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THE ASSESSMENT OF GINGIVAL MARGINS OF MAXILLARY CANINES IN UNTREATED ADOLESCENT PATIENTS WITH CONGENITALLY MISSING PERMANENT MAXILLARY LATERAL INCISORS Gregory W. Carr, D.M.D. An Abstract Presented to the Graduate Faculty of Saint Louis University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Dentistry 2013 Abstract Introduction: A significant number of people in the population are congenitally missing permanent maxillary lateral incisors. In these patients, the adjacent permanent maxillary canine frequently erupts in a more mesial position within the dental arch closer to the maxillary central incisor. No study to date has looked at the natural gingival margin relationship between permanent maxillary central incisors and mesial erupted permanent maxillary canines. Purpose: The purpose of this study is to determine, in patients who are congenitally missing permanent maxillary lateral incisors, if the natural gingival margin relationship between the maxillary central incisor and the more mesial erupted maxillary canine is similar to the natural gingival margin relationship between the maxillary central incisor and maxillary lateral incisor. Materials and Methods: The sample consisted of 60 patients (29 male, 31 female) between 10 and 18 years of age who were congenitally missing at least one permanent maxillary lateral incisor. A total of 81 maxillary quadrants qualified to be used in the sample. Plaster casts were obtained from the initial records of each patient in the sample and then scanned using a 3D scanner. 1 The distance from the gingival margin of the maxillary central incisor and maxillary canine to a horizontal plane was measured in order to show their gingival margin relationship. Descriptive statistics for these parameters were calculated and non-parametric tests were run to evaluate left vs. right quadrants and male vs. female quadrants. Results: Of 81 maxillary canines, compared to the maxillary central incisor, the gingival margin for 33 of them was apical to the gingival margin of the central incisor, 12 were 0.0 - 0.5 mm incisal, 17 were 0.5 – 1.0 mm incisal, and 19 were greater than 1.0 mm incisal to the gingival margin of the central incisor. Conclusions: Mesial erupted permanent maxillary canines in adolescents who are congenitally missing permanent maxillary lateral incisors have a gingival margin that is apical to the gingival margin of the permanent maxillary central incisor 40.30% of the time, and incisal to the gingival margin of the permanent maxillary central incisor 59.30% of the time. 2 THE ASSESSMENT OF GINGIVAL MARGINS OF MAXILLARY CANINES IN UNTREATED ADOLESCENT PATIENTS WITH CONGENITALLY MISSING PERMANENT MAXILLARY LATERAL INCISORS Gregory W. Carr, D.M.D. A Thesis Presented to the Graduate Faculty of Saint Louis University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Dentistry 2013 COMMITTEE IN CHARGE OF CANDIDACY: Professor Eustaquio A. Araujo, Chairperson and Advisor Associate Professor Ki Beom Kim Associate Clinical Professor Donald R. Oliver i DEDICATION I dedicate this thesis to my supportive and wonderful family. To my wife and best friend, Jenna, who has supported me and been my rock through this whole journey: Thank you for always being there for me and lifting me up during the tough times of school. Thank you for all of the sacrifices that you have made during the past 8 years. I could not have made it this far without you by my side. Thank you for taking a chance and marrying me. To my three amazing children: Brinley, Julianne, and McKay. life. Thank you for bringing so much joy and love into my I am grateful to be your daddy. To my parents, Michael and Carole Carr: Thank you for teaching me the value of hard work and perseverance. Thank you for always encouraging me to reach for my dreams and for the great example that you have been to me in life. And lastly, to the faculty of Saint Louis University: I am honored to have been trained under your guidance. Thank you for caring so much about my education and my future success. This has been an amazing 2½ years. ii ACKNOWLEDGEMENTS This project could not have been completed without the help and support of the following individuals: Dr. Eustaquio Araujo, Dr. Ki Boem Kim, and Dr. Donald Oliver. Thank you for all the time, effort, and guidance that each of you gave to me in planning and completing this project. Dr. Heidi Israel. Thank you for your assistance with the statistical analysis for this thesis. iii TABLE OF CONTENTS List of Tables.............................................v List of Figures...........................................vi CHAPTER 1: INTRODUCTION....................................1 CHAPTER 2: REVIEW OF THE LITERATURE Tooth Agenesis ..................................5 Tooth Agenesis Theories .........................7 Management of a Missing Maxillary Lateral Incisor ................................10 Canine Substitution ............................12 Single-Tooth Implants..........................14 Tooth-Supported Restorations...................16 Eruption of Permanent Maxillary Canines........17 Lateral Incisor Gingival Margin Level..........19 Statement of thesis ............................21 Literature Cited ...............................23 CHAPTER 3: JOURNAL ARTICLE Abstract .......................................30 Introduction ...................................32 Materials and methods ..........................36 Sample.....................................36 Statistical Analysis.......................41 Reliability................................41 Results ........................................42 Discussion .....................................47 Conclusion .....................................53 Literature Cited ...............................54 Vita Auctoris............................................. 57 iv LIST OF TABLES Table 3.1 Descriptive statistics for U1-P, U3-P, and U1-U3............................42 Table 3.2 Descriptive statistics for U1-P, U3-P, and U1-U3 of the right quadrants...........43 Table 3.3 Descriptive statistics for U1-P, U3-P, and U1-U3 of the left quadrants............43 Table 3.4 Descriptive statistics for U1-P, U3-P, and U1-U3 of the male quadrants............45 Table 3.5 Descriptive statistics for U1-P, U3-P, and U1-U3 of the female quadrants..........46 v LIST OF FIGURES Figure 3.1 Construction of horizontal reference plane......................................38 Figure 3.2 Measurements from the highest point of contour on the buccal gingival margin of maxillary central incisor and maxillary canine to the horizontal reference plane...39 Figure 3.3 Maxillary canine gingival margin relationship to the maxillary central incisor gingival margin....................44 Figure 3.4 Maxillary canine gingival margin relationship to the maxillary central incisor gingival margin: Left vs. Right quadrants..................................45 Figure 3.5 Maxillary canine gingival margin relationship to the maxillary central incisor gingival margin: Male vs. Female quadrants..................................46 vi CHAPTER 1: INTRODUCTION To close or not to close; which is better? This is the age old question that orthodontists have been trying to answer for years when treatment planning patients who are missing maxillary lateral incisors. A significant number of people in the population are congenitally missing permanent maxillary lateral incisors.1-5 The demand for orthodontic treatment by these people is high because of the obvious impact that this condition has on both dental and facial esthetics.6 This is a challenging situation that every orthodontist will encounter on a regular basis. There are multiple options when treatment planning these patients.6 One option is to close the lateral incisor space by moving the canine until it is adjacent to the central incisor and then reshaping it to look like the lateral incisor through a process called canine substitution. The other option is to place the canine at its natural position within the dental arch, filling the void left by the missing lateral incisor with either a single-tooth implant or a tooth-supported restoration.7-11 A thorough diagnostic protocol should be used in determining which option is best for each patient.6 1 Many articles have been written suggesting that there are certain dental and facial criteria that should be analyzed before deciding which option to choose. They include malocclusion, amount of crowding, profile, canine shape and color, and level of the lip.6, 11-14 Another criteria to consider, that isn’t mentioned often in the literature is the position in the dental arch where the canine erupts. A recent study by Rendon found that when the permanent maxillary lateral incisor was missing, the canine erupted in a more mesial position within the dental arch closer to the midalveolar plane.15 Araujo also suggests that in patients with congenitally missing maxillary lateral incisors, canines frequently show a mesial pattern of eruption, with a final position in the dental arch that is