Root-End Resection, Retro-Preparation and Retrograde Root-End Filling Materials

CONTENTS

1 Introduction

2 Historical Perspective

3 Review of literature

4 Root end resection
A) Definition
B) Indications
C) Extent of root end resection
D) Bur selection
E) Angle of resection

5 Root end preparation
A) Technique of root end preparation
B) Long axis preparation
C) Preparation perpendicular to the cut root surface
D) Vertical slot preparation
E) Transverse slot preparation
F) Reverse canal instrumentation
G) Recent advances
H) Ultrasonic root end preparation
I) Laser root-end preparation

6 Root end filling materials
A) Classification
B) Ideal requirements
C) Role of root end filling

7 Materials
A) Amalgam
B) Silver cones
C) Gallium alloy
D) Gold foil
E) Gutta-percha
F) Zinc oxide eugenol
G) Zinc phosphate cement
H) Polycarboxylate cement
I) Glass ionomer cement
L) IRM (Intermediate Restorative Material)
M) Cavit
N) EBA Cements
O) Super EBA Cement
P) Diaket
Q) Composite resins
R) Retroplast
S) Geristore
T) Compomer
U) Mineral trioxide aggregate (MTA)
V) Biodentine
W) VERRM
X) Ceramicrete
Y) Bioaggregate
Z) Endosequence
AA) I Root BP
AB) Resilon/Epiphany System

8 Conclusion

9 Appendices

10 Bibliography

Words are inadequate to record my profound gratitude to Almighty for His countless blessings on me and my greatest regards to Him for bestowing upon me the courage to face the complexities of life and write this book successfully. I thank Him for my wonderful Parents, I am grateful to my dad Mr. Popatlal C. Phabyani for giving me the life I ever dreamed. I can’t express my gratitude for my mom Mrs. Yashoda P. Phabyani in words, whose unconditional love has been my greatest strength.

The constant love and support of my dearest sister Dr. Jyoti P. Phabyani, are sincerely acknowledged. Their inspiration and guidance kept me focused and motivated. To them I am forever grateful.

Dr. Pooja P. Phabyani

About the Author

Dr. Pooja Popatlal Phabyani

Senior Lecturer

BDS: from Vidya Shikshan, Prasarak, Mandal’s Dental College and Research Centre

MDS: in Conservative Dentistry and Endodontics from MGV’s KBH Dental College and Hospital, Panchavati, Nashik.

Currently working as Senior Lecturer at Swargiya Dadasaheb Kalmegh Smruti Dental College and Hospital, Nagpur.

PREFACE

This book is composed of ten chapters, and begins with the need for root-end resection. The succeeding chapters deal with the method and concept of root-end resection, root end preparation to receive the material, ideal requirements of the materials to be placed in the resected & prepared root-end. The concluding chapters describe various root-end materials available in the market so far and their properties, focusing on each individual material one by one, their advantages and disadvantages. This book will prove useful to Endodontists and researchers in the field of Endodontic surgeries & root-end filling materials. Also it would provide the undergraduate and postgraduate students an easy way of reference for covering a broad spectrum of Root-end filling materials that have been introduced into dentistry from eighteenth century till the latest materials available today, in lucid and simple language.

“Small things add to perfection but perfection is not a small thing”, well, inspite of sincere efforts, elements of human error or shortcomings are likely; the readers are welcome to point out all such mistakes and render valuable suggestions for further improvement and shall be greatly acknowledged.

DR. POOJA POPATLAL PHABYANI

INTRODUCTION

The major goals of root canal treatment are to clean and shape the root canal system and seal it in 3 dimensions to prevent reinfection of the tooth. Although initial root canal therapy has high degree of success, failures can still occur after treatment. Recent studies reported failure rates of 14%–16% for initial root canal treatment.[1] Lack of healing is attributed to persistent intraradicular infection residing in previously uninstrumented canals, dentinal tubules, or in the complex irregularities of the root canal system. The extraradicular causes of endodontic failures include periapical actinomycosis, a foreign body reaction caused by extruded endodontic materials, an accumulation of endogenous cholesterol crystals in the apical tissues, and an unresolved cystic lesion.

When conventional endodontic treatment is unsuccessful, surgical endodontic therapy is needed to save the tooth. The aim of periradicular surgery is to remove the cause of the disease and to provide a favourable environment for healing of the surgical wound. This procedure includes exposure of the involved apex, resection of apical end of root, preparation of class I cavity and insertion of a root end filling material.[2] The main objective of a root-end filling material is to provide an apical seal that prevents the movement of bacteria and the diffusion of bacterial products from the root canal system into the periapical tissues.[3] It has been proposed that an ideal root- end filling material should adhere to the preparation walls forming a tight seal in the root canal system. It should be easy to manipulate, radiopaque, dimensionally stable, non absorbable, nontoxic, well tolerated by the periradicular tissues and promote healing.[4] Also an ideal root-end filling material should not be affected by the presence of moisture. However, no filling material satisfies all the requirements of an ideal material.

For the improvement in endodontic surgery many solutions have been proposed to improve the clinical outcome. The first major change has been to use alternate root end filling materials in order to improve the apical seal and reduce toxicity. The second is the realization that a bevel on the root-end which improves surgical access, opens up many channels of communication (dentinal tubules) between the infected canal system and the surrounding tissues. Thus, beveling the root end allows intradental infection to cause persisting inflammation. The third improvement is thorough canal cleaning at the resected root-end using ultrasonic instruments that penetrate and shape the apical root canal. The fourth improvement is with the beginning of microsurgery era in 1990’s.[5]

Endodontic microsurgery, combines the magnification and illumination provided by the microscope with the proper use of new microinstruments. The advantages of microsurgery include easier identification of root apices, smaller osteotomies and shallower resection angles that conserve cortical bone and root length. In addition, a resected root surface under high magnification and illumination readily reveals anatomical details such as isthmuses, canal fins, microfractures, and lateral canals. Combined with the microscope, the ultrasonic instrument permits conservative, coaxial root-end preparations and precise root-end fillings that satisfy the requirements for mechanical and biological principles of endodontic surgery.[6]

Throughout the dental history, many materials have been introduced for root end filling in endodontic surgery. Metals such as gold-foil, silver posts, titanium screws, tin posts, amalgam and gallium alloy are some of the commonly used retro-filling materials. Cements and sealers such as ZnOE Cement, Intermediate Restorative Material (IRM), Super EBA, Cavit, Zinc polycarboxylate, Zinc phosphate and Glass Ionomer cements, Mineral Trioxide Aggregate, Calcium phosphate cement and Bone cement have also been employed for retro-fillings. Other commonly used materials are composite resin (with and without bonding agent) and gutta-percha. The less commonly used materials are laser, citric acid demineralization, ceramic inlay, teflon, mixture of powdered dentin & sulfathiazole and cynoacrylates. Recently, calcium silicate based materials like MTA, Biodentine, Bioaggregate, Endosequence Root Repair Material, iRoot BP Plus have been introduced. MTA is the most widely used material. It is considered to be a gold standard and is used to compare other materials with it .[7] In this library dissertation, emphasis will be laid on the root end filling materials previously used and which are being used.

