Intraoral Scanning and Digital Impression Techniques in Dentistry

 Mupparapu M. Intraoral Scanning and Digital Impression Techniques in Dentistry. J Orofac Sci [serial online] 2019 [cited 2019 Aug 13];11:1-2. Available from: http://www.jofs.in/text.asp?2019/11/1/1/264189

Based on the available evidence on the introduction of intraoral scanning (IOS) techniques in the dental profession dating back to the early 1980s, it is fair to say now that the technology is more mature than ever. IOS has become integral part of many restorative, implantology, and orthodontic procedures for capturing surface details of teeth for fabrication of inlays, onlays, or crowns (both laboratory-based and chair-side) as well as applications in implantology for fabrication of custom abutments or screw-retained crowns and surgical guides for accurate placement of root form implants. In orthodontics, the intraoral scanners are being used for digital storage and on-demand model production in 3D printers, digital impressions, 3D aligner treatment plans, to name but a few. Many of these digital impression techniques are drawn into lab-based services for fabrication of restorations and hence the companies that offer these services have invested in the development of the digital impression systems via scanners as well as in the development of logistics for digital transmissions and fabrication of restorations, crowns, and surface coverages used for aligning teeth.

The technologies differ in the acquisition of images and their storage, although the end products are quite similar. For example, the CEREC system (Serona, Bensheim, Germany) is designed in 1987 with the concept of “triangulation of light.”[1] Since surfaces with uneven light dispersion reduce the accuracy of the scans, opaque power coating of titanium dioxide is recommended for the scanning. One of the latest generations of CEREC scanners called CEREC ACBluecam uses LED blue diode as its light source.[1]

Another system called the LAVA C.O.S. system (3M ESPE, Seefeld, Germany) was introduced to clinical dentistry in 2008 that works using the principle of active wavefront sampling based on a single-lens camera. Three sensors capture data simultaneously, creating more than 2400 data sets to increase the surface accuracy. This system has the smallest scanner tip in the market with 13.2 mm width. This system also needs opaque power coating.[1]

The iTero system (Cadent Inc., New Jersey) came to the market in 2007. This system captures images based on laser and optical scanning using the principle of parallel confocal imaging. The iTero is an open software system in the treatment of crowns, FPDs, implants, aligners, and retainers. The system exports digital image files in .STL format that can be shared by other labs equipped with CAD/CAM systems.[1]

The E4D system (D4D Technologies, LLC, Richardson, TX) uses the principle of optical coherence tomography and confocal microscopy. Using red laser as a light source and micromirrors to vibrate 20,000 cycles per second, it creates a digital 3D impression that is also interactive. This system is power free.[1]

Finally, the TRIOS system (3Shape, Copenhagen, Denmark) introduced in 2011 uses the principle of ultrafast optical sectioning and confocal microscopy. Since it acquires up to 3000 images per second, movement artifacts are reduced or minimized. Like the iTero and E4D, this is also a power-free system.[1]

In a study conducted by Syrek et al.,[2] the authors concluded that the ceramic crowns fabricated from a digital impression had a better fit than those made from conventional impressions.

Overall, optical impressions reduced patient discomfort, are time-effective, simplify clinical protocols, and allow better communication with the lab and patients. Although the literature supports the use of intraoral scanners for accurate capture of dental topography and fabrication of inlays, onlays, coping, frameworks, single crowns and fixed partial dentures, smile designing, post and core fabrication as well as removable of partial prosthesis and obturators, it does not support the use of IOS in long-span restorations with natural teeth or implants as yet. The utilization of IOS in implant dentistry is also well documented and use of IOS orthodontics for fabrication of aligners and custom-made devices is on the rise. Total elimination of traditional impression techniques is a good possibility in the near future.

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Dental plaque pH in predicting caries relapse after general anaesthesia – an exploratory study

First published: 11 August 2019

Abstract

Objectives

Numerous caries risk assessment tools have been proposed in the literature, with few validated in preschool children especially those receiving oral rehabilitation under general anaesthesia (GA). Past caries experience, the best predictor thus far, may not be a reliable indicator after effective clinical intervention. Hence, this longitudinal study was aimed to explore the potential role of plaque pH in predicting future caries incidence after GA among preschool children.

