Experimental periodontitis and peri-implantitis in dogs

Peri-implantitis with a potential axis to brain inflammation: an inferential review

Peri-implantitis (PI) is a chronic, inflammatory, and infectious disease which affects dental implants and has certain similarities to periodontitis (PD). Evidence has shown that PD may be related to several types of systemic disorders, such as diabetes and insulin resistance, cardiovascular diseases, respiratory tract infections, adverse pregnancy outcomes, and neurological disorders. Furthermore, some types of bacteria in PD can also be found in PI, leading to certain similarities in the immunoinflammatory responses in the host. This review aims to discuss the possible connection between PI and neuroinflammation, using information based on studies about periodontal disorders, a topic whose connection with systemic alterations has been gaining the interest of the scientific community. Literature concerning PI, PD, and systemic disorders, such as neuroinflammation, brain inflammation, and neurological disorder, was searched in the PubMed database using different keyword combinations. All studies found were included in this narrative review. No filters were used. Eligible studies were analyzed and reviewed carefully. This study found similarities between PI and PD development, maintenance, and in the bacterial agents located around the teeth (periodontitis) or dental implants (peri-implantitis). Through the cardiovascular system, these pathologies may also affect blood-brain barrier permeability. Furthermore, scientific evidence has suggested that microorganisms from PI (as in PD) can be recognized by trigeminal fiber endings and start inflammatory responses into the trigeminal ganglion. In addition, bacteria can traverse from the mouth to the brain through the lymphatic system. Consequently, the immune system increases inflammatory mediators in the brain, affecting the homeostasis of the nervous tissue and vice-versa. Based on the interrelation of microbiological, inflammatory, and immunological findings between PD and PI, it is possible to infer that immunoinflammatory changes observed in PD can imply systemic changes in PI. This, as discussed, could lead to the development or intensification of neuroinflammatory changes, contributing to neurodegenerative diseases.

Intracellular infection of Cutibacterium acnes in macrophages of extensive peri-implantitis lesions: A clinical case series

Cutibacterium acnes is a facultative anaerobic, gram-positive rod, and a commensal bacterium of the body surface including oral cavity. A causal relationship between C. acnes and chronic granulomatous diseases, such as sarcoidosis and orthopedic implant-associated infections, has been previously reported. Typically, C. acnes has been observed inside macrophages, allowing evasion of host immunity, and triggering a persistent inflammatory response. However, such findings have not been reported in peri-implantitis lesions. In this case series, we collected inflamed tissues from extensive peri-implantitis lesions of eight patients. Out of the eight samples, seven tested positive for the 16 s rRNA gene of C. acnes by polymerase chain reaction, and six were positive by immunohistochemistry. Immunohistochemical staining revealed the presence of C. acnes in the cytoplasm of macrophages, suggesting a role in lesion formation. This finding may enhance our understanding of the pathophysiology of persistent peri-implantitis lesions and provide implications for future therapy.

The systemic impact of non-surgical treatment of peri-implantitis with or without adjunctive systemic metronidazole: Secondary analysis of a randomized clinical trial

OBJECTIVES

The aim of this study was to evaluate the systemic effect of non-surgical peri-implantitis treatment (NSPIT) with or without the administration of systemic metronidazole.

METHODS

In this secondary analysis from a previously published clinical trial (NCT03564301), peri-implantitis patients were randomized into two groups: test, receiving NSPIT plus 500 mg of oral systemic metronidazole three times a day for 7 days (n = 10); and control group, receiving NSPIT plus placebo (n = 11). Serum samples were obtained at baseline, 3 and 6 months after therapy to determine levels of inflammatory biomarkers, lipid fractions and complete blood counts.

RESULTS

Both treatment modalities produced improvements in clinical and radiographic parameters. After 6 months from NSPIT, a substantial reduction in C-reactive protein (6.9 mg/dL; 95% CI: 3.7 to 9.9, p < .001) and low-density lipoprotein cholesterol (21.8 mg/dL; 95% CI: -6.9 to 50.5, p = .013) as well as a modest increase in neutrophils counts (0.4 × 103/μL; 95% CI: -0.4 to 1.1, p = .010) was observed in the control group while the test group showed a significant reduction of TNF-α (110.1; 95% CI: 38.9 to 181.4, p = .004).

CONCLUSIONS

NSPIT showed a short-term beneficial systemic effect regardless of adjunctive use of systemic metronidazole.

Immune cell composition and inflammatory profile of human peri-implantitis and periodontitis lesions

Peri-implantitis (PI) and periodontitis (PD) are common oral inflammatory diseases, which seem to exhibit critical differences in some of their molecular features. Thus, we assessed the immune cell composition of PI and PD lesions and the corresponding inflammatory profile in soft tissues and crevicular fluid. PI, PD, and control patients were recruited (n = 62), and soft tissue biopsies were collected during surgery. Crevicular fluid around implant or tooth was collected. The proportions of major immune cell populations in tissues were analyzed by flow cytometry, and the inflammatory profile in tissue and crevicular fluid by a multiplex immunoassay. No significant difference was seen between PI and PD lesions in the proportions of immune cells. PI tissues showed an increased frequency of B cells in comparison with control tissues, along with higher levels of IL-1β, TNF-α, IL-4, and BAFF in tissue and crevicular fluid. Moreover, TNF-α, IL-17A, and BAFF were higher in PI tissues, but not in PD, than in control tissues. The immune cell composition did not differ significantly between PI and PD, but an enhanced inflammatory profile was seen in PI tissue. PI lesions were enriched in B cells, and displayed increased levels of IL-1β, TNF-α, IL-4, and BAFF in both tissue and crevicular fluid.

Prediabetes and poorly controlled type-2 diabetes as risk indicators for peri-implant diseases:A systematic review and meta-analysis

OBJECTIVE

The study answers the PECO question: "In adults with dental implants (P), do subjects suffering from type-2 diabetes or prediabetes (E) have worse peri-implant conditions (O) than subjects without type-2 diabetes and prediabetes (C)?". Prediabetes (5.7-6.4 % HbA1c), and the different qualities of glycemic control in type-2 diabetes; well-controlled (>8 % HbA1c), and poorly controlled (>8 % HbA1c) individuals; were classified according to the recommendations of the American Diabetes Association.

DATA

Predefined search keys were used with search terms including: Dental implant, diabetes mellitus, glycemic control and HbA1c.

SOURCES

An electronic search in the MEDLINE, Embase, and Cochrane libraries were conducted without any filters or language restrictions. Additionally, manual search of the reference lists were carried out to identify all relevant articles.

STUDY SELECTION

Eligibility criteria were cohort, case-control and cross-sectional studies that answerd our PECO question with at least 1 year of follow-up. From a total of 2660 records, 35 articles (1761 individuals) were included in the analysis. Meta-analytic difference in means for crestal bone loss was 1.2 mm [95 % CI=0.4; 2.1] in patients with prediabetes, 1.8 mm [CI=1.0; 2.7] in poorly controlled patients, whereas 0.4 mm [CI=-0.3; 1.1] in well-controlled individuals. Meta-regression showed that 1 % increase in HbA1c increased crestal bone loss by 0.24 mm.

CONCLUSIONS

Within the limitations of the study, patients with poorly controlled type-2 diabetes or prediabetes may have worse peri-implant conditions compared to patients without diabetes and well-controlled type-2 diabetes. Well-controlled type-2 diabetes is not a risk indicator for peri-implant diseases.

CLINICAL SIGNIFICANCE

Clinicians should measure blood HbA1c levels when planning implant-supported restorations, thus patients with undiagnosed or poorly controlled type-2 diabetes can be identified, that allows for glycemic level adjustment prior to dental implant surgery, ensuring peri-implant health. PROTOCOL REGISTRATION NUMBER: (CRD42022375263).

Preclinical comparison study of experimental peri-implantitis between alveolar ridge preservation and spontaneous healing sites in infected and noninfected tooth: a randomized blinded in vivo study

BACKGROUND

This study compared the progression of experimental peri-implantitis between alveolar ridge preservation (ARP) and spontaneous healing (SH) sites in infected (IT) and noninfected tooth (NIT).

METHODS

Bilateral mandibular third or fourth premolars of six beagle dogs were randomly assigned to IT and NIT groups. Before extraction, chronic dehiscence defects were created at the mesial root of mid-buccal area in IT group. Four weeks later, the mesial roots of the third and fourth premolars were extracted in all groups.ARP procedure was randomly conducted on one side of the extraction sockets using collagenated bovine bone substitutes and resorbable collagen membrane, and contralateral side was allowded spontaneous healing. After 12 weeks of healing, bone-level implants (ϕ 3.6 × 8.0 mm) were placed at the extraction sockets. Three months of ligature induced peri-implantitis and three months of spontaneous progression were allowed, with radiographs taken at each phase. Biopsies were retrieved at the implant site for histomorphometric, immunohistochemical, and polarized light-microscopic analyses.

