Prosthodontics: Maxillo-Mandibular Relation Records and Tooth Selection

Vocabulary review flashcards covering maxillo-mandibular records, vertical dimensions, centric relations, facial landmarks, phonetic considerations, and anterior/posterior complete denture tooth selection.

Natural Dentition vs. Complete Denture Occlusion

Natural teeth are suspended in bone by the periodontal ligament (PDL), which acts as a shock absorber, whereas denture teeth are attached to a denture base that rests on movable and displaceable tissues.

Goals of Complete Denture Occlusion

The four main objectives are: 1. Limit trauma to the supporting structures; 2. Preserve remaining structures; 3. Enhance stability of the dentures; 4. Restore esthetics, speech, and mastication.

Balanced Occlusion

The simultaneous contacting of the maxillary and mandibular teeth on the right and left sides, as well as in the anterior and posterior occlusal areas, when the jaws are in centric or eccentric relations.

Facebow Record

A record that captures the spatial orientation of the maxilla to the terminal hinge axis and provides the same relative opening axis on the articulator as the mandible has to the temporomandibular joint (TMJ).

Ivoclar Facebow

A specific facebow system designed to orient the maxilla to the transverse axis of the mandible in three dimensions.

Denar Facebow

A facebow instrument system consisting of a bite fork assembly and bow used to transfer the spatial relationship of the maxilla to an articulator.

Hanau Facebow

An earbow/facebow device utilized to record and transfer the relationship of the maxillary arch to the transverse horizontal axis of rotation.

Hinge Axis

A hypothetical line passing through the two mandibular condyles around which the mandible may rotate.

Arbitrary Hinge Axis

An estimated hinge axis location that places the center of rotation within $\pm 6\,\text{mm}$ of the true hinge axis, commonly utilizing the external auditory meatus as a reference point via earbows.

Camper's Line (Camper's Plane)

An anatomical reference line running from the inferior border of the ala of the nose to the superior border of the tragus of the ear; the posterior occlusal plane of the maxillary wax rim is adjusted parallel to it.

Fox Plane

An instrument used extraorally and intraorally to ensure the occlusal plane of the maxillary occlusion rim is parallel to the interpupillary line anteriorly and Camper's plane posteriorly.

Vertical Dimension of Rest (VDR)

The vertical separation of the jaws and measurable length of the face when the opening and closing muscles of the mandible are in a normal resting state of tonic contraction.

Vertical Dimension of Occlusion (VDO)

The distance measured between two selected anatomic points (typically the tip of the nose and the chin point) when the teeth or occlusal rims are in maximum intercuspation or contact.

Interocclusal Rest Space (Free-way Space)

The distance between the occluding surfaces of the maxillary and mandibular teeth when the mandible is in its physiologic rest position, calculated as: $\text{Free-way Space} = \text{VDR} - \text{VDO}$, with a normal range of $2-4\,\text{mm}$.

Excessive VDO (Inadequate Interocclusal Rest Space)

A condition characterized clinically by clicking of the teeth, a tense or strained facial appearance, difficulty closing lips and swallowing, soreness under the denture base, and increased residual ridge resorption from excessive trauma.

Inadequate VDO (Excessive Interocclusal Rest Space)

A state of overclosure that causes potential damage to the TMJ, limited tongue space, drooping of the labial commissures, flabby facial musculature, and predilection to angular cheilitis.

Closest Speaking Space

The clearance measured during the physiologic function of speech while pronouncing 's' sounds (e.g., counting from 60 to 70), used as the final clinical evaluation to verify that the established VDO is correct.

Centric Occlusion (CO)

The tooth-to-tooth relation of opposing occlusal surfaces that provides maximum intercuspation when natural or artificial teeth are present.

Centric Relation (CR)

A bone-to-bone, repeatable maxillomandibular relationship where the condyles articulate with the thinnest avascular portion of their discs in the anterior-superior position against the slopes of the articular eminences; in complete denture prosthodontics, $CR = CO$.

Protrusive Record

An interocclusal registration made with the mandible protruded a minimum of $5-6\,\text{mm}$ to adjust and program the condylar inclinations of the semi-adjustable articulator for eccentric movements.

Dentogenics / Dynesthetic Concept

An esthetic tooth selection system formulated by Fisher and Frush that dictates mold, form, and arrangement based on the patient's age, sex, and personality.

Personality Tooth

The maxillary lateral incisor, regarded as having the greatest degree of variation in size, form, and position compared to any other anterior tooth.

