Relining and Rebasing Relining The procedure used to

Relining and Rebasing

Relining : The procedure used to resurface the tissue side of denture with new base material thus producing an accurate adaptation to the denture foundation area, Rebasing : laboratory process to replace the entire denture base material on an existing prosthesis.

Indication for relining and rebasing when to do relining /rebasing: Ø loss of retention and stability Ø loss of orientation of occlusal plane. Ø loss of vertical occlusal dimensions. Ø facial tissue support is lost. Ø immediate denture at 3 -6 months after their original construction. Ø when patient cannot afford new denture. Rebasing is usually done when tissue surface damage is more

General consideration. Ø The occlusal vertical dimension should be satisfactory. Ø Centric occlusal should coinside with centric relation , it is allowable if slight as to be correctable. Ø The patient appearance must be acceptable to the patient and dentist the shape, size shade arrangement of artificial teeth must be satisfactory , Ø The oral tissue should be in optimal health. Ø The posterior limit of maxillary denture should be correct.

Ø The denture base extension should be adequate. Ø The interocclusal distane is correct Ø Speech is satisfactory with existing tooh arrangement Ø No existing hard or soft tissue condition that will interfere with technique , such as severe osseous undercuts

CONTRAINDICATIONS : Ø Excessive resorption of alvelor ridges Ø When abuse soft tissue are present Ø Temporomandibularual joint problems until accurate diagonsis and treatment of problem has been accomplished relining and rebasing is contraindicated. Ø If dentures have poor esthetics. Ø Unsatisfactory jaw relationships. Ø If major speech problem due to denture Ø serve osseous undercuts.

DIAGNOSIS AND TREATMENT PLAN: Diagnosis in essential to plan the treatment patient usually returns due to looseness, soreness, chewing inefficiency, or esthetic changes, These may be due to occlusal disharmony changes in the supporting tissue that may or may not associated with occlusal disharmony

TREATMENT PLAN : In cases of dentures with built in error in occlusion may not require relining only occusal correction is sufficient. If supporting tissue is badly destructed surgical correc is needed prior to relining

CLINICAL PROCEDURES : Tissue preparation : Ø excessive hypertropic tissue should be surgically removed. Ø The oral mucosa should be free of irritants Ø dentures must be removed during sleep for several weeks before treatment. Ø The dentures should be left out of the mouth at least two to three days before making the impression. Ø daily massage of soft tissue.

DENTURE PREPARATION : Ø pressure areas on the tissue surface of the dentures should be relieved. Ø minor occlusal disharmony is corrected by selective grinding. Ø small border in adequacies must be corrected. Ø A posterior palatal seal area should be established using stick compound or auto polymerizing resin before final impression.

PRINCIPAL PITFALLS : Principal pitfalls that must be avoided are : - Ø do not increase the occlusal vertical dimension. Ø multiple even contacts should be present in centric relation. Ø do not permit maxillary denture move forward during impression making. Ø ensure that centric relation and centric occlusion are identical. Ø ensure that an accurate palatal seal has established. Ø an equal thicknedd of final impression material should be used.

There are 3 types of clinical procedures *static method closed and open mouth technique *functional method *chair side method

CLOSED MOUTH RELINING TECHNIQUE MAXILLARY DENTURES. It is done using either existing centric occlusion or New centric relation with modelling compound is made Technique A: centric relation is recorded using modelling compound or wax Denture preparation : all the undercuts are relieved and tissue. surface is relieved by 1. 5 -2 cms

ØThe borders are relieved by 1 -2 mm except for the posterior border of max dentures palatable section could be removed for visibility during impression Making then border moulding is done using low fusing modeling compound

Ø impression is taken with zinc oxide eugenol impression paste during both border moulding and impression making patient is asked to close his mouth lightly in premade occlusal record, Ø Then the impression with the exposed palatal part is made with quick setting plaster.

ØADVANTAGES : --- Opening of palatal section will allow better setting of denture and alleviate the increase in vertical dimension pitfall. --- Premade interocclusal record helps in positioning denture during impression making and to orient the denture on articulator. --- Reduces the possibility moving the max denture forward during impression making.

DISADVANTAGES : - Ø Possibility of moving the denture forward is still a major problem. Ø The wax interoccusal record is not an accurate record. Ø Technique does not suggest any soultion for relining and rebasing both dentures at same time.

