cronicon · 2020. 1. 3. · cronicon open access ec dental science research article photogrammetry...

CroniconO P E N A C C E S S EC DENTAL SCIENCEEC DENTAL SCIENCE

Research Article

Photogrammetry is Superior to Conventional Impression Techniques in Cases Requiring Six or More Implants

Rodríguez-Fernández Emilio1*, Sánchez-Gil Andrea2 and Salama Maurice3 1Master Program Department of Implant dentistry, University of Alfonso X el Sabio, Spain2Oral Surgery Department, Hospital Universitario de Alcalá de Henares, Spain3Prosthodontics Department, University of Pennsylvania, United of States of America

Citation: Rodríguez-Fernández Emilio., et al. “Photogrammetry is Superior to Conventional Impression Techniques in Cases Requiring Six or More Implants”. EC Dental Science 19.2 (2020): 01-09.

*Corresponding Author: Rodríguez-Fernández Emilio, Master Program Department of Implant dentistry, University of Alfonso X el Sabio, Spain.

Received: December 03, 2019; Published: January 03, 2020

Abstract

Impression techniques are continuously evolving. New technologies such as photogrammetry impression techniques have long been considered a viable alternative to conventional impressions. The aim of this study was to compare the level of passive fit ob-tained with photogrammetry with the level achieved using conventional interventions relying on addition silicone open trays and splinting impression techniques. A randomized, controlled, single-center trial was conducted which included patients who were pre-scribed 5 or more implants. The PICDental® system was used to determine the spatially implant positions in the photogrammetry group. The primary outcome of the study was the accuracy of the methods. The secondary outcome was the precision of the two types of interventions, as defined by number of implants, intervention times, number of healing cap or attachment connections/discon-nections, and radiation exposure times. Twenty-two patients who fulfilled the inclusion criteria were enrolled in the study. These represented 24 clinical cases. There was a strongly significant difference in mean fit between the two study groups (conventional vs photogrammetry) in favor of photogrammetry (p < 0.01). In cases of more than 6 implants, passive fits were not achieved in any of the cases. There was a mean intervention time of 36.66 minutes in conventional cases in contrast a mean value of 13.23 min for the photogrammetry group, a significant difference (p < 0.001). A mean radiation time of 40.54 s was observed in the group who under-went conventional impressions, and a mean value of 13.20s in all cases where photogrammetry was used, a significant difference (p < 0.001). In summary, the results of this study have demonstrated the superiority of photogrammetric impression techniques over conventional ones, in terms of passive fit, radiation exposure times, intervention times, and the number of connections and discon-nections required per implant.

Keywords: Photogrammetry; Dental Implants; Digital Impressions; CAD-CAM; Oral Scanners; Conventional Impressions; Passive Fit; Accuracy

Abbreviations

s: Seconds; min: Minutes; 3D: Three Dimensional; CBCT: Cone Beam Computed Tomography; CAD/CAM: Computer-Aided Design and Computer-Aided Manufacturing; STL: Standard Tessellation Language; Md: Median; IQR: Interquartile Range; SD: Standard Deviation



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Introduction

Impression techniques have evolved since the early days of implantology [1,2]. However, the emergence of digital procedures ushered in a qualitative leap in implant science. Some of technological innovations in the field of implantology included 3D printing, dental cone beam computed tomography (CBCT), planning with specific software, intra-oral scanners, and computer-aided design and computer-aided manufacturing (CAD/CAM) [3,4]. In vitro studies have demonstrated that there is no manufacturing process which provides absolute precision. Therefore, the clinical factors inherent in each impression technique cannot be ignored [5]. Up until now, implant impressions using digital technology have not resulted in outcomes as positive as impressions relying on conventional technologies. This is particularly true in the case of full mouth or complex restorations involving a large number of implants [6,7]. Photogrammetry was proposed as a valid alternative to traditional implant impression techniques at the beginning of the 21st century [8]. Photogrammetry is the process of obtaining metric information about an object using the measurements from photographs. Geometric relationships are established between the image and the object when the photo is taken. Information about the object is then extracted from the images [9]. Photogrammetry has only been studied in in vitro laboratory models [10] or in small cases series. Therefore, the evidence is scarce regarding its validity in comparison to conventional techniques [11]. More research is required in order to conclude whether or not photogrammetry is suitable as a routine clinical practice. The aim of this work is to assess the passive fits of multiple-implant full arch impressions carried out using photogrammetry and to compare the results to conventional impressions that rely on silicones, open trays, and splinted impressions. The Precise Implants Capture (PICDental®) system was used to carry out the photogrammetry. Radiation exposure times, intervention times and the frequency of connections and disconnections in healing caps and attachments were also assessed.

