Journal of the World Federation of Orthodontists · Miniscrew implants Molar distalization abstract Various appliances have been used for the correction of Class II malocclusion.

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Journal of the World Federation of Orthodontists

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Journal of the World Federation of Orthodontists 5 (2016) 35e43

Case Report

Miniscrew implant-supported Frog� appliance for maxillary molardistalization

Ankit H. Shah a,*, Darshit H. Shah b

a Private Practice, Dallas, TexasbOrthodontic Resident, Center for Advanced Dental Education, Saint Louis University, Saint Louis, Missouri

a r t i c l e i n f o

Article history:Received 8 August 2015Accepted 4 February 2016

Keywords:Frog� applianceMiniscrew implantsMolar distalization

All authors have completed and submitted the ICPotential Conflicts of Interest, and none were reported

Authors have obtained and submitted the patienpublication.* Corresponding author: 1001 Lake Carolyn Parkwa

E-mail address: [email protected] (A.H. Sh

2212-4438/$ e see front matter � 2016 World Federahttp://dx.doi.org/10.1016/j.ejwf.2016.02.003

a b s t r a c t

Various appliances have been used for the correction of Class II malocclusion. The majority of theseappliances depend on patient compliance for a successful treatment outcome. An 11-year-old girl wasreferred to our clinic for orthodontic treatment. She had a mild skeletal Class II malocclusion with Class IImolar and canine relationship on both sides. The treatment plan included bilateral distalization of themaxillary first molars using a miniscrew implant-supported frog appliance along with comprehensiveorthodontics. Successful correction of Class II malocclusion was achieved with the use of a relatively newintraoral distalization applianceethe Frog� Appliance. Proclination of maxillary incisors was minimaldue to the use of miniscrew implants. This article presents an effective, noninvasive, and compliance-freeintraoral distalization appliance for achieving maxillary molar distalization.

� 2016 World Federation of Orthodontists.

1. Introduction

Various distalization appliances have been developed to over-come compliance issues: the pendulum appliance [1], the distal jet[2], the Jones jig [3], the first-class appliance [4], the Carriere dis-talizer [5], appliances with nickel-titanium springs [6], and thesimplified molar distalizer, also known as the Frog� Appliance(Forestadent, Pforzheim, Germany) [7]. Although all of theseappliances achieve distalization of the maxillary molars, thereciprocal forces produce undesirable side effects, such asproclination of maxillary incisors, maxillary molar distal-crowntipping, and bite opening. Recently, miniscrew implants (MSIs)have been used clinically to reinforce anchorage duringdistalization and to avoid these side effects.

Use of a skeletally anchored Frog Appliance was first reported in2011 [8]. This appliance constitutes of an expansion screw and aremovable distalizing spring that connects the expansion screw tothemaxillary first molars (Fig. 1). The distalizing spring is fabricatedfrom 0.032-in. TMA� (Ormco, Orange, CA) or stainless steel wirewith adjustment loops. These adjustment loops are used to adjust

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y, #452, Irving, TX 75039.ah).

tion of Orthodontists.

the distalizing spring as needed. The ends of the distalizing springhave double back bends, which insert into the lingual sheaths of themaxillary first molar bands. The entire assembly is anchored to apair of MSIs placed on either side of midline of the anterior palate. Itis attached to the MSIs by using a modified acrylic Nance palatalbutton.

This case report describes an 11-year-old girl who presentedwith a Class II malocclusion and maxillary crowding, includingpartially blocked-out canines (Figs. 2 and 3). The maxillarysecond molars were still in the tooth-bud stage when orthodonticappliances were placed, and an MSI-supported Frog Appliance wasfitted.

2. Etiology and diagnosis

The patient had a mesocephalic facial form with competent lipsand no significant facial asymmetries (Fig. 2). Intraorally, she hadAngle Class II molar relation on both sides (Figs. 2 and 3). She hadmild mandibular crowding, a 3-mm overjet, 75% overbite, andcoincident maxillary and mandibular midlines. Soft tissue analysisrevealed that she had normal upper lip, retrusive lower lip, andretrusive chin (Table 1).

No abnormalities were noted on the panoramic radiograph(Fig. 4). Clinical examination did not reveal any temporomandibularjoint problems. Periodontal health was found to be within normallimits.

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Fig. 1. The Frog� appliance.

