# Heat Generated during Dental Implant Placement: A Scoping Review
## 4 Discussion  
Preparation and insertion of implants into bone tissue requires a surgical technique that minimizes trauma. The biomechanical implications of heat generation during implant site preparation are significant, as thermal injury on bone healing could hinder primary implant stability and increase the risk of implant failure [5; 6; 132; 133; 134; 135]. In fact, heat generation during bone preparation can damage hard tissues, leading to osteonecrosis and cell death. Previous studies have defined the critical bone temperature thresholds above which bone necrosis can occur [136]. [PERSON] et al. [133] noted that, when threaded titanium implants were placed in the rabbit tibia, heating the implants to a temperature of 50 \({}^{\circ}\)C for one minute was sufficient to reduce bone formation. This was not an immediate event, but a gradual process that took place over a 4-week period; the bone was replaced by fat cells, which prevented the implant from being incorporated. It only takes a temperature of 47 \({}^{\circ}\)C for 1 min to impair osseointegration of an implant [6]. In terms of bone type (compact or cancellous), most studies indicate that a challenging clinical scenario is linked to bone implantation on D1 bone, which has a higher thermal conductivity and develops higher temperatures for the same amount of heat supplied [14; 15; 16; 17; 18]. When faced with the demanding task of bone bed preparation on D1 bone, clinicians should consider adopting a few simple precautions. These include using a new or lightly used drill [127], applying a refrigerated coolant [20], implementing intermittent drilling with continuous irrigation even when drilling pauses, and combining internal and external cooling [23; 100]. Specifically, for type 1 bone, it seems sensible to avoid prolonged use of the implant trephine drill. Internal and/or external irrigation [114; 100] with adequate quantities [6] and low-temperature (below 10 degrees Celsius) saline solution has proven effective as a cooling agent. In general, external cooling is beneficial for both compact and cancellous bone [29; 78; 115; 118; 120]. The role of irrigation has already been partially discussed, and as far as temperature and flow rate are concerned, the simple precaution of lowering the saline temperature (to 20 degrees Celsius), which resulted in a significant drop in temperature, should be considered. Nevertheless, the average temperature rise was below the critical threshold when using either refrigerated or non-refrigerated cooling solutions. However, findings regarding flow rate are mixed: one study [78] suggests that using a flow rate greater than 120 mL/min does not necessarily result in a reduction in temperature. The combination of external and internal cooling appears to be advantageous, particularly in very dense and compact bones, given their heightened sensitivity to heat. In this case, an internal and external cooling system is a practical solution for all bone drilling and reaming systems [23; 100]. The shape of the drill is among the various factors that can influence bone heating during implant osteotomies [26]. Heat generation can be reduced by using tapered drills [24], but in the dental literature, other shapes like cylindrical and trephine drills do not exceed the specified limit. The use of a piezoelectric device is both safe and effective [19; 72; 73], but attention must be paid to the load applied and the specific bed preparation protocol [53; 54]. Although early studies suggested that drilling speed had a negative impact on heat generation [136; 137], the current literature fails to identify an ideal milling speed [138]. Lower milling speeds enable better control of drill movement, at the expense of higher heat generation. This is particularly important when working close to delicate anatomic structures such as the maxillary sinus and inferior alveolar nerve. It is advisable to adhere to indications provided by manufacturers, including recommended RPM settings and regularly replacing drills.