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Dental Implantology - Science topic

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as CT better resolution and accurate image of an object true scale 1:1 than CBCT.
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The radiation dose needs to be considered before prescribing CBCT with clinical judgement. If a three dimensional radiograph is recommended, CBCT would lead to less radiation than CT.
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the crown can be pulled off directly  by the universal testing machine without need to use a set up or jig
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Why do you want to test tensile force!? Pure tensile is not present inteaoral!
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Is it safe? Any references?
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Calcium sulfites maybe done. If we let the bone cement solidification first and shattered to chips, then put chips to autoclave, maybe it can be used. However the chips were dissolved very quickly within two weeks, so only can be used at socket preservation or bone graft at sinus lift.
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accuracy of 3D printer while printing 3D digital surgical guide for dental implant placement
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Biomaterials
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Can you please explain little bit more about your concern. Question is not clear.
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There have been numerous studies on loss of dimension, changes in micrometers, surface change observed with electron microscope, etc. I cant find any that address the change in weight of tooth/enamel. can anyone help???
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Answer 1: Definitely erosion of enamel can occur due to continuous intake of lemon juice; however no studies have been reported or available in the literature as far as weight change of teeth is concerned in vivo. Effect of fluoride on demineralized enamel is a very well known phenomenon as countless number of studies had been carried out throughout the globe. It is also a known phenomenon that saliva replenished with fluoride ions helps in remineralizing the tooth structure. Fluoride present in whole saliva ranges from 0.01 to 0.05 ppm. If fluoride application has been carried out then concentration of fluoride in saliva could be very high even hours later. Saliva is separated from the tooth surface by a layer of plaque. This serves as a very important source of fluoride because it can concentrate fluoride to very high levels. When the pH drops, this fluoride is released and it combines with hydrogen ions to form HF, which diffuses into enamel. Fluoride can be weakly or strongly adsorbed onto the tooth surface. If present on the tooth surface it is released during an acid challenge. Even low concentration i.e. 0.1 ppm fluoride is sufficient to encourage crystal growth. These crystals are larger and deposition occurs at a faster rate in the presence of fluoride. More importantly the deposition occurs in form of fluoridated hydroxyapatite. Hence, it is the presence of fluoride in the aqueous phase in the oral fluids that is very important. This can occur when fluoride is applied frequently to the tooth surface at concentrations low enough to diffuse into enamel or through the use of high fluoride containing products which result in the formation of calcium fluoride. The formation of calcium fluoride was considered a drawback because of its high solubility in water as demonstrated in some in-vitro experiments. But this situation is not replicated in-vivo. In the oral cavity, calcium fluoride has been found to be retained for a much longer period of time. This is because of the presence of a phosphate-protein-rich protective layer on the calcium fluoride globules. Furthermore, this product gets converted to fluorapatite under cariogenic challenges.
NaF applied topically reacts with hydroxyapatite crystals to form CaF2 which is the dominant product of reaction. This solubility product CaF2 is formed at a faster rate due to high concentration of fluoride (9,000 ppm) in 2% NaF and this initial rapid reaction is followed by drastic reduction in its rate and the phenomenon is called choking off. This occurs because once a thick layer of CaF2 gets formed it interferes with the further diffusion of fluoride from the topical fluoride solution to react with hydroxyapatite. Due to this reason sodium fluoride solution once applied is left to dry for 4 minutes. Then CaF2 reacts with HA (hydroxyapatite) to form fluoridated hydroxyapatite.
            CaF2 + 2Ca5 (PO4)3 OH                             2Ca5 (PO4)3 F + Ca (OH)2
            This reaction leads to manifold anticaries effect by increasing the concentration of surface fluoride which makes the tooth structure more stable and less susceptible to dissolution by acids, interferes with plaque metabolism through anti-enzymatic action and also helps in remineralization of the initial decalcified areas.
