Introduction of Crown and Fixed Partial Dentures Dr. Recep Uzgur Department of Prosthodontics

COMMON TERMS USED IN FIXED PROSTHODONTICS A fixed prosthesis is defined as, “A restoration which is attached by a cementing to natural teeth, roots, implants.”. These dentures are often termed as Bridges. It is a cemented extracoronal restoration that covers or veneers the outer surface of the clinical crown.

If the prosthetic crown covers all five surfaces of the clinical crown it is referred to as a Full Crown. If the prosthetic crown does not cover the entire clinical crown, it is referred to as a Partial Crown.

An inlay is It is an intracoronal restoration, which is used for medium sized single tooth proximo-occlusal and gingival lesions. An onlay is an intracoronal restoration, which is used to restore a more extensively damaged posterior tooth with a wide mesio- occluso-distal lesion.

An abutment is any tooth, root or implant which, gives attachment and support to the fixed partial denture. The artificial tooth that replaces a missing tooth in a fixed partial denture is called a pontic. It is the connection that exists between the pontic and retainer

Fixed Partial Denture; Prosthetic appliance that permanently attached to remaining teeth or implants and replaces one or more missing teeth. In years past, this type of prosthesis was known as a bridge, a term that has fallen from favor and is no longer used.

INDICATIONS FOR FİXED PARTIAL DENTURE Existing of missing teeth Esthetic reasons Short span edentulous arches Presence of sound teeth that can offer sufficient support adjacent to the edentulous space. Cases with ridge resorption where a removable partial denture cannot be stable or retentive. Patient’s preference Mentally compromised and physically handicapped patients who cannot maintain the removable prosthesis.

CONTRAINDICATIONS FOR FIXED PARTIAL DENTURE Large amount of bone loss as in trauma. Very young patients where teeth have large pulp chambers. Presence of periodontally compromised abutments. Long span edentulous spaces. Bilateral edentulous spaces, which require cross arch stabilization. Congenitally malformed teeth, which do not have adequate tooth structure to offer support.

Mentally sensitive patients who cannot cooperate with invasive treatment procedures. Medically compromised patients (e.g. leukemia, hypertension). Very old patients. Distal extension denture bases as in class I and II cases.

DIAGNOSIS AND TREATMENT PLANNING Diagnosis and treatment planning play an important role in the success of any prosthetic treatment. The success of a fixed partial denture depends on the health of the abutment teeth. Factors like dental caries, periodontal diseases can affect the health of the abutment leading to total failure of the treatment. For making a proper diagnosis, history taking, clinical examination, radiological examination and preparation of diagnostic casts are vital.

History Various psychological and medical conditions will affect the success of the prosthesis. The some important following conditions should be considered during diagnosis: Diabetes: In diabetic patients the risk of occurrence of a periodontal lesion is very high. In such patients, a fixed prosthesis will increase the risk of abutment failure. Patients with diabetes should be made aware of these problems and medical treatment should be instituted to control the condition.

Xerostomia: Decreased salivary flow can predispose to caries due to accumulation of debris and decreased buffering capacity. In such patients, a fixed prosthesis will increase the risk of abutment failure as well. In cases with Xerostomia should be under control. Cardiovascular diseases: Patients using pace makers have to be treated with caution. All electrosurgical procedures are contraindicated for these patients. Adrenaline is avoided in the local anaesthetic and the gingival retraction cord should be free of adrenaline.

Miscellaneous conditions: Patients should be enquired on any history of drug allergy, nickel sensitivity. He should be examined for presence of any infectious diseases to prevent cross infections.

Clinical Examination Clinical examination can be grouped as: • Systemic examination • Local examination — Extraoral examination — Intraoral examination

Systemic examination; Along with history, a thorough check-up should be made for presence of any systemic disease. Local examination; includes TMJ and facial examination. Objective and subjective symptoms of pain and discomfort in the TMJ should be examined. Further examination and treatment should be carried out if there is a sign of disease of the TMJ Along with TMJ evaluation, the muscles of mastication. Decreased mouth opening, psin during movement, clicking, swelling vb.. For facial examination, any asymmetry should be examined.

Intraoral Examination It includes hard tissue and soft tissue examination. First, the patient’s oral hygiene should be examined, following which, the presence of attached gingiva and the presence of any occlusal disharmony should be examined. Other factors that require observation include, risk of dental caries and periodontitis, amount of residual ridge and presence of tooth wear. The type of occlusion should be examined.

Diagnostic Casts These casts should be mounted on a semi- adjustable articulator with interocclusal records. Mounted diagnostic casts serve the following purposes: • To assess the dimensions of the edentulous space. • The height, rotations, inclination of the abutment teeth can be observed. • The number, size and position of wear teeth can be seen. • It gives an idea about the occlusion and the morphology of the opposing teeth. It also guides us in determining the amount of occlusal load anticipated from the opposing teeth.

