Quick Technique for Evaluation of Interocclusal Space

Figure 1. A partially edentulous mouth, presenting limited access for intraoral measurement of the existing space. Figures 2a and 2b. Existing interarch distance as demonstrated by a vinyl polysiloxane (Regisil Rigid [DENTSPLY Caulk]) index and measured using a periodontal probe. (a) An index sectioned longitudinally along the crest of ridge. (b) Longitudinally sectioned index placed intraorally over the ridge, demonstrating the accuracy of oral evaluation. Figure 3. The restored dental arches using 2 individual implant-supported metal ceramic restorations on teeth Nos. 14 and 19.

INTRODUCTION
Analysis of an existing interarch distance is one of the first steps that must be carried out in planning for the restoration of missing teeth in a partially edentulous mouth.¹ When missing teeth are not replaced, the space previously occupied by the teeth may not be present any longer. The available space may also be restricted because of the potential extrusion or migration of the opposing dentition or tuberosity enlargement. Early identification of the lack of space would prevent complications in designing and constructing a fixed partial denture (FPD) or a removable partial denture (RPD) for a partially edentulous mouth.^2-4 However, intraoral visual or evaluation using measuring instruments is often limited and unreliable because of the limited access to the area of interest; in particular, the posterior segment of the arches.
The indirect procedure employs preliminary impressions made to generate the study casts and mount them on an articulator to examine the relation of the teeth and edentulous ridge area.^5,6 When hand articulation of the casts does not provide solid occlusal contacts (such as in an extension situation), the relation of the maxillary and mandibular casts is achieved with the aid of record bases and occlusion rims. The interarch distance is assessed and measured with a ruler on an articulator to determine the available space in seeking possible treatment options to restore the missing dentition.⁵ This indirect measurement of the interarch space, however, requires multiple clinical and laboratory procedures, a number of materials and instruments, and relies on the accuracy of the cast relation.
The purpose of this article is to describe a simple and reliable procedure for precise measurement of an existing interarch distance intraorally with the use of a silicone bite registration material.

CLINICAL TECHNIQUE
Conduct an intraoral visual examination of the partially edentulous mouth to identify the region of edentulous area and assess occlusal relation, orientation of occlusion plane, and incisal guidance (Figure 1). Then, dry the opposing dentition and isolate the residual ridge of the edentulous area by evacuating saliva and displacing the cheek and the tongue. Next, extrude the fast setting vinyl polysiloxane (VPS) bite registration material (Regisil Rigid [DENTSPLY Caulk]) over the ridge between the buccal and lingual vestibules. Guide the mandible to relate against the opposing arch in the maximal intercuspal position and hold it until the material sets. Remove the processed VPS material out of the mouth, trim the excess, and return it to the mouth to verify its accuracy. Section the index either sagitally across the ridge at the site of interest, or longitudinally along the crest of ridge, using a surgical blade (No. 25 surgical blade [Miltex]). Finally, measure the thickness of the silicone index using either a ruler or periodontal probe (Figure 2a) and determine the sufficiency/insufficiency of the existing interarch distance to restore the missing dentition (Figure 2b). You may then show the index to the patient to enhance the understanding of the existing condition, extend further discussion on alternative treatment options, and to seek further consultation if needed.

DISCUSSION
Restoration of a partially edentulous mouth is only possible when the existing interarch space is sufficient enough to position artificial teeth for function and aesthetics.^1-4 With limited access to the posterior segment of the arch, an indirect evaluation based upon mounting of the study casts ensures correct assessment of the interarch distance, which requires multiple procedures.^5,6 Omission of this important step can lead to a critical error in designing and constructing either FPDs or RPDs.^3,4,6 When encountering problems with the lack of interarch distance while executing procedures of prostheses fabrication, patients’ misunderstanding may evoke the loss of trust and delay the entire time frame of construction.
The silicone bite registration material does not displace the mucosa in the edentulous area, sets fast, and is rigid and dimensionally stable. The processed material is sectioned either longitudinally along the crest of ridge or sagitally across the ridge at the site of interest. The thickness of the material is measured with a ruler or periodontal probe to determine the existing interarch distance and formulate possible treatment options in restoring the partially edentulous mouth. The early detection of the space at chairside enables the dentist to predict difficulties and complications related to further dental procedures and enhance patients’ understanding by visually demonstrating the available space as indicated by the thickness of the silicone index.
The patient presented in this article accepted a proposed treatment plan, which included extraction of teeth Nos. 14 and 15 (both extruded with furcation involvements) and restoration of the missing teeth (at Nos. 14 and 19 sites) with 2 individual metal ceramic implant restorations. The interarch space was divided to restore functions and aesthetics by constructing 2 opposing crowns and correcting the orientation of occlusal plane. The patient functions as normal at the one-year postinsertion as indicated by lack of gingival inflammation and stability of bony architecture around the dental implants (Figure 3).

CONCLUSION
The use of a silicone bite registration material expedites an analysis of the existing interarch distance and may reduce errors occurring from omission of careful diagnosis and treatment plan. Precise measurement of an available distance at chairside facilitates communication with patients for alternative treatment options, assists with consultations when using a multidisciplinary approach, and ensures successful treatment of partially edentulous patients in a timely manner.

References

1. Igarashi Y, Yamashita S, Kuroiwa A. Changes in interarch distance and condylar position related to loss of occlusal support for partially edentulous patients. A pilot study. Eur J Prosthodont Restor Dent. 1999;7:107-111.
2. Burns DR, Ward JE. A review of attachments for removable partial denture design: Part 2. Treatment planning and attachment selection. Int J Prosthodont. 1990;3:169-174.
3. Wakabayashi N, Mizutani H, Ai M. All-cast-titanium removable partial denture for a patient with a severely reduced interarch distance: a case report. Quintessence Int. 1997;28:173-176.
4. Alsiyabi AS, Felton DA, Cooper LF. The role of abutment-attachment selection in resolving inadequate interarch distance: a clinical report. J Prosthodont. 2005;14:184-190.
5. AbuJamra NF, Stavridakis MM, Miller RB. Evaluation of interarch space for implant restorations in edentulous patients: a laboratory technique. J Prosthodont. 2000;9:102-105.
6. Chaimattayompol N, Arbree NS. Assessing the space limitation inside a complete denture for implant attachments. J Prosthet Dent. 2003;89:82-85.

Dr. Oh is a clinical associate professor in the Department of Biologic and Materials Sciences Division of Prosthodontics at the University of Michigan School of Dentistry in Ann Arbor. He can be reached at (734) 615-2168 or at ohws@umich.edu.

Dr. Saglik is a clinical assistant professor in the Department of Biologic and Materials Sciences Division of Prosthodontics at the University of Michigan School of Dentistry in Ann Arbor. She can be reached at (734) 615-5019 or via e-mail at bernats@umich.edu.

Disclosure: Drs. Oh and Saglik report no disclosures.