GISTA

D. CONTROLLED ALTERATION OF CRANIOFACIAL GROWTH

The question of whether craniofacial morphology and growth could be purposefully altered has been long debated (see Chapter 4). The reasons for the time needed to resolve this argument are of interest. Many in North America thought it was impossible and were preoccupied with developing precision bracketed appliances to move teeth and reshape the alveolar processes. Claims were made in the European literature concerning the stimulation of mandibular growth with functional jaw orthodontic appliances, but there was no satisfactory scientific evidence.

It seems ironic that the question of whether bone growth and morphology could be altered should have been argued so heatedly by orthodontists who have done much of the best research and routinely apply the biologic concepts in practice. In fact, if bone were not so plastic and adaptable, orthodontics would not exist. The biologic concepts of this important subject are discussed in Chapter 4, and the cephalometric analysis of treatment effects and their segregation from growth is discussed in Chapter 12.

D. Perubahan yang terkontrol pada pertumbuhan kraniofasial

Pertanyaan apakah morfologi dan pertumbuhan kraniofasial bisa sengaja diubah telah lama diperdebatkan (lihat Bab 4). Alasan waktu yang dibutuhkan untuk menyelesaikan argumen ini yang menarik. Banyak orang Amerika Utara berfikir itu mustahil dan telah banyak disibukan mengembangkan peralatan presisi braket untuk memindahkan gigi dan membentuk kembali prosesus alveolaris. Klaim yang dibuat pada literatur Eropa mengenai stimulasi pertumbuhan mandibula dengan peralatan ortodontik rahang secara fungsional, tetapi tidak ada bukti ilmiah yang memuaskan.Tampaknya ironis bahwa pertanyaan apakah pertumbuhan dan morfologi tulang dapat diubah telah diperdebatkan begitu sengit oleh para ortodontis yang telah melakukan banyak penelitian terbaik dan secara rutin menerapkan konsep biologis dalam praktek. Kenyataannya, jika tulang tidak begitu plastik dan beradaptasi, ortodontik tidak akan ada. Konsep biologis yang penting ini dibahas dalam Bab 4, dan analisis cephalometri dari hasil perawatan dan segregasinya dari pertumbuhan dibahas dalam Bab 12.

1. The NasomaxilIary Sutural System

Experimental and clinical studies prove that it is possible to influence sutural adaptation and maxillary growth. A prerequisite is a patent suture before natural fusion (synostosis) has occurred. Purposeful nasomaxillary displacement is possible because the sutures uniting membranous bones depend largely on local conditions for tbeir growth and physiologic adaptation. The position, orientation, direction, and even number of facial sutures seem to beclosely related to various forces. Their proliferlltion is dictated by the tensions received from the bones which they unite and the soft tissue by which they are surrounded: increased tension leads to increased sutural width and length.

1. Sistem sutural nasomaksilariPenelitian dan studi klinis menunjukan bahwa mungkin untuk menjadikan sutura beradaptasi dan pertumbuhan maksilla. Studi eksperimental dan klinis membuktikan bahwa adalah mungkin untuk mempengaruhi adaptasi sutural dan pertumbuhan maksila. Prasyarat adalah jahitan paten sebelum fusi alami (synostosis) telah terjadi. Perpindahan nasomaxillary tujuan ini dimungkinkan karena jahitan menyatukan tulang membran tergantung pada kondisi lokal untuk pertumbuhan dan adaptasi fisiologis tbeir. Posisi, orientasi, arah, dan bahkan jumlah jahitan wajah tampaknya beclosely terkait dengan berbagai kekuatan. Proliferlltion mereka ditentukan oleh ketegangan yang diterima dari tulang yang mereka bersatu dan jaringan lunak di mana mereka dikelilingi: ketegangan meningkat menyebabkan lebar sutural meningkat dan panjang.

Much of our most basic and practical knowledge of altered nasomaxillary growth has come from animal experimentation, yet it may seem difficult to understand what experimental changes mean clinically, as the laboratory model is so different from dental practice. In experimental animals a normal craniofacial form is made abnormal, while in humans the clinician wants tp change an abnormal skeletal relationship into a more normal one. Further, animals are often under better control than patients.

During compression by heavy extra-oral forces the sutures become 2 to 3 times wider than normal and show signs of great cellular activity. The serpentine configuration with interdigitations disappears, and the fibers lose their orientation. The bone surfaces reveal Howship's lacunae with active osteoclasts. This stage ofdirect re sorption is frequently preceded by local hyalinization (Fig13-36). Hyalinization is even observed in control animals duringnormal growth.