A.H. Shah, D.H. Shah / Journal of the World Federation of Orthodontists 5 (2016) 35e4336

The pretreatment lateral cephalometric radiograph (Fig. 5) andanalysis (Table 1) demonstrated a skeletal Class II malocclusion(A point, nasion, B point [ANB] ¼ 5�). The maxillary incisors had a19� angle relative to the nasion point A line, and the mandibularincisors had a 100� angle relative to the mandibular plane. The

Fig. 2. Pretreatment facial an

Frankfort mandibular plane angle (FMA) of 18.5� and sella nasion(SN)-mandibular plane (GoGn) angle of 28� revealed the hypo-divergent skeletal pattern. A 6-mm space requirement in themaxillary arch and a 3-mm space requirement in the mandibulararch were found on study model analysis.

2.1. Treatment objectives

Treatment objectives for this patient were to (1) relievemaxillary and mandibular crowding, (2) distalize the maxillarymolars to establish a Class I molar and canine relationship, (3)achieve a well-intercuspated occlusion, (4) achieve ideal overbiteand overjet, and (5) improve the skeletally hypodivergent profileand soft-tissue profile.

2.2. Alternative treatment plans

The patient’s chief concern was crowding in maxillary andmandibular arches. Treatment alternatives for this case were(1) distalization of maxillary molars using an extraoral headgear,(2) distalization of maxillary molars using the Frog Appliance,(3) extraction of maxillary first premolars only, (4) extraction ofmaxillary first premolars and mandibular second premolars, and(5) fixed orthodontic treatment with growth modification by usinga functional appliance.

d intraoral photographs.

Fig. 3. Pretreatment dental casts.

A.H. Shah, D.H. Shah / Journal of the World Federation of Orthodontists 5 (2016) 35e43 37

Due to the patient’s parents’ opposition to the extraction ofhealthy teeth for orthodontic purposes and the patient’s reluctanceto wear headgear, intermaxillary elastics, or a functional appliance,the distalization of maxillary molars was evaluated as a treatmentplan option. This treatment planwas selected by the patient and herparents.

2.3. Treatment progress

Preadjusted fixed appliances (0.022 � 0.028-inch, MBT system�

3M Unitek, Monrovia, CA) were placed in both arches for initialleveling and alignment. After 4 months of initial leveling andalignment, two MSIs were placed in the anterior palate. One MSIwas placed on either side of the midline approximately 1 to 2 mmfrom the midpalatal suture and 5 to 6 mm behind the incisalpapillae. A maxillary impression was taken for fabrication of theFrog Appliance. The Frog Appliance was cemented in the oral cavity1 week later (Fig. 1). This appliance was activated by performingthree rotations each at 4-week intervals. Then 5� to 10� of “toe-in”bends were placed in the double back bends of the springs asneeded to prevent the undesirable rotation of maxillary molarsduring distalization.

Table 1Pretreatment and posttreatment lateral cephalometric analysis data

Measurement Pretreatment Posttreatment

SNA angle (�) 80 81SNB angle (�) 75 77ANB angle (�) 5 4Wits appraisal (mm) 3 1FMA (�) 18.5 24SN-Go Gn (�) 28 28Upper incisor to NA (mm) 0 2Upper incisor to NA (�) 19 20Lower incisor NB (mm) 3 6Lower incisor to NB (�) 25 29IMPA (�) 100 101Interincisal angle (�) 132 127Upper lip to E line (mm) �1 �1Lower lip to E line (mm) �1 0

ANB, A point, nasion, B point; FMA, Frankfort mandibular plane angle; Gn, gnathion;Go, gonial; IMPA, incisor to mandibular plane angle; NA, nasion point A; NB, nasionpoint B; SN, sella nasion; SNA, sella nasion point A; SNB, sella nasion point B.

Appliance stability and distalization progress were evaluated ateach appointment. Themaxillary first molars were distalized until aClass I molar relationship was achieved on both sides (Fig. 6). Thiswas completed within 5 months of appliance cementation. Theappliance was left in place for an additional period of 4 months toprevent any mesial movement of molars. Pull from the transseptalfibers helped in the distal drifting of maxillary canines andpremolars during this period. Complete distalization of maxillarycanines and premolars was achieved by using continuous archwiresand power chains. The Frog Appliance was removed after13 months of overall treatment. MSIs were removed 1 week afterthe removal of the Frog Appliance.

After a Class I canine relationship was achieved on both sides,0.019 � 0.025-in. TMA� (Ormco, Orange, CA) archwire with “tear-drop” loops was used in the maxillary arch to retract the anteriorteeth. Detailing bends were placed in 0.016-in. stainless steel wiresto improve alignment of the teeth. Coordinated archwires andsettling elastics were used to gain maximum intercuspation of theteeth. The orthodontic appliances were removed after 21 months oftreatment. Hawley retainers were fabricated for retention in botharches.

3. Results

The patient’s chief concern of crowding was resolvedwhile idealoverbite and overjet were achieved. Posterior occlusion wasimproved to a bilateral Class I molar relationship. Class I caninerelationship was also achieved on both sides (Figs. 7 and 8).

