And Radiographic Evaluation

The likelihood of patients walking through the door requesting treatment with, or asking for information on implants is clearly on the rise and many readers may already have come across such a request as a result of the Increasing coverage of this topic in the media. It is no longer acceptable to tell the patient that this is still experimental treatment, as this constitutes misleading advice. Such a request demands an evaluation of the situation based on a sound understanding of what can be achieved with dental implants.

it is often the case that patients are not suitable for treatment with implants, or that a conventional alternative may be preferable. A decision based on a thorough knowledge of the patient's medical and dental history, along with a full radiographic evaluation, will determine suitability. These areas will be covered in this chapter.

Initial consultation

At the initial consultation it is Important to determine the patient's prime motivation for enquiring about implants1 . As a cardinal rule it should be understood that aesthetics alone are NOT a good reason for seeking implants. It is likely that a new conventional bridge or indeed a more aesthetically pleasing denture, so long as it is functionally sound, will solve this problem at a fraction of the cost.

Function is the key complaint that should arouse your attention, A failing conventional bridge, the en-duringly loose full denture, and the free end saddle (particularly unilateral) are classic scenarios which deserve consideration for rehabilitation with implants.

Psychologically based concerns also deserve attention, with caution. There are a number of interesting reasons that one can come across, for patients seeking implants. Such concerns often arise through sexual sell awareness and/or embarrassment.

An example of this might be young patients who have lost anterior teeth which have been replaced with a partial denture due to the unrestored nature of the abutment teeth {which

MEDICAL HISTORY

GP's Name:

1

Diabetes

11

Radiation

2

Hypertension

12

Steroids

3

Heart Disease

13

Allergies

4

Bleeding Diseases

14

Drug Sensitive

5

Lung Disease

15

Specify

6

GIT Disease

16

Epilepsy

7

Rheumatoid

17

Headaches

8

Osteoarthritis

18

Alcohol

9

Osteoporosis

19

Smoking

10

HIV/HBV Test

20

Other

21 Details of past history

22 Ongoing Medication

23 Patient's Signature .

24 Surgeon's Signature

Fig 1-1 An appropriate dental card medical history.

Tabfe 1-1 Contra Indications to Placement of Dental implants

Absolute contra indications

Uncontrolled diabetes Psychosis — unrealistic expectalions, dysmorphophobia Drug and alcohol abuse Kidney dialysis Pre-pubertal age

Possible contra indications (Require further investigation)

Systemic haematological disorders Irradiation of jaws Liver and kidney disorders Osleoporosis/low bone mineral content Local pathology their dentist would prefer not to prepare for fixed bridgework). This can lead to a loss of confidence due to the fact that their front teeth are "removable". Another example is the concerns of individuals who are unable to partake of intimate kissing etc.. due to the embarrassing looseness of their dentures. These very real concerns might be addressed successfully by dental implants, but it is often difficult to extract this kind of information from patients. Furthermore it is equally important that an understanding of the patient's expectations is clarified. A disproportionately high expectation represents one of the principal contra-indications and others have suggested that, should there be any doubt, a psychological assessment be sought.1-2

A full medical history is required, and the use of a standard dental card history is inadequate. It only takes a short time to construct a full medical history sheet like that shown in figure 1-1, and this should be signed and stored with the patient's details. A list of contra-indications to treatment are given in table 1 -1.

It should be understood that the placement of dental implants represents Invasive dento-alveolar surgery. As such patients with stabilised cardiac disease should be prepared in the same way as all such patients for minor oral surgery, that is with appropriate antibiotic prophylaxis and consideration regarding the use of adrenaline based local anaesthetics. Clearly there is no substitute for conferring with a patient's medical practitioner prior to surgery. Surprisingly old age is not a contraindication, subject to good systemic and mental health but pre-pubertal youth does present problems due to the fact that Implants are essentially ankylosed, and consequently they become submerged as skeletal alveolar growth progresses.

Osteoporosis is particularly relevant for the post menopausal woman, and it may be worthwhile seeking Bone Mineral Content evaluation as part of a routine Bone Metabolic Counsel ling procedure, especially if the patient is not on Hormone Replacement Therapy.3

The dental history will of course involve an oral examination, a radiographic examination, and a diagnostic evaluation using articulated study models.

The oral examination should take the form of a routine assessment of hard and soft tissues, of the oral and circum-oral structures. Do not assume that a clinically atrophic mandible infers that there is inadequate bone, this is rarely the case. Conversely a well formed maxilla may be mostly sinus cavitation. All clinical findings should therefore be considered in association with further investigations. A dental and periodontal evaluation will elicit information on the presence of caries, periodontal disease, and oral hygiene status. It is of paramount importance that a patient be treated with any conventional dentistry indicated, since a sound dental status must exist prior to implant placement.

