CASE REPORT
Premolar transplantation in a patient with solitary median maxillary central incisor syndrome Bernhard C. Pseiner Vienna, Austria This case report describes the orthodontic treatment of an 11-year-old girl with solitary median maxillary central incisor syndrome, a presumed microform of holoprosencephaly. Because both second premolars were missing in the maxilla, deciduous molar extraction and orthodontic space opening were performed, moving the solitary median maxillary central incisor electively off-center. A mandibular second premolar was transplanted to replace the missing incisor. The resulting spaces could be orthodontically closed in both arches. Prosthodontic reshaping of the transplanted tooth after debonding completed the dental treatment. (Am J Orthod Dentofacial Orthop 2014;146:786-94)
S
olitary median maxillary central incisor (SMMCI) syndrome was first introduced by Hall et al1 in 1997, describing a developmental abnormality with an uncertain etiology. An incidence of 1 in 50,000 live births was estimated.2 The characteristic and most prominent trait of this condition is the single incisor that develops and erupts precisely in the midline of the maxillary dental arch in both the deciduous and permanent dentitions. The crown morphology of the SMMCI is strictly symmetric. Further oral features are a pseudonotched or arch-shaped appearance of the upper lip with an indistinct philtrum, the absence of a labial frenulum, and a V-shaped palate with an unusual narrow ridge along the midpalatal suture.1 According to Kjaer et al,3 SMMCI syndrome is the mildest form of holoprosencephaly, a developmental defect affecting the forebrain, with cyclopia as its most severe expression. The spectrum of associated anomalies shows wide variability; however, the following features were found to be typical of the syndrome: preterm birth and low birth weight in 37% of cases, potentially lifethreatening congenital nasal airway obstruction (choanal atresia, midnasal stenosis, or nasal pyriform aperture stenosis in over 90%), short stature in 50%, small head
Resident, Division of Orthodontics, Bernhard Gottlieb University Clinic of Dentistry, Medical University of Vienna, Vienna, Austria. The author has completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. This case report formed part of the requirement for provisional membership in the European Board of Orthodontists. Address correspondence to: Bernhard C. Pseiner, Sensengasse 2a, A-1090 Vienna, Austria; e-mail, [email protected]. Submitted, September 2013; revised and accepted, November 2013. 0889-5406/$36.00 Copyright Ó 2014 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2013.11.027
786
circumference in 33%, hypotelorism in 45%, intellectual disability varying in degree in 50% (from slow learning to intellectual retardation), possible association with epilepsy and attention-deficit/hyperactivity disorder, and deviant sella turcica and pituitary gland morphologies.2 Regarding comprehensive orthodontic treatment in patients with SMMCI syndrome, there are only 2 reports in the literature: Bolan et al4 described rapid maxillary expansion in a 6-year-old boy monitored with cone-beam computed tomography. Although his posterior crossbite could be clinically corrected, the tomography showed no opening of the midpalatal suture because of probable fusion of the anterior sutural region, where the SMMCI is typically located. Lygidakis et al5 reported on a 14-year follow-up of a male patient with SMMCI syndrome. After maxillary expansion at the age of 4, anterior space was created orthodontically to insert a Maryland bridge for replacement of the missing central incisor at the age of 16. This report concentrates on the orthodontic management of a patient with SMMCI syndrome and promotes premolar transplantation as an advantageous treatment approach. DIAGNOSIS
An 11-year-old girl presented with a single maxillary central incisor at the orthodontic department of the Medical University of Vienna in Austria. Her parents requested a second opinion concerning orthodontic treatment. After having made records alio loco, both the panoramic and the lateral skull radiographs were already available. Allergies to pollen, animal hair, and penicillin were reported. There was no family history of hereditary disease. The patient's medical history indicated respiratory distress and surgery soon after birth. Neither the surgeon
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Fig 1. Pretreatment facial and intraoral photographs.
nor the pediatrician could be contacted for details. However, narrowing of her nasal airways persisted to some extent, resulting in habitual mouth breathing. Bruxing was reported by the parents, causing the first signs of dental wear on the mandibular incisors. Neither temporomandibular joint problems nor a centric relation-centric occlusion discrepancy was found. The clinical examination showed a dolichocephalic, symmetric face with harmonious facial thirds and a narrow nose (Fig 1). The profile was convex with a decreased nasolabial angle and a retrognathic chin. A high central portion of the upper lip with an indistinct philtrum was the extraoral characteristic of the SMMCI syndrome. The maxillary central incisor was positioned precisely in the facial midline. Intraorally, the patient was in the late mixed dentition with 3 remaining second deciduous molars (Fig 2). A surplus of space could be detected in both arches (1 mm in
the mandibular arch considering leeway space, 3.9 mm in the maxillary arch). There were both a Class I molar relationship on the left side and a Class II tendency (a quarter unit) on the right side. Overjet accounted for 3 mm, and overbite for 4 mm. The mandibular dental midline was shifted 1 mm to the right. The typical intraoral features of SMMCI syndrome were a V-shaped palate with a marked midpalatal vomerine ridge, the absence of the labial frenulum of the upper lip, and the symmetric crown form of the SMMCI with normal crown dimensions. The contour of both approximal surfaces of this incisor had the characteristic anatomic shape of the distal surface of a normal central incisor. In addition to the absence of a maxillary central incisor, the panoramic radiograph showed agenesis of both maxillary second premolars (Fig 3). The corresponding deciduous molars were still present. The left second deciduous molar was also persistent in the
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Fig 2. Pretreatment dental casts.