Historical perspective

Gene Norman Barry et al (1976)[8] conducted an in vitro study on 400 roots. These were retrofilled with amalgam, polycarboxylate cements, Durelon, PCA, and Poly C respectively (n=100). The results showed that all cements performed inferiorly to amalgam, an already accepted retrofilling material.

Kaplan SD et al (1982)[9] investigated the apical seal of ninety extracted maxillary central incisors. Samples were divided into following groups retrograde amalgam, heat-sealed gutta-percha, and apicoectomy. The results showed that apical seal produced by cold-burnished gutta-percha allows less than half the penetration of the best of the other techniques and gave the most consistent results.

Szeremeta-Browar TL, VanCura JE, Zaki AE (1985) [10] conducted an in vitro study where single-rooted teeth were obturated with gutta percha and treated by various retrograde procedures and then compared the leakage of the various techniques. Statistical analysis indicated that lateral condensation produced a significantly better seal than any retrograde technique tested except retrofilling with Super EBA cement. Significantly worst seal was obtained with amalgam retrofill when compared to all retrograde techniques except cold- burnished gutta-percha following apicoectomy.

L Zetterqvist et al (1988)[11] compared microleakage of retrograde fillings of amalgam, glass ionomer cement and heat-sealed gutta-percha using dye-leakage technique. The results showed statistically significant higher degree of leakage of amalgam was demonstrated both after 24 hours and after 1year in teeth with radiographically dense root fillings. Statistical analysis also showed a significantly higher incidence of leakage of retrograde fillings of amalgam when the root canals were not filled with gutta-percha compared with retrograde filling of glass ionomer cement under the same conditions.

D. H. Edmunds and J.Thirawat (1989)[12] investigated the sealing ability of amalgam retrograde root fillings in vitro . The results were compared with a group of teeth filled with laterally condensed gutta-percha alone and another with laterally condensed gutta-percha plus root resection but with no retrograde filling. It was concluded that increasing the length of the amalgam filling did not improve the seal, also prior filling of the canal did not improve the seal, that retrograde root fillings were no worse than laterally condensed gutta-percha alone and that root resection of teeth filled with laterally condensed gutta-percha without retrograde filling was no worse than those filled with laterally condensed gutta-percha without root resection or retrograde root filling.

N. J. Mcdonald & T. C. Dumsha (1990)[13] compared retrograde apical leakage of four dentine bonding procedures with amalgam and hot burnished gutta-percha. Single-rooted teeth were obturated with gutta-percha and sealer and randomly divided into seven groups. Groups I and Group II were apically bevelled, and dentine bonding agent with composite resin and dentine bonding agent with unfilled resin was applied. Groups III, Group V and Group VI were apically bevelled and dentine bonding agent with composite resin, amalgam with cavity varnish and amalgam without cavity varnish was applied, respectively. Group IV had dentine bonding agent and unfilled resin applied tothe apical third of the root, and Group VII was apically bevelled and the gutta-percha hot burnished. The lowest mean leakage value was recorded in Group I, i.e. dentine bonding agent and composite resin, and the highest value was observed in Group VII, i.e. hot burnished gutta-percha.

T. R. Pitt Ford & G. J. Roberts (1990)[14] investigated the peripical tissue response to glass ionomer cement retrograde root fillings both in the presence and in the absence of fillings in the root canals of upper incisor teeth. One canal in each pair was filled with laterally condensed gutta-percha immediately after canal preparation. The other canals were prepared but left open to oral contamination. The teeth with root canal fillings showed little or no periapical inflammation. This study showed that adhesive retrograde root fillings were successful when the root canal was completely filled, but in the absence of a gutta-percha canal filling they failed to provide a seal.

E. Pissiot, G. Sapounas and L. S. W. Spangberg (1991)[15] compared the apical microleakage of amalgam with silver glass inomer cements. Four groups were made from fourty instrumented human teeth. First Group I -silver glass ionomer (SGI), Group II (SGII) with previous acid wash of the cavity; Group III (SGIII) in a previously acid washed cavity, protected with varnish; and Group (IV) zinc free amalgam. Statistical analysis showed that Group I had the least microleakage of all. It was concluded that SGI cement can be considered an alternative retrograde filling material.

B. S. Chong, T. R. Pitt Ford & T. F. Watson (1993)[16] investigated glass ionomer cement as a retrograde root seal total 40 extracted single-rooted teeth were selected. After performing apicectomy, samples were divided into four groups. In one group, a retrograde cavity was prepared, and the light-cured glass ionomer cement was placed as a retrograde root filling. No retrograde cavities were prepared in the three remaining groups. The light-cured glass ionomer cement was applied directly onto the apicected root face. Two different thicknesses of light-cured glass ionomer cement were used. Conventional glass ionomer cement was used in the last group. It was found that the light-cured glass ionomer cement was only suitable as a retrograde root seal when a thin layer (1 mm) was used.

Torabinejad M. et al (1994)[17] evaluated the apical marginal adaptation of orthograde and Retrograde root end filling by a dye leakage and scanning electron microscopic study. He gave a case report examining the apical adaptation of three orthograde fillings and four retrograde amalgam root end fillings from four radiographically successful teeth & one unsuccessful cases by using dye leakage and scanning electron microscopic methods.

