CLINICAL RELEVANCE

This review provides clear and comprehensive model selection strategies for researchers in the field of peri-implant diseases, thereby enhancing understanding of disease pathogenesis and providing possibilities for developing new treatment strategies.

Dynamic interactions between Candida albicans and different streptococcal species in a multispecies oral biofilm

The oral cavity is colonized by a plethora of bacteria, fungi, and archaea, including streptococci of the mitis group (MSG) and the yeast Candida albicans. This study aims to investigate the role of streptococcal species in the development of oral biofilm and the cross-kingdom interactions between some of the members of the commensal MSG and the pathogen yeast C. albicans using a multispecies supragingival biofilm model. A total of nine different in vitro biofilms were grown, quantified with culture analyses, and visually examined with confocal laser scanning microscopy (CLSM). A four-species biofilm without any streptococcal species was used as a basic biofilm. In each subsequent inoculum, one species of MSG was added and afterward combined with Streptococcus mutans. The eight-species biofilm contained all eight strains used in this study. Culture analyses showed that the presence of S. mutans in a four-species biofilm with Streptococcus oralis or S. oralis subsp. tigurinus did not differ significantly in C. albicans colony-forming unit (CFU) counts compared to biofilms without S. mutans. However, compared to other mitis species, Streptococcus gordonii combined with S. mutans resulted in the lowest CFUs of C. albicans. Visual observation by CLSM showed that biofilms containing both S. mutans and one species of MSG seemed to induce the formation of filamentous form of C. albicans. However, when several species of MSG were combined with S. mutans, C. albicans was again found in its yeast form.

The clinical effect of sodium hypochlorite oral rinse on peri-implantitis lesion: A pilot study

Peri-implantitis poses an imminent challenge to the field of implant dentistry. Considering the promising findings of sodium hypochlorite and periodontal lesions, the aim of the present study was to evaluate the clinical effects of sodium hypochlorite oral rinse on peri-implantitis lesions. Twelve peri-implantitis patients were instructed to rinse with 15 mL of a fresh solution of 0.25% sodium hypochlorite for 30 s twice a week for 3 months. At baseline and 3-month visits, probing depth and modified sulcular bleeding index were recorded at 6 points per lesion (mesiobuccal, buccal, distobuccal, mesiolingual, lingual, and distolingual). Individual and total bacterial loads of 18 pre-designated species of microorganisms were analyzed by real-time PCR methods. Probing depth decreased after the experiment, with an average difference of 1.1 mm and a standard deviation of 1.7 mm. The modified sulcular bleeding index decreased by a mean value of 0.8 with a standard deviation of 1.1. This study demonstrated the clinical effects of sodium hypochlorite oral rinse on peri-implantitis lesions and the reduction of periodontal probing depth and gingival bleeding index. This study suggested that the concentration of 0.25% be used for treatment of peri-implantitis.

Influence of eight debridement techniques on three different titanium surfaces: A laboratory study

OBJECTIVES

Debridement methods may damage implant surfaces. This in vitro study investigated eight debridement protocols across three implant surfaces to assess both biofilm removal and surface alterations.

MATERIAL AND METHODS

One hundred sixty commercially pure titanium discs were treated to simulate commercially available titanium implant surfaces-smooth, abraded and abraded and etched. Following inoculation with whole human saliva to create a mixed species biofilm, the surfaces were treated with eight debridement methods currently used for clinical peri-implantitis (n = 10). This included air abrasion using powders of glycine, sodium bicarbonate and calcium carbonate; conventional mechanical methods-piezoelectric scaler, carbon and stainless steel scalers; and a chemical protocol using 40% citric acid. Following treatment, remaining biofilm was analysed using scanning electron microscopy and crystal violet assays. For statistical analysis, ANOVA was applied (p < 0.05).

RESULTS

All debridement techniques resulted in greater than 80% reduction in biofilm compared with baseline, irrespective of the surface type. Glycine powder delivered through an air polishing system eliminated the most biofilm. Mechanical instruments were the least effective at eliminating biofilm across all surfaces and caused the greatest surface alterations. Citric acid was comparable with mechanical debridement instruments in terms of biofilm removal efficacy. Titanium surfaces were least affected by air abrasion protocols and most affected by mechanical methods.