adjacent and parallel to the central incisors, and that such a condition favors canine substitution.6 In patients that are congenitally missing maxillary lateral incisors, one more criteria to consider that isn’t mentioned in the literature is the gingival margin of the maxillary canine that erupts into the space normally occupied by the maxillary lateral incisor, and its relationship to the gingival margin of the maxillary central incisor. Is the relationship between the gingival margins like a normal maxillary central incisor/maxillary 2 canine relationship, where the gingival margins are at the same level? Or, is the relationship between the gingival margins of the maxillary central incisor and canine more like a maxillary central incisor/maxillary lateral incisor relationship, where the lateral incisor gingival margin in more incisal than the gingival margin of the maxillary central incisor? Multiple studies have tried to determine what the most esthetic gingival margin relationship is between a maxillary central incisor and a maxillary lateral incisor. This was accomplished by using smiling photographs of the same smile in which only the gingival margin relationship between the maxillary central and lateral incisors had been altered in certain increments. Lay people, dentists, and dental specialists were then asked which photographs they thought were the most esthetic.16-19 Other studies tried to determine what the most common relationship was between maxillary central incisors and maxillary lateral incisors in the dental arch. This was accomplished by obtaining measurements directly from plaster model casts using digital calipers and from digital photographs of model casts using computer software.20, 21 One study looked at smiling photographs of a patient who was congenitally missing a maxillary lateral incisor 3 and had the space closed by canine substitution. Each photograph was different only in the gingival margin relationship between the maxillary central incisor and the maxillary canine that had been moved into the lateral incisor position adjacent to the canine. Lay people, dentists, and orthodontists were then asked to rank the pictures according to attractiveness to determine which gingival margin relationship between the maxillary central incisor and a substituted maxillary canine was the most esthetic.22 To my knowledge, no study to date has looked at the natural gingival margin relationship between maxillary central incisors and maxillary canines that have erupted into the maxillary lateral incisor position, before being treated with orthodontics. The purpose of this study is to determine, in patients who are congenitally missing permanent maxillary lateral incisors, if the natural gingival margin relationship between the maxillary central incisor and the more mesial erupted maxillary canine is similar to the natural gingival margin relationship between the maxillary central incisor and maxillary lateral incisor. 4 CHAPTER 2: REVIEW OF THE LITERATURE Tooth Agenesis Agenesis of one or more teeth, also known as hypodontia, is the most common developmental dental anomaly in man.23, 24 Several terms are used in the literature to describe missing teeth; Anodontia is the complete absence of teeth; Oligodontia is referred to as partial anodontia, characterized by having six or more teeth absent, not including the third molars; Hypodontia is a term used to denote that teeth are missing, but usually less than six.25 Hypodontia not only describes missing teeth, but it also may denote that the size or shape of teeth are reduced as well.26 Tooth agenesis affects the permanent dentition more frequently than the primary dentition. The incidence for permanent tooth agenesis ranges from 2.30% - 6.01%, excluding third molars.1-3, 27, 28 In the primary dentition, tooth agenesis ranges from 0.20% - 0.90%.29, 30 The most common missing tooth is the third molar, with an incidence of about 20%.27 As for which tooth is the second and third most common, the literature varies. studies show that the maxillary lateral incisor is the 5 Some second most commonly missing tooth.1, 28 Others show that the absence of the mandibular second premolar is more frequent than the maxillary lateral incisor.2-5 According to the literature, there are a number of correlations that exist with respect to agenesis and the permanent dentition. Females have a higher frequency of tooth agenesis than males.1, 31, 32 Silverman and Bailit found in their respective studies that agenesis more commonly occurs bilaterally than unilaterally and is symmetric, except in cases involving the maxillary lateral incisor.3, 33 On the other hand, Polder and colleagues found tooth agenesis to be more common unilaterally, except in cases involving the maxillary lateral incisor, which they found to occur more often bilaterally.4 A study by Muller et al found an interesting correlation between the number and type of missing teeth. The study examined 14,940 adolescents and noticed in those who were congenitally missing only one or two teeth, the greatest frequency was related to the maxillary lateral incisor. However, in those adolescents who were missing more than two teeth, the mandibular second premolar was missing more often.1 Alvesalo and Portin found a relationship between missing teeth and abnormalities in the shape of the remaining teeth. The authors noticed that 6 when one maxillary lateral incisor was missing, the contralateral maxillary lateral incisor could be smaller than normal.34 Tooth agenesis theories The etiology of tooth agenesis is not very clear. Is it genetic, environmental, or evolutionary? Or, could it be multifactorial and may be due to a combination of these? Many attempts have been made, and many theories have been hypothesized, to explain why tooth agenesis occurs. It has been shown that genetic factors with a marked degree of penetrance play a major role in dental agenesis. Grahnen suggested that tooth agenesis is usually transmitted as an autosomal dominant trait with incomplete penetrance and variable expressivity.35 In Woolf’s study, it was found that the frequency of individuals with a missing maxillary lateral incisor was significantly increased in the parents and siblings of the examined subject as compared with the frequency of the parents and siblings of the control subjects. The study concludes that agenesis of maxillary lateral incisors consists of a 7 dominant autosomal gene showing reduced penetrance and variable expressivity.36 Sofaer et al postulated that for teeth developing in a confined space, there is a compensatory interaction between tooth germs during development. In their study, they examined Hawaiian children and noticed that if the central incisor is large, then the adjacent lateral incisor tends to be absent. If the lateral incisor is peg-shaped, then the central incisor is present, but tends to be smaller than normal. They propose that agenesis occurs when there is insufficient primordium for tooth germ initiation, and peg-shaped laterals occur when there is sufficient primordium but a poor environment.37 Since the maxillary lateral incisor develops after the maxillary central incisor, their initiation depends on the availability of the necessary local requirements.33, 37 In 1939, Butler proposed a theory as to why some teeth fail to form more than others. According to his theory, the mammalian dentition can be divided into three developmental fields consisting of incisors, canines, and premolars/molars. Within each field, one tooth is designated at the “key” tooth, meaning that it is more stable developmentally. On either side of this key tooth, 8 the remaining teeth within the developmental field become more and more unstable. Considering each quadrant separately, the key tooth in the premolar/molar field would consist of the first molar with the second and third molars on the distal end of the field and the first and second premolars on the mesial end of the field. According to Butler’s theory, the third molar and first premolar would be the most variable in size and shape. Many clinicians would agree with this theory in respect with the third molar, but not so with the first premolar. It is important to observe that the earliest mammals had four premolars and some of the higher primates, including humans, have lost the first two. The remaining premolars in reality should be called the third and fourth premolars. Therefore, as Butler’s theory predicted, the two lost premolars would have been farthest from the first molar, and in an evolutionary sense considered unstable.33 Clayton noticed in a study with 3,557 human subjects that the terminal or most posterior tooth of a tooth series (incisors, premolars, molars) was most frequently missing, and hypothesized that those teeth most often missing were “vestigial organs” that had little practical value for modern man.27 Hence, in the evolutionary process, these 9 teeth provide no selective advantage and therefore have been lost.38 Management of a missing maxillary lateral incisor The demand for orthodontic treatment