Improper maintenance.Raw pull force before cleaning is 5.5 lbs.And after cleaning is 7.4 lbs.Debris found inside the autochuck.Recommend raw pull force per iso standard is 6.2 lbs.Minimum.Other potential contributed factors: excessive air pressure and speed.Excessive air pressure and over speed limit can cause slippage of the bur.Bur extension: dental bur does not fully insert into autochuck may cause slippage.( send autochuck to manufacture for further investigation).Bur shank is under size: per iso standard, the dental bur diameter must be 1.6mm +0.000/-0.002mm.(we do not have the dental drill that was used on this handpiece when the incident occurred).
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