The questionnaire revealed several creative steps, based on laboratory considerations, being taken to prevent veneer chipping and fractures, a frequent and problematic prosthetic complication (Q12) (Figure 7). Technicians were taking into account metal (including zirconia) coping designs (36.3%), covering only the distal-most part of the molar region with metal (24%), using veneering composite resin (15.7%), and using metal occlusal designs (15.1%).

The type of coping is important in preventing veneer fractures, and it is necessary to secure adequate veneering material thickness and to consider the dispersion of stress [48]. Particularly as zirconia becomes more common, there has been a move to improve coping designs using CAD/CAM and to exercise care concerning the prevention of veneering porcelain fracture [49,50]. Responses to this survey support the idea that this concept has been gaining popularity among technicians in recent years.

Conversely, it was not expected that 15.7% of respondents would indicate that they use composite resin to prevent veneering material fractures. Moreover, there is no evidence that veneering composites are more resistant to fracture than porcelain (as they are more prone to chipping) [45,46]. As noted above, veneering composites are often used in Japan, and one theory is that this trend is driven by a conceptual assumption that veneering composites are softer than porcelain and less likely to fracture from a materials science standpoint. It can be concluded that the ability to repair prostheses directly in the mouth is also a deciding factor.

More than half of all repair requests for IODs (i.e., complications) (Q13) (Figure 8) involve fracturing of the denture base or denture tooth detachment (53.8% of all repair requests). The questionnaire also revealed that reconstruction of occlusion because of wear or attrition of denture teeth (24.1%) is a frequent issue leading to laboratory orders. While the literature includes reports of frequent IOD-related prosthetic complications such as attachment-related compromised retention, detachment or fracturing of denture teeth, relining, and attachment damage [25,28,29], this survey showed a somewhat different trend. It can be inferred that these results differ from actual complication trends because they constitute responses to cases sent to labs as repair requests, and because the survey targeted dental technicians. The causes of this phenomenon can be found in responses to other questions as described above. In short, the questionnaire suggested the possibility that inadequate awareness of prosthetics is making IOD complications in Japan more complex, with issues including the comparatively frequent use of resin bases, problems with implant location and orientation, and inadequate consideration of occlusion by dentists.