Introduction
The objective of this study was to evaluate short and long-term results of the application of the alternate rapid maxillary expansion/constriction (Alt-RAMEC) technique in patients with skeletal Class III malocclusion.
Methods
Forty-two white patients were consecutively treated with the Alt-RAMEC technique. The average age of the patients was 12.7 ± 1.6 years (range, 9.4-15.9 years) before protraction. The average age at long-term follow-up was 19.4 ± 2.8 years (range, 17.2-26.9 years). A sample of nontreated patients with Class III malocclusion from the archives of orthognatic surgery in our hospital was used as a control group. The initial records were matched for sex, the severity of Class III malocclusion, and age (mean, 12.1 ± 1.4 years; range, 9.7-14.1 years) with the old records available in the archive. The control sample had records presurgery (mean, 19.8 ± 2.2 years; range, 16.6-21.6 years).
Results
The sagittal advancement of A-point, after the application of the technique, was 5.43 ± 2.71 mm. Some mandibular dentoalveolar adaptation was noted. The position of the maxilla was stable in the long term. In contrast, the control group showed limited growth at the maxillary level during the long-term follow-up period.
Conclusions
Our results showed that the Alt-RAMEC technique, performed at the correct time, with a double-hinged expander, followed by Class III spring or elastic traction, 24 h/d, allows for satisfactory maxillary protraction, with stable long-term results. The comparison with a sample of matched nontreated patients with Class III malocclusion allowed to suggest the positive effect of the treatment on the maxillary position vs the natural evolution of the Class III skeletal discrepancy.
Highlights
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Alt-Ramec in patients with Class III malocclusion.
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Sagittal advancement of the maxilla was >5 mm and was stable in the long term.
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The control group showed limited growth at the maxillary level during long-term follow-up.
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Less than 15% of the patients needed further treatment.
The incidence of maxillary hypoplasia in the white population is reported to be about 5%. Developing midfacial retrusion in children has been conventionally treated with protraction facemasks at an early age. Rapid maxillary expansion (RME) loosens the articulations of the maxillary complex from the rest of the skull, whereby rendering more effective maxillary protraction. A metric average anterior movement of more than 3 mm at point A was reported in a meta-analysis on maxillary skeletal base protraction with facemask and RME in patients with Class III malocclusion. Although Woon and Thiruvenkatachari, in a recent systematic review, noted the lack of evidence of any lasting long-term effect of early maxillary protraction. The alternate RME and constriction (Alt-RAMEC) technique is a protocol that allows disarticulating the circummaxillary sutures in patients who are close to the end of craniofacial growth; the technique uses a 2-hinged rapid palatal expander, which is unique in its biomechanics, expanding and rotating each half of the maxilla outward. Timing of treatment seems fundamental for the success of the technique in the long term. The treatment is started when the vertebral stage of maturation is between V2 and V3 (second and third stage of vertebral maturation). Liou has shown a significant advancement of A-point in cleft patients (5.8 mm) in 6 months, and those results remained stable without significant maxillary relapse after 5 years. Similar results (5.7 mm) were reported by Meazzini et al in patients with unilateral cleft lip and palate.
The objective of this study was to assess the long-term validity of this technique in patients with noncleft Class III malocclusion. This study followed the principles of the declaration of Helsinki.
Material and methods
A modification of the Liou-Alt-RAMEC and maxillary protraction technique has been applied by the authors in 117 patients: of these patients, 49 had noncleft, nonsyndromic, Class III malocclusion.
Inclusion criteria for this study were (1) white patients; (2) patients with noncleft, nonsyndromic Class III malocclusion consecutively treated with the Alt-RAMEC and maxillary protraction technique; (3) vertebral stage of maturation V2 − V3 at the beginning of treatment (usually corresponding to late deciduous or permanent dentition); (4) skeletal Class III malocclusion with no functional shift; (5) no mandibular asymmetries were included; and (6) full cooperation of the patients during treatment.
