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Orthodontic diagnosis and treatment analysis—concepts and values. Part I
SPECIAL ARTICLE
Orthodontic diagnosis and treatment analysis-concepts and values. Part I Thomas R. Gebeck, DDS, MS, and L. Levern Merrifield, DDS
Grosse Pointe, Mich., and Ponca Ci~ Okla. This article examines some of the differences between successfully and unsuccessfully treated malocclusions. The sample consists of an untreated control group, a successfully treated group, and an unsuccessfully treated group. On both treatment groups an 0.022 edgewise appliance with directional forces mechanics was used. The skeletal and dental differences between these groups at the end of the treatment time interval are studied and discussed. The patient records of unsuccessful correction and of successful correction are presented for comparison. (AM d ORTHOD DENTOFAC ORTHOP 1995;107:434-43.)
E x c e l l e n c e , or the pursuit of it, has been the buzzword of orthodontic programs and articles for the last decade. These presentations give the practitioner the impression that a "latest piece of information" must be accepted if he or she is to continue to provide the best for his/her patients. Excellence seems to be relative to the technique one uses. Each of the techniques purports to be the best and therefore the dilemma. What is best? Excellence, by definition, means o u t s t a n d i n g - i t does not mean perfection. It is doubtful that there will ever be the perfect orthodontic technique. It is hoped that efforts in striving for excellence will permit the evolvement to a technique that works in harmony with normal skeletodental development, and not against i t - o n e that takes advantage of growth rather than adversely affecting it. Our orthodontic heritage is rich in persons, techniques, research, and responsibility. There has also been no shortage of professionals and dental supply companies proposing new treatment modalities or those willing to try them. With any new treatment approach or modification, responsibility dictates that basic clinical research be conducted to justify continued use and interest. Edward H. Angle introduced the edgewise appliance 1"2 and presented numerous case reports that supported its efficacy. This appliance afforded the specialty an initial step forward in its quest for excellence. One of Angle's primary goals during the development of the appliance was to offer a method of maintaining a full complement of teeth that were properly aligned. In the late thirties and early forties, Charles H. Tweed identified his orthodontic treatment objccCopyright © 1995 by the American Association of Orthodontists. 0889-5406/95/$3.00 + 0 8/1/54928
434
tives 3'4 and presented modifications in both the edgewise appliance and its use. His treatment objectives demanded that esthetics, function, health of the tissues, and limits of the dentition be assessed before concluding success or failure of orthodontic treatment. His clinical research provided the specialty a method of treatment planning based on the diagnostic facial triangle. 5 The use of the triangle gave the specialty an esthetic guideline (FMIA), 6 defined the anterior limit of the denture (IMPA), 7 and an awareness of vertical control (FMA). The benefits, to the specialty and the public, were improvements in facial esthetics and stability of the treated malocclusion. L. Levern Merrifield began working closely with Tweed in the 1950s. Several years ago Merrifield presented a modification to Tweed's basic edgewise technique and labeled it the directional force system. s Directional forces were defined as: A group of force systems using directional control to precisely position the teeth in both arches so they are in optimum harmony with their environment. As the consistency of treatment improved, continued clinical research allowed Merrifield to present sound clinical data that provided an assessment of facial esthetics, 9 and a definition of the posterior limit of the denture. 1° METHOD
In today's orthodontic practice, the majority of problems involve Class II, Division 1 malocclusions and Class I dentoalveolar protrusions. All "Tweed technqiue treated" patients do not finish with stable teeth, improved facial esthetics, healthy mouth tissues, and functional occlusions. This article will examine some of the differences beween successful and unsuccessfully treated malocclusions when directional force mechanics are used. The sample for this study consisted of (1) an un-
American Journal of Orthodontics and Dentofacial Orthopedics Volume 107,No. 4
7 Palatal Plane 8 Occlusal Plane 9 Z Angle 10 Posterior Facial Height {PFH) 11 Anterier Facial Height AFH)
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Fig, 1. Cephalometric tracing with usual values. treated control or growth group (44 patients); (2) a successfully treated group (40 patients); and (3) an unsuccessfully treated group (16 patients). Both treated groups consisted of Class II, Division 1 and Class I dentoalveolar protrusion malocclusions. The patient's records were selected for their respective samples depending on how well the results satisified original treatment objectives. The cephalometric films of 44 patients, 23 girls and 21 boys, were selected from the University of Michigan's University School Growth Study. The majority of the films were taken at ages 12 and 14 years. However, a few of the patients selected were 13 and 15 years of age. The pretreatment and posttreatment cephalometric films of 40 patients whose treatment was deemed successful (FMA and occlusal plane were controlled; the FMIA increased), 26 girls and 14 boys, closely matched the control with respect to age. All posttreatment patient records satisfied the requirements of Tweed's four treatment objectives. These objectives were: esthetics, health, function, and stability. The pretreatment and posttreatment cephalometric films of 16 patients, nine females and seven males, demonstrating unsuccessful treatment were obtained from the same clinicians. These patient records did not reflect attainment of Tweed's treatment objectives. (The FMA opened, occlusal plane tipped downward.) The pretreatment and posttreatment cephalograms of each of the three samples were traced; the following skeletal and dental values were recorded.