Methods

Oral examination, plaque pH measurements and questionnaire survey were performed, among pre‐schoolers indicated for GA, at baseline (n = 92), 6‐month (6M; n = 83), 12‐month (12M; n = 79) and 24‐month (24M; n = 66) recall visits after GA. Multivariable logistic regression and receiver‐operating characteristic analysis were performed to evaluate the predictive value of models with plaque pH and past caries experience.

Results

Individuals with low resting plaque pH at 6M and 12M were shown to be at high risk of 1‐year caries incidence at 12M [relative risk (RR) 1.41, 95% confidence interval (CI) 1.09–1.48] and 24M (RR 1.61, 95% CI 1.22–1.73) recall visit, respectively. Moreover, plaque pH demonstrated a statistically significant predictive value in the 12M and 24M models (12M/24M: 85%/77%) compared with past caries experience, which was not a significant predictor in both models (both P > 0.05).

Conclusions

Plaque pH may be a promising prognostic and predictive marker for early identification of high‐risk children undergoing oral rehabilitation under GA.

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Oral lesions and associated factors in breast cancer survivors

First published: 12 August 2019

 

Abstract

Aim

To evaluate the prevalence of oral lesions (OL) and associated factors among survivors of breast cancer (BC).

Methods

A cross‐sectional study involving 150 BC survivors was conducted at a public hospital in southern Brazil. Data were collected on socioeconomic aspects, treatment characteristics and oral problems. The decayed, missing and filled teeth index and the occurrence of OL were evaluated. Logistic regression was performed to determine independent variables associated with the outcome.

Results

24% of the women had at least 1 OL and 33.3% of these had more than one lesion. Melanotic macule was the most prevalent lesion. Duration of tamoxifen use, radiotherapy, missing teeth and xerostomia were associated with the occurrence of OL (P < .05). In the adjusted analysis, women with more than 13 missing teeth and xerostomia had 2.39‐fold (95% confidence interval [CI], 1.06‐5.40) and 2.71‐fold (95% CI, 1.14‐6.42), respectively, greater odds of exhibiting OL.

Conclusion

Approximately 1/4 of the BC survivors exhibited OL, which were associated with tooth loss and xerostomia. These findings could assist in the establishment of oral health strategies for women with BC.

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RPD lodged in the Larynx

Surgeons dislodge man’s false teeth from his voicebox

Doctors deduce 72-year-old must have breathed them in during a previous operation.

A man who turned up in the ER coughing up blood and having difficulty swallowing has surprised doctors who discovered he had false teeth lodged in his larynx.
Doctors deduced that the 72-year-old must have breathed them in during an operation several days earlier in which he was put under general anaesthetic to have a benign lump removed from the wall of his abdomen. The case has prompted a warning to doctors to take note of whether patients have false teeth, and to keep track of where they are during operations.

X-ray of false teeth lodged in man's larynx.

A man who turned up in A&E coughing up blood and having difficulty swallowing has surprised doctors who discovered he had false teeth lodged in his larynx.
Doctors deduced that the 72-year-old must have breathed them in during an operation several days earlier in which he was put under general anaesthetic to have a benign lump removed from the wall of his abdomen.
The case has prompted a warning to doctors to take note of whether patients have false teeth, and to keep track of where they are during operations.
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Retention force and allowable range of the angle of an implant-supported overdenture attachment system using healing screws and a silicone resilient denture liner

The Journal of Prosthetic Dentistry

Available online 2 August 2019

The Journal of Prosthetic Dentistry

Abstract

Statement of problem

Changes in the intraoral condition immediately after implant placement and in patients using fixed prosthetic appliances with implant abutments cause problems that require the use of an easily adjustable implant-supported overdenture system.

