口腔疾病医学

1、ORTHODONTICSFang BojunNormal occlusion versusmalocclusion Fundamental to orthodontic diagnosis is understanding the concept of ideal occlusion”. Traditionally, any deviation from ideal occlusion” lias represented what Guilford termed mabocclusion. Of course ? ideal occlusion rarely exists in nature

2、and so perhaps it is better to call this concept the imaginary ideal”. Unfortunately there is no clearcut or acceptable definition of normal occlusion”; thus much of our diagnosis in orthodontics is based on this highly arbitraiy concept of the ideal. What we today call ideal occlusion was described

3、 as early as the eighteenth centuiy buy Hunter. Carabelli in the mid nineteenth century firstly described the abnonnal relationships of the upper and lower dental arches in a systematic wayedge to edge bite and overbite.Incidence of malocclusion The incidence of malocclusion varies widely in differe

4、nt countries of the world. In primitive and isolated societies there is less variation in occlusal patterns than is observed in more heterogeneous populations. The variation between primitive and modern groups has been attributed to the effect of natural selection, inbreeding versus out breeding, an

5、d environmental factors. The reported rate of malocclusion is higher in developed than in primitive countries. For example, the rate of malocclusion in the USA is more than 75%，while that of the African is less than 30% In China the number is about 33% to 50%. A major difficulty in assessing need fo

6、r orthodontic treatment is that malocclusion can be either a condition that，although detectable，causes no functional or esthetic difficulty and does not warrant treatment or a problem that does need treatment. Malocclusion creates problems in three major circumstances: (1) it causes or predisposes d

7、isease, (2) it leads to disturbances in jaw function (TMJ syndrome and related conditions) or affects other oral functions (e.g., speech), and (3) its effect on facial esthetics causes psychosocial problems.Etiology of orthodontic problem Fundamental to rational classification is the concept that th

8、e etilogy should be included in any classification scheme. In orthodontics we can say that there are environmental and hereditaiy factors in the etiology of malocclusion or，stated another way, that genotype plus environmental factors yield the phenotype. Regrettably, we often are not able to ascerta

9、in which malocclusions are detennined largely on a genetic basis, which result largely from environmental factors, and which are a combination of hereditaiy and environmental factors. At the two extremes it is sometimes easy to place the patient in one of these two categories. A chronic thumb sucker

10、 with an anterior open bite, for example, can most likely be labelled as having a problem stemming from local causes. By the same token a patient who has an otherwise nornial dentition with the exception of one or more congenitally missing teeth can probably be classified as having a problem of gene

11、tic origin. However, the majority of patients whom the orthodontist treats are not easily placed in one or the other of these categories A relatively small number of orthodontic patients are affected by known genetic syndromes that affect the oral strictures. But it is widely acknowledged that most

12、malocclusions have a genetic component, and it has been extremely difficult to quantify how much of a given problem is likely to be genetic and how much has been influenced by prenatal or postnatal environmental factors. Genealogies and pedigrees, although helpful in recording the patients family hi

13、story, are not very revealing in regard to exact patterns of dentofacial inheritance. This is undoubtedly due to the polygenic inlieritance of craniofacial and dental characteristics or traits, and thus it is component of most malocclusions. Certain malocclusions do, however, show a familial tendenc

14、y, such as some Class III malocclusions and some open bite problems. Continued mandibular growth and the development of true prognathism are much more likely when there is a familial incidence of such a condition than when there is not Studies if twins and of triplets have shown a high concordance o

15、f dentofacial traits in monozygotic individuals, which suggests a large heritable component in the etiology of malocclusion. Alteration of growth pattern is the mechanism by which the environment can produce occlusal dishannony. Since genetic influences also affect growth, it can be extremely diffic

16、ult to judge whether heredity or environment is the cause of growth problems or, if both are involved, which part of the problem is genetic and which environmental.Diagnosis The data base for orthodontic diagnosis: (1) History and generalevalutio n. Datecollection for the orthodontist begins with th

17、e veiy first encounter with the patient. You may know the chief orthodontic concern： then follows with the medicodental histoiy and the social- behavioral histoiy. (2) Clinical examination data. It should include three major areas: dentofacial proportions and facial esthetics, health of the intraora

18、l soft and hard tissues, and function of the oral strictures including an evaluation of swallowing、speech mastication and TMJ function. (3) Diagnostic records needed. Diagnostic records for orthodontic puiposes may be divided into four major categories It consist of dental casts and occlusal records

19、 photographic records and radiographic records.Classification Edward Angle contributed the concept that if the mesiobuccal cusp of the maxillaiy first molar rests in the buccal groove of the mandibular first molar and if the rest of the teeth in the arch are aligned then ideal occlusion will result

20、Angle described three basic types of malocclusion, all of which represented deviations in an anteroposterior dimensio n. Lischer later tenned Anglers Class I occlusion neutron-occlusion his Class II occlusion disto-occlusioif； and his Class III relationship mesio-occlusion The Angle classification w

21、as readily accepted by the dental profession, since it brought order out of what previously had been confusion regarding dental relationships.Planning treatment After the data base is complete, there are three steps that must be accomplished before designing specific force systems and mechanotherapy

22、: (1 )generation of alist of discrete and carefully defined problems; (2)proposal of tentative treatment plans for each of the problems; (3) synthesis of the tentative treatment plans into a unified detailed treatment plan. To extract or not to extract teeth is a basic treatment planning problem The

23、re are many kinds of extraction modes, while extract the four first premolars is the most frequent extraction modes.Therapy The possible general treatment approaches consist of extractions, dental expansion, orthopedics, surgery or combination. The appliances of orthodontics consist of removable app

24、liances and fixation appliances.Removable Appliance Removable Appliance is the appliance that can be removed by the patient himself, it contains of mechanical removable appliance and functional appliance What is the advantage and disadvantage of the removable appliances?Advantages of removableapplia

25、nce The majority of malocclusions, which require simple tipping of the teeth, can satisfactorily be treated by removable appliance; Many tooth movement, especially tipping and overbite reduction, can be undertaken as readily with a removable as with a fixed appliance Removable appliance can incoipor

26、ate bite platfbnus to eliminate occlusal interferences and displacement This is not possible with fixed appliances. Tooth movements undertaken are simple and only a few teeth should be moved at any time. This means that control is less complex than with a fixed appliance but careful attention to det

27、ail is still essential. Simple malocclusions may be treated by the general dental practitioner who has received adequate training in diagnosis and treatment planning With increasing demands for orthodontic treatment, this allows the specialist to concentrate on more difficult cases. Removable applia

28、nces are manufactured in the laboratoiy and adjustments take less chairside time. This means the operator can increase his patient load. They are relatively inexpensive to constmct and dental practitioner using only removable appliances does not need to stock a large range of expensive bands and att

29、achments.Limitations of removableappliances With removable appliance, the force is applied to a singe point on the crown and so the tooth tips about a fulcmm within the root; While the rotation of one or two upper incisors can be dealt with, multiple rotations cannot readily be treated; Multiple too

30、th movements have to be carried out a few at a time and this will prolong treatment in more complex cases; When extractions are necessary but provide excess space, controlled forward movement of buckle segments to close residual spaces is difficult or impossible; Lower removable appliance are not well tolerated due to encroachment on tongue space and retention problems; The uncooperative patient may sometimes leave out his appliance; Should the appliance be damaged so that the patient is in pain，it can be removed for a short period of time u