In vitro evaluation of the accuracy and precision of intraoral and extraoral complete-arch scans.

STATEMENT OF PROBLEM: The accuracy of intraoral and extraoral scanners for different models of edentulousness is unclear. PURPOSE: The purpose of this in vitro evaluation was to determine the accuracy (trueness and precision) of complete-arch scans made by 3 intraoral and 1 extraoral scanners compared with an industrial 3D scanner. MATERIAL AND METHODS: Digital scans were made of a reference cast with 3 intraoral scanners (CEREC Omnicam; Dentsply Sirona, TRIOS 3; 3shape A/S; Carestream CS 3600; Carestream Dental) and an extraoral scanner (Deluxe scanner; Open Technologies). A dental maxilla model was used for tooth preparation for ceramic restorations with a shoulder finishing line. Maxillary right central and lateral incisors and third molar and maxillary left second premolar and first and third molar teeth were removed. One operator scanned the reference cast 10 times with each scanner. All the recorded standard tessellation language (STL) files were imported into an inspection software program and individually overlaid on the STL file for the reference model made by the 3D scanner. The measured distance between the distal point of the maxillary left second molar tooth and the mesial point of the maxillary left first premolar was defined as distance 1; distance 2 was defined as the distance between the mesial point of the maxillary second molar tooth and the distal point of the maxillary right first premolar tooth. The Levene test for homoscedasticity of variances was used to evaluate precision, and a 2-way repeated-measures ANOVA and Bonferroni-corrected Student t tests were used to evaluate trueness (α=.05). RESULTS: A statistically significant difference was found between the Carestream scanner and the other scanners when scanning both mucosa and teeth. The Carestream scanner had the lowest accuracy and highest magnitude mean deviation of all the scanners. CONCLUSIONS: Obtaining an accurate partial-arch impression is still challenging for some intraoral scanners. The Carestream scanner's trueness was outside the acceptable range. However, other scanners tested here appeared to be suitable alternatives to conventional impression techniques.

Marginal Bone Loss Around One-Piece Implants: A 10-Year Radiological and Clinical Follow-up Evaluation.

PURPOSE: This study was conducted to investigate one-piece narrow-diameter implants installed in maxillary lateral and mandibular incisor sites using immediate nonfunctional loading. MATERIALS AND METHODS: In this 10-year clinical trial study, 42 narrow-diameter (3.0-mm) one-piece implants for 35 patients were inserted. Clinical and radiographic measurements were recorded in 10 years and analyzed statistically using t test. RESULTS: A total of 26 patients (20 females and 6 males) with 30 implants were available for the 10-year follow-up. The 10-year implant survival rate was 100%. A statistically significant mean marginal bone loss was observed between 12 months and 10 years (0.18 ± 0.29 mm). The mean pocket depth increase was statistically significant (0.68 ± 0.83 mm). No bleeding on probing was observed around 90% of the implants. Full-mouth plaque index was registered at 20% of the implants. CONCLUSION: The results obtained in this analysis suggest that modest marginal bone loss was observed around the implants. One-piece narrow-diameter implants (Maximus 3.0; BioHorizons) can predictably restore missing maxillary lateral incisors and mandibular incisors in cases of careful patient selection.

In Vitro Comparison of Microbial Leakage of the Implant-Healing Abutment Interface in Four Connection Systems.

