Computer-aided design expertise affects digital wax patterns of CAD/CAM laminate veneers more than single crowns

AIM

There is controversy in the literature regarding clinical outcomes of CAD/CAM laminate veneers. The aim of the present study was to assess the impact of different levels of CAD expertise and different software programs on the reliability and reproducibility of digital wax patterns of laminate veneers and single crowns.

MATERIALS AND METHODS

The present preliminary in vitro study was performed on 10 prepared maxillary central incisors available in dental study models. Of the total, five central incisors were prepared with shoulder finish lines for single crowns, whereas the other five underwent incisal shoulder preparation for laminate veneers. The models were scanned using an intraoral scanner. Four dentists (group DENT) and four CAD dental technicians (group CAD) with expertise in different software programs performed digital diagnostic waxing on all prepared teeth. The resulting digital wax patterns (n = 80) were exported as standard tessellation language (STL) files and superimposed on gold standard digital wax patterns (obtained from the original shape of the teeth before preparations). 3D mesh deviations at the cervical margins as well as distal, mesial, and incisal/palatal surfaces between each STL and the gold standard digital wax patterns were calculated in millimeters using a CAD software program. The mean time required by each operator to perform digital waxing was also recorded. Paired comparisons between groups DENT and CAD as well as between nondental and dental software programs were performed for the crowns and laminate veneers using the Wilcoxon signed-rank and paired t tests (α = 0.05).

RESULTS

For group DENT, median deviations for single crowns were 0.15 mm (range: 0.08 to 1.05 mm) and for laminate veneers they were 0.15 mm (range: 0.08 to 0.76 mm). For group CAD, median deviations for single crowns were 0.16 mm (range: 0.09 to 0.73 mm) and for laminate veneers they were 0.10 mm (range: 0.06 to 0.53 mm). The Wilcoxon signed-rank test revealed a statistically significant difference between groups DENT and CAD (P = 0.041) and between the software programs (P = 0.029) for laminate veneers, but not for single crowns (P > 0.05). Furthermore, mean times required for group CAD and for dental software programs were significantly shorter than those for group DENT (P = 0.001) and for nondental software programs (P = 0.001), respectively.

CONCLUSION

Within the limitations of the present study, the findings suggest that CAD expertise and the software program significantly affect digital wax patterns for laminate veneers, but not for single crowns. (Int J Comput Dent 2022;25(4):361-0; doi: 10.3290/j.ijcd.b3555819).

Occlusal onlays as a modern treatment concept for the reconstruction of severely worn occlusal surfaces

According to the Fifth German Oral Health Study, the caries experience in the German population is declining sharply. The number of teeth still present at an advanced age has also increased significantly in recent decades. This shows a clear trend towards long-term tooth preservation - possibly with fixed dental prostheses - which is further supported by the possibility to place implants to increase the number of abutments. The pronounced decline in caries experience has given Germany a leading international position in terms of dental health. But there is increasing evidence of risks associated with dental hard-tissue damage because of erosion/biocorrosion, attrition, and abrasion. The defect morphology of these wear-related lesions is different from that of caries lesions; occlusal surfaces are more often affected in the posterior region. Against this background, restorative treatment concepts have become significantly more differentiated in recent decades. Predominantly subtractive concepts to provide mechanical retention for the restoration using traditional cements are now replaced by less invasive, primarily defect-oriented procedures wherever feasible. In the case of pronounced dental hard-tissue loss, additive approaches also allow restorations that restore function. In addition, there are modifications of traditional procedures, such as defining the treatment goal in the lead-up to the treatment itself with the aid of a diagnostic wax-up. The wax-up provides orientation for the subsequent tooth preparation and allows a particularly economical approach to the removal of healthy dental hard tissue. Furthermore, the introduction of new preparation designs has contributed significantly to the preservation of dental hard tissue on the teeth to be restored. This article describes the principles of minimally invasive treatment using occlusal onlays for the reconstruction of severely worn occlusal surfaces.

A Single Visit Direct Technique to Provisionally Restore Occlusion for a Full-Mouth Rehabilitation: A Clinical Report

Attrition of the dentition can negatively affect esthetics and function. When reconstructing patients with attrition who require restoration at increased occlusal vertical dimension (OVD), it is necessary to first evaluate the OVD using a removable interim prosthesis to ensure that the patient will tolerate the new position. The transition to fixed interim prostheses has to be carefully planned to achieve the desired OVD. One approach is to prepare all teeth in a single day and place full-arch interim prostheses; however, this can be tiring for the patient and prosthodontist. An alternative approach is to prepare one arch and place interim prostheses, while using composite resin in the opposing arch to maintain the newly established OVD. A diagnostic wax-up at the proposed OVD is completed and duplicated in stone. A vacuform matrix is loaded with composite resin and applied to the unprepared etched teeth of the opposing arch to restore form and occlusion until full contour interim prostheses are placed at a later visit.

Full-mouth rehabilitation of a case of generalized enamel hypoplasia using a twin-stage procedure

The dilemma confronting many dentists today is that innovations and well-defined specializations have greatly enlarged the treatment realm for tooth preservation as well as tooth replacement. The objectives should be preservation of the remaining tooth structure, restoration of optimum function, esthetics with least invasive procedures, cost effective, and short treatment time. The number of remaining natural teeth is one of the most widely used method for evaluating oral health and the prosthetic treatment of patients with a mutilated dentition. Though the treatment of these patients can be complex, but there are some important principles applicable in most cases. This case report demonstrates a satisfying full mouth rehabilitation using the Hobo and Takayama twin-stage procedure for a patient with esthetically and functionally compromised dentition. The final prosthesis with this twin-stage technique ensured a restoration with a predictable posterior disclusion and anterior guidance in harmony with the condylar path.