average values. The morphology of the pituitary fossa appeared to be normal. In terms of other syndrome-associated anomalies, the patient had no intellectual disability and showed no hypotelorism. She had a slightly shorter stature than her 1-year-younger sister. TREATMENT OBJECTIVES
Fig 3. Pretreatment panoramic radiograph.
mandible, indicating an asymmetric tooth eruption pattern of the mandibular second premolars. The maxillary second molars were about to erupt. The germs of the mandibular third molars could be identified. No caries lesions or fillings were detectable. The narrow nasal cavity with a slight asymmetric nasal septum was characteristic of SMMCI syndrome. The cephalometric data indicated a considerably vertical Class I relationship with a vertical jaw relationship: ANS-PNS/Go-Gn, 31 (Fig 4). Both jaws were retrognathic (SNA angle, 79 ; SNB angle, 76 ) and posteriorly inclined (S-N/ANS-PNS, 10 ; S-N/Go-Gn, 41 ). Dental and dento-basal relationship measurements showed
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The treatment goals included orthodontic space opening in the maxillary incisor region and autogenous transplantation of a mandibular second premolar, consecutively. Space closure would be performed in the donor tooth region as well as in the maxilla, where the second premolars were missing, achieving a Class II molar relationship on the right side and a Class I relationship on the left side. Finally, recontouring of the maxillary incisors was planned. Since the SMMCI did not have the morphology of a right or left central incisor, orthodontic space opening would be performed on the left, where more space was initially available. Thus, the recipient site for the transplant was determined to be the left central incisor region. TREATMENT ALTERNATIVES
The only way to achieve an esthetically satisfying result for a patient with SMMCI syndrome with a symmetric Class I occlusion is to provide space for a second
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Fig 4. Pretreatment lateral cephalogram and tracing.
Fig 5. Intraoral photographs after space opening in the anterior maxillary region.
Fig 6. Radiographic evaluation 3 months after premolar transplantation.
central incisor. Because most patients prefer fixed prosthodontic rehabilitation, a single-tooth implant and a bridge are possible alternatives. However, especially in adolescents, both have disadvantages. The preparation
for bridgework is often too invasive for the abutment teeth at this age. Dental implantation should only be performed when alveolar growth has ceased in this region, since an implant acts as an ankylosed tooth.
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At the halfway point of the treatment, the patient was diagnosed with type 1 diabetes, but this did not affect compliance or tooth movement negatively. TREATMENT RESULTS
Fig 7. Transplanted tooth after bite blocking.
Therefore, growing patients must use removable retainers with an artificial tooth permanently for many years until implantation is recommendable. Alternatively, Maryland bridges with minimal enamel reduction can serve as interim restorations. TREATMENT PROGRESS
Fixed appliances were used, involving a straight-wire appliance with a slot dimension of 0.022 in and a 9-mm transpalatal bar made of stainless steel. Leveling and aligning of the maxillary arch were done first, and then the maxillary deciduous molars were extracted. Palatally positioned, crossed-lever arms (0.9-mm stainless steel) were applied to move the neighboring incisors bodily apart.6 After 11 months of treatment (Fig 5), the mandibular left second premolar was transplanted into the region of the left central maxillary incisor and directly bonded to the stainless steel wire for 3 months (Fig 6). For details on the appropriate surgical technique of autotransplantation of developing premolars, refer to the recent article by Plakwicz et al.7 Because positioning of the transplant in infraocclusion was omitted by the surgeon, bite blocking was necessary to prevent occlusal trauma postoperatively (Fig 7). At this stage, gradual grinding of the palatal cusp of the transplanted premolar was initiated, and the mandibular dental arch was bonded. The 3 extraction sites in the premolar regions were eventually closed with sliding mechanics and appropriate use of elastics to reinforce anchorage. To obtain a harmonious gingival contour height of the transplanted tooth, substantial intrusion was required after the use of provisional composite buildups to adapt its morphology properly. Careful intrusion (starting again with a 0.012-in nickel-titanium wire) prolonged the treatment time significantly: The transplanted tooth was gradually elongated with composite to be able to reposition the bracket more incisally. After 4 years 1 month, the brackets were debonded, and the transplanted tooth could be restored with a ceramic crown.