Skeletal values Nine familiar cephalometric criteria (Fig. 1): FMA, FMIA, IMPA, SNA, SNB, ANB, palatal plane, occlusal plane, and Z-angle were used. Three not so familiar values: posterior face height (PFH), anterior face height (AFH), and mandibular response (MR) were used. The nine familiar values need no description, but the three unfamiliar criteria do.
Fig. 2. Maxillary dental variables.
Fig. 3. Mandibular dental variables. Posterior face height (PFH) is a linear measurement from articulare, along a line tangent to the posterior border of the mandible, to the intersection with the mandibular plane. Anterior face height (AFH) is a linear measurement from palatal plane to menton, measured perpendicular to palatal plane. Mandibular response (MR) is a measurement of mandibular change, in millimeters, due to growth and treatment. It is defined in part II of this article.
Maxillary dental variables (Fig. 2) The change in the horizontal position of the maxillary first molar was determined by dropping a line perpendicular to Frankfort horizontal (transferred from pretreatment to posttreatment) from the most posterior and superior point on the pterygomaxillary fissure to Frankfort horizontal. A linear measurement in millimeters was made from the pterygoid perpendicular to the mesial contact point of the maxillary first molar. The vertical movement of the maxillary first molar
436
Gebeck, Merrifield, and Vaden
American Journal of Orthodontics and Dentofacial Orthopedics April 1995
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Fig. 4. Maxillary and mandibular molar response.
was determined by measuring the distance from the tip of the mesiobuccal cusp of the maxillary first molar to the palatal plane. The vertical movement of the maxillary central incisor was determined by measuring the distance from the tip of the central incisor to the palatal plane.
Mandibular dental variables (Fig. 3) The vertical movement of the mandibular first molar was determined by a linear measurement from the tip of the mesiobuccal cusp of the mandibular first molar, perpendicular to the mandibular plane. The change in horizontal position of the mandibular first molar was determined by measuring the distance from the mesial of the first molar along the occlusal plane to the point of the intersection of a perpendicular drawn from X point on the lingual symphysis. The vertical change in the mandibular central incisor was determined by measuring the distance from the tip of the incisor to the mandibular plane.
Statistical method The statistical model chosen for comparing the data was the analysis of variance, i.e., the Student t test. Means and standard deviations were generated for each sample. Means of the differences were also found for each sample, and differences of the means provided a comparison between samples. (Note: Tables with statistical data can be obtained directly from the author.)
Findings FMA: Closes 1.42 ° in the control. Closes 0.47 ° in the successful sample. Opens 2.96 ° in the unsuccessful sample. FMIA: Increases 1.12 o in the control. Increases 8.78 ° in the successful sample. Decreases 0.90 ° in the unsuccessful sample.
IMPA: Stays the same in the control. Uprights 8.81 ° in the successful sample. Uprights 2.09 ° in the unsuccessful sample. ANB angle: Remains same in the control. Reduces 2.860 in the successful sample. Reduces 1.620 in the unsuccessful sample. Palatal plane: Control - Upward and forward 0.19 °. Successful - Downward and backward 0.45 °. Unsuccessful - Downward and backward 1.31 °. Occlusal plane: Control - Upward and forward 0.93 °. Successful - Downward and backward 0.16 °. Unsuccessful - Downward and backward 3.12 °. Z-angle: Control - Increases 2.22 °. Successful - Increases 10.51 °. Unsuccessful - Increases 3.86 °.
Effects of the maxillary and mandibular molar responses (Fig, 4) The vertical and horizontal responses of the maxillary and mandibular molars can be summarized as follows: Untreated group. The maxillary molars relocated in a downward and forward direction, and the mandibular molars relocated upward and forward. The F M A closed, and B point came forward. Successful group. The maxillary molars demonstrated less downward and forward movement when compared with the untreated sample. The F M A remained the same, and B point came forward. Unsuccessful group. The maxillary molars relocated significantly downward and minimally forward when compared with the untreated sample. The mandibular molars relocated considerably upward and forward. The F M A opened, while B point moved backward.
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Fig. 5. Maxillary and mandibular incisor response. Effects of the mandibular incisor vertical and horizontal response (Fig. 5) Untreated group. The mandibular incisor significantly erupted 1.51 ram. The horizontal change was nonexistent, as demonstrated by no change in the IMPA. Minimal FMIA changes were a result of closure of the FMA. Successful group. The vertical change in mandibular incisor position was insignificant. However, the horizontal change in the mandibular incisor was very significant as demonstrated by the -8.8 ° change in the IMPA. The lingual uprighting of the mandibular incisors produced a significant positive response in the FMIA that allowed a favorable facial change to occur. Unsuccessful group. The vertical change in the mandibular incisor was 2.85 ram, 1.31 mm more than observed during normal growth. Excessive vertical response of the mandibular incisor was necessary to compensate for the significant increase in AFH, which occurred during unsuccessful treatment. There was minimal lingual horizontal change of the mandibular incisor as demonstrated by the IMPA change of - 2.09 °. This small lingual movement of the mandibular incisor, when coupled with the opening of the FMA, prevented changes in the FMIA. The resultant effect produced little change in the facial profile. Effects of the maxillary incisor vertical and horizontal response (Fig. 5) Untreated group. The maxillary incisor erupted 0.99 mm downward and forward in the untreated sample. There was no significant change in the palatal plane. The occlusal plane significantly changed in an upward and forward direction. Successful group. The maxillary incisor was intruded 1.33 mm while being retracted. There was a corresponding SNA angle decrease of 2.2 °. The palatal and occlusal planes remained the same. After study of the successful sample, it is apparent that in the treatment of Class II and Class I dentoalveolar protrusion malocclusions, maxillary incisor directional
control is a key of success. It can be achieved if a range of variables have responded favorably to proper directional management and control. Unsuccessful group. The maxillary incisor responded to treatment in a downward direction. The magnitude with which the maxillary incisor responded was not significant. Of significance was the fact that it could not be intruded because of the additive effect of multiple directional changes not found to be in harmony with the normal growth response.
