Commentary: Treatment of Periodontitis: Destroyed Periodontal Tissues Can Be Regenerated Under Certain Conditions

Insights and Advancements in Periodontal Tissue Engineering and Bone Regeneration

The regeneration of periodontal bone defects continues to be an essential therapeutic concern in dental biomaterials. Numerous biomaterials have been utilized in this sector so far. However, the immune response and vascularity in defect regions may be disregarded when evaluating the effectiveness of biomaterials for bone repair. Among several regenerative treatments, the most recent technique of in situ tissue engineering stands out for its ability to replicate endogenous restorative processes by combining scaffold with particular growth factors. Regenerative medicine solutions that combine biomaterials/scaffolds, cells, and bioactive substances have attracted significant interest, particularly for bone repair and regeneration. Dental stem cells (DSCs) share the same progenitor and immunomodulatory properties as other types of MSCs, and because they are easily isolable, they are regarded as desirable therapeutic agents in regenerative dentistry. Recent research has demonstrated that DSCs sown on newly designed synthetic bio-material scaffolds preserve their proliferative capacity while exhibiting increased differentiation and immuno-suppressive capabilities. As researchers discovered how short peptide sequences modify the adhesion and proliferative capacities of scaffolds by activating or inhibiting conventional osteogenic pathways, the scaffolds became more effective at priming MSCs. In this review, the many components of tissue engineering applied to bone engineering will be examined, and the impact of biomaterials on periodontal regeneration and bone cellular biology/molecular genetics will be addressed and updated.

Lacticaseibacillus rhamnosus GG Improves Periodontal Bone Repair via Gut-Blood Axis in Hyperlipidemia

Periodontal bone regeneration remains a clinical challenge, and hyperlipidemia can aggravate alveolar bone resorption. Probiotics have recently been reported to improve bone mass. We aimed to determine the role of Lacticaseibacillus rhamnosus GG (LGG) in periodontal bone regeneration improvement within the context of periodontitis with hyperlipidemia. A Sprague Dawley rat model for periodontitis, hyperlipidemia, and periodontal fenestration defect was constructed (n = 36) and administered LGG gavage for 6 wk (the rats were subsequently sacrificed). Fecal microbiota from donor rats 3 wk after LGG gavage was transplanted into recipient rats to evaluate the role of LGG-modulated gut microbiota in periodontal bone regeneration. Regenerated bone mass was detected using micro-computerized tomography and hematoxylin and eosin stain. Gut microbiota was analyzed using 16S ribosomal RNA sequencing. Serum metabolites were detected by liquid chromatography-mass spectrometry (6 wk after LGG gavage). The pro-osteogenic effects of screened serum metabolite were verified in vitro on bone marrow mesenchymal stem cells (BMMSCs). We found that the bone mineral density, bone volume (BV), trabecular bone volume fraction (BV/TV), and trabecular thickness of the regenerated periodontal bone increased after LGG gavage (P < 0.05) but had little effect on oral flora. After LGG gavage, Staphylococcus, Corynebacterium, and Collinsella in the gut of donors were significantly changed, and these differences were maintained in recipients, who also showed increased trabecular thickness of the regenerated periodontal bone (P < 0.05). These key genera were correlated with BV/TV and BV (P < 0.05). In addition, LGG gavage significantly regulated bone-related blood metabolites, of which selenomethionine promoted BMMSC osteogenesis. Notably, selenomethionine was associated with key gut genera (P < 0.05). Collectively, LGG improved periodontal bone regeneration in the context of periodontitis with hyperlipidemia by modulating gut microbiota and increasing pro-osteogenic metabolites in the blood. These results reveal new insights into the use of probiotics to promote periodontal bone regeneration via the gut-blood-bone axis.

