In vivo efficacy of various retrofills and of CO2 laser in apical surgery

Lasers in Apicoectomy: A Brief Review

Since the invention of laser, various applications for lasers in endodontics have been proposed, such as disinfection of the root canal system, canal shaping, pulp diagnosis, and apico-ectomy. One of the major applications of laser in endodontics is apicoectomy. The aim of this article is to review the benefits and drawbacks of laser applications in apicoectomy, including effect on apical seal, effect on dentin permeability, effect on postsurgery pain, effect on crack formation, effect on root-end morphology, effect on treatment outcome, and connective tissue response to laser-treated dentin.

Surgical Endodontics in Dogs: A Review

Surgical endodontic therapy (apical surgery) is a treatment alternative aimed at removing periapical inflammatory tissue followed by apical resection and retro-filling of the root canal. These procedures are performed through a trans-osseous approach. Terminology pertinent to this article include: apical (periapical) curettage – a surgical procedure to remove diseased tissue from the alveolar bone in the apical region of a pulpless tooth; apical cyst – a cyst in bone at the apex of a pulpless tooth. It is believed that such cysts arise after the death of the pulp from noxious physical, chemical, or bacterial stimulation of epithelial rests of Malassez; apicoectomy (apical resection) – amputation of the apical portion of the root and removal of soft tissue in the bone; epithelial rests of Malassez – cords, strands, or clusters of ectodermal cells in the periodontal ligament (or sometimes alveolar bone) derived from remnants of Hertwig's epithelial root sheath. These cells frequently begin proliferating when inflammation occurs in the periodontal ligament and are believed to be responsible for the genesis of the epithelial lining of apical cysts.

Apicectomy with the Er:YAG laser or bur, followed by retrograde root filling with zinc oxide/eugenol or sealer 26

OBJECTIVE

This study evaluated the influence of root resection, by means of the use of erbium:YAG laser in sealing two different materials, OZE and Sealer 26, in retrograde obturations.

BACKGROUND DATA

Few studies with sufficient data have been conducted in this area.

METHODS

Forty uniradicular teeth were used. They were biomechanically prepared using the step-back technique and obturated using the lateral condensation technique. The teeth were divided into two groups of 20 teeth, one group using the erbium:YAG laser (350 mJ and 6 Hz) for the resection process and the other using the Zekrya Drill, in high rotation. Then, the retrograde cavities were prepared using a micro counter-angle with a number 2 spherical bur. After preparing the cavities, the teeth were impermeabilized and divided into two subgroups. One subgroup used the retrograde obturation technique with Sealer 26 cement, and the other subgroup used OZE. After completing the retrograde obturation, the teeth were immersed in 2% methylene blue for a 7-day period. Teeth were then removed from the dye, washed, scraped, and sectioned in the vestibule-lingual direction.

RESULTS

The results were analyzed with the aid of a magnifying lens, and scores were attributed based on the magnitude of infiltration. The data were then submitted to statistical analysis.

CONCLUSIONS

No statistical difference was noticed regarding the root resection methods; however, in comparing materials, Sealer 26 was statistically superior to OZE. In the subgroup comparison, a significant difference was noticed in the Laser and Sealer 26 and the Laser and OZE and bur and OZE.

Lasers in endodontics

With the rapid development of laser technology, new lasers with a wide range of characteristics are now available and being used in various fields of dentistry. In the past two decades, much experience and knowledge has been gained. This article provides an overview of the current and possible future clinical applications of lasers in endodontics, including their use in alleviating dentinal hypersensitivity, modification of the dentin structure, pulp diagnosis, pulp capping and pulpotomy, cleaning and shaping of the root canal system, and endodontic surgery. Endodontic procedures for which conventional treatments cannot provide comparable results or are less effective are emphasized.

