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Authors: Dr. Rathika Rai, Dr. Soniya C, Dr. M.A. Eswaran

INTRODUCTION

The traditional approach in prosthetic dentistry is to replace missing, damaged and severely decayed tooth either by a removable prosthese or by fixed prostheses to improve masticatory function. Initially it is necessary to replace all missing tooth, but that concept has changed by shortend dental arch. The concept of shortened dental arch (SDA) was proposed by ArndKayser in 1981 to refer a functionally acceptable occlusal model with a reduced dentition in the posterior segments.This condition is frequently seen in molars, are often lost by caries and periodontal diseases. Due to reduced support, however, shortened dental arches may be susceptible to occlusal instability. This might result in a condition which has been described as occlusal collapse or collapse of the bite. To provide care for the partially-dentate or edentulous patient, the dentist must consider a number of factors, such as oral functionality, vertical dimension, occlusion, maintenance of hard tissue, and temporomandibular joint health, as well as patient comfort1.

  1. The term ‘shortened dental arches’ (SDA) was first used in 1981 by the Dutch prosthodontistArndKayser for a dentition with loss of posterior teeth
  2. The shortened dental arch (SDA) may be defined as having an intact anterior region but a reduced number of occluding pairs of posterior teeth.
Classification2

A classification for the shortened dental arch, suggested by “KAYSER”,according to the number of teeth remaining in the arch and symmetry of shortening is as follows :-

Symmetrically shortened dental arch (SSDA) Extremely Shortened Dental Arch with Asymmetry (ESDA)



Present Criteria for Healthy and Physiologic Occlusion (developed by Mohl et al, Ash and Ramfjord)3
  1. Maintainence of social and biologic functions like self esteem, esthetics, speech, mastication, taste and oral comfort
  2. Pathologic manifestations to be absent
  3. Satisfactory functioning of dentition
  4. Variability in form and function
  5. Adaptive capacity of oral environment to changing situations
Need for replacing lost teeth4
  1. To prevent occlusal instability
  2. To prevent craniomandibular dysfunction
  3. To restore oral function
  4. To preserve esthetics
Oral functionality

In 1992, the World Health Organization stated that the retention, throughout life, of a functional, esthetic, natural dentition of not less than 20 teeth and not requiring recourse to prostheses should be the treatment goal for oral health. It is not possible, however, to quantify the minimum number of teeth needed to satisfy functional demands because these demands vary from individual to individual. Furthermore, both dental and financial considerations strongly influence the treatment plan, and, in fact, dental arches comprising the anterior and premolar regions meet the requirements of a functional dentition.5,6 It follows that the replacement of missing molar teeth by cantilevers, resin-bonded fixed partial dentures, implant-supported prostheses, or distal extension removable partial dentures may amount to over-treatment for patients with shortened dental arches



Masticatory efficiency

Masticatory efficiency and masticatory ability are important components of oral functionality, but patient adaptation to changes in dental arch length with progressive loss of teeth is critical to successful treatment. 2 broad categories, subjective and objective evaluations.1 Subjective masticatory function or masticatory ability usually is evaluated through interviews with patients assessingtheir own masticatory functionality. Objective evaluation of masticatory function or masticatory efficiency commonly involves measurement of the patient’s ability to grind food.The literature indicates that masticatory ability closely correlates with the number of teeth and is impaired when there are fewer than 20 uniformly distributed teeth in the mouth.Subjects with 0 to 2 pairs of occluding premolars had severely limited masticatory ability1. Likewise, subjects with asymmetric arches and unevenly distributed teeth reported greater masticatory difficulty than subjects with complete dental arches. Differences in masticatory ability were exacerbated with harder foods. Overall, if the premolar region are intact and there is atleast 1 pair of occluding molars, the studies concluded that an SDA does not impair masticatory efficiency1. In contrast, there is severely impaired masticatory ability when the patient has a reduced number of occluding premolars or asymmetric arches, especially with hard food.However, that SDAs do not lead to alterations in food selection although patients only have sufficient masticatoryability, when 20 or more “well-distributed” teeth remain i.e when anteriorsand premolars are present.Thus, impaired masticatory ability and associated changes or shifts in food selection are manifested only when there are less than 10 pairs of occluding teeth1.

Prosthodontic considerations

Prosthodontic considerations in patient treatment include occlusal stability, establishing the correct vertical dimension, and preserving the health of the soft and hard tissues as well as that of the temporomandibular joint. While occlusal stability can be defined as the absence of the tendency for teeth to migrate other than the normal physiologic compensatory movements occurring over time7,8,9 A better definition may be the stability of tooth positioning relative to its spatial relationship in the occluding dental arches.Occlusal stability is determined by a number of factors, including periodontal support, the number of teeth in the dental arches, the interdental spacing, occlusal contacts, andtooth wear.Occlusal stability is thought to be reduced in extreme shortened dental arches of 0-2 occluding pairs and greater in 3-4 occluding pairs.

