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TRANSVERSE ARCH DIMENSIONAL CHANGES IN ClASS I NONEXTRACTION, EARLY AND LATE FIRST BICUSPID EXTRACTION PROTOCOLS

Michael Larson, D.D.S.

An Abstract Presented to the faculty of the Graduate School of Saint Louis University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Dentistry 2010

Abstract

The primary reason for treatment sought by patients is crowding. Among the possible ways to alleviate crowding, With the

extraction is one of the treatments of choice.

use of extractions and fixed orthodontic appliances the crowding is resolved and the remaining spaces are closed and as a result alignment of the dentition is complete. The purpose of this study was to evaluate maxillary and mandibular arch development in the transverse dimension utilizing extractions at varying times (early vs. late protocols). In this study we defined "early" as a period

of time before the permanent maxillary cuspids have erupted and "late" as the period of time following eruption of the permanent maxillary cuspids. The sample consisted of 90 dental casts from a population of orthodontically treated Class I malocclusion mixed dentition subjects. All dental models were collected

from a single private practice and all records were final models taken at time of fixed appliance removal. Specific

points on the dentition were measured to gather information including: intercanine width, intermolar width, and arch depth.

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Analysis of the data showed no significant difference between the early extraction and late extraction groups. All values in the early group were slightly less in dimension than the late extraction group. Statistical

analysis showed significance when the maxillary and mandibular intermolar dimensions and maxillary intercanine dimensions of the nonextraction group were compared to the extraction groups. The nonextraction intermolar dimensions

were larger than both extraction groups. The late extraction group had a larger intercanine transverse measure. The consideration of tooth removal has been thought to negatively affect the breadth of the arch and accordingly smile esthetics. Extractions before total canine eruption

have no narrowing effects in comparison to extractions in the permanent dentition.

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TRANSVERSE ARCH DIMENSIONAL CHANGES IN CLASS I NONEXTRACTION, EARLY EXTRACTION AND LATE FIRST BICUSPID EXTRACTION PROTOCOLS

Michael Larson, D.D.S.

A Thesis Presented to the Faculty of the Graduate School of Saint Louis University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Dentistry 2010

COMMITTEE IN CHARGE OF CANDIDACY: Professor Eustaquio Araujo, Chairperson and Advisor Professor Rolf G. Behrents Assistant Professor Ki Beom Kim

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Dedication

To my girlfriend Jessica who has given more than her fair share of compassion and support these past several years. The example she has set has enabled me to endure I love her

academics and our long distance relationship.

much and appreciate her tireless love and support.

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Acknowledgements I would like to extend special thanks Dr. Araujo for his guidance and expertise through this project. Araujo's knowledge has been invaluable. Dr.

As well, Dr.

Kittleson has entrusted his time and office resources for this study. Without his generosity I would have not been able to collect my data at a convenient time. I am also grateful for Dr. Behrents availability and insight on this project. generosity of time. Dr. Kim's time investment has been much help. I thank him for his dedication and inspiration through this busy time. I have much appreciation for his

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Table of Contents

List of Tables.........................................v List of Figures.......................................vi CHAPTER 1: Introduction................................1 CHAPTER 2: Literature Review History.....................................4 Extractions................................10 Dental arch development....................16 General transverse arch changes............17 Intercanine width..........................19 Intermolar width...........................21 Sexual dimorphism..........................22 Arch length................................24 Effects of treatment on arch form..........26 Reference List.............................28 CHAPTER 3: Journal Article Abstract...................................32 Introduction...............................34 Materials and Methods......................37 Statistical Analysis.......................39 Results....................................41 Discussion.................................45 Conclusions................................53 References.................................54 Vita Auctoris.........................................57

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List of Tables

Table 2.1

Indications and contraindications for serial extraction procedure.........................13

Table 3.1

Wilcoxon signed-rank test....................39

Table 3.2

Descriptive statistics for nonextraction group .............................................42

Table 3.3

Descriptive statistics for early extraction group........................................42 Descriptive statistics for late extraction group........................................42

Table 3.4

Table 3.5

Independent samples t-test for nonextraction versus early extraction and late extraction groups.......................................43 Independent samples t-test for early versus late extractions.............................44

Table 3.6

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List of Figures

Figure 2.1

Four first bicuspid extraction trend: 40 Year study................................8

Figure 2.2

Stages of root development..................16

Figure 2.3

Human development: Cephalocaudal growth from 2 months to 25 years of age.................17 Average transverse arch changes from birth to 25 years.................................19 Intercanine distance........................21

Figure 2.4

Figure 2.5

Figure 2.6

Intercanine width changes between sexes; mixed dentition, early permanent and late permanent dentitions........................23 Intermolar width changes in males and females.....................................23 Male and female arch length changes.........26 Transverse arch dimensions..................40 Arch depth dimensions.......................40 Maxillary mean transverse measurements for nonextraction, early extraction and late extraction groups...........................48 Mandibular mean transverse for nonextraction, early extraction and late extraction groups...........................48

Figure 2.7

Figure 2.8 Figure 3.1 Figure 3.2 Figure 3.3

Figure 3.4

Figure 3.5

Mean arch transverse dimensions for serial extraction study compared to early extraction study...........................51

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Figure 3.6

Mean arch values for nonextraction data from Bishara study compared to early and late extraction transverse data.................52

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Chapter 1: Introduction

The patient's best interest are at heart when orthodontic therapy is sought. Technology has assisted Modern cements have

practitioners in reaching this goal.

been employed allowing for a significant decrease in the use of orthodontic bands, prescription bracketry, and specialized x-ray equipment allow orthodontists to thoroughly consider all options for the patient. When a

patient presents with a differential between arch size and excess tooth mass, extraction is a treatment of choice. There are three primary reasons for extraction therapy; 1)dental crowding,2)incisor protrusion and 3)camouflaging of skeletal imbalances. Dental crowding ranks highest

amongst indications for extraction.1 When it is determined that dental crowding is evident at an early age, for example in the mixed dentition, when should orthodontic intervention occur? For a clinician to

orchestrate procedures at varying ages it is important that an understanding of growth and the differing effect treatments could have on arch development. Arch development is facilitated by the eruption of succedaneum teeth and accompanying bone. The teeth as well

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as the supporting bone add width and height to a patient's smile.2 The literature regarding arch development primarily consider anteroposterior arch changes. Moorrees

investigated the changes in arch length from the primary dentition to the permanent dentition, with special consideration of leeway space.3 This facilitated the

rationale for a resurgence of early treatment mid-century. It came in the form of a procedure referred to as serial extraction. Serial extraction allowed for decreased

crowding, decreased treatment duration, to name a few advantages. This procedure was not without

shortcomings,including lingual tipping of incisors, increased overbite, and mesial migration of the buccal segments.4-7 This era was followed by retention studies

concluding that no greater stability of the arches was achieved with serial extraction.8 Of the studies that exist which evaluate the effects of early extractions of first bicuspids on the developing dentition few address changes in the transverse dimension.9,10 This study will explore the effects of four bicuspid extraction in the transverse dimension of the upper and lower dental arches performed at different time points. In

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this study "early" is defined as a period of time before the permanent maxillary cuspids have erupted and "late" as the period of time following eruption of the permanent maxillary cuspids. treatment casts. The data will be collected from post-

The sample will consist of three groups;

the first group will consist of a non-extraction protocol, the second group will involve an early extraction protocol and the third group will involve extractions at a later time. The purpose in this study will be to determine whether four bicuspid extraction performed at different times(early versus late) would have an impact on arch dimensions in the transverse dimension.

