RELINING AND REBASING IN COMPLETE DENTURES

Dr. Dipal MawaniPost Graduate student

CONTENTS • INTRODUCTION

• DEFINITION

• TREATMENT RATIONALE

• INDICATIONS and CONTRAINDICATIONS

• PRETREATMENT PROCEDURES

• REQUIREMENTS OF SUCCESSFUL MATERIALS

• TYPES OF RESILIENT LINERS

• CLINICAL IMPRESSION PROCEDURES

• LABORATORY PROCEDURES

• CAUSES OF FRACTURE IN DENTURES

• METHODS FOR REPAIR

• SUMMARY

• REFERENCES

INTRODUCTION

•Both biological supporting tissues and materials used in complete denture fabrication are vulnerable to time- dependent changes.

•When denture needs to be refitted, it usually indicates undermined retention, sore spots, and variable denture bearing tissue hyperemia.

•The relining and rebasing of complete dentures involves solving all of the problems encountered in the construction of new dentures, except positioning individual teeth.

DEFINITIONSRELINING –

- It is the process of adding some material to the tissue side of a denture to fill the space between the tissue and the denture base. (Winkler)

Or

the procedures used to resurface the intaglio of a removable dental prosthesis with new base material, thus producing an accurate adaptation to the denture foundation area (GPT-9)

REBASING –

- It is a process of replacing all the base material of a denture. (Winkler)

Or

- The laboratory process of replacing the entire denture base material on an existing prosthesis. (GPT-9)

TREATMENT RATIONALE

► The foundation that supports a denture changes adversely as a result of varying degrees and rates of residual ridge resorption.

► These changes may be insidious or rapid, but they are progressive and inevitable and are accompanied by:-

Loss of retention and stability.

Loss of vertical dimension of occlusion.

Loss of support for facial tissues.

Horizontal shift of dentures:- Incorrect occlusal relationships.

Reorientation of occlusal plane.

Reline Rebase

Minimal to moderate Moderate to maximal

changes changes

► The reasons for relining are:-

1) To Improve Retention & Stability:-

- Loss of fit will make the maintenance of peripheral seal impossible and will greatly impair the retentive effects of adhesion & cohesion.

2) To Restore the Vertical Dimension:-

- If the vertical dimension to which a denture was made is reduced, masticatory efficiency is impaired, but the previous efficiency can usually be restored by relining.

3) To Improve the Appearance:-

4) To Restore the Evenness of Occlusal Pressure:-

- When there is any alteration in the fit of the dentures, there will be some alteration of the pressure transmitted to the tissues when the teeth are brought into occlusion.

5) To Relieve Pain:-

- If a denture has been worn with comfort and then becomes painful, it is usually due to the alteration in the supporting tissues allowing the dentures to tilt, rock or move, and transmit undue pressure on one area.

INDICATIONS► Immediate dentures at 3-6 months after their original construction.

► When the residual alveolar ridges have resorbed and the adaptation of the denture bases to the ridges is poor.

► Persistent denture sore mouth.

► Congenital or acquired oral defect: (Acquired defect due to surgery for malignancy, trauma, congenital defects like cleft palate)

► The need for promotion of mucosal healing.

► Irregular foundation: Sharp knife edge residual ridge, maxillary or mandibular tori, prominent mylohyoid ridge.

► Single denture opposing natural teeth.

► Radiation therapy for tumors of face and neck.

CONTRAINDICATIONS

PRETREATMENT PROCEDURES► TISSUE PREPARATION:-

DENTURE PREPARATION:-

► PRINCIPAL PITFALLS:- 1) Do not increase the occlusal vertical dimension.

2) Multiple even contacts should be present in centric relation.

3) Do not permit the maxillary denture to move forward during impression making.

4) Ensure that CR and CO are identical.

5) Ensure that an accurate PPS has been established.

6) An equal thickness of final impression material should be used.

Ideal requirements of successful materials

►Ease of processing

► Dimensional stability during and after processing

► Low water absorption

► Adequate bond strength to rigid denture base resin

► High abrasion resistance: To resist rupture during use.

