## 3 Results
### Primary and Secondary Implant Stability  
Mean ISQ at insertion after averaging the values for palatinal and vestibular measurements were 68.59 \(\pm\) 8.8 (range: 43-86) for SPI and 72.34 \(\pm\) 8.4 (range: 39-87) for STR. Median ISQ values at insertion were higher for mandibular implants compared to maxillary implants (\(p\)\(<\) 0.001) and were highest in the mandibular molar tooth region (\(p\)\(<\) 0.001) (Figure 3). This was observed in both implant groups, STR and SPI. In contrast, implants in the maxillary molar tooth region showed lower median ISQ values than the front or premolar tooth region (\(p\)\(<\) 0.01). A multivariable linear mixed regression model of the included predictive factors revealed that implant diameter (reg. coeff. : 3.28, 95% CI: 1.89-4.66, \(p\)\(<\) 0.001), implant length (reg. coeff. : 0.67, 95% CI: 0.26-1.08, \(p\)\(<\) 0.001), STR vs. SPI implant system (reg. coeff. : 4.58, 95% CI: 3.05-6.10, \(p\)\(<\) 0.001), and maxillary vs. mandibular (reg. coeff. : \(-\)7.45, 95% CI: \(-\)8.70-(\(-\)6.20), \(p\)\(<\) 0.001) were significantly associated with primary implant stability (Figure 4). Mean ISQ values at exposure for SPI and STR implants were 71.45 \(\pm\) 7.9 (range: 49-86) and 74.54 \(\pm\) 8.1 (range: 36-88), respectively. \begin{table}
\begin{tabular}{l c c c} \hline \multicolumn{1}{c}{**Bone situation**} & & & \\ Fully ossified situation & 482 (82.82) & 366 (84.72) & 116 (77.33) \\ Internal sinus elevation & 9 (1.55) & 7 (1.62) & 2 (1.33) \\ (immediate insertion) & 54 (9.28) & 34 (7.87) & 20 (13.33) \\ One step/ two-step insertion after & 24 (4.12) & 16 (3.70) & 8 (5.33) \\ sinus elevation & 13 (2.23) & 9 (2.08) & 4 (2.67) \\
**ISQ \$ insertion** & & & \\ Vestibular (mean \(\pm\) standard deviation) & 71.26 \(\pm\) 8.9 & 72.33 \(\pm\) 8.6 & 68.15 \(\pm\) 8.9 \\ Vestibular (median and range) & 72 (37–87) & 74 (37–87) & 69 (41–86) \\ Palatinal (mean \(\pm\) standard deviation) & 71.19 \(\pm\) 8.8 & 72.13 \(\pm\) 8.6 & 68.49 \(\pm\) 8.9 \\ Palatinal (median and range) & 72 (41–88) & 73 (41–88) & 68.5 (43–86) \\
**ISO \$ exposure** & 83 (13.22) & 8 (8.60) & 21 (14.29) \\ Vestibular (mean \(\pm\) standard deviation) & 73.44 \(\pm\) 8.3 & 74.31 \(\pm\) 8.1 & 70.95 \(\pm\) 8.4 \\ Vestibular (median and range) & 75 (36–88) & 75 (36–88) & 71 (48–88) \\ Palatinal (mean \(\pm\) standard deviation) & 73.74 \(\pm\) 8.3 & 74.52 \(\pm\) 8.3 & 71.51 \(\pm\) 7.8 \\ Palatinal (median and range) & 75 (36–89) & 75.5 (36–89) & 72 (49–87) \\ \hline \end{tabular} \({}^{\dagger}\) STR: Straumann implants; \({}^{\ddagger}\) SPI: Thommen implants; \({}^{\lx@sectionsign}\) ISQ: implant stability quotient.  
\end{table} 
Table 1: Cont. Figure 3: Boxplots showing ISQ values at insertion stratified by implant system and localizations. STR: Straumann implants. SPI: Thommen implants. ISQ: implant stability quotient. Figure 2: Distribution of the bone insertion technique, stratified by implant system (**A**) and distribution of sex, implant system, and implant location shown as percentage of all patients in our study cohort (**B**) (\(n=582\)). STR: Straumann implants; SPI: Thommen implants; F: female; M: male. Figure 5 shows the mean ISQ at implant insertion and exposure, along with other study variables grouped by implant region (maximally vs. mandibular) and implant system (STR vs. SPI). Mean healing time was 118.79 \(\pm\) 59.1 days and was similar in the Straumann (118.03 \(\pm\) 60.1 days) and Thommen implant group (120.98 \(\pm\) 56.3 days). Median ISQ values at exposure were higher than the respective ISQ values at insertion, regardless of implant localization and implant system. Figure 4: Regression model of factors influencing primary implant stability. STR: Straumann implants. SPI: Thommen implants. ISE: Internal sinus elevation. Reg. coeff. : regression coefficient. 95% CI: 95% confidence interval. Figure 5: Distribution of study variables among the study groups.