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Chapter 2: Literature Review

This literature review will proceed through the factors correlated to extractions in orthodontics and the effect they have on the dentition. For a complete understanding

of the development of the human dentition this review will initiate thoughts and concerns of dental arch development and a discussion of arch length and its maturation and changes through an individual's life. Though past

literature has given much consideration to arch depth and how this factor contributes to Angle's Class I occlusion a discourse on arch width will be the focus of this review. History In the early nineteenth century extractions were commonplace. The primary rational was removal of teeth The method and reasoning of

that were severely malaligned.

this liberal time fell out of favor in the late nineteenth century as E.H. Angle's philosophy came into prominence. Angle's ideals surrounded the concept of focusing on the relationships of the teeth and jaws and balance. With

these set in place harmony and proportions would follow. Angle's philosophy necessitated a full complement of teeth in their normal positions thus balance, harmony and proper proportions would be achieved.11 Additionally, this

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philosophy of expansion was consistent with Wolff's law that bone would form in response to stress placed on it, hence bone would follow where teeth were placed. Angle's prominence was wide-spread. Angle was the

first to start an orthodontic school and thus able to influence many educators. His influence lasted for many

years and even now some of his philosophy continues to be practiced. In the late 1800s one opponent to Angle's nonextraction dogma was Calvin S. Case. Case placed emphasis

on facial esthetics and their relationship to orthodontics and extractions. In "The extraction debate of 1911" Case

confronted the nonextractionists with a strong statement, "While I should dislike to destroy or even weaken the theological belief of anyone who finds comfort in his religion, I feel that a question of such importance demands the whole truth from the advanced standpoint of evolution." It opened an important discussion on extractions in orthodontics. Case presented 15 bimaxillary protrusion

cases to clarify that in rare instances a need for extractions should be considered.12 He had a persuasive

argument suggesting that the public would demand better profiles and that would cause orthodontics to reflect upon changes. The level of extractions suggested by him was a

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small percentage in the practice of orthodontics, 6%.13 Unfortunately, Case's ideas were generally ignored by mainstream orthodontia. Events unfolded and the non-extraction dogma began to weaken. Roughly 30 years passed with stability issues The primary issue that

arising from the expansion camp. arose was relapse.

Lundstrom introduced the term apical The

base and its association with orthodontic limits.14

author believed that if teeth are placed over a deficient apical base relapse will occur at the end of the retention period. Following Lundstrom's thesis Tweed and Begg Tweed was disappointed with

philosophies became prominent.

profile changes and relapse and followed up on 100 cases with four 1st bicuspid extractions. Tweed developed his

analysis with a main focus on the position of the mandibular incisors. Many followed Tweed's principles and

are still convinced they are able to provide a better diagnosis and treatment. Seminars were and still are On a similar note Begg Located

conducted on his philosophy.

independently abandoned the non-extraction policy.

in Australia, Begg devised his own treatment mechanics with the multiloop light-wire technique. Begg made the

assumption that the tooth size variation was the cause for malocclusion and without natural interproximal wear

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crowding would result.15

The author suggested that tooth

size irregularity was as much at fault to malocclusion as jaw size. By mid-twentieth century the extraction debate was once again reopened. A publication by Riedel in the late

1950s highlighted facial esthetics as the prime objective of orthodontic therapy. This study investigated profiles It is stated

of beauty contestants in Seattle, Washington.

that soft tissue is closely related to the skeletal and dental tissues beneath. The top contestants recorded

measurements within one degree or one millimeter of Down's means. In many ways the publics' concept of facial

esthetics are in close agreement with orthodontists' standards of normal occlusion, however, a more protrusive profile was sought by those who judged the participants.16 For an understanding of the changes in extraction frequency over the past century the data from the University of North Carolina serves as a benchmark for reference. In this clinical review Proffit outlines a The extraction trends observed are

forty year time period.

most pertinent to the removal of four first bicuspids. Other extraction choices, for example one lower incisor or three first bicuspids and one second bicuspid over the duration of the study were consistently approximated at 15%

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of the total extraction frequency and were not statistically significant. During the early 1950s

extractions were utilized in approximately 30% of the total patient population. The peak of extractions took place in

the 1960s with 76% of patients receiving extraction therapy. By the early 1990s extraction protocols were on

the decline, constituting approximately 28% of the orthodontic therapies.17 This trend can be observed in the

first bicuspid extraction frequency in Figure 2.1.

Four first Bicuspid extractions

60 Percent Patients 50 40 30 20 10 0 1953 1958 1963 1968 1973 Year 1978 1983 1988 1993

Figure 2.1 Four decades of extraction trends at UNC. Adapted from Proffit.17

The trend of extraction protocols has shown a rise and fall over the past century. Early in the twentieth century

the push by Calvin Case for extractions surrounded the 8

topic of esthetics and the need to provide a therapy for the protrusive profiles that expansion treatments were falling short of.13 By the 1930s stability was in question, Both Begg and

arches collapsed and relapse was a concern.

Tweed who were taught under the expansion philosophy chose to abandon the non-extraction treatment and devise their own mechanics and/or modify what was in use. They led the

discussion on this philosophy, each having his own idea for the nature of collapsed arches.17 Unfortunately, their

methods were unsubstantiated and relapse still occurred. Little and co-workers contributed with relapse studies. Little's 10 year longitudinal study highlighted the fact that a significant percentage of patients(73%) experienced unsatisfactory anterior alignment postretention.8 Additionally, esthetics became a factor and the public felt that profiles were being flattened and the greater dental community was criticizing orthodontist's extraction guidelines.18 Despite literature supporting a lack of

connection between extractions and temporomandibular dysfunction the threat of lawsuits also helped decrease extractions.19 Along with these concerns technology also had a part, contributing to changes in extraction decision making. Managing borderline extraction cases became easier with

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decreased interproximal band material and the introduction of bonded brackets with modern cements.20 Andrew's straight

wire appliance also eased the technical difficulties encountered with standard edgewise appliances.21 Orthopedics became a factor with the re-introduction of extraoral anchorage by Silas Kloehn, palatal expansion and the popularity of functional appliances.22 Earlier

treatment was then proposed with literature supporting the use of leeway space to help resolve crowding. Gianelly

reported that 72% of cases with an average of 4.4 mm of crowding can be resolved by preserving the leeway space. Furthermore, patients that lost a primary canine early can expect even more crowding and a 40% chance of resolving this level of crowding with leeway space preservation.23 Management of borderline cases helped as well with more approaches to expansion of the arches.24 Furthering the

incentives for nonextraction protocols are literature stating a 3-6 month less treatment time than extraction treatments.25 With all these factors practitioners nowadays

highly consider nonextraction treatment. Extractions One of the most common reasons patients seek orthodontic therapy is to correct dental crowding. In general,

practitioners have three primary methods to choose from

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when correcting crowding: extraction, expansion, and molar distalization. This discussion will touch lightly on

expansion and distalization, yet focus on extractions and how this form of therapy can be best used to meet the patient's chief complaint of a crowded dentition. Goals for extraction therapy cover three primary areas; 1)dental crowding, 2)incisor protrusion, and 3)camouflaging of skeletal imbalances. Baumrind and co-workers elaborated on why clinicians would choose to extract. Four main areas were noted,

dental crowding, incisor protrusion, improved profiles, and camouflaging of skeletal imbalances. Upon review of the

findings, crowding was found in 72% of the individual clinician decisions to extract, followed by incisor protrusion with 35%, and profile improvement at 27%. 71% of the entire sample at least one of these three criteria were consistently considered first when the decision to extract was made.1,26 In agreement with these In

extraction criteria Paquette and co-workers found that in the decision to extract three of the four mentioned by Baumrind are also chosen; crowding, protrusion and profile.27 Strang believed that with the extraction of dental units and the distalization of the canines came slight