W. P. Saunders, E. M. Saunders and J. L. Gutmann (1994)[18] studied the effect of three methods of root-end preparation following apical resection, on the apical seal of root-end fillings . Among 116 single rooted teeth, 3 groups were made: Group I a size 010 round bur was used to prepare an apical cavity 2-3 mm; Group II treatment as per Group 1 followed by a 60-seconds rinse with a solution of 10:3 (10% citric acid: 3% Fe2Cl3); and Group ID an ultrasonic retrotip was used to prepare a 2-3 mm deep apical cavity. Apical leakage was determined. Results showed that there was no significant difference in leakage between the groups at each time interval but there was increased leakage after 7 months. Cracking of the root surface was seen most often with the ultrasonically prepared roots.

T. R. Pitt Ford et al (1995)[19] studied the effect of Super-EBA cement as a root-end filling placed in teeth before replantation. The tissue response to Super-EBA was very mild, with only a few inflammatory cells being observed at the root end of 3 of the 8 roots filled. It was concluded that the tissue response to Super-EBA as a root-end filling is acceptable and considerably more favorable than that of amalgam.

Randolph P. O’ Connor, Jeffery W. Hutter and James O. Roahen (1995)[20] compared filling using two preparation technique and surgical microscopy. Sixty-four single rooted teeth were instrumented and obturated with gutta-percha. Teeth were randomly placed into four groups. Two groups received perpendicular root end resections, 3 mm deep ultrasonic root-end preparations, and either amalgam with varnish or Super EBA root-end fillings. Statistical analysis showed that, Super-EBA leaked significantly less than amalgam with varnish. There was no significant difference between the root- end resection and preparation techniques.

T. R. Pitt Ford et al (1995)[21] examined the effect of various zinc oxide materials as root-end fillings on 35 molar teeth. After extraction, root ends were resected, the canals contaminated with oral bacteria, root-end cavities prepared and fillings placed prior to replantation. Twelve roots were filled with IRM plus dentine chips, and six with Cavit. It is concluded that the tissue response to IRM with or without added dentine, Super EBA and Cavit was similar and mild; it was less severe than that to zinc oxide-eugenol and Kalzinol. All these materials had a much more favourable response than amalgam.

K. Gulabivala, A.A. Sayed & M. Wilson (1995)[22] studied the effect of retrograde cavity design on microleakage of amalgam fillings. Root resection, retrograde cavity preparation and filling with amalgam were done with extracted teeth. Three different designs of retrograde cavities were evaluated: the conventional class 1 cavity, the slot cavity and a previously unreported approach, the funnel cavity. Teeth were subjected to microleakage tests by placing radiolabelled lipopolysaccharide in a reservoir created coronal to the retrograde fillings. Leakage was quantified by measurement of radioactivity in scintillation counter. It was found that the retrograde fillings in the funnel cavity leaked significantly less than those in the other two cavity designs.

J. M. Whitworth & A. Q. Khan (1995)[23] evaluated the sealing ability of amalgam and Gallium Alloy Gallium Filling (GF) root-end fillings. Root- end cavities were prepared in 100 roots and filled with amalgam (50 teeth) or Gallium Alloy GF (50 teeth). The other 25 teeth from each group were incubated in Ringer's solution for 12 weeks before leakage assessment by the same method. Control teeth were included in each component of the study. Gallium Alloy GF provided a better apical seal than amalgam, both at baseline and following storage.

Pritesh M et al (1996)[24] did an in vitro study to assess the radiopacity of some potential root end filling materials (amalgam, Kalzinol, IRM, Super EBA, Vitrebond, Fuji II LC, Chemfil, gutta-percha) according to ISO 6876. The results showed that commercial glass ionomer cements (Vitrebond, Fuji II LC, Chemfil) had radiopacities below the international standard for root canal sealers (< 3-mm aluminum); three zinc oxide-eugenol cements (Kalzinol, Super EBA, IRM) had radiopacities equivalent to 5 to 8 mm aluminum; and gutta-percha had a radiopacity equivalent to 6.1mm aluminum. They concluded that the recommend root-end filling materials should have a radiopacity greater than that for root canal sealers.

Frank Gerhards and Wilfried Wagner (1996)[25] investigated the sealing ability of Amalgam, Harvard-cement, Diaket, Gold-leaf and Ketac- endo as retrofilling materials. Retrofills with ketac-Endo showed significantly less leakage compared with amalgam. There was no significant difference between the Amalgam and Diaket groups. The sealing ability of Harvard- cement and gold foil was lower than amalgam. It was concluded that retrograde filling with Ketac-Endo or Diaket can be considered as alternatives for amalgam.

B S Chong, Pitt Ford TR, Kariyawasam SP (1997)[26] evaluated the short-term tissue responses to two potential root-end filling materials, a light- cured glass ionomer cement (Vitrebond) and reinforced zinc oxide-eugenol cement (Kalzinol), which were compared with that of amalgam on 27 premolar teeth. The tissue response to amalgam fillings after 4 and 8 weeks was marked by moderate or severe inflammation, and extended > 0.5 mm in 10 out of 18 roots. In contrast, after 8 weeks, the majority of roots filled with Kalzinol showed little or moderate inflammation while the tissue response to Vitrehond was the best of the three materials, and was also less extensive.

Chun-Pin Lin et al (1998)[27] compared qualitatively the quality of the root-end preparation techniques prepared by a specially ultrasonic retrotip with those prepared in a traditional manner by a microhandpiece bur. Results showed that the ultrasonic root-end preparations produced more conservative and less perforated cavities than those made with conventional microhandpiece bur preperations.

Massimo Gangliani, Silvio Taschieri, raffaella Molinari (1998)[28] evaluated the apical root resected angle and the influence of cavity made by ultrasonic retrotips on the apical seal. Results showed that there was less infiltration both in dentin and in space between the filling and the dentinal wall in the group with 90[0] angle, but this difference was statistically significant only for the dentin. None of the samples showed leakage greater than the depth of the preparation. An apical cavity of 3 mm or more along the vertical axis can produce safe and effective seal.

Qiang Zhu (2000)[29] did an in vitro study on the adhesion of human osteoblasts to root-end filling materials (Mineral Trioxide Aggregate, composite, and amalgam) by scanning electron microscopy. The results showed that osteoblasts attached and spread on MTA and composite by forming a monolayer. Osteoblasts also attached on amalgam, but with a few cells spreading. In the presence of IRM, osteoblasts appeared rounded with no spreading. These results indicate that osteoblasts have a favourable response to MTA and composite resin compared with IRM and amalgam.

