CONTROVERSIES IN ORTHODONTICS
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
INTRODUCTION Orthodontics, Dentistry’s first speciality is rich in it’s history and also in it’s controversy. Controversies unlike disputes never end. They cannot be settled totally by scientific evidence substantiating any one side of the argument.
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CONTROVERSIES IN ORTHODONTICS
Extraction-nonextraction controversy. Functional appliances Early treatment Bracket design Esthetic need for orthodontic treatment Classification of malocclusion Orthognathic surgery Retention and relapse. www.indiandentalacademy.com
EXTRACTION-NONEXTRACTION CONTROVERSY The extraction – non extraction controversy is the oldest and most enduring controversy in orthodontics. The controversy is still alive today almost 90 years since it first started. The controversy was between the Angle’s school of thought and it’s followers like Martin Dewey and Calvin Case who believed in extraction therapy. In a 1902 article, Angle sets forth his line of reasoning toward the development of his treatment philosophy. In this article he recounts his conversations with his friend, the artist Edmund Wuerpel, whose help led to his concepts of facial beauty and harmony. He believed that all humans were created to have a full complement of natural teeth which would go hand in hand with an ideal occlusion and a harmonious face. He idealized an occlusion thus which contained a full compliment of well aligned teeth which occluded along his line of occlusion.
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It is first of all evident from the statements of Angle that his philosophic basis was creationist dogma rather than ideals backed by strong scientific basis. The battle was really begun in 1911 in what has become to be known as "The Extraction Debate of 1911." At the 1911 meeting of the National Dental Association, Calvin Case presented an article entitled "The Question of Extraction in Orthodontia," . In the article Case strongly criticizes the creationist belief of the Angle school and their disregard of heredity as a cause or malocclusion and their belief that all causes of malocclusion were local and replacing teeth in their intended positions would lead to a harmonious face. To substantiate the case further he presented a patient whose dental protrusion would have worsened had a non extraction treatment had been done. Thus emphasizing that all cases cannot be treated non extraction to achieve a harmonious face.
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DID ANGLE REALLY PRACTICE WHAT HE BELIEVED IN‌.? Earlier, in 1887, Angle wrote on his new system to regulate and retain the teeth. In that same year, the first edition of his book on the same subject was published. Other editions supposedly followed up to 1897 when the fifth edition, expanded in scope, came out. This was followed by the enigmatic sixth edition, which was supposedly withdrawn by Angle from publication. This edition, which has never been referred to previously in the literature as, and seems never to have been referred to in lectures by Angle and/or his supporters, is enigmatic because of the large number of extraction cases presented in it.. However, what is even more fascinating is that the subsequent seventh edition which was published was completely stripped of all the extraction case material present in the sixth edition.
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The battle ironically was finally won by Charles Tweed a student of Angle who in 1952 presented case reports of patients who were treated initially non extraction using Angles treatment philosophies and were later retreated with a all first premolar extractions. The Tweed philosophy was born and extractions were finally accepted into orthodontics due to the great work of Tweed which provided scientific evidence towards the need of extraction in treatment. Around the same time Begg in Australia was developing another appliance system which was also based on therapeutic exraction. Begg developed his appliance on the theory of attritional occlusion. It should be noted here that though both Tweed and Begg believed in therapeutic extraction Tweed had a more scientific basis to back his technique whereas Begg only had a theory – the attritional occlusion theory to justify his extractions. With the development of the Tweed edgewise philosophy and the Begg appliance came a period in orthodontics where premolars were indiscriminately extracted for correction of malocclusion. This lead to unfavorable facial appearances. Now with orthodontists paying more importance to facial harmony and esthetics the indiscriminate extraction of premolars have been reduced and with www.indiandentalacademy.com
Advance in mechanotherapy the use of non extraction therapy is now on the rise. Wick Alexander now claims only 10% of his cases are treated with extraction and the rest being treated non extraction. Norman Cetlin who used to treat 95% cases with extraction treats only 10% with extraction. The current dogma against non extraction treatment is: • upper molars cannot be distalised bodily. •Arches cannot be expanded in any direction. •Lower canine width cannot be increased. •Long term retention is necessary for stability. However currently non extraction treatment is confined to the following cases: •8mm or less of crowding •Severely mesially and lingually tipped posterior teeth. •Cooperative and growing patients.