Soft tissues are further assessed for health and quality in terms of being keratinised or non-keratinlsed. The presence of non-keratinised tissue around an emerging abutment is not considered ideal, and may indicate the need for an autogenous gingival graft to increase the peri-implant zone of keratinised tissue.4-7 An assessment of soft tissues should also determine their thickness. This can be done by measuring soft tissue thickness with a periodontal probe. It is then possible to map out the soft tissue thickness on a sectioned duplicate cast, thus highlighting residual ridge width (Fig 1-2). Alternatively bony ridge thickness can be measured directly using bone callipers.0 This is referred to as ridge mapping.

Master study casts should be mounted and articulated, since an assessment of occlusal vertical dimension is necessary to determine the space available for the prosthetic superstructure, Furthermore, instructions should be given to the technician for a diagnostic wax-up to be fabricated (Fig 1-3), based on the proposed treatment plan. A useful hint is to ask the technician to place brass retention pins into the cast, to indicate the ideal position of the implants in relation to the diagnostic wax-up (Fig 1-4). The information and subsequent use of the diagnostic wax-up, reproduced as a surgical template {Fig 1 -5) is discussed below. In order to assess a case correctly, it is essential to undertake a full radiographic evaluation. As a minimum requirement an orthopantomograph (OPT) and intra-oral radiographs (IOR) are advised, The use of a Lateral Cephlogram (LC) is helpful in the edentulous case to determine lingual inclination of the atrophic mandible (Fig 1 -6). When planning for implants it is important to extract as much useful information as possible from your radiographs in order to aid in the evaluation and pre-surgical preparation,

Fig 1 -2 A diagnostic study model is sectioned and trimmed according to ridge mapping measurements, demonstrating the true alveolar ridge width available for implant placement.

Fig 1-3 Articulated study models, provide useful information to aid treatment planning, A diagnostic wax-up further delineates the prosthetic, and hence surgical field, also providing vital information regarding occlusal form.

Fig 1 -4 The use of brass retention pins, located in the study model, help support each unit of the diagnostic wax-up. and provide valuable visual information on the ideal mesio-distal positioning of the implants.

Fig 1-5 The diagnostic wax-up is conveniently reproduced in clear acrylic to act as a surgical template. This will ensure accurate positioning of the implants during the surgical procedure.

Fig 1-6 For ibe edentulous patient a lateral cephalogram allows an assessment of the pattern of resorption, highlighting the degree of mandibular lingual inclination The use of ball bearings also allows an assessment of the relative position oftheincisaledge to the crest of the ridge

Fig 1-7 Foil spots, of a defined size, are punched out of the foil of a periapical film and stuck to the surface of each looth. on the patient's denture, thus relating their position !o the OPT, and providing information regarding variable distortion

!f measurements for bone height are to be deduced from such radiographs, it is necessary to always place a radiographic marker, such as a ball bearing, in the planned operative field; this will allow you to determine distortion. An average OPT machine will give a distortion factor of between 20-40% magnification, depending on the age of the machine. Dividing the measured bone height by this factor will give an accurate estimate of true bone height (TBH) available. In order to define the surgical field, it is useful to place a radiopaque stent in the patient's mouth. For the denture wearer, it is possible to place foil spots on each tooth of the denture

(Fig 1-7), so as to transfer tooth position to the radiograph (Fig 1-8), For partially dentate cases, the diagnostic wax-up is essential (Figs 1 - 9 & 1-10), and it is useful to have a suck down splint produced over a cast of such wax-ups which can then be placed in the mouth priortotaking the OPT (Fig 1-11). The use of Barium Sulphate powder (Fig 1-12), painted on the surface of the splint will demonstrate the position of the teeth satisfactorily. Highlighting in soft pencil, vital structures on the radiograph, such as inferior dental nerves, ridge crests, nasal floor, sinuses, and adjacent teeth will clearly demonstrate the confines of the surgical field. It is now

Kennedy Nasal Splint

Fig 1-8 The position ot each denture tooth is clearly transferred to the OPT as individual radiopaque spots. The position of each implant is drawn in pencil on the radiograph to coincide with these markers.

Fig 1-9 A Kennedy class I mandibular case is provisionally assessed with bilateral diagnostic wax-ups to restore the free end saddles. Diagnostic wax-ups should provide accurate information on occlusal table width, buccolingual form, and the mesiodistal position of each dental unit.