RESULTS

Radiography demonstrated that the changes in the marginal bone level during the spontaneous progression period showed no significant differences between ARP and SH sites. Only small and/or nonsignificant differences in the progression of peri-implantitis were observed between ARP and SH sites in histomorphometric, immunohistochemical, and polarized light microscopic analyses. Additionally, the IT and NIT groups exhibited similar outcomes for most parameters.

CONCLUSION

ARP with xenogenic bone substitutes might provide similarly robust results as SH sites regarding the progression of experimental peri-implantitis, irrespective of the infected or noninfected nature of the site before tooth extraction.

Advanced Antimicrobial and Anti-Infective Strategies to Manage Peri-Implant Infection: A Narrative Review

Despite reductions in bacterial infection and enhanced success rate, the widespread use of systemic antibiotic prophylaxis in implant dentistry is controversial. This use has contributed to the growing problem of antimicrobial resistance, along with creating significant health and economic burdens. The basic mechanisms that cause implant infection can be targeted by new prevention and treatment methods which can also lead to the reduction of systemic antibiotic exposure and its associated adverse effects. This review aims to summarize advanced biomaterial strategies applied to implant components based on anti-pathogenic mechanisms and immune balance mechanisms. It emphasizes that modifying the dental implant surface and regulating the early immune response are promising strategies, which may further prevent or slow the development of peri-implant infection, and subsequent failure.

Characteristics of healthy peri-implant tissues

This article forms part of the themed issue on dental implants, with the general dentist being the main intended reader and with particular relevance to primary care dental professionals. It aims to describe the various characteristics of the implant in health, address contemporary developments in implant dentistry and offer some novel insights on the prevention of peri-implant diseases. A healthy implant exhibits specific histological, clinical and radiographic characteristics. Understanding such aspects leads to proper diagnosis and measures to maintain tissue integrity and prevent the development and progression of peri-implant diseases. Moreover, internationally and widely accepted definitions and recommendations based on expert consensus have been put forward to guide day-to-day clinical practice. This information should provide general practitioners with the means necessary to achieve the best possible outcome for their patients.

Single-cell analysis reveals a unique microenvironment in peri-implantitis

AIM

This study aimed to reveal the unique microenvironment of peri-implantitis through single-cell analysis.

MATERIALS AND METHODS

Herein, we performed single-cell RNA sequencing (scRNA-seq) of biopsies from patients with peri-implantitis (PI) and compared the results with healthy individuals (H) and patients with periodontitis (PD).

RESULTS

Decreased numbers of stromal cells and increased immune cells were found in the PI group, which implies a severe inflammatory infiltration. The fibroblasts were found to be heterogeneous and the specific pro-inflammatory CXCL13+ sub-cluster was more represented in the PI group, in contrast to the PD and H groups. Furthermore, more neutrophil infiltration was detected in the PI group than in the PD group, and cell-cell communication and ligand-receptor pairs revealed most neutrophils were recruited by CXCL13+ fibroblasts through CXCL8/CXCL6-CXCR2/CXCR1. Notably, our study demonstrated that the unique microenvironment of the PI group promoted the differentiation of monocyte/macrophage lineage cells into osteoclasts, which might explain the faster and more severe bone resorption in the progression of PI than PD.

CONCLUSIONS

Collectively, this study suggests a unique immune microenvironment of PI, which may explain the differences between PI and PD in the clinic. These outcomes will aid in finding new specific and effective treatments for PI.

Etiology, pathogenesis and treatment of peri-implantitis: A European perspective

Peri-implantitis is a plaque-associated pathological condition occurring in tissues around dental implants. It is characterized by inflammation in the peri-implant mucosa and progressive loss of supporting bone. Over the last 30 years, peri-implantitis has become a major disease burden in dentistry. An understanding of the diagnosis, etiology and pathogenesis, epidemiology, and treatment of peri-implantitis must be a central component in undergraduate and postgraduate training programs in dentistry. In view of the strong role of European research in periodontology and implant dentistry, the focus of this review was to address peri-implantitis from a European perspective. One component of the work was to summarize new and reliable data on patients with dental implants to underpin the relevance of peri-implantitis from a population perspective. The nature of the peri-implantitis lesion was evaluated through results presented in preclinical models and evaluations of human biopsy material together with an appraisal of the microbiological characteristics. An overview of strategies and outcomes presented in clinical studies on nonsurgical and surgical treatment of peri-implantitis is discussed with a particular focus on end points of therapy and recommendations presented in the S3 level Clinical Practice Guideline for the prevention and treatment of peri-implant diseases.

Comprehensive treatment protocol for peri-implantitis: an up-to date narrative review of the literature

This narrative review describes up-to-date treatment options for peri-implantitis and proposes a treatment protocol and flowchart based on the current scientific evidence. Peri-implantitis treatment should be based on the phased treatment protocol for periodontitis, which is a continuous flow of decisions for extraction, nonsurgical and surgical treatments with step-by-step re-evaluation. The protocol's goals are to fulfill the success criteria for peri-implantitis treatment (probing depth of ≤5 mm, and absence of bleeding on probing, suppuration, and progressive bone loss) and to halt disease progression. Fixtures with peri-implantitis can initially be classified as failed or failing. A failed implant needs to be removed. In contrast, nonsurgical and surgical treatments can be applied to a failing implant. Nonsurgical treatment should be the initial treatment for failing implants; however, sole nonsurgical treatment was regarded as inefficient for peri-implantitis. Recent studies have found that the adjunctive use of antibiotics to nonsurgical debridement increased the success of nonsurgical treatment for peri-implantitis. Surgical treatments can be classified into resective, access, and reconstructive surgeries. The technique should be selected according to the patient's bone defect configuration, which relate to regenerative potential. Various combinations of decontamination methods (e.g., mechanical, chemical, and pharmacological approaches) are required to achieve absolute surface decontamination. Clinicians should select an appropriate surface decontamination strategy according to the purpose of surgery. After signs of disease disappear and its progression is halted through active peri-implantitis treatment, it is necessary to enroll patients into maintenance programs. Compliance of patients with the maintenance program reduces the recurrence of peri-implantitis and sustains clinical success after treatment. Maintenance visits should include professional plaque control and hygiene care reinforcement for patients, and their interval should be set according to individual peri-implantitis risk. Clinicians should remind that peri-implantitis treatment is not a single procedure, but rather a continuing cycle of treatment and re-evaluation.

Titanium particles in peri-implantitis: distribution, pathogenesis and prospects

Peri-implantitis is one of the most important biological complications in the field of oral implantology. Identifying the causative factors of peri-implant inflammation and osteolysis is crucial for the disease's prevention and treatment. The underlying risk factors and detailed pathogenesis of peri-implantitis remain to be elucidated. Titanium-based implants as the most widely used implant inevitably release titanium particles into the surrounding tissue. Notably, the concentration of titanium particles increases significantly at peri-implantitis sites, suggesting titanium particles as a potential risk factor for the condition. Previous studies have indicated that titanium particles can induce peripheral osteolysis and foster the development of aseptic osteoarthritis in orthopedic joint replacement. However, it remains unconfirmed whether this phenomenon also triggers inflammation and bone resorption in peri-implant tissues. This review summarizes the distribution of titanium particles around the implant, the potential roles in peri-implantitis and the prevalent prevention strategies, which expects to provide new directions for the study of the pathogenesis and treatment of peri-implantitis.

Mucosal bleeding correlates with submucosal microbial dysbiosis in peri-implant mucositis of patients with periodontitis

OBJECTIVES

This study aimed to investigate the relationship between microbial communities and the severity of peri-implant mucosal bleeding in peri-implant mucositis.

MATERIALS AND METHODS

Submucosal plaque samples were collected from 54 implants divided into the healthy implant (HI) group, peri-implant mucositis (PM) group, and peri-implantitis (PI) group. Sequencing of 16S rRNA was performed using the Illumina MiSeq platform. Alpha diversity (i.e., Shannon and Chao index) and beta diversity were used to measure microbial diversity within and between microbial communities, respectively. Differences in microbial taxa between groups were assessed via linear discriminate analysis effect size. Correlation between the modified sulcus bleeding index (mSBI) and microbial dysbiosis index (MDI) was examined using Spearman correlation analysis and linear models.

RESULTS

The submucosal bacterial richness (Chao index) was positively correlated with the mean mSBI in the PM group. As the mean mSBI increased in the PM group, the beta diversity became closer to that of the PI group. In the PM group, the abundances of 47 genera were significantly correlated with the mean mSBI, and the MDI was positively associated with the mean mSBI. Fourteen of the forty-seven genera were discriminative taxa between the HI and PI groups, and the abundances of these biomarkers became closer to those in the PI group in the progression of peri-implant disease.

