## 2 Materials and Methods  
For the present study, cases of lateral ridge augmentation were re-examined, in which autogenous dentin from endodontically and non-endodontically treated teeth were used between 1 June 2019 and 31 March 2020. The electronic medical records of the individual patients were used to screen for potential cases for inclusion in this study. All the surgical procedures were performed by an experienced oral surgeon (MK). The study protocol was reviewed and approved by the Institutional Review Board of Baden-Wurttemberg Medical Council (ID: F-2020-068-z). The study was conducted according to the Declaration of Helsinki and the EQUATOR guidelines. The inclusion criteria for this study considered the following conditions:  
Inclusion criteria:  
Age > 18 years;  
Alveolar crest augmentation of a lateral bony defect with the tooth shell technique;  
Lateral alveolar crest defect of at least 4 mm in the region of implant placement prior to augmentation;  
Restoration with a fixed denture is intended;  
Lendentulous region of maximum of two missing teeth.  
Exclusion criteria:  
Age < 18 years;  
Untreated or residual periodontitis;  
Uncontrolled diabetes mellitus with HbA1c > 7%;  
A malignant neoplasm;A history of therapy with bisphosphonates or other antiresorptive medication (e.g., RANKL inhibitors);  
A history of radiotherapy in the head and neck region;  
Immunosuppression or immunosuppressivement therapy;  
A lateral alveolar crest defect of less than 4 mm in the region of implant placement prior to augmentation;  
The restoration of the implant with a removable denture is intended.  
In all patients, either a hopeless tooth or a tooth not worth preserving (such as a wisdom tooth) that would have been suitable for grafting was present in the prospective region of implantation. In all cases, the width of the bucco-palatal bone was measured with preoperative cone beam computed tomography (CBCT) before augmentation. At least 1.5 mm of bone/autogenous dentin should cover the implants on the buccal and palatal surfaces. The achieved ridge width was a result of the desired implant diameter, a 1.5 mm buccal and 1.5 mm oral lamella of original bone or autogenous bone/dentine graft. The desired ridge width was of at least 7.2 mm when the implant diameter was 4.2 mm. An increase in hard tissue of at least 4 mm was a requirement for the augmentation procedure in all cases.  
The patients were divided into the following two groups:  
Group 1:  
Endodontically treated teeth (ETT): 17 patients (11 female, 6 male) with 18 regions and 21 implants.  
Group 2 (control group):  
Non-endodontically treated teeth (NETT): 17 patients (8 female, 9 male) with 22 regions and 24 implants.  
The following data from electronic medical records were extracted for study documentation:  
- Demographic data: Age and gender;  
- The endodontic status of the tooth used for grafting;  
- Data on restoration and maintenance therapy;  
- Complications: The loss of the graft or implant, dehiscence, and infections/inflammation;  
- Implant data: type, length/diameter, and region;  
- After augmentation with simultaneous implantation, a CBCT image was taken to assess the surgical procedure. These X-rays were analyzed;  
- At the time of implant exposure--3 months after augmentation--CBCT was performed to assess osseointegration, the buccal lamella, and horizontal hard tissue loss. These CBCT images were analyzed.  
The target parameters were biological complications, horizontal hard tissue loss, osseointegration, and integrity of the buccal lamella. The biological complications include the following:  
Complications concerning the hard and soft tissue:  
- The dehiscence of the wound;  
- Infection with or without suppuration;  
- Severe peri-implant bone loss;  
- Implant loss;  
- Others.