Although Class II elastics have been widely used in the correction of Class II malocclusions, there is still a belief that their side effects override the intended objectives. The aim of this systematic review was to evaluate the true effects of Class II elastics in Class II malocclusion treatment.
A search was performed on PubMed, Scopus, Web of Science, Embase, Medline, and Cochrane databases, complemented by a hand search. Study eligibility criteria were the application of Class II elastics in Class II malocclusion treatment and the presentation of dental or skeletal outcomes of treatment. All age groups were included.
The search indentified 417 articles, of which 11 fulfilled the inclusion criteria. Four studied the isolated effects of Class II elastics, and 7 were comparisons between a single use of elastics and another method for Class II malocclusion correction. Because of the differences in treatment modalities in these articles, a meta-analysis was not possible.
Based on the current literature, we can state that Class II elastics are effective in correcting Class II malocclusions, and their effects are primarily dentoalveolar. Therefore, they are similar to the effects of fixed functional appliances in the long term, placing these 2 methods close to each other when evaluating treatment effectiveness. Little attention has been given to the effects of Class II elastics on the soft tissues in Class II malocclusion treatment.
Class II malocclusion is a major reason that patients seek orthodontic treatment. Combinations of dental and skeletal factors ranging from mild to severe provide the multiple characters of this discrepancy. Among other factors, the treatment protocols can widely vary according to professional ability, malocclusion severity, and patient compliance.
There are a number of orthodontic techniques and appliances to treat Class II malocclusion; among these are Class II elastics. In spite of their popularity, some authors have attributed several side effects to the use of Class II elastics—eg, loss of mandibular anchorage, proclination of mandibular incisors, extrusion of maxillary incisors, and even worsened smile esthetics because of increased gum exposure—thus suggesting minimal use of intermaxillary elastics. Also, there is the claim that the occlusal relationships produced might look good on dental casts but be less satisfactory from the perspective of skeletal relationships and facial esthetics. It also has been stated that Class II elastics can extrude the mandibular molars and the maxillary incisors, causing clockwise rotation of the occlusal plane and the mandible.
Therefore, the main objectives of this systematic review were to evaluate whether Class II elastics are effective in correcting Class II malocclusions; to determine the true dental, skeletal, and soft-tissue effects when they are used as the primary Class II anteroposterior discrepancy treatment device in the short and long terms; and to compare the results with other Class II treatment modalities.
Material and methods
With the objective to determine the most frequent uses and the main effects of Class II elastics in Class II malocclusion treatment, a search was performed in PubMed, Scopus, Web of Science, Embase, Medline, and Cochrane databases, complemented by a hand search, with no date limitation ( Table I ). The keywords were chosen with the help of a senior librarian.
|Database||Search strategy ∗||Results||Selected|
|PubMed||((“malocclusion”[All Fields] AND class[All Fields] AND II[All Fields]) OR “Malocclusion, Angle Class II”[Mesh]) AND (elastic[All Fields] OR elastics[All Fields] OR “rubber”[All Fields] OR rubbers[All Fields])||117||7|
|Scopus||TITLE-ABS-KEY(ma ∗ occlus ∗ OR ma ∗ oclus ∗ OR malocclus ∗ OR maloclus ∗ AND class ∗ OR classe ∗ OR clase ∗ AND 2 OR ii AND elastic OR elastics OR rubber OR rubbers)||142||7|
|Web of Science||TS = (ma ∗ occlus ∗ or ma ∗ oclus ∗ or malocclus ∗ or maloclus ∗ ) AND TS = (class ∗ or classe ∗ or clase ∗ ) AND TS = (2 OR II) AND TS = (elastic or elastics or rubber or rubbers)||46||6|
|Embase||(malocclus ∗ OR maloclus ∗ ) AND class AND ii AND (elastic OR elastics OR ‘rubber’/exp OR ‘rubber’ OR ‘rubber’/exp OR rubber OR rubbers)||4||0|
|Medline||(malocclus ∗ OR maloclus ∗ ) AND class AND ii AND (elastic OR elastics OR ‘rubber’/exp OR ‘rubber’ OR ‘rubber’/exp OR rubber OR rubbers)||92||7|
|Cochrane||(malocclusion and class and ii and elastic)
(malocclusion and class and ii and elastics)
(malocclusion and class and ii and rubber)
(malocclusion and class and ii and rubbers)
|Total articles retrieved||417||29|
|Total without repetitions||162||7|
To be accepted in this review, the application of Class II elastics in Class II malocclusion treatment should have been used in the clinical studies and mentioned in the abstracts. By clinical studies, we meant any study conducted with patients, either retrospective or prospective. The studies should show the dental or skeletal outcomes of Class II elastics in Class II malocclusion treatment, and all age groups were included. Only articles in English were searched. The major reasons for exclusion were articles in which Class II elastics were used for purposes other than Class II correction—eg, surgical fixation, Class III surgery preparation, midline correction, open-bite correction, interdigitation, and molar extrusion. Some abstracts were retrieved simply because the author briefly commented on their use in Class II treatment or mentioned that Class II elastics were not used. These articles were also excluded.