DISCUSSION There can be many causes for an unsuccessful treatment response. They include mouthbreathing habits, weak musculature, poor patient cooperation during anchorage preparation, lack of high-pull headgear wear to the maxillary anterior segment of the dentition, and improper diagnosis and treatment planning. It is clear that use of the high-pull J-hook headgear for vertical control was paramount to successful treatment. Minimal high-pull headgear wear to the maxillary anterior area of the dentition forces the practitioner to obtain a Class I molar relationship through the extensive use of Class II elastics and vertical elastics. These auxiliaries, when used for long periods of time, will excessively tax mandibular anchorage and extrude the mandibular molars beyond normal limits. This type of treatment relies on a downward and backward rotation of the occlusal plane to achieve a Class I dental relationship. It produces no facial improvement and guarantees relapse, since all posttreatment studies suggest that the occlusal plane changes directionally to its pretreatment value. Figs. 6 through 11 display superimpositions on the maxilla, mandible, and on the cranial base. A profile of these samples suggests the following:
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American Journal of Orthodontics and Dentofacial Orthopedics April 1995
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Fig. 6. Superimposition- control group - maxillary-mandibular.
Fig. 8. Superimposition-successful dibular.
--_
Fig. 7. Superimposition-control
group-cranial base.
Control or normal growth (Figs. 6 and 7). The maxillary molar descended more than the mandibular molar erupted, and the mandibular incisor erupted more than the maxillary incisor descended. The result was an upward and forward change in the occlusal plane. Successful treatment (Figs. 8 and 9). The maxillary molar descended less than the mandibular molar extruded, and the maxillary incisor intruded while the mandibular incisor remained the same. The occlusal plane remained the same and will rotate upward and forward only if the mandibular molar and maxillary incisor are successfully controlled. Unsuccessful treatment (Figs. 10 and 11). The maxillary molar descended less than the mandibu-
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Fig. 9. Superimposition-successful
group-maxillary-man-
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group-cranial base.
lar molar extruded. Both changed a greater degree than they did during normal growth. The mandibular incisor extruded more than the maxillary incisor descended. The magnitude of these changes forced a downward and backward rotation of the occlusal plane. PATIENT R E C O R D S
The orthodontic specialist must be able to control individual teeth as well as groups of teeth. This control drastically influences the growth and development of the immature patient. To illustrate this statement, the records of two patients are shown, one selected from the unsuccessful group, and one from the successful.
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Fig. 12. Patient 1: Pretreatment facial photographs. Fig. 10. Superimposition-unsuccessful mandibular.
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Patient no. 1
The first patient, from the unsuccessful group, is a y o u n g b 0 y who has an acceptable profile but who exhibits moderate fullness of the lips and a retrognathic chin (Fig. 12). The Pretreatment casts (Fig. 13) exhibit a Class I dental malocclusion with an excessive overjet and overbite. The occlusal view displays moderate maxillary and mandibular crowding. The pretratment cephalometric tracing (Fig. 14) shows that the patient has a moderately high F M A of 32 °. Other values were FMIA 61 °, IMPA 88 °, SNA angle 78.5 °, SNB angle 75 °, and Z-angle 54 °. The diagnosis of the patient was not
Fig. 13. Patient 1: Pretreatment casts.
correct. For the patient to have had any chance for successful treatment, the diagnostic decision to remove some teeth would have to have been made. The posttreatment casts (Fig. 15) testify that an
440
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American Journal of Orthodontics and Dentofacial Orthopedics April 1995
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Fig. 15. Patient 1: Posttreatment casts.
excellent dental occlusion was achieved. The posttreatment cephalometric tracing (Fig. 16) reveals the undesirable response. The F M A increased from 32 ° to 37 °, FMIA decreased from 61 ° to 57 ° while IMPA decreased from 88 ° to 85.5 °. The SNA
Patient
1:
Pretreatment-posttreatment
superim-
angle decreased from 78.5 ° to 76 °, but the SNB angle decreased from 75 ° to 71.5 °. The Z-angle increased only from 54 ° to 63 °. There was an increase in P F H from 44.5 to 49.6 mm, but A F H increased from 69.3 to 82.5 ram. The palatal, occlusal, and mandibular planes rotated downward and backward (Fig. 17). Superimposition on the maxilla and mandible (Fig. 17) shows that extrusion of all teeth beyond normal growth parameters caused this negative effect. After the fact, one could blame this poor treatment result on mouthbreathing, poor cooperation, weak musculature or many other things, but ultimately, the primary cause must be a d d r e s s e d - i m p r o p e r diagnosis. This patient, if treated comprehensively in the first place, should have had the second premolars extracted. The effect of nonpremolar-extraction treatment on the face is demonstrated in Fig. 18.
