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1. determining the central ratio of
the jaws and the height of the
lower face in dental prosthetics

2. Introduction
• 1. Central Ratio of the Jaws: The central ratio of the jaws
refers to the relationship between the upper and lower jaws in
terms of their size and alignment. This ratio plays a vital role in
achieving proper occlusion, stability, and functionality of
dental prostheses, such as complete dentures. By accurately
determining the central ratio, dental professionals can ensure
that the artificial teeth and jaw structures are harmoniously
balanced, leading to improved esthetics, speech, and chewing
ability for the patient.
• 2. Height of the Lower Face: The height of the lower face, also
known as vertical dimension, is the distance between specific
anatomical landmarks in the face. It is a critical factor in dental
prosthetics as it determines the proper positioning and
support of the artificial teeth. Accurate measurement of the
lower face height helps in achieving optimal facial aesthetics,
restoring facial proportions, and maintaining proper muscle
function.

4. Anthropometric Method for Determining
the Central Ratio of the Jaws
• The anthropometric method is a technique used
to determine the central ratio of the jaws in the
complete absence of teeth. It involves
measurements and assessments based on
anatomical landmarks and facial proportions.

5. stages of this method
• 1. Determining the State of Physiological Rest:
• - Physiological rest refers to the position of the
mandible when the muscles are in a relaxed state.
• - To determine this position, the patient is instructed
to sit comfortably with their head supported, lips gently
closed, and teeth slightly apart.
• - The dentist or clinician observes and palpates the
patient's jaw, noting the position where the muscles are
most relaxed and the mandible is in a stable, balanced
state.
• - This position is crucial for accurate measurements
and establishing the correct relationship between the
upper and lower jaws.

7. stages of this method
• 2. Measuring the Height of the Lower Face:
• - After determining the state of physiological rest, the
height of the lower face is measured using specific
landmarks.
• - One common landmark used is the distance between
the tip of the chin (menton) and the base of the nose
(nasion).
• - Measurements may also involve assessing the
distance between the lower lip and the chin, or the
angle between the forehead and the nose.
• - These measurements help to determine the vertical
dimension of the face, providing valuable information
for dental prosthetics.

9. Fitting a Wax Base with an Occlusal
Roller to the Upper and Lower Jaws
• - The first step is to take an impression of the upper and
lower jaws using dental impression materials. This
impression captures the exact shape and contours of
the patient's mouth.
• - Using the impression, a stone cast or model is
created to replicate the patient's oral structures.
• - A wax base is then fabricated and shaped to fit the
stone cast, mimicking the contours of the patient's
upper and lower jaws.
• - An occlusal roller made of wax or a similar material
is attached to the wax base. The occlusal roller is
designed to simulate the occlusal plane, which is the
biting surface of the teeth.
• - The occlusal roller is positioned in a way that
ensures proper alignment and contact between the
upper and lower jaws.

11. Fixation of Occlusal Ridges and
Application of Anthropometric Landmarks
• - Occlusal ridges are created on the wax base
to establish reference points for measurements
and assessments.
• - These ridges may be marked using materials
of a different color or by creating indentations
or grooves on the wax.
• - Anthropometric landmarks, such as the
nasion (base of the nose) and the menton (tip
of the chin), are identified and marked on the
wax base.
• - These landmarks serve as reference points
for measuring the height of the lower face and
determining the central ratio of the jaws.

13. Advantages and Limitations of the
Anthropometric Method
• - Advantages:
• - The anthropometric method provides a systematic and
standardized approach to determine the central ratio of the jaws.
• - It relies on established anatomical landmarks and
measurements, which can aid in achieving better aesthetic and
functional outcomes in dental prosthetics.
• - The use of occlusal ridges and anthropometric landmarks
allows for accurate and reproducible measurements.
• - Limitations:
• - The anthropometric method relies on average values and
established norms, which may not be applicable to every
individual.
• - Individual variations in facial proportions, age, gender, and
ethnicity should be considered alongside anthropometric
measurements.
• - The accuracy of the method can be influenced by factors such
as patient cooperation, examiner experience, and variations in
impression techniques.