After this primary selection and subsequent reading of the articles and evaluation of their aims by 3 blinded evaluators (R.S., T.M.F.F., and N.C.C.B.), those that dealt with causes of increased treatment time, temporomandibular dysfunction, muscle activity, apical root resorption, patient compliance indicators, anchorage preparation, laboratory studies, and atypical use or use of Class II elastics merely as an adjunct were not considered in this review because our main interest was to determine the results of clinical studies of this specific treatment procedure as the 1 protocol or when compared with other methods. Also, to raise the quality level of the studies retrieved, a minimum of 10 was established for the sample size. After this final selection, 7 articles remained from the database search and 4 from the hand search ( Tables II and III ).
|Articles||Year of publication||Groups (n)||Prescription||Strength||Mean treatment time||Treatment effect||Authors’ conclusion|
|Combrink et al||2006||Class II elastics only effects (35)||–||4 oz||–||SNA, −1.58°
Overjet, −3.81 mm
Maxillary incisors-mandibular incisors, −21.77°
Anterior nasal spine to nose point, +2.56 mm
Upper lip thickness, +0.7 mm
Lower lip thickness, +1.2 mm
|Elastics were successful for the correction of Class II discrepancies, promoting mainly dentoalveolar effects.|
|Nelson et al||1999||Class II elastics only effects (18)||24 h/d||1-2 oz||–||Jaw base relationship, −1.1 mm
Overjet, −5.8 mm
Maxillary incisors, −3.7 mm
Mandibular incisors, +1.0 mm
Molar relationship, +3.0 mm
Maxillary molar, 0 mm
Mandibular molars, +2.0 mm
Overbite, −3.0 mm
Lower anterior facial height, +5.0 mm
Nasion-sella line/mandibular line angle, +1.0°
|The changes contributing to Class II correction were mostly dental. Vertically, the net effects of treatment were increases in the mandibular plane angle and lower anterior facial height.|
|Meistrell et al||1986||Class II elastics only effects (42)||–||1-2 oz||–||Maxillary molar, +0.22 mm mesially and +2.1 mm occlusally
Mandibular molar, +1.2 mm mesially and +2.6 mm occlusally
LI, +1.68 mm
Holdaway soft-tissue angle, −1.48°
|The maxillary first molar maintained its anteroposterior position at the same time that SNA was reduced. The mandibular first molar moved forward by 1.2 mm. Vertical changes in both the maxilla and the mandible were within normal ranges. No significant change in occlusal or mandibular plane angles was observed.|
|Tovstein||1955||Class II elastics only effects (81)||–||–||–||OP.SN, +4 mm in growing patients
OP.SN, +7.48 mm in nongrowing patients
|Patients with the greatest growth had the least change in the inclination of the occlusal plane; conversely, patients with the least growth had the greatest change in the occlusal plane. However, changes in inclination of the occlusal plane have a tendency to return to the original condition.|
|Articles||Year of publication||Groups (n)||Prescription||Strength||Mean treatment time||Treatment effect||Authors’ conclusion|
|Serbesis-Tsarudis and Pancherz||2008||Class II elastics (24) and Herbst (40)||–||2.5 oz||–||Class II elastics group: Co/RLp, −1.1 mm; Co/RL, +6.7 mm; Pg/RLp, +1.2 mm; Pg/RL, −6.0 mm; RL, −0.1°.