Seven of the consecutively treated patients had to be excluded because of a severe lack of cooperation. Therefore, the actual total study sample was 42. The average age of the patients in the sample was 12.7 ± 1.6 (range, 9.4-15.9) years before (T0) and 14.0 ± 1.1 (range, 10.4-15.4) years after maxillary protraction (T1). Of these patients, 21 had follow-up records longer than 6 years. The average age at long-term (Tlt) was 19.4 ± 2.8 (range, 17.2-26.9) years.
A group of patients with Class III malocclusion, extrapolated from our archives of orthognatic surgery, were searched. Only 17 out of the 120 patients with Class III malocclusion had early records, which could be matched for sex, cephalometric severity of Class III malocclusion, and average age (12.1 ± 1.4 years; range, 9.7-14.1 years) at T0 and used as a control sample. The sample had preorthognathic surgical records (Tlt) at an average age of (19.8 ± 2.2 years, range 16.6-21.6 years).
The double-hinged maxillary expander (DHME) consisted of a jackscrew in the center and 2 hinges of rotation posteriorly ( Fig 1 , A ). In the mandibular arch, a double lingual arch with anterior hooks was soldered on molar and premolar bands ( Fig 1 , B ). The treatment protocol, as suggested by Liou, consisted in 7 cycles with 7 days of expansion and 7 days of constriction, 1 mm per day, alternatively. After 7 weeks of alternate expansion-constriction, mild mobility of the whole maxilla was felt clinically, and a mild discomfort was reported by the patient, especially at the paranasal area. In 30% of the patients, there was a need to go up to 9 or 11 cycles to achieve mildly perceivable maxillary mobility.
We modified the original protocol by adding temporary skeletal anchorage devices (TADs) provided by 2 maxillary and 2 mandibular titanium miniscrews (Cortical Anchorage Miniscrews; Forestadent, Pforzheim, Germany) ( Fig 1 , C ). Two TADs were positioned in the maxilla between the roots of the first molars and the second premolars, in the mandible between the roots of the canines and the lateral incisors. TADs were used indirectly, with ligature wires to the dental appliances. In 10 of the patients who had significant lower anterior crowding and missing maxillary teeth (incisors, premolars, or in 1 patient’s first molars), some dental movement was desirable to close the space and relieve mandibular crowding, and therefore no TADs were used.
After the completion of the expansion/constriction cycles, the technique included 5-8 months of active maxillary protraction.
The maxillary protraction was delivered by a pair of noncompliant tooth-borne, intraoral maxillary protraction springs ( Fig 1 , D ). The springs produced 300 g of force per side. Given the relatively frequent breakage of the β-titanium springs, all patients continued protraction with intraoral elastics (300 g), to be used 24 hours a day, also during mealtimes ( Fig 1 , C ).
For each patient, a lateral cephalometric radiograph was obtained at T0 and T1 and the long term (Tlt). Cone-beam computed tomography systems scans were not offered by our national health system until recently and were, therefore, not available for most patients.
Lateral cephalometric tracings were digitized with software (version 1.5.1; Delta-Dent, Milan, Italy) and superimposed on the anterior cranial base, orienting on Sella-Nasion (SN) line. For linear measurements, a constructed true horizontal line at 7° to SN was used ( Fig 2 , A ). The method was previously described. , Superimpositions of the tracings at T0 and Tlt in 1 treated and 1 nontreated patient are depicted in Figure 2 , B and C . Lateral x-rays and clinical photographs pretreatment, posttreatment, and at long-term follow-up of 2 patients are shown in Figures 3 and 4 .
Statistical analysis
After the Shapiro-Wilk normality test, descriptive statistics of data at T0, T1, and Tlt were calculated for the treated sample. A Student t test was carried out to check if there were any skeletal differences or any age difference between the treated sample and the nontreated control (for correct age and skeletal matching). A chi-square test was used to assess differences in gender distribution between the sample and control group (for correct gender matching).
