In this article, we attempt to answer the following question: Has the teaching of posterior composite restorations in U.S. dental schools developed in response to the increasing use of resin-based composites in posterior teeth in clinical practice?

	SUBJECTS AND METHODS

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In 2005, we distributed a questionnaire via e-mail to the person in each of the 52 dental schools in the United States with responsibility for the operative dentistry curriculum, including the teaching of composite placement in posterior teeth. (We identified this person either by consulting the academic staff members listing on the dental school’s Web site or by contacting the dean of the dental school.) The questionnaire included 19 closed-end statements (respondents were given a number of possible responses to a statement and asked to identify the most appropriate one) and 10 open-ended statements (respondents were given space in which to write a response to a question). We entered this information onto an electronic spreadsheet and obtained descriptive results. To further describe the responses, we divided the schools according to geographical location: Northeast, Southeast, Northwest and Southwest United States. The study conformed to relevant ethical expectations and requirements.

	RESULTS

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Forty-seven schools returned completed questionnaires (90 percent response rate). One school was unable to reply, given a major restructuring of its curriculum. Four schools did not respond to any of the e-mailed requests or to subsequent telephone calls made to their relevant departments. Either the head of the department or a senior member of the faculty with specific responsibility for teaching placement of posterior composite restorations completed the questionnaires. For ease of presentation, we grouped the information collected into the following categories.

Restoration design. All 47 schools reported that they teach students how to place resin-based composite restorations in occlusal cavities of posterior teeth, as well as two-surface occlusoproximal composite restorations in premolars. Ninety-eight percent of schools teach the placement of two-surface occlusoproximal composite restorations in permanent molars. Eighty-nine percent of schools teach students how to place three-surface occlusoproximal composite restorations in premolars, while 68 percent of schools teach the use of three-surface occlusoproximal composite restorations in molars.

One school in the Southeast reported that it does not teach the placement of two-surface occlusoproximal composite restorations in molars and does not plan to do so during the next five years. Five schools (three Northeast, one Southwest, one Southeast) do not teach placement of three-surface occlusoproximal composites in premolars; two of these (both Northeast) said they will begin doing so within the next five years. Twelve schools reported that they do not teach students how to place three-surface occlusoproximal composites in molars (eight Northeast, two Southwest, one Southeast, one Northwest); three of these schools (all Northeast) will introduce this to their curriculum during the next five years.

Eighty percent of the schools teach students how to place amalgam before teaching them how to place posterior composite restorations. The remaining 20 percent of schools teach the placement of posterior composite restorations first. More schools in the Northeast (95 percent) than in any other geographical region teach the placement of amalgam first. The greatest percentage of schools (40 percent) that teach the placement of resin-based composites first is in the Southwest. During the next five years, 49 percent of schools anticipate that they will teach the placement of composites before teaching placement of amalgam. However, 51 percent of schools responded that they will continue to teach students how to place amalgam restorations first.

Respondents anticipate that preclinical teaching of posterior composite restoration placement will increase, on average, to 150 percent of its current level during the next five years. Conversely, respondents anticipate that preclinical teaching of amalgam placement will decrease to 75 percent of its current level within five years. Our survey data show that 60 percent of posterior restorations placed by dental students are amalgam, while 30 percent are resin-based composites. Within the next five years, respondents anticipate that, on average, 42 percent of posterior restorations placed by dental students will be amalgam (minimum = 5 percent, maximum = 85 percent) and 50 percent will be composite (minimum = 8 percent, maximum = 95 percent). The remainder includes indirect intracoronal restorations, such as inlays.

Cavity design and contraindications to placement. Eighty-one percent of the schools responding to our survey teach the use of rounded internal line angles, 55 percent of schools teach the use of proximal slots (no occlusal component), 49 percent of schools teach the use of beveled proximal box margins and 28 percent of schools teach the use of beveled occlusal margins for posterior composite restorations. The table summarizes the contraindications to placing posterior composite restorations, as taught by the schools.

Although 98 percent of schools reported that they teach a total-etch approach for shallow cavities (outer one-third of dentin) and 70 percent of schools teach it for moderate cavities (middle one-third of dentin), less than 10 percent of schools reported that they teach this technique for deep cavities (inner one-third of dentin). Thirty percent of schools responded that they teach the use of a glass-ionomer cement base when restoring teeth with moderate cavities. To treat teeth with deep cavities, 91 percent of schools teach the use of a glass-ionomer cement base, with 67 percent of these schools also using a hard-setting calcium hydroxide liner.

With regard to the restoration of teeth with occlusoproximal cavities, 2 percent of the schools responded that they teach the use of transparent matrix bands and light-transmitting wedges solely. The remaining 98 percent teach the use of a circumferential or sectional metal band in combination with a wooden wedge. Fifteen percent of these schools also teach the use of transparent matrix bands and light-transmitting wedges.

