GROWTH OF MAXILLA AND CRANIUM
INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
CONTENTS
Introduction
Maxilla
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Pre-natal growth of maxilla Post-natal growth of maxilla
Growth of cranium
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Cranial vault Cranial sutures
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Base of cranium Basicranial synchondroses
Clinical considerations Conclusion References www.indiandentalacademy.com
INTRODUCTION Man has inherited a complex of craniofacial bones and tissues that is hundreds of millions of years old. The basic “bony� support of the cephalic complex in the early organisms was cartilage. This cartilage ultimately became bone, forming the cranial base and some of the midline structures of the face. www.indiandentalacademy.com
Today, the human craniofacial complex manifests its ancient heritage with two kinds of bone: cartilaginous (cranial base, nasal septum) and membranous (cranial vault, most of facial skeleton).
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MAXILLA
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The maxilla is the second largest bone of the facial skeleton, the first being the mandible. It is a pneumatic bone that is paired and forms the upper jaw. It is an irregularly shaped bone that contributes to the formation of the roof of the oral cavity, the orbit, the nasal cavity, the infratemporal fossa and the pterygomaxillary fossa. www.indiandentalacademy.com
The body of the maxilla has four surfaces: • Anterior or facial surface • Posterior or infratemporal surface • Superior or orbital surface • Medial or nasal surface. It has four processes: • Frontal • Zygomatic • Alveolar • Palatine. www.indiandentalacademy.com
PRE-NATAL GROWTH OF MAXILLA
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Origin of the maxilla •
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Lateral and inferior the cranial base cartilages, ossification centers appear nasal, premaxillary, maxillary, lacrimal, zygomatic, palatine and temporal they expand till they appear as bones seperated only by sutures. The maxillary processes of the first branchial arch give rise to main bulk of the body of the maxilla. The anterior part of the maxilla and part of the nose develop from the frontonasal process. www.indiandentalacademy.com
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At the end of 3rd week of intra-uterine life, this process grows downwards to meet the maxillary processes of the first branchial arch, which grow forward.
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These processes unite at the end of the 4th week I.U. to form the maxillary jaw.
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Ossification of the maxilla
At 6 ½ weeks I.U., the future body of the maxilla constitutes the main mass and its frontal, zygomatic, alveolar and palatal processes. In the 7 ½ week I.U., the lamella begins to grow forward, backward and downward to form the frontal process and alveolar wall. After the 3rd month I.U., there is generalized enlargement of the face in all directions. www.indiandentalacademy.com
Development of the bony palate. •
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In the 8th week I.U., bilaterally located bony centers in the anterior palate give rise to the premaxilla and maxilla. The palatal shelves are horizontal and grow towards the midline.
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At 9 weeks, the shelves are in near contact and the premaxillary – maxillary ossification centers appear.
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At 10 weeks, the soft tissue of the palate has fused and ossification centers of the premaxilla – maxilla grow medially.
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At 14 weeks, the premaxillary bone supports the incisors and the maxillary bone supports the cuspids and first molars.The palatine bone supports the second molars.
• A midline suture extends the length between the premaxillary, maxillary and palatine bones. A bilateral suture also appears between the palatal aspects of the premaxilla and maxilla. www.indiandentalacademy.com
POST-NATAL GROWTH OF MAXILLA
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Enlow & Bang (AJO 1965) studied the
complete right halves of the maxillary bones from twelve well-preserved human skulls, all with either deciduous or mixed dentition.
Due to the complex shape and contours of the maxilla, the entire bone was divided into several sections and the growth of each part was studied individually. www.indiandentalacademy.com
The Maxillary Tuberosity
During growth, the entire maxilla is moved and repositioned in a progressive anterior direction. As this takes place, apposition occurs on periosteal surfaces of the maxillary tuberosity.
Since this surface faces posteriorly and laterally, bone deposition here causes growth in corresponding directions.
