Dental Occlusion

• Occlusion marks the act or process of closure between maxillary and mandibular teeth.
• Static occlusion refers to the relationship between the teeth when they approach each other at rest or during function, either statically or dynamically.
• Functional occlusion involves contacts of the maxillary and mandibular teeth during mastication and deglutition.
• Occlusal relationships and stability are key for successful masticatory function and tooth restoration.
• Occlusal therapy requires careful planning as it can be fundamental and irreversible.
• Centric relation is the superoanterior position of the condyles in the articular fossae, fully seated and resting against the posterior slopes of the articular eminence with the discs properly interposed.
• Maximum intercuspation (MI), also known as intercuspal position (ICP), refers to the complete intercuspation of opposing teeth independent of condylar position.
• Centric occlusion (CO) is the occlusion of opposing teeth when the mandible is in centric relation, and may or may not coincide with the maximal intercuspal position; represents where teeth first contact in CR.
• Orthopedic instability is when the condyles are in centric relation.
• Orthopedic stability is joint stability determined by muscles that pull across the joint and prevent dislocation of articular surfaces.
• The directional forces of muscles determine the optimum orthopedic stable joint position.
• Each joint has a musculoskeletal position.
• Orthopedic stability occurs when the stable intercuspal position (ICP) of the tooth is in harmony with the MS position of the condyles.
• When MI/ICP are in harmony with MS/CR, all teeth are in contact.
• With teeth apart, elevator muscles maintain the condyles in their musculoskeletal stable positions, which indicates joint stability.
• Orthopedic instability is a discrepancy between ICP/MI and MS/CR and it's a common occurrence.
• Occlusal contact strongly influences the muscular control of mandibular position.
• When closure of the mandible in the MS position creates unstable occlusal conditions, the neuromuscular system feeds back appropriate muscles action to locate a more stable mandibular position.
• A stable condylar position equals the MS position (condyles) with no occlusal contacts (teeth apart).
• Stable condylar position also occurs when the MS position (condyles) has stable occlusal contacts in MI (everything touching) and MI/ICP is in harmony with MS/CR.
• Orthopedic instability is when the MS position (condyles) has unstable occlusion (teeth contact), resulting in orthopedic instability or a shifted ICP mandible.
• Centric slide marks the shifting of the mandible from CR to MI.
• Criteria for optimal functional occlusion include occlusal conditions that minimize pathological effects based on the masticatory system's anatomic and physiological features.
• Effective treatment aims to have condyles in CR equal to MS (a reproducible position following muscle forces), even and simultaneous contact on posterior teeth, occlusal forces directed along the long axis of the teeth, and anterior teeth separating posterior teeth in eccentric movements.
• In an upright and alert feeding position, posterior contacts should be slightly heavier than the anterior contacts.
• Dynamic individual occlusion revolves around the health and function of the masticatory system, and not limited to a specific occlusal configuration.
• A masticatory system without pathology is physiological, needing proper and functional occlusal contacts.

Diagnostic Impressions and Casts

• Alginate impressions are used for cast fabrication.
• Diagnostic cast represents life-size reproductions of oral cavity and/or facial structures for study and treatment planning.
• Crowns are not made on the cast but recorded.
• Accurate impressions reproduce occlusal surfaces and tissues, must be poured, inspected, manicured, and trimmed.
• Working casts reproduce prepared teeth, ridge areas, and other areas of the dental arch.
• Working casts are used to fabricate restorations, prosthesis, and devices such as bite guards, crowns, and indirect restorations.
• Alginate is a popular impression material for diagnostic casts and is an irreversible hydrocolloid.
• Irreversible hydrocolloids feature gelatinous (colloidal) particles that cannot return to liquid form once jelled.
• As a flexible gel it has the ability to flex and rebound within limits.
• It rebounds better from sudden stress than prolonged stress and can be classified as fast set (1-2 minutes) or regular set (2-4 1/2 minutes).
• It is available in bulk or individual packs.

Alginate Composition

• Sodium or potassium alginate salt (alginic acid) dissolves in water.
• Calcium sulfate reacts with dissolved alginate to form insoluble calcium alginate.
• Sodium phosphate acts as a retarder, slowing down the reaction time with calcium sulfate to prolong working time.
• Diatomaceous earth controls mix consistency and flexibility.
• Potassium sulfate or potassium zinc fluoride counteracts the inhibiting effect of alginate on gypsum setting.
• Organic glycol coats powder particles to minimize dust.

