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CATEGORY LINICAL

PMMA-GRAPHENE: a new restorative material for digital work flow

Dr Oriol Canto-Naves

By Dr Oriol Canto-Naves DDS, PhD, Universitat Internacional de Catalunya-Barcelona oriolcanto@uic.es

I n recent years, implantological rehabilitation has changed a lot, especially due to the use of digital technology (CAD-CAM) and the realization of monolithic prostheses, that is, made with a single restorative material. Whether in single crowns, partial prostheses or full arch, zirconia has emerged as one of the most widely used materials. 1, 2 Undoubtedly, zirconia has great virtues, such as esthetics, biocompatibility, low adhesion of dental plaque, hardness. 1, 2 We know from the extensive literature that there are patients at higher risk for peri-implantitis, such as smokers, patients with poor oral hygiene, predisposing genetic factors, patients with a previous history of periodontitis, uncontrolled diabetics, alcoholics... 3-8 . But in recent years, new risk factors have appeared, such as the absence of keratinized gingiva or restorative material. In all these patients with a high risk of peri-implantitis there is a common factor: gingival in ammation 3-8 . e literature concludes that gingival in ammation associated with occlusal load, functional or parafunctional, is the cause of peri-implantitis. 5-7 For this reason, the exhaustive control of gingival in ammation, through rigorous peri-implant maintenance, is fundamental for the survival of dental implants. But in patients who are at risk, those who, however much we may not like it, present and will present gingival in ammation, the material chosen for the rehabilitation is of utmost importance. ere are two factors that we have to take into account: the transmission of the impact generated by any dynamic force (chewing, bruxismand swallowing) exerted that generates stress on the implant and the weight of the rehabilitation. In both cases, the main objective of the rehabilitation is to achieve a reduction of the stress generated in the implant-bone-gingiva-prosthesis area. e lower stress in this area, the lower risk of peri-implantitis. Numerous articles, using Finite Elements Analysis, conclude that, in single crowns, the restorative material used does not matter, since in all cases, the stress

generated in the neck of the implant is the same 9-12 . But, in all these articles, the force exerted to obtain the result is a static force, very unusual in an oral environment. It would be a clenching force. Most of the forces exerted in the oral cavity are dynamic forces. On this point, articles in which a dynamic force (impact of a ball sliding down a slope, robotic simulation of mastication, percussion by means of a Periometer®) 13-16 or by means of dynamic FEA 17,18 , show that the material does matter when it comes to transferring more or less stress to the implant-bone zone. Materials such as metals, ceramics and zirconia tranfer much more stress (50-60% more) than absorbent-dissipative materials such as polymers (PEEK, carbon ber, glass ber, quartz ber), composites/hybrid composites or resins (PMMA, PMMA Graphene). e second point I have made to take into account is the weight of the rehabilitation. e greater the weight of the rehabilitation, the greater the impact exerted. e greater the weight of the restoration

or the antagonist, the greater the kinetic energy, that is, the greater the impact, causing greater stress in the implant area. If lighter weight materials are used, they will generate, in the same patient, less stress in the implants and fewer problems in the restorations. is point is of greater importance in large restorations, such as hemi-arches or full-arches. A new restorative material has recently emerged, PMMA-Graphene, which com bines many virtues: reduction of stress generated to implants, hardness, biocom patibility, low weight, esthetics, durability... and it is used as a monolithic material, being able to follow a CAD-CAM digital ow. Graphene has numerous applications in dentistry as a coating for implants to increase osseointegration, in membranes for bone regeneration, in endodontics, caries risk reduction, bone regeneration. 19-29 and in dental and implant rehabilitations when incorporated into PMMA 19,30,31 . e material is presented in milling discs with di erent shades of the VITA guide, where, if desired, a light stain is applied to improve the esthetics. In this article, I would like to present di erent rehabilitations with this promising new material, from a single crown, partial denture and full-arch. u

Figure 1: More mass/weight, more Kinetic energy (impact)

Different images of implant rehabilitations using PMMA-Graphene: single crown, partial prosthesis and full-arch.

Table 1: List of density of different materials used on implant rehabilitation. More density, more mass/ weight, more impact.

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86 AUSTRALASIAN DENTIST