Cementum periodontal ligament (PDL) and alveolar bone (AB) constitute the periodontium, an integrated and functional unit. The periodontal ligament is one of the three tissues that comprise the periodontium [1–3]. It is firmly attached to the AB and cementum, useful for mechanical stimulation while chewing, and provides a barrier against oral pathogens. The periodontium is a very complicated structure in which both tensile and compressive forces can regulate hard tissue remodeling through mechanical stress on soft tissue. Such cross-tissue communication is critical for maintaining microenvironmental homeostasis and regulating tissue remodeling [4–7].

In this regard, periodontitis is a multifactorial infectious disease characterized by inflammation of the supporting tissues of the tooth caused by periodontal bacteria organized in a complex biofilm [4–8], which, if not properly treated, can lead to the destruction of periodontal tissues and tooth loss in the long term. The onset and successive progression of periodontitis represent an unbalanced immune reaction of the host against an organized dysbiotic biofilm [1–4]. Nonetheless, periodontitis disrupts this mechanism and causes the degradation of both hard and soft tissues. This is accompanied by a cascade of cytokines and prostanoids that leads to the destruction of periodontal tissue. Even after the inflammation caused by periodontitis has been rebuilding the bone-PDL-cementum complex to a healthy level after it has been diminished remains a challenging endeavour [8, 9].

Because periodontitis accelerates the deterioration of tooth-supporting tissues and ultimately results in tooth loss, there have been a number of investigations into periodontal tissue regeneration. Some authors proposed that the kind of dominating cells on the root surface of periodontal wound tissue determined the style of tissue recovery. On the basis of this notion, new periodontal treatment strategies, such as directed guided tissue regeneration (GTR), have been presented [1–3]. The objective of GTR is the development of a new bone-PDL-cementum complex, the success of which has not yet been realized due to the limitations of regenerated bone, the absence of local vascularization, and the unpredictability of functional periodontium regeneration. The process of periodontal tissue repair is analogous to that of tissue healing during wound repair, which can be broken down into three phases: blood clot formation and inflammatory phase, proliferative phase, and remodeling phase [1, 10–12]. In this regard, other periodontal regeneration therapy techniques such as the use of growth factors (GFs) and amelogenin were developed. In periodontal regenerative medicine, combining cell regeneration together with biomaterials containing bioactive chemicals determined the development of a second- and third-periodontal regeneration technique [13, 14].

Therapies of the fourth and fifth generation for bioengineering periodontal tissue analogues, based on biomaterial and cell sheet constructs or genetically modified stem cells have evolved as a complement to existing therapeutic treatments. However, controlled clinical trials must be conducted to evaluate the danger and long-term efficacy of new bioimplants based on cell scaffolds. Embryonic stem cells (ESCs) and induced pluripotent stem (IPS) and [15–18] permit individualized cell therapy and periodontal regeneration can be enhanced by cell therapy, however, their usage is constrained by genetically modified cells. Moreover, there are areas of uncertainty in IPS biology, and it is proposed that their usage as bioimplants be implemented first in clinical trials on dental bone or periodontal abnormalities, where they can be conveniently monitored in long-term studies. It is proposed that recently acquired immortalized human periodontal cells replace embryonic constituents during periodontal tissue regeneration. Evolving tissue analogues made by three-dimensional (3D) cell printing methods aim for similarity to in vivo tissue properties and theragnostic applications, however, their functioning is still lacking [19, 20].

Based on the healing mechanism, the fundamental concept of periodontal regeneration is to enhance cell function and manage the local microenvironment at each phase. This article provides a summary of the characteristics of the microenvironment and the difficulties encountered during these crucial phases of periodontal regeneration. It also seeks to outline existing biomaterials and tactics for the modulation of critical biological events in each phase, which provides a theoretical foundation for in vivo research and clinical application of tissue-engineered periodontal regeneration.

In collaboration with the tissue-engineering technique, it is crucial to research two necessary substances: regulated drug delivery systems and the scaffold. The periodontal regeneration procedure employs two strategies, namely tissue engineering and the GTR. Clinical systems have made considerable use of GTR for periodontal therapy. It follows a regenerative surgical method that comprises the process of elevating, planning root surfaces, scaling, placing a barrier membrane beneath the gingiva for a period of time, and placing a mucous-gingival flap around the damaged teeth [21].

