Abstract : In recent times, Hobo &Takayama's Twin Stage technique for full mouth rehabilitation has emerged as a popular choice for the clinicians to rehabilitate functionally and esthetically compromised dentition. Hobo's twin stage technique first establishes the occlusal morphology in such a way that any eccentric movement, predictably results into posterior disocclusion. This philosophy is a modified version of Hobo's earlier twin table technique. The positives of the theory lies in reduced chair side time as well as predictable disocclusion. Negatives include a complicated and technique sensitive procedure which relies heavily on pre designed mathematical formulas.

1 Dr. Ritu Mohindra (Sr. Lecturer),2Dr. Dheeraj Kumar (Professor & HOD), 3Dr. Pratibha Katiyar (Reader), 4Dr. Archana Malviya (MDS)

FULL MOUTH REHABILITATION BY USING HOBO'S TWIN STAGE TECHNIQUE -A Case Report

Keywords :Hobo twin stage, Cuspal angle,Occlusal rehabilitation

Source of support : NilConflict of interest: None

Journal of Dental Sciences

University

CaseReport

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INTRODUCTION Hobo in 1991 proposed the twin table technique, which was later on modified by Hobo and Takayama in 1997 and was called as Twin Stage technique. This theory is proposed for doing a variety of workranging from Full mouth rehabilitation to single crowns. The concept utilizescuspal angle as the main

1, 2determinant of articulation in eccentric movements .

The three factors which determine the tooth contact during eccentric movements are; Condylar path, Incisal path & Cusp angle. Hobo and Takayama stated that traditionally Condylar guidance has been used in Prosthodontics as the main guiding factor to develop occlusion. These are used to derive anterior guidance and Cuspal inclination as well. However, scientifically it is not possible to prove that it provides reliable

4disocclusion during eccentric movements .In the twin stage procedure, first a standard cusp angle is created on the posterior restoration. It is followed by creation of anterior guidance based on complex mathematical and geometrical analysis. Hobo and Takayama gave predetermined values for all the three type of occlusion that is mutually protected occlusion, Group function occlusion&balanced occlusion.

Twin stage techniquebroadly consists of two stages:Stage 1 (Condition 1) - Standard cusp angle is created on the articulator using predetermined adjustment values.

Stage 2 (Condition 2) -The adjustment values are used to create the anterior guidance.

The application of both the conditions described, to fabricate the cusp angle and anterior guidance is termed as “Twin stage procedure”.This method of Occlusal rehabilitation gives predictable disocclusion during eccentric movements, therefore preventing detrimental horizontal forces adversely affecting the teeth and associated structures.

CASE REPORT

A 30 year old female patient reported to the Department of Prosthodontics, Chandra Dental College and Hospital, Barabanki, Lucknow with the chief complaint of poor esthetics and difficulty in chewing food. The patient gave no significant medical history. The patient did not report any symptoms of Temporomandibular disorder.

In Clinical Examination; the patient had no facial asymmetry or muscle tenderness. The mandibular range of motion was within normal limits. There were multiple grossly carious teeth. An over bite of 6mm was recorded. Interocclusal gap of 5mm was measured in the first premolar region.

An elaborate discussion of the Patients condition was discussed with the patient. It was explained to the patient that no satisfactory result can be achieved without restoring and rehabilitating each tooth of the arch. After getting the consent from the patient, we decided to rehabilitate the patient utilizing Hobo and Takayama twin stage technique.

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(Fig.1)- OPG

Based on radiographical analysis and diagnostic cast, we decided to go for Extraction of 13, 12, 16, 17, 26, 36, 37, 46, and 47. It was followed by Endodontic treatment along with post and core in maxillary anteriors (fig.-2)

(Fig.2)- Preoperative photographFull Mouth Rehabilitation utilizing Hobos twin stage technique was planned. For the procedurea new diagnostic impression was made with irreversible hydrocolloid and the diagnostic casts were obtained. It was followed by the mounting of maxillary cast on a semi adjustable articulator with the help of a face bow. Interocclusal records were taken to articulate the mandibular cast (Fig.3&4).

(Fig.3) - Diagnostic Mounting (Fig.4) - Diagnostic wax-up

To determine the correct orientation of occlusal plane, Broadrick' socclusal plane analysis was done. Following inferences were drawn: Mutilated dentition, Anterior guidance requires alteration, Existing occlusion scheme requires alteration, Vertical dimension need to be changed. It was followed by diagnostic wax up of full mouth restoration, following mock preparation which was carried out at the increased vertical dimension (Fig.5).

(Fig.-5)-Occlusal splint in mouth

Diagnostic wax up was done for the purpose to determine proposed arch shape and contour, to rehearse a proposed restorative plan, to establish the occlusion, Prepare Provisional restoration and to provide additional information to the technician. An occlusal splint was fabricated to raise the VDO by 3mm. The patient was kept in diagnostic and observational period of 4 weeks, with weekly recalls. After 4 weeks, when the patient was comfortable with the proposed increase in vertical dimension the actual procedure was started. Because the canines were missing, we decided to utilizes group function occlusion rather than mutually protected occlusion As we all know that twin stage technique utilizes predetermined values (Table-1) given by authors to develop the standard cusp angle of 25 degree and

5subsequently deriving anterior guidance out of it.

