Journal of Functional Morphology and Kinesiology

Article Elastics Selector Gauge as Device Applied to Inter-Maxillary Traction during Correction

Sergio Sambataro 1, Salvatore Bocchieri 1 , Luigi Bafumi 2, Luca Fiorillo 1,3 , Gabriele Cervino 1 and Marco Cicciù 1,*

1 Department of Biomedical and Dental Sciences and Morphological and Functional Imaging, Messina University, 98100 Messina ME, Italy 2 Private practice, 95100 Catania CT, Italy 3 Multidisciplinary Department of Medical-Surgical and Odontostomatological Specialties, University of Campania “Luigi Vanvitelli”, 80121 Naples, Italy * Correspondence: [email protected]

 Received: 19 June 2019; Accepted: 19 August 2019; Published: 26 August 2019 

Abstract: Elastics are the simplest device that can be used during a class correction in orthodontics, and despite the simplicity of a latex band, they are very effective and powerful. The resultant inter-maxillary force affects not only the teeth, but even the mandibular position, and consequently the temporomandibular joints (TMJ). The purpose of our work is to simplify the use of elastics, and to reduce the amount of inventory for orthodontists, because there is a lot of merceology available on the market, and different ways of using the elastics. The use of elastics in clinical practice is based on the force extension values, which are given by the manufacturer for the different sizes of the elastics, generally when they are stretched to three times their lumen size. Various configurations allow for the correction of different . We propose a new classification and a new device, the elastic selector gauge, in order to allow clinicians to quickly and easily choose the right elastic in all conditions.

Keywords: elastics; inter-maxillary traction; class II correction; orthodontics; selector gauge

1. Introduction In order to understand the application of inter-maxillary elastics, it would be well to understand things from their beginning. Angle laid the claim to being the first person to use a force from one arch to the other, by the means of a rubber elastic. However, he used it from the lower arch, to an impacted canine on the upper, apparently thinking that the availability of movement of a single tooth was all that was possible. Since the first cases discussed more than a century ago by Calvin S. Case, and later by Henry A. Baker, who was the clinician who Angle credited with starting the use of elastics in clinical practice—as devices for correcting arch relationships—elastics become a valuable auxiliary of any orthodontic treatment. When combined with good patient cooperation, their use provides the clinician with the ability to correct both antero-posterior and vertical discrepancies. Prior to that time, orthodontists had attempted to practice “bite-jumping”, with mandibular propulsion as the chief method for correcting Class II malocclusion. When that did not work for Class II correction, they resorted to the extraction of the upper first premolars, for the purpose of gaining space to retract the upper anterior segment. Anterior retraction was frequently done with extra-oral traction, without the thought of molar correction with that modality.

J. Funct. Morphol. Kinesiol. 2019, 4, 63; doi:10.3390/jfmk4030063 www.mdpi.com/journal/jfmk J. Funct. Morphol. Morphol. Kinesiol. Kinesiol. 20192019,, 44,, x 63 FOR PEER REVIEW 2 of 13 12

With the demonstration of from the lower arch to the upper, and with the use of elastics,With Angle the demonstrationchanged his opinion of anchorage from extraction from the to lowernon-extraction arch to the, which upper, was and to be with manifested the use ofin hiselastics, teachings Angle in changed his career his thereafter. opinion from He show extractioned that to elastics non-extraction, were tied which in, and was demonstrated to be manifested that molarin his teachingscorrection in with his careerinter-maxillary thereafter. elastics He showed could thatbe achieved elastics werein three tied months in, and [1,2 demonstrated]. that molarThe correction most common with inter-maxillary type of elastic elastics currently could used be is achieved the latex in type, three which months is manufactured [1,2]. in the sameThe manner most as common the India type rubber of elastic band. currently A rubber used tubing is the is prepar latex type,ed by which a dipping is manufactured process on a in steel the mandrelsame manner of varying as the thickness: India rubber the band.more dips, A rubber the thicker tubing the is prepared tube. The by elastic a dipping is then process sliced from on a steelthat tubingmandrel inof varying varying widths. thickness: Manufact the moreurer dips,s refer the to thicker“light” theor “heavy” tube. The elastics, elastic isdepending then sliced on from the wall that thicknesstubing in varyingof the tubing. widths. Four Manufacturers factors play a refer part to in “light” the tubing or “heavy” quality elastics,and characteristics: depending onThe the size wall of thethickness lumen ofof the tubing, tubing. the Four thickness factors of play the awall, part the in thewidth tubing of the quality cut, and and the characteristics: properties of the The elastic size material.of the lumen of the tubing, the thickness of the wall, the width of the cut, and the properties of the elasticDifferent material. factors influence the effects of an elastic on a tooth: such as, the site of application, the distributionDifferent through factors influencethe periodontal the eff ectsligament of an, elasticthe direction, on a tooth: length, such diameter as, the site, and of application,contour of the root,distribution the alveolar through process, the periodontal the tooth ligament,rotation and the direction,health, age length,, and above diameter, all the and co contour-operation of the of root, the patient.the alveolar The f process,orce produced the tooth by rotationthe elastics and on health, a tooth age, or teeth and above does n allot thedepend co-operation only on its of magnitude. the patient. The forceDifferent produced sizes and by the force elastics levels on are a toothavailable or teeth on the does market, not depend but this only oblige ons its orthodontists magnitude. to buy a lot Di offf erent material sizes; for and example force levels, Ormco are available (Sybron on Dental the market, Specialties, but this Glendora, obliges orthodontists CA, USA) offers to buy 36 a differentlot of material; types forof elastic example, packs, Ormco American (Sybron Orthodontics Dental Specialties, (Sheboyagan, Glendora, WI, CA, USA) USA) offers offers 31 36 different different types,types of3M elastic Unitek packs, (Monrovia, American CA, OrthodonticsUSA) offers 30 (Sheboyagan, different types WI,, while USA) Rocky offers Mountain 31 different Orthodontics types, 3M (Denver,Unitek (Monrovia, CO, USA) CA,offers USA) 27 different offers 30 types. different types, while Rocky Mountain Orthodontics (Denver, CO, USA)The aim off ersof this 27 di studyfferent is types. to give to the profession a simple scientific approach toward selecting the properThe aim elastic of thiss for study the iscorrection to give to of the malocclu professionsions a simple, and to scientific reduce approachthe inventory toward of selectingorthodontic the properoffices. elastics for the correction of malocclusions, and to reduce the inventory of orthodontic offices.

