NEET MDS Synopsis
Hypophosphatasia in Children
PedodonticsHypophosphatasia in Children
Hypophosphatasia is a rare genetic disorder characterized by defective
mineralization of bones and teeth due to a deficiency in alkaline phosphatase,
an enzyme crucial for bone mineralization. This condition can lead to various
dental and skeletal abnormalities, particularly in children.
Clinical Findings
Premature Exfoliation of Primary Teeth:
One of the hallmark clinical findings in children with
hypophosphatasia is the premature loss of anterior primary teeth.
This loss is associated with deficient cementum, which is the tissue
that helps anchor teeth to the alveolar bone.
Teeth may be lost spontaneously or as a result of minor trauma,
highlighting the fragility of the dental structures in affected
children.
Absence of Severe Gingival Inflammation:
Unlike other dental conditions that may cause tooth mobility or
loss, severe gingival inflammation is typically absent in
hypophosphatasia.
This absence can help differentiate hypophosphatasia from other
periodontal diseases that may present with similar symptoms.
Limited Alveolar Bone Loss:
The loss of alveolar bone associated with hypophosphatasia may be
localized, often limited to the anterior region where the primary teeth
are affected.
Pathophysiology
Deficient Alkaline Phosphatase Activity:
The disease is characterized by improper mineralization of bone and
teeth due to deficient alkaline phosphatase activity in various tissues,
including serum, liver, bone, and kidney (tissue nonspecific).
This deficiency leads to inadequate mineralization, resulting in the
clinical manifestations observed in affected individuals.
Increased Urinary Phosphoethanolamine:
Patients with hypophosphatasia often exhibit elevated levels of
urinary phosphoethanolamine, which can serve as a biochemical marker for
the condition.
Comparisons of primary and permanent teeth:
Pedodontics
1. Crown Dimensions
Primary Anterior Teeth: The crowns of primary anterior
teeth (incisors and canines) are characterized by a wider mesiodistal
dimension and a shorter incisocervical height compared to their permanent
counterparts. This means that primary incisors are broader from side to side
and shorter from the biting edge to the gum line, giving them a more squat
appearance.
Primary Molars: The crowns of primary molars are also
shorter and narrower in the mesiodistal direction at the cervical third
compared to permanent molars. This results in a more constricted appearance
at the base of the crown, which is important for accommodating the
developing permanent teeth.
2. Root Structure
Primary Anterior Teeth: The roots of primary anterior
teeth taper more rapidly than those of permanent anterior teeth. This rapid
tapering allows for a more pronounced root system that is essential for
anchoring the teeth in the softer bone of children’s jaws.
Primary Molars: In contrast, the roots of primary molars
are longer and more slender than those of permanent molars. This elongation
and slenderness provide stability while also allowing for the necessary
space for the developing permanent teeth beneath them.
3. Enamel Characteristics
Enamel Rod Orientation: In primary teeth, the enamel
rods in the gingival third slope occlusally (toward the biting surface)
rather than cervically (toward the root) as seen in permanent teeth. This
unique orientation can influence the way primary teeth respond to wear and
decay.
Thickness of Enamel: The enamel on the occlusal surfaces
of primary molars is of uniform thickness, measuring approximately 1 mm. In
contrast, the enamel on permanent molars is thicker, averaging around 2.5
mm. This difference in thickness can affect the durability and longevity of
the teeth.
4. Surface Contours
Buccal and Lingual Surfaces: The buccal and lingual
surfaces of primary molars are flatter above the crest of contour compared
to permanent molars. This flatter contour can influence the way food is
processed and how plaque accumulates on the teeth.
5. Root Divergence
Primary Molars: The roots of primary molars are more
divergent relative to their crown width compared to permanent molars. This
divergence is crucial as it allows adequate space for the developing
permanent dentition, which is essential for proper alignment and spacing in
the dental arch.
6. Occlusal Features
Occlusal Table: The occlusal table of primary molars is
narrower in the faciolingual dimension. This narrower occlusal surface,
combined with shallower anatomy, results in shorter cusps, less pronounced
ridges, and shallower fossae. These features can affect the functional
aspects of chewing and the overall occlusion.
