Is toothpaste dangerous? Could it even potentially harm erections and erectile strength?
After you read what they put in modern toothpastes, I think you'll agree that one could hardly devise a more dangerous cocktail of chemicals to use in your mouth (and gut since you invariably swallow some of it). And, yes, the potential is there for the stuff to actually affect your sex life as I'll show below.
By the way, this is another beautiful example of a health-desiring person possibly sabotaging his (or her) health thanks to what I consider indefensible consumer product marketing. Again, no one is going to watch out for your health except you!
NOTE: See my link on Real Natural Toothpaste Alternatives for some very practical information. Of course, discuss with your dentist before actually making any changes.
Without even going into the flouride controversy, here are just a few of the rather blatant risk in standard toothpastes (at least here in the U.S.):
1. Triclosan and Erections. As I covered in my link on Antimicrobial Soaps, someone got the bride idea to put an insecticide and fungicide in toothpaste and now almost all the big sellers in the U.S. do so. Now why, on God's green earth, would someone put an insecticide/fungicide in toothpaste? Simple: it kills not just bugs and fungus but also bacteria.
Bacteria in the mouth are what, depending on how you look at it, cause the plaque buildup on the enamel of your teeth. So, applying standard military tactics to this simple health problem, the enemy needs to be eliminated and triclosan does the job quite well. Many studies have shown that triclosan reduces plaque for example. 
What many guys probably do not consider is that the bacteria in one's mouth is one of the big engines of your nitric oxide production. Furthermore, as you age, this pathway becomes even more important since the L-Arginine pathway generally becomes impaired with age.
CAUTION: Good dental hygiene is very imporant. I have to admit that many studies have shown that those who take care of their mouth with brushing. etc. have improved cardiovascular outcomes.  The reason? Any "infection" in the mouth can increase system, whole body inflammation and that leads to accelerated heart disease. So, ironically, diflucan may protect your arteries somewhat but limit your nitric oxide output. More study work should be done.
To all of this, I can only say, "There has got to be a better way!" Fyi: I have found that by not eating sweets, I get almost no plaque in my mouth and get comments from my dentist of the same. Let's be honest here: maybe the diflucan is only necessary because of the sugars and processed carbs that we consume?
2. Chloroform. Consumer product companies used to put choloroform directly in toothpastes. Fortunately, the FDA banned this. So how did the manufacturers get around this? Triclosan! That's right - a lot of research has shown that this insecticide actually degrades into chloroform when exposed to the chlorine in tap water. 
So what's a little chloroform among friends?? Well, it causes birth defects in animals, but we'll skip that since this is a men's site. The primary reason for us males is that chloroform has been shown in many studies to cause cancer, especially of the liver.  Yes, in this case the FDA was watching out for you. Unfortunately, toothpaste manufacturers were not.
NOTE: The Nazis used chloroform and the notorious Dr. Mengele used it to kill patients instantly by injecting it into the heart. 
3. Sodium Lauryl Sulfate. You may recognize this chemical from your reading your shampoo bottle sometime when you were bored. So what is it doing in your toothpaste? Because sodium lauryl sulfate is a strong detergent and also foaming agent. In fact, it is strong enough to clean your tile and floors and is used in some commerical products due to its cleaning powers.
Now so far it does not appear to cause cancer, but it is definitely an irritant. Furthermore, it can be contaminated with a side chemical that is a strongly suspected carcinogen.  That nice clean, foamy mouth feeling after you brush? You can thank corporate American for putting an industrial detergent into your mouth!
So are there any better solutions? Well, this is a bit tricky I'm afraid and you'll have to do a bit of research on your own and/or discussion with your dentist. One natural solution that I am investigating is Pomegranate Extract. One recent study looks very promising and found that pomegranate was as effective as chlorhexidine, a standard antiseptic mouthwash that was once prescription-only (at least here in the U.S.) at preventing plaque buildup on teeth and enamel  This verified previous study work that found pomegranate was anti-plaque. 
NOTE: See also my link on Periodontitis Prevention for other natural ideas and solutions as well.
CAUTION: Discuss with your dentist. Dental plaque and periodontitis is potentially serious and leads to systemic inflammation that can hurt long term cardiovascular health.
1) J. Antimicrob. Chemother, 2000, 45(2):153-158, "The effect of triclosan toothpaste on enamel demineralization in a bacterial demineralization model"
2) ANALYTICAL AND BIOANALYTICAL CHEMISTRY, 383(7-8):1119-1126, "Aquatic degradation of triclosan and formation of toxic chlorophenols in presence of low concentrations of free chlorine"
3) Environ Health Perspect, 1986 Nov; 69:49-58, "Enhancement of the hepatotoxicity of chloroform in B6C3F1 mice by corn oil: implications for chloroform carcinogenesis"
4) Environ Health Perspect, 1982 Dec, 46:141-149, "Dose-response study of chloroform carcinogenesis in the mouse and rat: status report"
7) Circulation, 2011, 124:A17704, "Abstract 17704: The Association of Tooth Scaling and Decreased Cardiovascular Disease -A Nationwide Population-Based Study"
8) Quintessence Int, 2011 Jan, 42(1):29-36, "The antiplaque efficacy of pomegranate mouthrinse"
9) J of Herbal Pharmacotherapy, 2006, 6(2):79-92"Punica granatum (Pomegranate) Extract Is Active Against Dental Plaque"