Monday, May 9, 2016

Complications in Implant Dentistry


Case # 18   “My Implant Crown Never Felt Tight Like the Others”

Patient has a tissue level Straumann implant that is placed and allowed to integrate for 8 weeks. Impressions are made for a screw retained crown. The crown is delivered by an exceptionally skilled and experienced referral and torqued to 32 N/cm.  Shortly after this time the patient notes some movement in the crown; having other implants he questions this.  The abutment screw is retorqued; it is tight but still has some side to side movement, although almost clinically unperceivable. There was no pain on torquing the screw.  He lives with this for a year and notes it is slowly getting more mobility.

He presents to our office for evaluation.  First step is PA radiograph and CBCT that look fine.  Next is clinical exam and there is a rotational movement from left to right very minimally when the crown is grasped between the fingers.  It is barely perceivable but is present. On percussion the crown sounds solid

Diagnosis would include implant loosing integration.  Loose abutment screw and or loose crown.  Each interface must be checked systematically.  Since this is a screw retained crown that eliminates the need for drilling through the crown to access the prosthetic screw to remove it. It also eliminates the possibility of the cement union failing.  Although on a side note for the future there are many lab techniques using milled restorations that are advocating cementation of a crown to an abutment to create a screw retained restoration, only time will tell if this interface will weaken in some cases. In this case it was a cast UCLA type abutment.

The composite was removed a small cotton pellet was removed and the screw was reversed.  The screw was very tight and required a torque wrench to counter torque.  It caused no pain or distress to the patient when this was done. The area was irrigated after the crown was removed; a small amount of metal particulate consistent with a grinding movement of the crown was evident in the implant body.

To test the implant it was percussed and sounded solid an implant mount was placed and the implant was torqued and counter torqued with no pain or movement...  It was determined the implant was solid.  There was some debris in the implant consistent with the friction from abutment mobility.  

So next the internal integrity of the implant was tested to make sure the abutment had not degraded the internal connection. This was done by the placement of a transfer type impression coping it was place and tightened and attempts were made to rotate it. There was no movement.  This confirmed the implant internal connection was not damaged or rounded by the crown movement.  So continuing in a bottom to top analysis. The abutment was tested.

The abutment was tested by placing the screw retained crown on a brand new implant analog.  The model and original analog was not used since these sometimes become accidently modified in the lab setting.  It was noted that the crown ucla abutment did not fit flush to the implant analog.  There was a gap caused by a small hang up on the buccal where the porcelain extended to the metal junction. When the crown was placed on the analog mounted in the model as supplied by the lab it sat flush.   This was removed carefully under magnification incrementally until the crown fit snuggly on the new implant analog.  At this time the restoration was transferred to the mouth and fit snuggly with no rotational mobility.  A new abutment screw was placed and torqued to 32 N/cm, contacts and occlusion were tested Teflon tape and composite were used to seal the access hole.

A good example of a common problem that does occur in implant dentistry and why it is important to have a supply of impression copings and analogs as well as abutment screws always in stock so the this type of diagnosis can be made and corrected for the patient.


Saturday, August 29, 2015

July 2015 Conejo/Simi Implant Study Club

Our July implant study club was graciously sponsored by Carol Sachs of Nobel Biocare.  We had the pleasure of listening to Dr. Kyle Stanley.  The following is a synopsis of his lecture.

Dr. Stanley is a USC Graduate and did a residency in Brazil, where he focused on implant dentistry and performed research with regards to the position of the anterior teeth and smile.  He teaches with Dr. Pascal Magne at USC, who is one of his mentors and somebody that he works with in biomimetic dentistry.  He lectures for Nobel Biocare.   On a regular basis works with Dr. Sacha Jovanovic at UCLA.  At the lecture he talked about new techniques including, 1) digital smile planning 2) abutment modification and 3) custom impression copings.

Dr. Stanley feels the biggest problem in implant dentistry today is; lack of planning and knowledge, and not beginning with the end in mind.  His goal is to create a natural look and thinks of the face, lips, gums and teeth as a single unit that has to flow naturally.  He is exceptionally critical of incisal edge position and that is the starting point when he designs a smile. The anterior display of the teeth at rest is very important, as well as the lip length, the age, race and sex of the patient.  For instance, when treating a 30-year-old patient, he allows 3-10 mm of tooth to be shown, in a 70-year-old patient, it is about 0-0.5 mm of incisal edge of the maxillary centrals shown at rest.  Women tend to have two times as much show of teeth as men and aging loses the elasticity in the upper lip so it sags more and you show less teeth.  At the same time, the teeth become worn down and they become shorter.