The tissue engineering strategy employs bioactive chemicals to build a biomimetic system and progenitor/stem cells to trigger new tissue creation. This strategy for periodontal regeneration is characterized as scaffold-free or scaffold-based, depending on the type of biomaterials used. In a scaffold-free method, either cell aggregates or individual cells are transported to a wound site lacking a cell carrier. Numerous cell types, including adipose-derived stem cells (ADSCs), bone marrow-derived dental pulp stem cells (DPSCs), and bone marrow mesenchymal stem cells (BMSCs), as well as DPSCs, have been validated for dental regeneration. In contrast to the cell suspension in swine periodontal defect cells, sheet therapy induced a unique bone growth process [22, 23].

The Cell Sheet Protocol is only able to regenerate a tissue layer with the most basic configuration. If the regeneration of the AB complex and PDL cementum involves the complex structural design of periodontium involving soft tissue PDL and two hard tissues (AB and cementum), then the only viable option is a scaffold-based one. To simulate periodontal cells, scaffolds with different properties in each phase are necessary. Particularly, the architecture, cellular structure, and biochemical arrangement of each component must be tuned to achieve periodontal healing. On the basis of the number of GFs and medications, explanations of scaffolding design and biomaterials are provided. In a mono-drug delivery procedure, a GF or medicine is administered to achieve a specified goal. Bone morphogenetic protein-2 (BMP-2) was used to expedite mandibular bone defect healing and promote bone regeneration. Non-covalent methods, such as ionic complexation and physical entrapment, can be utilized to combine bioactive chemicals with biomaterials. However, these methods are incapable of managing the burst release, which is undesirable for drug delivery operations. Frequently, the bioactive compounds’ activity declines during the manufacturing procedure (Figure 1) [24].

In the extracellular matrix (ECM), certain natural biomaterials, such as heparin sulfate and heparin glycosaminoglycan, include binding sites that produce strong interactions with bioactive chemicals. In this manner, the bioactive molecules are protected by this glycosaminoglycan (like GFs). Therefore, proteolytic degradation must be prevented, resulting in a longer and more sustainable release and denaturation. On the basis of this role for bone-tissue regeneration, a new technique, hierarchical nano-spheres encapsulating microspheres, has recently been created [20, 25, 26]. By using this technique, BMP-2 and, heparin was encapsulated in a gelatin nano-spheres heparin-conjugated system, which was then attached to microsphere nanofibers. This method makes it possible to include the control GF delivery system into a single injectable microsphere. BMP-2 has heparin-binding sites, which govern the sustained release of heparin and stabilize the protein. In addition, encapsulation in gelatin nano-spheres microspheres resembled the structure of collagen fibers and offered certain universal properties, such as a controlled disintegration rate, a larger surface area, and a reduced density value with high porosity. The nano-fibrous design inspired by the ECM enhanced the formation of new tissue, proliferation, adhesion, and differentiation of mesenchymal stem cells (MSCs) obtained from bone marrow. As demonstrated by an in vitro study, hierarchical microsphere nanofibers loaded with BMP-2 exhibited remarkable carrier capabilities and significantly enhanced bone regeneration. Combining regulated GF transport with an injectable biomimetic scaffold opens up new possibilities for cell-instructive scaffolds [22, 27].

Periodontal treatment is most effective when it combines the distribution of an osteogenic agent with the elimination of contaminants. The dual-drug delivery device successfully satisfies further GTR technical requirements [26, 28]. The dual-drug delivery procedure can sequentially release osteogenic and antibacterial medications, making it a viable method for periodontal therapy. In previously reported work, phase separation and a thermally-induced method were used to efficiently introduce a 3D dual-drug delivery system scaffold loaded with naringin (NAR) and metronidazole (MNA). The NAR and MNA were discharged in a sequentially structured fashion, with the MNA being discharged rapidly and the NAR following a more regular schedule. Numerous characteristics are created during the production of GTR electrospinning membrane: (a) broad adaptability and common methodologies; (b) with a varied structure, it can modulate fiber mats that improve cell attachment, achieve continuous and accurate local drug delivery, and boost drug loading. A unique core/shell configuration has been produced through the process of coaxial electrospinning, a novel type of spinning. By means of coaxial electrospinning, pharmaceuticals can be placed in the shell section and core portion simultaneously. Therefore, coaxial electrospinning is suitable for spinning multifunctional dual-drug delivery system membranes [13, 29–31].