2. Materials Materials and Methods ThThee largelarge varietyvariety of of merceology merceology creates creates confusion, confusion, as itas is it di iffis cultdifficult to select to select the most the emostfficient efficient elastic elasticin different in different clinical clinical situations. situations. We firstfirst recommend the adoption of of one one size size of of wall wall thickness, thickness, which which is is small small enough enough to fit fit under under the wing of a bracket, and so for this study we chose the 5 oz elastics, and decided to vary only the lenlengthgth of the elasticselastics in the selection (Figure(Figure1 1).).

FigureFigure 1. 1. 3/163/16”,”, 1/4 1/4”,”, and and 5/16” 5/16” 5 5-oz-oz elastics Energy Pak™ Pak™ from Rocky Mountain Orthodontics.

Four aspects must be evaluate evaluatedd in order to choose the right elastics for the orthodontic needsneeds of the patients patients,, and they are: (1)1) DistancesDistances 2) RootIn order mass to calculations have an average of distances in common malocclusions, we studied a sample of N50 3)class Vector II models analysis (40 cases T1–T2, of which 20 were in full class II, 20 were in neutro-occlusion, and 10 were4) Decay extraction rate cases, all in neutro-occlusion). The distances were taken from the distal third of the 1)lower In first order and to second have an molars, average to of the distance mesials third in common of the upper malocclusions, canines, as we the studied points ofa sample application of N50 of elasticsclass in II a Classmodels II (40 correction. cases T1 This–T2, partof which is an 20 in were vitro in study full class on cast II, models.20 were in neutro-occlusion, and (2) Root10 were mass extraction calculations cases, all in neutro-occlusion). The distances were taken from the distal third of the lower first and second molars, to the mesial third of the upper canines, as the points of applicationThe amount of of elastics force needed in a Class for teethII correction movements. This can part be is obtained an in vitro by study calculating on cast from mode thels rating. 2)scale The for rootsamount (Figure of force2). Itneeded considers for teeth in square movements millimeters can be the obtained root surface by calculating exposed to from the bone,the rating in a directscale line for of roots movements. (Figure 2 The). It experimentsconsiders in square [3–11] millimeters led to the conclusion the root surface that one exposed gram to per the square bone, J. Funct. Morphol. Kinesiol. 2019, 4, x FOR PEER REVIEW 3 of 13

J. Funct. Morphol. Kinesiol. 2019, 4, 63 3 of 12 in a direct line of movements. The experiments [3–11] led to the conclusion that one gram per square millimeter of root surface is a basic reference for tooth movement. According to these millimeterstudies of, root the surfaceforce to iscorrect a basic the reference class II formalocclusion tooth movement. moving According distally for to thesethe upper studies, first the molar force is to correct120 g the. class II malocclusion moving distally for the upper first molar is 120 g.

FigureFigure 2. 2.Mean Mean values values of of root root surface surface presentation presentation on on three three dimensions dimensions of of space space for for permanent permanent teeth: teeth: Sagittal,Sagittal, transverse, transverse and, and vertical. vertical. Rotation Rotation values values are are equals equals to to sagittal sagittal data. data. (3) Vector analysis 3) An elastic in the right position determines an angle that can be considered with a vector analysis Anof elasticthe force. in the When right vector position diagrams determines are anused, angle the that horizontal can be considered and vertical with components a vector analysis can be of thecalculated. force. When The vector calculation diagrams is are made used, by the taking horizontal the forces and verticalused and components estimating can the be angle calculated. of the The calculationelastic as it is crosses made by the taking occlusal the plane forces and used then and multiplying estimating theit by angle the cosine of the elasticof the asangle it crosses for the the occlusalhorizontal plane, and and then then the multiplying sine of the it angle by the for cosine the vertical of the anglepull. As for you the can horizontal, see in Figure and then 2, in the the sine ofinitial the angle condition for the, the vertical distance pull. of As the you point can seeof inthe Figure application2, in the of initial the elastic condition, is longer the distance, whilst ofthe the pointvertical of the component application is shorter, of the elastic and the is longer,horizontal whilst component the vertical is greater component. is shorter, and the horizontalIt is for this component reason that isgreater. the elastic is hooked as far distally as possible on the molar, and as far as Itpossible is for this mesially reason that on the the canine.elastic is During hooked the as far correction distally, asor possible in an extraction on the molar, case, and the as vertical far as possiblecomponent mesially onwill the increase canine. and During the horizontal the correction, component or in an will extraction decrease. case, the vertical component will increase and the horizontal component will decrease. J. Funct. Morphol. Morphol. Kinesiol. Kinesiol. 20192019,, 44,, x 63 FOR PEER REVIEW 4 of 13 12

Different patterns of rest position were studied by Ricketts [12], and the average was 3°, which is importantDifferent patterns in order of to rest evaluate position the were reciprocal studied by position Ricketts of [12both], and the themaxillary average and was mandibular 3◦, which is importantarches. in In order addition, to evaluate we considered the reciprocal the angle position between of both the the elastics maxillary and andthe mandibularlower arch wire arches. at In addition,different we distances considered (Figure the angle 3). between the elastics and the lower arch wire at different distances (Figure3).