This study sought to assess microbial leakage through the implant-healing abutment interface in 4 dental implant connection systems. Ten implants of each of the 3i (double hexagon + flat to flat; group 1), IDI (internal hexagon + Morse taper; group 2), Swiss Plus (external bevel + internal octagon; group 3), and Tapered Screw-Vent (internal bevel + internal hexagon; group 4) systems were used in this in vitro, experimental study. Healing abutments were screwed to the implants with 10 Ncm torque. Implants were immersed in Escherichia coli suspension for 24 hours. Samples were taken of the internal surface of implants and cultured. The number of grown colonies was counted after 24 hours of culture and after 7 and 14 days of immersion in microbial suspension. The same was repeated with healing abutments torqued to 10 and 20 Ncm. With 10 Ncm torque, all specimens in all groups showed microleakage at one day with the highest microleakage in one sample in group 3. At 7 days, the highest microleakage was noted in one specimen in group 2. With 20 Ncm torque, group 3 showed significantly higher microleakage than other groups at 1 and 7 days (P < .05). Increasing the torque decreased microleakage in all groups except for group 3. Microbial leakage occurred in almost all implant systems in our study. In one-stage implant placement, healing abutments should be preferably torqued to 20 Ncm to minimize microleakage. Optimal torque for healing abutment insertion should be analyzed individually for each system.

Effects of Excessive Implant Angulation on Retention of Two Types of Overdenture Attachments during Cyclic Loading.

AIM: This study investigated the effects of implant angulation and cyclic dislodgment on retention of Locator and Dalbo Plus attachments. MATERIALS AND METHODS: Fifty pairs of acrylic blocks for five implant angulations (0, 10, 20, 30 and 40 degrees) and two attachment systems (locator and Dalbo Plus®; n = 5) were fabricated. In each pair, one block contained two implant analogs connected to their attachments, and the other block contained matrix parts of the attachments. 1440 cycles of insertion and removal were implicated on specimens after mounting the blocks in the universal testing machine. The retention was registered at cycle numbers 1, 120, 360, 720, and 1440. Data were analyzed using one-way analysis of variance (ANOVA) and Duncan's multiple range test (p ≤ 0.05). RESULTS: Data analysis showed that implant angulation had significant effects on retention of both attachments at all different angles (p ≤ 0.05). Dalbo Plus showed no significant differences between 30 and 40 degrees (p ≥ 0.05), but between 0 and 30 degrees, differences were significant (p ≤ 0.05). Moreover, cyclic loading had significant effects on retention of both attachments at all different loading cycles (p ≤ 0.05). On evaluating combined effects of cyclic loading and implant angulation on retention, a significant decrease in retention was noted for both Locator and Dalbo Plus attachments at angulations of 0, 10, 20 degrees after 1440 cycles (1 year of clinical use; p ≤ 0.05). CONCLUSION: Both angulation and cyclic loading have negative effects on implant-supported overdentures and decrease retention over time. Furthermore, as the angle between implants increases, decrement of retention becomes more significant. CLINICAL SIGNIFICANCE: Inter-implant angulation could play a significant role in overdenture retention Keywords: Dental implants; Dental prosthesis; Implant angula-tion; Implant-supported Overdenture; Retention.

Effect of Interimplant Distance and Cyclic Loading on the Retention of Overdenture Attachments.

AIM: The purpose of this in vitro study was to investigate the effect of interimplant distance and cyclic loading on the retention of two locator attachment systems. MATERIALS AND METHODS: A total of 72 acrylic resin blocks were fabricated and divided into six groups of six pairs each. Locators of DIO and 3i implant systems were positioned on analogs in three different interimplant distances (19, 23, and 29 mm). The blocks were attached to a universal testing machine, and 1,440 dislodging cycles by the force of 136 N were applied. After 0, 120, 360, 720, and 1,440 cycles, the retention was recorded. Three-way analysis of variance (ANOVA) was used to test for differences in retention between the various combinations of the locator, interimplant distance, and cyclic loadings. RESULTS: Interimplant distance was significantly associated with retention, independent of the locator system used, and dislodge-ment force cycles. Mean retention was significantly higher under the 3i system relative to the DIO system (p < 0.0001). This association varied with both interimplant distance (p > 0.0001) and dislodgement force (p < 0.0001) as well as across the various combinations of distance and cycle (p < 0.0001). CONCLUSION: Interimplant distances could affect the initial retention of locator attachments. There was little difference in retention between distances of 23 and 29 mm across all cycles when both locator systems were combined. Distance of 23 mm was associated with superior retention in the DIO system. With regard to the speed of retention decrease, the 23 mm distance was associated with better performance. CLINICAL SIGNIFICANCE: Interimplant distance could play a significant role in overdenture retention with locator attachments.

