For many years, endodontists have tried to see deeper into the pulp chambers and into the very root canal spaces themselves. The theory was that the more that could be seen, the better all the canals could be located, cleaned, shaped and filled. Simple magnifying lenses, then magnifying loupes and finally surgical loupes have been used. These optical devices provided magnification, but there were many drawbacks.
The prime problems were lack of depth of field and inadequate lighting into the pulp chamber spaces. The platform these devices were mounted on, the operator, was not stable or vibration free, which becomes problematic as the magnification becomes greater. A third problem was the fact that the assistants could not see the same field that the dentist was visualizing.
In otolaryngology, vascular microsurgery, ophthalmology and plastic surgery, these issues were resolved with the development and use of the surgical operating microscope. In the late 1980’s and early 1990’s, endodontists began to use the surgical operating microscope in many endodontic offices. The advent of Dental Microscope has opened great vistas for the Endodontist, Periodontist and the Oral Surgeon.
The Dental Microscope has made the process of diagnosis and cure very fast and simple which has resulted in innovative therapeutic approaches to dental problems. The hitherto inaccessible area of oral cavity has now become accessible due to the microscope.
With the help of the microscope the treatments like removal of broken instruments from canals, and treatment of calcified canals has become possible and made the tooth preservation possible, whereas the same would have, without the help of microscope, led to tooth extraction. It is now realized that the microscope could and should be applied to all phases of endodontic treatment. In modem endodontics, the microscope is used in every phase of treatment from access opening to placement of retrograde fillings in apical surgery procedures.
Few years back, the American Dental Association’s Commission on Dental Accreditation revised the standards for Advanced Specialty Education in endodontics to include microscopy in the cuniculum. The revision took effect on January 1, 1998. Today, microscopy is part of the curriculum of endodontic postgraduate programs in many developed countries.
The basic microscope used in dentistry consists of two eyepieces mounted on an inclinable base for stereoscopic viewing, a turret containing a series of lenses for varying the magnification, and an objective lens to bring everything into sharp focus. Depending on the brand of microscope and the number of lenses in the revolving turret, the magnification range for most microscopes is from 4x to 25x.
The number of steps varies from three to six steps, with more expensive microscopes having a zoom lens for step-less magnification ranges. A fiber optic light source provides bright, collateral illumination to the field. Collateral illumination is necessary to provide shadow free lighting to the exact location that the operator sees. To solve the problem of the assistant involvement, there are two approaches.
The first and more expensive option is to provide an assistants viewing scope, which gives the assistant the identical visual as that of the endodontist. The second option is to have a video camera mounted to the microscope, and have the assistant visualize the procedure on a television monitor. This is not quite as efficient as the co-observer viewing port, but at least the assistant is directly involved in the same procedure.
For legal or teaching purposes, a VCR could be included and all procedures recorded for later viewing and evaluation. Still cameras (35 mm or digital) can be attached to further enhance presentations and patient education. Because of the powerful magnification available, conventional instruments are too large and obscure the visual field. To circumvent this problem, new micro instruments have been designed. These include mirrors with a 2-5 mm diameter, niicroscalpel blades and miniature explorers.
Microscope can be ceiling mounted, wall mounted or placed on moveable base for use in different operatory environment. It can be configured with a magnification ranging from four to 26 times. The magnification can either be controlled manually with a three or five step changer or motorized.
The microscope can be fitted with a 200 mm objective lens, inclinable binocular tube and a fibre-optic light source for illumination. The 200 mm objective lens provides a convenient working distance between the patient and the microscope. An operating microscope should be modular to allow the attachment of a co-observer binocular tube, which can be used by a nurse for assisting or by a student for hands-on training.
The rotatable eyecups ensure that the eyeglass wearers can also enjoy a optimum field of view, IPD adjustment helps in focussing the objective. Diopter adjustment also helps the bespectacled doctor. Many of the microscopes have been provided with orange filters for avoiding premature hardening of composite resin. They also used to have a red filter which eliminates the pronounced red tones during surgery.
