DISCUSIÓN

Clinical analysis of our experience in over 100 cases of maxillary sinus lift

Elevación de seno maxilar. Análisis clínico de nuestra experiencia en más de 100 casos

Pedro Villarreal Renedo¹, Lorena Gallego López²

¹FEA del Servicio de Cirugía Oral y Maxilofacial. Hospital Universitario Central de Asturias. Práctica privada. Oviedo, España.
²MIR del Servicio de Cirugía Oral y Maxilofacial. Hospital Universitario Central de Asturias. Oviedo, España.

This work shows us the experience that that a Service Hospital of Oral and Maxillofacial Surgery of bone grafts of maxillary sinus over 12 years with excellent results. Although it is a retrospective study and with an asymmetrical distribution of variables, it exhaustively analyzes and scientifically validates the results obtained.

The authors present a large series of sinus bone grafts carried out in one hospital, although the sample could be heterogeneous because the operations were carried out over many years(during which time the technique had progressed and changed progressively) and the study doesn't specify if the operations were carried out by the same surgeon or by various surgeons. The implant success rate (96.91%) is without a doubt the highest of any series in the literature.

The term "Maxillary sinus lift" should be replaced by "bone graft of the Maxillary sinus". The first term is literally translated from English "Sinus lift" and refers to the detachment and elevation of the Schneider membrane which is the first step when carrying out a sinus bone graft. It would only be correct to use this term if we didn't perform the graft with any additional material. If we graft any material that is of "non bone" origin, it would be correct to talk about sinus graft and yes, as in the majority of cases, the bone graft material from one nature or another should be referred to as sinus bone graft.

It is shocking that all of the patients had radiological control before and after surgery using a orthopantomograph and dental CT. At the past Board Conference about Bone grafts of the Maxillary Sinus in Oviedo they established the convenience of carrying out a preoperative study using CT (aside from the OPT) in an attempt to analyze the existence of a previous sinus pathology and anatomic deformities or irregularities that could make grafting difficult. The necessity to have a post operative CT would only be justified in the cases where implants were delayed to evaluate the bone available. Without a doubt, the hospital environment where these jobs were performed has allowed its authors to carry out such precise studies, circumventing, among other things the economic cost and the quantity of radiation that the patients received.

Due to this, it is surprising that 76.2% of the cases were carried out under general anesthesia. Without a doubt, this technique can be performed using a local anesthetic in the majority of the cases. General anesthetic is only necessary when the grafts are being taken from extra oral locations like the iliac crest or the calvarium, necessary acts except when apposition grafts are carried out simultaneously.

The authors indicate the collection of instruments that are used to carry out the lateral anthrostomy without emptying for anything special or specifying when each one is used and under what circumstances. This is probably because these cases were performed such a long time ago. This article also does not specify if the cases of membrane tear were caused by the use of specific instruments or if sinusitis cases were related to membrane tears. It is obvious that this information is relevant when drawing conclusions about the data.

The article describes the different types of grafts used throughout the long period of the study; however it does not mention the reasons or criteria used when deciding which graft to use. We can conclude hat they used bovine derivative and autologous bone in cases where apposition grafts were not needed and iliac crest or calvarium grafts when an apposition graft was needed. There should have been a lot of transversal bone atrophy in many of the cases that reflects the high percentage of patients that had apposition bone grafts (41%) this conforms to the amount of cases that iliac crest and calvarium grafts were used (35%). Its behavior coincides with the current general opinion: the first indication of a sinus bone graft without apposition grafts are xenografts and small quantities of autologous bone retrieved using bone scrapers. In cases where apposition grafts were needed we could use intraoral donor zones (ramus or mandible symphysis) if we don't need to increase the width of the bone crest or if the transversal bone atrophy is extreme, calvarium or iliac bone grafts.

Placement of the implants was done simultaneously (64.7%) when the initial bone height was at least 5mm, subtly achieving stability that could justify the magnificent results. Without a doubt the implant success rate depends more on primary implant stability than the type of implant used. When placing implants simultaneously, aside from the importance of the preoperative alveolar ridge height, the density and quality of the residual crest bone is very important. This can be evaluated if preoperative tomography is taken, like it was in this project. If we also make post operative CT's available it is a shame not to have studied the neoformed bone quality, the crestal and lingual peri-implant resorption. If in addition to this we take post operative CT, it is a shame that the neoformed bone quality was not studied and the peri-implantary and lingual resorption through out the study. If these data were studied perhaps the results would have been worse for smokers.

The greatest success rate (statistically significant) in terms of the immediate survival of placed implants seemed to be, according to the authors unimportant and clinically undervalued. However, these results encourage us to continue placing them in this way whenever the primary stability is sufficient. The advantages are numerous and clear(less wait time and less surgical interventions).

This article does not specify any criteria that helps decide when to place delayed implants or set the prosthesis. The differences we found in terms of wait time for delayed implants and setting doesn't have any real value. Because of this reason I understand, it was carried out according to both, the experience of the surgeons and what is written and recommended in the scientific literature(less time when using autologous bone) We can not conclude because of the results we obtained in this study, that when using autologous bone grafts less waiting time is needed for implant placement or prosthetic setting. We are missing a clinical parameter that indicates the state of bone maturity; this can only be measured using CT studies and checked using a histological study.

We should congratulate the authors for their work and excellent results, encouraging them to continue to investigate from their privileged position at their hospital, about the advantages and inconveniences of the new bone graft materials. We also invite them to go deep inside the new cell cultivating and tissue engineering techniques and in the unknown: like bone maturation that is produced with each biomaterial; the causes of complications and the most importantly the right moment to place and load implants.

References

1. Hage G. Crestal sinus floor elevation. En: Khoury F, Antoun H, Missica P ed. Bone augmentation in oral implantology. Berlin, Quintessence Publishing Co, Ltd. 2007:321-39.        [ Links ]

2. Achong RM, Block MS. Sinus floor augmentation: simultaneous versus delayed implant placement. En: Jensen OT ed. The Sinus bone graft. 2º ed. London, Quintessence Publishing Co, Ltd. 2006.        [ Links ]

3. Use of xenograt for sinus augmentation. Froum SJ, Wallace SS, Cho S, Tarnow D. En: Jensen OT ed. The Sinus bone graft. 2º ed. London, Quintessence Publishing Co, Ltd. 2006.        [ Links ]