CONCLUSIONS

A higher mSBI value corresponded to a higher risk of microbial dysbiosis in peri-implant mucositis. The biomarkers identified may be useful for monitoring the progression of peri-implant disease.

Progression of experimental peri-implantitis in guided bone regeneration and pristine bone: A preclinical in vivo study

BACKGROUND

Guided bone regeneration (GBR) is the most widely used technique for overcoming the deficiency of alveolar bone. However, the progression of peri-implantitis in regenerative and pristine bone sites has not been fully investigated. The aim of this study is to compare experimental peri-implantitis around implants placed in pristine bone and GBR sites.

METHODS

Bilateral  mandibular first molars were extracted from six beagle dogs, and standardized horizontal ridge defect was simultaneously created at predetermined site in unilateral mandible. After 8 weeks, guided bone regeneration procedure was conducted at the defect site. After 16 weeks, implants (ϕ 3.6×8.0 mm) were placed at both extracted sites. This study included 3 months of active breakdown and another 3 months of spontaneous progression period. Radiographs were taken at each phase and specimens were obtained for histological, immunohistochemical, and polarized light microscopic analysis.

RESULTS

Marginal bone loss around implant did not show the significant differences between pristine bone and GBR sites during spontaneous progression period. In immunohistochemical analysis, inflammatory and immune-related cells were predominantly detected in peri-implantitis-affected area rather than unaffected area. In the polarized light microscopic analysis, substantial reductions in the amount and thickness of collagen fibers were observed in peri-implantitis-affected area compared with unaffected tissues. However, there were no significant differences in histological, immunohistochemical, polarized light microscopic outcomes between pristine bone and GBR sites.

CONCLUSION

Previous hard tissue grafting at the implant sites did not affect experimental peri-implantitis and exhibited similar radiographic, histological, immunohistochemical, and polarized light microscopic outcomes compared with those of pristine bone sites.

Influence of antiresorptive/antiangiogenic therapy on the extension of experimentally induced peri-implantitis lesions

OBJECTIVES

To investigate the extension of experimentally induced peri-implantitis lesions under various antiresorptive and antiangiogenic medications.

MATERIAL AND METHODS

Fourty-eight albino rats had randomly received the following medications (dual application, n = 8 each): (1) amino-bisphosphonate (zoledronate) (Zo), (2) RANKL inhibitor (denosumab) (De), (3) antiangiogenic (bevacizumab) (Be), (4) Zo+Be, (5) De+Be, or (6) no medication (Co). Ligature- and lipopolysaccharide-induced peri-implantitis lesions were established at 2 maxillary implants over a period of 16 weeks. Histological (e.g., apical extension and surface area of the inflammatory cell infiltrate-aICT, ICT; defect length; defect width; CD68 positive cells) and bone micromorphometric (μCT) outcomes were assessed. The animal was defined as a statistical unit.

RESULTS

A total of n = 38 animals (Zo = 6, De = 6, Be = 8, Zo + Be = 6, De + Be = 5, Co = 7) were analyzed. ICT's were commonly marked by a positive CD68 antigen reactivity. Comparable median aICT (lowest-Zo: 0.53 mm; highest-Be: 1.22 mm), ICT (lowest-De + Be: 0.00 mm2; highest-Co: 0.49 mm2), defect length (lowest-Zo: 0.90 mm; highest-Co: 1.93 mm) and defect width (lowest-De+Be: 1.27 mm; highest-Be: 1.80 mm) values were noted in all test and control groups. Within an inner (diameter: 0.8 mm) cylindric volume of interest, the bone microstructure did not significantly differ between groups.

CONCLUSIONS

The present analysis did not reveal any marked effects of various antiresorptive/ antiangiogenic medications on the extension of experimentally induced peri-implantitis lesions.

CLINICAL RELEVANCE

The extension of peri-implantitis lesions may not be facilitated by the antiresorptive and antiangiogenic medications investigated.

Antibacterial Evaluation of Zirconia Coated with Plasma-Based Graphene Oxide with Photothermal Properties

The alternative antibacterial treatment photothermal therapy (PTT) significantly affects oral microbiota inactivation. In this work, graphene with photothermal properties was coated on a zirconia surface using atmospheric pressure plasma, and then the antibacterial properties against oral bacteria were evaluated. For the graphene oxide coating on the zirconia specimens, an atmospheric pressure plasma generator (PGS-300, Expantech, Suwon, Republic of Korea) was used, and an Ar/CH₄ gas mixture was coated on a zirconia specimen at a power of 240 W and a rate of 10 L/min. In the physiological property test, the surface properties were evaluated by measuring the surface shape of the zirconia specimen coated with graphene oxide, as well as the chemical composition and contact angle of the surface. In the biological experiment, the degree of adhesion of Streptococcus mutans (S. mutans) and Porphyromonas gingivalis (P. gingivalis) was determined by crystal violet assay and live/dead staining. All statistical analyzes were performed using SPSS 21.0 (SPSS Inc., Chicago, IL, USA). The group in which the zirconia specimen coated with graphene oxide was irradiated with near-infrared rays demonstrated a significant reduction in the adhesion of S. mutans and P. gingivalis compared with the group not irradiated. The oral microbiota inactivation was reduced by the photothermal effect on the zirconia coated with graphene oxide, exhibiting photothermal properties.

Physiopathology of peri-implant diseases

BACKGROUND

Peri-implant health is characterized by the absence of clinical signs of soft tissue inflammation. Peri-implant diseases are initiated by the presence of bacterial biofilms and share a similar etiology as that involved in the onset of periodontal diseases.

PURPOSE

To summarize available evidence on the physiopathology of peri-implant diseases with emphasis on similarities and differences with periodontal diseases.

MATERIALS AND METHODS

Evidence on the biologic mechanisms involved in the pathogenesis of peri-implant mucositis and peri-implantitis were explored in the recent scientific literature.

RESULTS

Findings of studies in animals and in humans indicate that experimental peri-implant mucositis leads to a larger inflammatory connective tissue infiltrate and to a higher frequency of bleeding sites around implants compared with teeth. Tissue destruction at experimental peri-implantitis sites is more pronounced compared with that at experimental periodontitis sites. Although human periodontitis and peri-implantitis lesions share similarities with respect to etiology and clinical features, they represent distinct entities from a physiopathologic point of view.

CONCLUSIONS

Diagnosis of peri-implant health requires a clinical examination to confirm absence of peri-implant soft tissue inflammation. In order to make a correct diagnosis and select the appropriate therapeutic steps to manage peri-implant diseases, knowledge of their pathogenetic mechanisms is required.

Bone defect development in experimental canine peri-implantitis models: a systematic review

PURPOSE

To provide a systematic overview of preclinical research regarding bone defect formation around different implant surfaces after ligature-induced peri-implantitis models in dogs. Two focused questions were formulated: 'How much bone loss can be expected after a certain time of ligature induced peri-implantitis?' and 'Do different implant types, dog breeds and study protocols differ in their extent of bone loss?'

MATERIALS AND METHODS

A systematic literature search was conducted on four databases (MEDLINE, Web of Science, EMBASE and Scopus). Observations, which consisted of bone defects measured directly after ligature removal in canine models, were included and analysed. Two approaches were used to analyse the relatively heterogeneous studies that fulfilled the inclusion criteria. First, separate simple linear regressions were calculated for each study and implant surface, for which observations were available across multiple time points. Second, a linear mixed model was specified for the observations at 12 weeks after ligature initiation, and assessing the potential influencing factors on defect depth was explored using lasso regularisation.

RESULTS

Thirty-six studies with a total of 1082 implants were included after. Bone loss was determined at different time points, either with clinical measurements radiographically or histologically. Different implant groups [e.g. turned, sand-blasted-acid-etched (SLA), titanium-plasma-sprayed (TPS) and other rough surfaces] were assessed and described in the studies. A mean incremental defect depth increase of 0.08 mm (SD: -0.01-0.28 mm) per week was observed. After 12 weeks, the defect depths ranged between 0.7 and 5 mm. Based on the current data set, implant surface could not be statistically identified as an essential factor in defect depth after 12 weeks of ligature-induced peri-implantitis.

CONCLUSION

Expectable defect depth after a specific time of ligature-induced peri-implantitis can vary robustly. It is currently impossible to delineate apparent differences in bone loss around different implant surfaces.

Influence of epigenetics on periodontitis and peri-implantitis pathogenesis

Periodontitis is a disease characterized by tooth-associated microbial biofilms that drive chronic inflammation and destruction of periodontal-supporting tissues. In some individuals, disease progression can lead to tooth loss. A similar condition can occur around dental implants in the form of peri-implantitis. The immune response to bacterial challenges is not only influenced by genetic factors, but also by environmental factors. Epigenetics involves the study of gene function independent of changes to the DNA sequence and its associated proteins, and represents a critical link between genetic and environmental factors. Epigenetic modifications have been shown to contribute to the progression of several diseases, including chronic inflammatory diseases like periodontitis and peri-implantitis. This review aims to present the latest findings on epigenetic influences on periodontitis and to discuss potential mechanisms that may influence peri-implantitis, given the paucity of information currently available.

