Os lec# 4 14/10/2014 Dr. 7azem



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Os lec# 4

14/10/2014

Dr. 7azem

Done by Tasneem

Stereolithography:

  1. Used in complicated cases usually (like resoroped bone), because we can’t plan dental implant theoretically unless we have detailed image about alveolus so we can avoid perforation of bone plate or nerve and other consequences that we won’t.

  2. Not used in simple cases where enough ridge width and height because we have here safety margin. Here we use conventional way.

  3. Give us detailed image.

  4. Very precise dental implant.

Technique:

You take CT scan and produce sterolithograph(3D model or printing)

As an example (bottle put it in 3D laser machine then by software print it as a wax model) this the concept of stereolithography.

We can use it in surgery of skull to facilitate the surgery like broken orbit on one side but other side is sound so we can use sound one to do template for the other.

Now in dental implants we use CT scan image and by software program we can put treatment plan for your implants (length, diameter, site,….) and you can put prosthetic part to see end result. Once you finish that you can print your trt plan ,now you can prepare surgical template (acrylic) on this final model.

Surgical guide it’s look like night guard but here with cylindrical holes. Why cylindrical? To prevent inclination for twist drill so prevent perforation for lingual plate for example. Surgical guide should be fit on final model.

The problem of stereolithograhy or computer assisted treatment plan is average error in treatment plan (1-2mm deviation for implant site) and other studies reported (6mm) which is not accepted.

surgical phase of implant

2 stages of this phase:



Stage 1: is placement of implant (last lec)

How much do we wait after placement? Usually 2 months and in maxilla about 3 but there are many systems improve surface treatment of implant so we can wait just 3 wks. But when we talk about conventional implant we wait 2 months in mandible and 3 in maxilla.



Stage 2:

Pt come to clinic we take x-ray to examine bone around implant. If there is good bone around implant we need to open or to uncover the implant. Which 2nd stage.

As we know we have non submerged and submerged implants.

When we have non submerged we don’t need 2nd stage because it is ready for loading.

But in submerged implant we need to open or uncover and remove healing screw then put temporary healing abutment (cylindrical one that have screw) then leave it for 2-3 wks for soft tissue healing and contouring for gum happen then after that we put final abutment.

How do we uncover or open it??



  1. Tissue punch: circular punch.

  2. Or crestal incision.

  3. Or apically repositioned flap: used when minimal keratinized tissue found so we try to keep it not to cut it. Why do we need keratinized tissue? To prevent infections and gingival ression.

3-4mm (as minimum) of attached gingiva is needed around implant. So when little keratinized tissue is found we don’t use tissue punch or crestal incision we use apically repositioned.

This sheet discuss difficult cases like resorbed ridge, proximity to vital structure like sinuses we know that after extraction of post teeth the sinus pneumtize so we should be careful , ID nerve (it’s very annoying for pt to be parasethized lower lip) and nasal cavity. So:



Advanced surgical techniques:

  1. Immediate implant placement: last time we talked about conventional implant placement. Now we can place implant immediately after extraction but there is special technique. Now we have anterior zone and posterior one.

In anterior zone the problems that we can face:

  • if incisor or canine has infection or periodontal problems here it could be associated with resorbed labial plate so we need CBCT and evaluate labial plate if it is definitely resorbed we can’t proceed immediate implant we need to wait. So we can’t always do immediate implant (in infected teeth or extracted with loss bone). Other opinions to do Socket preservation: after extraction we put bone graft (synthetic or natural) to minimize bone resorption not prevent it.

in posterior zone we have:

  • multirooted teeth so the shape of roots is unfavorable as we know the shape of implant it is single not multi so what do we do here?? We usually examine the sockets we try to choose the one that run with long axis of future prosthesis so here we need good planning for inclination of implant to be placed. Usually second part (abutment) manufactured by companies in different angulation (25,30-45 degree) to facilitate crown fitting on abutment. So if dentist places implant that inclined up to 30 degree he can put 30 degree angulated abutment. Again we take x-ray and evaluate interdental bone if its good we can place implant inside it if not you have to choose one of the roots and leave others.

  • Bone resorption either vertically or horizontally. Usually vertical bone loss is worse than horizontal it is not easy to put bone graft so usually what happened that osteointegration occur with exposed threaded of implant so here you should be careful by either change the planed place or to postponed the implant. If vertical bone loss we do bone graft but if horizontal we might think if loss more than 3mm we do.

  • Primary stability. Because of the large bone defect after extraction for multirooted tooth due to wide socket we depend on apical portion for primary stability of implant so we prepare apically with twist drills and place implant so we get the primary stability from apical portion not coronal. Coronal wider than implant , do we need to put bone graft at same time here?? No it is just around 1-2mm which is not indicated. Usually for bone graft we need to be more than 3mm defect and this again to minimize buccal bone resorption.

