Dr. Cannon received his degree in dentistry from Emory University and his orthodontic degree from the University of Montreal. He presently maintains a private orthodontic practice in Clermont, Georgia. Over the past thirty plus years, he has worked as a consultant for several orthodontic companies including Lancer Orthodontics, American Orthodontics, and Unitek. He has been awarded eight patents by the United States Patent Office for his unique ideas. His first patent was for the DualFlex archwire. This archwire was composed of nickel titanium in the anterior and stainless steel in the posterior. The anterior and/or posterior portions could be either round, square or rectangular.  His other patents relate to bracket design.  He developed the Cannon Cephalometric Analysis which clearly points out those cases with a true arch discrepancy. He has lectured extensively on the mechanics of orthodontic treatment and cephalometrics in the United States, Canada, Australia and Europe. He is presently a guest lecturer at Vanderbilt University School of Orthodontics in Nashville, Tennessee.  His philosophy of treatment might be best summed up by the following statement: The design of an orthodontic bracket should not dictate the final torques and angulations but rather enable their establishment.  Combining his years of experience in bracket design with his unique talents, he has developed a bracket system, the Cannon Ultra II, that carries the concept of the programmed edgewise bracket to its next level.

Philosophy   

Before Dr. Lawrence F. Andrews introduced the pre-adjusted bracket, first, second and third order bends were placed into the archwires to properly align the teeth. The degree to which these bends were made in the archwires were not governed by fixed angles or distances but rather by what was necessary to properly align and position the teeth in each arch so as to accomplish optimum interdigitation of the teeth upon closure.  We applaud Dr. Andrews for his hard work and great contribution of the pre-adjusted bracket to orthodontics.  Dr. Andrews states on page 181 of his book, STRAIGHT WIRE The Concept and Appliance, the following concerning the maxillary and mandibular incisor, "There must be at least three standard brackets, each with a different base inclination to accommodate one of the three acceptable but different post-treatment inter-jaw relationships."  Apical base class I, II and III are the different but acceptable inter-jaw relationships.  Dr. Andrew’ prescription for apical base class II and III cases modifies only the base inclination for the maxillary and mandibular incisors.  His prescription is inadequate because the majority of the change in the inclination of the incisors is the distal or mesial movement of the root, not the mesial or distal movement of the incisal edge.  His failure to recognize that the angulation angles of the maxillary and mandibular cuspids and bicuspids must be altered to achieve optimum interdigitation of the teeth is another reason, prehaps the primary reason, that his prescription for the treatment of apical base class II and III is inadequate.  With apical base class II inter-jaw relationship cases, Dr. Andrews prescribes a decrease of five degrees in the base inclination from his apical base class I prescription for the maxillary central and lateral brackets.  He prescribes an increase of five degrees in the base inclination from the apical base class I prescription for the mandibular incisors brackets.  A decrease of five degrees in the base inclination of the maxillary incisor brackets will result in only one-half millimeter of distal positioning of the incisal edge of these teeth.  A five degree increase in the base inclination of the mandibular incisors will likewise position the incisal edge of these teeth mesially by one-half millimeter.   A total of only one millimeter is inadequate for treating most apical class II cases.  The same concept but with the base inclination changes reversed, is utilized in Dr. Andrews’ prescription for treating apical base class III inter-jaw relationship cases. 

Illustration 1:  Maxillary Central Incisor : How +2, +7 and +12 degrees of bracket base inclination  effect the anterior/posterior position of the incisal edge.

Point A is the incisal edge. Point B is where the line through the long axis of the tooth intersects the line vertical to the occlusal plane.   Notice that point A moves approximately one-half millimeter forward toward the vertical plane for each five degree increase in the inclination of the base.

 Illustration 2:  Mandibular incisors:  How +4, -1 and -6 degrees of bracket base inclination effect the anterior/posterior position of the incisal edge.  Notice that point A moves approximately one-half millimeter backward from the vertical plane for each five degree reduction in the base inclination.