Herbst group: Co/RLp, −2.7 mm; Co/RL, +7.5 mm; Pg/RLp, +3.8 mm; Pg/RL, −6.2 mm; RL, +0.7° (RL, a line from the incisal edge of the mandibular central incisor to the distobuccal cusp of the maxillary first molar; RLp, a line perpendicular to RL through sella)
|On a long-term basis, it seems that Class II elastics and the Herbst appliance have the same effect on the mandible.|
|Jones et al||2008||Class II elastics (34) and Forsus (34)||24 h/d||–||–||Forsus group: mandibular molar, +1.1 mm, and molar correction, +0.8 mm, than Class II elastics group
Class II elastics group: maxilla, +1.5 mm mesially; mandible, +3.8 mm mesially; maxillary molars, +0.6 mm; mandibular molars, +0.7 mm mesially; total molar change, +2.4 mm; mandibular incisors, +0.8 mm mesially; maxillary incisors-mandibular incisors, −2.8 mm of anteroposterior change
|No statistically significant differences were found in the treatment changes between the groups.|
|Nelson et al||2007||Class II elastics (15) and Herbst (15)||–||–||–||Class II elastics group: overjet relapse, +1.5 mm; maxillary incisors, 2.6 mm of proclination; SNA, +1.2°; SNB, +2.3° greater than the Herbst group||The final outcome of treatment of a Class II malocclusion might be similar and independent of the orthodontic device used.|
|Uzel et al||2007||Class II elastics (15) and RMCC (15)||24 h/d||3.5 oz||8.5 mo||RMCC group: maxillary molar, +2.3 mm distalization; mandibular molar, +3.4° mesial tipping; molar relationship improvement, −4.5 mm than the Class II elastics group
In both groups: increase in LFH, maxillary incisors were retroclined and retruded, mandibular incisors tipped forward, and mandibular molars extruded and mesialized
Class II group: overjet, −5.2 mm; overbite, −3.5 mm; labiomental angle, +17.8°
|The RMCC appliance is a valuable alternative treatment method for Class II dental malocclusion in selected patients.|
|Nelson et al||2000||Class II elastics (18) and Herbst (18)||–||–||–||Class II elastics group: A-Olp, +1.3 mm; Pg-Olp, +1.6 mm
Overjet reduction: Class II elastics group, 6.7 mm; Herbst group, 4.6 mm
Maxillary incisors: Class II elastics group, 5.0 mm posteriorly; Herbst group, 2.2 mm posteriorly
Mandibular incisors: Class II elastics group, proclined 1.4 mm; Herbst group, unchanged
Molar correction: 3.2 mm in the Class II elastics group; 3.5 mm in the Herbst group
Overbite reduction: 4.1 mm in the Class II elastics group; 2.4 mm in the Herbst group
Lower anterior facial height: Class II elastics group, 4.2 mm; Herbst group, 3.2 mm
Mandibular plane angle: increased 1.3° in the Class II elastics group; remained unchanged in the Herbst group
|The long-term results are interesting because continuing growth and development might wipe out the effects of treatment and perhaps make the 2 groups comparable again.|
|Ellen et al||1998||Cortical (30) and standard (26)||–||–||–||Cortical group: mandibular incisors, +2.43 mm; mandibular molar, +3.68 mm
Standard group: mandibular incisors, +3.07 mm; mandibular molar, +3.23 mm
|Molar anchorage was neither enhanced nor compromised by establishing cortical anchorage.|
|Gianelly et al||1984||Fränkel (16) and headgear (17) and Class II elastics (16)||–||–||–||Class II elastics group: SNA, −0.37°; SNB, +0.34°; NSGn, +0.81°; SNGoGn, +1.25°; face height (N-M), +6.12 mm; Ar-Gn, +2.9 mm; pogonion, +1.62 mm||The results indicate no treatment response that is uniquely related to a specific technique.|
With these data, the articles were analyzed and separated according to the type of study: an “elastics only” category comprised the articles in which only Class II elastics protocols were tested, and a “comparative studies” category included the use of Class II elastics compared with any other Class II treatment appliance. In this stage of the research, the outcome measures of dental, skeletal, and soft-tissue effects were evaluated. Additionally, the usage protocol, the details of its prescription, and the main results achieved with Class II elastics were quantified ( Tables II and III ). The accepted articles were evaluated in terms of elastic diameter, strength, appropriate archwires, prescription, treatment duration, and predominance of skeletal or dentoalveolar effects clearly resulting from the use of Class II elastics. After this analysis, 3 criteria were created to establish the article scores: sample quality, elastic usage description, and adequacy of the statistical analysis. The sample was evaluated by scoring the following 3 descriptions: malocclusion occlusal severity, sample size, and age. Elastic usage description was also evaluated by scoring 3 descriptions: strength, prescription, and mean treatment time ( Table IV ). For these first 2 criteria, scores were given considering the number of descriptions available in the article. If 3 descriptions were provided, the article was considered adequate; if 2 descriptions were provided, the article was considered partially adequate; and if only 1 or no description was provided, the article was considered inadequate ( Table V ). The last criterion, adequacy of the statistical analysis, was scored as adequate or inadequate. All these data were independently abstracted by 3 investigators (R.S., T.M.F.F., and N.C.C.B.) and then discussed to reach a common agreement.