DentistryUnited.com Newsletter

 


                    D e n t a l    F o l l i c l e               

             The        Monthly     E-newsletter                   Vol - I       Number- X            March  2007

In this Issue:

  • Editorial

  • News

  • Laughter the best Medicine

  • Evaluation of the efficacy of a collagen GBR membrane (BioMend Extend) supported by autogenous bone grafts,     for the treatment of peri-implant bony defects, during implant placement."Part II- Dr.Yousef Abd ElGhaffar

  •  RASHA RECOMMENDS  - Dr. Rasha Seragelden

  • Laser Dentistry - A basic Comparison between Er:YAG and Er,Cr:YSGG - Dr.Maziar Mir
     

 

Editorial :

      Dear Fellow Dentist,

                          Continuing Dental Education , Dental Research and Dental Tourism are close to my heart said the president DCI at IIDC , Mumbai! A small report on the same follows this Edition! Dr.Anil Kohli's speech at the IIDC Mumbai can be heard on www.DentistryUnited.com .You'll need a Real Player Plugin to listen.

In the next edition a short notes on Dr.Tarnow's lecture will follow DentistryUnited on Yahoo groups is growing day by day! Looking Forward for your feedback .

 

Click here to join DentistryUnited
Click to join DentistryUnited

Yours truly

Dr.S. Nabeel

Editor of Dental Follicle & WebMaster www.DentistryUnited.com

News :

         

                       

Laughter The Best Medicine :

A guy goes to visit his grandmother and he brings his friend with him. While he's talking to his grandmother, his friend starts eating the peanuts on the coffee table, and finishes them off.

As they're leaving, his friend says to his grandmother, "Thanks for the peanuts." She says, "Yeah, since I lost my dentures I can only suck the chocolate off 'em."

"

                                             Continuing Dental Education Made Mandatory In India -

      A new chapter opens in the Indian dentistry this summer! Speaking  at the IIDC inauguration in Mumbai , The President of Dental council of India Dr Anil Kohli said

"   We have the largest number of dental schools, we have the largest number of dentists! Finally this January  2007 has enabled to make our  government   agree dental education  or renewal; of license is not possible and it has been made possible with Government of India"

   He also said that the government is very keen that dental tourism with tourism ministry to be initiated in this country

  Surely the time of Dr.Anil Kohli will be the called the golden period in the history of Indian Dentistry .

 

                                          Listen to the President of DCI Dr.Anil Kohli here!

          

            

Evaluation of the efficacy of a collagen GBR membrane (BioMend Extend) supported by autogenous bone grafts, for the treatment of peri-implant bony defects, during implant placement."

Part - II

Dr . Yousef Abd ElGhaffar ,   

BDSc, MDSc,  Cairo University, Egypt

Fellow of ICOI and Member of AAID.

Email : dr_yousefabdelghaffar@hotmail.com

 

The grafts used are either cortical, cancellous or corticocancellous. The corticocancellous grafts are considered the best to use as they carry the benefits of both cortical grafts which are rigidity, stability and higher content of BMPs that will initiate the osteoinductive process by its release, and the cancellous grafts benefits by having viable osteobslats and undifferentiated mesenchymal cells (Misch et al. 1998).

The extraoral autografts are used generally to restore severely resorbed alveolar ridges. The preferred extraoral sites for autogenous bone grafts are iliac crest, tibial shaft, rib, and parietal bone of the skull. Grafts harvested from membranous bone as the cranium have faster revascularization than grafts harvested from endochondoral bone (Kusiak et al. 1985).

Although iliac crest is the most common extraoral site used to harvest bone for purpose of augmenting anatomically compromised alveolar ridges, patients still describe considerable pain and walking difficulties post-operatively. Harvesting from tibial shaft is considered to be a relatively fast and complication free procedure. Donor site morbidity was much less than iliac crest when using tibial shaft trephined grafts (Ilankovan et al. 1998).

The main advantage of intraoral bone grafts is their convenient surgical access. The close proximity of donor and recipient sites can reduce operative and anesthesia time with avoidance of general anesthesia, making them ideal for implant surgery. Another advantage is that there is no visible external scar. In addition patients report minimal discomfort and these areas may offer decreased morbidity from graft harvest. Also, bone harvested from intraoral sites is associated with less resorption when compared to iliac crest, tibial shaft, and rib grafts. The only disadvantage of intraoral grafts is that there is less bone available than from extraoral sites (Misch and Misch 1998).