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buccal expansion.28

Strang suggested this movement was in

better agreement with the muscular balance. The above criteria addresses patients in the permanent dentition, however, if the patient arrives at a period of time that correction of the malocclusion could occur at a younger age should consideration be given to initiate orthodontic therapy? For example, if an exam is completed

at a young age with special notes made to space analysis yielding an arch length discrepancy, should the extractions begin at this time? Serial extraction was widely used in orthodontics, especially in the 1950s and 1960s. It is a well known

procedure that severe dental crowding in the mixed dentition can be addressed through a sequential removal of deciduous and permanent teeth. The approximate age range It is often indicated

for serial extraction is 7-10 years.

for Class I skeletal and dental relationships and for severe crowding ranging from 7-10mm. This procedure

necessitates a sequential and timely removal of specific primary and permanent teeth in order to guide the eruption of the permanent teeth and thus minimize the severity of

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Table 2.1 Indications and contraindications for serial extraction procedure. Indications Arch length discrepancy Impacted lateral incisors Unilateral deciduous canine loss Contraindications Class II Diagnosis Class III Diagnosis Crowding in one arch only Inability to follow case to completion Abnormal resorption Gingival recession at mandibular incisors the malocclusion.29 Congenitally missing teeth

Table 2.1 outlines indications and

contraindication for serial extraction procedures. Though other extraction sequences can be chosen the most common extraction sequence for serial extraction is the removal of primary followed by permanent dental units, deciduous Cs and Ds and first bicuspids.30 The use of periapical radiographs in guiding the timing of extractions is recommended.31 It was believed

that extraction of primary dental units prior to their exfoliation could influence the erupting succedaneous dentition. Dewell believed that early extractions of

primary teeth delayed the development and growth of an already compromised dental arch. Furthermore, he suggested

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that early enucleation of dental follicles would impede the growth of the alveolar process.32 Fanning's studies advanced knowledge of the effects of timing of primary extractions in relation to accompanying succedaneous tooth eruption. Fanning conducted a

longitudinal study on tooth eruption and was a split mouth design where half the arch underwent unilateral early extraction of primary molars. The control side underwent The

normal development and eruption of permanent teeth.

findings suggested a spurt in the eruption of the first premolars regardless of its stage of development or the age at which the primary molar was removed. And the extraction

of primary units had no effect on root development of the permanent premolar. Additionally, the eruption of first

premolars was observed early only when the primary tooth was extracted with a more mature permanent tooth root. Otherwise, if permanent root development is not mature enough a delay will be experienced in its eruption velocity. Fanning suggested that the delay is related to

scar tissue development.33 Moorrees et al. combined a previous study of tooth maturity to clarify the timing of early extractions in the mixed dentition. The use of periapical radiographs allowed

the grouping of 3 key intervals, ¼ to ½, ½ to ¾ and ¾ to

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fully a developed root(figure 2.2).

This publication

established the importance of timing and in general ¾ of root development was achieved before eruption of succedaneous teeth. The emphasis was to gauge extractions The

on root development and not chronological age.

requirement was made that periapical radiographs should be taken every three to six months to follow the root's development. Moorrees et al. advised that extraction of

primary dental units may occur with a minimum of ½ root development for a delay in the eruption of the succedaneous tooth not to occur. The only exception to this protocol is

if the developing tooth is in close proximity to the alveolar crest, thus just ¼ root development would be required in this scenario.34

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Figure 2.2 Stages of root development. Correlation of root development to dental maturity.34

Dental arch development Much is known about the growth and development of the head and face. In general, growth and development For example, in The head

progresses in a cephalocaudal direction. Figure 2.3 body proportions are depicted.

consumes approximately fifty percent of a two month old fetus as compared to 30% by birth.17 During growth the

skull changes in shape and size are determined by sutural, cartilaginous, periosteal and endosteal bone deposition and resorption.35 Overlayed on these basic trends is the

dimensions of the face that terminate their growth at set times during development. The first dimension to finalize

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is the face's width at approximately 12 years of age or just before puberty, then the anteriorposterior dimension at approximately 14 years followed by height, and this dimension will continue to grow thoughout an individual's life.

Figure 2.3 Human development. Cephalocaudal growth from 2 months to 25 years of Age.17

General transverse arch changes A review in the area of arch width normally surrounds three variables, intercanine, intermolar and general transverse arch changes. latter. The review will begin with the

The growth of the dental arches generally precedes

the eruption of the groups of teeth and further there is similarity in the maxillary and mandibular arch width changes.36 Burson chose to use as the reference of

beginning of the growth spurt the eruption of the lower

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incisors because he noted that a relationship existed between the spurt and the eruption of the permanent incisors.33,37,38 The majority of cases in Burson's sample

began their growth spurt one to two years before the lower central incisors erupted, or approximately five to six years of age in the deciduous dentition. Sillman

highlights this character by the use of five time points, 4, 8, 12, 16, and 20 years of age(figure 2.4).36 Generally

from birth to 4 years much of the transverse jaw growth is achieved. From four years of age on the growth increments The difference between the mandible

are less pronounced.

and the maxilla is seen between the time intervals of 8 and 12 years with the maxilla having a larger rate of change than the mandible. And the decrease in transverse

dimension observed from ages 16 to 20 years may not be clinically perceptible. Completion of growth in width

according to Burson is six years past the eruption of the central incisors(11 years of age). Similarly, Morrees's

average intercanine graphs indicate a plateau at approximately the same time, six years post eruption of the central incisors or 11 years of age. Conversely, authors

Barrow and White and Sillman argue that intercanine width

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Figure 2.4 Average transverse arch changes from birth to 25 years.36

decreases during the maturation of the permanent dentition.39 Intercanine width A University of Iowa longitudinal study by Knott reports on growth findings over a twenty year span. width between the permanent canine teeth averaged approximately 2.0mm greater than between the deciduous canine teeth. Mean increases for males and females are The

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between 5.5 and 6.0mm for deciduous maxillary incisor width to permanent incisor width, roughly 3.5 mm for mandibular incisor width and 2.8 mm for both maxillary and mandibular deciduous canine width.40 When addressing intercanine dimension Barrow states: The essential findings under this heading were: (1) there was little intercanine arch width change from 3 to 5 years of age; (2) the intercanine width increased very rapidly from 5 to 8 or 9 years of age. (The amount of change was approximately 4mm in the maxillary arch and 3mm. in the mandibular arch.) (3) in most cases the maxillary and mandibular intercanine arch widths steadily decreased in amount varying between 0.5mm. and 1.5mm. after 14 years of age.39

Moorees et al. agree with this general trend.