This produces lengthening and slight widening of the maxillary arch at its posterior end. www.indiandentalacademy.com
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Thus, growth at the tuberosity increases the longitudinal dimensions of the maxilla and also lengthens the dental arch as the teeth increase in number. Also, growth of the middle cranial fossa causes secondary displacement of the maxilla in a downward and forward direction. www.indiandentalacademy.com
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The Zygomatic Process of Maxilla ď Ž
Apposition occurs on the posterior surface of the zygomatic process, with simultaneous resorption on its anterior or facial surface.
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This region moves in a posterior direction towards the base of the skull as the entire maxillary bone increases in size. www.indiandentalacademy.com
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Thus, the anterior surface of the zygomatic process of maxilla and the facial surface of the maxillary body are relocated in a continuous posterior direction in order to maintain their constant relative positions in the growing maxilla as a whole.
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The orbital side of the frontal process, anterior face of zygomatic bone and lateral rim of the orbit are all resorptive and grow posteriorly.
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Thus, the zygomatic bone is relocated posteriorly, corresponding to the posterior growth of the maxillary tuberosity and the zygomatic processes. www.indiandentalacademy.com
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Simultaneous with these movements, the zygomatic arch also increases in general size by apposition on its lateral surface and resorption from the medial side.
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The Maxillary Arch
The dominant area of growth occurs at the posterior margin of the arch on the maxillary tuberosity.
Along with this, bone deposition takes place along the entire inner or palatal side of the arch, with contralateral resorption from the labial and buccal sides V – principle. www.indiandentalacademy.com
As the maxilla grows in a posterior direction, the entire bone is ‘thrust’ anteriorly.
The width of the dental arch increases by apposition on the lateral (buccal) surface of the tuberosity in the molar area posterior to the zygomatic process.
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The Palatine Processes of the Maxilla
Growth in this region corresponds to the Vprinciple.
Apposition occurs on the oral surface, with corresponding proportionate removal from the nasal surface.
The palatal arch thus increases in size and undergoes a downward movement. www.indiandentalacademy.com
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The Premaxilla ď Ž
The labial surface of the cortex in the premaxillary region is resorptive in nature; the lingual side of the cortex receives periosteal deposits of bone.
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This relocates the premaxilla in a downward, and slightly posterior direction.
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The nasal spine also moves in the downward direction, with apposition on its inferior surface and contralateral resorption from the nasal side. www.indiandentalacademy.com
The Orbit
The orbital surface of the maxillary bone faces in 3 directions – laterally, anteriorly and superiorly.
Deposition of bone on these surfaces brings about an increase in size and corresponding growth movement in each of these directions. www.indiandentalacademy.com
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The medial walls of the orbits move farther apart, thus increasing the breadth of the nasal bridge and the underlying nasal cavities.
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Apposition on the inner floor of the orbital cavity relocates it anteriorly and laterally, while maintaining the internal dimensions of the orbit in constant proportion. www.indiandentalacademy.com
Orbit grows by the V - principle www.indiandentalacademy.com
The Maxillary Sinus ď Ž
The inner cortical lining of the sinus is resorptive in nature.
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This contributes to enlargement of the sinus during maxillary growth by resorption from the inside and regional deposition on the various outer surfaces. www.indiandentalacademy.com
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The Nasal Region
The lateral wall of the nasal cavity (frontal process of maxilla) is oriented in three directions – lateral, anterior and superior.
Appositional bone growth causes simultaneous growth in these directions.
Inner or mucosal side of the frontal process is resorptive enlarges breadth of nasal cavities. www.indiandentalacademy.com
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The adjacent nasal bones also serve to increase the dimensions of the nasal cavity by bone deposition on their facial surface and resorption from their inner (mucosal) surface.
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The Forehead ď Ž
Inner table of the forehead drifts anteriorly as long as the frontal lobe of the cerebrum grows. This ceases by 6-7 yrs. of age.
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The outer table continues to drift anteriorly, leading to seperation of the two tables.
Enlargement of frontal sinus.
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Vertical lengthening of the nasomaxillary complex involves : Remodelling growth. Displacement.
