CHAPTER 12 Diagnosis and Treatment Planning
The purpose of dental treatment is to respond to a patient’s needs, both the needs perceived by the patient and those demonstrated through a clinical examination and patient interview. Although similarities have been noted between partially edentulous patients (such as Classification designations), significant differences exist, making each patient, and the ultimate treatment, unique.
The delineation of each patient’s uniqueness occurs through the patient interview and diagnostic clinical examination process. This includes four distinct processes: (1) understanding the patient’s desires or chief concerns/complaints regarding his or her condition (including its history) through a systematic interview process, (2) ascertaining the patient’s dental needs through a diagnostic clinical examination, (3) developing a treatment plan that reflects the best management of desires and needs (with influences unique to the medical condition or oral environment), and (4) executing appropriately sequenced treatment with planned follow-up. The ultimate treatment is individualized to address disease management and the coordinated restorative and prosthetic needs that are unique to the patient. Provision of the best care for a patient may involve no treatment, limited treatment, or extensive treatment, and the dentist must be prepared to help patients decide the best treatment option given his or her individual circumstances.
Although oral health is an important aspect of overall health, it is an elective health pursuit for most individuals. Consequently, the patient presents for professional evaluation (1) to address some perception of an abnormality that requires correction, or (2) to maintain optimum oral health. In either situation, but especially for the patient presenting with some chief complaint (often with an important history related to that complaint), it is mandatory that the dentist clearly understand what brings the patient to this evaluation. Failure to do so leads to the chance that the patient will be unhappy with the treatment result, as it might not address the very reason he or she came for help. With experience, this subtle point becomes a major component of a clinician’s management focus.
A fundamental objective of the patient interview, which accompanies the diagnostic examination, is to gain a clear understanding of why the patient is presenting for evaluation; this involves having the patient describe the history related to the chief complaint. For complicated clinical problems, the interview and diagnostic examination require two appointments to allow complete gathering of all diagnostic information needed to formulate a complete plan of treatment.
The interview, an opportunity to develop rapport with the patient, involves listening to and understanding the patient’s chief complaint or concern about his or her oral health. This can include clinical symptoms of pain (provoked or unprovoked), difficulty with function, concern about appearance, problems with an existing prosthesis, or any combination of symptoms related to the teeth, periodontium, jaws, or previous dental treatment. It is important to listen carefully to what the patient has stated is the reason for presenting for evaluation; this is because all subsequent information gathered will be used to discuss these concerns and to relate whether the proposed treatment will affect the patient in any way. Such a discussion at the outset of patient care helps to outline realistic expectations.
It is from the above interaction that patient uniqueness, as mentioned earlier, is best defined. The expectations described by the patient are critical to an understanding of whether a removable partial denture will satisfy the stated treatment goal(s). The fact that removable partial dentures by necessity require material bulk and often use oral soft tissues for support may be hard to comprehend by patients with no such prosthetic history. Helping the patient understand the normal phase of accommodation to such a prosthesis is an important discussion point in selection of a prosthesis. For those patients with a negative past prosthesis experience, it is necessary to determine before treatment is started whether the design, fit, occlusion, or lack of maintenance of the prosthesis can be improved to provide a more positive experience.
When helping patients understand their oral health status, comprising both disease and deficit considerations, and the means to address both, we should carefully consider what it is they need to hear from us. For most partially edentulous patients, the discussion may involve fairly complex rehabilitation options for addressing their missing teeth. Because of this complexity, our responsibility is to help them sort through the options in an attempt to help them come to the best decision for them. Using a communication model termed shared decision making gives structure to a process where the provider and the patient identify together the best course of care. This process recognizes that there may be complex “trade-offs” in care choice, and it addresses the need to fully inform patients about risks and benefits of care options, as well as ensuring that patient values and preferences play a prominent role in the process. Although it is clear that not all patients desire to participate equally in care decisions, because the options can vary significantly (some are more invasive, have greater risks, are accompanied by higher treatment burden than others; there are often varying maintenance needs between options), we should actively engage them in the process. This is more important given the fact that the tooth replacement is often an elective pursuit, and because of this, there is seldom great urgency involved in making a decision.
