The Role of Apical Instrumentation in Root Canal Treatment: A Review of the Literature

Abstract

The issue of final apical preparation size remains controversial despite considerable clinical and in vitro research. The astute clinician must be aware of this research before choosing any instrumentation system because the informed clinician's decision must be guided by the best available evidenced-based information. This review article generated a Medline-based search strategy to disclose these studies and provides a critique and summary of the results.From the University of Pittsburgh School of Dental Medicine, Pittsburgh, Pennsylvania.Address request for reprints to Dean Baugh, DDS. E-mail address: baughdf@yahoo.com.Copyright © 2005 by the American Association of Endodontists T he most important objective of root canal therapy is to minimize the number of microorganisms and pathologic debris in root canal systems to prevent or treat apical periodontitis. This process of chemomechanical debridement, or cleaning of the root canal systems, has been described as the removal of all of the contents of the root canal systems before and during shaping. Grossman (1) described mechanical cleaning as the most important part of root canal therapy. Schilder (2) also considered cleaning and shaping as the foundation for successful endodontic therapy.Thorough instrumentation of the apical region has long been considered to be an essential component in the cleaning and shaping process. It was discussed as a critical step as early as 1931 by Groove (3). Simon (4) later recognized the apical area as the critical zone for instrumentation. Other authors (5, 6) concluded that the last few millimeters that approach the apical foramen are critical in the instrumentation process. Mechanical instrumentation and irrigation are sound endodontic principles and essential components of successful endodontics (7,8). Research has shown that mechanical instrumentation greatly reduces the number of microorganisms remaining in the root canal system. Mechanical instrumentation (9) has been shown to reduce bacterial count even without irrigants or dressings. A combination of mechanical instrumentation and irrigation (9, 10) further reduced the number of microorganisms by 100 to 1000 times. However, mechanical instrumentation with irrigation does not reliably disinfect an infected root canal system (11-14).Manufacturers developed nickel-titanium rotary instrumentation systems to facilitate the cleaning and shaping process. They are popular because of their apparent ease of use and reduced number of instruments. However, Spangberg (6) noted that the strong emphasis on reducing the number of instruments and limiting apical preparations to small sizes does not produce clean apical preparations in diseased teeth. Given this controversial and important topic, we conducted a broad-based Medline search of the literature to characterize the major factors involved in apical canal instrumentation. Table 1 provides the Medline search strategy used to identify relevant articles for this review. A secondary search was then conducted using the refere...

Effect of “Apical Clearing” and “Apical Foramen Widening” on Apical Ramifications and Bacterial Load in Root Canals

“…One study has suggested that a large diameter at the coronal orifice and a gradual taper towards the apical constriction offers the ideal instrumentation technique for thermo-plasticized obturation 31) . Indeed, many instrumentation techniques have been designed with the obturation phase in mind, rather than achieving optimal chemomechanical debridement of the infected root canal systems 1) . Apical clearing (a) removes existing and created dentin chips and soft tissue debris compacted in the apical region; (b) permits deeper placement of an irrigation needle for more effective final irrigation; and (c) enlarges and produces a more uniform shape in the apical region in order to facilitate placement and fit of the master cone 12) .…”

“…However, such studies have often been retrospective or included confounding factors, which has rendered their results inconclusive 1) . One recent clinical study found a correlation between apical width and the success of root canal treatment; an improvement in outcome was observed with increase in apical enlargement.…”

Calcium hydroxide fillings in curved canals: influence of apical enlargement using the rotary systems ProTaper, K3, and two hand instrumentation techniques

“…Although there is disagreement amongst endodontic specialists about the ideal apical diameter of root canal preparation, there is universal consensus that the ideal size depends on anatomical, microbiological, and mechanical factors 31,32 .…”

Apical prepration size in infected root canals

“…7,8) 따라서 치근단 3 mm 이내 지역인"critical zone"에서의 적절한 근관확대의 크기는 개개 치아의 근단공의 해부학적 형태와 직경 및 근관감염 정도를 토대로 신중하게 결정해야 한다. 9,10) How can we estimate the size of apical constriction as accurate as possible? …”