The increased bioactivity, biological, and physiochemical features of dental membrane bioceramics have attracted a great deal of interest. Numerous studies have combined bioceramics such as bioactive glasses (BGs), hydroxyapatite (HA), and calcium phosphate (CP) in the field of dentistry due to their important biological properties, such as osteoinductivity and osteo-conductivity, and their capacity to reduce the natural inorganic bone constituent. Due to its favourable osteo-conductivity, bioactivity, and extreme in vivo resorb ability, beta-tricalcium phosphate (β-TCP) [32, 33] has been utilized as an exceptional bioceramic for bone healing/repair applications and dental membranes in a number of medical settings. Numerous types of membranes, including fibers, gels, foams, and mats, have been utilized. These membranes have been manufactured using a variety of techniques, including electrospinning, particle leaching, freeze-drying, self-assembly, solvent casting, and moulding. Nanofibers are promising for dental applications due to their ability to resemble ECM with a large porous structure, linked pores, and a high surface-to-volume ratio.

As an amorphous biomaterial capable of biodegradation, bioactive glass is mostly composed of sulphur dioxide (SO₂) as its main component. Bioactive glass is capable of discharging calcium (Ca) and silicon (Si) ions, thereby enhancing the osteoblast’s activity and forming a bond with the bone. The deposition of minerals on the surface of osteoblast cells is promoted by BGs encased in biodegradable membranes, it has been discovered. Maximum bioceramic remains unsuitable for use in dental regeneration as a result of its high brittleness and poor flexibility as a result of manufacturing processes involving elevated pressure and temperature [34].

In gene therapy, the regeneration of the periodontium ex vivo and its dissemination in vivo involves two major approaches: ex vivo and in vivo. Even though in vivo distribution is a one-step process, its therapeutic efficacy is low and it elicits a strong immunological response from the host. Ex vivo, on the other hand, is a two-step process in which tissues and cells of interest can be extracted, and the improved in vitro location, strength, and efficacy of the transduced cells can be costly and labor-intensive.

Even though gene therapy in dental regeneration is in its infancy and requires further suggestions for clinical trials, the treatment efficacy of gene therapy in the dental regeneration process can generate promising therapeutic opportunities and increase the likelihood of well-designed, integrated periodontium regeneration.

Carbon nanotubes (CNTs) [25, 35–37] not only facilitate the regeneration process but also function as a stable mechanical component. Due to their specific chemical, physical, and mechanical properties, CNTs have demonstrated considerable potential in the biomedical field. In vivo studies have demonstrated the bioactivity of multi-walled CNTs (MWNTs) in a variety of cells, especially osteoblast cells. Numerous researches have discovered that HA improves the biological properties of polylactic acid (PLA) and that nano-sized HA crystallites are optimally arranged on the surface of MWNTs [38].

Hydrogel is a cross-linked macromolecular polymer with hydrophilic strength and adequate absorption characteristics. As a hydrogel, several types of biomolecules can be created. The advantages of a hydrogel structure consist of bioactivity, a higher water content, and a flexible construction process. Numerous types of hydrogel have been used to regenerate the periodontium. When biphasic CP (BCP) and a collagen membrane were coupled with hydroxypropylmethyl cellulose (HPMC), the membrane produced exceptional outcomes, including the prevention of soft tissue attack into periodontium defects and considerable bone repair [39].

The lack of mechanical strength is a significant limitation of hydrogel in tissue engineering. Numerous surveys used a chemical modification to circumvent the obstacle to a certain extent.

Wool keratin and polylactic-co-glycolic acid (PLGA) are two excellent biological substances. These two biomaterials have applications in the field of GTR technology. However, due to the lack of inherent strength of molecular recognition sites on the PLGA side, they can bind the PLGA application in the medical field to a specific place and block specific cell adhesion [38]. Therefore, materials with greater cell affinity, such as HA and collagen, are predominantly reformatted with PLGA to improve biocompatibility. Wool keratin is an organic biomaterial. It is capable of causing the biodegradation of harmless compounds in vivo and in vitro without eliciting an immunological or inflammatory response. In addition, its treatment performance is superior, and it may be manipulated into many forms. However, keratin biomaterials often have limited mechanical strength, as the membranes of pure wool keratin exhibit fragility [40, 41]. Consequently, wool keratin is mixed with PLGA to produce composite GTR membranes. However, wool keratin can reduce the rate of PLGA-induced sterile infection and boost PLGA’s bioactivity and cell affinity. By enhancing the mechanical properties of wool keratin with PLGA, an ideal GTR membrane may be manufactured in accordance with the specifications. Using solvent casting and electrospinning, a bilayer-graded membrane with a bottom layer of non-porous PLGA and wool keratin membrane and a top layer of porosity PLGA/wool keratin membrane was created. The porous layer encourages regeneration, but the thick layer can inhibit gingival epithelium and connective tissue from interfacing with the root surface: remodel periodontal ligament, cementum, and AB; make a new link; and ultimately accomplish periodontal tissue regeneration. The resultant membranes were then utilized in a GTR technique on beagle dogs. The research will create the groundwork for a deeper comprehension of bilayer wool keratin/PLGA membranes for the treatment of dental problems and the use of GTR [42].