The objectives of any prosthodontic treatment may be stated as follows: (1) the elimination of disease; (2) the preservation, restoration, and maintenance of the health of the remaining teeth and oral tissues (which will enhance the removable partial denture design); and (3) the selected replacement of lost teeth; for the purpose of (4) restoration of function in a manner that ensures optimum stability and comfort in an esthetically pleasing manner. Preservation is a principle that protects from decisions that place too high a premium on cosmetic concerns, and it is the dentist’s obligation to emphasize the importance of restoring the total mouth to a state of health and of preserving the remaining teeth and surrounding tissues.
Diagnosis and treatment planning for oral rehabilitation of partially edentulous mouths must take into consideration the following: control of caries and periodontal disease, restoration of individual teeth, provision of harmonious occlusal relationships, and the replacement of missing teeth by fixed (using natural teeth and/or implants) or removable prostheses. Because these procedures are integrally related, the appropriate selection and sequencing of treatment should precede all irreversible procedures.
The treatment plan for the removable partial denture, which is often the final step in a lengthy sequence of treatment, should precede all but emergency treatment. This allows abutment teeth and other areas in the mouth to be properly prepared to support, stabilize, and retain the removable partial denture. This means that diagnostic casts, for designing and planning removable partial denture treatment, must be made before definitive treatment is undertaken. After the major factors that create functional forces are evaluated and those that resist it are understood, the removable partial denture design is drawn on the diagnostic cast, along with a detailed chart of mouth conditions and proposed treatment. This becomes the master plan for the mouth preparations and the design of the removable partial denture to follow.
As was pointed out in Chapter 1, failure of removable partial dentures can usually be attributed to factors that result in poor stability. These can result from inadequate diagnosis and failure to properly evaluate the conditions present. This results in failure to prepare the patient and the oral tissues properly before the master cast is fabricated. The importance of the examination, the consideration of favorable and unfavorable aspects relative to movement control, and the importance of planning the elimination of unfavorable influences cannot be overemphasized (see Chapter 2).
As was mentioned earlier, for complex treatment, two appointments are often required. The first will likely include a preliminary oral examination (to determine the need for management of acute needs), a prophylaxis, full-mouth radiographs, diagnostic casts, and mounting records if baseplates are not required. The follow-up appointment includes mounting of the diagnostic casts (when baseplates and occlusion rims are needed), a definitive oral examination, review of the radiographs to augment and correlate with clinical findings, and arrangement of additional consultations when required. Following collection and synthesis of all patient and clinical information, including surveying of the casts, a treatment plan (often with options) is presented.
A complete oral examination should precede any treatment decisions. It should include visual and digital examination of the teeth and surrounding tissues with a mouth mirror, explorer, and periodontal probe, vitality tests of critical teeth, and examination of casts correctly oriented on a suitable articulator. Clinical findings are augmented by and correlated with a complete intraoral radiographic survey.
During the examination, the objective to be kept foremost in mind should be the consideration of possibilities for restoring and maintaining the remaining oral structures in a state of health for the longest period of time. This is best accomplished by an evaluation of factors that generate functional forces and those that resist them. The stability of tooth and prosthesis position is the goal of such an evaluation. The following sequence of examination allows attention to be paid to aspects of each of these critical features of evaluation for removable partial denture service.
An oral examination should be accomplished in the following sequence: visual examination, pain relief and temporary restorations, radiographs, oral prophylaxis, evaluation of teeth and periodontium, vitality tests of individual teeth, determination of the floor of the mouth position, and impressions of each arch.
Figure 12-1 Complete intraoral radiographic survey of remaining teeth and adjacent edentulous areas reveals much information vital to effective diagnosis and treatment planning. The response of bone to previous stress is of particular value in establishing the prognosis of teeth that are to be used as abutments.
Visual examination will reveal many of the signs of dental disease. Consideration of caries susceptibility is of primary importance. The number of restored teeth present, signs of recurrent caries, and evidence of decalcification should be noted. Only those patients with demonstrated good oral hygiene habits and low caries susceptibility should be considered good risks without resorting to prophylactic measures such as the restoration of abutment teeth. At the time of the initial examination, periodontal disease, gingival inflammation, the degree of gingival recession, and mucogingival relationships should be observed. Such an examination will not provide sufficient information to allow a definitive diagnosis and treatment plan. For this purpose, complete periodontal charting that includes pocket depths, assessment of attachment levels, furcation involvement, mucogingival problems, and tooth mobility should be performed. The extent of periodontal destruction must be determined with appropriate radiographs and use of the periodontal probe.
