hobo technique.pdf

J. Adv Oral Research Case Report

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Journal of Advanced Oral Research, Vol 3; Issue 2: May-Aug 2012 www.ispcd.org

Full mouth rehabilitation of a patient with

enamel hypoplasia using hobo’s twin-tables

technique for occlusal rehabilitation-A case

Report

Hemal S. Agrawal * Neha H. Agrawal† Rupal J. Shah

‡

*MDS, Assistant Professor, Department of Prosthodontics, Government Dental College and Hospital,

Ahmedabad. †MDS, Senior Lecturer, Department of Conservative Dentistry and Endodontics,

Karnavati School of Dentistry, Gandhinagar, Gujarat, India. ‡MDS, Professor and Head, Department

of Prosthodontics, Government Dental College and Hospital, Ahmedabad, Gujrat, India.

Email:[email protected]

Abstract:

Restoration of the extremely worn

dentition present a substantial challenge to the

dentist. Molar disclusion which is crucial in

any occlusal rehabilitation is determined by

the cusp-shape factor and angle of hinge

rotation. This article discusses the diagnostic

evaluation and treatment planning for

complete occlusal rehabilitation using Hobo’s

twin-tables technique for a patient who was

suffering from enamel hypoplasia.

Keywords: Hobo’s twin-tables technique,

anterior guidance, posterior disclusion, incisal

records, canine guided occlusion, cusp-shape

factor, angle of hinge rotation.

Introduction:

Planning and executing the restorative

rehabilitation of a decimated occlusion is

probably one of the most intellectually and

technically demanding tasks facing a

prosthodontist. The expectations are high and

failure is costly. The term occlusal

rehabilitation is defined as restoration of

functional integrity of dental arches by the use

of inlays, crowns, FPDs and partial dentures.

The aim is to provide an ordered pattern of

occlusal contact and articulation to optimize

oral function, health, occlusal stability,

esthetics and comfort.

The indications for occlusal

rehabilitation include the following conditions

– restoration of multiple teeth which are

broken, worn, missing or decayed, faulty FPD

work, discolored dentition, developmental

defects and worn out dentition.[1]

The following goals should be achieved

when planning for an occlusal rehabilitation:

1) Static coordinated occlusal contact of the

maximum number of teeth when the condyle is

in comfortable, reproducible position.

2) An anterior guidance that is in harmony

with function in lateral eccentric position on

the working side.

3) Disclusion by the anterior guidance of all

posterior teeth in eccentric movements.

4) Axial loading of teeth in centric relation,

interproximation, and function.[2]

In some cases like acidic erosion,

congenital anomalies, excessive oral habits,

etc. there may be an actual loss of vertical

dimension of occlusion. In treatment of such

cases, it is necessary to increase vertical

dimension to provide sufficient space for

reconstruction but this increase should be

within extent of lost vertical dimension and

should not exceed the accommodating limit of

musculature.

Many different occlusal schemes have

been suggested by various authors for full

mouth rehabilitation patients which includes

Pankey-Mann Schulyer concept, Hobo’s Twin

tables concept, Youdelis concept, Nyman and

Lindhe concept etc. Hobo’s Twin tables

technique is a methodical approach in which

first occlusal morphology of posterior teeth is

reproduced without anterior segment i.e. cusp

angle coincident with standard value of

Serial Listing: Print-ISSN (2229-4112) Online-ISSN (2229-4120) Formerly Known as Journal of Advanced Dental Research Bibliographic Listing: Indian National Medical Library, Index Copernicus, EBSCO Publishing Database, Proquest, Open J-Gate.

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effective cusp angle produced according to the

condylar guidance recorded and secondly

anterior morphology reproduced with anterior

segment and anterior guidance provided which

produced a standard amount of disclusion.

Case report:

A hindu male patient, 26 years of age

came to OPD of G.D.C.H, Ahmedabad with

chief complaint of sensitivity in relation with

lower posterior teeth, discoloration and wear

in relation with all teeth. Patient was suffering

from enamel hypoplasia and had a family

history of enamel hypoplasia too.

Thorough clinical evaluation was done

and diagnostic casts were made. Full mouth

radiological examination was done through

OPG and following finding were noted

(Fig.1):

Severe wear of occlusal surfaces of all

upper and lower posterior teeth and

reduction in axial height of clinical

crowns.

Significant attrition leading to flattening of

incisal edges of upper and lower anterior

teeth.

RCT was done in 47,45, Class II amalgam

fillings were present in 17, 16, 25, Class I

amalgam fillings were present in 17, 47,

48, occlusal pit, filling was present in 26,

and glass ionomer restorations were

present in 36, 38.

15 was missing and space was present

between 13 and 14 for an additional

pontic (Fig.2,3,4).

Treatment plan:

Periodontal phase

Scaling and root planning done.

Crown lengthening done in relation with

all upper and lower posterior teeth.

Patient was advised to use 2%

chlorhexidine mouthwash and taught

proper oral cleansing habits.