Figure 3. Degrees of mouth opening at rest position. Figure 3. Degrees of mouth opening at rest position. (4) Decay rate 4) The decay rate of orthodontic elastics was measured by us in vivo, in three different patients: The decay rate of orthodontic elastics was measured by us in vivo, in three different patients: each each wearing two 3/16”, 1/4”, and 5/16” 5-oz elastics (Energy Pak™ from Rocky Mountain wearing two 3/16”, 1/4”, and 5/16” 5-oz elastics (Energy Pak™ from Rocky Mountain Orthodontics, Orthodontics, Denver, USA) for a week. Every 24 h, we measured with a dynamometer the force Denver, USA) for a week. Every 24 h, we measured with a dynamometer the force developed from the developed from the elastics at different lengths (for the distances that we have studied on casts, elastics at different lengths (for the distances that we have studied on casts, see Section3). see Section 3.1). One factor which does seem to be common is the sizing, which has been graduated in 1/16 inch increments.One factor Thus, which a graduation does seem exists, to be such common as: 1/ 8is or the 2/ 16,sizing 3/16,, which 1/4 or has 4/16, been 5/16, graduated 3/8 or 6/16, in 1 /1/162 or inch 8/16; whichincrements are the. Thus, usual a sizes.graduation For simplification exists, such theas: elastics1/8 or 2/16, were 3/16, labeled 1/4 #2,or 4/16, #3, #4, 5/16, #5, #63/8 etc., or 6/16, referring 1/2 or to 8/16each; sixteenthwhich are of the an inch.usual sizes. For simplification the elastics were labeled #2, #3, #4, #5, #6 etc., referrinWeg considered to each sixteenth the outer of an diameter inch. of each of the elastics: The #3 elastic is 6 mm, the #4 elastic is 8 mm,We and considered the 5# elastic the outer is 10 mm.diameter of each of the elastics: The #3 elastic is 6 mm, the #4 elastic is 8 mmFor, and these the reasons,5# elastic we is suggest10 mm. pulling the 5-oz elastics to four times the size of their outer diameter, in orderFor tothe havese reason a greaters, we range suggest of lengths, pulling with the a5- constantoz elastics force to atfour the times same the distance size of for their one week,outer diameterand with, thein order proper to distalization have a greater force, range considering of lengths the, with following a constant formula: force at the same distance for one week, and with the proper distalization force, considering the following formula: Fd = Fel d Fes Fd = Fel −− d − Fes FdFd= = distalization force FelFel= = forceforce of a new elastic

dd= = 25%25% decaydecay (Fel(Fel × 00.25).25) × FdecFdec= = decayeddecayed forceforce (Fel − d)d) − FesFes= =extrusive extrusive forceforce (Fdec(Fdec × sin of angle angle between between arch arch wires) wires) × In the correction of ClassClass II malocclusion, from from a clinical point of of view, the only variable that changes in thethe selectionselection ofof thethe elasticelastic isis the the distance distance from from the the molar molar to to the the canine. canine. For For this this reason, reason, it isit isuseful useful and and desirable desirable to have to have a tool a thattool quicklythat quickly suggests suggests the correct the correct elastic toelastic use, basedto use on, based the distance on the distancefrom the from molar the to molar the canine. to the canine.

3. Results Results We focused ourour work on analyzing three aspects: T Thehe distance, the vector analysis analysis,, and the decay decay of the elastic. We obtained the following results inin the aspectsaspects investigatedinvestigated inin MaterialsMaterials andand Methods:Methods: 1) Distance J. Funct. Morphol. Kinesiol. 2019, 4, 63 5 of 12

(1)J. Distance: Funct. Morphol. Kinesiol. 2019, 4, x FOR PEER REVIEW 5 of 13 J. Funct.We calculatedMorphol. Kinesiol. the 2019 distances, 4, x FOR present PEER REVIEW from the lower molars to the canines in our sample,5 and of 13 we We calculated the distances present from the lower molars to the canines in our sample, and we simulated all of the conditions in class II at the beginning of the correction, during the correction, simulated all of the conditions in class II at the beginning of the correction, during the correction, and and afterWe the calculated correction, the evendistances in the present cases wherefrom the (for lower orthodontic molars to needs) the canine fours premolars in our sample, were and extracted we simulatedafter the correction, all of the conditions even in the in casesclass IIwhere at the ( forbeginning orthodontic of the needs correction,) four duringpremolars the correctionwere extracted, and (extraction cases). Identifying the correct distance is the starting point for a correct choice of elastics. after(extraction the correction, cases). Identifying even in the the cases correct where distance (for orthodonticis the starting needs point) four for apremolars correct choice were of extracted elastics. For better understanding, we represent the different kinds of the possible clinical conditions in (extractionFor better cases). understanding Identifying the, we correct represent distance the different is the starting kinds pointof the forpossible a correct clinical choice conditions of elastics. in Figures4–8. These are the averages we found in our in vitro study: FigureFors 4better–8. These understanding are the average, wes represent we found the in ourdifferent in vitro kinds study: of the possible clinical conditions in 45Figure45 mm mm froms from4–8 the. Thesethe lower lower are second thesecond average molar molars we in in fullfound full ClassC lassin our IIII (Figure(inFigure vitro 44study:)) 404540 mm mm from from the thethe lower lowerlower second secondsecond molar molarmolar in inin mild fullmild C ClassClasslass II II (Figure (Figure(Figure 4 4)4 )) 354035 mm mm from from the thethe lower lowerlower second secondsecond molar molarmolar after inafter mild correctioncorrection Class II ( (Figure(Figure 545))) 35 mm from the lower first molar in full Class II (Figure 6) 3535 mm mm from from the the lower lower first second molar molar in full after Class correction II (Figure (Figure6) 5) 30 mm from the lower first molar in mild Class II (Figure 6) 3035 mm mm from from the the lower lower first first molar molar in inmild full C Classlass II II (Figure (Figure 6)6 ) 3025 mm from thethe lowerlower firstfirst molarmolar inafter mild correction Class II (Figure(Figure 6)7) 25 mm from the lower first molar after correction (Figure7) 2520 mm from thethe lowerlower firstfirst molarmolar afterin extractive correction cases (Figure (Figure 7) 8) 20 mm from the lower first molar in extractive cases (Figure8) 20 mm from the lower first molar in extractive cases (Figure 8)