The integrated video camera inside the microscope can be used to store images in digital database for future reference. The video camera when connected to a projection unit, can be used to educate the patient about the exact nature of problem by imaging the problem on a screen, and thus obtain the patient’s concurrence for the procedure with complete faith in the doctor’s diagnosis. The camera can also he used to give live demonstration to dental students.
The Manual Surgical Operating Microscope is designed to be user friendly and its ergonomic design allows the doctor to work without additional stress.
Using the microscope takes time and there is a learning curve. The common problems associated with the learning process include an altered eye and hand coordination, restricted body movement and loss of orientation.
Microscopes are available in a wide variety of configurations, but most of the microscopes used in modern dentistry used to have following desirable properties:
Magnification: Manual or motorised The magnification which is 5 step and up to 26x coupled with coaxial cold light illumination via fiber optic, gives a clear three dimensional view of the root canals, isthmus, perforations, lateral canals, microfractures, etc.
• Fine Focus: Manual or motorised
• Mount: Floor, ceiling or wall
• Microscope Magnifications
Low magnification: 2.5x to lOx – Used to center objective
Moderate magnification: lOx to 20x – Used for operating
High magnification: 20x to 30x – Used for operating and scrutinising details
CLINICAL APPLICATIONS OF MICROSCOPES
The use of dental microscope in Restorative Dentistry guarantees the ultimate in precision throughout the entire process — from the dental laboratory to the final setting of the prosthesis.
In periodontics, the Dental Microscope proves its worth right form the initial diagnosis stage, like for the recognition of subgingival concrements and the assessment of gingival pocket tissue. It is of paramount use during a surgical procedure where minute details need to be observed. The Surgical Operating Microscope with a learning curve of upto 60 hours for doctors sounds very intimidating. But the features more than compensate for the initial discomfort the operator might feel.
USE IN ENDODONTICS
Having visual access is critical in endodontic treatment, as it is important for the operator to be able to see exactly what he or she is treating in order to do it well. The operating microscope provides high quality illumination and magnification which can be varied to suit the different clinical situations.
Microscopes can be used in conventional or surgical endodontics. They are adjuncts and are especially useful in situations requiring excellent visual access such as locating calcified canals or fractures, repairing perforations, retrieving separated instruments or surgical endodontics (microsurgery). Often in such instances, their usage significantly contributes towards a successful treatment outcome.
LOCATING CALCIFIED CANALS OR FRACTURES
The microscope is used to scrutinize the pulpal floor for subtle changes in the dentine morphology, colour and calcification patterns. Such subtle changes serve as clues, helping the dentist uncover any calcified obstructions to reveal the canal underneath.
A one per cent methylene blue dye solution is used to stain developmental grooves, canal orifices or fracture lines and provide a map that makes detection easier. Microscopes can ald in the search for the second mesiobuccal (MB II) canal of the maxillary first molar, which is commonly located within a developmental groove between the mesiobuccal and palatal orifices.
RETRIEVING BROKEN INSTRUMENTS
Instrument break in a canal can be an intimidating problem in dentistry, The microscope can be of assistance in removing posts or in retrieving broken or separated instruments. The level of difficulty in retrieving such instruments generally depends on:
(1) How tightly the separated instrument is bound to the canal wall?
(2) How far down the canal the separated instrument is, and the length of the instrument?
Instruments separated apically past severe curvatures, are poor cases for retrieval. Using the microscope to see, ultrasonic spreader or slim JIM tips can be used to trough circumferentially around the separated instrument. The microscope helps the operator see the instrument within the canal and pinpoint precisely where to, trough. Such precise detail during troughing, prevents the excessive or unnecessary removal of dentin that can result in perforation or weakening of tooth structure.