Guided Tissue and Bone Regeneration Membranes: A Review of Biomaterials and Techniques for Periodontal Treatments

This comprehensive review provides an in-depth analysis of the use of biomaterials in the processes of guided tissue and bone regeneration, and their indispensable role in dental therapeutic interventions. These interventions serve the critical function of restoring both structural integrity and functionality to the dentition that has been lost or damaged. The basis for this review is laid through the exploration of various relevant scientific databases such as Scopus, PubMed, Web of science and MEDLINE. From a meticulous selection, relevant literature was chosen. This review commences by examining the different types of membranes used in guided bone regeneration procedures and the spectrum of biomaterials employed in these operations. It then explores the manufacturing technologies for the scaffold, delving into their significant impact on tissue and bone regenerations. At the core of this review is the method of guided bone regeneration, which is a crucial technique for counteracting bone loss induced by tooth extraction or periodontal disease. The discussion advances by underscoring the latest innovations and strategies in the field of tissue regeneration. One key observation is the critical role that membranes play in guided reconstruction; they serve as a barrier, preventing the entry of non-ossifying cells, thereby promoting the successful growth and regeneration of bone and tissue. By reviewing the existing literature on biomaterials, membranes, and scaffold manufacturing technologies, this paper illustrates the vast potential for innovation and growth within the field of dental therapeutic interventions, particularly in guided tissue and bone regeneration.

Influence of melatonin associated with the Bio-Gide® membrane on osteoblast activity: an in vitro Study

Melatonin (MLT) is a hormone responsible for regulating several physiological processes. It has been shown that MLT can be an important mediator in bone formation and stimulation, promoting osteoblast differentiation. In clinical practice, in tissue regeneration procedures, it is necessary to use membranes or barriers, associated with biomaterials, or not. The aim of this in vitro study was to assess the effect of melatonin on the activity of osteoblastic cells, associated, or not, with a resorbable collagen membrane (Bio-Gideä). For this, mice-derived pre-osteoblastic cells MC3T3 obtained from the ATCC (American Type Culture Collection) were used. Cultured cells were subject to the following treatments: MLT with a concentration of 1mM, a Bio-Gideä membrane and a membrane associated with MLT (Bio-Gideä + MLT). Proliferation and cell viability assays and protein lysate (ELISA test) quantification for the BMP-2 protein were carried out, in periods of 72 hours, 7 days and 10 days. After analyzing the data (one-way ANOVA, alpha=5%) it was observed that when MLT was used in isolation, there was an increase in cell proliferation and viability in osteoblastic cells (p<0.05). But, when MLT was associated with resorbable membranes, there was an inverse behavior, both in terms of proliferation and viability (p<0.05). In the case of the ELISA test, no secretion of BMP-2 was detected in any of the analyzed groups. It is concluded that MLT has a stimulatory effect on osteoblasts, but, when associated with Bio-Gideä resorbable membranes, it does not show any viable action in osteoblastic cell stimulation.

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.

Potential of Bone-Marrow-Derived Mesenchymal Stem Cells for Maxillofacial and Periodontal Regeneration: A Narrative Review

Bone-marrow-derived mesenchymal stem cells (BM-MSCs) are one of the most widely studied postnatal stem cell populations and are considered to utilize more frequently in cell-based therapy and cancer. These types of stem cells can undergo multilineage differentiation including blood cells, cardiac cells, and osteogenic cells differentiation, thus providing an alternative source of mesenchymal stem cells (MSCs) for tissue engineering and personalized medicine. Despite the ability to reprogram human adult somatic cells to induced pluripotent stem cells (iPSCs) in culture which provided a great opportunity and opened the new door for establishing the in vitro disease modeling and generating an unlimited source for cell base therapy, using MSCs for regeneration purposes still have a great chance to cure diseases. In this review, we discuss the important issues in MSCs biology including the origin and functions of MSCs and their application for craniofacial and periodontal tissue regeneration, discuss the potential and clinical applications of this type of stem cells in differentiation to maxillofacial bone and cartilage in vitro, and address important future hopes and challenges in this field.

Morphological Assessment of the Effect of Nanosecond Diode Laser Radiation With a Wavelength of 1265 nm on Periodontal Tissue in the Treatment of Apical Periodontitis: An Experimental Study