Apical Microleakage of Root-End Cavities Prepared by CO2 Laser

This in vitro study in extracted human teeth was designed to compare the degree of dye penetration of root-end cavities prepared by CO2 laser, ultrasonic retrotip, or rotary instrument. Eighty-two human anterior teeth were prepared and obturated with laterally condensed gutta-percha and sealer. Root-end resection was performed at 90 degrees, 3 mm from apex. Root-end cavities were prepared by CO2 laser beam, ultrasonic retrotips, or bur and were filled with amalgam. The teeth were isolated and immersed in basic fuchsin at 36 degrees C for 48 hours. The roots were split longitudinally and examined by a stereomicroscope. Leakage was quantified by linear measurement of dye penetration with the aid of image-analyzing software. Apical leakage in the CO2 laser group was significantly less than in the ultrasonic retrotip and bur groups. The difference between the ultrasonic and bur groups was insignificant. Based on the results of this in vitro study, application of CO2 laser for root-end cavity preparation appears to decrease the apical leakage.

The effect of CO2 laser irradiation on PDL cell attachment to resected root surfaces

OBJECTIVES

The effect of CO2 laser irradiation on PDL attachment to resected root ends was evaluated.

STUDY DESIGN

Forty dentin wafers were divided into 4 equal groups. Groups I and II were not subjected to laser irradiation. Groups III and IV were subjected to irradiation with CO2 laser (wave length 10.6 mm). PDL cells attachment to the resected root surface (lased/non lased) and cell attachment to the root end filling material (gutta percha and MTA) were evaluated utilizing immunoflouresence microscopy and SEM.

RESULTS

PDL cell attachment was observed on dentin surfaces (control samples) and dentin away from the laser strikes (irradiated samples). PDL cell attachment was observed on MTA but was absent on gutta percha.

CONCLUSION

Absence of PDL attachment to laser irradiated dentin could be attributed to morphological surface changes in dentin produced by laser irradiation.

The use of glass ionomer cements in both conventional and surgical endodontics

The capacity to bond to dental tissues, especially to dentine, their long-term fluoride release and their biocompatibility make glass ionomer cements (GICs) advantageous for use in endodontics, as well as in restorative dentistry. This review provides information on the basic properties of GICs, such as adhesion, antimicrobial effects and biocompatibility, particularly as they relate to use in endodontics. Indications for the use of GICs in endodontics are orthograde root canal sealing, root-end filling, repair of perforations and root resorption defects, treatment of vertical fractures and maintenance of the coronal seal. The paper includes a review on each of these indications. It is concluded that in spite of the critical handling characteristics and the inconclusive findings regarding sealing ability and antimicrobial activity, there is substantial evidence to confirm their satisfactory clinical performance. Both soft tissue and bone compatibility make them suitable for use during endodontic surgery.

Leakage associated with intermediate restorative material and glass-ionomer cement retrograde fillings: a human and sheep teeth comparison with 2 different aging procedures

OBJECTIVES

Leakage around retrograde fillings is an important cause of endodontic surgery. This in vitro study sought to compare the following: (1) methylene blue dye leakage linked to retrofillings in human and sheep teeth with the degree of dye penetration when intermediate restorative materials and Chemfil were used as retrofillings, (2) the apical microleakage in filled with that in unfilled root canals, and (3) 2 storage techniques, incubator-based and subcutaneous implantation in rats.

STUDY DESIGN

Tested were 198 human and 196 sheep teeth that were retrofilled with intermediate restorative material or Chemfil, then stored in an incubator or subcutaneously in rats for 10, 20, and 30 days before immersion in methylene blue dye for 24 hours. Linear dye penetration was evaluated, and the results were statistically analyzed by means of analysis of variance.

RESULTS

Leakage between sheep and human teeth was significantly different (P <.05). Chemfil had significantly less leakage than intermediate restorative material after storage in rat (P <.05) for up to 20 days, but not after 30 days. No differences were found between leakage of unfilled and filled human root canal teeth.