►Permanent resiliency: It should retain its resilience for longer period

► Color stability

►Minimum solubility in saliva: Plasticizer should not leach out

► No adverse effect on denture base: Like distortion, reduction of strength, crazing or blanching.

►Ease in cleansing

► Biocompatibility

Types of Resilient liners

►Natural rubbers.

►Vinyl co-polymers.

►Hydrophilic polymers.

►Silicone based compounds.

►Acrylic based compounds.

►Treatment liners (soft conditioners)

Room temperature polymerized condensation silicone rubber.

γ-methacrylate propyl trimethoxy silaneheat polymerized silicone rubbers

(molloplast B )

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Relining procedure

Clinical procedure Laboratory procedure

1. Static methods

2. Functional method

3. Chair-side technique

1. Articulator method

2. Jig method

3. Flask method

Closed–mouthtechnique

Open- mouthTechnique(Bouchers)

STATIC IMPRESSION TECHNIQUE

Static impression technique involves the use of either a closed

or open mouth reline/rebase procedure.

In closed mouth technique the dentures are used as an

impression trays and either the existing centric relation

occlusion (CRO) is used or the centric relation (CR) is

recorded before the impressions are made.

TECHNIQUE A

Centric relation: - a new centric relation record is made using wax

or modelling compound

Denture preparation: -

•large undercuts are relieved

•borders are reduced 1-2 mm except the posterior border of maxillary

denture

Shaffer FW, Filler WH: Relining complete denture with minimum occlusal error. J Prosthet Dent 1971;25:366-370

Closed Mouth Relining Techniques:- Maxillary Denture

Special suggestion:-

Shaffer FW, Filler WH: Relining complete denture with minimum occlusal error. J Prosthet Dent 1971;25:366-370

A part of the palate of the maxillary denture is removed to aid in the proper positioning of the denture when the final impression for the reline is made.

Border molding:- The borders of the dentures are reformed to their

functional contours by using low-fusing modelling compound.

Impression:- Zinc oxide-eugenol impression paste is suggested as

the impression material.

Shaffer FW, Filler WH: Relining complete denture with minimum occlusal error J Prosthet Dent 1971;25:366-370

Light jaw closure on the interocclusal record is maintained with the mandible in centric relation until the final impression material has set.

A fast-setting impression plaster fills the palatal opening in the denture.

Advantages:

1.The opening of the palatal portion will allow better seating of the

maxillary denture

2.The premade interocclusal record helps to position the dentures

Shaffer FW, Filler WH: Relining complete denture with minimum occlusal error J Prosthet Dent 1971;25:366-370

Disadvantages

1.The possibility of moving the maxillary denture

2.The wax interocclusal record is not an accurate and safe record

3.Relining of both dentures at the same time.

Shaffer FW, Filler WH: Relining complete denture with minimum occlusal error J Prosthet Dent 1971;25:366-370

TECHNIQUE B

• Centric relation Existing centric occlusion and intercuspation are

used as a means to seat the dentures.

• Denture preparation The same as for technique A.

Hansen NJ: Rebasing and relining complete dentures: A technique. Dent Clin North Am 1964;8:693-704

Special suggestion A large part of the palatal section is prepared to be

removed as follows:

•outline of the area should be indicated and deepened on the polished

surface up to half the thickness of the base.

•Holes are drilled at 5- to 6-mm intervals inside this groove.

Hansen NJ: Rebasing and relining complete dentures: A technique. Dent Clin North Am 1964;8:693-704

• This procedure is suggested for easy removal of the palatal portion

during packing and processing

Border molding Low-fusing modelling compound (green stick) is

suggested for border molding.

Impression: Impression wax is material of choice in this technique

Hansen NJ: Rebasing and relining complete dentures: A technique. Dent Clin North Am 1964;8:693-704

Disadvantages

(1) Wax impression material is difficult to work with and the possibility

of distortion exists.

(2) Errors of existing centric occlusion can produce an inaccurate

impression.

Hansen NJ: Rebasing and relining complete dentures: A technique. Dent Clin North Am 1964;8:693-704

TECHNIQUE C

Centric relation The same as in technique B.