Figure 4. Distance from the lower second molar in Class II. Figure 4. Distance from the lower second molar in Class II. Figure 4. Distance from the lower second molar in Class II.

Figure 5. Distance from the lower second molar after correction.

J. Funct. Morphol. Kinesiol. 2019, 4, x FOR PEER REVIEW 6 of 13 J. Funct. Morphol. Kinesiol. 2019, 4, x FOR PEER REVIEW 6 of 13 Figure 5. Distance from the lower second molar after correction. J. Funct. Morphol. Kinesiol. 2019Figure, 4, 63 5. Distance from the lower second molar after correction. 6 of 12

Figure 6. Distance from the lower first molar in Class II. Figure 6. Distance from the lower first molar in Class II. Figure 6. Distance from the lower first molar in Class II.

J. Funct. Morphol. Kinesiol. 2019, 4, x FOR PEER REVIEW 7 of 13 Figure 7. Distance from the lower first molar after correction. Figure 7. Distance from the lower first molar after correction. Figure 7. Distance from the lower first molar after correction.

Figure 8. Distance from the lower first molar in the extractive case.

Figure 8. Distance from the lower first molar in the extractive case.

2) Vector analysis: Consequently, we calculated in our models the angles formed by the lower arch wire, and the elastic applied from the molar to the canine, in order to obtain the vertical component (extrusive), and the horizontal one (distalizing). We found the following results: for a distance between 40–45 mm, the angle is 14° (second molar) (Figure 4) for a distance between 30–35 mm, the angle is 20° (first molar) (Figure 6) for a distance between 20–25 mm, the angle is 25° (extractive cases) (Figure 8) 3) Decay: We found that the decay rate in one week is about 25%, so the latex elastics can be employed for one whole week maintaining 75% of their pull, which will produce a constant force for a long period, as advocated by many authors [4,7,10]. For this reason, it is advisable to ask to the patients to change their elastics every week (Figures 9 and 10).

Figure 9. Force delivered by an elastic #4 during a week. J. Funct. Morphol. Kinesiol. 2019, 4, x FOR PEER REVIEW 7 of 13

J. Funct. Morphol. Kinesiol. 2019, 4, 63 7 of 12 Figure 8. Distance from the lower first molar in the extractive case. (2) Vector analysis: 2) Vector analysis: Consequently, we calculated in our models the angles formed by the lower arch wire, and the Consequently, we calculated in our models the angles formed by the lower arch wire, and the elastic applied from the molar to the canine, in order to obtain the vertical component (extrusive), elastic applied from the molar to the canine, in order to obtain the vertical component (extrusive), and the horizontal one (distalizing). We found the following results: and the horizontal one (distalizing). We found the following results: for a distance between 40–45 mm, the angle is 14 (second molar) (Figure4) for a distance between 40–45 mm, the angle◦ is 14° (second molar) (Figure 4) for a distancefor a distance between between 30–35 30 mm,–35 themm angle, the angle is 20◦ is(first 20° (first molar) molar) (Figure (Figure6) 6) for a distancefor a distance between between 20–25 20 mm,–25 themm angle, the angle is 25◦ is(extractive 25° (extractive cases) cases) (Figure (Figur8) e 8) (3)3) Decay: Decay: WeWe found found that that the the decay decay rate rate in in one one weekweek is about 25 25%,%, so so the the latex latex elastics elastics can can be be employed employed for for oneone whole whole week week maintaining maintaining 75% 75% ofof theirtheir pull,pull, which will will produce produce a aconstant constant force force for for a long a long period period,, asas advocated advocated by by many many authors authors [ 4[4,7,10,7,10].]. ForFor thisthis reason, it it is is advisable advisable to to ask ask to to the the patients patients to tochange change theirthe elasticsir elastics every every week week (Figures (Figure9s 9and and 10 10).).

J. Funct. Morphol. Kinesiol. 2019, 4, x FOR PEER REVIEW 8 of 13 FigureFigure 9. 9.Force Force delivereddelivered by an elastic elastic #4 #4 during during a aweek. week.

Figure 10. Force delivered by an elastic #4 during a week. Figure 10. Force delivered by an elastic #4 during a week.

