Apicoectomy Using Er:YAG Laser in Association with Microscope: A Comparative Retrospective Investigation

Abstract

Objective: This retrospective clinical investigation intends to examine the effectiveness of an Er:YAG laser used in conjunction with a dental operation microscope for apicoectomy, in comparison with the traditional surgical procedure. Background data: The Er-YAG laser has shown great potential in application to periapical surgery; however, clinical data are rare. Methods: To this end, 78 patients who had undergone apicoectomy in a private dental office were selected; 41 patients were treated by the traditional surgical technique for apicoectomy and 37 patients were treated using an Er:YAG laser under microscopic control. The five cardinal symptoms of inflammation were taken as clinical parameters/examination criteria and evaluated after postoperative days 1, 7, and 180, where days 7 and 180 after the operation can be regarded as the customary times for follow-up controls at the private dental office. Results: Microscopically guided, laser-assisted treatment seems to favor a better healing process overall. After the first postoperative day, redness and swelling of the operation area were significantly reduced (p<0.001 and p=0.0048). Seven days after the operation, all inflammation parameters were statistically significantly lower in the laser-treated group (p<0.05). On day 180, 6 out of 41 patients in the control group still displayed a disturbed function of the treated teeth, whereas none of the patients in the laser group experienced further complaints. Conclusions: As a result, it can be ascertained that the use of an Er:YAG laser as an adjuvant tool in periapical surgery, with additional control by an operation microscope, displays significantly better results in terms of postoperative healing, in comparison with the conventional surgical treatment of apicoectomy.

Introduction

S ince the Er:YAG laser was approved by the United States Food and Drug Administration (FDA) in 1997, this laser wavelength has been put to widespread use in the daily routine of dental offices. Advanced technical developments and ongoing scientific study have steadily expanded the indications for this type of laser. In addition to being used for preparing dental enamel and dentin in caries therapy, there are today also applications for the erbium laser in endodontics. Among the approved indications are root canal debridement and cleaning, and root canal preparation, including enlargement and apicoectomy.¹ The advantages of using a laser in general, and specifically in periapical surgery, are its high precision, less discomfort for the patients as a result of less vibration, bacteria reduction, and a reduced risk of traumatizing surrounding tissue.² A biostimulatory effect of Er:YAG laser irradiation is the subject of discussion and is considered to be one of the reasons for more rapid and better healing, for example, in patients with osteonecrosis on bisphosphonate therapy.³

Root resection is the therapy of choice, if root-end canal treatment is either not possible or if it fails.⁴ The success rate depends upon the experience of the dental surgeon and the technique used.⁵ Under optimum conditions, the healing rates are 80–90%.⁶ Many different pre-clinical and clinical trials described positive results when using a laser in this field.⁷ Based on these data and the advantages of laser application generally described in the literature, the laser is also used for root resection in daily, routine practice. Nevertheless, there is so far no clear evidence that the use of a laser has real advantages in this indication. There are no results from controlled clinical trials or recommendations from scientific societies.

The aim of the present investigation was to compare the success of laser-assisted root resection with that of the conventional surgical method. Clinical cases from the daily routine of a private dental office specializing in oral surgery were examined retrospectively to this end.

Materials and Methods

The study population consisted of a total of 78 patients undergoing apicoectomy in a private dental office between October 2009 and October 2011. The medical records of all patients who matched the criteria described here were selected for the retrospective investigation. Prior to the start of treatment, all patients were free to choose whether the laser was to be used as adjuvant therapy. It should be noted that use of the laser in the private office entailed additional costs for the patient. Consequently, the cost factor was very often the reason for deciding on one therapy or the other. Informed consent was obtained from all patients before treatment. Retrospective analysis of the data was according to the guidelines of the Helsinki Declaration of the World Medical Association (2008).

Clinical and radiological examinations indicated at least one tooth requiring apicoectomy.

The inclusion criteria were:

• Age ≥18 years

• Not pregnant

• Not suffering from any serious general complaints

• Having an indication for apicoectomy with retrograde preparation of the root canal

The indication for periapical surgery existed:

• In the event of persistent apical periodontitis with clinical symptoms, or increasing, radiological osteolysis following complete or partial root canal filling or re-treatment, if this could not be removed or improved, or only by taking unreasonable risks (e.g., in patients with complex dentures and particularly with retention pins)

• Following root canal filling with overfilled root canal cement and clinical symptoms

• If conservative root treatment was not feasible, or in the event of substantial morphological variation of the roots that prevented complete root canal filling

• In the event of teeth with obliterated root canals that were no longer accessible with instruments, together with clinical and/or radiological symptoms

• If an apical lesion >5 mm was present

• In cases of persistent apical periodontitis, as an alternative to conservative endodontic re-treatment, if this was rejected by the patient

For the purpose of the present study, all groups of teeth (incisors, canines, premolars and molars) with one, two, and three roots were included.

