Implant Treatment: Basic Concepts and Techniques

Hard Tissue Interface

The primary goal in implant placement is to achieve and maintain an intimate bone-to-implant connection. This concept is known as osseointegration . Histologically defined, osseointegration is the direct structural and functional connection between organized, living bone and the surface of a load-bearing implant without intervening soft tissue between the implant and bone. Osseointegration clinically is defined as the asymptomatic rigid fixation of an alloplastic material (the implant) in bone with the ability to withstand occlusal forces ( Fig. 14.1 ).

For osseointegration to occur in a predictable fashion, several important factors are required:

• 1

  A biocompatible material (the implant)

• 2

  Atraumatic surgery to minimize tissue damage

• 3

  Implant placement in intimate contact with bone

• 4

  Immobility of the implant, relative to bone, during the healing phase

Titanium is the material of choice for dental implants. Titanium is biologically inert and therefore does not elicit a foreign body rejection reaction from host tissue. For the implant to have intimate contact with bone, the implant site must be prepared with a precise technique. All implant systems have specially designed drills that are used in a specific sequence to remove bone as atraumatically as possible. The drill sizes are matched to the size and shape of the implant being placed, creating the precision necessary for developing initial bony contact and stability.

Atraumatic surgical technique in an aseptic environment is critical to minimize mechanical and thermal injuries to bone. This involves using sharp, precision osteotomy drills run at slow speed with high torque while maintaining gentle, intermittent pressure and providing copious irrigation. Irrigation can be accomplished either externally or internally using special handpieces and burrs with internal ports. The goal is to maintain bone temperatures below 47°C during implant site preparation. Any variance causing temperatures to exceed 47°C is likely to cause bone necrosis and failure of osseointegration.

Initial stability of the implant must be achieved and maintained for formation of bone at the implant surface. Stability at the time of placement is predicated on the volume and quality of bone that intimately contacts the implant as well as the length and diameter of the implant ( Fig. 14.2 ). The best-case scenario would be a long, wide-diameter implant that engages a thick superior cortical plate surrounded by dense cancellous bone and terminally engages a thick inferior cortical plate (i.e., anterior mandibular) ( Fig. 14.3 ). Conversely, a short, narrow-diameter implant placed in an area that has a thin superior cortical plate and minimally dense cancellous bone but does not engage the inferior cortical bone would provide considerably less stability and resistance to immobility (i.e., posterior maxilla).

During the time required for osseointegration to occur, it is imperative that immobility of the implant be maintained. Therefore, in areas where implant primary stability may be less, a submerged, nonloaded healing period followed by surgical uncovering of the implant would be required (two-stage surgery) ( Fig. 14.4 ). In a clinical situation in which adequate primary stability is achieved, a single-stage, nonsubmerged implant would be appropriate. In such a case the implant may be loaded immediately after surgery.

Soft Tissue–Implant Interface

Historically, most basic science and clinical efforts were spent on studying the bone-implant interface of osseointegration. Considerably less attention was given to overlying soft tissues. In contemporary implant dentistry, however, this subject is being researched with great zeal. Driven primarily by the need for satisfactory esthetics as well as maintenance of a soft tissue seal or barrier against bacterial invasion, soft tissue has become a major focus of interest.

It is critical to understand both the striking similarities and the obvious differences between the peri-implant soft tissue and periodontal soft tissue ( Fig. 14.5 ). Peri-implant and periodontal soft tissues do share a number of similarities and only subtle differences. Each emerges from alveolar bone through soft tissue. Soft tissue consists of connective tissue covered by epithelium, which is continuous with an epithelium-lined gingival sulcus, the apical-most portion being lined with junctional epithelium forming an attachment. From that point down to the level of alveolar bone, both types of soft tissue possess a zone of dense connective tissue. This zone of supracrestal connective tissue is responsible for maintaining a stable interface between soft tissue and the implant and acts as a seal or barrier to the oral environment. It is the orientation of the connective tissue fibers adjacent to an implant that differ from a natural tooth. This zone of connective tissue has been measured to be 1 to 2 mm in height. Clinically this becomes important when examining the health of peri-implant soft tissue. Probing depths in a healthy implant would be approximately 1 to 2 mm less than the total measured dimension from the crest of the sulcus to the alveolar bone crest. The other obvious difference between teeth and implants is that teeth have a periodontal ligament with connective tissue fibers that suspend teeth in alveolar bone. The implant, however, is in direct contact with bone without any intervening soft tissue. This difference has a dramatic impact on the biomechanics, proprioception, and prosthetic consideration for implants versus natural teeth. Because an implant, unlike a tooth, does not have cementum, most connective tissue fibers run in a direction more or less parallel to the implant surface.

