997.e78 CHAPTER 35 Functional Appliances J K L M N FN OL P -75% -24.5% 75% 92% 19.9% 25% 12.3% 75% Functional correction with growth O Functional correction without growth FIGURE 35-38, cont’d A B C FIGURE 35-39 JM, a 12½-year-old male patient, had a Class II malocclusion by virtue of retro- gnathic mandible (SNB = 71 degrees, Pogonion to Nasion Perpendicular line = −17 mm), overjet of 9 mm associated with deep bite (6 mm), and hypoplasia of upper lateral incisors. Pretreatment records: A, Profile. B, Smile. C, Frontal view. CHAPTER 35 Functional Appliances 997.e79 D E F G H I J K FIGURE 35-39, cont’d D, E, Treated with the functional magnetic system (approximately 24 months) because of an initial poor compliance that required bonding the appliance for 3 weeks. F, G, The upper central incisors served as abutments for the functional magnetic system appliance by reason of the delayed eruption of the upper canines. H, The bite clearance was increased to facilitate the guidance of eruption of the posterior segment. I, Posttreatment occlusion included restorative recontouring of the lateral incisors with composite. The pubertal gingival hypertrophy was left untreated because of expected self-improvement after bracket debonding. J, K, Post- treatment profile and smile. L, Schematic illustration of functional correction, mandibular skeletal contribution was reduced by one half (20.2%) when growth was considered. This reduction was followed by an increase in upper distalization contribution (from 27.3% to 40%). OLp, Occlusal line perpendicular. (A–H courtesy Costas Ergatoudes; I–K courtesy Vasilis Kalamatas.) 997.e80 CHAPTER 35 Functional Appliances JM OLP −36.4% −17.4% 27.3% 40% 57% 63.6% 20.2% 45.5% Functional correction with growth L Functional correction without growth FIGURE 35-39, cont’d Maxilla fm se fe lm em pm NS SO zm ptp Mandible C FIGURE 35-41 Average natural displacement pattern of the maxilla (Point A) and the mandible (pogonion), relative to the anterior cranial base. The horizontal and vertical vectors (white) and the resultant vector of displacement are shown. In an average facial growth pattern, the forward component of the mandibular symphysis displacement is slightly greater FIGURE 35-40 Growth directions of the cranial base and facial than that of the anterior apical base of the maxilla. The differ- sutures, with a resultant expanding V, is accomplished as the cra- ence is marked at the bottom. Of course, as Coben points out, nial portion moves upward and forward from the sphenooccipi- if superimposition occurred on the entire cranial base, includ- tal synchondrosis (SO) and the facial portion moves downward ing the sphenooccipital synchondrosis, then the result would and forward. C, Reflection of condylar and ramal growth; NS, be different. nasal septum growth vector; se, sphenoethmoidal suture; pm, pterygomaxillary fissure; ptp, pterygopalatine suture; fe, frontoethmoidal suture; em, ethmoidal-maxillary suture; lm, lacrimal-maxillary suture; fm, frontomaxillary suture; zm, zygo- maticomaxillary suture. (Adapted from Coben SE: Growth and Class II Treatment, Am J Orthod Dentofacial Orthop 52:5-26, 1966. With permission from the American Association of Ortho- dontists.) CHAPTER 35 Functional Appliances 997.e81 Maxilla Maxilla Mandible Mandible FIGURE 35-42 The concept of stimulating specific forward growth, with mandibular displacement (black) to bring about the so-called jumping of the bite in Class II treatment with FIGURE 35-43 Reduction of the sagittal component of maxil- functional orthopedics, can be an unfulfilled orthodontic lary skeletal and dentoalveolar structures (black) is compared “dream” because the actual change that occurs without with the average values. Stöckli and Teuscher believe that this appliance interference cannot be measured at the same possibility is more realistic with functional appliances, despite time. The morphogenetic pattern, treatment timing, appli- the research of McNamara and others, which shows little effect ance used, and patient compliance are important determin- of functional appliances on the maxilla. The use of an extraoral ing factors. For these reasons, forecasting is a difficult, if not appliance (headgear) does enhance sagittal withholding or impossible, task. a distalizing effect on the maxilla, hence the justification for combined functional appliances and headgear. In many cases, however, rotational and elongating reactions by the maxilla and provide the desired correction.