In fact, the assessment of surgical difficulty is a relevant issue in the field of oral surgery since allows health professionals to plan operations more accurately helping to minimize surgical trauma, and risks of accidents and complications. This concern is highly relevant to patients treated with bisphosphonates due to the jaws osteonecrosis risk.
The assessment of extraction difficulty has been measured via a wide range of variables  and, among of them, the extraction time [11, 12] and complications frequency [13, 14] are well recognized indicators. For this reason, we selected these two variables as the outcome measures to evaluate the relationship of bisphosphonate therapy with surgical difficulty.
Our findings demonstrated that teeth extractions in animals treated with bisphosphonate require more surgical time when compared to control animals following simple extraction technique. In our opinion, the main reason to justify this surgical time difference is related to the presence of an increased bone density and consequently decrease bone elasticity, that are well recognized difficult factors to teeth extractions [1, 2] and are a result of Bps treatment .
Even with the absence of bone density evaluation and measurement methods, it is reasonably to believe that Bps treated animals presented a high bone density that is supported by the following points:
It is known that the bone effect of Bps is cumulative and assumes a bone absorption linear aspect until 5 mg/kg endovenously dosages . Therefore, the long-term treatment of Bps in high dosages (1 and 3 mg/kg) used in this study resulted in an expressive Bps bone effect.
Bps were administered by subcutaneous route that are as effective as endovenously route regarding to drug bioavailability . By this route it is estimated that more of 50% of the drug is available for bone matrix incorporation [16, 17].
Due to the high bone turnover in cortical alveolar bone is believed that, although controversial, the Bps bone absorption is higher when compared to other skeletal sites , which can be justify by the alveolar lamina dura sclerosis seen in Bps treated patients with BRONJ in initial stage . Besides, the mandibular bone has by itself a higher tissue degree of mineralization when compared to maxillae, been more prone to Bps effects and naturally increases surgical difficulty .
In this way, when it is opted to a simple exodontias technique, there is a highly dependence of the tooth to expand the bone tooth socket walls to allow its avulsion and in situations of an alveolar bone increased density there is a lack of sufficient socket expansion which obviously limits the teeth avulsion axis. Consequently, as it happened in this study, requires more surgical manipulation, thereby prolonging operating time , as well as the surgical trauma and increases the risk of accidents and complications.
Teeth fractures have been considerate the most frequent accidents during exodontias, in oral surgery practice . They are usually related to inadequate instrumental use and excessive force use, which was one of the reasons that could justify the high frequency of teeth fractures in animals treated with Bps observed in this paper. The concern about this issue is that many efforts have been made to reduce the surgical trauma during teeth extractions by using atraumatic protocols in Bps treated patients [7, 8] since exodontias have been considerate as one the most frequent trigger factor to BRONJ [4–6].
In this context, as stated previously, in situations of an increased surgical difficulty degree there is a tendency to prolong surgical length and increase tissue trauma which in field of ONJ can lead to relevant implications:
Increase the inflammation of the alveolar bone , which could act in favor of the BRONJ lesions development according to the inflammatory theory .
Result in delayed extraction wound healing due to the compression of bone lining the socket impairing vascular penetration and results in thrombosis of the vessels , which could act in favor of the BRONJ lesions development according to the angiogenic theory .
Increase the risk of dento-alveolar fractures, since when bone tissue becomes too highly mineralized, it also becomes brittle . Moreover, it also makes the tissue more prone to microcrack initiation , which act in favor to the BRONJ lesions development according to the bone suppression theory .
Another concern that can be discussed regarding to the teeth fractures is about the approaches after these accidents:
If opted to extract the residual fragment, the surgical time can be prolonged and increases the tissue trauma, being sometimes necessary to perform bone removal techniques, which can contribute to BRONJ lesions as stated previously.
If opted to keep the residual fragment and follow the patient, the surgical trauma will be obviously lower; however, eventually tooth or bone fragments/remnants can lead to an increase in the risk of socket infection , which could also increase the risk of osteonecrosis according to the infectious theory .
Considering that the more atraumatic is the teeth extraction the better is for the healing process, with special mention in Bps treated patients, we highlight the strategies that can reduce the force intensity and the risk of teeth fracture during the exodontias, such as odontotomy techniques. Extractions without tooth sectioning might be responsible for a more traumatic and difficult surgery, especially in light of difficulty factors, such as increased bone density that can lead to several complications related to BRONJ lesions.