CONCLUSIONS

Mechanical protocols for non-surgical debridement should be approached with caution. Glycine powder in an air polisher and 40% citric acid application both gave minimal alterations across all implant surfaces, with glycine the superior method in terms of biofilm removal.

Antibacterial Adhesion Strategy for Dental Titanium Implant Surfaces: From Mechanisms to Application

Dental implants are widely used to restore missing teeth because of their stability and comfort characteristics. Peri-implant infection may lead to implant failure and other profound consequences. It is believed that peri-implantitis is closely related to the formation of biofilms, which are difficult to remove once formed. Therefore, endowing titanium implants with anti-adhesion properties is an effective method to prevent peri-implant infection. Moreover, anti-adhesion strategies for titanium implant surfaces are critical steps for resisting bacterial adherence. This article reviews the process of bacterial adhesion, the material properties that may affect the process, and the anti-adhesion strategies that have been proven effective and promising in practice. This article intends to be a reference for further improvement of the antibacterial adhesion strategy in clinical application and for related research on titanium implant surfaces.

The Effect of Microcosm Biofilm Decontamination on Surface Topography, Chemistry, and Biocompatibility Dynamics of Implant Titanium Surfaces

Since the inception of dental implants, a steadily increasing prevalence of peri-implantitis has been documented. Irrespective of the treatment protocol applied for the management of peri-implantitis, this biofilm-associated pathology, continues to be a clinical challenge yielding unpredictable and variable levels of resolution, and in some cases resulting in implant loss. This paper investigated the effect of microcosm biofilm in vitro decontamination on surface topography, wettability, chemistry, and biocompatibility, following decontamination protocols applied to previously infected implant titanium (Ti) surfaces, both micro-rough -Sandblasted, Large-grit, Acid-etched (SLA)-and smooth surfaces -Machined (M). Microcosm biofilms were grown on SLA and M Ti discs. These were treated with TiBrushes (TiB), combination of TiB and photodynamic therapy (PDT), combination of TiB and 0.2%CHX/1%NaClO, plus or minus Ultraviolet-C (UV-C) radiation. Surface topography was evaluated by Scanning Electron Microscopy (SEM) and Laser Surface Profilometry. Surface function was analysed through wettability analysis. Surface chemistry evaluation of the discs was performed under SEM/Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Biocompatibility was tested with the cytocompatibility assay using human osteoblast-like osteosarcoma cell line (MG-63) cells. Elemental analysis of the discs disclosed chemical surface alterations resulting from the different treatment modalities. Titanium, carbon, oxygen, sodium, aluminium, silver, were identified by EDX as the main components of all the discs. Based on the data drawn from this study, we have shown that following the decontamination of Ti surfaces the biomaterial surface chemistry and topography was altered. The type of treatment and Ti surface had a significant effect on cytocompatibility (p = 0.0001). Although, no treatment modality hindered the titanium surface biocompatibility, parameters such as the use of chemical agents and micro-rough surfaces had a higher cytotoxic effect in MG-63 cells. The use of smooth surfaces, and photofunctionalisation of the TiO₂ layer had a beneficial effect on cytocompatibility following decontamination.

Efficiency of biofilm removal by combination of water jet and cold plasma: an in-vitro study

Background

Peri-implantitis therapy is a major problem in implantology. Because of challenging rough implant surface and implant geometry, microorganisms can hide and survive in implant microstructures and impede debridement. We developed a new water jet (WJ) device and a new cold atmospheric pressure plasma (CAP) device to overcome these problems and investigated aspects of efficacy in vitro and safety with the aim to create the prerequisites for a clinical pilot study with these medical devices.