by patients with missing maxillary lateral incisors is high because of the obvious impact that this condition has on facial esthetics. Not only can this condition adversely affect someone’s self-esteem, but it may also adversely affect the way other people view them in society.39, 40 Treatment planning for these patients can be challenging. There are many concerns one needs to be aware of when planning these cases because the congenital absence of one or both of these teeth introduces an imbalance in maxillary and mandibular dental arch lengths in the permanent dentition. The most predictable way to achieve the optimal esthetic and functional result is to use an interdisciplinary team consisting of a general dentist, orthodontist, periodontist, oral surgeon, and prosthodontist.7, 12, 14, 41, 42 Together, they should elaborate and create the patient’s treatment plan and communicate throughout the course of treatment to make sure that all 10 aspects of treatment are considered and the overall treatment objectives are achieved.12 There are multiple options that exist for treating these patients. The space sometimes closes spontaneously. If not, the space can be closed orthodontically through a process called canine substitution. This is done by moving the maxillary canine into the position normally occupied by the maxillary lateral incisor and then reshaping it to look more like the lateral incisor. The other option is to place the canine at its normal position within the arch, creating space for either a single-tooth implant or a tooth-supported restoration.7-11 When deciding which treatment option to use, primary consideration should be given to the least invasive option that conserves tooth structure and satisfies the expected esthetic and functional objectives. Whichever option is chosen, it is important to complete a diagnostic wax-up. This helps the interdisciplinary team evaluate the final occlusion and determine if an esthetic final result is obtainable.8, 10, 43 11 Canine substitution There are certain facial and dental criteria that need to be evaluated before deciding upon canine substitution as the treatment of choice for patients that are missing maxillary lateral incisors. They include malocclusion, amount of crowding, profile, canine shape and color, and level of the lip.12, 13 There are two principal types of malocclusion that allow for canine substitution to occur. The first one is an Angle Class II malocclusion with no crowding in the mandibular arch indicating that no extractions are necessary. II. This scenario would leave the molars in Class The second one is an Angle Class I malocclusion with enough crowding in the mandibular arch indicating that extractions are necessary. In these cases, the molar relationship would be Class I.7, 11, 44 Generally, a convex to straight profile would respond well to canine substitution.7 The shape and color of the canines are also important factors to look at before deciding upon canine substitution. The canine is a significantly larger tooth than the lateral incisor, and its buccal surface is more convex. Because of this size discrepancy, an anterior 12 tooth size excess in the maxillary arch would be created and anatomical adjustment must be performed to reduce the discrepancy and to establish an anterior occlusion with a normal overbite and overjet relationship.12 As the canines are recontoured for esthetic and functional purposes, one must take into account the darker color and less translucent that the canine will display compared to the adjacent teeth.11 This can be corrected by either bleaching the canine or placing a veneer on it.7, 10 If the patient’s lip level when smiling is in a position that allows the gingival margins to be visible, the gingival margin of the canine should be placed 0.5 1.0 mm incisal to the gingival margin of the central incisor.7 Also, according to Senty, if the patient has a high smile line, a prominent canine root eminence could generate an esthetic concern.43 An advantage of closing space by canine substitution is the permanence of the final result, eliminating the need for long-term temporary restorations that are often needed until the patient is old enough for a permanent prosthesis, and avoiding the long-term maintenance required for the prosthesis over the patient’s lifetime which can be costly.8-10, 22 Multiple clinicians have found that patients who had canine substitution were also healthier 13 periodontally than those who had a prosthesis placed.5, 11, 45 And some studies have shown that patients who had canine substitution were more satisfied with the appearance of their teeth than those who had a prosthesis placed.5, 11 The disadvantages of canine substitution include the need to remove tooth structure on the canine and first premolar, and potential additional expenses if the canines need cosmetic bonding to improve the esthetic result.8-10 Robertsson and Mohlin found in their study that patients who had canine substitution were dissatisfied with the lack of color balance of the maxillary canine and the adjacent teeth.5 Single-tooth implants Many patients do not meet the ideal facial and dental criteria for canine substitution. For these patients, some form of restoration must be considered.14 Today, one of the most common treatment alternatives for replacing missing teeth is the single-tooth implant.46-48 Advantages of opening up space for implants include maintaining the canine in its natural position within the dental arch and preserving tooth structure of the canine and the adjacent teeth, making this the most conservative 14 of the prosthodontic options for replacing missing lateral incisors.8, 10, 49 Various studies have shown high success rates of implants and long-term function of the restorations supported by single-tooth implants.50 With the hard and soft tissue grafting procedures that are available today, a more esthetic outcome has become increasingly predictable.51, 52 One of the disadvantages of opening up space to place an implant is that implants cannot be placed until facial growth is complete. If an implant is placed before facial growth is complete, significant periodontal, occlusal, and esthetic problems can occur.53 As the face grows and the mandibular rami lengthen, the natural teeth erupt to stay in occlusion. Once implants are osseointegrated in the bone they become static and cannot erupt. The timing for implant placement after the end of facial growth is usually about 16 - 17 years of age for girls and 20 - 21 years of age for boys.41 Other disadvantages include the additional expense of a dental prosthesis and the potential recurrence of these expenses throughout the patient’s life, and the need for long-term maintenance of the space with a temporary retainer until the patient’s facial growth has ceased.8-10 15 Tooth-supported restorations In situations when the patient does not meet the criteria for canine substitution and does not want an implant, some form of tooth-supported prosthesis can be used. The three most common tooth-supported restorations used today are resin-bonded fixed partial dentures (FPD), cantilevered FPD, and conventional full-coverage FPD. The ideal treatment should be the least invasive and should satisfy the expected esthetic and functional objectives.14 The most conservative tooth-supported restoration is the resin-bonded FPD because it requires only a minimal amount of tooth structure be removed from the adjacent teeth. These restorations can be used successfully, but certain criteria must be met to ensure optimal esthetics and long-term success.14 54, 55 A classic resin-bonded FPD relies solely on adhesion as it is bonded to the lingual surfaces of adjacent teeth without any grooves or pins. The success rate for these restorations varies widely from a 54% failure rate over 11 years to a 10% failure rate over 11 years, with debond as the primary cause of failure.54-57 The second most conservative tooth-supported restoration is the cantilevered FPD. 16 It can be designed as either a partial coverage or full coverage retainer using the canine as the abutment. If the facial esthetics of the canine abutment is acceptable, a partial coverage retainer is best. A full coverage retainer is a better choice if the facial contour of the canine needs to be changed to improve the esthetics.14 Decock et al found in their study of 137 cantilever FPDs a success rate of 70% over an 18 year period, with secondary caries as the main cause of failure.58 The least conservative tooth-supported restoration is the conventional full-coverage FPD. This restoration is the best choice if an existing FPD needs to be replaced or if the adjacent teeth require restorations for either structural reasons or alteration of the facial esthetics. Due to the significant amount of tooth structure that is removed to make these restorations, it is not the ideal treatment for young patients missing maxillary lateral incisors.14 Eruption of permanent maxillary canines Before the maxillary canine begins eruption, it’s dental follicle is located above