The number of teeth remaining, the location of the edentulous areas, and the quality of the residual ridge will have a definite bearing on the proportionate amount of support that the removable partial denture will receive from the teeth and edentulous ridges. Tissue contours may appear to present a well-formed edentulous residual ridge; however, palpation often indicates that supporting bone has been resorbed and has been replaced by displaceable, fibrous connective tissue. Such a situation is common in maxillary tuberosity regions. The removable partial denture cannot be supported adequately by tissues that are easily displaced. When the mouth is prepared, this tissue should be recontoured or removed surgically, unless otherwise contraindicated. A small but stable residual ridge is preferable to a larger unstable ridge for providing support for the denture. The presence of tori or other bony exostoses must be detected and their presence in relation to framework design must be evaluated. Failure to palpate the tissue over the median palatal raphe to ascertain the difference in its displaceability as compared with the displaceability of the soft tissues covering the residual ridges can lead to a rocking, unstable, uncomfortable denture and to a dissatisfied patient. Adequate relief of the palatal major connectors must be planned, and the amount of relief required is directly proportionate to the difference in displaceability of the tissues over the midline of the palate and the tissues covering the residual ridges.
During the examination, not only each arch but also its occlusal relationship with the opposing arch must be considered separately. A situation that looks simple when the teeth are apart may be complicated when the teeth are in occlusion. For example, an extreme vertical overlap may complicate the attachment of anterior teeth to a maxillary denture. Extrusion of a tooth or teeth into an opposing edentulous area may complicate the replacement of teeth in the edentulous area or may create occlusal interference, which will complicate the location and design of clasp retainers and occlusal rests. Such findings subsequently will be evaluated further by careful analysis of mounted diagnostic casts.
The fee for examination, which should include the cost of the radiographic survey and the examination of articulated diagnostic casts, should be established before the examination is performed and should not be related to the cost of treatment. It should be understood that the fee for examination is based on the time involved and the service rendered, and that the material value of the radiograph and diagnostic casts is incidental to the effectiveness of the examination.
The examination record should always be available in the office for future consultation. If consultation with another dentist is requested, respect for the hazards of unnecessary radiation justifies loaning the dentist the radiograph for this purpose. However, duplicate films should be retained in the dentist’s files.
A diagnostic cast should be an accurate reproduction of all the potential features that aid diagnosis. These include the teeth locations, contours, and occlusal plane relationship; the residual ridge contour, size, and mucosal consistency; and the oral anatomy delineating the prosthesis extensions (vestibules, retromolar pads, pterygomaxillary notch, hard/soft palatal junction, floor of the mouth, and frena). Additional information provided by appropriate cast mounting includes occlusal plane orientation and the impact on the opposing arch; tooth-to-palatal soft tissue relationship; and tooth-to-ridge relationships both vertically and horizontally.
A diagnostic cast is usually made of dental stone because of its strength and the fact that it is less easily abraded than is dental plaster. Generally the improved dental stones (die stones) are not used for diagnostic casts because of their cost. Their greater resistance to abrasion does, however, justify their use for master casts.
The impression for the diagnostic cast is usually made with an irreversible hydrocolloid (alginate) in a stock (perforated or rim lock) impression tray. The size of the arch will determine the size of the tray to be used. The tray should be sufficiently oversized to ensure an optimum thickness of impression material to avoid distortion or tearing on removal from the mouth. The technique for making impressions is covered in more detail in Chapter 15.
Figure 12-4 A, Following mounting of the diagnostic casts, tooth arrangement for the mandibular occlusal plane requirements can be accomplished. B, Following placement of the maxillary anterior teeth in an ideal position, diagnostic arrangement of occlusion results in a space posterior to surveyed crown #27. If such a finding were objectionable, alternative arrangements could be investigated. This is not possible unless a diagnostic workup is completed. C, Occlusion of the mandibular removable partial denture will be enhanced by improving the maxillary posterior occlusal plane of the super-erupted molars.
Figure 12-5 Proposed mouth changes and design of the removable partial denture framework are indicated in pencil on the diagnostic cast in relation to the previously determined path of placement. This serves as a means of communicating with the patient and as a chair-side guide to tooth modification.