Biomechanical Considerations

As described earlier, sound surgical technique, use of precision instrumentation, an aseptic environment, and intimate contact between bone and the implant are all paramount in achieving osseointegration. Once the implant is properly placed, the long-term success is heavily dependent on restorative biomechanical factors—that is, how the stresses imposed on the functioning implant or prosthetic unit or units will be controlled or distributed. The axiom is simple: The load-bearing capacity of the integrated implant has to be greater than the anticipated load during function. If applied loads are greater than the load-bearing capacity, it is likely to lead to mechanical failure, biologic failure, or both. Mechanical failure may present simply as porcelain fracture or as a loosened or fractured prosthetic screw (the screw that attaches the abutment or framework to the implant). The most devastating mechanical failure occurs when the force is destructive enough to actually fracture the implant fixture. A biologic failure can occur when the functional load exceeds the load-bearing capacity of the implant-bone interface. This initially presents clinically as bone loss around the platform of the implant. If the loss is severe enough and the provocation is long enough, the bone loss may progress around the entire implant and result in complete failure of the implant. The clinician must remember that an implant-retained restoration lacks the “shock absorbing” periodontal ligament that a natural tooth-retained restoration possesses. The periodontal ligament allows slight physiologic movement of teeth, and in the absence of microbe-induced inflammation, natural teeth can move and adapt to the forces without pathologic bone loss. This, however, is not possible with an osseointegrated implant.

The load-bearing capacity of implants is qualified by several factors, including the number and size of the implants, the arrangement and angulation of the implants, and the volume and quality of the bone-implant interface. The same factors that maximize initial implant stability in hard tissue continue to be important. Thick cortical bone and dense trabecular bone surrounding a long, wide-diameter implant that is positioned to be in line with the functional load, would offer the greatest load-bearing capacity and the best prognosis for long-term success. Conversely, a short, narrow-diameter implant placed in an area of thin cortical bone and less dense trabecular bone and in an off-axis angulation would have far less load-bearing capacity and a poorer prognosis for success. The angulation of the implants as it relates to the occlusal plane and the direction of the occlusal forces is an important determinant in optimizing the translation of the forces to the implants and the surrounding bone ( Fig. 14.6 ). Loads directed through the long axis of the implants are tolerated very well. Slight off-axis loads are usually not clinically detrimental, but loads applied at angles greater than 20 degrees or more can result in load magnification and initiate bone loss at the implant-bone interface. Again, if excessive loads persist, bone loss will continue and will likely lead to implant failure.

The number of implants placed in multitooth edentulous spans affects the load-bearing capacity of the implanted prosthesis. If there is a three-tooth edentulous span, the fixed prosthetic options would be to place three implants with three splinted crowns, three implants with three single-unit crowns, two implants as terminal abutments for a three-unit fixed partial denture, or two adjacent implants with a fixed partial denture with a cantilevered pontic. The load-bearing capacity decreases with each successive option.

Straight-line or linear arrangement of multiple implants should be avoided as this provides the least biomechanical advantage and is the least resistant to torqueing forces caused by off-center occlusal and lateral loads. Implants should be placed in a more curvilinear or staggered fashion ( Fig. 14.7 ).

Connecting a single integrated implant to one natural tooth with a fixed partial denture will effectively create an excessively loaded cantilever situation. Because of the immobility of the implant compared with the mobility of the natural tooth, when the loads are applied to the fixed partial denture, the tooth can move within the limits of its periodontal ligament. This can create stresses at the implant abutment junction up to two times the applied load on the prosthesis ( Fig. 14.8 ). Additional problems with a tooth to implant-supported, fixed partial dentures include breakdown of osseointegration, cement failure on the natural abutment, screw or abutment loosening, and possible failure of the implanted prosthetic components.

Detrimental forces can be applied iatrogenically by placing nonpassive, ill-fitting frameworks on implants. When the screws are tightened in an attempt to seat the ill-fitting framework, compressive forces are placed on the implant-bone interface. This excessive force can lead to bone loss and potential implant failure

Initial Observations and Patient Introduction

At the first meeting with the patient, the experienced clinician begins observing the patient's physicality, physique, complexion, hands, eyes, facial features, voice, posture, personality, and so on. These same initial characteristics will continue to be observed throughout the consultation and through the continuum of the patient's treatment.