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Indication, contraindication, surgical techniques in details and prognosis
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please, our researchers i want documented answers if possible
thanks
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There are many solutions which permit the use of implants even in the severely atrophic mandible, including submandibular cadaver grafting.
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The connection between the abutment and the implant is a critical factor. The original Brånemark implant had an external hex on top of the implant to allow it to be driven into the bone. However, mechanical problems including screw loosening and fractures led to the development of internal connections. Another kind of internal connection used by some implant manufacturers is the Morse taper design, which is a mechanically locking friction fit connection.
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At Pi Dental center we have enjoyed great clinical success with over 42,000 Branemark external hex implants.  The external hex is more prosthetically friendly when using tilted implants, such as in the ALL ON 4 treatment concept.  It allows the angulated abutments more accurat alignment for prosthetic screw access.
It is also the best connection for zygomatic implants.
Load distribution is ideal with the external hex.
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Displacement of implant in the maxillary sinus is the common complication occur because of improper evaluation of available bone volume or inadequate osteotomy preparation.
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In agreement with the other comments, implant removal should be done quickly with either intra-oral approach by lateral window or functional endoscopic sinus surgery
(FESS). The attached paper might be of your interest.
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Does the implant failure is a responsibility of dentist ?
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How in any case could this be thinkable ? Any medical doctor is obliged to "deliver state-of-the-art-work" after an informed consent (risks of non-osseoimtegration, post-surgical implant-loss due to infection, short- and long-term implant loss due to periimplantitis/overload etc.) by the patient. No physician is responsible or can guarantee the success of a treatment even if performed stat-of-the-art. The patient has to KNOW that keeping the implants means: to clean it more careful than the tooth the patient lost in the same spot (which is the reason for the implant). Patient also has to know that and to agree that dental implants (like any other implant - hips, knees etc. - in the mammal body) have an unknown life-span inside the bone depending on so many factors that no physician ever will be able to calculate. Theeth get lost, joints "get lost", skin elasticity gets lost, regenerative capacities get lost in the process of deterioration by aging. 
No dental implant is forever.
ONLY in case the implant was not inserted and prosthetically treated state-of-the-art  (taking into consideration the more than wide range of scientific opinions) THEN a jury of experts has to decide if it was malpractice or not.
Why do we discuss and investigate "success-rates" (1yr./2yrs.,5yrs) in implant-procedures ? Because we look for concepts to get as close as possible to 100% which we will never ever achieve. That means: implants WILL get lost by no means and the patient has to know that before his decision to take the risks .........
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I need full text of the mechanical complication and causes!!!! 
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Dear Dr. Reyes,
I think that the recommendation that Dr. Nwhator gave is absolutely correct. You should do a Medline search which will generate a large number of "hits". Then you look at the  Titles and abstracts of these identified potential reference papers and you order the papers that are most relevant to your research question. You can order these articles from a medical library or you might be able to go into that medical library and make copies of the articles the old-fashioned way with a xerox machine.
You have to be aware that there are copyright laws to prevent distribution of articles even if you are talking to the original author of that article. If an author submits an article to a journal they give away the copyright to that article in that copyright is owned by the Journal. The abstracts are shared by the journals with Medline because it is in the interest of the publisher to gain interest in articles published in their journals. Distribution of free copies however would not be thought of as generally acceptable. There are exceptions, online full access journals  do exist. If the references that you are interested in are found in those journals you should be able to download those articles from  the Internet sites of those journals. In some instances you may have an electronic subscription to a specific journal which would allow you to download a specific article, one copy, but to ask for a blanket responsive receipt of free copies of articles on a specific topic is really not appropriate and would violate copyright law.
So  it comes down to your having to do the investigational work. You have to understand that  literature reviews are indeed secondary research and if you are interested in the results of secondary research you should be willing to make that effort. The task is to first perform the Medline search, this is called item generation, then you look at the titles and abstracts and eliminate the ones that are clearly inappropriate for the topic that you are trying to search, this is called item reduction but there are a number of steps to item reduction. Even after you read the full text article you might find in an article has no particular relevance towards your research question.  Honestly, this is the expectation in research. Anyone who has been involved in research can tell you that you have more dead ends then you have revelations. That should not stop you  from performing research but it is a recognition that you have to have.