The facial lingual rotational force created by the union of the edgewise slot and the rectangular archwire results in the tooth rotating around the facial axis point (FA) of the maxillary and mandibular incisors. The center of the edgewise slot should be located on that point. Even in the maxillary central incisors the distance from the center of the edgewise slot to the incisal edge is usually no more than five millimeters, while the distance from the center of the edgewise slot to the apex of the root is approximately three times that length. Therefore, the apex of the root will move approximately three times the distance as does the incisal edge. A point located five millimeters from the point of rotation, rotating clockwise or counter clockwise five degrees, moves only one half millimeter in a forward or backward direction. Therefore, an increase or decrease of five degrees in the base inclination will have very little effect on the anterior/posterior position of the incisal edge of the maxillary central incisors, and/or the mandibular incisors. Andrews’ Straight Wire prescription for the maxillary central incisor bracket for an apical base class I is plus seven degrees base inclination, plus two degrees base inclination for apical base class II, and plus twelve degree base inclination for apical base III. The lateral incisors base inclination is four degrees less than the central incisor, minus two degrees, plus three degrees and plus eight degrees respectively. Andrews’ Straight Wire prescription for the mandibular incisors are as follows: Apical base class I, minus one degree base inclination; Apical base class II, plus four degrees of base inclination; Apical base class III, minus six degrees base inclination.

The total dental compensation accomplished with  Andrews’ Straight Wire  prescription for apical base class II and III would be approximately one millimeter, one half millimeter from the maxillary incisors and one half millimeter from the mandibular incisors.  In other words, the incisal edge of the maxillary incisors would move mesially or distally only one half millimeter, and the incisal edge of the mandibular incisors would move mesially or distally only one half millimeter.  One millimeter of dental compensation is not adequate for most apical base class II and III inter-jaw relationships.

What about the "row-boat effect"  when the base inclination is increased or decreased in the maxillary or mandibular incisors?   Will the lingual or facial rotational force on the maxillary or mandibular incisors roots be of such a magnitude as to move the teeth in the maxillary arch forward or backwards?  Because of the apical base class I angulation angles in the brackets of the cuspid and bicuspid brackets, any forward or backward movement of the cuspids, bicuspids and molars would be of a bodily nature.  The force from the lingual or facial root torque on the maxillary or mandibular incisors will not be of a magnitude that will move all the teeth forward or backward in the required bodily manner.  If the angulation angle in the brackets of the cuspids and bicuspids were increased or decreased as appropriate, some "row-boat effect" might very well occur with the addition of the distal or mesial rotational force on the cuspids and bicuspids roots.

Dental compensation in apical base class II and III cases can be accomplished much easier by utilizing tipping of the teeth. With tipping of a tooth, the rotation point is at the approximate junction of the top and middle one-third of the root. The distance from this point to the incisal edge is approximately three times the distance from the middle of the root to the apex of the root. The result is that the incisal edge of the tooth moves approximately three times the distance as does the apex of the tooth.

Illustration 3: When the incisors are tipped, A is the approximate location of the point of rotation. The maxillary central is rotated five degrees, from plus seven degrees (solid line) to plus twelve degrees (dotted line).  The mandibular incisor is rotated five degrees from minus one degree (solid line) to minus six degrees (dotted line).

Illustration 3 demonstrates how the full clinical crown comes forward approximately 2 millimeters when the tooth is rotated five degrees by a tipping action.  Unlike in illustration 1 where the rotation point is the FA point, whereby that portion of the clinical crown above the FA point actually moves backward.  In apical base class ll and III cases, dental compensation of four millimeters can be easily accomplished.  Two millimeters in the maxillary incisors and two millimeters in the mandibular incisors.  Four millimeters of dental compensation is usually adequate to treat apical base discrepancy cases from plus five millimeters to minus five millimeters Wits.  Illustration 3 demonstrates dental compensation for apical base class III discrepancies.  The same concept is employed for apical base class II case, the difference being, that the maxillary and mandibular incisors would be tipped in the opposite direction as they are for apical base class III cases.