Alginate Chemical Reaction

• Soluble components like sodium or potassium salts of alginic acid and calcium sulfate react to form insoluble calcium alginate gel.
• Alginate, when set as a gel, contains an entangled framework of solid colloidal particles.
• Syneresis is the contraction of a gel with liquid separating, leading to shrinkage.
• Imbibition means absorption of water when immersed causes swelling and therefore dimensional changes that will decrease accuracy.
• Storage in humid air approaching 100% relative humidity yields the least dimensional change.
• Setting time is impacted by warm water, which sets alginate faster.
• Setting time is best controlled via water temperature, rather than water/powder ratio.
• Tear strength resistance to deformation increases with time.
• Clinically, it is required to ensure complete set, use a timer, and allow 2-3 minutes after initial set to avoid material fractures when bending.
• Permanent deformation occurs when alginate is compressed on removal to avoid less compression (undercut).
• Additional clinical requirements are to ensure reasonable alginate bulk between the tray and teeth, and to remove the tray using a snapping motion.
• Tearing is more common in thin sections.
• Tearing decreases with increased rate of removal
• Higher water/powder ratios decrease strength.
• Clinical requiremnts for alginate impressions: adequate thickness of material at 3-5mm, snap removal of impression, following mixing instructions
• Saliva, blood, and syneresis degrade casts.
• Free water dilutes stone, making the cast soft and chalky.
• Prolonged contact with alginate degrades the cast surface.
• Use cold water to rinse your impressions/casts.
• Disinfect and rinse again the dental impressions/casts.
• Remove free water before pouring cast.
• Pour within 12 minutes.
• Retrieve cast at reasonable time = 45 minutes
• Dimensional stability is subjected to shrinkage due to water loss via syneresis where gell filaments contract and squeeze out water.
• Alginate absorbs water on immersion.
• Unsupported alginate distorts
• Fulfill clincal requirements such as: Pour within 12 minutes and store in 100% humidity until pouring
• Wrap in damp towels or place in plastic bag. DO NOT immerse into water
• Rigidity that helps with accuracy for less distortion is important to consider when working with casts
• It is also importnat to make sure the dental material stays within the pores so you should retain impression material, particularly metal trays in order to reduce distortion
• Impressions should evaluate the patients dental arch and arch's width
• The tray should match the arch's width and not the length
• Length can be added in if needed
• Seat posterior to anterior so the dentist stands behind and to the side when working on the maxillary arch of a patient

Alginate: How to Mix

• Use cold water to increase working time.
• You can use tap or distilled water.
• Water Temperature is very important
• Use a dry bowl and put water in first before the power in order to reduce the amount of air trapped.
• Pour slowly to wet the stone evenly as you increase the mixing speed.
• spatulate against the side of bowl

Alginate: How Load the Tray

• You'll want a smooth creamy mix
• Loading the try to avoid trapping air by filling the tray to the level or flanges within 30 seconds.
• Air dry teeth and wipe some alginate onto occlusal surfaces of maxillary teeth after loading tray.
• Line up tray with simulator and seat tray by making it posterior to anterior
• You should avoid over seating the tray as well as contacting the cusps of teeth
• After holding the seat in position for 4-5 mins remove if by breaking the seal in the posterior area for the area by the 1est molar.

How remove the Mandibular impression

• Right front: 7
• Make a toungue space with alginate

How to pour alginate impressions

• Needles should read between 25 - 30
• Pour each impression eperately using 32mL of water
• Hand mix should last 10-15 seconds
• Working time should be between 3-6 seconds while under a vacum to add slow increments of stone.
• Begin at one end with gentle vibration for flow
• Remove your case after 45mins
• The cast should be ~10mm at its thinnest portion.
• MX: center of hard palate
• MD: depth of lingual sulcus

Casts

• Not allowed to fill voids on occlusal surfaces - these must have retake impressions and casts
• You can't repour Alginate
• There must be detailed teeth and soft tissue
• Your casts must: have accurate - free of distortion, detailed - reproduces surface features, complete - all necessary anatomical parts are captured.

1 - most common mistakes with alginate impressions and casts fabrication Alginate

• teeth reproduction: voids or bubbles on incisal edges or cusp tips
• lack of buccal clearance
• Tray being off centered
• palatal void, lack of hard or soft tissue on the anterior region

Facebow Record Transfer

• Face-bow Record Transfer is designed to mount casters
• There are many advantages include: Accurately mounted casts and more accurate representation of patient functional components
• Can use the facebow to mount maxillary cast precisely on the articulator reproducing the 3D position of the maxilla.
• can use face-bow to establish the relationship of the maxillary teeth to certain anatomic reference points

Face-bow Transfer: Has 3 Reference Points: arbitrary (not exact but good enough)

• Has 2 posteriors: hinge axis of the condyles

• Has 1 anterior: nasion or orbital point

• If done right: Maxillary cast is mounted on the upper member of the articulator establishing the axis-orbital plane

• It can allow an estimator to the position of maxilla in the head with relation to the mandible: using semi adjustable articulator

• Allows for a mandibular closing arc can be established for each tooth to tooth contacts in closure

• The distance between the rotational centers of the 2 condyles equals the intercondylar distance.