Introduction: There is a morphological assessment of the damaged area and the inflammatory response of periodontal tissues after therapy. It seems relevant to evaluate the reaction of the periapical tissues of the teeth of experimental animals after the treatment of simulated apical periodontitis using laser photodynamic therapy (PDT) and non-pigment laser transcanal microablation using morphological research. Methods: The lower incisors of 15 rabbits were used to simulate acute apical periodontitis of pulpal origin. Subsequently, the traditional treatment of teeth canals using mechanical cleaning and irrigation with antiseptic solution started. Then, three groups underwent different therapies - using PDT (n = 5; photosensitizer chlorin e6, [l = 660 nm, 60 mW/cm² ] for 2 minutes), using a new technology of transcanal laser ablation (n = 5; diode laser [l = 1265 nm, 180 mW/cm² ] for 3 minutes), and without additional treatment (n = 5). Laser therapy in two groups was carried out for 10 days once in 2 days. The animals were euthanized 10 days after the treatment started, decapitation was performed, and morphological specimens were studied under a microscope. Descriptive analysis (study of inflammatory apical infiltrate, bone regeneration of the alveoli and periodontal ligament) and quantitative analysis were performed. The data were statistically processed using the Kruskal-Wallis test. Results: The group treated with the new laser technology showed the best results with moderate lymph-macrophage infiltration and congested vessels, moderate neoangiogenesis and fibrogenesis. The size of the lesion was 506.4 mm², compared with the PDT group - 872.0 mm² (P ≤ 0.05). Conclusion: A decrease in the focus of inflammation, moderate neoangiogenesis and fibrogenesis in the periapical region when using transcanal laser microablation indicate the prospects of using the new technology in clinical practice in the complex therapy of apical periodontitis.

Current and future trends in periodontal tissue engineering and bone regeneration

Periodontal tissue engineering involves a multi-disciplinary approach towards the regeneration of periodontal ligament, cementum and alveolar bone surrounding teeth, whereas bone regeneration specifically applies to ridge reconstruction in preparation for future implant placement, sinus floor augmentation and regeneration of peri-implant osseous defects. Successful periodontal regeneration is based on verifiable cementogenesis on the root surface, oblique insertion of periodontal ligament fibers and formation of new and vital supporting bone. Ultimately, regenerated periodontal and peri-implant support must be able to interface with surrounding host tissues in an integrated manner, withstand biomechanical forces resulting from mastication, and restore normal function and structure. Current regenerative approaches utilized in everyday clinical practice are mainly guided tissue/bone regeneration-based. Although these approaches have shown positive outcomes for small and medium-sized defects, predictability of clinical outcomes is heavily dependent on the defect morphology and clinical case selection. In many cases, it is still challenging to achieve predictable regenerative outcomes utilizing current approaches. Periodontal tissue engineering and bone regeneration (PTEBR) aims to improve the state of patient care by promoting reconstitution of damaged and lost tissues through the use of growth factors and signaling molecules, scaffolds, cells and gene therapy. The present narrative review discusses key advancements in PTEBR including current and future trends in preclinical and clinical research, as well as the potential for clinical translatability.

6-Bromoindirubin-3'-oxime Promotes Osteogenic Differentiation of Periodontal Ligament Stem Cells and Facilitates Bone Regeneration in a Mouse Periodontitis Model

Effective bone tissue engineering is important to overcome the unmet clinical challenges of periodontal tissue regeneration. Successful bone tissue engineering comprises three key factors: stem cells, growth factors, and scaffolds. 6-Bromoindirubin-3'-oxime (BIO) is an inhibitor of glycogen synthase kinase-3 (GSK-3) that can activate the Wnt signaling pathway by enhancing β-catenin activity. In this study, the effects of BIO on the proliferation, migration, and osteogenic differentiation of periodontal ligament stem cells (PDLSCs) were investigated. Poly(lactic-co-glycolic acid) (PLGA) and hyaluronic acid (HA) emerged as promising biomaterials; thus, we developed a novel HA hydrogel embedded with BIO-encapsulated PLGA microspheres and injected the formulation into the gingival sulcus of mice with experimental periodontitis. The release speed of this system was fast in the first week and followed a sustained release phase until week 4. In vivo experiments showed that this PLGA-BIO-HA hydrogel system can inhibit periodontal inflammation, promote bone regeneration, and induce the expression of bone-forming markers alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), and osteocalcin (OCN) in a mouse periodontitis model. Therefore, this PLGA-BIO-HA hydrogel system provides a promising therapeutic strategy for periodontal bone regeneration.

