Discussion:
SMMCI syndrome is a complex disorder characterized by neurodevelopment defects of the midline structures6.
If the history of dental trauma was not reported, the absence of a permanent central incisor may be considered a rare form of hypodontia. However, the association of anatomical abnormalities in the middle line is used to alert the clinician to the possible existence of SMMCI syndrome which may require specialist care.
SMMCI was initially reported by Scott who described a girl with the presence of a single maxillary central incisor placed in the median position, in view of an isolated observation.
Later, another cases of SMMCI reported in addition to the single central incisor, short stature, congenital heart disease, microcephaly and scoliosis7.
Although, in the present case, differently from what previously reported in literature, SMMCI may be associated with other systemic disorders such as autosomal dominant holoprosencephaly, growth retardation and midline developmental defects4,7,8.
The etiology is uncertain but some studies such as those conducted by Nanni et al. 2001 have shown, following DNA sequencing, mutations of the Sonic Hedgehog (SHH) gene both in SMMCI syndrome and in holoprosencephaly frameworks 9.
The diagnosis of SMMCI can be made prenatally at the 18th-22nd week owing to the mid-trimester routine ultrasound4.
Increasingly, presumptive diagnoses are being made at birth with confidence when the multiple defects are present 4,6 .
Once the primary SMMCI tooth has erupted, diagnosis can later be confirmed by a pediatric dentist clinically and radiologically at 7–8 months of age6.
Kjaer et al. in 2001 examined the clinical features and craniofacial morphology of 10 patients with SMMCI aged between 8 and 17 years.10
Also Bertolacini et al. study in 2009 consisting of 11 patients with SMMCI, who underwent radiological investigation.11
The results of the two studies showed that the craniofacial morphology of the patients with SMMCI compared to the normal craniofacial parameters showed hypoplasia of the anterior cranial base, a hypoplastic and post-rotated maxilla, and a retrognathic and post-moved jaw.
In addition, these groups of patients had features such as: nasal obstruction, septal deviation, absence of frenulum of the upper lip and incomplete mid-palatal suture10,11.
In the present clinical case the patient showed the same signs of manifest SMMCI which confirmed our diagnoses.
In this complex disorder, management and treatment are complex and delicate. First of all, the evaluation of the psychological impact that this syndrome has on the patient and how the clinician can improve it, is important. Secondly, an interdisciplinary evaluation is fundamental for a correct management of the case. The treatment can be either by extraction of the SMMCI with space closure or by space opening associated to a prosthodontic replacement for the a maxillary central incisor with either an implant borne crown or a resin bonded bridge. Thus, an early orthodontic evaluation for a proper planning of the treatment timing is encouraged 7.
Conclusion :
Early diagnoses of SMMCI grant more appropriate clinical follow-ups and an appropriate treatment which could have a great advantage on the young patient quality of life.
Pediatric dentists should recognize this disorder at an early age since it is characterized by specific orofacial manifestations and should not consider it as a simple dental anomaly in order to establish a proper treatment for these patients.
References:
  1. CARE Case Report Guidelines. CARE Case Report Guidelines. https://www.care-statement.org
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