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in electrochemical in-vitro experiment of the dental implant surface, what' s the best solution to refresh the surface between the tests and for how long ? to not affect the treatment on surface. 
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thanks doctor but my Question not related to biological studies neither osseointgration, my inquiry is if u use those implants in the lab for electrochemical tests so what is the best refreshment solution for the sample after each tests ?  
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In case if the surgeon faced problem in initial stability for immediate implant after implantation and while the flab still opened, is it possible to remove the aborted fixture and implant it on another site or it's risky because the fixture exposed to air and the surface treatment already affected by implantation process ? 
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No
It is not feasible at this point in time to re-sterilize this implant and then to insert it into another osteotomy. Contact of the implant with the environment will  alter the oxide layer of the implant and this will have negative effects on performance of that implant. I am not sure how things work in the rest of the world but in the United States there are virtually no implant companies that would not replace an implant that was contaminated during the time of surgical placement. So if you had three osteotomy's prepared and you contaminated one of the implants it was placed into one of those osteotomy's you would simply set that implant aside and open up a new implant to go into each of the sites.
If you are working with an implant system that does not utilize this approach, replacing contaminated implants, it might then be time to consider a new implant system with a more patient friendly policy.
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Is there any significant difference between them regarding primary stability, alveolar bone loss, and/or the success rate?
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Immediate, Delayed-Immediate, and Delayed implant placement: Which one is superior over the others? 
Is there any significant difference between them regarding primary stability, alveolar bone loss, and/or the success rate?
 ITI describes the immediate, early and traditional or conventional loading protocols. Are you talking about loading protocols or implant placement protocols relative to tooth removal?
Tooth extraction followed by implant placement (immediately or after a few months of healing) does not seem to result in any implant survival differences.  Most authors report a slightly improved been response if the implant is placed on the day of tooth extraction but this is often dependent upon the location in the dental arch.
Considering loading protocols there certainly is a difference in implant performance relative to loading protocol.  Of course there are factors that favor each protocol in different instances.  I suggest looking at the article by Gallucci et al that documents the consensus conference of ITI recommendations.  There is no straightforward simple answer.
Consensus statements and clinical recommendations for implant loading protocols. Gallucci GO, Benic GI, Eckert SE, Papaspyridakos P, Schimmel M, Schrott A, Weber HP. Int J Oral Maxillofac Implants. 2014;29 Suppl:287-90. doi: 10.11607/jomi.2013.g4. 
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What is your opinion about chair-side pickup for mandibular or maxillary IODs. The technique in which the housings are incorporated onto the existing denture (maxillary or mandibular) and no lab steps are involved. 
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Chair-side intra-oral pickup is such a simple and time saving technique with good serviceability, I used it in a study to pick up O-ring attachments for four implant retained maxillary over-dentures while patients were biting in centric.
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Is it possible to achieve favorable maxillofacial re-construction from a natural and physiological standpoint, if implant placement is involved during treatment planning?
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It all depends upon how you look at the question of maxillofacial rehabilitation.
Are you looking at situations where you are doing primary reconstruction? If you're doing primary reconstruction without an ora-nasal (meaning that the communication was closed surgically), or any other, communication and if you have relatively thin mucosa, in contrast to thick skin, implant should proved to be a great benefit in the reconstruction of the patient as you are trying to replace dental units (Teeth).
The thing that we have to be careful of however is the notion that teeth are involved in trituration but not in manipulation of the food bolus.(see Curtis, D et al). So if there has been A fundamental change in the anatomy of the buccal mucosa, buccal musculature, Hard or soft palate, tongue, Floor the mouth, etc. The issues related to manipulation of the food bolus are probably more critical than the patient's ability to triturate food. Manipulation of the bolus puts that bolus of food either on the occlusal table or fails to put it in a position where trituration would occur. The functional deficit in this situation is the poor manipulation of the food bolus more so than the poor trituration of the bolus.
