NEET MDS Synopsis
Dens in Dente
PedodonticsDens in Dente (Tooth Within a Tooth)
Dens in dente, also known as "tooth within a tooth," is a developmental
dental anomaly characterized by an invagination of the enamel and dentin,
resulting in a tooth structure that resembles a tooth inside another tooth. This
condition can affect both primary and permanent teeth.
Diagnosis
Radiographic Verification:
The diagnosis of dens in dente is confirmed through radiographic
examination. Radiographs will typically show the characteristic
invagination, which may appear as a radiolucent area within the tooth
structure.
Characteristics
Developmental Anomaly:
Dens in dente is described as a lingual invagination of the enamel,
which can lead to various complications, including pulp exposure,
caries, and periapical pathology.
Occurrence:
This condition can occur in both primary and permanent teeth,
although it is most commonly observed in the permanent dentition.
Commonly Affected Teeth
Permanent Maxillary Lateral Incisors:
Dens in dente is most frequently seen in the permanent maxillary
lateral incisors. The presence of deep lingual pits in these teeth
should raise suspicion for this condition.
Unusual Cases:
There have been reports of dens invaginatus occurring in unusual
locations, including:
Mandibular primary canine
Maxillary primary central incisor
Mandibular second primary molar
Genetic Considerations
Inheritance Pattern:
The condition may exhibit an autosomal dominant inheritance pattern,
as evidenced by the occurrence of dens in dente within the same family,
where some members have the condition while others present with deep
lingual pits.
Variable Expressivity and Incomplete Penetrance:
The variability in expression of the condition among family members
suggests that it may have incomplete penetrance, meaning not all
individuals with the genetic predisposition will express the phenotype.
Clinical Implications
Management:
Early diagnosis and management are crucial to prevent complications
associated with dens in dente, such as pulpitis or abscess formation.
Treatment may involve restorative procedures or endodontic therapy,
depending on the severity of the invagination and the health of the
pulp.
PFM Alloys
Dental Materials
PFM Alloys
Applications-substructures for porcelain-fused-to-metal crowns and bridges
Classification
o High-gold alloys
o Palladium-silver alloys
o Nickel-chromium alloys
Structure
Composition
o High-gold alloys are 98% gold. platinum. And palladium
o Palladium-silver alloys are 50% to 60% palladium and 30 to 40% silver
o Nickel-chromium alloys are 70% to 80% nickel and 15% chromium with other metals
Manipulation
o Must have melting temperatures above that of porcelains to be bonded to their surface
o More difficult to cast (see section on chromium alloys)
Properties - Physical
Except for high-gold alloys, others are less dense alloys
Alloys are designed to have low thermal expansion coefficients that must be matched to the overlying porcelain
Chemical-high-gold alloys are immune, but others passivate
Mechanical-high modulus and hardness
Relationship Classification
Dental Anatomy
Angle classified these relationships by using the first permanent molars
Normal or neutral occlusion (ideal):
Mesiobuccalgroove of the mandibular first molar align with the mesiobuccal cusp of the max laxy first permanent molar
ClassI malocclusion normal molar relationships with alterations to other characteristics of the occlusion such as versions, crossbites, excessive overjets, or overbites
Class II malocclusion a distal relation of the mesiobuccal groove of the mandibular first permanent molar to the mesiobuccal cusp of the maxillary first permanent molar
Division I: protruded maxillary anterior teeth
Division II: one or more maxillary anterior teeth retruded
Class III malocclusion a mesial relation of the mesiobuccal groove of the mandibular first permanent molar to the mesiobuccal cusp of the maxillary molar
MANDIBULAR CUSPIDS
Dental Anatomy
MANDIBULAR CUSPIDS
Mandibular canines are those lower teeth that articulate with the mesial aspect of the upper canine.