Immediate implant its very successful:

  1. pt doesn’t need another surgery. Doesn’t wait for healing.

  2. theoretically it minimizes possibility of bone resorption because within 2-3 wks it loaded and this stimulate bone deposition and preserve the alveolus.

It is common good practice to do immediate implant.

  1. Guided tissue regeneration used in bone defect. Now what happen usually when there is bone defect and put bone graft without GTR?? Usually soft tissue regenerate faster than bone then invade and fill the defect. In this teq we put membrane on bone graft to separate it from surrounding tissue (gum and epithelium) and this retard soft tissue regeneration. We have many types resorbable and non resorbable. The conventional is Goretex. How do we place it?? We need to make sure that the membrane larger than defect then place first the bone graft then fix the membrane on it away from adjacent teeth by stretches or special pins. See slides(61-64). As you see there is defect in ridge width, we place synthetic bone graft (hydroxyapitate), then cover it by the membrane.

Grafitting methods: to provide bone for deficient area:

  1. Local manipulation: take bone from adjacent area (anterior nasal septum, chin, intersptal bone from extraction site) any bone we can use it. Ridge expansion without need for bone grafting: used when narrow ant. Maxilla or madible ridge we bring osteotome and break ridge in the middle and put osteotome and expand the ridge (slide66) you can see microfracture in labiopalatal cortex then we can put implant after expansion.

  2. In extensive grafitting (large or gross defect or atrophic jaw): bimaxillary surgery (sandwich teq), they do osteotomy cut in maxilla to advance it downward then they graft bone in between the maxilla and midface. (not common).

  3. Distraction osteogensis: they do osteotomy cut in jaw and stimulate formation of bone and callus by elongated distance between 2 fragments so they put device that activate it everyday 1-2mm that distract fragments from each other. So we can apply this teq in dental implant to elongate the atrophic ridge but the problem it is expensive.

  4. Tissue engineering: stimulate bone generation by tissue mediators (morphgenic protein) that stimulate the formation of osteoblasts to deposit more bone.



  1. Sinus lifting: common in dental implant. After extraction the sinus pneumtize downward with just 2or3 mm away from crest. And the minimum length of the implant is 6mm so if we put implant here it goes in the sinus and there is no primary stability. So what we can do is sinus lifting:

    1. Direct sinus lifting: slide 67 on buccal side we move to sulcus make a window 2-5 mm (cadluk procedure) we elevate the opening itself and the membrane up and then we insert synthetic bone then we wait 6 months for bone healing and generation then take radiograph to make sure of bone height. Now 6mm of bone height is not enough to support the implant so we do 2 procedures sinus lifting and bone graft. Direct sinus lifting is very predictable procedure almost the success is100%. Synthetic bone graft isn’t always successful but when used with sinus lifting it succeed. Some literatures show success of sinus lifting even without bone graft. Main principle is to elevate the membrane without tearing which is the common problem of sinus lifting. What we can do when the membrane tears is putting GTR membrane and cover the perforated area then proceed as usual. Another solution is to use piezosyrgery which ultrasonic cutting device it cuts bone without affecting soft tissue so it doesn’t cut the sinus lining membrane. And we can use it in mandible so it doesn’t injure the ID nerve.

    2. Indirect sinus lifting: here we use it when there is good bone but we need few mms to be enough. so from the socket and after extraction we insert blunt instrument (blunt that doesn’t injure the lining membrane) slide 68 the left pic. Blunt instrument push the membrane up then we insert bone graft then we can put longer implant than estimated alveolar bone height.

Dr show his case (70-84): panoramic radiograph show very resorbed ridge almost 2 mm btn sinus and crest. If we do implant without sinus lifting we will end up with sinus perforation and compromised primary stability. he planned sinus lifting bilateral. Slide 71 show left side he did incision and elevated the bone. 72 he cut in the wall of sinus without perforating the lining membrane.74 show the membrane. clinically you can see the membrane move up and down as pt breath . 76 by special elevator we elevate the membrane. 77 you can see the gap. 79 place synthetic bone graft in the sinus. Reposition the bone and close the flap. 86 panoramic view after 6monthes procedure.

Materials used for bone graft

We should know some terms first :



Osteoconductive: work as network or frame for cells and bone deposition.

Osteoinductive: stimulate bone deposition by natural cells –osteoblast,osteocytes…) and tissue mediators. Like natural bone.



