A Modified Partial Platform Technique to Retrieve Instrument Fragments from Curved and Narrow Canals: A Report of 2 Cases Narasimhan B, Vinothkumar TS, Praveen R, Setzer FC, Nagendrababu V. A (J Endod 2021;47:1657–1663

1. A Modified Partial Platform Technique to
Retrieve Instrument Fragments from Curved
and Narrow Canals: A Report of 2 Cases
Narasimhan B, Vinothkumar TS, Praveen R, Setzer FC, Nagendrababu V. A (J Endod 2021;47:1657–1663.)
Presented by
Dr Nadeem Aashiq
MDS 2nd year

2. Introduction
• Retained instrument fragments were reported in 3.3% of endodontic cases, of which
78.1% were nickeltitanium (NiTi) and 15.9% stainless steel instruments. Both NiTi and
stainless steel instruments have a higher fracture risk in the apical third (52.5%)
compared with the coronal (12.5%) and middle thirds(27.5%) of the root canal,there by
increasing the difficulty of retrieval.
• Fracture of NiTi rotary instruments may occur without any signs or warnings and may
lead to patient and clinician distress. In infected canals, a remaining instrument
fragment may impede complete debridement and thereby jeopardize the outcome.
• Retrieval of these fractured instruments is challenging for clinicians. Practical
alternatives to removing fragments are bypassing or leaving them for further
observation.
• The optimal management includes retrieval of fractured instruments with minimum
complications and adequate cleaning and shaping of the root canal space.

3. • Most contemporary instrument removal sequences are microscope aided and include
coronal access, radicular straight-line access to the instrument fragment using Gates
Glidden (GG) burs, a staging platform (SP), and retrieval using ultrasonics or a
microtube.
• GG drills are often modified by shortening them perpendicularly to their long axis to
facilitate preparation of the SP, which increases adequate fragment visualization and
creates space.
• However, the rigidity of GG drills may cause canal transportation in curved canals.
Flexible NiTi LightSpeed and ProFile instruments with modified tips were suggested as
alternatives but still produced transportations. The superelastic property of many NiTi
instruments may force a fragment against the outer canal curvature, often resulting in
excessive dentin loss with SP or microtube techniques.

4. • Complications may also include ledge formation, perforation, loss of root strength, or
vertical root fractures.
• Piezoelectric units with specific ultrasonic tips were described as an ideal choice to
expose the coronal third of fragments with minimal loss of tooth structure. Although
many techniques and devices have been recommended for removing separated
instruments from root canals, the retrieval success rate ranges between 55% and 87%.
This success rate decreases as the time required for the complete fragment removal
increases.
• This report presents 2 cases that illustrate a modified technique that allows for the
effective and efficient retrieval of broken instrument fragments named the “Burrow
platform (BP) technique.” The BP technique uses an angulated approach to the SP
rather than a straight access, allowing for minimized canal damage in situations of
slender roots with instrument fragments in the middle or apical thirds of curved canals

5. BP TECHNIQUE
• Preoperative Assessment
Preoperatively, diagnostic radiographs in different horizontal angulations and/or a
conebeam computed tomographic image should be acquired to analyze the
amount of dentin around the coronal third of the fragment.
Specifically, the root canal’s outer and inner walls containing the instrument
fragment in the smaller mesiodistal dimension should be evaluated to identify the
most favorable access to expose the head of the fragment (Fig. 1A). The technique
has 4 sequential steps.

6. Step 1: Coronal Access
A coronal access is prepared using a highspeed handpiece and a fissure carbide
or diamond bur with a safety tip to establish straight-line access to all canal
orifices, similar to a conventional SP technique (Fig. 1B).
Step 2: Radicular Access
While the conventional SP method that aims straight at the top of an instrument
fragment, the BP technique reaches the fragment at a slight angle. This angle is created
by placing the coronal aspect of the radicular access pathway into the outer curvature
wall of the root canal and the apical aspect above the instrument fragment into the inner
curvature wall.
Rather than relying on GG drills, this is achieved by a thin, tapered, and diamond coated
ultrasonic tip (e.g., ET20D, ET40D, Satelec, Merignac, France, or similar) driven by a
piezoelectric unit (e.g., Suprasson P5 Booster, Satelec) at a low power setting (3-5)
without water coolant is selected.

7. Coronal flare is established starting from the orifice level towards the head of
the fragment engaging the ultrasonic tip in an intermittent vertical motion.
Ultrasonic activation should not exceed 15 seconds to avoid heat
accumulation.
On its way apically towards the instrument fragment, the tip should be guided
to terminate at the inner curvature wall immediately adjacent to the
fragment. Radicular access will be complete once the top of the fragment
becomes visible (Fig. 1C and D).