CONCLUSIONS

The sheep incisor is a poor experimental model of the human tooth, and both aging procedures demonstrate extensive leakage of retrofilling materials after long-term storage.

Lasers in endodontics: a review

Since the development of the ruby laser by Maiman in 1960 and the application of the laser for endodontics by Weichman in 1971, a variety of papers on potential applications for lasers in endodontics have been published. The purpose of this paper is to summarize laser applications in endodontics, including their use in pulp diagnosis, dentinal hypersensitivity, pulp capping and pulpotomy, sterilization of root canals, root canal shaping and obturation and apicectomy. The effects of laser on root canal walls and periodontal tissues are also reviewed. The essential question is whether a laser can provide equal or improved treatment over conventional care. Secondary issues include treatment duration and cost/benefit ratio. This article reviews the role of lasers in endodontics since the early 1970s, summarizes many research reports from the last decade, and surmises what the future may hold for lasers in endodontics. With the potential availability of many new laser wavelengths and modes, much interest is developing in this promising field.

Histological study of periapical tissue healing in the rat molar after retrofilling with various materials

We histologically examined the effects on the periapical tissue of various dental filling materials applied as retrofillings in rats and compared them with those of amalgam. The 4-META-TBB resin Superbond and the light-cured composite resin produced the least severe inflammatory reaction, with the greatest amount of new bone. In these specimens, regeneration of a part of the periodontal ligament was also observed. These results indicate that these materials might be very biocompatible and thus foster the natural regeneration of the periapical tissue.

The carbon dioxide laser as an aid in apicoectomy: an in vitro study

OBJECTIVE

To achieve the required goal of optimally sealing the apical section and the root-canal when performing an apicoectomy, the authors decided to use the CO2 laser as an additional aid.

SUMMARY BACKGROUND DATA

The CO2 laser has previously shown to have an excellent sealing effect on dentin surfaces.

METHODS

In this in vitro study, the authors examined the effects of CO2 laser application in apicoectomies with the help of color penetration tests and scanning electron microscopic (SEM) examinations. Sections and root canals were irradiated with low power (0.5 W) in continuous wave mode for totally 20 sec. The thermal stress for the adjacent tissues attaching thereto is moderate as shown by infrared-spectroscopy.

RESULTS

A comparison with nonirradiated samples revealed that CO2 laser irradiation reduced color penetration at the section to a minimum. Also, irradiation of the root-canal wall resulted in satisfactory sealing of the surface. These findings were supported by the results of the SEM examinations.

CONCLUSIONS

CO2 laser treatment optimally prepares the tooth for final intraoperative filling because of sealing of the dentinal tubules, the resultant elimination of niches for bacteria and the sterilizing effect of the laser.

Prospective study of two retrograde endodontic apical preparations with and without the use of CO2 laser

This article covers a 4-year study that reports 320 cases in which endodontic surgery was performed for residual apical lesions or lesions that could not be treated in a conventional way. Four groups of 80 teeth each were formed and they were followed up after a 12-month interval. The first group comprised cases treated with a micro bur, retrograde filling and IRM; the second, cases treated at the apical and radicular portions with a CO2 laser; the third, cases in which the retrograde cavity was prepared with an ultrasonic device instead of a micro bur; and the fourth group comprised cases treated in a similar way to the second group, i.e., cases treated at the apical and radicular portions, but with a CO2 laser instead of a micro bur. After 12 months, the results showed a better prognosis with ultrasonic treatment. Regardless of technique, the CO2 laser did not improve the healing process.

