Accuracy of Guided Implant Surgery in 25 Edentulous Arches: A Laboratory Observational Study.

PURPOSE: To assess the accuracy of template-guided implant surgery for edentulous arches. MATERIALS AND METHODS: The stone master casts of 25 edentulous arches treated with either 4 or 6 implants with CBCT generated template-guided surgery were included in this observational cohort study. The stone casts generated from the surgical templates (group one) prior to implant placement were digitized into Standard Tesselation (STL) files with a reference scanner. For comparison, the stone master casts derived from intraoral complete-arch impressions after implant placement (group two) were also digitized. The resultant STL files were superimposed and best-fit-alignment algorithm was used to quantify the 3D deviations present between the two groups. Descriptive statistics were computed for all categorical variables. Due to the presence of nonindependent samples between maxillary and mandibular casts, a mixed-effects model was used. RESULTS: Deviations between the implant analogs of the stone casts representing digitally planned versus actually placed implants were found. The mean root-mean-square error (RMSE) between all 25 arches was found to be 0.2 mm (SD ± 0.15). The mean RMSE between presurgical and postsurgical maxillary stone casts were 0.19 ± 0.15 mm, while between mandibular stone casts were 0.21 ± 0.16 mm and were not significant (p = 0.67). The mean RMSE between presurgical and postsurgical stone casts arches with 4 versus 6 implants were found to be significant (p = 0.01). CONCLUSIONS: According to the results of the study and based on the amount of 3D deviations between the digitally planned implant positions and the actually placed implants, template-guided surgery is a safe treatment modality for implant placement in edentulous arches.

Virtualization and cloud computing in dentistry.

The use of virtualization and cloud computing has changed the way we use computers. Virtualization is a method of placing software called a hypervisor on the hardware of a computer or a host operating system. It allows a guest operating system to run on top of the physical computer with a virtual machine (i.e., virtual computer). Virtualization allows multiple virtual computers to run on top of one physical computer and to share its hardware resources, such as printers, scanners, and modems. This increases the efficient use of the computer by decreasing costs (e.g., hardware, electricity administration, and management) since only one physical computer is needed and running. This virtualization platform is the basis for cloud computing. It has expanded into areas of server and storage virtualization. One of the commonly used dental storage systems is cloud storage. Patient information is encrypted as required by the Health Insurance Portability and Accountability Act (HIPAA) and stored on off-site private cloud services for a monthly service fee. As computer costs continue to increase, so too will the need for more storage and processing power. Virtual and cloud computing will be a method for dentists to minimize costs and maximize computer efficiency in the near future. This article will provide some useful information on current uses of cloud computing.

Automated Process Incorporating Machine Learning Segmentation and Correlation of Oral Diseases with Systemic Health.

Imaging fluorescent disease biomarkers in tissues and skin is a non-invasive method to screen for health conditions. We report an automated process that combines intraoral fluorescent porphyrin biomarker imaging, clinical examinations and machine learning for correlation of systemic health conditions with periodontal disease. 1215 intraoral fluorescent images, from 284 consenting adults aged 18-90, were analyzed using a machine learning classifier that can segment periodontal inflammation. The classifier achieved an AUC of 0.677 with precision and recall of 0.271 and 0.429, respectively, indicating a learned association between disease signatures in collected images. Periodontal diseases were more prevalent among males (p=0.0012) and older subjects (p=0.0224) in the screened population. Physicians independently examined the collected images, assigning localized modified gingival indices (MGIs). MGIs and periodontal disease were then cross-correlated with responses to a medical history questionnaire, blood pressure and body mass index measurements, and optic nerve, tympanic membrane, neurological, and cardiac rhythm imaging examinations. Gingivitis and early periodontal disease were associated with subjects diagnosed with optic nerve abnormalities (p<; 0.0001) in their retinal scans. We also report significant co-occurrences of periodontal disease in subjects reporting swollen joints (p=0.0422) and a family history of eye disease (p=0.0337). These results indicate cross-correlation of poor periodontal health with systemic health outcomes and stress the importance of oral health screenings at the primary care level. Our screening process and analysis method, using images and machine learning, can be generalized for automated diagnoses and systemic health screenings for other diseases.