14. Anatomical and Physiological Method for
Determining the Central Ratio of the Jaws

15. 1. Introduction and Significance of the
Anatomical and Physiological Method
• - The anatomical and physiological method
considers the structural and functional aspects of
the jaws, which are essential for achieving proper
occlusion and stability in dental prosthetics.
• - This method focuses on determining the central
ratio of the jaws based on the anatomical position
of the condyle within the temporomandibular joint
and the physiological rest position of the mandible.
• - By considering these factors, dental professionals
can achieve a more accurate and functional
alignment of the prosthetic teeth.

17. 2. Determination of the Central
Ratio of the Jaws
• - The first step involves establishing the centric relation (CR)
position, which is the most retruded and stable position of
the mandible within the temporomandibular joint.
• - Various techniques can be used to determine the CR
position, such as utilizing bimanual manipulation, leaf gauge
registration, or electronic recording devices.
• - Once the CR position is established, it serves as a
reference point for determining the central ratio of the jaws.
• - Measurements are then taken to determine the
horizontal and vertical distances between anatomical
landmarks, such as the condyles and specific reference
points on the maxilla and mandible.
• - These measurements help in calculating the central ratio,
which represents the relationship between the horizontal
and vertical dimensions of the jaws.

19. Fitting a Wax Base with an Occlusal
Roller to the Lower Jaw
• - To begin, a dental impression is taken of the
lower jaw using appropriate dental impression
materials. This captures the exact shape and
contours of the patient's lower arch.
• - Using the impression, a stone cast or model is
created to replicate the patient's lower jaw
structures.
• - A wax base is then fabricated and shaped to fit
the stone cast, following the contours of the lower
jaw.
• - An occlusal roller made of wax or a similar
material is attached to the wax base. The occlusal
roller simulates the occlusal plane and should be
designed to achieve proper alignment and contact
with the upper jaw.

20. Measuring the Height of the Lower Face
in the Centric Relation Position
• - The centric relation (CR) position, which
represents the most retruded and stable
position of the mandible within the
temporomandibular joint, is established.
• - With the patient in the CR position, the
height of the lower face is measured using
specific anatomical landmarks.
• - Common landmarks used include the
distance between the tip of the chin (menton)
and the base of the nose (nasion), or the
distance between the lower lip and the chin.
• - These measurements provide information
about the vertical dimension of the lower face.

21. • Benefits:
• - The fitting of a wax base with an occlusal roller allows for
the assessment and adjustment of the occlusal plane,
ensuring proper alignment and contact between the upper
and lower jaws.
• - Measuring the height of the lower face in the CR position
provides valuable information for achieving facial proportions
and aesthetics in dental prosthetics.
• - This method considers the individual's specific jaw
relationship and functional parameters, leading to improved
occlusion and functionality of the prosthetic appliance.
• Potential Challenges:
• - Achieving the centric relation position can be challenging,
as it requires patient cooperation and proper technique to
ensure accurate results.
• - The accuracy of the measurements may be influenced by
variations in impression techniques and patient factors such
as muscle tone and relaxation.
• - Interpretation of anatomical landmarks and their
relationship to the desired esthetics can be subjective and
require clinical judgment.

22. Functional-Physiological Method for
Determining the Central Ratio of the Jaws

23. • The functional-physiological method is an approach
used to determine the central ratio of the jaws by
considering the functional aspects of the jaw and
facial height determination. This method takes into
account the dynamic movements of the jaw during
various functional activities and their influence on
the relationship between the upper and lower jaws.

24. 1. Introduction and Purpose of the
Functional-Physiological Method
• - The functional-physiological method focuses on
understanding the dynamic movements and
functional relationships of the jaw during activities
such as speaking, chewing, and swallowing.
• - The purpose of this method is to determine the
central ratio of the jaws based on the functional and
physiological parameters that influence the
occlusion and stability of dental prosthetics.
• - By considering the functional aspects, dental
professionals can achieve a more harmonious and
functional relationship between the upper and
lower jaws.

25. 2. Functional Aspects of the Jaw
• - The functional-physiological method involves studying
the movements of the jaw during various functional
activities.
• - Observations and assessments are made to
determine the position and movements of the mandible
during speaking, chewing, and swallowing.
• - The relationship between the upper and lower jaws
is analyzed in terms of the occlusal contacts and stability
achieved during these activities.
• - The functional movements of the jaw help in
determining the ideal occlusal plane and the central
ratio of the jaws.

