Cephalometry is the study and measurement of the head the human head by medical imaging such as radiography. Craniometry, the measurement of the cranium, is a large subset of cephalometry. Cephalometry has a history in phrenology, the study of personality and character as well as physiognomy, the study of facial features. Cephalometry as applied in a comparative anatomy context informs biological anthropology. In clinical contexts such as dentistry and oral and maxillofacial surgery, cephalometric analysis helps in treatment and research; the history of cephalometry can be traced through art and anthropology. The origins of the important method of measuring has its origins in the Renaissance. Leonardo da Vinci is the most well known scientist and artist studying facial proportions during the Renaissance. Da Vinci along with others utilized grids to study the proportions of the face and make generalizations about them. Da Vinci looked for divine proportions in his quest to understand facial proportions.
The divine proportion has since been found to exist in 20th centuries of facial proportions as they relate to esthetics. Beginning with Petrus Camper in the 18th century angles began to be employed in the measurement of facial form. Camper began the practice of ethnographic grouping based on facial form. Anders Retzius defined classified different shapes of the head. Brachycephalic refers to a rounded head. Dolichocephalic refers to a long head. Mesocephalic refers to a medium-sized head between the brachycephalic and dolichocephalic sizes. Anders Retzius Defined the Cephalic index. 1931, orthodontists consecrated the era of cephalometry. 1960s began the era of computed cephalometric radiology. 1961 Donald and Brown published an article about using ultrasounds for fetal head measurement correlation of diameter and fetal weight. Cephalometric analysis is used in dentistry, in orthodontics, to gauge the size and spatial relationships of the teeth and cranium; this analysis informs treatment planning, quantifies changes during treatment, provides data for clinical research.
Cephalometry focuses on linear and angular dimensions established by bone and facial measurements. It has been used for measurements of hard and soft tissues of the craniofacial complex. Ultrasound cephalometry is useful for determining baby growth in utero. Cephalometry can determine if an unborn child will pass through the birth canal. Certain 3D imaging applications are now used in obstetric cephalometry. In 1961, Donald and Brown employed ultrasound technique for measurement of the fetal head. Other scientists tried the method and found that the ultrasound technique was 3mm different than the post-natal measurement with calipers; this method requires that the transponder be placed on the maternal abdomen over the area of the fetal head. The transponder is moved until a pair of echos are equal; this indicates. The distance of the reflections equal the biparietal diameter. From this, the size of the head and the fetal weight can be determined with incredible accuracy; the use of ultrasound cephalometry is meant to be used in addition to other radiographic techniques.
Thus far, no ill effects have been reported to the fetus or the mother using the ultrasound fetal cephalometry. Cephalometry can be used to assist in forensic investigations. Researchers work to compile databases of population-level craniometric data. Due to variations in cranial measurements by population these types of databases can help assist investigators working in a known region. One such database was utilized to test whether craniometric measurements can be utilized to measure stature when only fragmentary remains are available. Researchers created a database cranial measurements utilizing cephalograms of Garo women living in Bangladesh. Head circumference, head length, facial height from'nasion' to'gnathion', bizygomatic breadth and stature were all measured and documented; the measurements of the women were placed into a database and a normative value was given for each measurement within that population. Results indicated that the only head circumference was positively statistically correlated with stature.
One way in which cephalograms can be utilized is for accurate age estimation but not for sex estimation. One study confirmed that the mandibular ramus length is related to chronological age and can be utilized to predict whether an individual is older than 18 years or older with a significant degree of accuracy. If the ramus length is 7.0 cm or more the individual has an 81.25% probability of being 18 years or older. Further, the study confirmed that there is not a strong degree of sexual dimorphism between mandibular ramus length until an individual reaches 16 years of age; the accuracy of predicting sex with mandibular ramus length is only 54% making it an unreliable indicator of sex in forensic contexts. The study has impacts for providing age estimation of living people; this could be applicable in immigration and civil investigations, adoption of children, or old-age pension requests. The study utilized scanned cephalometric radiographs to conduct the study. Cephalometry remains to be the most popular and useful method for investigating the craniofacial skeletal morphology.