TECHNIQUE B Existing centric occlusion is used here Denture moulding is done with green stick. Impression is taken with wax that flow at mouth temperature such as kerr’s impression wax (IOWA WAX ) Impression is made in two steps 1) In first step areas except labial flange and the crest of the alvelor ridge between the canines is made then 2)The labial falnge and the crest of the alveolar ridge between the canine is made

ADVANTAGES : - ØTwo - step impression techniques reduces the possibility of movement of dentures DISADVANTAGES : - ØDifficult to work with wax impression material and possibility of destortion. ØErrors of existing centric occlusion can produce an inaccurate impression.

TECHNIQUE C : Centric relation and denture preparation is same as for technique A Additional the labial and palatal flanges are perforated to reduce the pressure inside the denture during impression making there by preventing the displacement of denture. Border moulding and impression making is done as technique A No specific impression material is suggested for this technique

ADVANTAGES AND DISADVANTAGES : Same as for technique A and B. TECHNIQUE D Existing centric occlusion is used to seat the denture in prepared by releiving the undercuts. The borders are reduced by 1 -2 mm and softened to make flat. A large opening is made palatal portion of denture.

ØAdhesive tape should be attached over the buccal and labial surface 2 mm away from border. ØDeef groove with the help of knife edge stone should be cut into the buccal and labial surface of the denture at the junction of impression material and filled with molten baseplate wax. ØBorder moulding is usually not suggested ØImpression with zinc oxide eugenol is taken in first step.

Then impression for palatal portion is taken in second step with plaster of Paris. ADVANTAGES : Same as for technique A DISADVANTAGES : The existing error in centric occlusion may produce faulty impression.

CLOSED MOUTH RELINING TECHNIQUE MANDIBULAR DENTURE ØHere existing centirc occlusion is used secondary impression ØSoftened modelling compound is luted to mandibular posterior teeth to correct the loss of vertical dimension patient is instructed to pronunce letter “m” repeatedly. ØThe record is chilled trimmed and slightly heated and procedure is repeated till satisfactory occlusal vertical dimension is obtained

ØThen lower work impression is made Øpour impression and mount lower denture on articulator ØRemove denture clean and remove undercuts ØDentured is luted to maxillary denture in maximum intercuspation ØSoftened modelling compound is placed inside the mandibular denture and the articulator is closed to contact the incisal guiding pin

ØNow the amount of vertical dimension indicated by compound over occlusal surfaces is transferred to the base of mandibular denture ØImpression is made using zinc oxide eugenol

ADVANTAGES Ø Loss of vertical dimension can be compensated Ø Error in centric occlusal can be reduced during lab stage. DISADVANTAGES Ø Time consuming technique Ø occlusal vertical dimension establishment is highly questionable.

OPEN MOUTH IMPRESSION TECHNIQUE ØBoucher’s technique is the only one described in literature that explains a method of relining and rebasing the mandibular and maxillary dentures at the same time ØHere existing centric occlusion is not utilized and dentures are used as special trays

Øposterior palatal seal is formed in modelling compound on maxillary denture ØThis tissue surface is trimmed by 1 mm and borders by 1 mm

ØIn lower denture the buccal surface of the lingual flange are ground to minimize the pressure against the mylohyoid ridges and between the tissue of the floor of mouth and the buccal side of lingual flanges. ØThe lingual flange between premylohyoid eminence is shortened by 1 mm.

ØTwo grooves are cut on the buccal side of the lingual flanges to facilitate removal of retromylohyoid eminence after cost has poured.

ØModelling compound handle in formed over lower anterior teeth ØAdhesive tape is adapted over the polished surfaces of tooth dentures and over teeth

ØBorder moulding is done if flanges are inadequate ØImpression is made using zinc oxide eugenol ØExactly 15 sec after the denture has been placed in mouth the patient is asked to pull his upper lip down and open his mouth wide. This action mould the material over border.

