## 3 Results and Discussion  
The authors have previously reported on the preliminary physical properties of the Ga-GPCs [61]. To summarize, the starting glasses were all characterized and were determined to be amorphous with a particle size range of approximately 7-13 \(\upmu\)m, with individual mean particle sizes of 9.3 \(\upmu\)m (_Control_), 9.8 \(\upmu\)m (_LGa-1_), and 9.3 \(\upmu\)m (_LGa-2_) [61]. Utilizing a similar particle size for the glass phase of each GPC is critical, as this significantly influences the dissolution rate during cement curing. This contributes to the fact that any differences in cement properties will be due to the inclusion of Ga, and not due to physical differences in the glass particles. Previous studies by the authors [61] have described the physical properties, i.e., working (T\({}_{\text{w}}\)) and setting (T\({}_{\text{s}}\)) times and mechanical properties (both compressive and biaxial flexural strength), and Ga-addition to the glass phase of these GPCs has had a positive influence on the rheological properties, while the mechanical properties were reduced. The effect of Ga on the glass structure was also described usingX-ray photoelectron spectroscopy and MAS-NMR, which determined that Ga assumes a network-modifying role in these glasses [61]. The current work elucidates the ion-release profiles and the resulting bioactivity of this cement series. Simulated body fluid (SBF) testing, cell culture analysis, and antimicrobial activity have been investigated in this study. The ion-release data are presented in Figure 1a,b, which present the release of silica (Si) and zinc (Zn), respectively. Also, the rates of ion release are presented for each cement, and the potential cumulative release is determined by time. Si release (Figure 1a) was 37-77 mg/L over 1-30 days for the _Control_ cement, where the highest release rate was experienced for the 30-day sample (48%). A similar trend was observed with _LGa-1_ and _LGa-2_. The _LGa-1_ Si release ranged from 36-72 mg/L over 1-30 days, _LGa-2_ ranged from 60-90 mg/L over 1-30 days, and both Ga-GPCs experienced the highest release rates after 30 days, with _LGa-1_ at 72 mg/L (50%) and _LGa-2_ at 90 mg/L (42%). Zn release is also presented in Figure 1b, and the release rates were much lower compared to Si. In each case, the majority of the Zn release occurred after 1 day: _Control_ at 6 mg/L (89%), _LGa-1_ at 8 mg/L (72%), and _LGa-2_ at 8 mg/L (83%). Zn release was found to significantly reduce over time, where the 30-day release rates range from 2 to 11% for the _Control_, _LGa-1_, and _LGa-2_. Calcium (Ca) and gallium (Ga) ion release is presented in Figure 2a,b. Figure 1: Ion-release profiles of Ga-GPCs considering (**a**) silica and (**b**) zinc in addition to the rate of Si and Zn ion release with respect to time. Ca release (Figure 2a) was highest in the _Control_ GPC and ranged from 4 to 5 mg/L over 1-30 days. The release of Ca followed a similar trend to Zn, where the release rates were low and the trend showed that the majority of Ca release was experienced after 1 day for each cement. The _Control_ released 5 mg/L (55%), _LGa-1_ released 4 mg/L (63%), and _LGa-2_ released 5 mg/L (69%). Ga release is presented in Figure 2b and was released at lower rates than each of the other ions tested. No Ga was detected from the _Control_ GPCs at any time and was only detected from _LGa-1_ and _LGa-2_ after the extended time periods. _LGa-1_ released 1.1 mg/L (100%) of its Ga only after 30 days of incubation, while _LGa-2_ was found to release 0.6 mg/L (23%) of the Ga concentration, and at 30 days, 2.0 mg/L (77%) was released. Other studies conducted on Ga have also seen high release rates of Ga over a similar period [62]. The solution pH was also recorded at each time interval, and the data are presented in Figure 3.  
From Figure 3, it is evident that there was a slight reduction in solution pH recorded, which is attributed, more specifically, to the increase in Ga concentration within the glass.