the follicle of the maxillary first premolar.59 Once eruption begins, it moves 17 in a mesial, occlusal direction to reach its proper position within the arch. As it erupts, it also increases its crown inclination mesially until a maximum inclination is reached at about 9 years of age. At this time, the tip of the maxillary canine contacts the distal aspect of the root of the lateral incisor, causing the canine to gradually upright itself in a more vertical position and complete its eruption in a buccal, occlusal direction.60 The final position of the permanent maxillary canine is influenced by the permanent maxillary lateral incisor. The intimate relationship between the maxillary canine and the distal aspect of the root of the maxillary lateral incisor appears to be an important factor in guiding the normal eruption pathway of the maxillary canine.61 If the lateral incisor is absent, peg, or smaller than normal, the canine may lose its guidance and move toward a different pathway that might involve the distal aspect of the root of the maxillary central incisor, or it could move in a palatal direction and become impacted.61-63 Rendon looked at the effect of congenitally missing lateral incisors on the eruption of the maxillary canine.15 He found that when the maxillary lateral incisor was missing, the canine initially has a similar position to the canine in a normal dentition, but during its eruption the 18 maxillary canine moves more toward the mesial so that it has a final position in the arch with the crown more inclined mesially and located closer to the midalveolar plane.15 Lateral incisor gingival margin level One of the main reasons why patients seek orthodontic care is to improve the esthetics of their smile. The relationship between the gingival margins of the maxillary central, lateral, and canine teeth is one of the aspects 12, 64 65 that create an esthetic smile. Many clinicians believe that the gingival margins of the maxillary central incisor and the maxillary canine should be at the same level, with the gingival margin of the maxillary lateral incisor slightly more coronal.20-22, 66 However, opinions vary as to how coronal the gingival margin of the lateral incisor should be when compared to the maxillary central and canine. Chu et al looked at a sample of 20 patients between 20 - 47 years of age and found the maxillary lateral incisor on average 1.0 mm coronal to the maxillary central incisor and canine teeth.21 Charruel and co-authors investigated 103 young adults and found that 81% of the lateral incisors 19 were coronal to the central incisor and canine, with 54% being between 0.0 - 1.0 mm, and 27% being greater than 1.0 mm.20 Kokich and Spear, however, suggests that ideally the maxillary lateral incisor should be 0.5 mm coronal to the maxillary central incisor and canine teeth.12 When lay people were surveyed using photographs to determine what they thought was the most esthetic gingival margin relationship, Springer and others found the ideal discrepancy between maxillary central and lateral incisors to be 0.4 mm.17 In Kokich’s study, lay people found the maxillary lateral incisor to be most esthetic when its gingival margin was 1.0 mm coronal to the gingival margin of the maxillary central incisor.16 What about the gingival margins of canines that have been moved into the lateral incisor position by canine substitution? An investigation by Brough, Donaldson, and Naini studied 120 people, equally divided between lay people, orthodontists, and dentists, and ranked a series of images of a smiling mouth from a patient treated with canine substitution.22 The image ranked most attractive had the gingival margin of the canine in the lateral incisor position as 0.5 mm coronal to the level of the adjacent central incisor. 20 Statement of Thesis The literature shows a significant number of missing teeth in the population, specifically the permanent maxillary lateral incisor.1-5 In these cases, there are multiple options for treatment.6-11 Multiple studies have shown how the presence or absence of the permanent maxillary lateral incisor can affect the eruption pathway and final position of the permanent maxillary canine.15, 61-63 Some studies have shown what the most esthetic and most common relationship is between the gingival margins of the maxillary central incisor and the adjacent lateral incisor.16-21 One study even showed what the most esthetic relationship is between a maxillary central incisor and a maxillary canine that has been substituted for a maxillary lateral incisor.22 No study to date has looked at the gingival margins of permanent maxillary canines that have erupted into the position within the dental arch where the permanent maxillary lateral incisors normally are, and the relationship between its gingival margin and the gingival margin of the maxillary central incisor, in untreated 21 adolescents who are congenitally missing permanent maxillary lateral incisors. The hypothesis of this study is that the permanent maxillary canine that erupts into the lateral incisor position will have a similar gingival relationship to the maxillary central incisor as a natural lateral incisor would have if present. 22 Literature Cited 1. Muller TP, Hill IN, Peterson AC, Blayney JR. A survey of congenitally missing permanent teeth. J Am Dent Assoc. 1970;81:101-7. 2. Boruchov MJ, Green LJ. Hypodontia in human twins and families. Am J Orthod. 1971;60:165-74. 3. Silverman NE, Ackerman JL. Oligodontia: a study of its prevalence and variation in 4032 children. ASDC J Dent Child. 1979;46:470-7. 4. Polder BJ, Van't Hof MA, Van der Linden FP, KuijpersJagtman AM. A meta-analysis of the prevalence of dental agenesis of permanent teeth. Community Dent Oral Epidemiol. 2004;32:217-26. 5. Robertsson S, Mohlin B. The congenitally missing upper lateral incisor. A retrospective study of orthodontic space closure versus restorative treatment. Eur J Orthod. 2000;22:697-710. 6. Araujo EA, Oliveira DD, Araujo MT. Diagnostic protocol in cases of congenitally missing maxillary lateral incisors. World J Orthod. 2006;7:376-88. 7. Kokich VO, Jr., Kinzer GA. Managing congenitally missing lateral incisors. Part I: Canine substitution. J Esthet Restor Dent. 2005;17:5-10. 8. Tuverson DL. Orthodontic treatment using canines in place of missing maxillary lateral incisors. Am J Orthod. 1970;58:109-27. 9. Sabri R. Management of missing maxillary lateral incisors. J Am Dent Assoc. 1999;130:80-4. 10. Rosa M, Zachrisson BU. Integrating esthetic dentistry and space closure in patients with missing maxillary lateral incisors. J Clin Orthod. 2001;35:221-34. 11. McNeill RW, Joondeph DR. Congenitally absent maxillary lateral incisors: treatment planning considerations. Angle Orthod. 1973;43:24-9. 23 12. Kokich VG, Spear FM. Guidelines for managing the orthodontic-restorative patient. Semin Orthod. 1997;3:3-20. 13. Zachrisson BU. Improving orthodontic results in cases with maxillary incisors missing. Am J Orthod. 1978;73:274-89. 14. Kinzer GA, Kokich VO, Jr. Managing congenitally missing lateral incisors. Part II: tooth-supported restorations. J Esthet Restor Dent. 2005;17:76-84. 15. Rendon J. Effect of congenitally missing lateral incisors on the eruption and impaction of the maxillary canine: Saint Louis University; 2005. 16. Kokich VO, Jr., Kiyak HA, Shapiro PA. Comparing the perception of dentists and lay people to altered dental esthetics. J Esthet Dent. 1999;11:311-24. 17. Springer NC, Chang C, Fields HW, Beck FM, Firestone AR, Rosenstiel S, Christensen JC. Smile esthetics from the layperson's perspective. Am J Orthod Dentofacial Orthop. 2011;139:e91-e101. 18. Chang CA, Fields HW, Jr., Beck FM, Springer NC, Firestone AR, Rosenstiel S, Christensen JC. Smile esthetics from patients' perspectives for faces of varying attractiveness. Am J Orthod Dentofacial Orthop. 2011;140:e171-80. 19. An KY, Lee JY, Kim SJ, Choi JI. Perception of maxillary anterior esthetics by dental professionals and laypeople and survey of gingival topography in healthy young subjects. Int J Periodontics Restorative Dent. 2009;29:535-41. 20. Charruel S, Perez C, Foti B, Camps J, Monnet-Corti V. Gingival contour assessment: clinical parameters useful for esthetic diagnosis and treatment. J Periodontol. 2008;79:795-801. 21. Chu SJ, Tan JH, Stappert CF, Tarnow DP. Gingival zenith positions and levels of the maxillary anterior dentition. J Esthet Restor Dent. 2009;21:113-20. 24 22. Brough E, Donaldson AN, Naini FB. Canine substitution for missing maxillary lateral incisors: the influence of canine morphology, size, and shade on perceptions of smile attractiveness. Am J Orthod Dentofacial Orthop. 2010;138:705 e1-9; discussion -7. 23. Shapiro SD, Farrington FH. A potpourri of syndromes with anomalies of dentition. Birth Defects Orig Artic Ser. 1983;19:129-40. 24. Stamatiou J, Symons AL. Agenesis of the permanent lateral incisor: distribution, number and sites. J Clin Pediatr Dent. 1991;15:244-6. 25. Vastardis H. The genetics of human tooth agenesis: new discoveries for understanding dental anomalies. Am J Orthod Dentofacial Orthop. 