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Though the extraction – non extraction controversy may not be plagued by as much as dogmas as it was almost 100 years ago both treatment options are still open. With improved biomechanical appliances it is more possible to move molars bodily. Studies by De Paoli have shown that increased mandibular canine width achieved using a lip bumper along with a Cetlin appliance are found to be stable in the long run provide they are used during a period when the inter canine width is developing. The amount of arch expansion though seems to be limited. the option to treat either extraction or non extraction should be made objectively for each case based on strong evidence rather on some ones opinion ‘that it woks’
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Functional appliances The use and mode of action of functional appliance is shrouded in controversy. The reason behind this is because of the different philosophies and basis on which each designer constructed his appliance. There may not be a specific modus operandi behind all functional appliances. But do functional appliances work in the first place…? – as they are intended to. Or is natural growth responsible for the changes. And even if they do are the changes produced clinically significant? An interesting incident is quoted in Birte Melsen’s texbook on controversies in orthodontics. A patient with severe Class II and horizontal growth pattern was given a FR II. The patient had an impressive class II correction in six months. the only problem was that the patient carried the appliance in her purse during the course of treatment. The controversies discussed here will be in relation to : • modus operandi of functional appliance •Growth changes with functional appliances. www.indiandentalacademy.com
Modus operandi of functional appliances
Functional appliances evolved from different concepts of the interrelationship between the orofacial musculature , dentition and plasticity of growth. Each led to a working hypothesis expressed as an appliance design. It was Kingsley who first used a vulcanite maxillary appliance that repositioned the mandible anteriorly and guided dental eruption in an attempt to “jump the bite” as he termed it. The classic monobloc was used by Pierre Robin at the beginning of the twentieth century to treat the glossoptotic syndrome. But it was later found that these patients will usually have a period of spontaneous “catch up” growth with or without appliance therapy. www.indiandentalacademy.com
Andresen of Norway modified the Kingsley vulcanite eruption control appliance to “activate” the musculature to create a functionally favorable environment for functionally induced anatomical change. The working hypothesis behind the Andresen activator was that the protractor muscles of the mandible could be stimulated or “activated” to assist in achieving a dental saggital correction. The isotonic contractile forces of the stretched muscles were transmitted to the teeth in contact with the appliance. The Andresen appliance was intended as a functional appliance for dento alveolar correction only. A dentofacial orthopedic correction which may have been a side effect was not part of his original objective. The effects of the activator were substantiated by Pancherz when he studied 30 patients treated with the activator activator treatment seemed to inhibit maxillary growth, move the maxillary incisors and molars distally, and move the mandibular incisors and molars mesially. Mandibular growth appeared not to be affected by activator treatment. Thus by way of contraction of the muscles to keep the loosely fitting appliance in place intermittent forces are transmitted to the teeth which move in desired direction to correct the dental mal relationships www.indiandentalacademy.com
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The andresen activator was later modified by andresen and Haupl in an attempt to optimize the the orthopedic change that could be affected by these removable appliances. the activator was constructed with a working bite well beyond the resting length of the muscles to ensure that forces be transferred to the jaws as well.
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The compensatory contracture and myotactic reflex of these muscles during function supplied mechanical forces needed to redirecct the growth or remodelling processes of the bones of the jaw. www.indiandentalacademy.com
The andresen activator was further modified into a vertically overextended splint by Harvold, Woodside and Demisch . A construction bite was taken in the direction of desired correction. The bite was opened 5 to 6 mm beyond the freeway space. The extreme stretch of the muscles helped the appliances to be in place even during sleep. The appliances produced a side effect of dental intrusion. This ultimately produced a autorotation of the mandible and a relative class II correction. The design of this system assumed that the viscoelastic properties of the tissues under this stress produced a compensatory anotomic www.indiandentalacademy.com correction.
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Petrovics growth studies however have come to show that increased condylar cartilage growth is associated with a forward posturing of the mandible. The modus operandi of functional appliances was explained as follows.
FUNCTIONAL APPLIANCES INCREASED CONTRACTILE ACTIVITY OF LPM INCREASE IN GROWTH STIMULATING FACTORS ENHANCEMENT OF LOCAL MEDIATORS REDUCTION IN LOCAL REGULATORS ADDITIONAL GROWTH OF THE CONDYLAR CARTILAGE ADDITIONAL SUBPERIOSTEAL OSSIFICATION SUPPLEMENTARY LENGTHENING OF THE MANDIBLE www.indiandentalacademy.com
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Growth relativity hypothesis ď Ž
The hypothesis was put forth by John Voudouris et al to explain the modus operandi of functional appliances and the cause for relapse. DISPLACEMENT+VISCOELASTICITY+REFFERED FORCE. www.indiandentalacademy.com
LPM myectomy studies on animals by Whetten and Johnston showed that there is little evidence that LPM traction had any pronounced effect on condylar growth. Dubner and Voudoris conducted permanently implanted longitudinal muscle monitoring techniques and observed that condylar growth was associated with decreased postural and functional activity of LPM. Pancherz, Ingervall and Auf de Mauer observed similar findings in humans. www.indiandentalacademy.com
Can mandibular growth be modified beyond it’s true genetic potential?
The answer seems to be elusive. As is shown by the use of the Milwakee braces. However the Milwaukee braces phenomenon also shows us the remarkable rebound capacity of the hard tissue system and the dominance of inherent growth potential
While Angle strongly believed that the mandible could be made to grow Case disagreed. As Case states.. “Malrelations of this character point directly to heredity. The claim and recently repeated inference that the mandible can be made to grow by artificial stimuli beyond its inherent size is not in accord with any law of organic development." Baring future chemical or genetic manipulation, this still appears to be a valid principle, although there are others who strongly believe otherwise.
Case writes that "While the rapidity of their early growth may be hastened, while inhibited developments may be stimulated to normal growth, and while the forms of the bones may be varied slightly by bending, I doubt if it has ever been authentically proved that natural or artificial forces have made them grow interstitially longer than their inherent normal size. www.indiandentalacademy.com
Gianelly through various studies has sown that the mean growth modification of 2mm can be achieved by functional appliance treatment. Thus when compared to a 6mm correction of class II relation to a class I the effects of functional appliances may
not be clinically significant. Harvold found significantly higher increments in mandibular length during treatment than after treatment. But however when he compared the results with untreated controls matched for age and growth status he found that the changes can
only be ascribed to normal age related changes. Studies by McNamara on the Frankl appliance and Herbst appliance effects on the mandible and the dentition have shown both appliances had influenced the growth of the craniofacial complex in treated persons. Significant skeletal changes were noted in both treatment groups, with both groups showing an increase in mandibular length
and in lower facial height, as compared with controls.