Denture preparation The same as in techniques A and B.

Special suggestion The labial and palatal flanges of the denture are

perforated.

Christensen FT: Relining techniques for complete dentures. J Prosthet Dent 1971;26:373-381

Border molding The same as techniques A and B.

Impression No specific impression material recommended.

•Pt is cautioned to use light force and only tap the teeth together as

occlusal pressure may squeeze too much of impression material out

of dentures resulting in sore points.

Christensen FT: Relining techniques for complete dentures. J Prosthet Dent 1971;26:373-381

TECHNIQUE D

Centric relation The existing centric occlusion is used to seat the

maxillary denture.

Denture preparation The same as in the other techniques.

Jorden LG : Relining the complete denture. J Prosthet Dent 1972;28:637-641

Impression Plaster of Paris or zinc oxide eugenol is suggested for the first step of

impression making, and plaster of Paris for the second step (the palatal portions).

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m

A BUCCAL GROOVE IS CUT INTO THE DENTURE AND FILLED WITH WAX.

m

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Disadvantage :- the existing errors of centric occlusion may produce

some pressure points and a faulty impression can result.

Jorden LG : Relining the complete denture. J Prosthet Dent 1972;28:637-641

Closed Mouth Relining Technique

—Mandibular denture

Technique E:- Gillis RR: A relining technique for mandibular dentures. J Prosthet

Dent 1960;10:405-410

Centric Relation:- Existing centric occlusion used to seat dentures.

Advantages:-

1) The loss of vertical dimension can be compensated for during relining procedures.

Disadvantages:-

1) Time consuming.

2) The procedure for establishment of occlusal vertical dimension is questionable.

OPEN-MOUTH IMPRESSION TECHNIQUE

TECHNIQUE-F BOUCHER CO: THE RELINING OF COMPLETE DENTURES. J PROSTHET DENT 1973;30:521-

526

Centric relation :-recorded with plaster

Denture preparation

Special suggestion The lower denture is prepared for the reline

impression

•Handel is formed over the lower anterior teeth

•Adhesive or masking tape is adapted over the polished surfaces of both dentures and over the teeth.

Boucher CO: The relining of complete dentures. J Prosthet Dent 1973;30:521-526

Border molding If the flanges are inadequate, the borders should be

corrected with modelling compound.

Impression Zinc oxide-eugenol impression

Boucher CO: The relining of complete dentures. J Prosthet Dent 1973;30:521-526

Advantages

1.No occlusal interference during impression making.

2.It is possible to verify the centric relation record if necessary

3.The interocclusal record, which is made with quick-setting plaster, is a

reliable one.

Boucher CO: The relining of complete dentures. J Prosthet Dent 1973;30:521-526

Disadvantages

1.Although this technique seems simple, the performance of the

procedures is not easy.

2.This technique requires more clinical and laboratory time.

Boucher CO: The relining of complete dentures. J Prosthet Dent 1973;30:521-526

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Tissue conditioner in dentures

Plastic stage (tissue conditioner) Denture base responds to functional/ parafunctional stresses; fit is improved

(Few hours to few days)

Elastic stage Stress is cushioned;tissue (tissue conditioner) recovery takes place

(1 to 2 weeks)

Firm stage Surface is similar to polymerized (reline impression) resin surface, except it is vulnerable to deterioration

3) Chairside Technique:-

Disadvantages:-

1) The materials often produce a chemical burn on the mucosa.

2) The result often was porous and developed a bad odour.

3) Colour stability was poor.

4) If the denture was not positioned correctly, the material could

not be removed easily to start again.

LABORATORY PROCEDURE FOR RELINING

► ARTICULATOR METHOD:-

Impression is made in the denture to be relined.

Denture impression is poured in dental stone.

Modeling clay adapted denture,

blocking out all the denture

surfaces,except occlusal surfaces

of the teeth.

Stone is placed on the lower

member and smoothed with

spatula. Denture is settled is

the stone mix.

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Cast is attached to the upper member of the

articulator with dental stone.

Modeling clay removed from

denture surface.

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All impression material must be removed

from the denture.

