Prospective Healing Assessment After Application of Endodontic Microsurgery for Elimination of Apical Pathology By Use of Either a Rotary Bur for Osteotomy and Apical Root Resection, or Piezoelectric Unit for the Same Clinical Procedures
Phase: NA
Conditions: Periapical Periodontitis, Endodontic Microsurgery, Osteotomy
Sponsor: National and Kapodistrian University of Athens

 
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Prospective Healing Assessment After Application of Endodontic Microsurgery 
for Elimination of Apical Pathology, By Use of Either a Rotary Bur for 
Osteotomy and Apical Root Resection, or Piezoelectric Unit for the Same 
Clinical Procedures. 
 
 
09/11/2025 
 
 
 
 
 
 
 
 
 
 

 
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Study Protocol + Statistical Analysis 
 
 
Introduction  
 
     
  Persistent and recurrent apical periodontitis can be treated predictably by modern 
endodontic surgery. Unlike traditional surgery, modern microsurgical techniques 
incorporate the use of an operating microscope, ultrasonic tips for precise root-end 
preparation, and biocompatible root-end filling materials, such as mineral trioxide 
aggregate (MTA), and more recently other bioceramic-based materials such as 
Endosequence Root Repair Material (RRM; Brasseler, Savannah, GA)1-3. These 
materials offer a better seal and apical tissue response1-3. Endodontic microsurgery 
is a minimally invasive procedure. Osteotomy diameter is 3-4mm, just enough to 
allow for access to the apical lesion, a 3mm apical root resection, root end 
preparation and root end filling1,2.  Weighted pooled success rates have been 

 
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established in a meta-analysis with cumulative outcomes for the traditional 
approach of apical surgery at 59.0% and for endodontic microsurgery at 93.5%4. 
The significantly higher success of the modern microsurgical procedure has been 
repeatedly concluded in several investigations5,6. 
 
            Traditional use of surgical manual instruments or even rotary burs for 
osteotomy resulted in a significant increase of temperature or even bone injury 
during surgery, because of the application of excessive pressure on the bone7. In 
order to overcome these limitations, researchers have introduced the application of 
units that utilize the principles of ultrasonic microvibration to make precise and 
selective cut on the bone in harmony with the surrounding tissues7,8.  One of the 
novel methods to incorporate these properties of ultrasonics is Piezosurgery. This is 
a relatively new alternative for bone-related procedures introduced in the field of 
dentistry. It has a wide potential for usage with the devices running according to the 
piezoelectric principles and capable of cutting by way of ultrasonic vibration9,10. 
These vibrations are low frequency modulated vibrations at 25 to 30 khz which 
selectively cut the bone without damaging adjacent soft tissues and delicate 
structures, such as the Schneiderian membrane or a nerve10.  
 
 
 
 
 

 
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Aims and Objectives 
 
      
The aim of this study is to prospectively compare postsurgical healing after the use 
of microsurgical technique to eliminate apical pathology, either by use of rotary 
burs for osteotomy and root resection, or by use of piezoelectric surgery for the 
same clinical procedures.  Null hypothesis is that there is no difference in healing 
and buccal bone thickness reformation between the two surgical procedures.  
    Another purpose of the study is to prospectively evaluate healing after the 
application of a novel buccal bone preservation technique, called the ‘bone window’ 
technique. The technique will be applied in a subgroup of patients on maxillary and 
mandibular premolar and molar teeth with an intact buccal cortical bone, and  
healing and buccal bone reformation will be assessed at follow up. Null hypothesis 
in this part, is that there is no difference in healing and buccal bone preservation 
between osteotomy with a bur and the ‘bone window’ technique. 
        
 
   Khoury and Hensher in 1987 were the first ones who reported a “bone 
window” (lid) approach, which provided better access and intraoperative visibility 
to the desired lesion location while avoiding extensive removal of alveolar bone11. 
This was performed in the pre-Cone Beam Computed Tomography (CBCT) era and 

 
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relied on clinicians’ experience. The primary aim of performing a bone window 
technique is to preserve more bony structure and to maintain the integrity of the 
healthy cortical plate12. 
 
    In endodontic microsurgery, a significant reduction of osteotomy size resulted in 
the preservation of more bony structure while obtaining access to the target roots 
compared with the pre-microsurgery era1. Animal histologic sections showed that 
the cortical plate is the last component to heal, with a healing rate of 70% at the 6-
month follow-up13. Furthermore, cone-beam computed tomographic (CBCT) 
assessment after apical surgery in humans revealed that only 54.1% of cases 
showed cortical plate healing at a 1-year follow-up14. The extent of cortical plate loss 
and its limited healing potential may require the need of regenerative techniques 
with graft materials.    
             
 
Methods and Materials 
 
    For this prospective investigation, patients will be randomly allocated into two 
groups. In group 1 (experimental group), endodontic microsurgery will be 
performed by use of a rotary bur for osteotomy and apical root resection and in 
group 2 (control group), piezoelectric surgery will be used for the same clinical 
procedures. Removal of the periapical pathology, root end preparation and root end 
filling will be done in both groups following the same protocol, technique and 

 
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materials. All surgical procedures will be performed by one operator.  Postsurgical 
healing as well as certain preoperative and postoperative parameters will be 
assessed and compared in the two groups.   Limited field of view (FOV) CBCT scan 
will be performed presurgically, postsurgically and at follow up examination by use 
of a Veraviewepocs 3D F40 (Morita, Irvine, CA) unit: Field Of View (FOV)  4 x 4 cm, 
voxel size = 0.125 mm. 
 