Skull measurements are important for facial reconstruction in cases of disputed identity. In the Punjab study, the mesocephalic was the most common craniotype followed by dolicocephalic in the trop
Heredity is the passing on of traits from parents to their offspring, either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic information of their parents. Through heredity, variations between individuals can accumulate and cause species to evolve by natural selection; the study of heredity in biology is genetics. In humans, eye color is an example of an inherited characteristic: an individual might inherit the "brown-eye trait" from one of the parents. Inherited traits are controlled by genes and the complete set of genes within an organism's genome is called its genotype; the complete set of observable traits of the structure and behavior of an organism is called its phenotype. These traits arise from the interaction of its genotype with the environment; as a result, many aspects of an organism's phenotype are not inherited. For example, suntanned skin comes from the interaction between a person's sunlight. However, some people tan more than others, due to differences in their genotype: a striking example is people with the inherited trait of albinism, who do not tan at all and are sensitive to sunburn.
Heritable traits are known to be passed from one generation to the next via DNA, a molecule that encodes genetic information. DNA is a long polymer; the sequence of bases along a particular DNA molecule specifies the genetic information: this is comparable to a sequence of letters spelling out a passage of text. Before a cell divides through mitosis, the DNA is copied, so that each of the resulting two cells will inherit the DNA sequence. A portion of a DNA molecule that specifies a single functional unit is called a gene. Within cells, the long strands of DNA form condensed structures called chromosomes. Organisms inherit genetic material from their parents in the form of homologous chromosomes, containing a unique combination of DNA sequences that code for genes; the specific location of a DNA sequence within a chromosome is known as a locus. If the DNA sequence at a particular locus varies between individuals, the different forms of this sequence are called alleles. DNA sequences can change through mutations.
If a mutation occurs within a gene, the new allele may affect the trait that the gene controls, altering the phenotype of the organism. However, while this simple correspondence between an allele and a trait works in some cases, most traits are more complex and are controlled by multiple interacting genes within and among organisms. Developmental biologists suggest that complex interactions in genetic networks and communication among cells can lead to heritable variations that may underlie some of the mechanics in developmental plasticity and canalization. Recent findings have confirmed important examples of heritable changes that cannot be explained by direct agency of the DNA molecule; these phenomena are classed as epigenetic inheritance systems that are causally or independently evolving over genes. Research into modes and mechanisms of epigenetic inheritance is still in its scientific infancy, this area of research has attracted much recent activity as it broadens the scope of heritability and evolutionary biology in general.
DNA methylation marking chromatin, self-sustaining metabolic loops, gene silencing by RNA interference, the three dimensional conformation of proteins are areas where epigenetic inheritance systems have been discovered at the organismic level. Heritability may occur at larger scales. For example, ecological inheritance through the process of niche construction is defined by the regular and repeated activities of organisms in their environment; this generates a legacy of effect that modifies and feeds back into the selection regime of subsequent generations. Descendants inherit genes plus environmental characteristics generated by the ecological actions of ancestors. Other examples of heritability in evolution that are not under the direct control of genes include the inheritance of cultural traits, group heritability, symbiogenesis; these examples of heritability that operate above the gene are covered broadly under the title of multilevel or hierarchical selection, a subject of intense debate in the history of evolutionary science.
When Charles Darwin proposed his theory of evolution in 1859, one of its major problems was the lack of an underlying mechanism for heredity. Darwin believed in the inheritance of acquired traits. Blending inheritance would lead to uniformity across populations in only a few generations and would remove variation from a population on which natural selection could act; this led to Darwin adopting some Lamarckian ideas in editions of On the Origin of Species and his biological works. Darwin's primary approach to heredity was to outline how it appeared to work rather than suggesting mechanisms. Darwin's initial model of heredity was adopted by, heavily modified by, his cousin Francis Galton, who laid the framework for the biometric school of heredity. Galton found no evidence to support the aspects of Darwin's pangenesis model, which relied on acquired traits; the inheritance of acquired traits was shown to have little basis in the 1880s when August Weismann cut the tails off many generations of mice and found that their offspring continued to develop tails.
Scientists in Antiquity had a variety of ideas about heredity: Theophrastus proposed that male flowers caused f
The phenotype of an organism is the composite of the organism's observable characteristics or traits, including its morphology or physical form and structure. An organism's phenotype results from two basic factors: the expression of an organism's genetic code, or its genotype, the influence of environmental factors, which may interact, further affecting phenotype; when two or more different phenotypes exist in the same population of a species, the species is called polymorphic. A well-documented polymorphism is Labrador Retriever coloring. Richard Dawkins in 1978 and again in his 1982 book The Extended Phenotype suggested that bird nests and other built structures such as caddis fly larvae cases and beaver dams can be considered as "extended phenotypes"; the genotype-phenotype distinction was proposed by Wilhelm Johannsen in 1911 to make clear the difference between an organism's heredity and what that heredity produces. The distinction is similar to that proposed by August Weismann, who distinguished between germ plasm and somatic cells.
