# Biomechanical Rationale for a Novel Implant Design Reducing Stress on Buccal Bone
## 4 Discussion  
Measuring insertion torque, primary implant stability and peri-implant strain, this experiment attempted to compare a novel implant design characterized by a change in core diameter (AlfaGate) to an existing, well-established tapered implant design (BLT). Of course, any other implant system could have been chosen as a control group and would certainly have led to a different but implant-specific insertion torque curve and strain curve. During the insertion of BLT implants, both, emerging strains and insertion torque continuously increased, indicating that primary stability mostly resulted from compressing cortical bone [9, 12]. In AlfaGate implants, the maximum torque was measured when the middle portion coincided with the cortical layer indicating that primary stability was mostly obtained by compressing trabecular bone. With the implant types not differing with respect to primary stability, it appears that the tapered BLT implants derived stability \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{2}{c}{**BLT**} & \multicolumn{2}{c}{**AG**} & \multirow{2}{*}{\(t\)**-Test (\(p\)-Value)**} \\ \cline{2-2} \cline{4-6}  & **Mean** & **SD** & **Mean** & **SD** & \\ \hline Maximum insertion torque [Ncm] & 55.16 & 1.95 & 50.9 & 2.6 & **0.0016** \\ \hline Position of maximum insertion torque [Ncm] & 63.14 & 2.97 & 54.5 & 3.95 & **0.0001** \\ \hline Final insertion torque [Ncm] & 52.11 & 2.22 & 30.55 & 5.47 & **<0.00001** \\ \hline Maximum strain [\(\mu\)m/m] & 11,370.18 & 4206.6 & 8236.39 & 2176.31 & 0.1069 \\ \hline Position of maximum strain & 912.29 & 57.48 & 716.9 & 50.59 & **<0.0001** \\ \hline Final strain [\(\mu\)m/m] & 10,834.31 & 3923.14 & 5798.27 & 1868.82 & **0.0137** \\ \hline Periotest [PTV] & 8.415 & 3.003 & 6.685 & 3.072 & 0.219 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mean values and standard deviations recorded for all parameters for both implant types. Results of \(t\)-tests for comparisons between the two implant groups are given as \(p\)-values with significant differences (\(p\) < 0.05) written in bold. Figure 4: Strain development over time during implant insertion for both groups investigated with continuously increasing strain levels for Straumann BLT. Lower maximum strain was seen in AlfaGate implants coinciding with the bulky central part of the implant passing the cortical plate. from cortical bone while AlfaGate engaged the bony walls over the whole depth of the osteotomy. Given the comparable levels of primary stability achieved, AlfaGate implants should be applicable in the same indications as BLT implants. Determining implant stability using the Periotest device may be considered as being old-fashioned but appeared to be only option as neither SmartPegs nor MultiPegs were available for the novel implant as a prerequisite for resonance frequency analysis. [PERSON] and coworkers [37] used an identical approach in studying individually fabricated implants. In addition, both the maximum as well as final torque and strain values were lower in AlfaGate implants although a greater amount of undersizing of the osteotomy was realized here as compared to BLT implants with a conical outer shape, i.e., less bone had to be removed for inserting the implant. The slower insertion of AlfaGate implants may be attributed to the lower thread pitch realized here and to the osteotomy size relative to the implant size. In the BLT group, implants could be inserted into the osteotomy to a much greater extent prior to engaging bony walls as compared to AlfaGate implants (see Figure 2b). While it may be argued that longer insertion time is critical from a clinical perspective, it has to be kept in mind that potentially fewer drill steps will be required for placing the novel implant type. From a methodological point of view, the difference in insertion time hindered from directly comparing whole graphs but required the determination of specific torque and strain points for comparison.