Orientation in space Errors and Complications

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4.4 Orientation in space

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One of the major aspects of the surgery is spatial orientation in the wound and anatomical-topographical relations. Evaluating the situation in the mouth cavity before the surgery, we plan our future actions depending on the shape and relief of the soft tissue. But as soon as we lift mucoperiosteal flaps, we see absolutely different volume and topography. At this point, it is very easy to deviate from the previously made plan, or even lose your way in the wound and fail to observe the distances and angles defined before the surgery. This can result in a number of common problems – injury to the teeth adjoining the surgery site, perforation of the alveolar bone walls or sinuses.

most difficult thing is to calculate the angulation of the implant to the adjoining teeth, especially when implants are inserted at the site of missing first premolars near existing canine teeth.

The first thing to do after lifting the flaps is to calculate the distance from the distal surface of the canine tooth to the centre point of bone preparation. The best and easiest way is to make the distance from the tooth equal to the diameter of the installed implant. To do this, you need to have a sterilisable sliding caliper in your surgery kit. If you don’t have it, just put a depth gauge of the necessary diameter to the tooth. Orientate by the crown of the tooth. In your mind, make a straight line through the middle of the cutting edge to the middle of the tooth neck. Parallel to this line, set the angulation of the drill 2.5-1B.

Never try to drill to the full depth immediately. Perforate the bone 4-5 mm deep, put the thinnest depth gauge into the hole and try to imagine where the drill will be if you drill the bone as deep as the length of the chosen implant. Remember that the diameter of the hole will increase with each drill. Ask the patient to turn his/her head to each side and look at the angulation of the depth gauge not only with regard to the adjoining teeth but buccolingually. If you have discovered that the angulation is to be changed, do it at once and not when you’ve made a hole of the necessary depth and maximum diameter. Withdraw the drill from the bone almost completely, change the angulation and go on drilling through the same entry hole you’ve just made.

4.4-1A The drilling axis and the axis of the implant installation accordingly must lie in the axis of the tooth angulation.

4.4-1B The implant is inserted in the bone. The distance from the tooth to the implant is clearly seen. But note the real distance from the implant to the tooth in the mouth and that on the X-ray! You can hardly see the distance on the X-ray picture though it is there!

4.4-2 Carefully evaluate the topographic anatomy of the teeth adjoining the implant site. Distal inclination of the tooth root apex is not a rare thing.

4.4-3 If the tooth root has been injured by the implant or not, can only be said after getting computed tomography scans.

4.4-4 If the implant and the tooth axes are not parallel, it can lead to root injury or pulp necrosis.

4.4-5 Often images of the area of the teeth #3 to 5 have distorted projections due to the shape of the dental curve and the rigid algorithm of the orthopantomograph. The more oral the inclination of the alveolar part is or the more prominent the defect of the vestibular wall is, the greater the illusion of overlapping is.

PROBLEMS OF IMPLANT SITE PREPARATION

Probably the main problems during implant site preparation result from violation of the intermittent preparation technique, insufficient irrigation, using blunt drills, and excessive pressure on the instrument. Each of these factors or a combination of them lead to critical local overheating of bone tissue, its necrosis and, as a result, the loss of the implant.

During intermittent preparation make sure that the axis of the drill is the same each time it enters the bone. Each time the drill must enter the drilling hole in the bone with perfect precision!

Otherwise, the entry hole will be destroyed and get an irregular – oval – shape and the size exceeding the diameter of the drill, thus decreasing implant stretching and primary implant stability.

Also, remember to keep the drill rotating when entering and extracting it from the bone during preparation! You mustn’t stop the drill when it is deep in the bone and then just pull it out.

DISTANCE BETWEEN IMPLANTS

It is essential to try to preserve sufficient interdental septa between several adjacent implants. It is usually considered that their optimal width must be at least 2 mm, otherwise the septa may get lysed. Here it is necessary to mention that it is not always so, much depends on their angulation towards each other, careful preparation of the implant site (remember about thermal injury), local trophicity and the following prosthetic procedure.

The provided case 4.4-6 is quite common (e.g. implantation on the site of the lost teeth 36 and 37 and tooth 38 converging in the direction of the defect). There is space left which is too big for one implant and too small for two. It is indeed more appropriate to insert two implants rather than one. Only you shouldn’t try to make the implants parallel to each other.

Try to insert the distal implant parallel to the axis of tooth #38 and at an angle to the mesial implant 4.4-7.

4.4-6 The problems here must have appeared not because the implants were too close, but because of the thermal injury during the surgery. Note that there is loss of bone tissue not only in the area of the interimplant papilla but round the periphery.

4.4-7 Even the slightest angulation of one implant to the other allows to increase the width, and thus the trophicity and resistance to load of the interdental septum between them. Believe me, this will not in the least make the prosthetic procedure more complicated.