Interproximal attachment gain: The challenge of periodontal regeneration

The new classification of periodontal diseases recognizes the key role of the interdental clinical attachment for defining the periodontal status and the extent of disease severity. Regenerating interdental clinical attachment not only improves the prognosis of the tooth, but it also lessens the severity of the disease condition. This manuscript provides a state-of-the-art review on surgical reconstructive approaches for treating papillary deficiency associated with soft and hard tissue interproximal defects. Combination therapy of papilla preservation, connective tissue grafting, and coronally advanced flaps may result in regeneration of the intrabony defect coupled with root coverage. Future research highlighted here may have the potential, especially in combination approaches, to repair challenging interproximal soft and hard tissue deficiencies.

Biomechanical pathways of dentoalveolar fibrous joints in health and disease

Spatial and temporal adaptations within periodontal tissues and their interfaces result from functional loads. Functional loads can be physiologic and/or pathologic in nature. The prolonged effect of these loads can alter the overall biomechanics of a dentoalveolar fibrous joint (dentoalveolar joint) by changing the form of the tooth root and its socket. This "sculpting" of the tooth root and alveolar bony socket is a consequence of several mechano-biological changes that occur within the periodontal complex of a load-bearing dentoalveolar joint. These include changes in biochemical expressions, structure, elemental composition, and mechanical properties of alveolar bone, the underlying tissues of the roots of teeth, and their interfaces. These physicochemical changes in tissues continue to prompt mechano-responsive biochemical activities at the attachment sites of periodontal ligament (soft) with bone (hard), and ligament with cementum (hard), which are the entheses of a load-bearing dentoalveolar joint. Forces at soft-hard tissue attachment sites between disparate materials with different stiffness values theoretically generate strain singularities or discontinuities. These discontinuities under prolonged functional loading increase the probability for failure to occur specifically at the enthesial zones. However, in a normal dentoalveolar joint, gradual stiffness gradients exist from ligament to bone, and from ligament to cementum. The gradual transitions in stiffness from softer ligament (lower stiffness) to harder bone or cementum (higher stiffness) or vice versa optimize tissue and interfacial strains. Optimization of tissue and ligament-enthesial physical and chemical properties facilitates transmission of cyclic forces of varying magnitudes and frequencies that collectively maintain the overall biomechanics of a dentoalveolar joint. The objectives of this review are 3-fold: (i) to illustrate physicochemical adaptations at the periodontal ligament entheses of a human periodontal complex affected by subgingival calculus; (ii) to demonstrate how to "program" the hallmarks of periodontitis in small-scale vertebrates in vivo to generate spatiotemporal maps of physicochemical adaptations in a diseased dentoalveolar joint; and (iii) to correlate dentoalveolar joint biomechanics in healthy and diseased states to spatiotemporal maps of physicochemical adaptations within respective periodontal tissues. This interdisciplinary approach demonstrates that physicochemical adaptations within periodontal tissues using the mechanics of materials (tissue mechanics), materials science (tissue composition), and mechano-biology (matrix molecules) can help explain the mechano-adaptation of dentoalveolar joints in normal and diseased functional states. Multiscale biomechanics and mechano-biology approaches can provide insights into the functional competence of a diseased relative to a normal dentoalveolar joint. Insights gathered from interdisciplinary and multiscale biomechanics approaches include the following: (i) physiologic loads related to chewing maintain a balance between mineral-forming and-resorbing biochemical cellular events, resulting in gradual stiffness gradients at the periodontal ligament entheses, and, in turn, sustain the overall biomechanics of a normal "healthy" dentoalveolar joint; (ii) pathologic loads resulting from tissue degradation and physical changes to the periodontal complex promote an abrupt stiffness gradient at the periodontal ligament entheses. The shift from gradual to an abrupt stiffness gradient could prompt a shift in the biochemical cascades, exacerbate mechano-responsive biochemical expressions at periodontal ligament entheses farther away from the site of insult, and culminate in joint degradation; (iii) sustained pathologic function on periodontally diseased joints exacerbates degradation of periodontal ligament entheses providing insights into "rescue therapy", such as the use of an adequate "mechanocal dose" to regain joint function; and (iv) spatiotemporal maps of changes in biochemical expressions, and physicochemical properties of strain-dominated affected sites, including the periodontal ligament entheses, can guide anatomy-specific therapeutics for tissue regeneration and/or disease control with the purpose of regaining dentoalveolar joint function. Modulation of occlusal loads could minimize disease progression and potentially assist in regaining functional attachment of ligament to bone and/or ligament to cementum of the dentoalveolar joint. Elucidating mechanisms that drive the breakdown of the functionally active periodontal complex burdened with microbes will provide the required critical insights into regenerative medicine and/or biomimetic approaches that would facilitate rescue/regain of dentoalveolar joint function.