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McNamara and Bryan studied the Long-term mandibular adaptations to protrusive function on 11 experimental animals.. At the end of the 144-week experimental period, the mandibles of the treated animals were 5 to 6 mm longer than those of the control animals. They concluded that the results of this study do not support the hypothesis that the mandible has a genetically predetermined length
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Different studies have shown varying results. This is due to the varying landmarks used to analyze mandibular growth.
If one measures prognathism as related to a perpendicular to the cranial base through sella most authors agree that pogonion moves anteriorly more than normal with functional appliances. If the condylar increment is measured as Cd-Pg diisatance the dispersion of findings becomes more evident. This brings into question the role of functional appliances in glenoid fossa remodelling.
The experiments on Rhesus maccaca monkeys by Woodside, Metaxas and Altuna clearly suggest that a mandibular repositioning can occur due to glenoid fossa changes and condylar growth with the latter being more age dependent. They observed bone apposition on the anterior surface of the post glenoid spine.
The search for good evidence for the use of functional appliances may be difficult to find due to the methodology of current clinical research. www.indiandentalacademy.com
Limitations of current clinical and animal research:
A double blind study is not possible in testing functional appliances and thus bias cannot be eliminated. The orthodontist is well aware of the type of appliance he is using and it’s probable treatment effects it can produce based on other studies and thus already has something in mind to expect. And functional appliance unlike drugs are tested for their treatment effects and not for their side effects. In cases of drugs treatment effects are well proven in animal studies and can be extrapolated to humans. Thus the patient as well as the orthodontist undertake the study with a desired result in mind.
Growth versus treatment changes should always be compared with untreated controls matched for age, sex and growth status. Even though so much criteria may be taken the experimental samples and control samples may not be totally matched because the growth potential of two people may not be the same unless they are monozygotic twins. And if monozygotic twins were even used it would be unethical to treat one sibling while leaving the other untreated.
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Some growth studies use class I individuals as controls while some study's do not mention the nature of controls used. Studies by McNamara, Bookstein, Baumrind and Righellis have used untreated Class II as controls. Though compliance may not be improved in animal research and and histological changes can be studied, the animals used donot have any growth defeciencies and treatment responses are those for normally growing animals. Most of the studies done by Petrovic and coworkers which substantiated increased cell proliferation and increases in mandibular length with bite jumping appliances were done on rats. Whether findings on other mammalian mandibles can be extrapolated to humans is another question which needs to be answered.
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EARLY TREATMENT
Can be defined as…” early orthodontic and orthopedic intervention provided during the mixed dentition and occasionally during the late deciduous dentition” Advantages of early treatment:
The need for complicated surgical and orthodontic procedures elimmintaed by early orthpedic intervention Reduced costs A abnormality is prevented from occurring – better than wait to manifest itself in it’s fullest form www.indiandentalacademy.com
EARLY TREATMENT
The argument..
Orthodontists prefer to wait until the permanent teeth have erupted so a more straight forward treatment plan can be done within a predictable duration of time. The question of remaining growth manifesting as relapse does not occur. Some malocclusions like skeletal class III due to prognathic mandible are best treated after all skeletal growth is complete. Patient co operation may be the biggest challenge in early treatment – Graber. Patient burn out due to a long treatment duration may not help the orthodontists cause during a second phase of fixed appliance treatment. An extremely long duration of treatment may be a night mare for practice management. Unreasonable treatment duration may lead to disillusionment of the general population to orthodontic treatment. www.indiandentalacademy.com
EARLY TREATMENT
General guidelines on timing of early treatment:
Treatment of class I tooth-size/arch-size discrepancy to be initiated after the eruption of the four lower incisors and the upper central incisors. Treatment of class III is earlier than treatment of any other malocclusion. It should be initiated with the loss of upper deciduous incisors and while the permanent upper incisors are erupting. Class II malocclusions are best treated in the late mixed dentition when the patient is in the circumpubertal age. Studies petrovic, stutzmann and Mcnamara have supported this concept. www.indiandentalacademy.com
Functional appliances and two phase treatment ď Ž
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Gregory king et al (2003) conducted a study based on PAR of patients undergoing two phase treatment and single phase treatment. Though at the end of treatment there was no significant difference in the PAR of both groups, the two phase treatment group showed significantly lesser PAR before beginning phase 2, which may indicate that early treatment does influence PAR and may provide social and psychological benefits to the patient. Further a multicenter, randomized controlled trial of 174 children to study the dental, skeletal and psychosocial effects of Twin Block have shown that all changes produced were purely dento alveolar and skeletal changes were actually so minimal as to be considered clinically insignificant. However results did show that early Twin Block use did result in an increase in self concept and a reduction of negative social experiences.
