NATURAL ABUTMENT OR ORAL IMPLANT
Introduction
Abutment can be defined as ‘Tooth, root, or implant used to support and/or anchor a fixed or removable prosthesis’. 1
Dental implant can be defined as
An alloplastic material or device that is surgically placed into the oral tissue beneath the mucosal or periosteal layer or within the bone for functional, therapeutic, or aesthetic purposes. 2
To insert a graft or alloplastic device into the oral hard or soft tissues for replacement of missing or damaged anatomical parts, or for stabilization of a periodontally compromised tooth or group of teeth. 2
Fundamental differences between natural tooth or abutment are mentioned in Table 1
EVIDENCES IN SUPPORT OF PROPERLY TREATED NATURAL TOOTH OVER DENTAL IMPLANT
Properly treated natural teeth with healthy but markedly reduced periodontal support, are able to carry extensive fixed prosthesis for a very long time. They have survival rates of about 90%, if the periodontal disease was eradicated and prevented from re-occurring. The natural tooth is not an obstacle but a possibility for whether or not the treatment is to include implant placement. On the basis of assumptions that implants perform better than periodontally compromised teeth, teeth that could be saved and used as support, are extracted and replaced with implants, sometimes even on doubtful indications.’4 Peri-impantitis with loss of at least 2 mm of marginal bone, at one or more implants have been found to occur in 16-28% of implant patients after 5-10 years and with higher prevalence among patients with multiple implants.4
‘Oral Implants when evaluated after 10 years of service; did not surpass the longevity of natural teeth. They were not even able to surpass the longevity of those that are compromised, for either periodontal or endodontic reason. 5
Teeth with reduced marginal bone support have a better prognosis than implants with reduced marginal bone support. Such teeth should be preserved and shouldn’t be advised for extraction. No evidence exists to support an aggressive approach in early extraction of teeth, to preserve bone for later implant placement. 6
‘Partnership with commercial enterprise now dominates continuing education. Emphasis should be on preservation of properly treated natural teeth, free from periodontal disease. ‘ The integrity of purpose and scientific rigor that characterized the original osseo-integration clinical research has been largely discarded as passe’.7
‘The risk of yet another anarchic phase in treatment decision making has resurfaced. ‘New lecture circuit celebrities keep being recruited to promote osseo-integration's newer and expanded promises, albeit it falls significantly outside the technique’s initial oral ecological context.’ Safety, simplicity and prudence is being risked in clinical judgment.’ 7
A systematic review was carried out to compare the outcomes, benefits, and harms of root canal treatment and a crown, an extraction followed by an implant and crown, extraction and replacement with a denture and extraction without replacement. Based on available evidence it appeared that initial endodontic treatment has high long-term survival rate for periodontally sound teeth that have pulpal and/or periapical pathosis. Equivalent long-term survival rates were reported for extraction and replacement of the missing tooth with an implant-supported restoration. Substantially lower long-term survival rates were reported for extraction and replacement of the missing tooth with fixed partial dentures. For patients with periodontally sound teeth that have pulpal and/or periradicular pathosis, implant, endodontic, and fixed prosthodontic treatments had superior psychosocial outcomes, primarily with respect to patient self-image, compared to extraction without replacement or with replacement using a fixed partial denture. 8
Fundamental differences between endodontic and implant therapies are listed in Table 2
EVIDENCES IN SUPPORT OF DENTAL IMPLANT
Three major indications can be defined for the use of oral implants: 9
‘ To increase subjective chewing comfort
‘ To preserve natural tooth substance and adequate, existing reconstructions
‘ To replace strategically important missing teeth.
Studies have demonstrated that the installation of a small number of mandibular implants (two to four) in edentulous mandibular ridge showing severe resorption, may dramatically improve chewing function. If natural tooth substance can be preserved, oral implants are ideal abutments, but the preparation of a tooth to serve as an abutment for a crown or a bridge anchor opens about 40,000 to 70.000 dentinal tubules per mm2, which in turn will compromise the vitality of natural tooth. 9
It has been documented that only a small proportion of abutment teeth will lose their vitality immediately as a sequelae of the preparation procedure but approximately 10% of all vital abutments will lose their vitality after 10 years 10;11;12.
Hence, the most biologically sound way of replacing a missing tooth is an implant installation avoiding tooth preparation. Loss of a strategically important natural abutment or tooth may lead to costly, time consuming and complex restorative treatment planning. Installation of an oral implant may be performed for prosthetic reconstructions. In such cases presence of bone dehiscence and inadequate bone volume may require bone augmentation procedures. 9
Di Fiore et al.13 who reported that dental students preferred implants more than dental faculty, and the newer graduates on the dental faculty opted for implants more than more experienced dentists that may be due to the fact that implants are a relatively recent inclusion in the dental curriculum.
Predictors of implant success or failure are listed in Table 3
Conclusion
Unless affected by oral diseases or service interventions, teeth will last for life. Many retained teeth ae thus an indicator of positive oral health behaviour throughout the life course. Tooth longevity is largely dependent on the health status of the periodontium, the pulp or periapical region and the extent of reconstructions. Multiple risks lead to a critical appraisal of the value of a tooth and it’s longevity in oral cavity.5
When evaluated after 10 years of service, oral implants present with a longevity; that does not surpass that of even compromised, but successfully treated and maintained teeth. Oral implants have become valuable, indispensable, and welcome treatment alternatives to traditional dental reconstructions.
If subjective chewing comfort has to be increased, natural tooth substance or existing satisfactory reconstructions have to be preserved or strategically important missing teeth have to be replaced; oral implants are best used as abutments in restorative dentistry. Oral implants should only be incorporated in oral cavities with healthy conditions, i.e. a thorough periodontal treatment has to precede restorative therapy. 9