Difference between revisions of "4° Clinical case: Temporomandibular disorders"

</center>In figure 9c and 9d, we can see not only the well balanced centric contacts but above all the mediotrusive excursions. A few more words should be spent on this subject. Benedikt Sagl et al.<ref>Sagl B, Schmid-Schwap M, Piehslinger E, Rausch-Fan X, Stavness I. The effect of tooth cusp morphology and grinding direction on TMJ loading during bruxism. Front Physiol. 2022 Sep 15;13:964930. doi: 10.3389/fphys.2022.964930. eCollection 2022.PMID: 36187792 </ref> state, in their study in which the contribution of tooth inclination, medio-otrusive and laterotrusive excursion and von Mises stresses on the articular disc was analysed, that mediotrusive bruxing generates higher loads than laterotrusive simulations. In this sense it is not clear whether the mediotrusive contacts are a protective or a pejorative element in the generation of temporomandibular joint disorders. So much so that an article by Walton TR and Layton DM<ref>Walton TR, Layton DM. Mediotrusive Occlusal Contacts: Best Evidence Consensus Statement. J Prosthodont. 2021 Apr;30(S1):43-51. doi: 10.1111/jopr.13328.PMID: 33783093</ref> increases the confusion as they first state that the presence of TM interference in patient populations is large and varies from 0% to 77% and then conclude that TM interference should be avoided in any occlusal treatment regimen to minimize pulpal, periodontal, structural and mechanical complications or exacerbation of temporomandibular disorders (TMD). The confusion increases when he concludes that natural molar MT interferences should only be eliminated if signs and symptoms of TMD are present. The question that arises is the following

{{q2|Which came first, the chicken or the egg?|.... are the interferences that cause the grinding and consequently damage to the atm or are the natural interferences protective on the system?}}It would be necessary to put some order on the subject starting with specifying what is meant by interference.

A study by Leitão AWA et al.<ref>Leitão AWA, Borges MMF, Martins JOL, Coelho AA, Carlos ACAM, Alves APNN, Silva PGB, Sousa FB. Celecoxib in the treatment of orofacial pain and discomfort in rats subjected to a dental '''occlusal''' '''interference''' model. Acta Cir Bras. 2022 Aug 15;37(5):e370506. doi: 10.1590/acb370506. eCollection 2022.PMID: 35976283</ref> is extraordinarily significant having objectively simulated the interference in the animal and histologically analyzed the changes in the trigmeinal ganglion contextually with the behavior of the animal when treated with or without selective cyclooxygenase 2 (COX-2) inhibitor. Furthermore, the authors treated the animals with a daily infusion of 0.1 ml/kg of saline (DOI+SAL) and 16 or 32 mg/kg of celecoxib (DOI+cel -8, -16, -32 ). They noted that animals subjected to masseter nociceptive stimulation and interference DOI + SAL showed an increase in isplateral (P < 0.001) and contralateral (P < 0.001) nociception, an increase in the number of bites (P = 0.010), scratching (P < 0.001) and grimacing scores (P = 0.032) while in the DOI+cel-32 group, these parameters were reduced.

This interesting study shows the correlation between interference, decrease in pain threshold and contextually recovery with celecoxib infusion and therefore neuro-occlusal correlation.

Si-Yi Mo et al.<ref>Mo SY, Xue Y, Li Y, Zhang YJ, Xu XX, Fu KY, Sessle BJ, Xie QF, Cao Y. Descending serotonergic modulation from rostral ventromedial medulla to spinal trigeminal nucleus is involved in experimental occlusal interference-induced chronic orofacial hyperalgesia. J Headache Pain. 2023 May 10;24(1):50. doi: 10.1186/s10194-023-01584-3.PMID: 37165344 </ref> reinforces the above neuro-occlusal correlation by demonstrating that the descending pathway from serotonergic (5-HT) neurons in the rostral ventromedial medulla (RVM) to 5-HT3 receptors in the spinal trigeminal nucleus (Sp5), plays an important role in facilitating the maintenance of orofacial hyperalgesia after delayed removal of experimental occlusal interference (REOI).

Up to now we have a broader view on the subject of interference confirmed by the neuro-occlusal correlation but the phenomenon can also be seen locally in the articular disc. Another study by Cui SJ et al.<ref>Cui SJ, Yang FJ, Wang XD, Mao ZB, Gu Y. Mechanical overload induces TMJ disc degeneration via TRPV4 activation. Oral Dis. 2023 Apr 27. doi: 10.1111/odi.14595. Online ahead of print.PMID: 37103670</ref> experimentally demonstrated that the effect of mechanical overload on TMJ discs in an in vivo rat occlusal interference model, inhibition of transient mechanoinductive receptor vanilloid potential 4 (TRPV4) alleviated TMJ disc degeneration in the rat occlusal interference model.

In conclusion, as we hope to share, the question is much more complex than what clinicians think and they hurry to eliminate the interferences, for example, mediotrusive because if the load induced on the joint, perhaps by a neuromotor hyperexcitability (see chapter Spasm Eimasticatorio and Cavernosa Pineale) the mediotrusive excursion could be a protective element perhaps to the detriment of the tooth itself.

 

For this reason, the term 'Mediotrusive Interference' should be re-evaluated

 

In figure 9c and 9d the mediotrusive path highlighted with the articulation paper was constructed by calculating the angle determined by the unilateral Root-MEPs which displaces the mandible by about 1/2mm on each side. By programming the Denar joint (figure 10) it was possible to construct an excursion with different angles between the TMJ, molar and canine. This procedure generates a natural path in which the canine guides together with the mediotrusion to protect the TMJ from the masticatory load that exists beyond bruxism.