Methods

We compared the efficiency of a single treatment with a WJ or curette and cotton swab (CC) without or with adjunctive use of CAP (WJ + CAP, CC + CAP) to remove biofilm in vitro from rough titanium discs. Treatment efficacy was evaluated by measuring turbidity up to 72 h for bacterial re-growth or spreading of osteoblast-like cells (MG-63) after 5 days with scanning electron microscopy. With respect to application safety, the WJ and CAP instruments were examined according to basic regulations for medical devices.

Results

After 96 h of incubation all WJ and CC treated disks were turbid but 67% of WJ + CAP and 46% CC + CAP treated specimens were still clear. The increase in turbidity after WJ treatment was delayed by about 20 h compared to CC treatment. In combination with CAP the cell coverage significantly increased to 82% (WJ + CAP) or 72% (CC + CAP), compared to single treatment 11% (WJ) or 10% (CC).

Conclusion

The newly developed water jet device effectively removes biofilm from rough titanium surfaces in vitro and, in combination with the new CAP device, biologically acceptable surfaces allow osteoblasts to grow. WJ in combination with CAP leads to cleaner surfaces than the usage of curette and cotton swabs with or without subsequent plasma treatment. Our next step will be a clinical pilot study with these new devices to assess the clinical healing process.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-022-02195-1.

Mechanical removal of biofilm on titanium discs: An in vitro study

The objective of this in vitro study was to evaluate surface cleanness and cytocompatibility following mechanical instrumentation of biofilm-contaminated titanium surfaces. Titanium discs (non-modified [Ti(s)] and shot-blasted surfaces [Ti(r)]) contaminated with Streptococcus gordonii were instrumented using four different techniques: (i) gauze soaked in saline (GS), (ii) ultra-sonic device (US), (iii) rotating nickel-titanium brush (TiB), or (iv) air-polishing device (AP). Non-contaminated, untreated titanium disks were used as controls (C). Residual deposits and cytocompatibility for osteoblast-like cells were evaluated using scanning electron microscopy, immunofluorescence, and reverse transcriptase polymerase chain reaction. While the number of residual bacteria on Ti(s) discs was close to 0 in all treatment groups, significantly higher mean numbers of residual bacteria were observed on Ti(r) discs for GS (152.7 ± 75.7) and TiB (33.5 ± 22.2) than for US (0) and AP (0). Instrumentation with US resulted in deposition of foreign material (mean area% of foreign material: 3.0 ± 3.6% and 10.8 ± 9.6% for Ti(s) and Ti(r) discs, respectively). AP was the most effective decontamination procedure in reducing bacteria without depositing residual foreign material on Ti(r) discs. TiB and AP were superior methods in restoring cytocompatibility, although no method of mechanical decontamination resulted in pristine levels of cytocompatibility.

Efficacy of titanium brush, 915 nm diode laser, citric acid for eradication of Staphylococcus aureus from implant surfaces

BACKGROUND

This study aimed to assess the efficacy of titanium brush, 915 nm diode laser, citric acid and the combination of latter two with titanium brush for decontamination of SLA surface mini-implants.

METHODS

Seventy-five mini-implants contaminated with Staphylococcus aureus (S. aureus) were randomly divided into five experimental groups (n = 12) of titanium brush (TiB), laser, citric acid (CA), brush-laser, and brush-acid, positive [n = 12; chlorhexidine mouthwash (CHX)] and negative [n = 2; phosphate buffered saline (PBS)] control groups and one no-treatment group (n = 1). After counting the colony forming units (CFUs), data were analyzed using the Kruskal-Wallis and Dunn post-hoc tests.

RESULTS

Regardless of the no-treatment and negative control groups, maximum and minimum CFUs were noted in the titanium brush and positive control groups. After CHX, minimum CFUs were noted in brush-acid group followed by brush-laser, laser, and acid groups. Generally, the Kruskal-Wallis test revealed a significant difference between the groups regarding the colony count (P < 0.001). Dunn post-hoc test showed that the difference between the titanium brush and acid-brush group was significant (P < 0.001) while the differences between the brush and laser groups with the brush-laser group were not significant (P > 0.077).

