Lesions must be to the DEJ, if your prep extends beyond Ideal you must get permission to do so and if you have a pulpal exposure you must anticipate it and let the floor instructor know that you may have a pulpal exposure. Preps that extend beyond ideal, must be based to ideal.
Someone in my class passed with a pulpal exposure, but another failed because the examiners said that the exposure was "well managed, but unnecessary."
Both my lesions were ideal, only to the DEJ and my class 3 I don't even think was to the dej, but the examiner let it slide.
Getting px is difficult, if you know someone in dental school get them to help, or if you know any practicing dentist they may be able to help you.
I think the problem with perio is that the examiners don't even know how to detect calculus effectively and that the subjectiveness of how you tilt the probe. All I know is that when I took the exam everyone who had perio the first day did well, but those on the second day nearly all failed the section - but still passed the exam.