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Maxillary growth - summary
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3 dimensional growth of the maxilla as revealed by the implant method
Arne Bjork and V. Skieller (BJO 1977), described the growth of the maxilla studied by the implant method with the help of lateral and PA cephalograms, in nine 4 year old boys with normal primary occlusion who were followed annually up to the age of 21 years. www.indiandentalacademy.com
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The tantalum pins inserted in the zygomatic process of the maxilla at 4 years of age were referred to as the lateral implants.
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The increase in distance between these measured on a PA cephalogram indicated the increase in width of median suture at level of 1st molars. www.indiandentalacademy.com
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The implants placed in the anterior aspect of the maxilla after full eruption of permanent incisors (10-11yrs) were referred to as anterior implants. The increase in distance between these implants measured on the frontal film indicates the growth in width of the median suture anteriorly, at level of incisors. www.indiandentalacademy.com
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A line drawn from one of the anterior implants to the midpoint between the lateral implants on one side, on a lateral cephalogram, was referred to as the implant line.
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A change in inclination of implant line at different ages in relation to Nasion-Sella line indicates vertical rotation of the maxilla in relation to the cranial base. www.indiandentalacademy.com
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Also, superimposition of various radiographs on implant line is used to analyse remodeling of maxilla.
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Growth of Maxilla analysed by means of Lateral Implants from age of 4 years. Maxillary height: ď Ž ď Ž
Sutural lowering of the maxilla was found on average to be 11.2 mm (range 9-13.5mm). Orbits do not increase in height from childhood to adolescence to the same extent as the nasal cavity, and apposition at the floor of the orbit is on average, 6.4 mm ( range 5-8 mm) www.indiandentalacademy.com
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The height of the nasal cavity increased up through puberty as result of resorptive lowering of nasal floor of the order of 4.6 mm ( range 1.5-7.5 mm). This was about one-third of the increase in sutural height of nasal cavity.
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Appositional growth in the height of the alveolar process was about 14.6 mm, which was one third greater than the increase in alveolar process height as a result of resorption of nasal floor. www.indiandentalacademy.com
Maxillary width: ď Ž
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Bjork showed that growth in the suture continues until puberty. By measuring the distance of separation between the lateral implants on the frontal cephalogram over time, it was shown that sutural growth was the most important factor in the development of the width of the maxilla. www.indiandentalacademy.com
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The mean transverse growth in the median suture, measured between the lateral implants, from childhood to adulthood was 6.9mm.
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The curves for cumulative growth in the width of the median suture from year to year followed the same pattern as the curves for the growth in body height. www.indiandentalacademy.com
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The curves also showed that the time of the pubertal growth spurt and sutural growth coincided, but that sutural growth terminated earlier than growth in body height.
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The pubertal growth spurt in the median suture however coincided exactly with growth maximum in the facial sutures in the sagittal plane. www.indiandentalacademy.com
Bimolar width:
Bjork’s implant studies show that though growth in the median suture from eruption of 1st permanent molars to adulthood is 4.8 mm, increase in arch width during this period was on average, 3.1 mm.
The reason for this difference in growth in width is related to transverse rotation of the maxillae. www.indiandentalacademy.com
Bicanine width: ď Ž
The development in width of the dental arches between the canines was different from that of molar region. Though there was an overall increase of 3.1 mm in intercanine width from 4 years to adulthood, most of this increase occurred early, with only 1.1 mm increase from age 6 years to adulthood.
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Coordinated 3 dimensional growth of maxilla analyzed by means of anterior and lateral implants from age of 10-11 years. ď Ž
Bjork’s implant studies show that the anterior surface of the maxilla is stable sagittally, with the anterior surface of the maxilla retaining its close relation to the anterior implants.
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Transverse mutual rotation of the two maxillae: ď Ž
Comparison of increase in width between the anterior and the lateral implants showed that increase in width between the lateral implants was on average, 3.5 times greater than that between the anterior implants.(3 mm and 0.9 mm respectively).
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This indicates that the two maxillae rotate in relation to one another in the transverse plane, which results in decreased length of the maxilla in the mid sagittal plane. www.indiandentalacademy.com
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Mutual transverse rotation of maxillae also results in greater separation of lateral segments of dental arch posteriorly, than anteriorly.