Facial: The mandibular canine is noticeably narrower mesidistally than the upper, but the root may be as long as that of the upper canine. In an individual person,the lower canine is often shorter than that of the upper canine. The mandibular canine is wider mesiodistally than either lower incisor. A distinctive feature is the nearly straight outline of the mesial aspect of the crown and root. When the tooth is unworn, the mesial cusp ridge appears as a sort of 'shoulder' on the tooth. The mesial cusp ridge is much shorter than the distal cusp ridge.
Lingual: The marginal ridges and cingulum are less prominent than those of the maxillary canine. The lingual surface is smooth and regular. The lingual ridge, if present, is usually rather subtle in its expression.
Proximal: The mesial and distal aspects present a triangular outline. The cingulum as noted is less well developed. When the crown and root are viewed from the proximal, this tooth uniquely presents a crescent-like profile similar to a cashew nut.
Incisal: The mesiodistal dimension is clearly less than the labiolingual dimension. The mesial and distal 'halves' of the tooth are more identical than the upper canine from this perspective. In the mandibular canine, the unworn incisal edge is on the line through the long axis of this tooth.
Production of Hormones
Physiology
Production of Hormones
The kidneys produce and interact with several hormones that are involved in the control of systems outside of the urinary system.
Calcitriol. Calcitriol is the active form of vitamin D in the human body. It is produced by the kidneys from precursor molecules produced by UV radiation striking the skin. Calcitriol works together with parathyroid hormone (PTH) to raise the level of calcium ions in the bloodstream. When the level of calcium ions in the blood drops below a threshold level, the parathyroid glands release PTH, which in turn stimulates the kidneys to release calcitriol. Calcitriol promotes the small intestine to absorb calcium from food and deposit it into the bloodstream. It also stimulates the osteoclasts of the skeletal system to break down bone matrix to release calcium ions into the blood.
Erythropoietin. Erythropoietin, also known as EPO, is a hormone that is produced by the kidneys to stimulate the production of red blood cells. The kidneys monitor the condition of the blood that passes through their capillaries, including the oxygen-carrying capacity of the blood. When the blood becomes hypoxic, meaning that it is carrying deficient levels of oxygen, cells lining the capillaries begin producing EPO and release it into the bloodstream. EPO travels through the blood to the red bone marrow, where it stimulates hematopoietic cells to increase their rate of red blood cell production. Red blood cells contain hemoglobin, which greatly increases the blood’s oxygen-carrying capacity and effectively ends the hypoxic conditions.
Renin. Renin is not a hormone itself, but an enzyme that the kidneys produce to start the renin-angiotensin system (RAS). The RAS increases blood volume and blood pressure in response to low blood pressure, blood loss, or dehydration. Renin is released into the blood where it catalyzes angiotensinogen from the liver into angiotensin I. Angiotensin I is further catalyzed by another enzyme into Angiotensin II.
Angiotensin II stimulates several processes, including stimulating the adrenal cortex to produce the hormone aldosterone. Aldosterone then changes the function of the kidneys to increase the reabsorption of water and sodium ions into the blood, increasing blood volume and raising blood pressure. Negative feedback from increased blood pressure finally turns off the RAS to maintain healthy blood pressure levels.
Refractory Material
Conservative DentistryRefractory materials are essential in the field of dentistry, particularly in
the branch of conservative dentistry and prosthodontics, for the fabrication of
various restorations and appliances. These materials are characterized by their
ability to withstand high temperatures without undergoing significant
deformation or chemical change. This is crucial for the longevity and stability
of the dental work. The primary function of refractory materials is to provide a
precise and durable mold or pattern for the casting of metal restorations, such
as crowns, bridges, and inlays/onlays.
Refractory materials include:
- Plaster of Paris: The most commonly used refractory material
in dentistry, plaster is composed of calcium sulfate hemihydrate. It is mixed
with water to form a paste that is used to make study models and casts. It has a
relatively low expansion coefficient and is easy to manipulate, making it
suitable for various applications.
- Dental stone: A more precise alternative to plaster, dental
stone is a type of gypsum product that offers higher strength and less
dimensional change. It is commonly used for master models and die fabrication
due to its excellent surface detail reproduction.