Purpose

The purpose of this in vitro study was to develop a simulated implant-supported overdenture attachment system by using healing screws for the patrix and a silicone resilient denture liner for the matrix and to investigate the initial retention force, time-course changes, and allowable range of the angle between attachments.

Material and methods

Tests on the retention force and allowable range of the angle were performed. Attachments using tissue-level healing screws (height: 2.0 and 3.0 mm) for the patrix and a silicone resilient denture liner for the matrix were prepared. In the retention force measurement test, the frequency of insertion and removal was set at 3 per day to simulate a 4-month relief period. The joined attachment model was pulled apart, and the maximum traction (N) required to remove it was defined as the retention force. The retention force was measured every 90 times (representing the number of insertions and removals per month). To test the allowable angle range, 2 patrices were used. The angle between the 2 patrices was set at 0, 10, 20, and 30 degrees, and the angular limit for joining with the matrix was measured. The initial retention force of the healing screw attachments was compared with that of a polymeric O-ring by using 1-way layout ANOVA followed by the Bonferroni test (α=.05). To analyze time-course changes in the 2 types of healing screw attachments, the retention force before insertion and removal was compared with that after repeated insertions and removals for each simulated period using 1-way layout ANOVA followed by the Dunnett test (α=.05).

Results

The initial retention force of the 2.0- and 3.0-mm healing screws was 2.4 ±0.1 and 2.6 ±0.2 N. After repeating insertions and removals to simulate use for 4 months, the retention force of the 2.0- and 3.0-mm healing screws was 1.8 ±0.2 and 2.2 ±0.1 N, respectively, both showing significant differences from the initial retention force (P<.05). The allowable angle range test revealed that insertion and removal of the healing screws was possible up to 30 degrees.

Conclusions

Under the conditions of this in vitro study, repeated insertion and removal attenuated the retention force but was still equivalent to the retention force of the O-ring. The allowable range of the angle between patrices for insertion and removal was up to 30 degrees.
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Effects of precementation on minimizing residual cement around the marginal area of dental implants

The Journal of Prosthetic Dentistry

Available online 2 August 2019

The Journal of Prosthetic Dentistry

Abstract

Statement of problem

Residual cement is detrimental to the long-term success of dental implants with a cement-retained restoration. The complete elimination of excess cement remains a challenge.

Purpose

The purpose of this in vitro study was to evaluate the effects of precementation technique on minimizing the residual cement and retention of restorations.

Material and methods

Four custom cobalt-chromium alloy (Co-Cr) abutments were manufactured by computer-aided design and computer-aided manufacturing (CAD-CAM) as precementation abutments with height and radius reductions of 25 μm (A25), 50 μm (A50), 75 μm (A75), and 100 μm (A100). Fifty CAD-CAM–fabricated standard Co-Cr abutments and corresponding crowns were randomly matched and treated as follows: 10 specimens were cemented with the conventional cementation procedure with glass ionomer cement (G0), and 40 were precemented with precementation abutments (n=10) before the definitive cementation with standard abutments (G25, G50, G75, G100). The weight of the cement in the cement space was calculated, and the marginal sealing was evaluated by using a stereoscopic microscope. The effects of precementation with resin cement on minimizing residual cement around the marginal area of dental implants were further evaluated extraorally. The influence of precementation with glass ionomer and resin cement on the retention force was analyzed by using a universal testing machine at a crosshead speed of 0.5 mm/min. One-way ANOVA was used to analyze cement mass and marginal sealing values. Two-way ANOVA was used to compare the retention forces (α=.05).

Results

The cement weight of G50 (7.2 ±0.6 mg) was significantly higher than that of G25 (6.0 ±1.1 mg, P<.05), while no significant differences in cement weights were found among G50, G75, and G100. Consistently, the G50, G75, and G100 had higher marginal sealing values than that of the G25 (P<.01). Extraoral experiments showed that the precementation with A50 reduced subgingival residual cement without affecting retention.

Conclusions

These in vitro results suggest that precementation with a precisely manufactured precementation abutment minimized the residual cement around implant abutments, and 50 μm could be a preferable precementation space.
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