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FIG 2a-e: Bone harvested using this protocol retains
bone morphogenic proteins and growth factors. As
the gold standard for grafting, it can be used to
augment the implant site.

perature increases. They often look at the immediate histological ining current evidence in this sector. At 44°C for one minute, the
impact on the bone cells without considering that the heat damage team found no differences from histologically normal bone, but
occurs weeks after tissue injury, likely to be a secondary result of that seven minutes at this temperature could potentially cause bone
ischemia. Maintaining blood flow is critical, a concept on which the damage.
Swedish team concentrated. Regardless, we had evidence by the end of the 1980s that tem-
Later, the same group discovered that 30% of the bone around perature and duration of exposure are crucial for bone health, and
implants resorbed after drilling at 50°C for one minute and 47°C these values have not altered much. The literature often suggests
for five minutes. They theorized that this was due to fat cell inva- that 44°C is the safe limit, and some studies continue to quote 47°C
sion, which occurs when, with greater insult, larger proportions of as the safe limit. I am just explaining why, as a generally risk-averse
fat cells undergo necrosis. Fat cells regenerate when the vasculature implant dentist, I consider 40°C my accepted safe temperature
recovers and these new fat cells infiltrate the surrounding bone where possible. Spending nearly seven cumulative minutes on a
more aggressively than existing fat cells. The greater the thermal single osteotomy preparation would be rare.
trauma to the connective tissues, the greater the degree of bone
resorption. When exposed to 47°C for a minute, some sites only WHY SLOW DRILLING?
experienced 10% bone resorption. Others experienced up to 30% Why have I dragged a reader interested in the relevant, practical
resorption. component of a slow drilling protocol through so much of the his-
The study concluded that 47°C for one minute is the bordering torical history of bone temperature research? The answer is that it
temperature for the occurrence of bone tissue damage. But the is crucial to appreciate that there is a solid evidence base behind this
inconsistency in bone resorption rates at this temperature suggests technique – but that there might also be some hidden clues to the
that this is an unpredictable and potentially dangerous safe tem- modern clinical problems that we face in implant dentistry.
perature to accept. With the advent of social media as a form of 'study club' in mod-
ern implantology, conversations surrounding implant problems
FURTHER INVESTIGATION centred on a clinical case are becoming more common. On closed
The team's research thus continued along the same path, with mul- forums, such as the Association of Dental Implantology (ADI)
tiple studies leading on to each other, using this tried and tested Members' Forum on Facebook, one case demonstrated the loss of
methodology. They found that at 50°C for one minute, there was a integration of a five-year-old implant.
loss of bone and vascularity adjacent to the implant. The most frequent reasons for this tend to be fremitus or peri-
At 47°C for one minute, there were histological differences from implantitis, but the atypical radiographic appearance suggested this
normal bone, but this is the safe temperature still quoted in some was not the case. The resulting debate led to a colleague suggesting
in vitro studies that look at temperature changes when placing that this may be down to a 'late reactionary process, which made
implants with guided surgery. As a result, be cautious while exam- me wonder whether the fat cells could play a part here. What if the

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Dental Practice // November-December 2022 // Vol 18 No 6 55