Effect of digital complete dentures manufactured using the custom disk method on masticatory function.

Statement of problem: The effect of using the custom disk method (CDM) for fabricating digital dentures on patients' masticatory function should be studied to support its use in clinical practice. Purpose: To investigate the effect of digital dentures fabricated using CDM on patients' masticatory function. Material and methods: This single-center prospective clinical study included 20 patients with edentulous maxillary and mandibular arches who used a complete denture. The digital impression and complete denture manufacturing procedures using CDM have already been reported by Kanazawa et al. (2018) [32] and Soeda et al. (2022) [18] Thedigital dentures fabricated with CDM were delivered to the participants, and periodic adjustments were made until the patient could use the denture without pain. A color-changeable chewing gum, two types of gummy jellies that can evaluate the masticatory function, and pressure-sensitive sheets were used to evaluate the participants' masticatory function at baseline, 1 month, and 6 months following adjustment of the new digital complete dentures fabricated with CDM. These masticatory function values had already been measured in the previous conventional dentures and were recorded as baseline values. Results: The study participants included 8 women and 12 men (mean age, 77.6 years). The color-changeable chewing gum analysis indicated that there was no significant improvement of masticatory function from baseline to 1 M (P = .083) and 6 M (P = .157).The gummy jelly analysis indicated no significant differences between the masticatory function baseline and 1 month (P = .387); however, a significant improvement was observed from baseline to 6 months (P = .020). Tests with Glucolum indicated a significant improvement from baseline to 1 month (P = .012) and 6 months (P = .003). The maximum bite force and occlusal contact area showed no significant difference at any time point. Conclusions: Significant improvement in masticatory function was observed upon evaluation with gummy jelly and Glucolum 6 months after delivering the new digital complete dentures. Under limited conditions, the digital denture fabricated using CDM resulted in good recovery of the masticatory function in elderly edentulous patients. The present results combined with the cost-effectiveness and patient satisfaction associated with CDM indicate its clinical utility.

Effect of support structures on the trueness and precision of 3D printing dentures: An in vitro study.

Purpose Additive manufacturing has revolutionized the fabrication of complete dentures. However, this process involves support structure, which is a construction part that holds the specimen during printing, and may prove to be disadvantageous. Therefore, this in vitro study compared the effect of support structure reduction on various volume and area distributions of a 3D-printed denture base to determine optimal parameters based on accuracy.Methods A complete maxillary denture base construction file was used as reference. Twenty denture bases were 3D printed under four conditions (total n=80): no support structure reduction (control), palatal support structure reduction (Condition P), border support structure reduction (Condition B), and palatal and border support structure reduction (Condition PB). Printing time and resin consumption were also recorded. The intaglio surface trueness and precision of all acquired data were exported to a 3D analysis software, and the dimensional changes to the denture base were analyzed using the root-mean-square estimate (RMSE) to assess geometric accuracy and generate color map patterns. Nonparametric Kruskal-Wallis and Steel-Dwass tests (α=0.05) analyzed the accumulated data.Results Control had the lowest RMSE values for trueness and precision. Nevertheless, it demonstrated a significantly lower RMSE than that of Condition B (P=0.02) in precision. Owing to negative deviation at the palatal region, Conditions P and PB had higher retention than Control and Condition B regarding the color map pattern.Conclusions Within the limitations of this study, the reduction of palatal and border support structures showed optimal accuracy with resource and cost savings.

Effect of New Complete Dentures and Simple Dietary Advice on Cognitive Screening Test among Edentulous Older Adults: A Randomized Controlled Trial.

Mild cognitive impairment (MCI), including memory loss, has been attracting attention in Japan. This study assessed the effect of new complete dentures provision alone and with dietary intervention on cognitive functions assessed using the Japanese version of the Montreal Cognitive Assessment (MoCA-J). A randomized controlled trial was conducted with 70 older adults who required new complete dentures. The participants had new complete dentures fabricated and were randomly classified into the intervention or control group. The intervention group received simple dietary advice, and the control group only received denture care advice. Cognitive function was assessed using the MoCA-J before and at 3 and 6 months after treatment. The between-group comparison and within-group comparison were analyzed. No significant differences were reported for comparisons between the intervention and control groups. A significant increase was revealed in the within-group comparisons for the total scores between the 3- and 6-month assessments (p = 0.002) and between the baseline and 6-month assessments (p = 0.012) in the intervention group. In the control group, a significant increase in the total scores was not revealed between any of evaluation period. Complete denture replacement combined with simple dietary intervention may help improve MoCA-J scores in edentulous older adults.

