Hi,

I knew that a tooth that completed the root c{*filter*}treatment will be very
brittle. If  such tooth being a molar the occlusal force from the
opposing tooth may be so large that fracture may occur. (in my case,
vertical fracture) Will bonding a copper ring help? Or will that be
other preventive measures?

Other than that, I want to ask what is the use of protusive record in
complete denture. Thanks a lot!

Regards,
Yo

Molar teeth after root c{*filter*}should always receive full coverage
restorations.
Typically these are done as crowns.
A copper band may not prevent a fracture from occurring.
It may only hold the fractured piece against the rest of the tooth.

A protrusive record is used when mounting a case on an articulator.
The articulator simulates the relation of the patients upper and lower jaws.
Since the jaw joint rotates and translates (slides forward and down when
opening)
the protrusive record is used to simulate this angle of translation to allow
the cusped teeth to be set at optimum postion for denture wear.

Hope this information helps.
Rob.