Biometric diagnostics

In recent times, the use of surface electromyography (SEMG), joint vibration analysis and jaw trackers, have provided dental practitioners with the essential tools they require to correctly diagnose and, hence treat, various muscular, joint and occlusal dysfunctions. This is confirmed in recent research studies, which concluded that objective measurements can enhance both diagnosis and treatment.

The objective of Biometric Dentistry (BMD) is to reduce a patient's occlusal adaptive requirements. We can use BMD to evaluate these requirements and improve functionality within the stomatognathic system (teeth, muscles and joints). In reality, the occlusion and the musculature are inseparable.

Any procedure that changes the vertical, lateral or antero-posterior position of the mandible can require adaptive changes by the teeth, muscles and/or temporomandibular joints. While many patients are able to adapt, it is the objective of biometric dentistry (BMD) to reduce patient's adaptive requirements. BMD is an approach to evaluating and treating the entire stomatognathic system (teeth, muscles and joints) that focuses on idealizing both craniofacial function and aesthetics. This becomes particularly significant when we realize that few patients arrive in our offices with perfectly functioning joints, muscles or occlusions.

A broken cusp and/or worn teeth are red flags that all is not well within this stomatognathic system. BMD is focused on improving the function of the system within the limits of the pre-existing conditions. While it is not always possible to idealize both aesthetics and function, by evaluating with BMD we can do much more than hope for a successful outcome.

The approaches of gnathology, centric relation dentistry, and neuromuscular dentistry are often seen as cookbook recipes offering one standard solution for whatever is wrong with the patient. However, with a biometric approach the practitioner employs a comprehensive approach to individualized diagnosis and treatment. This concept has evolved from the acknowledged interdependence between the triad of the teeth, TM joints and the neuromusculature.

BMD begins with the patient's chief complaint, a comprehensive health history, a thorough clinical examination and is followed by sophisticated but inexpensive objective testing. It is customary to evaluate the temporomandibular joint status first, since treatment options may be somewhat limited. This can be done quickly, easily and accurately with joint vibration analysis (JVA) (fig 1). A JVA finding of significant pathology indicates that sophisticated imaging can be justified. The first step is to determine whether the pathology is primarily intra-capsular or extra-capsular. When this has been accomplished, a decision, whether or not to treat joint pathology, is needed before proceeding with other areas of treatment.

In reality the occlusion and the musculature are inseparable. BMD recognizes that a well functioning masticatory system requires many factors to be within the individual patient's adaptive range. Therefore, a number of tests may be needed before a clear diagnosis can be achieved and without which the practitioner can only hope for a good result.

A simple, non-invasive way to evaluate muscle function is through surface electromyography (SEMG) (fig 2). Evaluation of SEMG activity can be very helpful in detecting maxillo-mandibular mal-relation, functional imbalances and/or chewing interferences. Jaw movement can be recorded simultaneously with a jaw tracker (fig 3). Distortions in the movements compared to normal subjects, together with abnormal muscle function can identify a wide range of mal-adaptations.

Recent research studies1-11 have concluded that objective measurements can enhance both diagnosis and treatment. This is accomplished biometrically by measuring the patients' joint, muscle and occlusal functions. As the clinician learns the normal patterns of muscle and jaw function, the dysfunctional patterns become easily differentiated. Consequently, it is no longer necessary to guess whether occlusal interferences, joint dysfunctions or muscle inco-ordination are present (fig 4).

Conclusion

The use of simple tools such as SEMG, joint vibration analysis, and jaw trackers can provide practitioners with a clear insight into a patient's stomatognathic system. It is this insight that will help in the necessary diagnosis that can aid in the treatment and management of a patient's muscle, joint and occlusal dysfunctions, without having to take a guess and hope for a good result.

References

1. Sano T, Widmalm SE, Westesson PL, Yamaga T, Yamamoto M, Takahashi K, Michi KI, Okano T. Acoustic characteristics of sounds from temporomandibular joints with and without effusion: an MRI study. J Oral Rehabil 2002 Feb;29(2):161-6
2. Widmalm SE, Williams WJ, Ang BK and McKay DC. Localization of TMJ sounds to side. J Oral Rehabil. 2002 29()1-7.
3. Radke J, Garcia R Jr, Ketcham R. Wavelet transforms of TM joint vibrations: a feature extraction tool for detecting reducing displaced disks. Cranio 2001 Apr;19(2):84-90.
4. Garcia AR, Madeira MC, Paiva G, Olivieri KA. Joint vibration analysis in patients with articular inflammation. Cranio 2000 Oct;18(4):272-9.
5. Throckmorton GS, Ellis E 3rd, Hayasaki H. Jaw kinematics during mastication after unilateral fractures of the mandibular condylar process. Am J Orthod Dentofacial Orthop. 2003 Dec;124(6):695-707.
6. Radke JC, Ketcham R, Glassman B, Kull R. Artificial neural network learns to differentiate normal TMJs and nonreducing displaced disks after training on incisor-point chewing movements. Cranio. 2003 Oct;21(4):259-64. Erratum in: Cranio. 2004 Jan;22(1):A-5.
7. Rodrigues Garcia RC, Oliveira VM, Del Bel Cury AA. Effect of new dentures on interocclusal distance during speech. Int J Prosthodont. 2003 Sep-Oct;16(5):533-7.
8. Buzinelli RV, Berzin F. Electromyographic analysis of fatigue in temporalis and masseter muscles during continuous chewing. SP, Brazil. J Oral Rehabil 2001 Dec;28(12):1165-7.
9. Kerstein R. Combining technologies: A computerized occlusal analysis system synchronized with a computerized electromyography system. J Craniomandib Pract 2004; 22(2):96-109.
10. Mahony D. Refining occlusion with muscle balance to enhance long-term orthodontic stability. Int J Ortho (Winter) 2004; 15(5):1-6.
11. Kamyszek G, Ketcham R, Garcia R Jr, Radke J. Electromyographic evidence of reduced muscle activity when ULF-TENS is applied to the Vth and VIIth cranial nerves. Cranio 2001 Jul;19(3):162-8.

Images available on request or refer to The Dentist May issue page 82–84.