Temperature rise produced by different light-curing units through dentin.

AIM: This study investigated the temperature rise caused by different light curing units and the temperature increase in dentin of different thicknesses. METHODS AND MATERIALS: Dentin discs of 1.0 and 2.0 mm thicknesses were prepared from extracted human mandibular molars. Temperatures were recorded directly at the surface of the light guide tip, under dentin discs with different thicknesses, and through a sandwich composed of 2 mm thick cured composite and dentin using a K-type thermocouple. The curing units used were two quartz-tungsten-halogen lights (Spectrum and Elipar Trilight-ET) and a light-emitting diode (LED). RESULTS: The highest temperature rise was observed under a Mylar strip using ET standard mode. Under 1 and 2 mm thick dentin barriers, the lowest temperature rise was measured for the LED curing light. Significant differences in temperature rise existed among all curing units except between the Spectrum and ET exponential modes under a 1 mm thick dentin barrier with cured composite. Temperature rises were insignificant between the Spectrum and ET exponential modes and between two modes of Trilight when the same experimental setup was used under a 2 mm thick dentin barrier. CONCLUSION: For all curing units, temperature elevation through 2 mm of dentin was less than for 1 mm of dentin thickness. The ET standard mode produced the highest and the LED produced the lowest temperature rise for all tested conditions. The thickness of dentin and light-curing unit might affect temperature transmission.

Three-dimensional surface profile analysis of different types of flowable restorative resins following different finishing protocols.

AIM: The aim of this study was to investigate the surface roughness of different types of flowable restorative resins and compare the effectiveness of diamond finishing burs followed by aluminum oxide discs with aluminum oxide discs alone in producing smooth surfaces. METHODS AND MATERIALS: Twenty-four specimens (10 mm X 2 mm) for each flowable resin (flowable microhybrid composite, flowable liquid microhybrid composite, flowable compomer, and flowable ormocer) were fabricated in an acrylic mold and randomly assigned to three groups. In group I samples were left undisturbed after the removal of a Mylar strip (control). In group II samples were polished with diamond finishing burs, followed by aluminum oxide discs. In group III samples were finished with only aluminum oxide discs. The mean surface roughness (Ra, microm) was determined with 3-D non-contact interferometry. Data were subjected to one way analysis of variance (ANOVA), and post hoc comparison was accomplished using Tukey's HSD. RESULTS: Although significant differences in surface roughness (Ra) values were observed among the materials using a Mylar strip (control), no significant differences between restorative materials were found when all finishing/polishing methods were combined. For all flowable restorative resins tested, the Mylar strip produced surfaces smoother than those produced by a diamond finishing bur followed by a disc or by using discs alone. Surface roughness values were statistically similar for a diamond finishing bur followed by a disc and for disc treated surfaces within each material except for Dyract Flow, a flowable compomer. CONCLUSION: Although the surface roughness of flowable restorative resins differs among the types, this difference can be overcome with different finishing/polishing methods.

Comparison of temperature changes in the pulp chamber induced by various light curing units, in vitro.