  1. Synthetic bone: osteocondutive. Minerals like hydroxyapitate, Tricalium phosphate. Biocompatible.

  2. Natural bone (best): osteoconductive, osteogenic, osteoinductive. Like Auto genus bone graft is the gold standard .

Adjunctive implant techniques:

  1. Sinus lift : long term success.

  2. Rib graft : not common, because most implant procedures elective one. But in large constructive procedure like trauma or cancer we can use.

so we usually we choose simple procedure like we take bone from oral cavity, or to use synthetic material, or use short implant.

Q : why the rib not other site??

Because the rib has favorable shape like mandible so don’t need a lot of modification. And we not affect the donor site.

But actually you can take graft from everywhere like tibia, radius, iliac crest, clavicle. Each one has own morbidity but the easiest one is the iliac crest. Here we chose rib due to favorable shape.



Slide 91: they did sinus lift without bone graft. They put materials used in tissue engineering and they found it’s successful .

  1. Onlay grafting : replacing large bone loss, however we face sever resorption rate. We take from iliac crest or from another place. We don’t prefer this teq.

  2. Pterygoid & maxillary tuberosity implants: the idea here is to place implant in difficult area like tuberosity or pterygiod if we have atrophic maxilla but it’s not common.

Special consideration in atrophic mandible:

  1. Interforaminal area: between 2 mental foramina is safe usually we have good bone height but the problem the ridge is very thin. So we can depend on anterior region for ex. If we plan to place overdenture we can place 4or 3 even 1 implant in anterior region.

  2. Behind mental foramen: the problem here is ID canal it’s very close when we have atrophic mandible. What can we do??

    1. Nerve repositioning: we do incision , take nerve out the canal laterally or medially , place bone graft, then place dental implant. So implant enter to lower border without injury for the nerve. But the problem here that we might injure the nerve during this manipulation. Piezosurgery is one of option. But again nerve injury is the side effect. Difficult to pt they not accept.

    2. Short wide implant: 6mm implant length. Most atrophic post mandible ridge height is 7mm so it can do the job. If we have big load we can place more than 1 implant to distribute it. Pts accept this option.

    3. Lingually positioned implant: the idea is to place implant lingually behind ID nerve. How?? By computer assisted dental planning , you plan angulated implant lingaully, produce stent or guide, place implant. It is not easy to do.

Q: in this option could we injure the lingual nerve??? No because it outside the mandible anatomy, it is between mandible and soft tissue. This happen if operator perforate lingual plate and retract soft tissue but not from Implant.

Complications:

  1. Sinus perforation: you can prevent by good planning (good radiograph, length of implant….)

  2. Perforation of ID canal is serious. You might injure the nerve and induce parasthsia or anesthesia. If this happen you should remove implant or replace by short one. And wait nerve healing which takes weeks to months or year.

  3. Perforation of buccal or lingual plates: due to bad planning or surgeon didn’t see lingual undercut in mandible.

  4. Wound dehiscence: tension of suture.

  5. Implant failure : there are many causes (early, late failure). The important thing is technical error that we should avoid like overheating for bone during preparation, and contamination, perforation. Otherwise implant success is v.very high it can reach 100% if well planned even if your pt has systemic problems.

The most failure causes related to operator.

  • When you have parasethsia due to nerve impingement you have very limited options to restore function of nerve, you just can remove the impingent and wait for healing (3-6months). But if it is complete cut you can think about other options.

Growth and transplantation of a custom vascularised bone graft in a man





  • Now allograft same tissues from different pt. they treat the tissue remove antigens and check them for viruses and aids. then produce this tissue as powder or paste after treatment. It is not good as autogenus because not contain cells. It contain dead cells so it is bone graft without inductive ability .

  • Xenograft tissues from different species. Like hydroxyapatite from coral, caws (fears about caw disease that can be translated to human), membranes from pigs.

  • Usually in dental practice we deal with autograft or synthetic bone like hydroxyapatite or Tricalium phosphate.

  • Donor sites for dental implant

    • Extraoral: rib, iliac crest, clavicle……

    • Intraoral: chin (incision from canine to canine, exposed the area, cut bone from apices of teeth to chin without any change in contour of the chin so there is no side effect aesthetically nor functionally complete healing without any defeciency, take thin blocks better blood supply than thick and less porn to resorption, transfers to recipient site, fix it with screws, cover it with synthetic bone and membrane to make it thicker) , retromolar area, anterior ramus laterally, coronoid, …..

  • Healing cap (healing abutment), you put it after osteointgration, this in submerged implant but non submerged we don’t need. The aim of it to allow healing of gum after punch or incision, the gum needs healing.

What dr want from us to understand are:

Indications of bone graft, options, how to diagnose defects whether 2D or 3D, horizontal or vertical, complication, how to avoid by good planning.



Good luck 


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