Root apices of a total of 37 teeth were resected by Er:YAG laser treatment under an operation microscope (method 1: laser with microscope), and 41 teeth were treated by the traditional surgical procedure (hereinafter referred to as method 2), described subsequently.

All treatments were performed in a private dental office by the same dental surgeon, who had many years of clinical experience.

Surgical procedure

All apicoectomies were performed with the patient under local anesthetic. After the application of surface anesthesia with Xylocain^® Pumpspray dental (Astra Zeneca GmbH, Wedel, Germany), either an infiltration and/or a block anesthetic was administered using Ultracain^® D-S (Sanofi Aventis, Berlin, Germany), depending upon the location of the tooth involved.

A local anesthetic without vasoconstrictors (Ultracain D^®, Sanofi Aventis, Berlin, Germany) was administered to those patients with a contraindication for the use of adrenalin. A waiting time of at least 10 min was observed, until the local anesthetic took effect. After adjustment and alignment of the ProErgo dental operation microscope (Carl Zeiss, Jena, Germany), treatment was started and then performed solely under the microscope.

A semicircular vestibular Partsch's incision was performed in all patients. The initial incision was made using a 15c scalpel blade (Martin, Tuttlingen, Germany) in the vestibule area of the tooth involved. Thereafter, a mucoperiosteum flap was prepared with a periosteal elevator (Martin, Tuttlingen, Germany). The root apex was detected by following the tooth axis toward the apex. In some cases, the apical cortical bone was already disintegrated by osteolytic decay, so that only a little osseous preparation was necessary. In the cases in which teeth still displayed an intact apical cortical bone, the defect was exposed using a round burr (Brasseler Komet, Lemgo, Germany). After presentation of the osseous defect, resection of the root apex involved was undertaken, along with simultaneous removal of the pathological tissue. The root apex concerned was ablated using the Er:YAG laser. To this end, the laser system (KEY Laser 3⁺, KaVo, Biberach, Germany) was set to an energy of 450 mJ and a repetition rate of 6 Hz. The 2060 handpiece was used in focused mode (spot size of 0.63 mm) for this treatment, under cooling with a continuous air/water mist (1 mL/min). The settings used resulted in a fluence of 145 J/cm². The osseous defect was subsequently “decontaminated” with the laser, using the same settings mentioned, but in defocused mode (target distance ∼15 mm).

Thereafter, retrograde preparation of the root canal was performed, up to 3 mm toward the crown, using ultrasonic equipment (Sirona, Bensheim, Germany) fitted with special attachments. A special zinc oxide-eugenol cement (Hermetic^®, lege artis Pharma GmbH, Dettenhausen, Germany) was used for retrograde filling of the root canal.

After the cement had entirely cured, the area of the osseous defect was debrided with a sharp curette until bleeding occurred. Concluding wound closure was performed by means of individual button sutures, using Silon monothread suture material of size 5.0 (Chirmax, Prague, Czech Republic).

In the control group, apicoectomy was performed according to the same guidelines, but without using an operation microscope or a laser. Here, the root apex was removed using a Lindemann burr.

All patients were instructed, both orally and in a written instruction sheet, to refrain from cleaning their teeth on the day of dental treatment, in order to avoid trauma in the area. Between days 2 and 7, the teeth were to be cleaned only with a toothbrush. In addition, rinsing was prescribed after cleaning the teeth in the morning and evening, using a mouthwash of chlorhexidine digluconate 0.2% rinsing solution (GlaxoSmithKline, Buehl, Germany).

Postoperative examinations

The follow-up controls were geared to the standard procedure in the private dental office. The patients first came for an examination 1 day after the operation. The stitches were removed after 7 days, at which time a postoperative assessment was also made. In the absence of complaints, the follow-up control to confirm the success of root resection is customarily performed after a period of 6 months (180 days).

An radiographic control was performed immediately after apicoectomy. Depending upon the location of the tooth and the tolerance of the patient, this involved individual digital images or half-side shots, which were taken with a Sirona Heliodent plus or Orthophos XG 3 X-ray device (Sirona, Bensheim, Germany).

As described, patients were examined on postoperative days 1, 7, and 180. The clinical examination included a visual check of the operated area, as well as of the structures adjacent to it. A palpatory examination was also performed. A decision (positive [1] and negative [0]) was made regarding the occurrence of the relative criteria/parameters described subsequently.

Definition of the criteria/examination parameters

Redness, heat, pain, swelling, and disturbed function in the operation area were considered as the cardinal signs of inflammation.

