Damage to root dentin during retreatment procedures.

Purpose: to assess the influence of retreatment procedure on the appearance of defects on the root canal walls

Materials and Methods:

•N = 200 extracted mandibular premolars were standardized.

•4 groups (n= 50, average diameter was 0.7 mm)

•Teeth were examined to exclude presence of cracks.

•Group (1): left unprepared. Group (2-4): C/S with ProTaper to F4. Passive Ultrasonic was used at the end. All groups (2-4) were filled with lateral condensation (MAF= 40, spreader with controlled load 2 kg, AH26 sealer). oGroup (1): unprepared and no obturation.

oGroup (2): Prepared, obturated but no retreatment.

oGroup (3): Retreated with ProTaper retreatment files (D1, D2, D3) with chloroform.

oGroup (4): Retreated with H-files + chloroform.

•Part One: Evaluation under operating microscope. Part II: roots were sectioned horizontally and examined under stereomicroscope.

Most highlighted Results: 

  • Group (1): unprepared and no obturation: No defects
  • Group (2): prepared and obturated: almost 30% defects were found
  • Group (3): prepared and obturated, then retreated with ProTaper: almost 38 % defects were found
  • Group (4): prepared and obturated, then retreated with  H-file: almost 55% defects were found üGroups 3 and 4 were compared to group 2. No difference between groups 3 and 4

Clinical significance: The lower success noted in retreatment may be attributed to further damage to roots resulted from the procedure.

Analysis of temperature rise and the use of coolants in the dissipation of ultrasonic heat buildup during post removal.

Summary: 

Purpose:  to calculate probabilities for tissue injury and to measure effective- ness of various coolant strategies in countering heat buildup produced by dry ultrasonic vibration during post removal.

N= 10 single canal (premolars or canines).

Materials & Methods:

  • All teeth were standardized; access, C/S, and obturation.
  • Post spaces were prepared 10 mm in depth with #5 ParaPost drill. Posts cemented with Panavia 21. adhesive resin cement .
  • Two K-type Chromega-Alomega thermocouples attached to tooth and post. Data set consisted of cervical and apical measures of temperature increase at 1-second intervals from baseline during continuous ultrasonic instrumentation until a 10oC increase in temperature at the cervical site was registered and the teeth were allowed to cool under the assistance of 5 cooling methods. : (1) air only from 3-way syringe; (2) water spray from 3-way syringe; (3) small cotton pellet #3 sprayed for 2 seconds with Endo-Ice and applied; (4) large cotton pellet #0 sprayed for 2 seconds with  Endo-Ice applied to the post; (5) cooling by ambient air.

Most highlighted Results: 

1.Injurious temperatures are easily reached in less than 1 minute during dry ultrasonic instrumentation of metallic posts.

2.Endo-Ice applied with large cotton pellet was the most efficient coolant method, but this was not statistically significant over less costly options. 3.The 4 active coolants used in this study were all effective in reducing the probability of temperature damage caused by instrumentation.

Clinical significance: Cycles of short instrumentation times with active coolants are effective in reducing the probability of tissue damage when teeth are instrumented dry.

Analysis of Heat Generation Using Ultrasonic Vibration for Post Removal

Summary: 

Purpose: to answer the question regarding temperature changes occurring along the post and the root surface with the use of ultrasonic instrumentation for post removal.

n:  10 max CI and LI

Materials/Methods:

•Canals were prepared using Profile rotary instrument in a crown down tech and obturated with GP and Roth’s 801 sealer.

•#5 Parapost drill was used to prepare the post space; post was cemented using zinc phosphate cement.

•Ultrasonic handpiece with a CPR 1-C (post removal tip) positioned on the top of the post in an axial direction with a static 500 g force for 1 min at maximum amplitude. No water coolant was used.

•Type K chromel/alumel thermocouples was attached at the post and 2 mm apical to CEJ, the other end was connected to the computer.

• The temperature was recorded on the computer at 15 s intervals.

•Time of ultrasonic application (15, 30, 45 and 60) at 2 location (post and root surface) were measured.

Most highlighted Results:

  •Table 1 shows the mean temperature changes at each location and time period.

•There was a significantly greater temperature increase at the post surface than at the root surface

•There was a significant temperature increase at both the post and root surface as the length of time of ultrasonic vibration increased

Clinical significance: 

Dentin is a poor thermal conductor and a small difference in dentin thickness may have a large effect in heat conduction. Teeth with thin roots and large posts could be more susceptible to the heat generation from ultrasonic application during post removal.

Incidence of root fractures and methods used for post removal

Summary:  

•Purpose: to determine how successful various post removal techniques were and the incidence of root fractures during post removal .

•N=  1600 teeth (part 1; incidence of fracture), 234 (part2; detailed analysis) •Materials/Methods: 

•Part one was a review of patient records for teeth that had posts removed. •No clinical or radiographic signs or symptoms to suggest the presence of a root fracture prior to post removal. 