Onlay bone augmentation and bilateral open sinus lifting with simultaneous implant placement in a cherubic patient.

A 20-year-old edentulous woman, who was previously treated with the shave of the inferior border of the mandible and malar prominent region for aesthetic facial contouring, was selected for full mouth rehabilitation of the maxillomandibular region. The patient was treated with bilateral open sinus lifting through a lateral approach in the posterior of the maxilla and an onlay bone graft with lateral ramus as a donor site in the mandible anterior. Eight implants in the maxilla and 7 in the mandible were inserted, and implant-supported prostheses were fabricated. The 18-month follow-up showed good bone condition that suggests graft interventions and implant treatment as a good treatment modality for patients with cherubism.

Evaluation of the accuracy of digital and conventional implant-level impression techniques for maxillofacial prosthesis.

Objectives: This study aims to evaluate the accuracy of digital impression making based on trueness and precision measurements of dental implants placed in maxillofacial lesions to produce Maxillofacial prosthesis substructures. Methods: Two intra-oral scanners (Trios 3 and CS 3700) and one Desktop scanner (open technology) were examined in this study. A Model of a patient with a lesion in the ear region was created as a reference. The reference model was scanned by each scanner 10 times. Standard Tessellation Language files were provided from each scanner and were examined in terms of Trueness and Precision aspects. Results: In Distance 1, in the one-way analysis of variance test, there was a significant difference between the three scanners. The Trios group has less deviation than the Open Technology group (P = 0.015) compared with the CareStream (CS) group that showed more deviation (P < 0.000). There is a statistically significant difference in distance 2 among scanners. The Trios group showed more deviation as compared with the Open Technology group (P < 0.000). While this deviation is not statistically significant compared with the CS group (P = 0.0907). Open Technology Group compared with the CS group also has less deviation in distance 2, which has been statistically significant (P < 0.000). The preparation of a precise model of maxillofacial lesions is still difficult for some Intraoral scanners. Conclusion: There were significant statistical differences in Trueness and Precision among scanners. Used scanners can be applied as an alternative to conventional impression methods.

The Clinical Evaluation of the Effects of Low-Level Laser Therapy on the Donor and Recipient Sites of the Free Gingival Graft: A Case Series.

Introduction: Free gingival grafting is among the most foreseeing procedures for increasing the zone of keratinized attached gingiva and enhancing soft tissue around the teeth and dental implants. Nowadays low-level laser therapy (LLLT) is a promising approach in providing patients with more pleasing results in terms of esthetics and comfort. This study aims to investigate the effects of LLLT on gingival recessions treated with free gingival graft (FGG). Methods: This case series was conducted on 12 individuals requiring a bilateral gingival graft in the mandibular region. There was a 30-day interval between the two operations. The test side was selected randomly and irradiated by a low-level laser (LLL) just before surgery. The patients did not know which side was irradiated. LLLT was applied to the donors' as well as recipients' site immediately after the operation and 48 hours later. The patients were instructed to record their post-operative pain in a visual analogue scale (VAS) 3 and 24 hours and 7 days after the surgical procedure. The clinical photographs were taken immediately and 30 days after surgical treatment were graded by three experienced periodontists for color matching to adjacent tissues. Results: Ten individuals could finish the study. The test group presented significantly better shade matching and wound healing at the palatal donor site on days 7, 14 and 21. There was a significant reduction in post-operative pain after 24 hours (P = 0.007). No statistically significant difference was found between both groups in terms of clinical periodontal indices. Conclusion: LLLT could reduce post-operative pain 24 hours after surgical treatment. Furthermore, the application of LLLT could improve the donors' site healing and the recipients' site color matching.