CONCLUSIONS

Combined use of titanium brush and citric acid yielded superior results compared to other groups in reduction of S. aureus on implant surface.

In vitro evaluation of chemical decontamination of titanium discs

Peri-implant diseases are caused by bacterial biofilm colonizing implant surfaces. Prevention and management of peri-implant mucositis and peri-implantitis rely on effective biofilm removal. This study aimed to evaluate biofilm removal and cytocompatibility following chemo-mechanical surface decontamination of biofilm-coated titanium discs. Biofilm-coated (Streptococcus gordonii) discs, with either non-modified (smooth) or modified (rough) surfaces, were instrumented using a sterile gauze soaked in one out of four solutions: saline (NaCl), alkaline electrized water (AEW), citric acid (CA) or N-acetyl-l-cysteine (NAC). Non-contaminated, untreated titanium discs served as controls (C). Residual deposits (bacteria and gauze fibers) and cytocompatibility for osteoblast-like cells were evaluated using SEM and immunofluorescence. Cytotoxicity was assessed using WST-8 assay and immunofluorescence. All protocols were equally effective in removing bacteria from smooth surfaces, while AEW and CA were found to be superior at rough surfaces. AEW and NAC were superior in promoting cytocompatibility over NaCl. NAC and CA had a strong cytotoxic effect on osteoblast-like and fibroblast cells. In conclusion, AEW may be beneficial in the decontamination of implant surfaces, effectively removing bacterial biofilm and restoring cytocompatibility.

Introducing a Novel Experimental Model for Osseo-Disintegration of Titanium Dental Implants Induced by Monobacterial Contamination: An In-Vivo Feasibility Study

Background and Objectives: The aim of the current study was to establish an osseo-disintegration model initiated with a single microorganism in mini-pigs. Materials and Methods: A total of 36 titanium dental implants (3.5 mm in diameter, 9.5 mm in length) was inserted into frontal bone (n: 12) and the basis of the corpus mandible (n: 24). Eighteen implants were contaminated via inoculation of Enterococcus faecalis. Six weeks after implant insertion, bone-to-implant contact (BIC) ratio, interthread bone density (ITBD), and peri-implant bone density (PIBD) were examined. In addition to that, new bone formation was assessed via fluorescence microscopy, histomorphometry, and light microscopical examinations. Results: Compared to the sterile implants, the contaminated implants showed significantly reduced BIC (p < 0.001), ITBD (p < 0.001), and PBD (p < 0.001) values. Around the sterile implants, the green and red fluorophores were overlapping and surrounding the implant without gaps, indicating healthy bone growth on the implant surface, whereas contaminated implants were surrounded by connective tissue. Conclusions: The current experimental model could be a feasible option to realize a significant alteration of dental-implant osseointegration and examine novel surface decontamination techniques without impairing local and systemic inflammatory complications.

Antimicrobial Photodynamic Therapy (aPDT) as a Disinfection and Biomodulation Approach in Implant Dentistry

This article is a highlight of the paper by Choe et al. in this issue of Photochemistry and Photobiology. In that review paper, the disinfection and biomodulation outcomes promoted by antimicrobial photodynamic therapy (aPDT) on peri-implantitis infection were stated and discussed. The killing of the oral pathogens by aPDT is based on the generation of reactive oxygen species (ROS). Besides that, biomodulation can also be provided by aPDT and improve the healing and modulate the inflammatory process. Although aPDT has shown positive effects on the treatment of peri-implantitis disease mainly as a complimentary technique, the authors suggested that more and standardize clinical studies are needed to support the clinical application of aPDT for that purpose. Also, the standardization of parameters related to the light source and photosensitizers is required. In addition, nano-based materials may improve aPDT performance against oral biofilms and could increase the hopes of overcoming dental implant failures.

Evaluation of decontamination methods of oral biofilms formed on screw-shaped, rough and machined surface implants: an ex vivo study

Background

To evaluate the effect of several representative decontamination methods of oral biofilms on different implant surfaces.