An analysis of variance (ANOVA) for repeated measurements (within-subjects ANOVA for correlated samples) at 3-time points (T0, T1, and Tlt) was performed for all the cephalometric measurements (as the same variable was being analyzed at different time points) to detect any overall changes in mean scores over 3-time points in the treated group.
To compare the differences in the linear and angular measurements at T0 and Tlt between treated and nontreated patients, an independent samples t test was carried out.
Given a large number of multiple comparisons, a Benjamini-Hochberg correction procedure was applied. The Raw P values, significant using the Benjamini-Hochberg procedure with the false discovery rate, were used.
A power analysis was run for each test, given the sample size reached in the collection of the data, setting α (type I error) at 0.05 and a large population size effect. The power (1 − β) of each test was over 0.89 with G∗Power (Heinrich Heine University, Duesseldorf, Germany.
A Cronbach α intraclass correlation coefficient was used to assess cephalometric intraexaminer reliability. Point detection and measurements were performed twice by the same operator (C.T.) at 6-month intervals on 10 randomly selected patients, which is suitable to assess test-retest reliability. Statistical analysis was carried out with Stata software (version 10; StataCorp, College Station, Tex).
Results
The intraclass correlation coefficient used to assess the consistency of the single rater was 0.892, thus indicating good intrarater reliability. After the Benjamini-Hochberg correction, the P value was set at 0.029. Matching of the treated and nontreated samples was adequate ( Table I ).
| Values | Treated sample (T0) | Nontreated control (T0) | Diff treated vs control (T0) | Treated sample (Tlt) | Nontreated control (Tlt) | Diff treated vs control (Tlt) |
|---|---|---|---|---|---|---|
| Age, y | 12.7 ± 1.6 (9.4-15.9) | 12.1 ± 1.4 (9.7-14.1) | 0.6 | 19.4 ± 2.8 (17.2-26.9) | 19.8 ± 2.2 (16.6-21.6) | 0.4 |
| Gender | 73% F; 27% M | 69% F; 31% M | 4 | 73% F; 27% M | 69% F; 31% M | 4 |
| Postretention period, y | 6.7 ± 3.3 | 7.7 ± 4.0 | 1.0 | |||
| SNA, ° | 78.01 ± 4.76 | 79.06 ± 4.12 | −1.05 | 82.26 ± 4.15 | 79.41 ± 4.43 | 2.80 ∗ |
| SNB, ° | 80.51 ± 5.03 | 80.99 ± 3.82 | −0.48 | 80.88 ± 4.82 | 83.86 ± 5.18 | −3.02 |
| ANB, ° | −2.50 ± 2.79 | −1.93 ± 3.30 | −0.57 | 1.38 ± 2.46 | −3.89 ± 4.29 | 5.27∗∗ |
| PNS-ANS × GoGn, ° | 26.64 ± 5.59 | 27.63 ± 4.94 | −0.99 | 27.10 ± 5.49 | 26.97 ± 4.34 | 0.02 |
| Wits appraisal, mm | −7.33 ± 3.41 | −7.23 ± 2.90 | −0.10 | −2.31 ± 2.67 | −8.49 ± 6.60 | 6.18∗∗ |
| UI × PNS-ANS, ° | 115.09 ± 8.69 | 118.07 ± 9.02 | 2.98 | 113.30 ± 6.63 | 118.60 ± 9.37 | 5.23∗∗ |
| UI × Li. ° | 130.47 ± 10.81 | 119.88 ± 25.17 | 10.59 | 132.55 ± 9.58 | 128.04 ± 9.37 | 4.80 |
| SN × GoGn, ° | 35.80 ± 11.85 | 34.21 ± 4.91 | 1.59 | 33.96 ± 6.61 | 32.58 ± 6.02 | 1.05 |
| H Symph, mm | 35.54 ± 3.03 | 36.01 ± 4.03 | 0.47 | 39.74 ± 3.96 | 36.42 ± 5.31 | 3.32 |
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