## 1 Introduction
on bovine rib cortical bone pieces suggests that bone temperature remains in the safe zone during osteectomies performed using classical surgical guides and external irrigation with saline solution at room temperature [18]. They found that, despite the presence of the surgical guide, external cooling was effective: the mean temperature rise ranged from 3.3 \({}^{\circ}\)C to 5.2 \({}^{\circ}\)C when the irrigation was used, and from 7.0 \({}^{\circ}\)C to 9.4 \({}^{\circ}\)C in the absence of cooling. The bone damage threshold was exceeded only once when irrigation was applied, and in 32% of the cases when it was not [18]. To further improve cooling efficacy, [PERSON] et al. proposed adding an internal irrigation channel to a surgical guide of regular geometry and found a roughly twofold reduction in the temperature rise elicited by guided drilling [19]. [PERSON] et al. proposed a digital design and three-dimensional (3D) printing workflow for incorporating an irrigation fluid channel in a personalized surgical guide suitable for dental implant site preparation [20]. [PERSON] et al. created a 3D-printed surgical template with a built-in coolant duct that enabled rinsing the burr at the point of entry into the target tissues. Most importantly, they applied it in the clinics [21]. [PERSON] et al. presented detailed design steps and a clinical application of a 3D-printed surgical template with an incorporated coolant pipe [22]. The successful clinical applications motivated quantitative studies of the rise in bone temperature during osteectomies performed using surgical templates with internally routed irrigation. The study of [PERSON] et al., conducted on bovine rib pieces, had a surprising outcome: the surgical guide with internal irrigation had no significant advantage over the classical one in terms of the intraosseous temperature elevation [23]. The authors attributed this result to the clogging of the final portion of the irrigation channel by bone chips, as revealed by cone beam computed tomography of the surgical guides taken after the osteectomies. In contrast, [PERSON] et al. observed a significant decrease in the temperature rise while using a surgical guide outfitted with a pair of internal irrigation channels [24]. [PERSON] et al. developed an innovative surgical template that included both an entry and an exit channel for the irrigation fluid. They observed a significant drop in peak temperatures compared to a classical surgical guide with external irrigation [25]. [PERSON] et al. investigated the rise in bone temperature caused by guided drilling into the cortical layer of porcine femur pieces, and compared surgical guides with internal cooling pipe, guides with C-shaped open sleeve, and classical guides [26]. The mean temperature elevations were 2.1 \({}^{\circ}\)C, 2.7 \({}^{\circ}\)C, and 3.2 \({}^{\circ}\)C, respectively, demonstrating the value of internal cooling. Nevertheless, the differences between them were marginally insignificant according to the one-way analysis of variance (\(p=0.056\)). In this study, we sought to eliminate biological variability by using artificial bone models that mimic the geometry and density of the alveolar bone of the human mandible. We designed and printed a surgical template that wrapped the bone model and featured four pairs of guides--one classical and one with internal cooling in each pair. The guide with internal cooling incorporated just one irrigation fluid channel because we hypothesized that a coolant exit channel is not necessary if the guide provides a stand-off distance from the target site. On each bone specimen, surgical drilling was performed sequentially, starting with a cortical perforation drill of 2.7 mm in diameter followed by 3.3 mm and 3.7 mm drills. We monitored the intraosseous temperature using a thermocouple inserted in a predrilled hole whose bottom was 0.8 mm away from the anticipated margin of the final osteotomy.