The genotype-phenotype distinction should not be confused with Francis Crick's central dogma of molecular biology, a statement about the directionality of molecular sequential information flowing from DNA to protein, not the reverse. The term "phenotype" has sometimes been incorrectly used as a shorthand for phenotypic difference from wild type, bringing the absurd statement that a mutation has no phenotype. Despite its straightforward definition, the concept of the phenotype has hidden subtleties, it may seem that anything dependent on the genotype is a phenotype, including molecules such as RNA and proteins. Most molecules and structures coded by the genetic material are not visible in the appearance of an organism, yet they are observable and are thus part of the phenotype, it may seem that this goes beyond the original intentions of the concept with its focus on the organism in itself. Either way, the term phenotype includes inherent traits or characteristics that are observable or traits that can be made visible by some technical procedure.
A notable extension to this idea is the presence of "organic molecules" or metabolites that are generated by organisms from chemical reactions of enzymes. Another extension adds behavior to the phenotype. Behavioral phenotypes include cognitive and behavioral patterns; some behavioral phenotypes may characterize psychiatric syndromes. Phenotypic variation is a fundamental prerequisite for evolution by natural selection, it is the living organism as a whole that contributes to the next generation, so natural selection affects the genetic structure of a population indirectly via the contribution of phenotypes. Without phenotypic variation, there would be no evolution by natural selection; the interaction between genotype and phenotype has been conceptualized by the following relationship: genotype + environment → phenotype A more nuanced version of the relationship is: genotype + environment + genotype & environment interactions → phenotype Genotypes have much flexibility in the modification and expression of phenotypes.
The plant Hieracium umbellatum is found growing in two different habitats in Sweden. One habitat is rocky, sea-side cliffs, where the plants are bushy with broad leaves and expanded inflorescences; these habitats alternate along the coast of Sweden and the habitat that the seeds of Hieracium umbellatum land in, determine the phenotype that grows. An example of random variation in Drosophila flies is the number of ommatidia, which may vary between left and right eyes in a single individual as much as they do between different genotypes overall, or between clones raised in different environments; the concept of phenotype can be extended to variations below the level of the gene that affect an organism's fitness. For example, silent mutations that do not change the corresponding amino acid sequence of a gene may change the frequency of guanine-cytosine base pairs; these base pairs have a higher thermal stability than adenine-thymine, a property that might convey, among organisms living in high-temperature environments, a selective advantage on variants enriched in GC content.
Richard Dawkins described a phenotype that included all effects that a gene has on its surroundings, including other organisms, as an extended phenotype, arguing that "An animal's behavior tends to maximize the survival of the genes'for' that behavior, whether or not those genes happen to be in the body of the particular animal performing it." For instance, an organism such as a beaver modifies its environment by building a beaver dam. When a bird feeds a brood parasite such as a cuckoo, it is unwittingly extending its phenotype.
Royal intermarriage is the practice of members of ruling dynasties marrying into other reigning families. It was more done in the past as part of strategic diplomacy for national interest. Although sometimes enforced by legal requirement on persons of royal birth, more it has been a matter of political policy or tradition in monarchies. In Europe, the practice was most prevalent from the medieval era until the outbreak of World War I, but evidence of intermarriage between royal dynasties in other parts of the world can be found as far back as the Late Bronze Age. Monarchs were in pursuit of national and international aggrandisement on behalf of themselves and their dynasties, thus bonds of kinship tended to promote or restrain aggression. Marriage between dynasties could serve to reinforce or guarantee peace between nations. Alternatively, kinship by marriage could secure an alliance between two dynasties which sought to reduce the sense of threat from or to initiate aggression against the realm of a third dynasty.
