#6 What I Learned Today

Essentials of Clinical Practice

We continued with discussing infection control, focusing mainly on setting up and cleaning a dental clinic, and sterilizing dental equipment. The school has strict policies in maintaining a clean clinic environment; almost all surfaces which are in direct contact with either the patient or the dental practitioner is cleaned prior to appointment and covered with a protective plastic covering. Regulated waste is disposed up through proper disposal procedures.

Dental unit waterlines are often a primary reservoir for bacterial biofilms, and thus lines need to be cleaned often. Another option is to have units that have detachable water bottles which can be filled and clean at the beginning and end of each day. Water being used in most dental treatments must meet regulatory standards set forth for drinking water, which is a heterotrophic bacterial count of less than 500 CFU/mL. In case of a boil water advisory, water must either be boiled, or bought in bottles. Lines should be ran for a period of time afterward once the advisory has been lifted.

All reusable instruments must be sterilized between uses. There are a number of different sterilizing techniques, including steam, dry heat, and flash sterilization. Each type of sterilization has its own procedures (duration, temperature, whether packaging can be used) to be followed.

Gross Anatomy I

Today we began our look at the thoracic cavity; specifically the heart and the circulatory system. Both the lungs and the heart have serous membranes to minimize amount of friction occurring to the organs. There are two separate linings, with serous fluid in between them. The heart layers are the parietal pericardium (lines the pericardial cavity) and the visceral pericardium (lines the heart). Fibrous pericardium attach the heart to the diaphragm (actually moves the heart when you breath!).

The heart has four chamber: left & right atrium, and left & right ventricle. Deoxygenated blood flows into the right atrium from three places: the superior and inferior vena cava, and the coronary sinus. It passes through tricuspid valve and into the right ventricle, where the blood is pumped through the pulmonary semilunar valve to the lungs. It is oxygenated, and returned to the left atrium. From there, it passes through the bicuspid (mitral) valve, where it pumped from the left ventricle through the aortic semilunar valve and out to the circulatory system.

The heart starts by supplying oxygenated blood to itself first, through the left coronary artery and the right coronary artery. These arteries are special in that the blood is not pumped through them, but rather passively flows through between heart beats. The two arteries split into a number of different arteries, including the anterior and posterior interventicular arteries, and the marginal artery. The anterior and posterior interventicular arteries meet up at anastomoses.

Gross Anatomy I Lab

Lab was pretty simple today. We started by cutting open the thoracic cavity of our cadaver. The pectoralis major and minor muscles were isolated, along with the medial and lateral thoracic nerves (which innervate the pecs). Also, we managed to find the cephalic vein, which is situated between the deltoid muscle and the pec major.

We finished off by cracking open the ribs on both sides, and the anterior part of the sternum in order to gain access to the lungs and heart, which we will be dissecting next week.

#5 What I Learned Today

Professionalism and Ethics I

Today's lecture focused on theoretical aspects of ethics. Some philosophical viewpoints were studied, including:

• consequentialism: judging actions to be right or wrong based on the end results
• deontologicism: judging actions based on inherent characteristics or principles, and not on end results
• utilitarianism: action is right if it does more good than any alternative action (ie. the greatest good for the greatest number)
• value theory: to decide on an action based on looking at both good and harmful aspects
• virtue theory: to decide on an action based on one's specific inherent moral values

We also looked at the differences between codes and oaths. Codes are standards that guide a health practitioner into making certain decisions, while oaths are public, ethical statements that one volunteers to follow.

Examples being the American Dental Association Code of Ethics, and the personal oath that my class recited at our white coat ceremony.

Biochemistry

In Biochem, we finished up our introduction to carbohydrates and moved onto reviewing the steps in carbohydrate metabolism.

We started by looking at glycolysis. Simply, it is the conversion of glucose into pyruvate, which results in the net release of energy in the form of 2 ATP and 2 NADH. A number of enzymes are needed to complete the process. As well, two molecules of ATP are necessary in the initial steps of molecule rearrangement. Both the first and last step of glycolysis are reversible, while the middle steps are reversible. Wikipedia has a good summary of all the steps.

Also, another important side reaction that is necessary for glycolysis to occur is 2,3-bisphosphoglycerate formation. It helps maintain the activity of phosphoglycerate mutase, which is an enzyme found in the mid-stage of glycolysis.