A review of five major orthodontic company’s catalog reveals the fact that no other orthodontic company recognizes the need for such prescriptions.  We in orthodontics must recognize and accept that different inter-jaw relationships require different angles between the long axis of the teeth and the occlusal plane.  The major focus of all the major orthodontic companies is to market a single set of pre-adjusted brackets and claim that their set of brackets will correctly position the teeth for all individuals regardless of the inter-jaw relationship. This concept has been marketed so successfully that it has become dogma. This dogma must be overturned before orthodontics can proceed to a higher quality of treatment. This can only be accomplished by understanding that each individual is unique and most often requires an individualized approach to treatment. In an effort to make the work of the practice of orthodontics easier, we in orthodontics are constantly looking for a quicker, faster and easier way of treatment. We in orthodontics must protect the "Profession of Orthodontics". We must pass it on to the next generation with higher standards. These standards must produces a quality of treatment higher than when we accepted the profession from the previous generation. To do otherwise is to accepts failure. The concept of the pre-adjusted bracket is so appealing that it has literally wiped out all competitive systems. However, the pre-adjusted bracket technique is limited in value for many cases and usually requires the bending of wire in treatment for nearly all cases. It’s time to admit this, move on, and explore other options that may result in the further evolution of the concept of the pre-adjusted bracket. As we move on we should carry with us the many valuable contributions that those associated with the pre-adjusted bracket have made to orthodontics.  

FOOD FOR THOUGHT

1. Review the catalog of any of the major orthodontic companies in regard to the number of different pre-adjusted bracket systems.  They all claim that their system is the only correct system even though they market several systems that have different base inclinations for the same teeth.

2.  When reviewing the catalogs, notice that there are numerous maxillary and mandibular incisors brackets with different base inclinations.  Why is the angulation in the cuspids and bicuspids almost uniformly the same?  The angulation of the cuspids is a major factor in the anterior posterior positioning of the incisors.  The fact is that if the base inclination of the maxillary and mandibular incisors are increased or decreased the angulation of the cuspids and bicuspids should be changed accordingly. 

3.  Ormco, 3M Unitek and American Orthodontics combined offer approximately 31 different prescriptions for pre-adjusted bracket systems.  Only one prescription even mentions the need for a different bracket system when treating apical base class II and III cases.  Most of them have a popular orthodontist name attached to them or a catchy name implying that the system is somehow superior to all others.  There is an obsession with numbers.  The importance of +7 degrees, +12 degrees and +17 degrees torque for the maxillary, for example, is heatedly debated among orthodontist.  These same orthodontist seldom if ever utilize a full size archwire to finish a case, and therefore never realize the full torque built into these brackets.

4. One of the major elements in the concept of the pre-adjusted bracket systems is the in/out relationship between the teeth. The more prominent the crown of a tooth, the smaller the base thickness of the bracket designed for that tooth, and vice versa.  The mandibular incisors and the maxillary laterals have brackets with the greatest base thickness due to their smaller crown prominence.  In an effort to give the orthodontist what they think they want and need, a low profile bracket system, the in/out between the maxillary centrals, laterals and cuspids and the mandibular cuspids and incisors have been greatly compromised.  However, these systems are marketed as fully pre-adjusted bracket systems.

5. Andrews base inclination for the maxillary central incisor in apical base class I case is +7 degrees.  Roth, with much fanfare, decided that it should be +12 degrees to have the teeth more forward for a bigger smile.  The 5 degree increase in the base inclination resulted in the maxillary central being one-half millimeter more forward. 

6.  Why have there been a continued increase of the base inclination in the maxillary incisors and at the same time have a continued decrease in the mandibular incisors?  Could it possible be to overcome technique problems with the pre-adjusted bracket and has nothing to do with the final positioning of the teeth?

