How to Place Neighboring Implants Parallel to Each Other (Part II)?

The implant at the site of #14 turned out to be not parallel to the tooth #13 (root) or the implant at the site of  #15 (Fig.4), when the retainer (crown) of #13 was used as surgical guide.

How can we do better? 

Before figuring it out, can you take a look at our rough journey of placing this implant?

Xin Wei, DDS, PhD, MS 1st edition 09/30/2013, last revision 10/02/2013