Succinate Supplement Elicited "Pseudohypoxia" Condition to Promote Proliferation, Migration, and Osteogenesis of Periodontal Ligament Cells

Most mesenchymal stem cells reside in a niche of low oxygen tension. Iron-chelating agents such as CoCl₂ and deferoxamine have been utilized to mimic hypoxia and promote cell growth. The purpose of the present study was to explore whether a supplement of succinate, a natural metabolite of the tricarboxylic acid (TCA) cycle, can mimic hypoxia condition to promote human periodontal ligament cells (hPDLCs). Culturing hPDLCs in hypoxia condition promoted cell proliferation, migration, and osteogenic differentiation; moreover, hypoxia shifted cell metabolism from oxidative phosphorylation to glycolysis with accumulation of succinate in the cytosol and its release into culture supernatants. The succinate supplement enhanced hPDLC proliferation, migration, and osteogenesis with decreased succinate dehydrogenase (SDH) expression and activity, as well as increased hexokinase 2 (HK2) and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), suggesting metabolic reprogramming from oxidative phosphorylation to glycolysis in a normal oxygen condition. The succinate supplement in cell cultures promoted intracellular succinate accumulation while stabilizing hypoxia inducible factor-1α (HIF-1α), leading to a state of pseudohypoxia. Moreover, we demonstrate that hypoxia-induced proliferation was G-protein-coupled receptor 91- (GPR91-) dependent, while exogenous succinate-elicited proliferation involved the GPR91-dependent and GPR91-independent pathway. In conclusion, the succinate supplement altered cell metabolism in hPDLCs, induced a pseudohypoxia condition, and enhanced proliferation, migration, and osteogenesis of mesenchymal stem cells in vitro.

Is selective protein adsorption on biomaterials a viable option to promote periodontal regeneration?

Periodontitis is an inflammatory condition that can induce significant destruction of the periodontium, the set of specialized tissues that provide nourishment and support to the teeth. According to the guided tissue regeneration principles, the periodontium can be regenerated if the spatiotemporal control of wound healing is obtained, namely the tune control of cell response. After material implantation, protein adsorption at the interface is the first occurring biological event, which influences subsequent cell response. With the regard of this, we hypothesize that the control of selective adsorption of biological cues from the surrounding milieu may be a key-point to control selective cell colonization of scaffolds for periodontal tissue regeneration.

Radiographic alveolar bone level and levels of serum 25-OH-Vitamin D3 in ethnic Norwegian and Tamil periodontitis patients and their periodontally healthy controls

BACKGROUND

Studies suggest association between low serum 25-OH-Vitamin D₃ (VitD) and chronic destructive periodontal diseases. The main sources of VitD is sun exposure and fat fish. Subjects with dark skin will therefore generate less VitD as response to sun exposure. The aim of the study was to assess the radiographic bone level and levels of serum VitD in ethnic Norwegian and Tamil periodontitis patients and their respective healthy controls.

METHODS

Twenty-seven Tamil periodontitis patients living in Norway were compared to 21 Tamil controls as well as to 21 Norwegian periodontitis patients and 23 Norwegian controls. Marginal bone level was diagnosed on radiographs. VitD levels were diagnosed in blood samples by high-performance liquid chromatography-mass spectrometry.

RESULTS

VitD levels were lower in Norwegian periodontitis patients than in controls, while no significant differences were observed between Tamil periodontitis patients and controls despite the significant difference between RBL between the periodontitis patients and controls in both groups. When calculating the odds ratio for having periodontal disease in both populations together, it appeared that one unit increased serum VitD (i.e. 1 nmol/L) decreased the odds of having radiographic bone loss by 4%.

CONCLUSION

According to logistic regression, and after correcting for confounding factors, VitD levels showed significant association with the presence of periodontitis, as expressed by radiographic bone loss, in all patients combined.