If you are not looking at reconstruction of the defect but instead are looking at a communication between the oral and nasal cavities and you are using an obturator to close that defect the immobility of the implants is a bit of a disservice because the obturator generally does move, hopefully just a little, in function. The patient generally does not chew on the side of the defect but that doesn't mean but nothing ever goes on to that side. If I have my preference I would prefer retention of teeth to support an obturator because there is physiologic mobility which is then magnified by the length of the lever arm before you get to supporting areas within the defect such as the pterygoid plate.
If you're talking about a mandibular defect, Whether reconstructed or not, there is almost always some discrepancy from the normal, Let's call that the pre-surgical, condition. This generally means that if you are using implants there is a horizontal discrepancy in many instances that must be accommodated. Of course if the lateral border of the tongue was also resected, which happens frequently when a mandibular discontinuity defect is created whether it is restored or not, the question of manipulation of the food bolus comes into play once again.
The short answer to your question is that dental implants usually serve the valuable purpose in the management of a maxillofacial defect. The long answer however is that there are a number of new and different considerations that must be made when implants are used in the management of maxillofacial defect. The thought processes that we may have used 30 years ago may need to be rethought as we introduce a new components into the treatment armamentarium. Implants are often an acceptable root substitute but they are not always going to function in the same way as the natural tooth root and we need to be cognizant of this and must modify our treatment appropriately.
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Branemark studies are from 1969. But he was doing researh like ten years ago before 1969.
so, is there any long time implant survival study?
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Here a study although with a small number of implants that covers an observation period of 10 to 20 years. Various reconstructions
 
Clin Oral Implants Res. 2001 Jun;12(3):252-9.
Long-term evaluation of non-submerged hollow cylinder implants. Clinical and radiographic results.
Merickse-Stern R1, Aerni D, Geering AH, Buser D.
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Abstract
From 1974 various types of hollow cylinder ITI-implants were placed before the new generation of Bonefit ITI-implants was developed in the mid-eighties. The aim of this study was the clinical and radiographic evaluation of hollow cylinder implants that were inserted during the time period of 1978-1987 in partially and completely edentulous patients to support overdentures, fixed partial prostheses and single crowns. Altogether, 71 patients with a total of 132 hollow cylinder ITI-implants still in situ had been followed regularly during the entire observation period of 11.4 to 19.7 years (mean 14.1). Thirteen implants had to be removed before an observation period of 10 years was completed, 4 additional implants were lost after being in function for over 10 years and two further implants were considered to be failures at the time of the examination. Thus 91.4% of the implants were still in situ after 10 years and the survival rate for a mean observation period of 14.1 years was 84.6%. Periimplant parameters were used to assess the clinical conditions of the implants. On the radiographs, horizontal bone loss or angular defects could be detected on 40% of all implants if compared to the base-line situation. The probing depths around these implants were significantly increased compared to implants with an unchanged bone level, however the mean probing depths did not exceed 3.5 mm and 2.8 mm respectively. From this clinical evaluation one may conclude that with the early generation of hollow cylinder ITI-implants favorable long-term results were achieved.
Here another study with an observation period of 10 to 24 years with a limited number of edentulous patients having two interforaminal implants.
Int J Oral Maxillofac Implants. 2011 Mar-Apr;26(2):365-72.
Long-term results of mandibular implants supporting an overdenture: implant survival, failures, and crestal bone level changes.
Ueda T1, Kremer U, Katsoulis J, Mericske-Stern R.
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Abstract
PURPOSE:
The present study summarizes the long-term clinical observations of edentulous patients treated with mandibular implant-supported overdentures.
