An esthetic clinical approach for the management of an infrapositioned implant-retained maxillary incisor crown.

Infrapositioning of implants in the maxillary anterior region can cause esthetic complications, including soft tissue problems. These complications commonly occur in implants placed in young adults. However, there are many clinical reports of implant infrapositioning in the maxillary anterior region after the fourth decade of life. This clinical report describes a case of infrapositioning of the maxillary central incisor wherein esthetic results were obtained through surgical and prosthetic approaches. The surgical approach improved the gingiva shape using the tunnel technique, and the prosthetic approach increased gingiva thickness by adjusting the shape of the abutment, resulting in a shape similar to the natural teeth.

Effect of scan body designs and internal conical angles on the 3-dimensional accuracy of implant digital scans.

STATEMENT OF PROBLEM: Axial displacement is inevitable when connecting scan bodies to implants for digital scans using intraoral scanners, and axial displacement may reduce implant position accuracy in digital casts. However, studies assessing scan body type and accuracy are lacking. PURPOSE: The purpose of this in vitro study was to assess the linear and angular displacements of implants in digital casts using 2 scan body types with or without a vertical stop to minimize the axial displacement and 2 internal conical connection implants (ICCIs) with different internal conical angles. MATERIAL AND METHODS: Two identical reference casts were fabricated from epoxy resin by duplicating a partially edentulous mandibular dentiform. Each cast received 3 implants in the left first premolar, first molar, and second molar regions. One cast received an ICCI with a 7-degree internal conical angle (7-degree ICCI), and the other received an ICCI with an 11-degree internal conical angle (11-degree ICCI). A 10-mm polyetheretherketone (PEEK) cube was attached to the buccal area of the mandibular second premolar of each reference cast. A vertical stop was used in the experimental scan bodies to minimize the axial displacement, and conventional scan bodies were hand tightened to the implants in the reference casts. An intraoral scanner was used to fabricate 4 digital cast groups (2 implant types and 2 scan body types; each group had 10 casts). A coordinate measuring machine and digital inspection software program were used to measure the implant platform centroids (x, y, z) and projection angles (θXY, θYZ, θZX) of implant long axes in the reference and digital casts, respectively. One-way analysis of variance (ANOVA) and linear mixed model both with Tukey post hoc and 2-way ANOVA tests were performed to assess the significance of linear and angular displacements between groups (α=.05). RESULTS: Significant differences were noted in all linear displacement variables among the 4 digital cast groups, except for Δx in the left first premolar implant. For the 7-degree ICCI, the linear displacement was statistically similar in the experimental and conventional scan bodies. However, for the 11-degree ICCIs, the experimental scan body group resulted in significantly smaller Δy, Δz, and Δd (Δd2=Δx2+Δy2+Δz2) than the conventional scan body group (P<.05). Overall, the 11-degree ICCIs demonstrated a significantly greater linear displacement than the 7-degree ICCI, regardless of the scan body type (P<.05). Significant differences between the test groups were observed for 10 of the 12 angular displacement variables (P<.05). CONCLUSIONS: The 11-degree ICCIs demonstrated significantly greater linear displacements in Δy, Δz, and Δr than the 7-degree ICCIs. The experimental scan bodies with a vertical stop demonstrated significantly smaller linear displacements in the 11-degree ICCIs.

Comparative Analysis of Bone Regeneration According to Particle Type and Barrier Membrane for Octacalcium Phosphate Grafted into Rabbit Calvarial Defects.