#4 What I Learned Today

Introduction to Operative Dentistry

The focus of our lecture today was on the operative removal of carious lesions. The preparation and restoration of dental caries is usually dependent on disease progress. Off-coloured lesions that are isolated to the enamel may be treated through prophylactic means such as fluoride treatment, diet modification, or better dental hygiene. However, once a lesion has progressed passed the dentinoenamel junction and into the dentin, restoration intervention is usually necessary. The physiological makeup of dentin differs from enamel, and is much less resistant to the bacterial attack. Carious lesions that progress to the pulp usually need root canal treatment or extraction.

Caries are typically detected through the use of three senses: tactile, auditory and visual. Lesioned dentin tissue typically has a 'tacky' or 'mushy' texture that can be felt through the use of an explorer or spoon excavator. However, the dentist must be careful t0 use light touch in order to avoid damaging enamel that is going through demineralization. When an explorer is contacted with the carious lesion, a 'dull' sound is given off; this differs from the 'tingy' sound one expects from sound tooth tissue. Finally, visual detection of caries can be made. Carious enamel usually has a white/brown/black colour, while carious dentin shows signs of yellow/brown/orange. Generally carious tooth tissue is dull and does not reflect light. One colour exception that needs to be noted is that amalgam sometimes stains tooth tissue a grey colour over time, and this should not be confused with carious tissue. The decision to ultimately perform a restoration should be done based on radiographic evidence and patient history.

Carious removal is performed through the use of a 'target' technique. All stained tissue is removed up to the dentinoenamel junction using a high speed bur, such as the straight fissure bur #256. Next, carious tissue found in the dentin (in this instance, the pulpal and axial floors of the preparation) using the slow speed handpiece with the largest bur possible (typically a round bur such as #2/#4/#6/#8). When nearing the pulp chamber, patient should be made aware of possible exposure, which may result in further treatment.

And of course, all operative dentistry should be done in the mind frame of minimal intervention and maximal tooth conservation.

#3 What I Learned Today

Essentials of Clinical Practice

The topic of interest for today was infection control. Safety of the dental healthcare practitioner, other memebers of the healthcare team, and the patient are paramount. There are numerous legal bodies enforcing rules which allow for everyone to work and be treated in a safe environment. The Center for Disease Control (CDC) acts as a non-regulatory body which monitors and maintains records for diseases in the US, and makes recommendations on what constitutes safe guidelines. These rules are enforced by the Occupational Safety and Health Administration (OSHA). Further guidelines are laid out by state regulatory bodies, which supercede those of OSHA.

The regulation of bloodborne pathogens monitors many different areas and situations that occur in a dental setting. These include topics such as hand hygiene, protection from sharp injury (ie. needlesticks), sterilization of equipment, water quality, etc.

The best way for a dentist to protect himself or herself, the staff, and patients from bloodborne pathogens is to promote the use of standard precautions. These include wearing masks, eyewear, gloves, handwashing and coats to cover up exposed skin. Patients should wear eye wear to protect themselves as well.

Common sense goes a long way too!

General and Oral Histology

Histology was a review of a lecture which focused on muscle tissue and nerve tissue. Since these topics have a bunch of information made easily available by the web, I'll summarize both as quickly as possible

Muscle cells are striated, and undergo contraction through the movement of actin and myosin filaments by way of nervous stimulation. The microfilaments are arranged in a specific banding pattern, with I bands (only thin filaments), H zones (only thick filaments), and others. Muscle fibers are divided into three types: Type 1 (slow twitch), Type 2a (fast twitch, fatigue-resistant), and Type 2b (fast twitch, fatigue-prone). Muscle cells are found in three distinct types of muscle tissue: skeletal muscle cells (multinuclated and striated), smooth muscle cells (mononucleated, non-striated), and cardiac muscle cells (mononucleated and striated).

Nerves send impulses to muscles and organs to illicit function. A simple nerve consists of dendrites, soma, and an axon (in differing forms). Two specific types of neurons include sensory neurons (afferent) and motor neurons (efferent). They are often sheathed by myelin and myelin-producing cells. Schwann cells produce myelin in the PNS, and oligodendrocytes produce myelin in the CNS.

Obviously the topic goes into greater depth, but this will give you a small idea of what was talked about.

#2 What I Learned Today

Biochemistry

Did an introduction lecture into carbohydrates, specifically the differing forms (D- versus L-isomers). Will post more on this later when I get some clarification on some of the work.

Principles of Dental Materials

We spent most of the class talking about electectrical properties, classes of solids, and internal structures of materials.

Two major electrical properties experienced in dental materials include galvanism and electrochemical corrosion. This can occur due to the fact that you can have metals (amalgam, gold) coming into contact with dissimilar metals (see prior), and electrolytes through saliva, salt water, etc. This allows for currents to be generated, which can cause pain and corrosion.