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There is thus, greater increase in intermolar width than intercanine width, and also a corresponding decrease in arch length.
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Thus, shortening of arch length is related to transverse growth of the maxilla. www.indiandentalacademy.com
Vertical rotation of the maxillary complex. ď Ž
Downward and forward displacement of the maxilla during growth is associated with varying degrees of forward rotation.
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The inclination of the nasal floor to the anterior cranial base is however maintained as a result of compensatory differentiated resorption. www.indiandentalacademy.com
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Forward rotation of the maxilla is associated with greater resorption of the nasal floor anteriorly than posteriorly.
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Forward rotation of the face occurs because of greater facial growth posteriorly than anteriorly, associated with development in height of the cranial base. www.indiandentalacademy.com
The Zygomatic process ď Ž
No striking remodeling of the anterior surface of the zygomatic process takes place in the antero posterior direction.
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The posterior surface however is appositional, with the greatest apposition downwards.
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The infrazygomatic crest is also appositional, being displaced downward and backward on the maxillary corpus.
Thus, the anterior contour of the zygomatic process is strikingly stable.
These findings are in contrast to those of Enlow and Bang (1965) who stated that the anterior surface was resorptive in nature. www.indiandentalacademy.com
GROWTH OF CRANIUM
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THE CRANIAL VAULT
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The bones forming the calvarium include the frontal, parietal, occipital, sphenoid and temporal bones. The suture systems associated with these are the coronal, sagittal and lamboidal sutures and a temporary metopic suture that divides the frontal bone (permits rapid transverse expansion prenatally and postnatally). www.indiandentalacademy.com
Growth of calvarium ď Ž
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As the brain expands, the separate bones of the calvaria are displaced in an outward direction passive movement. This primary displacement causes a tension in the sutural membranes, which respond by depositing new bone on the sutural edges. Each separate bone thus enlarges in circumference. www.indiandentalacademy.com
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At the same time, there is apposition on the flat surfaces of both the ectocranial and endocranial sides increases thickness of bone. The arc of curvature of the whole bone decreases, and the bone becomes flatter. Reversal of growth may occur in areas adjacent to the sutures outside/inside surface resorption can take place reduces the curvature. www.indiandentalacademy.com
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Darkly stippled areas Resorption.
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Light areas
Deposition.
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The brain case grows in height mainly by the activity of the parietal sutures along with the occipital, temporal and sphenoid osseous structures. Growth in length of brain case – Davenport Birth 63% 6 mos. 76% 1 yr. 82% 2 yrs. 87% 3 yrs. 89% 5 yrs. 91% 10 yrs. 95% 15 yrs. 98% www.indiandentalacademy.com
Growth in width of head – Davenport
9 6 6 1 2 3
mos. before birth mos. – 12 – 2 yrs. – 3 yrs. – 4 yrs.
100 mm. 50 mm. 20 mm. 9 mm. 1.5 mm. 0.5 mm. per year
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Closure of fontanelles ď Ž
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Fontanelles are the regions of incomplete fusion of the sutures of the calvarium at the time of birth. The anterior fontanelle (intersection of metopic, coronal and sagittal sutures) closes at 6 to 20 mos. of age. The posterior fontanelle (intersection of lambdoidal and sagittal sutures) closes at 3 mos. www.indiandentalacademy.com
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The metopic suture disappears by 7 mos.
Endocranial closure of the sagittal and coronal sutures begins in the 30s.
The lambdoidal suture fuses at about 40 yrs.
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Huggare and Ronning (ACTA Odontol Scand. 1995). The activity in the sutures is important for the cranial vault growth, and any factor affecting the sutural growth is associated with a profound and widespread effect on the size and shape of the vault. Extracranial pressure. Symmetrically deformed skulls have significantly shorter cranial bases and maxillae, while asymmetrically deformed cranial vaults are associated with asymmetry of the cranial base. ď Ž
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Intracranial pressure.