2000;117:650-6. 26. Townsend GC, Brown T. Heritability of permanent tooth size. Am J Phys Anthropol. 1978;49:497-504. 27. Clayton J. Congenital dental anomalies occurring in 3,557 children. ASDC J Dent Child. 1956;23:206-8. 28. Werther R, Rothenberg F. Anodontia: a review of its etiology with presentation of a case. Am J Orthod Dentofacial Orthop. 1939;25:61-81. 29. Brabant H. Comparison of the characteristics and anomalies of the deciduous and the permanent dentition. J Dent Res. 1967;46:897-902. 30. Jarvinen S, Lehtinen L. Supernumerary and congenitally missing primary teeth in Finnish children. An epidemiologic study. Acta Odontol Scand. 1981;39:83-6. 31. Meskin LH, Gorlin RJ. Agenesis and Peg-Shaped Permanent Maxillary Lateral Incisors. J Dent Res. 1963;42:14769. 32. Dermaut LR, Goeffers KR, De Smit AA. Prevalence of tooth agenesis correlated with jaw relationship and dental crowding. Am J Orthod Dentofacial Orthop. 1986;90:204-10. 33. Bailit HL. Dental variation among populations. An anthropologic view. Dent Clin North Am. 1975;19:12539. 25 34. Alvesalo L, Portin P. The inheritance pattern of missing, peg-shaped, and strongly mesio-distally reduced upper lateral incisors. Acta Odontol Scand. 1969;27:563-75. 35. Grahnen H. Hypodontia in the permanent dentition: a clinical and genetical investigation. Odont Revy. 1956;7:1-100. 36. Woolf CM. Missing maxillary lateral incisors: a genetic study. Am J Hum Genet. 1971;23:289-96. 37. Sofaer JA, Chung CS, Niswander JD, Runck DW. Developmental interaction, size and agenesis among permanent maxillary incisors. Hum Biol. 1971;43:36-45. 38. Graber LW. Congenital absence of teeth: a review with emphasis on inheritance patterns. J Am Dent Assoc. 1978;96:266-75. 39. Shaw WC, Addy M, Ray C. Dental and social effects of malocclusion and effectivenessof orthodontic treatment: a review. Community Dent Oral Epidemiol. 1980;8:36-45. 40. Shaw WC. The influence of children's dentofacial appearance on their social attractiveness as judged by peers and lay adults. Am J Orthod. 1981;79:399-415. 41. Kokich VO, Jr., Kinzer GA, Janakievski J. Congenitally missing maxillary lateral incisors: restorative replacement. Counterpoint. Am J Orthod Dentofacial Orthop. 2011;139:435, 7, 9 passim. 42. Kinzer GA, Kokich VO, Jr. Managing congenitally missing lateral incisors. Part III: single-tooth implants. J Esthet Restor Dent. 2005;17:202-10. 43. Senty EL. The maxillary cuspid and missing lateral incisors: esthetics and occlusion. Angle Orthod. 1976;46:365-71. 44. Biggerstaff RH. The orthodontic management of congenitally absent maxillary lateral incisors and second premolars: a case report. Am J Orthod Dentofacial Orthop. 1992;102:537-45. 26 45. Nordquist GG, McNeill RW. Orthodontic vs. restorative treatment of the congenitally absent lateral incisor-long term periodontal and occlusal evaluation. J Periodontol. 1975;46:139-43. 46. Naert I, Koutsikakis G, Duyck J, Quirynen M, Jacobs R, van Steenberghe D. Biologic outcome of single-implant restorations as tooth replacements: a long-term follow-up study. Clin Implant Dent Relat Res. 2000;2:209-18. 47. Vermylen K, Collaert B, Linden U, Bjorn AL, De Bruyn H. Patient satisfaction and quality of single-tooth restorations. Clin Oral Implants Res. 2003;14:119-24. 48. Garber DA, Salama MA, Salama H. Immediate total tooth replacement. Compend Contin Educ Dent. 2001;22:210-6, 8. 49. Richardson G, Russell KA. Congenitally missing maxillary lateral incisors and orthodontic treatment considerations for the single-tooth implant. J Can Dent Assoc. 2001;67:25-8. 50. Mayer TM, Hawley CE, Gunsolley JC, Feldman S. The single-tooth implant: a viable alternative for singletooth replacement. J Periodontol. 2002;73:687-93. 51. Davarpanah M, Martinez H, Etienne D, Zabalegui I, Mattout P, Chiche F, Michel JF. A prospective multicenter evaluation of 1,583 3i implants: 1- to 5year data. Int J Oral Maxillofac Implants. 2002;17:820-8. 52. Romeo E, Chiapasco M, Ghisolfi M, Vogel G. Long-term clinical effectiveness of oral implants in the treatment of partial edentulism. Seven-year life table analysis of a prospective study with ITI dental implants system used for single-tooth restorations. Clin Oral Implants Res. 2002;13:133-43. 53. Thilander B, Odman J, Lekholm U. Orthodontic aspects of the use of oral implants in adolescents: a 10-year follow-up study. Eur J Orthod. 2001;23:715-31. 54. Priest GF. Failure rates of restorations for singletooth replacement. Int J Prosthodont. 1996;9:38-45. 27 55. Probster B, Henrich GM. 11-year follow-up study of resin-bonded fixed partial dentures. Int J Prosthodont. 1997;10:259-68. 56. Creugers NH, Kayser AF, Van't Hof MA. A seven-and-ahalf-year survival study of resin-bonded bridges. J Dent Res. 1992;71:1822-5. 57. Boyer DB, Williams VD, Thayer KE, Denehy GE, DiazArnold AM. Analysis of debond rates of resin-bonded prostheses. J Dent Res. 1993;72:1244-8. 58. Decock V, De Nayer K, De Boever JA, Dent M. 18-year longitudinal study of cantilevered fixed restorations. Int J Prosthodont. 1996;9:331-40. 59. Broadbent B. Ontogenic development of occlusion. Angle Orthod. 1941;11:223-41. 60. Fernandez E, Bravo LA, Canteras M. Eruption of the permanent upper canine: a radiologic study. Am J Orthod Dentofacial Orthop. 1998;113:414-20. 61. Becker A, Smith P, Behar R. The incidence of anomalous maxillary lateral incisors in relation to palatallydisplaced cuspids. Angle Orthod. 1981;51:24-9. 62. Brin I, Becker A, Shalhav M. Position of the maxillary permanent canine in relation to anomalous or missing lateral incisors: a population study. Eur J Orthod. 1986;8:12-6. 63. Al-Nimri KS, Bsoul E. Maxillary palatal canine impaction displacement in subjects with congenitally missing maxillary lateral incisors. Am J Orthod Dentofacial Orthop. 2011;140:81-6. 64. Kokich VG, Nappen DL, Shapiro PA. Gingival contour and clinical crown length: their effect on the esthetic appearance of maxillary anterior teeth. Am J Orthod. 1984;86:89-94. 65. Kokich VG. Esthetics: the orthodontic-periodontic restorative connection. Semin Orthod. 1996;2:21-30. 28 66. Sarver DM, Ackerman MB. Dynamic smile visualization and quantification: Part 2. Smile analysis and treatment strategies. Am J Orthod Dentofacial Orthop. 2003;124:116-27. 29 CHAPTER 3: JOURNAL ARTICLE Abstract Introduction: A significant number of people in the population are congenitally missing permanent maxillary lateral incisors. In these patients, the adjacent permanent maxillary canine frequently erupts in a more mesial position within the dental arch closer to the maxillary central incisor. No study to date has looked at the natural gingival margin relationship between permanent maxillary central incisors and mesial erupted permanent maxillary canines. Purpose: The purpose of this study is to determine, in patients who are congenitally missing permanent maxillary lateral incisors, if the natural gingival margin relationship between the maxillary central incisor and the more mesial erupted maxillary canine is similar to the natural gingival margin relationship between the maxillary central incisor and maxillary lateral incisor. Materials and Methods: The sample consisted of 60 patients (29 male, 31 female) between 10 and 18 years of age who were congenitally missing at least one permanent maxillary lateral incisor. A total of 81 maxillary quadrants qualified to be used in the sample. 30 Plaster casts were obtained from the initial records of each patient in the sample and then scanned using a 3D scanner. The distance from the gingival margin of the maxillary central incisor and maxillary canine to a horizontal plane was measured in order to show their gingival margin relationship. Descriptive statistics for these parameters were calculated and non-parametric tests were run to evaluate left vs. right quadrants and male vs. female quadrants. Results: Of 81 maxillary canines, compared to the maxillary central incisor, the gingival margin for 33 of them was apical to the gingival margin of the central incisor, 12 were 0.0 - 0.5 mm incisal, 17 were 0.5 – 1.0 mm incisal, and 19 were greater than 1.0 mm incisal to the gingival margin of the central incisor. Conclusions: Mesial erupted permanent maxillary canines in adolescents who are congenitally missing permanent maxillary lateral incisors have a gingival margin that is apical to the gingival margin of the permanent maxillary central incisor 40.30% of the time, and incisal to the gingival margin of the permanent maxillary central incisor 59.30% of the time. 31 Introduction To close or not to close; which is better? This is the age old question that orthodontists have been trying to answer for years when treatment planning patients who are congenitally missing maxillary lateral incisors. A significant number of people in the population are congenitally missing permanent maxillary lateral incisors.15 The demand for orthodontic treatment by these people is high because of the obvious impact that this condition has on both dental and facial esthetics.6 This is a challenging situation that every orthodontist will