• There is a face-bow with quick toggle lock assembly

Bite fork registration:

• Place bite fork on teeth aligning the center mark on the fork with facial midline and let sit for ~2 minutes
• To prevent torquing of the facebow, hold it with one hand

Obtaining a Face-Bow:

Before in patient:

• Face-bow: loosen the central knob
• The technician should check if the fork remains parallel to pupil line or to the floor

Mounting the Maxillary Cast on Articulator

• You have two methods that can be used: Direct mounting method (facebow) and indirect-mounting method (assembled by itself)

CR Record

• This is an introcculsal record with 2 types of introcculsal records: Intercuspal position (ICP) or maximum intercuspation (MI) record and Centric relation record

• It is more effective to mount diagnostic casts to MI and working casts where occlusal schemes are stable

• It is best to adhere by the current occlusal scheme with hands on teeth

• CR REcords are used to mount diagnostic casts when there aree major occlusal contacts for cases such as:

• • Evaluate slide between CR and MI: detect premature tooth contacts
• • Determine the need for any occlusal correction before complex:

• -restorative / prosthodontic treatment

• Always Require an interocclusal record*

• CR : the most superoanterior position of the condyles in the articular fossae, fully seated and resting against the posterior slopes of the articular eminence with the discs properly interposed

• Finding the musculoskeletal stable joint position-Mandibular deprogrammer device: jig, Leaf gauge, Bilateral manipulation technique

How to Bilateral manipulation

• Patient reclined with the chin directed upward
• Dentist sits behind the patient
• Fingers should rest on bone and not soft tissues

How to ocate CR, the anterior teeth should not be separated more than 10 mm (rotation, not translation)

• Use articulating paper in the miller's forceps

Bilateral Manipulation with an Anterior Stop

Elevator muscles will set the condyles to superoanterior position : Ex) lucia jig and a device to create multiple plastic leaves ( leaf gauge)

Leaf Gauge Technique to Identify the First Point of Contact

Goal: to release the lateral pterygoid, while using the elevator muscles to seat the condyles in CR

• Evaluate overbite and overjet: Excessive overjet: more leaves needed to separate the back teeth Deep overbite: does not take many leaves to separate back teeth Open bite: use a lot of leaves
• ALWAYS ask patient to move forward and back then half hard bite when swallowing with each increment of leaves removed"

Leaf Gauge Technique: Getting Ready for Bite Registration

-Use leaf gauge to createn adequate space, it should be within 2mm, and use as close to a fully seated condyle as possible.

Occlusal Analysis with CEREC Software

• We analyze skeletal structure and anatomy by ensuring the Frankfort Horizontal: infraorbital rim to tragus of the ear(corresponds to articulator being parallel to floor); Camper's Plane: ala of nose to tragus of ear - thought to correspond to the angulation of the maxillary occlusal plane -Analogue to Digital Occlusal Analysis with Capture a bilateral buccal bite while squeezing the middle of the typodont
• Then go back to "administration to turn on articulator
• Record contact strength MI where Heavy contact = red > Medium contact = yellow > Light contact = green > Close proximity = shades of blue

Fabrication of Diagnostic Casts: Clinical Sessions - Infection Control- masks eye wear of faceshields:

• A properly fitted surgical mask and protective eyewear (with side shields) should be worn during procedures likely to cause splashing

Disinfectant must not be in contact with patient

Eccentric Records: Lateral and Protrusive Mandibular Movements

• Inferior lateral pterygoid muscle: -Bilateral contraction - protrusion of the mandible
• Lateral movements: Contraction of right inferior lateral pterygoid and Right condyle moves anteriorly, medially, and inferiorly
  • non working or orbiting condyle

If we're in the Left laterotrusive movement:

• the contact should stay in between the canine Otherwise the contact will occur between inner surfaces

Lateral and protrusive records

• Can determine condylar inclination, bennett angle, Most used settings: 15 degree Bennett Angle

• Semi Adjustable Articulator: permits variability vs the non adjustable articulator

To avoid eccentric contact in protrusive, cuspal inclination must bel be less than the condylar guidance angle.

• We can test:
• Condylar guidance
• The steeper the guidance
• We test the Curve of Spee
• The lesser Acute The curve, the shorter the posterior cusps

obtaining Eccentric Records

• Immerse wax wafers in water bath (115 degrees F) for ~5 minutes or until soft

Before verifying each record: Release the centric latch and set both condylar guides to the o degree angle LEFT lateral record: establish RIGHT bennett angle

• Firmly tighten the left side shift knob :
• This process helps with a comparitive analysis when comparing results after performing casts.