MATERIALS AND METHODS:
From 1984 to 1997, edentulous patients were consecutively admitted to treatment with mandibular implant overdentures. The treatment plan was to connect the dentures to only two implants by means of single ball anchors or bars; in patients with special oral conditions, three implants would be placed. Regular maintenance care was provided at least one time per year. The cumulative implant survival rate was calculated. Implant failures were described according to clinical signs at the time of removal and related to the patient's specific history. Crestal bone measurements were performed using computer software.
RESULTS:
In all, 147 patients with 314 implants were evaluated for 10 to 24 years. Of these, 101 patients were still available; of the 46 patients who were not evaluated, 26 had died or were not ambulatory. Thirteen implants failed during the observation period, resulting in a cumulative survival rate of 85.9% after 24 years. The reasons for removal of implants were peri-implantitis (two implants) and mobility (11 implants). Mean crestal bone loss was 0.54 ± 0.7 mm per implant site after an average observation time of 16.5 ± 3.9 years. The duration of loading had a statistically significant effect on bone loss.
CONCLUSIONS:
The present data exhibit a satisfactory survival rate of implants. An individual analysis of implants with late failures did not reveal a typical failure pattern, but loss of implants without signs of infection was more frequent than loss of implants with signs of peri-implantitis.
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Try in of dental bridge
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Menat, it is important to consider:
  • General fit and stability (check for rocking) - often defects on the fitting surface can prevent full seating. Silicone can be useful here to line the prosthesis and identify areas of close contact. Powder sprays can also be used by I would be careful not to contaminate the surface excessively
  • Marginal fit should be checked, and shouldn't be larger than a straight probe tip
  • The occlusion should be checked with shimstock and GHM articulating paper
  • Aesthetics should be checked
  • Wider tooth parameters should be confirmed such as periodontal status, exclusion of periapical pathology and occlusal scheme
Hope this helps!
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Kennedy Class IV.
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Thank you.
An interesting  question about  a historic  approach . However,in my view,cross arch stabilisation is very much  yesterday's game.
There can be very little ,if any, justification now  for removing 62-73% of sound tooth tissue (Edelhof and sorenson 2002) for multiple preparations to provide one path of insertion for such prostheses.
The concept was founded on the   now discredited  idea that distributing  occlusal load across multiple teeth to provide rigidity  stopped periodontal disease.
Most of  have  not believed that for over forty years (Axelsson and Lindhe). Double abutting as a concept  can contain the seeds of  later failure due to pulpal or structural problems .Splinting teeth  for cross arch stabilisation also makes it more difficult for the average person to keep things clean -hence later failure.
Just ask yourself-"would I have that  destruction done to your own remaining sound teeth if you were missing those teeth"
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Please see the attached images.
Personally I think Straumann
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hi ; Ithink that  this is a Straumann implant
like the one i am showing here which is an actual " Straumann implant"
hope that help
Cheers
prof galil
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As many practitioners select patients for dental implant based on panaromic x-ray reports for quantity of bone without going into the qualitative analysis of bone, there are many cases of failure of dental implants due to poor selection of cases or the implants designs. Ideally all patients must undergo dexa analysis for bone density. So I am trying to check the reliability of mandibular bone indices with dexa absorptiometry, so that the clinicians can determine the quality of bone before taking up the cases for implants as well high risk patients may be directed for dexa analysis. So I am looking for supporting articles with full text which will give me clear ideas about precise calculations of these indices. As well anyone having any mathematical formula or software for this study please forward. Do you have any great ideas related to this research is welcome. Thank you.
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OPG has overlap of parts of mandible and it can be an issue when you try to standardise it unlike spine which can permit measurements without overlaps. Also the area of interest may have a specific less bone density when you are studying for implant placement. So it will mean that you must be able to use DEXA at that particular area. It may be possible to measure bone density with other custom methods if all one requires is measurement of the bone density at the particular place (locally for implant placement). One study used a standard stepped aluminium strip with known densities and used a software to compare density of the area of interest with the known density. Also you can use fractal analysis. One study used a strip of different metals of known density for a similar study. These are standardised first using DEXA analysis and later applied to a large segment of patients.