Intraoral sources of autogenous bone grafts include edentulous spaces, maxillary tuborosity, mandibular ramus, mandibular symphysis, and extraction sites. Bone from a recent extraction site (within 6-12 weeks) may have advantage of increased osteogenic activity as compared with other sites. The maxillary tuborosity provides a more cellular source of autogenous bone as compared with other sites. However, the trabecular nature of this site provides a lesser quantity of mineralized matrix and the resultant total volume of bone available for grafting is often inadequate. For greater amount of bone, it is more desirable to harvest bone from the mandibular ramus or symphysis (chin). The bone grafts obtained from mandibular ramus and symphysis are typically more cortical which can be harvested and used as a block graft or ground or shaved into small fragments and used as a granulate graft (Newman et al. 2002).

A study was performed to compare intraoral donor sites for onlay grafting prior to implant placement. The choice of donor site, either symphysis or ramus, was determined preoperatively based on defect morphology and recipient site location. The ramus grafts gave rise to no complications in comparison with symphysis graft, however the procedure is more difficult, with restricted access and risks to inferior alveolar nerve need to be considered (Misch 1997).

The morbidity of donor site for autogenous bone grafts harvested from symphysis region was investigated. The osteotomies were accomplished with the use of trephines to obtain corticocancellous grafts, or thin carbide burs to obtain individually shaped monocortical bone grafts. Some complications were observed with group of patients who were subjected to harvesting of bone procedures from the chin such as, bruising at the lower face (100%), bruising of the upper neck (12%), and paresthesia (15%) (Dennis et al. 1999).

The timing of graft placement is either prior to the placement of implants (staged approach) or simultaneously with the implants (combined approach). The staged approach method is primarily chosen in situations with large bony defects. The main advantages of placing the implants after graft maturation are better graft evaluation and appropriate implant selection; decreased time required for the initial surgical stage and a more accurate surgical template can be constructed on the improved underlying bone for better site selection and implant angulation. The combined approach method offers some advantages such as decreased patient morbidity, decreased treatment time, and decreased costs (Misch and Dietsh 1994).

The autografts may be used as corticocancellous block or corticocancellous granulates. The extent of osseointegration of implants in corticocancellous blocks was less than it was in corticocancellous blocks. Also, the bone granulates showed better adaptation to the receptor site and lower rate of graft resorption. Using bone blocks alone showed high rate of graft resorption and graft rejection was also reported in some cases (Lew et al. 1994).

Osseous defects adjacent to dental implants can be grafted with small autogenous bone granulates, which results in significant improvement. In a study of Becker et al. 1994, the initial mean vertical defect depth was 5.7 mm, and the average residual depth at second stage surgery was 0.03 mm. These changes were statistically (p<0.001) significant and clinically relevant.

Although osseous defects adjacent to oral implants have been successfully treated with intraoral autogenous bone alone, there is lack of evidence as to the ultimate fate of these bone grafts. Some authors claimed that using the grafts alone in treating peri-implant defects may lead to graft resorption, also loss of graft or even incomplete defect coverage may occur.  (Curtis and Ware 1983).

The development of guided bone regeneration (GBR) has substantially influenced the possibilities for using implants. The use of bone augmentation procedures has extended the use of oral implants to jaw bone areas with insufficient bone volume. The treatment of alveolar defect conditions through guided bone regeneration (GBR) is a treatment modality that provides clinicians with the possibility of a successful outcome and diminishes the complications associated with the graft itself (Dahlin et al. 1989).

Numerous publications have indicated that guided bone regeneration (GBR) is a viable method for enhancing bone formation in peri-implant defects (Becker et al. 1992, Kohal et al. 1999, Nemcovasky et al. 2000, Hämmerle and Lang 2001, Rosen and Reynolds 2001, Brunel et al. 2001, and Dogan et al. 2003).

Regeneration may be defined as a biological process by which the    architecture and function of the lost tissues are completely renewed. In periodontal therapy, guided cell repopulation, or guided tissue regeneration (GTR), describes procedures designed to manipulate the cells that repopulate the wound healing site to ensure that this repopulation includes cells that lead to regeneration (American Academy of Periodontology 1992).