It could enhance the prospect of territorial acquisition for a dynasty by procuring legal claim to a foreign throne, or portions of its realm, through inheritance from an heiress whenever a monarch failed to leave an undisputed male heir. In parts of Europe, royalty continued to marry into the families of their greatest vassals as late as the 16th century. More they have tended to marry internationally. In other parts of the world royal intermarriage was less prevalent and the number of instances varied over time, depending on the culture and foreign policy of the era, it was not until the study of genetics began in the early twentieth century that the harm caused by inbreeding was recognized. Looking backwards, it is easy to see its relation to royal biological problems, most noticeably in the case of the last Spanish Habsburg monarch, Charles II of Spain, incapable of procreation. While the contemporary Western ideal sees marriage as a unique bond between two people who are in love, families in which heredity is central to power or inheritance have seen marriage in a different light.
There are political or other non-romantic functions that must be served and the relative wealth and power of the potential spouses may be considered. Marriage for political, economic, or diplomatic reasons, the marriage of state, was a pattern seen for centuries among European rulers. At times, marriage between members of the same dynasty has been common in Central Africa. In West Africa, the sons and daughters of Yoruba kings were traditionally given in marriage to their fellow royals as a matter of dynastic policy. Sometimes these marriages would involve members of other tribes. Erinwinde of Benin, for example, was taken as a wife by the Oba Oranyan of Oyo during his time as governor of Benin, their son Eweka went on to found the dynasty. Marriages between the Swazi and Thembu royal houses of southern Africa are common. For example, the daughter of former South African president and Thembu royal Nelson Mandela, Zenani Mandela, married Prince Thumbumuzi Dlamini, a brother of Mswati III, King of Swaziland.
Elsewhere in the region, Princess Semane Khama of the Bamangwato tribe of Botswana married Kgosi Lebone Edward Molotlegi of the Bafokeng tribe of South Africa. Examples of historical and contemporary royal intermarriages throughout Africa include: Princess Mantfombi Dlamini, sister of Mswati III of Swaziland, Goodwill Zwelithini, King of the Zulus, as his chief queen consort The Toucouleur emperor Umar Tall and Princess Maryem, the daughter of the sultan Muhammed Bello of Sokoto Chief Nfundu Bolulengwe Mtirara of the Thembu people, a great-nephew of Nelson Mandela, Princess Nandi of Zululand, a daughter of King Goodwill Zwelithini. Fadlallah, son of Rabih az-Zubayr of Borno, Khadija, a daughter of Sheik Mohammed al-Mahdi al-Sanusi of the Senoussi people. Princess Owawejokun, a daughter of the Owa Atakumosa of Ijeshaland, Olofinleyo, the Ajapada of Akure. Oranyan, the Alafin of Oyo, Torosi, a princess of the Nupe people; the Chakri Dynasty of Thailand has included marriages between royal relatives, but marriages between dynasts and foreigners, including foreign royals, are rare.
This is in part due to Section 11 of 1924 Palace Law of Succession which excludes members of the royal family from the line of succession if they marry a non-Thai national. The late king Bhumibol Adulyadej was a first-cousin once removed of his wife, the two being a grandson and a great-granddaughter of Chulalongkorn. Chulalongkorn married a number of his half-sisters, including Savang Vadhana and Sunandha Kumariratana; the Lý dynasty which ruled Dai Viet married its princesses off to regional rivals to establish alliances with them. One of these marriages was between a Lý empress regnant and a member of the Chinese Trần clan, which enabled the Trần to topple the Lý and established their own Trần dynasty. A Lý princess married into the Hồ family, of Chinese origin and established the Hồ dynasty which took power after having a Tran princess marry one of their members, Hồ Quý Ly; the Cambodian King Chey Chettha II married the Vietnamese Nguyễn lord Princess Nguyễn Thị Ngọc Vạn, a daughter of Lord Nguyễn Phúc Nguyên, in 1618.
In return, the king granted the Vietnamese the right to establish settlements in Mô Xoài, in the region of Prey Nokor—which they colloquially referred to as Sài Gòn, which became Ho Chi Minh City. Marriage policy in imperial China differed from dynasty to dynasty. Several dynasties practiced Heqin, which involved marrying off princesses to other royal families
Maximilian I, Holy Roman Emperor
Maximilian I was Holy Roman Emperor from 1508 until his death. He was never crowned by the Pope, he was instead proclaimed Emperor elect by Pope Julius II at Trent, thus breaking the long tradition of requiring a papal coronation for the adoption of the imperial title. Maximilian was the son of Frederick III, Holy Roman Emperor, Eleanor of Portugal, he ruled jointly with his father for the last ten years of the latter's reign, from c. 1483 to his father's death in 1493. Maximilian expanded the influence of the House of Habsburg through war and his marriage in 1477 to Mary of Burgundy, the heiress to the Duchy of Burgundy, though he lost the Austrian territories in today's Switzerland to the Swiss Confederacy. Through marriage of his son Philip the Handsome to eventual queen Joanna of Castile in 1498, Maximilian helped to establish the Habsburg dynasty in Spain, which allowed his grandson Charles to hold the thrones of both Castile and Aragon. Maximilian was born at Wiener Neustadt on 22 March 1459.
