Every patient is unique, including the patient’s oral envi- ronment and general physiology. This provides a unique set of circumstances and challenges for implementing successful materials choices in a treatment plan. In the next section, we present a rationale for selecting materi- als, based on the treatment design approach proposed by Spear and Kokich. They advocate a treatment plan- ning process that starts with an assessment of overall esthetics and proceeds to consider function, structure, and biology in that order. Decisions made at every stage directly affect the following stages. Treatment begins with the acute problems then progresses logically to facilitate a stepwise sequence that can be clearly defined and communicated among the clinicians involved in delivering care to the patient. Table 3.2 presents a TABLE 3.1 Assessing the Quality of Evidence
Study Quality Diagnosis
Treatment/Prevention/
Screening Prognosis
Level 1: good-quality, patient-oriented evidence
Validated clinical decision rule SR/meta-analysis of high- quality studies
High-quality diagnostic cohort studya
SR/meta-analysis or RCTs with consistent findings High-quality individual RCTb
All-or-none studyc
SR/meta-analysis of good-quality cohort studies Prospective cohort study with good follow-up
Level 2: limited-quality patient-oriented evidence
Unvalidated clinical decision rule
SR/meta-analysis of lower quality studies or studies with inconsistent findings
Lower quality diagnostic cohort study or diagnostic case-control study
SR/meta-analysis of lower quality clinical trials or of studies with inconsistent findings
Lower quality clinical trial Cohort study
Case-control study
SR/meta-analysis of lower quality cohort studies or with inconsistent results Retrospective cohort study or prospective cohort study with poor follow-up Case-control study Case series
Level 3: other evidence Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease- oriented evidence (intermediate or physiologic outcomes only), or case series for studies of diagnosis, treatment, prevention, or screening
RCT, Randomized controlled trial; SR, systematic review.
aHigh-quality diagnostic cohort study: cohort design, adequate size, adequate spectrum of patients, blinding, and a consistent, well-defined reference standard.
bHigh-quality RCT: allocation concealed, blinding if possible, intention-to-treat analysis, adequate statistical power, adequate follow-up (greater than 80%).
cIn an all-or-none study, the treatment causes a dramatic change in outcomes, such as antibiotics for meningitis or surgery for appendicitis, which precludes study in a controlled trial.
From Newman MG, Weyant R, Hujoel P. JEBDP improves grading system and adopts strength of recommendation taxonomy grading (SORT) for guidelines and systematic reviews. J Evid Based Dent Pract. 2007;7:147–150.
TABLE 3.2 Decision Matrix for selecting Dental Materialsa Assessment and Factors Query
Relevant Dental Materials and Properties (Chapter No.) ESTHETICS: MAXILLARY
Central incisors relative to upper lip • Is the incisal edge display of the maxillary
centrals sufficient? Surface characteristics (4) Light, reflection, color (4) Resin composites (9) Ceramics (11)
Adhesives and cements (9, 13) Midline and inclination of incisors • Does the maxillary midline need
correction?
• Does the inclination of the maxillary incisors need correction?
Surface characteristics (4) Light, reflection, color (4) Resin composites (9) Ceramics (11)
Adhesives and cements (9, 13) Posterior occlusal plane • Does the maxillary posterior occlusal
plane need correction?
• Is sufficient tooth structure present?
• What are the surface characteristics of the opposing dentition?
Forces and wear (4) Core buildup (9) Provisional materials (9) Resin composites (9)
Adhesives and cements (9, 13) Metals and alloys (10) Ceramics (11) Gingival levels • Do gingival margins need correction? Resin composites (9)
Glass ionomers (9) Ceramics (11)
Adhesives and cements (9, 13) ESTHETICS: MANDIBULAR
Same factors as for maxillary: Midline, inclination, posterior occlusal plane, and gingival levels ESTHETICS AND FUNCTION
Missing teeth • Are missing teeth in need of replacement?