Mesial Cervical Ridge: Primary molars exhibit a
prominent mesial cervical ridge, which serves as a distinguishing feature
that helps in identifying the right and left molars during dental
examinations.
7. Root Characteristics
Root Shape and Divergence: The roots of primary molars
are not only longer and more slender but also extremely narrow mesiodistally
and broad lingually. This unique shape contributes to their stability while
allowing for the necessary divergence and minimal curvature. Additionally,
primary molars typically have little or no root trunk, which is a stark
contrast to the more complex root structures of permanent molars.
Cerebral palsy and Treatment
PedodonticsCerebral palsy (CP) is a neurological disorder resulting from damage to the
brain during its development before, during, or shortly after birth. This
condition is non-progressive, meaning that it does not worsen over time, but it
manifests as a range of neurological problems that can significantly impact a
child's mobility, muscle control, and posture.
Causes:
The primary cause of CP is any factor that leads to decreased oxygen supply
(hypoxia) to the developing brain. This can occur due to various reasons,
including complications during pregnancy, childbirth, or immediately after
birth.
Classification of Cerebral Palsy:
Based on Anatomical Involvement:
Monoplegia: One limb is affected.
Hemiplegia: One side of the body is affected.
Paraplegia: Both legs are affected.
Quadriplegia: All four limbs are affected.
Based on Neuromuscular Involvement:
Spasticity: Characterized by stiff and tight muscles; this
is the most common type, seen in 70% of cases. Affected individuals may
have limited head movement and a limp gait.
Athetosis: Involves involuntary, writhing movements, seen in
15% of cases. Symptoms include excessive head movement and drooling.
Ataxia: Affects balance and coordination, seen in 5% of
cases. Individuals may exhibit a staggering gait and slow tremor-like
movements.
Mixed: A combination of more than one type of cerebral
palsy, seen in about 10% of cases.
1. Spastic Cerebral Palsy (70% of cases)
Characteristics:
Limited Head Movement: Individuals have restrictions in moving their
head due to increased muscle tone.
Involvement of Cerebral Cortex: Indicates that the motor control areas
of the brain (especially those concerning voluntary movement) are affected.
Limping Gait with Circumduction of the Affected Leg: When walking, the
patient often swings the affected leg around instead of lifting it normally,
due to spasticity.
Hypertonicity of Facial Muscles: Increased muscle tension in the facial
region, contributing to a fixed or tense facial expression.
Unilateral or Bilateral Manifestations: Symptoms can occur on one side
of the body (hemiplegia) or affect both sides (diplegia or quadriplegia).
Slow Jaw Movement: Reduced speed in moving the jaw, potentially leading
to functional difficulties.
Hypertonic Orbicularis Oris Muscles: Increased muscle tone around the
mouth, affecting lip closure and movement.
Mouth Breathing (75%): The individual may breathe through their mouth
due to poor control of oral musculature.
Spastic Tongue Thrust: The tongue pushes forward excessively, which can
disrupt swallowing and speech.
Class II Division II Malocclusion (75%): Dental alignment issue often
characterized by a deep overbite and anterior teeth that are retroclined,
sometimes accompanied by a unilateral crossbite.
Speech Involvement: Difficulties with speech articulation due to muscle
coordination problems.
Constricted Mandibular Arch: The lower jaw may have a narrower
configuration, complicating dental alignment and oral function.
2. Athetoid Cerebral Palsy (15% of cases)
Characteristics:
Excessive Head Movement: Involuntary, uncontrolled movements lead to
difficulties maintaining a stable head position.
Involvement of Basal Ganglia: Damage to this area affects muscle tone
and coordination, leading to issues like chorea (involuntary movements).
Bull Neck Appearance: The neck may appear thicker and less defined,
owing to abnormal muscle development or tone.
Lack of Head Balance, Drawn Back: The head may be held in a retracted
position, affecting posture and balance.
Quick Jaw Movement: Involuntary rapid movements can lead to difficulty
with oral control.
