# Method for predicting orthodontic upper permanent canine teeth retention correction results

FIELD: medicine.

SUBSTANCE: method involves carrying out X-ray examination and determining longitudinal axis tilt of retained tooth and computer tomography. Maxillary computer tomography is carried out in three-dimensional Descartes coordinates with central occlusion being preliminarily fixed with individual silicon gumshield. The gumshield has 2-4 mm thick bilateral occlusion surface. Calculated free space value being found greater than thickness (vestibulo-oral size) of the retained tooth, positive prognosis for successful moving out is determined by building geometrical model, carrying out mathematical analysis of received data. The calculated free space value being found equal to retained tooth thickness, prognosis for difficult moving out is produced. The calculated free space value being found less than retained tooth thickness, unfavorable prognosis for moving out is produced.

EFFECT: high accuracy in predicting orthodontic correction results in three-dimensional space.

18 dwg, 1 tbl

The invention relates to medicine, namely to orthodontics.

Violation of the integrity of the dentition associated with impaired mechanisms for the change of teeth (retention), which leads to morphological, functional, aesthetic disorders in the oral cavity and social adaptation. From 4 to 18% of adult patients with impaired functional occlusion seek medical assistance orthodontic or orthopedic) about such pathology. Today, thanks to the popularization of fixed orthodontic appliances - Aguis Russian dentists have the opportunity to refuse the removal of impacted teeth and subsequent prosthetic dentistry, taking the path of subsaharienne[1, 2, 3].

The closest in technical essence is a method for prediction of orthodontic treatment retention [4], consisting in predicting successful orthodontic treatment retention teeth, which consists in the determination of the angle of the longitudinal axis of impacted tooth on the orthopantomogram performed in the frontal plane. Thus define the outer angle formed by a horizontal plane connecting the Vestibulo-distal cusps of the first molars and the line drawn on the distal surface of the first molars. In the case when the angle is less than 104°reveal pological the economic result for the normal eruption of impacted tooth, for angle 105°...125° - normal teething difficult for angle of more than 126° adverse eruption of the tooth.

However, the information content of the method of radiological examination of the resulting images are planar, not allowing the doctor (radiologist, orthodontist, prosthodontist and surgeon) to get an idea about the object of interest (impacted tooth) in the three-dimensional coordinate system in real time without angular and linear distortion.

The task can be represented forecasting orthodontic correction of retention of the upper permanent canines in the three-dimensional coordinate system.

This object is achieved by computed tomography (CT) of the upper jaw (topogram, axial tomograms, 2 - and 3-dimensional reconstructions), the construction of the geometrical model, a mathematical analysis of the obtained data.

The method is as follows.

The patient with impacted upper permanent canines conduct a CT scan on the scanner Somatom AR "Siemens" (Germany) and Piker PQ 5000 (USA). Before conducting computerized radiographic examination of the patient, record the position of Central occlusion with silicone mouth guard with bilateral occlusal surface thickness of 2-4 mm, projectors, is prepared by the method of thermal vacuum pressing apparatus Vacfomat-2000 on a pre-prepared models of super plasters. Then start an x-ray with traditional topogram using anatomical landmarks. In the subsequent perform native studies at step tomography 1-2 mm and the width of the tomographic slice 1-2 mm. Zone of the study extend from the occlusal surfaces of the teeth of the upper jaw (easily identifiable thanks to the individually divided occlusion) to alveolar sinus maxillary sinus (cavity), expanding as necessary to the object of study (impacted tooth). After performing tomographic studies are multiplanar image and 2-, 3-dimensionai (2D, 3D) reconstruction on the desired anatomic-topographic level and located near organochemical at the scanning rate of one layer 2-5 seconds with instant playback image in black and white or color version. After computerized x-ray studies on the obtained scans is building a geometric model of the area of interest of the dentition with the obligatory account of linear and angular displacements of the first premolar, impacted canine and the lateral incisor relative to the occlusal plane. Determine the angle of the Central axis of impacted tooth; the angles formed by the Central axis of the impacted tooth with semidesertobia coordinate system; geometrical parameters of the part of the dentition, which is retained tooth.