In vivo model for assessing the functional efficacy of endodontic filling materials and techniques

Endodontic fillings were challenged with bacterial ingress in mandibular premolars of 4 beagle dogs. Groups 1, 2, and 3 (n = 9), had canals filled with gutta-percha and sealer, gutta-percha alone, and sealer alone, respectively. After 2 wk, pulp chambers were inoculated with plaque. Group 4 (n = 9) and group 5 (n = 5) had canals either filled as in groups 1 to 3 or unfilled, respectively, but not inoculated. Group 6 (n = 5) had canals unfilled and inoculated. Teeth were radiographed periodically for 14 wk, dogs terminated, and jaw blocks retrieved and processed for light microscopic examination. Rarefying osteitis appeared in group 6 at 3 wk and in groups 2, 3, and 5 at 11 wk. Periradicular inflammation was none, mild, or severe. Occurrence of severe inflammation in groups 1 to 6 was 0, 11%, 33%, 0, 60%, and 100%, respectively. Groups 1 to 3 combined differed significantly from group 4 (repeated-measures ANOVA, p < 0.05). This model could be used to assess the functional efficacy of endodontic fillings in vivo.

Laser irradiation of bone. I. An in vitro study concerning the effects of the CO2 laser on oral mucosa and subjacent bone

The purpose of this study was twofold: first, to evaluate the histologic effects of CO2 laser irradiation on biopsies of porcine oral mucosa and underlying bone under conditions that simulate the applications of the laser during gingival surgery; and second, to evaluate the histologic effects on cortical bone following irradiation with increasing energy densities. Specimens consisting of mucosa and underlying bone were subjected to multiple passes of the laser beam in the same line of incision at energy densities ranging from 240 to 1,032 J/cm2. A second group of specimens consisting only of cortical bone was irradiated by a single pass of the laser at energy densities ranging from 40 to 2,062 J/cm2. In both groups the mean depth of ablation, width of surface damage, and widths of the zones of thermal necrosis and thermal damage were determined. Results showed a direct correlation between increasing energy density and/or number of energy beam passes and increasing depths of ablation and widths of surface damage. Further, more than three passes at 1,032 J/cm2 penetrated the mucosal layer to involve underlying bone. The mean depth of ablation for bone specimens following a single pass of the energy beam ranged from 0.02 mm at 160 J/cm2 to a maximum of 0.75 mm at 2,062 J/cm2. Using those energy densities most common to oral soft tissue surgery, the mean depth of ablation in bone specimens ranged from 0.17 mm at 240 J/cm2 to 0.28 mm at 640 J/cm2 to 0.35 mm at 1,032 J/cm2. All specimens regardless of tissue composition, energy density, or number of energy beam passes exhibited a distinct layer of residual carbonized tissue, a zone of thermal necrosis characterized by tissue coagulation, and a zone of tissue exhibiting thermal damage.

Radiological assessment of the effects of potential root-end filling materials on healing after endodontic surgery

The effects of three root-end filling materials on healing following endodontic surgery were assessed radiologically and correlated with histological findings reported elsewhere. The materials compared were a light-cured glass ionomer cement (Vitrebond), a reinforced zinc oxide-eugenol cement (Kalzinol) and amalgam. The root canals of 27 two-rooted mandibular premolar teeth of six beagle dogs were inoculated with endodontic pathogenic bacteria to induce periradicular lesions. The roots were apicected and root-end cavities filled with the tested filling materials. The teeth and surrounding jaw were removed after 4 weeks (30 roots) or 8 weeks (24 roots). Radiographs were taken of each jaw section and subjected to image analysis. Healing was evaluated based on measurements of the size of the periradicular radiolucent areas. ANOVA disclosed no statistically significant differences in the size of the periradicular areas either between time periods or between materials. These results did not correlate with the tissue responses in the same material as assessed histologically and previously reported. The use of radiographs alone to assess healing after endodontic surgery in the dog mandible is unsatisfactory, and should not be regarded as a substitute for histological examination for the determination of healing.

Healing of apical periodontitis in dogs after apicoectomy and retrofilling with various filling materials

OBJECTIVE

To histologically assess the efficacy of various retrofilling materials in apical surgery.