Hypotonic Orbicularis Oris Muscles: Reduced muscle tone around the mouth
can lead to drooling and lack of control of oral secretions.
Grimacing and Drooling: Facial expressions may be exaggerated or
inappropriate due to muscle tone issues, and there may be problems with
managing saliva.
Continuous Mouth Breathing: Patients may consistently breathe through
their mouths rather than their noses.
Tissue Biting: Increased risk of self-biting due to lack of muscle
control.
Tongue Protruding: The tongue may frequently stick out, complicating
speech and intake of food.
High and Narrow Palatal Vault: Changes in the oral cavity structures can
lead to functional difficulties.
Class II Division I Malocclusion (90%): Characterized by a deep bite and
anterior open bite.
Speech Involvement: Affected due to uncontrolled muscle movements.
Muscle of Deglutition Involvement: Difficulties with swallowing due to
affected muscles.
Bruxism: Involuntary grinding or clenching of teeth.
Auditory Organs May be Involved: Hearing impairments can coexist.
3. Ataxic Cerebral Palsy (5% of cases)
Characteristics:
Slow Tremor-like Head Movement: Unsteady, gradual movements of the head,
indicative of coordination issues.
Involvement of Cerebellum: The cerebellum, which regulates balance and
motor control, is impacted.
Lack of Balance Leading to Staggering Gait: Individuals may have
difficulty maintaining equilibrium, leading to a wide-based and unsteady
gait.
Hypotonic Orbicularis Oris Muscles: Reduced muscle tone leading to
difficulties with oral closure and control.
Slow Jaw Movement: The jaw may move slower, affecting chewing and
speech.
Speech Involvement: Communication may be affected due to poor
coordination of the speech muscles.
Visual Organ May be Involved (Nystagmus): Involuntary eye movements may
occur, affecting visual stability.
Varied Type of Malocclusion: Dental alignment issues can vary widely in
this population.
4. Mixed:
Mixed cerebral palsy involves a combination of the above types, where the
individual may exhibit spasticity, athetosis, and ataxia to varying degrees.
Dental Considerations for Mixed CP:
- Dental care for patients with mixed CP is highly individualized and depends on
the specific combination and severity of symptoms.
- The dentist must consider the unique challenges that arise from the
combination of muscle tone issues, coordination problems, and potential for
involvement of facial muscles.
- A multidisciplinary approach, including occupational therapy and speech
therapy, may be necessary to address oral function and hygiene.
- The use of sedation or general anesthesia might be considered for extensive
dental treatments due to the difficulty in managing the patient's movements and
ensuring safety during procedures.
Associated Symptoms:
Children with CP may exhibit persistent reflexes such as the asymmetric tonic
neck reflex, which can influence their dental treatment. Other symptoms may
include mental retardation, seizure disorders, speech difficulties, and joint
contractures.
Dental Problems:
Children with cerebral palsy often experience specific dental challenges:
They may have a higher incidence of dental caries (tooth decay) due to
difficulty in maintaining oral hygiene and dietary preferences.
There is a greater likelihood of periodontal disease, often exacerbated
by medications like phenytoin, which can lead to gum overgrowth and dental
issues.
Dental Treatment Considerations:
When managing dental care for children with cerebral palsy, dentists need to
consider:
Patient Stability: The child’s head should be stabilized, and their back
should be elevated to minimize swallowing difficulties.
Physical Restraints: These can help manage uncontrolled movements during
treatment.
Use of Mouth Props and Finger Splints: These tools can assist in
controlling involuntary jaw movements.
Gentle Handling: Avoid abrupt movements to prevent triggering the
startle reflex.
Local Anesthesia (LA): Administered with caution, ensuring stabilization
to prevent sudden movements.
Premedication: Medications may be given to alleviate muscle
hypertonicity, manage anxiety, and reduce involuntary movements.
General Anesthesia (GA): Reserved for cases that are too challenging to
manage with other methods.
Types of Springs
Orthodontics
Types of Springs
In orthodontics, various types of springs are utilized to achieve specific
tooth movements. Each type of spring has unique characteristics and
applications. Below are a few examples of commonly used springs in orthodontic
appliances:
1. Finger Spring
Construction: Made from 0.5 mm stainless steel wire.