The signs and symptoms related to increased intracranial pressure depend on the age of the patient at onset. • During infancy ventricular dilatation and increased cranial circumference. Sutures show diastasis. • After cranial suture closure resorption of inner table of cranial vault and cranial surface of basicranium. www.indiandentalacademy.com
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CRANIAL SUTURES
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Sutures (sutura vera, true sutures) are articulations found only in the skull. A suture is classified as a synarthrosis bones are joined by fibrous tissue, and the junction is so strong that no movement can occur. • • •
The main biologic functions of sutures are: To unite bones. To act as areas of growth. To absorb mechanical stress, thus protecting its osteogenic tissue. www.indiandentalacademy.com
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Two types of movements occur between bones at suture sites: Displacement of bones – this, along with the intrinsic deformation of the bones allows ‘molding’ of the skull as the head passes through the birth canal. Displacement of bones relative to each other as part of skull growth. www.indiandentalacademy.com
Sutural Bone Growth ď Ž -
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The intensity of bone deposition at the suture margins varies: between various sutures on opposite sides of the same suture along the same suture. Cranial suture growth occurs as a response to expanding neurocranial content. www.indiandentalacademy.com
The suture is a tension adapted tissue.
The presence of any unusual pressure on the suture triggers bone resorption due to disruption of its vascular and cellular components.
The stimulus for sutural bone growth is the tension produced by the displacement of the bone. www.indiandentalacademy.com
Physiologic Fusion of Sutures ď Ž
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Most sutures of the cranial vault fuse between 25 to 30 years of age. Suture closure occurs slightly earlier endocranially than ectocranially. Most facial sutures remain patent till the 8th decade of life. The palatal suture closure begins during the 3rd decade (large individual variations). The difference and age variation in suture closure between the cranial and facial sutures may be attributed to the differences in the functional environment of the suture. www.indiandentalacademy.com
Sutural Response to Orthopedic Forces
Widening of the mid-palatal suture by traction was first advocated by Angell in 1860. The mechanical response to traction includes a widening of the suture and changes in the orientation of fiber bundles and cells. Areas of compression and tension develop in the tissue, accompanied by bone deposition. www.indiandentalacademy.com
Katsaros, Zissis, Bresin &Kiliaridis (AJO DO 2006) studied the influence of reduced ď Ž
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masticatory muscle function on sutural bone apposition in growing rats. Their findings suggest that reduced masticatory muscle function results in decreased bone apposition rate in the facial sutures. They concluded that this might be a nechanism responsible for osteogenesis in the facial sutures. www.indiandentalacademy.com
THE CRANIAL BASE
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The cranial base or basicranium, the ventral part of the cranium, is the most complex structure of the skeleton. Its main function is to protect and support the brain and to provide a platform for facial growth. The cranial base is important in integrated craniofacial development and growth – especially the anterior cranial base, which has direct connections with upper-middle face and integrates with the facial elements into a growth complex (ethmomaxillary complex). www.indiandentalacademy.com
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Origin of Basicranium ď Ž ď Ž ď Ž
The anterior cranial base is derived from the neural crest. The posterior cranial base is formed by the paraxial mesoderm. Unlike other facial bones, the basicranium is formed through endochondral ossification. In this, a cartilage plate, known as the chondrocranium, is formed first and soon replaced by bones. Individual bones are then connected by cartilaginous structures termed synchondroses. www.indiandentalacademy.com
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The paired individual elements of the cranial base are the sclerotome cartilages, parachordal cartilages (precursor of basioccipital), hypophyseal cartilages (precursor of basisphenoid), presphenoid (trabecular) cartilages, orbitosphenoid (precursor of less wing) and alisphenoid (precursor of great wing) These cartilages extend and fuse with each other. They are connected by the synchondroses that function as growth centers. www.indiandentalacademy.com
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Thus, the cranial base is mainly a midline structure composed of basioccipital, sphenoid, ethmoid and frontal bones in the midline and temporal bones laterally.