A. Rainwater, B. G. Jeansonne and N. Sarkar (2000)[30] compared the root-end preparations made with conventional ultrasonic (CUS) tips, diamond- coated ultrasonic (DUS) tips, and high-speed stainless-steel burs (HSB) for the incidence of microcracks and dye leakage. There was no significant difference among CUS, DUS, or HSB for the number or type of cracks.

Gerald J. Gray et al (2000)[31] compared the frequency of cracking and chipping in two groups, cadaver and extracted teeth, using an indirect resin technique. Preparations were performed using either a 33%2 inverted cone bur in a high-speed handpiece, or with ultrasonics using a CT-2 tip at either high or low intensity. In extracted teeth (n = 15), rotary instrumentation produced less chipping than either ultrasonic technique. Varying the intensity was not significant. There was no significant difference between any instrumentation group in cadaver teeth (n = 10) related to the amount of chipping.

REVIEW OF LITERATURE

Aqrabawi J et al (2000)[32] compared the sealing ability of amalgam, super-EBA cement and MTA when used as retrograde filling materials by using methylene blue dye penetration, leakage was seen under stereomicroscope at a magnification of X10. He found out that MTA cement provided a better seal than amalgam and EBA cement when used as retrograde filling but the extrapolation of this result into a clinical practice might be questionable.

Siquera JF et al (2001)[33] evaluated the ability of three materials – a resinous root canal sealer (sealer 26), reinforced zinc oxide-eugenol cement (IRM), and glass-ionomer cement (Fuji 9) in preventing bacterial leakage. The results showed that leakage was observed in all teeth of the Fuji 9 group, and in 95% of the teeth retrofilled with IRM. Sixty-five percent of the teeth retrofilled with Sealer 26 showed leakage. No difference was detected between Fuji 9 and IRM. However Sealer 26 was significantly more effective in preventing bacterial leakage when compared with other materials tested.

Howard M et al (2001)[34] evaluated the microleakage of various root- end filling materials such as amalgam, IRM, a dentin bonded resin, Super- EBA, and MTA using a fluid filtration system on 60 extracted teeth. The crowns were removed, the canals prepared, and root-end fillings placed. The samples were divided into two control and five experimental groups. The results showed that amalgam root-end fillings demonstrated significantly more microleakage than Super-EBA, dentin-bonded resin, or MTA. There was no significant difference between amalgam and IRM. However, IRM was also not significantly different from the other three groups.

Regan JD, Gutman JL, and Witherspoon DE (2002)[35] conducted an in vivo study to evaluate on a comparative basis the potential for Mineral Trioxide Aggregate and Diaket to promote periradicular tissue regeneration when used as surgical root-end filling material. Surgical access to the root ends was established and roots with filled with of either MTA or thickly mixed Diaket. The results showed that both Diaket and MTA can support almost regeneration of the periradicular periodontium when used as root-end filling materials in periradicular surgery on non-infected teeth.

Martell B. and Chandler NP (2002)[36] compared the electrical and dye leakage of three root-end filling restorative materials. Thirty three human canine teeth were prepared and filled using gutta-percha and sealer. Stainless steel rods into the root canals as anode and the teeth were varnished. The apical 3 mm of each teeth was resected, and a 3 mm root-end preparations were used MTA, Super EBA and IRM were used to restore 10 teeth eeach, and three teeth were varnished as controls. Following 24 hours setting, in blood the specimens were placed in 1% potassium chloride electrolyte, and leakage was recorded electrically for 20 days. The teeth were then submerged in methylene blue dye for 72 hours and then sectioned longitudinally, and scored for leakage by 6 examiners. In both the tests, MTA leaked significantly less than the IRM and Super-EBA restoration.

BS Chong, Pitt Ford TR , Hudson MB (2003)[37] conducted an in vitro study to assess the success rate of the root-end filling material, Mineral Trioxide Aggregate (MTA) with Intermediate Restorative Material (IRM). The root was resected perpendicularly and a root-end cavity was prepared ultrasonically and filled. The results showed that highest numbers of teeth with complete healing at both times were observed when MTA was used. However, statistical analysis showed no significant difference in success between materials at both 12 and 24 months.

Pereira CL et al (2004)[38] examined the sealing ability of MTA (MTA Angelus), reinforced Zinc Oxide Eugenol cement (Super-EBA), Vitremer and amalgam as root-end filling materials. Root canals of 80 human lower molar teeth were assessed, cleansed, shaped and obturated. Apexes were resected and cavities were prepared. Teeth were divided into 4 groups of 40 cavities, root- end filled with the materials, and immersed in methylene blue dye for 72 hours at 37[0] celcius. Roots were then sectioned transversally at each mm and evaluated under magnification, observing the dye penetration in each section. The crescent order of microleakege therefore obtained was MTA < Vitremer < Super-EBA < Amalgam. Higher leakage levels were observed in the first mm section of amalgam, vitremer when compared with the third mm section.

Khabbaz MG et al (2004) [39] Examined dentinal walls of root-end cavities for the presence of cracks and debris in correlation with the area of the root surfaces that remained after the resection. Preparation with smooth stainless steel ultrasonic tips produced few intradentin cracks. Dentin debris was more frequently seen in rotary preparations whereas gutta-percha remnants were seen mainly at ultrasonically prepared teeth.

Braga CX et al (2005)[40] evaluated the root-end sealing ability through dye leakage evaluation and the marginal adaptation through scanning electron microscopy of MTA-Angelus, Super-EBA, and Vitremer. Roots were sections transversally at each millimeter, in three sections and evaluated. The results showed that MTA leaked significantly less than Vitremer while Vitremer presented highest microleakage than others. Statistical analysis showed significant differences among the three materials in relation to the sealing ability (p<0.05). Concerning marginal adaptation, MTA-Angelus presented the best results (p<0.01). There were no statistical differences between Super EBA and Vitremer.

Hui CK et al (2005)[41] studied the physical properties and sealing ability of Viscosity Enhanced Root Repair Material (VERRM) and compared them with Mineral Trioxide Aggregate (MTA). The results showed that VERRM had physical properties similar to WMTA. VERRM and WMTA showed significantly greater dye penetration than GMTA when used as a root-end filling material. There was no significant difference in depth of dye penetration between VERRM and WMTA. Further development of VERRM is indicated to produce a biocompatible root-end filling material with superior handling characteristics.