Calculated Width of Incisor Formula

A photographic estimation method formulated as: $\text{Calculated width of incisor} = \frac{\text{photographic width of incisor} \times \text{actual PD}}{\text{photographic PD}}$.

Ivoclar-Vivadent Facial Meter

A measurement gauge based on the clinical relationship between the inner canthus distance and the distance between the distal surfaces of the maxillary lateral incisors, used to select proper maxillary anterior molds.

Almagauge (Incisal Length)

An instrument applied to complete dentures to gauge the vertical incisal length of maxillary anterior teeth from anatomical denture landmarks.

Almagauge (Labial Incisal Position)

The instrument configuration used to establish the horizontal distance from the incisive papilla to the labial surface of the central incisors (normally $8-9\,\text{mm}$).

Average Incisal Length Position

The anatomical average vertical distance from the labial sulcus reflection to the incisal edge of the maxillary central incisor, measuring approximately $22\,\text{mm}$.

Smile Line

The curvature formed by the incisal edges of the maxillary anterior teeth, which should parallel the curvature of the vermilion border of the lower lip upon smiling; females generally display greater curvature, whereas older males exhibit less curvature.

Labiodental Sounds

Speech sounds ('f' and 'v') produced by light contact between the incisal edges of the maxillary anterior teeth and the posterior third of the wet lower lip.

Linguopalatal Sounds

Speech sounds ('s') produced by air escaping through a narrow channel between the tip of the tongue and the anterior rugae area; an overly small air channel produces a whistle, whereas an excessively broad, thin channel converts 's' into 'sh' (lisping).

Linguodental Sounds

Speech sounds ('th') produced when the tip of the tongue extends $3-6\,\text{mm}$ anteriorly beyond the incisal edges of the upper and lower anterior teeth.

Square Denture Mold Form

An anterior tooth mold with an angular outline and a dominant central incisor offering maximum light deflection and creating a bold effect.

Ovoid Denture Mold Form

An anterior tooth mold characterized by a pronounced gingivo-incisal curvature that disperses light reflection to generate a softened, rounded appearance.

Buccolingual Width of Posterior Teeth

A dimension that should be intentionally reduced compared to natural teeth to limit masticatory forces transferred to the ridge, prevent displacement, preserve buccal corridors, and avoid food escapement.

Mesiodistal Length of Posterior Teeth

The total span of artificial posterior teeth, which must never exceed the distance from the distal of the canine to the anterior border of the retromolar pad, and must not be placed over steep upward slopes or displaceable pad tissue.

Anatomic Posterior Teeth

Artificial posterior teeth possessing $30^\circ$ cuspal angulation (e.g., Pilkington-Turner / SR Postaris) designed to resemble newly erupted natural teeth and provide optimal esthetics and crushing efficiency.

Semi-Anatomic Posterior Teeth

Modified cusp forms featuring shallow inclinations of $10^\circ$ to $20^\circ$ (e.g., SR Orthotyp / Anatoline) that reduce lateral shearing forces while maintaining moderate chewing efficiency.

Lingualized Occlusion Form

An occlusal scheme utilizing prominent maxillary lingual cusps that articulate into shallow or flat mandibular fossae (e.g., SR Ortholingual), providing a mortar-and-pestle bolus penetration effect that centralizes forces vertically.

Lingualized vs. Monoplane Occlusion

A comparative arrangement pairing an anatomic or lingualized maxillary mold (Ortholingual) against a flat, non-anatomic mandibular mold (Orthoplane) to facilitate balance and minimize lateral destabilizing forces.

Monoplane (Cuspless) Teeth

Flat occlusal surfaces with $0^\circ$ cusp angles (e.g., SR Orthoplane) indicated for severe ridge atrophy, poor neuromuscular coordination, skeletal Class II or crossbite discrepancies, which eliminate lateral horizontal interferences.

Christensen's Phenomenon

The posterior separation of opposing occlusal surfaces that occurs when the mandible protrudes or moves eccentrically; in flat or monoplane setups, this posterior space causes anterior tipping and excessive force on the anterior ridge.

Acrylic vs. Porcelain Denture Teeth

Acrylic teeth bond chemically to acrylic denture bases, show no percolation, produce no clicking sounds, and cause less trauma, but have low abrasion resistance; porcelain teeth bond mechanically, display high abrasion resistance and no staining, but may click, chip, and transmit higher impact forces to supporting ridges.