His father, Frederick III, Holy Roman Emperor, named him for an obscure saint, Maximilian of Tebessa, who Frederick believed had once warned him of imminent peril in a dream. In his infancy, he and his parents were besieged in Vienna by Albert of Austria. One source relates that, during the siege's bleakest days, the young prince would wander about the castle garrison, begging the servants and men-at-arms for bits of bread; the young prince was an excellent hunter, his favorite hobby was the hunting for birds as a horse archer. At the time, the dukes of Burgundy, a cadet branch of the French royal family, with their sophisticated nobility and court culture, were the rulers of substantial territories on the eastern and northern boundaries of France; the reigning duke, Charles the Bold, was the chief political opponent of Maximilian's father Frederick III. Frederick was concerned about Burgundy's expansive tendencies on the western border of his Holy Roman Empire, and, to forestall military conflict, he attempted to secure the marriage of Charles's only daughter, Mary of Burgundy, to his son Maximilian.
After the Siege of Neuss, he was successful. The wedding between Maximilian and Mary took place on 19 August 1477. Maximilian's wife had inherited the large Burgundian domains in France and the Low Countries upon her father's death in the Battle of Nancy on 5 January 1477. Before his coronation as the King of the Romans in 1486, Maximilian decided to secure this distant and extensive Burgundian inheritance to his family, the House of Habsburg, at all costs; the Duchy of Burgundy was claimed by the French crown under Salic Law, with Louis XI of France vigorously contesting the Habsburg claim to the Burgundian inheritance by means of military force. Maximilian undertook the defence of his wife's dominions from an attack by Louis XI and defeated the French forces at Guinegate, the modern Enguinegatte, on 7 August 1479. Maximilian and Mary's wedding contract stipulated that their children would succeed them but that the couple could not be each other's heirs. Mary tried to bypass this rule with a promise to transfer territories as a gift in case of her death, but her plans were confounded.
After Mary's death in a riding accident on 27 March 1482 near the Wijnendale Castle, Maximilian's aim was now to secure the inheritance to his and Mary's son, Philip the Handsome. Some of the Netherlander provinces were hostile to Maximilian, and, in 1482, they signed a treaty with Louis XI in Arras that forced Maximilian to give up Franche-Comté and Artois to the French crown, they rebelled twice in the period 1482–1492, attempting to regain the autonomy they had enjoined under Mary. Flemish rebels managed to capture Philip and Maximilian himself, but they were defeated when Frederick III intervened. Maximilian continued to govern Mary's remaining inheritance in the name of Philip the Handsome. After the regency ended and Charles VIII of France exchanged these two territories for Burgundy and Picardy in the Treaty of Senlis, thus a large part of the Netherlands stayed in the Habsburg patrimony. Maximilian was elected King of the Romans on 16 February 1486 in Frankfurt-am-Main at his father's initiative and crowned on 9 April 1486 in Aachen.
He became ruler of the Holy Roman Empire upon the death of his father in 1493. Much of Austria was under Hungarian rule when he took power, as they had occupied the territory under the reign of Frederick. In 1490, Maximilian entered Vienna; as the Treaty of Senlis had resolved French differences with the Holy Roman Empire, King Louis XII of France had secured borders in the north and turned his attention to Italy, where he made claims for the Duchy of Milan. In 1499/1500 he drove the Sforza regent Lodovico il Moro into exile; this brought him into a potential conflict with Maximilian, who on 16 March 1494 had married Bianca Maria Sforza, a daughter of Galeazzo Maria Sforza, duke of Milan. However, Maximilian was unable to hinder the French from taking over Milan; the prolonged Italian Wars resulted in Maximilian joining the Holy League to counter the French. In 1513, with Henry VIII of England, Maximilian won an important victory at the battle of the Spurs against the French, stopping their advance in northern France.