For diagnostic purposes, casts should be related on an anatomically appropriate articulator to best understand the role occlusion may have in the design and functional stability of the removable partial denture. This becomes increasingly important as the prosthesis replaces more teeth. If the patient presents with a harmonious occlusion and the edentulous span is a tooth-bound space, simple hand articulation is generally all that is required. However, when the natural dentition is not harmonious and/or when the replacement teeth must be positioned within the normal movement patterns of the jaws, the diagnostic casts must be related in an anatomically appropriate manner for diagnosis. This means placement of the maxillary cast in a position relative to the opening axis on the articulator, which is similar to the position of the maxilla in relation to the temporomandibular joint of the patient (Figure 12-6). The mandibular cast is then placed beneath the maxillary cast in a horizontal position dictated by mandibular rotation without tooth contact, at a minimal vertical opening.
The Glossary of Prosthodontic Terms* describes an articulator as a mechanical device that represents the temporomandibular joints and jaw members, to which maxillary and mandibular casts may be attached. Because the dominant influence on mandibular movement in a partially edentulous mouth is the occlusal plane and the cusps of the remaining teeth, an anatomic reproduction of condylar paths is probably not necessary. Still, movement of the casts in relation to one another as influenced by the occlusal plane and the cusps of the remaining teeth, when mounted at a reasonably accurate distance from the axis of condylar rotation, permits a relatively valid analysis of occlusal relations. This is more anatomically accurate than a simple hinge mounting.
It is better that the casts be mounted in relation to the axis-orbital plane to permit better interpretation of the plane of occlusion in relation to the horizontal plane. Although it is true that an axis-orbital mounting has no functional value on a nonarcon instrument because that plane ceases to exist when opposing casts are separated, the value of such a mounting lies in the orientation of the casts in occlusion. (An arcon articulator is one in which the condyles are attached to the lower member as they are in nature, the term being a derivation coined by Bergström from the words articulation and condyle. Many of the more widely used articulators such as the Hanau H series, Dentatus, and improved Gysi have the condyles attached to the upper member and are therefore nonarcon instruments.)
The facebow is a relatively simple device used to obtain a transfer record for orienting a maxillary cast on an articulating instrument. Originally, the facebow was used only to transfer a radius from condyle reference points, so that a given point on the cast would be the same distance from the condyle as it is on the patient. The addition of an adjustable infraorbital pointer to the facebow and the addition of an orbital plane indicator to the articulator make possible the transfer of the elevation of the cast in relation to the axis-orbital plane. This permits the maxillary cast to be correctly oriented in the articulator space comparable with the relationship of the maxilla to the axis-orbital plane on the patient. To accommodate this orientation of the maxillary cast and still have room for the mandibular cast, the posts of the conventional articulator must be lengthened. The older Hanau model H articulator usually will not permit a facebow transfer with an infraorbital pointer.
A facebow may be used to transfer a comparable radius from arbitrary reference points, or it may be designed so that the transfer can be made from hinge axis points. The latter type of transfer requires that a hinge-bow attached to the mandible should be used initially to determine the hinge axis points, to which the facebow is then adjusted for making the hinge axis transfer.
A facebow transfer of the maxillary cast, which is oriented to the axis-orbital plane in a suitable articulator, is an uncomplicated procedure. The Hanau series Wide-Vue 183-2, all 96H2-0 models, the Whip-Mix articulator (Whip-Mix Corp, Louisville, KY), and the Dentatus model ARH (Dentatus USA, New York, NY) will accept this transfer. The Hanau earpiece facebow models 153 and 158, the Hanau fascia facebow 132-2SM, and the Dentatus facebow type AEB incorporate the infraorbital plane to the articulator. None of these are hinge axis bows; they are used instead at an arbitrary point.
The location of the arbitrary point or axis has long been the subject of controversy. Gysi and others have placed it 11 to 13 mm anterior to the upper third of the tragus of the ear on a line extending from the upper margin of the external auditory meatus to the outer canthus of the eye. Others have placed it 13 mm anterior to the posterior margin of the center of the tragus of the ear on a line extending to the corner of the eye. Bergström has located the arbitrary axis 10 mm anterior to the center of a spherical insert for the external auditory meatus and 7 mm below the Frankfort horizontal plane.
