01 June 2021

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Early treatment with a slow maxillary ni-ti spring-expander. Narrative review of the literature

Authors:Ludovica Brotto, Andrea Abate, Davide Cavagnetto, Andrea Fama, Danilo Lucarelli, Luca Esposito

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The aim of this narrative review is to perform a narrative review and analize the available literature on the clinical outcomes of a particular appliance for slow maxillary expansion that consists in one ore more nickel-titanium springs.

The main medical databases (Scopus, Web of Sciences, Pubmed and Google Scholar) were scanned up to january 2020 using "slow maxillary expan*", "slow palatal expan*", "leaf expander" and "NiTi Palatal Expander" as keywords. Skeletal changes of the maxilla after expansion with Leaf Expander or similar appliances were taken into consideration while reviewing interesting manuscripts. The review focuses on the comparison between the leaf expander and conventional expanders (i.e. Haas and Hyrax) regarding the increase in both the distance between palatal cusps of upper  first molars and the distance between palatal cusps of upper second deciduous molars, the increment of nasal structures and pain connected to expansion procedures.

Bibliographic research retrieved 32 articles that were considered eligible for the present study. The limited number of articles currently available in international medical databases is allegedly partly due to the fact that these expanders are currently produced by only one patent holder company, which affects its diffusion.

The analysis of literature data validate the effectiveness of the slow maxillary expander L.E for treatment of maxillary hypoplasia and for the resolution of the posterior crossbite in growing patients. Clinical results have therefore demonstrated the effectiveness, efficiency and ease of use of the L.E device; Slow maxillary expander with nickel-titanium leaf springs represents a valid alternative for the treatment maillary costrictions in deciduous/mixed dentition. Studies comparing the L.E. and the rapid palate expander (REP) have shown the following disadvantages: the greater perception of pain, especially at the beginning of therapy, the need for compliance by parents and / or small patients and the need for more close visits. Further multicenter studies, on larger samples, are needed to confirm the promising preliminary data collected so far on a more solid scientific basis.

Despite the reduced number of published articles, due to the recent introduction of the L.E. device, most of the authors have found that the effects of the latter are clinically and radiographically comparable to those achievable with the rapid palatal expander. In summary, the main advantages of the maxillary expander with nickel-titanium leaf springs are the following: absence of collaboration from patients and parents; visual control of activation, reducing the risk of operator-employee error; safety in use; mainly body movement of the teeth; predetermined, light and constant forces; predictability of the result; ease of activation; simplification of clinical procedures, reducing the number of appointments.

The slow expander with nickel-titanium leaf springs can be a pain-free alternative proposal, simplifying clinical procedures, reducing the number of activations and the need for clinical checks. These characteristics are expressed in an increase in the predictability of the results and a decrease in operator-dependent error.