The boom in implant dentistry is attributed to a combination of various reasons: prolonged life span of aging individuals, failures associated with removable and fixed prostheses, advantages, and predictable outcomes associated with the use of implants. Before placement of the implant, local bone defects and general poor bone quality necessitate bone reconstruction. Besides this, localized bone loss around the implant fixture represents the clinical challenge, especially in the case of gingival recession, which requires further surgical interventions. With loss of natural teeth, periodontal ligament (PDL) cells are lost as well. Therefore, these cells cannot participate in wound healing around endosseous implants, which are inserted for replacement of lost teeth. Thus, at present, optimal healing around implants is considered to be intimate bone-to-implant contact, called osseointegration.
Currently, osseointegrated implants are generally agreed to be the most acceptable implants because of their high long-term clinical survival rate. These problems could be resolved, if implant with PDL could be developed, which could be achieved by LIGAPLANTS, a combination of the PDL cells with implant biomaterial. Because osseointegrated implants are “ankylosed” and do not have the same mobility as natural teeth with a PDL, efforts have been made for years to compensate for this obvious difference by “shock-absorbing systems” built into the implant or its suprastructure.
Ligaplants are a new treatment modality, which are being clinically tried in vivo and in vitro. Moreover, in animal studies, they have shown good results, although in vivo results are yet to be correlated. Several successful experiments have been conducted to devise “implant supported by the periodontium” that can maintain form function and potential proprioceptive responses similar to a natural tooth. Based on these strong evidences, the possibility of the future clinical use of such implant can be strongly stated which would revolutionize the implant dentistry and favored by the patients as well.
PROPERTIES OF LIGAPLANTS
- It acts like a shock absorber, giving the tooth some movement in the socket
- It also provides proprioception
- The PDL also has an important interaction with the adjacent bone, playing the role of the periosteum, at the bone side facing the root
- It contains vital cells such as osteoclasts, osteoblasts, fibroblasts, cementoblasts, cementoclasts, and most importantly, the undifferentiated mesenchymal stem cells
- These cells are all important in the dynamic relationship between the tooth and the bone.
- It alleviates problems such as gingival recession and bone defects of the missing tooth
- Mimics natural insertion of natural tooth roots in the alveolar process
- Ligaplants become firmly integrated without interlocking and without direct bone contact, despite the initial fitting being loose to spare PDL cell cushion.
- The culturing of ligaplants should be done with caution. i.e., the temperature, the cells that are used for culturing, the duration of the culturing, and others. If some problem evokes during the culturing, the ligaplants may fail as other nonperiodontal cells may develop
- Besides, the cost of this implant is high due to limited facilities
- The factors affecting the host to accept the implant or the growth of PDL in the socket is unpredictable, which may result in failure of implant
- The prolonged cell culturing may favor the appearance of non-PDL cell types.
Clinical importance of ligaplants
For reconstruction and regeneration, the important elements required are as follows:
- Matrix or a scaffold
- Signaling molecules
Tissues prepared in laboratory are cultivated with In vitro technique. The cells are cultured on the biodegradable scaffolds or matrix with the help of signaling molecules, following which they are transplanted into the body. Whereas, when all the cultivated vital elements are placed in a tissue defect and undergoes a natural healing process in the body giving rise to regeneration, it is called as in vivo technique.
It induces intrinsic healing activity at the site of tissue defect using the three elements. This can be done by both in vitro and in vivo.
Transplantation of tooth with double PDL stimulation is one of the best examples of its healing capacity. The donor tooth is extracted and immediately replanted in its original alveolus, 14 days before transplantation. Cell proliferation and differentiation is seen as this deliberate trauma triggers a healing process within the PDL.
The transplantation of the tooth can be performed with millions of cells attached to its root by new Sharpey's fibers after 14 days, when the cell culture reaches its peak of activity.
Buser et al. showed that titanium dental implants when placed in contact with retained root tips, the PDL of these roots served as a source for cells which could populate the implant surface during healing. Now, tissue engineering has opened a new vista in periodontal regeneration and more so in the treatment of dental implants. From various scaffolds to matrices, all have proved their ability to regenerate the entire periodontium. In another study, Gault et al. used ligaplants (combination of PDL cells with implant biomaterial) for tooth replacement. The study involved animal experiments on mice and canine models as well as human clinical investigation. In the canine model, PDL formation was observed and a new layer of tissue resembling repair cementum was formed on the ligaplant surface. In humans, after surgery, a desmodontal gap, corresponding to PDL space of normal width, was evident around one ligaplant, and the structure of the lamina dura resembled that around a natural tooth. In one ligaplant, radiographs indicated that it had moved inside apparently intact bone, indicating the presence of newly formed PDL.
In the field of periodontal regeneration, debates still exist on the type of cells possessing the capability of forming new cementum on previously exposed root surfaces. Some authors reported that cells residing in the alveolar bone are responsible for cementum production, whereas some investigators reported that only PDL cells can produce cementum, revealing the significance of PDL around dental implants.
Kiong and Arjunkumar stated that ligaplants as tooth replacement have decisive advantages as compared with osseointegration devices, due to their periodontal tissue regeneration. The ligaplants surgery is moderately simple, because the implant is not tightly fitted to its site. Besides that, the patient may not have to undergo bone grafting, inconvenience, and discomfort with the ligaplants placement.
SUCCESS OF THE LIGAPLANTS??
The development of a regenerative PDL depends on site-specific signaling, which in turn is mediated by an anatomic code, written in expression patterns of homeogene-coded transcription factors. Hence, the homeoproteins influence the synthesis of cell surface and signaling components, and signals from the cell surface feedback to modulate homeogene expression, whereby cell identities are established according to the anatomic site and tissue type.
RISK FACTORS OF LIGAPLANTS
The development of PDL for the generation of PDL depends majorly on site signaling, which is largely mediated by anatomic code and homeogene-coded transcription factors. These homeoproteins are quintessential for the synthesis of cell surface and signaling components. The factors affecting the growth of PDL in the desired site are often unpredictable, and hence, it becomes a major risk factor for the treatment results to be obtained.
As with all emerging technologies, a successful future for ligaplant will only be achieved through research finding and testing. Current research in ligaplant is focusing on extending this initial observation to clarify and to further pursue the implications of this type of healing around dental implants with titanium surfaces evaluation of whether this phenomenon occurs around implants with other surfaces. Further research on humans with long-term follow-up could only validate the feasibility and success of ligaplants.
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Conflicts of interest
There are no conflicts of interest.
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