Role of chitosan in titanium coatings. trends and new generations of coatings

Survival studies of dental implants currently reach high figures. However, considering that the recipients are middle-aged individuals with associated pathologies, research is focused on achieving bioactive surfaces that ensure osseointegration. Chitosan is a biocompatible, degradable polysaccharide with antimicrobial and anti-inflammatory properties, capable of inducing increased growth and fixation of osteoblasts around chitosan-coated titanium. Certain chemical modifications to its structure have been shown to enhance its antibacterial activity and osteoinductive properties and it is generally believed that chitosan-coated dental implants may have enhanced osseointegration capabilities and are likely to become a commercial option in the future. Our review provided an overview of the current concepts and theories of osseointegration and current titanium dental implant surfaces and coatings, with a special focus on the in vivo investigation of chitosan-coated implants and a current perspective on the future of titanium dental implant coatings.

Study on the immunopathological effect of titanium particles in peri-implantitis granulation tissue: a case-control study

Objectives

To identify titanium particles (TPs) in biopsy specimens harvested from peri‐implantitis lesions and secondarily to study the histopathological characteristics in peri‐implantitis compared to periodontitis, in order to evaluate whether the presence of TPs could alter respective inflammatory patterns.

Material and methods

Biopsies containing granulation tissue were harvested during routine surgical treatment in 39 peri‐implantitis cases and 35 periodontitis controls. Serial sections were obtained using titanium‐free microtome blades. The first and last sections of the peri‐implantitis specimens were used for identification of TPs by scanning electron microscopy coupled with dispersive X‐ray spectrometry. Intermediate sections and periodontitis specimens were processed for descriptive histological study using haematoxylin–eosin staining and for immunohistochemical analysis using CD68, IL‐6, Nf‐kB and VEGF markers.

Results

TPs were identified in all peri‐implantitis specimens as free metal bodies interspersed within granulation tissue. However, presence of macrophages or multinucleated giant cells engulfing the TPs were not identified in any specimen. Peri‐implantitis granulations were characterized by a chronic inflammatory infiltrate rich in neutrophils. About half of peri‐implantitis patients exhibited a subacute infiltrate characterized with lymphocytes interweaved with neutrophils and eosinophils. When compared to periodontitis, peri‐implantitis tissues showed higher proportions of macrophages and a more intense neovascularization, based on significantly higher expression of CD68 and VEGF respectively.

Conclusion

TPs were identified in all peri‐implantitis specimens, but without evidencing any foreign body reaction suggestive for direct pathological effects of TPs. The peri‐implantitis granulation tissue was characterized by intense neovascularization and presence of a chronic inflammatory infiltrate dominated by plasma cells, neutrophils and macrophages.

3D engineered human gingiva fabricated with electrospun collagen scaffolds provides a platform for in vitro analysis of gingival seal to abutment materials

In order to advance models of human oral mucosa towards routine use, these models must faithfully mimic the native tissue structure while also being scalable and cost efficient. The goal of this study was to develop a low-cost, keratinized human gingival model with high fidelity to human attached gingiva and demonstrate its utility for studying the implant-tissue interface. Primary human gingival fibroblasts (HGF) and keratinocytes (HGK) were isolated from clinically healthy gingival biopsies. Four matrices, electrospun collagen (ES), decellularized dermis (DD), type I collagen gels (Gel) and released type I collagen gels (Gel-R)) were tested to engineer lamina propria and gingiva. HGF viability was similar in all matrices except for Gel-R, which was significantly decreased. Cell penetration was largely limited to the top layers of all matrices. Histomorphometrically, engineered human gingiva was found to have similar appearance to the native normal human gingiva except absence of rete pegs. Immunohistochemical staining for cell phenotype, differentiation and extracellular matrix composition and organization within 3D engineered gingiva made with electrospun collagen was mostly in agreement with normal gingival tissue staining. Additionally, five types of dental material posts (5-mm diameter x 3-mm height) with different surface characteristics were used [machined titanium, SLA (sandblasted-acid etched) titanium, TiN-coated (titanium nitride-coated) titanium, ceramic, and PEEK (Polyetheretherketone) to investigate peri-implant soft tissue attachment studied by histology and SEM. Engineered epithelial and stromal tissue migration to the implant-gingival tissue interface was observed in machined, SLA, ceramic, and PEEK groups, while TiN was lacking attachment. Taken together, the results suggest that electrospun collagen scaffolds provide a scalable, reproducible and cost-effective lamina propria and 3D engineered gingiva that can be used to explore biomaterial-soft tissue interface.

Antibacterial Effect of Functionalized Polymeric Nanoparticles on Titanium Surfaces Using an In Vitro Subgingival Biofilm Model

This investigation aimed to evaluate the antibacterial effect of polymeric nanoparticles (NPs), functionalized with calcium, zinc, or doxycycline, using a subgingival biofilm model of six bacterial species (Streptococcus oralis,Actinomyces naeslundii, Veillonela parvula, Fusobacterium nucleatum, Porphyromonas gingivalis, and Aggregatibacter actinomycetemcomitans) on sandblasted, large grit, acid-etched titanium discs (TiDs). Undoped NPs (Un-NPs) or doped NPs with calcium (Ca-NPs), zinc (Zn-NPs), or doxycycline (Dox-NPs) were applied onto the TiD surfaces. Uncovered TiDs were used as negative controls. Discs were incubated under anaerobic conditions for 12, 24, 48, and 72 h. The obtained biofilm structure was studied by scanning electron microscopy (SEM) and its vitality and thickness by confocal laser scanning microscopy (CLSM). Quantitative polymerase chain reaction of samples was used to evaluate the bacterial load. Data were evaluated by analysis of variance (p < 0.05) and post hoc comparisons with Bonferroni adjustments (p < 0.01). As compared with uncovered TiDs, Dox-NPs induced higher biofilm mortality (47.21% and 85.87%, respectively) and reduced the bacterial load of the tested species, after 72 h. With SEM, scarce biofilm formation was observed in Dox-NPs TiDs. In summary, Dox-NPs on TiD reduced biofilm vitality, bacterial load, and altered biofilm formation dynamics.

Intranuclear cell uptake and toxicity of titanium dioxide and zirconia particles as well as bacterial adhesion on dental titanium- and zirconia-implants

OBJECTIVE

Previous studies have shown that particles can be released from dental titanium (Ti)- and zirconia (ZrO₂)-implants. Titanium dioxide (TiO₂)- and ZrO₂-particles were compared regarding their toxicity and intranuclear cell uptake as well as the adhesion of various anaerobic bacteria on Ti- and ZrO₂-implants.

METHODS

Cyto- and genotoxicity of TiO₂-microparticles (TiO₂-MPs) and TiO₂-nanoparticles (TiO₂-NPs) in periodontal ligament (PDL)-hTERT cells were determined with XTT test and DNA damage with comet assay. Particle sizes of TiO₂- and ZrO₂-particles were measured with scanning electron microscope. Intranuclear uptake in PDL-hTERT cells was determined with laser scanning confocal microscopy. Adhesions of relevant anaerobic mouth bacteria Porphyromonas gingivalis, Prevotella intermedia and Aggregatibacter actinomycetemcomitans on Ti- and ZrO₂-implants were investigated by cultivation and counting bacterial colonies.

RESULTS

Particle size measurements revealed that 99% of the TiO₂-NPs had a size below 100 nm and 88% of the TiO₂-MPs sizes were between 50 and 200 nm. Following EC₅₀ values were found for particles (mg/l): 92 (TiO₂-MPs) and 15 (TiO₂-NPs). A significant increase in olive tail moment (OTM) was found for TiO₂-NPs at a concentration of 1/10 EC₅₀. TiO₂- and ZrO₂-NPs had a higher intranuclear cell uptake efficiency, compared to corresponding TiO₂- and ZrO₂-MPs. All investigated particles could be detected in cell nucleus. Adhesion of all investigated bacterial species was significantly higher on Ti-implants, compared to ZrO₂-implants.

CONCLUSION

Ti usually develops an oxide layer (TiO₂). Particles released from Ti-implants should be TiO₂-particles or Ti-particles coated with a TiO₂-layer. Toxicity of released Ti-particles depends on their oxidation state and on their size (NP or MP). Particularly, NPs were more cyto- and genotoxic compared to the corresponding MPs. TiO₂- and ZrO₂-NPs showed a significant increase in the intranuclear cell uptake ratio at higher exposure concentration, compared to lower concentrations and consequently might lead to a higher potential of DNA damage. Adhesion of bacteria to ZrO₂-implants is reduced, compared to Ti-implants. Therefore, ZrO₂-implants might contribute to reduced biological complications (e.g. periimplantitis).