Material and methods

Eleven participants wore a hard resin splint carrying 6 rough (GC Aadva® implant; 3.3-mm diameter, 8-mm length) or machined (not commercially available) surface implants for 4 days to accumulate dental plaque naturally on the titanium surfaces of the implants. Apart from surface roughness, the morphology of all implants was identical. After detaching the implants from the splints, the ability of the following decontamination methods—gauze soaked in saline (G), ultrasonic scaler (US), air abrasive (Air), rotary stainless steel instrument (Rot), and Er:YAG laser (Las)—to cleanse the contaminated implant surface for 1 min extra-orally was tested. The control (Cont) group did not receive any decontamination. Scanning electron microscopic (SEM) investigation of one participant’s samples was employed to examine the post-instrumented implant surface for qualitative analysis, and bacterial culture of the remaining 10 participants’ samples was performed to count the number of colony-forming units (CFU) for quantitative analysis. The experimental sequence was initially performed for the rough surface implants and then similarly repeated for the machined surface implants. Bacterial CFU counts among the six groups were analyzed using the Steel-Dwass test, and differences between rough and machined surface implants were determined using the Mann-Whitney U test.

Results

G and Rot eliminated most biofilms on machined surface implants according to SEM analysis. G, Air, and Rot removed significantly more of the biofilms on rough and machined surface implants compared with US according to CFU counts. Moreover, G significantly reduced more biofilms than Las on machined surface implants. The analysis between rough and machined surface implants showed that Cont, G, and US were better able to cleanse biofilms on machined surface implants compared with rough surface implants.

Conclusions

Gauze soaked in saline and rotary stainless steel instruments may be advantageous for cleansing contaminated implant surfaces based on the qualitative and quantitative analyses. In contrast, air abrasives were not shown to be preferable in the qualitative analyses. Additionally, apart from the Er:YAG laser, the reduction of biofilms assessed in both qualitative and quantitative analyses demonstrated that all decontamination methods were better at cleansing machined surface implants compared with rough surface implants.

Análise físico-química da superfície de titânio após tratamento químico de descontaminação com clorexidina: estudo in vitro

Resumo Introdução Tratamentos têm sido propostos para a peri-implantite com o objetivo de descontaminar a superfície dos implantes, removendo microrganismos que podem estar associados à doença. Objetivo O objetivo deste estudo foi avaliar a ação in vitro de diferentes métodos de aplicação de digluconato de clorexidina (CLX) na descontaminação de discos de titânio (Ti) com microtopografia e seu efeito físico-químico sobre a superfície. Material e método Vinte discos de Ti foram expostos a inóculo de Escherichia coli por 24 horas. Foram distribuídos em quatro grupos de descontaminação (n=5): 1 - um minuto de exposição à solução de CLX 0,12%; 2 - dois minutos de exposição à solução de CLX 0,12%; 3 - esfregaço durante um minuto com gel de CLX 1%; 4 - esfregaço durante um minuto com gel de CLX 2%. O produto de cada disco foi diluído e plaqueado individualmente. Após 24 horas, realizou-se contagem das unidades de colônias formadas (UFC). Resultado O grupo com o menor número de crescimento de UFC foi o grupo 4 (0,20±0,37), com apenas UFC em uma das amostras. Seguido do grupo 2 (0,40±0,73), grupo 1 (18,60±33,96). O grupo 3 apresentou as maiores quantidades de UFC (36,07±41,39). Em todas as amostras, foi possível observar uma diminuição estatisticamente significante da concentração superficial de Ti, assim como um aumento de Oxigênio. Conclusão Pode-se concluir que o uso de CLX gel a 2% em superfícies de Ti com microtopografia contaminadas com E. coli propicia a eliminação das UFC e que sua aplicação resulta em diminuição do percentual de Ti e aumento do teor de O.