Next, perform mathematical analysis and creation of mathematical model of the area of the dentition.

When the estimated value of the free space greater than the thickness (Vestibulo-oral size) of impacted tooth, reveal a positive Outlook for its successful launch. For the calculated values of free space equal to the thickness (Vestibulo-oral-size) of impacted teeth, difficult to ascertain excretion, calculated for the amount of free space is less than the thickness of impacted tooth - adverse removal of the tooth.

For the proposed method for predicting treatment retention upper permanent canines as reference systems are Cartesian coordinates, the axes of which are formed by the intersection of planes by Simon [5]: mid-sagittal, ear-orbital, frontal. These planes are mutually perpendicularly to one another (figure 1). By analogy with the third key by Andrews (angle definition inclinatio in vestibular-oral direction between the perpendicular to the occlusal plane and a line tangent to the facial axis of the clinical crown of the tooth in its middle facies point) [6]. The scans obtained using computed tomography, expect coal is between the Central axis of each tooth, included in the mathematical model (the first premolar, retained canine, lateral incisor, and the axes of the coordinate system (figure 2). Then calculate the amount of free space for the impacted tooth. For the calculation of the deficit of space in the dental arch anomalina located tooth determine mesio-distal dimensions of the crowns of all anterior and posterior teeth, compare their sum with the length of the dental arches in the interdental line of Andrews [6]; the length of the front area of the dental arch on Korkhaus [5]; the width of the dental arch in the region of the premolars and molars on Pono [5]; the positions of the centers of the cross sections of the crown part and the root tips of the teeth in the Cartesian coordinate system.

The coordinates of points generated geometric model, which calculate the true linear dimensions of the teeth along their Central axes, the tilt angles of the Central axes of the teeth, where ED is the Central axis of the first premolar; SV - Central axis of the canine; AO Central axis of the lateral incisor (figure 2).

On the basis of the received data plan tactics and strategy of orthodontic treatment.

A specific example

The scans into three-dimensional coordinate system define the positions of the centers of the cross sections of the crown part and the tops of the teeth. Coordinates of points defining the position of the Central axis of the teeth, and the thickness of the teeth, traced shadow (figure 3), calculate the deficit of the dentition (figure 2).

<> In table 1 (figure 2) specified linear dimensions 2, 3 and 4 teeth (AO; ED and SW), respectively, the X, Y and Z.In mathematical formulas, the symbol 2 marked side cutter, symbol 3 is marked impacted Fang, symbol 4 marked the first premolar. The dimensions in figure 2 and figure 3 and in mathematical formulas are given in mm scale 1:2.

The mathematical analysis is carried out according to the following algorithm:

where- the linear dimension of the lateral incisor in the projections on the axes of a Cartesian coordinate system;

α_{2}that β_{2}that γ_{2}the angles between the Central axis of the side cutter and the respective axes of a Cartesian coordinate system.

where- the linear size of the canine, the projections on the axes of a Cartesian coordinate system;

α_{3}that β_{3}that γ_{3}the angles between the Central axis of the canine and the respective axes of a Cartesian coordinate system.

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where- the linear size of the first premolar in the projections on the axes of a Cartesian coordinate system;

α_{4}that β_{4}that γ_{4}the angles between the Central axis of the first premolar and the respective axes of a Cartesian coordinate system.

From these data, calculate the main parameters determining the mutual spatial orientation of the teeth,

- the distance between the Central axes of the cross sections of the crown portions of the teeth lateral incisor, canine, first premolar

,,linear dimensions between the Central axes of the first premolar and canine (coronal sections) of the projections on the axes of a Cartesian coordinate system;

- the linear dimension between the Central axis (coronal sections) of the first premolar and canine.

where,,linear dimensions between the Central axes of the lateral incisor and canine (coronal sections) of the projections on the axes of a Cartesian coordinate system;

- the linear dimension between the Central axis (coronal sections) of the lateral incisor and canine.

where,,linear dimensions between the Central axes of the first premolar and lateral incisor (coronal sections) of the projections on the axes of a Cartesian coordinate system;

- the linear dimension between the Central axis (coronal sections) of the first premolar and lateral incisor.

