Full mouth rehabilitation of a severely worn dentition using intraoral scanner and the CAD/CAM double scanning technique / 대한치과보철학회지

With the evolution of the computer-aided design/computer-aided manufacturing (CAD/CAM) technology, the intraoral scanners are playing an increasingly important role, as they are the first step towards a completely digital workflow. The CAD/CAM double scanning technique has been used to transfer the information from provisional restorations to definitive restorations. In this case, a 67-year-old male with esthetically compromised anterior teeth, generalized severe attrition of teeth, and reduced vertical dimension was treated with full mouth rehabilitation including a re-establishment of the lost vertical dimension of occlusion assisted by the crown lengthening procedure. The provisional restorations were fabricated using an intraoral scanner and the CAD/CAM double scanning technique. After the period of adaption, the definitive monolithic zirconia restorations were delivered. The CAD/CAM double scanning technique successfully transferred the occlusal and morphological characteristics, obtained from the provisional restorations, to the definitive restorations.

Computer-aided design and manufacturing-based full mouth rehabilitation for a patient with excessive attrition and restricted vertical dimension: A case report / 대한치과보철학회지

This study reported the treatment of a patient with excessive worn dentition and limited maxillo-mandibular space for restoration, utilizing the computer-aided design and computer-aided manufacturing (CAD/CAM) technology. After the thorough examination of the patient's occlusal vertical dimension (OVD), full mouth rehabilitation was planned with increase of the OVD. The patient was satisfied with the provisional restorations establishing the increased OVD. The horizontal and vertical data of the patient's jaw relation that the provisional restorations contained were transferred to the definitive metal ceramic fixed prostheses by double scanning and three-dimensional printing. After the fixed restorations were cemented to the abutments, electronic surveying and three-dimensional printing were used to fabricate metal frameworks for the patient's removable partial dentures. The mandibular definitive removable prostheses were delivered to the patient's mouth and the full mouth rehabilitation procedures were completed. The digital technologies used for this case produced fixed and removable restorations satisfactory in masticatory, phonetic and aesthetic functions to both the patient and the dental clinician.

Full mouth rehabilitation of a patient using monolithic zirconia and dental CAD/CAM system: a case report

An accurate implant placement with ideal location is significant for long-term success of the implant. An exact evaluation of nearby anatomic structures such as quality of residual bone, an inferior alveolar bone and a maxillary sinus is required. For a prosthetic-driven treatment, planned surgery, precise prosthesis and communication with the patient are significant requisites especially for full-mouth rehabilitation. In this case, the patient with severe alveolar bone resorption had a CT guided surgery supported by CT data and the data from scanning diagnostic wax-up. Afterward, edentulous area was restored by full mouth implant-supported prosthesis by using monolithic zirconia and CAD/CAM technique. This paper reports the outcome of the procedure which was remarkable both esthetically and functionally.

Three-dimensional finite element analysis according to the insertion depth of an immediately loaded implant in the anterior maxilla / 대한치과보철학회지

PURPOSE: The purpose of this study was to investigate the effects of the insertion depth of an immediately loaded implant on the stress distribution of the surrounding bone and the micromovement of the implant using the three-dimensional finite element analysis. MATERIALS AND METHODS: A total of five bone models were constructed such that the implant platform was positioned at the levels of 0.00 mm, 0.25 mm, 0.50 mm, 0.75 mm, and 1.00 mm depth from the crest of the cortical bone. A frictional coefficient of 0.3 and the insertion torque of 35 Ncm were simulated on the interface between the implant and surrounding bone. A static load of 178 N was applied to the provisional prosthesis with a vertical load in the axial direction and an oblique load at 30°with respect to the central axis of the implant, then a finite element analysis was performed. RESULTS: The implant insertion depth significantly affected the stress distribution on the surrounding bone. The largest micromovement value of the implant was 39.34 µm. The oblique load contributed significantly to the stress distribution and micromovement in comparison to the vertical load. CONCLUSION: Increasing the implant insertion depth was advantageous in dispersing the concentrated stress in the cortical bone and did not significantly affect the micromovement associated with early osseointegration failure.

Full mouth rehabilitation of edentulous patient with intellectual disability using implants and monolithic zirconia / 대한치과보철학회지

People with class I intellectual disability need lifelong assistance and protection from their surroundings due to impaired adaptive functioning. They have poor oral health and show higher prevalence of dental caries, periapical inflammation and tooth loss that require proper prosthetic restoration. Because removable prostheses for intellectually disabled patients often lack stability, retention, and maintenance, fixed prostheses are essential and the only available option is dental implants. In this case, a 45 year-old male patient with class I intellectual disability had poor oral hygiene with most of his teeth missing and visited the clinic to recover his masticatory function. Due to such systemic conditions, the definitive restoration of choice was the implant-supported fixed dental prosthesis made of biocompatible and highly strong monolithic zirconia. In consequence of the treatment process, the patient was able to improve his oral environment aesthetically and functionally.