Materials and Methods

This study consisted of a randomized, controlled, single-center trial. Between 2013 and 2015, 22 patients of a private dental office in Madrid were enrolled in the study and received either full-arch restorations, complex fixed prostheses, or both.

All patients were of legal age. Patients were either generally in good health or under medical supervision for chronic diseases such as hypertension, diabetes and hypo- or hyperthyroidism. An intervention that included five or more implants was required for patient inclusion in the study. Subjects who had undergone radiotherapy or chemotherapy treatments in the previous six months were excluded because of the risk of early withdrawal from the study. Also excluded were those who did not require complex oral rehabilitation, even if the intervention required multiple implants. All subjects were informed about the study methodology and completed an informed consent form prior to participating. The clinical cases were randomly assigned to two groups. Patients in Group 1 received an intervention that relied on conventional impressions that relied on addition silicones, open trays, and splinted transfers. Patients in Group 2 received an intervention that relied on photogrammetry-based impressions. In the latter case, the PICDental® impression technology was used to determine the position of the implants.

Impression techniques

Each patient from Group 1 received two impressions. The first impression was carried out using the direct technique and standard plastic trays with splinted transfers (Figure 1). A second impression was subsequently performed to both confirm and improve the accuracy of the first. Each impression was washed and disinfected before being cast to prevent potential alterations caused by the patients’ saliva (Figure 2).

For the photogrammetry group, the PICabutments® were screwed into the implants (Figure 3). Images were captured using the PICamera®. The output was a file in the Standard Tessellation Language (STL) format. Once removed, the healing caps were attached to the implants and alginate impressions were taken in order to get an imprint of the soft tissues. A dental stone model was produced based


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on the alginate impressions. The stone model was subsequently digitized and new STL files were created. The two digital models were then compared. The next phase consisted of a computer-aided design and computer-aided manufacturing (CAD/CAM) step (Figure 4).


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Results

As a primary outcome measure, the accuracy of the impression was determined by comparing the two groups based on the mean fit of the data obtained using a digital X-ray and the NemoScan® quantification operating system (Nemotec SL, Arroyomolinos, Spain). The secondary outcomes were determined by comparing the two groups according to the precision of the intervention. Precision was defined according to the number of implants, intervention times, and the number of connections/disconnections of the healing caps or attachments, and the radiation exposure time. Exposure time was determined by counting the number of X-rays performed using the VATECH® PAX-400C X-ray system as well as noting the times recorded by this device. All patients were followed-up on over a twelve-month period.

A descriptive analysis of the demographic and clinical characteristics of all patients enrolled in the study was carried out. An initial baseline analysis comparing both groups was carried out after the randomization step. Normality tests were carried out on the continuous variables in order to determine whether a parametric or non-parametric statistical test was appropriate for statistical analyses of the variables. The parametric Student’s t-test was used in the case the data was normally distributed. Meanwhile, the Mann-Whitney U non-parametric test was used in the case the data was not normally distributed. The chi-squared test or Fisher’s exact test was used to evaluate categorical variables. All comparisons were two-tailed, with an alpha value set to 0.05. The SPSS 21 (IBM Corporation, Armonk, NY) software package was used for all statistical analyses.

