Journal of Craniomandibular Function, 03/2022

When utilizing CAD/CAM systems to design and manufacture dental prostheses and occlusal splints, one soon wonders: How accurate is virtual occlusion? Conventional methods involving dental impressions, plaster casts, articulators, and manual verification tools such as articulating paper have well-known sources of error and error chains, and tried and tested error-handling strategies for many of them already exist. Digital workflows, on the other hand, are still very new and unfamiliar to some dentists. Besides digital processes such as intraoral scanning and optoelectronic jaw motion tracking, analog processes may also be required. The penetration of maxillary and mandibular dental models is one aspect of digital dentistry that immediately attracts attention. Virtual penetration occurs because digital technology, like every measuring system, is subject to measurement error, and because virtual reality can only approximate the true variable nature of the physiologic masticatory system. The present article aims to identify and discuss variables that affect the accuracy of virtual occlusion. Some errors are first discovered in the digital world. Virtual capabilities open up new perspectives that have yet to be explored and understood. Keywords: occlusion, virtual articulator, intraoral scan, jaw motion tracking

Objectives: Total alloplastic temporomandibular joint replacement (TMJR) requires detachment of the masseter muscle and often resection of the coronoid process. The present study investigated masticatory muscle activity and maximum voluntary clenching (MVC) force after insertion of a unilateral TMJR. Materials and methods: Muscle activity of the masseter and temporalis anterior muscles (surface electromyographic – sEMG) and MVC as well as muscle symmetry (POC) were determined on both sides preoperatively (T0) and 1-year postoperatively (T3). Results: 28 patients (18 females, 10 males; aged 47.25 ± 17.54 years) with preservation of the mandibular angle (MA) (n = 15) and with resection of the MA (n = 10) were studied. In patients with MA, muscle activity increased bilaterally at a constant POC from T0 to T3. In patients without MA, activity increased contralaterally in both muscles. Ipsilaterally, muscle activity increased in the temporalis muscle and remained constant in the masseter muscle. POC showed an increase in the temporalis muscle and a decrease in the masseter muscle. Both groups showed an increase in MVC ipsilaterally and a constant MVC contralaterally. Conclusion: The anterior fibers of the temporalis muscle were preserved despite resection of the coronoid process. Reattachment of the masseter muscle was likely. In the group with resection of the MA, residual activity/the mimic muscles were probably derived ipsilaterally. Keywords: TMJR, temporomandibular joint replacement, resection, maximium voluntary clenching force, masticatory muscles, muscle activity, sEMG, muscle symmetry, reattachment

Aim: To evaluate the effectiveness of manual therapy in the treatment of myofascial pain related to temporomandibular disorders. Methods: Randomized clinical trials were searched in the Cochrane Library, MEDLINE, Web of Science, Scopus, LILACS, and SciELO databases using the following keywords: temporomandibular joint disorders; craniomandibular disorders; myofascial pain syndromes; myofascial pain; exercise therapy; myofunctional therapy; physical therapy modalities; clinical trial; prospective studies; and longitudinal studies. Studies using the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) and manual therapy for myofascial pain were included. All studies were evaluated using the Cochrane Risk of Bias tool. Results: Five studies were included in the present review. Of 279 total patients, 156 were treated with manual therapy only or manual therapy with counseling. Manual therapy was efficient for pain relief in all studies evaluated; however, manual therapy was not better than counseling or botulinum toxin. Conclusions: Manual therapy was better than no treatment in one study and better than counseling in another study; however, manual therapy combined with counseling was not statistically better than counseling alone, and manual therapy alone was not better than botulinum toxin. Manual therapy combined with home therapy was better than home therapy alone in one study. Further studies are required due to the inconclusive data and poor homogeneity found in this review. Keywords: exercise therapy, myofascial pain, myofascial pain syndromes, systematic review, temporomandibular joint disorders

Casts mounted in the articulator should depict the patient’s clinical situation as accurately as possible. The more precise the match, the fewer functional and esthetic problems can be expected later on. Currently, a great variety of options are available on the dental market for transferring the patient’s situation into the articulator with reference to the cranium. Common methods of mounting are average value-based mounting (Bonwill) using arbitrary or localized axes, esthetic mounting using bite registration records, and digital procedures. Furthermore, different systems are found within these defined categories, which has led to uncertainty over the years as to what the advantages and disadvantages or weaknesses of the individual methods might be. Questions also arise concerning the usefulness of the application in terms of time and cost management and the improvement to be made in the functional and esthetic quality of the final result. What is established, well-founded or even scientifically verified? People like to try out ‘newer,’ more up-to-date systems and to combine the ‘advantages’ of the different systems, ie, criticism of long-established and traditional systems is being voiced. The present article is based on practical experiences in everyday life. The aim is to demonstrate whether the supposed effectiveness of cranium-related systems is still state of the art. Can cranium-related mounting systems actually reflect the anatomy of billions of patients? Can a single system represent all these conditions? These and other questions are explored, not in a theoretical, scientific manner, but on the basis of established procedures in the dental laboratory. After all, this is ultimately where the restorations for our patients come from, not from the textbook. Keywords: functional reference, esthetic reference, dentofacial analysis, esthetic plane, mobile table plane