Gebeck, Merrifield, and
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Vaden
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Fig. 18, Patient 1: Pretreatment-posttreatment facial photographs.
Fig. 20. Patient 2: Pretreatment casts.
Fig. 19. Patient 2: Pretreatment facial photographs.
Much can be learned from the treatment of this patient. Patient no. 2
A more successful result was achieved for the patient whose facial photographs are shown in Fig. 19. She had a Class II, Division 1 dentoalveolar protrusion problem. Her lips were very protrusive, distorting the face. The pretreatment casts (Fig. 20) showed a Class II dental relationship with an extreme overjet and impinging overbite. The occlusal views showed moderate mandibular crowding. The cephalometric tracing (Fig. 21) revealed a low Frankfort mandibular plane angle with a protrusive maxilla. The mandible was in a relatively good relationship to the maxilla, but the maxillary anterior teeth were very protrusive. The patient
~A Ft~A SNA SNB ANe Op-FH Z
97 61 85 79 6 8 61
Fig. 21. Patient 2: Pretreatment cephaiometric tracing.
was diagnosed properly when maxillary first premolars and mandibular second premolars were extracted. The posttreatment cephalometric tracing (Fig. 22) reveals that the occlusal and mandibular
442
FMA ~A lVMIA SNA SNB ANB OY-FH Z
Gebeck, Merrifield, and Vaden
American Journal of Orthodontics and Dentofacial Orthopedics April 1995
15 96 69 84 81 3 7 80
Fig. 22. Patient 2: Posttreatment cephalometric tracing.
~
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J
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Fig. 23. Patient 2: Pretreatment-posttreatment position.
.
Fig. 24. Patient 2: Posttreatment casts.
superim-
planes rotated in an upward and forward direction, and the maxillary incisors were signifiantly intruded and retracted. Superimpositions (Fig. 23) show how these changes were facilitated. Note the minimal extrusion of the maxillary and mandibular molars and the substantial intrusion and retraction of the maxillary incisors. This was accomplished with proper anchorage preparation and superb high-puU headgear wear to the maxillary incisors. The posttreatment casts (Fig. 24) exhibit good dental correction. The occlusal views display that the original arch form has been maintained. Comparison of the pretreatment (Fig. 19) and posttreatmerit facial photographs (Fig. 25) reveals that excellent facial balance has been achieved'. The pa-
Fig. 25, Patient 2: Pretreatment, posttreatment facial photographs.
tient has a beautiful smile along with her corrected dentition (Fig.26). CONCLUSION
This clinical study clearly supports the view that orthodontic mechanics influences the dynamic de-
American Journal of Orthodontics and Dentofacial Orthopedics /olume 107, No. 4
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velopment of skeletal and dental relationships. Direction of growth can be influenced to deviate from the normal course of development. Such deviation can be positive or negative relative to specific treatment objectives. Therefore it becomes imperative that diagnostic and treatment efforts be constantly refined to produce more consistent positive effects. REFERENCES 1. Angle EH. Treatment of malocclusion of the teeth. 7th ed. Philadelphia: S.S. White Dental Manufacturing Co., 1907. 2. Angle EH. The latest and best in orthodontic mechanism. Dent Cosmos 1928;70;1154. 3. Tweed CH. The application of the principles of the edgewise arch in the treatment of Class II, Division 1: part II. Angle Orthod 1936;6:256. 4. Tweed CH. Indications for the extraction of teeth in orthodontic procedures. AM J ORTHOD ORAL SUNG 1944;30; 405-28. 5. Tweed CH. A philosophy of orthodontic treatment. AM J ORTHOD ORAL SUNG 1945;31:74-103. 6. Tweed CH. The Frankfort-mandibular incisor angle (FMIA) in orthodontic diagnosis, treatment planning and prognosis. AM J ORTHOD ORAL SUNG 1954;24:121-69. 7. Tweed CH. Evolutionary trends in orthodontics, past, present, and future. AM J ORTHOD 1953;39:81-108. 8. Merrifield LL. Edgewise sequential directional force technolognj. J Charles Tweed Found 1986;14:22-37. 9. Merrifield LL. The profile line as an aid in critically evaluating facial esthetics. AM J ORTHOD 1966;52:804-22.
Fig. 26. Patient 2: Posttreatment smiling photograph.
