What are the most common causes of dental phobia?

• Bad experiences: Dental phobia is most often caused by bad, or in some cases horrific, dental experiences (studies suggest that this is true for about 80 -85% of dental phobias, but there are difficulties with obtaining representative samples). This not only includes painful dental visits, but also psychological behaviours such as being humiliated by a dentist.
• A history of abuse: Dental phobia is also common in people who have been sexually abused, particularly in childhood. A history of bullying or having been physically or emotionally abused by a person in authority may also contribute to developing dental phobia, especially in combination with bad experiences with dentists.
• Uncaring dentist: It is often thought, even among dental professionals, that it is the fear of pain that keeps people from seeing a dentist. But even where pain is the person's major concern, it is not pain per se that is necessarily the problem. Otherwise, dental phobics would not avoid the dentist even when in pain from toothache. Rather, it is pain inflicted by a dentist who is perceived as cold and controlling that has a huge psychological impact. Pain inflicted by a dentist who is perceived as caring is much less likely to result in psychological trauma (Weiner et al, 1999).
• Humiliation: Other causes of dental phobia include insensitive, humiliating remarks by a dentist or hygienist. In fact, insensitive remarks and the intense feelings of humiliation they provoke are one of the main factors which can cause or contribute to a dental phobia. Human beings are social animals, and negative social evaluation will upset most people, apart from the most thick-skinned individuals. If you're the sensitive type, negative evaluation can be shattering.
• Vicarious learning: Another cause (which judging by our forum appears to be less common) is observational learning. If a parent or other caregiver is scared of dentists, children may pick up on this and learn to be scared as well, even in the absence of bad experiences. Also, hearing other people's horror stories about visits to the psychodentist can have a similar effect.
• Preparedness: Some subtypes of dental phobia may indeed be defined as "irrational" in the traditional sense. People may be inherently "prepared" to learn certain phobias, such as needle phobia. For millions of years people who quickly learned to avoid snakes, heights, and lightning (and sharp objects, such as needles, which would not have been sterilized in those days, apart from giving you a nasty sting!) probably had a good chance to survive and to transmit their genes. So it may not take a particularly painful encounter with a needle to develop a phobia.
• Post-Traumatic Stress: Research suggests that people who've had horrific dental experiences (unsurprisingly) suffer from symptoms typically reported by people with post-traumatic stress disorder (PTSD). This is characterized by intrusive thoughts of the bad experience and nightmares about dentists or dental situations.

This was summed up by Stefan Bracha and his colleagues (2006) in an article in the Hawaii Dental Journal:

"In this article, we suggest that the term "dental phobia", as commonly applied to the experience of dental fear and anxiety, is typically a misnomer. The problem with using the term "phobia" in a dental-care context is as follows: by definition, phobias involve a fear that is "excessive or unreasonable", which the individual recognizes as such, and in which the anxiety, panic attacks and phobic avoidance are not better accounted for by another disorder, including posttraumatic stress disorder (PTSD). In our experience, most individuals who experience dental anxiety or fear do not view their symptoms as "excessive or unreasonable" and in that sense, resemble individuals with PTSD. Further, our review of the dental-care literature suggests that true (innate) dental phobias (akin to unreasonable fear at the sight of blood or a syringe) probably account for a smaller percentage of cases, and that a larger subset of dental-care anxiety (DA) cases stem from dental experiences that are, at a minimum, aversive and/or painful, and at times highly traumatizing. Research has documented that individuals who reported having experienced painful dental treatments and perceived a lack of control in the dental situation were approximately 14 times more likely to also report higher dental fear, and approximately 16 times more likely to report being less willing to return to the dental treatment. Based on the current available research, we propose that this psychological condition should be conceptualized as Posttraumatic Dental-care Anxiety (PTDA), and should be classified as part of the Posttraumatic Stress Disorder (PTSD) spectrum in the forthcoming Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-V)."