STUDY DESIGN

The pulps of mandibular premolars in seven beagle dogs were infected; this resulted in periapical lesions. Apical surgery was performed without disinfection of the root canals. Super EBA (Harry J. Bosworth Co., Skokie, III.), two formulations of glass ionomer cement, amalgam with varnish, IRM,(Caulk Co., Ltd., Densply International, Milford, Del.) and a light-cured composite resin were the retrofilling materials used. Roots infected and apicoectomized without retrofilling were positive controls. After 6 months the dogs were killed. The experimental roots and surrounding apical tissues were prepared and histologically examined and relative percentages of bone and inflammation were calculated.

RESULTS

Super EBA was consistently the best. In overall periapical condition, Super EBA was statistically superior to all materials except IRM. IRM was superior to the glass ionomer cements but not the other materials. As to percentage of bone, Super EBA was the best overall; it was superior to glass ionomer, composite resin, and the positive control but not different from amalgam or IRM. When comparing remaining numbers of inflammatory cells, Super EBA was superior with the lowest number of inflammatory cells present.

CONCLUSION

Although not statistically different from IRM, Super EBA was consistently the best retrofilling material tested when compared with all retrofilling materials studied.

Efficacy of XeCl-308 excimer laser in fusing hydroxyapatite to seal the root apex

Sealing the root apex during apical surgery is important for a successful outcome. The effect of XeCl-308 nm excimer laser irradiation on the fusion and seal of hydroxyapatite to the root apex was tested in extracted human teeth. Twenty-four roots of intact single-rooted premolars were instrumented to size 30 K-file at the apex leaving a patent apical foramen. The apex of each tooth was covered with a freshly prepared paste of hydroxyapatite powder mixed with saline. The samples were then divided into two groups. In 12 teeth, the apical area was irridiated with XeCl-308 nm excimer laser at a fluence of 0.7 J/cm2 for 5 s with pulse repetition rate of 25 Hz and a spot size of 0.13 cm2 immediately after the hydroxyapatite application. In the other 12 teeth, no laser treatment was performed after the hydroxyapatite application. The roots were mounted on a model for the detection of radicular leakage of hydrogen peroxide. The hydrogen peroxide leakage of each sample was measured and the difference between the test groups compared. The ability of the hydroxyapatite plug to prevent hydrogen peroxide leakage at the apex was also tested by applying compressed air from the triple syringe on the coronal access preparation for 2 min. Apical leakage was found in four teeth in the lased group and in eight teeth in the non-plased group. However, the difference between the groups was not statistically significant. Compressed air applied to the coronal access caused hydrogen peroxide leakage in all the teeth.(ABSTRACT TRUNCATED AT 250 WORDS)

A study in vitro of threaded titanium pins used for retrograde obturation of root canals

The microleakage of four retrograde filling materials was compared in vitro. Fifty-three single rooted teeth were instrumentated and root filled with resin chloroform and gutta-percha. The gutta-percha cones were left extruding from the access opening. All teeth were apicected and retrograde fillings placed. The materials used were a non gamma 2 amalgam (Amalcap), a glass ionomer cement (ChemFil II), threaded titanium pins cemented with a glass ionomer cement (ChemFil II) and identical titanium pins cemented with a silicone material (Adheseal). After removal of the gutta-percha with tweezers, a radioactive isotope solution was placed in the teeth. Extraradicular samples were taken at 3, 7, 28, 77 and 104 days. All retrograde fillings showed some microleakage. The group with titanium pins cemented with silicone showed the least leakage: significantly less than the teeth with glass ionomer cement (P < 0.01) and with amalgam (P < 0.01). No significant differences were found between other groups.