Chief Complaint

The patient's chief complaint is a statement in his or her own words that conveys the perceived problem, concerns, expectations, and so on. The goal of the clinician is to explore, conversationally, the details of the patient's concerns, desire for treatment, apprehensions, and goals for the desired outcome. The clinician must assess how realistic the patient's expectations are. Is the patient looking strictly for a functional replacement, or is there a strong esthetic expectation? How does the patient's expectation fit his or her perceived timeline or financial investment? Ultimately, it becomes the clinician's responsibility to sift through all of the information conveyed by the patient and determine the available treatment options that would meet or exceed the patient's expectations and to educate the patient about these options. If the doctor and the patient do not understand each other's expectations, there will inevitably be less satisfaction at the conclusion of the treatment.

Medical History and Medical Risk Assessment

A thorough medical history is required and must be documented for every dental patient. As with any patient planning a surgical procedure, the patient must be assessed preoperatively to evaluate his or her ability to tolerate the proposed procedure, heal, and to have a favorable prognosis.

When the medical history form is completed, it is the responsibility of the clinician to review it and use the reported data as the basis for an efficient verbal medical history taking or interview. This interview is used to gain additional insight or information necessary to fully understand the patient's health status. The interview also allows an opportunity to fill important gaps in the history, as patients often fail to list significant medical information on the questionnaire.

There are only a few absolute medical contraindications to implant therapy. Absolute contraindications to implant placement based on surgical and anesthetic risks are limited primarily to patients who are acutely ill and those with uncontrolled metabolic disease. Often these contraindications are limited in duration; once the illness resolves or the metabolic disease is controlled, the patient may become a good candidate for implant therapy. Relative contraindications are concerned with medical conditions that affect bone metabolism or the patient's ability to heal. These include conditions such as diabetes, osteoporosis, immune compromise (e.g., human immunodeficiency virus infection, acquired immunodeficiency syndrome), medications (e.g., bisphosphonates—oral and intravenous), and medical treatments such as chemotherapy and irradiation (e.g., of the head and neck).

Some psychological or mental conditions could be considered absolute or relative contraindications, depending on their severity. Patients with psychiatric syndromes (e.g., schizophrenia, paranoia) or mental instabilities (e.g., neurosis, somatic symptom disorder), those who have mental impairment or are uncooperative, or those who have irrational fears, phobias, or unrealistic expectations may be poor candidates for implant treatment. Certain habits or behavioral considerations such as smoking, tobacco use, substance abuse (e.g., drugs and alcohol), and parafunctional habits (bruxing and clinching) must be scrutinized as potential contraindications as well. Smoking, in particular, has been documented as a significant risk factor resulting in decreased long-term stability and retention of implants.

Dental History

Like the medical history, a thorough dental history must be obtained from every dental patient, and it is initiated with a history questionnaire. The clinician seeks information regarding the patient's past experiences with restorative dentistry, periodontics, oral surgery, endodontics, orthodontics, and prosthetics. By understanding the patient's prior dental history, the clinician can gain insight into the patient's potential as a candidate for implant therapy. For example, if a patient presents with complex dental needs and has a history of seeking dental care in a consistent and mindful fashion, the clinician may feel that the patient is an above-average risk. However, because of the patient's compliance history, he or she may be a suitable candidate for comprehensive dental treatment. Conversely, if a patient presents with complex dental needs and has shown very little commitment to past dental treatment and has demonstrated very little effort to take care of his or her dentition, the clinician may consider this patient a much higher risk and may suggest a less complex and more easily serviced treatment plan.

Equally as important, the clinician needs to explore the patient's emotional connection to his or her dental history. Has the patient had positive dental experiences in the past, or is the patent extremely apprehensive because of prior experiences? Surgical or restorative implant dentistry requires significant commitment from both the patient and the clinician. It is imperative that the dentist-patient relationship be as constructive as possible.