The effect of single-implant overdentures on cognitive function in older adults: A 3-year follow-up report.

OBJECTIVE: To investigate the occurrence of mild cognitive impairment in edentulous patients up to 3 years after they received single-implant overdentures (1-IODs). METHODS: This was a follow-up study for a crossover randomized controlled trial comparing 1-IODs and conventional complete dentures, with patient satisfaction as the primary outcome. In the present study, the cognitive function of the patients, measured with the Japanese version of the Montreal cognitive assessment (MoCA-J), was evaluated as the secondary outcome at baseline and 2 months, 1 year, 2 years, and 3 years after 1-IOD placement. The total and domain (memory, executive function, visuospatial skills, language, attention, and orientation) MoCA-J scores of the patients at each timepoint were analyzed and compared. RESULTS: Twenty-two patients with edentulous mandibles received 1-IODs. Within-group comparisons revealed that the total MoCA-J scores at 1 year and 3 years after 1-IOD placement were significantly increased compared with baseline scores. Additionally, the memory domain scores at all timepoint were significantly increased compared with the baseline scores, and the executive function domain scores at the 2-month, 2-year and 3-year timepoint were significantly increased compared with the baseline scores. CONCLUSION: Patients with edentulous mandibles who underwent 1-IOD placement showed significantly improved total scores of MoCA-J after 1 year and 3 years of wearing 1-IODs. In addition, they showed significantly improved memory domain scores at 2 months, 1 year, 2 years, and 3 years after 1-IOD placement and executive function domain scores at 2 months, 2 years, and 3 years after 1-IOD placement. CLINICAL SIGNIFICANCE: The results of this study suggest that 1-IOD treatment for older adults, especially those with edentulous mandibles, may prevent cognitive decline regardless of the condition of the maxilla.

Fabrication of milled removable partial dentures using a custom plate with prefabricated artificial teeth.

PURPOSE: Although digital removable partial dentures have been previously described, there have been no reports on how to fabricate them in one piece. This study proposes a new method for fabricating patient-specific digital removable partial dentures using a custom plate. METHODS: First, a gypsum model was scanned using a laboratory scanner and a removable partial denture was designed using computer-aided design (CAD) software based on standard tessellation language data. The metal clasp was fabricated from Ti-6Al-4V using a 3D printer. For custom plate fabrication, a resin plate frame was designed using computer-aided design (CAD) software and fabricated using a 3D printer. An artificial tooth and metal clasp were fixed on the base surface of the frame, an auto-polymerizing resin was poured into the frame for the denture base, and the artificial tooth and metal clasp were packed to form a custom plate. The plate was cut using a milling machine. Subsequently, the support attached to the denture was removed and polished for complete fabrication of the denture. CONCLUSIONS: Our novel removable partial denture fabrication method is more efficient than the conventional method. The obtained removable partial dentures demonstrated satisfactory accuracy.

Prediction accuracy of incisal points in determining occlusal plane of digital complete dentures.

PURPOSE: This study aimed to predict the positional coordinates of incisor points from the scan data of conventional complete dentures and verify their accuracy. MATERIALS AND METHODS: The standard triangulated language (STL) data of the scanned 100 pairs of complete upper and lower dentures were imported into the computer-aided design software from which the position coordinates of the points corresponding to each landmark of the jaw were obtained. The x, y, and z coordinates of the incisor point (XP, YP, and ZP) were obtained from the maxillary and mandibular landmark coordinates using regression or calculation formulas, and the accuracy was verified to determine the deviation between the measured and predicted coordinate values. YP was obtained in two ways using the hamular-incisive-papilla plane (HIP) and facial measurements. Multiple regression analysis was used to predict ZP. The root mean squared error (RMSE) values were used to verify the accuracy of the XP and YP. The RMSE value was obtained after cross-validation using the remaining 30 cases of denture STL data to verify the accuracy of ZP. RESULTS: The RMSE was 2.22 for predicting XP. When predicting YP, the RMSE of the method using the HIP plane and facial measurements was 3.18 and 0.73, respectively. Cross-validation revealed the RMSE to be 1.53. CONCLUSION: YP and ZP could be predicted from anatomical landmarks of the maxillary and mandibular edentulous jaw, suggesting that YP could be predicted with better accuracy with the addition of the position of the lower border of the upper lip.