10. Merrifield LL. Dimensions of the denture. AM J ORTHOD DENTOFAC ONTHOP [In press].
Reprint requests to: Dr. Thomas Gebeck 660 Cadieux Rd. Grosse Pointe, MI 48230
Orthodontic diagnosis and treatment analysis-concepts and values. Part I Thomas R. Gebeck, DDS, MS, and L. Levern Merrifield, DDS
Grosse Pointe, Mich., and Ponca Ci~ Okla. This article examines some of the differences between successfully and unsuccessfully treated malocclusions. The sample consists of an untreated control group, a successfully treated group, and an unsuccessfully treated group. On both treatment groups an 0.022 edgewise appliance with directional forces mechanics was used. The skeletal and dental differences between these groups at the end of the treatment time interval are studied and discussed. The patient records of unsuccessful correction and of successful correction are presented for comparison. (AM d ORTHOD DENTOFAC ORTHOP 1995;107:434-43.)
E x c e l l e n c e , or the pursuit of it, has been the buzzword of orthodontic programs and articles for the last decade. These presentations give the practitioner the impression that a "latest piece of information" must be accepted if he or she is to continue to provide the best for his/her patients. Excellence seems to be relative to the technique one uses. Each of the techniques purports to be the best and therefore the dilemma. What is best? Excellence, by definition, means o u t s t a n d i n g - i t does not mean perfection. It is doubtful that there will ever be the perfect orthodontic technique. It is hoped that efforts in striving for excellence will permit the evolvement to a technique that works in harmony with normal skeletodental development, and not against i t - o n e that takes advantage of growth rather than adversely affecting it. Our orthodontic heritage is rich in persons, techniques, research, and responsibility. There has also been no shortage of professionals and dental supply companies proposing new treatment modalities or those willing to try them. With any new treatment approach or modification, responsibility dictates that basic clinical research be conducted to justify continued use and interest. Edward H. Angle introduced the edgewise appliance 1"2 and presented numerous case reports that supported its efficacy. This appliance afforded the specialty an initial step forward in its quest for excellence. One of Angle's primary goals during the development of the appliance was to offer a method of maintaining a full complement of teeth that were properly aligned. In the late thirties and early forties, Charles H. Tweed identified his orthodontic treatment objccCopyright © 1995 by the American Association of Orthodontists. 0889-5406/95/$3.00 + 0 8/1/54928
434
tives 3'4 and presented modifications in both the edgewise appliance and its use. His treatment objectives demanded that esthetics, function, health of the tissues, and limits of the dentition be assessed before concluding success or failure of orthodontic treatment. His clinical research provided the specialty a method of treatment planning based on the diagnostic facial triangle. 5 The use of the triangle gave the specialty an esthetic guideline (FMIA), 6 defined the anterior limit of the denture (IMPA), 7 and an awareness of vertical control (FMA). The benefits, to the specialty and the public, were improvements in facial esthetics and stability of the treated malocclusion. L. Levern Merrifield began working closely with Tweed in the 1950s. Several years ago Merrifield presented a modification to Tweed's basic edgewise technique and labeled it the directional force system. s Directional forces were defined as: A group of force systems using directional control to precisely position the teeth in both arches so they are in optimum harmony with their environment. As the consistency of treatment improved, continued clinical research allowed Merrifield to present sound clinical data that provided an assessment of facial esthetics, 9 and a definition of the posterior limit of the denture. 1° METHOD
In today's orthodontic practice, the majority of problems involve Class II, Division 1 malocclusions and Class I dentoalveolar protrusions. All "Tweed technqiue treated" patients do not finish with stable teeth, improved facial esthetics, healthy mouth tissues, and functional occlusions. This article will examine some of the differences beween successful and unsuccessfully treated malocclusions when directional force mechanics are used. The sample for this study consisted of (1) an un-
American Journal of Orthodontics and Dentofacial Orthopedics Volume 107,No. 4
7 Palatal Plane 8 Occlusal Plane 9 Z Angle 10 Posterior Facial Height {PFH) 11 Anterier Facial Height AFH)
Gebeck, Merrifield, and Vaden
435
/
_J
Fig, 1. Cephalometric tracing with usual values. treated control or growth group (44 patients); (2) a successfully treated group (40 patients); and (3) an unsuccessfully treated group (16 patients). Both treated groups consisted of Class II, Division 1 and Class I dentoalveolar protrusion malocclusions. The patient's records were selected for their respective samples depending on how well the results satisified original treatment objectives. The cephalometric films of 44 patients, 23 girls and 21 boys, were selected from the University of Michigan's University School Growth Study. The majority of the films were taken at ages 12 and 14 years. However, a few of the patients selected were 13 and 15 years of age. The pretreatment and posttreatment cephalometric films of 40 patients whose treatment was deemed successful (FMA and occlusal plane were controlled; the FMIA increased), 26 girls and 14 boys, closely matched the control with respect to age. All posttreatment patient records satisfied the requirements of Tweed's four treatment objectives. These objectives were: esthetics, health, function, and stability. The pretreatment and posttreatment cephalometric films of 16 patients, nine females and seven males, demonstrating unsuccessful treatment were obtained from the same clinicians. These patient records did not reflect attainment of Tweed's treatment objectives. (The FMA opened, occlusal plane tipped downward.) The pretreatment and posttreatment cephalograms of each of the three samples were traced; the following skeletal and dental values were recorded.