Fig 1-10 Study models are mounted on a semi-adjustable articulator. to allow assessment of occlusal function on both working and non-working sides.

Front Teeth Impant Without The Teeth

Fig 1-11 A suck down splint is manufactured over a solid cast duplicate of the diagnostic wax-ups. For the partially dentate patient this is a useful template since it benefits from tooth borne support, and is not displaced during surgery. For diagnostic radiographs, additional information can be sought by providing radiographic markers such as bal! bearings

Fig 1-12 The use of BariumSulphate painted on lo the surface of the template is another method that allows the transfer of tooth position to the diagnostic radiograph, thus confirming the mesio-distal position of each dental unit.

possible to superimpose the shape of the implants, using a pre-magnified radiographic template (Fig 1 -13), and to determine both position and length of implants from the information provided (Fig 1 -14). This is a useful exercise to do in front of the patient as it gives valuable insight into the treatment plan and often stimulates the right kind of questions. Tied in with the diagnostic wax-up. this leaves the patient in little doubt about treatment aims and aspirations. The splint can now be stored for use at a later date as a surgical template during implant insertion. This will ensure accurate positioning of implants in the mesio-distal, axial, and bucco-lingual relations, as indicated on the diagnostic radiograph and study models, When faced with potential complications, such as thin ridges or implants placed over the inferior dental nerves, it is often considered advisable to arrange for a Computed Tomography Scan (CT scans).9-13 The CT scan is able to provide information in three dimensions, with insignificant distortion (Fig t -15.1 -16) As such it is possible to determine ridge width and the amount of avail-

Dental Implant Radiographic Evaluation

Fig 1-13 Some implant companies provide clear radiographic fixture guides (Astra Tech AB, Molndal, Sweden) for differing degrees of distortion. These can be used to trace the position of an implant on to a radiograph itself or a tracing of the radiograph.

Astra Osseospeed Radiograph

Fig 1-14 The diagnostic OPT can be used to highlight the surgical field, the mesio-distal position of each implant to be placed, and their relation to any vital structures. It is of paramount importance that an assessment of distortion is made and that the relative fixture guide is chosen to relate the correct implant dimensions to the radiograph (see Fig l-ll).

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Fig 1-15 The use of CT scans may be essential when implants are to be placed close to vital structures, or where conventional radiographs fail to provide the desired information. Specific software (3D/Dental software. Columbia Scientific Incorporated. Columbia, MD) is available to allow high quality images in, iransverse section, panoramic views and 3 Dimensions.

Dental Implant Radiographic Evaluation

Fig 1-16 The use of CT scans may be essential when implants are to be placed close to vital structures, or where conventional radiographs fail to provide the desired information. Specific sofl ware (3D/Dental software, Columbia Scientific Incorporated, Columbia, MD) is available to allow high quality images in transverse section panoramic v/ews and 3 Dimensions

Fig 117 The use of CT scans may be essential when implants are to be placed close to vital structures, or where conventional radiographs fail to provide the desired Information. Specific software (3D/Dental software, Columbia Scientific incorporated, Columbia, MD) is available to allow high quality images in transverse section, panoramic views and 3 Dimensions.

able bone around vital structures with greater accuracy. It is also possible to build a 3-D picture of the underlying bony morphology,14 which can help in preplanning of surgery (Fig 1 -1 7). However CT scans are expensive, and can cause some concern to the patient, who may need to lay motionless for as much as twenty minutes while the scan is taken. It is also important to weigh up risk versus benefit in respect of radiation dosage which may vary from scanner to scanner, particularly in the light of other techniques described, which may allow the accurate placement of implants adjacent to vital structures using conventional dental radiographic techniques.15 When referring cases to a surgeon it is often useful to classify ridge morphology on the basis of degrees of atrophy. In implantology the most commonly quoted classification is that proposed by Lekholm and Zarb,16 which also gives an indication of bone quality (Fig 1-18, 1-19). Other more complex but accurate classifications are also occasionally utilised.17

Having completed your assessment and confirmed patient suitability it is advisable to send the patient away with an instruction booklet, which should describe in full detail all the

Lekholm And Zarb Bone Classification

Fig I -18 Classification for residua! ridge morphology as proposed by Lekholm & Zarb: (A) most of the alveolar ridge is present; (B) moderate residual ridge resorption has occurred; (C) advanced residual ridge resorption has occurred and only basal bone remains; (D) some resorption of the basal bone has started: {E) extreme resorption of the basal bone has taken place.