With the

emergence of the permanent maxillary and mandibular incisors comes an increase in arch width(figure 2.5).34 an average boy or girl the arch has enough space to accommodate the difference in size of the permanent incisors, approximately 7.4mm. wider than the primaries.41 Moorrees agrees with a decrease in intercanine distance from 10 to 12 years, however it does not indicate a steady decrease, conversely he suggests that intercanine width will remain stable into adulthood. Sinclair, as well In

agrees on the finding that intercanine width will remain stable once permanent canines have erupted.34 Moorrees

illustrates that intercanine width in the mandibles and

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maxillas of males and females does not change significantly past age 10 and 12, respectively.

Figure 2.5 Transverse canine dimension from deciduous to permanent dentition.34

Intermolar width Barrow studied 528 sets of serial casts from 51 children and drew conclusions on arch width.39 In the

primary dentition, between the ages of 5 and 10 years width measured at the second primary molars in maxillary and

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mandibular arches increased approximately 1.5mm.

This

increase in width is likely due to remodeling of alveolus and transverse jaw growth.

For the transverse dimension of the permanent first molars Barrow indicates: from 7 to 11 years of age the average increase in intermolar width was 1.8mm in the maxillary arch and 1.2mm in the mandibular arch. From 11 to 15 years of age there was an average decrease in intermolar width of 0.4mm in the maxillary arch and 0.9mm in the mandibular arch. This decrease in intermolar width following the 11 year reading was due, in our opinion, to mesial drift of the first permanent molars after the loss of the primary molars.2

Moorrees disagree with a decrease in intermolar widths between ages nine and 14. Their paper describes a

significant increase in intermolar width during this time. In ages beyond 14 years the dimension stays the same.3 Sinclair agrees with intermolar widths remaining stable.41

Sexual dimorphism When considering sexual dimorphism and intercanine widths, Sinclair reports that both sexes displayed significant decreases of mandibular intercanine width from mixed to early adulthood(figures 2.6,2.7).

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26 Intercanine width (mm)

25.5 Male Female

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24.5

24 T1 T2 Time T3

Figure 2.6 Intercanine width changes between sexes. Intercanine changes at mixed, early permanent, late permanent dentitions, T1, T2, and T3 respectively. Adapted from Sinclair.41

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Intermolar width (mm)

44 Female 43 Male

42 T1 T2 T3

Time

Figure 2.7 Intermolar width changes in males and females. Intermolar changes at mixed, early permanent, late permanent dentitions, T1, T2, and T3,respectively. Adapted from Sinclair.41

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Males had a gradual decrease and females had a major decrease between early permanent and early adult dentitions. For the entire sample both populations showed significant changes in intermolar width between timepoints T1 and T3. Between T2 and T3 females had a significant And an increase was observed

decrease in intermolar width. in the male population.41

Arch length The literature has many references to crowding and the importance of arch length. This dimension is the focus of

many discussions when comparing deciduous to permanent dentitions. For example, utilization of leeway space for

late mixed dentition treatments is the rationale for employing early treatment. In the analysis of 49

individuals the total arch depth decreased from deciduous to permanent dentitions according to Speck.42 Similarly,

Moorrees et al. recorded a decrease in arch length during the transition to permanent dentition. Referring to figure

2.8 the arch length is greatest at age three, at three years of age the primary dentition is complete. The next

significant change that occurs is upon the exfoliation of the primary second molars at approximately 10 years of age.

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With the loss of primary dental units the space that is lost is mesial to the first molars. The arch length will

roughly stabilize by age 14 in most individuals with the eruption of the permanent second molars. From the Moorrees

data arch length remains stable up to 18 years of age. Sillman agrees with this trend of loss of arch length and stability in arch length up to the eruption of the third molars. The maxilla arch length decreases 1.5mm per side and 2.0 mm per side in the mandible.36 Additionally, these

values have been reported with values of 1.2mm loss per side in the maxilla and 2.2mm loss in the mandible.3 With

progressing age arch length will continue to decrease by a small amount.2,43 DeKock found a one percent difference between the sexes(males with greater loss) regarding arch length loss thus, concluded no sexual dimorphism existed as it related to arch length.44

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Figure 2.8 Male and female arch length changes.34

Effects of treatment on arch form With the literature to date practitioners are hard pressed to find definitive answers regarding treatment for borderline extraction cases. Even with the addition of

headgear, TADs, technologically advanced cements and prescription brackets on many occasions it comes down to, do we extract or expand? Extraction therapy allows space

for teeth in the arch as well could cause widening of the arches that are controversial in their own right.28,45-47 Some have stated that stable expanded arch dimensions can

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be maintained while others require a lifetime of retention to maintain any and all orthodontic therapies.8,48-50 Paquette and coworkers state that between their longitudinal study of borderline extraction and nonextraction the two groups displayed virtually the same pattern of relapse during post-treatment. Here this

stability problem was correlated to variable growth amongst individuals than on treatment protocol.27 difficult concept to predict. Growth is a

How can orthodontists debate

that expansion or extraction is a better philosophy when many changes that occur are regulated by the individual's genetics already. Diversity is the rule when it comes to Further

growth and development amongst subjects.

complicating an analysis of changes is where to place landmarks. Which are most reliable since we are

essentially placing a lot of emphasis on what is accessible; intermolar, intercanine and contact points, for instance. These locations are inherently labile and can So

change easily with torque or tip placed in brackets.

yes we need to assess the fruits of our labor by measuring these locations and realize that they can be seen as a clinically significant outcome by simply placing brackets and wire on the arches.

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Reference List 1. Baumrind S, Korn EL, Boyd RL Maxwell R. The decision to extract Part 1-Interclinician agreement. Am J Ortho Dentofac Orthop 1996;109:297-309 2. Barrow,G. Developmental Changes of the maxillary and mandibular dental arches. Am J Orthod 1952;22:41-46. 3. Moorrees CF, Gron AM, Lebret LM, Yen PK, Frohlich FJ. Growth studies of the dentition: A Review. Am J Orthod 1969;55:600-616. 4. Ringenberg, Q.M. Influence of Serial extraction on growth and development of the maxilla and mandible. Am J Orthod 1967:53:19-26. 5. Dewell,B. Serial extraction: Its limitation and contraindications in orthodontic treatment. Am J Orthod 1967;53:904. 6. Graber T.M. Serial extraction: A continuous diagnostic and decisional process. Am J Orthod 1971;60: 541-575. 7. Wagner, M. Serial extraction or premolar extraction in the permanent dentition? Comparison of duration and outcome of orthodontic treatment. J Orof Orthop 2000;61:207-216. 8. Little RM, Serial extraction of first premolarsPostretention evaluation of stability and relapse. Angle Orthod 1994;60:213-226. 9. Wilson, JR, Little RM, Joondeph DR, Doppel DM. Comparison of soft tissue profile changes in serial extraction and late premolar extraction. Angle Orthod 1999;69:165-174. .