• Is a fixed or removable prosthesis preferred?
• Should adjacent teeth be involved in the replacement?
• What are the surface characteristics of the opposing dentition?
Forces, stress, and wear (4) Provisional materials (9) Adhesives and cements (9, 13) Denture materials (9) Metals and alloys (10) Ceramics (11)
Impression materials (12) Casting materials (12) Implants (15) FUNCTION
Occlusion • Does the occlusal relationship need correction?
• What are the surface characteristics of the opposing dentition?
Forces, stress, and wear (4) Resin composites (9) Metals and alloys (10) Ceramics (11)
Impression materials (12) Casting materials (12) Adhesives and cements (9, 13) Implants (15)
Articulator BIOLOGIC
Oral environment: enamel, dentin,
pulp, and periodontal ligament • Is acute disease present?
• Are conditions in the oral environment favorable (e.g., saliva pH, salivary flow, oral hygiene, diet, supporting bone structure, pulp, occlusal habits)?
Oral environment (2) Forces, stress, and wear (4) Biocompatibility (6) Intermediary materials (8) Tissue engineering (16)
aThis table augments the sequence and logic presented in the section “Planning for Dental Treatment” with factors, queries, and references to chapters in this textbook.
summary of the approach with queries for each stage, and relevant materials and properties to be considered.
An esthetics appraisal analyzes the position of the midline and the length of the maxillary and mandibular incisors, which influence the position of the posterior occlusal plane, which in turn influ- ences function. The esthetics appraisal starts with an assessment of the position of the maxillary cen- tral incisors relative to the upper lip. If the incisal edge display is insufficient, lengthening of the inci- sal edges can be done surgically or by orthodontic treatment, or by restorative methods using dental materials. Most cultures would prefer materials that mimic natural dentition in color, texture, and reflectance. Ceramics and resin composites exhibit these properties. A number of options exist for these two classes of materials. Ceramics are discussed in Chapter 11. Resin composites are discussed in Chapter 9.
The next consideration in the esthetics appraisal is position of the midline and inclination of the max- illary incisors. The labial surface characteristics and inclination influence the light reflectance of the inci- sors. Maximum light reflectance is achieved when the labial surface is perpendicular to the occlusal plane. Corrections to the midline and to the labial inclination can be done by orthodontics or restor- ative dentistry. Surface characteristics, light, reflec- tion, and color are discussed in Chapter 4.
The next step assesses the maxillary posterior occlusal plane relative to an ideal position of the max- illary incisal edge. Corrections to the posterior occlu- sal plane can be achieved by surgery or restorative procedures. Materials for adjusting the posterior occlusion can be the same as for anterior restorations;
however, the function of posterior teeth and occlusal relationships should be considered in the selection of materials. The wear of materials in contact as well as the resistance to occlusal forces are important consid- erations. Forces and wear are discussed in Chapter 4.
Metals and alloys are discussed in Chapter 10.
Gingival levels of the anterior teeth play a large role in esthetics. Similarly, the appearance of the gin- gival margin of anterior restorations will influence their overall esthetics. Ceramics can be used to fab- ricate restorations with an esthetic gingival margin.
The combination of ceramics and metal at the gin- gival margin, as in ceramic-metal restorations, can make the esthetic gingival margin more difficult to achieve. Ceramic-metal materials are discussed in Chapters 10 and 11.
After completing the assessment and plan for the maxillary anterior and posterior teeth, the mandibu- lar anterior and posterior teeth can be assessed and designed. Missing teeth can be restored by a fixed or removable dental prosthesis, or a dental implant.
Materials for a fixed dental prosthesis include metals
and ceramics. Removable prostheses or removable partial dentures can include these materials and polymers. Polymers for removable dentures are dis- cussed in Chapter 9. Single or multiple missing teeth can be restored by dental implants that mimic the shape and position of the tooth root onto which res- torations such as a crown or fixed dental prosthesis are secured. Implants are discussed in Chapter 15.
