Full mouth rehabilitation of a patient with enamel hypoplasia using hobo s twin-tables technique for occlusal rehabilitation-a case Report

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1 J. Adv Oral Research Case Report All Rights Res 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. dr_hemal@rediffmail.com 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. Serial Listing: Print-ISSN ( ) Online-ISSN ( ) Formerly Known as Journal of Advanced Dental Research Bibliographic Listing: Indian National Medical Library, Index Copernicus, EBSCO Publishing Database, Proquest, Open J-Gate. 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

2 24 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, 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

3 25 Fig 1: OPG of the patient Fig 2: Pretreatment condition of patient s dentition Fig 5: Diagnostic casts mounted on semiadjustable articulator Fig 3: Pretreatment condition of patient s dentition Fig 4: Occlusion before treatment Fig 6: Anterior portion of maxillary cast is made removable by using dowel pins

4 26 Fig 7: Incisal records without and with disclusion Fig 8: Final impression made with rubber base impression material Fig 10: Completed wax-up Fig 11: Permanent porcelain fused to metal restorations cemented in patient s mouth Fig 9: Crown preparations as seen on the working casts

5 27 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.

6 28 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 cuspshape 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. 3 rd ed. U.S.A: Mosby. 2001; Peter E. Dawson. Evaluation, Diagnosis, and Treatment of Occlusal Problems. 2 nd ed. U.S.A: Mosby. 1989; Hobo S. Twin-tables technique for occlusal rehabilitation : Part II Clinical procedures. J PROSTHET DENT 1991;66(4): Linda J. Thornton. Group function/canine guidance. A literature review. J PROSTHET DENT 1990;64(4): Ashwini Kumar kar. Full mouth rehabilitation of a case of generalized enamel hypoplasia using a twin-stage procedure.

7 29 Contemporary Clinical Dentistry 2010;1(2): Kazis H. Complete mouth rehabilitation through restoration of lost vertical dimension. J Am Dent Assoc 1948;37: Hausman M, Hobo S. Occlusal reconstruction using transitional crowns. J PROSTHET DENT 1961;11: Braly BV. A preliminary wax-up as a diagnostic aid in occlusal rehabilitation. J PROSTHET DENT 1966;16: 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: Hobo S. A kinematic investigation of mandibular border movement bymeans of an electronic measuring system : Part III : Rotation center of lateral movement. J PROSTHET DENT 1984;52: 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: Binkley TK, Binkley CJ. A practical approach to full mouth rehabilitation. J PROSTHET DENT 1987;57: Hobo S, Takayama H. Effect of canine guidance on the working condylar path. Int J Prosthodont 1989;2: Schuyler H. The function and importance of incisal guidance in oral rehabilitation. J PROSTHET DENT 2001;86(3): Hobo S. Twin-tables technique for occlusal rehabilitation : Part I Mechanism of anterior guidance. J PROSTHET DENT 1991;66(3): Source of Support: Nil Conflict of Interest: No Financial Conflict

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