10. Johnson DK, Smith RJ. Smile esthetics after orthodontic treatment with and without extraction of four first premolars. Am J Orthod Dentofac Orthop 1995;108:162-7. 11. Bernstein L. Edward H Angle versus Calvin S. Case: Extraction versus nonextraction. Historical revisionism Part II. Am J Orthod Dentofac Orthop 1992;102:546-551. 12. Case C. The extraction debate of 1911 by Case, Dewey and Cryer. Am J Orthod 1964;50:900-912.

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13. Wahl, N. Orthodontics in 3 millennia. Chapter 6: More early 20th-century appliances and the extraction controversy. Am J Orthod Dentofac Orthop 2005;128:795-800. 14. Lundstrom A. Malocclusions of the teeth regarded as a problem in connection with the apical base. Int J Orthod Oral Surg 1925;11:591-612. 15. Begg PR. Stone age man's dentition. Am J Orthod 1954; 40:373-383. 16. Riedel RA. An analysis of dentofacial relationships. Am J Orthod 1957;43:103-119. 17. Proffit WR. Forty-year review of extraction frequencies at a university orthodontic clinic. Angle Orthod 1994;64:407-414. 18. Erdinc AE, Nanda RS, Dandajena TC. Profile changes of patients treated with and without premolar extractions. Am J Orthod Dentofac Orthop 2007;132:324-331. 19. Luther F. Orthodontics and the temporomandibular joint: Where are we now? Part 1.Orthodontic treatment and temporomandibular disorders. Angle Orthod 1998;68:295-304. 20. Evans LS, McGrory KR, English JD, Ontiveros JD, Powers JM, Frey GN, Duke J. A comparison of shear bond strengths among different self-etching primers. Tex D J 2009;126:3129. 21. Andrews LF. The straight wire appliance. J Clin Orthod 1976;114:174-195. 22. Darendeliler N, Taner-Sarisoy L. The influence of orthodontic extraction treatment on dental structures: a two-factor evaluation. Eur J Orthod 2001;23:295-303. 23. Gianelly AA. Treatment of crowding in the mixed dentition. Am J Orthod Dentofac Orthop 2002;121:569-571. 24. Brust EW. Arch dimensional changes concurrent with expansion in the mixed dentition[thesis]. Ann Arbor: University of Michigan, 1992. 25. Skidmore KJ, Brook KJ, Thomson WM, Winifred JH. Factors influencing treatment time in orthodontic patients. Am J Orthod Dentofac Orthop 2006;229:230-8.

29

26. Baumrind S, Korn EL, Boyd RL Maxwell R. The decision to extract: Part II. Analysis of clinicians' stated reasons for extraction. Am J Ortho Dentofac Orthop. 1996;109:393402. 27. Paquette DE, Beattie JR, Johnston LE. A long-term comparison of nonextraction and premolar extraction edgewise therapy in "borderline" Class II patients. Am J Ortho Dentofac Orthop 1992;104:1-14. 28. Strang RHW. The fallacy of denture expansion as a treatment procedure. Angle Orthod 1949;19:12-17. 29. Araujo EA. The effect of serial extraction on Class I malocclusions: A one year report on the behavior of the incisors and canines. Masters thesis, University of Pittsburgh 1981. 30. Dewell BF. A critical analysis of serial extraction in orthodontic treatment. Am J Orthod 1959;45:424-455. 31. Hotz RP. Guidance of eruption versus serial extraction. Am J Orthod 1970;58:1-20 32. Dewell BF. Serial extraction in orthodontics: Indications, objectives and treatment procedures. Am J Orthod 1954;40:906-926 33. Fanning EA. Effect of extraction of deciduous molars on the formation and eruption of their successors. Am J Orthod 1962;32:44-53. 34. Moorrees CF, Fanning EA, Gron AM. Consideration of dental development in serial extraction. Angle Orthod 1963;33:44-59. 35. Enlow DH, Bang S. Growth and remodeling of the human maxilla. Am J Orthod 1965;51:446-464. 36. Sillman JH. Dimensional changes of the dental arches: Longitudinal study from birth to 25 years. Am J Orthod 1964;50:824-842. 37. Meredith HV, Hopp WM. A longitudinal study of dental arch width at the deciduous second molars on children 4 to 8 years of age. J D Res 1956;35:879-889.

30

38. Goldstein MS, Stanton FL. Changes in dimension and form of the dental arches with age. Int J Orthod Oral Surg 1935;21:357-380. 39. Barrow GV, White JR. Developmental changes of the maxillary and mandibular dental arches. Angle Orthod 1952;22:41-46. 40. Knott V. Longitudinal study of dental arch widths at four stages of dentition. Angle Orthod 1972;42:387-394. 41. Sinclair P. Maturation of untreated normal occlusions. Am J Ortho Dentofac Orthop 1983;83:114-123. 42. Speck NT. A longitudinal study of developmental changes in human lower dental arches. Angle Orthod 1950:20:215-228. 43. Brown VP, Dagaard-Jensen I. Changes in the dentition from the early teens to the early twenties. Acta Odontol Scand 1951;9:177-192. 44. DeKock WH. Dental arch depth and width studied longitudinally from 12 years of age to adulthood. Am J Orthod 1972;62:56-66. 45. Steiner CC. Orientation of the teeth in the dental arches. Angle Orthod 1934;4:35-56. 46. MacCauley D. The canine and its function in retention. Int J Orthod 1944;30:196-205. 47. Uhde MD,Sadowsky C, Begole EA. Long-term stability of dental relationships after orthodontic treatment. Angle Orthod 1983;53:240-252. 48. Walter DC. Changes in the form and dimensions of dental arches resulting from orthodontic treatment. Am J Orthod 1953;23:3-18. 49. Sadowsky C, Schneider BJ, BeGole EA, Tahir E. Long-term stability after orthodontic treatment: Nonextraction with prolonged retention. Am J Ortho Dentofac Orthop 1994;106:243-9. 50. Glenn G. Nonextraction orthodontic therapy: Postreatment dental and skeletal stability. Am J Orthod 1987;92:321-8.

31

Chapter 3: Journal Article

Abstract The primary reason for treatment sought by patients is crowding. Among the possible ways to alleviate crowding, With the

extraction is one of the treatments of choice.

use of extractions and fixed orthodontic appliances the crowding is resolved and the remaining spaces are closed and as a result alignment of the dentition is complete. The purpose of this study was to evaluate maxillary and mandibular arch development in the transverse dimension utilizing extractions at varying times (early vs. late protocols). In this study we defined "early" as a period

of time before the permanent maxillary cuspids have erupted and "late" as the period of time following eruption of the permanent maxillary cuspids. The sample consisted of 90 dental casts from a population of orthodontically treated Class I malocclusion mixed dentition subjects. All dental models were collected

from a single private practice and all records were final models taken at time of fixed appliance removal. Specific

points on the dentition were measured to gather information including: intercanine width, intermolar width, and arch depth.

32

Analysis of the data showed no significant difference between the early extraction and late extraction groups. All values in the early group were slightly less in dimension than the late extraction group. Statistical

analysis showed significance when the maxillary and mandibular intermolar dimensions and maxillary intercanine dimensions of the nonextraction group were compared to the extraction groups. The nonextraction intermolar dimensions

were larger than both extraction groups. And the late extraction group had a larger intercanine transverse measure. The consideration of tooth removal has been thought to negatively affect the breadth of the arch and accordingly smile esthetics. Extractions before total canine eruption

have no narrowing effects in comparison to extractions in the permanent dentition.