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The posttreatment photographs showed a slim and symmetric face with a prominent chin (Fig 8). Although the patient's facial appearance remained dolichocephalic, a relaxed lip closure was possible. The relationship of the upper and lower lips was harmonized in the frontal and lateral views. When she was smiling, the vertical and transverse positions of the teeth seemed satisfactory, although the gingiva and the teeth had a better display on the left side. Her facial profile definitely improved during growth and treatment, presenting an excellent projection of the chin with a pleasing chinthroat distance. Oral hygiene was always fairly good; hence, no detrimental effects on the hard or soft tissues could be detected in this regard. The occlusion showed a rather solid interdigitation with a full Class II molar relationship on the right, and a full Class I molar relationship on the left (Fig 9). The mandibular dental arch was asymmetric because the fourth quadrant was the only one with 2 premolars. Whereas the mandibular dental midline was still slightly shifted to the left, the maxillary midline coincided nicely with the facial midline. Incisal overjet and overbite were only just within normal limits, and overjet of the second molars could have been further improved. There were minimal height differences of the interproximal ridges between the first and second molars in quadrants I to III. The mandibular canines could have been more elongated, and the maxillary right canine and its lateral incisor had slightly too much labial crown torque. Reshaping of the symmetric SMMCI and the lateral incisors, which were slightly too narrow, was refused by the patient. After the already extensive treatment, she only wanted to adjust the transplanted tooth to create the anatomic form of a left central incisor by an indirect restoration. Considering the gingival contour of the transplanted tooth, a marginal tissue recession in the midfacial aspect of the tooth was evident. No centric relation-centric occlusion discrepancy could be detected. The masticatory muscles and the temporomandibular joints remained symptom-free; however, bruxing persisted, resulting in dental wear of the mandibular molars and front teeth. In the intraoral radiographs, the transplanted premolar demonstrated a rather normal root length, obliteration of the crown pulp, and hardly any sign of apical root resorption at 3 years after surgery (Fig 10). However, its root appeared thinner than those of the other premolars. There was adequate root parallelism of the dentition
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Fig 8. Posttreatment facial and intraoral photographs.
(except for the second molars and the mandibular left first premolar) with sparse signs of root resorption in the incisal regions (especially the maxillary left lateral incisor and mandibular left central incisor). Monitoring of the development of the mandibular third molars was scheduled. If they erupt, extraction of these teeth will be recommended because of the missing maxillary third molars. The skeletal relationships remained quite stable throughout the treatment, especially in the sagittal aspect (Fig 11). Only slight changes in mandibular inclination (from 41 to 43.5 ) and vertical jaw relationship (from 31 to 33 ) indicated further vertical facial growth. Maxillary incisor inclination decreased (from 113 to 108 ), and mandibular incisor inclination remained rather steep (88 and 89 ), compensating for the vertical growth pattern. Overjet and overbite could be harmonized. The main objectives of the retention phase were to keep the transplanted tooth in situ and the other teeth aligned. After a solid interdigitation was achieved, 2 bonded lingual retainers were used: from canine to
canine in the mandibular arch, and from lateral incisor to lateral incisor in the maxillary arch. Because of the persistent bruxing, nighttime wear of a maxillary occlusal splint was recommended both to protect the enamel and the incisal crown, and to retain the arch form and the small spaces distal to the lateral incisors until the patient was willing to have the appropriate buildups made. DISCUSSION
The presence of a single maxillary incisor without a reported history of trauma should always be considered as a sign of a potentially serious developmental anomaly.2 SMMCI syndrome was previously presumed to be a simple midline defect of the dental lamina, but it is now recognized as a possible predictor of holoprosencephaly of varying degrees. Therefore, differential diagnosis is crucial to be able to commence interdisciplinary management of these patients at an early stage. Depending on the severity of the condition, various specialties need to be involved: neonatal or developmental pediatrics, plastic or general surgery, pediatric dentistry, neurology, otolaryngology,
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Fig 9. Posttreatment dental casts.
Fig 10. Radiographic evaluation 3 years after premolar transplantation.
and genetics are among them.2 In patients with mild SMMCI only and nasal airway narrowing (such as this patient), pediatric dental care and genetic counseling are the central tasks. Because there is evidence that early maxillary expansion during the deciduous or mixed dentition phase might not improve the dimensions of the nasomaxillary complex, orthodontic treatment may be recommended only after eruption of the permanent teeth.4 The SMMCI is primarily an esthetic problem that is ideally managed by a combination of orthodontics, prosthodontics, and oral surgery.2 The reported options usually comprise a dental implant or bridgework to replace the missing incisor after orthodontic space opening. The favorable alternative of tooth transplantation in such a
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specific case has not been mentioned in the scientific literature to date. Czochrowska et al8,9 demonstrated that transplantation of developing premolars has a successful and predictable outcome even decades later, comparing favorably with other treatment modalities for replacing missing teeth. Depending on the duration of the observation time, survival rates of autotransplanted teeth range from 90% to 100%,7,8,10 with success rates of 79% to 91%, indicating the absence of pathology, ankylosis, and decreased root length.7,8 Unlike an osseointegrated implant, a transplanted tooth has the capacity for functional adaptation and preservation of the alveolar ridge, which is especially needed in growing adolescents.8 Premolar transplants and adjacent hard
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Fig 11. Posttreatment lateral cephalogram and tracing.
