The health history should be reviewed for any condition that might put the patient at risk for adverse reactions or complications. Any disorder that may impair the normal wound-healing process, especially as it relates to bone metabolism, should be carefully considered as a possible risk factor or contraindication to implant therapy. Knowing a patient's medical background assists the clinician in determining how the periodontal tissue may respond to the implant and what special precautions or modifications may be required in treatment procedures.
Dental Factors
A review of the patient's dental history is an essential part of the overall evaluation, including previous surgeries and prosthetics, recurrent or frequent abscesses, the number of dental restorations, compliance with previous dental recommendations and current oral hygiene practices. If there is a history of dissatisfaction with past treatment, the patient may have similar difficulties with implant therapy or implant-supported restorations. This may also be indicative of potential practice management problems.After a thorough intraoral examination, the clinician can evaluate potential implant sites. All sites should be clinically assessed to measure the availability of sufficient bone for the placement of the implants and adequate interarch space for prosthetic tooth replacement with proper size and shape. The mesial-distal and buccal-lingual dimensions of edentulous spaces can be approximated wit a periodontal probe or other measuring instrument.
Keys to successful treatment planning begin with a thorough restorative evaluation.
Diagnostic Wax-Up: Mounted study models are an excellent means of assessing potential sites for dental implants. Properly articulated models with a wax representation of the proposed restorations allow both the restorative and surgical clinician to evaluate the available space and to determine potential limitations of the planned treatment. This is particularly useful when multiple teeth are to be replaced with implants or when dealing with a cosmetically sensitive restoration.
The amount of available bone is the next criteria to evaluate. A visual examination may identify deficient areas. Manual palpation can reveal anatomic defects and variations in the anatomy of the anterior region. It is essential to evaluate the timing of tooth extractions and consider bone grafting options for ridge preservation procedures before the teeth are removed. Treatment planning for these extractions can often avoid more involved ridge augmentation procedures after the alveolar ridge resorption has occurred.
The Timing of Implant Placement relative to the time of extraction depends on the quantity, quality and volume of existing bone, as well as the preferences of the clinician and patient.
Immediate implant placement occurs simultaneously with the extraction. The advantages of immediate implant placement is the prevention of ridge collapse and the maintenance of soft tissue papilla, in addition to the reduction of total surgical healing time. Because the implant is placed at the time of extraction, the bone-to-implant healing begins immediately with extraction site healing.
Delayed implant placement is performed approximately 6-8 weeks after extraction to allow for soft tissue healing. The primary advantage of delayed implant placement is that by allowing for soft tissue healing and closure of the extraction site, mucogingival flap advancement is not necessary. This is especially true when bone grafting procedures are anticipated because it alleviates the need for additional surgeries to correct mucogingival discrepancies.
Staged implant placement allows for substantial bone healing within the extraction site, which typically requires four to six months or longer. Staged implant placement allows for complete hard and soft tissue healing and permits the placement of implants into prosthetically favorable positions exhibiting adequate coverage by hard and soft tissues.
Maxillary-Sinus Elevation: When there is inadequate vertical height on the alveolus in the maxillary posterior region, it may be necessary to perform a sinus bone graft to elevate the Schneiderian membrane which creates space. The newly-created space can then be filled with bone or a suitable bone substitute material to increase the total vertical height of bone in the posterior maxilla.
The lateral window technique is probably the most effective and efficient way to elevate the sinus floor for multiple implants or when very limited crestal bone is present. If 3-4mm of alveolar bone height is available, an osteotome sinus lift technique can be utilized through the implant osteotomy site. The osteotome technique is usually performed simultaneous with implant placement. If there is minimal alveolar bone and/or multiple implants are planned, the lateral window approach is more advantages. Occasionally implants can also be placed at the time of the lateral window technique if there is sufficient native bone in a vertical dimension to stabilize the implant.
Maxillary Ridge Width Defects: In cases where there are large horizontal deficiencies in the maxillary ridge which may result in significant exposure of implant threads beyond the confines of the alveolar bone, it may be advisable to reconstruct the bone before implant placement. Horizontal alveolar deficiencies may be reconstructed with bone augmentation (onlay) grafts or ridge splitting techniques.
Fabrication of a Surgical Guide: Surgical guides are most often created from the diagnostic wax-up provided by the restorative dentist. However, advanced surgical guidance to guarantee precise implant placement in complex implant cases is now possible using sophisticated computed tomography (CT).
Utilizing one of several software programs, the clinician can simulate the placement of implants on the computer screen.
These interactive planning programs provide the clinician the opportunity to perform "virtual surgery," placing implants in optimal positions. Furthermore, such advanced technology ensures that the sites chosen will provide sufficient surrounding bone for each implant and good positioning of the implants in relation to each other. Additionally, the clinician can measure the quality (density) of alveolar bone surrounding each implant fixture.
Implant planning software can reformat the CT into a three-dimensional image from which a stereolithographic model can be constructed. The model is machined with CAD CAM technology into an accurate anatomic replica of the jaw.
Once a treatment plan has been carefully evaluated and designed, a customized surgical drill guide can be constructed from the three-dimensional reconstruction of the CT data. Built precisely from the selected treatment plan and based on the patient's exact measurements, these guides ensure safe, predictable implant surgery.
Anatomical Factors Affecting Implant Placement: Familiarity with several important anatomic structures found close to desired areas of implant placement in the maxilla and mandible is important in treatment planning and implant placement. In the maxilla, these include the floor and anterior loop of the mandibular canal and submandibular fossa.
The existence of anatomic variants, such as incomplete healing of an extraction site, sinus location, or absence of a well-defined, corticated canal should be recognized.
Tri-dimensional positioning will aid surgical placement of the implant and prevent encroachment on these structures, thereby avoiding unwanted complication and unnecessary morbidity.
Soft Tissue Considerations: Evaluation of the quality, quantity and location of soft tissue in relation to the proposed implant site helps identify the type of tissue - keratinized or nonkeratinized -- that will surround the implants after treatment is completed. Areas with minimal or nonexistent keratinized mucosa may be augmented with gingival or connective tissue grafts. Additionally, any mucogingival concerns, such as frenum attachments or pulls, should be thoroughly evaluated.
To learn more about treatment planning complex dental implant cases, visit http://www.theperiogroup.com/ and submit your questions to Philadelphia Periodontist Dr. I. Stephen Brown.