33

Introduction

The patient's best interests are at heart when orthodontic therapy is sought. Technology has assisted

practitioners in reaching this goal; modern cements have been employed allowing for a significant decrease in the use of orthodontic bands, prescription bracketry, and specialized x-ray equipment allow orthodontists to thoroughly consider all options for the patient. When a

patient presents with a differential between arch size and excess tooth mass, extraction is a treatment of choice. There are three primary reasons for extraction therapy; 1)dental crowding,2)incisor protrusion and 3)camouflaging of skeletal imbalances. Dental crowding ranks highest

amongst indications for extraction.1,2 When it is determined that dental crowding is evident at an early age, for example in the mixed dentition, when should orthodontic intervention occur? For a clinician to

orchestrate procedures at varying ages it is important that an understanding of growth and the differing effect treatments could have on arch development. Arch development is facilitated by the eruption of succedaneum teeth and accompanying bone.3 The teeth as well

34

as the supporting bone add width and height to a patient's smile. The literature regarding arch development primarily consider anteroposterior arch changes. Moorrees

investigated the changes in arch length from the primary dentition to the permanent dentition, with special consideration of leeway space.4 This facilitated the

rationale for a resurgence of early treatment mid-century. It came in the form of a procedure referred to as serial extraction. Serial extraction allowed for decreased

crowding, decreased treatment duration, to name a few advantages. This technique was not without

shortcomings,including lingual tipping of incisors, increased overbite, and mesial migration of the buccal segments.5-8 This era was followed by retention studies

concluding that no greater stability of the arches was achieved with serial extraction.9 Of the studies that exist which evaluate the effects of early extractions of first bicuspids on the developing dentition few address changes in the transverse dimension.10,11 This study will explore the effects of four bicuspid extraction in the transverse dimension of the upper and lower dental arches performed at different time points. In

35

this study "early" is defined as a period of time before the permanent maxillary cuspids have erupted and "late" as the period of time following eruption of the permanent maxillary cuspids. treatment casts. The data will be collected from post-

The sample will consist of three groups;

the first group will consist of a non-extraction protocol, the second group will involve a early extraction protocol and the third group will involve extractions at a later time. Our purpose in this study will be to determine whether four bicuspid extraction performed at different times(early versus late) would have any impact on arch form in the transverse dimension.

36

Materials and Methods

The inclusion criteria for the two extraction groups included bilateral extractions of first bicuspids indicated in both jaws. The sample consisted of 90 dental casts from

a population of orthodontically treated CI malocclusion subjects. All dental models were collected from a single All records were final models taken at The total sample was

private practice.

time of fixed appliance removal.

divided into three groups of 30 each, following these criteria. Group 1, nonextraction, Group 2, early four

bicuspid extraction performed before the eruption of the maxillary canines, Group 3, late four bicuspid extraction, extraction following maxillary canine eruption with moderate to severe crowding followed by fixed appliance therapy. The inclusion criteria for the nonextraction

group was mild crowding, full complement of teeth and fixed appliance therapy. Subjects for all three groups were

excluded in cases of congenitally missing primary or permanent teeth excluding permanent third molars, single or multiple tooth crossbite, Class II or Class III Angle classification, anterior openbite, and impacted or ankylosed teeth.

37

The orthodontic casts were randomly assigned a sequential number by the treating orthodontist and were then evaluated for inclusion by the principal investigator. Data collection involved photocopying dental casts on an office copy machine. All copies were made on the same A 100mm ruler was

photocopier by the investigator.

utilized during copying to account for magnification error that occurred through recording. To further decrease the

likelihood of magnification error the casts were placed with the occlusal plane face down and as parallel to the surface of the copier as possible. The sample was digitized using Dentofacial Planner software. A total of seven landmarks were recorded. The

digitized landmarks are, the cusp tip of each permanent canine, midpoint of contact point between the permanent central incisors, contact point of permanent second bicuspid and first molar, and the centroids of the molars. These seven landmarks were used to determine six variables between the maxillary and mandibular arches: intercanine width was calculated by the straightline connecting right and left canine cusp tips within each arch, intermolar width was measured by a similar straightline value taken from between the molars, and arch depth was calculated by taking the line that connects the contact points of the

38

first molar and second premolar and intersect this line with the contact of the central incisors(Figures 3.1 and 3.2). Reliability was established by randomly choosing 10% of the sample to re-digitize one month after the data was entered in Dentofacial Planner software. The reliability No

was tested using the Wicoxon rank-signed Test.

significance was found for both the maxillary and mandibular measurements(Table 3.1). All data was reliable.

Table 3.1 Wilcoxon signed-rank test Group Maxillary Intercanine Mandibular Intercanine Maxillary Intermolar Mandibular Intermolar Maxillary Arch Depth Mandibular Arch Depth * Significant at p < 0.05. Significance 0.187 0.717 0.203 0.167 0.831 0.722

Statistical Analysis Descriptive statistics were computed for the six values mentioned earlier. To test between the three groups All

an Independent samples t-test was performed.

differences in mean measurements were held to the 5% confidence level.

39

Figure 3.1 Transverse arch dimensions. Distance between centroids of molars for intermolar width and canine cusp tips for intercanine widths.12

Figure 3.2 Arch depth dimensions. Arch depth calculated from line connecting contact points of second premolar and molar to contact of central incisors.12

40

Results Each group comprised 30 patients for a total of 90 individuals with measurements taken from the maxillary and mandibular dental models. The entire sample had 63 female

and 27 male patients and was divided into three groups of 30 each, following these criteria. Group 1, nonextraction,

Group 2, early four bicuspid extraction performed before the eruption of the maxillary canines, Group 3, late four bicuspid extraction, extraction following maxillary canine eruption. In Table 3.2 the nonextraction descriptive values are represented. This group has 23 females and 7 males. Table

3.3 represents the early extraction sample with 15 female and 15 male patients. Table 3.4 shows the late extraction

sample with 25 female and 5 male patients. For comparison of nonextraction to early extraction and late extraction independent samples t-tests were performed. Three linear measurements in the early and late

extraction groups, maxillary intercanine, maxillary intermolar and mandibular intermolar distances were significantly different (p < .05)(Table 3.5)from the nonextraction group. The mean maxillary intercanine

distance for late extraction was 35.09 mm, maxillary intermolar distance for late extraction was 44.07mm,

41

Table 3.2 Nonextraction group descriptive statistics,minimum, maximum, average and standard deviation. NonExtraction Group Maxillary Intercanine Mandibular Intercanine Maxillary Intermolar Mandibular Intermolar Maxillary Arch Depth Mandibular Arch Depth Min. 32.2 24.0 42.8 36.7 24.9 21.0 Max. 38.0 28.3 54.2 46.6 31.1 26.6 X 34.18 25.96 47.28 41.09 26.96 23.21 S.D. 1.53 0.94 2.54 2.36 1.17 1.26