Solid materials is broken down into three different categories: metals, nonmetals and polymers. Typical metals include steel, aluminum, brass, titanium, gold and silver. They have metalliac lusters, are opaque, have thermal and chemical conductivities, and tend to be strong, ductile, tough and stiff. Ceramics are compounds of metals and nonmetals, with common examples being porcelain, glass, concrete and abraisives. They tend to be translucent, non-conductive, and are hard, brittle and stiff. Polymers are organic-based compounds, such as plastics, rubbers and waxes. They tend to be transparent or opaque, and are soft, weak, flexible and lightweight.

Chemical bonding in compounds occurs by covalent bonding, metallic bonding, ionic bonding, and Van Der Waals bonding (in order from highest to lowest bond strength).

Finally, we started into studying the nanostructure, microstructure and macrostructure of materials. Nanostructures form lattices, with the lattice being made up of repeated unit cells (types include cuboidal, face-centered, body-centered and hexgonal close packed). Materials are often defined and identified by compostion and structure. This can be determined in relation to temperature through the use of phase diagrams (google for an example image).

Dental Anatomy

The focus of today's lecture was the mandibular central and lateral incisors. We looked at them from all aspects, including the labial, lingual, mesial, distal and incisal surfaces.

Mandibular Centrals

From the labial view, you typically find that the lateral incisors are slightly bigger mesiodistally than the central incisors (note, this is flipped from the maxillary). The both the mesioincisal and distoincisal line angles are very sharp (almost 90 degrees) with very straight surfaces running to the cervical.

From the mesial and distal view, both sides have height of contours in the incisal third of the tooth. The cemento-enamel junction on the distal side tends to curve much more gradually to the incisal than the mesial.

From the lingual view, you typically find not very distinct features (mesial and distal ridges, fossa). The cingulum is slightly angled to the distal.

The root is obviously single, and you may find fossa on the distal (I think?).

Mandibular Laterals

Obviously, very similar to the Centrals with some few exceptions. One, the distoincisal angle is more rounded, and the incisal edge itself is twisted towards the distolingual. Also, the height of contour on the distal of the lateral drops towards the cervical a little more (though it's still considered to be in the incisal third) and is larger.

Thanks for reading.

#1 What I Learned Today

Essentials of Clinical Practice

We spent most of the day lecturing about the purpose of monitoring vital signs in a clinical setting, and how to successfully determine them. For every patient that enters the clinic, the practitioner will need to check pulse and blood pressure.

Why is it important to do so? One of good reasons is to screen for high blood pressure. Patients with hypertension can be referred to their physician for further consultation. As well, patients who do have high blood pressure and are taking medications to counteract it can have possible oral complications. This includes changes to the ginigiva (in the forms of lichnoid mucositis and gingival hyperplasia.

Taking pulse is pretty simple. All you need to do is find the radial artery (located superiorly from thumb, on wrist), and count pulses for a minute. It is important to make sure as a practitioner not to use your own thumb, as it has its own pulse which may disrupt your ability to measure. A weak pulse is defined as bradycardia, while a fast pulse is defined as tachycardia. A clinician should be aware of this as it may be an indication of infection or dehydration.

To take blood pressure, a cuff is attached to the arm, and a stethescope is placed over the brachial artery on the inner upper arm. The cuff is inflated to roughly the patient's base BP plus 30 mm Hg. The air is released from the cuff so pressure falls about 3 mm Hg per second. At the onset of two consecutive beats, the systolic pressure is read. When the beats become muffled, the diastolic pressure is recorded.

Gross Anatomy I

Today we lectured about a range of topics, covering bones, arteries and nerves in the pectoral region. We discussed the make-up of the external, internal and innermost intercostal muscles, and how they contract during inhalation and exhalation. We talked about basic innervation, where dorsal root bring sensory information to the spinal cord, and how ventral roots relay motor information from the spinal cord to the muscles. Also discussed was the lymphatic system of the mammary glands. It's unfortunate to note that with many breast cancers, metastasis is a major concern due to the fact that the lymph system has multiple pathways to other areas including the other breast, liver, axillary nodes, etc.

In Laboratory, we began dissection on our cadavers. Very interesting stuff; we began by removing the cutaneous tissue from the posterior of the leg, and isolated some of the major muscles. This isolation included the semitendinosus, semimembranosus and rectus femoris muscles, which make up what is typically called the major 'calf' muscles. Also, we were able to find the sciatic nerve, which is the longest nerve in the human body. It's size was simply startling.

Long story short, fun day.