At this time 4 mm of maxillary central incisor shown at rest is the new norm for a common esthetic look. He showed a lip lift technique by Dr. Perenack developed in 2005 which uses an external incision under the nose removing a small amount of tissue and then allowed the lip to be lifted superiorly.  There is a scar with this technique and in 2011 the technique was modified and the incision was made through the nose and held up with a retention suture eliminating the scar.   The planning of the esthetic lip length is crucial and is often overlooked when it comes to smile design.  He likes to display about 2 mm of gingiva apical to the teeth while smiling and thinks this is ideal. With the incisal edge a little lower, he likes that to be 0.2 mm from the lower lip, so he came up with the 42.2 rule.  The 42.2 rule summarizes the measurements above.

In talking about central incisor width, it is 78% ratio in younger patients and 87% ratio in older patients.  This is because as the patient ages, they grind down the teeth and the teeth become shorter and thus the ratio becomes a higher percentage.  When he looks at the dentogingival esthetics at the zenith of the lateral incisor teeth, he says that the doctors at UCLA like to have the laterals and centrals at the same height where USC likes the laterals lower than the centrals and slightly shorter, thus the gingival display design is different, he uses digital smile planning to evaluate this.  He likes to take photos at rest, with a small smile, large smile, and calibrated photo with the calibrator showing mm so it could be used by the laboratory and a full face shot with good retractors so that the plane of occlusion could be identified by the dental laboratory.  He likes to add composite with no bonding agents in it to the incisal length of teeth to see how patients will appreciate that and whether other friends and family would find their teeth to be to short or too long and then he just chips that off after the fact, but he does take photos with that in place.

He spent a significant amount of time talking about the new ASC (angle screw channel) from Nobel Biocare and how it works noting it is a three-piece design, that the screw holds the zirconia abutment in place to the titanium abutment.  It is blue in color to understand which screws are used is important, and it is torqued to 35 Newton cm.  He says that you can use the ASC on molar teeth with the screw axis coming forward if you cannot open too well as another option for a screw retained molar.  This is a practice saver and it allows him to do an excellent job maintaining screw retained anterior teeth in areas where normally it would not be possible.  There is about a 25 degree angle this will accommodate. Still when doing temporaries, he uses a straight chimney on the temporaries and has that come out the incisal edge if that is the way the implants were placed and then just covers that with composite, but when he does his final impressions, then he moves to the ASC and uses the screw retained crown in a more traditional lingual or palatal position.

He then talked about the Nobel Connect and Nobel Clinician viewer for the i-pad. This is something that we use in the office and we are well versed in using guided surgery techniques.  Dr Stanley felt that the new workflow was to take an impression and then do an ideal wax up (beginning with the end in mind) and then do a CT scan. The CT and wax up together are scanned and that makes for a co-mingling of those through the Nobel Clinician software.
Then you are able to make a guide that is restorative driven, driven by the ideal position of the final teeth thus giving us the depth, angulation and position of the implant to optimize the restorative result.  He uses guided surgery on a high percentage of his cases.  The ideal gingival margin should be 3 mm below the CEJ of an adjacent tooth and that pretty much has stayed the same.  He definitely is a big fan of doing screw retained crowns wherever possible to eliminate cement margins.   

The next thing he talked about is abutment modification for his temporaries.  He feels he must maintain the papilla and that titanium provisional abutments are much better than any other material when it comes to gingival contact, so he takes the straight titanium abutment and he takes the additional collar and polishes it off to keep the chimney narrow and no wider than the implant itself eliminating impingement at the abutment interface.  He does not like the plastic temporary cylinders.  He does take the abutments and narrows them with the implant interface and likes to have all his restorations emerging off the implant without widening or flaring the platform to keep the buccal gingiva from moving apical on the maxillary incisor teeth.  He uses shade A1 opacifier on the abutments and you want 1.5 to 2 mm straight up, then taper until 1-2 mm in all titanium.  He does not like the fat impression copings and he wants to use narrow impression copings on all of the impressions making sure to fabricate a custom impression coping that allows for the ability to transfer the full information to the lab and by having a custom impression coping, the lab knows they can’t create a crown that is any wider than what is given to them. They cannot modify that in any way because that ends up leading to buccal gingival creep in an apical direction if they do not maintain those guidelines, so again he is not a fan of fat impression copings, but of the narrow impression copings and custom modified by using the standard technique for making a custom impression copings.  He does use cross polarized lights on teeth.  Cross polarized lighting in photography allows the lab to understand where the mamelons and various portions of the teeth are and by doing that is just another adjunct.