7.  Ormco explains, when describing the Damon system that to best utilize the clinical advantages of the passive self-ligation brackets, it is strongly recommended not to exceed .019 x .025 archwire dimension in an .022 x .028 bracket slot, because this needed play allows for seven degrees of torque play in both directions.  Ormco further explains that this needed play between the archwire and the slot makes closing space, leveling, arch form changes, closing open bites, and the finishing, settling and detailing of the occlusion much easier.  Is Ormco describing Straight Wire or  Light Wire?

PERSONAL COMMENT:  Dr. Andrews’ concept of Straight Wire is valid in the treatment of apical base class l non-extraction cases.  The concept begins to have problems when extractions are necessary even with apical base class I cases, and totally falls apart when treating apical class II and III cases, either extraction or non-extraction.  The tendency has been, even in apical base class I extraction cases, to increase the base inclination in the maxillary incisors and decrease the base inclination in the mandibular incisors.  This creates better anchorage in the mandible incisors and increases lingual root torque in the maxillary incisors.  The changes in base inclination in both the maxillary and mandibular incisors are technique related, not to change the actual final positioning of the teeth.  In apical base class II and III cases, it is impossible to alter the base inclinations of the brackets to the extent required for most apical base class II and III cases.  The pre-adjusted bracket system, when treating apical base class II and III cases, can actually make treatment more difficult.  A bracket system which takes advantage of the great qualities of the pre-adjusted edgewise slot combined with a tipping slot which allows for dental compensation would make orthodontic treatment much easier and give  better treatment results.  The design of orthodontic brackets should not dictate the final torques, inclinations, and in/out of the teeth, but rather enable their establishment.

CENTRIC OCCLUSION AND CENTRIC RELATION

 Knowing how to determine centric occlusion and centric relation, and understanding their differences is perhaps the most important factors of all diagnostic procedures.  Centric occlusion is defined as the relationship between the arches that will, upon closing, results in the maximum interdigitation of the teeth.  Centric relation is defined as the relationship between the arches that will, upon closing, results in the head of the condyle being positioned in the most posterior, superior, unstrained position in the glenoid fossa.  When centric occlusion and centric relation is different, the most common cause is the anterior positioning of the mandible by the patient so that a better interdigitation of the teeth can be accomplished.  There are many different approaches to establish centric relation.  Perhaps the simplest procedure is to recline the patient back in the dental chair, get them to relax so that you can freely take control of the opening and closing of the mandible.  Place your thumbs end to end on the point B region of the chin, and your fingers anterior and posterior to the angle of the mandible.  Exert a light clockwise rotational and distal force on the mandible.  Once the mandible can be opened and closed freely, without resistance from the patient, insert a soft bite material and close the mandible until the initial contact is made between the teeth  Hold the mandible in that position until the bite material hardens.  Always insert the bite between the teeth when taking a cephalometric x-ray and trimming or mounding the models.  Upon completion of orthodontic treatment always check to be sure that centric occlusion and centric relation are one and the same.  Faulty orthodontic treatment can create a difference in centric occlusion and centric relation when there was no difference at the beginning of treatment.  Centric occlusion and centric relation must be one and the same to establish quality orthodontic treatment and to insure tempromandibular health. 

CEPHALOMETRIC ANALYSIS

Cephalometric analysis is used extensively by some orthodontist as a diagnostic tool, while others seriously question its value and seldom, if ever, utilize it in their diagnostic procedures.  Perhaps the reason is simply due to the state of utter confusion surrounding cephalometrics.  We in orthodontics have used cephalometric landmarks such as sella, nasion, orbitale and etc. to establish linear and angular cephalometric standards that we utilize to evaluate pre and post treated cases.  These measurements are not standards or norms.  They are simply averages of a selected population .  The average height of the American male might be 5 foot 10 inches.  You cannot, however, establish 5 foot 10 inches as the standard or norm and proclaim that any American male not 5 feet 10 inches is abnormal.  The concept that cephalometric landmarks occupy the same relative position throughout the general population is not valid.  These landmarks tend to maintain a somewhat predictable relationship as growth occurs for a single individual, but they do not necessarily start out with the same relative relationships for all individuals, even in selected populations.

