Improvement of Methods for Diagnosing Dento-Maxillary Anomalies by Means of Computer Technologies

The dissertation is devoted to improving methods for the diagnostics of dento-maxillary anomalies through the use of computer technologies. The study aims to overcome the limitations of traditional anthropometric and graphic methods of measuring plaster models of the jaws, which are associated with high labour intensity, subjectivity, and the risk of inaccuracies. The author carried out a comparative analysis of classical methods for evaluating the dimensions and shape of dental arches, including the Hawley-Gerber-Herbst method, and modern computer-based approaches. Within the framework of the work, a graphic method for determining the individual norm of dental arch dimensions, taking into account all the teeth, and software for express diagnostics of anomalies of teeth and dental arches were developed; the software superimposes graphic models of normal and actual dental arches according to facial and cranial parameters. A total of 103 patients aged 12–26 years with physiological occlusion, sagittal incisor disocclusion, and mesial occlusion were examined. The results obtained confirm that it is possible to increase the accuracy and shorten the time of diagnostics by using the proposed software package.

Relevance of the problem.

High-quality and comprehensive diagnostics of anomalies of the dento-maxillary system is one of the most important tasks of an orthodontist, since it provides the basis for drawing up a treatment plan and determining its scope. Over many years, orthodontists have proposed various methods for examining the patient's face and plaster models of the jaws (Ustimenko V.D., 1954; Ilyina-Markosyan L.V., 1976; Snagina N.G., 1972 and others). Radiological diagnostic methods are constantly being developed and improved—orthopantomography of the jaws and cephalometry of the head (cephalometric radiography, CR) in frontal and lateral projections (Khoroshilkina F.Ya., 1976; Malygin Yu.M., 1990; Anikienko A.A., 1990; Jacobson A., 1995; and others).

In particular, anthropometric examination of plaster models of the jaws is widely used in the diagnostics of anomalies of teeth and dental arches. Individual teeth, the length and width of the dental arches as a whole, and their individual segments are measured on the models. The drawback of these studies is that they take up a great deal of the doctor's time, and there is also a high probability of errors arising from inaccurate measurements.

For the diagnostics of anomalies of the shape of dental arches, the Hawley-Gerber-Herbst method is most often used (Hawley, 1939; Herbst, 1939; Gerber, 1962), in which drawings of normally shaped dental arches are constructed on the basis of the patient's tooth dimensions. However, when using this method it is impossible to identify the points by which the resulting normal-shape arch can be superimposed on the patient's dental arch. The literature describes repeated attempts to improve this diagnostic method. In particular, templates have been proposed for determining the shape of dental arches in patients (Kuznetsova G.V., 1997). In this case the time spent by the doctor is substantially reduced, but exact superimposition of the template on the patient's diagnostic model is likewise impossible, since reference points for superimposition are lacking. Some authors have attempted to achieve exact superimposition of the normal and actual dental arches by creating a complete mathematical model of the Hawley-Gerber-Herbst diagram (Kuznetsova I.L., Sablina G.I., Shlafman V.V., 1998). It should be noted that in calculating the dimensions of the dental arch, only the mesiodistal dimensions of the incisors and canines are used. The teeth of the lateral segment of the dental arch are not taken into account, which may lead to considerable errors in calculating the length of the dental arch because of the high variability of their dimensions. It should be noted that in recent years studies have been carried out as a result of which it has become possible to determine the correct position of the dental arches relative to cranial and facial parameters. In the developed diagnostic device, the patient's models were compared with templates of normally shaped dental arches (Lendengol'ts Zh.A., 2001). This made it possible not only to diagnose anomalies of the size and shape of the dental arches, but also to determine whether the entire dental arch is displaced in the transverse and sagittal planes. The drawbacks of this method were its labour intensity and the impossibility of saving the examination results in graphic format for storage and subsequent study. It is obvious that to achieve this goal it is necessary to use computer technologies, which in recent years have been finding ever-increasing application in orthodontics. Thus, there exist computer programs that make it possible to examine plaster models of the jaws in the required scope and to store these data (Mutinelli S., Manfredi M., Cozzani M., 1999; Chen-Hsing Yen, 1991; Keim R.G., 1992; Slavicek R., 1998). In the work of S. Mutinelli et al. (1999) plaster models of the jaws are analysed in three-dimensional space. This provides for the diagnostics of anomalies of the dental arches in three planes, but at the same time the analysis takes a great deal of time, and the equipment for such studies is rather expensive. All of this makes it impossible to use this diagnostic method in everyday practice. In the work of Chen-Hsing Yen (1991) examination of jaw models is carried out with the aid of computer technology in a two-dimensional coordinate system. However, the jaw models were analysed in isolation, without taking facial and cranial parameters into account. Images of normal-shape dental arches were previously superimposed on images of patients' dental arches at points on the cusps of the canines, which does not allow an exact evaluation of the shape and dimensions of the dental arches because of the variability of canine position. Imprecise superimposition of the normal and actual dental arches in all the aforementioned cases is inadmissible, since it leads to an incorrect diagnosis and, consequently, to an incorrectly chosen method of treatment. Taking into account the relevance and practical significance of this problem, the present study is planned.