In discussing cements he thinks the excess cement can cause inflammation plus residual pain.  Excess cement is a risk factor if you have a depth of 1 mm or greater of attached gingiva surrounding an implant. You will always have cement, not sometimes, but always.  Implants are not teeth and they do not have an attachment like teeth do, so do not treat them like teeth. One of the biggest problems with the cement retention is bacterial colonization and all cements are different.  It turns out in all the studies that Temp-Bond original is the best cement to not allow bacterial colonization.  The Temp-Bond Non-Eugenol does have a lot of colonization so do not use that one or a cement like Multi-Link again has a lot of colonization of bacteria in the studies that he quoted. So as far as decreasing the amount of bacteria, the Temp-Bond original was the best.  Next, he talked about making a duplicate abutment with Teflon that you could then place in the crown and in so doing, you can get the excess cement out of that area and just have the minimal amount of cement that is present.  By doing this, you end up with a much less likelihood of having cement pour out into the adjacent tissues.  He talked about the strength of removing the crown from an abutment in the clinical lab and it turns out the Temp-Bond is the same as any of the others tested, so the strength is as good yet the bacterial colonization is much less.  The other thing that he talked about which was radiographic evidence and again he showed that the Temp-Bond shows up as well as Flecks on x-rays, none of the others show up on radiographs so you would not be able to make a confirmation of whether there was anything left behind.   So Temp-Bond is highly recommended to cement implant restorations.


He showed a case where a mom's tooth was lost coronally and using biomimetic dental techniques, they reduced it and sealed the dentin and then following this, took the daughter's 3rd molar that was recently extracted and went through a series of steps with the Cerec machine to mill the internal of the daughter's tooth to match the existing root structure of the mother's tooth, at which time it was bonded in place, so instead of having a crown restoration, she actually had the daughter's tooth bonded to her existing molar as a restorative aspect.  He went on to show multiple cases with regards to the esthetic zone and periimplantitis and finished his discussion with some really interesting and well done cases. His lecture was very well received by the members of the study club.

Tuesday, September 23, 2014

September 2014 Conejo/Simi Implant Study Club Meeting


We had the pleasure of attending the lecture that was sponsored by Sean Fisher of Zimmer Corporation.  The two featured speakers were Gregg Stebbins of Zimmer Trabecular Metal Technologies and Joanna Dorgan of Zimmer Dental. 

The lecture started with Mr. Stebbins talking about the metal Tantalum, which is the material that is behind their Zimmer Trabecular Metal Technology.  It is a porous biomaterial.  Originally, it was utilized by NASA in an effort to promote flying objects from getting into jet engines.  It was then owned by a company called Ultramet.  Ultramet was unsuccessful in creating this porous material for that specific utilization. In their research for other models to use Trabecular Metal in, they came across a biological model.  The microstructure of  Trabecular Metal is similar to coral.  There was significant research being done on utilization of coral as a allographic material and he felt there might be a place for Trabecular Metal to be used as an allograft.  There are 250 clinical papers backing up the success of this material and 15 years of proven utilization in orthopedic surgery, particularly in hip socket and joint restoration. 


The three things that make it a superior metal are the structure is similar to bone, in the function and physiology that it maintains.  It is a 99.9% pure metal.  It is not an alloy.  Tantalum is #73 on the periodic table and has a periodic weight of 180.95.  It is inert, noncorrosive to alloys, and when heated forms a 440 mcg average pore size dodecahedron that allows bone formation in the areas.  They coined this osseoincorporation, which is equal to bone ingrowth plus the addition of bone ongrowth, and it takes approximately 14 days for this to take effect.  It is a difficult procedure to make, done under high heat using a carbon core block that has been treated in a Tantalum gas chamber that deposits a fine layer of the Tantalum and takes 2-1/2 weeks for the material to adhere and approximately 6 weeks beyond that for fabrication of a dental implant.  

The dental implant that has been created was talked about by Joanna Dorgan of Zimmer Dental, the product brand manager. It is very similar to their Tapered Screw-Vent implants and it uses the press-fit internal connection that is common to all Tapered Screw-Vent products.  It has a trabecular metal band, a titanium upper, and a one piece welded at the apex of titanium.  The prosthetics are all common to a cross platform of Tapered Screw-Vent implants.  It comes in lengths of 10, 11.5 and 13 mm, and widths of 3.7, 4.1, 4.7 and 6 mm.  The advantage to the product is it has a final loading date of 2 weeks after insertion, which is twice as fast as the next competitor and about four times as fast as most other dental implant systems.  The drill sets used to place this are the exact same drill sets that we would consistently see with the Tapered Screw-Vent system from Zimmer Dental.  So it has a very high insertion torque and a higher surface area than the other implant models, thus giving it fine and rapid initial stability.  