Prx1 Expressing Cells Are Required for Periodontal Regeneration of the Mouse Incisor

Previous studies have shown that post-natal skeletal stem cells expressing Paired-related homeobox 1 (PRX1 or PRRX1) are present in the periosteum of long bones where they contribute to post-natal bone development and regeneration. Our group also identified post-natal PRX1 expressing cells (pnPRX1+ cells) in mouse calvarial synarthroses (sutures) and showed that these cells are required for calvarial bone regeneration. Since calvarial synarthroses are similar to dentoalveolar gomphosis (periodontium) and since there is no information available on the presence or function of pnPRX1+ cells in the periodontium, the present study aimed at identifying and characterizing pnPRX1+ cells within the mouse periodontium and assess their contribution to periodontal development and regeneration. Here we demonstrated that pnPRX1+ cells are present within the periodontal ligament (PDL) of the mouse molars and of the continuously regenerating mouse incisor. By means of diphtheria toxin (DTA)-mediated conditional ablation of pnPRX1+ cells, we show that pnPRX1+ cells contribute to post-natal periodontal development of the molars and the incisor, as ablation of pnPRX1+ cells in 3-days old mice resulted in a significant enlargement of the PDL space after 18 days. The contribution of pnPRX1+ cells to periodontal regeneration was assessed by developing a novel non-critical size periodontal defect model. Outcomes showed that DTA-mediated post-natal ablation of pnPRX1+ cells results in lack of regeneration in periodontal non-critical size defects in the regeneration competent mouse incisors. Importantly, gene expression analysis of these cells shows a profile typical of quiescent cells, while gene expression analysis of human samples of periodontal stem cells (PDLSC) confirmed that Prx1 is highly expressed in human periodontium. In conclusion, pnPRX1+ cells are present within the continuously regenerating PDL of the mouse incisor, and at such location they contribute to post-natal periodontal development and regeneration. Since this study further reports the presence of PRX1 expressing cells within human periodontal ligament, we suggest that studying the mouse periodontal pnPRX1+ cells may provide significant information for the development of novel and more effective periodontal regenerative therapies in humans.

Tissue Engineered Constructs for Periodontal Regeneration: Current Status and Future Perspectives

The periodontium, consisting of gingiva, periodontal ligament, cementum, and alveolar bone, is a hierarchically organized tissue whose primary role is to provide physical and mechanical support to the teeth. Severe cases of periodontitis, an inflammatory condition initiated by an oral bacterial biofilm, can lead to significant destruction of soft and hard tissues of the periodontium and result in compromised dental function and aesthetics. Although current treatment approaches can limit the progression of the disease by controlling the inflammatory aspect, complete periodontal regeneration cannot be predictably achieved. Various tissue engineering approaches are investigated for their ability to control the critical temporo-spatial wound healing events that are essential for achieving periodontal regeneration. This paper reviews recent progress in the field of periodontal tissue engineering with an emphasis on advanced 3D multiphasic tissue engineering constructs (TECs) and provides a critical analysis of their regenerative potential and limitations. The review also elaborates on the future of periodontal tissue engineering, including scaffold customization for individual periodontal defects, TEC's functionalization strategies for imparting enhanced bioactivity, periodontal ligament fiber guidance, and the utilization of chair-side regenerative solutions that can facilitate clinical translation.

Local Injection of Allogeneic Stem Cells from Apical Papilla Enhanced Periodontal Tissue Regeneration in Minipig Model of Periodontitis

BACKGROUND

Discovering suitable seeding cells and simple application technique will be beneficial for MSC-mediated treatment of periodontitis. Stem cells from apical papilla (SCAPs) might be the candidate seeding cell for the periodontal tissues regeneration based on their origin and characters. In this research, we investigated the effect of SCAPs on periodontal tissue regeneration in swine by local injection.

METHODS

We established experimental periodontitis model in miniature pigs and then treated them with SCAPs by local injection. Clinical assessments, computed tomography (CT) scanning, histologic examination, and quantitative measurements were used to evaluate the effect of periodontal tissues regeneration.

RESULTS

At 12 weeks after injection, clinical assessments showed that probing depth, gingival recession, and attachment loss values were 5.44±0.77 mm versus 7.33±1.0 mm (p<0.01), 2.33±0.33 mm versus 2.11±0.69 mm (p>0.05), and 7.78±0.84 mm versus 9.44±1.07 mm (p<0.01) in SCAPs group and 0.9% NaCl group, respectively. CT scan results showed a significant increase of 12.86 mm3 alveolar bone regeneration in SCAPs group compared with 0.9% NaCl group. In addition, histopathology results demonstrated remarkable regeneration in SCAPs group, whereas regeneration of periodontal tissue was hardly found in 0.9% NaCl group.