Selcuk E et al (2006)[42] performed an in vitro dye leakage study to test the sealing ability of IRM, MTA, amalgam and zinc-phospate cement materials on forty single rooted extracted human teeth. After sectioning the roots longitudinally linear dye penetration in denting and cement was measured with a caliper under stereomicroscope. The specimens which received reverse IRM fillings showed significantly more dye penetration than the reverse amalgam (p = 0,022) and MTA fillings (p = 0. 0005) There was no significant difference between the specimens received reverse IRM fillings and zinc-phospate cement fillings (p = 0,123).

Igor T et al (2006)[43] compared the outcome of surgical endodontic treatment preformed using the traditional versus modern techniques. 110 patients were treated. The traditional technique included root-end resection with a 45 degrees bevel angle, and the modern technique with minimal or no bevel. Complete healing rate for the teeth treated with the modern technique (91.1%) was significantly higher than that for teeth treated using the traditional technique (44.2%).

Ayce UE et at (2006)[44] evaluated the antibacterial activity of leachable components of selected root-end filling materials: amalgam, ProRoot MTA (mineral trioxide aggregate), Intermediate Restorative Material (IRM), Super Bond C&B, Geristore, Dyract, Clearfil APX composite with SE Bond, or Protect Bond. IRM and ProRoot MTA were generally more potent inhibitors of bacterial-growth than the other tested materials.

Maltezos C et al (2006)[45] compared the sealing ability of Resilon, ProRoot MTA and Super-EBA as a root-end filling materials by a bacterial leakage method and found out that there is no statistical difference between Resilon-Epiphany system and MTA. Resilon-Epiphany system may be a viable option as a root-end filling material with good surgical isolation.

Kim S et al (2006)[46] found out the importance of evaluation of microsurgery. By using the state-of-the-art equipment, instruments and materials that merge biological concepts with clinical practice, microsurgical approaches produce predictable outcomes in the healing of lesions of endodontic origin.

Bernabe PFE et al (2007)[47] assessed the histological response associated with grey mineral trioxide aggregate (GMTA) and zinc oxide eugenol (ZOE) as root-end filling materials in teeth where the root canals were not filled and the coronal access cavities were not restored. GMTA was associated with less periapical inflammation and tissue response when used as a root-end filling material, even when no root filling or coronal restoration was present.

Pelliccioni GA et al (2007)[48] used ProRoot Mineral Trioxide Aggregate cement as a retrograde filling material without addition of water in an in-vitro study to evaluate its microleakage and found out that lack of water addition during the preparation of the cement did not affect the in-vitro sealing ability of ProRoot MTA.

Saini D, Nadig G, Saini R (2008)[49] compared the microleakage of three root end filling materials Mineral trioxide aggregate (MTA), Glass ionomer cement (GIC) and Silver GIC (Miracle Mix) using dye penetration technique under stereomicroscope on forty-five extracted human maxillary central incisors. Microleakage was found to be significantly less in MTA (0.83 mm) when compared to GIC (1.32 mm) and with Miracle Mix.(1.39mm).

Jordi GA, José MA, Cosme GE (2008)[50] performed a comparative study of the histological effects of silver amalgam versus compomer (DyractR) 90 days after placement as retrograde filling materials in experimental animals. The comparative study of the histological findings showed greater inflammation but also greater root cement growth in the compomer group versus the controls.

Galhotra V et al (2008)[51] evaluated microleakage comparing it with composite resin bonding agent, light cured glass ionomer cement and resin modified zinc oxide eugenol cement and found out that the sealing ability of MTA was better than composite resin bonding agent followed by light cured glass ionomer cement followed by zinc oxide eugenol cement.

Al-sa’eed dula R et al (2008)[52] evaluated the effects of six root-end filling materials, IRM, Retroplast, Geristore, Super-EBA, MTA for any leachable components from the materials for the cell viability and found out that IRM and MTA did not affect cell viability. High perspective liquid chromatography and atomic absorption spectroscopy showed that there was variation in the amount of leached components from the materials. The results showed that Retroplast, Geristore, Ketac Fil increased cell proliferation whereas Super-EBA decreased cell viability.

Norberto B et al (2009)[53] evaluated the time required and quality of retrograde cavity preparations using ultrasonics or ErCr:YSGG laser. The Waterlase showed the highest mean time for preparation of the root end cavities (p < 0.05), and there was no significant difference between the CVD and EMS groups. Fractures in the cavosurface angle occurred only in G2. G1 and G2 showed better scores for quality of preparation than G3. These results suggest that root end cavities should be prepared by ultrasonic tips.

Christiansen R et al (2009)[54] compared healing after root-end resection with a root-end filling of mineral trioxide aggregate (MTA) or smoothing of the orthograde gutta-percha (GP) root filling. Forty-four patients, average age of 54.6 years participated in a randomized clinical trial (RCT) comparing the MTA and GP treatment methods. Radiographs produced 1-week and 12 months post-operatively were compared after blinding for treatment method, and healing was assessed as complete, incomplete, uncertain, or unsatisfactory. Teeth treated with MTA had significantly better healing (96%) than teeth treated by smoothing of the orthograde GP root filling only (52%).

Torabinejad M et al (2009)[55] evaluated the outcomes of Nonsurgical Retreatment and and endodotic surgery. On the basis of the results, he found out that endodontic surgery offers more favourable initial success but nonsurgical retreatment favours a more favourable long-term outcome.

Thomas VA, Miguel PA, and Storgard J (2010)[56] did meta-analysis to review clinical articles on apical surgery with root-end filling in order to assess potential prognostic factors. The statistical method of Mantel-Haenszel was applied to estimate the odds ratios and their 95% confidence intervals. With regard to tooth-related factors, the following categories were significantly associated with higher healed rates: cases without preoperative pain or signs, cases with good density of root canal filling, and cases with absence or size #5 mm of periapical lesion. With regard to treatment-related factors, cases treated with the use of an endoscope tended to have higher healed rates than cases without the use of an endoscope.

Bedar M et al (2010)[57] worked out on whether the medication with calcium hydroxide could improve the marginal adaptation of Mineral Trioxide Aggregate apical barrier. He prepared and apically resorbed forty single rooted teeth using sulphuric acid for 4 days. Teeth were allocated into two groups according to whether calcium hydroxide was placed into the canals for one week (medicated group) or not (non medicated group) before placing a 4 mm apical plug in the canals. The roots were mounted on aluminium tube, the root apex was viewed from the top under the Scanning Electron Microscope and the maximum distance between MTA and the surrounding dentin was observed. The marginal gap widths in the medicated and the non medicated group were 70.2 micrometer and 130.o micrometer (p<0.05).