and soft tissues in the maxillary incisor region were shown to be physiologically similar to natural incisors.11 Depending largely on the prosthodontic restoration, though, transplanted premolars reshaped to replace maxillary incisors are perfectly able to match the natural contralateral incisor and meet the esthetic demands of both patients and professionals.9 Success rates are highest when the donor teeth are premolars and have half to two thirds of their root development.12 Since it was clear that space opening would need some time in this patient, the mandibular second premolar on the left side was selected as the donor tooth because it was the least developed premolar at the time of treatment planning. Apart from the time-consuming and difficult space opening with the lever arms in the narrow anterior palate, the most problematic issues were the intraoperative insertion and the position of the transplanted tooth postoperatively. The press-fit approach of the surgeon (no fixation suture was used) might have resulted in the gingival recession at the end of treatment. However, lag time between transplantation and initiation of the necessary intrusion could have been longer in this regard. Czochrowska et al13 suggested orthodontic tooth movement not earlier than 6 months after transplantation. The problems with the transplanted tooth (surgical positioning too occlusally, gingival recession) show the importance of precise coordination between the oral surgeon and the orthodontist. In this patient, the treatment time and the esthetic result might have differed
considerably if interdisciplinary communication had been better. If the gingival status of the transplanted tooth deteriorates, periodontal surgery should be considered. Although the gingival recession diminishes the accomplishments of the treatment slightly, the patient's facial and smile esthetics improved significantly. CONCLUSIONS
1.
2. 3.
4. 5.
A single maxillary incisor with no history of trauma should be considered a possible predictor of holoprosencephaly. Interdisciplinary management of a patient with SMMCI syndrome is obligatory. Premolar transplantation can be considered an advantageous alternative in the dental treatment of patients with SMMCI syndrome. With tooth transplantation, a well-coordinated team is crucial for success in the long term. Despite the long treatment duration of 4 years, the orthodontic result of this patient appeared satisfactory from biologic and esthetic perspectives.
REFERENCES 1. Hall RK, Bankier A, Aldred MJ, Kan K, Lucas JO, Perks AG. Solitary median maxillary central incisor, short stature, choanal atresia/ midnasal stenosis (SMMCI) syndrome. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997;84:651-62. 2. Hall RK. Solitary median maxillary central incisor (SMMCI) syndrome. Orphanet J Rare Dis 2006;1:12.
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3. Kjaer I, Becktor KB, Lisson J, Gormsen C, Russell BG. Face, palate, and craniofacial morphology in patients with a solitary median maxillary central incisor. Eur J Orthod 2001;23:63-73. 4. Bolan M, Derech CD, Correa M, Ribeiro GL, Almeida IC. Palatal expansion in a patient with solitary median maxillary central incisor syndrome. Am J Orthod Dentofacial Orthop 2010;138: 493-7. 5. Lygidakis NN, Chatzidimitriou K, Petrou N, Lygidakis NA. Solitary median maxillary central incisor syndrome (SMMCI) with congenital nasal puriform aperture stenosis: literature review and case report with comprehensive dental treatment and 14 years follow-up. Eur Arch Paediatr Dent 2013;14:417-23. 6. Kucher G, Weiland FJ, Bantleon HP. Modified lingual lever arm technique. J Clin Orthod 1993;27:18-22. 7. Plakwicz P, Wojtowicz A, Czochrowska EM. Survival and success rates of autotransplanted premolars: a prospective study of the protocol for developing teeth. Am J Orthod Dentofacial Orthop 2013;144:229-37. 8. Czochrowska EM, Stenvik A, Bjercke B, Zachrisson BU. Outcome of tooth transplantation: survival and success rates 17-41 years
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9.
10.
11.
12.
13.
posttreatment. Am J Orthod Dentofacial Orthop 2002;121: 110-9. Czochrowska EM, Stenvik A, Zachrisson BU. The esthetic outcome of autotransplanted premolars replacing maxillary incisors. Dent Traumatol 2002;18:237-45. Andreasen JO, Paulsen HU, Yu Z, Bayer T, Schwartz O. A long-term study of 370 autotransplanted premolars. Part II. Tooth survival and pulp healing subsequent to transplantation. Eur J Orthod 1990;12:14-24. Czochrowska EM, Stenvik A, Album B, Zachrisson BU. Autotransplantation of premolars to replace maxillary incisors: a comparison with natural incisors. Am J Orthod Dentofacial Orthop 2000;118: 592-600. Schwartz O, Bergmann P, Klausen B. Autotransplantation of human teeth. A life-table analysis of prognostic factors. Int J Oral Surg 1985;14:245-58. Czochrowska EM, Semb G, Stenvik A. Nonprosthodontic management of alveolar clefts with 2 incisors missing on the cleft side: a report of 5 patients. Am J Orthod Dentofacial Orthop 2002;122:587-92.