(Table-1) -Predetermined values for group function

Teeth preparation was started and finished for the teeth in maxillary and mandibular arches for metal ceramic restoration. Third molars were prepared in the last to maintain the vertical dimension. Impressions for maxillary and mandibular teeth were made and casts were poured in die stone (Fig.6a,6b)

(Fig.-6a,6b) – Teeth preparation compleleted in maxillary & mandibular arches

The maxillary cast was mounted on whip mix articulator using the face bow and centric record at the previously determined vertical dimension (fig.7a.7b).

(Fig.-7a,7b) – facebow transfer and articulation done using interocclusal record.

Diagnostic wax up was used to fabricate provisional

restoration with the provisional restorations. Patient was

evaluated for esthetics, comfort and phonetics (Fig.-8).

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(Fig.-8) – patient sent off after cementation of provisionals

The wax pattern for metal coping was carved (fig.9&10).

It must be mentioned that we utilized non rigid connectors at Locations 13, 14, 15, 16, 23, 24, 25, and 26 in maxillary arch. All the wax patterns were cast and the metal copings were tried in the patient's mouth (fig.11a,11b)

(Fig.11a,11b)- Coping try in done for the maxillary and mandibular arches

After verification of the castings, they were placed on the articulator and balancing was done along with ceramic application and firing. First, the cuspal angle was generated (condition-1) with the maxillary anterior segment removed Second the maxillary anterior segment was replaced and anterior guidance was developed (condition-2) (fig.12a,12b).

(Fig.12a)-Unglazed Condition-1 (Fig.12b)-Unglazed Condition-2

Following the occlusal adjustments, the ceramic units were glazed. Definite restorations with PFM crowns exhibiting a vital and natural appearance with proper contour, shade and

Condition 1-cusp angle is generated without anterior segment the anterior maxillary segment

Condition 2- Anterior guidancegenerated after replacing

optimal translucency were fabricated. Permanent cementation was done with GIC (fig.13a,13b).

(Fig.13a,13b)- Final Prosthesis Cemented

DISCUSSIONFull mouth rehabilitation in the case of severely attrited teeth is one of the most challenging aspects of prosthodontics. As already discussed; there are many theories and concepts of Full mouth rehabilitation. In this case, we chose Hobo's technique for FMR .The rationale was to ensure that the occlusion which developed eventually resulted into predictable disocclusion of the posterior teeth during various eccentric movements. It is necessary to point at this stage that in most of the cases of generalized attrition, this is perhaps the most important thing to achieve. Apart from this, the number of patient visit is kept to a minimum in this technique resulting into better patient compliance.

In Hobo &Takayama technique, Pre- determined values are used for calculations and the operator can choose the type of occlusion, required for the case. The values are available for mutually protective occlusion, Group function occlusion & balanced occlusion. The authors chose Group function occlusion in this case. The amount of disocclusion achieved in Group function in Hobo's technique is 1.0 mm. in protrusion, 0.5 mm. on non working side & obviously 0 mm. on the working side.

In the twin stage technique, a standard cusp angle needs to be generated and then a standard incisal angle needs to be computed to result into predictable disocclusion during eccentric movements. Theincisal guidance created in this manner starts effectively controlling the condylar path as well, sinceincisal path is one of the main controlling factor of condylar guidance.

For the success of this technique,an articulator is required which can predictably reproduce the mandibular movements. On this articulator, Condition 1 of this procedure, which is to generate the cuspal angle followed by Condition 2 of the procedure, which is to develop the incisalguidance which would always be such that while during eccentric movements, incisal guidance overrides cuspal angle and results into disoocclusion. The articulator adjustment values are developed by computations. Though Twin-Hoby articulator has been designed for this purpose, any reasonable semi-adjustable articulator serves the purpose. In this case, we used Whip–mix articulator which is a semi-adjustable,Arcon articulator.

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Twin stage technique used here is an advanced version of the twin table technique developed by Hobo. Many disadvantages of the earlier technique were eliminated in this technique. Some of the advantages of this technique are; measurement of the condylar path is not required, all the guidelines and values used for the procedure are clearly defined therefore eliminating operator variables, can be used in any restorative procedure be it a single crown, completedentures, implants or Full mouth rehabilitation. Because condylar path is not required, it is suitable for those patients who have some form of TMDs. Contraindications of this procedure are: Abnormal curve of spee, Abnormal curve of Wilson, Abnormally rotated teeth, Abnormally inclined teeth.

CONCLUSION

Since this concept does not rely on the accurate measurement of the condylar path, elaborate instrumentation is not required. This procedure is much simpler than gnathological procedures. In our opinion restoring the optimal oral health of this patient utilizing twin stage technique resulted into a very satisfied and happy patient. Needless to say that a satisfied patient results into a more satisfied operator.

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CORRESPONDING AUTHOR:Dr. Ritu Mohindra( MDS) Senior LecturerChandra Dental College & Hospital, BarabankiE-mail: dr_ritum@yahoo.comMob. No.- 9936184000