ABSTRACT: Endodontically treated grossly destructed teeth when left untreated for a long

period of time may cause supraeruption, drifting, tipping, and rotation of adjacent and opposing

teeth. This may be challenging to the restorative dentist, when fabricating a crown because of

inadequate interocclusal space. This case report describes a simple technique to restore an

endodontically treated mandibular second premolar with the loss of coronal tooth structure and

lack of interocclusal space. The mandibular second premolar had a single root canal and was

endodontically treated. The opposing upper premolar had supraerupted results in reducing the

interocclusal space. A minimally invasive and esthetic technique was used to restore the tooth

with limited interocclusal clearance. In such cases additional retention and support of the

restoration are difficult to achieve. Richmond crown (post-core & crown as a single unit) give

this additional amount of retention & support and proves to be very promising in long term. In this

article we have discussed a case report showing successful restoration of functionally &

structurally compromised endodontically treated posterior tooth with Richmond crown.

1 2 3Rajashekar Sangur, Achyut Sinha, Neha Sonali Massey1 2,3Professor & Head, Post Graduate Student Department of Prosthodontics, Rama Dental College Hospital & Research Centre , Kanpur

INTRODUCTION : Root canal therapy cannot be

summarized by saying, “fill it, shut it, forget it”. The final

restoration over an endodontically treated tooth is as

important or probably even more important than the actual

root canal therapy itself. The main aim of endodontics and

restorative dentistry is to retain the natural teeth with maximal

function and pleasing esthetics.

Endodontically treated teeth are more prone to fractures than

the vital teeth. Fracture occurrence is more in posterior teeth

than anterior teeth as the masticatory forces are higher and

teeth are weaker.[1] The endodontically treated tooth has got

an impaired neurosensory feed- back mechanism because of

the lack of pulpal tissue i.e. the protective property of

'proprioception' is lost. This renders the tooth more vulnerable

to fracture under normal masticatory forces. So, a person can

un-intentionally bite too hard on the RC treated tooth

compared to a vital tooth, which can lead to its fracture and

failure. An accountable percentage of structural integrity is

lost because of the root canal therapy itself due to access

cavity preparation and canal instrumentation leading to

increased flexing of the tooth and ultimately its fracture.

Some authors quote an alteration in the composition of the

dentin such as a change in the collagen cross linking,

dehydration etc. weakening the tooth structure which can also

lead to increase chances of fracture of an endodontically

treated tooth.

Endodontically treated teeth with the loss of coronal tooth

structure when left untreated for a long period may cause

supraeruption, drifting, tipping, rotation of neighboring and

opposing teeth. This may be challenging to the clinician,

when fabricating a restoration because of lack of interocclusal

space. Many methods have been advocated for treatment of

localized loss of space such as minor tooth movement,

reducing the opposing teeth, elective root canal treatment and

restoration with post retained restorations or combination of

two or more of the above.[2] All these methods of gaining

TREATING AN ENDODONTICALLY TREATED PREMOLAR WITH LIMITED INTEROCCLUSAL CLEARANCE USING RICHMOND CROWN : A CASE REPORT

Keywords:

Limited interocclusal

clearance, Richmond

crown, endodontic treated

tooth, cast post.

Source of support: Nil

Conflict of interest: Nil

Journal of Dental Sciences

University

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University J Dent Scie 2017; No. 3, Vol. 1

CaseReport

space require removal of healthy tooth structure and are time

consuming.

Wherever remaining crown structure is insufficient to retain

full coverage crown then post and core is necessary means to

increase retention and resistance form of tooth.[3,4]

However, post and core procedure can give rise to

complications such as dislodgement of assembly, fracture of

post/root, loss of restorative seal and periodontal injury.[5-8]

Such situations further get complicated when there is limited

interocclusal clearance in posterior teeth; as occlusal forces

are maximum and core reduction should be adequate to

provide indicated thickness for metal ceramic crown to

achieve desirable esthetics. Richmond crown is best indicated

solution in such conditions.

The Richmond crown was introduced in 1878 and

incorporated a threaded tube in the canal with a screw retained

crown. It was later modified to eliminate the threaded tube

and was redesigned as a one piece dowel and crown.[9] It is

easier to make cast metal restorations with the aid of posts for

retention and lasting service for limited interocclusal

clearance cases. However, whenever possible, the metal can

be camouflaged by veneering with tooth-colored restorations.

The aim of this case report is to describe a simple and

minimally invasive technique to restore an endodontically

treated tooth with limited interocclusal space.

CASE REPORT : A female patient aged 46 years reported

to the Department of Prosthodontics, with the chief complaint

of dislodgement of crown in lower left back tooth region.

On intra-oral examination, it was observed that the tooth 35

was root canal treated with very little crown structure

remaining to hold the crown. Tooth 36 was also root canal

treated. (PHOTOGRAPH 1)

Inter arch space was not enough for the conventional post and

core and thus it was planned to prepare RICHMOND

CROWN for tooth 35 and a conventional porcelain fused to

metal crown for the tooth 36 .

PHOTOGRAPH 1: PRE OPERATIVE

C L I N I C A L P R O C E D U R E : P O S T S P A C E

PREPARATION : Using peeso reamer, the remaining

cement/ weak dentine layer was removed taking care not to

disturb the apical seal (PHOTOGRAPH 2). The undercuts

within the canal were blocked with glass ionomer cement and

using H-file, (PHOTOGRAPH 3) the walls of the canal are

smoothened in order to seat the casting and resist torque, a slot

was prepared near the orifice region.