C3-targeted host-modulation approaches to oral inflammatory conditions

Periodontitis is an inflammatory disease caused by biofilm accumulation and dysbiosis in subgingival areas surrounding the teeth. If not properly treated, this oral disease may result in tooth loss and consequently poor esthetics, deteriorated masticatory function and compromised quality of life. Epidemiological and clinical intervention studies indicate that periodontitis can potentially aggravate systemic diseases, such as, cardiovascular disease, type 2 diabetes mellitus, rheumatoid arthritis, and Alzheimer disease. Therefore, improvements in the treatment of periodontal disease may benefit not only oral health but also systemic health. The complement system is an ancient host defense system that plays pivotal roles in immunosurveillance and tissue homeostasis. However, complement has unwanted consequences if not controlled appropriately or excessively activated. Complement overactivation has been observed in patients with periodontitis and in animal models of periodontitis and drives periodontal inflammation and tissue destruction. This review places emphasis on a promising periodontal host-modulation therapy targeting the complement system, namely the complement C3-targeting drug, AMY-101. AMY-101 has shown safety and efficacy in reducing gingival inflammation in a recent Phase 2a clinical study. We also discuss the potential of AMY-101 to treat peri-implant inflammatory conditions, where complement also seems to be involved and there is an urgent unmet need for effective treatment.

Adjunctive benefits of systemic metronidazole on non-surgical treatment of peri-implantitis. A randomized placebo-controlled clinical trial

AIM

To study clinical, radiographic, and microbiological outcomes after non-surgical therapy of peri-implantitis with or without adjunctive systemic metronidazole.

MATERIALS AND METHODS

A randomized placebo-controlled clinical trial was carried out in 32 subjects (62 implants) diagnosed with peri-implantitis. Implants received a mechanical non-surgical debridement session and systemic metronidazole or placebo. Clinical, radiographic, and microbiological outcomes were evaluated at baseline, 3, 6, and 12 months.

RESULTS

After 12 months, the test treatment resulted in significantly greater PPD reduction (2.53 vs. 1.02 mm) and CAL gain (2.14 vs. 0.53 mm) (p value <.05) in comparison with placebo. The test treatment also resulted in additional radiographic bone gain (2.33 vs. 1.13 mm) compared with placebo (p value <.05). There was a significantly greater decrease in Porphyromonas gingivalis, Tannerella forsythia, and Campylobacter rectus counts compared with the control group (p value <.05). At the end of follow-up, 56.3% of patients met the success criteria in the test group and 25% in the control group.

CONCLUSIONS

The use of systemic metronidazole as an adjunct to non-surgical treatment of peri-implantitis resulted in significant additional improvements in clinical, radiographic, and microbiological parameters after 12 months of follow-up. This study is registered in ClinicalTrials.gov (NCT03564301).

Pre-Clinical Models in Implant Dentistry: Past, Present, Future

Biomedical research seeks to generate experimental results for translation to clinical settings. In order to improve the transition from bench to bedside, researchers must draw justifiable conclusions based on data from an appropriate model. Animal testing, as a prerequisite to human clinical exposure, is performed in a range of species, from laboratory mice to larger animals (such as dogs or non-human primates). Minipigs appear to be the animal of choice for studying bone surgery around intraoral dental implants. Dog models, well-known in the field of dental implant research, tend now to be used for studies conducted under compromised oral conditions (biofilm). Regarding small animal models, research studies mostly use rodents, with interest in rabbit models declining. Mouse models remain a reference for genetic studies. On the other hand, over the last decade, scientific advances and government guidelines have led to the replacement, reduction, and refinement of the use of all animal models in dental implant research. In new development strategies, some in vivo experiments are being progressively replaced by in vitro or biomaterial approaches. In this review, we summarize the key information on the animal models currently available for dental implant research and highlight (i) the pros and cons of each type, (ii) new levels of decisional procedures regarding study objectives, and (iii) the outlook for animal research, discussing possible non-animal options.

Histopathological characterization of peri-implant diseases: A systematic review and meta-analysis

OBJECTIVE

To conduct a systematic review of the inflammatory elements in peri-implantitis (PI) and peri-implant mucositis (PM) in comparison with healthy peri-implant tissues (HI) and periodontal disease.

DESIGN

The PubMed, Embase, Web of Science, and Scopus databases were searched up to December 2020. English articles that evaluated human soft tissue biopsies of PI or PM were included. Values reported for the surface area of the infiltrated connective tissue (ICT) were pooled using the random-effect model meta-analysis to estimate the mean (95% CI).

RESULTS

A total of 33 articles were included. Of 30 studies on PI, the majority evidenced significantly increased vascularization and inflammatory cell counts dominated by plasma cells in PI compared with HI. Studies that compared PI with chronic periodontitis primarily reported more severe inflammatory infiltrates in PI. This was confirmed by the meta-analysis results since the surface area of the ICT was significantly larger in PI (p < 0.001). Only seven studies analyzed the PM lesions and reported increased inflammatory infiltrates and vascularization in PM compared with HI. Based on the meta-analysis results, the surface area of the ICT was 3.00 [1.50, 4.51] mm ² in PI and 0.23 [0.02, 0.44] mm ² in PM lesions. Based on the available evidence, presence of foreign body particles considerably increased the inflammatory infiltrate; however, smoking did not have a significant effect.

CONCLUSIONS

There was controversy regarding the prevalence of various inflammatory cell types in peri-implant diseases; however, a considerably high ICT surface area in PI indicates the aggressive nature of the disease.

What is the influence of implant surface characteristics and/or implant material on the incidence and progression of peri-implantitis? A systematic literature review

OBJECTIVES

To answer the focused question, 'In animals or patients with dental implants, does implant surface characteristics and/or implant material have an effect on incidence and progression of peri-implantitis?'

MATERIAL AND METHODS

Pre-clinical in vivo experiments on experimental peri-implantitis and clinical trials with any aim and design, and ≥5 years follow-up, where the effect of ≥2 different type of implant material and/or surface characteristics on peri-implantitis incidence or severity, and/or progression, implant survival or losses due to peri-implantitis, and/or marginal bone levels/loss was assessed.

RESULTS

Meta-analyses based on data of pre-clinical experiments, using the ligature induced peri-implantitis model in the dog, indicated that after the spontaneous progression phase implants with a modified surface showed significantly greater radiographic bone loss (effect size 0.44 mm; 95%CI 0.10-0.79; p = .012; 8 publications) and area of infiltrated connective tissue (effect size 0.75 mm² ; 95%CI 0.15-1.34; p = .014; 5 publications) compared to non-modified surfaces. However, in 9 out of the 18 included experiments, reported in 25 publications, no significant differences were shown among the different implant surface types assessed. Clinical and/or radiographic data from 7605 patients with 26,188 implants, reported in 31 publications (20 RCTs, 3 CTs, 4 prospective cohort, and 4 retrospective studies; 12 with follow-up ≥10 years), overall did not show significant differences in the incidence of peri-implantitis, when this was reported or could be inferred, among the various implant surfaces. In general, high survival rates (90-100%) up to 30 years and no clinically relevant differences in marginal bone loss/levels, merely compatible with crestal remodelling, were presented for the various implant types.

CONCLUSION

Pre-clinical in vivo experiments indicate that surface characteristics of modified implants may have a significant negative impact on peri-implantitis progression, while clinical studies do not support the notion that there is a difference in peri-implantitis incidence among the various types of implant surfaces. No assumptions can be made regarding the possible impact of implant material on incidence and/or peri-implantitis progression due to limited information.

Direct-Deposited Graphene Oxide on Dental Implants for Antimicrobial Activities and Osteogenesis

Objective

To determine the effects of graphene oxide (GO) deposition (on a zirconia surface) on bacterial adhesion and osteoblast activation.

Methods

An atmospheric pressure plasma generator (PGS-300) was used to coat Ar/CH₄ mixed gas onto zirconia specimens (15-mm diameter × 2.5-mm thick disks) at a rate of 10 L/min and 240 V. Zirconia specimens were divided into two groups: uncoated (control; Zr) group and GO-coated (Zr-GO) group. Surface characteristics and element structures of each specimen were evaluated by field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and contact angle. Additionally, crystal violet staining was performed to assess the adhesion of Streptococcus mutans. WST-8 and ALP (Alkaline phosphatase) assays were conducted to evaluate MC3T3-E1 osteoblast adhesion, proliferation, and differentiation. Statistical analysis was calculated by the Mann–Whitney U-test.