The dimension analysis of prepared natural teeth for developing customized zirconia block / 대한치과보철학회지

PURPOSE: Unpredictable shrinkage of zirconia during sintering process causes discrepancy. Therefore, there have been attempts to reduce discrepancy by milling zirconia after sintering. However, due to the hardness of sintered zirconia, milling takes longer time, causes damage to the machine and causes chip formation. With customized zirconia block using the mean dimension of prepared natural dentition, it is expected to overcome these shortcomings. MATERIALS AND METHODS: The mean dimension of prepared natural dentition was analyzed as STL file after scanning of prepared teeth treated at SNUDH. The transverse, frontal and sagittal planes were set using Mimics and Photoshop. 3D volume was projected on each plane, and the outer line was measured through external tangent line, and the inner line was measured through inflection point of tangent line. RESULTS: The mean height of prepared incisal (N = 57) is 6.60 ± 1.05 mm, mesiodistal length is 2.98 ± 0.73 mm, buccolingual length is 2.04 ± 0.73 mm. The mean height of prepared premolar (N = 15) is 5.37 ± 1.49 mm, mesiodistal length is 4.10 ± 1.78 mm, buccolingual length is 5.86 ± 1.55 mm. And the mean height of prepared molar (N = 13) is 5.11 ± 1.29 mm, mesiodistal length is 6.80 ± 1.18 mm, buccolingual length is 7.34 ± 1.40 mm. CONCLUSION: Using the mean dimension of prepared natural dentition, it is expected to be able to fabricate customized zirconia block.

Full mouth rehabilitation of the patient with severely worn dentition using monolithic zirconia prosthesis: A clinical report / 대한치과보철학회지

Excessive occlusal wear causes loss of tooth structure, occlusal plane disharmony, impaired function and esthetic problems. Although the decrease of occlusal vertical dimension may be compensated by the growth of alveolar bone and tooth eruption, minimal increase of occlusal vertical dimension may be required for esthetics and retention of prosthesis. In this case, a 44-year-old male patient visited Seoul National University Dental Hospital with chief complaint of severe tooth wear and shade disharmony. Based on assessment of diagnostic wax-up, 3 mm increase of occlusal vertical dimension was determined. Removable occlusal splint and interim prosthesis was used to ascertain patient's comfort and adaptation. After the adaptation period, definitive prosthesis fabricated with full-contour monolithic zirconia were delivered and the patient was recommended to wear a nightguard device for prosthesis protection. This report presents a case of full mouth rehabilitation with the elevation of patient's occlusal vertical height, resulting in satisfactory esthetics and functions.

Effect of the amount of thickness reduction on color and translucency of dental monolithic zirconia ceramics

PURPOSE: This study investigated the effect of amount of thickness reduction on color and translucency of dental monolithic zirconia ceramics. MATERIALS AND METHODS: One-hundred sixty-five monolithic zirconia specimens (16.3 mm x 16.3 mm x 2.0 mm) were divided into 5 groups (Group I to V) according to the number of A2-coloring liquid applications. Each group was then divided into 11 subgroups by reducing the thickness up to 1.0 mm in 0.1-mm increments (Subgroup 0 to 10, n=3). Colors and spectral distributions were measured according to CIELAB on a reflection spectrophotometer. All measurements were performed on five different areas of each specimen. Color difference (DeltaE*(ab)) and translucency parameter (TP) were calculated. Data were analyzed using one-way ANOVA and multiple comparison Scheffe test (alpha=.05). RESULTS: There were significant differences in CIE L* between Subgroup 0 and other subgroups in all groups. CIE a* increased (0.523.7) were obtained between Subgroup 0 and other subgroups. TP values generally increased as the thickness reduction increased in all groups (R2>0.89, P<.001). CONCLUSION: Increasing thickness reduction reduces lightness and increases a reddish, bluish appearance, and translucency of monolithic zirconia ceramics.