Patient comfort

Patients must adapt functionally and psychosocially to dentures, and some may never achieve this goal. As a result, while the inserted prosthesis may satisfy all objective criteria regarding fit, quality, and appearance, a patient may be dissatisfied and occasionally intolerant of a denture based on subjective evaluation of comfort, functionality, and esthetics.

Requirement of occluding pairs for satisfactory oral function
Age (in years) Functional level Occluding Pairs
20 – 50 I(Optimal) 12
40 – 80 II(Sub-optimal) 10 (SDA)
70 – 100 III(Minimal) 8 (ESDA)
 
Minimum number of teeth required to meet functional demands
Biting 12 anteriors + 4 premolars
Esthetics 12 anteriors + 4 premolars in maxilla
Mastication 8 premolars + 4 molars
Speech 12 anteriors
Mandibular stability 12 anteriors + 8 premolars + 4 molars
  • Criteria for patient selection according to Kayser4,10
    1. Progressive caries and periodontal disease confined to molars.
    2. Good long term prognosis for anterior teeth and premolar .
    3. Financial or other limitations of dental care.
  • Contraindications for patient selection4,10
    1. Patient below age of 50years.
    2. Anterior open bite.
    3. Severe maxillomandibular discrepancy such as Class II and Class III.
    4. Parafunctionalhabits .
    5. Preexistingcraniomandibulardysfunction .
    6. Marked pathological tooth wear .
    7. Marked reduction in alveolar bone support .
  • Advantages of SDA3,11
    1. Simplification of extensive restorative management .
    2. Easy maintenance of dentition both for patient and dentist .
    3. Simplification of oral hygiene maintainence .
    4. Good prognosis for remaining teeth.
  • Prognosis of SDA depends on12
    1. Maintenance of good oral health .
    2. Maxillomandibularrelation .
    3. Age of patient.
    4. Periodontal status of anterior and premolar teeth.
    5. Adaptive potential of TMJ Occlusal stability.
Summary

The literature indicates that dental arches comprising the anterior and premolar regions meet the requirements of a functional dentition. By offering the partially dentate patient a treatment option that ensures oral functionality, improved oral hygiene, comfort, and possibly reduced costs, the shortened dental arch (SDA) treatment approach appears to provide an advantage without compromising patient care. The SDA concept does not contradict current occlusion theories and appears to fit well with the problem-solving approach favoured in modern dentistry. Advocating the SDA offers some important advantages, one of which may be a decreased emphasis on restorative treatments for the posterior regions of the mouth.

References
  1. DeboraArmellini et al. The shortened dental arch: A review of the literature. J Prosthet Dent 2004;92:531-5
  2. Kayser AF. Limited treatment goal – shortened dental arches. Journal of Periodontology 2000: 1994;4:7-14.
  3. Witter DJ, Allen PF, Wilson NH, Kayser AF. Dentist’s attitude to shortened dental arch concept. J Oral Rehab 1997;24:143-7.
  4. Vemie A, Fernandes, VidyaChitra. The shortened dental arch concept. A treatment modality for partially dentate patient. JIPS 3.134-9.
  5. World Health Organization. Recent advances in oral health. WHO Technical Report Series No. 826. WHO, Geneva; 1992. p. 16-17.
  6. Witter DJ, De Haan AF, Kayser AF, Van Rossum GM. A 6-year follow-up study of oral function in shortened dental arches. Part II: Craniomandibular dysfunction and oral comfort. J Oral Rehabil 1994;21:353-66.
  7. Mohl ND. Introduction to occlusion. In: Mohl ND, Zarb GA, Carlsson GE, Rugh JD, editors. A textbook of occlusion. Chicago: Quintessence; 1988. p. 15-23.
  8. Sarita PT, Kreulen CM, Witter DJ, van’t Hof M, Creugers NH. A study on occlusal stability in shortened dental arches. Int J Prosthodont 2003;16:375-80
  9. Witter DJ, van Elteren P, Kayser AF. Migration of teeth in shortened dental arches. J Oral Rehabil 1987;14:321-9.
  10. Jepson NJ, Allen PF. Short and sticky options in treatment of partially dentatepatient. Br Dent J 1999;187:646-52.
  11. Allen PF, Witter DJ, Wilson NH. The role of the shortened dental arch concept in the management of reduced dentition. Br Dent J 1995, 178, 355- 8.
  12. Kayser AF. Shortened dental arches and oral function. J Oral Rehab 1981:8:457- 462.

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