Overdentures

Synonyms: Tooth supported complete dentures, overlay dentures, telescope dentures, biologic dentures and hybrid dentures.

Definition: It is defined as a dental prosthesis that replaces the lost or missing natural dentition and associated structures of maxilla and/or mandible and receives partial support and stability from one or more modified natural teeth.

Indications: Loss of the remaining teeth at very young age. Overdentures can even be considered in geriatric patients with good

mental and physical stability. Maxillary complete denture case opposed by mandibular natural anterior

teeth Where retention is compromised and additional retention is needed, in

such cases attachments to cast copins can serve the purpose. Xerostomia Increased residual ridge resorption Congenital defects like clefting.

Contraindications: Expense and time Mental and physical liabilities of the patient Poor oral hygiene High cries susceptibility Periodontal considerations

Class III mobility Increased crown:root ratio Soft tissue and osseous defects Gingival recession Ridge resorption

Endodontic consideration vertical fracrutere of the roots Mechanical perforation of the abutment tooth Internal resorption Broken instrument within the canal Horizontal fracture of the abutment tooth below the level of the

alveolar crest.

Patient selection:

Where and FPD or CPD/RPD cannot be fabricated with the support from the remaning dentition an overdenture should be considered.

Abutment tooth must be endodontically and periodontically sound.

Adequate width of attached gingival Minimum of 6-7 mm of alveolar bone present Periodontal status: horizontal bone loss is more favourable than

vertical bone loss Crown:root ratio should be minimum Minimum mobility Free from pockets and inflammation. Good oral hygiene Low carious activity Adequate gingival attachment Cuspids and bicuspids are favoured since they are easy to

prepare and endo treatment is easier in single rooted teeth than multirooted posterior teeth.

Incisors are considered only in special cases or else incisors support leads to bone loss and periodontal breakdown.

Implant supported overdentures. Congenital and acquired defects like clefting.

Requirements / Rationale: Maintenance of health of the abutment tooth to be selected. Evaluation of the periodontal condition. Reduction in crown root:ratio because it reduces the amount of

torquing or the leverage forces acting on the abutment tooth Intimate adaptation to the basal seat tissues for even

distribution of the occlusal load. Simplicity of the construction Easy to use by the patient, i.e. easy to remove or insert.

Advantages:

When the forces exerted on the abutment teeth supporting the denture are with in the physiologic limits, they exert tensile stresses on the oblique group of fibres of the periodontal ligament which in turn are stimulated to deposit new bunble bone

Thus it helps in bone repair mechanism and preservation of the residual alveolar ridge.

They act as vertical stops for the denture base. Consider a case where the complete maxillary debture is opposed by natural

mandibular anterior teeth. In this case, due to forces exerted on the maxillary denture there is excessive resorption of the residual alveolar ridge and hypertrophy of the soft tissues. This can be prevented by retaining few maxillar anterior teeth which would serve os a support for the overdenture.

Increased support and stability to the denture Psychological benefit to the patient since all the tooth are not extracted/lost and

the feeling that few natural teeth are still remaning can be a bosst for the psychology of the patient.

Results in fewer post insertion problems If the periodontal ligament of the abutment tooth are viable then they help to

maintain proprioceptive responses and neuromuscular coordination which is not the case with complete dentures.

Increased retention can be obtained with attachments fixed to the cast copings. Convertibility: easy to adjust with the use of auto-polymerising resins Preserves the harmony of the arch form.

Disadvantages: Caries susceptibility: carious breakdown of the abutment tooth Meticulous home care, oral hygiene measures needs to be instituted. Professional fluoride application. Several endodontic and periodontal considerations have to be taken into

account before the planning of the overdenture cases. Comparatively expensive modality of treatment Plaque accumulation, inflammation, pocke formation and eventual

eriodontal breakdown of the abutment teeth may occur if the overdenture isn’t maintained properly.

Overcontouring, undercontouring bony undercuts, hyper trpohied soft tissue will result in improper fabrication and loss of aesthetics with encroachment of the inter occlusal distance.

Classification:

Based on the method of abutment preparation along with contemporary clinical terminology

Non coping abutments Non coping abutments with endodontic therapy Coping abutments Coping abutments with endodontic therapy Abutments with attachments

Non coping abutments: In this procedure remaining teeth are merely reshaped to eliminate

undercuts and reduced in vertical height. Thus for this procedure sufficient inter ridge distance should be exisiting

so that minimal preparation is required and vital pulps receeded to a sufficient degree so that the tooth will not be sensitive to oral environment during function (mastication, hot n cold fluids..)

This procedure is indicated in partially anodontia patients or in patients with severe abrasion.

Thus the crown:root ratio is relatively higher.

Non coping abutments with endodontic therapy: This procedure is indicated when the inter ridge distance is normal and

that for sufficient space to be created adequate amounts of tooth reduction is necessary.

This necessitates the use of endodontic therapy in such abutment teeth. After the tooth is endodontically treated an amalgam restoration is placed

in the tooth in the coronal portion and polished throroughly Even hypermobile teeth may be used as abutments in this method.

Coping abutments: Some times cast metal copings with a dome shaped surface and chamfer

finish line is made on the abutment teeth. The purpose of the coping is to reduce the sensitivity or as a caries control

method Since much reduction is not done in this procedure, the abutment teeth

doesn’t require endodontic therapy. Thus the crown:root ratio is relatively higher. The abutment tooth should have adequate bony support and good

periodontal health. There are two types of copings: Short copings: 2-3 mm long (crown : root ratio is lesser) Long copings: 5-8 mm long (crown : root ratio is higher)

Coping abutments with endodontic therapy:

The indications are similar to the abutment tooth preparation with endodontic therapy with amalgam plug with the exception that instead of the amalgam plug a coping is placed on to the abutment teeth

Coping is used to prevent recurrent caries or to reduce the hypersensitivity The coping may or may not have a post attatched to it. The post serves for additional retention. The margins of the coping are kept slightly short of the gingival margins

to allow for proper finishing and easy repair if needed.

Abutment teeth with some form of attachments: Used in situations where stability and significant improvement in retention

is needed as well. Also adding the attachments to the coping on the abutment tooth doesn’t

reduce the crown:root ratio as much. And attatchment increases the leverage forces on the abutment teeth. Thus a sound periodontium with low caries indes and adequate bone

support is the primary requisite along with sufficient inter ridge distance. The procedure is relatively expensive and time consuming as compared to

other methods describes above.

Various attatchments used are: Stud attachments Gerber attachment Dalbo attachment Ceka attachment Zest anchor Rothermann attachment Introfix attachment Schubiger attachment Quinlivan attachment Magnets Bar attachment Hader bar Dolder bar Baker clip Ackerman clip and CM clip

Submerged vital roots:They are the area of recent interest and research.

They obviate the problems associated with conventional procedures like,Caries gingivitisPeriodontitisEndodontic therapy

Selected roots are reduced to 2 mm beow the crest of the alveolar bone and covered with a mucoperiosteal flap

Problems encountered: dehiscence of the retained rootsPulpal pathosisThe procedure is still in the cocoon and experimental and its use is not indicated in clinical trials so far.

Why cast copings?Reduces sensitivityGrossly carious or broken abutment toothReduces the attrition of abutment teethIncreases the longetivity and strnght of the abutment teethSpecifically in case of bruxism, etc..