Prosthodontic phase

After all the above treatment procedures

were completed, the freeway space was

evaluated to decide whether the VD

should be increased or not. Sufficient

space was present and so it was decided to

work at the same vertical dimension of

occlusion by using Hobo’s twin-tables

technique of occlusal rehabilitation.

A semiadjustable Hanau articulator with

box-shaped fossa element was used for the

entire procedure.

The cusp-shape factor and the angle of

hinge rotation is derived primarily from

the condylar path.

The maxillary diagnostic cast is made with

a removable anterior segment. Face bow

transfer is done and cast is mounted to the

articulator. Mandibular cast is mounted

with help of centric relation record

(Fig.5,6). The condylar path (guidance) is

recorded by using interocclusal plaster

records. The working condylar guidance is

set on the articulator so that the working

condyle moves straight outward along the

transverse horizontal axis. The maxillary

anterior segment is removed and the

articulator is moved through eccentric

movements to eliminate interferences that

impede an even, gliding motion. This

procedure results in a cusp-shape factor

that harmonizes with the condylar path.

With the anterior segment of the maxillary

cast removed, the posterior teeth do not

disclude during eccentric movements.

Chemical cure acrylic resin is molded on

the incisal table by moving the incisal pin

through eccentric movements. Same

procedure is repeated and another record

made to complete two incisal records

without disclusion.

One of the incisal records without

disclusion is placed on the table on the

articulator. Two 3mm spacers are placed

behind the condyles to simulate a

protrusive position. A 1.1mm thick spacer

is placed on the mesiobuccal cusp tip of

the mandibular first molars and the

articulator is closed. A resin cone is made

between the incisal pin and the incisal

table to establish the angle of hinge

rotation for an average disclusion during

protrusive movement.

Next one 3mm spacer is placed behind one

condyle in the articulator. A 1mm spacer

is placed on the non-working side and a

0.5mm spacer on the working side at the

mesiobuccal cusp tip of the mandibular

first molar to simulate a lateral movement

position. A resin cone is made between the

incisal pin and table. The procedure is

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Fig 1: OPG of the patient

Fig 2: Pretreatment condition of patient’s

dentition

Fig 3: Pretreatment condition of patient’s

dentition

Fig 4: Occlusion before treatment

Fig 5: Diagnostic casts mounted on

semiadjustable articulator

Fig 6: Anterior portion of maxillary cast is

made removable by using dowel pins

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Fig 7: Incisal records without and with

disclusion

Fig 8: Final impression made with rubber base

impression material

Fig 9: Crown preparations as seen on the

working casts

Fig 10: Completed wax-up

Fig 11: Permanent porcelain fused to metal

restorations cemented in patient’s mouth

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Fig 12: Occlusion established after treatment

Fig 13: Smile of satisfaction

repeated for the other condyle. This

created the angle of hinge rotation for an

average disclusion during lateral

movement.

The three cones are connected with

additional resin to form walls. More resin

is added and the articulator is directed

through eccentric movements to complete

the three-dimensional incisal record . This

completes the incisal table with disclusion

(Fig.7).

Now the crown preparations are completed

segment wise maintaining the vertical

dimension and provisional restorations

given.

An accurate final impression is made with

a rubber base impression material (Fig.8).

The maxillary working cast is again made

with a removable anterior segment using

dowel pins. A facebow is used to transfer

the maxillary working cast and a centric

relation record is used to articulate the

mandibular working cast (Fig.9).

The anterior segment is removed and the

incisal record without disclusion is used to

wax the posterior occlusion through

eccentric movements. This establishes the

cusp-shape factor that forms the molar

cuspal inclination parallel to the condylar

path.[3]

Now the incisal record with disclusion was

used and the anterior segment was

repositioned on the maxillary cast.

Anterior wax-up was completed by

moving the articulator through eccentric

movements (Fig.10). A canine guided

occlusion was established i.e. canine

shaped to ensure disclusion of other teeth

in mandibular excursions.[4]

This

procedure established the angle of hinge

rotation and develops anterior guidance in

harmony with the condylar path. Since the

anterior guidance programmed in this

manner is steeper than the condylar path

and the molar cuspal inclinations, the

posterior restorations provide a

predetermined disclusion during eccentric

movement.

The wax trial is checked in the patient’s

mouth for predetermined disclusion.

After that the patterns were invested and

metal trial was taken.

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Porcelain fused to metal restorations were

fabricated for the entire upper and lower

arches with predetermined disclusion

(Fig.11).

The restorations were cemented using

permanent cement (Fig.12).

Patient was kept on regular follow-up and

advised strictly to maintain good oral

hygiene.

