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Shortened Dental Arch SDA

Occlusion seminar 2013
by

Alaa Otaibi

on 4 January 2013

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Transcript of Shortened Dental Arch SDA

Shortened Dental Arch (SDA)
By:
Ala'a AlOtaibi - For a long time the old dogma that tooth loss must always be replaced and a full complement of teeth is a prerequisite for a healthy masticatory system and satisfactory oral function was stated in practically all textbooks in prosthodontics and taught in most dental schools. the SDA concept is still considered controversial by many clinicians. It has been criticized because loss of molars is associated with:

(1) Higher rates of temporomandibular disorders
(2) Loss of occlusion stability (tooth migration, overeruption and increased wear).
(3) Insufficient chewing efficiency and performance.
(4) Relation between SDA and Periodontal health
(5) Compromised aesthetics. And until now there are many dentists suffered from the ‘28-tooth syndrome’ (Lewin) although numerous clinicians and researchers questioned this opinion,

Karlsen stated that the dental profession cannot ascertain the number of teeth that each individual needs.

De Van wrote, ‘Many times it is much better to preserve what is left instead of replacing what has been lost.

But according to recent research demonstrates that the historical approach to preserve or replace all 28 teeth to maintain occlusion has become obsolete (Mohl et al. 1988). Ash and Ramfjord (1995) delineate the modern move towards the physiologic occlusion by deviating from the theoretical ideal. And They stated physiology occlusion characteristics which are:
1- Absence of pathological processes
2- Satisfactory function – mastication, swallowing and speech.
3- Variations of form and function
4- Ability to adapt to structural changes The term ‘shortened dental arches’ (SDA) was first used in 1981 by the Dutch prosthodontist Arnd Ka¨yser for a dentition with loss of posterior teeth. The World Health Organization (WHO) in 1982 report that there is no need for prosthetic replacement if an individual has 20 teeth without occlusal disharmony causing myofascial pain or temporomandibular joint disorders. The concept of a minimum of 20 teeth is supported by studies on acceptable functional and aesthetics dentitions. SDA Concept Definition:
“The SDA concept is that adequate oral function can be maintained with a reduced dentition, consisting of 9 or 10 occluding pairs of teeth” (Kayser,1981) Objectives:
1- Provision of satisfactory oral function without the use of removable partial dentures.
2- Priority is to maintain anterior and premolar dentition in one or both jaws. Indication:
- Patient is able to function comfortably.
- Patient is able to chew food without pain.
- 10 occluding pairs with good prognosis.
- No evidence of trauma from occlusal contacts.
- Biological price of providing a RPD is too high.
- Limited possibilities for extensive restorative care.
- Patient is not motivated to pursue a complex treatment plan. Contraindication:
-marked dento alveolar relationship.
- para function.
- preexisting TMD.
- advanced pathological tooth-wear.
- advanced periodontal disease.
- the pt is under the age of 40 years. Requirement:
Requires anterior teeth + 4 occlusal units (symmetric loss) or 6 occlusal units (asymmetric loss) for acceptable function.

Opposing PM =1 unit, opposing molars = 2 units. The anterior teeth and the premolars can compensate for the function of the molars but the opposite is not true. The molars are affected most frequently and most seriously by caries and periodontal disease. while articles reviewing i noticed !! - Few studies are reported on the prevalence of temopromandibular joint (TMJ) problems in adults with shortened dental arches.

- According to clinical study done be Kyser and his colleagues the absence of molar support did not appear to provoke signs and symptoms of mandibular dysfunction. The presence of bilateral premolar support seemed to provide sufficient mandibular stability (1988).

- Other recent study done in 2003 concluded that no evidence that SDA provoke signs and symptoms associated with TMD. However, when all posterior support was unilaterally or bilaterally absent, the risk for pain and joint sounds seemed to increase. Occlusal stability is determination factors:

1- Periodontal support.
2- The number of teeth in the dental arches.
3- the interdental spacing.
4- Occlusal contacts.
5- Tooth wear. Occlusal stability: the absence of the tendency for teeth to migrate other than the normal physiologic compensatory movements occurring over time. Occlusal stability is thought to be reduced with extremely short dental arches, that is, only 0 to 2 pairs of occluding premolars.

While occlusal stability is reported to be greater with longer dental arches, that is, 3 to 4 occluding units, older patients generally experience increased changes in occlusal integrity. (Kayser, 2003) Distal tooth migration occurs in SDAs, and this may result in an increased anterior load which, in turn, increases the number and intensity of anterior occlusal contacts as well as the interdental spacing. In 1987 Kayser and his group found that there is a systemic effect of SDA has been found on interdental spacing but they conclude that this migration is within acceptable levels (Kyser,1987). In clinical study done by dutch group in 1994, they examined the occlusal stability at start, after 3 and 6 year and they found that:

1- SDA provided durable occlusal stability
2- changes in occlusal stability couldn't be prevented by free-end RPD
3- the combination of existing periodontal involvement and increased occlusal loading such as in a reduced dentition, approved to be a potential risk factor for further loss of teeth. In another study done by the same group in 2001 they conclude that SDA could provide long term occlusal stability and the occlusal changes were self-limiting, indicating a new occlusal equilibrium.
- Chewing ability been measured in study done in 2003 and the author conclude that shortened dental arches with intact premolar regions and at least one occluding pair of molars provided sufficient chewing ability.