Intraoral Examination

The oral examination helps assess the current health and condition of existing teeth as well as the oral hard and soft tissues. It is imperative to recognize any pathologic conditions present in any of the hard or soft tissues or the presence of acute or chronic infection. The implant-focused intraoral examination should address the restorative or structural integrity of existing teeth, existing prosthetics, vestibular depths, palatal depths, edentulous ridge topography, periodontal status, oral lesions, infections, occlusion, orthodontic assessment, jaw relationships, interarch space, maximum opening, parafunctional habits, and oral hygiene. Specific attention should be paid to the edentulous ridge anatomy and soft tissue morphology. The height and width of the ridges are evaluated visually, followed by palpation of the area to locate topographic determinants such as undercuts or bony defects.

As previously described, the soft tissue surrounding dental implants contributes to their success and longevity. While examining the periodontal health of the patient, the clinician must consider the health of soft tissue around existing teeth, the edentulous areas, and any previously placed implant. Soft tissue is examined for zones of keratinization (e.g., quantity and location), clinical biotype (e.g., thin, moderate, or thick), redundancy and mobility, and pathology. Clinical inspection of soft tissue often requires radiographic verification, particularly if soft tissue is thick, dense, and fibrous. Thick fibrous tissue can often mask a thin underlying bony architecture. In locations planned for implant placement, the more site-specific evaluation centers on the quality, quantity, and location of keratinized tissue and nonkeratinized mucosa. If the clinician feels that keratinized tissue is inadequate to maintain the health of the implant or is lacking in esthetic support of the planned implant or restorative complex, then soft tissue grafting or augmentation must be considered.

While examining the patient, the clinician should also evaluate the surgical ergonomics, that is, how wide the patient can open the mouth, how resilient the cheeks are, the size of the tongue, perioral musculature, exaggerated gag reflex, airway liability, and overall patient cooperation.

More specific aspects of the hard and soft tissue examination will be presented when addressing specific implant areas. All of the details of the intraoral examination need to be charted and documented. The intraoral examination allows the clinician to then determine what radiographs and other diagnostic records may be required to further evaluate the patient and his or her dental needs.

Diagnostic Casts and Photographs

Mounted study models as well as intraoral and extraoral photographs complete the records collection process. Study models and photographs are often overlooked in preoperative history taking, but both contribute significantly to the assessment and treatment planning phases of implant dentistry.

Study models mounted on a semiadjustable articulator using a face-bow transfer give the clinician a three-dimensional working representation of the patient and provide much information required for surgical and prosthetic treatment planning.

Elements that can be evaluated from accurately mounted models include the following:

• 1

  Occlusal relationships

• 2

  Arch relationships

• 3

  Interarch space

• 4

  Arch form, anatomy, and symmetry

• 5

  Preexisting occlusal scheme

• 6

  Curve of Wilson and curve of Spee

• 7

  Number and position of the existing natural teeth

• 8

  Tooth morphology

• 9

  Wear facets

• 10

  Edentulous ridge relationships to adjacent teeth and opposing arches

• 11

  Measurements for planning future implant locations

• 12

  Visualizing force vectors, both present and planned

Mounted study models have tremendous value when interdisciplinary treatment planning is required. Multiple individuals involved in the treatment of the patient can efficiently evaluate and contribute to the assessment and treatment planning without the patient being present. Medicolegally, the mounted study models are preserved as an exact reference of the preoperative condition.

Intraoral photographs are equally important. They allow visual evaluation of the patient's soft tissue (e.g., quantity, quality, location, texture, color, symmetry). Extraoral photographs provide views of the patient from many different esthetic perspectives. Elements that are easily assessed are as follows:

• 1

  Facial form

• 2

  Facial symmetry

• 3

  Patient's degree of expression and animation

• 4

  Patient's appearance (e.g., facial features, facial hair, complexion, eye color)

• 5

  Smile line

• 6

  Incisal edge or tooth display

• 7

  Buccal corridor display

• 8

  Potential esthetic demand

Radiographic Examination

Several radiographic imaging options are available for diagnosis and for planning of dental implantation. Options range from standard intraoral projections (e.g., periapical, occlusal) and extraoral projections (e.g., panoramic, cephalometric), to more complex cross-sectional imaging (e.g., computed tomography [CT], cone-beam computed tomography [CBCT]).