As a profession, we continue to use measurements that have been shown to be, if not invalid, certainly questionable as to their value for some cases.  The continued use of ANB to determine the linear relationship between the arches is one prime example. It has been clearly shown by several authors that the utilization of the ANB angle to determine the linear relationship between the arches can, in many cases, be very misleading.  The evidence demonstrates that cases with a short cranial base, and/or a high SN to OP angle, are the type cases where the ANB angle is most leading.  In either of these situations, the ANB angle can be of such a magnitude as to falsely suggest a linear discrepancy between the arches.  In those cases with both a high SN to OP and where nasion is positioned posteriorly, the ANB angle becomes obviously incorrect. 

The cephalometric measurements commonly referred to as standards and routinely applied to all cases, have been established through the study of a general population, including without categorizing, convex, concave and straight profile individuals.  The field of orthodontics, for some unexplainable reason, long ago decided that the low SN to OP angle straight profile individuals represent the standards that must be approximated in all cases if we are to consider our orthodontic treatment successful.  These standards are almost universally used to evaluate treatment results, but seldom, if ever, are the effects of a steepening SN to OP angle or the anterior/posterior position of nasion taken into consideration when applying these standards. 

The importance of soft tissue analysis appears to be primarily divided into two groups.  One group believes that the soft tissue analysis should be the major tool utilized in determining the treatment plan.  Their reasoning is that the "FACE" is what we see, and therefore, consideration of the soft tissue should take priority over the positioning of the teeth. The other group feels that as the teeth go, so goes the soft tissue.  Their reasoning is that the anterior posterior position of the lips is about the only soft tissue that can be effected by orthodontic treatment.  The author’s position is that neither group is correct.  As with all orthodontic treatment, treatment plans must be individualized.  There are cases where soft tissue should be the major factor and there are cases where the placement of the teeth take priority.  In an article entitled "Integumental Contour And Extension Patterns" by Dr. Charles J. Burstone he explains the manner in which priorty should be placed on soft tissue, and placement of the teeth, in establishing individual treatment plans.  The following statement appears in the topic DISCUSSION.  "An awareness of integumental extension and contour is an essential element of case analysis.  Since considerable variation may occur in the soft tissue mass of the face, treatment based on arbitrary dentoskeletal standards cannot be expected  to consistently produce desirable facial form.  In many individuals application of an absolute standard will lead to increased facial disharmony or the substitution of one type of disharmony for another.  Since the soft tissue as well as dentoskeletal structures demonstrate variations, both should be considered in establishing the anterioposterio-positioning of the denture, and the axial inclination of the anterior teeth."  He continues. "In an orthodontic case, esthetics is closely related to stability.  Rarely should facial esthetics be achieved at the expense of denture stability.  Stability and esthetics need not be separate objectives, for those same muscular imbalances that operate to produce denture instability may also be responsible for disharmony in facial contour."

If properly utilized and understood, cephalometric measurements can be a vital tool in establishing certain parameters in orthodontic diagnosis. 

DETERMINING ARCH DISCREPANCY

Before beginning treatment, especially when utilizing a pre-adjusted bracket system, the apical base relationship  between the arches must be accurately determined.  The utilization of ANB to determine arch discrepancies can be very misleading particularly in high angle cases and patients with prominent or flatten foreheads.

