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THE CONCEPT OF TEETH ROWS ORTHOPEDIC TREATMENT
Orthopedic treatment of damaged teeth rows considers the general state of the patient's health, i.e. a systematic approach is applied. Nevertheless, along with estimating the condition of internal organs, insufficient attention is paid to the functions of chewing muscles, which carry physiological, mechanical work during the processes of opening and closing of mouth cavity, of crashing food and of lateral shifts of the lower jaw.
This process causes emergence of forces of normal reaction (elasticity) N and friction (F) on the slopes of the occlusive surface, their resultant being the force of supporting reaction (Rn). However, it is essential to consider all the forces of supporting reaction to get an idea with regard to teeth stability (balance). Therefore it is necessary to measure full pressure (reaction) - R. [ 1 ]
Only taking into account the angle between the force of reaction (R) and the tooth axis, can the doctor estimate the angles of the bend of the slopes of the chewing surface accurately and forward this data to the laboratory. Unfortunately, dental technicians don't have access to this data when they have to solve issues as to the degree of the bend of the slope hillocks, whereas teeth stability depends on this factor.
Full pressure of the whole occlusive surface - R - should act along the axis of a tooth or at a slight angle to it (18 - 20º) [ 2 ]. It is mostly important to take into account the moments of the force (M) in denture making, because they loosen teeth [ 3 ]. The moment of force appears every time when food is swallowed, i.e. several thousand times a day. On the other hand, provided that the forces of tolerance of the whole organism and the tooth periodontium exceed the moment of force, teeth will be well balanced. However, one can often witness the opposite situation, when teeth are to be extracted. The moment of force is the force of reaction multiplied by the distance between the axis along which the force acts and the core of the tooth: M = R · L. The moment of force is the major parameter describing teeth stability or loosening (fig. 1) [ 2 ].
Danger of the moment can be avoided if the correlation of the tooth slopes is 5:3. In this case when food is swallowed, reaction amounts to zero, therefore the arm of force is absent [ 2 ].
That is why making dentures requires familiarity with the general state of health of the patient and later on - with the directions of force parameters (N, F, L, R n, R) emerging from the chewing muscles [ 4 ].
Every case implies statistic analysis carried out by the doctor and sketching the contours of supporting lateral teeth, the angles of the bend of their longitudinal axes, and after that - all the necessary parameters. Statistic analysis contains the most vital indexes in the process of making dentures, which presume the directions of force parameters, as without this one could only rely on the resources of the organism, but not on planning [ 5 ].
Unfortunately, doctors often underestimate the fact that the mouth cavity, with its teeth performing chewing function, is the beginning of the digestive system. Consequently, statistic analysis of the directions of force parameters should be compulsory for every orthopedist [ 6 ].
All of the above corresponds to the level of a high-qualified stomatologist - orthopedist of the XXI century. Otherwise a modern orthopedist will be similar to a tooth doctor of the previous century [ 2 ].
Axioms of physics and clinical practice applied in orthopedic stomatology.
1) There are two forces acting on the slopes of the chewing surface - elasticity (normal reaction) N and friction F. Their resultant is the power of supporting reaction R n, which is the pressure of every slope.
2) Distance between the centre of the tooth root on its axis and the axis of the force R n is called the arm of force L.
3) Full pressure R and its direction as to the tooth axis must be measured in order to shape the artificial crown in an accurate way. Pressure should act approximately along the axis.
4) M - moment of force - is characteristic of stability or loosening of a tooth:
a) when there is food pressure on the slope;
b) when food is swallowed;
c) approximate "equality of moments";
d) when the force is applied to the hillock of the slope;
e) depending on the longitude of the occlusive overlays.
5) "Biomechanical homeostasis" - amortization, damping of pressure
6) R and M are the two parameters characteristic of the tooth position in case of central occlusion (IKR) and central correlation (RKP).
The moment of force, which may loosen the tooth, especially during the act of swallowing, should be equal to zero or of extremely irrelevant value.
7) When the first tooth is damaged, it requires undertaking measures to slow down the bend of the neighboring teeth.
8) Two forces act when tooth slopes are present, but there is only one active force when occlusion is leveled. Friction itself, friction cone, TMJ syndrome.
9) Slope correlation 2:1; 2,5 :1,5 ; 5:3.
10) Shaping slopes of occlusive surface with teeth correlation 5:3
11) Teeth setting (5:3) for making dentures with 15 and 25º slopes.
12) Modification of present day teeth setting.
13) Correlation of the cutting surface (cutting teeth platform) of the front teeth.
14) Draft representation of the effect of forces N, F, R n with slope bends equal to 15; 30; 45; 60; 75; 81,5º.
15) The lower jaw acts like the arm of the third kind and provides benefits in power when food is being swallowed.
16) Pressure acts vertically and diagonally (at an angle) on the slope, and horizontally on the tooth crown.
17) Lingual occlusion (1:1). Slope bends depend on the teeth axes.
18) The same situation observed when implants are present (1:1).
19) The same in case of slope correlation 5:3.
20) Shaping slopes of occlusive surface in such a way that RKP pressure acts along the tooth axis (M = 0).
21) Force parameters:
a) value (full pressure divided between all the 28 teeth)
b) direction (at an angle not exceeding 18 - 20º)
c) point of application of pressure (possible in the middle of the chewing surface only provided that slope correlation is equal to 5:3, which corresponds to the law discovered by one of the outstanding German orthopedists A. Motsch (in 1978), naming the spending of minimum muscle energy plus maximum effectiveness of the chewing act as one of the characteristics of harmonic occlusion.
© Alexander Shwartz
Alexander Shwartz
Senior Researcher, veteran of WWII
Key words
Biomechanical phenomena
N - force of normal reaction,
F - force of friction,
Rn - force of supportive reaction of a slope,
R - full reaction of all supportive teeth,
M - moment of the force,
M1 - moment acting in the direction of the tongue,
M2 - moment acting in the direction of the cheek
Resume: "The Concept of Orthopedic treatment of Damages Teeth Rows"
Chemical energy of the nervous system is transformed into mechanical energy on every slope of the occlusive surface of lateral teeth. As a result, forces of normal reaction (elasticity) N and of friction (F) emerge, with their resultant being the force of supportive reaction (Rп).
Full reaction of lateral teeth is the full pressure (R).
These parameters, as well as the moment of the force (M) should be marked on a draft, and after that, it is necessary to measure the angle between the force of reaction (R) and the tooth axis. The moment of the force (M) characterizes the stability of the tooth (M = R · L, where L - the arm of the force - is the distance from the axis of the force of reaction to the centre of the tooth spinning.
The parameters of the force (N, F, Rn, R) and the moment of the force (M) are the major indexes of the biomechanical phenomena in the mouth cavity.
The slope correlation of the occlusive surface 5:3 is more efficient than 1:1, which is defined by the draft.
References
1) Targ S.M. - Short Course of Theoretical Mechanics, 1964, Moscow. 478
2) Schwartz A.D. - Contemporary Issues of Orthopedic Stomatology. Biomechanics. Moscow, LAB, 2006, no.1, p. 43-47
3) Kopeykin V.N. - Ortopedic Stomatology. M. Medicine 1998. 496
4) Gavrilov E.I. - Theory and Clinical Practice of Prosthetics with Partial Dentures. M. Medicine, 1966. 275
5) Alexander R. - Biomechanics (Eng - Rus translation). M. World. 1970. 148-167
6) Marxkors R. Funktiontller Zahnersatz 1981 Munchen, Wein 123
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