It is worth saying plainly that most people do not choose a dentist this way. In a survey of 445 residents of Riyadh asked what mattered to them when selecting a dentist, 66.1 percent expressed no preference at all about their dentist's nationality.[1] Riyadh is not Dubai and 2015 is not today, so read that as an indication rather than a measurement. The direction is clear enough, though, and this page is written for the people for whom it does matter, not on the assumption that it matters to everyone.
When researchers have looked for why shared background sometimes helps, the answer has not been the background itself. In a study of 214 patients and 29 primary care physicians, patients' sense of similarity to their doctor separated into two distinct things: personal similarity, meaning shared beliefs and values, and ethnic similarity. Race concordance was the main predictor of the ethnic kind. What predicted trust, satisfaction and intention to follow the advice was personal similarity, together with the doctor's patient-centred communication. Perceived personal similarity was itself predicted by the patient's age, education and that communication, and not by racial concordance.[2] Shared origin can be a shortcut to feeling understood. Feeling understood is the thing that matters, and other roads reach it.
Language is a different question, and there the evidence is stronger. A systematic review of 33 studies of patients with limited English proficiency in the United States found that 25 of the 33 showed at least one outcome better when care was delivered in the patient's own language, 5 showed no difference, and 3 showed worse outcomes.[3] The authors were careful to note that none of those studies had measured the clinician's actual language proficiency in any standardised way. A second systematic review, covering 38 quantitative studies, found the results split between a positive association and no association at all.[4] So it is worth having and it is not magic. None of that work was carried out in dentistry, and none of it shows that a dentist of a particular nationality places a better filling.
So the honest position is this. Talking to your dentist in your own language is supported by the evidence and is worth having. Sharing a nationality with your dentist is not a clinical variable, and no claim of that kind is made here. Dr. Khalid being Iraqi is the reason he can hold the conversation in Iraqi Arabic. It is not a claim to treat anyone better, and it gives nobody preferential access.