DISCUSIÓN

MG-Osseous implants. A multicentric retrospective study

Los implantes MG-Osseous. Estudio multicéntrico retrospectivo

Jaime Baladrón Romero¹; Luis Manuel Junquera Gutiérrez²

1 Médico especialista en Cirugía Oral y Maxilofacial. Práctica Privada (Oviedo, España).
2 Médico especialista en Cirugía Oral y Maxilofacial. Escuela de Estomatología. Hospital Central de Asturias (Oviedo, España)

In this work the authors describe their experience with an implant system designed in Spain and made in North America: MG-Osseous. This is a titanium implant system with a self-tapping design and a surface that has been treated with RBM.

During the decade of the eighties there was a relatively small number of dental implant systems. Implants developed slowly during this decade, and all the changes in designs or surfaces were backed by years of experimental and clinical studies.^1,2

During the following decades, the number of companies making implants grew enormously in relation to the increase in demand from the general public for this "new" treatment. Commercial pressure and competition among the different companies led to new designs and surfaces being introduced into the market, on many occasions with little or no scientific literature to support them.^3,4 This phenomenon has been+ accentuated in recent years. In today’s highly competitive market, companies are constantly trying to introduce "new features" in order to differentiate their product from that of their competitors. No longer do they wait years while studies of their products are carried out before introducing them into the market. On many occasions it is the clinicians themselves that have to "try out" these new treatments on patients coming to their surgeries. From the medical point of view, this is not the best scenario.

The follow-up time in implantology in most of the studies published has become shorter and shorter, and it has gone from being initially 5 to 10 years,⁵ to as little as 12- 18 months.^6,7 The strict success criteria applied initially were no longer used in many studies, and they were substituted by a less demanding implant survival percentage. All this has led to published results being better every time, and they are fast approaching an "impossible" 100% success rate.^9,10

The waiting period for implant loading is being reduced progressively. This has gone from six to three months, then down to week, days and hours. On the other hand, inclusion and exclusion criteria have also changed, and many situations that were considered inadvisable with regard to implant placement have stopped being so at the present time (diabetic patients, smokers, those with osteoporosis are routinely included in most of the current studies). Although this should have led to the results being poorer "a priori", this has not been the case, probably as a result of changes in the older, smooth machined surfaces to the new irregular, treated surfaces that allow better results to be achieved.^11,12

Many of the initial paradigms regarding osseointegration have fallen by the way side. Single-phase protocols are replacing two-phase protocols. Now we find immediate placement of implants after extraction, and there is immediate rehabilitation in days or hours for those edentulous patients needing "aesthetic" or "functional" restorations.^13-17 On occasions "traditional" surgical protocols have been substituted by transmucosal fixture placement guided or not by splints designed by specific computer software.^19-21 Many clinicians report cases in courses and conferences of patients undergoing multiple simultaneous extractions, curettage of periapical infectious lesions, placement of implants and immediate prostheses, violating to a greater or lesser degree the "traditional" protocols that require waiting for a prudent space of time between each treatment phase.^22-24 In this constantly changing context where it would seem that "everything goes" it is very important not to lose sight of the original concept behind implantology: scientific studies that support or not the "apparent" advantages of the new implant designs and surfaces that are introduced into the market by companies.

The work we have the pleasure of discussing is a clinical study that is multicentric and professionals from different areas of the country participate in it. The number of patients and implants included in the study is high: 247 patients and 1001 implants. All this gives the study authenticity and it is foreseeable that these results will be reproduced in other similar studies with similar characteristics. By comparison, the design of the study is retrospective and probably the rate of complications has been lower than if it had been an analogous but prospective study.

In their study the authors report an implant survival percentage rate of 97.8%. There results are excellent and comparable with the best series published on implants with treated surfaces. The Ti-Unite surface from Nobelbiocare has been documented in prospective studies with a 1-2 year followup and a failure rate of 3%.²⁵ The SLA surfaces from Straumann are backed by prospective studies that show high clinical efficiency (99% success rate) and a follow-up of 1-2 years.²⁶ The Osseotite surface from 3i is backed by prospective clinical studies with a success rate of 95-99% and a follow- up up to 5 years.^27,28 The Tio-blast surface from Astra Tech is backed by studies with good results and a follow-up of more than seven years.²⁹

In order to achieve such a high survival rate, the authors have applied a philosophy of "traditional" prudent treatment, and they have included only occasionally in their series cases of implants placed immediately after extractions (2.89%), cases of immediate loading (2.19%) and transmucosal implants (1.29%). This is a philosophy that we personally share in an attempt to reduce the failure rate in our patients to the maximum.

The authors have also been careful and prudent with regard to the selection of patients included in the study. The type of implant most commonly used in the study is the one with the standard diameter (3.75 mm) and longer lengths (13 and 15 mm). The percentage of grafts used was not high (88.43% of the implants did not need bone regeneration techniques). All this suggests that the cases included in the sample were selected wisely and that this probably contributed to the excellent rate of osseointegration of the fixtures reported by the authors in their work.

The results of the study refer, as in most of the current studies, to the percentage of implant survival (only the implants removed because of lack of stability are considered a "failure"). If stricter criteria had been applied, such as those described by Smith and Zarb,⁸ finding a higher complication rate would have been reasonable.

The study period of the patients included in the study is relatively short. Although the paper refers repeatedly to a follow-up of "two years" the study mentions that the implants were placed in 2004 and 2005, that most (68.24%) were placed in two surgical phases, and that the waiting period for the second phase and for checking the osseointegration of the fixtures varied between three and six months. This would seem to indicate that the follow-up time of the more than one thousand implants included in the study, has in reality ranged from a few months (for the last implants placed) to a maximum of two years (for the first implants in the study). This observation period is extremely short, as is that of many of the current studies. As a general rule, the complications registered during the first year of prosthetic loading are considered to have a surgical origin, while those registered later are of a prosthetic origin. If the follow-up period had been longer, the rate of complications would presumably have increased.³⁰

In short, this is a study that sums up the experience of a group of Spanish surgeons with an implant designed in Spain. The survival rate for the implants is excellent. This probably reflects the adequate design and manufacturing of the implant, and the extensive clinical and surgical experience of the authors.

It would be desirable for all companies to have studies of similar characteristics before the introduction of their products on the market. And ideally, multicentric prospective studies should have a longer follow-up time (a minimum of five years),^31,32 and that, in addition to survival as a percentage rate, other criteria for success be used such as crestal bone preservation³³ or the aesthetic results of the restorations.

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