The Cephalometric Analysis Of Guangdong Students With Normal Occlusion

Radiographic cephalometry is an important method for diagnosis, treatment planning and scientific researching in orthodontists and oral surgeons. It was introduced simultaneously by Hofrath (1931) in Germany and Broadbent (1931) in the United States of America. From then on, orthodontists introduced kinds of cephalometric analysis, and obtained cephalometric standard values of different races, genders and locals. Arnett, Ricketts, Jarabak, Mcnamara analysis are provoked more and more attention for the past few years. It is well established that cephalmotric standard values provide useful guidelines in orthodontic diagnosis and treatment planning. This issue was to evaluate the theoretical and practical significance of the four methods on people with normal occlusion in Guangdong region.Arnett cephalometric analysis came out in 1999, and it allows important soft tissues of midface (orbital rim, cheekbone, subpupil, and alar base) to be seen easily by metallic markers for the first time. The lateral headfilm was obtained with the model positioned in natural head position, seated condyles, and with passive lips, which is also its special feature.Seated condyles mean Centric Relation (CR). CR position is the relationship of mandible to the maxilla when the properly aligned condyle-disk assemblies are in the most superior position against the eminentiae irrespective of vertical dimension or tooth position. CR position is the single most important factor of occlusion.Roth established functional occlusion standard the last century, and he presumed that CR position should be incident with CO position, only in this way, we can get stability.Analysis of the mandible-to-maxilla relationship when the condyles are in CR position presents a completely different picture from maximum intercuspation. So that ignoring the position of the TMJs when examining the occlusion is not acceptable. Just putting the casts together in maximum intercuspation dose not provide the necessary information regarding how the mandibular teeth relate to the maxillary teeth when the condyles are in their completely seated CR position, nor does it show what must be done to achieve harmony between the occlusion and the TMJs. Diagnoses without CR position are responsible for many mistakes of orthodontic treatment decisions.Although the coordination of dentition and TMJ is a standardization of functional occlusion, lots of orthodontists pay little attention to condyles when diagnose. They always examine the occlusion in CO position and try to get a static occluding relation. Unfortunately, they cannot get functional occlusion simultaneously, so instability happens. Once adaptability descent, patients may suffer from TMD.Natural head position (NTP) is defined as the head position evaluated as "natural", It is much more reliable than traditional analysis which intracranial reference lines have been used. Several authors have, however, questioned the validity of intracranial reference because of their variability to the horizontal plane.Ricketts analysis, Jarabak analysis, Mcnamara analysis have their own special features, and there are no standard values provided for these methods in Guangdong.Steiner analysis, TWEED analysis, Wits analysis are universally used, but there are no standard values provided for these methods in Guangdong..Objective(1) To obtain the referred value of Arnett analysis, Ricketts analysis, Jarabak analysis, Mcnamara analysis in Guangdong students with normal occlusion. In order to provide guideline for orthodontic diagnosis and treatment planning.(2) To provide theory foundation for diagnosis in CR position.(3) To obtain the referred value of Steiner analysis, Tweed analysis, Wits analysis in Guangdong students with normal occlusion. In order to provide guideline for orthodontic diagnosis and treatment planning.(4) Compare the measurements between males and females to investigate occlusal surface form, structure, size of Guangdong students with normal occlusion.MethodsStudents in GUANGDONG were extensively surveyed,44 subjects (20 males and 24 females) with normal occlusion were selected. The criteria for selection were based on:①Individual normal occlusion (normal anterior overbite and overjet, neutral relationship of molar and canine, the crowding of upper and lower arch was less than 2mm, the space of upper and lower dentition was less than lmm, good occlusal contact of full-mouth teeth, no obvious abrasion), complete dentition in addition to third molar;②Symmetrical face;③No dental emergency, no dental traumatic or broken history;④No orthodontic and/or orthognathic surgery history, no restorative treatment history;⑤No history of bruxism or a tight biting habit, no unilateral chewing habit;⑥No TMDs, no relevant medical history, no otitis media, no temporomandibular joint trauma and / or surgery history, no chronic systemic diseases affecting on temporomandibular joint (such as rheumatoid joints disease);⑦Maxillofacial and neck without scars or history of trauma;⑧Good health, no mental disorders;⑨All participants understand the objective and process of this experiment, and signed an informed consent form.1 The lateral cephalograms for Arnett analysis was taken.