This animal study was aimed to evaluate the efficacy of new bone formation and volume maintenance according to the particle type and the collagen membrane function for grafted octacalcium phosphate (OCP) in rabbit calvarial defects. The synthetic bone substitutes were prepared in powder form with 90% OCP and granular form with 76% OCP, respectively. The calvarial defects were divided into four groups according to the particle type and the membrane application. All specimens were acquired 2 weeks (n = 5) and 8 weeks (n = 5) after surgery. According to the micro-CT results, the new bone volume increased at 2 weeks in the 76% OCP groups compared to the 90% OCP groups, and the bone volume ratio was significantly lower in the 90% OCP group after 2 weeks. The histomorphometric analysis results indicated that the new bone area and its ratio in all experimental groups were increased at 8 weeks except for the group with 90% OCP without a membrane. Furthermore, the residual bone graft area and its ratio in the 90% OCP groups were decreased at 8 weeks. In conclusion, all types of OCP could be applied as biocompatible bone graft materials regardless of its density and membrane application. Neither the OCP concentration nor the membrane application had a significant effect on new bone formation in the defect area, but the higher the OCP concentration, the less graft volume maintenance was needed.

Impact of profile angle of CAD-CAM abutment on the marginal bone loss of implant-supported single-tooth posterior restorations.

STATEMENT OF PROBLEM: Although the emergence angle has been related to marginal bone loss, information regarding the relationship between the transmucosal configuration of a computer-aided design and computer-aided manufacturing (CAD-CAM) abutment at specific subgingival levels and the amount of marginal bone loss is lacking. PURPOSE: The purpose of this retrospective clinical study was to evaluate the influence of CAD-CAM abutment profile angles, measured at different subgingival positions, on the marginal bone loss of posterior single-tooth implant-supported restorations. MATERIAL AND METHODS: A total of 260 posterior single-tooth implant-supported restorations using CAD-CAM abutments were analyzed in 206 patients. All implants had internal conical seal connections with a platform-switched design. The following data were extracted using digital periapical radiography: emergence profile, profile angle at distance ranges of 0 to 1 mm, 1 to 2 mm, and 2 to 3 mm from the implant-abutment junction, and peri-implant marginal bone loss (MBL). The MBL was measured from the time of delivery of the restorations up to 7 years or more. A linear mixed model was applied to investigate whether there was a significant difference in MBL based on the emergence profile and time, followed by the Bonferroni correction post hoc test. A Pearson correlation analysis was used to analyze the correlation between the profile angle and MBL at each distance range. The cut-off points for each distance range were determined by using the c-index, and independent t tests were conducted based on these cut-off values to evaluate the statistical differences (α=.05 for all statistical analyses). RESULTS: The convex emergence profile exhibited greater MBL than the concave and straight profiles at each follow-up visit (P<.001). A significant correlation was found between the profile angle and MBL in the 0 to 1 mm, 1 to 2 mm distance ranges. However, no significant correlation was found between the profile angle and MBL in the 2 to 3 mm distance range (P>.05). The cut-off points were 34 degrees at the mesial and 28 degrees at the distal in the 0 to 1 mm range, and 33 and 20 degrees at the mesial and distal in the 1 to 2 mm range. CONCLUSIONS: The profile angle near the implant-abutment junction and the type of emergence profile of the CAD-CAM abutment were closely associated with MBL in implants with internal conical seal connection with a platform switch design.

Digital mounting accuracy of 2 intraoral scanners with a single anterior or bilateral posterior occlusal scan: A three-dimensional analysis.