American Journal of Orthodontics and Dentofacial Orthopedics
Premolar transplantation in a patient with solitary median maxillary central incisor syndrome Bernhard C. Pseiner Vienna, Austria This case report describes the orthodontic treatment of an 11-year-old girl with solitary median maxillary central incisor syndrome, a presumed microform of holoprosencephaly. Because both second premolars were missing in the maxilla, deciduous molar extraction and orthodontic space opening were performed, moving the solitary median maxillary central incisor electively off-center. A mandibular second premolar was transplanted to replace the missing incisor. The resulting spaces could be orthodontically closed in both arches. Prosthodontic reshaping of the transplanted tooth after debonding completed the dental treatment. (Am J Orthod Dentofacial Orthop 2014;146:786-94)
S
olitary median maxillary central incisor (SMMCI) syndrome was first introduced by Hall et al1 in 1997, describing a developmental abnormality with an uncertain etiology. An incidence of 1 in 50,000 live births was estimated.2 The characteristic and most prominent trait of this condition is the single incisor that develops and erupts precisely in the midline of the maxillary dental arch in both the deciduous and permanent dentitions. The crown morphology of the SMMCI is strictly symmetric. Further oral features are a pseudonotched or arch-shaped appearance of the upper lip with an indistinct philtrum, the absence of a labial frenulum, and a V-shaped palate with an unusual narrow ridge along the midpalatal suture.1 According to Kjaer et al,3 SMMCI syndrome is the mildest form of holoprosencephaly, a developmental defect affecting the forebrain, with cyclopia as its most severe expression. The spectrum of associated anomalies shows wide variability; however, the following features were found to be typical of the syndrome: preterm birth and low birth weight in 37% of cases, potentially lifethreatening congenital nasal airway obstruction (choanal atresia, midnasal stenosis, or nasal pyriform aperture stenosis in over 90%), short stature in 50%, small head
Resident, Division of Orthodontics, Bernhard Gottlieb University Clinic of Dentistry, Medical University of Vienna, Vienna, Austria. The author has completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported. This case report formed part of the requirement for provisional membership in the European Board of Orthodontists. Address correspondence to: Bernhard C. Pseiner, Sensengasse 2a, A-1090 Vienna, Austria; e-mail, [email protected]. Submitted, September 2013; revised and accepted, November 2013. 0889-5406/$36.00 Copyright Ó 2014 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2013.11.027
786
circumference in 33%, hypotelorism in 45%, intellectual disability varying in degree in 50% (from slow learning to intellectual retardation), possible association with epilepsy and attention-deficit/hyperactivity disorder, and deviant sella turcica and pituitary gland morphologies.2 Regarding comprehensive orthodontic treatment in patients with SMMCI syndrome, there are only 2 reports in the literature: Bolan et al4 described rapid maxillary expansion in a 6-year-old boy monitored with cone-beam computed tomography. Although his posterior crossbite could be clinically corrected, the tomography showed no opening of the midpalatal suture because of probable fusion of the anterior sutural region, where the SMMCI is typically located. Lygidakis et al5 reported on a 14-year follow-up of a male patient with SMMCI syndrome. After maxillary expansion at the age of 4, anterior space was created orthodontically to insert a Maryland bridge for replacement of the missing central incisor at the age of 16. This report concentrates on the orthodontic management of a patient with SMMCI syndrome and promotes premolar transplantation as an advantageous treatment approach. DIAGNOSIS
An 11-year-old girl presented with a single maxillary central incisor at the orthodontic department of the Medical University of Vienna in Austria. Her parents requested a second opinion concerning orthodontic treatment. After having made records alio loco, both the panoramic and the lateral skull radiographs were already available. Allergies to pollen, animal hair, and penicillin were reported. There was no family history of hereditary disease. The patient's medical history indicated respiratory distress and surgery soon after birth. Neither the surgeon
Pseiner
787
Fig 1. Pretreatment facial and intraoral photographs.
nor the pediatrician could be contacted for details. However, narrowing of her nasal airways persisted to some extent, resulting in habitual mouth breathing. Bruxing was reported by the parents, causing the first signs of dental wear on the mandibular incisors. Neither temporomandibular joint problems nor a centric relation-centric occlusion discrepancy was found. The clinical examination showed a dolichocephalic, symmetric face with harmonious facial thirds and a narrow nose (Fig 1). The profile was convex with a decreased nasolabial angle and a retrognathic chin. A high central portion of the upper lip with an indistinct philtrum was the extraoral characteristic of the SMMCI syndrome. The maxillary central incisor was positioned precisely in the facial midline. Intraorally, the patient was in the late mixed dentition with 3 remaining second deciduous molars (Fig 2). A surplus of space could be detected in both arches (1 mm in
the mandibular arch considering leeway space, 3.9 mm in the maxillary arch). There were both a Class I molar relationship on the left side and a Class II tendency (a quarter unit) on the right side. Overjet accounted for 3 mm, and overbite for 4 mm. The mandibular dental midline was shifted 1 mm to the right. The typical intraoral features of SMMCI syndrome were a V-shaped palate with a marked midpalatal vomerine ridge, the absence of the labial frenulum of the upper lip, and the symmetric crown form of the SMMCI with normal crown dimensions. The contour of both approximal surfaces of this incisor had the characteristic anatomic shape of the distal surface of a normal central incisor. In addition to the absence of a maxillary central incisor, the panoramic radiograph showed agenesis of both maxillary second premolars (Fig 3). The corresponding deciduous molars were still present. The left second deciduous molar was also persistent in the
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Fig 2. Pretreatment dental casts.