Maxillofacial rehabilitation of hemi-maxillectomy patient using a closed hollow bulb obturator fabricated by one-step polymerization technique: a clinical report / 대한치과보철학회지

The maxillary defects lead to anatomical and functional deformity of the maxillofacial region. As far as functions are concerned, such defects can produce difficulty in speech, mastication, and deglutition. Obturator prostheses play a very important role in functional recovery for post-maxillectomy patients. To achieve rigidity of the obturator, appropriate retention should be given, and the weight of the prosthesis be reduced. There are two types of hollow bulb obturator: open and closed. A closed type has many advantages. Nevertheless, some problems, including complexity of fabrication and water leakage into the bulb, have the closed hollow obturator not be widely used. The one-step polymerization technique described in this case overcomes the shortcomings by easily constructing a small hollow bulb with two thermoplastic resin sheets.

In vivo comparison between the effects of chemically modified hydrophilic and anodically oxidized titanium surfaces on initial bone healing

PURPOSE: The aim of this study was to investigate the combined effects of physical and chemical surface factors on in vivo bone responses by comparing chemically modified hydrophilic sandblasted, large-grit, acid-etched (modSLA) and anodically oxidized hydrophobic implant surfaces. METHODS: Five modSLA implants and five anodized implants were inserted into the tibiae of five New Zealand white rabbits (one implant for each tibia). The characteristics of each surface were determined using field emission scanning electron microscopy, energy dispersive spectroscopy, and confocal laser scanning microscopy before the installation. The experimental animals were sacrificed after 1 week of healing and histologic slides were prepared from the implant-tibial bone blocks removed from the animals. Histomorphometric analyses were performed on the light microscopic images, and bone-to-implant contact (BIC) and bone area (BA) ratios were measured. Nonparametric comparison tests were applied to find any significant differences (P0.05). CONCLUSIONS: Within the limitations of this study, the hydrophilicity of the modSLA surface may have a stronger effect on in vivo bone healing than optimal surface roughness and surface chemistry of the anodized surface.

Effect of working time on the film thickness of dental resin cements / 대한치과보철학회지

PURPOSE: The aim of this study was to compare the film thicknesses of several resin cements as a function of time after mixing and to examine the effect of working time on the film thicknesses. MATERIALS AND METHODS: The film thickness (microm) of 4 resin cements (n=10), 1 composite resin (Panavia F 2.0), 3 self-adhesive resin (Clearfil SA luting, Zirconite, RelyX U200) cements was measured at 20-second intervals after mixing of the cements up to 200 seconds under a load of 50 N. Linear regression was fitted to verify the effect of working time on the film thickness of each cement. Data were compared to the working time recommended by manufacturers using Wilcoxon test (alpha=.05). RESULTS: All of the materials showed a positive linear correlation between the film thickness and working time. There was no statistically significant difference between the working time based on our results and the values recommended by the manufacturers even though there was a discrepancy between those two values. CONCLUSION: The film thickness of resin cements could increase with the increase of working time. Working time to meet the ISO standard of 50-microm maximum film thickness could be different from the manufacturer's recommended value.

A root submergence technique for pontic site development in fixed dental prostheses in the maxillary anterior esthetic zone

PURPOSE: This case report discusses the effect of a root submergence technique on preserving the periodontal tissue at the pontic site of fixed dental prostheses in the maxillary anterior aesthetic zone. METHODS: Teeth with less than ideal structural support for fixed retainer abutments were decoronated at the crestal bone level. After soft tissue closure, the final fixed dental prostheses were placed with the pontics over the submerged root area. Radiographic and clinical observations at the pontic sites were documented. RESULTS: The submerged roots at the pontic sites preserved the surrounding periodontium without any periapical pathology. The gingival contour at the pontic site was maintained in harmony with those of the adjacent teeth, as well as the overall form of the arch. CONCLUSIONS: The results of this clinical report indicate that a root submergence technique can be successfully applied in pontic site development with fixed dental prostheses, especially in the maxillary anterior esthetic zone.

Effect of water storage on the fracture toughness of dental resin cement used for zirconia restoration / 대한치과보철학회지

PURPOSE: The aim of this study was to compare the fracture toughness of currently available resin cements for zirconia restorations and evaluate the effect of water storage on fracture toughness of those resin cements. MATERIALS AND METHODS: Single-edge notched specimens (3 mm x 6 mm x 25 mm) were prepared from three currently available dual cure resin cements for zirconia restorations (Panavia F 2.0, Clearfil SA luting and Zirconite). Each resin cement was divided into four groups: immersed in distilled water at 37degrees C for 1 (Control group), 30, 90, or 180 days (n=5). Specimens were loaded in three point bending at a cross-head speed of 0.1 mm/s. The maximum load at specimen failure was recorded and the fracture toughness (K(IC)) was calculated. Data were analyzed using one-way ANOVA and multiple comparison Scheffe test (alpha=.05). RESULTS: In control group, the mean KIC was 3.41 +/- 0.64 MN.m(-1.5) for Panavia F, 2.0, 3.07 +/- 0.41 MN.m(-1.5) for Zirconite, 2.58 +/- 0.30 MN.m(-1.5) for Clearfil SA luting respectively, but statistical analysis revealed no significant difference between them. Although a gradual decrease of K(IC) in Panavia F 2.0 and gradual increases of KIC in Clearfil SA luting and Zirconite were observed with storage time, there were no significant differences between immersion time for each cement. CONCLUSION: The resin cements for zirconia restorations exhibit much higher K(IC) values than conventional resin cements. The fracture toughness of resin cement for zirconia restoration would not be affected by water storage.