The following formulas contain our results for every elastic that we considered: #3 Fd = Fel − d − Fes Fd = 235 − (235 × 0.25) − (176.25 × 0.42) Fd = 235 – 58.75 – 74.025 = 102.225 gr Fd = distalization force

Fel = force of a new elastic d = 25% decay (Fel × 0.25) Fdec = decayed force (Fel − d) Fes = extrusive force (Fdec × sin of angle between arch wires 25°) = 24 gr #4 Fd = Fel − d − Fes Fd = 235 − (235 × 0.25) − (176.25 × 0.34) Fd = 235 – 58.75 – 59.92 = 116.33 gr Fd = distalization force Fel = force of a new elastic d = 25% decay (Fel × 0.25) Fdec = decayed force (Fel − d) Fes = extrusive force (Fdec × sin of angle between arch wires 20°) = 32 gr #5 Fd = Fel − d − Fes Fd = 235 − (235 × 0.25) − (176.25 × 0.29) Fd = 235 – 58.75 – 51.125 = 125.125 Fd = distalization force Fel = force of a new elastic d = 25% decay (Fel × 0.25) Fdec = decayed force (Fel − d) Fes = extrusive force (Fdec × sin of angle between arch wires 17°) = 40 gr

Studying the parallelogram of force, you can see that the vertical pull over the treatment period will average to about one-third of the oblique pull, while two-thirds of it is horizontal; so, the longer the distance between the ends, where the elastic is attached, the more horizontal the pull becomes. For this reason, it is desirable to apply the elastic from the lower second molar, when it is present, to the upper canine. Thus, you may reduce the vertical component, which results in the extrusion of the upper arch (as an undesirable side effect). J. Funct. Morphol. Kinesiol. 2019, 4, 63 8 of 12

The following formulas contain our results for every elastic that we considered:

#3 Fd = Fel d Fes − − Fd = 235 (235 0.25) (176.25 0.42) − × − × Fd = 235 - 58.75 - 74.025 = 102.225 gr

Fd = distalization force

Fel = force of a new elastic

d = 25% decay (Fel 0.25) × Fdec = decayed force (Fel d) − Fes = extrusive force (Fdec sin of angle between arch wires 25◦) = 24 gr × #4 Fd = Fel d Fes − − Fd = 235 (235 0.25) (176.25 0.34) − × − × Fd = 235 58.75 59.92 = 116.33 gr − − Fd = distalization force

Fel = force of a new elastic

d = 25% decay (Fel 0.25) × Fdec = decayed force (Fel d) − Fes = extrusive force (Fdec sin of angle between arch wires 20◦) = 32 gr × #5 Fd = Fel d Fes − − Fd = 235 (235 0.25) (176.25 0.29) − × − × Fd = 235 58.75 51.125 = 125.125 − − Fd = distalization force

Fel = force of a new elastic

d = 25% decay (Fel 0.25) × Fdec = decayed force (Fel d) − Fes = extrusive force (Fdec sin of angle between arch wires 17◦) = 40 gr × Studying the parallelogram of force, you can see that the vertical pull over the treatment period will average to about one-third of the oblique pull, while two-thirds of it is horizontal; so, the longer the distance between the ends, where the elastic is attached, the more horizontal the pull becomes. For this reason, it is desirable to apply the elastic from the lower second molar, when it is present, to the upper canine. Thus, you may reduce the vertical component, which results in the extrusion of the upper arch (as an undesirable side effect). Furthermore, it is also advisable to use the hook extensions incisally on the upper arch, in order to make the pull more horizontal. It is also important to underline that when you stretch the elastics to four times their lumen, the force is the same for the three different types of the elastics that we have used. J. Funct. Morphol. Kinesiol. 2019, 4, 63 9 of 12

4. Discussion Different kinds of malocclusions can be corrected with different approaches and appliances, but in some cases, it is necessary to extract healthy teeth in order to reduce the convexity, and this is extractive therapy [7,8]. In young patients with a dolichofacial pattern, cervical headgear is the best approach to correct the class II malocclusion by orthopedic maxillary alteration, with a superb control of the vertical dimension [13]. In very difficult cases, in which the skeletal discrepancy is too much, or in protocol surgery first [14], the condition could be solved with orthognatic surgery which allows us to treat severe conditions [15–17]; but surgery exposes the patients to risks [18–20]. Sometimes surgical correction is the only option, but certain orthodontic approaches can reduce the need of maxillo-facial surgery [21,22], and the use of drugs [18,23–25] and their side effects [26,27]—considering that the final objective of an orthodontic therapy is the stability of occlusion, and consequently the equilibrium of the kinetic chain of the body [28,29]. Class II correction is one of the most common conditions, especially in the Caucasian race [30,31]. Different strategies of therapy were carried out, but inter-maxillary traction made by elastics is nowadays the simplest strategy, and one of the most efficient, if correctly used [32]. Elastics can be also used for different reasons: To reinforce anchorage in a case where an extraction has been done, to allow the maxillary incisors to move backwards, to correct midline deviation, and to move the lower denture forward. The side effects of Class II elastics should be considered before using them [32]. The common side effects, from the improper use of elastics are: The steepening of the occlusal plane, the extrusion of the lower first molar, the flaring of the lower incisors, and the extrusion of the upper incisors. The first three effects could be avoided by the use of skeletal anchorage, or cortical anchorage. Skeletal anchorage is achieved by using temporary anchorage devices (TADs), which are small screw-like dental implants made of a titanium alloy. As the name implies, they are temporary, as they usually only remain in place during some months of the treatment, and then they are removed. They are placed through the cortical bone in order to become an application point for the elastic traction [33]. Cortical anchorage is a biological method to obtain a valid application site of elastics during Class II correction. When the roots engage the cortical plates, the action will become static and a tooth root becomes a point of resistance, and hence it becomes an anchor for an undetermined period of time. The most efficient tool in order to obtain cortical anchorage is the utility arch. Compact bone not only offers resistance to the tooth movement, but, conversely, it can be used for anchorage, and is recognized and employed to this advantage. This is accomplished by the teeth situated behind the compact elements of bone, so that the pressure of the root is almost in direct contact with the bone, and incapable of easy backward resorption [30]. The extrusion of the upper incisors, with the consequent decreasing of their torque, and the deepening of the bite, produces a gummy smile. This could be avoided by using sectional mechanics, that consist in the cutting of the upper archwire at the level of the canine; thereby excluding the upper incisors from the traction made by the elastics. The two sections obtained could be used to transfer the force applied on the canine directly to the upper molars. Furthermore, the sections could be activated with an bend that produces 50 g of force, that will prevent the extrusion of the canine as given by the vertical component of the elastic pull. As we have seen, in order to correct the class II malocclusion, we need 120 g of force to move the upper molar distally. Hence, we chose 5 oz elastics and we stretched the #3, #4, #5, #6 elastics to four times the outer diameter (about five times if we consider the inner diameter), and this produced the same force, which was about 235 g, with the different lengths of elastics. This amount of force must not scare, as by subtracting the correction factors (vector and decay) that we consider in our formula, we have obtained the effective distalization force that we wanted. Studies of orthodontic elastics have typically used the manufacturer’s recommendations for extending the elastics to three times their lumen, when examining force extension characteristics [34–38]. Some studies used extensions of 20–50 mm, proposing that it was the normal range for clinical J. Funct. Morphol. Kinesiol. 2019, 4, x FOR PEER REVIEW 10 of 13