Effects of Nd:YAG laser on apical seal of teeth after apicoectomy and retrofill

The application of Nd:YAG laser to tooth surface can change its surface permeability. The purpose of this study was to investigate the effects of Nd:YAG laser on the permeability of dentin following apicoectomy and retrofill. Sixty single-rooted teeth were randomly assigned to six groups of 10 teeth each. The six groups were arranged in three pairs, experimental and control groups. The canals of teeth in pairs 1 and 2 were cleaned, shaped, obturated, and their apical 2 mm were resected. A class I preparation was prepared and filled with amalgam in each tooth in pair 1. The apical 2 mm of each tooth in pair 3 was removed, and a class I preparation was prepared and filled with amalgam. The apical surface of resected roots in half of the samples in each pair was lased twice by using Nd:YAG laser. The duration of lasing and the number of pulses were recorded for each tooth. After application of nail polish to the unoperated surface of each tooth, the teeth were placed in 0.5% methylene blue dye for 48 h. The amount of dye penetration in sagittal sections of each tooth was measured. The amount of dye penetration was significantly lower in lased roots than in nonlased ones (p < 0.05). Based on our results, it appears that application of Nd:YAG laser reduces the permeability of resected roots.

Tissue response following CO2 laser application in apical surgery: light microscopic assessment in dogs

The potential advantages of CO2 laser in apical surgery have not been established histologically. Therefore, the long-term effects of CO2 laser on the apical and periapical tissues were examined histologically in dogs 6 months after apical surgery. Lased specimens and unlased controls showed periapical inflammatory and osteogenic reactions. Lased root surfaces revealed craters with a superficial charred layer closely associated with new cementum-like matrix. The subjacent dentin appeared tubule-free and eosinophilic. Lased bone trabeculae showed a charred layer with a deeper osteocyte-free zone. The charred layer was covered by new bone. Detached charred segments in the marrow space and periapical inflammatory infiltrate were intimately associated with multinucleated giant cells, some containing minute char particles. Such cells were absent from the root and trabecular char linings. In addition, the charred surfaces were free of hard tissue resorption. These results suggest that CO2 laser does not hinder healing when applied in apical surgery.

Follow-up after periapical surgery: the value of the one-year control

A total of 474 teeth treated with periapical surgery were examined after one year. Complete healing was unequivocally demonstrated for 250 teeth. Two hundred and fourteen teeth were scheduled for further follow-up, and of these, 194 (91%) could be followed until a stable situation was recorded. Of 41 cases judged as completely healed after one year, but with initial observer disagreement, only 2 (5%) failed later. The 76 cases showing incomplete healing (scars) after one year with few exceptions ended as completely healed or persisted as incomplete healings. The uncertain group (n = 72) was equally re-distributed as successes (completely or incompletely healed) or failures at the end control. Five cases showing no healing after one year all ended as failures. Based on these findings it is concluded that the one-year control will provide a valid diagnosis for the majority of cases. Only a minor number, the uncertain healings, need further follow-up.

Retrograde approaches in endodontic therapy

The routine use of retrograde fillings during apical surgery, as well as the material of choice for that purpose, have been debated. A retrograde filling is placed so as to seal an infected root canal causing periapical pathosis. Therefore, retrograde root canal fillings should be performed routinely during apical surgery regardless of the apparent technical quality of the root canal obturation, unless orthograde endodontic treatment is performed in conjunction with surgery. When orthograde treatment is not performed, retrograde root canal filling enhances the prognosis of apical surgery. An array of potential retrograde filling materials have been extensively investigated in vitro and in vivo. Once that the biocompatibility of the materials is confirmed a clinical comparison, rather than in vitro sealability studies, is the most valid evaluation method. Some of the difficulties encountered in long term clinical studies in patients may be avoided in animal studies. The review of the relevant literature of the past decade suggests that amalgam used in conjunction with cavity varnish is the retrograde filling material of choice. It must be stressed, however, that retrograde filling is not comparable to debridement and obturation of the entire root canal. Therefore, when the only way to approach the root canal is from the apical direction, rather than placing an apical retrograde filling, a retrograde endodontic treatment of the entire canal should be preferred, if it is feasible.