average values. The morphology of the pituitary fossa appeared to be normal. In terms of other syndrome-associated anomalies, the patient had no intellectual disability and showed no hypotelorism. She had a slightly shorter stature than her 1-year-younger sister. TREATMENT OBJECTIVES
Fig 3. Pretreatment panoramic radiograph.
mandible, indicating an asymmetric tooth eruption pattern of the mandibular second premolars. The maxillary second molars were about to erupt. The germs of the mandibular third molars could be identified. No caries lesions or fillings were detectable. The narrow nasal cavity with a slight asymmetric nasal septum was characteristic of SMMCI syndrome. The cephalometric data indicated a considerably vertical Class I relationship with a vertical jaw relationship: ANS-PNS/Go-Gn, 31 (Fig 4). Both jaws were retrognathic (SNA angle, 79 ; SNB angle, 76 ) and posteriorly inclined (S-N/ANS-PNS, 10 ; S-N/Go-Gn, 41 ). Dental and dento-basal relationship measurements showed
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The treatment goals included orthodontic space opening in the maxillary incisor region and autogenous transplantation of a mandibular second premolar, consecutively. Space closure would be performed in the donor tooth region as well as in the maxilla, where the second premolars were missing, achieving a Class II molar relationship on the right side and a Class I relationship on the left side. Finally, recontouring of the maxillary incisors was planned. Since the SMMCI did not have the morphology of a right or left central incisor, orthodontic space opening would be performed on the left, where more space was initially available. Thus, the recipient site for the transplant was determined to be the left central incisor region. TREATMENT ALTERNATIVES
The only way to achieve an esthetically satisfying result for a patient with SMMCI syndrome with a symmetric Class I occlusion is to provide space for a second
American Journal of Orthodontics and Dentofacial Orthopedics
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Fig 4. Pretreatment lateral cephalogram and tracing.
Fig 5. Intraoral photographs after space opening in the anterior maxillary region.
Fig 6. Radiographic evaluation 3 months after premolar transplantation.
central incisor. Because most patients prefer fixed prosthodontic rehabilitation, a single-tooth implant and a bridge are possible alternatives. However, especially in adolescents, both have disadvantages. The preparation
for bridgework is often too invasive for the abutment teeth at this age. Dental implantation should only be performed when alveolar growth has ceased in this region, since an implant acts as an ankylosed tooth.
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Pseiner
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At the halfway point of the treatment, the patient was diagnosed with type 1 diabetes, but this did not affect compliance or tooth movement negatively. TREATMENT RESULTS
Fig 7. Transplanted tooth after bite blocking.
Therefore, growing patients must use removable retainers with an artificial tooth permanently for many years until implantation is recommendable. Alternatively, Maryland bridges with minimal enamel reduction can serve as interim restorations. TREATMENT PROGRESS
Fixed appliances were used, involving a straight-wire appliance with a slot dimension of 0.022 in and a 9-mm transpalatal bar made of stainless steel. Leveling and aligning of the maxillary arch were done first, and then the maxillary deciduous molars were extracted. Palatally positioned, crossed-lever arms (0.9-mm stainless steel) were applied to move the neighboring incisors bodily apart.6 After 11 months of treatment (Fig 5), the mandibular left second premolar was transplanted into the region of the left central maxillary incisor and directly bonded to the stainless steel wire for 3 months (Fig 6). For details on the appropriate surgical technique of autotransplantation of developing premolars, refer to the recent article by Plakwicz et al.7 Because positioning of the transplant in infraocclusion was omitted by the surgeon, bite blocking was necessary to prevent occlusal trauma postoperatively (Fig 7). At this stage, gradual grinding of the palatal cusp of the transplanted premolar was initiated, and the mandibular dental arch was bonded. The 3 extraction sites in the premolar regions were eventually closed with sliding mechanics and appropriate use of elastics to reinforce anchorage. To obtain a harmonious gingival contour height of the transplanted tooth, substantial intrusion was required after the use of provisional composite buildups to adapt its morphology properly. Careful intrusion (starting again with a 0.012-in nickel-titanium wire) prolonged the treatment time significantly: The transplanted tooth was gradually elongated with composite to be able to reposition the bracket more incisally. After 4 years 1 month, the brackets were debonded, and the transplanted tooth could be restored with a ceramic crown.