Biodegradable polymer (BP) has also been used in the dental regenerative technique as powders or scaffolds for tissue engineering, and microparticles to stimulate local tissue healing or solutions. Previous studies indicated that an inorganic covering can promote implant surface differentiation, mineralization, cell proliferation, and early cell adhesion [41, 43]. In order to retain alveolar ridge volume after extraction, resveratrol is placed onto electro-spun PLA and polycaprolactone (PCL) membranes. The two membranes were able to release resveratrol in a continuous manner adjustable, and kinetically diverse manner simultaneously on two fronts as promoting new bone formation and inhibiting bone resorption [9, 26, 35, 43–46].

Scaffolds primarily serve as a platform for cell adhesion, tissue ingrowth, and early structural support in tissue engineering. In GTR, non-degradable or degradable membranes limit epithelium growth by contact, allowing for a rather gradual (4–6 weeks) repair of periodontal connective tissue and PDL. However, a protracted duration of periodontitis may diminish the efficacy of GTR by diminishing the healing capacity of PDL cells, impeding the immunological response of the host, or denaturalizing cellular matrix (CM) to an extreme degree [27, 47].

Biomaterials should ideally be distinguished by their biocompatibility, ease of surgical site adaption and placement, maintenance of space, clot stability, tissue integration, cell invasion/guidance, and encouragement of cellular proliferation. On the basis of their origin, scaffolds are categorized as allogenic, xenogeneic, alloplastic, or living structures (when they include cells) [40–44].

Scaffolds used for the regeneration of periodontal tissues can provide contact guidance that enhances the migration of cells into periodontal defects in a timely manner, leading to increased regeneration. Various bioactive cues, like GFs and cytokines, serve as stimuli and have also been supplied with scaffolds to enhance cell migration and tissue ingrowth. To the best of our knowledge, however, there is no experimental evidence that scaffold-mediated periodontal repair is as rapid as GTR. Still, insufficient evidence suggests that scaffold-mediated periodontal repair is equivalent to GTR [48–50].

The majority of prior investigations on biodegradable scaffolds [4, 7, 30, 31]. Previous authors created a PCL, collagen type I (COL-I), and recombinant human cementum protein 1 (rhCEMP1)/amorphous CP (ACP) electrospun multiphasic scaffold that promoted the formation of a CM-like structure when implanted in the calvarium of rats carrying periodontal ligament stem cells (PDLSCs) [16, 51].

Several prior works also utilized tri-phasic scaffolds to facilitate the regeneration of CM, PDL, and AB [48–51]. The tri-phasic scaffolds with spatiotemporal delivery of three separate bioactive signals and dental stem/progenitor cells efficiently stimulated the creation of a periodontium-like multi-tissue construct when implanted on the dorsum of immunodeficient mice for six weeks. Furthermore, some authors created tri-phase, 3D printed scaffolds with regionally distinct micro-architectures that have the ability to promote the integrated healing of multi-tissue periodontium by PDLSCs [52].

In this context, acellular dermal matrix (ADM) is a soft tissue transplant derived from decellularized human skin. Devoid of epithelium and cellular components, the ECM functions as a scaffold to enable cellular migration and revascularization from the surrounding host tissues [52–55]. A potential explanation may be that the ADM is incapable of promoting keratinization of the overlaying epithelia, which appears to be a favorable predictor of gingival margin stability. In the existence of a specific amount of keratinized tissue width at baseline, it is possible to achieve comparable root coverage outcomes with ADM as with connective tissues, according to studies [52–56].