encounter on a regular basis. There are multiple options when treatment planning these patients.6 One option is to close the lateral incisor space by moving the canine until it is adjacent to the central incisor and then reshaping it to look like the lateral incisor through a process called canine substitution. The other option is to place the canine at its natural position within the dental arch, filling the void left by the missing lateral incisor with either a single-tooth implant or a tooth-supported restoration.7-11 A thorough diagnostic protocol should be used in determining which option is best for each patient.6 32 Many articles have been written suggesting that there are certain dental and facial criteria that should be analyzed before deciding which option to choose. They include malocclusion, amount of crowding, profile, canine shape and color, and level of the lip.6, 11-14 Another criterion to consider that isn’t mentioned often in the literature is the position in the dental arch where the canine erupts. A recent study by Rendon found that when the permanent maxillary lateral incisor was missing, the permanent maxillary canine erupted in a more mesial position within the dental arch closer to the midalveolar plane.15 Araujo also suggests that in patients with congenitally missing maxillary lateral incisors, maxillary canines frequently show a mesial pattern of eruption, with a final position in the dental arch that is adjacent and parallel to the central incisors, and that such a condition favors canine substitution.6 In patients that are congenitally missing maxillary lateral incisors, one more criteria to consider that isn’t mentioned in the literature is the gingival margin of the maxillary canine that erupts into the space normally occupied by the maxillary lateral incisor, and its relationship to the gingival margin of the maxillary central incisor. Is the relationship between these 33 gingival margins like a normal maxillary central incisor/maxillary canine relationship, where the gingival margins are at the same level? Or, is the relationship between the gingival margins of the maxillary central incisor and canine more like a maxillary central incisor/maxillary lateral incisor relationship, where the lateral incisor gingival margin in more incisal than the gingival margin of the maxillary central incisor? Multiple studies have tried to determine what the most esthetic gingival margin relationship is between a maxillary central incisor and a maxillary lateral incisor. This was accomplished by using smiling photographs of the same smile in which only the gingival margin relationship between the maxillary central and lateral incisors had been altered in certain increments. Lay people, dentists, and dental specialists were then asked which photographs they thought were the most esthetic.16-19 Other studies tried to determine what the most common relationship was between maxillary central incisors and maxillary lateral incisors in the dental arch. This was accomplished by obtaining measurements directly from plaster model casts using digital calipers and from digital photographs of model casts using computer software.20, 34 21 One study looked at smiling photographs of a patient who was congenitally missing a maxillary lateral incisor and had the space closed by canine substitution. Each photograph was different only in the gingival margin relationship between the maxillary central incisor and the maxillary canine that had been moved into the lateral incisor position adjacent to the canine. Lay people, dentists, and orthodontists were then asked to rank the pictures according to attractiveness to determine which gingival margin relationship between the maxillary central incisor and a substituted maxillary canine was the most esthetic.22 To my knowledge, no study to date has looked directly at the natural gingival margin relationship between maxillary central incisors and maxillary canines that have erupted into the maxillary lateral incisor position, before being treated with orthodontics. This knowledge would be useful to orthodontists in treatment planning patients who are congenitally missing permanent maxillary lateral incisors by adding another criterion to look at when deciding which treatment option to choose. The purpose of this study is to determine, in patients who are congenitally missing permanent maxillary lateral incisors, if the natural gingival margin relationship 35 between the maxillary central incisor and the more mesial erupted maxillary canine is similar to the natural gingival margin relationship between the maxillary central incisor and maxillary lateral incisor. A secondary purpose of this study is to determine if the gingival margin relationship between the permanent maxillary central incisor and the more mesial erupted permanent maxillary canine is similar in relation to male vs. female and left vs. right side of the dentition. Materials and Methods Sample This is a retrospective study approved by the Institutional Review Board at Saint Louis University. The sample consisted of 60 patients (29 male, 31 female) who had either finished orthodontic treatment or had already started orthodontic treatment at the Center for Advanced Dental Education at Saint Louis University. The mean age of the sample was 13 years and 4 months, with a range from 10 to 18 years of age. Of the 60 patients in the sample, 21 were bilaterally missing the maxillary lateral incisor and 39 were unilaterally missing the maxillary lateral incisor. 36 A total of 81 maxillary quadrants with a missing lateral incisor were used in the sample. Forty-one quadrants were on the right side and 40 quadrants were on the left side. The subjects were selected based on the following criteria: (1) Caucasian, (2) must have had at least one congenitally missing permanent maxillary lateral incisor, (3) the permanent maxillary canine on the same side as the missing permanent maxillary lateral incisor must have already completely erupted into the dental arch, (4) the permanent maxillary canine must have erupted into a position that is more mesial than the normal canine position, (5) the patient could not have been treated previously with orthodontics. No control group was used. Instead, a review of the literature was performed to determine that the most common gingival margin relationship between the permanent maxillary central incisor and the permanent maxillary lateral incisor is between 0.5 – 1.0 mm.19-21 Maxillary and mandibular dental casts were obtained from the initial records of each patient in the sample. The casts were scanned using a 3D scanner (R700, 3Shape A/S, Copenhagen, Denmark), and measurements were obtained using the OrthoAnalyser software (3Shape A/S). 37 Reference points were marked on the digital images in order to obtain the needed measurements. A horizontal reference plane was first created by making and connecting three marks on each scanned model (Figure 3.1). The first mark was placed at the highest point of contour on the palatal gingival margin of the maxillary right central incisor. The second mark was placed on the palatal gingival margin directly vertical from the distolingual groove of the maxillary right first molar. The third mark was placed exactly like the second mark, except on the maxillary left first molar. Figure 3.1 - Construction of horizontal reference plane. After the horizontal plane was established, a mark was made at the highest point of contour on the buccal gingival 38 margin of the maxillary central incisor and the adjacent maxillary canine. The software then measured the distance between each mark and the horizontal plane (Figure 3.2). Figure 3.2 - Measurements from the highest point of contour on the buccal gingival margin of maxillary central incisor and maxillary canine to the horizontal reference plane. There were 3 measurements obtained from the software. They included: (1) the distance from the buccal gingival margin of the maxillary central incisor to the horizontal plane (U1-P), (2) the distance from the buccal gingival margin of the maxillary canine to the horizontal plane (U3P), and (3) the distance from the distal surface of the maxillary central incisor to the mesial surface of the mesial erupted permanent maxillary canine (D-U1/U3). 