GTR (guided tissue regeneration) had been developed, based on the principle of guiding the proliferation of the various periodontal tissue components during healing following periodontal surgery using membrane barriers (Gottlow et al. 1986 and Caffesse et al. 1988). These membranes were used to prevent apical migration of the gingival epithelium and the connective tissue fibroblasts along the root surface and to create a space over the defect to allow the remaining periodontal ligament and alveolar bone cells to selectively repopulate the root surface (Nyman et al. 1982).

Guided tissue regeneration (GTR) therapeutic modalities had led to the development of the principle of guided bone regeneration (GBR), which aims at regeneration of alveolar bone defects around dental implants. Guided bone regeneration can be of value in restoring horizontal and vertical alveolar ridge defects, treating dehiscence and fenestration defects associated with implants and in obtaining bone fill associated with immediate post-extraction and failing dental implants (Parodi et al. 1998).

The application of GBR for improvement of dental implants prognosis may take several forms. One form is a one phase treatment of implant bed preparation, in which the implant is surgically placed at the same time as GBR (Buser et al. 1993). Another form is two phase treatment, in which surgical implant placement is performed after the GBR procedure, when new bone has matured (Buser et al. 1996). Other treatment forms include repair of bony peri-implant defects secondary to advanced forms of peri-implantitis (Francisco et al. 2001).

Successful clinical outcomes can be obtained if the used GBR barrier membrane possesses certain requirements: 1) Cell exclusion: Certain cells must be excluded from the area targeted for regeneration. The used barrier membrane should prevent gingival fibroblasts and/or epithelial cells from gaining access to the wound site and forming fibrous connective tissue. 2) Tenting: The membrane is carefully fitted and applied in such a manner that a space is created beneath the membrane, completely isolating the defect to be regenerated from the overlying soft tissue. To accomplish this tenting function and to completely isolate the defect, it is important that the membrane be trimmed so that it extends 2-3 mm beyond the margins of the defect in all directions. 3) Scaffolding: The cells will come from adjacent bone or bone marrow occupying the tented space which serves as a scaffold for the ingrowth of progenitor cells. 4) Framework: In non-space maintaining defects such as dehiscences or fenestrations, the membrane must be supported to prevent collapse. Bone-replacement grafts consisting of autografts, allografts, xenografts, alloplasts, or combinations of these materials are often used for this purpose. Stiffer membranes such as titanium-reinforced membranes have also been used for this purpose. 5) Stabilization: The membrane must also protect the clot from being disturbed by movement of the overlying flap during healing, so the membrane should be fixed in place by retentive means including sutures, mini bone screws, bone tacks, or fixed by the covering screws of the implants. Sometimes, the edges of the membrane are simply tucked beneath the margins of the flaps at the time of closure (Hardwick et al. 1994 and Lang et al. 1999).

There are two main classes of membranes that can fulfill the above mentioned requirements, the non-resorbable and the resorbable membranes.  Non-resorbable membranes are barriers that are not degraded by the tissue. They are placed underneath the flap and removed one month later by re-entry procedure. The non-resorbable membranes are numerous. They include expanded polytetraf-luoroethylene (e-PTFE), titanium reinforced (e-PTFE), titanium mesh, and titanium foil.

Expanded polytetrafluoroethylene (e-PTFE) was used to enhance the regenerative potential in periodontal defects. The (e-PTFE) may provide protection to the blood clot and prevent apical migration of junctional epithelium. Many studies have used (e-PTFE) barriers and it was claimed to be the current standard in the field of (GBR), but there has been a drawback associated with the use of this material which is the need for secondary surgery for membrane removal (Rominger et al. 1994).

Micro titanium mesh was also used to protect and stabilize autograft in place to treat dehiscence and fenestration bony defects around dental implants. This was described in a study by Von Arx and Kurt 1998 that included 6 patients requiring bone augmentation. Resorption of graft varied from 0 to 8% of the total graft height. It was concluded that the use of a micro titanium mesh has been shown to provide the combined space maintenance due to its improved mechanical strength, and it may be left over the long-term due to its inherent biocompatibility.