- Investment materials: Used in the casting process of fabricating indirect
restorations, investment materials are refractory and encapsulate the wax
pattern to create a mold. They can withstand the high temperatures required for
metal casting without distortion.
- Zirconia: A newer refractory material gaining popularity,
zirconia is a ceramic that is used for the fabrication of all-ceramic crowns and
bridges. It is extremely durable and has a high resistance to wear and fracture.
- Refractory die materials: These are used in the production of
metal-ceramic restorations. They are capable of withstanding the high
temperatures involved in the ceramic firing process and provide a reliable
foundation for the ceramic layers.
The selection of a refractory material is based on factors such as the intended
use, the required accuracy, and the specific properties needed for the final
restoration. The material must have a low thermal expansion coefficient to
minimize the thermal stress during the casting process and maintain the
integrity of the final product. Additionally, the material should be able to
reproduce the fine details of the oral anatomy and have good physical and
mechanical properties to ensure stability and longevity.
Refractory materials are typically used in the following procedures:
- Impression taking: Refractory materials are used to make models from the
patient's impressions.
- Casting of metal restorations: A refractory mold is created from the model to
cast the metal framework.
- Ceramic firing: Refractory die materials hold the ceramic in place while it is
fired at high temperatures.
- Temporary restorations: Some refractory materials can be used to produce
temporary restorations that are highly accurate and durable.
Refractory materials are critical for achieving the correct fit and function of
dental restorations, as well as ensuring patient satisfaction with the
aesthetics and comfort of the final product.
Hepatitis A virus.
General Pathology
Hepatitis A virus.
- Hepatitis A (HAV) is a self-limited hepatitis caused by an RNA virus
- Symptoms last 2 to 4 weeks.
- There is no risk of developing chronic hepatitis in the future.
- Incubation period is short, lasting 2 to 6 weeks.
- Infection is identified by HAV-specific antibodies (IgM if acute, IgG if past disease).
- The usual route of infection is fecal-oral transmission by contaminated food. There is no carrier state and no chronic disease
- Laboratory diagnosis: ELISA test for IgM antibody.
- Vaccine: killed virus.
- Prevention: serum immunoglobulins are available.
OCCLUSION AND DENTAL DEVELOPMENT-Stages-Deciduous dentition period
Dental Anatomy
Deciduous dentition period.
-The deciduous teeth start to erupt at the age of six months and the deciduous dentition is complete by the age of approximately two and one half years of age.
-The jaws continue to increase in size at all points until about age one year.
-After this, growth of the arches is lengthening of the arches at their posterior (distal) ends. Also, there is slightly more forward growth of the mandible than the maxilla.
1. Many early developmental events take place.
-The tooth buds anticipate the ultimate occlusal pattern.
-Mandibular teeth tend to erupt first. The pattern for the deciduous incisors is usually in this distinctive order:
(1) mandibular central
(2) maxillary central incisors
(3) then all four lateral incisors.
-By one year, the deciduous molars begin to erupt.
-The eruption pattern for the deciduous dentition as a whole is:
(1) central incisor
(2) lateral incisor
(3) deciduous first molar
(4) then the canine
(5) then finally the second molar.
-Eruption times can be variable.
2. Occlusal changes in the deciduous dentition.
-The overjet tends to diminish with age. Wear and mandibular growth are a factor in this process.
-The overbite often diminishes with the teeth being worn to a flat plane occlusion.
-Spacing of the incisors in anticipation of the soon-to-erupt permanent incisors appears late. Permanent anterior teeth (incisors and canines) are wider mesiodistally than deciduous anterior teeth. In contrast, the deciduous molar are wider mesiodistally that the premolars that later replace them.
-Primate spaces occur in about 50% of children. They appear in the deciduous dentition. The spaces appear between the upper lateral incisor and the upper canine. They also appear between the lower canine and the deciduous first molar.