Skeletal values Nine familiar cephalometric criteria (Fig. 1): FMA, FMIA, IMPA, SNA, SNB, ANB, palatal plane, occlusal plane, and Z-angle were used. Three not so familiar values: posterior face height (PFH), anterior face height (AFH), and mandibular response (MR) were used. The nine familiar values need no description, but the three unfamiliar criteria do.
Fig. 2. Maxillary dental variables.
Fig. 3. Mandibular dental variables. Posterior face height (PFH) is a linear measurement from articulare, along a line tangent to the posterior border of the mandible, to the intersection with the mandibular plane. Anterior face height (AFH) is a linear measurement from palatal plane to menton, measured perpendicular to palatal plane. Mandibular response (MR) is a measurement of mandibular change, in millimeters, due to growth and treatment. It is defined in part II of this article.
Maxillary dental variables (Fig. 2) The change in the horizontal position of the maxillary first molar was determined by dropping a line perpendicular to Frankfort horizontal (transferred from pretreatment to posttreatment) from the most posterior and superior point on the pterygomaxillary fissure to Frankfort horizontal. A linear measurement in millimeters was made from the pterygoid perpendicular to the mesial contact point of the maxillary first molar. The vertical movement of the maxillary first molar
436
Gebeck, Merrifield, and Vaden
American Journal of Orthodontics and Dentofacial Orthopedics April 1995
il
SUCC]E~SSFL~
UNSUCC]ESSFUL
Fig. 4. Maxillary and mandibular molar response.
was determined by measuring the distance from the tip of the mesiobuccal cusp of the maxillary first molar to the palatal plane. The vertical movement of the maxillary central incisor was determined by measuring the distance from the tip of the central incisor to the palatal plane.
Mandibular dental variables (Fig. 3) The vertical movement of the mandibular first molar was determined by a linear measurement from the tip of the mesiobuccal cusp of the mandibular first molar, perpendicular to the mandibular plane. The change in horizontal position of the mandibular first molar was determined by measuring the distance from the mesial of the first molar along the occlusal plane to the point of the intersection of a perpendicular drawn from X point on the lingual symphysis. The vertical change in the mandibular central incisor was determined by measuring the distance from the tip of the incisor to the mandibular plane.
Statistical method The statistical model chosen for comparing the data was the analysis of variance, i.e., the Student t test. Means and standard deviations were generated for each sample. Means of the differences were also found for each sample, and differences of the means provided a comparison between samples. (Note: Tables with statistical data can be obtained directly from the author.)
Findings FMA: Closes 1.42 ° in the control. Closes 0.47 ° in the successful sample. Opens 2.96 ° in the unsuccessful sample. FMIA: Increases 1.12 o in the control. Increases 8.78 ° in the successful sample. Decreases 0.90 ° in the unsuccessful sample.
IMPA: Stays the same in the control. Uprights 8.81 ° in the successful sample. Uprights 2.09 ° in the unsuccessful sample. ANB angle: Remains same in the control. Reduces 2.860 in the successful sample. Reduces 1.620 in the unsuccessful sample. Palatal plane: Control - Upward and forward 0.19 °. Successful - Downward and backward 0.45 °. Unsuccessful - Downward and backward 1.31 °. Occlusal plane: Control - Upward and forward 0.93 °. Successful - Downward and backward 0.16 °. Unsuccessful - Downward and backward 3.12 °. Z-angle: Control - Increases 2.22 °. Successful - Increases 10.51 °. Unsuccessful - Increases 3.86 °.
Effects of the maxillary and mandibular molar responses (Fig, 4) The vertical and horizontal responses of the maxillary and mandibular molars can be summarized as follows: Untreated group. The maxillary molars relocated in a downward and forward direction, and the mandibular molars relocated upward and forward. The F M A closed, and B point came forward. Successful group. The maxillary molars demonstrated less downward and forward movement when compared with the untreated sample. The F M A remained the same, and B point came forward. Unsuccessful group. The maxillary molars relocated significantly downward and minimally forward when compared with the untreated sample. The mandibular molars relocated considerably upward and forward. The F M A opened, while B point moved backward.
Gebeck, Merrifield, and Vaden 437
American Journal of Orthodontics and Dentofacial Orthopedics Volume 107, No. 4
\'°-"6
I~$UCCESSFUI.