39 Once these measurements were gathered, the gingival margin relationship between the maxillary central incisor and maxillary canine (U1-U3) was calculated by subtracting U3-P from U1-P. If U1-U3 was a negative number, the gingival margin of the canine was more apical than the gingival margin of the central incisor. If U1-U3 was a positive number, the gingival margin of the canine was more incisal than the gingival margin of the central incisor. The gingival margin relationship (U1-U3) was further divided into one of six categories: (1) the gingival margin of the maxillary canine is apical to the gingival margin of the maxillary central incisor between 0.01 - 0.50 mm, (2) the gingival margin of the maxillary canine is apical to the gingival margin of the maxillary central incisor between 0.51 – 1.0 mm, (3) the gingival margin of the maxillary canine is apical to the gingival margin of the maxillary central incisor by more than 1.0 mm, (4) the gingival margin of the maxillary canine is incisal to the gingival margin of the maxillary central incisor between 0.01 - 0.50 mm, (5) the gingival margin of the maxillary canine is incisal to the gingival margin of the maxillary central incisor between 0.51 - 1.0 mm, and (6) the gingival margin of the maxillary canine is incisal to the gingival 40 margin of the maxillary central incisor by more than 1.0 mm. Statistical Analysis All of the statistics were calculated using SPSS software version 20.0 (SPSS Inc., Chicago, Illinois). Descriptive and frequency statistics were run for U1-P, U3P, and U1-U3 for each quadrant. Non-parametric Mann- Whitney U tests were run to compare the gingival margin relationship between the maxillary central incisor and the mesial erupted maxillary canine for left vs. right sides and for male vs. female. The significance level was set at an alpha of 0.05. Reliability All of the measurements were made by the same examiner. In order to assess intra-examiner reliability, approximately 10% of the total sample was chosen to be remeasured. A random number generator from random.org selected 10 quadrants to be re-measured. Measurement reliability was determined using Cronbach’s alpha. 41 Results Using Cronbach’s alpha for intra-examiner reliability, all of the variables were above 0.80, showing that the original measurements and repeated measurements were at an acceptable level of reliability for accuracy of measurements. The average distance from the distal surface of the permanent maxillary central incisor to the mesial surface of the mesial erupted permanent maxillary canine (D-U1/U3) in the right quadrants was 1.18 mm. the average was 1.26 mm. In the left quadrants, The overall average of both quadrants was 1.22 mm, with a range of 0.0 – 3.84 mm. Table 3.1 reports the descriptive statistics for the parameters used in this study. Tables 3.2 and 3.3 show the descriptive statistics for the parameters of the right and left quadrants. Table 3.1: Descriptive statistics for U1-P, U3-P, and U1U3. Parameter N Range Min Max Mean Std. Dev U1-P (mm) 81 4.98 0.90 5.88 3.22 1.10 U3-P (mm) 81 5.97 0.14 6.11 2.83 1.23 U1-U3 (mm) 81 4.96 -1.76 3.20 0.39 1.09 42 Table 3.2: Descriptive statistics for U1-P, U3-P, and U1-U3 of the right quadrants. Parameter N Range Min Max Mean Std. Dev U1-P (mm) 41 3.64 1.24 4.88 3.20 1.08 U3-P (mm) 41 4.62 0.68 5.30 2.82 1.24 U1-U3 (mm) 41 4.20 -1.10 3.10 0.38 1.13 Table 3.3: Descriptive statistics for U1-P, U3-P, and U1-U3 of the left quadrants. Parameter N Range Min Max Mean Std. Dev U1-P (mm) 40 4.98 0.90 5.88 3.23 1.14 U3-P (mm) 40 5.97 0.14 6.11 2.84 1.24 U1-U3 (mm) 40 4.96 -1.76 3.20 0.39 1.06 Figure 3.3 summarizes the gingival margin relationship between the maxillary central incisor and maxillary canine (U1-U3). Of 81 maxillary canines, compared to the maxillary central incisor, the gingival margin for 33 (40.70%) of them was apical to the gingival margin of the central incisor and 48 (59.30%) of them were incisal. Of the 33 that were apical, 15 (18.50%) were 0.01 - 0.50 mm apical, 10 (12.30%) were 0.51 – 1.0 mm apical, and 8 (9.90%) were greater than 1.0 mm apical to the gingival margin of the central incisor. 43 Of the 48 that were incisal, 12 (14.80%) were 0.01 - 0.50 mm incisal, 17 (21.00%) were 0.51 – 1.0 mm incisal, and 19 (23.50%) were greater than 1.0 mm incisal to the gingival margin of the central incisor. 70.00% Canine Relationship to Central Incisor 59.30% 60.00% 50.00% 40.00% 40.70% % 23.50% > 1.0 mm 9.90% 0.51 - 1.0 mm 30.00% 12.30% 21.00% 0.01 - 0.50 mm 20.00% 10.00% 18.50% 14.80% 0.00% Apical to central Incisal to central incisor incisor Figure 3.3 - Maxillary canine gingival margin relationship to the maxillary central incisor gingival margin. Figure 3.4 compares the gingival margin relationship of the maxillary central incisor and maxillary canine (U1U3) between the left and right sides. There were a total of 41 quadrants on the right side and 40 on the left. 44 50.00% 46.30% 45.00% 40.00% 35.00% 35.00% 30.00% 26.80% 25.00% 25.00% 20.00% Left Side 20.00% 20.00% 17.10% Right Side 15.00% 9.80% 10.00% 5.00% 0.00% Apical to central incisor 0-0.5 mm incisal 0.5-1 mm incisal > 1 mm incisal Figure 3.4 - Maxillary canine gingival margin relationship to the maxillary central incisor gingival margin: Left vs. Right quadrants. Tables 3.4 and 3.5 show the descriptive statistics for the parameters of the male and female quadrants. Table 3.4: Descriptive statistics for U1-P, U3-P, and U1-U3 of the male quadrants. Parameter N Range Min Max Mean Std. Dev U1-P (mm) 39 4.47 1.41 5.88 3.14 1.23 U3-P (mm) 39 5.16 0.14 5.30 2.61 1.19 U1-U3 (mm) 39 4.19 -1.09 3.10 0.54 1.14 45 Table 3.5: Descriptive statistics for U1-P, U3-P, and U1-U3 of the female quadrants. Parameter N Range Min Max Mean Std. Dev U1-P (mm) 42 4.39 0.90 5.29 3.29 0.98 U3-P (mm) 42 5.43 0.68 6.11 3.04 1.25 U1-U3 (mm) 42 4.96 -1.76 3.20 0.25 1.03 Figure 3.5 compares the gingival margin relationship of the maxillary central incisor and maxillary canine (U1U3) between males and females. There were a total of 39 male quadrants and 42 female quadrants. 50.00% 45.00% 40.00% 42.90% 38.50% 35.00% 30.80% 30.00% 23.80% 25.00% 20.00% 16.70% 17.90% Male 16.70% Female 12.80% 15.00% 10.00% 5.00% 0.00% Apical to central incisor 0-0.5 mm incisal 0.5-1 mm incisal > 1 mm incisal Figure 3.5 - Maxillary canine gingival margin relationship to the maxillary central incisor gingival margin: Male vs. Female quadrants. 46 The Mann-Whitney U test failed to show any statistically significant difference with relation to gender (p-value of 0.343) or left/right side (p-value of 0.788) for gingival margin relationship between the maxillary central incisor and the mesial erupted permanent maxillary canine. Discussion The purpose of this study was to determine, in patients who are congenitally missing permanent maxillary lateral incisors, if the natural gingival margin relationship between the maxillary central incisor and the more mesial erupted maxillary canine is similar to the natural gingival margin relationship between the maxillary central incisor and the maxillary lateral incisor. Multiple authors in the literature suggest that the gingival margins of the central incisors should be at the same level as the canines, with those of the lateral incisors positioned more incisal.12, 16-18, 23, 24 However, it is important to keep in mind that this is only their expert opinion of what the ideal gingival margin relationship is, not what it naturally is, and that none of these studies directly measured the natural relationship between the 47 gingival margins of the maxillary central and lateral incisors. Many of these authors formed their opinion based on surveys where people ranked photographs of the smile, with only the gingival margin relationship between the maxillary central and lateral incisors being altered.16-19 Other studies did actually measure the gingival margin relationship between the maxillary central and lateral incisor, either directly on plaster casts using digital calipers or indirectly using computer software and digital photographs of plaster casts.20, 21 Chu et al had a sample of 20 patients in which they measured directly on plaster casts the gingival margin relationship between the maxillary central and lateral incisors.21 They found the gingival margin of the maxillary lateral incisor on average to be about 1 mm (0.94 mm on the right side and 0.95 mm on the left side) incisal to that of the maxillary central incisor. In the present study, the gingival margin of the mesial erupted maxillary canine was found to be on average about 0.39 mm (0.38 mm on the right side and 0.39 mm on the left side) incisal to the gingival margin of the maxillary central incisor. Charruel et al investigated 103 patients using computer software and digital photographs of plaster casts to obtain measurements of the gingival margin relationship 48 between the maxillary central and lateral incisors.20 They found the gingival margin of the maxillary lateral incisor on average to be 0.68 mm incisal to the gingival margin of the maxillary central incisor. This is closer to the finding of the present study (0.39 mm incisal) than what Chu et al found in their study.21 Charruel et al also found in their study that about four percent of maxillary lateral incisors had their gingival margin apical to the gingival margin of the maxillary central incisor, 15% were at the same level, 54% were between 0.0 – 1.0 mm incisal, and 27% were greater than 1.0 mm incisal.20 In the present study, 40.7% of mesial erupted maxillary canines were found with the gingival margin apical to the gingival margin of the maxillary central incisor, 35.8% were between 0.0 – 1.0 mm incisal, and 23.5% were greater than 1.0 mm incisal. The present study found a much higher percentage of maxillary canines with a gingival margin more apical than that of the maxillary