📖 Prosthodontics
Complete Denture Occlusion
ProsthodonticsComplete Denture Occlusion
Complete denture occlusion is a critical aspect of prosthodontics, as it affects the function, stability, and comfort of the dentures. There are three primary types of occlusion used in complete dentures: Balanced Occlusion, Monoplane Occlusion, and Lingualized Occlusion. Each type has its own characteristics and applications.
Types of Complete Denture Occlusion
1. Balanced Occlusion
- Definition: Balanced occlusion is characterized by simultaneous contact of all opposing teeth in centric occlusion, providing stability and even distribution of occlusal forces.
- Key Features:
- Three-Point Contact: While a three-point contact (one anterior and two posterior) is a starting point, it is not sufficient for true balanced occlusion. Instead, there should be simultaneous contact of all teeth.
- Minimal Occlusal Balance: For minimal occlusal balance, there should be at least three points of contact on the occlusal plane. The more points of contact, the better the balance.
- Absence in Natural Dentition: Balanced occlusion is not typically found in natural dentition; it is a concept specifically applied to complete dentures to enhance stability during function.
- Importance: This type of occlusion is particularly important for patients with complete dentures, as it helps to minimize tipping and movement of the dentures during chewing and speaking.
2. Monoplane Occlusion
- Definition: Monoplane occlusion involves a flat occlusal plane where the occlusal surfaces of the teeth are arranged in a single plane.
- Key Features:
- Flat Occlusal Plane: The occlusal surfaces are designed to be flat, which simplifies the occlusion and reduces the complexity of the denture design.
- Limited Interference: This type of occlusion minimizes interferences during lateral and protrusive movements, making it easier for patients to adapt to their dentures.
- Applications: Monoplane occlusion is often used in cases where the residual ridge is severely resorbed or in patients with limited jaw movements.
3. Lingualized Occlusion
- Definition: Lingualized occlusion is characterized by the positioning of the maxillary posterior teeth in a way that they occlude with the mandibular posterior teeth, with the buccal cusps of the mandibular teeth being positioned more towards the buccal side.
- Key Features:
- Maxillary Teeth Positioning: The maxillary posterior teeth are positioned more towards the center of the arch, while the mandibular posterior teeth are positioned buccally.
- Functional Balance: This arrangement allows for better functional balance and stability during chewing, as the maxillary teeth provide support to the mandibular teeth.
- Advantages: Lingualized occlusion can enhance the esthetics and function of complete dentures, particularly in patients with a well-defined ridge.
Anatomy of Maxilary Edentulous Ridge
Prosthodontics
Anatomy of Maxilary Edentulous Ridge
LIMITING STRUCTURES
A) Labial & buccal frenum
- Fibrous band covered by mucous membrane.
- A v-shaped notch (labial notch) should be provided very carefully which should be narrow but deep enough to avoid interference
- Buccal frenum has the attachment of following muscles; levator anguli
- It needs greater clearance on buccal flange of the denture (shallower and wider) than the labial frenum.
B) Labial & buccal vestibule (sulcus)
- Labial sulcus is bounded on one side by the teeth, gingiva and residual alveolar ridge and on the outer side by lips.
- Buccal sulcus extends from buccal frenum anteriorly to the hamular notch posteriorly.
- The size of the vestibule is dependant upon:
i) Contraction of buccinator muscle.
ii) Position of the mandible.
iii) Amount of bone loss in maxilla.
C) Hamular notch
It is depression situated between the maxillary tuberosity and the hamulus of the medial pterygoid plate. It is a soft area of loose connective tissue.
- it houses the disto-lateral termination of the denture.
- Aids in achieving posterior palatal seal.
- Overextension causes soreness.
- Underextension poor retention
D) Posterior palatal seal area (post-dam)
It is a soft tissue area at or beyond the junction of the hard and soft palates on which pressure within physiological limits can be applied by a complete denture to aid in its retention.
Extensions:
1. Anteriorly – Anterior vibrating line
2. Posteriorly – Posterior vibrating line
3. Laterally – 3-4 mm anterolateral to hamular notch
SUPPORTING STRUCTURES
A) Primary stress bearing area / Supporting area
1. Posterior part of the palate
2. Posterolateral part of the residual alveolar ridge
B) Secondary stress bearing area / Supporting area
1. The palatal rugae area
2. Maxillary tuberosity
RELIEF AREAS
A) Incisive papilla
- Midline structure situated behind the central incisors.
- It is an exit point of nasopalatine nerves and vessels.
- It should be relieved if not, the denture will compress the nerve or vessels and lead to necrosis of the distributing areas and paresthesia of anterior palate.
B) Mid-palatine raphe
- Extends from incisive papilla to distal end of hard palate.