Butt N And Talwar S (2011)[58] evaluated various solvents 2% carbonic acid, 20% tartaric acid, 10% citic acid, 2% chlorhexidine gluconate, 5.25% sodium hypochlorite , normal saline for 10-20 seconds upto the intervals of 1 and 21 days of setting temperature for retrieval of Mineral Trioxide Aggregate and their effect on microhardness of dentin and found out that carbonic acid was effective in significantly reducing the surface hardness of WMTA on both 1 and 21 days followed by citic and tartaric acids (p<0.05).

Bird DC et al (2012)[59] evaluated the dentinal tubule penetration and biomineralization ability of a new root-end filling material Capasio comparing it with the mineral trioxide aggregate. The root-end preparations were filled with Capasio or MTA allowed to set for 4 weeks in synthetic tissue fluid and then sectioned at 1, 2 and 3 mm from resected surface. Depth of penetration was evaluated by using scanning electron microscopy. Next, capasio and MTA samples were prepared both in 1-g pellets and in root-end preparations. Samples were placed in synthetic tissue fluid (STF), allowed to set, and then characterized by using SEM, Energy dispersive X-ray analysis and X-ray diffraction techniques. Results showed that both capasio and MTA promote apatite deposition when exposed to synthetic tissue fluid (STF).

Aggarwal V et al (2013)[60] comparatively evaluated push-out bond strength of ProRoot MTA, Biodentine and MTA placement, furcation perforation repair and results showed that the push-out bond strength increased with time. The 24-hours push-out strength of MTA was less than that of Biodentine and blood contamination affecting the push-out strength of MTA plus irrespective of the setting time.

Balachandran A and Guruchandran (2013)[61] compared the sealing ability of bioactive bone cement, mineral trioxide aggregate and super-EBA as furcation repair materials in mandibular molars. Forty mandibular molars were randomly dividedaccording to the material used to repair perforations : Group I – MTA ; Group II- Bioactive Bone cement ; Group III-Super-EBA ; Group IV- Control ( furcation left unrepaired) all samples were subjected to the grade and retrograde methylene blue dye challenge followed by dye extraction with 65% nitric acid. Samples were analyzed using Ultraviolet Visible Spectrophotometer. The results showed that Bioactive bone cement provided an excellent seal for furcal perforation repair and at the same time it provided comfortable handling properties ahich could overcome the potential disadvantages as faced with MTA.

Anand S. et al (2014)[62] evaluated the effect of 15% disodium hydrogen phosphate on the immediate (after 72 hours) and delayed (after 2 months) sealing ability of MTA when used as an apical plug in an in-vitro study and found out that all the accelerators significantly accelerated the setting of WMTA, of which 23.1% chlorhexidine gluconate shared the best results of all followed by 15% disodium hydrogen phosphate and 10% calcium chloride. The sealing ability of all the experimental groups was significantly superior after 2 months as compared with that after 72 hours.

Bhardwaj A. et al (2014)[63] evaluated the antifungal activity of white colored MTA on different starins of candida albicans in-vitro and shared white MTA in concentration of 100 and 50 mg/dml is effective in inhibiting the several tested strains of C.albicans for periods upto 1 week.

ROOT-END RESECTION

DEFINITION:

Root end resection: The removal of the apical portion of the root and attached soft tissues. Also known as Apicectomy; apico osteotomy; apical amputation, partial root resection.[64]

Root end preparation: A method of sealing the apical extent of the root canal system through cavity preparation in the resected root and placement of a restorative filling material. Root end filling is also called as apical root fill, retrograde fill; retrofill; apical seal; reverse fill.[62]

INDICATIONS FOR ROOT-END RESECTION AND RETROGRADE FILLING

These are the following indications for the resection of the apical portion of the root during periapical surgery.

1. Removal of pathological processes: This includes resorptive processes, fractured root tips, contaminated root apices, root apices with tenaciously attached pathological tissue.
2. Removal of anatomical variations: The anatomical variations most commonly cited are accessory canals, apical canal bifurcations, apical deltas, lateral canals and calcification. These variations also include severely curved main canal system or C- shaped canal systems which cannot be properly cleaned, shaped, and obturated non surgically.
3. Removal of operator errors in nonsurgical treatment: Depending on the skill and expertise of the operator, and the difficulty of the case treated, non-surgical root canal treatment can be fraught with complications such as ledges, blockages, zips, perforations and separated instruments. When these situations occur it is usually recommended to obturate canal system and observe the case. If symptoms and signs ensue, root-end resection will often being necessary to remove these artificially created anomalies.
4. Enhanced removal of the soft tissue lesion: Root resection is often necessary to gain access to deeply place soft tissue around the root and to secure a biopsy.
5. Access to the canal system: In cases where the major canal systems are blocked due to post-core restoration and the apical portion of the canal has not been properly clean, shaped or obturated, root end resection will be necessary to manage the untreated portion of the root canal system.
6. Evaluation and creation of the apical seal: When the canal obturation is questionable, yet access to the entire root system for non-surgical retreatment is impractical or impossible.
7. Reduction of fenestrated root apices: This situation is common in maxillary premolars and molars. In order to eliminate the inflammation in the periosteum and provide an osseous covering of the roots, the apical segment of the root is removed or sculptured, placing the remainder of root within its bony housing.
8. Evaluation for aberrant canals and root fractures: Often, extra canals which transverse the length of the root, or split off the main canal in the mid-root or apical portion of the root, cannot be detected clinically or radiographically. In these cases the root canal obturation is often judged to be satisfactory and the etiology of failure is not evident. Root-end resection will potentially expose these aberrant communications, in vertical fractures, complete or incomplete can often be detected on the resected phase.[64]
9. Quality of apical seal is improved with the use of root-end filling material[65]:

According to El- Swiah and Walker[66] the most common biological factors were persistent symptoms and continued presence of periradicular lesion. The most common technical factors were the presence of post and core restorations, crown teeth without posts, irretrievable root canal obturating materials and procedural accidents.

CONSIDERATIONS PRIOR TO ROOT-END RESECTION

Three important factors that must be considered prior to performing a root-end resection include the type of bur or laser energy used for the resection procedure, how much root end should be removed, and the angle at which the root end should be beveled.