Adhesives and cements for securing prostheses to tooth structure are discussed in Chapters 9 and 13.
The esthetic plan is integrated with the functional occlusion by replicating the patient’s dentition and occlusal relationships, then positioning these casts on an articulator. Materials for replicating dentition and oral tissues are called impression materials.
These materials form a negative replica or mold of the tissues into which a rigid-setting material, often gypsum, is poured to make a positive replica of the oral tissues. Impression and casting materials are dis- cussed in Chapter 12.
The biological assessment wraps up the diagnos- tics and planning. In this phase, the health of the sup- porting periodontal tissues including the periodontal ligament is evaluated, along with the conditions of the oral environment, and condition of the enamel, dentin, and pulp. If acute disease such as dental car- ies is present, intermediary materials can be used to stabilize the condition before definitive materi- als are used. Intermediary materials are discussed in Chapter 8. The oral environment is discussed in Chapter 2.
As mentioned at the start of this chapter, patient behaviors and preferences are also an important con- sideration. The patient may need instruction and coaching on prevention and maintenance of den- tal treatment. Preventive materials are discussed in Chapter 8. The performance of prior dental treatment is evaluated. Reactions to materials used in prior res- torations should be considered. Biocompatibility and tissue reactions are discussed in Chapter 6.
Refer to Table 3.2 for questions to consider in each stage of treatment design along with relevant dental materials and properties. Chapter numbers are listed for the materials and properties for further informa- tion and review.
Bibliography
American Dental Association. ADA Center for Evidence-Based Dentistry. <http://ebd.ada.org/>; Accessed 03.10.17.
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Forrest JL. Introduction to the basics of evidence-based dentistry: concepts and skills. J Evid Based Dent Pract.
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Forrest JL, Miller SA. Translating evidence-based decision making into practice: EBDM concepts and finding the evidence. J Evid Based Dent Pract. 2009;9(2):59.
Miller SA, Forrest JL. Translating evidence-based decision making into practice: appraising and applying the evi- dence. J Evid Based Dent Pract. 2009;9(4):164.
Newman MG, Weyant R, Hujoel P. JEBDP improves grad- ing system and adopts strength of recommendation tax- onomy grading (SORT) for guidelines and systematic reviews. J Evid Based Dent Pract. 2007;7:147–150.
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29 Restorative dental materials are subjected to a very hostile environment, in which pH, salivary flow, and mechanical loading fluctuate constantly and often rapidly. These challenges have required substantial research and development to provide products for the clinician. Much of this is possible through the application of fundamental concepts of materials sci- ence. The understanding of properties of polymers, ceramics, and metals is crucial to their selection and design of dental restorations.
No single property defines the quality of a mate- rial. Several properties, determined from standard- ized laboratory and clinical tests, are often used to describe quality. Clinical tests are expensive and inherently difficult to carry out, so laboratory tests are usually performed before clinical tests to provide standardized measures for comparing materials and guiding the interpretation of clinical trials.
Standardization of laboratory tests is essential, however, to control quality and permit comparison of results between investigators. When possible, test specimens should mimic the size and shape of the structure in the clinical setting, using the same mix- ing and manipulating procedures as those used in routine clinical conditions.
Although standardized laboratory tests are useful to compare values of properties of differ- ent restorative materials (e.g., different brands), they are also essential to know the characteris- tics of the supporting hard and soft tissues. Many restorations fail clinically because of fracture or deformation. This is a material property issue.
Some well-constructed restorations become unser- viceable because the dentin or enamel fails. This is an interface or substrate failure. Consequently, when designing restorations and interpreting test results, it is important to remember that the suc- cess of a restoration depends not only on the phys- ical qualities of the restorative material, but also on the biophysical or physiological qualities of the supporting tissues.
The physical properties described in this chapter include mechanical properties, thermal properties, electrical and electromechanical properties, color, and optical properties.