Thin layer of resin must be removed

from the inferior of the denture

with the acrylic bur.

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Borders are reduced 2-3mm with bur.

Frena notches are deepened with

Straight fissure bur.

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Resin grindings removed with

stream of air.

Posterior palatal seal is placed in the cast,

unless provided in impression.

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Paint cast with tinfoil substitute.

Mix autopolymerizing resin and place in

denture. Avoid air entrapment.

Place resin on cast and in border reflections

Denture is seated in indentations,

and articulator closed.

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Relined denture cured in pressure container

at 15-20psi for 30min.

Relined denture removed

and examined for voids and

nodules.

Finished and polished.

► JIG METHOD:-

Stone index formed on lower member

of duplicator or jig.

Denture mounted on its cast in a reline jig

with stone and secured with locknuts

Porcelain denture teeth are removed from denture by

heating with alcohol torch or hot spatula.

Porcelain teeth replaced in their

indentations in the stone index

Adapt a layer of base plate wax to cast

and assemble the jig

Wax-up the denture teeth to base plate wax, remove cast, flask and process with heat cure denture base resin.

Cured denture replaced on jig to check occlusion, then finished and polished.

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►FLASK METHOD:-

Denture is half flasked

Silicone mold material painted

on denture and teeth.

Flask is opened.

Porcelain teeth Resin teeth

Cast and investing stone painted

with tinfoil substitute

Cured denture ready for

finishing and polishing.

REPAIR OF COMPLETE DENTUREREPAIR OF COMPLETE DENTURE

Tooth replacement Fractured dentures

Anterior teeth Posterior teeth

Non-separated parts

Separated parts

Missing parts

Denture repairDenture repair

► Complete dentures often fractures when in function or when dropped onto a hard surface.

►The most common denture fractures are those along the maxillary and mandibular midline.

►The repair of dentures is often handled as a laboratory procedure, but a knowledge of preparation as well as the technical phase is essential for successful repair.

CAUSES OF FRACTURE OF DENTURE1) FRACTURE OF THE DENTURE BASE► Improper mandibular occlusal plane► High frenum attachments► Occlusal morphology► Beyli M.S. (1981) concluded that midline fracture of a denture base

was a flexural fatigue failure resulting from cyclic deformation of the denture base during function. Buccally arranged upper posterior teeth to the crest of the ridge will transmit flexing component of forces to the midline of the denture during function and leads to midline fracture.

► Denture base thickness: The denture lined with resilient denture base liners are more susceptible for fracture due to excessive reduction of the denture base to allow the space for liner material will result in thinning of denture base and prone for fracture.

► Overdenture abutment too prominent.

METHODS FOR REPAIR

► Anterior Tooth Replacement:- Fractured tooth is

removed by grinding

with no. 8 round bur.

Care must be taken not

to perforate denture base

Labial gingival margin should

be left intact to preserve

esthetics.

Remove the resin from the lingual

aspect of the denture base .

Select a resin tooth

of same size and

shade and grind its

ridge lap for proper

positioning on the

denture.

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Verify the tooth position and secure it in

position with sticky wax.

If the tooth position is

acceptable, pour a

plaster index or silicone

index onto the labial

surface of the tooth to

be replaced and on the

labial surfaces of adjoining

teeth on each side.

After plaster sets, the index and tooth

are separated and sticky wax removed.

Shallow indentations can be

placed in the ridge laps of the

tooth with a no. 6 bur to ensure

stronger repair.

Replace the index and

tooth on the denture,

and carefully paint the

autopolymerizing resin

to the lingual or palatal

prepared area,

allowing the resin to flow between

ridge lap and denture base.

Resin is added to build up slight

excess, which will be finished to

original contour after polymerizing.

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Repaired denture is placed in a pressure pot of warm water, and

cured at 20 psi for 30min.

Remove the denture, and reduce the excess bulk with no. 8 bur and resin is smoothed with mounted rubber point and repair is polished with flour of pumice & handpiece mounted prophy cup.

Posterior Tooth Replacement:-

Mount the denture in an articulator

Remove the fractured resin tooth by grinding it with a no. 8 round

bur. Take care to preserve the facial

gingival margin of the denture base

and not to perforate the base.