Extent of root-end resection:

Figure has been removed due to copyright reasons.

Fig.1: Extent of root-end resection

There is no agreement on how much of the root end should be resected (Fig.1). The extent of root end resection will be related to what is to be accom- plished with the surgical procedure and a number of variable factors that must be evaluated on an individual case-by-case basis. There is no predetermined amount of root-end removal that will be appropriate for all clinical situations. Routinely removing the entire root end apical to the most coronal extent of the bony crypt is not valid.[67] In some instances, more of the root end may have to be sacrificed in order to visualize and gain access to roots and other structures that lie lingual to the root in question. The shape of the root and the number and location of canals within the root may dictate the amount of root resection. When a root-end filling is required, enough of the root end must be resected so that the root-end filling material is surrounded by sound dentin. The amount to be resected may also be dictated by the location of perforation defects, ledges, separated instruments, and the apical extent of posts and orthograde obturating materials. The level of the crestal bone and the presence of periodontal defects will be major factors in determining how much root end can or should be resected. The conservation of root length should not compromise the goals of the surgical procedure.[68]

Bur selection: The bur type and choice of either a high -or slow-speed handpiece are important considerations in performing root-end resections.[64] According to gutmann[69] efficient root-end resection is accomplished with a high speed handpiece (45[0] or 90[0] angled handpiece) (Fig.2) and surgical length fissure bur. Ingle et al[64] recommended using a #702 tapered fissure bur or #6 or #8 round bur in a slow-speed straight handpiece for this procedure. They stated that a large round bur was best because it could be easily controlled and would prevent gouging and the formation of sharp line angles. In 1914 Buckley[70] recommended using multiple slow-speed fissure burs because they will clog in a moist field. Here also, gouging may occur with an irregular root face or sharp edges of root structure protruding, especially along the proximal walls. While Nichlolls[71] has stated that convex, flat and concave shapes to the root-end have all been advocated at one time or another and different instruments for cutting the root and recommended accordingly – there is no proof that any one of these gives a superior prognosis.[71]

In an ex vivo study, Nedderman et al[72] used the scanning electron microscope (SEM) to examine the resected root face and gutta-percha fillings following root-end resection with a variety of bur types using both hi- and slow-speed handpieces. They reported that the use of round burs at both speeds resulted in scooping or ditching of the resected root surface. Crosscut fissure burs at both speeds produced the roughest and most irregular resected root surfaces with the gutta-percha being smeared across the root face. The plain fissure bur, both at hi- and slow-speed, produced the smoothest resected root surface, and the plain fissure bur at slow-speed resulted in the least distortion of the gutta-percha.

Angle of the root-end resection: From biological prespective, most appropriate angle of root-end resection is prepebdicular to long axis of tooth.[73] Kim and Kratchman[6] noted that there is no biological justification for creating a steep bevel on the resected root end. They noted that the steeper the bevel, the more potential there is for damage to the buccal supporting bone.

Mehlhaff et al[74] in a study found that the average root-end bevel required when using rotary burs was 35.1%. The angle of root-end resections, when used in periradicular surgery, should be 30° to 45° from the long axis of the root facing toward the buccal or facial aspect of the root. The purpose for the angled root-end resections was to provide enhanced visibility to the resected root end and operative access to enable the surgeon to accomplish a root-end preparation with a bur in a slow-speed handpiece.

Several author[75],[76],[77] have presented evidence indicating that beveling of the root-end results in opening of dentinal tubules on the resected root surface that may communicate with the root canal space and result in apical leakage, even when a root-end filling has been placed. Ichesco and associates, using a spectrophotometric analysis of dye penetration, concluded that the resected root end of an endodontically treated tooth exhibited more apical leakage than one without root-end resection. Beauty[78], using a similar dye penetration analysis, examined apical leakage at different root-end resection angles. He reported that significantly more leakage occurred in those roots where the root-end filling did not extend into the prepared root-end preparation to the height of the bevel. If infection were to persist within the root canal system in an area not sealed by the root-end filling, the likelihood of bacteria and/or bacterial byproducts spreading outside of the root canal system is likely to occur. In another study using the fluid filtration method to determine leakage, it was found that there was a significant increase in leakage as the angle of the bevel increased.

Timers BG and Arrow-smith[77] examined the root surface following root- end resections at angles between 45° and 60° approximately 3 mm from the root apex. Using scanning electron microscopy, they reported the presence of an average of 27,000 dentinal tubules per mm[2] on the resected root face midway between the root canal and the dentino-cementum junction. To ensure complete resection a small amount of methylene blue dye can be applied to the root surface for 5 to 10 seconds. The area is then irrigated with sterile saline; the periodontal ligament will appear dark blue, highlighting the root outline.

According to Kim and Kratchman[6] with the introduction of the Endodontic microsurgery the bevel angle degree has been reduced to 0-10[0] which was 45-65[0] in the traditional approach (Fig.3). The advantages of reduced bevel are that it minimizes removal of the buccal plate, resulting in a more stable tooth and faster healing of the osteotomy. It also exposes fewer dentinal tubules, thus preventing excess leakage and contamination.

Figure has been removed due to copyright reasons.

Fig.2: Angle of root-end resection

Additional criteria employed to determine the angle and direction of the bevel include the root inclination and curvature, number of the roots, thickness of the bone and the position of the root in the bone and the arch.[79] The root end can be resected and beveled in one of the two ways. Once the root has been exposed, the bur and the handpiece are positioned at the desired angle and the root is shaved away, beginning from the root apex, cutting coronally. The bur is moved from mesial to distal at the desired angle, shaving the root smooth and flat, and exposing the entire canal system and root outline.

Figure has been removed due to copyright reasons.

Fig.3: Diagrammatic representation of root-end resection

The second technique is to predetermine the amount of root to be resected. The bur and handpiece are positioned at the ideal angle and the root apex is resected by cutting through the root from mesial to distal. More often than not, though, additional root structure must be shaved from the root until the desired exposure of the root face is achieved.[46]

ROOT-END PREPARATION

IDEAL RETROPREPARATION:

The definition of an ideal retropreparation is a class I preparation at least 3.0 mm into root dentin with walls parallel to and coincident with the anatomic outline of the pulp space.[51]

TECHNIQUE OF ROOT END PREPARATION:

Can be prepared by using either straight slow speed handpiece or miniature contra angle handpiece using small burs or by using ultrasonic root end preparation.