Discussion:

Full mouth reconstructions involving full

arch preparations, impressions, provisional

restorations , and master casts are regarded as

simultaneous constructions.[5]

When all of the

prepared teeth are on a single articulator, there

is flexibility in developing the occlusal plane,

occlusal theme, embrasures, crown contour,

and esthetics. The chairside disadvantages

include ardous, unpredictable patient visits,

full arch anaesthesia, full arch chairside

treatment restorations, multiple occlusal

records and possible loss of the vertical

dimension of occlusion. [6-11]

. The cost and

laboratory time involved in fabricating the

processed acrylic resin temporary restorations

are a limitation but the complexity of the

patient’s treatment warrants the extra effort.[12]

One of the prime goals of any successful

occlusal rehabilitation is disclusion by the

anterior guidance of all posterior teeth in

eccentric movements. Posterior disclusion

refers to no contact on any posterior teeth in

any position but centric relation. It can be

accomplished easily with cusp tip to fossa

morphology. The mechanism of anterior

guidance was reviewed from recent

mandibular movement studies to provide a

basis for understanding the twin-stage

technique, which is practical method for

establishing anterior guidance from the

condylar path.[13]

Anterior guidance is the

influence on mandibular movements provided

by the contacting surfaces of the maxillary and

mandibular anterior teeth.[14]

Anterior guidance is crucial in human

occlusion because it influences molar

disclusion that controls horizontal forces.

Anterior guidance and the condylar path have

been considered independent factors. In a

recent study, it was revealed that the anterior

guidance influenced the working condylar path

and even changed when the lateral incisal path

deviated from the optimal orbit. This supports

the hypothesis that anterior guidance and

condylar path are dependent factors. When

setting anterior guidance, it is recommended to

set the working condyle so that it moves

straight outward along the transverse

horizontal axis. The angle of hinge rotation

created by the angular differenced between

anterior guidance and condylar path assists the

posterior disclusion but is not solely

responsible. The anatomy of the cusps is

created by establishing the appropriate form of

the posterior cusps aligned to the condylar

path so that it also contributed to posterior

disclusion.

Posterior disclusion is crucial in

controlling harmful lateral forces. The molars

must disclude slightly more than the deviation

in the condylar path to avoid occlusal

interferences.[15]

Conclusion:

1) Molar disclusion is determined by the cusp-

shape factor and the angle of hinge rotation.

2) A new twin-tables technique has been

introduced for developing molar

disclusion by using two incisal records. It is a

relatively uncomplicated technique and does

not require special equipment.

3) The final prosthesis with the twin-tables

technique ensures a restoration with a

predictable posterior disclusion and anterior

guidance in harmony with the condyle path.

The uniqueness of this case report and

Hobo’s technique is that the entire final full

mouth prosthesis is cemented in a single

appointment. The treatment greatly improved

the patient’s esthetic appearance. The patient

was very much satisfied with the treatment

outcome (Fig.13).

References:

1.Rosentiel, Land, Fujimoto. Contemporary

Fixed Prosthodontics. 3rd

ed. U.S.A: Mosby.

2001;202-13.

2.Peter E. Dawson. Evaluation, Diagnosis, and

Treatment of Occlusal Problems. 2nd

ed.

U.S.A: Mosby. 1989;261-3.

3.Hobo S. Twin-tables technique for occlusal

rehabilitation : Part II – Clinical procedures. J

PROSTHET DENT 1991;66(4):471-7.

4.Linda J. Thornton. Group function/canine

guidance. A literature review. J PROSTHET

DENT 1990;64(4):479-82.

5.Ashwini Kumar kar. Full mouth

rehabilitation of a case of generalized enamel

hypoplasia using a twin-stage procedure.

29


Contemporary Clinical Dentistry

2010;1(2):98-102.

6.Kazis H. Complete mouth rehabilitation

through restoration of lost vertical dimension.

J Am Dent Assoc 1948;37:19-39.

7. Hausman M, Hobo S. Occlusal

reconstruction using transitional crowns. J

PROSTHET DENT 1961;11:278-87.

8. Braly BV. A preliminary wax-up as a

diagnostic aid in occlusal rehabilitation. J


9. Hobo S. A kinematic investigation of

mandubular border movement by means of an

electronic measuring system : Part II : A study

of the Bennett movement. J PROSTHET

DENT 1984;51:642-6.

10. Hobo S. A kinematic investigation of

mandibular border movement bymeans of an

electronic measuring system : Part III :

Rotation center of lateral movement. J


11. Hobo S. Formula for adjusting the

horizontal condylar path of the semiadjustable

articulator with interocclusal records : Part I :

Correlation between the immediate side shift,

the progressive side shift, and the Bennett

angle. J PROSTHET DENT 1986;57:422-6.

12.Binkley TK, Binkley CJ. A practical

approach to full mouth rehabilitation. J


13.Hobo S, Takayama H. Effect of canine

guidance on the working condylar path. Int J

Prosthodont 1989;2:73-9.

14.Schuyler H. The function and importance

of incisal guidance in oral rehabilitation. J

PROSTHET DENT 2001;86(3):219-32.

15. Hobo S. Twin-tables technique for occlusal

rehabilitation : Part I – Mechanism of anterior

guidance. J PROSTHET DENT

1991;66(3):299-303.

Source of Support: Nil

Conflict of Interest: No Financial Conflict

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