Redness extending 2 mm around the incision was rated as a positive result. The parameter heat was documented as positive if the patients and the treating dental surgeon considered the operated area, together with the adjacent structures, to have an elevated temperature. Regarding the parameter pain, a positive result was defined as a sensation of pain at rest, without any external mechanical, manual, or chemical interference. The parameter swelling was considered positive if swelling of ≥2 mm was both visually and palpably detectable. Thereafter, the parameter disturbed function was documented as positive if a patient indicated speech, facial, and/or masticatory restrictions. Specifically, this parameter was rated as positive after 180 days if the patient stated, for example, that the tooth could not be used properly, or if other abnormal sensations were reported.

Statistical evaluation

The statistical investigation was restricted primarily to verification of the contingency tables, with the alternatives of affiliation to a group and (non-)incidence of inflammation parameters, by means of a χ² test and a significance test using Fisher's exact test. As the hypothesis was formulated in favor of the laser/microscope treatment, only such a one sided test result is cited. The calculations were performed with SPSS 17.0 software.

Results

After the first postoperative day, overall inflammation in all patients in the group treated with laser therapy was less. Nevertheless, only two of the parameters showed a statistically significant difference. Redness and swelling of the operation area were less in the laser-irradiated patients (p<0.001 and p=0.048, Table 1).

Table 1.

The Incidence of Inflammation Parameters After the 1st Postoperative Day

After 1st day	Control group	Laser treatment	Test statistic χ²	Fisher's exact test Sig. 1 sided
Patients	41	37
Inflammation parameters
Redness
Patients	20	4	13.163	0.000
% within group	48.8%	10.8%
Pain
Patients	31	21	3.111	0.064
in % of group	75.6%	56.8%
Heat
Patients	5	1	2.468	0.125
% within group	12.2%	2.7%
Swelling
Patients	22	12	3.564	0.048
% within group	53.7%	32.4%
Disturbed function
Patients	21	16	0.496	0.317
% within group	51.2%	43.2%

Bold signifies statistically significant differences.

On Day 7, hardly any symptoms were ascertained in the patients treated by laser. All investigated parameters were statistically significantly lower in the laser-treated group (p<0.05, Table 2).

Table 2.

The Incidence of Inflammation Parameters After the 7th Postoperative Day

After 7th day	Control group	Laser treatment	Test statistic χ²	Fisher's exact test Sig. 1 sided
Patients	41	35
Inflammation parameters
Redness
Patients	8	0	7.633	0.005
% within group	19.5%	0.0%
Pain
Patients	11	1	8.161	0.004
% within group	26.8%	2.9%
Heat
Patients	7	0	6.582	0.010
% within group	17.1%	0.0%
Swelling
Patients	9	0	8.715	0.002
% within group	22.0%	0.0%
Disturbed function
Patients	10	1	7.072	0.007
% within group	24.4%	2.9%

Bold signifies statistically significant differences.

Both groups no longer showed any signs of acute inflammation after 180 days. Only the disturbed function parameter was given a positive rating by 6 of the 41 patients in the control group. No further complaints were experienced in the group of patients treated by laser. This result was also statistically significant (p=0.021, Table 3).

Table 3.

The Incidence of Inflammatory Parameters 180 Days After Treatment

After 180th day	Control group	Laser treatment	Test statistic χ²	Fisher's exact test Sig. 1 sided
Patients	41	35
Disturbed function
Patients	6	0	5.561	0.021
% within group	14.6%	0.0%

Bold signifies statistically significant differences.

If it is assumed that the assessment of the type of treatment is less relevant as regards specific inflammation symptoms, it would seem acceptable to subsume them into an index and thus evaluate their quantities and/or frequency and means. On the basis of this condensed information, a significant difference between the combined laser/microscope treatment and the control group can be detected in the follow-up control, even after the first postoperative day (Fig. 1).

FIG. 1.

Mean inflammation index for laser treatment and control group according to postoperative days. The table contains standard deviations. The groups are statistically significantly different for the whole observation period (p<0.05).

Discussion

The present investigation had the objective of examining the effectiveness of using an Er:YAG laser in combination with a dental OP microscope for endodontic surgery. Therefore, we retrospectively selected the medical records of patients who had undergone apicoectomy in a private dental office. Two groups were compared – combined laser/microscope treatment versus conventional treatment – with the first group representing the “most modern” technique.