- the distance between the tops of the roots of teeth lateral incisor, canine, first premolar:

where,,linear dimensions between the Central axes of the first premolar and canine (in the region of the root apex) in the projections on the axes of a Cartesian coordinate system;

- the linear dimension between the Central axes (in the region of the root apex of the first premolar and canine.

where,,linear dimensions between the Central axes of the lateral incisor and canine (in the region of the root apex) in the projections on the axes of a Cartesian coordinate system;

- the linear dimension between the Central axes (in the region of the root apex) of the lateral incisor and canine.

where,,linear dimensions between the Central axes of the first premolar and lateral incisor (in the region of the root apex) in the projections on the axes of a Cartesian coordinate system;

- the linear dimension between the Central axes (in the region of the root apex of the first premolar and lateral incisor, where the value of the missing dimensions (lack of space) in the coronal parts of the first premolar and lateral incisor Δ_{42}is calculated by the formula

- taking into account the rotation of the first premolar tooth about the axis DE before you install it in the position which yields the maximum distance between the first premolar and lateral incisor, where- the highest average nominal diameter of the crown portion of the first premolar. Then, exploring the 7 and 8 scans, find the maximum nominal diameter of impacted tooth -. Given the scale Δ_{42}=4.5 mm,and crowns of the first premolar and lateral incisor should be separated into

Thus, using the proposed method can be implemented forecast successful removal of impacted upper loyal to egov and creating a mathematical model of the area of the dentition to calculate accurate values of movement of any tooth (smpeg-17).

Computed tomography safe and no complications.

Table | ||||||

Axis | 2 tooth | 3 tooth | 4 tooth | |||

O (mm) | A (mm) | In (mm) | (Mm) | D (mm) | E (mm) | |

X | 0 | -10 | 8 | 1 | 16 | 14 |

Y | 0 | 0 | -12 | -14 | -6 | -4 |

Z | 0 | 14 | 10 | 26 | 0 | 12 |

Sources of information

1. Part arsenina I., Stadnicka I.E. the Use of modern orthodontic techniques in the treatment of patients with impacted teeth.// New in dentistry." Specvp., 1/97 (51)-p.32-34.

2. Budkova T.S., Sigurt YOU, Khoroshilkina FA the Retention of teeth, the plan and the treatment.// New in dentistry." Spec. vol. 1/97 (51), -p.46-53.

3. Makushina E.A., E.A. Bragin, saddle CENTURIES, Grigorenko P.A. Improvement of methods of exposure crowns of impacted teeth.// "Orthodontics", 1999, No. 3, pp.2-6.

4. Patent No. 1917 (13) F1, "prediction Method of orthodontic techniques cured the I in the treatment of retention of teeth by the definition of angle". Bulletin "Inventions Of The Republic Of Moldova". MD - BOPI 5/2002.

5. Khoroshilkina FA Elimination of functional, morphological and aesthetic disturbances in the treatment subcluster-facial anomalies aguais technique.// M.: OOO "Pump". -1995, -182 C.; Il..

6. If the GT Kirchen A.D. straight arch Technique: a modern view. TRANS. from English. L.A. Loginova. - M.: "Artdent", 1996, - 51 S., 4 Il.

A method for predicting treatment retention upper permanent canines containing x-ray examination, determination of the angle of the longitudinal axis of impacted tooth, characterized computed tomography in a three-dimensional Cartesian planes of the upper jaw, with preliminary fixation of the Central occlusion individual silicone mouthguard with bilateral occlusal surface, the thickness of 2-4 mm, creating the geometric model, taking into account the linear and angular displacements of the first premolar, impacted canine and the lateral incisor relative to the occlusal plane, determine the angle of the Central axis of the impacted tooth, the angles formed by the Central axis of the impacted tooth with the axes of a Cartesian coordinate system, with the subsequent mathematical analysis and creation of mathematical models plot of the dentition, and the estimated amount of free space greater than the thickness of impacted tooth is - successful breeding, when the estimated amount of free space equal to the thickness of impacted tooth - difficult excretion, and when the estimated amount of free space is less than the thickness of impacted tooth - adverse removal of the tooth.

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