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Endodontics

Authors: Dr. Annil Dhingra
 

The services of a restorative dentist and an endodontist are often desirable for the successful treatment outcomes by a prosthodontist. Rarely are crowns or fixed partial dentures providedwithout initial therapy of a multidisciplinaryand often extensive nature.

During the initial data collection, attention must be directed toward potential endodontic and restorative needs of thepatient. The clinical examination should include vitalitytesting of all teeth in the dental arch. Tenderness to percussionshould also be noted. The teeth bearing carious lesions which have to serve as abutments for removable partial dentures must be restored and defective restorations replaced.As a general rule, conventional (or orthograde)rather than surgical (or retrograde) endodontics should be performed if possible not only becauseadditional trauma results from the surgical approachbut also because apicoectomy adversely affectsthe crown/ root ratio and thus the support of the planned prosthesis. All teeth with pulpal or periapical pathology are candidates for root canal treatment. There are also situations where elective root canal treatment is the treatment of choice which include :

Post space

A vital tooth may have insufficient tooth substanceto retain a jacket crown so the tooth mayhave to be root-treated and restored with a post retainedcrown.

Overdenture :

An overdenture is a complete or removable partial denture that has one or more tooth roots or implants to provide a support.The key factor to this procedure is the effective endodontics. This allows for a shortened dental crown, which creates adequate space for the overlying artificial denture tooth and denture base. Endodontic stabilizersare indicated for overdenture abutment teeth with extremely short roots, with conical roots, with minimumbone support and excessive mobility, and when anoverdenture is indicated and no other tooth is suitableas an abutment. The endodontic stabilizer converts a weak or questionable tooth into one that can serve as a functionaloverdenture abutment tooth.

Teeth with doubtful pulps :Root treatment should be considered for anytooth with doubtful vitality if it requires an extensiverestoration, particularly if it is to be a bridgeabutment. Such elective root canal treatment hasa good prognosis as the root canals are easy toaccess and are not infected. If the indications are ignored and the treatment deferred until the pulp becomes painful or even necrotic, access through the crown or bridge will be more restricted, and treatment will be significantly more difficult, with a lower prognosis.

Risk of exposure: Preparing teeth for crowning in order to alignthem in the dental arch can risk traumatic exposure.In some cases these teeth should be electivelyroot-treated.

Periodontal disease:

In multirooted teeth there may be deep pocketingassociated with one root or the furcation.The possibility of elective devitalisation followingthe resection of a root should be considered

Pulpal sclerosis following trauma: If progressive narrowing of the pulp space isseen due to secondary dentine, elective root canal treatment may be considered while the coronal portion of the root canal is still patent.1

CONSIDERATIONS REGARDING
ENDODONTICALLY TREATED TEETH

A prosthodontist often has to encounter endodontically treated teeth which need reinforcement with a post and a core in order to enhance the longevity and stress-bearing capabilities of the treated tooth/teeth. To achieve optimum results, the material used for the post should have physical propertiessimilar to that of dentin, can be bonded to the tooth structure, and biocompatible in the oral environment. It has been suggested that ET teeth are more brittle and may fracture more easily than non-ET teeth.2 It is believed that it is the loss of tooth structure from caries, trauma or both that makes ET teeth more susceptible to fracture.3 Some clinicians believe that a post should be placed into the root after endodontic treatment to strengthen or reinforce it. Some studies, however, point out that posts do not strengthen teeth, but instead that the preparation of a post space and the placement of a post can weaken the root and may lead to root fracture.4

Perhaps using new adhesive materials and technology, clinicians can bond the post securely to the dentin in the root canal space, the core to the post and the final restoration to the core and tooth.

The evaluation of whether a post is needed is based on how much natural tooth substance remains to retain a core buildup and support the final restoration after caries removal and endodontic treatment are completed. Many ET molars do not require a post because they have more tooth substance and a larger pulp chamber to retain a core buildup.5 Premolars have less tooth substance and smaller pulp chambers to retain a core buildup after endodontic treatment than do molars, and posts are required more often in premolars. A few studies have concluded that a post is not necessary in an ET anterior tooth with minimal loss of tooth structure.6 These teeth may be restored conservatively with a bonded restoration in the access cavity.7

Types of posts. There are two main categories of posts: custom-fabricated and prefabricated. Custom-fabricated cast gold post and core has been used for decades as a foundation restoration to support the final restoration in ET teeth. One six-year retrospective study reported a success rate of 90.6 percent using a cast post and core as a foundation restoration.8

Many practitioners prefer to use a cast gold post and core for ET anterior teeth. Its major disadvantage, however, is esthetics, as the metal shows through the newer all-ceramic restorations. One way to overcome this is to make a porcelain fused- to-metal post and core from a metal ceramic alloy to mask the shade of the metal.9

A photoelastic stress analysis of post design led to the conclusion that cement-retained posts and parallel posts were the least stressful to the root, but they also were the least retentive.10

Materials. Stainless steel, titanium and titanium alloys, gold plated brass, ceramic and fiber reinforced polymers have been used as materials for prefabricated posts. The ideal post and core material should have physical properties— such as modulus of elasticity, compressive strength and coefficient of thermal expansion—that are similar to those of dentin. In addition, prefabricated posts should not be corrosive and should bond easily and strongly to dentin inside the root using suitable cement so that the entire assembly of a post and core resembles the original tooth. Unfortunately, no such material is available to date even though fiber-reinforced posts look promising.11