Clinical trends in the placement of posterior composite restorations and the quality of composite materials and bonding systems have advanced significantly in recent years.

Sixty-two percent of schools reported that they instruct students in the use of traditional quartz-halogen lights solely when placing posterior resin-based composite restorations. Seventeen percent of schools teach the use of light-emitting diode (LED) lights only. Twenty-one percent of schools instruct students in the use of both types of curing lights. Responses were similar across all geographical areas, except in the Northwest, where 100 percent of schools teach the use of quartz-halogen lights only. No school responded that it teaches students how to use plasma-arc lights.

Composite and bonding system brands. Ninety-one percent of schools instruct students in the use of hybrid or microhybrid composites to restore teeth with occlusal or occlusoproximal cavities. In addition, 11 percent of schools teach the use of microfilled composites, and 2 percent teach the use of macrofilled and flowable composites. The most commonly used brands of resin-based composite were the following: Point 4 (SDS Kerr, Orange, Calif.) (23 percent of schools), Esthet-X (Dentsply Caulk, York, Pa.) (19 percent of schools), Herculite XRV (SDS Kerr) (15 percent of schools) and Z250 (3M ESPE, St. Paul, Minn.) (15 percent of schools). The most commonly used bonding systems in the dental schools were as follows: Optibond Solo (SDS Kerr) (40 percent of schools), Prime & Bond (Dentsply Caulk) (30 percent of schools) and Scotchbond Multi-Purpose (3M ESPE) (21 percent of schools).

Finishing techniques. All schools responded that they teach immediate finishing of posterior composite restorations. Sixty percent of the schools teach this procedure without the use of water cooling. Popular finishing instruments included finishing burs/points (85 percent of schools), finishing discs (85 percent of schools), finishing strips (77 percent of schools) and finishing diamonds (72 percent of schools).

Fees. All schools charge fees for restorations placed by students. The average fee was $43 for an occlusal amalgam restoration, $53 for an occlusal composite restoration, $57 for an occlusoproximal amalgam restoration and $68 for an occlusoproximal composite restoration.

Indirect composite restorations. Eighty-seven percent of the schools responding to our survey reported that they teach students how to place indirect composite restorations. Of these, 54 percent provide didactic instruction only, while 46 percent also include clinical instruction.

	DISCUSSION

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Previous studies that have examined dental schools’ instruction in the use of posterior composite restorations in the United States have shown that, although increasing, such teaching has remained limited in nature. Students graduating in the 1980s or early 1990s received little or no education or clinical training in the placement of posterior composite restorations.^18,19 A survey of U.S. dental schools in 1997 confirmed that there had been some improvement, but most graduates still had "minimal clinical experience with Class I and Class II composite restorations."¹³

Clinical trends in the placement of posterior composite restorations in dental practice and the quality of composite materials and bonding systems have advanced significantly in recent years. Resin-based composite now is an established restorative material for posterior teeth; the evidence base supports this and patients increasingly request its use.¹ Our survey findings demonstrate that further increases have taken place since the last survey was conducted in 1997 with regard to instructing U.S. dental students and providing them with the opportunity to gain clinical experience in the use of posterior composite restorations.

To advance the delivery of oral health care to patients, it is important that all recent dental school graduates are skilled in a range of techniques, including the restoration of posterior teeth with materials such as resin-based composite. It is important to consider that students graduating today may continue to practice dentistry into the 2040s, and they may experience difficulty achieving competence in the placement of posterior composite restorations if the procedure is not addressed adequately in dental school.^12,13

This survey found that 33 percent of direct restorations placed by dental students in posterior teeth are made of resin-based composite, and the schools anticipate that within five years, this proportion will increase to 50 percent. These proportions are similar to those found in a recent study that we conducted in dental schools in Ireland and the United Kingdom.¹⁷

Dental schools in the United States estimated that preclinical teaching of posterior composite restoration placement during the next five years will increase on average (with regard to number of hours) to 170 percent of its current level. Some schools (mainly in the Northeast) mentioned that they would like to spend more time teaching the use of posterior composite restorations than they currently do. However, because state and regional clinical licensing examinations still focus predominantly on the use of amalgam restorations in posterior teeth, some schools may be limiting the time spent teaching the use of composites in posterior teeth. They may limit their development of dental school curricula with regard to teaching new techniques, such as the placement of composite restorations in posterior teeth.

Another problem revealed in our survey was the variation between dental schools with regard to teaching principles and techniques of posterior composite restoration placement. Such inconsistencies do little to ease new graduates’ confusion when working with new products or dealing with representatives in the dental marketplace selling new materials and devices.^13,20 Specific observations from the survey follow.