SUCCESS]~JL
Fig. 5. Maxillary and mandibular incisor response. Effects of the mandibular incisor vertical and horizontal response (Fig. 5) Untreated group. The mandibular incisor significantly erupted 1.51 ram. The horizontal change was nonexistent, as demonstrated by no change in the IMPA. Minimal FMIA changes were a result of closure of the FMA. Successful group. The vertical change in mandibular incisor position was insignificant. However, the horizontal change in the mandibular incisor was very significant as demonstrated by the -8.8 ° change in the IMPA. The lingual uprighting of the mandibular incisors produced a significant positive response in the FMIA that allowed a favorable facial change to occur. Unsuccessful group. The vertical change in the mandibular incisor was 2.85 ram, 1.31 mm more than observed during normal growth. Excessive vertical response of the mandibular incisor was necessary to compensate for the significant increase in AFH, which occurred during unsuccessful treatment. There was minimal lingual horizontal change of the mandibular incisor as demonstrated by the IMPA change of - 2.09 °. This small lingual movement of the mandibular incisor, when coupled with the opening of the FMA, prevented changes in the FMIA. The resultant effect produced little change in the facial profile. Effects of the maxillary incisor vertical and horizontal response (Fig. 5) Untreated group. The maxillary incisor erupted 0.99 mm downward and forward in the untreated sample. There was no significant change in the palatal plane. The occlusal plane significantly changed in an upward and forward direction. Successful group. The maxillary incisor was intruded 1.33 mm while being retracted. There was a corresponding SNA angle decrease of 2.2 °. The palatal and occlusal planes remained the same. After study of the successful sample, it is apparent that in the treatment of Class II and Class I dentoalveolar protrusion malocclusions, maxillary incisor directional
control is a key of success. It can be achieved if a range of variables have responded favorably to proper directional management and control. Unsuccessful group. The maxillary incisor responded to treatment in a downward direction. The magnitude with which the maxillary incisor responded was not significant. Of significance was the fact that it could not be intruded because of the additive effect of multiple directional changes not found to be in harmony with the normal growth response.
DISCUSSION There can be many causes for an unsuccessful treatment response. They include mouthbreathing habits, weak musculature, poor patient cooperation during anchorage preparation, lack of high-pull headgear wear to the maxillary anterior segment of the dentition, and improper diagnosis and treatment planning. It is clear that use of the high-pull J-hook headgear for vertical control was paramount to successful treatment. Minimal high-pull headgear wear to the maxillary anterior area of the dentition forces the practitioner to obtain a Class I molar relationship through the extensive use of Class II elastics and vertical elastics. These auxiliaries, when used for long periods of time, will excessively tax mandibular anchorage and extrude the mandibular molars beyond normal limits. This type of treatment relies on a downward and backward rotation of the occlusal plane to achieve a Class I dental relationship. It produces no facial improvement and guarantees relapse, since all posttreatment studies suggest that the occlusal plane changes directionally to its pretreatment value. Figs. 6 through 11 display superimpositions on the maxilla, mandible, and on the cranial base. A profile of these samples suggests the following:
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American Journal of Orthodontics and Dentofacial Orthopedics April 1995
t
Fig. 6. Superimposition- control group - maxillary-mandibular.
Fig. 8. Superimposition-successful dibular.
--_
Fig. 7. Superimposition-control
group-cranial base.
Control or normal growth (Figs. 6 and 7). The maxillary molar descended more than the mandibular molar erupted, and the mandibular incisor erupted more than the maxillary incisor descended. The result was an upward and forward change in the occlusal plane. Successful treatment (Figs. 8 and 9). The maxillary molar descended less than the mandibular molar extruded, and the maxillary incisor intruded while the mandibular incisor remained the same. The occlusal plane remained the same and will rotate upward and forward only if the mandibular molar and maxillary incisor are successfully controlled. Unsuccessful treatment (Figs. 10 and 11). The maxillary molar descended less than the mandibu-
"
Fig. 9. Superimposition-successful
group-maxillary-man-
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group-cranial base.
lar molar extruded. Both changed a greater degree than they did during normal growth. The mandibular incisor extruded more than the maxillary incisor descended. The magnitude of these changes forced a downward and backward rotation of the occlusal plane. PATIENT R E C O R D S
The orthodontic specialist must be able to control individual teeth as well as groups of teeth. This control drastically influences the growth and development of the immature patient. To illustrate this statement, the records of two patients are shown, one selected from the unsuccessful group, and one from the successful.
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Fig. 12. Patient 1: Pretreatment facial photographs. Fig. 10. Superimposition-unsuccessful mandibular.
group-maxillary-
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Patient no. 1
The first patient, from the unsuccessful group, is a y o u n g b 0 y who has an acceptable profile but who exhibits moderate fullness of the lips and a retrognathic chin (Fig. 12). The Pretreatment casts (Fig. 13) exhibit a Class I dental malocclusion with an excessive overjet and overbite. The occlusal view displays moderate maxillary and mandibular crowding. The pretratment cephalometric tracing (Fig. 14) shows that the patient has a moderately high F M A of 32 °. Other values were FMIA 61 °, IMPA 88 °, SNA angle 78.5 °, SNB angle 75 °, and Z-angle 54 °. The diagnosis of the patient was not
Fig. 13. Patient 1: Pretreatment casts.
correct. For the patient to have had any chance for successful treatment, the diagnostic decision to remove some teeth would have to have been made. The posttreatment casts (Fig. 15) testify that an
440
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Vaden
American Journal of Orthodontics and Dentofacial Orthopedics April 1995
7
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54
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Fig. 14. Patient 1: Pretreatment eephalometric tracing.
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Pig. 16. Patient 1: Postrreatment cephalometric tracing.