STATEMENT OF PROBLEM: Although intraoral scanners (IOSs) are popular, few studies have evaluated the accuracy of digital mounting by using IOSs. PURPOSE: The purpose of this in vitro study was to compare the accuracy of digital mounting by using 2 IOSs and 2 occlusal scanning methods. MATERIAL AND METHODS: Fourteen Ø5-mm zirconia balls were attached approximately 5 mm apical to the free gingival margin of both second molars, second premolars, and canines and between the central incisors in maxillary and mandibular epoxy casts. A polyetheretherketone hexagonal cube with a 10-mm-long edge was attached to the buccal side of the missing mandibular right first molar area, and the cube was used to set a part coordinate system. Two IOSs (TRIOS 3, Primescan) were used to assess the intra-arch and interarch accuracies. For intra-arch assessment, each IOS was used to digitally scan the mandibular epoxy cast 15 times and fabricate 15 datasets. The deviation of each zirconia ball centroid was statistically compared between the IOSs. For interarch assessment, each IOS was used to digitally scan the maxillary and mandibular epoxy casts, and the data were digitally mounted by using a single anterior occlusal scan (A) or bilateral posterior occlusal scan (P). Both occlusal scans were performed 15 times; therefore, 4 groups (15 datasets per group) of mounted digital datasets were assigned. The deviation of each maxillary zirconia ball centroid, as well as the interarch distance between the corresponding maxillary and mandibular zirconia ball centroids, were compared among the 4 groups. For statistical analysis, the Mann-Whitney U test and Kruskal-Wallis test with Bonferroni correction were used (α=.05). RESULTS: Primescan had less deviation than TRIOS 3 in the complete arch scan. When the zirconia balls were close to the origin, the bilateral posterior occlusal scan produced less deviation of their centroids. Primescan produced decreased interarch distance in the anterior and posterior dentition, while TRIOS 3 produced increased interarch distance in the anterior dentition and decreased interarch distance in the posterior dentition. CONCLUSIONS: A significant difference was noted in intra-arch accuracy between the IOSs, and the difference influenced the digital mounting accuracy. The type of occlusal scan and IOS significantly influenced the accuracy of digital mounting. Both IOSs produced decreased interarch distances in the second molar area.

Comparison of the clinical outcomes of resin-modified glass ionomer and self-adhesive resin cementations for full-coverage zirconia restorations.

OBJECTIVES: Both resin-modified glass ionomer cement (RMGIC) and self-adhesive resin cement (SAC) may be suitable for cementation of full-coverage zirconia restorations. This retrospective study aimed to investigate the clinical outcomes of zirconia-based restorations cemented with RMGIC and compare them with those cemented with SAC. METHODS: Cases of full-coverage zirconia-based restorations cemented with either RMGIC or SAC between March 2016 and February 2019 were evaluated in this study. The clinical outcomes of the restorations were analyzed according to the type of cement used. In addition, cumulative success and survival rates were evaluated according to the cement and abutment types. Non-inferiority, Kaplan-Meier, and Cox hazard tests were conducted (α=.05). RESULTS: A total of 288 full-coverage zirconia-based restorations (natural teeth, 157; implant restorations, 131) were analyzed. Loss of retention occurred in only one case; a single-unit implant crown cemented with RMGIC, which decemented 4.25 years post-restoration. RMGIC was non-inferior to SAC in terms of loss of retention (<5%). For single-unit natural tooth restorations, the four-year success rates in the RMGIC and SAC groups were 100% and 95.65%, respectively (p=.122). For single-unit implant restorations, the four-year success rates in the RMGIC and SAC groups were 95.66% and 100%, respectively (p=.365). The hazard ratios of all the predictor variables, including cement type, were not significant (p>.05). CONCLUSIONS: Cementation of full-coverage zirconia restorations of both natural teeth and implants using RMGIC and SAC yields satisfactory clinical outcomes. Furthermore, RMGIC is non-inferior to SAC in terms of cementation success. CLINICAL SIGNIFICANCE: Cementation with RMGIC or SAC for full-coverage zirconia restorations has favorable clinical outcomes in both natural teeth and implants. Both RMGIC and SAC have advantages in the cementation of full-coverage zirconia restorations to abutments with favorable geometries.

Up to a 15-Year Survival Rate and Marginal Bone Resorption of 1780 Implants with or without Microthreads: A Multi Center Retrospective Study.