The terms skeletal class I, II and III became popular with the introduction of Steiner’s SNA, SNB and ANB angles. The SNA angle has been used to establish the anterior/posterior relationship between the maxilla and cranial base. The accepted norm for the SNA angle is 82 degrees. The SNB angle has been used to establish the anterior/posterior relationship between the mandible and cranial base. The accepted norm for the SNB angle is 80 degrees. The ANB angle has been used to establish the relationship between the maxilla and the mandible. The accepted norm for the ANB angle is +2 degrees (SNA of 82 degrees minus SNB of 80 degrees = ANB of +2 degrees). An ANB angle of 0 to +5 degrees is considered to be a skeletal class I. An ANB angle of +6 and over is considered a skeletal class II. An ANB of –1 or less is considered a skeletal class III. These averages have been routinely applied to all cases in total disregard of the fact that sella does not necessarily occupy the same relative superior/inferior position for all individuals, nor does nasion always occupy the same anterior/posterior position for individuals, even in a specific population.  If nasion is positioned in a abnormal anterior position the ANB angle will be falsely decrease.  If nasion is positioned in a abnormal posterior position the ANB angle will be falsely increased, and neither direction would have any effect on the angle formed between the maxillary and mandibular teeth, nor the angle formed between the teeth and the occlusal plane.   As the FH-OP angle steepens point B usually rotates down and back.  This will result in an increase in the ANB angle, but again will have no effect on the relationship between the maxillary and mandibular teeth to each other or to the occlusal plane.  The terms skeletal class I, II and III are defined by differing ANB angles; however, they have absolute nothing to do with the angular relationship between the teeth. They very accurately describe the shape of the profile, but do not necessarily accurately define the jaw relationship.

 "Wits" is a measurement which accurately describes jaw relationships.  "Wits" describe the jaw relationship as apical base class I, II and III.  "Wits" is not effected by a high FH to OP angle or an abnormal positioning of nasion.  The terms apical base class I, II and III are defined by differing "Wits" measurements.  They accurately define jaw relationships, but make no statement in regard to the shape of the profile.

Perhaps what is not recognized is that a person can have a rounded profile, skeletal class II, with an apical base class I jaw relationship.  Also, a person can have a straight profile, skeletal class I, with an apical base class III.  A rounded profile is no more or no less abnormal than a straight profile, and a straight profile is no more or no less normal than a rounded profile. A retrognathic mandible is not always deficient.  If a pre-adjusted bracket system is utilized, ANB should not be the determining measurement to establish jaw relationships.

If the above in understood, then it must be understood that as the "Wits" measurement changes the bracket base inclination, needed for optimum treatment results, will need to change appropriately.  It should be obvious that a "Wits" measurement of +3mm will require different bracket base inclinations than will a "Wits" measurement of -3mm.    

Not all orthodontist utilize cephalometrics.  Not to use cephalometrics when your appliance is a pre-adjusted bracket system makes no sense.  The Cannon Dual Plane Cephalometric Analysis is an analysis developed specifically to determine apical base relationships between the arches and its ramifications on treatment.  It places the importance on the occlusal plane that here-to-fore has been placed on the S-N plane.

Illustration 4: The effects of variations of cranial base length on ANB and Wits.
 

Variations in cranial base length alters the ANB angle even though there have been no changes in the relationship between the arches. The Wits measurement is not effected by changes in cranial base length.

Illustration 5: The effects of variations of the SN-OP angle and cranial base length on ANB and Wits
 

The ANB angle is altered by variations in cranial base length due to the abnormal position of nasion, and the steepness of the SN - OP angle; the Wits measurement is not altered.

Surprising, there are a relative large number of apical base class III discrepancy cases that have a straight profile. Finishing these cases with the apical base class III discrepancy is necessary since surgical correction would result in unacceptable changes in the profile. It appears that mandibular growth is such that pogonion does not rotate posteriorly and inferiorly, but remains in a forward position. In all these cases the OP-SN angle is well above the accepted norm. It must be concluded that a straight profile does not always result in an apical base class I relationship between the arches. The Wits measurement will usually be -4mm or less. ANB is usually around 0 to -2mm. Again ANB describes the profile and Wits gives the relationship of the arches.