CONCLUSION

Local injection of SCAPs could effectively restore tissue defects brought about by periodontitis in the swine model. Thus, SCAPs, as an easily accessible dental-deriving stem cell, may serve as an alternative application for periodontitis treatment.

Local icariin application enhanced periodontal tissue regeneration and relieved local inflammation in a minipig model of periodontitis

Periodontitis is an inflammatory autoimmune disease. Treatment should alleviate inflammation, regulate the immune reaction and promote periodontal tissue regeneration. Icariin is the main active ingredient of Epimedii Folium, and it is a promising compound for the enhancement of mesenchymal stem cell function, promotion of bone formation, inhibition of bone resorption, alleviation of inflammation and regulation of immunity. The study investigated the effect of icariin on periodontal tissue regeneration in a minipig model of periodontitis. The minipig model of periodontitis was established. Icariin was injected locally. The periodontal clinical assessment index, a computed tomography (CT) scan, histopathology and enzyme-linked immune sorbent assay (ELISA) were used to evaluate the effects of icariin. Quantitative analysis results 12 weeks post-injection demonstrated that probing depth, gingival recession, attachment loss and alveolar bone regeneration values were (3.72 ± 1.18) mm vs. (6.56 ± 1.47) mm, (1.67 ± 0.59) mm vs. (2.38 ± 0.61) mm, (5.56 ± 1.29) mm vs. (8.61 ± 1.72) mm, and (25.65 ± 5.13) mm³ vs. (9.48 ± 1.78) mm³ in the icariin group and 0.9% NaCl group, respectively. The clinical assessment, CT scan, and histopathology results demonstrated significant enhancement of periodontal tissue regeneration in the icariin group compared to the 0.9% NaCl group. The ELISA results suggested that the concentration of interleukin-1 beta (IL-1β) in the icariin group was downregulated compared to the 0.9% NaCl group, which indicates that local injection of icariin relieved local inflammation in a minipig model of periodontitis. Local injection of icariin promoted periodontal tissue regeneration and exerted anti-inflammatory and immunomodulatory function. These results support the application of icariin for the clinical treatment of periodontitis.

A Chinese herbal supplement could treat an inflammatory autoimmune disease of the tissues surrounding the teeth. Zhipeng Fan and colleagues at Capital Medical University in Beijing, China found reduced inflammation and improved tissue regeneration in induced periodontitis in miniature pigs, three months following local injections with the Chinese herbal extract icariin. Periodontitis is an overactive immune response to bacterial invasion in the gums, leading to the breakdown of supportive tissue and bone, and potential tooth loss. Clinical assessment, CT scans and microscopic examination showed icariin injections promoted gum and bone regeneration, possibly by stimulating local stem cells. It also reduced signs of inflammation, including significantly decreasing the expression of IL-1β, an immune response mediator. Further studies are needed to confirm icariin’s mode of action and optimal dosage for potential clinical use.

Relationship Between Periodontal Screening and Recording Index Scores and Need for Periodontal Access Surgery

BACKGROUND

The validity of using pretreatment Periodontal Screening and Recording (PSR) index sextant scores to estimate periodontal access surgery needs is evaluated in patients with chronic periodontitis before and after completion of non-surgical periodontal therapy.

METHODS

In 110 adults, pretreatment probing data identified 486 sextants with PSR scores of 4 and 125 sextants with PSR scores of 3. Periodontal access surgery needs for all sextants were determined prior to treatment and after completion of non-surgical periodontal therapy for 213 sextants in 38 patients by two experienced periodontist examiners.

RESULTS

PSR scores of 4 identified untreated sextants with periodontal access surgery needs significantly better than PSR scores of 3 (odds ratio = 27.8; P <0.001) in multilevel, mixed-effects, logistic regression modeling analysis. However, only 37.6% of sextants with both pretreatment PSR scores of 4 and a pretreatment periodontal access surgery need continued to have surgical access needs after completion of non-surgical periodontal therapy. A higher percentage of sextants with PSR scores of 4 or 3 revealed periodontal access surgical needs when Class II or III furcation involvements and/or Grade II or III tooth mobility were also detected in the sextant than when these parameters were not detected.