Components:
Helix: 2 mm in diameter.
Active Arm: The part that exerts force on the
tooth.
Retentive Arm: Helps retain the appliance in place.
Placement: The helix is positioned opposite to the
direction of the intended tooth movement and should be aligned along the
long axis of the tooth, perpendicular to the direction of movement.
Indication: Primarily used for mesio-distal movement of
teeth, such as closing anterior diastemas.
Activation: Achieved by opening the coil or moving the
active arm towards the tooth to be moved by 2-3 mm.
2. Z-Spring (Double Cantilever)
Construction: Comprises two helices of small diameter,
suitable for one or more incisors.
Positioning: The spring is positioned perpendicular to
the palatal surface of the tooth, with a long retentive arm.
Preparation: The Z-spring needs to be boxed in wax
prior to acrylization.
Indication: Used to move one or more teeth in the same
direction, such as proclining two or more upper incisors to correct anterior
tooth crossbites. It can also correct mild rotation if only one helix is
activated.
Activation: Achieved by opening both helices up to 2 mm
at a time.
3. Cranked Single Cantilever Spring
Construction: Made from 0.5 mm wire.
Design: The spring consists of a coil located close to
its emergence from the base plate. It is cranked to keep it clear of
adjacent teeth.
Indication: Primarily used to move teeth labially.
4. T Spring
Construction: Made from 0.5 mm wire.
Design: The spring consists of a T-shaped arm, with the
arms embedded in acrylic.
Indication: Used for buccal movement of premolars and
some canines.
Activation: Achieved by pulling the free end of the
spring toward the intended direction of tooth movement.
5. Coffin Spring
Construction: Made from 1.2 mm wire.
Design: Consists of a U or omega-shaped wire placed in
the midpalatal region, with a retentive arm incorporated into the base
plates.
Retention: Retained by Adams clasps on molars.
Indication: Used for slow dentoalveolar arch expansion
in patients with upper arch constriction or in cases of unilateral crossbite.
Non-odontogenic cysts
Oral Pathology
Nasopalatine cyst
Radiology
The nasopalatine cyst appears as a well-defined, round radiolucency in the midline of the anterior maxilla . Sometimes it appears to be 'heart-shaped' because of super-imposition of the anterior nasal spine.
Radiological assessment should include examination of the lamina dura of the central incisors (to exclude a radicular cyst) and assessment of size (the nasopalatine foramen may reach a width of as much as 10 mm).
Pathology
The cyst is lined by a layer of pseudostratified ciliated columnar epithelium and/or stratified squamous epithelium. The capsule of the cyst is fibrous and may include the incisive canal neurovascular bundle.
Nasolabial cyst
Radiology
'Bowing' inwards of the anterolateral margin of the nasal cavity has been recorded
Pathology
The nasolabial cyst is lined by non-ciliated pseudostratified columnar epithelium, which is often rich in mucous cells.
Pulp
Dental Anatomy
Pulp
1. Four zones—listed from dentin inward
a. Odontoblastic layer
(1) Contains the cell bodies of odontoblasts.
Note: their processes remain in dentinal tubules.
(2) Capillaries, nerve fibers, and dendritic cells may also be present.
b. Cell-free or cell-poor zone (zone of Weil)
(1) Contains capillaries and unmyelinated nerve fibers.
c. Cell-rich zone
(1) Consists mainly of fibroblasts. Macrophages, lymphocytes, and dendritic cells may also be present.
d. The pulp (pulp proper, central zone)
(1) The central mass of the pulp.
(2) Consists of loose connective tissue, larger vessels, and nerves. Also contains fibroblasts and pulpal cells.
2. Pulpal innervation
a. When pulpal nerves are stimulated, they can only transmit one signal pain.
b. There are no proprioceptors in the pulp.
c. Types of nerves:
(1) A-delta fibers
(a) Myelinated sensory nerve fibers.
(b) Stimulation results in the sensation of fast, sharp pain.
