Implant Prosthesis Procedure Notes

Prosthetic Teeth Introduction

Artificial teeth or prosthetic teeth are considered a major factor determining the chewing efficiency of patients with prostheses. A variety of artificial teeth in terms of anatomy and materials are available in the market. One should know how to select the correct teeth which is most suitable for a particular patient. It is chapter focuses on important aspects of artificial teeth.

Classification Of Prosthetic Teeth

According to Material Used for Fabrication:

• Acrylic teeth
• Porcelain teeth
• Composite teeth

Read and Learn  More: Preclinical Prosthodontics Notes

• Acrylic teeth with amalgam inserts
• Acrylic teeth with metal occlusion.

According to Occlusal Anatomy of Teeth:

• Anatomical teeth
• Semi-anatomical teeth
• Nonanatomical teeth

Acrylic Teeth

Acrylic teeth are made up of acrylic, which bond chemically with denture base resin. They are available in various shapes and shades. They are the most widely used denture teeth.

Indications:

• When opposing teeth are acrylic teeth.
• When opposing teeth have metal occlusion.
• When less interarch space is available (in such cases acrylic teeth can be trimmed easily to accommodate in available space).

Acrylic Teeth Advantages:

• They chemically bond with denture base material.
• They can be trimmed very thin to fit in available space.
• They do not abrade the opposing natural teeth.
• They can be easily polished.
• They can be easily modified to establish occlusal contact with opposite teeth.
• They have less/softer impact sound (sound produced when opposite teeth come in contact).
• Less traumatic to denture foundation.

Acrylic Teeth Disadvantages:

• They wear with time.
• Subjected to abrasion if cleaning is done with abrasive/rough substances.
• Due to wear, masticatory efficiency is reduced over a period of time.
• Stain and discolor easily.
• May need to be replaced due to excessive wear.
• Rebasing is difficult as acrylic teeth are chemically attached to the denture base.

Interpenetrating Polymer Network Acrylic Resin Teeth (IPN Resin Teeth):

To overcome the low wear resistance of conventional acrylic teeth, an interpenetrating polymer network (IPN) was developed. For IPN, a material with a highly cross-linked copolymer is used. This material has minimum or no fillers.

The advantages of IPN acrylic resin teeth are:

• Harder
• More abrasion resistant
• More heat resistant
• More stain/discolor resistant.

Porcelain Teeth

They are made up of porcelain (ceramic). There is no chemical bonding between porcelain teeth and acrylic resin. Porcelain teeth have metal pins or diatoric holes in the ridge lap area, these features help in mechanical bonding between porcelain teeth and denture base acrylic resin.

Porcelain Teeth Indications:

• Used where interarch space is sufficient and teeth placement can be done without trimming.
• Used with well-formed ridges.
• When a patient demands high esthetic.
• When a patient abrades acrylic teeth in a short time, porcelain teeth are selected.

Porcelain Teeth Advantages:

• More resistant to wear compared to acrylic teeth.
• Good esthetic.
• Does not stain or discolor easily.
• Rebasing can be done easily as porcelain teeth are mechanically attached to the denture base with the help of metal pins and channels within teeth.

Porcelain Teeth Disadvantages:

• No chemical bond with the acrylic denture base.
• If used, opposite to the natural teeth they cause abrasion of natural teeth.
• As porcelain is a brittle material, chipping and fracture are common with porcelain teeth.
• They have a sharp impact sound (clicking noise comes when porcelain teeth contact with opposing arch porcelain teeth).
• Causes more trauma to the denture foundation.

Composite Teeth

Composite teeth bond chemically to acrylic denture base material. Composite teeth have greater wear resistance compared to conventional acrylic resin teeth. They are more aesthetic. They can be used in opposition to natural dentition and to acrylic teeth.

Acrylic Teeth With Amalgam Inserts/Stops

In some clinical cases, the acrylic resin teeth are placed opposite to porcelain teeth (when two opposite arches are not treated at the same time). In such cases, acrylic teeth abrade very quickly due to opposite porcelain teeth.

To reduce these acrylic teeth wear, amalgam stops or inserts are prepared on acrylic teeth. To prepare these stops, cavities are prepared on occlusal surfaces of acrylic teeth and amalgam is placed in cavities.

The contacts are established with opposite teeth before the amalgam sets completely. This will establish the amalgam stops with proper occlusal contacts. Whenever the patient chews, the amalgam stops coming in contact with the porcelain teeth preventing direct contact of acrylic with porcelain teeth and reducing acrylic wear.