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The posttreatment photographs showed a slim and symmetric face with a prominent chin (Fig 8). Although the patient's facial appearance remained dolichocephalic, a relaxed lip closure was possible. The relationship of the upper and lower lips was harmonized in the frontal and lateral views. When she was smiling, the vertical and transverse positions of the teeth seemed satisfactory, although the gingiva and the teeth had a better display on the left side. Her facial profile definitely improved during growth and treatment, presenting an excellent projection of the chin with a pleasing chinthroat distance. Oral hygiene was always fairly good; hence, no detrimental effects on the hard or soft tissues could be detected in this regard. The occlusion showed a rather solid interdigitation with a full Class II molar relationship on the right, and a full Class I molar relationship on the left (Fig 9). The mandibular dental arch was asymmetric because the fourth quadrant was the only one with 2 premolars. Whereas the mandibular dental midline was still slightly shifted to the left, the maxillary midline coincided nicely with the facial midline. Incisal overjet and overbite were only just within normal limits, and overjet of the second molars could have been further improved. There were minimal height differences of the interproximal ridges between the first and second molars in quadrants I to III. The mandibular canines could have been more elongated, and the maxillary right canine and its lateral incisor had slightly too much labial crown torque. Reshaping of the symmetric SMMCI and the lateral incisors, which were slightly too narrow, was refused by the patient. After the already extensive treatment, she only wanted to adjust the transplanted tooth to create the anatomic form of a left central incisor by an indirect restoration. Considering the gingival contour of the transplanted tooth, a marginal tissue recession in the midfacial aspect of the tooth was evident. No centric relation-centric occlusion discrepancy could be detected. The masticatory muscles and the temporomandibular joints remained symptom-free; however, bruxing persisted, resulting in dental wear of the mandibular molars and front teeth. In the intraoral radiographs, the transplanted premolar demonstrated a rather normal root length, obliteration of the crown pulp, and hardly any sign of apical root resorption at 3 years after surgery (Fig 10). However, its root appeared thinner than those of the other premolars. There was adequate root parallelism of the dentition
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Fig 8. Posttreatment facial and intraoral photographs.
(except for the second molars and the mandibular left first premolar) with sparse signs of root resorption in the incisal regions (especially the maxillary left lateral incisor and mandibular left central incisor). Monitoring of the development of the mandibular third molars was scheduled. If they erupt, extraction of these teeth will be recommended because of the missing maxillary third molars. The skeletal relationships remained quite stable throughout the treatment, especially in the sagittal aspect (Fig 11). Only slight changes in mandibular inclination (from 41 to 43.5 ) and vertical jaw relationship (from 31 to 33 ) indicated further vertical facial growth. Maxillary incisor inclination decreased (from 113 to 108 ), and mandibular incisor inclination remained rather steep (88 and 89 ), compensating for the vertical growth pattern. Overjet and overbite could be harmonized. The main objectives of the retention phase were to keep the transplanted tooth in situ and the other teeth aligned. After a solid interdigitation was achieved, 2 bonded lingual retainers were used: from canine to
canine in the mandibular arch, and from lateral incisor to lateral incisor in the maxillary arch. Because of the persistent bruxing, nighttime wear of a maxillary occlusal splint was recommended both to protect the enamel and the incisal crown, and to retain the arch form and the small spaces distal to the lateral incisors until the patient was willing to have the appropriate buildups made. DISCUSSION
The presence of a single maxillary incisor without a reported history of trauma should always be considered as a sign of a potentially serious developmental anomaly.2 SMMCI syndrome was previously presumed to be a simple midline defect of the dental lamina, but it is now recognized as a possible predictor of holoprosencephaly of varying degrees. Therefore, differential diagnosis is crucial to be able to commence interdisciplinary management of these patients at an early stage. Depending on the severity of the condition, various specialties need to be involved: neonatal or developmental pediatrics, plastic or general surgery, pediatric dentistry, neurology, otolaryngology,
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Fig 9. Posttreatment dental casts.
Fig 10. Radiographic evaluation 3 years after premolar transplantation.
and genetics are among them.2 In patients with mild SMMCI only and nasal airway narrowing (such as this patient), pediatric dental care and genetic counseling are the central tasks. Because there is evidence that early maxillary expansion during the deciduous or mixed dentition phase might not improve the dimensions of the nasomaxillary complex, orthodontic treatment may be recommended only after eruption of the permanent teeth.4 The SMMCI is primarily an esthetic problem that is ideally managed by a combination of orthodontics, prosthodontics, and oral surgery.2 The reported options usually comprise a dental implant or bridgework to replace the missing incisor after orthodontic space opening. The favorable alternative of tooth transplantation in such a
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specific case has not been mentioned in the scientific literature to date. Czochrowska et al8,9 demonstrated that transplantation of developing premolars has a successful and predictable outcome even decades later, comparing favorably with other treatment modalities for replacing missing teeth. Depending on the duration of the observation time, survival rates of autotransplanted teeth range from 90% to 100%,7,8,10 with success rates of 79% to 91%, indicating the absence of pathology, ankylosis, and decreased root length.7,8 Unlike an osseointegrated implant, a transplanted tooth has the capacity for functional adaptation and preservation of the alveolar ridge, which is especially needed in growing adolescents.8 Premolar transplants and adjacent hard
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Fig 11. Posttreatment lateral cephalogram and tracing.