- In study done in 1988 evaluating the chewing efficiency in SDA patients, the result was the chewing function, food perception, food selection and actual food consumption were hindered but within acceptable degree in SDA group. However, the oral function was not evidently improved by the insrtion of free-end RPD component of oral function:
Masticatory efficiency and masticatory ability literatures review done by T. KANNO in 2006
on shortened dental arches published by the Ka¨yser 1981 There is sufficient adaptive capacity to maintain adequate oral function in SDA when at least four occlusal units are left, preferably in a symmetrical position 1987 Although a systemic effect of SDA has been found on interdental spacing, it was concluded that this migration is within acceptable levels. 1988 the chewing function, food perception, food selection and actual food consumption were hindered but within an acceptable degree. The absence of molar support did not appear to provoke signs and symptoms of mandibular dysfunction. The presence of bilateral premolar support seemed to provide sufficient mandibular stability. Oral function was not evidently improved by the insertion of a free-end RPD. 1989 1990 absence of pain or distress, acceptable chewing ability and appearance of the dentition SDA appeared to provide sufficient oral comfort and free end RPD did not contribute to oral comfort. The combination of increased occlusal loading, as in a reduced dentition, and existing periodontal involvement appeared to represent a potential risk
factor for the loss of teeth 1991 SDA therapy was widely accepted by consultants in restorative dentistry in the UK, but not widely practised by the members of this group 1996 Most of the qualified members of staff were of the view that the SDA concept has a useful place in clinical practice. 1997 1998 96% of respondents agreed that the approach was acceptable in clinical practice 2003 SDA concept was considered an acceptable strategy for dentists in Tanzania. However, many dentists did not use it in clinical practice No evidence that SDA provoked signs and symptoms associated with TMD. However, when all posterior support was unilaterally or bilaterally absent, the risk for pain and joint sounds seemed to increase 2003 Signs of increased risk to occlusal stability seemed to occur in extreme SDA, whereas no such evidence was found for intermediate categories of SDA Shortened dental arches with intact premolar regions and at least one occluding pair of molars provided sufficient chewing ability 2003 2003 How to measure?
1- Masticatory ability: usually measured subjectively by patient interviewing,
2- Masticatory efficiency or performance: determined objectively by the dentist. - patient adaptation to changes in dental arch length with progressive loss of teeth is critical to successful treatment (Kayser,1981). Insufficient chewing efficiency and performance and relation with SDA: SDA Consideration (de Sac Frias V, 2004):

(i) The treatment goals are changing from the preservation of complete dental arches.
(ii) Anterior and premolar regions are functionally and esthetically strategic parts of the dentition. and are considered a priority in rehabilitation.
(iii) It is based on circumstantial evidence.
(iv) It does not contradict current theories of occlusion.
(v) It fits well with a problem-solving approach.
(vi) It meets the requirements of the normal oral function.
(vii) Molars are high-risk teeth for caries and periodontal diseases.
(viii) it reduce the need for complex restorative treatment in the posterior region.
- The combination of increased occlusal loading, as in a reduced dentition, and existing periodontal involvement appeared to represent a potential risk factor for the loss of teeth (Witter,1991).

- However, as indicated by the periodontal breakdown of premolars in some subjects with SDA, the combination of an existing severe periodontal involvement and a SDA is considered to be an unfavourable situation so the SDA is contraindication in existing periodontal problem. 5- Relation between SDA and Periodontal health: Dentists Attitude toward the SDA concept:


There was an obvious discrepancy between the theoretical and practical acceptance of SDA among dentists in many countries This demonstrates the difficulty in changing concepts that has once been learn in their school, which may obstruct a more general acceptance of the SDA approach. -SDA therapy is widely accepted by consultants in restorative dentistry in the UK but not widely practiced by members of this group. - Most of the qualified members of staff of restorative dentistry in Nijmegen were of the view that the SDA concept has a useful place in clinical practice. 96% of european prosthodontic association members agreed that approach was acceptable in clinical practice. And also in Tanzania the SDA concept considered an acceptable strategy for dentists. Recent assessment study done indian dentists concluded that specialist prosthodontists had an overall positive opinion toward the SDA concept. However, a good share among them observed that the patients considered for SDA expressed reservation (C Kumar, 2012). Thank you
Happy new year
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