So there are indeed ways but one must only think to get the idea into play. I am not sure exactly what you have in mind when you say you wish to standardize OPG with Dexa ... but there are ways to do so even without using Dexa is what I was implying (and that would be better as using DEXA method for analysis / study will mean additional exposure ..) Also the question arises, is DEXA analysis for all patients indiscriminately an option ? It may be permitted in patients with suspected osteoporosis but using it as a blanket procedure for screening for every implant case may be subject to severe criticisms. Another issue is, OPG is a 2D measure and will not accurately reflect on the bone density with respect to the alveolar bone quality.
And if there indeed a bone deficiency / thin bone, how would we plan to address the issue ? We might require an additional CBCT or CT scan to accurately analyse which areas have deficiency.
For example, let's consider two scenarios - one patient with thinned bone in a particular area following trauma (cortical bone thinning/loss) and another patient with a localized bone loss due to periodontal problem. How would your analysis differentiate between these two cases ? As DEXA only analyses the intensity modulation of a beam traversing the bone and exiting it on the other side. While both these scenarios may have similar readings / values, it would not be clinically useful data for implant placement as the case with cortical bone loss would be more difficult to manage than a case with internal alveolar bone thinning, I believe.
What exactly are we trying to measure in this scenario ? How would be make sure that our idea would be clinically relevant for implantology ? Another issue is how are we going to use DEXA for alveolar bone at a particular area of interest ? The alveolus is not easily accessible like fingers or spine! Also another important parameter is that the DEXA gives the "average" bone density across the area it measures using two differnet xray sources. So it still may not reflect on the ability to choose if a particular place has local bone defects which require different management etc;
A quantitative approach using fractal analysis of a digitized or digital xray would be good (an IOPA which has minimal overlap in the bon region) is my suggestion instead of OPG. Or using a comparative parameter would be a good idea as well if you are planning on using this bone density parameter in different persons. If you just want comparison of bone density in just the same patient or pre-post bone density around implants, you can use other techniques using standard intraoral structures like enamel / dentin of a sound tooth in the oral cavity. This way the exposure/ time/ mA, kV and distance are not critical as we are going to get a 'ratio' which will be constant and comparable. It's another technique to analyse the density. Infact, this technique of 'density analysis' is frequently used in CT scans when it's read by radiologists. They select the Hounsfield units for the area of interest and compare it to hounsfield units of known structures to suspect the contents of a lesion / tumor/swelling etc; Similarly we can use software to compare the pixel density to get this data. It sounds complicated but it is not all that if we pay attention to details.
Regards,
Dr. Akilesh. R
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some times sufficient amount of crestal bone loss takes place around around a healthy functioning implant during the first year of functioning , what could be the reason for that?
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This is a very in-depth topic and I'll try to respond by summarizing various points within the topic.
1) I don't think that function is the issue here -- initial peri-implant bone loss will occur in similar fashion around implants that are merely subjected to placement of healing abutments.  The focus here is on a number of things -- biologic width, and micromotion and microleakage at the IAJ -- and these things generally only come into play one the implant-supported componentry protrudes transgingivally.
2) Three rationales are generally provided for initial peri-implant bone loss:
-IAJ microleakage / inflammatory zone of the IAJ
-IAJ micromotion
-apical shift of biologic width
Hermann et al. performed a number of investigations from 1997 to 2011 that looked at initial peri-implant bone loss and factors such as one-piece (no IAJ) and two-piece (yes IAJ) fixtures, subcrestal vs. supracrestal placement of the IAJ and soldered vs. regular healing abutments (in an attempt to isolate micromotion from the presence of an IAJ) and with these papers combined, along with those by Abrahamsson in 1997 and 2003, the following conclusions were derived:
- bone is generally lost to 1.5-2mm from the IAJ when the abutments are dis/reconnected multiple times
-bone tends to be lost on smooth / polished surfaces up until the rough/smooth border when the smooth / polished surface is placed subcrestally
What defines "multiple times" is a good question still under consideration.  If abutments are dis/reconnected, the speculation is that introduction of bacterial products into the IAJ space generates a circumferential halo of inflammation that leads to bone loss.