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Fig. 15. Patient 1: Posttreatment casts.
excellent dental occlusion was achieved. The posttreatment cephalometric tracing (Fig. 16) reveals the undesirable response. The F M A increased from 32 ° to 37 °, FMIA decreased from 61 ° to 57 ° while IMPA decreased from 88 ° to 85.5 °. The SNA
Patient
1:
Pretreatment-posttreatment
superim-
angle decreased from 78.5 ° to 76 °, but the SNB angle decreased from 75 ° to 71.5 °. The Z-angle increased only from 54 ° to 63 °. There was an increase in P F H from 44.5 to 49.6 mm, but A F H increased from 69.3 to 82.5 ram. The palatal, occlusal, and mandibular planes rotated downward and backward (Fig. 17). Superimposition on the maxilla and mandible (Fig. 17) shows that extrusion of all teeth beyond normal growth parameters caused this negative effect. After the fact, one could blame this poor treatment result on mouthbreathing, poor cooperation, weak musculature or many other things, but ultimately, the primary cause must be a d d r e s s e d - i m p r o p e r diagnosis. This patient, if treated comprehensively in the first place, should have had the second premolars extracted. The effect of nonpremolar-extraction treatment on the face is demonstrated in Fig. 18.
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Vaden
441
Fig. 18, Patient 1: Pretreatment-posttreatment facial photographs.
Fig. 20. Patient 2: Pretreatment casts.
Fig. 19. Patient 2: Pretreatment facial photographs.
Much can be learned from the treatment of this patient. Patient no. 2
A more successful result was achieved for the patient whose facial photographs are shown in Fig. 19. She had a Class II, Division 1 dentoalveolar protrusion problem. Her lips were very protrusive, distorting the face. The pretreatment casts (Fig. 20) showed a Class II dental relationship with an extreme overjet and impinging overbite. The occlusal views showed moderate mandibular crowding. The cephalometric tracing (Fig. 21) revealed a low Frankfort mandibular plane angle with a protrusive maxilla. The mandible was in a relatively good relationship to the maxilla, but the maxillary anterior teeth were very protrusive. The patient
~A Ft~A SNA SNB ANe Op-FH Z
97 61 85 79 6 8 61
Fig. 21. Patient 2: Pretreatment cephaiometric tracing.
was diagnosed properly when maxillary first premolars and mandibular second premolars were extracted. The posttreatment cephalometric tracing (Fig. 22) reveals that the occlusal and mandibular
442
FMA ~A lVMIA SNA SNB ANB OY-FH Z
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American Journal of Orthodontics and Dentofacial Orthopedics April 1995
15 96 69 84 81 3 7 80
Fig. 22. Patient 2: Posttreatment cephalometric tracing.
~
_
J
"
Fig. 23. Patient 2: Pretreatment-posttreatment position.
.
Fig. 24. Patient 2: Posttreatment casts.
superim-
planes rotated in an upward and forward direction, and the maxillary incisors were signifiantly intruded and retracted. Superimpositions (Fig. 23) show how these changes were facilitated. Note the minimal extrusion of the maxillary and mandibular molars and the substantial intrusion and retraction of the maxillary incisors. This was accomplished with proper anchorage preparation and superb high-puU headgear wear to the maxillary incisors. The posttreatment casts (Fig. 24) exhibit good dental correction. The occlusal views display that the original arch form has been maintained. Comparison of the pretreatment (Fig. 19) and posttreatmerit facial photographs (Fig. 25) reveals that excellent facial balance has been achieved'. The pa-
Fig. 25, Patient 2: Pretreatment, posttreatment facial photographs.
tient has a beautiful smile along with her corrected dentition (Fig.26). CONCLUSION
This clinical study clearly supports the view that orthodontic mechanics influences the dynamic de-
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velopment of skeletal and dental relationships. Direction of growth can be influenced to deviate from the normal course of development. Such deviation can be positive or negative relative to specific treatment objectives. Therefore it becomes imperative that diagnostic and treatment efforts be constantly refined to produce more consistent positive effects. REFERENCES 1. Angle EH. Treatment of malocclusion of the teeth. 7th ed. Philadelphia: S.S. White Dental Manufacturing Co., 1907. 2. Angle EH. The latest and best in orthodontic mechanism. Dent Cosmos 1928;70;1154. 3. Tweed CH. The application of the principles of the edgewise arch in the treatment of Class II, Division 1: part II. Angle Orthod 1936;6:256. 4. Tweed CH. Indications for the extraction of teeth in orthodontic procedures. AM J ORTHOD ORAL SUNG 1944;30; 405-28. 5. Tweed CH. A philosophy of orthodontic treatment. AM J ORTHOD ORAL SUNG 1945;31:74-103. 6. Tweed CH. The Frankfort-mandibular incisor angle (FMIA) in orthodontic diagnosis, treatment planning and prognosis. AM J ORTHOD ORAL SUNG 1954;24:121-69. 7. Tweed CH. Evolutionary trends in orthodontics, past, present, and future. AM J ORTHOD 1953;39:81-108. 8. Merrifield LL. Edgewise sequential directional force technolognj. J Charles Tweed Found 1986;14:22-37. 9. Merrifield LL. The profile line as an aid in critically evaluating facial esthetics. AM J ORTHOD 1966;52:804-22.
Fig. 26. Patient 2: Posttreatment smiling photograph.
10. Merrifield LL. Dimensions of the denture. AM J ORTHOD DENTOFAC ONTHOP [In press].
Reprint requests to: Dr. Thomas Gebeck 660 Cadieux Rd. Grosse Pointe, MI 48230