## 8 Factors Influencing Temperature and Mechanical Properties of PMMA Bone Cement  
Studies have confirmed that different types of mixing have various effects on the level of heat generated during PMMA polymerization. Vacuum mixing has been shown to reduce the temperature peak compared to manual mixing. During vacuum mixing, the oxygen concentration is lower, in turn reducing the setting time and peak temperatures. Syringe delivery can also help control the distribution of cement, making it easier to obtain an equal mantle thickness and helping reduce localized heat generation [25]. The equal distribution of cement, meaning the amount of cement and the thickness of the cement mantle, are critical factors influencing heat generation. Thicker cement mantles produce higher peak temperatures (reaching over 55 \({}^{\circ}\)C), while a thinner cement mantle produces significantly lower temperatures. This is supported by the studies conducted by [PERSON] et al. and [PERSON] et al. that have shown that thicker cement mantles (\(\geq\)5 mm) result in an increase in osteophyte death compared to a thinner mantle (e.g., 2.5 mm) [26; 67]. The quality of the bone tissue is also a potential risk for thermal injury. Osteoporotic bone, with its reduced density and altered vascularity, is more susceptible to thermal injury. Bones' natural cooling mechanism, such as blood flow, is critical in moderating the thermal injury of tissue. Blood flow helps dissipate heat faster, reducing the peak temperatures at the cement-bone interface. A study conducted on periodontal blood flow has shown that it significantly decreases peak temperatures during thermoplastic obturation [68]. The thickness of PMMA bone cement has a direct correlation to the mechanical properties of the said cement, but also to the temperature values reached during the polymerization reaction. Thicker mantles retain more heat, leading to longer exposure times and influencing both the curing process and the mechanical properties of the cement. A thicker cement mantle leads to higher peak temperatures and longer exposure times due to heat retention. Since the cement mantle retains heat, heat dissipation is reduced in the bone-cement interface. This increased temperature can enhance the degree of polymerization, improving mechanical strength by reducing the amount of leftover monomer. However excessive heat leads to more severe thermal damage, leading to the degradation of the interface and affecting the integrity of the cement fixation [23; 26; 34; 61; 69; 70]. The retained heat inside the cement mantle serves as a constant source of heat exposure for the bone tissue, increasing the risk of thermal necrosis. To avoid complications of thermal necrosis, surgeons need to pay careful attention to the thickness of the cement mantle, making sure to utilize the minimum thickness of the mantle that still offers proper fixation while keeping the risk of heat retention to a minimum. Thinner cement mantles also have lower peak temperature values during polymerization [24]. The preparation technique, including control over the starting temperature of bone cement and the implant, influences the maximum temperature reached during the exothermic polymerization reaction, as described in [PERSON] et al. 's study [34]. Maintaining the components at room temperature, particularly in conjunction with vacuum mixing, can help in controlling peak temperatures during polymerization. The study highlights that polymerization was conducted under controlled ambient conditions and suggests that cement cooling at 4 \({}^{\circ}\)C can optimize curing dynamics. Vacuum mixing, which reduces air entrapment, further supports a consistent and lower exothermic peak, minimizing the thermal impact on surrounding tissue. Additionally, the study provides insights into thermal characteristics: standard force applications and compression testing demonstrated slight variations in deformation at different mineral load levels, with vacuum-mixed samples exhibiting enhanced structural integrity.