DZZ International, 02/2021

Question: What is the importance of the deglutition act/swallowing reflex with regard to the regulation and feedback mechanisms of the stomatognathic system? Background The deglutition act represents one of the most frequent motor functional processes in our body, which coordinates more than 50 pairs of muscles. It can be understood as a complex reflux event. In the wake state, we swallow around 0.5–1.5 ml of saliva per minute, mostly unconsciously. During deep sleep, salivation and swallowing activities are largely at rest. In addition to regulating salivary flow, the deglutition act also appears to have an important influence on the regulatory and feedback mechanisms of the entire stomatognathic system. Since the lower jaw usually moves dorsally and the dental arches of the maxilla and mandible come into brief contact during the swallowing act [2, 4, 7], a physiological sequence of the swallowing activity is essential for controlling the masticatory muscles. During the physiological deglutition act, feedback is provided via the receptors in the periodontal attachment apparatus, as well as, those in the masticatory muscles and temporomandibular joint; this feedback is responsible for establishing impor¬tant control variables of the stomatognathic system, such as the rest position of the mandible when the masticatory muscles are relaxed. Each muscle works by shortening itself. However, a muscle which is constantly shortening (working) also requires information about what "length" it should maintain or set in the relaxed rest mode. Skeletal muscles, for example, use feedback from their direct antagonists' activity for establishing their "length" at rest; hence, an interplay between "flexors" and "extensors" is involved. In the stomatognathic system, this simple interplay as it occurs in the extremities is not so obvious. It is also necessary to consider that the stomatognathic system has to serve two functions. On the one hand, it performs the function of mastication, while on the other hand, it is a part of the organ of speech, so that, different centers in the brain – which partially compete with each other – exert their control functions on the stomatognathic system. In this manner, a "reset" through which the stomatognathic system always finds its physiological rest position represents a necessary set of rules for the undisturbed function of the stomatognathic system. The fact that the mandible can reliably and reproducibly be brought into the centric position during swallowing, and because this happens very frequently and unconsciously in the waking state, suggests that swallowing activity has an important control function. The occlusal contact which takes place between the upper and lower dental arches during the swallowing cycle generates a vertically acting force of approximately 30 N. The occlusal forces that are elicited during swallowing can modify the resulting force system. The force is thus not constant meaning that there is a continuous increase and decrease.

3D diagnostics – i.e. CBCT – has become indispensable in endodontic and endosurgical diagnostics, treatment and control (follow-up) and has become a real "gamechanger" not only for experienced colleagues and specialists. With the increasing complexity of cases, the superimposition-free and dimensionally accurate display of even the smallest details is gaining in impor-tance and offers an excellent assessment of the prognosis of the teeth to be treated, thus allowing a high degree of certainty in treatment planning as well as (evidence-based) patient education. This is especially relevant for endosurgical procedures with their close relationships to anatomically significant structures (e.g.: maxillary sinus or nervous structures). Nevertheless, CBCT requires a high degree of responsibility with regard to the use of ionizing radiation. The ALARA principle ("As Low As Reasonably Achievable") is more and more replaced by ALADA ("As Low As Diagnostically Acceptable"). It is always necessary to decide whether the patient's well-being is more compromised by not taking the X-ray than by the ionizing radiation and its consequences. Even though there is current evidence that exposure to low-dose radiation with a cumulative dose of up to 100 mSv does not appear to increase the risk of cancer, each CBCT-scan is a justifiable, indication-based, case-by-case decision that must always be made on the basis of a thorough history and clinical examination, taking into account any previous images that may be available. Keywords: CBCT, apical surgery, endodontics, microsurgery, radiation exposure, radiography, surgical, treatment outcome

Introduction: Current systems for activating irrigation solutions mainly use sound, ultrasound or laser. The simple form of manual dynamic activation must be differentiated. Methods: In comparison to the conventional irrigation technique, the described methods generally result in a greater cleaning effect under experimental conditions (removal of pulp tissue and debris, penetration depth into the root dentin, antibacterial effect, removal of calcium hydroxide). Gradual differences seem to be the result of the chosen experimental setup and the material used. Result and Conclusion: Given that comparative clinical studies are largely lacking and the advantages of a defined irrigation protocol involving the activation of the irrigation solution have not been clinically proven so far, only a recommendation for their application can be derived from existing experimental studies. Also, with respect to the activation method, different approaches can be justified. Keywords: activated root canal irrigation, laser, root canal preparation, root canal treatment, ultrasound