ØOn lower impression the loaded tray is placed above the ridge ØThe patient is asked to raise tongue “just a little bit” ØThe index finger are kept on the 1 st molar teeth and seated with downward pressure

ØAfter 15 sec PT is asked to open mouth wide and put the tongue against lower front teeth and hold it there. ØThis does all the border moulding necessary for lower impression

ADVANTAGES : Ø Special trimming helps to make reasonable impression during selective pressure technique Ø Separate interocclusal record will allow operator to concentrate on recording jaw relation Ø Possible to verify centric relation record Ø Interocclusal record made is reliable

DISADVANTAGES : - Ø Procedure is not easy Ø Time consuming This technique is based on the use of tissue conditioning material as an impression material

CLINICAL PROCEDURE : - Ø Patient is educated not to wear denture overnight Ø The old denture are examined and occlusal errors are corrected Ø The basal surface of the denture is reduced Ø This surface is dried before material is placed

Ø The minimum thickness of the tissue conditioning material is placed over the tissue surface of denture and inserted in mouth Ø After removal from mouth the material is trimmed to remove all excess Ø Overextended borders should be removed and voids shold be filled Ø The PT is instructed in the care of the resilient lining before being dismissed

Ø When the patient returns to the dentist after 3 -5 days the denture should be examined for denuded area Ø Releive the pressure area Ø Underextended border should be corrected with impression compound Ø The material is renewed periodically it is never allowed to remain in denture for more than a week as material itself may become a source of irritation

Ø when the tissue becomes normal impression making is scheduled zinc oxide eugenol or light bodies is used Ø Impression is poured and casts are made polysulphide rubber wash impression are used Ø During one of the appointment an accurate face bow transfer of the maxillary denture should be made. Ø After cast are made mount the maxillary cast on semiadjustable articulator using face bow transfer record

Ø Relate the mandibular to maxillary denture which is already mounted using interoccusal records Ø If an occusal disrepancy exists it should be corrected before seperating impression from cast. Ø After finishing of denture remount plaster casts are made and mounted on articulator. Ø A new interoccusal record is used to mount lower denture in centric relation. Ø Occlusion is adjusted by selective grinding

CHAIR SIDE RELING TECHNIQUE Ø Using this technique acrylic or plastic material can be added to denture and allowed to set in mouth for instant relining and rebasing.

DISADVANTAGES : - ØMaterial produces chemical burn of mucosa. ØResultant reline was porous and develops bad odour. ØLow colour stability. ØMaterial is difficult to remove if denture is not positioned properly.

LAB PROCEDURES FOR RELINING /REBASING For relining ØArticulator method ØRelining JIG method

ARTICULATOR METHOD Procedure ØBox the denture with impression material ØPour the cast

Ø After the stone has set remove the cast with denture in place and index base Ø Point the base with repeating medium. Ø Fill the palatal section of maxillary and Lingual mandibular denture with clay Ø Adapt clay to the facial surafce of teeth exposing the occlusal 3 rd of teeth

Ø Mix stone and put on the lower member of articulator then seat denture on it Ø Place the cast over denture and close the articulator and do mounting Ø After some sets remove modelling clay

ØSeparate the denture from cast and remove impression material ØRemove thin layer of resin from interior of denture reduce 2 -3 mm borders

ØDeepen the frenal notch ØPlace the posterior platal seal area in cast

ØPaint the cast with tin foil substitute

ØMix autopolymerizing resin and add on denture surface and on cast filling the borders ØSeat the denture in dentation and close the articulator

Ø Curing is done after curing denture is removed finishing and polishing is done

RELINING JIG METHOD ØHere relining JIG is used instead of articulator same procedure is done on it as for above

ØThen carefully remove the denture from cast.

ØAfter mixing and applying resin assemble the relining JIG and screw it with colour nuts

ØCure the relived denture in pressure pot ØFinish and polish it

FOR REBASING : Required when existing denture base is discoloured or too thin. Done by ØJIG method Øflask method

JIG METHOD Procedure Ø Mount the denture on cast as done for relining Ø Open JIG and carefully remove denture from the cast

Ø Remove the teeth from the denture base by cutting with help of bur and seat them in indentitions

Øadapt a layer of base plate wax on cast and assemble the JIG and wax the denture teeth

Ø Waxed up denture is ready on jig denture is removed and flasked ØHeat cure denture base resin can be used

ØREBASED DENTURE IS REPLACED ON JIG

FLASK METHOD PROCEDURE: Ø Pour a cast in the denture as done earlier Ø Half flask the denture

Ø Ø Paint silicone mold material over the denture Do complete flasking of denture Open flask after stone has set Remove porcelain or resin teeth from denture base