Trueness and precision of artificial teeth in CAD-CAM milled complete dentures from custom disks with a milled recess.

STATEMENT OF PROBLEM: Studies on the movement of artificial teeth during the manufacturing of computer-aided design and computer-aided manufacturing (CAD-CAM) complete dentures using the custom disk method with milled recesses and on whether the movement is within a clinically acceptable range are lacking. PURPOSE: The purpose of this in vitro study was to assess the trueness and precision of the artificial teeth on custom disks the recesses of which were manufactured using a milling machine and to compare the results with the recesses manufactured using a 3-dimensional (3D) printer. MATERIAL AND METHODS: Four types of artificial teeth (maxillary left central incisors [Max-L1], mandibular left central incisors [Man-L1], maxillary left first premolars [Max-L4], and maxillary left first molars [Max-L6]) were prepared. Milling data were created, and 3 of each type of tooth were attached to each disk made up of 3 concentric circles (large, medium, and small). Five each of the 3D-printed custom disks and custom disks with milled recesses were milled based on the milling data. Standard tessellation language data were obtained through cone beam computed tomography and superimposed by using a CAD software program. Mean absolute error (MAE) values were calculated to assess trueness and precision; MAE values of artificial teeth in custom disks with milled recesses and 3D-printed custom disks were statistically compared by using the 2-way analysis of variance test with 2 factors, 2 types of custom disks and 4 types of artificial teeth, and the Tukey post hoc comparison (α=.05). RESULTS: Regarding position trueness, the MAE value of Man-L1 on the milling custom disk was significantly lower than that of the 3D-printed custom disk (P<.001), whereas the MAE values of Max-L4 and Max-L6 on the milling custom disk were significantly higher than those on the 3D-printed custom disk (P<.001). No significant difference was found in the MAE value of the position trueness of Max-L1 between the milling and 3D-printed custom disks. Regarding position precision, the MAE values of Max-L1, Man-L1, and Max-L4 on the milling custom disk were significantly lower than those on the 3D-printed custom disks (P=.002, P<.001, P=.025, respectively). However, no significant difference was seen in the MAE value of position precision of Max-L6 between the milling and 3D-printed custom disks (P=.180) CONCLUSIONS: Movement of artificial teeth during the manufacture of dentures using the custom disk method and custom disks with milled recesses was within a clinically acceptable range.

Oral function of implant-assisted removable partial dentures with magnetic attachments using short implants: A prospective study.

OBJECTIVES: This prospective study aimed to compare the oral functions of removable partial dentures (RPDs) with those of implant-assisted removable partial dentures (IARPDs) with short implants and magnetic attachments in patients with mandibular Kennedy class I and II. MATERIAL AND METHODS: Thirty participants with mandibular Kennedy class I or II and at least three distal missing teeth were recruited. Oral functions, including mixing ability, comminuting ability, maximum bite force, and occlusal contact area, were assessed for RPDs (stage 0), IARPDs with healing caps (stage 1), and IARPDs with magnetic attachments (stage 2). The implants were loaded with occlusal force in stages 1 and 2. Finally, the data of the 27 participants who completed the evaluation at stage 2 were analyzed. The Wilcoxon signed-rank test with Bonferroni correction was used to assess the differences in the oral functions among the different stages. RESULTS: The implant survival rate was 93.8%. There were significant differences in the comminuting ability and occlusal contact area between stages 0 and 2 (p < .001 and p = .036, respectively) and stages 1 and 2 (p = .003 and p = .015, respectively). Regarding the maximum bite force, there was a significant difference between stages 1 and 2 (p = .018). However, there was no significant difference in the mixing ability between the three stages. CONCLUSIONS: Within the limitations of this study, it was concluded that IARPDs in the mandible with short implants and magnetic attachments may improve oral functions.

