Introduction

The application of dental implants to support prosthetic constructions has evolved into a viable alternative to conventional prosthetic procedures, although implant procedures in the posterior maxilla often pose a problem due to insufficient pre-existing bone. An insufficient volume of bone to allow for reliable primary placement of implants can be solved by a maxillary sinus floor elevation procedure using autogenous bone, bone substitutes, or a mixture of autogenous bone and bone substitutes, as grafting materials. Currently, the most reliable and well studied grafting materials for sinus floor augmentation surgery are autogenous bone and mixtures of autogenous bone with bovine bone material (BioOss ^® ; Geistlich Pharma AG, Wolhusen, Switzerland). It is questionable, however, whether adding autogenous bone to biomaterials such as BioOss ^® is necessary, as the morbidity of the procedure might be considerably less when no donor site is needed.

In recent animal studies it has been shown that seeding BioOss ^® with mesenchymal stem cells (MSCs) derived from concentrated, non-mineralized tissue may result in bone-forming kinetics comparable to bone-forming kinetics in a region solely reconstructed with autogenous bone. These promising results from an in vitro and animal study prompted a study in humans. In a randomized controlled trial, differences in bone formation occurring after maxillary sinus floor elevation surgery with BioOss ^® combined with either an autogenous bone marrow concentrate (enriched in MSCs) or autogenous bone was assessed. The primary endpoint was the percentage of new bone formed at 3 months after the elevation procedure, i.e. at the time of implant placement. From this trial it was concluded that MSCs derived from an aspirate of the posterior iliac crest seeded on BioOss ^® particles indeed can induce the formation of a sufficient volume of new bone to allow for the placement of implants within a time-frame comparable to that of applying either solely autogenous bone or a mixture of autogenous bone and BioOss ^® . This time-frame is considerably shorter than when only BioOss ^® is applied. Adding MSCs to a bone substitute could be an alternative to the use of autografts as a grafting material, thereby reducing donor site morbidity, particularly when larger grafts are needed. For example, as the iliac crest is commonly used as the donor site for patients who need a bilateral, vertical maxillary sinus lift, replacement of autogenous bone with bone substitutes might considerably decrease the morbidity and discomfort of the grafting procedure from the perspective of the patient.

As the results of the trial described above were very promising, the next step should be to assess whether, after loading, dental implants placed in an area reconstructed with MSC-enriched bone marrow concentrate perform at least as well as implants placed in an area reconstructed with a mixture of autogenous bone and BioOss ^® . Therefore, the aim of the current study was to assess implant survival and 1-year clinical performance of implants placed in the posterior maxilla that had been subjected to maxillary sinus floor elevation surgery with BioOss ^® mixed with MSCs or BioOss ^® mixed with autogenous bone.

Patients and methods

The study described in this paper was a clinical follow-up of 12 patients who were involved in the randomized, double-blind, split-mouth study of Rickert et al. on bone formation in maxillary sinuses reconstructed with a mixture of BioOss ^® and a bone marrow concentrate enriched in MSCs, or with a mixture of BioOss ^® and autogenous bone. The patients had been referred to the department of oral and maxillofacial surgery because of insufficient retention of their upper denture related to a severely resorbed maxilla and were selected on the basis of the following inclusion criteria: (1) severely resorbed maxilla (class V–VI) with reduced stability and retention of the upper denture; (2) ≤4 mm bone height between the maxillary sinus and the top of the maxilla on both sides; (3) class IV bone quality; (4) edentulous period of at least 1 year; (5) no history of radiotherapy in the head and neck region; (6) no history of reconstructive or pre-prosthetic surgery or previous oral implantology.

Orthopantomograms, lateral cephalograms, and postero-anterior oblique radiographs were made to assess the height of the maxillary alveolar bone, the dimensions of the maxillary sinus, and the antero-posterior relationship of the maxilla to the mandible. The radiographs were also screened for sinus pathology.

A bilateral sinus floor augmentation procedure of the atrophic maxilla was performed in these patients (mean age 60.8 ± 5.9 years, range 48–69 years). At random, by use of envelopes, the augmentation procedure was performed on one side with BioOss ^® seeded with a bone marrow concentrate from the posterior iliac crest enriched in MSCs (test side); the contralateral side was augmented with a mixture of 70% biomaterial (BioOss ^® ) and 30% autogenous bone (harvested from the retromolar area of the mandible; control side), as commonly applied in reconstructive surgery. Endosseous implants (Straumann Standard SLA ^® implants; diameter 4.1 mm, length 12 mm, RN; Institut Straumann AG, Basel, Switzerland) were placed 3–4 months after the sinus floor elevation procedure. Depending on the available intermaxillary space and prosthodontic needs, two to three implants were place on each side of the posterior maxilla. A total of 66 implants could be installed with primary stability. After an osseointegration period of 3 months, the prosthetic construction, being an implant-supported overdenture, was fabricated in accordance with the procedure described by Slot et al.

The treatment outcome of the 12 edentulous patients needing bilateral sinus floor elevation surgery was evaluated in the current study. The protocol was approved by the institutional ethics committee and the study was conducted in accordance with the Declaration of Helsinki. Informed consent was obtained from all patients.

Patients and methods

The study described in this paper was a clinical follow-up of 12 patients who were involved in the randomized, double-blind, split-mouth study of Rickert et al. on bone formation in maxillary sinuses reconstructed with a mixture of BioOss ^® and a bone marrow concentrate enriched in MSCs, or with a mixture of BioOss ^® and autogenous bone. The patients had been referred to the department of oral and maxillofacial surgery because of insufficient retention of their upper denture related to a severely resorbed maxilla and were selected on the basis of the following inclusion criteria: (1) severely resorbed maxilla (class V–VI) with reduced stability and retention of the upper denture; (2) ≤4 mm bone height between the maxillary sinus and the top of the maxilla on both sides; (3) class IV bone quality; (4) edentulous period of at least 1 year; (5) no history of radiotherapy in the head and neck region; (6) no history of reconstructive or pre-prosthetic surgery or previous oral implantology.

Orthopantomograms, lateral cephalograms, and postero-anterior oblique radiographs were made to assess the height of the maxillary alveolar bone, the dimensions of the maxillary sinus, and the antero-posterior relationship of the maxilla to the mandible. The radiographs were also screened for sinus pathology.

A bilateral sinus floor augmentation procedure of the atrophic maxilla was performed in these patients (mean age 60.8 ± 5.9 years, range 48–69 years). At random, by use of envelopes, the augmentation procedure was performed on one side with BioOss ^® seeded with a bone marrow concentrate from the posterior iliac crest enriched in MSCs (test side); the contralateral side was augmented with a mixture of 70% biomaterial (BioOss ^® ) and 30% autogenous bone (harvested from the retromolar area of the mandible; control side), as commonly applied in reconstructive surgery. Endosseous implants (Straumann Standard SLA ^® implants; diameter 4.1 mm, length 12 mm, RN; Institut Straumann AG, Basel, Switzerland) were placed 3–4 months after the sinus floor elevation procedure. Depending on the available intermaxillary space and prosthodontic needs, two to three implants were place on each side of the posterior maxilla. A total of 66 implants could be installed with primary stability. After an osseointegration period of 3 months, the prosthetic construction, being an implant-supported overdenture, was fabricated in accordance with the procedure described by Slot et al.

The treatment outcome of the 12 edentulous patients needing bilateral sinus floor elevation surgery was evaluated in the current study. The protocol was approved by the institutional ethics committee and the study was conducted in accordance with the Declaration of Helsinki. Informed consent was obtained from all patients.