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Growth of Basicranium Growth of the basicranium is carried out by a complex balance among sutural growth, elongation at synchondroses, and extensive cortical drift and remodelling. This combination provides: 1. Differential growth enlargement between the cranial floor and calvaria. 2. Expansion of confined contours in the various endocranial fossae. 3. Maintenance of passages and housing for vessels and nerves. www.indiandentalacademy.com
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The bony surface of the whole cranial floor (the endocranial side, in contact with the dura) is resorptive in nature.
The reason for this is the complex topography of this region. The cranial floor is compartmentalized into a series of endocranial fossae and other depressions. www.indiandentalacademy.com
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Darkly stippled areas Resorption.
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Light areas Deposition.
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The sutures of the cranial floor cannot alone accommodate the deepened fossae. ď Ž Growth occurs by direct cortical drift, with deposition on the outside and resorption on the inside of the fossae. This is the key remodelling process along with sutural and syndrochondroses growth. ď Ž
The elevated bony partitions separating the endocranial fossae are depository, in order to maintain the proportion of the fossae. ď Ž
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The floor of the cranium provides for the passage of cranial nerves and major blood vessels. The foramen enclosing each of these structures undergoes its own drift process (+ and -) to constantly maintain its proper position, and to keep pace with the corresponding movement of the nerve or vessel it houses. www.indiandentalacademy.com
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The posterior cranial base lengthens mainly by growth at the spheno-occipital synchondrosis. Growth in this region is partly responsible for lifting the cranium upward and forward from its articulation with the neck, providing room for the downward descent of the face. At birth, posterior cranial base is 56% of the adult length. By 4.5 yrs., it is 78% (males) and 84% (females) of adult dimensions. The total increase in the distance is approx. 2mm. www.indiandentalacademy.com
The anterior cranial base grows by growth at the sutures, as well as by apposition of bone. Its growth is essentially complete by 8 yrs. of age. The total increase is approximately 11mm., the most occuring during the first 3 yrs. postnatally. By 4.5 yrs., 86% - 87% of the adult anterior cranial base dimension is achieved. www.indiandentalacademy.com
Sejrsen, Jakobsen, Skovgaard and Kjaer (ACTA Odontol Scand. 1997) evaluated 45 crania from Calcutta, India for growth of external cranial base. 36 of these were from children and 9 from adults.
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The results showed a strong growth tendency of the cranial base upto the age of 4-5 years, followed by diminishing growth and finally, growth arrest. Growth in width of the maxia increased seemingy after the age at which it is expected to have ceased i.e. even after eruption of the permanent second molars (13-14 yrs.) www.indiandentalacademy.com
BASICRANIAL SYNCHONDROSES
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Origin The midline part of the cranial base is characterized by the presence of synchondroses. These are structures “left over� from the primary cartilages of the early cartilaginous cranial base after the endochondral ossification centers appear during fetal development. As the cartilages of the fetal cranium grow and fuse with each other, a part of them is retained at the region where two of these join. This retained portion forms the synchondosis and functions as a growth center. www.indiandentalacademy.com
Structure ď Ž
The basicranial synchondrosis can be characterized structurally as bipolar growth cartilages it is involved in endochondral ossification in two opposing directions.
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The synchondrosis is composed of wellorganised cell bands. www.indiandentalacademy.com
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From middle to distal ends, 3 zones are present: A resting zone composed of chondrocyte precursors which direct formation and organization of the synchondrosis. Proliferation zones Hypertrophic zones. www.indiandentalacademy.com
R – resting zone Pr – proliferating zone H – hypertrophic zone www.indiandentalacademy.com
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Three synchondroses are present in the midline of the cranial base: Spheno-occipital synchondrosis. Mid-sphenoidal synchondrosis. Spheno-ethmoidal synchondrosis.
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Sequence of synchondroseal fusion in humans:
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Mid-sphenoidal synchondrosis perinatal fusion. Spheno-ethmoidal synchondrosis juvenile or adolescent period. Spheno-occipital synchondrosis exact fusion time is not determined: Ford (1958) – at time of eruption of the 3rd molar. www.indiandentalacademy.com
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Melsen (1969) – after eruption of all the canines, premolars and 2nd molars. Ingervall and Thilander (1972) – average age of closure in females is 14 years and in males is 16 years. Enlow (1982) – before 20 years of age.