26. 3. Facial Height Determination
• - Facial height determination is an important
component of the functional-physiological method.
• - It involves assessing the vertical dimension of the
face to achieve a harmonious and aesthetically pleasing
appearance.
• - Measurements are taken to determine the
proportions between the upper and lower thirds of the
face.
• - The position and height of the lips, the curvature of
the facial profile, and the relationship between the
nose, lips, and chin are considered in determining the
facial height.

27. common techniques and measurements
used in functional-physiological method
• 1. Functional Analysis:
• - Functional analysis involves observing and
assessing the movements of the jaw during
activities such as speaking, chewing, and
swallowing.
• - It includes evaluating the range of
mandibular movements, occlusal contacts, and
stability achieved during functional activities.
• - Functional analysis helps in determining the
ideal occlusal plane and the functional
relationship between the upper and lower
jaws.

28. common techniques and measurements
used in functional-physiological method
• 2. Phonetics:
• - Phonetics involves analyzing the speech
patterns and sounds produced by the patient.
• - The position and movement of the jaw
during speech can provide valuable
information about the central ratio of the jaws.
• - Observing the position and contact of the
teeth during certain phonetic sounds can help
determine proper occlusion and alignment.

31. common techniques and measurements
used in functional-physiological method
• 3. Facial Height Measurements:
• - Facial height measurements are taken to
assess the vertical dimension of the face.
• - These measurements may include the
distance between specific anatomical
landmarks, such as the nasion (base of the
nose) to the chin or the upper lip to the
chin.
• - The proportions between the upper and
lower thirds of the face are considered to
achieve an aesthetically pleasing result.

32. • Advantages of the Functional-Physiological Method:
• - This method considers the dynamic movements and
functional aspects of the jaw, which can lead to improved
occlusion and stability in dental prosthetics.
• - By incorporating phonetics and speech analysis, the
functional-physiological method aims to achieve proper
occlusal contacts during speech, enhancing the patient's
ability to articulate clearly.
• - Facial height measurements help in achieving a balanced
and harmonious appearance of the face.
• Limitations of the Functional-Physiological Method:
• - The functional-physiological method requires a thorough
understanding of the functional dynamics of the jaw and the
ability to interpret and analyze the patient's movements
accurately.
• - It may be challenging to reproduce the exact functional
movements and occlusal contacts in the dental prosthetic,
leading to potential discrepancies between the theoretical
central ratio and the actual clinical outcome.
• - Individual variations in speech patterns, muscle activity, and
functional habits can impact the accuracy of the
measurements and the functional-physiological assessment.

33. Photographic Method for Determining
the Height of the Lower Face

34. • The photographic method is an alternative
approach used to determine the height of the lower
face. This method involves capturing photographs
and analyzing them to assess the facial height.

35. Introduction to the
Photographic Method
• - The photographic method utilizes photographs to
assess the height of the lower face and determine
proportions between different facial landmarks.
• - This method provides a visual representation
that can be analyzed and compared to established
norms and aesthetic standards.

36. Process of Capturing Photographs
and Analyzing Them
• - To begin, standardized photographs of the patient's
face are captured using a digital camera or other
imaging devices.
• - The photographs are taken in a standardized
position, typically with the patient in an upright and
relaxed posture.
• - Specific facial landmarks, such as the chin, lips, and
nose, are identified and marked on the photographs.
• - Measurements are then taken between these
landmarks to assess the proportions and determine the
height of the lower face.
• - Digital imaging software or specialized computer
programs can be used to analyze the photographs and
calculate the relevant measurements accurately.

37. Strengths of the
Photographic Method
• - The photographic method provides a non-invasive
and easily repeatable approach to assess the height
of the lower face.
• - It offers a visual representation that can be
objectively analyzed by dental professionals and
compared to established norms and aesthetic
standards.
• - This method allows for documentation and
monitoring of facial changes over time.

38. Limitations of the
Photographic Method
• - The accuracy of the measurements obtained through
photographs may be influenced by factors such as
camera angle, lighting, and patient positioning.
• - The interpretation and analysis of photographs
require expertise and an understanding of facial
proportions and aesthetics.
• - Photographs capture a static moment and may not
fully represent the dynamic movements and functional
aspects of the lower face.
• - Patient cooperation and consistent positioning
during photography sessions are necessary to obtain
reliable results.