Material and methods

To identify all studies about the effect of lingual arches as space maintainers, a computer search was conducted of PubMed, Medline, Lilacs, Cochrane Central, and Cochrane Database of Systematic Reviews from January 1980 to January 2009. The terms used in the literature search were “lingual arch , space maint , anchor , arch length, arch width, incisor crowding, and orthodontics.” The following journals were searched individually to locate any missing articles from the PubMed search: Angle Orthodontist , American Journal of Orthodontics and Dentofacial Orthopedics , Journal of Orthodontics , and European Journal of Orthodontics . The following inclusion criteria were chosen to initially select potential articles from the results in abstracts: human studies, prospective and retrospective studies, studies discussing the effect of lingual arches used as space maintainers in mandibular arch dimensions, and articles in English. Excluded articles were mainly animal studies, abstracts, in-vitro studies, discussions and interviews, case reports, case series articles in a language other than English, and studies that did not follow the objective of this review. No attempts were made at this stage to identify studies without adequate control groups or that did not report results as arch-dimension measurements. It was considered improbable that the abstracts would report sufficient information regarding this criterion, because this might exclude some articles.

All article abstracts that appeared to meet the initial inclusion criteria were selected, and the articles were collected. The articles ultimately selected were chosen with the following additional inclusion criteria: results expressed as millimetric or percentage data, a control group with no treatment, and a lingual arch used as a space maintainer as the only therapy in both arches.

Simultaneous use of fixed appliances was considered a confounder and a reason for exclusion.

The reference lists of the retrieved articles were also hand searched for additional relevant articles that might have been missed in the database searches.

Results

Eligible studies were selected based on their titles and abstracts. I found 262 abstracts.

Medline identified 158 abstracts; PubMed, 71; Cochrane Central, 26; and Cochrane Database of Systematic Reviews, 7.

From the total abstracts identified in the electronic databases, only a few fulfilled the initial inclusion criteria. Only 6 of the 262 identified articles fulfilled the initial selection criteria ( Table ).

In the study by Kinzinger et al, the study group included treated subjects in the mixed dentition and a control group of treated subjects in the permanent dentition. These patients had pendulum appliances and lingual arch appliances for a mean treatment time of 20 weeks. The results were reported in terms of molar uprighting; molar mesiobuccal rotation; transversal arch expansion in the molar, premolar, and canine regions; and incisor tipping. However, the study was not selected because lingual arches were used with a pendulum applied to the maxillary arch, and the control group did not include untreated patients.

Brennan and Gianelly analyzed the effect of lingual arch appliances used as space maintainers in 107 patients with an average treatment time of 8.6 years. They reported their results in term of arch-length decrease, but there was no control group of patients without treatment. For this reason, the study was not selected.

In the study of Miotti, the experimental group included 33 patients with a mandibular lingual arch, adapted as a passive space maintainer and placed immediately after extraction of the 4 first premolars. The control group (30 untreated subjects) and the study group were statistically similar in age, length of the observation period, sex, and skeletal pattern. In the experimental group, in some patients, the lingual arch was combined with another maxillary appliance. Thus, this article was excluded.

Odom compared treatment changes among cervical traction alone, cervical traction combined with banded maxillary incisors and a mandibular lingual arch, and untreated controls. Therefore, it was impossible to indentify the effect of the lingual arch, because it was not the only appliance placed.

Only two studies fulfilled the additional inclusion and exclusion criteria.

In this study of Villalobos et al, the sample group consisted of 23 white patients treated with a mandibular FLA on the first permanent molars. At the time of initial records, the patients were in the late transitional dentition, with the mandibular second deciduous molars already exfoliated or about to exfoliate. The patients had an average mandibular plane inclination (FMA, 24° ± 2°).

The mean ages of the subjects were 10.4 ± 0.6 years at the beginning of treatment and 12.3 ± 0.4 years at the end of treatment. The mean observation period for the experimental group was 18.3 ± 0.6 months. To serve as a control, longitudinal records of 24 untreated subjects with similar characteristics as the experimental group (ethnic origin, age, sex, FMA, and time of observation) were obtained. All patients in this group had 3 consecutive lateral cephalograms taken at 1-year intervals, from the ages of 10.6 to 12.6 years. The changes in the control sample were recorded separately for the first 12 months and 24 months of observation.

Measurements for the treatment group reflected a minimal mesial drift of 0.15 ± 0.67 mm and a backward tip of –0.54° ± 1.78°. In the control group for the 12-month observation period, the mandibular molars drifted mesially 1.15 ± 0.53 mm and tipped anteriorly 2.10° ± 1.54°. The differences were all statistically significant ( P <0.0001). In the treatment group, the mandibular incisors tipped posteriorly by –0.14 ± 0.73 mm and tipped by –0.51° ± 1.92° (uprighting); in the control group, the incisal edge also tipped posteriorly by –0.84 ± 0.63 mm, and the incisal angulation also had distal repositioning (uprighting) of –2.87° ± 1.36°. Both measurements were statistically significant at P <0.0001 and P <0.01, respectively. In the control group for the 24-month observation period, the mandibular molars moved more mesially by an average of 1.81 ± 0.75 mm, and the angular position showed anterior tipping of 2.68° ± 0.98°. The mandibular incisors showed their incisal edges with greater distal tipping, which measured –1.24 ± 0.91 mm. The incisal angulation had distal repositioning (uprighting) of –3.85° ± 1.59°. All variables when compared between groups (FLA vs control at 24 months) were statistically significant ( P <0.0001).

The study also considered the vertical extrusion of the molars and incisors, but these values were not included in my review.

In the study of Rebellato et al, the 30 subjects had both mandibular second deciduous molars with some clinical mobility, mandibular crowding of 3 mm or more, permanent molar relationships of end-on to Class I, overbite of 1 mm or greater, mandibular plane inclination average (MP-SN) of 32° ± 6°, and the lower lip less than 4 mm in front of the Ricketts E-line.

The treatment group contained 14 patients who had only mandibular lingual arch appliances; the control group contained 16 patients, with similar features, who received no treatment. All patients were observed at least monthly. Records for this study consisted of a baseline cephalometric radiograph, a tomographic radiograph of the randomly selected left or right buccal segment, and study models. The records were repeated after both mandibular premolars were at least 90% erupted.

In the treatment group, molar tipping was –0.54° (backward tip), the center of resistance was 0.33 mm, and the cusp tip was 0.29 mm.

The same measurements for the control group were 2.19°, 1.44 mm, and 1.73 mm, respectively. The differences were all statistically significant ( P <0.001).

The data for the treatment group indicated a 0.73° forward tip of the incisor, a 0.32-mm advancement of the center of resistance, and a 0.44-mm advancement of the incisal edge. In the control group, the incisor angulation change was –2.28° (backward tip), the center of resistance came back 0.34 mm, and the incisal edge came back 0.65 mm. These differences were all statistically significant ( P <0.0001).

The study models showed increases in intermolar widths in both the treatment group (1.15 mm) and the control group (only 0.14 mm). Arch depth decreased by a smaller amount in the treatment group (0.37 mm) than in the control group (1.46 mm). A decrease in total arch length of 2.54 mm in the control group was found, whereas the treatment group actually had a slight increase of 0.07 mm.

All differences between the treatment and control groups were statistically significant ( P <0.01).

The study also considered the vertical movements of molars and incisors, but these values were not included in my review.