Results

FE–SEM and Raman spectroscopy demonstrated effective GO deposition on the zirconia surface in Zr-GO. The attachment and biofilm formation of S. mutans was significantly reduced in Zr-GO compared with that of Zr (P < 0.05). While no significant differences in cell attachment of MC3T3-1 were observed, both proliferation and differentiation were increased in Zr-GO as compared with that of Zr (P < 0.05).

Significance

GO-coated zirconia inhibited the attachment of S. mutans and stimulated proliferation and differentiation of osteoblasts. Therefore, GO-coated zirconia can prevent peri-implantitis by inhibiting bacterial adhesion. Moreover, its osteogenic ability can increase bone adhesion and success rate of implants.

Will Zirconia Implants Replace Titanium Implants?

This review aims to discuss the advantages and disadvantages of zirconia implants compared with titanium implants. Moreover, it intends to review the relevant available long-term literature of these two materials regarding osteointegration, soft-tissue, microbiota, and peri-implantitis, focusing on clinical results. Briefly, titanium implants are a reliable alternative for missing teeth; however, they are not incapable of failure. In an attempt to provide an alternative implant material, implants made from ceramic-derivate products were developed. Owing to its optimal osseointegration competence, biocompatibility, and esthetic proprieties, zirconium dioxide (ZrO2), also known as zirconia, has gained popularity among researchers and clinicians, being a metal-free alternative for titanium implants with its main use in the anterior esthetic zones. This type of implant may present similar osseointegration as those noted on titanium implants with a greater soft-tissue response. Furthermore, this material does not show corrosion as its titanium analog, and it is less susceptible to bacterial adhesion. Lastly, even presenting a similar inflammatory response to titanium, zirconia implants offer less biofilm formation, suggesting less susceptibility to peri-implantitis. However, it is a relatively new material that has been commercially available for a decade; consequently, the literature still lacks studies with long follow-up periods.

Role of thin gingival phenotype and inadequate keratinized mucosa width (<2 mm) as risk indicators for peri-implantitis and peri-implant mucositis

BACKGROUND

There is growing evidence on the impact of thin gingival phenotype (TnP) and inadequate keratinized mucosa width (KMW <2 mm) around dental implants on peri-implant health. This study investigated the role of TnP and inadequate KMW (<2 mm) as risk indicators for peri-implantitis and mucositis and on dental patient-reported outcomes.

METHODS

Sixty-three patients with 193 implants (mean follow-up of 6.9 ± 3.7 years) were given a clinical and radiographic examination and a questionnaire to assess patient awareness of food impaction and pain/discomfort. Chi-squared tests and regression analysis for clustered data were used to compare outcomes.

RESULTS

Implants with TnP had a statistically higher prevalence of peri-implantitis (27.1% versus 11.3%; PR, 3.32; 95% confidence interval (CI), 1.64-6.72; P = 0.001) peri-implant mucositis (42.7% versus 33%; PR, 1.8; 95% CI, 1.12-2.9; P = 0.016) and pain/discomfort during oral hygiene (25% versus 5%; PR, 3.7; 95% CI, 1.06-12.96; P = 0.044) than thick phenotype. Implants with inadequate KMW had a statistically higher prevalence of peri-implantitis (24.1% versus 17%; PR, 1.87; 95% CI, 1.07-3.25; P = 0.027) and peri-implant mucositis (46.6% versus 34.1%; PR, 1.53; 95% CI, 1-2.33; P = 0.05) and pain/discomfort during oral hygiene (28% versus 10%; PR, 2.37; 95% CI, 1.1-5.1; P = 0.027) than the adequate KMW. TnP was strongly associated with inadequate KMW (PR = 3.18; 95% CI, 1.69-6.04; P <0.001).

CONCLUSION

TnP and inadequate KMW (<2 mm) may be significant risk indicators for peri-implant disease and pain/discomfort during brushing.

Development of a rat model for type 2 diabetes mellitus peri-implantitis: A preliminary study

OBJECTIVE

To develop an in vivo model to simulate the complex internal environment of diabetic peri-implantitis (T2DM-PI) model for a better understanding of peri-implantitis in type 2 diabetic patients.

MATERIALS AND METHODS

Maxillary first molars were extracted in Sprague-Dawley (SD) rats, and customized cone-shaped titanium implants were installed in the extraction sites. Thereafter, implants were uncovered and customized abutments were screwed into implants. A high-fat diet and a low-dose injection of streptozotocin were utilized to induce T2DM. Finally, LPS was locally injected in implant sulcus to induce peri-implantitis.

RESULTS

In the present study, T2DM-PI model has been successfully established. Imaging analysis revealed that abundant inflammatory cells infiltrated in the soft tissue in T2DM-PI group with concomitant excessive secretion of inflammatory cytokines. Moreover, higher expression of MMP and increased number of osteoclasts led to collagen disintegration and bone resorption in T2DM-PI group.

CONCLUSIONS

These results describe a novel rat model which stimulate T2DM-PI in vivo, characterized by overwhelming inflammatory response and bone resorption. This model has a potential to be used for investigation of initiation, progression and interventional therapy of T2DM-PI.

Immunohistochemical characteristics of lateral bone augmentation using different biomaterials around chronic peri-implant dehiscence defects: An experimental in vivo study

AIM

To investigate the immunohistochemical characteristics of a highly porous synthetic bone substitute and a cross-linked collagen membrane for guided bone regeneration.

METHODS

Three experimental groups were randomly allocated at chronic peri-implant dehiscence defect in 8 beagle dogs: (i) biphasic calcium phosphate covered by a cross-linked collagen membrane (test group), (ii) deproteinized bovine bone mineral covered by a natural collagen membrane (positive control) and (iii) no treatment (negative control). After 8 and 16 weeks of submerged healing, dissected tissue blocks were processed for immunohistochemical analysis. Seven antibodies were used to detect the remaining osteogenic and angiogenic potential, and quantitative immunohistochemical analysis was done by software.

RESULTS

The antigen reactivity of alkaline phosphatase was significantly higher in the test group compared to the positive and negative controls, and it maintained till 16 weeks. The intensity of osteocalcin was significantly higher in the positive control at 8 weeks than the other groups, but significantly decreased at 16 weeks and no difference was found between the groups. A significant large number of TRAP-positive cells were observed in the test group mainly around the remaining particles at 16 weeks. The angiogenic potential was comparable between the groups showing no difference in the expression of transglutaminase II and vascular endothelial growth factor.

CONCLUSION

Guided bone regeneration combining a highly porous biphasic calcium phosphate synthetic biomaterial with a crosslinked collagen membrane, resulted in extended osteogenic potential when compared to the combination of deproteinized bovine bone mineral and a native collagen membrane.

Effects of 2% sodium fluoride solution on the prevention of streptococcal adhesion to titanium and zirconia surfaces

Streptococci are associated with dental plaque formation as the early-colonizing bacteria that adhere to titanium (CpTi) and zirconia (TZP) implant abutment surfaces. Effective prevention of peri-implantitis may be possible by removing streptococci as target. This study aimed to evaluate the effects of 2% NaF on the prevention of streptococcal adhesion to CpTi and TZP. After immersion in 2% NaF for 90 min, surface characterization of mirror-polished CpTi and TZP disks were assesed using XPS, EPMA, and SEM. S. sanguinis, S. gordonii, and S. oralis were used as the streptococcal bacterial strains. After 24 h culture, bacterial adhesion was evaluated using an ATP-bioluminescent assay and SEM. In XPS, EPMA, and SEM analyses, fluoride was detected on the CpTi and TZP surfaces after 2% NaF immersion with no signs of localization, and no corrosion on the CpTi disks. Based on the adhesion assay, the adherences of S. sanguinis, S. gordonii, and S. oralis were significantly lower with NaF than without NaF in CpTi (p = 0.005, 0.001, and 0.001, respectively) and TZP (p = 0.003, 0.002, and 0.001). This was also confirmed by SEM. In conclusion, 2% NaF reduced the adhesion of streptococci to the CpTi and TZP surfaces.

Application of specialized pro-resolving mediators in periodontitis and peri-implantitis: a review

Scaling and root planning is a key element in the mechanical therapy used for the eradication of biofilm, which is the major etiological factor for periodontitis and peri‐implantitis. However, periodontitis is also a host mediated disease, therefore, removal of the biofilm without adjunctive therapy may not achieve the desired clinical outcome due to persistent activation of the innate and adaptive immune cells. Most recently, even the resident cells of the periodontium, including periodontal ligament fibroblasts, have been shown to produce several inflammatory factors in response to bacterial challenge. With increased understanding of the pathophysiology of periodontitis, more research is focusing on opposing excessive inflammation with specialized pro‐resolving mediators (SPMs). This review article covers the major limitations of current standards of care for periodontitis and peri‐implantitis, and it highlights recent advances and prospects of SPMs in the context of tissue reconstruction and regeneration. Here, we focus primarily on the role of SPMs in restoring tissue homeostasis after periodontal infection.