Lekholm And Zarb Classfication

Fig 1 -19 Classification of jawbone quality as proposed by Lekholm & Zarb; (1) almost the entire jaw is composed of homogenous compact bone; (2} a thick layer of compact bone surrounds a core of dense trabecular bone; (3) a thin layer of compact bone surrounds a core of dense trabecular bone of favourable strength; (4) a thin layer of cortical bone surrounds a core of low density trabecular bone possible ramifications of implant surgery, and how the treatment is likely to proceed.

An opportunity for patients to raise questions before final consultation is essential, allowing those last minute concerns to be discussed and hopefully quelled.

Final consultation should be arranged no more than one week prior to surgery. This ensures that ail final discussions are fresh in the mind of both you and your patient. At this consultation it is often desirable to have a third party present, preferably next-of-kin, so that there are no misunderstandings. Should it be decided to employ sedation or a general anaesthetic this is also a good opportunity to confirm arrangements for escort, and to discuss post operative care.

The use of consent forms is strongly indicated, and should cover consent for surgery and any anaesthetic procedure, as well as highlighting the patient's understanding of possible complications. The value of consent will vary depending on its structure and the medicolegal requirements of each individual country. The safest recommendation Is that you consult with your professional indemnity society, and seek their advice on this matter.

References

1 Laney, W.R. Selecting edentulous patients for tissue-integrated prostheses. Int J Oral Maxillofac Implants 1986; 1: 129-138.

2 Blomberg, S., Lindquist, L. W. Psychological reactions to edentulousness and treatment with jawbone-anchored bridges. Acta Psy-chiatr Scand 1983; 68: 251 - 262.

3 Roberts, W.E., Simmons, K.E., Garetto, L.P., DeCastro, PA. Bone physiology and metabolism in dental implantology: Risk factors for osteoporosis and other metabolic bone diseases. Implant Dent 1992; 1: 11-21.

4 Rapley, J.W., Mills, M.P., Wylam, J. Soft tissue management during implant maintenance. Int J Perlodont Rest Dent 1 992; 1 2: 373-381.

5 Hangorsky, U., Bissada, N. F. Clinical assessment of free gingival graft effectiveness on the maintenance of periodontal health. J Periodontol 1 980; 51: 274-278.

6 Wennstrom, J.L.. Lindhe, J. Plaque-Induced gingival inflammation in the absence of attached gingiva in dogs. J Clin Periodontol 1983;10:266-276.

7 van Sloenherghe, D. Periodontal aspects of osseointegrated oral implants ad modurn Brânemark. Dent Clin North Am 1988; 32: 355-370.

8 Wilson, D.J. Ridge mapping tor determination of alveolar ridge width. Int J Oral Maxillofac Implants 1989; 4: 41 -43.

9 Schwarz. M.S., Rothman, S.L.G.. Rhodes. M.L., Chafelz, N. Computed tomography: Part 1. Preoperative assessment of the mandible for endosseous implant surgery. J Oral Maxillofac Implants 1987; 2:137 -141.

10 Schwarz, M.S., Rothman, S L G, Rhodes, M.L., Chafetz, N, Computed tomography: Part 2. Preoperative assessment of the maxilla for endosseous implant surgery. Int J Oral Maxillofac Implants 1 987; 2:143-148.

11 Williams, M.Y.A.. Mealey, B.L., Halimon, W. \N. The role of computerized tomography in denial Implantology. Int J Oral Maxillofac Implants 1992; 7: 373-380.

12 McGivney, G.P., Haughton, V., Stradt, J. A., Eichhoiz, J.E., Lubar, D.M. A comparison of computer assisted tomography and datagathering modalities In prosthodontics. Int J Oral Maxillofac Implants 1986; 1: 55-56.

13 Quirynen, M„ Lamoral, Y.. Dekeyser, C., Peene, P., van Steenberghe, D„ Bonte, J., Baert, A.L. The CT Scan standard reconstruction technique tor reliable jaw bone volume determination. Int J Oral Maxillofac Implants 1990; 5: 384-389.

14 Kraut, R. A. Utilization of 3D/den1al software for precise implant site selection: Clinical reports. Implant Dent 1992: 1: 134-140.

15 Gelb, D.A. Gelb depth gauge: A diagnostic aid in implant placement Int J Peridont Rest Dent 1992; 12: 301-309.

16 Lekholm, U., Zarb, G.^. Patient selection and preparation. In: Tissue integrated prostheses. Osseointegratlon in clinical dentistry (eds Br&nemark, P.-t., Zarb, G., Albrektsson, T.), pp201 -209. Berlin: Quintessence, 1985.

17 Cawood, J.I., Howell, Ft. A, A classification of the edentulous jaws. Int J Oral Maxillofac Surg 1988; 17: 232-236.

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