Studies of orthodontic elastics have typically used the manufacturer’s recommendations for

J.extending Funct. Morphol. the elastics Kinesiol. 2019 to three, 4, 63 times their lumen, when examining force extension characteristic10s [34 of 12– 49]. Some studies used extensions of 20–50 mm, proposing that it was the normal range for clinical use [50–56]. In our study, extension distances were obtained from casts of our clinical cases, and we useshowed [39– 41that]. Inthe our range study, is 20 extension–45 mm. distances were obtained from casts of our clinical cases, and we showedIn theory, that the by range evaluating is 20–45 the mm. parallelogram of forces, we find an elastic yield of 75% of force horizontallyIn theory,, and by about evaluating 25% of the the parallelogram force to be effective of forces, in the we vertical find an (with elastic a 20° yield angle of of 75% pull of across force horizontally,the occlusal plane) and about. 25% of the force to be effective in the vertical (with a 20◦ angle of pull across the occlusalIn terms plane). of the decay rate, in our measurement (Figure 9) there is a decay of 25% after one day, and thInen terms the force of the remain decays rate,almost in constant our measurement for one week, (Figure and9 so) there the patient is a decay could of use 25% the after same one elastic day, andduring then this the period force. remains In this way, almost a co constantnstant force, for one as week,advocated and so by the Burstone patient, couldis more use effective the same on elastic tooth duringmovements this period.[4]. In this way, a constant force, as advocated by Burstone, is more effective on tooth movementsBy integrating [4]. all of the data at our disposal, and by applying the formula used to calculate the forceBy really integrating available all for of distalization, the data at our we disposal, created the and e bylastic applying selector the gauge formula (Figure used 11 to); a calculate device that the forceallows really practitioners available to for easily distalization, detect the we elastic created to be the used elastic to treat selector each gaugekind of (Figure malocclusion. 11); a device It is use thatd allowsby positioning practitioners the left to easilyend of detect the instrument the elastic at to the be useddistal to point treat of each the kind application of malocclusion. of the elastic It is, used and bythen positioning by detecting the leftthe endnumber of the of instrument the elastic at required the distal when point the of themesial application point of of the the application elastic, and thenfalls bybetween detecting the the notches number of of the the instrument. elastic required Just when three the elastic mesials point(#3, #4, of the #5) application can correct falls almost between all themalocclusion notches ofs. the instrument. Just three elastics (#3, #4, #5) can correct almost all malocclusions.

Figure 11. Our “elastic selector gauge”.

5. Conclusions Our classification, classification, in association with the elastic selector gauge, will allow clinicians to make the most e effectiveffective choice choice of of elastics elastics for class for class corrections correction in everys in condition; every condition without; without having a hav biging inventory, a big einventory,ffort, and wasteeffort, ofand time. waste of time. 6. Patents 6. Patents The results of this work encouraged us to apply for the patent for industrial invention for The results of this work encouraged us to apply for the patent for industrial invention for our our device, regularly registered at Italian patent and trademark office on 17/06/2019 with number device, regularly registered at Italian patent and trademark office on 17/06/2019 with number 102019000009261 entitled: “Elastic selector gauge as orthodontic device: ESGO”. 102019000009261 entitled: “Elastic selector gauge as orthodontic device: ESGO”. Author Contributions: Conceptualization, S.S. and L.B.; methodology, G.C. and L.F.; validation, G.C., M.C.; formalAuthor analysis,Contributions: S.S.; investigation, Conceptualization S.S.; data, S.S curation,. and L.B.; L.B.; methodology writing—original, G.C. and draft L.F. preparation,; validation S.B., G.C and., M.C L.F.;.; writing—reviewformal analysis, S.S.; and editing,investigation G.C.,,S.B.; S.S.;visualization, data curation M.C.;, L.B.;supervision, writing—original M.C. draft preparation, S.B. and L.F.; Funding:writing—rThiseview research and editing received, G.C no., S.B.; external visualization funding., M.C.; supervision, M.C. ConflictsFunding: ofThis Interest: researchThe received authors no declare external no funding conflict. of interest. Conflicts of Interest: The authors declare no conflict of interest. References