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BRACKET DESIGN Brackets are attachments on teeth placed to deliver the appropriate forces and moments onto the teeth. Their designs reflect the treatment concepts, philosophies and end of treatment ideal the bracket designer had in mind when he designed the appliance. With different philosophies developing over the years different bracket designs too have entered the market for the orthodontist to use. brackets are of basically two types – ribbon arch brackets and edgewise brackets. The ribbon arch brackets were first designed by Angle for his Ribbon arch appliance. The bracket was modified by inverting it by 180 degree and used by Raymond Begg for his light arch wire appliance. Since then it has gone little modification except by Brainerd Swain for his modern Begg technique where a edgewise slot was combined with a vertical slot to achieve better third order expression in stage IV. www.indiandentalacademy.com
Edgewise brackets though have undergone major changes since it was first concieved by Angel. Angle used what is called today as a single wing brackets. Later Twin brackets were designed first by Swain. The bracket designed by Angle was a non programmed bracket it was neither preangulated nor pretorqued. The first preangulated bracket was designed by Ivan Lee and Jarabak first designed Pretorqued and preangulated brackets. The credit goes to Andrwes for designing the first fully programmed brackets with first, second and third order values built into the brackets to achieve his six keys of occlusion. Since then numerous prescriptions with different tip and torque values have been designed for various tretment philosophies.
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controversies regarding bracket design include: • the use of 0.018 slot or the 0.022 slot
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BRACKET DESIGN
0.018 slot or 0.022 slot ?
E.H. Angle was the first to design the Edgewise type of bracket for his edgewise appliance. He used the 0.022x0.028 slot for his appliance. As the edgewise appliance originated before the discovery of stainless steel, Angle was forced to use gold alloy wires for making arch wires. Gold alloy wires had a low modulus of elasticity and therefore to increase the stiffness of the wire in bending and torsion and to increase the rigidity Angle had no other choice but to increase the dimensions of the wire and therefore had to use the 0.022 slot. www.indiandentalacademy.com
BRACKET DESIGN
0.018 slot or 0.022 slot ? It was Steiner who first proposed the 0.018 slot (0.018 x 0.028) and used it for the ‘Steiner’ brackets which were single width brackets with rotation wings. Swain later adopted the 0.018 slot for his Siamese brackets to improve wire characteristics due to the decreased inter bracket span. With the advent of stainless steel which is 50% stiffer than spring tempered gold it became essential to decrease wire dimensions to reduce force levels. The 0.022 slot today prevails over the 0.018 slot because of the development of newer orthodontic alloys such as TMA and NiTi. It was the discovery of TMA with it’s stiffness characteristics similar to gold that brought back the 0.022 slot back into the market. www.indiandentalacademy.com
BRACKET DESIGN
0.018 slot or 0.022 slot ?
ADVANTAGES OF 0.018 SLOT Decreased wire inventory Decreased treatment time Increased wire flexibity due to smaller dimension of wires.
DISADVANTAGES OF 0.018 SLOT
Desired third order M/F ratios may not be produced by newer orthodontic allloys. www.indiandentalacademy.com
BRACKET DESIGN
0.018 slot or 0.022 slot ?
DISADVANTAGES OF 0.022 SLOT Increased wire inventory Inability to attain third order control untill last stages of treatment Increased treatment time.
ADVANTAGES OF 0.022 SLOT Recommended for Orthognathic cases Can use newer orthodontic alloys with minimum patient discomfort
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BRACKET DESIGN
0.018 slot or 0.022 slot ?
The world however seems to be divided over the use of edgewise brackets. The 0.022 slot is widely used in the United States whereas the 0.018 (0.5mm) slot is popular in Europe.
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BRACKET DESIGN
Are the 0.018 and 0.022 slots truly 0.018 and 0.022 …….? Kusy and Whitley measured 24 brackets from eight manufacturers microscopically to 0.0001 inch . Three brackets were under sized whereas the rest were oversized. The largest 0.018 slot measured 0.0209 whereas the largest 0.022 slot measured 0.0237. www.indiandentalacademy.com
BRACKET DESIGN
Are the 0.018 and 0.022 slots truly 0.018 and 0.022 …….?
Factors contributing to this variability…. Lack of verification standards Varying manufacturer tolerances United states versus European tooling For example Europeans use metric tooling i.e mm, cm , m. Their target value for machining a bracket which would be 0.018 slot in the United states would be 0.5mm which is actually 0.0197 inches. www.indiandentalacademy.com
BRACKET DESIGN
Are the 0.018 and 0.022 slots truly 0.018 and 0.022 …….?
Therefore even the most accurately machined 0.018 slot in europe would be oversized even without manufacturer tolerance.
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BRACKET DESIGN
The 0.020 slot.
Rubin, peck and Kusy have proposed the use of an 0.020 slot (0.5 mm) This would reduce the burden on inventories of users of both 0.018 and 0.022 slots and reduce manufacturer costs.