The effect of microthreads at the implant neck on the amount of marginal bone resorption is controversial. This multicenter retrospective study compared the implant survival rate and amount of marginal bone resorption between two platform-switching internal connection implant systems with or without microthreads. Patient-related (age and sex), surgery-related (implant installation site, type, diameter, and length), and prosthesis-related (prosthesis type) data were collected from patient charts from the implant placement surgery to the final recall visit. A total of 1780 implants, including 1379 with microthreads and 401 without microthreads, were placed in 804 patients. For implants with and without microthreads, the longest follow-up period after prosthesis delivery was 15 and 6 years, respectively. Twenty implants failed during the 15-year follow-up period (98.8% survival rate) due to failed osseointegration, peri-implantitis, implant fractures, and non-functioning implants. The mean marginal bone loss was < 0.1 mm for both implant systems at the 1-year follow-up and 0.18 mm and 0.09 mm at the 4-year follow-up for implants with and without microthreads, respectively, without statistical significance. Microthreads did not significantly affect the amount of marginal bone loss or the implant survival rate for implants with an internal connection with a platform-switching design.

Advancements in Methods of Classification and Measurement Used to Assess Tooth Mobility: A Narrative Review.

Evaluating tooth mobility is clinically significant, not only for diagnosing periodontal tissues but also in determining the overall periodontal treatment plan. Numerous studies related to tooth mobility have been conducted over the years, including the proposal of various classifications as well as the development of electronic devices for objective measurement. However, there is still no consensus on the measurement methods and criteria for assessing tooth mobility. In this study, we provide a comprehensive review of past and current tooth mobility classification and measurement methods. In order to propose a new method to intuitively evaluate tooth mobility based on previous studies, a digital approach capable of recording tooth micromovements induced by dynamic load should be considered.

Reliability Verification of Damping Capacity Assessment Through In Vitro Analysis of Implant Micromotion in Peri-implant Bone Loss Model.

PURPOSE: This in vitro study aimed to determine the efficacy of a damping capacity assessment in evaluating the implant stability in a simulated peri-implant bone loss model. MATERIALS AND METHODS: The same type of implant was placed sequentially in 0.5-mm-depth increments in polyurethane bone of a constant density, resulting in 11 specimens with varying surrounding bone levels. The implant stability was evaluated by a damping capacity assessment consisting of six consecutive impacts in one set. The damping results, including the contact time and stability index, were measured by three repeated sets of stability tests for each specimen. All implant micromotions were recorded in real time using a laser scanning vibrometer during these stability tests. The micromotions were analyzed in terms of three parameters: maximum displacement, expected mobility, and vibration frequency. Additionally, two other stability indices were acquired three times each for reference. Pearson correlation analysis was used to confirm the correlations among all the variables; P < .05 was considered statistically significant. RESULTS: As the peri-implant bone level increased, the contact time results decreased gradually from 502 to 290 µs, and the stability index increased from 55 to 78. The implant micromotions of all specimens showed a damped sine waveform graph, which can be divided into impact displacement and self-vibration patterns by the contact end points. As the implant stability increased, these contact end points converged toward the third peak, the maximum displacement and expected mobility decreased, and the vibration frequency increased (ρ = -0.85, -0.88, and 0.99, respectively). Two other stability indices reflected the implant stability due to peri-implant bone loss. The statistical analysis indicated significant correlations among all measured variables; in particular, the three stability indices exhibited high correlations with each other (ρ = 0.99, -0.99, and -1.00, respectively). CONCLUSION: Within the limitations of this in vitro study, the implant stability measured by a damping capacity assessment was suitable for investigating the extent of implant micromotions, which were determined by 0.5-mm horizontal changes in the peri-implant bone level.

Ceramic Materials and Technologies Applied to Digital Works in Implant-Supported Restorative Dentistry.

Computer-aided design and manufacturing technology has been closely associated with implant-supported restoration. The digital system employed for prosthodontic restorations comprises data acquisition, processing, and manufacturing using subtractive or additive methods. As digital implantology has developed, optical scanning, computer-based digital algorithms, fabricating techniques, and numerical control skills have all rapidly improved in terms of their accuracy, which has resulted in the development of new ceramic materials with advanced esthetics and durability for clinical application. This study reviews the application of digital technology in implant-supported dental restoration and explores two globally utilized ceramic restorative materials: Yttria-stabilized tetragonal zirconia polycrystalline and lithium disilicate glass ceramics.

Comparison of implant stability measurements between a resonance frequency analysis device and a modified damping capacity analysis device: an in vitro study.