PHOTOGRAPH 2: POST SPACE PREPARATION

PHOTOGRAPH 3: Walls of the canal are smoothened using

H-file.

CROWN STRUCTURE PREPARATON: Carious dentine

was first removed and then the remaining crown was prepared

following the guidelines for porcelain fused to metal crown

keeping the finish line sub-gingivally. A slot or cloverleaf

preparation was prepared near the orifice region with a

tapered carbide bur which aids in the seating of the casting and

also resists torque.

INDIRECT METHOD TO RECORD POST SPACE : In

the prepared post space, first petrolatum jelly was applied.

Then a J-shaped pin was prepared such that the pin fits loosely

in the canal space to the prepared length (PHOTOGRAPH 4).

The canal was filled with the impression material (light body)

and a suitable lentulospiral is made to rotate within the filled

canal space followed by the insertion of pin (coated with tray

adhesive) (PHOTOGRAPH)[5]. The impression of the arch

was then made using the multiple mix technique. Once set, the

University Journal of Dental Sciences, An Official Publication of Aligarh Muslim University, Aligarh. India 63

University J Dent Scie 2017; No. 3, Vol. 1

impression was removed along with the J pin thereby giving

the impression of the canal as well. (PHOTOGRAPH 6).

PHOTOGRAPH 4: J- PIN

PHOTOGRAPH 5 : Placement of the J pin within the canal

space

'

PHOTOGRAPH 6: FINAL IMPRESSION

The obtained impression was poured with die stone, followed

by making wax pattern (PHOTOGRAPH 7) and casting of the

wax pattern was done. (PHOTOGRAPH 8)

PHOTOGRAPH7: MASTER CAST WITH WAX PATTERN

PHOTOGRAPH 8: CASTING PEPARED

This prepared metal casting was then checked in patient's

mouth to evaluate marginal fit and stability of the casting.

(PHOTOGRAPH 9)

PHOTOGRAPH 9 : METAL CASTING BEING CHECKED

IN PATIENT'S MOUTH

Metal trial was done, shade was selected and ceramic buildup

was done (PHOTOGRAPH 10) Bisque trial was done

followed by glazing and the respective crown with post is

cemented using glass ionomer cement.

PHOTOGRAPH 10: CEMENTATION OF FINAL

RESTORATION

This case was followed for a period of 06 months and there

was no complication.

DISCUSSION:

Restoration of endodontically treated tooth is complex and

success requires analysis of the situation.[9] Limited

interocclusal space may be a challenge to the clinician as there

is a reduced space for the restoration. Treatment for such

cases include intrusion of the upper supraerrupted premolar to

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University J Dent Scie 2017; No. 3, Vol. 1

regain space by orthodontic tooth movement, intentional root

canal treatment of the upper premolar and restorations for

both the upper and lower teeth, extraction followed by the

placement of an implant. All these treatment modalities are

complex, invasive, time consuming and expensive.

Mandibular first premolar in our case presented with the loss

of coronal tooth structure and had a single root with a single

canal which was endodontically treated. Such a root canal

anatomy was most favorable to fabricate a Richmond crown.

The Richmond crown is one piece dowel and crown, which

provide a better geometric adaptation to excessively flared or

elliptical canals and are indicated in roots with minimal

coronal tooth structure.

In the late 19th century, the “Richmond crown,” a single-

piece post-retained crown with a porcelain facing, was

engineered to function as a bridge retainer. Richmond crown

is not post and core system but it is customized, cast able post

and crown system as both are single unit and casted

together[10,11,12,13]. Design include casting of post and

crown coping as single unit over which ceramic is fired and

cemented onside canal and over prepared crown structure

having same path of insertion. Ferrule collar is incorporated to

increase mechanical resistance, retention apart from

providing anti-rotational effect. A major technical drawback

of this design is excessive tooth preparation in making two

different axis parallel which results in weakening of tooth and

also this design increases stresses at post apex causing root

fracture.

One piece restoration is indicated for the management of

mutilated tooth requiring post-core restorations where there is

reduced occlusal clearance. A single-unit post-core-crown

restoration has various advantages over two or three units

components. When the post and core are two separate parts;

different coefficients of thermal expansion of the various

components of post crown restoration may have a harmful

effect on the bonds between the tooth-post-core-cement-

crown complex. In addition, flexion of the post under

functional forces stresses the post-core interface, resulting in

separation of the core due to permanent deformation of

post.[14] By decreasing the number of interfaces between

components, the single unit restoration helps to achieve a

monoblock effect.

CONCLUSION : This case report discuss a simple and

minimally invasive restorative technique to salvage a tooth

with limited interocclusal clearance by Richmond crown. So

Richmond crown is an treatment option to replace the missing

tooth structure by the post and crown system which enables a

grossly mutilated tooth with very little crown height

remaining to achieve an added retention and support.

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Keshava Prasad. Restoration of badly broken,

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CORRESPONDING AUTHOR:

Dr. Rajashekar Sangur

Professor & Head,

Department of Prosthodontics,

Rama Dental College-Hospital & Research Centre

Kanpur – 208024.

Email : rsangur@yahoo.co.in

Mobile no.: 9839401902

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University J Dent Scie 2017; No. 3, Vol. 1