Acrylic Teeth With Metal Occlusion

To reduce the wear of acrylic teeth when opposing teeth are natural teeth porcelain teeth or metal restorations, the acrylic teeth are modified with metal occlusion. The occlusal surface of acrylic teeth is prepared and a wax pattern is made over it.

Casting is done to convert the wax pattern into metal occlusion. The metal occlusion is then cemented to acrylic teeth to prepare acrylic teeth with metal occlusion.

Anatomical Teeth

Shape:

Cuspal angulation: 33° or more.

Synonyms:

Cusp teeth.

Anatomical Teeth Indications:

• Well-formed ridges.
• When teeth to be arranged in balanced occlusion (anterior and posterior simultaneous contacts of teeth in any centric or eccentric position).
• Patients with good neuromuscular control.

Anatomical Teeth Advantages:

• They have better chewing efficiency compared to semi-anatomic and nonanatomic teeth.
• They have a more natural appearance.
• They penetrate food more easily.
• Act as a guide for proper jaw closure.
• Resist rotation of the denture bases through cusp interdigitations.

Anatomical Teeth Disadvantages:

• More time-consuming procedure to arrange in balanced occlusion.
• Posterior teeth placement is restricted by opposing fossa and cusps.
• Denture bases need frequent relining to keep occlusion stable and balanced.
• More occlusion disharmony during settling and difficult to correct by adjustment.
• Precise jaw closure and base stability are required for interdigitation.
• Difficult to adapt to abnormal jaw relationship (class II and class III).
• Increased horizontal forces due to deep cuspal angulation.

Semi-Anatomical Teeth

Shape:

Cuspal angulation: 20°.

Synonyms:

Low cusp teeth, modified cusp teeth.

Semi-Anatomical Teeth Indications:

• Well-formed ridges and fair ridges.
• When balanced occlusion is to be achieved.
• In patients with mild jaw discrepancies.

Semi-Anatomical Teeth Advantages:

• Balanced occlusion can be easily obtained.
• Good chewing efficiency compared to nonanatomic teeth.
• Better esthetic compared to nonanatomic teeth.
• Shallow cuspal inclination generates less horizontal forces compared to anatomic teeth.

Semi-Anatomical Teeth Disadvantages:

• Poor esthetic compared to anatomic teeth.
• Lesser chewing efficiency compared to anatomic teeth.

Nonanatomic Teeth

Shape:

Cuspal angulation: 0°.

Synonyms:

Cuspless teeth, monoplane teeth, monoline, and zero-degree teeth.

Nonanatomic Teeth Indications:

• Patient with a poor ridge (severely resorbed ridge).
• Patient with poor neuromuscular control.
• Patient with jaw discrepancies.
• When crossbite tooth relation is indicated.
• Indicated to use for patients with uncoordinated closure and poor neuromuscular control, i.e. patients suffering from parkinsonism, dyskinesia, and stroke.

Nonanatomic Teeth Advantages:

• Quick arrangement of teeth.
• Less force is transferred to the residual alveolar ridge.
• Prevent destruction of tissue.
• Freedom of occlusal movements (from centric to eccentric position).
• Do not lock the mandible in one position.
• Permits the use of less time-consuming techniques.
• Adapt easily to class II and class III jaw relations.
• More easily adjusted after changes in vertical and horizontal relations.
• Easier to arrange in crossbite.

Nonanatomic Teeth Disadvantages:

• Least chewing efficiency compared to semi-anatomic and anatomic teeth.
• Least esthetic compared to semi-anatomic and anatomic teeth.
• Difficult to arrange in balanced occlusion.

The Prosthetic Teeth Set

Prosthetic teeth are available as a full set of 28 teeth including six anterior and eight posterior teeth (A total of 14 teeth/arch) for each maxillary and mandibular arch. Some manufacturers provide anterior and posterior teeth separately. Artificial teeth sets do not have third molars. They are attached to the plastic card through wax. This plastic card is called a “tooth card” and the wax used for this is “carding wax”.

Shape:

Prosthetic anterior teeth are usually available in square, tapered, and ovoid shapes.

Shade:

They are available in various shades like A1, A2, A3, A3.5, A4, B1, B2, B3, B4, C1, C2, C3, C4, D2, D3, D4, E1, F1, and F2.

Size:

Artificial teeth are available in various sizes. The size of teeth is designated by a number. The number describes the combined width of anterior teeth and A2 is the shade.