In vitro study of the effect of implant position and attachment type on stress distribution of implant-assisted removable partial dentures.

Background/purpose: Implant assisted removable partial dentures (IARPDs) improved biomechanical behavior of removable partial dentures (RPDs), but information of the effect of attachment type and implant position is limited. This study aimed to investigate the effect of implant position and attachment type on the stress distribution of IARPDs. Material and methods: Four implants, 10 mm in length and 4.1 mm in diameter, were bilaterally placed close to first premolar and second molar regions of a mandibular Kennedy class I model having artificial dentition from canine to canine, vertical to the occlusal plane. Five IARPDs were fabricated to accommodate locator and magnetic attachments. Strain gauges were placed on the model surface to measure the strain around implants during loading. Unilateral vertical loading was applied to the right first molar area with magnitude of 120 N and crosshead speed of 10 mm/min. Measurements were recorded under following conditions: premolar IARPDs with locator or magnetic attachments, molar IARPDs with locator or magnetic attachments. Two-way multiple analysis of variance was performed to compare the maximum principal strain (MPS) around the implants with a significance level of 0.05. Results: Implant position had significant effect on the MPS of IARPD on loading and nonloading sides while attachment type only significant on nonloading side. Molar implants showed larger MPS than premolar implants with both locator and magnetic attachments during unilateral loading. Conclusion: The stress distribution of the IARPD is significantly affected by implant position wherein anteriorly placed implants exhibit lower MPS than relatively posteriorly placed implants.

Patient-reported outcome and cost-effectiveness analysis of milled and conventionally fabricated complete dentures in a university clinic: A retrospective study.

STATEMENT OF PROBLEM: The custom disk is a novel method of complete denture fabrication; however, patient-reported outcomes and fabrication costs are unknown. PURPOSE: The purpose of this retrospective study was to evaluate general patient satisfaction with complete dentures fabricated through the custom disk method. In addition, a comparative cost-effectiveness analysis was conducted for the custom disk method and conventional removable complete dentures. MATERIAL AND METHODS: Complete dentures were fabricated for 44 edentulous participants by using the custom disk method (n=20) or the conventional removable complete denture (n=24). General patient satisfaction was measured by using visual analog scales before and after denture fabrication and compared by using the Wilcoxon signed-rank test (α=.05); the fabrication cost for each method was investigated and compared by using the Mann-Whitney U test (α=.05). Cost-effectiveness was analyzed with the incremental cost-effectiveness ratio as incremental cost per change in general patient satisfaction for the custom disk method with respect to the conventional removable complete denture. RESULTS: The median general patient satisfaction with the custom disk method and conventional removable complete denture after the intervention was 84.0 mm and 91.0 mm, respectively. General patient satisfaction with the custom disk method was significantly higher after the intervention (P=.002). The median labor costs for the custom disk method and conventional removable complete denture were 24 516 and 36 583 Japanese yen, respectively, and the difference was statistically significant (P<.001). The median of the total cost of the custom disk method and the conventional removable complete denture was 41 104 and 45 276 Japanese yen, respectively, and the difference was statistically significant (P=.004). The incremental cost-effectiveness ratio was -251.4. CONCLUSIONS: The custom disk method improved general patient satisfaction. The labor and total costs of the custom disk method were significantly lower than those of the conventional removable complete denture. The incremental cost-effectiveness ratio demonstrated that the custom disk method was more cost-effective than the conventional removable complete denture.

Current educational concepts and techniques related to impression making of removable complete dentures.

The purpose of the present study is to gain an understanding of the current state of pre-clinical education for procedures of impression making. In 2019, a survey questionnaire was emailed to the senior professors and department heads of 29 Japanese dental colleges. The response rate was 100%. This cross-sectional survey clarified the impression making for removable complete denture fabrication in Japanese dental schools' education.

Effect of post-rinsing time and method on accuracy of denture base manufactured with stereolithography.