Table 3.3 Early extraction group descriptive statistics, minimum, maximum, average and standard deviation. Early Extraction Group Maxillary Intercanine Mandibular Intercanine Maxillary Intermolar Mandibular Intermolar Maxillary Arch Depth Mandibular Arch Depth Min. 31.3 24.0 39.7 33.9 17.9 15.7 Max. 39.2 29.0 47.6 41.7 24.1 25.6 X 34.59 26.13 43.66 37.68 20.82 18.03 S.D. 1.81 1.31 2.18 1.77 1.58 1.88

Table 3.4 Late extraction group descriptive statistics, minimum, maximum, average and standard deviation. Late Extraction Group Maxillary Intercanine Mandibular Intercanine Maxillary Intermolar Mandibular Intermolar Maxillary Arch Depth Mandibular Arch Depth Min. 31.4 24.1 39.4 33.2 19.1 15.3 Max. 38.5 29.4 46.8 41.2 24.9 20.9 X 35.09 26.53 44.07 37.78 20.93 17.92 S.D. 1.56 1.32 2.02 1.57 1.27 1.16

42

Table 3.5 Independent Samples t-test Non Extraction treatment versus Early and Late Extraction treatment results of independent t-test(2 tailed) and associated p values. Arch Dimension Non Extraction vs. Early Extraction p values Non Extraction vs. Late Extraction p values 0.028* 0.058 0.000* 0.000*

Maxillary Intercanine Mandibular Intercanine Maxillary Intermolar Mandibular Intermolar

0.353 0.567 0.000* 0.000*

* Significant at p <.05

and the mandibular intermolar was 37.78mm.

In comparison

to nonextraction dimensions; 34.18mm, 47.28mm, 41.09mm, respectively. The mean early extraction values that show

significance are the maxillary intermolar and mandibular intermolar dimensions, 43.66mm, 37.68mm in the early extraction group. The nonextraction respective mean

intermolar values are 47.28mm and 41.09mm. There were no statistical differences in intermolar, intercanine and arch length between the early and late extraction groups(Table 3.6). Furthermore arch depth was not evaluated when

comparing nonextraction to extraction therapies because the extraction of the first bicuspid obligates significance.

43

Table 3.6 Independent samples t-test Arch Dimension Maxillary Intercanine MandibularIntercanine Maxillary Intermolar Mandibular Intermolar Maxillary Arch Depth Mandibular Arch Depth Early Extraction vs. Late Extraction 0.261 0.242 0.458 0.824 0.761 0.774

* Significant at p <.05.

44

Discussion

Few studies have evaluated the transverse dimension of the dental arches with and without orthodontic treatment. The literature presents much discussion on the effects of anteroposterior changes, i.e. leeway space, 1st and 2nd bicuspid extraction effects and retention studies4,9,12 on the dental arches, but little in the transverse dimension. In addition, the literature that discusses this dimension mostly investigated qualitative factors. Few studies

evaluated quantitative changes in mixed and permanent dentitions with regard to bicuspid extraction in the transverse dimension. Lay people perceive their attractiveness based on their smile. This facial view obligates the orthodontist

to place greater attention to frontal photographs and enhancing these dentofacial characteristics for optimal facial esthetics. Additionally practitioners understand

that genetic makeup, environmental influences and cultural background all play an important role in a patient's appearance.13 Premolar extraction treatments have been

characterized by various authors to narrow the dental arches and a decrease the fullness of the dentition within the mouth during smiling.14,15 Also, the practitioner is

45

influenced by advertising supporting a full dentition, ie nonextraction, and the suggestion that this treatment will have a lesser degree of buccal corridors.16 In light of

these anecdotal criticisms the refereed literature evaluates extraction vs. nonextraction on the frontal facial form and contradicts what advertising and previous literature has stated supporting the nonextraction argument.17-20 Johnson and Smith report that there is no predictable relationship between the extraction of premolars and the width of the dentition or esthetics of the smile and suggested that the largest variable to smile esthetics was the practitioners themselves.11 Furthermore, Gianelly

reports that extraction patients do not have narrower arches in the anterior or posterior with 4 first-premolar extractions.21 Does the timing of first bicuspid extractions have an impact on the transverse dimension of dental arches? The

purpose of this study was to evaluate arch width and the impact extractions have on this dimension. Figures 3.3 and 3.4 present maxillary and mandibular arch measurements. For comparison of early extraction to

late extraction treatments, the early extraction group is slightly narrower in every dimension except mandibular arch

46

depth.

However, no values reached statistical significance

between early extraction and late extraction groups in the transverse or sagittal directions. Considering virtually identical transverse and sagittal arch values for the early and late extraction groups one must value the fact that growth was occurring at the time extractions occurred in both groups. The subjects

in the early extraction group underwent bicuspid extractions before the maxillary canines erupted, yet orthodontic appliances were not placed until the permanent dentition had fully erupted. The literature supports a

significant arch width development occurs from six to 10 years of age.3,22,23 By allowing the dentition to erupt

passively following the premolar extractions no hinderance to development in the transverse dimension occurred.

47

50 45 40 35 Millimeter(mm) 30 25 20 15 10 5 0 NE EE LE NE EE LE

26.96 20.82 20.93 34.18 34.59 35.09

47.28

43.66

*

44.07

*

*

NE

EE Mx I-Mol

LE

Mx Arch Depth

Mx I-Canine

Figure 3.3 Maxillary mean transverse measurements for three groups; NE=nonextraction, EE=early extraction and LE=late extraction.

45 40 35 Millimeter(mm) 30 25 20 15 10 5 0 NE EE LE NE EE LE 23.2 18 17.9 25.9 26.2 26.5

41.1

* * 37.7 37.8

NE

EE

LE

Mn Arch Depth

Mn I-Canine

Mn 1-Mol

Figure 3.4 Mandibular mean arch values for comparison of nonextraction, early extraction and late extraction groups. NE=nonextraction, EE=early extraction and LE=late extraction.

48

The nonextraction group differed significantly from both early and late extraction groups. The maxillary and

mandibular intermolar widths were both larger. And the late extraction group displayed significance with the maxillary

intercanine distance being approximately 1mm larger than the non-extraction group. The remaining transverse variables, mandibular intercanine in the early and late groups and the early maxillary intercanine values were very similar in measure to the nonextraction values. The

nonextraction measures for maxillary intermolar distance of 47.28mm and mandibular intermolar distance of 41.1mm were approximately 3mm, 4mm greater than the extraction groups, respectively. This finding suggests that molars were

mesially positioned to a narrower and more anterior location within the arches. In contrast, Gianelly reports

that maxillary and mandibular intercanine and intermolar measures are the same with the exception of the mandibular intercanine distance. The author reported a 0.94mm wider

mandibular intercanine measure in the extraction group.21 Contrary to Gianelly, West found statistical significance with maxillary intercanine and mandibular intermolar dimensions.24 Both values were found to be West's study

narrower in the serial extraction group.

investigated the effect serial extraction had on the

49

development in the transverse dimension.