(c) Found in the coronal (odontoblastic) area of the pulp.
(2) C-fibers
(a) Unmyelinated sensory nerve fibers.
(b) Transmits information of noxious stimuli centrally.
(c) Stimulation results in pain that is slower, duller, and more diffuse in nature.
(d) Found in the central region of the pulp.
(3) Sympathetic fibers
(a) Found deeper within the pulp.
(b) Sympathetic stimulation results in vasoconstriction of vessels.
Enzyme Kinetics
Biochemistry
Enzyme Kinetics
Enzymes are protein catalysts that, like all catalysts, speed up the rate of a chemical reaction without being used up in the process. They achieve their effect by temporarily binding to the substrate and, in doing so, lowering the activation energy needed to convert it to a product.
The rate at which an enzyme works is influenced by several factors, e.g.,
the concentration of substrate molecules (the more of them available, the quicker the enzyme molecules collide and bind with them). The concentration of substrate is designated [S] and is expressed in unit of molarity.
the temperature. As the temperature rises, molecular motion - and hence collisions between enzyme and substrate - speed up. But as enzymes are proteins, there is an upper limit beyond which the enzyme becomes denatured and ineffective.
the presence of inhibitors.
competitive inhibitors are molecules that bind to the same site as the substrate - preventing the substrate from binding as they do so - but are not changed by the enzyme.
noncompetitive inhibitors are molecules that bind to some other site on the enzyme reducing its catalytic power.
pH. The conformation of a protein is influenced by pH and as enzyme activity is crucially dependent on its conformation, its activity is likewise affected.
The study of the rate at which an enzyme works is called enzyme kinetics.
The Thyroid
Physiology
The thyroid gland is a double-lobed structure located in the neck. Embedded in its rear surface are the four parathyroid glands.
The Thyroid Gland
The thyroid gland synthesizes and secretes:
thyroxine (T4) and
calcitonin
T4 and T3
Thyroxine (T4 ) is a derivative of the amino acid tyrosine with four atoms of iodine. In the liver, one atom of iodine is removed from T4 converting it into triiodothyronine (T3). T3 is the active hormone. It has many effects on the body. Among the most prominent of these are:
an increase in metabolic rate
an increase in the rate and strength of the heart beat.
The thyroid cells responsible for the synthesis of T4 take up circulating iodine from the blood. This action, as well as the synthesis of the hormones, is stimulated by the binding of TSH to transmembrane receptors at the cell surface.
Diseases of the thyroid
1. hypothyroid diseases; caused by inadequate production of T3
cretinism: hypothyroidism in infancy and childhood leads to stunted growth and intelligence. Can be corrected by giving thyroxine if started early enough.
myxedema: hypothyroidism in adults leads to lowered metabolic rate and vigor. Corrected by giving thyroxine.
goiter: enlargement of the thyroid gland. Can be caused by:
inadequate iodine in the diet with resulting low levels of T4 and T3;
an autoimmune attack against components of the thyroid gland (called Hashimoto's thyroiditis).
2. hyperthyroid diseases; caused by excessive secretion of thyroid hormones
Graves´ disease. Autoantibodies against the TSH receptor bind to the receptor mimicking the effect of TSH binding. Result: excessive production of thyroid hormones. Graves´ disease is an example of an autoimmune disease.
Osteoporosis. High levels of thyroid hormones suppress the production of TSH through the negative-feedback mechanism mentioned above. The resulting low level of TSH causes an increase in the numbers of bone-reabsorbing osteoclasts resulting in osteoporosis.
Calcitonin
Calcitonin is a polypeptide of 32 amino acids. The thyroid cells in which it is synthesized have receptors that bind calcium ions (Ca2+) circulating in the blood. These cells monitor the level of circulating Ca2+. A rise in its level stimulates the cells to release calcitonin.
bone cells respond by removing Ca2+ from the blood and storing it in the bone
kidney cells respond by increasing the excretion of Ca2+
Both types of cells have surface receptors for calcitonin.
Because it promotes the transfer of Ca2+ to bones, calcitonin has been examined as a possible treatment for osteoporosis