PURPOSE: This in vitro study investigates the effect of different post-rinsing times and methods on the trueness and precision of denture base resin manufactured through stereolithography. MATERIALS AND METHODS: Ninety clear photopolymer resin specimens were fabricated and divided into nine groups (n = 10) based on rinsing times and methods. All specimens were rinsed with 99% isopropanol alcohol for 5, 10, and 15 min using three methods-automated, ultrasonic cleaning, and hand washing. The specimens were polymerized for 30 min at 40℃. For trueness, the scanned intaglio surface of each SLA denture base was superimposed on the original standard tessellation language (STL) file using best-fit alignment (n = 10). For precision, the scanned intaglio surface of the STL file in each specimen group was superimposed across each specimen (n = 45). The root mean square error (RMSE) was measured, and the data were analyzed statistically through one-way ANOVA and Tukey test (α < .05). RESULTS: The 10-min automated group exhibited the lowest RMSE. For trueness, this was significantly different from specimens in the 5-min hand-washed group (P < .05). For precision, this was significantly different from those of other groups (P < .05), except for the 15-min automated and 15-min ultrasonic groups. The color map results indicated that the 10-min automated method exhibited the most uniform distribution of the intaglio surface adaptation. CONCLUSION: The optimal postprocessing rinsing times and methods for achieving clear photopolymer resin were found to be the automated method with rinsing times of 10 and 15 min, and the ultrasonic method with a rinsing time of 15 min.

Effect of Different Filler Contents and Printing Directions on the Mechanical Properties for Photopolymer Resins.

Photopolymer resins are widely used in the production of dental prostheses, but their mechanical properties require improvement. We evaluated the effects of different zirconia filler contents and printing directions on the mechanical properties of photopolymer resin. Three-dimensional (3D) printing was used to fabricate specimens using composite photopolymers with 0 (control), 3, 5, and 10 wt.% zirconia filler. Two printing directions for fabricating rectangular specimens (25 mm × 2 mm × 2 mm) and disk-shaped specimens (φ10 mm × 2 mm) were used, 0° and 90°. Three-point bending tests were performed to determine the flexural strengths and moduli of the specimens. The Vickers hardness test was performed to determine the hardness of the specimens. Tukey's multiple comparison tests were performed on the average values of the flexural strengths, elastic moduli, and Vickers hardness after one-way ANOVA (α = 0.05). The flexural strengths and elastic moduli at 0° from high to low were in the order of 0, 3, 10, and 5 wt.%, and those at 90° were in the order of 3, 0, 10, and 5 wt.% (p < 0.05). For 5 and 10 wt.%, no significant differences were observed in mechanical properties at 0° and 90° (p < 0.05). The Vickers hardness values at 0° and 90° from low to high were in the order of 0, 3, 5, and 10 wt.% (p < 0.05). Within the limits of this study, the optimal zirconia filler content in the photopolymer resin for 3D printing was 0 wt.% at 0° and 3 wt.% at 90°.

Patient-reported outcomes with immediate-loaded two-implant-supported mandibular overdentures: Results of a 5-year prospective study.

BACKGROUND/PURPOSE: Few studies have comprehensively assessed long-term patient-reported outcomes for overdentures supported by two immediate implants. The purpose of the study was to evaluate patient-reported outcomes of immediately loaded two-implant-supported overdentures retained by ball attachments over a 5-year evaluation period. MATERIAL AND METHODS: Nineteen participants with edentulous mandibles were provided with immediately loaded two-unsplinted-implant-supported overdentures retained by ball attachments. The participants completed the Japanese version of the Oral Health Impact Profile (OHIP)-EDENT-19 and the Patient's Denture Assessment (PDA). Additionally, patient satisfaction was measured by a 100-mm visual analog scale (VAS). Measurements were performed at baseline, and at 1 and 5 years following implant surgery. RESULTS: Seventeen participants and 14 participants were evaluated at the 1-year and 5-year assessment, respectively. Considering the OHIP-EDENT-19, there was a significant decrease in the total (p = 0.046), "functional limitation" (p = 0.021), and "physical disability" (p = 0.034) scores at 1 year and the total (p = 0.045) and "physical disability" (p = 0.024) scores at 5 years following surgery, compared to the baseline scores. Considering the PDA, there was a significant increase in the "function" (p = 0.038) and "lower denture" (p = 0.003) scores at 1 year and the "function" (p = 0.032), "lower denture" (p = 0.008), and "esthetic and speech" (p = 0.043) scores at 5 years following surgery, compared to the baseline scores. Patient satisfaction at 1 year following surgery was significantly greater than that at baseline (p = 0.005). CONCLUSION: Immediately loaded two-unsplinted-implant-supported overdentures retained by ball attachments improved the oral health-related quality of life and self-assessment of dentures by the patients up to 5 years following implant surgery.