During tension of a suture, osteoblasts and Sharpey's fibers are incorporated into the bone surfaces by deposition of new bone layers. The sutures react to pressure and tension much in the same way as seen on the alveolar bone surface of the periodontal ligament during tooth movements (Fig 13-37). Reorganization with normalization of width and formation of new interdigitations occur when the force recedes.

Yen125 et al. found that the rate of collagen synthesis in stressed sutures was reached in 3 days, and higher values were maintained up to day 14. The rate of noncollagenous protein synthesis peaked at 5 days and was significantly different only on day 5. They suggest, therefore, a more significant role for collagenous protein synthesis in the control of remodeling.

Sebagian besar pengetahuan kita yang paling mendasar dan praktis pertumbuhan nasomaxillary diubah telah datang dari hewan percobaan, namun mungkin tampak sulit untuk memahami apa maksud perubahan eksperimental klinis, sebagai model laboratorium sangat berbeda dari praktek dokter gigi. Pada hewan percobaan bentuk kraniofasial yang normal dibuat normal, sedangkan pada manusia dokter ingin tp mengubah hubungan skeletal abnormal ke yang lebih normal. Selanjutnya, hewan sering di bawah kontrol yang lebih baik dibandingkan pasien.Selama kompresi oleh berat ekstra-oral kekuatan jahitan menjadi 2 sampai 3 kali lebih luas daripada normal dan menunjukkan tanda-tanda aktivitas selular yang besar. Konfigurasi serpentin dengan interdigitations menghilang, dan serat kehilangan orientasi mereka. Permukaan tulang mengungkapkan kekosongan Howship dengan osteoklas aktif. Tahap ini ofdirect kembali penyerapan sering didahului oleh hialinisasi lokal (Fig13-36). Hialinisasi bahkan diamati dalam pengendalian pertumbuhan duringnormal hewan.Selama ketegangan jahitan, osteoblas dan serat Sharpey yang dimasukkan ke dalam permukaan tulang dengan deposisi lapisan tulang baru. Para jahitan bereaksi terhadap tekanan dan ketegangan banyak cara yang sama seperti yang terlihat pada permukaan tulang alveolar dari ligamentum periodontal selama pergerakan gigi (Gambar 13-37). Reorganisasi dengan normalisasi lebar dan pembentukan interdigitations baru terjadi ketika gaya surut.Yen125 et al. menemukan bahwa tingkat sintesis kolagen di jahitan stres dicapai dalam 3 hari, dan nilai-nilai yang lebih tinggi tetap dipertahankan sampai dengan hari ke-14. Tingkat sintesis protein noncollagenous memuncak pada 5 hari dan berbeda bermakna hanya pada hari 5. Mereka menyarankan, oleh karena itu, peran yang lebih signifikan untuk sintesis protein kolagen dalam pengendalian renovasi.

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RARA

a) Posterior Forces against the Maxilla

Head gears and cervical traction devices can restrain alveolar process development and inhibit maxillary corpus growth. The gross" orthopedic effects" of heavy, continuous, extra-oral forces to the maxilla have been well documented in extensive animal studies. It has been shown by radiographic techniques that in small monkeys, during the late deciduous dentition stage, the midfacial complex can be moved posteriorly into a Class III relationship within 3 months, using heavy, continuous force (400 g per side) applied for 24 hours per day, producing a posterior displacement of up to the width of two teeth.

Posterior movement of the maxilla by external cervical forces in humans has been demonstrated. The response of the maxilla and maxillary dentition is complicated, depending on several factors including the direction of force application, mode of attachment of the extra-oral device, amount and duration of force, and the patient's craniofacial morphology. Class 11intermaxillary elastics are commonly used to move maxillary teeth distally, but their effect on nasomaxillary skeletal growth and morphology is not well known. The effect of intermaxillary Class II traction on mandibular growth has been studied.

