Since there are no clinical studies available comparing the gold standard (autogenous bone graft plus resorbable membrane) to the promising combination of xenogenic bone graft loaded with rhBMP-2 in combination with a collagen membrane for localized ridge augmentation, the present exploratory study has been designed.

The aim of the present study is therefore to test whether or not the application of a xenogenic bone block loaded with rhBMP-2 will results in clinically, radiographically and histologically similar outcomes as the gold standard (autogenous bone block) for the regeneration of chronic ridge defects.

The investigators expect that there is no difference in bone quantity and quality between the two methods and that the use of the test treatment will be more user and patient friendly according to the patient perception/acceptance since no second surgical site will be necessary as well as cause less complications.

Inclusion Criteria:

• requiring implant therapy for the reconstruction of 1 to 4 missing teeth
• revealing insufficient bone volume for implant placement (cases where less than 50% of the implant surface would be surrounded by native bone) requiring bone augmentation procedure

Exclusion Criteria:

• Medication with a contraindication for implant therapy
• Previous administration of InductOs
• Skeletal immaturity
• Any active malignancy or patient undergoing treatment for a malignancy
• An active infection at the operative site
• Persistent compartment syndrome or neurovascular residua of compartment syndrome
• Pathological fractures such as those observed in (but not limited to) Paget's disease or in metastatic bone
• Contraindications to the class of drugs under study, e.g. known hypersensitivity or allergy to class of drugs or the investigational product,
• Contraindications on ethical grounds,
• Pregnancy,
• Intention to become pregnant during the course of the study,
• Breast feeding,
• Treatment with other investigational products,
• Other clinically significant concomitant disease states (e.g., renal failure, hepatic dysfunction, cardiovascular disease, etc),
• Known or suspected non-compliance, drug or alcohol abuse,
• Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia or confusional state of the subject,
• Participation in another study with investigational drug within the 30 days preceding and during the present study,
• Previous enrolment into the current study,
• Enrolment of the investigator, his/her family members, employees and other dependent persons,
• Patients where autogenous bone cannot be harvested.