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13Dental Tribune Middle East & Africa Edition | July - August 2014 academia tribune > Page 14 Pulp protection in today clinical practice: what about the role of materials? ByDimitriosTziafas,DDS,PhD V ital Pulp Protection and Therapy (VPPT) is the treatment that maintains pulp tissue in a healthy and functional state, whenever the dentin-pulp complex has been compromised by caries, trauma or restorative procedures. Pulp vitality and function is not es- sential for mature tooth survival. Mature permanent teeth with- out a vital pulp can survive for a long time after a successful endodontic treatment. However, the maintenance of pulp vital- ity in both mature and develop- ing teeth provides benefits. Ιn immature permanent teeth the vital pulp plays a central role for continuation of root develop- ment and strengthening of the root canal walls. Furthermore, with living pulp the capacity of the dentin-pulp complex of ma- ture permanent teeth to repair dentin defects and to retain the damaged complex as a func- tional unit, is maintained (Ber- genholtz 2005). The objective of VPPT is to minimize revers- ible inflammatory reactions, to allow pulp tissue healing and to protect it from exogenous stim- uli. It is well recognized that the damaged dentin-pulp complex requires protection from ther- mal conduction, chemical injury from the overlying restorative materials and further bacterial invasion from dentinal caries or oral bacteria leakage. It must be clarified here that protection from thermal conduction de- pends mainly on the conductiv- ity of the main restoration and is beyond the aim of the present article. In order to assess the therapeutic validity of the cur- rently used techniques and ma- terials in vital pulp protection, the biology of dentin-pulp com- plex is briefly reviewed. Biology of dentin-pulp com- plex The pulp and the dentin have been widely considered as a complex, on the basis that they form an embryological and functional entity. The den- tal pulp is a connective tissue entirely enclosed by dentin in the pulp chamber of the tooth. Dentin is a collagenous miner- alized tissue characterized by the presence of parallel dentinal tubules, forming a semiperme- able substrate which is regu- lated by the defensive function of the pulp and is effective in protecting the pulp from leaking bacterial threats and chemical irritants. Pulp structure is not uniform, consisting of the pulp periphery and the pulp proper. The peripheral pulp region has two interconnecting structures: the odontoblast layer, which is a layer of highly differentiated cells (odontoblasts) and a zone of biosynthetic product of od- ontoblasts (predentin). Odonto- blasts are responsible for forma- tion of predentin, which further form the mineralized structure of dentin. Odontoblasts form pri- mary dentin during tooth devel- opment, secondary dentin dur- ing the whole life of pulp tissue, and tertiary reactionary dentin during the pulp-dentin com- plex repair. Since odontoblasts are post-mitotic cells, they are not able to proliferate. In case of severe iatrogenic, or physi- cal trauma, odontoblasts can be replaced by newly differentiated odontoblast-like cells, which can repair minor defects of the den- tin-pulp complex by producing tertiary reparative dentin. The predentin reflects the activity of odontoblast layer and its role is crucial in maintaining the ho- meostasis in the pulp environ- ment. The existence of intact pulp periphery seems to be the most important requirement for the long-term survival of dental pulp tissue. A network of inflammatory reactions of pulpal cells, micro- circulation and nerves, directly affect the outcome of the funda- mental defensive mechanisms in the dental pulp. Whenever the basic structure of pulp pe- riphery is affected due to exog- enous stimuli, regardless of the existence of pulpal exposure, a typical wound healing process of the pulp tissue takes place. Complete reconstitution of the pulp peripheral region, by re- pairing the biosynthetic activity of survived odontoblasts and/ or replacement of lost odonto- blast with odontoblast-like cells might be considered as the op- timal end result of the healing process in the dentin-pulp com- plex. Under pathological condi- tions in the pulp-dentin complex a wide spectrum of atypic forms of matrices could be formed at the pulp periphery. These atypic matrices are characterized from porosity due to their osteotypic appearance and they are not effective in protecting the pulp from leaking bacterial threats and non-destructive external ir- ritants. Clinical and experimen- tal data clearly show that the presence and quality of the tis- sue reconstituting pulp periph- ery in the damaged dentin-pulp complex is important prognostic factor for the long-term suc- cessful outcome of VPPT. The clinical exploitation of dentino- genic potential of pulp tissue to reconstitute the structural and functional specificity of pulp pe- riphery represents the basis of modern VPPT (Tziafas 2010). Clinical variables in VPPT Numerous experimental and clinical studies carried out over than 6 last decades clearly showed that the successful out- come for vital pulp therapy is primarily depended on the type of injury, while other variables relatedtothestatusofthedentin- pulp complex and the treatment modality have also been inves- tigated. In general and beyond the role of treatment modality (techniques and materials), as the most important mechanism in effective long-term protection of the damaged pulp which will be analysed below, other critical factors have attracted attention. The reader of the present article is encourage to study a number of excellent papers reviewing experimental and clinical ob- servations as well as the level of evidence in relative clinical research, which have been pre- sented in the symposium held on 2007 in Chicago, Illinois, on “Emerging science in pulp ther- apy: new insights into dilemmas and controversies” jointly spon- sored by American Association of Endodontists and American Academy of Pediatric Dentistry (see Pulp Symposium, Journal of Endodontics, July 2008, Volume 34, Number 7S). It has been well recognized that the following critical factors are playing a role: a.Treatment indications As has been well demonstrated the VPPT is indicated for teeth with healthy pulp or reversible pulpitis. More particularly: Pulp protection, where a material is placed on the pul- pal surface of a dentinal cavity to act as a barrier between the permanent restoration and the sound dentinal base of the cav- ity, is indicated for a. Carious or non-carious tooth cavities with remaining dentin thickness less than 1 mm, no history of linger- ing or spontaneous pain, nega- tive percussion and palpation tests and positive pulp vitality test, and ii. Young permanent teeth after luxation trauma and crown fracture exposing the in- ner third of the dentin, regard- less of the presence of clinical symptoms. Indirect pulp capping is a technique in symptom-free teeth with deep carious lesion where a thin zone of carious dentin is remained to avoid pulp exposure. The ultimate goal of this technique is to complete caries removal just before the pulp exposure, where the poten- tial of pulp healing can effective- ly protect the pulp and stimulate tertiary dentin formation. Pres- ence of symptoms of irreversible pulpitis, positive percussion and palpation tests, or radiographic appearance of apical lesion con- sist absolute contra-indications for indirect pulp capping. b.Control of infection It is well-known that the pulpal wound healing depends largely on the extent to which infection can be avoided (Bergenholtz 2005). Thus, control of pre-op- erative and post-operative infec- tion, is a critical clinical concern with various VPTT techniques. a. Pathology of dentin-pulp complex. Among various clini- cal variables that have been ac- counted as factors playing a role in the outcome of the VPT, most important are issues related to different patho-physiology and healing potential of the dentin- pulp complex, as in primary, im- mature and mature permanent teeth : • Dental treatment of primary teeth must satisfy different goals than treatment for mature per- manent teeth, due to the limited life span of primary teeth and their possible relationship to the permanent tooth successor. The anatomical structure, patho- physiology, and diagnosis of en- dodontic diseases are different between primary and perma- nent teeth. However, recent ad- vances in primary tooth biology demonstrated that primary teeth have also a potential for wound healing and tertiary dentin for- mation. In light of these observa- tions VPPT in primary dentition has been already re-evaluated and similar techniques as in per- manent teeth are widely used (American Academy of Pediatric Dentistry, 2006). • Similarly, dental treatment