and soft tissues in the maxillary incisor region were shown to be physiologically similar to natural incisors.11 Depending largely on the prosthodontic restoration, though, transplanted premolars reshaped to replace maxillary incisors are perfectly able to match the natural contralateral incisor and meet the esthetic demands of both patients and professionals.9 Success rates are highest when the donor teeth are premolars and have half to two thirds of their root development.12 Since it was clear that space opening would need some time in this patient, the mandibular second premolar on the left side was selected as the donor tooth because it was the least developed premolar at the time of treatment planning. Apart from the time-consuming and difficult space opening with the lever arms in the narrow anterior palate, the most problematic issues were the intraoperative insertion and the position of the transplanted tooth postoperatively. The press-fit approach of the surgeon (no fixation suture was used) might have resulted in the gingival recession at the end of treatment. However, lag time between transplantation and initiation of the necessary intrusion could have been longer in this regard. Czochrowska et al13 suggested orthodontic tooth movement not earlier than 6 months after transplantation. The problems with the transplanted tooth (surgical positioning too occlusally, gingival recession) show the importance of precise coordination between the oral surgeon and the orthodontist. In this patient, the treatment time and the esthetic result might have differed
considerably if interdisciplinary communication had been better. If the gingival status of the transplanted tooth deteriorates, periodontal surgery should be considered. Although the gingival recession diminishes the accomplishments of the treatment slightly, the patient's facial and smile esthetics improved significantly. CONCLUSIONS
1.
2. 3.
4. 5.
A single maxillary incisor with no history of trauma should be considered a possible predictor of holoprosencephaly. Interdisciplinary management of a patient with SMMCI syndrome is obligatory. Premolar transplantation can be considered an advantageous alternative in the dental treatment of patients with SMMCI syndrome. With tooth transplantation, a well-coordinated team is crucial for success in the long term. Despite the long treatment duration of 4 years, the orthodontic result of this patient appeared satisfactory from biologic and esthetic perspectives.
REFERENCES 1. Hall RK, Bankier A, Aldred MJ, Kan K, Lucas JO, Perks AG. Solitary median maxillary central incisor, short stature, choanal atresia/ midnasal stenosis (SMMCI) syndrome. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997;84:651-62. 2. Hall RK. Solitary median maxillary central incisor (SMMCI) syndrome. Orphanet J Rare Dis 2006;1:12.
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3. Kjaer I, Becktor KB, Lisson J, Gormsen C, Russell BG. Face, palate, and craniofacial morphology in patients with a solitary median maxillary central incisor. Eur J Orthod 2001;23:63-73. 4. Bolan M, Derech CD, Correa M, Ribeiro GL, Almeida IC. Palatal expansion in a patient with solitary median maxillary central incisor syndrome. Am J Orthod Dentofacial Orthop 2010;138: 493-7. 5. Lygidakis NN, Chatzidimitriou K, Petrou N, Lygidakis NA. Solitary median maxillary central incisor syndrome (SMMCI) with congenital nasal puriform aperture stenosis: literature review and case report with comprehensive dental treatment and 14 years follow-up. Eur Arch Paediatr Dent 2013;14:417-23. 6. Kucher G, Weiland FJ, Bantleon HP. Modified lingual lever arm technique. J Clin Orthod 1993;27:18-22. 7. Plakwicz P, Wojtowicz A, Czochrowska EM. Survival and success rates of autotransplanted premolars: a prospective study of the protocol for developing teeth. Am J Orthod Dentofacial Orthop 2013;144:229-37. 8. Czochrowska EM, Stenvik A, Bjercke B, Zachrisson BU. Outcome of tooth transplantation: survival and success rates 17-41 years
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9.
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posttreatment. Am J Orthod Dentofacial Orthop 2002;121: 110-9. Czochrowska EM, Stenvik A, Zachrisson BU. The esthetic outcome of autotransplanted premolars replacing maxillary incisors. Dent Traumatol 2002;18:237-45. Andreasen JO, Paulsen HU, Yu Z, Bayer T, Schwartz O. A long-term study of 370 autotransplanted premolars. Part II. Tooth survival and pulp healing subsequent to transplantation. Eur J Orthod 1990;12:14-24. Czochrowska EM, Stenvik A, Album B, Zachrisson BU. Autotransplantation of premolars to replace maxillary incisors: a comparison with natural incisors. Am J Orthod Dentofacial Orthop 2000;118: 592-600. Schwartz O, Bergmann P, Klausen B. Autotransplantation of human teeth. A life-table analysis of prognostic factors. Int J Oral Surg 1985;14:245-58. Czochrowska EM, Semb G, Stenvik A. Nonprosthodontic management of alveolar clefts with 2 incisors missing on the cleft side: a report of 5 patients. Am J Orthod Dentofacial Orthop 2002;122:587-92.
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