The ADM was first developed for the treatment of burn wounds but has since been extensively utilized for a variety of additional purposes, including face augmentation, dural replacement, breast reconstruction, and aesthetic plastic surgery. In the field of dentistry, ADM was initially tested for the enhancement of connected and/or keratinized gingiva. However, the clinical results of the ADM are inferior to those of the free gingival graft (FGG). Specifically, the ADM appears to be more susceptible to shrinking, which may potentially account for the decreased tissue thickness seen. Compared to FGG-treated sites, ADM-treated sites exhibit a “scar”-like tissue appearance, while a superior aesthetic and color match with the surrounding tissue has been noted.

As discussed previously, different scaffold methods have demonstrated considerable potential for periodontal regeneration. Recent technical advancements in micro-precise regional control in the construction of scaffolds have established a significant milestone in the direction of integrated regeneration of multi-tissue periodontium.

Periodontitis is a chronic infectious condition that necessitates efficient treatments for biological applications. GTR is a beneficial procedure for stimulating the challenging regeneration of tooth-supporting tissues. Present commercial GTR membranes are unable to achieve the desired therapeutic effects and exhibit a number of limitations, such as limited mechanical strength, a diminished capacity to stimulate the hierarchical periodontal regeneration process, and an unsuitable degradation rate, among others. To achieve therapeutic properties, novel GTR membranes must satisfy the following three requirements: (a) appropriate degradation, biocompatibility, and mechanical strength; (b) organized PDL regeneration activity and optimal AB; and (c) antibacterial activity. To ensure their exceptional biocompatibility, the proper additives, and biopolymers should be identified. Moreover, chemicals and biopolymers in the correct proportions make it possible to manage the membrane’s deterioration rate.

Synthetic polymers with high mechanical strength and natural polymers with biomedical uses and electrospinning capability can be combined to maximize their mutual advantages. An important characteristic required for GTR membranes is the capacity to stimulate periodontal regeneration. Due to their inherent potential to induce endogenous ECM, electrospun nanofibers are remarkably effective at inducing osteodifferentiation. MWNTs derived from carbon and inorganic ceramics are expected to facilitate tissue regeneration while simultaneously enhancing mechanical applicability. In addition, effective biomaterials, such as GFs and proteins, are utilized to induce degenerative pathways. In clinical employment, inflammation is the leading cause of GTR-related adverse effects. Immediate anti-inflammatory conditions and periodontal regeneration are promoted by the use of numerous medications. To date, several medicines and functional proteins such as antimicrobial peptides (AMPs), NSAIDs, metal nanoparticles such as silver nanoparticles (AgNPs), and oxide components such as zinc oxide (ZnO) have been incorporated into electro-spun nanofibers to generate an optimal anti-inflammatory environment and suppress bacterial growth. To maintain the control of drug release and bioactivity, polymer-based factors involving component weight and polymer weight, as well as drug-based factors including drug loadings, the crystallinity of pharmaceuticals, and molecular weight, must be considered. Due to the ever-increasing use of antibiotics in clinical settings, bacterial resistance has become a formidable obstacle in microbial prevention. Hence, it is vital to seek out more types of medications to effectively control periodontal inflammation and reduce bacterial resistance. The fast depletion of GFs in vivo drastically lowers their therapeutic effectiveness. The release of macromolecules is unnecessary when electrospun nanofibers are utilized. Electrospinning techniques can be combined with other procedures to create effective means for the convenient release of GFs and to detect the temporally unique discharge throughout the regeneration procedure.

Stem cells, such as PDLCs, play a vital role in periodontal tissue engineering. Dental cells cannot regenerate spontaneously due to a lack of viable stem cells. Using a tissue-engineering approach, it is possible to cultivate stem cells on a scaffold in vitro and then insert them into damaged sites to provide the necessary precursors for periodontal regeneration. However, the basis of stem cells, the in vitro culture state, the clinical impacts, and the viability of stem cells are thought-provoking in terms of their therapeutic applications. The subsequent step is to choose acceptable stem cells and GFs, identify adequate quantities in scaffolds and improve the viability of these stem cells for optimal periodontal regeneration.

Before human clinical trials, additional research is required to optimize the content and structure of new biomatrices for dental applications and to customize them to the specific needs of the patient population. For periodontal tissue engineering, the developed composite materials are beneficial for the production of bioactive implants incorporating dental cells. Using in vivo experimental models, it will be necessary to conduct additional research on osteoblast activity, differentiation, and the creation of ECM components in order to evaluate the efficacy of bioactive implants to induce bone defect repair. In addition, more biotechnological study on the production of bioactive implants and their inflammatory response after implantation is required. All of these innovative processes and techniques augur the creation of future therapeutic programs.