His campaigns in Italy were not as successful, his progress there was checked. The situation in Italy was not the only problem; the Swiss won a decisive victory against the Empire in the Battle of Dornach on 22 July 1499. Maximilian had no choice but to agree to a peace treaty signed on 22 September 1499 in Basel that granted the Swiss Confederacy independence from the Holy Roman Empire. In addition, the Cou
Orthodontics and dentofacial orthopedics referred to as orthodontia, is a specialty of dentistry that deals with the diagnosis and correction of malpositioned teeth and jaws. The field was established by such pioneering orthodontists as Edward Angle and Norman William Kingsley. "Orthodontics" is derived from the Greek orthos and -odont. The history of orthodontics has been intimately linked with the history of dentistry for more than 2,000 years. Dentistry had its origins as a part of medicine. According to the American Association of Orthodontists, archaeologists have discovered mummified ancients with metal bands wrapped around individual teeth. Malocclusion is not a disease, but abnormal alignment of the teeth and the way the upper and lower teeth fit together; the prevalence of malocclusion varies, but using orthodontic treatment indices, which categorize malocclusions in terms of severity, it can be said that nearly 30% of the population present with malocclusions severe enough to benefit from orthodontic treatment.
Orthodontic treatment can focus on dental displacement only, or deal with the control and modification of facial growth. In the latter case it is better defined as "dentofacial orthopedics". In severe malocclusions that can be a part of craniofacial abnormality, management requires a combination of orthodontics with headgear or reverse pull facemask and/or jaw surgery or orthognathic surgery; this requires additional training, in addition to the formal three-year specialty training. For instance, in the United States, orthodontists get at least another year of training in a form of fellowship, the so-called'Craniofacial Orthodontics', to receive additional training in the orthodontic management of craniofacial anomalies. Treatment for malocclusion can take anywhere from 1 to 3 years to complete, with braces being altered every 4 to 10 weeks by the orthodontist. There are multiple methods for adjusting malocclusion, depending on the needs of the individual patient. In growing patients there are more options for treating skeletal discrepancies, either promoting or restricting growth using functional appliances, orthodontic headgear or a reverse pull facemask.
Most orthodontic work is started during the early permanent dentition stage before skeletal growth is completed. If skeletal growth has completed, orthognathic surgery can be an option. Extraction of teeth may be required to aid the orthodontic treatment. Starting the treatment process for overjets and prominent upper teeth in children rather than waiting until the child has reached adolescence has been shown to reduce damage to the lateral and central incisors; however the treatment outcome does not differ. The majority of Orthodontic Appliance Therapy is delivered using fixed appliances, with the use of removable appliances being reduced; the treatment outcome for fixed appliances is greater than that of removable appliances as the fixed type produces biomechanics that has greater control of the teeth under treatment: being able to move the teeth in dimensions therefore the subsequent final tooth positions are more ideal. Indications for Fixed Appliances Fixed appliances are used when orthodontic treatment involves moving teeth through 3 axis planes in the mouth.
These movements would include: 1) Rotations where the teeth are not conforming to the arch shape and there are contact displacements. 2) Multiple tooth movements where there may be crowding involved and the correction would involve the movement of numerous teeth in differing planes. 3) Bodily movement may be required to move a map-aligned tooth into the arch where the broad long axis of the tooth are correct but the tooth requires moving back into the arch maintaining the axial positions. 4) Tipping or changing the incline of the long axis of the tooth where the tooth may be proclined or retroclined and the tooth angulation is altered. 5) Root torquing - where the angle of the long axis of the tooth is changed with the position of the root being altered to facilitate a more positioned crown and root prominence. Contra-indications - Poor oral hygiene: this predisposes to decalcification, gingival hyperplasia, periodontal breakdown - Active caries - Poor motivation: treatment will last at least several months, patient needs to be committed to maintaining the highest levels of oral hygiene throughout this period.