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BRACKET DESIGN THE RELEVANCE OF SLOT AND ARCH WIRE DIMENSIONS IN OUR EVERY DAY PRACTICE: Creekmore made a study on effective biomechanical torque produced by brackets and wires of various manufacturers based on the manufacturer tolerances supplied by them. His findings were as follows: • An .018 ´ .025 wire in an .022 slot has 15° of play. Thus if one uses Andrew’s brackets with 7 torque on centrals, 3 on the lateral and -7 on canine and premolars there would be absolutely no torque expression because the play or deflection angle itself is greater than the torque value of the brackets. if one uses a Roth prescription with 17 on incisors and 10 on laterals the amount of torque expressed would be 2 degree for the central and and 5 degree for the lateral. www.indiandentalacademy.com
•With an .019 ´ .025 wire in an .022 slot, there is 10½° of play. So again, all of the torques mentioned are ineffective with an .019 ´ . 025 wire in an .022 slot. •With an .0215 ´ .028 there would be 2° of play and thus at the end of treatment even with a full slot wire we would be still 2 degree away from the desired value. •.017 ´ .025 wire has 4.5° of play in an .018 slot, whereas an .018 square wire has only 3° of play. So, you would have better torque control with an .018 square than an .017 ´ .025.
Though both the 0.018 and 0.022 slot may still be used based on personal preferences, a uniform slot size and tooling units may be necessary for standardization and to know that we really use the slot size we wanted irrespective of where the manufacturer is based.
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ESTHETIC NEED FOR ORTHODONTIC TREATMENT ď Ž
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In countries where orthodontic treatment is widely available many clinicians accept esthetic impairment as sufficient cause for orthodontic treatment. Theratonale underlying such recommendations appears to be based oj the belief that impaired appearance usually results in negative self esteem and poor social adjustment. Others insist that orthodontic treatment should be provided only when physical health or functioning is at risk. They believe that a psychologically healthy individual will adjust to his or her appearance and that low only low self esteem triggers a negative self evaluation. www.indiandentalacademy.com
ESTHETIC NEED FOR ORTHODONTIC TREATMENT
The controversy is that whether we ru n the risk of denying treatment and social and psychological well being or whether we over treat our patients and force upon society standards of appearance that are both unrealistic and unattainable. Studies by Dion have shown that the attractiveness of physical appearance is an important determinant of how much even very young children are liked by their peers. Physically attractive individuals are percieved as posssesing a great number of socially desirable traits such as intelligence, friendliness, sensitivity and sincerity.
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Patzer through his research findings on physical attractiveness has proposed that facial attractiveness is possibly the most important determinant of physical beauty. Furthermore more studies have shown that the mouth is the most important component of facial attractiveness. In a study conducted by Shaw photographs of children were altered to show normal occlusion or malocclusion. Both children and adults described faces with normal occlusion as more attractive, more intelligent , less aggressive, and more desirable as friends.
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HELLER ET AL JUDGED APPRXIMATELY 33%OF YOUNG Canadian adults born wth facial clefts to have marginally inadequate psychological adjustment. In their study , pshycological functioning did not appear to be related to objective assessmnet of the severity of impairmrent but was strongly related with dissatisfaction with appearance.
Based on confidential interviews with 531 school children aged 9 to 13 years, Shaw et al found that teeth represesnted the fourth most common target of teasing after height, weight and hair.
Based on occupational rankings by Hollinshead, Rutzen found that treated subjects had achieved higher level of occupational status than had non treated individuals, even though the group did not differ in social a class or educational level.
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the theoretical and emperical work on responses to facial attractiveness leads us to at least one obvious generalization: percieved facial attractiveness is a social asset whereas percieved unattractiveness is a social liability. the decisions about the need for treatment cannot be made on objective assessment of functional or esthetic impairment alone. The concept of esthetic need for treatment is best framed by considering both the potential clinical improvement of facial attractiveness and the individuals psychological and social adjustment to perceptions of facial appearance. Thus the individuals evaluations of the impact on their lives of dentofacial disfigurement must play a key role in determining the actual need for treatment. a patient who acknowledges his severe malocclusion may not desire treatment despite the functional and esthetic problems and may be a difficult patient to treat, while a patient with far less severe impairment may be influenced by other social factors that lead him to extremely negative self evaluation and a strong desire for treatment. www.indiandentalacademy.com
CLASSIFICATION OF MALOCCLUSION Malocclusion presents itself in numerous ways. Classification involves the grouping together of various malocclusions into simpler or smaller groups. In order to have a system of classification, standards should be set that represent normalcy. The deviation from the accepted norms should also be grouped into various smaller divisions. The aim of every classification would be to help in diagnosis and treatment planning and to categorize malocclusions into groups which would ease communication between orthodontists. Being dentistry’s first specialty orthodontics today does not have a classification system which is universally accepted and followed – a classification system which would clearly denote the malocclusion present, aid in a treatment planning and indicate the severity of the malocclusion present. The classification system followed today is based on Angles classification which was perceived by him almost 100 years ago based on his treatment philosophies, ideals and paradigms of his time.
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CLASSIFICATION OF MALOCCLUSION What we today call normal occlusion was described as early as the eighteenth century by John Hunter. Carabelli, in the midnineteenth century, was probably the first to describe in any systematic way abnormal relationships of the upper and lower dental arches. The terms edge-to-edge bite and overbite are actually derived from Carabelli's system of classification Many orthodontists have developed classification methods, and among them are Kingsley, Angle, Case, Dewey, Anderson, Hellman, Bennett, Simon, Ackerman and Proffit, and Elsasser. Edward angle introduced a system of classifying malocclusion in the year 1899. angles classification is still in use after almost 100 years of it’s introduction due to it’s simplicity Edward H. Angle contributed the concept that if the mesiobuccal cusp of the maxillary first molar rests ill the buccal groove of the mandibular first molar, and if the rest of the teeth in the arch are aligned, ideal occlusion will result. (this is not the Class I as Angle actually saw it) Angle described three basic types of what he termed malocclusion, all of which represented deviations in an anteroposterior dimension.