Ridge lap area of

denture is hollow ground

and of the replacement

tooth is modified for the

correct placement of

tooth.

Close the articulator

and check the occlusion.

If correct, seal the

replacement tooth to

opposing tooth with

sitcky wax.

Paint the autopolymerising resin into the ridge lap area to seal the tooth to the denture base.

Place the denture in a pressure container of warm water, and cure it for 30min. at 20 psi. Adjust the occlusion and polish the repair.

Repairing Fractured Denture:- ( Non-separated Fracture)

Examine denture to determine the

extent of the fracture. Gently flexing

denture will aid this determination, but

take care to prevent breakage.

If fractured denture self-approximates,

block the undercuts with clay,

and pour the repair cast.

Full cast is not necessary if the

fracture is small.

If undercut is there in

the region of repair,

silicone mold material

can be placed in the

undercut, resulting in

flexible cast permitting

removal of denture,

Remove the denture from the cast, and

widen the fracture line from beginning

to end with no. 558 bur.

Widened cut is beveled outwards

to increase bonding area.

Dovetails can be placed on the

palatal surface to further strengthen

repair joint.

Paint the stone cast with tinfoil

substitute and allow it to dry.

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Denture is replaced on the cast carefully.

Repair resin is painted in groove,

taking care not to create voids.

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Excess resin is built up Denture is secured to the

for finishing cast with a rubber band, and

cured in a pressure container for 30 min.

Cured denture is removed, finished and polished

► Denture Fractured into Two or More Parts

Examine the denture to determine that all pieces are present.

Assemble the pieces and lute them with sticky wax.

Modeling clay can be used to hold pieces while luting denture with sticky wax and reinforcing with wood sticks before removing from clay.

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Alginate can be used in

pronounced undercuts

in mandibular denture.

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Remove the denture

from the cast. Bevel the

margins of each fragment

with bur and make grooves

and dovetail. Use wire

reinforcement to strengthen the desired region desired.

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Replace the denture on the cast, and paint autopolymerizing resin in each groove and dovetail, and build up excess.

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Secure the denture to the cast with plaster or rubber bands, and cure in a pressure container of warm water for 30min. at 20 psi

Finish and polish dentures

SUMMARY

►Resurfacing and replacement of the denture base of a complete

denture is complicated procedure requiring astute clinical judgment

and skill if the therapy is to be successful.

►When the denture bases are under-extended, when there has been a

gross loss in the occlusal vertical dimension , and when centric relation

and centric occlusion do not coincide, then fabrication of new denture

would be treatment of choice.

►Relined or rebased dentures should be given the same care as new

dentures, and the patient should be recalled as often as necessary for

examination of the tissues and the jaw relations.

REFERENCES Beyli M.S. : Repair of fractured acrylic resin. J.P.D. 1980; 44: 497-503.

Halperin A.R., Abadi B.J. : Repair of broken denture in resin undercuts. JPD, 1980; 44: 224-228.

Linear dimensional change of heat-cured acrylic resin complete dentures after reline and rebase Edmond H. N. Pow, T. W. Chow, and Robert K. F. Clark (J Prosthet Dent 1998;80:238-45.)

Beyli M.S. : An analysis of causes of fracture of acrylic resin dentures. JPD, 1981; 46: 238-241.

David E.H. : Immediate stabilization of a broken maxillary denture. J.P.D. 1983; 50: 289-292.

Rudd K.D., Morrow M.R. : Dental laboratory procedures, complete dentures. 1st edition 1986.

Sherif E.B., Carl R.S.: A metal insert to replace a fracture segment of a mandibular C.D. JPD, 1989; 61: 250-251.

Winkler S. : Essentials of complete denture prosthodontics. 2nd edn, 2000.

Swenson’s Complete denture: 5th edition.

GONZALEZ J.B. AND LANEY W.R. : Resilient material for denture prosthesis. J Prosth Dent. 1966 16: 438444.

Beyli M.S. : Repair of fractured acrylic resin. J.P.D. 1980; 44: 497-503.