Are marginal bone level changes around dental implants due to infection?

BACKGROUND

Peri-implant bone level values have been used as the clinical standard of reference to describe the status of a dental implant. Reduction of marginal bone levels in association with bleeding on probing have been claimed to be a sign of pathology and an indication of treatment needs.

PURPOSE

To assess the available evidence that peri-implant bone loss is caused by infection.

MATERIALS AND METHODS

This article is a narrative review on the interpretation of marginal bone level changes around dental implants as a consequence of infection.

RESULTS AND CONCLUSIONS

There is evidence that plaque accumulation induces an inflammatory reaction in the peri-implant soft tissues and that resumption of plaque control measures results in the reduction of the inflammation. Since plaque is always present in the oral cavity, a cause-effect relationship between plaque accumulation and peri-implantitis, defined as inflammation of the peri-implant soft tissues associated with marginal bone loss has been difficult to validate and has not been proven so far. There is no evidence of the mechanisms involved in the tissue reactions resulting in the conversion from a state of an inevitable inflammation contained in the soft tissues to a state of inflammation involving the loss of peri-implant marginal bone. There is today no consensus whether implants should be expected to be surrounded by tissues which are completely free from inflammation, or that an "immune-driven", chronic, subclinical inflammation should be expected at the foreign body implant. The infectious origin theory appears to be mainly supported by ligature-induced experimental peri-implantitis investigations in animal models that suffer of several methodological problems, and therefore, provide misleading information with regards to human clinical applications in large, routine populations.

Experimental peri-implantitis around titanium implants with a chemically modified surface with a monolayer of multi-phosphonate molecules: a preclinical in vivo investigation

OBJECTIVES

The purpose of this experimental in vivo investigation was to evaluate the influence of modifying the implant surface by adding a monolayer of multi-phosphonate molecules on the development of experimental peri-implantitis.

MATERIAL AND METHODS

Eight beagle dogs received 5 tests and 5 control implants each following a split-mouth design 3 months after premolar and molar extraction. On the most mesial implant of each side, a 3-mm buccal dehiscence was artificially created. Experimental peri-implantitis was induced by silk ligatures over a 4-month period; after ligature removal, peri-implantitis was left to progress for another 4 months without plaque control. Clinical, histological, and radiographic outcomes were evaluated.

RESULTS

Radiographically, both implant groups showed a similar bone loss (BL) at the end of the induction and progression phases. BL measured on the histological sections of the test and control groups was 3.14 ± 0.42 mm and 3.26 ± 0.28 mm, respectively; the difference was not statistically significant (p > 0.05). The remaining buccal bone to implant contact (bBIC) percentage of the test and control groups was 59.38 ± 18.62 and 47.44 ± 20.46%, respectively; the difference, however, was not statistically significant (p > 0.05). Bone loss observed at dehiscent sites compared to non-dehiscent ones showed no statistically significant difference (p > 0.05).

CONCLUSIONS

Addition of a monophosphonate layer to a moderately rough implant surface did not affect development of experimental peri-implantitis.

CLINICAL RELEVANCE

Influence of implant surface on peri-implantitis may condition implant selection by the clinician, especially on patients with disease risk factors. In that sense, monophosphate layer implants do not show higher peri-implantitis risk than control implants.

Prevalence and risk indicators of peri-implant diseases in a group of Moroccan patients

BACKGROUND

To report the prevalence of peri-implant diseases in a North African patient population, and to assess the concurrent associations of patient- and implant-level characteristics with probing depth and bone loss around dental implants METHODS: A total of 642 implants in 145 subjects were followed up for a mean 6.4 years. At the last follow-up visit the subjects were examined clinically and radiographically to assess the status of peri-implant tissues and teeth. Data analysis used the generalized linear mixed models RESULTS: The prevalence of peri-implant mucositis and peri-implantitis were 82.1% and 41.4% at the subject level, and 68.4% and 22.7% at the implant level, respectively. Inadequate plaque control, peri-implant inflammation, history of previous implant failures, and pain/discomfort at the implant site were significantly associated with both outcomes (increased probing depth and bone loss). Diabetes mellitus, inadequate implant restoration, single restorations (versus multi-unit), cement-retained restorations, and presence of occlusal wear facets on teeth were significantly associated with one of the two outcomes. Implants placed in the lower anterior jaw region had the most favorable outcome. Smoking, history of periodontitis, and type of implant surface did not show significant associations with higher frequency of peri-implant diseases in the multivariable analysis.

CONCLUSIONS

Peri-implant diseases are prevalent in this North African patient population. Multiple subject- and implant-level variables were associated with peri-implant diseases. Risk assessment of these effects should consist of a concurrent inclusion of these factors in multivariable analyses that also adjust for the complex variance structure of the oral environment.

Peri-Implant Diseases: Diagnosis, Clinical, Histological, Microbiological Characteristics and Treatment Strategies. A Narrative Review

Since the use of dental implants is continuously increasing, it is imperative for dental practitioners to understand the nature and treatment of peri-implant diseases. The purpose of this manuscript is to comprehensively review peri-implant diseases, their characteristics, as well as their non-surgical and surgical treatment. To that end, the current literature was searched and a narrative review was conducted. It is essential that the case definitions described in the 2017 World Workshop on the Classification of Periodontal and Peri-implant Diseases and Conditions are used to diagnose and classify peri-implant health, peri-implant mucositis and peri-implantitis. While recent epidemiologic studies on peri-implant diseases exist, there is great heterogeneity in the definition of these conditions. Several risk factors and indicators are reported in the literature, with smoking and diabetes being the most universally accepted. In peri-implant mucositis, non-surgical treatment seems to be sufficient. However, for the treatment of peri-implantitis, a surgical approach, which includes open-flap debridement, apically positioned flap and guided bone regeneration, is considered more appropriate. A great variety of adjuncts to mechanical treatment have been reported with controversial results. Finally, studies comparing results from different peri-implantitis treatments are warranted in randomized controlled clinical trials in order to provide stronger evidence-based approaches.

Differences in the progression of experimental peri-implantitis depending on the implant to abutment connection

OBJECTIVES

The aim was to evaluate the rate of bone loss progression during experimentally induced peri-implantitis using two different implant-abutment connections in implants with identical surface topography.

MATERIAL AND METHODS

Forty-eight Regular Neck tissue-level SLA implants with a matching implant to abutment connection (TL) and 36 bone-level SLA implants with a switching platform implant to abutment connection (BL) were subjected to experimental peri-implantitis in two independent in vivo pre-clinical investigations. Experimental peri-implantitis was induced by means of silk ligatures during 3 months (induction phase), and followed for one extra month without ligatures (progression phase). Radiographic and clinical outcomes were evaluated longitudinally along both studies and subsequently compared between experiments.

RESULTS

During the induction phase, radiographic bone loss was significantly higher in implants with matched abutments compared with those with platform switching connections (2.65 ± 0.66 mm vs 0.84 ± 0.16 mm, respectively, p = 0.001). During the progression phase, both types of implant-abutment connection exhibited similar rates of radiographic bone loss. Similar outcomes were observed clinically.

CONCLUSIONS

A platform switching connection resulted in a more benign development of peri-implantitis during the experimental induction phase of the disease. These differences, however, disappeared once the ligatures were removed (progression phase).

CLINICAL RELEVANCE

Influence of the implant-abutment connection in peri-implantitis progression may be relevant when considering implant selection in the moment of placement. In this sense, platform switching abutment demonstrated less peri-implantitis development when compared to implant matching connection.

Cellular expression of DNA damage/repair and reactive oxygen/nitrogen species in human periodontitis and peri-implantitis lesions

AIM OF THE STUDY

To evaluate differences in the cellular expression of DNA damage/repair and reactive oxygen/nitrogen species between human periodontitis and peri-implantitis lesions.

MATERIAL AND METHODS

40 patients presenting with generalized severe periodontitis and 40 patients with severe peri-implantitis were included. Soft tissue biopsies were collected from diseased sites in conjunction with surgical therapy and prepared for histological analysis. Four regions of interest were identified: the pocket epithelium (PE), the infiltrated connective tissue (ICT), which was divided into one inner area facing the PE (ICT-1) and one outer area (ICT-2). A non-infiltrated connective tissue area (NCT) lateral of the ICT was also selected.

RESULTS

It was demonstrated that the ICT of peri-implantitis specimens was considerably larger and contained significantly larger area proportions and densities of CD68-, MPO- and iNOS-positive cells than that of periodontitis samples. Cellular densities were overall higher in the inner ICT zone lateral of the PE (ICT-1) than in the outer ICT compartment (ICT-2). While the NCT area lateral of the ICT comprised significantly larger proportions and densities of y-H2AX-, iNOS-, NOX2-, MPO- and PAD4/MPO-positive cells in peri-implantitis than in periodontitis sites, a reverse difference was noted for the area proportion and density of 8-OHdG-positive cells in the PE.