Post length. Many authors have offered guidelines for determining the desired post length. It is not difficult to understand that the longer the post in the canal, the more retentive it is. However, increased post length also increases risk of fracture and perforation of the remaining root.12 It generally is accepted that the apical 3 to 6 mm of gutta-percha must be preserved to maintain the apical seal. Acceptable guideline for determining the post length include the following: the post length should be equal to the clinical crown length13; the post length should be equal to one-half to two-thirds of the length of the remaining root14; the post should extend to one-half the length of the root that is supported by bone.15

Post width. It is accepted widely that the post diameter makes little difference in the retention of the post. An increase in the post’s width, on the other hand, will increase the risk of root fracture.16 In general, the post width should not exceed one-third of the root width at its narrowest dimension, and clinicians should bear in mind that most roots are not perfectly rounded. A minimum of 1 mm of sound dentin should be maintained circumferentially, especially in the apical area where the root surface usually becomes narrower and functional stresses are concentrated.17

DO ENDODONTICALLY TREATED TEETH NEED CROWNS?

Sorensen and Martinoff (1984) reported the results of a retrospective study of 1,273 teeth and concluded that coronal coverage did not significantly improve the success of endodontically treated anterior teeth. This finding supports the placement of only resin in the access openings of otherwise intact anterior teeth. However some incisors and canines may need complete coverage crowns because of the presence of large and/or multiple previous restorations or unpleasant esthetic conditions that cannot be adequately addressed with more conservative forms of treatment. They also found a significant improvement in the clinical success of maxillary and mandibular premolars and molars when coronal coverage restorations were present to prevent fracture when occlusual forces attempt to separate the cusp tips. Another finding was if a premolar serves as an abutment, it receives significant lateral stresses, or the height of the clinical crown is tall in relation to the diameter of the root at the alveolar crest then a post is indicated. It was even found that premolars with access openings or conservative MOD preparations can be restored to near normal cusp fracture values with current dentin bonding and composite resin systems.

Rosenstiel et al (2001) noted that mandibular premolars and first molars with intact marginal ridges, and conservative assess cavities not subjected to excessive occlusal forces are possible exceptions to cuspal coverage.

INTERDISCIPLINARY MANAGEMENT OF
TEEH WITH EXCESSIVE WEAR

Patients with severe tooth wear may need extensiverestorative procedures to achieve appropriate function,esthetics, and comfort. The existing vertical dimensionof occlusion (VDO) has to be assessed. Sometimes thevertical dimension has to be restored or increased. Occlusal wear is most often attributed to attrition,which is defined as the wearing away of one toothsurface by another tooth surface. Excessive occlusalwear can result in pulpal pathology, impaired function,occlusal disharmony, and esthetic disfigurement.Both diurnal and nocturnal bruxism have been foundto be related to extensive tooth wear.While most of the cases can be managed without increasing the vertical dimension of occlusion (VDO),in some cases, the vertical dimension has to be increased. The first consideration is to identify and try to eliminateor reduce the factors that may contribute to excessive wear of teeth. If tooth wear is moderate, aesthetics is acceptable,and if there is absence of tooth sensitivity, no activeintervention may be a reasonable treatment alternative. As apreventive measure, a hard plastic interocclusal deviceis fabricated and the patient is asked to wear it at night or during the day. It is critical to verify loss of occlusal vertical dimension(OVD) before the restoration of an increased OVD. Thedifferent techniques that can be used are: use of phonetics,the use of interocclusal distance, and the evaluation ofsoft tissue contours.

TURNER AND MISSILRIAN CLASSIFICATION
  • Category-1: Excessive wear with loss of VDO.
  • Category-2: Excessive wear without loss of VDO but with space available.
  • Category-3: Excessive wear without loss of VDObut with limited space.

In a typical category-1 patient (loss of VDO), theclosest speaking space is more than 1 mm and theinterocclusal space is more than 4 mm and has someloss of facial contour that includes drooping of the corners of the mouth. At first, a removablesplint or partial denture is placed and observedperiodically for 6–8 weeks. Fixed provisional restorationsare placed for another 2–3 months before planningpermanent restorations. Patients in category-2 typically have a long history of gradual wear. In these patients,the OVD is maintained by continuous eruption. Toothpreparation to establish retention and resistance formmay be critical because of shorter crown length.Gingivoplasty may be needed to gain clinical crownlength. Enameloplasty of opposing posterior teeth mayprovide some space for the restorative material.In patients of category-3, there is excessive wear ofanterior teeth, which has occurred over a long period,and there is minimal wear of the posterior teeth. Centricrelation and centric occlusion are coincidental with aclosest speaking space of 1 mm and an interocclusal distance of 2–3 mm. In such cases vertical space mustbe obtained for restorative materials. This can beaccomplished by orthodontic movement, restorativerepositioning, surgical repositioning of segments, andprogrammed OVD modification.18

ENDODONTICS OR IMPLANTS

Functional survival rates are high for implant and endodontic restorations however areas for improvement exist for both treatment modalities. Some dental professionals have raised the question thatoverzealous use of implants could cause a serious decline in the need for endodontic treatment. A healthy, endodontically treated toothwith an adequate ferrule generally demonstrated a good prognosiswhen supporting a single crown; the prognosis diminishedwhen these teeth were used as supporting abutments, particularlyin longer spans. Clinicians must still rely primarily uponclinical judgment and patient expectations to determine thevalue ofmaintaining or removing compromised endodonticallytreated teeth and replacing them with implants.Endodontic treatment should be given priority in the treatment planning for periodontally sound teeth with pulpal or periradicular pathology, whereas implants should be given priority in the treatment planning for teeth that are to be extracted because of nonrestorability or other reasons.19

REFERENCES
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