1.R eferencesAsbell, M.B. A brief history of orthodontics. Am. J. Orthod. Dentofac. Orthop. 1990, 98, 176–183. [CrossRef] 2.1. Asbell,Eh, A. Malocclusion M.B. A brief ofhistory the Teeth of, orthodontics. 7th ed.; White Am. Dental J. Orthod. Manufacturing Dentofac. Orthop. Company: 1990 Lakewood,, 98, 176–183. NJ, USA, 1907. 3.2. Eh,Bench, A. Malocclusion R.G.; Gugino, of C.F.; the Teeth Hilgers,, 7th J.J. ed.; Bioprogressive White Dental Therapy Manufacturin part 6—Forcesg Company: used Lakewood, in Bioprogressive NJ, USA Therapy. 1907. 3. Bench,J. Clin. Orthod. R.G.; Gugino,1978, 12 C.F.;, 123–139. Hilgers, [PubMed J.J. Bioprogressive] Therapy part 6—Forces used in Bioprogressive 4. Therapy.Burstone, J. C.J.; Clin. Baldwin, Orthod. J.J.; 1978 Lawless,, 12, 123 D.T.–139. The Application of Continuous Forces to Orthodontics. Angle Orthod. 4. 1961Burstone, 31,, 1–14. C.J.; Baldwin, J.J.; Lawless, D.T. The Application of Continuous Forces to Orthodontics. Angle 5. Orthod.Lee, B. Relationship1961, 31, 1–14. between tooth movement rate and estimated pressure applied. J. Dent. Res. 1965, 44, 5. 1053.Lee, B. [CrossRef Relationship][PubMed between] tooth movement rate and estimated pressure applied. J. Dent. Res. 1965, 44, 6. 1053.Miura, F. Effect of orthodontic force on blood circula- tion in the periodontal membrane. In Transactions of the Third International Orthodontic Congress; Crosby Lockwood Staples: London, UK, 1973; pp. 35–41. J. Funct. Morphol. Kinesiol. 2019, 4, 63 11 of 12

7. Ricketts, R.M. Bioprogressive therapy as an answer to orthodontic needs Part II. Am. J. Orthod. 1976, 70, 359–397. [CrossRef] 8. Ricketts, R.M. Bioprogressive therapy as an answer to orthodontic needs Part I. Am. J. Orthod. 1976, 70, 241–268. [CrossRef] 9. Ricketts, R.M. Bioprogressive Therapy, Book One; Rocky Mountain Orthodontics: Denver, CO, USA, 1979; Volume 1, p. 367. 10. Ricketts, R.M. Concepet of Mechanics and Biomechanics; American Institute for Bioprogressive Education: Scottsdale, AZ, USA, 1998. 11. Storey, E.S. Force in orthodontics and its relation to tooth movement. Aust. J. Dent. 1952, 56, 11–18. 12. Ricketts, R.M. Laminagraphy in the diagnosis of temporomandibular joint disorders. J. Am. Dent. Assoc. 1953, 46, 620–648. [CrossRef] 13. Sambataro, S.; Fastuca, R.; Oppermann, N.J.; Lorusso, P.; Baccetti, T.; Franchi, L.; Caprioglio, A. Cephalometric changes in growing patients with increased vertical dimension treated with cervical headgear. J. Orofac. Orthop. 2017, 78, 312–320. [CrossRef] 14. Huang, C.S.; Hsu, S.S.; Chen, Y.R. Systematic review of the surgery-first approach in orthognathic surgery. Biomed. J. 2014, 37, 184–190. [CrossRef] 15. Proffit, W.R.; White, R.P., Jr. Who needs surgical-orthodontic treatment? Int. J. Adult Orthod. Orthognath Surg. 1990, 5, 81–89. 16. Hammoudeh, J.A.; Howell, L.K.; Boutros, S.; Scott, M.A.; Urata, M.M. Current Status of Surgical Planning for Orthognathic Surgery: Traditional Methods versus 3D Surgical Planning. Plast. Reconstr. Surg. Glob. Open 2015, 3, e307. [CrossRef] 17. Cicciu, M.; Cervino, G.; Herford, A.S.; Fama, F.; Bramanti, E.; Fiorillo, L.; Lauritano, F.; Sambataro, S.; Troiano, G.; Laino, L. Facial Bone Reconstruction Using both Marine or Non-Marine Bone Substitutes: Evaluation of Current Outcomes in a Systematic Literature Review. Mar. Drugs 2018, 16, 27. [CrossRef] 18. Cervino, G.; Fiorillo, L.; Monte, I.P.; De Stefano, R.; Laino, L.; Crimi, S.; Bianchi, A.; Herford, A.S.; Biondi, A.; Cicciu, M. Advances in Antiplatelet Therapy for Dentofacial Surgery Patients: Focus on Past and Present Strategies. Materials 2019, 12, 1524. [CrossRef] 19. Laino, L.; Cicciu, M.; Fiorillo, L.; Crimi, S.; Bianchi, A.; Amoroso, G.; Monte, I.P.; Herford, A.S.; Cervino, G. Surgical Risk on Patients with Coagulopathies: Guidelines on Hemophiliac Patients for Oro-Maxillofacial Surgery. Int. J. Environ. Res. Public Health 2019, 16, 1386. [CrossRef] 20. Lombardi, T.; Bernardello, F.; Berton, F.; Porrelli, D.; Rapani, A.; Camurri Piloni, A.; Fiorillo, L.; Di Lenarda, R.; Stacchi, C. Efficacy of Alveolar Ridge Preservation after Maxillary Molar Extraction in Reducing Crestal Bone Resorption and Sinus Pneumatization: A Multicenter Prospective Case-Control Study. Biomed. Res. Int. 2018, 2018, 9352130. [CrossRef] 21. Sato, S.A.; Matsumoto, A.; Shirasu, A.; Yoshida, J. Manual for the Clinical Application of the MEAW Tecnique: Orthodontic Theraphy Using Multiloop Edgewise Archwire; Meaw Publishing House: Yokosuka, Kanagawa, Japan, 2001. 22. Sato, S. A Treatment Approach to Malocclusion under the Considerations of Craniofacial Dynamics; Meaw Publishing House: Yokosuka, Kanagawa, Japan, 1991. 23. Fiorillo, L. Chlorhexidine Gel Use in the Oral District: A Systematic Review. Gels 2019, 5, 31. [CrossRef] 24. Fiorillo, L.; Cervino, G.; Herford, A.S.; Lauritano, F.; D’Amico, C.; Lo Giudice, R.; Laino, L.; Troiano, G.; Crimi, S.; Cicciu, M. Interferon Crevicular Fluid Profile and Correlation with Periodontal Disease and Wound Healing: A Systemic Review of Recent Data. Int. J. Mol. Sci. 2018, 19, 1908. [CrossRef] 25. Troiano, G.; Laino, L.; Cicciu, M.; Cervino, G.; Fiorillo, L.; D’Amico, C.; Zhurakivska, K.; Lo Muzio, L. Comparison of Two Routes of Administration of Dexamethasone to Reduce the Postoperative Sequelae After Third Molar Surgery: A Systematic Review and Meta-Analysis. Open Dent. J. 2018, 12, 181–188. [CrossRef] 26. Cervino, G.; Terranova, A.; Briguglio, F.; De Stefano, R.; Fama, F.; D’Amico, C.; Amoroso, G.; Marino, S.; Gorassini, F.; Mastroieni, R.; et al. Diabetes: Oral Health Related Quality of Life and Oral Alterations. Biomed. Res. Int. 2019, 2019, 5907195. [CrossRef] 27. Cervino, G.; Fiorillo, L.; Laino, L.; Herford, A.S.; Lauritano, F.; Giudice, G.L.; Fama, F.; Santoro, R.; Troiano, G.; Iannello, G.; et al. Oral Health Impact Profile in Celiac Patients: Analysis of Recent Findings in a Literature Review. Gastroenterol. Res. Pract. 2018, 2018, 7848735. [CrossRef] J. Funct. Morphol. Kinesiol. 2019, 4, 63 12 of 12

