The term is generaly used in begg techique . it  tips back the molars so as to cause intrusive forces in anterior segment

thanks Dr. Ravindra. I'm guessing it is one couple mechanic where the wire is bent gingival at the molar area so that intrusion of incisors occurs at the same time the molar is tipped distal if it is tipped mesial therefore upright it as well?

There are many types of intrusion arches. The most used are the Ricketts intrusion arch, the Burstone intrusion arch and the CIA (Connecticut intrusion arch) and three-piece base arch appliance. All of them follow the same principle as said Dr. Ravindra. I suggest you the follow article to know more: Deep overbite correction by intrusion

Charles R. Burstone. Farmington, Conn. 

Thank you Dr. Ferriera. I believe the 3 piece base arch is the one used by Dr. Bhavna Shroff?

Tip back bend also called anchor bend, tips the molar crown distally and roots mesially. The molars experience extrusive force whereas the incisors are subjected to intrusive force. If the wire is tied at one point anteriorly, it is one couple force system. But if the wire is engaged into the slots of all incisors, it is two couple force  system (indeterminate).

Reaction on the molars extrusion i.e u must tip arch distally 

 Thank you Dr. Ahmed and Dr. Jamal.

When we introduce a tip back bend in an arch and engaged it in the molars posteriorely, the reaction at the anterior teeth (Newton's third law) will be their intrusion.

You can easily find  free videos on youtube: use key words: intrusion archs  and tip back bends.

Let me know if i could help more

Thank you Dr. Nasser. The problem is in most diagrams even in Proffit's book, the molar is upright (not tipped). This is the reason why I asked the question. So, in order to tip back the molar it should appear tipped in the illustration followed by uprighted after true intrusion of incisors. It is very difficult to imagine without pre and post illustrations. In any case, I do know now that this tips back the molar to counteract its mesial sinking as the lower incisors are intruded when the wire is passive following intrusion.

If you attach an intrusion arch to the segmented arch connecting the front teeth, (you should never engage an rectangular or square intrusion arch into the bracket slots) the front teeth are intruded and protruded or  retruded according to the point of force application in front or behind the center of resistance of the front teeth. If the intruding force passes through the centrer of resistance a translatory intrusion will happen. On the molar this mechanics will produce an extrusive force and a moment which will tipp the molar back. I f you use te reverse approach with an extrusion arch, the incisors will be extruded and the molar mil be tipped forward.

Keep on learning

Best wishes

Ulrich

Thank you Dr. Ulrich