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An early criticism of the Angle system was that it merely described the relationship of the teeth and did not include a diagnosis. Simon, Lundstrom, Hellman, and most recently Horowitz and Hixon recognized the need to differentiate dentoalveolar and skeletal discrepancies and to evaluate their relative contributions toward the creation of a malocclusion. These authors suggested that classification should include this type of diagnosis and point logically to a treatment plan. Another drawback in Angles classification is that it does not deal with any malocclusion in it’s entirety. This gives rise to the issue of Analogous and homologous malocclusions Malocclusions having the same Angle classification may, indeed, be only analogous malocclusions (having only the same occlusal relationships) and not necessarily homologous (having all characteristics in common Homologous malocclusions require similar treatment plans, whereas analogous malocclusions may require different treatment approaches thereby clearly highlighting a great draawback of Angles classification. Since Angle and his followers did not recognize any need for the extraction of teeth, the Angle system does not take into account the possibility of arch-length problems. The reintroduction of extraction into orthodontic therapy has made it necessary for orthodontists to add archlength analysis as an additional step in classification. www.indiandentalacademy.com
Angle acknowledged that the first molar might erupt in an altered position when influenced by the malpositions of other teeth or the loss or non development of deciduous and permanent teeth anterior to the first molar. Therefore Angle recommended visualizing the upper first molar into its proper position relative to the jugal buttress before classifying the malocclusion. There are two problems with this concept. First, visualizing the "correct" position of the upper first molar to the jugal buttress and lining up the remaining dental units relative to it is a very subjective pursuit. It is quite probable that no two orthodontists would exactly visualize the same "correct" position. And second, modern orthodontists are more concerned with the proper position of the incisors relative to the profile for esthetic and stability concerns and are willing to adjust first molar position and even sacrifice teeth to better align the incisors (concepts Angle would never have accepted). Modern orthodontists advance molars in extraction treatments or distalize molars in nonextraction treatments with little concern for the immutable relationship of the upper first molar to the bony landmarks, such as the key ridge, as promulgated by Angle. A final, but not inconsequential, difficulty with Angle's classification procedure is that the classification does not indicate the complexity of the problem.
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The drawbacks of Angles classiication are made worse by the way most Orthodontists have interpreted his classification system. Every dental student learns the Angle "mesiobuccal cusp of the upper first molar fits into the buccal groove of the lower first molar“
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Angle described in minute detail each contacting cusp incline to prove his point that in ideal occlusion every tooth (except the lower centrals and upper third molars) should have two antagonists. In other words, even if a patient has the mesiobuccal cusp of the upper first molar fitting perfectly into the lower molar buccal groove the patient does not possess proper occlusion according to Angle,, unless the upper first molar also has a mesial crown tilt that allows the distal incline of the distal cusp of the upper first molar to occlude with the mesial incline of the mesial cusp of the lower second molar.
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Proper cuspal incline contacts of all teeth should be noted. Angle emphasized the importance of each premolar and canine contacting two occluding teeth. An occlusion where the first molars classically fit the criteria of the upper mesiobuccal cusp to lower molar groove, but the premolars and canine contact only one opponent tooth each, would be considered Class I by Angle (because Class I is a premolar-width range of abnormality). However, Angle would not have considered the occlusion as having met his standards for "ideal" occlusion of a well-treated case. Therefore all "ideal" occlusions are Class I, but not all Class I occlusions are "ideal."
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The original classification by Angle, had Class II as a full premolarwidth distoclusion and Class III as a full premolar-width mesioclusion. Assuming an average premolar width of 7.5 mm, then Class I ranged from 7 mm mesioclusion to 7 mm distoclusion, for a total range of Class I of 14 mm. This range was far too broad, and so in 1907, Angle revised his definition, making Class II more than half of a cusp distoclusion and Class III more than half of a cusp mesioclusion. Angle's modification reduced the range from 14 mm to a 7 mm range. However, 7 mm is still too broad a range to act as a treatment goal if an orthodontist is to treat with precision.
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Dewey later modified angle’s classification. He divided angles class I into five types and angles class III into three types
Class I modifications:
Tpe 1: class I malocclusion with crowded anterior teeth
Type: class I with protrusive maxillary incisors.
Type 3: class I malocclusion with anterior cross bite
Type 4: class I molar relation with posterior cross bite.
Type 5: permanent molar has mesially drifted mesially due to premature extraction of deciduous molars.
Class iii modifications:
The upper and lower dental arches when viwed separately are well aligned but when occluded have a dedge to edge incisal relationship
The mandibular incisors are crowded and are in lingual relationto the maxillary incisors
The maxillary incisors are crowded and are in cross bite to the mandibular incisors. www.indiandentalacademy.com
Simon’s classification ď Ž
In 1912, in a report to the British Society for the Study of Orthodontics, Norman Bennett4 suggested that malocclusions be classified with regard to deviations in the transverse dimension, the sagittal dimension, and the vertical dimension. This recommendation, rejected at the time, was later realized in the work of Simon and the development of his system of gnathostatics. Simon related the teeth to the rest of the face and cranium in all three dimensions of space.
