Introduction: Painful temporomandibular disorders (TMDs) are usually treated with physiotherapy, self-exercises, medication-based therapy and splint therapy. For splint therapy different types of splints are available. Therefore this randomized controlled study compared the effectiveness of a semi-finished occlusal appliance (SB) with a laboratory-made occlusal appliance (SS) in myofascial pain patients. Method: The trial subjects allocated to the experimental groups with the (SB) occlusal appliance and those provided with a laboratory-made occlusal appliance (SS) did, in addition, receive conservative treatment (self-exercises, drug-based and manual therapy). The control group was given conservative therapy (CO) only. Overall, a total of 63 patients participated in the study with each group consisting of 21 subjects. Results: When the first follow-up examination took place (14 days after splint insertion) mouth opening within the SB group was significantly enlarged. When the second examination was conducted (2.5 months after splint insertion) mouth opening was significantly enlarged in both splint groups when compared with the initial value. In the control group, no significant enlargement of mouth opening was detected. At no point there was a significant reduction in the number of pressure-sensitive areas of the TMJ. On palpation of the masticatory muscles however, a significant reduction in the number of pressure-sensitive areas could be observed within the CO group and the SS group after 2.5 months. When comparing pain reduction (muscle/joint pain) and mouth opening, no significant differences could be detected between the treatments. Conclusion: The results suggest that TMD should be treated conservatively. In cases of restricted mouth opening, the additional use of occlusal appliances can eliminate the patient’s discomfort more quickly. In this context, the tested, semi-finished occlusal appliance appears to offer an immediately available, temporary alternative to laboratory-made splints.