Illustration 6: High OP-SN; straight profile OP-SN = 24 degrees ANB = 0 degrees Wits = -4mm

Since the ANB angle makes no distinction between a deficient mandible and a retrognathic mandible, these two terms have become almost synonymous. Therefore, any mandible that is retrognathic has been generally thought of as being deficient. Convex profiles due to high SN - OP angles quite often have an ANB of at least +6 degrees, but with no apical base discrepancy between the arches. The confusion has resulted from the false idea that by comparing angular measurements of both the maxilla and the mandible to cranial base (SNA, SNB), the linear relationship of the maxilla to the mandible will be represented by the ANB angle. As the SN-OP angle gets steeper the maxillary/mandibular complex rotates in a clockwise direction. Point B rotates with the maxillary/mandibular complex to create a larger ANB angle without changing the relationship between the arches. It must be understood that as the maxillary/mandibular complex rotates clockwise, the relationship between the maxillary teeth and the mandibular teeth do not change. The inter-incisal angle does not change, nor does any angle formed between the teeth and the occlusal plane change.

Illustration 7: High OP-SN; angle convex profile OP-SN = 24 degrees ANB = +6 degrees Wits = 0 mm

Convex profiles due to a high SN-FOP angle are no more or no less abnormal than straight profiles. It also must be concluded that a convex profile does not always indicate a deficient mandible.

The Wits measurement is established by drawing a line that is perpendicular to the occlusal plane that originates at point B and proceeds past point A; the distance, in millimeters, between the line and point A is referred to as the Wits. If point A is anterior to the line, the Wits measurement is positive, if posterior to the line, the Wits measurement is negative. If the Wits falls within a +2 to –2 millimeter range, this would indicate an apical base class I. The "torque" and "angulation" angles of the pre-adjusted brackets are adequate to treat the case successfully. If the Wits falls outside the +2 to -2 parameter, this indicates that there is an apical base discrepancy between the arches of such a magnitude that dental compensation is necessary to achieve maximum interdigitation of the teeth. The important factor regarding the Wits analysis is that the functional occlusal plane is utilized to establish the apical base relationship between the maxilla and mandible. Once the teeth are aligned and the arches leveled, the occlusal plane and the plane of the archwire ( archwire inserted into the pre-adjusted slots of the brackets) become parallel. Therefore, the angles created between the teeth and the plane of the archwire inserted into the pre-adjusted slots will be the identical angles formed between the teeth and the functional occlusal plane. 

Illustration 8: Demonstrates that once the arches are level, the occlusal plane and the archwire, in the edgewise slots, is parallel.

Illustration 9: Wits Analysis as an indicator of the correct angle needed between the long axis of the maxillary and mandibular central incisors to the occlusal plane to accomplish maximum interdigitation between the teeth.

The Wits analysis gives a good indication of what the angle formed between the long axis of the maxillary and mandibular incisors to the occlusal plane should be to achieve maximum interdigitation of the teeth.

Illustration 10: Demonstrates apical base class I, (A) II (B) and III (C). 

Illustration 11: Dental compensation to achieve maximum dental interdigitation.

Wits = 0mm	Wits = + 4mm	Wits = - 4mm
A	B	C

We in orthodontics must accept the fact that the concept of the pre-adjusted bracket is impractical in apical base class II and III cases.  Even if the base inclination of the incisors could be of such angles that the needed dental compensation could be achieved,  the angulation angles in the cuspids and bicuspids must be addressed.  Bracket inventory would be unmanageable, and where is the crystal ball that determines which bracket is used and on each tooth. 

A bracket sytem with the pre-adjusted edgewise slot, and also a slot which allows for the controlled tipping of the individual tooth is needed.   The Cannon Ultra bracket is such a bracket.

  Summary 
 

 1.  The Straight Wire concept is not adequate when treating apical base discrepancy cases.  The pre-determined angles between the teeth and the occlusal plane must be customized by utilizing dental compensation for the individual case.

2.  The Wits Analysis gives a much clearer picture of arch discrepancies than does the ANB angle.

3.  A convex profile, due to a high FH - OP angle, is no more or no less abnormal than a straight profile.

4.  All retrognathic mandibles are not deficient.

5.  A straight profile does not always indicate harmony between the arches.

6.  Harmony between the arches can occur with a convex profile.

7.  The shape of the profile is not a valid indicator on whether or not the pre-adjusted bracket system is adequate to establish optimum treatment results.