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Historically, Simon attempted a canine-focused classification. His Law of the Canine considered the orbital plane (a line drawn from orbitale perpendicular to Frankfort horizontal) as coincident with the distal third of the maxillary canine in ideal occlusion. While modern orthodontists no longer consider Simon's law valid, the strategic position occupied by the canine makes it a favored tooth to reference for classification. www.indiandentalacademy.com
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Proffit ackermann classification
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Canine relation classification: ď Ž
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Classification was based on the sagittal relation of the maxillary canine to the mandibular canine. Maxillary canines are among the most stable of dental units because they are the longest rooted of all teeth and therefore very well anchored to the alveolar bone. The canine is the "keystone" tooth in the dental arch, and like the keystone of a stone archway, it provides a buttressing support for the incisors, as well as the posterior teeth. Also, canines provide a vital protective function in lateral excursive movements.
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However, the principal objection to a canine-derived classification relates to tooth anatomy. The maxillary canine exhibits a mesial incisal ridge that is shorter and less severely sloped than its distal incisal ridge. As a result, the central axis of the maxillary canine does not bisect the cusp tip. Tooth sizes and shapes vary, but the cusp tip averages 1 to 1.5 mm mesial to the center axis. Therefore the cusp tip of the maxillary canine does not directly fit into the embrasure formed by the mandibular canine and the first premolar, but rides up on the distal slope of the mandibular canine . Also, the cusp tip of the maxillary canine does not work well as a landmark because occlusal wear frequently alters the cusp tip from a point to a flat facet, and the modified architecture of its incisal edge obscures the true cuspal form. Although not ideal, one could use the imaginary center axis of the maxillary canine as a reference point, since it lines up with the mandibular canine-first premolar embrasure. www.indiandentalacademy.com
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The maxillary canine is one of the last teeth to erupt (other than third molars). This holds up classification efforts until the patient is 12 years, or older in slowly erupting patients. The deciduous canine offers little assistance with classification since it is smaller in mesiodistal width than its permanent successor, resulting in a center axis that is not coincident with the center axis of its future permanent replacement.
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Premolar classification: The premolar classification was put forth by Morton Katz as a modification to the Angle’s classification premolars usually present a sharply defined cusp tip, which is centered on the central axis of the premolar crown and which fits precisely into the opposing embrasure. Also, the cuspal inclines are steeper and deeper than molar cusps, which makes a more positive fit. From the negative perspective, orthodontists traditionally have not had high regard for premolars as functional dental units and have selected premolars most often of all tooth types for sacrifice in an extraction treatment. Also, premolars may have anomalous tooth size or shape. Furthermore, some judgment is required when less than a full complement of premolars are present
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A premolar-derived classification ď Ž
Class I :The most anterior upper premolar fits exactly into the embrasure created by the distal contact of the most anterior lower premolar.
In the rare instance where no premolar exists in a quadrant, then the center axis of the upper canine crown (not the cusp tip) should be used as a reference to the distal contact of the lower canine.
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Deciduous and mixed dentition classification ď Ž
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the center axis of the upper first deciduous molar should split the embrasure between both lower deciduous molars However, in the event that an upper first deciduous molar is prematurely lost, a line drawn through the center axis of the edentulous space should bisect the embrasure between the two lower deciduous molars
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Quantifying the classification ď Ž
This proposed modified classification designates ideal cusp-embrasure occlusion (as described by Angle) as zero (0). A plus sign (+) designates Class II direction and a minus sign (– ) designates Class III tendency. In this article the right side is evaluated first, then the left side. Ideal occlusion on both right and left sides is, therefore, (0,0). www.indiandentalacademy.com
Quantifying the classification ď Ž
For example, if a patient presents with ideal intermeshing on the right side, but a 2 mm Class II tendency on the left side, then the modified classification would read (0,+2)
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A third patient who is 1.5 mm Class II on the right and 3.5 mm Class III on the left side would be classified (+1.5,-3.5)
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From the above discussion it is clear that the system of classification we use today is inadequate in describing a dental anomaly in it’s entirety, aid in treatment planning or be easy to use. A universal classification system will be necessary which will be accepted by all orthodontists around the world. This would help us in standardizing malocclusion rather than disagreeing on the very nature of problem the patient has.
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ORTHOGNATHIC SURGERY
THE USE OF RIGID INTERNAL FIXATION
The most universally used method for stabilisation of ractures and osteotomies ha been the use of intermaxillary fixation (IMF). Common methods of IMF include the use of arch bars , Ivy loops, cast splints or simply the use of the orthodontic appliance. The introduction of rigid fixation has reduced the time required forIMF which would otherwise be 3 to 8 weeks of immobilisation. www.indiandentalacademy.com
ORTHOGNATHIC SURGERY
THE USE OF RIGID INTERNAL FIXATION
Controversies in the use of Rigid internal fixation include: Does RIF improve bony healing and post operative osteotomy strength? Does it improve long term stability? Is there a greater chance of developing TMD post operatively with RIF?
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ORTHOGNATHIC SURGERY
THE USE OF RIGID INTERNAL FIXATION It was Spiessl who first described the use of bone screws for fixation of a sagittal osteotomy in 1974. The various RIF systems include:
Lag screws Bone plating Pin systems www.indiandentalacademy.com
ORTHOGNATHIC SURGERY
Advantages of rigid fixation:
Reduction or elimination of IMF
Period of IMF can vary from 2to three weeks or the suregon may choose not to use IMF at all.