Twenty-two patients who fulfilled the inclusion criteria were enrolled in the study between February of 2013 and November of 2015. These represented 24 clinical cases because two patients required rehabilitation in both jaws. The mean age of the patients was 63.33 years (SD = 9.11 years).

Eighteen patients were female and six were male. The mean number of implants per patient was 6.13 (SD = 1.11) with a range of between 5 and 8. Fourteen implants were placed in the upper jaw and 10 were placed in the lower jaw. Implants were more often placed in the upper arch (62.5%) than in the lower arch. There were no statistically significant baseline differences observed between the groups in terms of sex, age, number of implants or location of implants (p > 0.05). Statistics are laid out in table 1.


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Cases Sex** Age** Method Implants** Localization**1 Female 71 Classic 8 Upper jaw2 Female 57 Classic 6 Upper jaw3 Female 46 Classic 7 Upper jaw4 Female 63 Classic 8 Lower Jaw5 Female 71 Classic 5 Lower jaw6 Female* 72 Classic 6 Upper jaw7 Male 71 Classic 6 Upper jaw8 Male* 76 Classic 6 Upper jaw9 Female 58 Classic 5 Lower Jaw

10 Female 52 classic 5 Lower Jaw11 Male 57 Classic 5 Lower Jaw12 Female 68 Classic 6 Upper jaw13 Male 48 Classic 6 Upper jaw14 Female 69 Classic 8 Upper jaw

Female: 71% x̄: 62.79 x̄: 6.21 Upper jaw: 64%15 Female* 72 PicDental 8 Lower Jaw16 Female 59 PicDental 8 Upper jaw17 Male* 76 PicDental 5 Lower Jaw18 Female 72 PicDental 6 Upper jaw19 Female 52 PicDental 5 Lower Jaw20 Female 70 Picdental 5 Lower Jaw21 Female 52 PicDental 6 Upper jaw22 Female 58 PicDental 6 Upper jaw23 Female 67 PicDental 6 Upper jaw24 Male 63 PicDental 5 Lower Jaw

Female: 80% x̄: 64.10 x̄: 6.00 Upper jaw: 50%

Table 1: Descriptions of clinical cases included in the study. * Participants treated in both groups. x̄: mean value. %: Percentage.

** P > 0.05. Without statistical significance between groups.

Efficacy

In Group 1 (conventional impressions), passive fits (0 mm) were achieved in only 5 cases. The mean misfit value in Group 1 was 0.37 mm, with a median (Md) of 0.11 mm, a mean misfit range of 1.05 mm, and an interquartile range (IQR) of 0.80. Meanwhile, in Group 2 (photogrammetry), the fit value was constant and no higher than 0 mm in 100% of the cases. A comparison of mean misfit values revealed a statistically significant reduction in misfit values Group 2 (p < 0.01). In Group 1, with cases of more than 6 implants, passive fits were never achieved (Table 2).


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Traditional impression techniques groupNumber of Implants Number of Cases Passive fit = 0 mm Percentage

5 4 4 100%6 6 2 33.3%7 1 0 0%8 3 0 0%

A

PicDental groupNumber of Implants Number of cases Passive fit = 0 mm Percentage

5 4 4 100%6 4 4 100%7 - - -8 2 2 100%

B

Table 2: Number of cases with a passive fit= 0 mm by number of implants in both groups.

Radiation exposure times were measured in seconds (s) of exposure. In Group 1 (conventional), the mean value was 40.54 s (SD 13.16s), while in Group 2 (photogrammetry) a mean value of 13.20s was observed (SD 0.0s). The latter value corresponded to a single X-ray. Between Group 1 and Group 2, there was a statistically significant decrease in radiation exposure time (p < 0.001) with a mean difference of 27.34s (95% CI = 19.74 - 34.94s). This outcome was a result of the more frequent use of X-rays during interventions with patients from Group 1. Patients in this group were administered a mean of 3.07 X-rays/patient (Md = 3.50, range = 2 - 4, IQR = 2). Between Group 1 and Group 2, there was a statistically significant decrease in the number of X-rays/case (p < 0.001) with a mean difference of 2.07 X-rays per case (95% CI 1.50 - 2.65) (Table 3).

