## 4 Discussion
A potential drawback of these decontamination procedures is their possible adverse effect on biological properties. The effectiveness of sodium hydroxide as a disinfectant, for example, is based primarily on its ability to cleave protein bonds and disintegrate the tertiary structure of proteins. This denaturation of proteins may hypothetically also affect structural proteins of the organic matrix and osteoinductive growth factors such as BMPs, IGF-II, and TGF-8. Thermal treatment such as autoclavation as an alternative for the decontamination of the dentin material prior to grafting may also result in protein denaturation. A preclinical animal study reported a significant decreased level of osseointegration (bone-implant contact) if the dentin was pretreated by autoclavation compared to untreated dentin [18]. In contrast, other animal models provided some evidence that in autoclaved dentin matrix dental pulp stem cells were preserved and kept the capability to promote new tissue formation [32]. Since the present study was a clinical study, there was no possibility to analyze bone-implant contact as a measure for osseointegration. In this study, osseointegration was evaluated by the resonance frequency analysis, as well as the clinical and radiographic evaluation of the hard tissues covering the implant. The resonance frequency analysis is a reproducible and validated method for assessing the implant stability quotient (ISQ) as a surrogate parameter for osseointegration [33; 34]. By definition, implants with an ISQ level exceeding 60 are considered to be sufficiently stable for being loaded. The high levels of implant stability (ISQ) observed in both groups (NETT: 75, ETT: 74) suggest a sufficient and equivalent level of osseointegration, which were comparable with the ISQ levels of implants placed simultaneously with the bone shell technique according to [PERSON] [31]. This is underlined by the clinical finding that, except for one case, no vertical peri-implant bone loss exceeding 0.5 mm could be detected. Traditionally, the radiographic analysis of osseointegration and crestal bone level is performed by two-dimensional radiographs [35]. This allows the assessment of the peri-implant bone level in the approximal aspect, but not of the bucco-oral dimension, in particular the buccal lamella which consists of grafted hard tissue only. In the present study, the radiographic evaluation was therefore performed by small-volume CBCT scans after augmentation and at re-entry after 3 months for implant exposure. The peri-implant bone level measured in the mesial and distal aspect of the implant shoulder, did not reveal any vertical bone loss. At time T2, the mean buccal lamella width at L4 was significantly lower for NETT than for ETT at the implant, region, and patient level. However, these values only show the comparison of the widths at a certain point in time and not the resorption over time. The mean resorption of the bucco-oral dimension of alveolar crest width between grafting and re-entry at 3 months amounted to 0.3 mm in the EET group and 0.5 mm in the NETT group and did not show any significant differences between the two groups. The major part of the resorption can be found with 0.2 mm in the ETT and 0.3 mm at the buccal lamella. However, at 30-40% of the dimensional change, a not inconsiderable proportion of this is accounted for the oral lamella, i.e., the native bone. The mean resorption of the buccal plate noted in this study suggests the stability of the dentin graft in the short-term aspect and underlines the findings that dentin grafts show a less pronounced resorption compared to bone [20]. This evaluation is limited by a relatively short observation period of 3 months. The effect of graft and bone remodeling on long-term dimensional changes needs to be addressed in future studies. A further limitation of this study is the lack of histological investigation.