Col Charlton: Your problem is not an uncommon one. Quite a few new triturators have been introduced to the market in the last five years. Not uncommonly, the manufacturer will neglect to include, or choose not to include, recommended mixing times for amalgam alloys. Usually, the clinician and assistant are left to their own devices to determine the appropriate mixing times. It is important to mix amalgam for the appropriate amount of time because it can affect the alloy's working time (i.e., the amount of time available for condensing and carving the amalgam), especially if the amalgam is an admixed type such as Dispersalloy (Dentsply/Caulk), Valiant Ph.D. (Vivadent), or Original D (Wykle Research). It is therefore important to have a method you can use to quickly and accurately determine the appropriate mixing time for your amalgam. One way of doing this is to follow the steps listed below:

The T-Scan II system is now available in the UK and EIRE. Here Robert B. Kerstein, DMD, a clinical consultant for Tekscan Inc, explains how the system works and how it simplifies occlusal adjustments

The T-Scan II Occlusal Analysis System measures occlusal contact timing sequences in real time, as well as the occlusal forces contained within the sequenced occlusal contacts. Evaluating occlusal forces is as simple as having your patient bite down on the ultra-thin sensor. The sensor sends real-time occlusal contact and force information to WindowsTM based software, which measures intraoral force in time increments as low as .01 seconds. The graphical interface uses WindowsTM toolbar icons to display the software features that are utilized to analyze occlusal contact information(1, 2).

Real-time recording of an occlusal contact event in .01 second increments (closing into MIP or CR, mandibular excursions, multiple clenches, any combination of these) is accomplished with the highly repeatable, High Definition Sensor(3). The .01 second incremental playback of the recorded contact sequence illustrates the exact order of tooth contacts, as well as their force content. The combination of contact order, duration, location, and force content, all determine the degree of contact simultaneity, and the force balance that is present or absent in a particular occlusal scheme(4).

Clinical applications of the T-Scan II system are numerous (1, 2, 4, 5, 6 – 10). Occlusal adjustment procedures performed upon on differing dental prostheses, implants, or natural teeth can be guided by computer analysis where the operator can predictably accomplish precision ideal measurable occlusal endpoints (1, 2, 4, 5, 6 – 10).

The T-Scan II helps the dentist reach these ideal endpoints because it measures the forces and timing in the articulating paper marks (whereas articulating paper cannot) so the operator has knowledge of what the paper marks mean.

Contact labelling with articulating paper/ribbon marks is believed to illustrate the nature of the timing and occlusal force that is contained within the labelling. The depth of colour, and the surface area of the occlusal marking, is perceived by the operator to describe the contact force.

But articulating paper marking materials have many use limitations. Studies by Schelb et al(11) Halperin et al(12) and Mori et al(13), describe paper thickness, marking ability and material types. But there are no studies in the dental literature that illustrate articulating paper can measure time or force. In short “Paper is just Paper” and paper is not capable of measuring force and time.

However, the T-Scan II records and measures tooth contact force and timing data in real-time by embedding 2000 .05 in2 pressure measurers (known as “sensels”) into a dental arch-shaped recording sensor. Each sensel is scanned for occlusal contacts 80 to 100 times per second. The recorded data is imported into the T-Scan II software and hardware by a handle that holds the sensor in place intraorally. The software and hardware combine to measure the order, duration, and force content, of the recorded occlusal contacts. The occlusal data is then displayed graphically for analysis in 2 or 3 dimensions as a dynamic movie that can be played forwards or backwards incrementally (14).

By viewing the force and time data, and correlating it to the locations (only) of articulating paper marks, the sequence of contacts and the forces contained within each labelling can be visualised, and interpreted. Then, corrective occlusal adjustments to natural teeth, dental prostheses and implant prostheses can be made with knowledge of the order and force content within a specific (or a series) of marks. Occlusal force control on dental materials, dental implants, and/or natural teeth can then be measurably designed to insure material, implant, or occlusal surface survival.

Bilateral contact simultaneity(4) can be clinically established through measurement of the occlusal contact sequence. This insures no one region of the dental arch contacts too early (forced to absorb excess early stress) or too late (unable to assist the other regions in force dissipation). Both precision force and time control is afforded to the operator through measurement with the recording sensor, which replaces the “hit or miss” operator subjective interpretation of coloured ink marks on teeth.

This force and time knowledge can be applied to any clinical situation from occlusal diagnosis to delivering dental prostheses. It is possible to make measured assessments followed by measured occlusal force and timing adjustments to any prosthesis or natural teeth to improve patient prosthesis acceptance, reduce MPDS symptoms(9, 10), and occlusal discomfort. Precision occlusal endpoints, where all teeth meet in .2 seconds or less(4), all posterior teeth disclude in .4 seconds or less from excursive commencement(5), and 50% right side - 50% left side force balance(4), is readily attainable when corrections are guided by the T-Scan II system..