The trends

observed between the current study and West's study are similar. The serial extraction group reported a lesser

value in transverse dimension than the group that had extractions performed in the permanent dentition. Similarly, this study's early extraction group had slightly lesser values than the late extraction group(figure 3.5). West attributed the smaller transverse dimension to the immediate placement of orthodontic appliances. West's

conclusions are reasonable considering our data were collected from a sample where the dentition was allowed to erupt fully before orthodontic appliances were placed. transverse arch values of this study display partial similarity to nonextraction transverse dimensions. to Figure 3.6 for comparison of transverse data. Refer The

The

nonextraction values are represented by a study performed by Bishara, maxillary and mandibular nonextraction intercanine measurements are within 1mm of the early and late extraction values.25 Where the data differ is in the

posterior, maxillary nonextraction intermolar mean values are approximately 8mm greater than extraction values. And

the mandibular nonextraction data are approximately 7mm greater than the extraction intermolar values. The

50

50 45 40 35 30 25 20 15 10 5 0

46.46 43.66

47.57 44.07 39.2 40.76 37.7 37.8

M illim eter (m m )

33.78 34.59 35.24 35.09 26.13 26.2 27.01 26.5

SE EE 4B i LE

SE EE 4B i LE

SE EE 4B i LE Mx I -Mol

Mx I-Canine

Mn I-Canine

Figure 3.5 Mean arch transverse dimensions for serial extraction study and early extraction study. Serial extraction study,24 SE=serial extraction,4Bi=extraction in permanent dentition. Current study, EE=early extraction, LE=late extraction.

intercanine measurements of both arches in the extraction groups support findings by Strang and King that as the the teeth are distalized there is a similar increase in width,26,27 see table 3.5 with a significantly wider maxillary intercanine dimension for the late extraction group in comparison to nonextraction. The same logic

applies to the molar transverse values where they were mesially positioned into a more anterior part of the arch thus filling the bicuspid extraction space and having a smaller transverse measurement.

51

SE EE 4B i LE Mn I -Mol

60

51.75

50 M illim e te r (m m ) 40 34.1 34.59 35.09 30 20 10 0 EE EE

25.5 26.2 26.5

43.66 44.07

44.45 37.7 37.8

EE

EE

LE

LE

LE

N Eb

N Eb

N Eb

Mx I-Canine

Mn I-Canine

Mx I -Mol

Figure 3.6 Mean arch values for nonextraction group from Bishara et al. study compared to early and late extraction transverse data.25 NEb=Bishara nonextraction, EE=early extraction, LE=late extraction

52

N Eb

Mn I -Mol

LE

Conclusions

The conclusions of this study indicate that: 1. Early versus late extraction protocols yield no significance with regard to transverse dimension. 2. Nonextraction maxillary and mandibular intermolar widths are significantly wider than both early and late extraction groups. 3. Late extraction maxillary intercanine width is significantly wider than nonextraction intercanine dimensions.

53

References 1. Baumrind S, Korn EL, Boyd RL Maxwell R. The decision to extract Part 1-Interclinician agreement. Am J Ortho Dentofac Orthop 1996;109:297-309. 2. Baumrind S, Korn EL, Boyd RL Maxwell R. The decision to extract: Part 2. Analysis of clinicians' stated reasons for extraction. Am J Ortho Dentofac Orthop 1996;109:393-402. 3. Barrow,G. Developmental Changes of the Maxillary and Mandibular Dental Arches. Am J Orthod 1952;22:41-46. 4. Moorrees CF, Gron AM, Lebret LM, Yen PK, Frohlich FJ. Growth studies of the dentition: A Review. Am J Orthod 1969;55:600-616. 5. Ringenberg, Q.M. Influence of serial extraction on growth and development of the maxilla and mandible. Am J Orthod 1967:53:19-26. 6. Dewell,B. Serial extraction: Its limitation and contraindications in orthodontic treatment. Am J Orthod 1967;53:904. 7. Graber T.M. Serial extraction: A continuous diagnostic and decisional process. Am J Orthod 1971;60:541-575. 8. Wagner, M. Serial extraction or premolar extraction in the permanent dentition? Comparison of duration and outcome of orthodontic treatment. J Orof Orthop 2000;61:207-216. 9. Little RM, Serial extraction of first premolarsPostretention evaluation of stability and relapse. Angle Orthod 1994;60:213-226. 10. Wilson, JR, Little RM, Joondeph DR, Doppel DM. Comparison of soft tissue profile changes in serial extraction and late premolar extraction. Angle Orthod 1999;69:165-174. 11. Johnson DK, Smith RJ. Smile esthetics after orthodontic treatment with and without extraction of four first premolars. Am J Orthod Dentofac Orthop 1995;108:162-7.

54

12. Moorrees CF, Fanning EA, Gron AM. Consideration of dental development in serial extraction. Angle Orthod 1963;33:44-59. 13. Burrow SJ. To extract or not to extract: A diagnostic decision, not a marketing decision. Am J Orthod and Dentofac Orthop 2008;133:341-2. 14. Spahl TJ, Witzig JW. The clinical management of basic maxillofacial orthopedic appliances. Littleton(Mass): PSG Publishing Co; 1987. 15. Dierkes JM. The beauty of the face: an orthodontic perspective. J Am Dent Assoc 1987;(special number):89-95E. 16. Damon D. Three keys to non-extraction therapy. Ortho Tribune 2006;1:13-14. 17. Hulsey CM. An esthestic evaluation of lip-teeth relationships present in the smile. Am J Orthod 1970;57:132-144. 18. Rigsbee OH, Sperry TP, BeGole EA. The influence of facial animation on smile characteristics. Int J Adult Orthod Orthgn Sur 1988;3:233-239. 19. Peck L, Cataja M. The gingival smile line. Angle Orthod 1992;62: 91-100. 20. Mackley RJ. An evaluation of smiles before and after orthodontic treatment. Angle Orthod 1993;63:183-190. 21. Gianelly AA. Arch width after extraction and nonextraction treatment. Am J Orthod Dentofac Orthop 2003;123:25-8. 22. Sillman JH. Dimensional changes of the dental arches:Longitudinal study from birth to 25 years. Am J Orthod 1964;50:824-842. 23. Moorrees CF, Reed R. Changes in dental arch dimensions expressed on the basis of tooth eruption as a measure of biological age. J Dent R 1965;44:129-141. 24. West LE. Arch area development: A comparative study of serial extraction versus extraction in the permanent dentition. Masters thesis, Saint Louis University 2002.

55

25. Bishara SE, Bayati P, Zahar AR, Jakobsen JR. Comparisons of the dental arch changes in patients with CII division I malocclusions: extraction vs. nonextraction treatments. Angle Orthod 1994;5:351-8. 26. Strang RHW. The fallacy of denture expansion as a treatment procedure. Angle Orthod 1949;19:12-17. 27. King EW. Relapse of orthodontic treatment. Angle Orthod 1974;44:300-315.

56

Vita Auctoris Michael Larson was born in Corning, California on August 28, 1976. He received his primary education in the Michael left high

California Public School District.

school early with a certificate of Proficiency and attended junior college at Shasta College in Redding California. At Shasta College he focused his education on the predental sciences. After five semesters he transferred to At Davis he majored in

University of California, Davis.

Physiology and completed his undergraduate education in 2001. Following his undergraduate career Mr. Larson was accepted into dental school at University of California, San Francisco in 2003. Mr. Larson focused on research

receiving two publications. The author was conferred the title of D.D.S. in 2007. In June of 2007, Michael commenced specialty training in orthodontics at Saint Louis University-Center for Advanced Dental Education. Here he is a candidate for the

degree, Master of Science in Dentistry, Orthodontics.

57

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