Guided bone regeneration using titanium foil was evaluated in a study by Gaggle and Schultes 1999. Forty-two patients with deep intra alveolar peri-implant defects were treated by means of a titanium foil-guided bone regeneration technique. Autogenous bone in combination with DFDBA composite was used for augmentation. Clinical and radiological control was performed 3, 6, and 12 months after surgery. In 37 cases, the average 12-month postoperative increase in bone was 4.2 mm, and the decrease in augmented bone was only 4% compared with the postoperative situation. The main problem with foil loss was denudation and infection 6 weeks after surgery.

The non-resorbable barriers showed high rate of complications such as exposure to the oral environment i.e. soft tissue dehiscence, with subsequently developing infection. Frequently, exposure rates may affect around 20% of the sites treated with a major negative effect on GBR around dental implants (Machtei 2001). Simion et al. 1994 reported significantly less bone gain when the membranes were exposed compared to non-exposed membrane treated sites (41.6% versus 96.6%). Impaired treatment outcomes, lack of predictability of the therapy and resorption of the already regenerated bone or even loss of parts of the pre-existing bone have been also reported as sequelae of these complications (Hockers et al. 1999).

To overcome the previously mentioned complications associated with non-resorbable barriers, as well as to obviate the need for a second surgery needed for membrane removal; various resorbable GBR materials have been evaluated. Researches in the field of barrier membranes have focused on the development and application of suitable resorbable materials for GBR (Schliephake et al. 2000).

 

 

                                                                   

 

 

  RASHA RECOMMENDS .............

-Dr.Rasha Seragelden

 Egypt

 

 

Laser Dentistry - A basic Comparison between Er:YAG and Er,Cr:YSGG

Maziar Mir

DDS, MSc, PhD

Assistant Prof. ZPP, RWTH Hospital, Aachen, Germany



When the Hibst and Keller have published the first articles about the ablation of tooth with Er:YAG laser on 1989 in English journals (some years after German versions), nobody was estimating that in 8 years the speed of cut (Volume of ablation) could be practically
suitable for dental daily needs. On that time the 4-6 pulses per second were recommended and the laser was cutting the tooth very slowly. On 1995, the number of pulses increased to 20 and Er,Cr:YSGG was also introduced to American dental society on 1997. At the same year both wave lengths were successfully cleared with FDA and delivered to dental clinics to be used
as an adjacent to drills!

On 2000, the discussions about the basics of mechanisms were hottest topic of dental congresses and WATER role was under the focus of investigators. On 2002 a basic study started by the author in Aachen RWTH Hospital following the advance advises of Prof.Dr. Norbert Gutknecht and guidances of Dr. Leon Vanweersch, Dr. Joerg Meister and Dr. Rene Franzen.

The project was done with the help of two HIGH TECH cameras. First one was able to make up to 40500 pictures per second. So, as is seen in Figure-1, the author was able to monitor any pulse (with a length of 140-180 microseconds) with looking at about 30 pictures. Therefore, the accurate interactions between laser light, water and enamel were accurately visualized.

Both wave lengths of 2780 nm (Er,Cr:YSGG) and 2940 nm (Er:YAG) were irradiated in a distance of 1 mm in front to the enamel surface. The water selected as the media between laser tip and tooth. By this method, the different phases of any pulse interactions with first micrometers of water layer at the start of pulse were reported. There was no difference seen between two wave lengths not only at start of pulse, but also in the rest of procedures.

The most important finding is that the basics of ablation with both wave lengths are more and less the same and the important characters of both in increasing the speed of cut would be the duration of pulses and energy of any pulse, as well as suitable amount of water between the laser irradiating tip and tooth surface.

This research have been presented in 2nd international congress of Laser Dentistry in Dubai on 11th January 2007 by the author and is IN PRESS in one of the high rank ISI indexed scientific journals. For more information the interested persons could kindly write to: mir.maziar@gmail.com

As a conclusion could be addressed that there are enough evidence which show 30 pulses per second of both wave lengths with a pulse energy of 300 mJ and pulse length of 60-90 microseconds, could cut the enamel even faster than high speed drills. The accuracy of cut margins with NON-CONTACT laser handpieces could be comparable also for preparing the
bevels and shoulders in the aim of Veneer, Inlay and Onlay, or crown and bridge preparations.

Our master students are using this applications daily and we present the clinical procedures world wide by video online lectures as you could see in Figure-2. It is the wish of author to be able in near future make the direct video conference presenting live cavity preparations with same methods for the Indian friends as well. The ideas are most welcome and the positive
and negative comments are open to be discussed in the dental forum of this web site...