3) Continually removing abutments also acts to disrupt the biologic width formation on the abutment.  Epithelial cells attach via hemidesmosomes to the abutment and connective tissue fibers align parallel to the abutment surface just apical to that while the most coronal aspect of the fixture is placed against bone in the osteotomy.  Biologic width can then form and remain supracrestally.  However, with repeated abutment dis/reconnection, the continually disrupted biologic width shifts apically to find a more stable location to develop and this will be the implant surface.  Bone loss is effected in order to make way for biologic width formation on the implant rather than the abutment.
4) Platform switching has been demonstrated to be favorable to this scenario.  Mean horizontal dimension of the influence of initial peri-implant bone loss was initially reported by Tarnow et al. 2000 as ~1.5mm, which generated the 3mm rule (1.5 + 1.5).  With platform switching, this value is diminished to ~0.7mm (Rodriguez-Ciurana 2009).  Mean vertical dimension of bone loss is similarly diminished when it comes to platform switching, also ~0.7 verses 1.5-2mm for platform matched (R-C 2009).
The explanation as to the basis for this improvement is as follows.  Exposed platforms due to platform switching provide greater surface area for biologic width formation, and so less bone loss due to apical shifting.  The IAJ -- source of microleakage / micromotion -- is placed onto the platform, recessed away from the margin of bone at the most coronal aspect of the osteotomy, and so its (the IAJ's) effect on bone is decreased.
5) In respect to Gaballah's post, I'd just like to comment that "bone remodeling" is an unfortunately poorly understood term and adds to confusion, really.  Check out the Wikipedia article on bone remodeling -- it's defined as the coupled process of bone resorption and deposition that continues throughout life and meant to counteract the cumulative effects of micro-damage, etc.  Post-extraction ridge resorptive processes is not related to this phenomenon.  It's much more closely related to bone modeling, which is how bone responds to trauma, but even that is somewhat of a stretch, because post-extraction ridge resorption is somewhat unique, following what may be explained according to Wolff's law and the functional matrix hypothesis (check out those on Wikipedia as well).
Anyway, there's lot's more to say, but that should provide a good starting point for discussion.
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Strauman dental implants is usually inserted subcrestal to alveolar bone.
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I assume that this question is related to the location of the micro gap relative to the soft and hard tissue. Before we even think about that sort of question we probably need to realize that there is never any answer that applies to all clinical situations. So if the question is should we place all implants below the crest of boneThe answer is unequivocally no. There are always exceptions as to why you don't place below or why you don't place above the level of the bone crest. There are implants that have no micro gap below the soft tissue level, there are one piece implants that certainly cannot be placed subcrestal.  No matter where you place an implant there is going to be a biologic response that establishes a thickness of bone, eight thickness of connective tissue Andy thickness of epithelium it must reach a harmonious level but the problem is that we don't know what harmonious level is required for each individualpatient. We don't have an instrument that tells us that patient a would respond well toA certain amount of bone in a horizontal dimension away from the implant, a buckle thickness lingual thickness mesial and distal thickness of bone in comparison to a certain height which might be vertical or horizontal depending upon how you handle the platform of the implant of connective tissue in and out of epithelium. Look at the classic biologic width article by Gargiulo et al and you will find that the numbers that they observed for connective tissue you and epithelium around natural teeth had a very broad range. What gets quoted is the biological with requirements for connective tissue and epithelium of about 1 mm each resulting in a total width of 2 mmbut that was nothing more then an average number in the range extended to a total of about nine from a minimum of about 0 mm. Will it be more or less predictable around implants?  The answer to that question is as variable as the implant design market. There are literally thousands of different implants in the marketplace all that have different nuances relative to design and all that are going to have different biological responses based upon the individual patient so take the variable of the implant design and the vamiable  of the patient biologic response and what we have is a pretty variable set of outcomes. Hence the reason that I said at the beginning of this response that if you ever ask a question that includes the word "all" in it you can pretty much guarantee that the answer is always going to be know that there is no universal answer for any question in the field of biology. In the field of chemistry you might have definitive answers but not when we depend upon biological responses as we doin the clinical practice of dentistry.