Full-mouth rehabilitation with CAD/CAM monolithic zirconia in dentinogenesis imperfecta: a case report / 대한치과보철학회지

Dentinogenesis Imperfecta, with a high incidence rate of 1 : 6 - 8000, is inherited by autosomal dominant genetic transmission. This dental disorder causes discoloration of the teeth and the enamel and dentin show hypoplastic or hypocalcified defects which lead to frequent fractures and rapid attrition. Therefore, timely treatment is necessary for the preservation of the remaining teeth. In this particular case, a 19-year-old patient suffering from Type 1 dentinogenesis imperfecta showed signs of brownish hued teeth with multiple fractures, a loss of vertical dimension, excessive interdental space in the maxillary anterior teeth, and a lack of 5 posterior teeth. To improve the esthetic appearance of the anterior teeth, the vertical dimension was increased. Resin caps were used to alleviate the difficulty of taking an impression of multiple teeth at once. Monolithic zirconia materials used in this case showed high fracture strength and the ability to mask the discoloration of the teeth and therefore, functionally and esthetically favorable results were achieved.

The reliability of an easy measuring method for abutment convergence angle with a computer-aided design (CAD) system

PURPOSE: The purpose of this study was to evaluate the intra-rater reliability and inter-rater reliability of three different methods using a drawing protractor, a digital protractor after tracing, and a CAD system. MATERIALS AND METHODS: Twenty-four artificial abutments that had been prepared by dental students were used in this study. Three dental students measured the convergence angles by each method three times. Bland-Altman plots were applied to examine the overall reliability by comparing the traditional tracing method with a new method using the CAD system. Intraclass Correlation Coefficients (ICC) evaluated intra-rater reliability and inter-rater reliability. RESULTS: All three methods exhibited high intra-rater and inter-rater reliability (ICC>0.80, P<.05). Measurements with the CAD system showed the highest intra-rater reliability. In addition, it showed improved inter-rater reliability compared with the traditional tracing methods. CONCLUSION: Based on the results of this study, the CAD system may be an easy and reliable tool for measuring the abutment convergence angle.

Measuring abutment convergence angles using stereovision dental image processing system

PURPOSE: The purpose of this study was to develop a dental image processing system using a three-dimensional (3D) camera and stereovision technology. The reliability of the system for measuring axial wall convergence angles was evaluated. MATERIALS AND METHODS: The new system predicted 3D coordinate points from 2D images and calculated distances and angles between points. Two examiners measured axial wall convergence angles for seven artificial abutments using a traditional tracing-based method (TBM) and the stereovision-based method (SVBM). Five wax abutment models of simplified abutment forms were made and axial wall convergence angles of wax models were measured by both methods. The data were statistically analyzed at the level of significance, 0.05. RESULTS: Intraclass correlation coefficients showed excellent intra-examiner and inter-examiner reliabilities for both methods. Bland-Altman plots and paired t-tests showed significant differences between measurements and true values using TBM; differences were not significant with SVBM. CONCLUSION: This study found that the SVBM reflected true angle values more accurately than a TMB and illustrated an example of 3D computer science applied to clinical dentistry.

Rheological properties of dental resin cements during polymerization / 대한치과보철학회지

PURPOSE: The purpose of this study was to observe the change of viscoelastic properties of dental resin cements during polymerization. MATERIALS AND METHODS: Six commercially available resin cement materials (Clearfil SA luting, Panavia F 2.0, Zirconite, Variolink N, RelyX Unicem clicker, RelyX U200) were investigated in this study. A dynamic oscillation-time sweep test was performed with AR1500 stress controlled rheometer at 32degrees C. The changes in shear storage modulus (G'), shear loss modulus (G"), loss tangent (tan delta) and displacement were measured for twenty minutes and repeated three times for each material. The data were analyzed using one-way ANOVA and Tukey's post hoc test (alpha=0.05). RESULTS: After mixing, all materials demonstrated an increase in G' with time, reaching the plateau in the end. RelyX U200 demonstrated the highest G' value, while RelyX Unicem (clicker type) and Variolink N demonstrated the lowest G' value at the end of experimental time. Tan delta was maintained at some level and reached the zero at the starting point where G' began to increase. The tan delta and displacement of the tested materials showed similar pattern in the graph within change of time. The displacement of all 6 materials approached to zero within 6 minutes. CONCLUSION: Compared to other resin cements used in this study, RelyX U200 maintained plastic property for a longer period of time. When it completed the curing process, RelyX U200 had the highest stiffness. It is convenient for clinicians to cement multiple units of dental prostheses simultaneously.