In a series of experiments reported by Beck, it was shown that the arbitrary axis suggested by Bergström falls consistently closer to the kinematic axis than do the other two. It is desirable that an arbitrary axis is placed as close as possible to the kinematic axis. Although most authorities agree that any of the three axes will permit transfer of the maxillary cast with reasonable accuracy, it would seem that the Bergström point compares most favorably with the kinematic axis.
The lowest point on the inferior orbital margin is taken as the third point of reference for establishing the axis-orbital plane. Some authorities use the point on the lower margin of the bony orbit in line with the center of the pupil of the eye. For the sake of consistency, the right infraorbital point is generally used and the facebow assembled in this relationship. All three points (right and left axes and infraorbital point) are marked on the face with an ink dot before the transfer is made.
Casts are prepared for mounting on an articulator by placing three index grooves in the base of the casts. Two V-shaped grooves are placed in the posterior section of the cast and one groove in the anterior portion (Figure 12-7).
Figure 12-7 The base of the cast has been prepared for mounting by placing three triangular grooves to allow indexing when mounted. The grooves are prepared with a 3-inch stone mounted in a laboratory lathe.
An occlusion rim properly oriented on a well-fitting record base should be used in facebow procedures involving the transfer of casts representative of the Class I and II partially edentulous situations. Without occlusion rims, such casts cannot be located accurately in the imprints of the wax covering the facebow fork. Tissues covering the residual ridges may be displaced grossly when the patient closes into the wax on the facebow fork. Therefore the wax imprints of the soft tissues will not be true negatives of the edentulous regions of the diagnostic casts.
For purposes of illustration, a facebow using the external auditory meatus as the posterior reference point, the Whip-Mix Facebow technique (DB 2000, Whip-Mix Corp, Louisville, KY), will be shown. The facebow fork is covered with a polyether, polyvinyl siloxane or a roll of softened baseplate wax with the material distributed equally on the top and on the underneath side of the facebow fork. Then the fork should be pressed lightly on the diagnostic casts with the midline of the facebow fork corresponding to the midline of the central incisors (Figure 12-8). This will leave imprints of the occlusal and incisal surfaces of the maxillary casts and occlusion rim on the softened baseplate wax and is an aid in correctly orienting the facebow fork in the patient’s mouth. The facebow fork is placed in position in the mouth, and the patient is asked to close the lower teeth into the wax to stabilize it in position. It is removed from the mouth and chilled in cold water and then replaced in position in the patient’s mouth. An alternative method of stabilizing the facebow fork and recording bases is to enlist the assistance of the patient.
Figure 12-8 Orienting the facebow fork to the maxillary cast and occlusion rims will avoid displacing the occlusion rim in the mouth through patient closure or another uneven force. Polyvinyl siloxane material has been evenly distributed around the facebow fork, and care is exercised to position the fork to be centered at the mid-incisal position without any fork extension posterior to the record base, which could cause discomfort.
If an earpiece facebow is to be used, the patient should be reminded that the plastic earpieces in the auditory canals will greatly amplify noise. With the facebow fork in position, the facebow toggle is slipped over the anterior projection of the facebow fork (Figure 12-9). The patient can assist in guiding the plastic earpieces into the external auditory meatus. The patient can then hold the arms of the facebow in place with firm pressure while the operator secures the bite fork to the facebow. This accomplishes the radius aspect of the facebow transfer.
Figure 12-9 The horizontal toggle clamp of the Whip-Mix earpiece facebow (1) is slid onto the shaft of the facebow fork protruding from the patient’s mouth. The patient then helps guide plastic earpieces into the external auditory meatus and holds them in place while the operator tightens three thumb screws (2) and centers the plastic nosepiece (3) securely on the nasion. The horizontal toggle clamp is positioned and secured near (but not touching) the lip. The T screw (4) on the vertical bar is tightened. note: Extreme care should be exercised not to tilt the facebow out of position when tightening.
If an infraorbital pointer is used, it is placed on the extreme right side of the facebow and angled toward the infraorbital point previously identified with an ink dot. It is then locked into position with its tip lightly touching the skin at the dot. This establishes the elevation of the facebow in relation to the axis-orbital plane. Extreme care must be taken to avoid any slip that might injure the patient’s eye.
