Some changes were noted in the cement selection between 2008 (Fig. 4.2) and 2013 (Fig. 4.3). Although most institutions taught the use of definitive cement for inserting the final implant prosthesis, there are no standards for cement selection for implant restorations, even within the same institution.

A resin-modified glass ionomer cement was found to be the most commonly used among both restorative departments (57 %) and advanced prosthodontic programs (59 %). Advanced prosthodontic programs included glass ionomer (19 %), resin cement (52 %), zinc phosphate (33 %), and polycarboxylate (22 %) cements. The restorative departments taught the use of the following definitive cements: glass ionomer (19 %), resin (33 %), zinc phosphate (19 %), and polycarboxylate cement (17 %).

Provisional cements, ZOE based, were widely used by predoctoral (40 %) and postgraduate (33 %) programs. Some institutions explained that they used a provisional cement to maintain retrievability or to ensure that the restoration was satisfactory prior to using a more retentive cement. The survey also asked the respondents what cements were used for conventional fixed restorations. Eighty-seven percent of the restorative departments taught the use of resin-modified glass ionomer, followed by composite resin, glass ionomer, and zinc phosphate. Acrylic urethane cements were also taught by 14 % of the predoctoral programs. Seventy percent of advanced prosthodontic directors taught the use of resin-modified glass ionomer and resin, glass ionomer, zinc phosphate, and polycarboxylate cements. Both predoctoral and postgraduate programs showed an increase in the use of resin cements and slight decrease of use of resin-modified glass ionomer cements between the 2008 and 2013 surveys, for both implant and conventional fixed restorations. With the increased availability of various all-ceramic restorations, this may have led to the increased use of resin cements for conventional fixed restorations and correspondingly to implant restorations. In general, there seems to be a similarity with cements used for implant restorations, which indicates that the same cements were probably selected from convenience, familiarity, and cost. Some of the literature has shown that the retentiveness of a particular cement for natural dentition may not correlate with implant components. Therefore, until more data is available, the clinician may or may not have the expected retention from the same cement for implant restorations.

The last question on the survey asked if there were any changes in cement for specific clinical situations. Of the 20 predoctoral and postgraduate programs that completed this section, the only trend seen was that a resin cement was used for either a zirconium- or aluminum-based abutment. A few responded that they changed cements depending on the type of ceramic used for the restoration. With regard to abutment and/or restorative material and design, the responses were few and, again, ranged from provisional to definitive cements. Since most of the schools did not respond to this question and there was great variability in cement types, it was assumed that, in general, the same cement is used for most all clinical situations.

Implants from various implant manufacturers are used at US dental institutions (Fig. 4.4). The 2013 survey showed the implant manufacturers most used, in order, were as follows: Nobel Biocare, Straumann, Biomet 3i, Astra Tech, and Zimmer. Other implant manufacturers were generally used by less than 37 % of dental schools; however, from 2008 to 2013, this group had increased from 21 %.

Although some schools used up to nine different implant manufacturer systems, most dental schools used only between one to four varieties. Differences also existed among departments in the same school as to the preference of implants used.

Schools were asked for their preference to abutment selection. Restorative chairpersons and prosthodontic residency directors responded that they mostly used either prefabricated abutments or the computer-aided, custom-milled abutments. Since the recent expense in gold and the introduction of computer-milled, custom abutments, the survey indicates that traditional custom cast, UCLA-type abutments, are used infrequently.

The survey also included the different surface preparations to either the implant abutment or the restoration prior to final cementation. Most institutions kept the preparation simple with either no modification or only one modification prior to inserting the definitive implant prosthesis. The most common procedure for both predoctoral and postgraduate programs was application of airborne-particle abrasion aluminum oxide to the internal surface of the implant restoration prior to cementation (Fig. 4.5).

The department chairpersons also indicated that students applied a ceramic primer to the intaglio of the restoration (35 %). Thirty-three percent indicated that grooves were added to the implant abutment to increase the resistance to retention and total convergence angle for the definitive implant cement-retained restorations. Other procedures taught by less than 14 % of predoctoral programs were polishing or abrading the implant abutment with a rotary instrument and the application of a metal primer, tin-plating, or placing a vent hole. Fifty-two percent of the prosthodontic residency directors applied a ceramic primer to ceramic restorations (Table 4.2). In a 2008 survey, only 3 % had reported placing a primer to ceramic restorations. This may indicate an increased use and confidence in cementing all-ceramic restorations on zirconium abutments. Nineteen percent of prosthodontic residency directors reported the placement of grooves on the implant abutments, as well as airborne-particle abrasion of the implant abutment. They also indicated that they polished the abutment, abraded the abutments with a rotary instrument, or used tin-plating to prepare the abutment or restoration prior to cementation. None of the postgraduate programs placed vent holes to aid in cementation. Some schools commented that they prepared the abutment and restoration the same way as cementing to natural dentition.

This was taught to predoctoral students in about 55 % of the dental schools and 70 % of the postdoctoral prosthodontic programs. For both pre- and postdoctoral programs, the preferred design for immediate provisionalization was screw-retained restorations. For the few that cemented their provisional restorations, many schools noted that a temporary abutment was placed and the restoration was temporarily cemented.

Both predoctoral and postdoctoral programs used various types and number of materials to fill the screw access hole. However, most taught their students and residents to fill the screw access completely to the top of the abutment. In 2008, 71 and 86 % of restorative and prosthodontic programs indicated that they teach their students/residents to fill the screw access opening completely. In 2013, the numbers declined slightly to 69 and 67 %, respectively. The survey did not ask for a specific reason; however, more schools may be concerned about controlling the flow of material during cementation. Several different materials and combinations of materials were used to fill the abutment screw access hole. Most schools seemed to use two to three materials, with a range of one to five for predoctoral and one to eight different materials for prosthodontic directors. The major difference between the surveys conducted in 2008 and 2013 was the increased use in PTFE tape as a material to fill the screw access. Table 4.3 shows the most frequently used combination of materials in 2008—note that PTFE (Polytetrafluoroethylene tape or plumbers tape) did not appear on this list. Both restorative and departmental chairpersons and prosthodontic residency directors most frequently filled the screw access hole with a cotton pellet followed by composite, or PTFE tape followed by composite.