The choice of laser was made by referring to earlier studies, which were able to show less thermal destruction and carbonization of tissue after treatment with an Er:YAG laser, in comparison with other lasers.^2,8 This is attributable, on the one hand, to its water cooling feature and, on the other hand, to the “thermomechanical” ablation process of the Er:YAG laser.⁹ Atalay et al. moreover confirm that use of a laser offers increased benefits in oral, dental and surgical therapy.¹⁰

In the case of apicoectomies in particular, the Er:YAG laser performs better ablations than the Ho:YAG laser, for example. A smoother and cleaner surface in the resection area was achieved without thermal damage.¹¹ Furthermore, Zhao et al. were able to demonstrate the superiority of the Er:YAG laser for apicoectomy in comparison with ultrasound and rotating-diamond instruments. The resultant reduction in postoperative complaints, as well as improved wound healing, was confirmed in this study.¹² Takeda et al. and Angiero et al. likewise show in their clinical studies that use of the Er:YAG laser leads to high success rates in root resection.^13,14 However, no control groups were examined in either of the studies.

The exact reasons for the described beneficial effects of Er:YAG laser irradiation in periapical surgery are not yet known. A biostimulatory effect and “disinfection” of the operation area by Er:YAG laser irradiation are the subject of discussion, and perhaps promote early healing.³ Furthermore, it has been shown in an animal model that Er:YAG laser irradiation seems to stimulate platelet-derived growth factor secretion and, therefore, enhances the healing of osteotomy sites.¹⁵ Aleksic et al. demonstrated in vitro that low-level Er:YAG laser irradiation enhances osteoblast proliferation through activation of the mitogen-activated protein kinase (MAPK)/extracellular signal regulated kinase (ERK) pathway. They suggest that Er:YAG laser irradiation is, perhaps, able to promote healing in periodontal or implant sites.¹⁶

A conventional surgical approach, using a scalpel and a rotating burr, was used in all patients in the present investigation. This was because laser incisions are generally considered to show slightly delayed healing because of thermal destruction of the tissue.^17,18 Even though the erbium laser causes the lowest thermal increase in soft tissue, there is so far no clear evidence of advantages of using lasers for this application.¹⁹ The Er:YAG laser seems well suited to the ablation of bone. Temperature increase during Er:YAG laser ostectomies is very low, and thermal alterations are minimal.^20,21 From an animal model comparing Er:YAG laser and burr, Martins et al. reported a thin layer of thermal damage and slightly reduced bone healing.²¹ Therefore, we decided to use the Er:YAG laser in the laser cohort only for root resection and “disinfection” of the osseous defect.

In this regard, statistically significantly better wound healing, compared with the control group, was ascertained for the examination parameters of redness and swelling, even after the first postoperative day in the present investigation. This observation was made for all five inflammation parameters after day 7. There was only one patient positive for the parameters pain and disturbed function. The success of performing apicoectomy with an Er:YAG laser in conjunction with an OP microscope is, therefore, clearly apparent after 180 days. In this respect, no further complaints were detected in any patient of the laser-treated group during the concluding control examination.

Furthermore, numerous studies have shown a lower postoperative pattern of discomfort, even in periodontal therapies, in patients treated by Er:YAG lasers.²² Even as far back as 1994, Aoki et al. had already shown that effective removal of subgingival plaque is possible by employing power densities of 10.6 J/cm² in the contact mode.²³ Furthermore, the efficacy of Er:YAG lasers as regards removal of debris and smear layers from the root canal walls has been confirmed in previous studies.²⁴ More recent studies show some positive onward developments of the laser systems, such as an innovative diode-pumped Er:YAG laser, which may represent a real alternative to currently familiar laser systems.²⁵

Another allegedly helpful aspect is the introduction and employment of the operation microscope, which Carr and Murgel described as a revolution in endodontics, as well as in apicoectomy.²⁶ The advantage of using magnification devices is, however, the subject of critical debate.^27,28 Nevertheless, the microdentistry and microsurgical approach seems to permit predictable success in the healing of endodontic lesions.⁶

Conclusions

In summary, the results of the present study reveal a correlation with the laser studies previously described. However, the question arises as to whether the significantly better results in this study were achieved only by employing both laser and microscope, or whether comparable results would have been equally possible using only one of these resources. For example, this could in turn be broken down into percentages indicating the contributions to success apparently made by the Er:YAG laser and by the operation microscope, in comparison with traditional apicoectomy.

Furthermore, we also need to mention the disadvantages of retrospective studies compared with prospective studies. Selection bias, information, and concealment bias cannot be completely ruled out.

The question should also be asked as to whether the patients felt a subjectively positive effect because of the use of “modern” technical equipment for treatment, without this being classed as scientifically significant objectivity. The patient satisfaction rate is usually extremely high when using lasers.²⁹

In the future, it will, therefore, definitely be possible to exploit the benefits of using Er:YAG lasers with the assistance of operation microscopes for apicoectomies in everyday practical dentistry.

However, this approach to the abovementioned differentiation between microscope-laser therapy and a variety of other treatment methods should be further verified by means of additional clinical research.

Footnotes

Author Disclosure Statement

No competing financial interests exist.

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