Patient-reported outcomes for the immediate loading of mandibular overdentures supported by two implants soon after implant surgery.

BACKGROUND/PURPOSE: No studies have comprehensively assessed short-term patient-reported outcomes after the provision of overdentures supported by two immediate implants. The purpose of this study was to evaluate short-term patient-reported outcomes for mandibular overdentures retained by ball attachments on two immediately loaded implants. MATERIALS AND METHODS: Nineteen participants with mandibular edentulism were provided with overdentures retained by ball attachments on two immediately loaded, unsplinted implants. The participants' self-assessment of their dentures and oral health-related quality of life were evaluated with the 22-item Patient's Denture Assessment (PDA), and the 19-item Japanese version of the Oral Health Impact Profile (OHIP-EDENT), respectively. Patient satisfaction was measured on a 100 mm visual analogue scale. Assessments were conducted at baseline, and at 1 and 6 months after implant surgery. RESULTS: There were significant increases in the PDA "Lower denture" (P = 0.009) at 1 month, as well as "Function" (P = 0.002) and "Lower denture" (P = 0.009) scores at 6 months. Patient satisfaction was also significantly increased at 1 month (P = 0.007) and 6 months (P ≤ 0.000). Significant decreases were observed in the OHIP-EDENT "Physical pain" (P = 0.046) score at 1 month, as well as the summary score (P = 0.033), "Functional limitation" (P = 0.020) and "Psychological discomfort" (P = 0.019) scores at 6 months. CONCLUSION: The use of two immediately loaded implants for lower mandibular complete overdentures is associated with improvements in patient's self-assessment of dentures, satisfaction, and oral health-related quality of life, up to 6 months after implant surgery.

CAD-CAM milled complete dentures with custom disks and prefabricated artificial teeth: A dental technique.

A digital complete denture was manufactured from a disk customized for each patient. The custom disk was made of resin and contained prefabricated artificial teeth. Both the denture base and the artificial teeth in the custom disk were milled in this technique, resulting in dentures with a high bond strength between the artificial teeth and denture base, excellent esthetics because of the prefabricated artificial teeth, and accurate occlusion because of the custom occlusal surface.

Evaluation of trueness and precision of stereolithography-fabricated photopolymer-resin dentures under different postpolymerization conditions: An in vitro study.

STATEMENT OF PROBLEM: Stereolithography (SLA) additive manufacturing (AM) technologies have become popular for the fabrication of complete dentures; however, the trueness and precision of the dentures under different postpolymerization conditions remain unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of different postpolymerization times and temperatures on the trueness and precision of SLA dentures. MATERIAL AND METHODS: Specimens simulating maxillary complete dentures were fabricated by SLA 3D printing. They were polymerized for 15 minutes or 30 minutes at different temperatures (40 °C, 60 °C, and 80 °C). The intaglio surface trueness of the specimens was evaluated by superimposing the postpolymerization standard tessellation language (STL) file on the original STL file for each specimen via a best-fit method (n=10). The precision was measured across specimens by superimposing the postpolymerization STL file from each specimen group and using the combination formula (n=45). Subsequently, root-mean-square estimates (RMSEs) and color map data were obtained, and a normality test was conducted on the obtained data. The results indicated that the distributions were not normal; therefore, nonparametric Kruskal-Wallis and Mann-Whitney tests were used to analyze the data (α=.05). RESULTS: For trueness, the lowest RMSE corresponded to the postpolymerization time of 30 minutes and a temperature of 40 °C. This result was significantly different from specimens those of the 15-minute and 60 °C, 15-minute and 80 °C, and 30-minute and 80 °C specimens (P<.001). For precision, the median of the lowest RMSE corresponded to the 30-minute and 40 °C specimens. This median value was significantly different from those of other specimens (P<.001). The findings indicate that the postpolymerization condition of 30 minutes and 40 °C affords the highest trueness and precision and the most favorable intaglio surface adaptation of the denture. CONCLUSIONS: The postpolymerization conditions influenced the RMSE values of the trueness and precision of a clear photopolymer resin. The RMSE and color map data associated with the 30-minute and 40 °C condition corresponded to the greatest trueness and precision of all the SLA denture specimens considered.