CONCLUSIONS

It is suggested that peri-implantitis lesions are associated with an enhanced and upregulated host response and contain larger numbers of neutrophils, macrophages and iNOS-positive cells than periodontitis lesions.

Efficacy of Local Minocycline Agents in Treating Peri-Implantitis: An Experimental In Vivo Study in Beagle Dogs

BACKGROUND

Local delivery agents (LDA) have the advantage of delivering the antibiotics at high concentrations to the targeted sites. However, the constant flow of gingival crevicular fluids and saliva may restrict their efficacy. Therefore, the drug sustainability and pharmacodynamic properties of any proposed LDA should be evaluated.

METHODS

Four dental implants were placed unilaterally in the edentulous mandible of six beagle dogs. Peri-implantitis were experimentally induced using silk-ligatures. Each implant was randomly allocated to receive one of the following four treatments: (i) MC (Chitosan-alginate (CA) minocycline), (ii) MP (CA-without minocycline), (iii) PG (Polyacrylate-glycerin minocycline), and (iv) Control (mechanical debridement only). Mechanical therapies and LDAs were administered into the gingival sulcus two times at a 4-week interval. Drug sustainability as well as clinical, radiographical, and immunohistochemical (IHC) analyses were conducted to evaluate the efficacies of treatments.

RESULTS

Reduced mean probing depth was observed in all of the test groups after the second delivery. A minimal marginal bone level change was observed during the treatment period (MP (-0.06 ± 0.53 mm) to PG (-0.25 ± 0.42 mm)). The distribution of IHC cell marker analysis of all targeted antibodies ranged from 6.34% to 11.33%. All treatment outcomes between the test groups were comparable. A prolonged retention of LDA was observed from CA microspheres (MC and MP) at both administrations (p < 0.017) and prolonged sustainability of bacteriostatic effect was observed from MC compared to PG after the second administration (p < 0.05).

CONCLUSIONS

Prolonged retention of CA microspheres was observed and the longer bacteriostatic effect was observed from the MC group. Mechanical debridement with adjunct LDA therapy may impede peri-implantitis progression, however, prolonged drug action did not lead to improved treatment outcome.

Microbial and host-derived biomarker changes during ligature-induced and spontaneous peri-implantitis in the Beagle dog

OBJECTIVE

To evaluate microbial and host-derived biomarker changes during experimental peri-implantitis in the Beagle dog.

BACKGROUND

Limited data exist on the microbial and biomarker changes during progressive bone loss as result of experimental peri-implantitis.

METHODS

In total, 36 implants (n_dogs  = 6) were assessed over 3 episodes of ligature-induced peri-implantitis followed by a period of spontaneous progression. Implants with hybrid (H) and completely rough (R) surface designs were used. Clinical and radiographic parameters were recorded at 4 timepoints. Peri-implant sulcus fluid was collected from the buccal and lingual aspects of the implants. The presence of 7 bacterial species and 2 host-derived biomarkers was assessed during the study period.

RESULTS

Total bacterial counts were significantly correlated with marginal bone loss (MBL) (r = .21; P = .009). Further, Phorphyromonas gulae (Pg) and Tannerella forsythia (Tf) were commonly correlated with MBL, suppuration (SUP) and the sulcular bleeding index scores (mSBI) (P < .05). Other bacteria were further correlated with SUP, mSBI, and MBL. While the analyzed bacteria dropped, Prevotella intermedia (Pi) further increased during the spontaneous progressive phase (P < .05). Total bacterial load did not differ significantly between H and R implants. Host-derived IL-10 was undetected along the study period. IL-1β positively correlated with probing pocket depth (r = .18; P = .03). During spontaneous progression, H implants displayed statistically significant lower levels of IL-1β (P = .003).

CONCLUSION

Experimental peri-implantitis is associated with an increase in bacterial counts. While Pg and Tf are associated with ligature-induced disease progression, Pi augmented its load during the spontaneous progressive phase. IL-1β is associated with pocket probing depth and influenced by implant surface characteristics during the spontaneous progression phase.

Are teeth superior to implants? A mapping review

STATEMENT OF PROBLEM

There is a long-held assumption that teeth are superior to implants because the periodontal ligament (PDL) confers a preeminent defense against biologic and mechanical challenges. However, adequate analysis of the literature is lacking. As a result, differential treatment planning of tooth- and implant-supported restorations has been compromised.

PURPOSE

Given an abundance and diversity of research, the purpose of this mapping review was to identify basic scientific gaps in the knowledge of how teeth and implants respond to biologic and mechanical loads. The findings will offer enhanced evidence-based clinical decision-making when considering replacement of periodontally compromised teeth and the design of implant prostheses.

MATERIAL AND METHODS

The online databases PubMed, Science Direct, and Web of Science were searched. Published work from 1965 to 2020 was collected and independently analyzed by both authors for inclusion in this review.

RESULTS

A total of 108 articles met the inclusion criteria of clinical, in vivo, and in vitro studies in the English language on the periradicular and peri-implant bone response to biologic and mechanical loads. The qualitative analysis found that the PDL's enhanced vascularity, stem cell ability, and resident cells that respond to inflammation allow for a more robust defense against biologic threats compared with implants. While the suspensory PDL acts to mediate moderate loads to the bone, higher compressive stress and strain within the PDL itself can initiate a biologic sequence of osteoclastic activity that can affect changes in the adjacent bone. Conversely, the peri-implant bone is more resistant to similar loads and the threshold for overload is higher because of the absence of a stress or strain sensitivity inherent in the PDL.

CONCLUSIONS

Based on this mapping review, teeth are superior to implants in their ability to resist biologic challenges, but implants are superior to teeth in managing higher compressive loads without prompting bone resorption.

Effects of peri-implant infection on serum biochemical analysis

BACKGROUND

Peri-implant disease (PID) has not been directly linked to pathological organ changes. The present study assessed the dynamics of serum biochemical parameters in a model of experimental peri-implantitis in dogs, followed by open flap debridement.

METHODS

Seven male beagle dogs comprised the study group. Procedures were performed as follows-extractions of two premolars and one molar on each mandibular quadrant (Day 0); bone healing time (week14); placement of four rough-surface endoosseous implants, two on each mandibular side; implant uncovering (week 28); induction of experimental peri-implantitis by the use of three ligatures (weeks 31, 34, 37) followed by open flap debridement (week 42). Serum biochemical analysis following each procedure was compared to baseline. Biochemical parameters were assigned into four subsets of variables-inflammation, renal function, liver function, and blood glucose. Wilcoxon paired tests were conducted in order to identify statistically significant differences between baseline data and values obtained after each procedure RESULTS: Following experimental peri-implantitis, the dynamics of renal parameters and blood glucose were minimal whereas statistically significant (P < 0.05) increases were noted for inflammatory (total protein and albumin concentrations) and hepatic (ALT, AST) parameters. A statistically significant (P < 0.05) decrease was only noted for total bilirubin. After open flap debridement, inflammatory (total protein and albumin concentrations) and hepatic (AST) parameters returned to baseline.

CONCLUSIONS

Within their limits, the present results indicate that: (a) PID affects inflammatory and hepatic serum biochemical parameters, and (b) following open flap debridement most of the values returned to baseline.

Locally Applied Slow-Release of Minocycline Microspheres in the Treatment of Peri-Implant Mucositis: An Experimental In Vivo Study

BACKGROUND

The objective of this is preclinical investigation was to evaluate the differential drug sustainability and pharmacodynamic properties of two local minocycline microsphere carriers: chitosan-coated alginate (CA) and poly(meth)acrylate-glycerin (PG).

METHODS

Four dental implants were placed unilaterally in the edentulous mandible of six beagle dogs. Each implant was randomly assigned to receive one of the following four treatments: (i) CA (CA-based minocycline), (ii) placebo (CA substrate without minocycline), (iii) PG (PG-based minocycline) and (iv) control (mechanical debridement only). After inducing peri-implant mucositis, the randomly assigned treatments were administered into the gingival sulcus twice at a 4-week interval using a plastic-tipped syringe. Drug sustainability and pharmacodynamic (clinical, radiographical and cell marker intensity) evaluations were performed after each administration.

RESULTS

The CA microspheres remained longer around the healing abutment compared to the PG microspheres at both administrations and a longer bacteriostatic effect was observed from CA (7.0 ± 5.7 days) compared to PG (1.2 ± 2.6 days). The efficacy of the applied therapies based on clinical, radiographical and histological analyses were comparable across all treatment groups.

CONCLUSIONS

CA microspheres showed longer carrier and bacteriostatic effect sustainability when compared to PG microspheres, however, longer drug sustainability did not lead to improved treatment outcomes.