The spheno-occipital synchondrosis is considered to be a major contributor to craniofacial growth. www.indiandentalacademy.com
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Role of the synchondroses in craniofacial growth. ď Ž
Although the periosteum and sutures participate in the growth of the cranial base, the main growth sites are the synchondroses, which contribute to the growth of the skull in all three dimensions.
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Bjork (1955) and Scott (1962) regard the synchondroses as having a role in the flexure of the human skull base. www.indiandentalacademy.com
The spheno-occipital synchondrosis is the principal “growth cartilage” of the cranial base.
It provides a pressure-adapted bone growth mechanism for the elongation of the midline portion or midventral axis of the cranial base (not the entire cranial floor). www.indiandentalacademy.com
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Overall enlargement of the midline portion is much less than of the laterally located middle and posterior fossae. This is because the lateral fossae contain the various lobes of the hemispheres, which enlarge more than the medulla, pituitary gland, hypothalamus, etc. ď Ž
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Moss and Greenberg (Angle Orthod. 1955) studied the postnatal growth of the human skull base using lateral cephalograms.
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Their results showed that the medial areas of the skull base are essentially stable while the lateral areas undergo prolonged change. www.indiandentalacademy.com
CLINICAL CONSIDERATIONS
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A study by Palomo, Hunt et al (AJO DO 2005) compared longitudnal changes in the shape and size of craniofacial structures between 16 untreated Class II division I girls and 16 untreated Class I Bolton girls. ď Ž
The results showed that the craniofacial complex underwent continuous shape change from ages 6 to 15 in both groups. www.indiandentalacademy.com
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Compared to class I sample, the Class II sample had:
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A longer facial pattern. Smallest mandibular shape difference at age 6 and largest at age 15. More protrusive maxillary landmarks at all ages compared with the Class I sample.
b) c)
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Vaughn, Mason, Moon & Turley (AJO DO 2005) conducted a 5-year clinical trial to quantify the effects of maxillary protraction with or without palatal expansion.
46 children aged 5 – 10 yrs. were assigned to one of 3 groups: - Facemask with palatal expansion. - Facemask without palatal expansion. - Observation for 12 months. www.indiandentalacademy.com
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This study demonstrated that facemask therapy with or without palatal expansion produced equivalent changes in the dentofacial complex that combined to improve the Class III malocclusion. Correction results from a combination of: Skeletal changes: anterior and vertical movement of maxilla, and posterior and downward movement of mandible. Dental changes. Soft tissue changes: more convex profile. www.indiandentalacademy.com
Lagravere, Major & Flores-Mir (Angle Orthod. 2005) evaluated long-term transverse, anteroposterior and vertical skeletal changes after rapid maxillary expansion.
They concluded that: - Long-tern stability of transverse skeletal maxillary increase is better in skeletally less mature individuals (pre-pubertal growth peak) than more mature (pubertal and postpubertal growth peak) individuals. www.indiandentalacademy.com
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Long-term transverse skeletal maxillary increase is approximately 25% of the total appliance adjustment (dental expansion) in pre-pubertal adolescents but not significant for post-pubertal individuals.
- RME did not produce significant anteroposterior or vertical changes in the position of the maxilla and mandible.
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CONCLUSION A thorough background in craniofacial growth and development is necessary for every orthodontist to distinguish normal variations from effects of abnormal or pathologic processes. Since orthodontists are heavily involved in the development of not just the dentition but the entire dentofacial complex, a conscientious practitioner may be able to manipulate facial growth for the benefit of the patient. This is not possible to accomplish without a thorough understanding of the pattern of normal growth and the mechanisms that underlie it. www.indiandentalacademy.com
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Lagravere MO, Major PW, Flores-Mir C. Longterm skeletal changes with rapid maxillary expansion: A systematic review. Angle Orthod. 2005, 75: 1046-1052. www.indiandentalacademy.com
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