Trueness and precision of artificial teeth in CAD-CAM milled complete dentures with custom disks.

STATEMENT OF PROBLEM: Insufficient information is available regarding the trueness and precision of artificial teeth in computer-aided design and computer-aided manufacturing (CAD-CAM) milled complete dentures fabricated from custom disks, including prefabricated teeth. PURPOSE: The purpose of this in vitro study was to determine the trueness and precision of the position of the artificial teeth arranged in CAD-CAM milled complete dentures manufactured by using a custom disk method and to compare the trueness and precision of different tooth types and the occlusal surface and entire surface of the teeth. MATERIAL AND METHODS: The milling data were designed by using a CAD software program. Four types of artificial teeth (maxillary-left central incisor, mandibular-left central incisor, maxillary-left first premolar, and maxillary-left first molar) were arranged concentrically in the disk with 3 corresponding teeth per disk. Five custom disks were milled based on the milling data. The sample size for maxillary-left central incisor, mandibular-left central incisor, maxillary-left first premolar, and maxillary-left first molar was 15. The standard tessellation language data were obtained by scanning the milled disks with cone beam computed tomography. The obtained data were superimposed by using a CAD software program to assess the trueness and precision of the tooth positions. For the occlusal surface, the data were superimposed after trimming to assess the trueness and precision of the tooth position with respect to the entire tooth surface. After data superimposition, the deviation was analyzed by using a 3-dimensional analysis software program to obtain the mean absolute error values and color maps. The data were analyzed by using 2-way ANOVA and the Games-Howell post hoc test (α=.05). RESULTS: Significant differences were found in the mean absolute error values of the position trueness of the entire surface between the different teeth, except for maxillary-left first premolar and maxillary-left first molar (P<.05). Moreover, significant differences in the mean absolute error values of the precision for the entire surface were observed between mandibular-left central incisor and maxillary-left first premolar, as well as between mandibular-left central incisor and maxillary-left first molar (P<.05). The mean absolute error values of the position trueness of the occlusal surface were significantly smaller than those for the entire tooth surface for mandibular-left central incisor, maxillary-left first premolar, and maxillary-left first molar (P<.05). Finally, the mean absolute error values of the position precision of the occlusal surface were significantly smaller than those for the entire tooth surface for mandibular-left central incisor and maxillary-left first premolar (P<.05). CONCLUSIONS: The trueness and precision of the posterior teeth were higher than that of anterior teeth. The trueness of the movement of the artificial teeth during the manufacturing of dentures by using the custom disk method was found to be within a clinically acceptable range.

Comparison of Mechanical Properties of PMMA Disks for Digitally Designed Dentures.

In this study, the physical properties of a custom block manufactured using a self-polymerizing resin (Custom-block), the commercially available CAD/CAM PMMA disk (PMMA-disk), and a heat-polymerizing resin (Conventional PMMA) were evaluated via three different tests. The Custom-block was polymerized by pouring the self-polymerizing resin into a special tray, and Conventional PMMA was polymerized with a heat-curing method, according to the manufacturer's recommended procedure. The specimens of each group were subjected to three-point bending, water sorption and solubility, and staining tests. The results showed that the materials met the requirements of the ISO standards in all tests, except for the staining tests. The highest flexural strength was exhibited by the PMMA-disk, followed by the Custom-block and the Conventional PMMA, and a significant difference was observed in the flexural strengths of all the materials (p < 0.001). The Custom-block showed a significantly higher flexural modulus and water solubility. The water sorption and discoloration of the Custom-block were significantly higher than those of the PMMA-disk, but not significantly different from those of the Conventional PMMA. In conclusion, the mechanical properties of the three materials differed depending on the manufacturing method, which considerably affected their flexural strength, flexural modulus, water sorption and solubility, and discoloration.