Deep sequencing of biofilm microbiomes on dental composite materials

Background: The microbiome on dental composites has not been studied in detail before. It has not been conclusively clarified whether restorative materials influence the oral microbiome. Methods: We used Illumina Miseq next-generation sequencing of the 16S V1-V2 region to compare the colonisation patterns of bovine enamel (BE) and the composite materials Grandio Flow (GF) and Grandio Blocs (GB) after 48 h in vivo in 14 volunteers. Applying a new method to maintain the oral microbiome ex vivo for 48 h also, we compared the microbiome on GF alone and with the new antimicrobial substance carolacton (GF+C). Results: All in vitro biofilm communities showed a higher diversity and richness than those grown in vivo but the very different atmospheric conditions must be considered. Contrary to expectations, there were only a few significant differences between BE and the composite materials GB and GF either in vivo or in vitro: Oribacterium, Peptostreptococcaceae [XI][G-1] and Streptococcus mutans were more prevalent and Megasphaera, Prevotella oulorum, Veillonella atypica, V. parvula, Gemella morbillorum, and Fusobacterium periodonticum were less prevalent on BE than on composites. In vivo, such preferences were only significant for Granulicatella adiacens (more prevalent on BE) and Fusobacterium nucleatum subsp. animalis (more prevalent on composites). On DNA sequence level, there were no significant differences between the biofilm communities on GF and GF+C. Conclusion: We found that the oral microbiome showed an increased richness when grown on various composites compared to BE in vitro, but otherwise changed only slightly independent of the in vivo or in vitro condition. Our new ex vivo biofilm model might be useful for pre-clinical testing of preventive strategies.

The effect of a decontamination protocol on contaminated titanium dental implant surfaces with different surface topography in edentulous patients

Objectives: To investigate if it is possible to achieve complete decontamination of dental implant surfaces with different surface characteristics.Materials and methods: Twelve implant pieces with an Osseotite^® surface and 12 implant pieces with a Ti-Unite^® surface were attached on to the complete lower dentures of six patients and were allowed to accumulate plaque for 30 days. When retrieved, the implant decontamination protocol used, involved both mechanical (PeriBrush™) and chemical (3% H₂O₂) decontamination. The number of colony forming units per millilitre was determined and the dominant micro-organisms in selected samples was identified by 16s rRNA gene amplicon sequencing. The effect of the titanium brush on the implant surface was examined by SEM.Results: Complete decontamination was achieved in five out of 24 implants (four Osseotite^® and one Ti-Unite^®). The mean CFU/ml detected after decontamination were 464.48 for Osseotite^® and 729.09 for Ti-Unite^® implants. On the surface of the implants in which complete decontamination was not achieved, all of the predominant bacteria identified were streptococci except for one which was identified as micrococcus. SEM images revealed that the surface features of the decontaminated implants were not significantly altered.Conclusions: Mechanical decontamination using a titanium brush supplemented with chemical treatment for one minute (3% H₂O₂) can achieve complete decontamination of implant surfaces in edentulous patients.

Osteoblast growth, after cleaning of biofilm-covered titanium discs with air-polishing and cold plasma

AIM

To investigate the effects of a combined biofilm removal with an optimized air polishing and a cold plasma device on cells in vitro.

MATERIALS AND METHODS

A 7-day-old biofilm was removed from rough titanium discs with an air-polishing device with erythritol powder (AP) or with a cold atmospheric pressure argon plasma (CAP) device or in combination of both (AP + CAP). The removal efficacy was evaluated by subsequent cell seeding of osteoblast-like cells (MG-63). The cell spreading was analysed after 5 days of incubation by scanning electron microscopy. Separately, the surface hydrophilicity was analysed by measuring the water contact angle (WCA) of the disc for each treatment method.

RESULTS

The mechanical plaque removal with AP rendered specimen conducive for cell growth, 85% of the surface was covered with cells. An advantage of the combination of AP + CAP was not detectable compared to AP (cell coverage ranged from 57% up to 75%). After sole CAP treatment, microorganisms re-grew and destroyed all cells. The WCA was reduced by all treatment methods.

CONCLUSION

An AP treatment has the potential to remove biofilm from rough implant surfaces completely. In contrast to our hypothesis, the combination of plasma and AP treatment did not enhance osteoblast spreading.