Specifically, as you look at the implant manufacturers that you described you have to understand that they have different product offerings for different clinical situations. Some implants are made to be placed at the level of the bone and some implants are being made to be placed at the level of the soft tissue. So the implant designs associated with these two manufactures are variable depending upon the clinical setting.
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What can we comment about the design of this particular implant and risk of implant fracture?
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Near the end of the last century in the beginning of this one there were a number of anecdotal reports on implant fracture that seem to suggest that implant fracture was pandemic within the implant dentistry. Balshi et al and Eckert et al published two independent studies, retrospective K-series but both of the K-series were over 4000 implants, demonstratingA low incidence of implant fracture in a clinical practice were in two different clinical practices both with multiple clinicians involved in the placement and/or restoration of the implants. Both of those studies look at commercially pure grade 1 implants that were in the screw shape. The study by Eckert demonstrated a 0.6% incidence of implant fracture with more implants fracturing in partially edentulous jaws been in fully edentulism jaws
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Another well conducted clinical follow-up study in patients with test (high torque) and control (low torque) has been published right in these days:
T. Grandi, P. Guazzi, R. Samarani, G. Grandi: Clinical outcome and bone healing of implants placed with high insertion torque: 12-month results from a multicenter
controlled cohort study. Int. J. Oral Maxillofac. Surg. 2012; xxx: xxx–xxx. # 2012
International Association of Oral and Maxillofacial Surgeons.
You may find this paper in ResearchGate, going to the page of the Authors.
Another piece in this intriguing puzzle!
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If they do expire then does this have anything to do with their HA coating?
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Hey,
Depends on what kind of implants you're looking at. Titanium implants are said to have a native oxide layer, which makes titanium implants behave more like ceramics; analogous to HA, which is part of the reason why osteoblasts are able to identify a "favourable" surface, and therefore osseointegration takes place.
Studies have shown that this native oxide layer is highly hydrophilic initially, but as time goes on, it becomes less and less hydrophilic (biological aging). So, it can be implied that the sooner after manufacture an implant is placed, the better it will be in terms of surface adsorption of proteins and cellular attachment.
You might want to read this paper:
ATT, W., HORI, N., TAKEUCHI, M., OUYANG, J., YANG, Y., ANPO, M. & OGAWA, T. 2009. Time-dependent degradation of titanium osteoconductivity: an implication of biological aging of implant materials. Biomaterials, 30, 5352-63.
The major issue with HA (or similar) coatings is delamination, which is specially a problem with plasma sprayed coatings. The particles used for coating only melt on the outside, leaving a solid core in the middle. When these "externally" softened particles reach the surface during the coating procedure, the surface is rapidly quenched, which stops re-crystallization of these particles on the outside. The result is a coating where the layer closest to the implant surface is amorphous, the middle layer is unmolten, and the outer most layer is amorphous again. When these implants are placed in vivo, the inner and outer most layers undergo dissolution and degradation faster than the "unmolten core". Eventually the entire coating may delaminate.
Alternately, HA coatings formed from solution (SBF soaking etc..) may dessicate, deform and crack, or may not be completely uniform, with thin and thick areas, leading to easy crack propagation. So in essence, yes coatings may have a hypothetical "shelf life" too.
I would tend to think bioactive glass coatings that are designed to degrade over time, allowing physiological apatite formation are more practical than HA coatings that degrade much slowly and instead of having a single (if i may say, strong) interface between the implant and bone, there are two interfaces, one between the implant and coating, and the other being between the coating and bone. Undoubtedly, chances of failure can he significantly higher in the latter.
I hope this helps :)