(1)The first tooth contact in CR position was recorded in the way that Dawson introduced:①Subject in a 45°sitting position, point the chin up;②Set a cotton to anterior teeth, the subject was asked to bite with posterior teeth. Insure that there's no contact of posterior teeth;③In 5 min, the assistant set Delar wax between anterior teeth;④Lock the subject's head enough;⑤Then gently position the four fingers of each hand on the lower border of mandible, with the little finger slightly behind the angle of the mandible, and keep all fingers tightly together. Bring the thumbs together to form a C with both hands. The thumb should fit in the notch above the symphysis. No pressure should be sent at this time;⑥With a very gentle touch, manipulate the jaw so it slowly hinges open and closed. As it hinges, the mandible will usually slip up into CR position;⑦Observe the fist tooth contact, and take out of Delar wax to cool;⑧The load testing to ensure CR and red wax is to check the fist tooth contact. Then maintain the Delar wax.(2)Metallic markers were placed on the right side of the face to mark key midface structures. The metallic beads were placed on the models midface with the following routine.①The orbital rim marker was placed directly over the osseous orbital rim and directly under the pupil with the eye in straight-ahead gaze;②Cheekbone marking required two perspectives. First, examined from left in 3/4 view and the right malar height of contour was marked with ink. Then, with the examiner standing directly in front of the subject, a metal bead was placed at the intersection of the right malar height of contour ink mark and a vertical line through outer canthus;③The alar base marker was then placed in the deepest depression at the alar base of the nose;④The subpupil marker was situated directly below the straight ahead gaze of the pupil. Vertically, the subpupil marker was placed one half of the vertical distance between the orbital rim and alar base markers;⑤The neck-throat point was then localized, and a metal marker was placed in that position.(3)The plumb line was set in front of subject.(4)Natural head posture①A mirror was set in front of the subject;②The subject was asked to relax;③The subject was asked to orthophoria his eyes in the mirror;④Ear-bar was seated to adjust the midsagittal plane.(5)The relaxed lip position was obtained in the following method:①The subject was asked to relax;②The lips were stroked gently;③The lateral cephalogram was taken while the subject is unaware of being observed.2 The lateral cephalograms for Ricketts analysis, Jarabak analysis, Mcnamara analysis, Steiner analysis, Tweed analysis, Wits analysis was taken. The subject was carried his head with the Frankfort horizontal parallel to the floor, occlusion was in CO position, and the lip was relaxed.3 The markers and the measurements were determined. Measurements were carried out with Winceph 7.0.4 Statistics analysis was performed with SPSS 17.0. Statistical analysis of the differences between males and females was done with t testing. A level of significance of 5% was assigned and P values were determined.Results(1) The referred value of Arnett analysis, Ricketts analysis, Jarabak analysis, Mcnamara analysis, Steiner analysis, Tweed analysis, Wits analysis in Guangdong students with normal occlusion were obtained.(2) Arnett analysis revealed that there are differences in some values of Arnett analysis between male and female students in Guangdong (P<0.05), such as Mx1 to MxOP, Upper lip thickness, Lower lip thickness, Facial height, Upper lip length, Lower lip length, Lower 1/3 of face, Maxillary height, Mandibular height, Orbital rim'-A point', and Orbital rims, Cheek bone, Subpupil, Alar base, Nasal projection, Mxl to TVL.(3) Ricketts analysis revealed that there are differences in some values between male and female of the students in Guangdong(P<0.05), such as OJ, ANS-Xi-PM, ANS- Sto, Ba-N and FH plane angle, CC-N, Go-CF, Xi-PM.(4) Jarabak analysis revealed that there are differences in some values between male and female of the students in Guangdong(P<0.05), such as saddle angle, anterior cranial base, posterior cranial base, ramus height, mandibular corpus, anterior facial height, posterior facial height.(5) Mcnamara analysis revealed that there are differences in some values of Mcnamara analysis between male and female of the students in Guangdong (P< 0.05), such as Cd- A, Cd-Gn, ANS- Me.(6) Steiner analysis revealed that there are differences in some values between male and female of the students in Guangdong (P<0.05), such as Pog-NB, SLConclusion1 Arnett analysis is much more comprehensive than Ricketts analysis on soft tissue2 The occlusal surface form, structure, size of Guangdong students with normal occlusion is special. Statistical analysis revealed that males and females are facially similar in some measures but different in others; Male faces were statistically larger facies cranal area, greater thick of soft tissue, larger posterior maxillofacial region, and better development of mandibular than female faces. Female faces were protrution in midface than male faces. Due to these differences, orthodontists should follow different diagnostic criteria when making treatment planning.