central incisor. This could be due to the fact that in previous studies, they had an extra category in which to place the gingival margin relationship. This category was for maxillary lateral incisors that had the gingival margin at the same level as the gingival margin of the maxillary 49 central incisors. The problem lies in that they didn’t specify how close the gingival margins had to be in order to be included in that category and excluded from the categories above and below it. In the present study, not one sample was exactly on the same level. Some were very close, but they were categorized as either apical or incisal to the maxillary central incisor. It is also possible that in the study by Charruel et al, some of the 15% of maxillary lateral incisors that were categorized as on the same level as the maxillary central incisor could be placed in either the 0.0 – 1.0 mm incisal category or the apical to the central incisor category, increasing the percentages of those categories and bringing them closer to the percentages found in the current study’s 0.0 – 1.0 mm (35.8%) and apical to the central incisor (40.7%) categories.20 In the studies by Chu et al and Charruel et al, their samples did not exclude patients that had orthodontic treatment previously.20, 21 By not making that part of the exclusion criteria, one is able to question the validity of their results because they didn’t really look at the natural relationship between gingival margins of maxillary central and lateral incisors. If some of their sample had 50 orthodontic treatment previously, then the measurements on those specific patients shouldn’t be considered natural. In a study by An et al, previous orthodontic treatment was one of their exclusion criteria.19 They examined 120 dental students and found 14.60% of gingival margins of maxillary lateral incisors to be apical to the gingival margins of maxillary central incisors, 25.90% were at the same level, and 59.40% were incisal. The present study had a similar finding, in that it found 59.30% of gingival margins of mesial erupted maxillary canines to be incisal to the gingival margins of maxillary central incisors. Again, by not specifying how close the gingival margins had to be to each other in order to be included in the “same level” category, one may assume that some of the 25.9% could actually be placed in either of the other two categories, increasing those percentages as well, which could make their findings more similar or different to those in the present study. The current study was similar to other studies in that it found no significant difference with relation to gender or left/right side for gingival margin relationship between the maxillary central incisor and a mesial erupted maxillary canine.20, 21 51 The results from the present study suggest that the gingival margin relationship between the permanent maxillary central incisor and a mesial erupted permanent maxillary canine should be included as another criterion in each doctor’s protocol when treatment planning patients who are congenitally missing a permanent maxillary lateral incisor. One of the limitations of the study was the small sample size (n=81 quadrants). Another limitation was the age of the patients in the sample. Because the sample consisted of patients between 10 – 18 years of age, there is always the possibility of tooth eruption affecting the gingival margins. The results from this study are grounds for new investigations in which the gingival margin relationships between the normally erupted permanent maxillary central incisor, maxillary lateral incisor, and maxillary canine can be compared to the missing permanent maxillary lateral incisor side. 52 Conclusions Based on the results of this study, one can conclude that: 1) Mesial erupted permanent maxillary canines in adolescents who are congenitally missing permanent maxillary lateral incisors have a gingival margin that is apical to the gingival margin of the permanent maxillary central incisor 40.70% of the time, and incisal to the gingival margin of the permanent maxillary central incisor 59.30% of the time. 2) There is no significant difference with relation to gender or left/right side for gingival margin relationship between the maxillary central incisor and a mesial erupted maxillary canine. 53 Literature Cited 1. Muller TP, Hill IN, Peterson AC, Blayney JR. A survey of congenitally missing permanent teeth. J Am Dent Assoc. 1970;81:101-7. 2. Boruchov MJ, Green LJ. Hypodontia in human twins and families. Am J Orthod. 1971;60:165-74. 3. Silverman NE, Ackerman JL. Oligodontia: a study of its prevalence and variation in 4032 children. ASDC J Dent Child. 1979;46:470-7. 4. Polder BJ, Van't Hof MA, Van der Linden FP, KuijpersJagtman AM. A meta-analysis of the prevalence of dental agenesis of permanent teeth. Community Dent Oral Epidemiol. 2004;32:217-26. 5. Robertsson S, Mohlin B. The congenitally missing upper lateral incisor. A retrospective study of orthodontic space closure versus restorative treatment. Eur J Orthod. 2000;22:697-710. 6. Araujo EA, Oliveira DD, Araujo MT. Diagnostic protocol in cases of congenitally missing maxillary lateral incisors. World J Orthod. 2006;7:376-88. 7. Kokich VO, Jr., Kinzer GA. Managing congenitally missing lateral incisors. Part I: Canine substitution. J Esthet Restor Dent. 2005;17:5-10. 8. Tuverson DL. Orthodontic treatment using canines in place of missing maxillary lateral incisors. Am J Orthod. 1970;58:109-27. 9. Sabri R. Management of missing maxillary lateral incisors. J Am Dent Assoc. 1999;130:80-4. 10. Rosa M, Zachrisson BU. Integrating esthetic dentistry and space closure in patients with missing maxillary lateral incisors. J Clin Orthod. 2001;35:221-34. 11. McNeill RW, Joondeph DR. Congenitally absent maxillary lateral incisors: treatment planning considerations. Angle Orthod. 1973;43:24-9. 54 12. Kokich VG, Spear FM. Guidelines for managing the orthodontic-restorative patient. Semin Orthod. 1997;3:3-20. 13. Zachrisson BU. Improving orthodontic results in cases with maxillary incisors missing. Am J Orthod. 1978;73:274-89. 14. Kinzer GA, Kokich VO, Jr. Managing congenitally missing lateral incisors. Part II: tooth-supported restorations. J Esthet Restor Dent. 2005;17:76-84. 15. Rendon J. Effect of congenitally missing lateral incisors on the eruption and impaction of the maxillary canine: Saint Louis University; 2005. 16. Kokich VO, Jr., Kiyak HA, Shapiro PA. Comparing the perception of dentists and lay people to altered dental esthetics. J Esthet Dent. 1999;11:311-24. 17. Springer NC, Chang C, Fields HW, Beck FM, Firestone AR, Rosenstiel S, Christensen JC. Smile esthetics from the layperson's perspective. Am J Orthod Dentofacial Orthop. 2011;139:e91-e101. 18. Chang CA, Fields HW, Jr., Beck FM, Springer NC, Firestone AR, Rosenstiel S, Christensen JC. Smile esthetics from patients' perspectives for faces of varying attractiveness. Am J Orthod Dentofacial Orthop. 2011;140:e171-80. 19. An KY, Lee JY, Kim SJ, Choi JI. Perception of maxillary anterior esthetics by dental professionals and laypeople and survey of gingival topography in healthy young subjects. Int J Periodontics Restorative Dent. 2009;29:535-41. 20. Charruel S, Perez C, Foti B, Camps J, Monnet-Corti V. Gingival contour assessment: clinical parameters useful for esthetic diagnosis and treatment. J Periodontol. 2008;79:795-801. 21. Chu SJ, Tan JH, Stappert CF, Tarnow DP. Gingival zenith positions and levels of the maxillary anterior dentition. J Esthet Restor Dent. 2009;21:113-20. 55 22. Brough E, Donaldson AN, Naini FB. Canine substitution for missing maxillary lateral incisors: the influence of canine morphology, size, and shade on perceptions of smile attractiveness. Am J Orthod Dentofacial Orthop. 2010;138:705 e1-9; discussion -7. 23. Kokich VG. Esthetics: the orthodontic-periodontic restorative connection. Semin Orthod. 1996;2:21-30. 24. Sarver DM, Ackerman MB. Dynamic smile visualization and quantification: Part 2. Smile analysis and treatment strategies. Am J Orthod Dentofacial Orthop. 2003;124:116-27. 56 VITA AUCTORIS Gregory William Carr was born on July 02, 1980 in Salt Lake City, Utah to Michael and Carole Carr. He is the youngest of four siblings. He grew up in Bountiful, Utah graduating from Viewmont High School in 1998. He then attended Ricks College for one year on a baseball scholarship before moving to The Philippines for two years to serve a mission for The Church of Jesus Christ of Latter-day Saints. Upon returning home, he attended Ricks College for one more year and then transferred to Brigham Young University where he graduated in 2005 with a B.S. in Biology. After college, he attended Temple University’s Kornberg School of Dentistry for his dental education and received his D.M.D. in 2011. He plans to receive his M.S. and certificate in Orthodontics from Saint Louis University in 2013. Dr. Carr met his wife Jenna while attending Brigham Young University and they were married on January 18, 2005 in Salt Lake City, Utah. They have three children: Brinley, Julianne, and McKay. 57