1	Growth of the Maxilla, Mandible, & Cranium Mark H. Taylor, D.D.S., F.A.C.D.
2	Objectives Quick review of bone formation and remodelling Maxillary and Mandibular Growth areas of growth direction of growth treatment possibilities Cranial Growth Cranial base Cranial vault
3	Methods of Bone Formation Intramembraneous: direct secretion (osteoblasts) of bone matrix within connective tissues Cranial vault, Max & body of Man Endochondral: osteoblasts deposit bone matrix around cartilage (formed by chondroblasts) model; cartilage matrix is eventually lost Cranial base, Man condyle
4	Definitions Deposition: the biological process of laying down the bone Resorption: the biological process of removing the bone Remodeling: A basic part of bone growth involves simultaneous deposition and resorption on all inner and outer surfaces of the entire bone. It provides regional changes in shape, dimensions, and proportions. Drift: Growth movement of an enlarging portion of a bone by the remodeling. The combinations of deposition and resorption result in growth movement toward the depository surface. Displacement: The growth movement of a whole bone as a unit. The bone is carried away from its articulation in relation to other bones. Direction of growth: the direction of drift the direction of displacement the net direction of drift and displacement.
5	Drift and Displacement Drift: the growth movement of an enlarging portion of a bone by the remodeling. Displacement: The growth movement of a whole bone as a unit. Direction of growth: the net growth direction of drift plus displacement
6	Maxillary Growth
7	Maxillary growth Predominant enlargement is posterior and superior Displaced downward and forward Intramembraneous growth
8	Maxillary Displacement & Growth
9	Midpalatal Suture Closes around age 8 May be opened into adolescence Mixed dentition treatment Class I crowded cases Class II cases Class III cases
10	Rapid Palatal Expansion (RPE)
11	Maxillary growth Deposition of bone on alveolar ridges increases face height no growth without teeth example: edentulous patient
12	What About Implants? A retrospective review of a limited number of adolescents with implants was conducted to compare the behavior of these implants with studies in which implants had been placed in growing animals. Implants placed in the growing alveolus behave like ankylosed teeth and become submerged as the surrounding bone grows. Cessation of facial growth should occur prior to implant placement in adolescents.
13	Maxillary Growth Deposition of tuberosity causes arch elongation to allow teeth to fit in Palate is depository, nasal floor is resorptive relocates palate inferiorly increases nasal airway
14	Tuberosity Growth
15	Inferior Relocation of Palate
16	V Principle of Growth
17	Mandibular Growth
18	Mandibular Growth Two methods of growth in the mandible endochondral in the condylar region intramembraneous at other growth sites Predominant trend of growth is posterior and superior, which displaces the mandible downward and forward Deposition of bone on posterior of ramus, resorption on anterior of ramus
19	Posterior Relocation of Ramus
20	Mandibular Growth Condylar growth growth site, not growth center condyle does not establish rate or amount of growth is adaptive
21	Condylar Growth
22	Mandibular Growth Symphyseal suture closes during 1st year therefore, hard to expand mandible Alveolar bone forms with development of teeth, and resorbs when teeth are lost increases/decreases vertical height
23	Mandibular Growth Tuberosity growth posterior direction allows for tooth eruption Chin button growth depository on chin resorptive at B point
24	Tuberosity Growth
25	Symphyseal Suture Closes at one year of age Not easily activated “Development of the arch” philosophies
26	Schwartz Appliance Does not open syphyseal suture Molar uprighting sometimes, this is good sometimes, this is bad
27	Chin Button Growth
28	Orthodontic Headgear
29	Bionator, Functional Appliance
30	Scammon’s Growth Curve
31	Tonsils on a 9 year old
32	Timing of Completed Growth 3 planes of space for maxilla and mandible Width completes first Mostly prior to adolescent growth spurt Intercanine width basically complete at 12 YOA Length completes second Females: 14-15 YOA Males: 18 YOA Height completes last Females: 17-18 YOA Males: early 20’s
33	Rotation Mandibular Rotation Overall forward rotation Decrease of 3-4 degrees mandibular plane angle, age 4 to adult Causes posterior incisor movement and decrease in arch length How does this relate to wisdom teeth? Short face type: more rotation than average Square jaw, low MPA, square gonial angle Long face type: jaw rotates backward Hi MPA, anterior open bite
34	Late Mandibular Growth Either mandible displaces distally TMJ disturbances Upper incisors flare Causes spaces Lower incisors displace distally Most common Lower incisors crowd
35	Pressure From 3rd Molars Pressure studies 3rd molars fail to exert adequate pressure to cause anterior crowding 1992 JADA article Late crowding occurs commonly in individuals with congenitally missing 3rd molars
36	Adult Facial Growth Behrents, early 80’s >100 patients who were in the Bolton Growth study in ’30s and ’40s FACIAL GROWTH CONTINUES THROUGHOUT ADULT LIFE! Changes in both size and shape Vertical changes > anteroposterior changes > width changes Per year changes small, but fairly large cumulative effect Rotation Males: forward, decrease MPA Females: backward, increase MPA Compensation of the dentition (occlusal relationships maintained)
37	Brain Case and Cranial Base
38	Cranial Vault Intramembranous bone formation without cartilaginous precursor Apposition of new bones at the cranial sutures, periosteal activity(remodeling) due to the pressure from the growing brain
39	Newborn Skull
40	Growth of the Brain Case Cranium grows because brain grows At age 5, 90% of growth of cranial vault completed Growth is sutural and appositional All intramembraneous growth; no endochondral growth in the brain case
41	Growth of the Cranial Base Cranial base is composed of: occipital sphenoid ethmoid frontal "Chondrocranium" in the fetus; very little remains at birth except SOS and nasal cartilage
42	Cranial Base Mostly formed by endochondral ossification. Bands of cartilage are formed between centers of ossification called synchondrosis: Spheno-occipital synchondrosis Inter-sphenoid synchondrosis Spheno-ethmoid synchondrosis
43	Cranial Base
44	Growth of the Cranial Base Anterior cranial base frontal ethmoid 1/2 sphenoid Posterior cranial base 1/2 sphenoid occipital capable of growth until the spheno-occipital synchondrosis ossifies in the late teens
45	Growth of the Cranial Base Anterior cranial base, minus the thickness of the frontal bone, is finished growing at approximately 8 years of age this area is used as a reference point to evaluate amount and direction of growth in other areas Overall, the cranial base grows in an intermediate fashion between the calvarium (neural pattern) and the face (general skeletal pattern)