CONCLUSIONS

Pretreatment PSR index scores of 4 were a strong indicator of periodontal access surgery needs in untreated dentition sextants but markedly overestimated surgical access needs remaining after completion of non-surgical periodontal therapy. These findings raise questions about the usefulness of pretreatment PSR evaluations for estimating potential periodontal access surgery needs in patients to be initially treated with non-surgical periodontal therapy.

Potential for Stem Cell-Based Periodontal Therapy

Periodontal diseases are highly prevalent and are linked to several systemic diseases. The goal of periodontal treatment is to halt the progression of the disease and regenerate the damaged tissue. However, achieving complete and functional periodontal regeneration is challenging because the periodontium is a complex apparatus composed of different tissues, including bone, cementum, and periodontal ligament. Stem cells may represent an effective therapeutic tool for periodontal regeneration due to their plasticity and their ability to regenerate different tissues. This review presents and critically analyzes the available information on stem cell-based therapy for the regeneration of periodontal tissues and suggests new avenues for the development of more effective therapeutic protocols.

Regenerative Medicine for Periodontal and Peri-implant Diseases

The balance between bone resorption and bone formation is vital for maintenance and regeneration of alveolar bone and supporting structures around teeth and dental implants. Tissue regeneration in the oral cavity is regulated by multiple cell types, signaling mechanisms, and matrix interactions. A goal for periodontal tissue engineering/regenerative medicine is to restore oral soft and hard tissues through cell, scaffold, and/or signaling approaches to functional and aesthetic oral tissues. Bony defects in the oral cavity can vary significantly, ranging from smaller intrabony lesions resulting from periodontal or peri-implant diseases to large osseous defects that extend through the jaws as a result of trauma, tumor resection, or congenital defects. The disparity in size and location of these alveolar defects is compounded further by patient-specific and environmental factors that contribute to the challenges in periodontal regeneration, peri-implant tissue regeneration, and alveolar ridge reconstruction. Efforts have been made over the last few decades to produce reliable and predictable methods to stimulate bone regeneration in alveolar bone defects. Tissue engineering/regenerative medicine provide new avenues to enhance tissue regeneration by introducing bioactive models or constructing patient-specific substitutes. This review presents an overview of therapies (e.g., protein, gene, and cell based) and biomaterials (e.g., resorbable, nonresorbable, and 3-dimensionally printed) used for alveolar bone engineering around teeth and implants and for implant site development, with emphasis on most recent findings and future directions.

Wound models for periodontal and bone regeneration: the role of biologic research

The ultimate goals of periodontal therapy remain the complete regeneration of those periodontal tissues lost to the destructive inflammatory-immune response, or to trauma, with tissues that possess the same structure and function, and the re-establishment of a sustainable health-promoting biofilm from one characterized by dysbiosis. This volume of Periodontology 2000 discusses the multiple facets of a transition from therapeutic empiricism during the late 1960s, toward regenerative therapies, which is founded on a clearer understanding of the biophysiology of normal structure and function. This introductory article provides an overview on the requirements of appropriate in vitro laboratory models (e.g. cell culture), of preclinical (i.e. animal) models and of human studies for periodontal wound and bone repair. Laboratory studies may provide valuable fundamental insights into basic mechanisms involved in wound repair and regeneration but also suffer from a unidimensional and simplistic approach that does not account for the complexities of the in vivo situation, in which multiple cell types and interactions all contribute to definitive outcomes. Therefore, such laboratory studies require validatory research, employing preclinical models specifically designed to demonstrate proof-of-concept efficacy, preliminary safety and adaptation to human disease scenarios. Small animal models provide the most economic and logistically feasible preliminary approaches but the outcomes do not necessarily translate to larger animal or human models. The advantages and limitations of all periodontal-regeneration models need to be carefully considered when planning investigations to ensure that the optimal design is adopted to answer the specific research question posed. Future challenges lie in the areas of stem cell research, scaffold designs, cell delivery and choice of growth factors, along with research to ensure appropriate gingival coverage in order to prevent gingival recession during the healing phase.