DENTAL IMPLANTS
What are Dental Implants? Dental implants are metal posts or frames that are surgically positioned into the jawbone beneath your gums. Once in place, they allow us to mount replacement teeth onto them.
- Endosteal implantsآ these are surgically implanted directly into the jawbone. Once the surrounding gum tissue has healed, a second surgery is needed to connect a post to the original implant. Finally, an artificial tooth (or teeth) is attached to the post-individually, or grouped on a bridge or denture.
- Subperiosteal implantsآ these consist of a metal frame that is fitted onto the jawbone just below the gum tissue. As the gums heal, the frame becomes fixed to the jawbone. Posts, which are attached to the frame, protrude through the gums. As with endosteal implants, artificial teeth are then mounted to the posts.
A typical conventional implant consists of a titanium screw (resembling a tooth root) with a roughened or smooth surface. The majority of dental implants are made of commercially pure titanium, which is available in four grades depending upon the amount of carbon, nitrogen, oxygen and iron contained.Cold work hardened CP4 (maximum impurity limits of N .05 percent, C .10 percent, H .015 percent, Fe .50 percent, and O .40 percent) is the most commonly used titanium for implants. Grade 5 titanium, Titanium 6AL-4V (signifying the titanium alloy containing 6 percent aluminium and 4 percent vanadium alloy) is slightly harder than CP4 and used in the industry mostly for abutment screws and abutments.Most modern dental implants also have a textured surface (through etching, anodic oxidation or various-media blasting) to increase the surface area and osseointegrationpotential of the implant.: If C.P. titanium or a titanium alloy has more than 85% titanium content, it will form a titanium-biocompatible titanium oxidesurface layer or veneer that encloses the other metals, preventing them from contacting the bone.Ceramic (zirconia-based) implants exist in one-piece (combining the screw and the abutment) or two-piece systems – the abutment being either cemented or screwed – and might lower the risk for peri‐implant diseases, but long-term data on success rates is missing. Hard tissue (bone) reconstruction
Bone grafting is necessary when there is a lack of bone. Also, it helps to stabilize the implant by increasing survival of the implant and decreasing marginal bone level loss.While there are always new implant types, such as short implants, and techniques to allow compromise, a general treatment goal is to have a minimum of 10 mm in bone height, and 6 mm in width. Alternatively, bone defects are graded from A to D (A=10+ mm of bone, B=7–9 mm, C=4–6 mm and D=0–3 mm) where an implant’s likelihood of osseointegrating is related to the grade of bone. To achieve an adequate width and height of bone, various bone grafting techniques have been developed. The most frequently used is called guided bone graft augmentation where a defect is filled with either natural (harvested or autograft) bone or allograft (donor bone or synthetic bone substitute), covered with a semi-permeable membrane and allowed to heal. During the healing phase, natural bone replaces the graft forming a new bony base for the implant. Three common procedures are:- Sinus lift
- Lateral alveolar augmentation (increase in the width of a site)
- Vertical alveolar augmentation (increase in the height of a site)
