## 4 Discussion  
The aim of the present retrospective study was to assess the feasibility of using reconditioned dentin from endodontically treated teeth for lateral ridge augmentation by means of the tooth shell technique. A total of 34 patients, in which the grafting procedures according to the TST (endodontically and non-endodontically treated teeth) with simultaneous implant placement were performed, were followed up with focus on clinical complications and short-term dimensional changes of the crestal width and the buccal lamella. One of the major concerns of using reconditioned dentin from endodontically treated teeth for grafting procedures was the potential risk of compromised healing with premature graft exposure or even the loss of the graft and/or the implant due to inflammatory processes which increases the patient's impairments by discomfort or necessary second \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{3}{c}{**Study Group**} & \multicolumn{2}{c}{**Two-Sample**} \\  & & & **t-Test** & **(\(p\)-Value)** \\ \hline
**Ratio from T1 to T2** & **Mean** & **ETT** & **NETT** & **(\(p\)-Value)** \\ \hline bucco-oral alveolar ridge & & & & \\ PL, \(n=34\) (SD) & 0.96 (0.08) & 0.97 (0.04) & 0.96 (0.10) & 0.680 \\ RL, \(n=40\) (SD) & 0.96 (0.07) & 0.97 (0.04) & 0.95 (0.09) & 0.568 \\ IL, \(n=45\) (SD) & 0.96 (0.07) & 0.97 (0.04) & 0.95 (0.09) & 0.402 \\ L0 & & & & \\ PL, \(n=34\) (SD) & 0.85 (0.29) & 0.85 (0.26) & 0.84 (0.33) & 0.917 \\ RL, \(n=40\) (SD) & 0.84 (0.29) & 0.87 (0.26) & 0.81 (0.31) & 0.521 \\ IL, \(n=45\) (SD) & 0.86 (0.30) & 0.88 (0.25) & 0.84 (0.34) & 0.588 \\ L2 & & & & \\ PL, \(n=34\) (SD) & 0.93 (0.18) & 0.96 (0.13) & 0.91 (0.22) & 0.457 \\ RL, \(n=40\) (SD) & 0.93 (0.19) & 0.97 (0.15) & 0.89 (0.22) & 0.199 \\ IL, \(n=45\) (SD) & 0.93 (0.18) & 0.98 (0.14) & 0.89 (0.21) & 0.125 \\ L4 & & & & \\ PL, \(n=34\) (SD) & 0.93 (0.19) & 0.97 (0.17) & 0.90 (0.20) & 0.286 \\ RL, \(n=40\) (SD) & 0.94 (0.19) & 0.97 (0.17) & 0.91 (0.20) & 0.363 \\ IL, \(n=45\) (SD) & 0.94 (0.18) & 0.97 (0.16) & 0.91 (0.19) & 0.239 \\ \hline \hline \end{tabular}  
* N: Number; SD: Standard deviation; ETT: Endodontically treated teeth; NETT: Non-endodontically treated teeth; PL: Patient level; RL: Region level; IL: Implant level.  
\end{table} 
Table 5: Ratio of residual ridge width of bucco-oral alveolar ridge and buccal lamella from T1 to T2. interventions. This would be in contrast with the advantage of the considerably lower invasiveness of the tooth shell technique compared to autogenous bone block grafts. The low incidence of non-severe clinical complications observed in our study (n = 3) is comparable with the results reported for autogenous bone grafts [3]. Soft tissue dehiscence with partial graft exposure occurred on two grafted sites (NETT n = 1; ETT n = 1) during the early recovery stage. At re-entry after 3 months, one implant in the NETT group exhibited a localized three-walled defect, which could be solved by re-augmentation. Severe complications such as loss of implant or massive resorption of the graft were not observed. The noted incidence of clinical complications corresponds to those reported in previous studies on this technique and bone shell technique [22; 31]. Preclinical animal studies have revealed slightly higher graft exposure rates for endodontically treated teeth compared to uncompromised teeth [20]. In the present study, this could not be observed. However, these grafts were only mechanically processed and not subjected to decontamination. The dentin preparation and decontamination procedure used in the present study is a commercially available method for preparing particulate dentin for grafting procedures, using sodium hydroxide in a 0.5 M solution and 70% ethanol for cleansing. However, there is a lack of basic research data regarding the bactericidal efficacy of this method, especially against bacterial infections in endodontic niches such as dentinal tubules.