All obturation techniques require a certain amount of root canal sealers in order to fill small irregularities along the canal wall. Epoxy resin-based sealers have been the gold standard to date. A more recent development is represented by calcium silicate-based sealers (CSS), which derive from calcium silicate-based cements (MTA). CSS are proven to be biocompatible and bioactive. A hydroxyapatite-like precipitate forms on the surface of CSS when they come in contact with tissue fluid so that these sealers are not recognized as foreign bodies, even in cases of sealer extrusion. After their setting, CSS release OH- and Ca2 ions over a longer period of time through which they potentially exhibit certain antibacterial effects and support the healing of periapical inflammation. For this reason, consideration has been given to the idea of filling root canals mainly with CSS and minimizing the proportion of gutta-percha. To date, however, no long-term clinical studies have been performed to confirm the advantages of this new concept. Although gutta-percha has been successfully used for root canal obturation for a very long time, there are different perspectives with regard to which root canal filling technique is better: cold or warm (thermoplastic) obturation. After the exposure of sufficiently filled root canals with saliva, microorganisms always infiltrate into the root canal system regardless of the obturation method. Until now, no known obturation method leads to a bacteria-proof sealing of the root canal. Thus, in terms of clinical success rates, no superiority of the frequently recommended thermoplastic root canal filling technique compared with cold lateral compaction could be demonstrated. As a rule, CSS are not approved for thermoplastic obturation, as these sealers are water-based; there is the concern that high temperatures of up to 200 °C will remove too much water from the sealer, which can have a negative impact on its properties. It is questionable whether such high temperatures are clinically achieved during thermoplastic obturation. A disadvantage of CSS is their higher solubility compared to epoxy resin sealers. In the long term, this can lead to the dissolution of the root canal filling. In the studies that have been performed to date, however, no difference in the clinical success rates between epoxy resin sealers and CSS has been determined. Overall, CSS represent an interesting alternative to conventional root canal sealers. In principle, the success of a root canal treatment depends not only on the obturation technique, but above all, on the complete removal of the infected tissue, the permanent disinfection of the root canal system and the bacteria-proof post-endodontic restoration. Keywords: calcium silicate, thermoplastic obturation, root canal filling techniques, root canal sealer

Based on the current state of knowledge, vital pulp treatment on teeth with deep carious lesions is indicated only in vital teeth which are asymptomatic, or at the most, show symptoms of reversible pulpitis. In cases of irreversible pulpitis, vital pulp extirpation and root canal treatment constitutes a reliable and established method that should still be considered the gold standard. However, recently published clinical studies show that, despite the diagnosis of "irreversible pulpitis", surprisingly high success rates can be achieved after partial or full pulpotomy. These findings do not only challenge the current treatment concepts for teeth affected by pulpitis, but also the current system for diagnosing different stages of the disease. Although the diagnosis of "irreversible pulpitis" is consistent with histologically detectable areas of bacterially infected or already necrotic tissue, these areas are localized beneath the carious lesion in the coronal pulp and do not affect the entire pulp tissue. Pulpotomy involves the complete removal of inflamed, and therefore heavily bleeding, pulp tissue up to the level where the remaining pulp tissue is healthy in order to create the necessary conditions for healing. To date, a total of 12 clinical studies with a focus on vital pulp treatment in teeth with deep carious lesions and irreversible pulpitis have been published. Success rates after observation periods of 1 to 5 years range between 85 % and 95 % in most studies, regardless of patient age and type of pulpotomy (partial or full). However, it must be taken into account that long-term studies are lacking, and the significance of the individual studies is limited by various qualitative deficits. In spite of these shortcomings, based on the current data, pulpotomy can be regarded as a valid treatment option for irreversible pulpitis and it certainly represents an alternative to vital pulp extirpation. Whereas the correct indication is critical, the success of a pulpotomy procedure mainly relies on the adequate performance of the necessary treatment steps. This includes, in addition to the aseptic treatment concept in combination with the consistent use of rubber dam and sterile instruments, the use of magnifying aids to enable a sufficiently precise amputation procedure, the endodontic expertise to assess the exposed pulp tissue, the application of appropriate disinfection measures and capping of the tissue with a bioactive material followed by an immediate coronal seal. Keywords: partial pulpotomy, pulpitis, vital pulp treatment, full pulpotomy