The inclusion criteria will be defined as follows: 
1. Age 18 years and older consenting to the surgical procedure as well as agreeing to 
preoperative, postoperative and at least 1 follow-up CBCT evaluation after 12 
months 
2. Noncontributory medical history (American Society of Anesthesiologists 
class I and II) 
3. A history of previous endodontic treatment with radiographic presence of apical 
periodontitis 
4. A true endodontic lesion: microsurgical classification A, B, or C according to Kim 
and Kratchman, 20061. 
5. Lesion size 10 mm or smaller in diameter measured on preoperative CBCT 
6. Coronal restoration should be present at the time of follow up examination. 
 
The exclusion criteria will be as follows: 
1. Nonconsenting patients and patients younger than 18 years of age 
2. Medical history with American Society of Anesthesiologists class III to V 

 
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3. Insufficient coronal restoration 
4. Nonrestorability or traumatized teeth 
5. Teeth with microsurgical classification D, E, or F  according to Kim and Kratchman 
20061. 
6. Mobility I or higher 
7. Radiographic presence of nonapical root resorption 
8. Teeth with a vertical root fracture or coronal/ midroot perforation  
9. Lesion size larger than 10 mm in diameter measured on preoperative CBCT 
10. Use of  bone graft  material for regeneration 
 
      
All participants will be thoroughly informed on the purpose and the details of the 
study and a written consent will be obtained. 
    Apical surgery following the protocol of endodontic microsurgery and the use of 
an operating microscope as described by Kim S, Kratchman S, 20061 will be 
executed in all patients. Briefly, local anesthesia is performed, flap is reflected and 
osteotomy and apical root resection is done either by use of a rotary bur or the tip of 
a piezoelectric unit. Apical granulomatous tissue is removed, followed by root end 
preparation and root end filling with modern bioactive materials. Flap is 
repositioned and sutured with resorbable sutures. A limited FOV CBCT will be 
acquired immediately postsurgically.  
     In a subgroup of patients having at least 2mm of intact buccal cortical bone 
thickness preoperatively, piezoelectric surgery will be used to prepare a rectangular 

 
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buccal ‘bone window’. The buccal bone thickness will be measured preoperatively 
on the coronal slices of the CBCT.  After completing the root end filling, the bone 
window will be repositioned at the original position and a collagen membrane will 
be placed in contact with the bone fragment to enhance bone healing and stabilize 
the fragment.   
     All patients will be recalled at minimum one year after periapical surgery for 
follow up examination. At follow up, clinical examination will be performed 
including percussion, palpation and periodontal probing. Radiographic examination 
will include a periapical radiograph and a limited FOV CBCT scan.   Healing will be 
evaluated using Molven et al, 19872 criteria for two dimensional radiographic 
assessment and modified Penn 3-dimensional criteria as described by Schloss et al, 
20173 for the three-dimensional examinations. 
A preoperative and postoperative volumetric assessment of the lesions will be 
performed by using a segmentation and volume measurement software. The sliced 
image data of cone-beam computed tomographic images before and after surgery 
and at follow up examination will be imported into the segmentation software and 
after segmentation, the volumes of periapical lesions will be measured, and the 
difference in the volume will be calculated  
   Particularly for the ‘bone window’ cases, a pair-matching of cases having intact 
buccal bone plate and similar apical defect volumetric dimensions will be done, 
utilizing either a bur for osteotomy and root resection or the piezoelectric unit for 
bone window preparation and apical root resection.    

 
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In addition, certain perioperative parameters, such as the time required to execute 
osteotomy and root resection in all surgeries in the two groups of patients will be 
calculated. 
        
          Statistical Analysis  
Data will be analyzed using STATA 18 software (StataCorp LLC, College Station, TX). 
Descriptive statistics will be calculated as means with standard deviations for 
continuous variables (volumetric analysis) and as frequencies with percentages for 
categorical variables (healing scores). Data normality will be tested. Comparisons of 
means between the two treatment groups will be done using Student’s t-test for 
data with normal distribution, or Mann–Whitney U-test for not normal distributions. 
Chi-Square or Fisher’s exact tests will be used to test the difference between the 
groups for categorical variables. To evaluate the outcome of the two treatment 
procedures at the 12-month follow-up, a multivariate binary logistic regression 
model will be calculated to correlate the independent variables with the success 
rate. The results will be reported in terms of odds ratios (ORs) with 95% confidence 
intervals . 
 
 
Conclusion 
 

 
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  This prospective healing evaluation after endodontic microsurgery either by use of 
a bur or piezosurgery aims to:  
- 
Compare the healing outcome between the two techniques 
- 
Highlight advantages and limitations of piezoelectric units for apical 
microsurgery 
- 
Evaluate the clinical advantages and the healing outcome of the novel ‘bone 
window’ technique.  
 
 
 
 
    References 
 
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J Endod 2006;32:601–23. 
 
2. Floratos S, Kim S. Modern endodontic microsurgery concepts: a clinical update. 
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3. Safi C, Kohli MR, Kratchman SI, Setzer FC, Karabucak B. Outcome of Endodontic 
Microsurgery Using Mineral Trioxide Aggregate or Root Repair Material as Root-end 

 
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Filling Material: A Randomized Controlled Trial with Cone-beam Computed 
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