8. Step 3: Partial Platform Preparation
• The BP technique only uses a partial platform of about 180 around the instrument
fragment, oriented toward the inner wall of the curvature. It should be prepared with the
same ultrasonic tip without irrigation.
• It is not recommended to extend the platform toward the outer curvature wall because
fragments tend to straighten and may produce undercuts into the dentin upon being
touched by an active ultrasonic instrument.
• In between ultrasonic instrumentation rounds, the canal space should be frequently
cleaned using ethanol for faster evaporation to remove debris and allow visual
inspection. Air cooling of the ultrasonic tip using the air/water syringe is advised (Fig. 1E).

9. Step 4: Exposure of the Fragment and Retrieval
• Smooth, tapered ultrasonic tips are used for troughing along the partial platform in a
counterclockwise motion to expose the coronal 2–3 mm of the fragment (Fig. 1F).
• Subsequently, activated ultrasonic tips are placed between the fragment and the inner wall,
enabling the instrument to loosen and disengage from the canal (Fig. 1G). Any suitable thin,
noncoated ultrasonic tip (eg, ET25 or ET40 [Satelec, Viry Chatillon, Ile-De-France, France] or
similar) may be used for this purpose.
• In situations in which retrieval attempts in dry mode are not immediately successful,
ultrasonically activated sodium hypochlorite or EDTA solution is recommended to enhance
loosening and disengagement of the instrument fragment.

10. CASE REPORTS
• Case 1
• A 60-year-old man was referred from a general dentist. He had discomfort in the
maxillary left molar region.
• Root canal therapy had been initiated about 1 week ago. The patient had no
contributing medical or family history. Intraoral examination revealed a dislodged
temporary restoration from the previous access on the maxillary left second molar.
• The tooth was percussion sensitive. Periodontal probing and mobility were within
normal limits. The preoperative periapical radiograph revealed adequately filled palatal
and distobuccal canals (Fig. 2A).
• The mesiobuccal canal had a separated rotary instrument fragment in the apical third
(ProTaper Gold S1; Dentsply Maillefer, Ballaigues, Switzerland). The diagnosis for the
maxillary left second molar was previously treated with symptomatic apical
periodontitis.

11. • A treatment plan for nonsurgical endodontic retreatment of the mesiobuccal canal was
laid out to the patient. The patient was informed about the associated risks, and
informed consent was obtained.
• The mesiobuccal root of the maxillary second molar was slender. The canal had a gentle
S-shaped curvature. The pathway for radicular access and the BP was planned using the
preoperative radiograph. The patient received local anesthesia of 2% lidocaine with
1:100,000 adrenaline (LOX 2%; Neon Laboratories Ltd, Mumbai, India) by infiltrating the
buccal and palatal mucosa.
• The tooth was isolated with a rubber dam, accessed, and the instrument fragment
removed using the BP technique. Figure 2B–F details the procedural steps. After file
removal, biomechanical instrumentation was completed using NiTi rotary files and
irrigation with 17% EDTA, saline, and 5.25% sodium hypochlorite. Calcium hydroxide
paste (Calcicur; VOCO, Cuxhaven, Germany) was placed as an intracanal medicament, and
the access cavity was sealed temporarily with a cotton pellet and Cavit (3M ESPE AG,
Seefeld, Germany).

12. • After 2 weeks, the patient presented again and was asymptomatic. Calcium
hydroxide was removed, and the canals were irrigated again and filled with gutta-
percha and AH Plus sealer (Dentsply Maillefer) using a warm vertical technique. A
coronal orifice seal for all canals was provided with 1 mm resin-modified glass
ionomer cement (Fuji II LC; GC Corporation, Tokyo, Japan).
• The remaining access cavity was restored with resin composite (Spectrum;
Dentsply International, York, PA) material (Fig. 2G). At a 2-year follow-up
appointment, the patient had remained asymptomatic. A radiograph did not show
any signs of a periapical lesion (Fig. 2H).