Troughing could be done only if there is sufficient tooth structure around the separated instrument. If the instrument is tightly bound, the ultrasonic spreader tip or a size 15 ultrasonic K file can be vibrated against the side of the instrument to loosen it before retrieval. Under microscopic vision a microsurgical forceps can he guided with maximum precision to grab and retrieve the instrument. Often these troughing and retrieving procedures are carried out in areas of the root canal that are poorly lit or apically too far down to be seen clearly.
SURGICAL ENDODONTICS (MICROSURGERY)
Microsurgery is defined as the dissection of tissues under the microscope. The incorporation of microsurgery into endodontics has dramatically revealed a wealth of details that have helped endodontists improve on their surgical techniques.
The advantages of microsurgery in an apicectomy are:
(1) The removal of bone overlying a root is nna
(2) The periapex can be examined for canal exits, extrusion of filling materials, previous retrofills and additional roots and with the aid of methylene blue staining, root fractures can be detected. In repeat surgeries, microscopes can reveal corroded and leaking old amalgam retrofills.
(3) The resected root apex can be inspected for an even resection.
(4) After resection, anatomical variations of the root canal system like isthmuses, lateral canals, C-shaped canals or fins, can be visualized and retro-prepared. Any missed canal, inadequately filled root canals or cracks can be detected.
(5) Retro-preparations can be executed precisely along the longitudinal axis of the canal space and extended to the proper bucco-lingual boundaiy.
(6) Retrofilling is more precisely done and any excess retrofilling material can be detected for removal. The marginal adaptation of the retrofilling to the canal wall call be checked.
Under good lighting and magnification, perforations on the floor of the pulp chamber and root canal can he internally repaired non- surgically. The repair is conducte4 by sealing the defect with or without a matrix.
ADVANTAGES OF USE OF MICROSCOPE IN ENDODONTICS
In endodontics operating microscope has the following advantages:
(1) Microscopic images are both magnified and illuminated. Under the microscope a whole new world of previously felt and visualized structures come alive. Magnification and enhanced clarity allow the examination of the periapex, pulpal floor and root canals in such minute detail that those details which were previously unnoticed become very obvious.
(2) Under the microscope, the endodontist sees the procedure he is doing in clear magnified detail, thereby eliminating guess work. Such precise images of the operating field give the endodontist greater control over his work and allow him to refine his technique to a level never seen before.
(3) There is no colour distortion in microscopic images. Natural colours of tissues are faithfully reproduced in their image; and together with high definition and clarity, it is much easier to differentiate tissues that look somewhat similar. For instance, under the microscope it is easier to see the difference between bone and dentin during surgery.
(4) Microscopes give three-dimensional images.
(5) When a microscope is connected to an audiovisual itcording device, the endodontist has the option to document an entire procedure for educational or medico-legal purposes.
STERILIZATION AND MAINTENANCE OF THE MICROSCOPE
Maintenance of the microscope is relatively simple. When in use the entire scope can be covered in plastic wrap, leaving only the eyepieces and the objective lens uncovered. After each patient use the plastic wrap is discarded, and the exposed surfaces are wiped with disinfecting solution.
Any debris that collects on the lens is easily removed with lens cleaning tissue. Bulbs have a life of about 100 hours and in most microscopes are easily replaceable. Some instruments have multiple bulbs in the housing, and if one bulb fails, another bulb can be made to work in a matter of seconds, without hampering the ongoing procedure.
The number of ways that the operating microscope can be used is only limited by the operator’s imagination. In endodontics, the uses include but are not limited to finding calcified canals, post removal, diagnosis, management of difficult “C” shaped canals, perforation detection and repair, evaluation of furcal involvement and detection of root fractures.
In endodontic surgical procedures, the uses of the microscope include soft tissue management, proper root resection, location of accessory canals, placement of retrograde fillings, locating fractures and location of anatomical landmarks. Procedures may be recorded and sent out to other institutions or classrooms for real time visualization. The diagnostic potential and teaching potential of this technique is unlimited.