Wednesday, July 23, 2014

July 4014 Conejo/Simi Implant Study Club

July 18, 2014



 Last Tuesday the Conejo Simi  Implant Study Club held a lecture featuring the guest speakers of Donald Nikchevich Jr DDS and Jonathan Shadi, DDS.  The study club met in the normal facility at Los Robles Regional Medical Center and Dr. Nikchevich began by explaining the new staffing at the Westlake Oral & Plastic Surgery office introducing Dr. Jonathan Shadi as the new associate to the practice and reiterating with the members of the study club that Dr. Bennion was working 3 days a week and had Mondays and Tuesdays off and Dr. Nikchevich and Dr. Newton were working 5 days a week.  Also that Dr. Wayne Ozaki was continuing to work on Thursdays at the office and the remaining 4 days would be spent at his new position at the University of California Los Angeles as the Director of Craniofacial Surgery. 

 The members of the study club had no questions with regards to this and the lecture began with Dr. Nikchevich talking about the emergency implant.  The emergency implant is an implant that is referred into the office on an emergency basis and treated immediately. The best examples of emergency implants and methods of temporization were all covered.  The Westlake Oral & Plastic Surgery office has almost a 20 year history of treating emergency implants and within the last 7-8 years, have treated about 5-6 emergency implants per week.  These are implants where the tooth was fractured traumatically, a crown was broken off due to caries, there was a chronic resorption that was noted by a referring dentist or there was minor apical pathology with pain.  All of these were great candidates for emergency implants.  Patients who would not be good candidates for an emergency implant would be those where there was significant frank pus, significant buccal erythema, high mobility with a broad range of radiolucency around any of the apical areas. 

With this knowledge base, the surgical technique that would be used would be the removal of the tooth atraumatically, curettage and irrigation of the area with copious amounts of normal saline, and then the placement of the implant.  Ideal placement of the implant would involve 3 mm or more of apical bone beyond the apices of the existing tooth for good stability.  A five wall defect is optimal where bone will heal in exceptionally.  Good thick gingival bio type is optimal and having adjacent teeth with no disease process is also optimal.  With these concepts in mind, the referral base understood what to look for in their referring of emergency implants.  At this time Dr. Nikchevich went over the basics of temporization which included the standard Flipper, the Essix retainer as well as an immediate temporization.  Slides were shown giving examples of immediate temporization using the immediate temporary abutment from Nobel Biocare versus standard screw retained temporary abutments that most manufacturers supply.  Clinical slides showed this in depth and also occlusion was talked about, how the patient would have to not bite heavily on the area, keep the area out of occlusion and the fabrication of these temporary restorations would not allow active loading by the patient during the healing phase.  Healing phases were discussed with the average being 10-12 weeks following the placement of implant with the patient being followed on average 3 times during that period.  Final radiograph and clinical testing would be done on the implant before they were referred back to the general dentist or the prosthodontist for impressions and fabrication of the restoration.  Statistics were given with regards to a 2 year from April 2012 to April 2014 study that showed the immediate extraction and immediate emergency implant placement with temporization and there were 848 implants, 26 of those were deemed non integrated giving us a 97% success rate. So that 97% success rate was within a 2 year period of consecutive implants placed immediately under emergency situations.  

That concluded the talk with regards to emergency implants and Dr. Shadi then took over the podium and described 3 cases that he had completed in his residency in the Fresno Hospital system.  These were all cases that involves significant bone grafting due to extensive defects.  The cases were in status right now, and had not received final restoration, but were progressing in that direction.  The materials used for these cases were a combination of Puros and Bioss and Bioguide membranes.  It was shown how significant releasing of the flaps was necessary to get primary closure and how the bulk of the grafts were significant due to overbulking initially.  One of the cases was the case that showed the complete absence of the maxilla secondary to a failed orthognathic procedure and this case was in its final process of being completed but showed a significant grafting in the area to lead to the placement of dental implants and a final restoration.  The study club ended at 9 o'clock and questions were fielded by the speakers.  The next study club would be in approximately 2 months at Los Robles Hospital, speaker to be determined.





DONALD NIKCHEVICH JR, DDS

Tuesday, May 20, 2014

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