Overview of Orthodontics, Cephalometric Analysis
Cephalometric analysis is a way doctors examine X-rays of the side of a person’s skull. This is done to understand the structure and dimensions of the bones in a person’s head and evaluate how complex a dental treatment might be. This technique is mostly used when a doctor is planning to move a person’s teeth forward or backward. It’s important to note that not all dental treatments need this analysis. It’s especially useful if substantial changes are expected to be made to a person’s front teeth position.
Cephalometric analysis has a rich background, starting in the late 1800s when X-rays were first used to research the head and neck. Fast forward to the 1930s, Holly Broadbent, a professor at the University of Michigan, took this a step further. He analyzed how teeth relate to the skull in structural terms. His groundbreaking work involved measuring different angles and distances on X-ray images, laying the groundwork for what we now know as cephalometric analysis. Subsequent decades have seen researches build and expand on Broadbent’s foundational work by introducing more methods like the Wits analysis. Today, cephalometric analysis is a fundamental part of contemporary dental practices. It plays a key role in diagnosing and treating various dental and bone-related conditions.
Anatomy and Physiology of Orthodontics, Cephalometric Analysis
Cephalometric analysis is a process used by doctors to examine the relationship and positioning of the jawbones in relation to the base of the skull. This examination typically focuses on the upper and lower teeth and their relationship to the jawbones. Doctors compare these characteristics to average measurements in the general population. This information helps them understand each patient’s unique facial structure. However, it’s important to remember that these measurements can vary, and this process does require careful interpretation. Differences in measurements could simply indicate unique features of a patient’s face or skull.
Doctors often use specific points on a patient’s face to make these calculations, referred to as ‘cephalometric points’. Here are some of the most commonly used points:
- Sella (S): The middle point of the sella turcica, a saddle-like part in the sphenoid bone of the skull.
- Nasion (N): The most forward point of the frontonasal suture, or where the frontal and nasal bones meet.
- Orbitale (Or): The lowest forward point on the lower edge of your eye socket.
- Porion (Po): The highest outside point of the external auditory hole in your skull, or the level of the top border of your lower jaw hinge.
- Anterior nasal spine (ANS): The tip of the anterior nasal spine, a pointed bone at the base of the cavity in your skull where nose formed.
In addition to these points, doctors use certain planes—or imaginary flat surfaces—as reference points. These cephalometric planes can help understand the relationship and orientation of different parts of the face. Some of these planes include:
- Sella-Nasion (SN): A horizontal line between the sella and nasion which helps in measuring the front-to-back relationship between the jaws and facial structure.
- Frankfort: A line joining the porion and orbitale that helps determine the vertical relationship between the jaws and facial structures.
- Mandibular: A line along the lower edge of the lower jaw. It helps evaluate the vertical position of the lower jaw (mandible).
Doctors often use these measurements and techniques to plan treatments, like orthodontic treatment to correct the positioning of a patient’s teeth.
Why do People Need Orthodontics, Cephalometric Analysis
Cephalometric analysis is a useful tool for identifying issues with the alignment of teeth and jaw structure, also known as dental and skeletal malocclusions. This approach is used to make a plan to correct these problems as well as to gauge the success of these treatments afterwards. Furthermore, it is also used to keep track of changes that occur due to growth over time.
How is Orthodontics, Cephalometric Analysis performed
Lateral cephalometric radiographs are a type of X-ray used to capture a side-view image of the head and neck. These X-rays are useful in assessing the measurement and position of your facial structures such as your jaw and skull. The images can provide valuable information about the size, shape, and position of these structures and how they relate to each other.
On the other hand, posteroanterior radiographs, which are taken from the front of the head, mainly measure the width of the face and relationship between the jaws. However, this type of X-ray is more difficult to interpret, so most doctors prefer to use lateral radiographs.
To take these X-ray images, a standard procedure is needed to ensure that the obtained images can be accurately compared over time and between different patients. A big part of this procedure involves correctly positioning the patient. You would have to position your head straight with a horizontal plane, rests placed in your external ear openings, and aligning the bridge of your nose with a certain point. You would also need to close your teeth together as you normally would.
The X-ray machine is positioned at a distance of about 5 feet from the midline of your body, with the X-ray film located about a foot away from this midline. A calibrated ruler is included in the image to ensure that exact measurements can be made.
Cephalometric Tracing is a process used to read these X-rays. Traditionally, this was done manually, with landmarks identified and marked on the film using a pencil. These marked points were then connected to form lines and angles, which were then measured and interpreted.
Nowadays, a digital tracing technique using specialized software makes this process much easier. The software identifies landmarks and calculates measurements automatically. More importantly, it provides standards based on factors like ethnicity, sex, and age, and can predict changes in soft tissues, growth, and the potential results of surgical procedures. Both manual and digital tracing techniques are suitable ways to read and interpret these X-ray images.
What Else Should I Know About Orthodontics, Cephalometric Analysis?
Cephalometric analysis is a scientific method that dentists and orthodontists use to understand the structure of your face and jaw by measuring different angles and distances in X-ray images of your head.
Firstly, we need to remember that the “average” measurements we use as a standard may vary between individuals due to differences in age, sex, ethnicity or other unique characteristics. Therefore, these measurements should only be taken as rough guidelines rather than hard rules.
Now, let’s look at some of the things your dentist can learn from a cephalometric analysis:
1. The Anteroposterior Evaluation helps understand the relative positions of the upper and lower jaws to the front part of the skull. For this, they measure angles called the SNA, SNB, and ANB angles. If these angles are much larger or smaller than the average, it could indicate a protruding or retruding position of the jaws, respectively.
2. Alternatively, they can use a method called the Wits Analysis. This involves drawing lines at right angles from certain points within the jaw structure, down to a line which represents the biting edge of your teeth. The distance between two distinct points (A and B), indicates if there is any improper alignment of the jaws.
3. Vertical Evaluation helps to understand if your upper and lower jaws are vertically aligned properly. The Maxillary-Mandibular Plane Angle (MMPA) indicates if one’s lower face is overly long or short compared to the upper jaw. A high or low MMPA could indicate an open bite (where teeth don’t meet when the mouth is closed) or a closed bite (where teeth overlap), respectively.
4. The dentist also assesses the position and angle of your front teeth (incisors). If the angles are greater than average, your teeth might be leaning too far forward, and if they’re less, your teeth might be leaning too far back.
5. Linear Evaluation of the incisors is another measurement done to check if your front teeth are too far ahead or behind the jaw bone.
Remember, the dentist is a professional trained to interpret these measurements and will explain their findings to you in a manner that you can easily understand. These analyses provide the dentist with valuable insights into how to proceed with your orthodontic treatment or surgery, ensuring you have the best outcome possible.
