When taking intraoral X-rays with a round collimator, the salivary glands and the thyroid gland are exposed to ionizing radiation. The rectangular collimator reduces the patient’s radiation dose. This study aims to analyze the impact of the rectangular collimator on the quality of intraoral X-rays taken by students of the University Clinics of Dental Medicine (Geneva, Switzerland). Intraoral X-rays, performed by 8 students with digital intraoral phosphor plates, were collected and a quality score was assigned to each X-ray. A total of 130 intraoral radiographs were analyzed. Half of the radiographs were taken with a rectangular collimator and 24.6% (32/130) were bitewings. The mean quality score of bitewings taken with or without a collimator was 11 ± 1.8 and 10.3 ± 0.9, respectively. The mean quality score of apical X-rays taken with or without collimator was 11.6 ± 1.0 and 11.5 ± 2.1, respectively. X-rays taken with a rectangular collimator were of excellent or sufficient diagnostic quality for 95% of the bitewings and 100% of the periapical radiographs. This quality control study showing that students perform quality intraoral X-rays with a rectangular collimator could encourage clinicians to use this device as a means of radiation protection in their daily practice.