* A study by Altenburger and dentoalveolar structures create additional vertical demands and 100 Ingervall, comparing combination headgear-activator results reduce the potential sagittal correction, causing an opening with the results achieved using an activator alone, still does not mandibular rotation that exacerbates the apical base discrep- show a significant distalizing effect with combination therapy. ancy (lower diagram). Because of dominant vertical growth, as 27 However, in a more recent study, Du, Hagg, and Rabie show shown by Buschang, appliance control of this vector is essential significant molar distalization when incorporating a headgear (i.e., vertical growth is much greater than sagittal growth). with the Herbst appliance. Again, the reader is referred to the excellent chapter by Stöckli and Teuscher in the second edition of this book for techniques and treatment.173 Figures 35-44 and 35-45 illus- teeth is a top priority, preventing unwanted opening of the bite. trate the activator-headgear appliance. Proper construction This two-jaw approach enhances anchorage and dentoalveolar implies that the extraoral force component considers any compensation and provides optimal growth guidance. Various possible rotational effect from extraoral force, which must functional appliances can be used—a Bionator, twin block, or pass as close as possible through the maxillary center of monobloc appliance—but with reduced bulk to permit full- resistance. time wearing. Perhaps the best compromise, ensuring optimal stability of the functional appliance when the headgear is worn, is to place Fixed Functional Appliances first molar bands and buccal tubes, insert the occipital pull Herbst Appliance extraoral force arms into the buccal tubes, and have the wire At the International Dental Congress of 1909 in Berlin, Emil clasps of the functional appliance snap above the buccal tubes Herbst presented a fixed bite-jumping device called Schar- to give maximal retention for day and night wear of the func- nier, or joint179 (Figs. 35-46 to 35-48). The idea of continually tional appliance. Three-dimensional control of molar anchor keeping the mandible forward and eliminating the need for patient compliance, as is required with removable functional appliances, appealed to clinicians. In 1934, Herbst and Martin * References 61, 113, 129, 158, 171, 175–178. Schwarz wrote a series of articles describing their case selection, A B C D E F G H I J K FIGURE 35-44 Activator-headgear appliance and extraoral attachments. A, Vestibular extensions and torquing springs are demonstrated. B, The appliance is placed on the lower cast. Note the anterior area with torquing springs, palatal extension of acrylic, and transpalatal wire. C, The appliance is placed on the upper cast with the facebow inserted. Note the lower lingual flange extension for engaging the mandib- ular arch, similar to the Hamilton appliance. D, Appliance view again shows the transpalatal bar, torquing springs, and lingual extensions. E, The activator-facebow is in place. F, The activator is in place on the lower arch, showing the insertion of the facebow. Note the tongue against the transpalatal Coffin spring. In this construction, labial and lingual wires are used instead of torquing springs.G, An anteriorly placed force vector is estimated in this case to pass just anterior to the center of resistance of the maxilla. Some anterior rotation of the dentition must be expected, and ample condylar growth is required. H, Average steepness of the force vector is estimated to pass slightly superior to the center of resistance of the upper dentition. The posterior rotational effect on the maxilla and the anterior rotational effect on the dentition should neutralize each other to ensure that no change is expected in the inclination of the occlusal plane. I, The posteriorly placed force vector is estimated in this case to pass just inferior to the center of resistance of the dentition. Posterior rotation of the maxilla and dentition must be anticipated. This setup is used for patients with an open bite tendency or when the prognosis of condylar growth is poor. J, K, Lateral cephalograms are provided to check force vectors (line connecting the circle at the end of the outer arms of the face- bow and the circle at the springs of the headcap) to the centers of resistance of the maxilla (white circle) and upper dentition (black dot). CHAPTER 35 Functional Appliances 997.e83 A B D C FIGURE 35-45 Maxillary component of the Stöckli-Teuscher appliance. A, Extension on the pal- atal side. Placement of headgear tubes and palatal wire; retention area of torquing springs. B, Occlusal and incisal replica relief of the upper teeth. C, Interocclusal placement of the headgear tube. D, Design and position of the torquing springs. Only the palatally curved tip should touch the crown, contiguous to the gingival margin. Note buccal tubes. FIGURE 35-46 Working hypothesis of the Herbst appliance. (Courtesy Dentaurum, Berlin, Germany.) 997.e84 CHAPTER 35 Functional Appliances experiences,