•trans- illuminating light was used immediately after post removal and at all subsequent appointments along with Periodontal probing during the endodontic re-treatment and follow-up examinations. 

•a sample of 234 of these 1600 teeth was analyzed in a prospective manner during a 2 years period to determine the tooth type, the type of post being removed, the device and method used to remove the post, and the time taken to remove the post and core and whether any roots had fractured during post removal. 

• Most highlighted Results:

1.All of the 1600 posts were successfully removed and only one root (0.06%) fractured during post removal. 

2.The mean time required to remove the 234 posts was 6.5 min, the mode was 3 min 

3.Most cast posts were removed with an Eggler post remover but some dislodged when the crown was removed. Table

4.Most parallel-sided posts were removed with ultrasonics and threaded posts were unscrewed. 

5.The Masserann kit and ultrasonics were combined to remove fractured cast posts and some parallel-sided posts. 

Clinical significance:    

If appropriate techniques and devices are used for the particular type of post being removed, then root fracture is a rare occurrence. 

Comparison of Two Techniques for Removing Fiber Posts

Summary: 

•Purpose:  to evaluate the time needed to remove three types of fiber posts with two different bur kits.

•Materials/Methods

•N=  60 extracted anterior teeth

•Root canals were instrumented using the crown-down technique with Profiles (#40 .06)

•Vertical condensation of gutta-percha, using the system B, back-filling was completed with the obtura syringe

•Access cavity was sealed with a noneugenol temporary filling

•After 2 days in water, temporary filling was removed, post space to a depth of 10 mm

. •The sample was randomly divided into 3 groups (n=20) each. 3 different types of posts: group 1, conic 6% tapered fiber posts; group 2, FRC poster fiber posts; and group 3, composipost carbon fiber posts (RTD).

•After 2 days in water, half of the specimens from each group (subgroup a), the RTD fiber post removal kit was used. First, with a very short working portion, prepares a hole on the surface of fiber post; second, following this opening, drills through the fiber post.

•The other half of each group (subgroup B), fiber posts were removed by an opening created on the head of the fiber post with the tip of a diamond bur, then, a #3 Largo bur was used to penetrate the post

• Most highlighted Results:

1.On average the least time was needed to remove composiposts (group 3), and difference was statistically significant

2.Procedure using a diamond and a largo bur (subgroup B) was less time consuming, difference was statistically significant

3.There was no significant interaction between type of post and type of bur as far as removal time is concerned

4.Regardless of the type of post inserted, time for post removal was always longer when the RTD kit was used.

Clinical significance:    

From a clinical standpoint, the time on average needed to remove a fiber post seemed, regardless of its type and the bur kit used, satisfactorily short.

Effect of ultrasonic vibration and various sealers and cement combinations on titanium post removal

Purpose:

To determine:

(i) whether ultrasonic vibration reduces the amount of tensile force required to remove a prefabricated titanium post luted with a resin cement; and

(ii) whether obturation with gutta-percha and a eugenol sealer compromises the retention of cemented posts, compared with teeth obturated with gutta-percha and a eugenol-free sealer control.

•Materials/Methods:

•N= 96 extracted canines.

•Teeth were decoronated, accessed, and instrumented using Series 29, .04 taper Profile rotary instruments to an apical preparation size #8 (ISO 60). •the canals were obturated with laterally condensed GP and  and one of two different sealers—Roth’s 801 Elite Grade cement, a sealer containing eugenol, or AH26, an epoxy resin sealer containing no eugenol.

•After 2 weeks, a 9-mm post space was created in each tooth for a #6 parallel-sided titanium Parapost.

•the teeth were then divided into 8 groups according to the sealer (Roth’s or AH26) and the cement used (zinc phosphate or Panavia 21 resin cement). (Fig.1)

•After 2 weeks, the teeth were mounted in acrylic, ultrasonic energy was applied to the post– dentin interface for a total of 16 min using P5 ultrasonic unit at maximum power.

•The subsequent tensile force required to dislodge each post was determined on an Instron Universal Testing Machine

Most highlighted Results: 

•there was a significant difference in the forces required to dislodge the posts based on the sealer used. The use of AH26 significantly increased the retention of the posts, compared with the Roth’s sealer.

•the groups subjected to US vibration exhibited significantly higher values of the forces required for post dislodgment than those in which no vibration was used.

•The differences for cement were not statistically different.

Clinical significance: 

In cases of well-adapted long posts, specially if cemented with resin cement, the use of ultrasonic vibration  may be ineffective in post removal. other treatment options may be considered.

Post removal prior to retreatment

Summary: 

Purpose: to present one clinical case illustrating the effectiveness of the Gonon post removing system.

Clinical Procedure:

•The post and the tooth are separated by pitting the tooth against the post and creating enough force to overcome the bond •Steps:

1.The first step is to free the head of the post from the coronal tooth structure. All restorations including crowns must be removed.

