Possibilities and limitations of computer-assisted implant planning and guided surgery in the anterior region

Three-dimensional (3D) implant positioning is an important prognostic factor for anterior dental implants. Modern 3D imaging and implant treatment planning systems are available today for precise dental implant planning and placement. The transfer of implant position information to industrially manufactured templates for guided implant surgery has been possible for years now. What is new is the possibility of combining the datasets with the surface scan data of a diagnostic wax-up and setup for prosthetic-driven implant planning. Digital setups can also be used. This article describes and discusses the available options for digital implant planning and guided surgery.

Randomized controlled within-subject evaluation of digital and conventional workflows for the fabrication of lithium disilicate single crowns. Part II: CAD-CAM versus conventional laboratory procedures

STATEMENT OF PROBLEM

Clinical studies are needed to evaluate the entire digital and conventional workflows in prosthetic dentistry.

PURPOSE

The purpose of the second part of this clinical study was to compare the laboratory production time for tooth-supported single crowns made with 4 different digital workflows and 1 conventional workflow and to compare these crowns clinically.

MATERIAL AND METHODS

For each of 10 participants, a monolithic crown was fabricated in lithium disilicate-reinforced glass ceramic (IPS e.max CAD). The computer-aided design and computer-aided manufacturing (CAD-CAM) systems were Lava C.O.S. CAD software and centralized CAM (group L), Cares CAD software and centralized CAM (group iT), Cerec Connect CAD software and lab side CAM (group CiL), and Cerec Connect CAD software with centralized CAM (group CiD). The conventional fabrication (group K) included a wax pattern of the crown and heat pressing according to the lost-wax technique (IPS e.max Press). The time for the fabrication of the casts and the crowns was recorded. Subsequently, the crowns were clinically evaluated and the corresponding treatment times were recorded. The Paired Wilcoxon test with the Bonferroni correction was applied to detect differences among treatment groups (α=.05).

RESULTS

The total mean (±standard deviation) active working time for the dental technician was 88 ±6 minutes in group L, 74 ±12 minutes in group iT, 74 ±5 minutes in group CiL, 92 ±8 minutes in group CiD, and 148 ±11 minutes in group K. The dental technician spent significantly more working time for the conventional workflow than for the digital workflows (P<.001). No statistically significant differences were found between group L and group CiD or between group iT and group CiL. No statistical differences in time for the clinical evaluation were found among groups, indicating similar outcomes (P>.05).

CONCLUSIONS

Irrespective of the CAD-CAM system, the overall laboratory working time for a digital workflow was significantly shorter than for the conventional workflow, since the dental technician needed less active working time.

Discoloration of the mucosa caused by different restorative materials - a spectrophotometric in vitro study

OBJECTIVES

To evaluate the discoloration of the mucosa caused by different ceramic and metal-based materials.

MATERIAL AND METHODS

On six pig maxillae, trap-door flaps were prepared bilaterally. Different ceramic and metal-based specimens were placed underneath the flap. To simulate increasing mucosal thicknesses (MC), connective tissue grafts (CTGs) were harvested. Spectrophotometric measurements were performed prior to flap elevation (T_BL ) and for each material under the flap alone (1 mm MC) (T_MC1 ), with a 1-mm CTG (2-mm MC) (T_MC2 ) and with a 2-mm CTG (3-mm MC) (T_MC3 ). Tested materials were as follows: Zr1 (zirconia), Zr2 (zirconia + pink ceramic), Zr3 (zirconia), Zr4 (fluorescent zirconia), Zr5 (zirconia), Zr6 (high translucent zirconia), Zr7 (low translucent zirconia) and Zr8 (low translucent zirconia), Gol (gold alloy), Ti1 (titanium alloy), Ti2 (anodized gold-shaded titanium alloy) and Ti3 (anodized pink-shaded titanium alloy). Color differences (ΔE) were calculated comparing the measurement of the native tissue (T_BL ) and the measurements with varying mucosal thicknesses (T_MC1-3 ).

RESULTS

For ceramic materials, the median ΔE values for the different time-point comparison ranged as follows: 3.80 (Zr4) - 7.47 (Zr2) (pooled); 3.15 (Zr4) - 8.13 (Zr2) (T_BL -T_MC1 ); 3.39 (Zr4) - 7.24 (Zr2) (T_BL -T_MC2 ); 4.31 (Zr8) - 6.99 (Zr2) (T_BL -T_MC3 ). For metal-based materials, the median ΔE values were as follows: 4.20 (Gol) - 5.82 (Ti3) (pooled); 3.21 (Gol) - 13.56 (Ti1) (T_BL -T_CM1 ); 4.0 (Ti1) - 5.27 (Gol) (T_BL -T_CM2 ); 3.11 (Ti1) - 5.11 (Gol) (T_BL -T_CM2 ). The comparison of the materials and the time points showed in the nonparametric linear mixed model a significant interaction effect between material and time point (P < 0.001). The side was not a significant main effect, nor as term in an interaction with the other two effects.

CONCLUSIONS

Reconstructive materials result in an evident discoloration of the mucosal tissue, tending to decrease with increasing mucosal thickness. The use of fluorescent zirconia (ceramic materials) or gold alloy (metal-based materials) lead to the least discoloration.

Criteria for the selection of restoration materials

Selection of the appropriate material for dental restoration has become more and more difficult owing to the increasing variety of restoration materials. A decision flow chart is presented to guide the treatment team (dentist and dental technician) in the selection of the restoration material. This material selection is based on the available interocclusal space, esthetic aspects (eg, brightness value or translucency of the neighboring teeth), as well as clinical evidence extracted from survival rates.

Advanced smile diagnostics using CAD/CAM mock-ups

Diagnostics are essential for predictable restorative dentistry. Both patient and clinician must agree on a treatment goal before the final restorations are delivered to avoid future disappointments. However, fully understanding the patient's desires is difficult. A useful tool to overcome this problem is the diagnostic wax-up and mock-up. A potential treatment outcome is modeled in wax prior to treatment and transferred into the patient's mouth using silicon indexes and autopolymerizing resin to obtain the patient's approval. Yet, this time-consuming procedure only produces a single version of the possible treatment outcome, which can be unsatisfactory for both the patient and the restorative team. Contemporary digital technologies may provide advantageous features to aid in this diagnostic treatment step. This article reviews opportunities digital technologies offer in the diagnostic phase, and presents clinical cases to illustrate the procedures.

Minimally invasive rehabilitation of a patient with amelogenesis imperfecta

This case report describes a minimally invasive step-by-step approach to treat a patient with amelogenesis imperfecta. This is a genetic developmental disorder of the dental enamel, which clinically manifests as white and dark discolorations of the teeth. The clinical examination did not reveal the true depth of the staining. Therefore, a step-wise treatment approach was chosen. The first step consisted of a home bleaching procedure, which led to a slight improvement of the esthetic appearance, but the stains were still clearly visible. The next step was the application of a microabrasion technique. This led to further improvement, but not to a satisfactory result for this patient who had high esthetic expectations. Thus, the third step was undertaken: it was planned to restore the maxillary incisors and canines with ceramic veneers. The dental technician prepared a wax-up, which served as a basis for a clinical mock-up. After discussing the mock-up and the treatment plan with the patient, crown lengthening was performed on teeth 11 and 23 to improve the pink esthetics. Subsequently, the teeth were prepared in a minimally invasive way and a final impression was taken. Following try-in, the six veneers were inserted with resin cement.