I would disagree that this study is clear and conclusive on anything, other than the dental health of athletes is far from optimal.
Here is the purpose of the study:
"We aimed to systematically review the epidemiology of oral disease and trauma in the elite athlete population and to investigate the impact of oral health on sporting performance."
It says nothing about studying the diet of athletes and in fact there was nothing done in the study to qualify athletes with various diets. There could have been people that ate high-carb, low-carb, or just a regular balanced diet, it has nothing to do with the study. The hypothesis was that generally people perceive athletes as being very healthy, but examining the dental health of athletes shows that, at least their dental health, is not very good.
Unfortunately, the study is somewhat poor due to a lack of a control group (an essential part of a good study):
"Only one of the studies attempted to compare the athletes with a control population"
"None of the other studies compared data with either controls or population norms. Owing to this lack of comparative data, it is difficult to make any statements regarding the oral health of elite athletes relative to a non-athlete population", in other words we have no idea if the dental health of athletes is better or worse than the regular population, all we can say is that the dental health of athletes is somewhat poor (and I think we all know that the dental health of the average population is also poor).
The study then goes on with the main content, types of dental trauma that athletes experience, the types of dental issues that were monitored, with absolutely no mention of diet or carbohydrates.
The mention of carbohydrates in the study comes as somewhat of a footnote at the end of the study:
"Possible sport-related causes of poor oral health include frequent dietary intake of carbohydrates,11 physiological changes such as decreased salivary flow and drying of the mouth during exercise44 and exercise-induced immune suppression.45 Demanding training regimes might make it difficult to access preventive care. Other challenges to oral health might include low levels of oral health literacy, beliefs of the athlete and their support network, and a lack of prioritisation of oral health within sport."
Basically, the people involved in the study are speculating, why do athletes not have good oral health? Maybe for these reasons, or maybe not, notice the word they use "possible". In other words, these had nothing to do with the actual study, they are just making observations about athletes and guessing as to if maybe some of these reasons could be factors. Going from this little footnote at the end of the study to a headline saying: 39 Published Studies Reveal that High Carb diets cause ROTTING TEETH, is just absurd and obviously someone that has an agenda. An unbiased headline for this study would be:
39 Published Studies Reveal that the Dental Health of Athletes is Somewhat Poor.
Here again they are pointing out the big problem with this study:
"A lack of data for comparison groups within studies—that is, matched other than elite sport participation—is another common issue. Without an understanding of the control group, it is more difficult to determine the portion of risk of disease attributable in some way to elite sport and also to compare differences between sports and locations"