- Mild malocclusions Risks DecalcificationPlaque accumulation around the margins of brackets and bands can result in areas of demineralisation of enamel. It is important that the patient maintains an excellent standard of oral hygiene throughout treatment. Root ResorptionThis occurs in orthodontic treatment, although it is small in amount, it is an irreversible outcome, difficult to predict. Fixed appliances cause more root resorption than removable appliances. Resorption occurs more in adults and with greater amounts of tooth movement. Root resorption stops as soon. Loss of periodontal support Loss of bone support Failed treatment Soft tissue traumaTypes of Fixed Appliances There are numerous fixed appliance systems that are in use today; these vary depending on personal preference. In basic terms, a bracket is bonded onto the center of the tooth and wires are placed in the bracket slot in order to control movement in all 3 dimensions; each individual bracket has a different shape and built in features for each particular tooth.
Chair-side fitted appliances include Edgewise, Lingual, Self-ligating bracket systems. Laboratory fabricated appliances include Herbst, Quadhelix and MIA, Lingual and Transpalatal arches and RME screw appliances
The mandible, lower jaw or jawbone is the largest and lowest bone in the human face. It holds the lower teeth in place; the mandible sits beneath the maxilla. It is the only movable bone of the skull; the bone is formed in the fetus from a fusion of the left and right mandibular prominences, the point where these sides join, the mandibular symphysis, is still visible as a faint ridge in the midline. Like other symphyses in the body, this is a midline articulation where the bones are joined by fibrocartilage, but this articulation fuses together in early childhood; the word "mandible" derives from the Latin word mandibula, "jawbone", from mandere "to chew" and -bula. The mandible consists of: The body, found at the front A ramus on the left and the right, the rami rise up from the body of the mandible and meet with the body at the angle of the mandible or the gonial angle; the body of the mandible is curved, the front part gives structure to the chin. It has two borders. From the outside, the mandible is marked in the midline by a faint ridge, indicating the mandibular symphysis, the line of junction of the two pieces of which the bone is composed at an early period of life.
This ridge divides below and encloses a triangular eminence, the mental protuberance, the base of, depressed in the center but raised on either side to form the mental tubercle. On either side of the symphysis, just below the incisor teeth, is a depression, the incisive fossa, which gives origin to the mentalis and a small portion of the orbicularis oris. Below the second premolar tooth, on either side, midway between the upper and lower borders of the body, is the mental foramen, for the passage of the mental vessels and nerve. Running backward and upward from each mental tubercle is a faint ridge, the oblique line, continuous with the anterior border of the ramus. From the inside, the mandible appears concave. Near the lower part of the symphysis is a pair of laterally placed spines, termed the mental spines, which give origin to the genioglossus. Below these is a second pair of spines, or more a median ridge or impression, for the origin of the geniohyoid. In some cases, the mental spines are fused to form a single eminence, in others they are absent and their position is indicated by an irregularity of the surface.
Above the mental spines, a median foramen and furrow are sometimes seen. Below the mental spines, on either side of the middle line, is an oval depression for the attachment of the anterior belly of the digastric. Extending upward and backward on either side from the lower part of the symphysis is the mylohyoid line, which gives origin to the mylohyoid muscle. Above the anterior part of this line is a smooth triangular area against which the sublingual gland rests, below the hinder part, an oval fossa for the submandibular gland. Borders The superior or alveolar border, wider behind than in front, is hollowed into cavities, for the reception of the teeth. To the outer lip of the superior border, on either side, the buccinator is attached as far forward as the first molar tooth; the inferior border is rounded, longer than the superior, thicker in front than behind. The ramus of the human mandible has four sides, two surfaces, four borders, two processes. On the outside, the ramus marked by oblique ridges at its lower part.
On the inside at the center there is an oblique mandibular foramen, for the entrance of the inferior alveolar vessels and nerve. The margin of this opening is irregular. Behind this groove is a rough surface, for the insertion of the medial pterygoid muscle; the mandibular canal runs obliquely downward and forward in the ramus, horizontally forward in the body, where it is placed under the alveoli and communicates with them by small openings. On arriving at the incisor teeth, it turns back to communicate with the mental foramen, giving off two small canals which run to the cavities containing the incisor teeth. In the posterior two-thirds of the bone the canal is situated nearer the internal surface of the mandible, it contains the inferior alveolar vessels and nerve, from which branches are distributed to the teeth. Borders The lower border of the ramus is thick and continuous with the inferior border of the body of the bone. At its junction with the posterior border is the angle of the mandible, which may be either inverted or everted and is marked by rough, oblique ridges on each side, for the attachment of the masseter laterally, the medial pterygoid muscle medially.
The anterior border is thin above, thicker below, continuous with the oblique l