This study compared the temperature increase in a pulp chamber as a result of using various light-curing units during resin composite polymerization, and it determined the effect of remaining dentin thickness on temperature rise. A Class II occlusodistal cavity with a remaining dentin thickness of 2 mm was prepared in an extracted human mandibular molar. A 2-mm layer of fine hybrid resin composite was placed on the floor of the proximal box. A K-type thermocouple was inserted into pulp chambers filled with heat sink compound, and pulp chamber temperature rise (starting temperature: 37.0 +/- 0.1 degrees C) during polymerization of the composite was measured. The light-curing units tested included two halogen lights, Spectrum 800 and Elipar Trilight (Standard and Exponential mode); a light-emitting diode (LED, Elipar Freelight) and a plasma arc (Virtuoso, Xenon Power Arc). Irradiation time was 40 seconds for the halogen and LED lights and 3 seconds for the plasma arc light. Five measurements were carried out for every light-curing unit. The same experimental design was conducted after the cavity preparation was modified, leaving a 1-mm thick dentin layer. The Kruskal-Wallis and multiple comparison tests were used to evaluate the differences among the tested curing units. Mann Whitney-U tests were used to compare the mean temperature rise in each curing unit for different remaining dentin thicknesses. The increase in pulp chamber temperature ranged between 1.40-3.8 degrees C. The highest temperature rise was observed when using Elipar Trilight Standard mode, and the lowest temperature rise was observed with light emitting diode for both remaining dentin thicknesses. The only significant differences in temperature rise were observed between Elipar Trilight Standard mode and LED. No significant difference (p > 0.01) existed for the different modes of Elipar Trilight. A statistically significant higher temperature rise was observed within each curing unit at a depth of 1 mm compared to 2 mm. Although the tested light-curing units caused a temperature rise in the pulp chamber, none exceed the critical value of 5.5 degrees C.

Influence of mastication and edentulism on mandibular bone density.

The aim of this study was to demonstrate that external loading due to daily activities, including mastication, speech and involuntary open-close cycles of the jaw contributes to the internal architecture of the mandible. A bone remodelling algorithm that regulates the bone density as a function of stress and loading cycles is incorporated into finite element analysis. A three-dimensional computational model is constructed on the basis of computerised tomography (CT) images of a human mandible. Masticatory muscle activation involved during clenching is modelled by static analysis using linear optimisation. Other loading conditions are approximated by imposing mandibular flexure. The simulations predict that mandibular bone density distribution results in a tubular structure similar to what is observed in the CT images. Such bone architecture is known to provide the bone optimum strength to resist bending and torsion during mastication while reducing the bone mass. The remodelling algorithm is used to simulate the influence of edentulism on mandibular bone loss. It is shown that depending on the location and number of missing teeth, up to one-third of the mandibular bone mass can be lost due to lack of adequate mechanical stimulation.

Risk factors affecting dental implant survival.

Given the predictability of dental implant success, the attention of the scientific community is moving from descriptions of implant success toward a more detailed analysis of factors associated with implant failure. The purposes of this study were (1) to estimate the 1- and 5-year survival of Bicon dental implants and (2) to identify risk factors associated with implant failure in an objective, statistically valid manner. To address the research purposes, we used a retrospective cohort study design and a study sample composed of patients who had one or more implants placed. The predictor variables were grouped into the following categories: demographic, health status, anatomic, implant fixture-specific, prosthetic, perioperative, and ancillary variables. The major outcome variable of interest was implant failure defined as implant removal. Overall implant survival was estimated using the Kaplan-Meier analysis. Risk factors for implant failure were identified using the Cox proportional hazard regression models. The study sample was composed of 677 patients who had 677 implants randomly selected for analysis. The overall 1- and 5-year survival of the Bicon implant system was 95.2% and 90.2%, respectively. After adjusting for other covariates in a multivariate model, both tobacco use (P = .0004) and single-stage implant placement (P = .01) were statistically associated with an increased risk for failure. The results of these analyses suggest that the overall survival of the Bicon dental implant is comparable with other current implant systems. In addition, after controlling for covariates, we identified 2 exposures associated with implant survival, tobacco use and implant staging. Of interest, both of these exposures are under the clinician's control.

Peri-implant bone remodeling around an extraction socket: predictions of bone maintenance by finite element method.