Satisfactory root parallelism was achieved as noted on theposttreatment panoramic radiograph (Fig. 9). No temporomandib-ular joint problems were noted. Improvement in soft-tissue profilewas noted. Lower lip position improved by 1 mm, and the upper lipposition was maintained with respect to the E line (Figs. 10 and 11and Table 1).

Maxillary growth was noted to be in a forward directionpredominantly (Fig. 11). Significant mandibular growth wasobserved in an anteroinferior direction. Bodily distal movementand simultaneous uprighting of maxillary first molars was alsonoted. Mandibular first molars demonstrated significantcompensatory mesial and occlusal movement as a response toskeletal mandibular growth [9]. The maxillary incisors proclinedminimally in a bodily fashion compared with their pretreatment

Fig. 4. Pretreatment panoramic radiograph.


position. The mandibular incisors also showed slight labialmovement (Fig. 11).

3.1. Case retention

The patient received Hawley retainers for maxillary andmandibular arches. The occlusion and treatment changes werestable at 1 year of posttreatment follow-up (Fig. 12).

4. Discussion

Distalization is one of the treatment modalities used byclinicians and practitioners for correction of Class II malocclusionswithout any major skeletal discrepancies. Use of various

Fig. 5. Pretreatment lateral c

noncompliance intraoral molar distalization appliances [1e8] hasbeen described in literature.

Several studies have reported that obtaining a bodily distalmovement of the maxillary first molars with minimal rotation andminimal distal-crown tipping remains a significant challenge ofmaxillary molar distalization [10e12]. In our patient, the FrogAppliance was oriented parallel to the occlusal plane andpositioned approximately 10 to 12mm apical to the occlusal surfaceof the maxillary first molar. This position is close to the trifurcationof roots of maxillary first molar and is considered its approximatecenter of resistance [13]. Positioning the appliance in this mannerallows the effective distalizing force vector to pass through thecenter of resistance of the maxillary first molars, thereby producingbodily distal movement. In our case, the maxillary first molarsmoved distally in a bodily fashion and also exhibited distal-root

ephalogram and tracing.

Fig. 6. Progress facial and intraoral photographs.


tipping (Fig. 11). This distal-root tipping is very critical in achievinga well-intercuspated posterior occlusion [14].

Another significant challenge is prevention of bodily mesialmovement, mesial tipping, and extrusion of maxillary firstpremolars during distalization [15,16]. A meta-analysis wasperformed to compare intraoral distalizer effects with conventionaland skeletal anchorage [17]. The analysis showed an average molardistalization amount of 3.34 mmwith conventional anchorage and5.10 mm with skeletal anchorage. This analysis also showedmesialization of premolars by 2.3 mm in studies with conventionalanchorage compared with �4.01 mm of premolar distalization instudies with skeletal anchorage [17]. This is a major drawback oftooth- and/or palate-borne distalization appliances. MSIs have beenshown to act as efficient anchorage units and help overcomethese limitations [18,19]. For our patient, mesial movement and/ormesial tipping of maxillary first premolars was avoided as theanchorage was obtained from MSIs instead of maxillary firstpremolars.

Finally, prevention of anchorage loss during distalization, whichis expressed as either proclination of the maxillary incisors withincreased overjet or maxillary anterior crowding, is equallyimportant [15,16]. The anterior teeth cannot resist the opposingforces of distalization without moving in the anterior direction.Satisfactory distalization results without anchorage loss have beenachieved in molar distalization studies using skeletal anchorage[18,19]. We were able to control the undesired proclination of

maxillary incisors due to the direct anchorage from MSIs (Fig. 11and Table 1).

5. Conclusion

The Frog Appliance is an effective, noninvasive, and compliance-free intraoral distalization appliance for achieving maxillary molardistalization. This case report should help other clinicians andpractitioners to consider adding this appliance as another tool intheir armamentarium for their Class II patients.

Acknowledgment

The authors would like to thank Dr. Khamir Patel for histechnical assistance.

Source of financial support: The authors have no financialrelationship to disclose.

References

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Fig. 7. Posttreatment facial an

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d intraoral photographs.
























































Fig. 8. Posttreatment dental casts.

Fig. 9. Posttreatment panoramic radiograph.


Fig. 10. Posttreatment lateral cephalogram and tracing.

Fig. 11. Superimpositions: pretreatment and posttreatment.


Fig. 12. Facial and intraoral photographs at 1-year follow-up.


Journal of the World Federation of Orthodontists · Miniscrew implants Molar distalization abstract Various appliances have been used for the correction of Class II malocclusion.

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