Patterns of stress and strain in complete-arch prostheses supported by four or six implants: A literature review of finite element analyses.

Background: Tilted implants have been recommended as an alternative to the bone graft procedures in implant sites although with possibly higher stress concentrations. This study reviews finite element studies to evaluate patterns of stress and strain in complete-arch prostheses supported by 4‒6 implants. Methods: A literature search was performed using the online databases. Articles published in English from 2003 to 2015 were reviewed. A total of 100 articles were found related to the subject and after evaluating the titles and abstracts, 18 studies were selected. Results: By increasing the number of implants, a reduction was detected in the amount of stress in the bone and implants, while in others, the stress level did not change with the increase in the number of implants. Conclusion: According to finite element analyses, placing a distal implant in an angular position results in better distribution of forces and stresses. Using less cantilever lengths would reduce the stress.

Correlation between frontal sinus dimensions and cephalometric indices: A cross-sectional study.

OBJECTIVE: Growth prediction plays a significant role in accurate diagnosis and treatment planning of orthodontics patients. It was hypothesized that the unique pattern of pneumatization of the frontal sinus as a component of craniofacial structure would influence the skeletal growth pattern and may be used as a growth predictor. MATERIALS AND METHODS: A total of 144 subjects (78 females and 66 males) with a mean age of 19.26 ± 4.66 years were included in this retrospective study. Posterior-anterior and lateral cephalograms (LCs) were used to measure the frontal sinus dimensions. The skeletal growth pattern and relations of craniofacial structures were analyzed on LC using variables for sagittal and vertical analyses. Correlation between the frontal sinus dimensions and cephalometric indices was assessed by the Pearson's correlation coefficient. RESULTS: The SN-FH and SNA angles had significant associations with frontal sinus dimensions in all enrolled subjects (P < 0.05). In males, the SN-FH, sum of posterior angles, Pal-SN, and Jarabak index were significantly associated with the size of frontal sinus (P < 0.05). In females, the associations of SN-FH and gonial angles with frontal sinus dimensions were significant (P < 0.05). CONCLUSION: The results show that larger size of frontal sinus was associated with reduced inclination of the anterior cranial base, increased anterior facial height (in males), and increased gonial angle (in females) in the study population.

The effect of deproteinized bovine bone mineral on saos-2 cell proliferation.

INTRODUCTION: Deproteinized bovine bone mineral (Bio-Oss) is a xenogenic bone substitute, widely used in maxillofacial bone regeneration. The aim of this in vitro study was to investigate its influence on the growth behavior of human osteosarcoma cell line, Saos-2 culture, and compare it with the physiologic dose of Dexamethasone, an inductive factor for osteoblasts. MATERIALS AND METHODS: Human osteosarcoma cells, Saos-2, were cultured on Bio-Oss and their growth rate was compared to Saos-2 cultures treated with Dexamethasone 10(-7) M in contrast to cells cultivated in PBS, in the control group. Assessment of proliferation was performed after 24, 36, and 48 hours by counting cells using trypan blue exclusion method. Alkaline phosphatase was measured spectrophotometrically at 405 nm with paranitrophenol buffer. RESULTS: After 48 hours, the number of Saos-2 cells increased significantly when subcultured with Bio-Oss. Bio-Oss was more effective on the enhancement of proliferation of Saos-2 cells when compared to the physiologic dose of Dexamethasone (P<0.05). Alkaline phosphatase activity increased in cells grown on Bio-Oss and dexamethasone 10(-7) M in contrast to cells cultivated in PBS control group. The greatest level of activity was observed in the group containing Bio-Oss after 48 hour. CONCLUSION: The significant increase of cell proliferation and alkaline phosphatase activity in cells cultured on Bio-Oss, compared to Dexamethasone-treated cells, suggests the important role of this bone substitute in promoting bone regeneration.