It has also been demonstrated, in humans, that both tooth movements and maxillary skeletal alterations can concomitantly effect the position of the mandible, as the mandibular elevators must accommodate the mandible to the maxilla during function. Theoretically, at least, extra-oral traction to the maxilla should also have an indirect effect on mandibular growth and morphology, although this point is not fully documented.

b) Anterior Forces against the Maxilla

Face masks can move maxillary teeth forward. They can also promote maxillary growth and sutural adaptation, resulting in a more ventral positioning of the corpus maxillarus. Heavy experimental forces of 300 to 400 g produce exten"sive anterior displacement of the maxillary complex on monkeys after three months. Sutural opening associated with fewer interdigitations occurs in the circummaxillary sutures. A simultaneous rotation of the maxilla in an upward direction is often seen associated with varying reactions in different sutures. Histologic studies confirm that the displacement seen cephalometrically is mediated by resorption and remodeling of the sutural articulations of the maxilla. Anterior movement of the maxillary complex has been demonstrated in patients by external forces through facial masks. Heavy forces applied as early as from 5 to 8 years of age seem to render the best results" (P. Rygh, unpublished data). It has been claimed that the use of face masks inhibits mandibular growth in the same way as the use of chin chaps, but no documentation has yet been presented.

c) Transverse Forces in the Maxilla

Widening of the maxilla by devices which separate the median palatal and associated sutures is a proven clinical procedure. The sutural response is largely tensional, and the maxillary translations, after sutural separation, are rapid and dramatic (see also Chapter 15). Although palatal expansion therapy has been used for many years to correct transverse inadequacies, only recently have we benefited from studies of the changes in the teeth and supporting structures in response to such lateral expansion. Strong reciprocal lateral forces are necessary to separate the median palatal suture, and some damage should be expected, particularly in the buccal periodontium of the maxillary molars and bicuspids. Greenbaum and Zachrisson compared three groups of patients.

ONO

The first underwent rapid maxillary expansion with a fixed split-acrylic appliance, the second underwent slow maxillary expansion with a Quad-Helix appliance, while the third or control group underwent routine edgewise appliance treatment but with no palatal expansion. The expansion groups showed an average mean increase in distance between the first molars of about 4.5 mm. The periodontial condition was good in all groups and attachment levels were similar, although there was individual variation in response. Marked periodontal breakdown occurred in a few individuals undergoing rapid maxillary expansion because expansion occurs before molar rotation when this appliance is used. These findings show that the periodontal condition can remain within acceptable levels with either rapid or slow expansion but that rotated molars are at some risk with the rapid maxillary expansion.

The skeletal changes associated with extensive maxillary skeletal expansion are surprisingly stable, and the periodontium can be maintained in a healthy state with good oral hygiene. However, resorption of the buccal aspects of the roots of which the palatal widening device has been placed has been demonstrated histologically. Such resorption may not be seen in periapical radiographs until it is quite extensive.

2. The Mandible and Temporomandibular Joint

Most of the arguments about the clinician's ability to alter craniofacial growth have centered on the mandible and whether or not its growth could be "stimulated," restricted, or altered. As the number and quality of research studies improved and cephalometric methods were refined, it became possible to gain perspective on this important topic (see also Chapter 4).

a) Functional Protrusion

Extensive experimentation on mandibular functional protrusion has been carried out, notably by Petrovic and coworkers and by McNamara, Carlson, and colleagues. Using devices similar to functional orthodontic appliances on rats (Petrovic) and monkeys (McNamara and Carlson), demonstrable histologic and radiographic changes have been produced (Fig 13-38). Cephalometric findings in humans are less clear because it is hard to discriminate dentoalveolar changes from condylar change and the growth changes which would have happened were appliances not worn. Pancherz, using Activators and Herbst appliances, reports significant changes in mandibular corpus and overall length. Others, for example, Janson and Bookstein," show that most of the differences between treated and untreated cases are the result of alterations localized in the dentoalveolar area. Bookstein noted the importance of shape changes often not discerned with conventional cephalometrics but revealed by tensor analysis. There is no doubt that functional appliances bring about more significant alterations in facial growth and morphology than was once thought.

b) Functional Restriction and Redirection

Experimental studies have shown conclusively that orthopedic forces similar to those used with human chin cup treatment produce significant alterations in mandibular form and growth. Graber concluded, after studying the effects of chin cup force on children during the late primary and early mixed dentition period, that there was a definite alteration of mandibular growth direction and mandibular morphology. Ramus height growth was retarded, and the direction of mandibular growth was significantly altered.

c) Intermaxillary Fixation

Intermaxillary fixation in monkeys rapidly altered the histologic character os the condylar cartilage, resulting in profound changes in the joint and mandibular growth.