With all elements tightened securely, the patient is asked to open, and the entire assembly is removed intact, rinsed with cold water, and set aside. The facebow records not only the radius from the condyles to the incisal contacts of the upper central incisors, but also the angular relationship of the occlusal plane to the axis-orbital plane.
The facebow must be positioned on the articulator in the same axis-orbital relation as on the patient. If an arbitrary-type facebow is used, the calibrated condyle rods of the facebow ordinarily will not fit the condyle shafts of the articulator unless the width between the condyles just happens to be the same. With a Hanau model 132-25M facebow, the calibrations must be reequalized when in position on the articulator. For example, they have read 74 (mm) on each side of the patient but must be adjusted to read 69 (mm) on each side of the articulator. Some later model articulators have adjustable condyle rods and may be adjusted to fit the facebow. It is necessary that the facebow be centered in either case. Some facebows are self-centering, as is the Hanau Spring-Bow (Whip-Mix Corp, Louisville, KY).
The third point of reference is the orbital plane indicator, which must be swung to the right so that it will be above the tip of the infraorbital pointer. The entire facebow with maxillary cast in place must be raised until the tip of the pointer contacts the orbital plane indicated. The elevation having thus been established, for all practical purposes the orbital plane indicator and the pointer may now be removed because they may interfere with placing the mounting stone.
An auxiliary device called a cast support is available; it is used to support the facebow fork and the maxillary cast during the mounting operation (Figure 12-10). With this device, the weight of the cast and the mounting stone are supported separately from the facebow, thus preventing possible downward movement resulting from their combined weight. The cast support is raised to supporting contact with the facebow fork after the facebow height has been adjusted to the level of the orbital plane. Use of some type of cast support is highly recommended as an adjunct to facebow mounting.
The keyed and lubricated maxillary cast is now attached to the upper arm of the articulator with the mounting stone, thus completing the facebow transfer (Figure 12-11). Not only will the facebow have permitted the upper cast to be mounted with reasonable accuracy, it also will have served as a convenient means of supporting the cast during mounting. Once mastered, its use becomes a great convenience rather than a time-consuming nuisance.
Figure 12-11 Facebow mounting is complete. The relationship of the maxillary cast to the articulator condylar components is anatomically similar to that between the patient’s maxilla and the bilateral temporomandibular joint (TMJ) complex. Any subsequent tooth arrangement and occlusal contact development will represent the mouth more accurately than more arbitrary mountings. The benefits of the anatomic similarity are seen in more accurate occlusion for the finalized prosthesis (i.e., less intraoral adjustment required).
It is preferable that the maxillary cast be mounted while the patient is still present, thus eliminating a possible reappointment if the facebow record is unacceptable for some reason. Not too infrequently, the facebow record has to be redone with the offset-type facebow fork repositioned to avoid interference with some part of the articulator.
One of the first critical decisions that must be made in a removable partial denture service involves selection of the horizontal jaw relationship to which the removable partial denture will be fabricated (centric relation or the maximum intercuspal position). All mouth-preparation procedures depend on this analysis. Failure to make this decision correctly may result in poor prosthesis stability, discomfort, and deterioration of the residual ridges and supporting teeth.
It is recommended that deflective occlusal contacts in the maximum intercuspal and eccentric positions be corrected as a preventive measure. Not all dentists agree that centric relation and the maximum intercuspal position must be harmonious in the natural dentition. Many dentitions function satisfactorily with the opposing teeth maximally intercusped in an eccentric position without either diagnosable or subjective indications of temporomandibular joint dysfunction, muscle dysfunction, or disease of the supporting structures of the teeth. In many such situations, no attempt should be made to alter the occlusion. It is not a requirement to interfere with an occlusion simply because it does not completely conform to a relationship that is considered ideal.
If most natural posterior teeth remain and if no evidence of temporomandibular joint disturbances, neuromuscular dysfunction, or periodontal disturbances related to occlusal factors exists, the proposed restorations may be fabricated safely with maximum intercuspation of remaining teeth. However, when most natural centric stops are missing, the proposed prosthesis should be fabricated so that the maximum intercuspal position is in harmony with centric relation. By far the greater majority of removable partial dentures should be fabricated in the horizontal jaw relationship of centric relation. In most instances in which edentulous spaces have not bee/>