Guided Infra-Zygomatic Screws: Reliable Maxillary Arch Retraction
Drs. John Jin-Jong Lin, Roberts WE.
The infra-zygomatic crest (IZC) is a buccal process on the maxilla, connecting to the zygoma. Intraorally it is a crest of bone emanating from the buccal plate of the alveolar process, lateral to the roots of the first and second maxillary molars (Fig. 1A). The ridge of bone extends 2cm or more superiorly to the zygomatic-maxillary suture, and the inferior portion can be subdivided into the IZC 6 and IZC 7 areas, respectively (Fig. 1B). The IZC is a common site for insertion of temporary anchorage devices (TADs). Melsen1 and Uribe2 placed routine TADs along the intraoral anatomical ridge of the IZC, and Villegas3 used a 25mm long screw to engage the superior aspects of the IZC, approximating the zygoma.
The amount of alveolar bone buccal to the maxillary molars is the critical factor for placing OrthoBoneScrew® (OBS, Newton’s A Ltd, Hsinchu, Taiwan) in an Extra-Radicular (E-R) position. Interradicular (I-R) TADs are also effective for maxillary retraction, if the screws avoid the path of distal tooth movement. This article reviews the relevant anatomy and clinical procedures for routinely achieving maxillary retraction with TADs, inserted directly into alveolar bone of the posterior maxilla. (Int J Orthod Implantol 2017;46:4-16)
Class II Crowded Malocclusion Treated Conservatively with a Passive Self Ligating Appliance: Expansion, Stability and Adaptation
Drs. Shih-Yung Lin, Chang CH, Roberts WE.
A 10-year-old female presented with a retrusive mandible (SNB 76°), Class I molars and Class II canines due to the delayed eruption of the maxillary second premolars. There was 7mm overjet, 5mm overbite, 7mm of lower arch crowding, steep mandibular plane angle (FMA 32°), and increased axial inclination of the lower incisors to the mandibular plane (102°). The Discrepancy Index (DI) was 21. Despite the indication for extraction of premolars, the patient and her parents preferred conservative (noninvasive) treatment with a simple, fixed appliance. The revised treatment plan was to open the bite with posterior bite turbos on lower first molars, expand the arches with a passive self-ligating (PSL) appliance, and correct the sagittal discrepancy with Class II elastics. During 30 months of active treatment there was an unfavorable vertical growth response, resulting in a posterior rotation of the mandible, which was associated with less natural development of arch length. Thus, increased expansion was required to resolve crowding and produce an excellent alignment, documented by a cast-radiograph evaluation (CRE) of 20, with a Pink & White dental esthetics score of 4. Despite the desirable result, there were stability concerns because the lower and upper canines, as well as the molars, were expanded 3-5 and 11-12mm, respectively. Both arches were retained with 3-3 fixed retainers, bonded to each tooth, and overlay appliances. The pleasing result was stable 6 years later indicating that arch expansion to correct crowding is a viable option if there is a commitment to permanent retention. (Int J Orthod Implantol 2017;46:20-37)
Key words: Arch expansion, posterior and anterior bite turbos, lower facial height, inter-canine and inter-molar widths, fixed retention, passive self-ligating brackets, vertical facial growth, Class II elastics
Trans-Alveolar Uprighting of a Horizontally Impacted Lower Canine with a Mandibular Buccal Shelf Bone Screw
Drs. Szu Rou Yeh, Angle Lee, Chang CH, Roberts WE.
A 10yr 6m female presented with an unerupted mandibular left canine and crowding of the maxillary incisors. Cone-beam computer tomography (CBCT) revealed the unerupted cuspid was a deep transalveolar impaction, positioned lingual to the roots of the left mandibular incisors and buccal to the root of the adjacent first premolar. Extraction posed serious surgical risks to the mental nerve, sublingual artery, and periodontium. So a carefully sequenced treatment plan was devised to reverse the etiology of the aberrant development, and recover the cuspid by uprighting it in an oblique plane corresponding to the long axis of the impaction. Two stages of conservative surgery exposed and progressively bonded the impaction as it was uprighted. To help avoid root resorption, the adjacent lateral incisor was not bonded and engaged on the archwire. The precise mechanics to upright the cuspid in the prepared oblique plane was provided by a rectangular lever arm anchored by a mandibular buccal shelf miniscrew (OrthoBoneScrew®). This very difficult malocclusion with a Discrepancy Index (DI) of 30 was treated to an excellent result in 36 months, as documented a Cast-Radiograph Evaluation (CRE) of 20 and Pink & White esthetic score of 2. (Int J Orthod Implantol 2017;46:40-56)
Key words: Sublingual trans-alveolar impacted cuspid, 3-D lever arm, minimally invasive surgery, progressive bracket bonding, moment to force ratio, buccal shelf screw, horizontal cuspid impaction
Archwire Sequence for Insignia® : a Custom Bracket System with a Bright Future
Drs. Angle Lee, Chang CH, Roberts WE.
Insignia® system is a reverse-engineered production of customized brackets, based on the desired final alignment: “begin with the end in sight.” Efficient sequencing is the key to efficient management of a malocclusion with progressive archwire therapy. Each step in active treatment is directed toward a specific objective, consistent with ensuring patient comfort, maximizing the potential of each step in treatment, and achieving alignment to place the final archwire as soon as possible. There are four phases in Insignia® progressive archwire therapy: (I) stock light round wires, (II) customized rectangular copper-nickel-titanium (CuNiTi) wires, (III) major mechanics as needed, and (IV) finishing. This article recommends archwire sequencing, based on clinical experience with the Insignia® bracket system. In addition to traditional progressive archwire therapy, the Insignia® system is well designed for segmental determinate mechanics, to decrease PDL compressive stress. Segmental mechanics, with extra-alveolar bone screw anchorage and anterior bite turbos, is designed to enhance outcomes and decrease treatment time by increasing the rate of tooth movement and controlling root resorption. (Int J Orthod Implantol 2017;46:60-69)
Key words:Insignia® system, passive self-ligating bracket, archwire sequence, custom bracket, custom torque, low PDL stress, enhanced rate of tooth movement, decreased root resorption
Class I Anterior Crossbite
Clinicians: Drs. Chris Chang, Ya Chen Chen, W. Eugene Roberts
Patient: Miss Lin
A 16 yr old female patient, with an anterior cross-bite and blocked-out upper canines presented for consultation. The cephalometric skeletal pattern was within normal limits (WNL) and the buccal segments were Class I bilaterally. All third molars were impacted, and both arches were constricted. Severe crowding was noted in both arches, but there was no functional shift nor history of temporomandibular disorder (TMD). The Discrepancy Index (DI) was 30. (Int J Orthod Implantol 2017;46:72-82)
Crowded Class II Division 2 Malocclusion
Clinicians: Drs. Chris Chang, Hsin-Yin Yeh, Sophia Pei-Wen Shu, W. Eugene Roberts
Patient: Miss Jhan
An 18 year old female presented with Class II Division 2 (Class II/2) malocclusion, deep overbite, severe crowding, and everted lower lip. Despite an overall retrognathic pattern, the first molars were Class I, because of blocked-in lower second premolars. Cephalometric radiography revealed a severe skeletal malocclusion (ANB 9˚) attributable to a protrusive maxilla (SNA 84˚) and retrognathic mandible (SNB 75˚). The panoramic radiograph showed congenitally missing maxillary right third molar, but the other third molars were developing normally. Although extraction of upper 4s and lower 5s was indicated, the patient preferred a non-extraction approach. (Int J Orthod Implantol 2017;46:86-96)