Multiple factors, however, influence the selection of radiographic techniques for any particular case. Such factors as cost, availability, radiation exposure, and the type of case must be weighed against the accuracy of identifying vital anatomic structures within a given bone volume and being able to perform the surgical placement without injury to these structures. Areas of study radiographically include the following:

• 1

  Location of vital structures

  • Mandibular canal

  • Anterior loop of the mandibular canal

  • Anterior extension of the mandibular canal

  • Mental foramen

  • Maxillary sinus (floor, septations, and anterior wall)

  • Nasal cavity

  • Incisive foramen

• 2

  Bone height

• 3

  Root proximity and angulation of existing teeth

• 4

  Evaluation of cortical bone

• 5

  Bone density and trabeculation

• 6

  Pathology (e.g., abscess, cyst, tumor)

• 7

  Existence of anatomic variants (e.g., incomplete healing of extraction site)

• 8

  Cross-sectional topography and angulation (best determined by using CT and CBCT)

• 9

  Sinus health (best evaluated by using CT and CBCT)

• 10

  Skeletal classification (best evaluated with the use of lateral cephalometric images)

Radiographic images allow for quantifying dimensions or for taking measurements. Traditional radiographs must be calibrated for potential magnification. Magnification on a traditional panoramic image can be as much as 25%. One way to determine magnification is to place a metal sphere near the plane of occlusion when taking the radiograph. By comparing the radiographic size with the actual size of the sphere, the magnification can be determined ( Fig. 14.9 ). Digitally acquired periapical, panoramic, lateral cephalometric images and CT and CBCT scans have bundled software applications that allow for very accurate measurement.

Critical measurements specific to implant placement include the following:

• At least 1 mm inferior to the floor of the maxillary and nasal sinuses

• Incisive canal (maxillary midline implant placement) to be avoided

• 5 mm anterior to the mental foramen

• 2 mm superior to the mandibular canal

• 3 mm from adjacent implants

• 1.5 mm from roots of adjacent teeth

CT and CBCT image data files can be reformatted and viewed on personal computers using simulation software. This allows the diagnosis and treatment planning processes to be more accurate with regard to measurements and dimensions. Critical anatomic structures can be visualized in all three coordinate axes so that their superoinferior, anteroposterior, and buccolingual locations can be identified ( Fig. 14.10 ).

Prosthetic Considerations in Implant Treatment Planning

The prosthetic assessment takes the diagnostic data that has been gathered and combines it with the clinical judgment of the clinician performing the restoration, the patient's expectations, and an understanding of what is surgically reasonable to form the treatment plan. Assessment for prosthetic treatment is multifactorial, is unique to each individual, and can range from simple to extremely complex.

A simple starting point is to determine what needs to be replaced: a single tooth, multiple teeth, or all of the patient's teeth. Will the replacement be more functional (e.g., a mandibular first molar), or will the replacement have a strong esthetic consideration (e.g., maxillary central incisor)? Is the patient expecting to have a fixed prosthetic option or one that is removable? Does the prosthetic solution include replacing just the tooth; the tooth and gingival tissue; or bone, gingival tissue, and the tooth ( Fig. 14.11 )?

In the partially edentulous patient, evaluation of existing natural teeth and their periodontal support is imperative. The prognosis for the remaining teeth and their value in the overall dental health of the patient must be determined. If the patient is only missing a single tooth and all the remaining teeth are healthy, then the prognosis for the patient's overall dental health is clear. If the patient only has a few teeth scattered throughout the maxillary and mandibular arches and the remaining teeth are heavily restored and periodontally compromised and their prognosis is questionable or guarded, decisions must then be made as to whether the remaining teeth hold any prosthetic value or are best removed.

The patient's occlusion needs to be examined. Are the components of occlusion favorable, or will they have to be reestablished? The clinician must evaluate the occlusal scheme (e.g., cuspid protected, group function, or some variation). The occlusion can be classified (e.g., class I, class II, class III) and compared with the patient's skeletal classification (e.g., class I, class II, class III). Open bites, deep bites, and crossbites need to be recognized and their liability assessed. The maxillary occlusal plane, curve of Spee, and curve of Wilson need to be evaluated. Compensatory conditions to the occlusion need to be taken into consideration (e.g., wear facets, abfraction lesions, gingival recession, mobility, tooth migration, anterior splaying, mesially inclined molars, and fractures). All of these conditions have a direct impact on the biomechanics of any proposed treatment.

Evaluation of the interarch space is critical in both the partially edentulous patient and the totally edentulous patient. The interarch space determines spatial limitations or an opportunity for specific prosthetic options. For example, a cement-retained, abutment-supported crown on an implant replacing the mandibular right first molar requires a minimum of 8 mm of interarch space from the osseous crest of the edentulous space to the occlusal surface of the opposing tooth. If 8 mm of interarch space is not available, then a screw-retained implant crown would be necessary. For the edentulous patient, approximately 15 to 17 mm of interarch space is required for a bar-retained overdenture. If less interarch space is available, then an abutment-retained (e.g., locator attachment, O-ring) overdenture would be necessary.