- Median suture area covered by thin submucosa
- Relief is to be provided as it is supposed to be the most sensitive part of the palate to pressure
C) Crest of the residual alveolar ridge
D) Fovea palatinae
Few areas like the cuspid eminence , fovea palatinae and torus palatinus may be relieved according to condition required.
Anatomy of MANDIBULAR Ridge
ProsthodonticsLIMITING STRUCTURES
A) Labial, lingual & buccal frenum
- It is fibrous band extending from the labial aspect of the residual alveolar ridge to the lip containing a band of the fibrous connective tissue the that helps in attachment of the orbicularis oris muscle.
- It is quite sensitive hence the denture should have an appropriate labial notch.
- The fibers of buccinator are attached to the buccal frenum.
- Should be relieved to prevent displacement of the denture during function.
- The lingual frenum relief should be provided in the anterior portion of the lingual flange.
- This anterior portion of the lingual flange called sub-lingual crescent area.
- The lingual notch of the denture should be well adapted otherwise it will affect the denture stability.
B) Labial & buccal vestibule
- The labial sulcus runs from the labial frenum to the buccal frenum on each side.
- Mentalis muscle is quite active in this region.
- The buccal sulcus extends posteriorly from the buccal frenum to outside back corner of the retromolar region.
- Area maximization can be safely done here as because the fibers of the buccinator runs parallel to the border and hence displacing action due to buccinator during its contraction is slight.
- The impression is the widest in this region.
C) Alveololingual sulcus
- Between lingual frenum to retromylohyoid curtain.
- Overextension causes soreness and instability.
It can be divided into three parts:
i) Anterior part :
- From lingual frenum to mylohyoid ridge
- The shallowest portion(least height) of the lingual flange
ii) Middle region :
- From the premylohyoid fossa to the the distal end of the mylohyoid region
iii) Posterior portion :
- From the end of the mylohyoid ridge end to the retromylohyoid curtain
- Provides for a valuable undercut area so important retention
- Overextension causes soreness and instability
- Proper recording gives typical S –form of the lingual flange
D) Retromolar pad
- Pear-shaped triangular soft pad of tissue at the distal end of the lower ridge is referred to as the retromolar pad.
- It is an important structure, which forms the posterior seal of the mandibular denture.
- The denture base should extend up to 2/3rd of the retromolar pad triangle.
E) Pterygomandibular raphe
SUPPORTING STRUCTURES
A) Primary stress bearing area / Supporting area
1. Buccal shelf area
- Extends from buccal frenum to retromolar pad.
- Between external oblique ridge and crest of alveolar ridge.
Its boundaries are:
1. Medially the crest of the ridge
2. Laterally the external oblique ridge
3. Distally the retromolar pad
4. Mesially the buccal frenum
The width of this area increases as the alveolar resorption continues.
B) Secondary stress bearing area / Supporting area
1. Residual alveolar ridge
- Buccal and lingual slopes are secondary stress bearing areas.
RELIEF AREAS
A) Mylohyoid ridge
- Attachment for the mylohyoid muscle.
- Running along the lingual surface of the mandible.
- Anteriorly: the ridge lies close to the inferior border of the mandible.
- Posteriorly it lies close to the residual ridge.
- Covered by the thin mucosa which may be traumatized by denture base hence it should be relieved.
- The extension of the lingual flange is to be beyond the palpable position of the mylohyoid ridge but not in the undercut.
B) Mental foramen
- Lies on the external surface of the mandible in between the 1st and the 2nd premolar region.
- It should be relieved specially in case it lies close to the residual alveolar ridge due to ridge resorption to prevent parasthesia.
C) Genial tubercle
- Area of muscle attachment (Genioglossus and Geniohyoid).
- Lies away from the crest of the ridge.
- Prominent in resorbed ridges therefore adequate relief to be provided.
D) Torus mandibularis
- Abnormal bony prominence.
- Bilaterally on the lingual side near the premolar area.
- Covered by thin mucosa so it should be relieved
Applegate's Rules
Prosthodontics→ Following rules should be considered to classify partially edentulous
arches, based on Kennedy's classification.
Rule 1:
→ Classification should follow, rather than precede extraction, that might
alter the original classification.
Rule 2:
→ If 3rd molar is missing and not to be replaced, it is not
considered in classification.
Rule 3:
→ If the 3rd molar is present and is to be used as an abutment, it
is considered in classification.
Rule 4:
→ If second molar is missing and is not to be replaced, it is not
considered in classification.
Rule 5:
→ The most posterior edentulous area or areas always determine the
classification.
Rule 6:
→ Edentulous areas other than those, which determine the classification are
referred as modification spaces and are designated by their number.
Rule 7:
→ The extent of modification is not considered, only the number of additional
edentulous areas are taken into consideration (i.e. no. of teeth missing in
modification spaces are not considered, only no. of additional edentulous spaces
are considered).
Rule 8:
→ There can be no modification areas in class IV.