Simplified V-Shape Incision Technique for Saving Hair Follicles

BACKGROUND: The scalp is the second most visible part of the anatomy next to the face. Thus, aesthetic considerations such as scars and alopecia are important when planning excision of a mass from the scalp. Aesthetic results have not been satisfactory due to scar widening and hair follicle injury. Many methods have been tried to improve these results, however, they require multiple procedures and longer operation time. METHODS: We evaluated a easy and time-saving V-shape incision for excising a scalp mass. This technique of simplified V-shape incision was performed in 32 patients with benign scalp masses treated from September 2011 to March 2013. The incisions were performed with a blade to make a V-shape margin and preserve deep hair follicles at the flap margins. The defect was closed by approximation of two edges. RESULTS: All tumors were benign and superficial. The size of the scalp masses was 0.4-2.0 cm in width and 1.0-5.0 cm in length. Many hairs from the deep hair follicles grew into the scar, making the scar line almost unnoticeable in all 32 patients. Although some scar widening was evident, the number of hairs per unit was high enough to camouflage the scars. CONCLUSIONS: The simplified V-shape incision was beneficial as a simple, mini-surgical, time-saving procedure. Although the scars were slightly wider, they were covered with penetrating hairs and became unnoticeable.

Comparative fracture strength analysis of Lava and Digident CAD/CAM zirconia ceramic crowns

PURPOSE: All-ceramic crowns are subject to fracture during function. To minimize this common clinical complication, zirconium oxide has been used as the framework for all-ceramic crowns. The aim of this study was to compare the fracture strengths of two computer-aided design/computer-aided manufacturing (CAD/CAM) zirconia crown systems: Lava and Digident. MATERIALS AND METHODS: Twenty Lava CAD/CAM zirconia crowns and twenty Digident CAD/CAM zirconia crowns were fabricated. A metal die was also duplicated from the original prepared tooth for fracture testing. A universal testing machine was used to determine the fracture strength of the crowns. RESULTS: The mean fracture strengths were as follows: 54.9 +/- 15.6 N for the Lava CAD/CAM zirconia crowns and 87.0 +/- 16.0 N for the Digident CAD/CAM zirconia crowns. The difference between the mean fracture strengths of the Lava and Digident crowns was statistically significant (P<.001). Lava CAD/CAM zirconia crowns showed a complete fracture of both the veneering porcelain and the core whereas the Digident CAD/CAM zirconia crowns showed fracture only of the veneering porcelain. CONCLUSION: The fracture strengths of CAD/CAM zirconia crowns differ depending on the compatibility of the core material and the veneering porcelain.

The influence of various core designs on stress distribution in the veneered zirconia crown: a finite element analysis study

PURPOSE: The purpose of this study was to evaluate various core designs on stress distribution within zirconia crowns. MATERIALS AND METHODS: Three-dimensional finite element models, representing mandibular molars, comprising a prepared tooth, cement layer, zirconia core, and veneer porcelain were designed by computer software. The shoulder (1 mm in width) variations in core were incremental increases of 1 mm, 2 mm and 3 mm in proximal and lingual height, and buccal height respectively. To simulate masticatory force, loads of 280 N were applied from three directions (vertical, at a 45degrees angle, and horizontal). To simulate maximum bite force, a load of 700 N was applied vertically to the crowns. Maximum principal stress (MPS) was determined for each model, loading condition, and position. RESULTS: In the maximum bite force simulation test, the MPSs on all crowns observed around the shoulder region and loading points. The compressive stresses were located in the shoulder region of the veneer-zirconia interface and at the occlusal region. In the test simulating masticatory force, the MPS was concentrated around the loading points, and the compressive stresses were located at the 3 mm height lingual shoulder region, when the load was applied horizontally. MPS increased in the shoulder region as the shoulder height increased. CONCLUSION: This study suggested that reinforced shoulder play an essential role in the success of the zirconia restoration, and veneer fracture due to occlusal loading can be prevented by proper core design, such as shoulder.