Many approaches to root end preparations have been advocated with variations based on access, root anatomy, armamentarium and surgeon expertise and philosophy.

i Class I cavity preparations down the long axis of the root within the confines of the canal.
ii A class I cavity prepared perpendicular to the root face at an approximate angle of 30 - 45° to the long axis of the root.[51]
iii A vertical slot type preparation is prepared perpendicular to the long axis of the root with a channel existing to the facial on buccal.
iv A transverse root slot is prepared from either the proximal surface or the buccal surface into the root to the depth of the lingual surface of the root canal before the root end resection.
v Reverse canal instrumentation is performed with modified root canal files.[80]

Long axis preparation:

Class I cavity is prepared in the root end with a small round bur, initially the hand piece head must be angled, once parallel to the long axis it continues to deepen the preparation to a depth of 3 - 5 mm.[81] The preparation is then undercut, with an inverted cone for retention.

Preparation perpendicular to the cut root surface:

This technique is one of the most common approach to root end preparation. Its use is dictated by access, root anatomy, armamentarium and surgeon experience. Any type of hand piece can be used with #1/2 or 1 round bur to create the initial preparations. This is followed by use of inverted cone bur for retention. Some surgeons prefer to use the inverted cone bur for the entire preparations.

Preparations commence with the placement of the bur perpendicular to the root face. The bur penetrates to an approximate depth of 2 - 3 mm, encompassing the entire outline of the visible canal system. Under cuts are made by lightly rocking the bur in a mesial and distal direction. Buccal retention is achieved with #12 or 14 wheel bur, which can be countersunk tooth buccally and proximally along the labial wall of the preparation.

The cross section the preparations will appear as an inverted cone perpendicular to the root face. On single canalled root the preparation will generally be oval to round, on dumbbell shaped depending on the shape of the cut canal system and root outline.

The multiple canalled roots with distinct foramina, each aperture can be cut as separate, class I preparation, when anastomoses are present class II approaches can be used. A slot type preparation is cut from the lingual to the buccal at an approximate angle of 45° to the cut surface,[82] exiting at the buccal most canal flush with the cut root surface. The greatest cavity depth is lingually placed.

Retention is achieved by moving the bur proximally during the cutting of the slot. However, this approach fails to consider a bulk of reverse filling material adjacent to the buccal canal and it lacks buccal retention.

The second option[53] is to prepare the buccal canal 1st, perpendicular to the root face, or if possible parallel to the long axis of the root. Subsequently 33 1/2 surgical length inverted cone bur is used for slot preparation and for retention. If necessary additional buccal retention is obtained with a wheel bur, when present anastomoses must be included in the root end preparation.

Vertical slot preparation:

When access is limited, the slot preparation is preferred when root is bended at a 45 degree angle then a tapered fissure bur is used to cut a 3-5 mm of slot along the facial aspect of the exposed root and then round bur is used to cut retentive groove. The final preparation gives the appearance of a keyhole.

Transverse slot preparation:

This technique is rarely advocated today for preradicular surgery. In this technique a sufficient amount of facial bone is removed to create direct access to the root. The preparation is made, prior to root end resection, from the proximal or directly from the buccal into the root to the depth of the lingual wall of the canal, depending on the tooth and its position in the arch. Retention is established internally, similarly to the vertical slot preparation, only rotated 90°. Once the preparation is filled, the tip of the root is shaved to the level of the amalgam filling at the foramen. This technique can either be used for access to buccal lingually wide roots or lingually placed roots, or with a softened gutta percha technique. Harnisch[83] claims this approach should be avoided because it requires the removal of excessive amounts of facial bone.

Reverse canal instrumentation:

This approach to root end preparation has been advocated when canal cleaning and shaping has not occurred through the crown or the canal space cannot be reached through the crown and periradicular surgery is necessary.[84] Indications that have been cited include poorly cleaned, shaped and obturated canal with a core present, coronal canal calcification with apical patency, separated instruments in the mid root, abutment teeth with artificial crown and short length which require surgery, and a perforation or ledge in the mid root portion which prevents access to the apical half of the canal.

This technique has been suggested for use with or without root end resection, K files or hedstrom files are bent at a 90° angle and held in a hemostat or special holder.[84] The patent position of the canal is cleaned and shaped for obturation with gutta percha points, injected cement or reverse silver points fills.[84]

Major errors of retropreparation with conventional techniques:

1. Retropreparation not placed down the longitudinal axis of the pulp Canal.
2. Retropreparation lack sufficient retention form.
3. Retropreparation lack proper extension to assure adequate seal
4. Retropreparation fails to include isthmus area
5. Retropreparation weakens delicate apical dentin by unnecessary over enlargement.

RECENT ADVANCES

Ultrasonic root end preparation:

Ultrasonic root end preparation technique was developed to address and solve the major inadequacies of conventional bur type retropreparations. Instead of using carbide burs to prepare dentin, small ultrasonic inserts were developed that enabled the clinician to prepare ideal retropreparations in nearly all clinical situations.

Performed correctly, ultrasonic root end preparations are easily and predictably placed down the longitudinal axis of the canals while being extremely conservative in the mesiodistal dimension.

Technique:

After the root end is resected, the lesion is removed and crypt hemostasis is achieved, the beveled root end is examined. Staining with methylene blue can be an invaluable aid in identifying the varied intricacies of the beveled surface. After an appropriate cavity design is planned, the entire extent of the preparation is scratched into the dentin by hand, using retrograde explores specially designed for this purpose. After etching a shallow groove into the dentin, a CT 5 ultrasonic tip or a UT 5 or slim Jim 5 tip is activated dry to deepen slightly the hand etched groove. The action of the tip is featherlike, similar to air brushing.

After the groove is depended to the point where the ultrasonic tip tracks back and forth in the groove without need for visual control, the tip is again activated, this time with water, and the tip moved back and forth rapidly without applying any noticible downward force. Ultrasonic root end preparations is a nearly passive type movement as opposed to bur type preparation, which require significant pressure.

Properly performed ultrasonic technique produces smooth, machined preparations that satisfy all the major requirements for ideal retro preparation. They are easily placed 3 mm down the longitudinal axis of the canal they have nearly walls for excellent retention and are conservative mesiodistal to preserve delicate root dentin. These preparations can confirm to the anatomic configurations present at the beveled root surface, whether simple or complex.

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