Increased post operative safety More rapid bone healing Ability to check the post operative occlusion in cases where segments have been displaced. Ability to stabilize osteotomies that would otherwise be difficult to stabilise Better control of bony segments www.indiandentalacademy.com
ORTHOGNATHIC SURGERY
Advantages of rigid fixation: Increased stability More rapid reduction of oedema Improved condition of the TMJ and muscles of mastication post operatively DISADVANTAGES: Technical difficulties Increased expense Increased risk of infection Need for plate and screw removal Neurosensory disturbances Tooth devitalisation TMJ symptoms www.indiandentalacademy.com
ORTHOGNATHIC SURGERY ď Ž
TMJ considerations in the use of RIF
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ORTHOGNATHIC SURGERY
Kundert compared condylar displacement in patients treated with sagittal osteotomies of the mandible with screw fixation and wire fixation. The authors noted condylar disraction in both groups with the magnitude slightly greater in the screw fixation group. A computed tomography study showed some medial rotation of the codylar segment. Varying inter condylar distances were also seen. Timmis et al compared 28 patients with rigid fixation 14 patients treated with wire fixation . The wire osteosynthesis group showed no statistical change in facial pain, TMJ pain or clinical signs after surgery. The rigid fixation group however showed significant decrease in TMJ noise, facialwww.indiandentalacademy.com pain, and TMJ pain.
Carter et al studied the effects of various fixation methods for mandibular advancement surgery, they concluded that:
After sagittal split osteotomies of the mandibular rami, horizontal rotation of the condyle usually occurs, regardless of the type of fixation or the position of the distal segment.
2. There were statistically significant changes (p < 0.001) in the intercondylar angles with all three types of fixation when the distal segments were measured in the anterior and posterior positions. However, the clinical significance of these changes was not proved.
3. In the three methods of fixation, the only statistically significant difference (p = 0.005) was between screw and wire osteosynthesis when the distal segments were in the forward position.
4. There were no consistent differences in horizontal rotation between the condyles that were fixed first and those that were fixed second, for either the left or right side.
5. The size of the original intercondylar angle did not affect the magnitude of change in the postoperative intercondylar angle, regardless of the position of the distal segment or the type of fixation used. www.indiandentalacademy.com
RETENTION AND RELAPSE
For many years clinicians did not agree about the need for retention. Different philosophies or schools of thought have developed and present day concepts generally combine several of these theories. The occlusion School: Kingsley stated that, “ The occlusion of the teeth is the most potent factor in determining the stability in a new position”. Proper occlusion is of primary importance in retention. The apical Base school: It was Axel Lundstrom who suggested that the apical base was an important factor in maintaining correct occlusion The mandibular incisor school: Grieve and Tweed suggested that the mandibular incisor must be kept upright over the basal bone. The musculature school: Rogers emphasised the need for establishing proper muscle balance for maintanence of occlusion.
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RETENTION AND RELAPSE
Relapse in lower anterior region: Many hypotheses have been put forward to explain the incidence of lower incisor crowding after treatment.
Relationship of third molars : the mesial eruptive force of the third molars give rise to lower anterior crowding. This led to therapeutic extractions and removal of impacted third molars. Ades et al compared four groups of patients 10 years out of retention. The groups includedthird molars erupted, third molar agenesis, third molar impaction, and third molar extraction cases. He found no difference in the mandibular incisor crowding, inter canine width between these groups. Mesial component of force and physiological mesial migration. Late mandibular growth and maximum intercanine width: continued mandibular growth even after maturation of inter canine width can lead to incisor crowding. A retention protocol untill completion of skeletal growth may be necessary in boys.
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RETENTION AND RELAPSE
Arguments against the apical base school and the mandibular incisor school:
Growth may play a major role in determing the apical base relationship to each other and the relation ship of the teeth to their apical bases. Patients treated in the growing age will be treated to axial inclination for their respective ANB angle or to an upright incisor position. Continued mandibular growt will lead to a decrease in FMA,ANB angles and flattening of the occ;usal plane. These changes lead to a more upright incisor positioning and a natural endency for the mandibular dentition to becoe more recessive in rekation to the skeletal base. Thus further growth of the patient may play an important role in deciding the retention prorocol.
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RETENTION AND RELAPSE
Arguments against the occlusion and musculature school:
Achieving post treatment stability by equilibration, elimination of cross arch deflective contacts may not be enough. Factors other than functional overload can lead to post treatment changes. The use of post treatment equilibration procedures to improve stabilit is debatable. www.indiandentalacademy.com
RETENTION AND RELAPSE
Duration of retention:
At the moment there is no agreement as to a specific duration of retention for patients. There is no clinical evidence as to whether a longer duration of retention ha s better post treatment stability than one of shorter duration.
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conclusion orthodontics may be the only speciality which has “pholosophies”. It was based on these philosophies that most work in Orthodontics was done. However treatment philosophies may not be enough in todays world. We need more scientific basis to back our treatment protocols. We need to follow ‘evidence based Orthodontics’ more than ‘opinion based orthodontics’. The only way this can be done is to improve our clinical research.
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