PURPOSE: A stability-measuring device that utilizes damping capacity analysis (DCA) has recently been introduced in the field of dental implantology. This study aimed to evaluate the sensitivity and reliability of this device by measuring the implant stability of ex vivo samples in comparison with a resonance frequency analysis (RFA) device. METHODS: Six implant beds were prepared in porcine ribs using 3 different drilling protocols to simulate various implant stability conditions. Thirty-six pork ribs and 216 bone-level implants measuring 10 mm in height were used. The implant beds were prepared using 1 of the following 3 drilling protocols: 10-mm drilling depth with a 3.5-mm-diameter twist drill, 5-mm drilling depth with a 4.0-mm-diameter twist drill, and 10-mm drilling depth with a 4.0-mm-diameter twist drill. The first 108 implants were external-connection implants 4.0 mm in diameter, while the other 108 implants were internal-connection implants 4.3 mm in diameter. The peak insertion torque (PIT) during implant placement, the stability values obtained with DCA and RFA devices after implant placement, and the peak removal torque (PRT) during implant removal were measured. RESULTS: The intraclass correlation coefficients (ICCs) of the implant stability quotient (ISQ) results obtained using the RFA device at the medial, distal, ventral, and dorsal points were 0.997, 0.994, 0.994, and 0.998, respectively. The ICCs of the implant stability test (IST) results obtained using the DCA device at the corresponding locations were 0.972, 0.975, 0.974, and 0.976, respectively. Logarithmic relationships between PIT and IST, PIT and ISQ, PRT and IST, and PRT and ISQ were observed. The mean absolute difference between the ISQ and IST values on a Bland-Altman plot was -6.76 (-25.05 to 11.53, P<0.05). CONCLUSIONS: Within the limits of ex vivo studies, measurements made using the RFA and DCA devices were found to be correlated under a variety of stability conditions.

Methods Used to Assess the 3D Accuracy of Dental Implant Positions in Computer-Guided Implant Placement: A Review.

The purpose of this review is to examine various assessment methods in order to compare the accuracy between the virtually planned and clinically achieved implant positions. In this review, comparison methods using pre- and post-operative computed topography (CT) data and digital impressions for definitive prosthesis will be described. The method for the displacement and strain for quantification of the error will also be explored. The difference between the planned and the actual implant placement position in guided implant surgery is expressed as an error. Assessing the accuracy of implant-guided surgery can play an important role as positive feedback in order to reduce errors. All of the assessment methods have their own inevitable errors and require careful interpretation in evaluation.

Photofunctionalization enhances bone-implant contact, dynamics of interfacial osteogenesis, marginal bone seal, and removal torque value of implants: a dog jawbone study.

OBJECTIVE: Ultraviolet (UV) light treatment of titanium, ie, photofunctionalization, has been extensively reported to enhance the osteoconductivity of titanium in animal and in vitro studies. This is the first study to examine whether photofunctionalization is effective on commercial dental implants in vivo. MATERIALS AND METHODS: Dental implants with a microroughened surface were placed into dog jawbones. Photofunctionalization was performed by treating implants with UV light for 15 minutes using a photo device immediately before placement. Four weeks after placement, bone-implant integration was evaluated using a removable torque test and static and dynamic histology. RESULTS: Implant surfaces were converted from hydrophobic to super-hydrophilic after photofunctionalization. Removable torque for photofunctionalized implants was significantly higher by 50% than that for untreated implants. Bone-implant contact (BIC) was significantly higher for photofunctionalized implants in all zones examined: marginal, cortical, and bone marrow zones. An intensive mineralized layer was exclusively present in marginal bone at photofunctionalized interface. Dynamic histology identified early-onset, long-lasting robust bone deposition at photofunctionalized interface. CONCLUSIONS: Photofunctionalization enhanced the morphology, quality, and behavior of periimplant osteogenesis, including the increased BIC, expedited robust interfacial bone deposition, and improved marginal bone seal and support.