Beveling. Twenty-eight percent of the schools responded that they teach students to perform surface beveling of occlusal cavosurface margins before placing posterior composite restorations. Such beveling generally is considered ill-advised,²¹ because thin occlusal extensions of composite may fracture under occlusal loading. Beveling also leads to significant lengthening of the cavosurface margin and an increased risk of extensive enlargement of preparations during subsequent repair or replacement of the restoration.²²

Diverse contraindications. We found it somewhat disappointing to find schools reporting such a diverse range of contraindications to placement of posterior composite restorations (Table). More than 50 percent of the schools agreed on less than 25 percent of the contraindications listed on the questionnaire. The most common contraindication taught was a "history of allergy to composites," which also was the most common contraindication taught in dental schools in Ireland and the United Kingdom.¹⁷ However, because little evidence exists in the literature documenting true patient allergies to composite,¹³ this response from schools may reflect medicolegal concerns more than instruction based on documented evidence.

Our survey results show clear agreement with regard to the use of rubber dams when placing posterior composite restorations. Although the advantages of using a rubber dam are well-documented,^2,23 a recent study found no difference in the survival of posterior composite restorations placed with the use of a rubber dam or cotton wool rolls.²⁴

Operatively exposed dentin. We found a wide diversity of opinion with regard to the treatment of operatively exposed tooth tissue in the middle layer of dentin. While 30 percent of schools stated that they teach students how to use a glass-ionomer cement base to restore such teeth, the remaining 70 percent reported that they teach students this is not necessary. These percentages were similar across all geographical areas. We also noted this diversity in our survey of dental schools in Ireland and the United Kingdom.¹⁷ These findings are most likely the result of a lack of consensus among teachers.

As stated above, 98 percent of U.S. dental schools teach the use of a circumferential or sectional metal matrix band and wooden wedge for placement of occlusoproximal composite restorations, while 17 percent of schools teach the use of a transparent matrix band and light-transmitting wedge for this purpose. An in vitro study published in 2003 demonstrated that the use of transparent matrixes and light-transmitting wedges may not be suitable for the placement of occlusoproximal composite restorations, because this approach can result in the formation of significant proximal overhangs.²⁵

Our survey results show a wide variety in the brands of composites and bonding systems used in the dental schools. This reflects either variation in thinking among schools as to the material best suited for the restoration of posterior teeth or a belief among teachers that the available products are not significantly different from one another. The selection of materials, such as composites and adhesive systems, should be based on the best evidence, rather than factors such as personal preferences or convenience (let alone selection that is driven inappropriately by cost or other incentives). Familiarity with more than one brand of composite material encourages students to compare materials, broadens their experience base and enables them to leave dental school without being wedded to specific materials and systems.

The most commonly used curing light was the traditional quartz-halogen light (62 percent of schools). Seventeen percent of schools teach the use of LED lights solely, and 21 percent teach students how to use both types of curing light. No school stated that it teaches the use of plasma-arc curing lamps. These findings are in keeping with available best evidence, which suggests that the long-term degree of polymerization achieved with LED lights is comparable to that achieved with quartz-halogen lights.²⁶

Clearly, the majority of students in U.S. dental schools are gaining experience in the placement of resin-based composites in posterior teeth. However, our survey results provide continuing evidence of much teaching diversity among schools and geographical areas. For example, dental schools in the Northeast tend not to teach the use of composite materials as much as do dental schools in other regions (in particular, the Southwest). We also found considerable diversity with regard to the teaching of contraindications to the placement of posterior composite restorations, design of cavity preparations, use of liners and bases, and the total-etch technique.

In an area of dentistry such as posterior composites, in which new materials and techniques are being developed continuously, it is important that dental students—the future dental work-force—have a clear understanding of the basic principles of clinical application of this knowledge. Teachers in the area of operative and restorative dentistry and those involved in licensing examinations and the accreditation of dental schools need to be proactive in developing effective teaching programs and examinations to ensure that graduating students are prepared to make the transition to clinical practice and lifelong learning. The extent to which this is happening in the United States in the area of posterior composite restorations is encouraging, as reflected by the increase in teaching since 1997.

	CONCLUSION

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Since the surveys of the 1980s and 1990s, there has been an increase in U.S. dental schools’ commitment to teaching students how to place resin-based composite restorations in posterior teeth, as demonstrated by the results of our survey. However, we found teaching diversity with respect to some principles of posterior composite restorations, such as contraindications to their use, design of cavity preparations and the use of liners and bases. Those who develop dental school curricula and licensing examinations should look to the future to ensure that students are well-prepared to adapt to modern clinical practice as it applies to the use of composite materials in posterior teeth.