Aim of the study. Improvement of methods for the diagnostics of anomalies of teeth and dental arches by means of computer technologies.

Objectives of the study.

1. To examine patients with various occlusion anomalies both by traditional methods and with the aid of the computer program.

2. To develop a method for determining the individual normal dimensions of dental arches.

3. To develop software that makes it possible to carry out anthropometric examination of plaster models of the jaws.

4. To evaluate the effectiveness of using the developed software for the diagnostics of dental arch anomalies.

5. To offer practical recommendations for improving traditional methods of diagnostics of anomalies of teeth and dental arches.

Scientific novelty of the study.

For the first time, software has been created and introduced into practice that makes it possible not only to determine the normal shape of dental arches but also to superimpose graphic models of normal and actual dental arches according to both facial and cranial parameters; to diagnose anomalies in the dimensions of the dental arches, in the position of individual teeth, and in the position of the dental arches in the sagittal plane. A graphic diagnostic method has been developed that makes it possible to determine the normal dimensions of dental arches with allowance for all the teeth present in the dental arch.

Practical significance of the work.

Introduction of the developed software into the practice of orthodontists will reduce the time required for anthropometric examination of plaster models of the jaws, increase the accuracy of measurements and calculations, and create databases for storing and processing examination results.

Use of the graphic method for determining the normal dimensions of dental arches will make it possible to avoid errors that arise in comparing actual dimensions with their statistical norm, which in turn will make it possible correctly to determine the necessary scope of orthodontic measures in the treatment of dental arch occlusion anomalies.

Use of the software developed by us in a number of cases replaces the examination of lateral cephalograms of the head, the production of which requires expensive apparatus and specially trained personnel. Thus, the cost of diagnostics is reduced, as is the radiation load on the patient.

Main propositions of the thesis submitted for defence.

1. Computer software for performing anthropometric examination of plaster models of the jaws.

2. Comparative characteristics of examination data of patients with various occlusion anomalies obtained in two ways: by the traditional method and with the use of the computer program.

Implementation of the results of the work.

The results obtained in the course of the study are used in the diagnostics of occlusion anomalies at the orthodontic clinic, as well as in lectures and practical classes with students, at the Faculty of Advanced Training of Doctors and Improvement of Teacher Qualifications of the Department of Orthodontics and Children's Prosthetics of MGMSU.

Personal contribution of the author.

The author examined 103 patients aged 12–26 years with physiological occlusion, physiological occlusion of the lateral teeth combined with sagittal incisor disocclusion, and with mesial occlusion. In the course of collecting material for the study, plaster models of the jaws were produced, and the anthropometric parameters of the jaw models and lateral cephalograms of the head were calculated and analysed. A graphic method for determining the individual norm of dental arch dimensions was developed; for this purpose, drawings of normally shaped dental arches were constructed by the Hawley-Gerber-Herbst method, and graphic models of dental arches were produced with their subsequent superimposition. The computer program «Express Diagnostics of Anomalies of Teeth and Dental Arches» was developed, and a registration certificate was obtained.

Approval of the work.

The materials of the thesis were reported and discussed at the 79th Congress of the European Orthodontic Society in Prague (Czechoslovakia, 2003); at the XXIII Final Inter-University Scientific Conference of Young Scientists (Moscow, 2001); the XXIV Final Inter-University Scientific Conference of Young Scientists (Moscow, 2002); at a departmental meeting of the Department of Orthodontics and Children's Prosthetics in September 2002 and in December 2008, as well as within the framework of the poster session of the XXII Congress of Orthodontists of Russia in April 2009.

Publications.

Nine printed works have been published on the topic of the thesis, including four works in a journal recommended by the VAK of the Ministry of Education and Science of the Russian Federation. A certificate of official registration of the computer program No. 2003610088 of 4 January 2003, «Express Diagnostics of Anomalies of Teeth and Dental Arches», has been obtained.

1. Dyachkova Ya.Yu. Diagnostics of anomalies of teeth and dental arches using computer technologies. // Ortodent-Info 2:2001, pp. 29-32. (Renamed the journal Ortodontiya in 2006)

2. Dyachkova Ya.Yu. Comparison of various methods for diagnosing dental arch anomalies. // Ortodent-Info, 2:2002, pp. 28-30. (Renamed the journal Ortodontiya in 2006)

3. Dyachkova Ya.Yu. Determination of displacement of dental arches in the sagittal direction in mesial occlusion. // Ortodontiya, 1:2009, p. 63.

4. Dyachkova Ya.Yu. Computer analysis of morphometric parameters of plaster models of the jaws. // Ortodontiya, 1:2009, p. 105.