In summary, the dentist can benefit during following dental procedures by employing T-Scan II analyses followed by measured corrective occlusal adjustments:

1. Finding occlusally activated painful teeth
2. Controlling occlusal forces on glass ceramic or all-porcelain restorations
3. Stabilising complete dentures by centering the occlusal force summation into the exact middle of the maxillary denture
4. Fixed prosthesis insertion force control
5. Removable prosthesis force control
6. Minimising forces that result in abfractions
7. Controlling damaging protrusive forces on Porcelain Veneers
8. Establish true and measurable 50% right side to 50% left side balance on TMD splints to insure that both TM joints are being loaded equally
9. When implants and teeth reside in the same arch, delaying implant occlusal contacts, so they receive minimal occlusal force (but are in contact) until after the nearby natural teeth occlude and move within the PDL fibers.
10. With complete arch implant prostheses, centering occlusal forces within the central distribution of implants to ensure axial loading reducing “shear stress” to implants 11. Developing measurable immediate posterior disclusion with complete anterior guidance control on natural teeth, or dental prostheses, so that fewer muscle fibres are recruited during excursive function. This “unloads” the occlusion from excess muscle activity during function.
12. Improving natural tooth occlusal adjustment procedures like Disclusion Time Reduction(5, 6, 9, 10) and Occlusal Equilibration(14).
13. Diagnosing occlusal problems without mounted diagnostic casts - The rapid data acquisition and playback of a given recording affords the operator instantaneous recall of a patient’s force and time aberrations that cannot be detected by mounting diagnostic casts.

Dr. Kerstein is a clinical consultant for Tekscan, Inc. He will receive no compensation from the sales of any Tekscan product.
References

1. Kerstein, R.B., Current Applications of Computerized Occlusal Analysis in Dental Medicine. General Dentistry 2001; 49(5); 521-530.
2. Kerstein, R.B.; Combining Technologies: A Computerized Occlusal Analysis System Synchronized with a Computerized Electromyography System, Journal of Craniomandibular Practice, April 2004, Vol. 22, No. 2, pp. 96-109.
3. Kerstein, RB., Radke, J., Lowe, M., Harty, M. A force reproduction consistency analysis of two recording sensors of a computerized occlusal analysis system. Accepted for Publication by Journal of Craniomandibular Practice, September 2005
4. Kerstein, R.B., Grundset, K., Obtaining Bilateral Simultaneous Occlusal Contacts With Computer Analyzed and Guided Occlusal Adjustments. Quintessence Int. 2001; 32:7-18
5. Kerstein, R.B., Wright, N., An electromyographic and computer analysis of patients suffering from chronic myofascial pain dysfunction syndrome; pre and post - treatment with immediate complete anterior guidance development. Journal of Prosthetic Dentistry 1991; 66(5):677 - 686.
6. Kerstein, R. Disclusion time reduction therapy with immediate complete anterior guidance development: the technique.Quintessence International. 1992;23:735 - 747.
7. Kerstein, R, B. Computerized Occlusal Management of a fixed /detachable implant prosthesis. Practical Periodontics and Aesthetic Dentistry November 1999, vol. 11(9):1093-1102
8. Kerstein, R, B. Non-Simultaneous Tooth Contact In Combined Implant and Natural Tooth Occlusal Schemes. Practical Periodontics and Aesthetic Dentistry 2001:13 (9);751-
9. Kerstein, R.B., Chapman R., and Klein, M., A comparison of ICAGD (Immediate complete Anterior Guidance Development) to "mock ICAGD" for symptom reductions in chronic myofascial pain dysfunction patients. Cranio, 15(1):21-37,1997
10. Kerstein, R.B., Treatment of myofascial pain dysfunction syndrome with occlusal therapy to reduce lengthy disclusion time - a recall study, Cranio, 1995; 13(2):105-115.
11. Schelb E., Kaiser DA, Bruki, CE. Thickness and marking characteristics of occlusal registration strips. J Prosthet Dent 1985, 54(11); 22-26.
12. Halperin GC, Halperin AR, Noting BK. Thickness strength and plastic deformation of occlusal registration strips. J Prosthet Dent 1982. 48(5); 575-578
13. Mori T, Kawaguchi T, Katto K, et al. Effects of articulating paper on mandibular paths in lateral and protrusive excursions Aichi Gakuin Daigaku Shigakkai Shi (Japan), Dec 1989, 27(4); 845-53
14. Maness, W.L., Force Movie. A time and force view of occlusion. Compendium 1989:10;404-8.
15. Dawson, PE. Diagnosis and Treatment of Occlusal Problems, ed. 2. St Louis, CV Mosby Co. 1989.