Radiographic Examination A full mouth radiographic examination should be carried out. The radiographs should be used to detect: • The number, size and location of caries. • Evidence of caries beneath existing restorations. • The level of alveolar bone. • Crown-root ratio of the abutment teeth. • Morphology of the roots of the abutment teeth.

• Quality of endodontic restorations. • Width of the periodontal ligament space. It is increased in patients with trauma from occlusion. • Presence of any root in the edentulous area. • Thickness of the soft tissues in the edentulous area.

Treatment Planning Treatment planning should be based on the choice of design of the partial denture that best suits the patient. Treatment planning for fixed prosthesis includes: Intraoral examination and selection of an appropriate prosthesis. Evaluation of the abutment and selection of an appropriate prosthesis Biomechanical considerations and fixed partial denture design

The patient’s needs. Type of material/technique that best suits the patient. Residual ridge of the patient and treatment of ridge defects. Occlusion with the opposing teeth.

1- Conventional tooth supported fixed partial dentures: It is indicated for the following cases; Patients with periodontally sound teeth. Short and straight edentulous span. Absence of any uncorrectable soft tissue defect. Presence of proper salivation

2- Resin bonded fixed partial denture It is indicated in: Presence of defect-free abutments. Presence of single missing anterior tooth or premolar. Sometimes a single missing molar with minimal opposing occlusal load. Presence of sound abutments on either side of the edentulous space.

Young patients with low-risk of caries and large pulp chambers. Abutments with less than 15o axial inclination. Absence of deep vertical overlap.

3- Implant supported fixed partial denture It is indicated in; Absence of sufficient number of abutments for a long edentulous span. Absence of distal abutment but presence of good density of bone. Broad flat ridge configurations. Single tooth replacements. High caries risk patients. Young adults.

Abutment Selection The role of an abutment is very crucial in accepting the load acting on a fixed partial denture. 1- Location, Position and Condition of the Tooth Teeth with the following characteristics are preferred abutments: Teeth adjacent to edentulous spaces. Pulp capped teeth should not be used as abutments because they are always under the risk of requiring root canal treatment Vital teeth are preferred, though endodontically treated teeth can also be used.

2- Root Configuration Roots with greater labiolingual widths are preferred. Roots with irregular curvatures are preferred. Teeth with longer roots serve as better abutments.

3- Crown Root Ratio Ideally the crown root ratio should be 2:3 (0.66). Ratios up to 1:1(1.0) are acceptable. Ratios above one (i.e. the length of the crown is longer than the root) are unacceptable. 4- Root Support The supporting alveolar bone should be healthy. It should have good trabecular architecture and show no signs of bone defects or bone loss. Intraoral radiographs should be used to evaluate the bone architecture

5- Periodontal Ligament Area The Ante’s law has been stated in the glossary as follows, “In fixed partial denture prosthodontics for the observation that the combined periodontal area of all the abutment teeth supporting a fixed partial denture should be equal to or greater in periodontal area than the tooth or teeth being replaced.

6- Assessment of Pulpal Health Usually unrestored abutments are preferred. If caries is present, regular preparation can be done. If large carious lesions are present they should be filled. If the abutment tooth has a carious lesion with pulpal involvement then root canal treatment is advised.

7- Replacement of a Single Missing Canine Replacement of a single missing maxillary canine is considered as a complex fixed partial denture because the tooth lies outside the inter- abutment axis and the adjacent teeth like the lateral incisor and the first premolar are very weak.

PONTICS It can be defined as, “An artificial tooth on a fixed partial denture that replaces a missing tooth, restores its functions and usually fills the space previously filled by a natural crown. Ideal Requirements of a Pontic It should restore the function of the tooth it replaces. It should provide good aesthetics. It should be comfortable to the patient It should be biocompatible

It should permit effective oral hygiene It should permit effective oral hygiene. It should be easy to clean and easy to maintain. It should preserve underlying mucosa and bone. Pontic Design Based on the amount of mucosal contact, pontics can be classified as: Saddle Pontic Ridge Lap Pontic Modified Ridge Lap Pontic Ovate Pontic Sanitary or hygienic pontics

Saddle pontic: A pontic with a concave gingival surface that overlaps the ridge buccally and lingually is called a saddle.

Ridge lap pontics; This pontic resembles a natural tooth Ridge lap pontics; This pontic resembles a natural tooth. It is designed to adapt closely to the ridge. It is avoided because it is difficult to maintain and often leads to inflammation of the tissues in contact.

Modified ridge lap pontic; Ridge lap pontics evolved from saddle pontics. Though the ridge lap pontics had relatively less tissue contact, they were also difficult to maintain. Hence, ridge lap pontics were modified and evolved as the modified ridge lap pontics. Modified ridge lap pontics were designed to further reduce the tissue contact

Ovate pontics; These pontics are used in cases where the residual ridge is defective or incompletely healed.

Sanitary or hygienic pontics; These pontics have zero tissue contact Sanitary or hygienic pontics; These pontics have zero tissue contact. Though they are easy to maintain, they are highly unaesthetic. Hence, they are used only for posterior teeth.