28. Sambataro, S.; Cervino, G.; Fiorillo, L.; Cicciu, M. Upper First Premolar Positioning Evaluation for the Stability of the Dental Occlusion: Anatomical Considerations. J. Craniofac. Surg. 2018, 29, 1366–1369. [CrossRef] 29. Sambataro, S.; Bocchieri, S.; Cervino, G.; La Bruna, R.; Cicciù, A.; Innorta, M.; Torrisi, B.; Cicciù, M. Correlations between Malocclusion and Postural Anomalies in Children with Mixed Dentition. J. Funct. Morphol. Kinesiol. 2019, 4, 45. [CrossRef] 30. Ricketts, R.M. The Widsom of Sectional Mechanics; American Institute for Bioprogressive Education: Scottsdale, AZ, USA, 1998. 31. Proffit, W.; Fields, H. Contemporary Orthodontics, 5th ed.; Elsevier: Amsterdam, The Netherlands, 2013. 32. Janson, G.; Sathler, R.; Fernandes, T.M.; Branco, N.C.; Freitas, M.R. Correction of Class II malocclusion with Class II elastics: A systematic review. Am. J. Orthod. Dentofac. Orthop. 2013, 143, 383–392. [CrossRef] 33. Mizrahi, E. The Use of Miniscrews in Orthodontics: A Review of Selected Clinical Applications. Prim. Dent. J. 2016, 5, 20–27. 34. Beattie, S.; Monaghan, P. An in vitro study simulating effects of daily diet and patient elastic band change compliance on orthodontic latex elastics. Angle Orthod. 2004, 74, 234–239. 35. Gioka, C.; Zinelis, S.; Eliades, T.; Eliades, G. Orthodontic latex elastics: A force relaxation study. Angle Orthod. 2006, 76, 475–479. 36. Kamisetty, S.K.; Nimagadda, C.; Begam, M.P.; Nalamotu, R.; Srivastav, T.; Gs, S. Elasticity in Elastics-An in-vitro study. J. Int. Oral. Health 2014, 6, 96–105. 37. Russell, K.A.; Milne, A.D.; Khanna, R.A.; Lee, J.M. In vitro assessment of the mechanical properties of latex and non-latex orthodontic elastics. Am. J. Orthod. Dentofac. Orthop. 2001, 120, 36–44. [CrossRef] 38. Seibt, S.; Salmoria, I.; Cericato, G.O.; Paranhos, L.R.; Rosario, H.D.; El Haje, O. Comparative analysis of force degradation of latex orthodontic elastics of 5/16” diameter: An in vitro study. Minerva Stomatol. 2016, 65, 284–290. 39. Kanchana, P.; Godfrey, K. Calibration of force extension and force degradation characteristics of orthodontic latex elastics. Am. J. Orthod. Dentofac. Orthop. 2000, 118, 280–287. [CrossRef] 40. Liu, C.C.; Wataha, J.C.; Craig, R.G. The effect of repeated stretching on the force decay and compliance of vulcanized cis-polyisoprene orthodontic elastics. Dent. Mater. 1993, 9, 37–40. [CrossRef] 41. Wang, T.; Zhou, G.; Tan, X.; Dong, Y. Evaluation of force degradation characteristics of orthodontic latex elastics in vitro and in vivo. Angle Orthod. 2007, 77, 688–693. [CrossRef]

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