PURPOSE: The aim of this study was to investigate peri-implant bone remodeling as a response to biomechanical factors, including implant size and contour, magnitude of occlusal load, and properties of osteogenic bone grafts through the use of a computational algorithm. MATERIALS AND METHODS: A bone-remodeling algorithm was incorporated into the finite element method, where bone remodeling takes place as a result of the biomechanical alteration caused by dental implant placement and continues until the difference between the homeostatic state and the altered state is minimized. The site-specific homeostatic state was based on a model consisting of a natural tooth. Three long (11-mm) implants and two short (5-mm) implants were investigated. A three-dimensional segment of the mandible was constructed from a computed tomographic image of the premolar region, and an extraction socket was filled with bone graft. RESULTS: Generally, the extent of bone loss in the cortical region was greater and denser bone developed at both the implant crest and apex with increased occlusal loads. The areas between implant threads were prone to bone resorption. Bone graft materials that were relatively stiff and that had high equilibrium stimulus values appeared to cause increased bone loss. CONCLUSIONS: Short implants are better for conserving the mechanotransductive signaling environment of the natural tooth than long implants. Also, short implants are predicted to lead to less interfacial bone loss at high loads over the long term, while long implants are associated with a more consistent level of bone loss for different amounts of loading. It is also predicted that in the long term, bone grafts with relatively low elastic modulus lead to lower levels of interfacial bone loss.

Evaluation of load transfer characteristics of five different implants in compact bone at different load levels by finite elements analysis.

STATEMENT OF PROBLEM: The external contour of an implant and the magnitude of occlusal loading can have significant effects on the load transfer characteristics and may result in different bone failure rates for different implant systems. PURPOSE: The goal of this study was to investigate the effects of external geometry and occlusal load magnitude on bone failure modes for 5 commercially available dental implant systems. MATERIAL AND METHODS: Five different implant systems; Ankylos, Astra, Bicon, ITI, and Nobel Biocare, comparable in size, but different in thread profile and crest module shapes, were compared using the finite element method. Type II bone quality was approximated and complete osseous integration was assumed. Occlusal loads of varying magnitudes (0 to 2000 N) were applied on the abutments supporting single tooth restorations at 11.3 degrees from the vertical axis with a 1-mm offset. Total overloaded bone area, where tensile and compressive normal stresses fell outside of the recommended limits of 100 and 170 MPa, respectively, was investigated for different load levels. RESULTS: For moderate levels of occlusal loads up to 300 N, the compact bone was not overloaded by any of the implant systems. At the extreme end of the occlusal load range (1000 N or more) the overloading characteristics of implants may be dependent on geometric shape. CONCLUSION: In general, overloading occurs near the superior region of compact bone, in compression, and it is primarily caused by the normal and lateral components of the occlusal load. At the region of intersection of compact and trabecular bone, overloading occurs in tension due to the vertical component of the occlusal load. For excessive forces greater than 1000 N, the overloaded areas of the bone varied considerably among 5 different implants systems evaluated.

Dentoalveolar reconstructive procedures as a risk factor for implant failure.

PURPOSE: Dentoalveolar reconstructive procedures (DRPs) are commonly used to enhance deficient implant recipient sites. It is unclear, however, if these procedures are independent risk factors for implant failure. The specific aim of this study was to assess the use of DRPs as a risk factor for implant failure. MATERIALS AND METHODS: To address the research aim, we used a retrospective cohort study design and a study sample derived from the population of patients who had one or more implants inserted between May 1992 and July 2000. The main predictor variable was the use of DRPs, such as external or internal sinus lifts, onlay bone grafting, or guided-tissue regeneration with autogenous bone grafts or autogenous bone graft substitutes, to enhance the recipient sites before implant insertion. The major outcome variable was implant failure. Appropriate descriptive, bivariate, and multivariate statistics were computed. RESULTS: The study sample was composed of 677 patients who had 677 implants randomly selected (1 implant per patient) for analysis. The overall 1- and 5-year implant survival rates were 95.2% and 90.2%, respectively. Bivariate analyses revealed 4 factors statistically or nearly statistically associated with implant failure: current tobacco use, implant length, implant staging, and type of prosthesis (P <.15). In the multivariate model, patients with DRPs did not have a statistically significant increased risk for implant failure (odds ratio = 1.4, P =.3). CONCLUSIONS: The results of this study suggest that the use of DRPs to reconstruct deficient implant recipient sites was not an independent risk factor for implant failure in either the unadjusted or adjusted analyses.