2.An ultrasonic device can be used to vibrate the post and disintegrate the cement.

3.In order to facilitate the centering of the trephine (Fig.3), a special bur included in the Gonon kit is used to taper the protruding head of the post.

4.The high strength trephine is used to bore and gauge the protruding post to the exact size of a corresponding mandrel which is specially manufactured to thread the post (Fig. 4).

5.Before the mandrel is screwed onto the post, three rings are positioned onto its shank (Fig. 5). This acts to cushion the mandrel and to spread the forces onto the root surface as the post is being extracted.

6.The extracting pliers are fixed on the mandrel (Figs. 6 and 7) and the jaws of the pliers are expanded by tightening the knurled knob. This procedure will separate the post from the tooth quickly and safely (Figs. 8 and 9) facilitating endodontic retreatment (Fig. 10).

Clinical significance:

  the Gonon post remover may be used safely and efficiently. It is extremely adaptable to anteriors and bicuspids. In molar areas where the intermaxillary distance is limited, post removal may be accomplished without the use of the pliers.

The Masserann technique for the removal of fractured posts in endodontically treated teeth.

Purpose: to describe the Masserann technique for the removal of fractured posts in endodontically treated teeth

Clinical procedure:

•Often, a clinical examination will reveal a fractured parapost at the cervical portion of the crown, with gingival hyperplasia covering a part of the exposed root (Figs. 1 and 2).

•After anesthesia, the root is exposed with electrosurgery to gain access. From the Masserann Kit (Fig. 3), the appropriate size trepan bur is determined by a gauge supplied in the kit.

•Since the trepan burs are hollow end-cutting tubes, they fit over the end of the post and slide down its outside. The instrument is turned by hand cutting a small trench around the post.

• After proceeding from one third to one half the way down the post, the trepan bur is replaced with the next smaller size, which will grip the end of the post to lift it out of the canal.

• After the parapost is removed (Fig. 4), the root canal is enlarged with a Peeso reamer so that a conventional cast post and core can be made (Fig. 5). Later an appropriate crown can be made for the tooth (Figs. 6 and 7).

Clinical significance:   

The advantages of this technique are that

(1) it is simple,

(2) little heat is generated,

(3) there is no danger of pushing fragments further into the root, and

(4) excessive forces are eliminated with little chance of perforation or splitting the root.

Selective Root Retreatment: A Novel Approach

Summary: 

Purpose: to introduce the approach of selective root retreatment .

Case report:

•57 y/o woman, has well-localized pain of 2 weeks’ duration, #18 painful on percussion, palpation and biting.

•Periapical RG shows missed DL root, confirmed with CBCT.  After presenting all options, patient opted selective retreatment.

Treatment:

•After profound anesthesia, under RD isolation, location of access was guided by measuring CBCT and transferring it to the crown. Then root canal treatment was done after WL measurement, C/S to 06/25 (vortex). irrigation protocol consisting .

•Obturation with continuous wave condensation.

•After 12 months, tooth is symptom free, no pain on percussion or palpation , periapical RG and CBCT showed complete healing.

Incidence of flare-ups and evaluation of quality after retreatment of resorcinol-formaldehyde resin (“Russian Red Cement”) endodontic therapy

Purpose: to determine the immediate treatment result and incidence of flare-ups after retreatment of teeth with resorcinol-formaldehyde (RF) resin fillings.

N= 58 cases of retreatment of root filled with RF resin material

Materials/Methods:

•Records of 34 patients with 58 teeth that were filled with RF and retreated in a postgraduate endodontic clinic were reviewed.

•Reason for retreatment (symptoms versus restorative) and occurrence of flare-ups (pain or swelling requiring an emergency visit) and the periapical status before retreatment were recorded.

•Radiographs were taken for initial (resin obturations) and posttreatment (gutta-percha obturations) evaluations were used.

•Before & after retreatment, the length of obturated canal was measured by starting at the coronal orifice and measuring to the apical-most extent of the filling. The length of unobturated canal(s) was measured from the apical-most extent of the filling to a point 1-mm from the radiographic apex of the root. The % of the filled canal space was calculated.

•After retreatment quality of obturation was rated as optimal if 100% of the canals were filled, improved if the percentage of canals filled was increased by at least 10%, unchanged if the increase in percentage of canals filled was <10%, and worse if an iatrogenic perforation or separated instrument occurred.

Most highlighted Results: 

  • 48% of the total canal space was filled before retreatment; 90% was filled after retreatment.
  • After retreatment, obturations were rated as optimal in 59%, improved in 33%, unchanged in 6%, and worse in 2%.
  • 12% had post-retreatment flare-ups.
  • No statistical relations was found  between the incidence of flare-ups and the quality of obturation before or after retreatment (in terms of length) or the presence of symptoms or PA lesions before retreatment.

Clinical significance:

Studies with larger sample size are needed to determine the variables related to flare up.