The crown-implant ratio needs to be carefully considered in the implant treatment planning. The clinician must measure the interarch space in the area planned for the crown and implant and reference that measurement against the intended implant length. For example, if the interarch space between the osseous crest of the edentulous site of the lower right first molar and the opposing occlusal surface is 10 mm and the longest implant that can be placed is 10 mm, then the crown-implant ratio is 1 : 1. Any ratio less than 1:1 provides increased confidence for favorable biomechanics (e.g., a crown height of 8 mm supported by an implant that is 13 mm in length). When the ratio becomes greater than 1:1, the clinician must understand the potential biomechanical liability of incrementally exceeding that ratio (e.g., a crown height of 15 mm supported by an implant that is 8 mm in length).

Implant spacing must be understood as a dimensional requirement. Implants need 1.5 mm of space from the outer surface of the implant to the adjacent root surface and 3 mm of space between adjacent implants. For example, if a 4-mm-diameter implant were planned to replace a missing tooth, the minimum edentulous space required would be 7 mm (1.5 + 4 + 1.5 mm = 7 mm). If two adjacent 4-mm implants were planned between natural teeth, the edentulous span would have to be at least 14 mm (1.5 + 4 + 3 + 4 +1.5 = 14 mm) ( Fig. 14.12 ).

The edentulous maxilla requires scrutiny in selecting prosthetic options. Because of the pattern of resorption (apically and palatally), consideration must be given to the intended location of the implant platform and the final position of teeth. In the case of a missing single tooth or a few anterior teeth, the ridge resorption may require grafting prior to implant placement ( Fig. 14.13 ). In a more severely resorbed atrophic maxilla opposing a dentate mandible, the anteroposterior difference may be too great to have a conventional, abutment-supported, fixed partial denture prosthetic option. In this case, a framework-supported, fixed hybrid prosthesis or a removable overdenture option would need to be utilized. Close attention must be paid to the upper lip esthetics as well. Many patients need the support provided by the labial flange of the maxillary denture to support their upper lip, while others can have an acceptable result without the flange. One of the major motivators for patients seeking implants to retain a maxillary denture is the possibility of having a prosthesis without any coverage of the hard palate. In most cases, with appropriate implant support, this is, indeed, possible, but in cases where there is an extremely shallow buccal vestibule and palatal vault, the prosthesis may require palatal coverage for stability and enhanced biomechanics.

A major determinate in overdenture support as well as fixed prosthetic options in the edentulous arch is the concept of the anteroposterior (AP) spread of the implants.

The AP spread is defined by the distance measured between a line drawn horizontally through the middle of the most anterior implant and a line drawn horizontally through the distal of the most posterior implant on each side of the arch. The greater the AP spread, the more stable the prosthesis will be. If a retentive bar or fixed framework needs to be cantilevered to increase its length and thus its support, the AP distance measured can be multiplied by a factor of 1.5 to determine the additional length that can be added to the bar or frame. Therefore if the distance measured from the center of the most anterior implant to the distal part of the most posterior implant is 10 mm, then a retentive bar or fixed framework could be extended 15 mm further posterior to the most posterior implant on that side ( Fig. 14.14 ). If the cantilevered distance is excessive, this may lead to failure of the prosthetic structure or may place undue stress on the implants, compromising implant integrity and potentially causing implant failure.

Many prosthetic options are available for implant reconstruction, each with a specific list of attributes and liabilities. The clinician must be aware of the pros and cons of each. Factors to take into consideration include cost, durability, retrievability (cement- or screw-retained), reparability (degree of difficulty, time, and cost), material choices (acrylic, resin, porcelain), fixed or removable, clinical demand, patient expectation, and patient dexterity. For example, a patient with a completely edentulous maxilla may be a candidate for a removable, attachment-retained overdenture or a fixed, all-ceramic, hybrid prosthesis. The cost and durability of the all-ceramic hybrid is considerably higher than that of the overdenture, but the retrievability and reparability of the overdenture is far easier and less expensive. The patient may have the financial means to afford the far more expensive all-ceramic hybrid prosthesis but may not have the physicality for the increased clinical demand or the dexterity to care for the fixed option.