13. • Case 2
• A 45-year-old female patient was referred by an endodontist with a chief complaint of
intermittent dull pain in the lower right molar region.
• The patient had a history of about 5–6 appointments for root canal therapy in the same area
that was initiated by a different dentist about 1 month ago. There were 2 failed attempts to
retrieve and bypass fragments that had fractured previously.
• Intraoral examination revealed an access cavity with a visible instrument in the distal canal
of the mandibular right first molar with tenderness to percussion. Radiographs revealed
well-defined periapical radiolucency around the mesial root with 2 separated instruments
overlapping in the middle third of the mesial canals and 2 fragments in the coronal and
apical third of the distal canal (Fig. 3A).
• The mandibular right first molar was diagnosed as previously initiated therapy with
symptomatic apical periodontitis. The treatment plan was nonsurgical endodontic
retreatment. Standard anesthesia was administered, and the tooth was accessed as
described previously. Figure 3A–F shows preoperative, intraoperative, and postoperative
radiographs with a description of the procedural steps of fragment removal.
• After 2 weeks of intracanal calcium hydroxide dressing (Calcicur), the root filling was
completed (Fig. 3F). Orifices were sealed with flowable composite (Filtek Supreme Ultra; 3M
ESPE Dental Products, St Paul, MN) and the access cavity itself with a posterior composite
material (P60, 3M ESPE Dental Products). The patient returned for a 6-month follow-up
without any signs of pain or swelling

15. DISCUSSION
• A variety of techniques and devices were introduced for the retrieval of fractured
instruments, including the instrument removal system, the Masserann kit, and the
use of a spinal tap needle.
• General factors affecting the successful retrieval of instrument fragments are tooth
type, canal configurations and accessibility,and the fragment location in relation to
the curvature.
• The retrieval success rate dropped from 83% to 43% when canal curvatures exceeded
20 degree The canal curvatures for both cases in this report were moderate
according to Schneider’s classification, which favored treatment planning and
execution. Both cases were successfully managed using periapical radiographs.
• Cone-beam computed tomographic imaging has been recommended as an additional
option to periapical radiographs for the nonsurgical retreatment of separated
instruments. However, the added risk of radiation exposure should only be
considered when conventional 2-dimensional radiographs do not meet the clinical
requirements

16. • Ramos Brito et al stated that periapical radiographs are accurate enough to
evaluate fractured instruments irrespective of the presence or absence of a root
canal filling.
• The SP technique may be the most widely tried technique for orthograde
instrument fragment removal. Its reported success rate of complete fragment
removal from mesiobuccal canals was 88% for maxillary molars, 91% for
mandibular molars, and 100% for straighter palatal and distal canals.
• The BP technique differs in how radicular access is gained, especially by avoiding
GG drills. Complications associated with GG drills include transportation and
excessive dentin removal.
• Greater tooth structure loss may increase root fracture susceptibility. Moreover,
the use of GG drills at 8000 rpm increased the external root temperature up to
10.85C.29 Temperature increases beyond 10C for more than 1 minute may
significantly damage bone.
• Also, particularly in narrow and curved canals, using GG drills may lead to ledge
formation and perforations, especially on the outer canal wall.

17. • The use of a conventional SP technique may result in significant deviation away from the
head of the fragment if the location of a fragment is in the apical third Improper radicular
access and visualization may result in complications such as further fragmentation of the
instrument remnant or extrusion through the apex.
• Using ultrasonic instruments with a dental microscope demonstrated favorable results.
Long and thin ultrasonic tips as suggested for the BP technique allow for excellent radicular
dentin preservation.
• Diamond-coated tips are more efficient in removing dentin compared with noncoated tips.
Ultrasonic tips may fracture if they are operated at a high intensity. The BP technique
recommends a low power setting without coolant. Prolonged ultrasonic application will
lead to a temperature rise and potential damage to the surrounding tissues.
• Accordingly, ultrasonics were used intermittently for a maximum of 15 seconds per cycle to
avoid excess heat accumulation. Secondary fractures of fragments may result from
excessive heat generation, particularly for NiTi instruments. Although no water coolant was
applied to allow for constant visibility throughout ultrasonication, the use of liquids to
transfer ultrasonic energy to a fragment may expedite its retrieval.

18. Strength and Limitations
• Retrieving a fractured instrument is a stressful situation per se and requires sound
experience and clinical skills for the operator to avoid the associated complications.
• The BP technique provides operator control and may preserve radicular dentin and
minimize complications, and the required armamentarium is readily available in most
endodontic offices.
• The BP technique offers an efficient and targeted approach to instrument fragments
within a root canal. However, the individual time frame to remove an instrument will still
vary greatly depending on various factors, such as tooth type and root, the location of
the fragment in relation to the length and curvature of the canal, the patient’s mouth
opening, and the operator’s experience and skills.
• Visualization and illumination of a fragment with a microscope plays a significant role for
accurate placement of a vibrating tip using the BP preparation. A limitation of the BP
technique is the inability to retrieve fragments that remain invisible beyond a curvature.
• Failure to retrieve a fragment by the BP technique may warrant the additional use of
surgical means.

19. CONCLUSION
This case report demonstrates the use of the novel BP technique for the retrieval of
fractured instruments from curved canals. Further clinical investigations are required to
evaluate the success rate of instrument retrieval and the prognosis of teeth subjected to
the BP technique.