Outcomes Mean classic group Mean PicDental Difference of

meansConfidence

Interval 95%P value

Mean misfit 3.72 0.00 3.72 0.12 - 0.62 P < 0.01Maximum mean misfit 0.86 0.00 0.86 0.33 - 1.39 P < 0.01

Radiology exposure time 40.54 13.20 27.34 19.74 - 34.94 P < 0.01Number of X-rays required 3.07 1.0 2.07 1.50 - 2.65 P < 0.01

Working time 36.66 13.23 23.43 16.88 - 29.98 P < 0.01Connections /disconnections 18.28 10.00 8.28 5.98 - 10.59 P < 0.01

Table 3: Statistical results for the outcomes studied.

The overall mean value of intervention time/case was 26.89 min (SD 14.54 min). Meanwhile, Group 1 (conventional) had a mean value of 36.66 min (SD 11.14 min) and Group 2 (photogrammetry) had a mean value 13.23 (SD 2.27). A statistically significant decrease in intervention time was observed between Group 1 and Group 2 (p < 0.001) with a mean difference of 23.43 min (95% CI 16.88 - 29.98).


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In addition, Group 1 showed a greater variability in intervention time per case than did group 2. The variability in intervention time observed in Group 1 was a consequence of the number of implants per case, with a correlation of 0.67 value of (p < 0.01). Meanwhile, the intervention time per case was constant in Group 2.

Discussion

The goal of this study was to compare the conventional impression techniques that rely on addition silicones, open trays and splinted transfers with digital techniques relying on photogrammetry driven by the PICDental® system.

Photogrammetry was found to be superior terms of passive fit, radiation exposure times, intervention times, and the number of connections and disconnections per implant.

Photogrammetry was first proposed in 1999 as viable alternative to conventional implant impression techniques [8]. Up until then, photogrammetry was employed as a tool to assess the passive fit between implants and frameworks [12]. In the present study, using photogrammetry led to passive fits of 0 mm in all cases, while a passive fit was only obtained in one-third of cases where conventional impressions were applied. Importantly, in trying to achieve a suitable fit, angle was not found to be as significant a factor as the number of implants [13]. Consistent with this observation, the level of passive fit obtained was inversely proportional to the number of implants applied. In the conventional method group, an increase in the number of implants coincided with an increase in the frequency of misfits, but this relationship did not hold for photogrammetry group. In the latter group, the frequency of misfits remained constant, regardless of the number of implants applied. Similar observations had already been made in previous case series studies [11].

Fixed implant rehabilitations require suitable passive fits [14]. Achieving a good passive fit is important because this facilitates a healthy tissue response [15]. In addition, the demand for immediate/early loading procedures is increasing over time. This makes it increasingly necessary to reduce the mechanical complications caused by a misfit. The PICDental® system was first reported in a 2014 case series study which found that using this system to perform impressions led to optimal outcomes in passive fit [16] without any mechanical or biological complications observed 12 months after inserting the prostheses. In the present in vivo study, the PICDental® methodology was used in 60 implants, with a mean of 6 implants per arch. Here, as in the other studies mentioned, a clinically suitable passive fit was achieved in all the cases, with no mechanical or biological complications during the 12-month follow-up period.

Photogrammetry based impressions emerged as an alternative with the appearance of modified reflex cameras. These original cameras were able to capture three images of an object at a time, with a precision of 17 microns. These images were easy to merge using a stereoscope, a device which would later transfer the data to a plotter for transformation in 3D [8]. Nowadays, the innovative camera of the PICDental® system is able capture the different spatial positions of implants in an automatic, fully digitized fashion. Using infrared radiation, this camera can take 10 images per second, with a precision of 6 microns.

The present study also took into account the radiation exposure times. X-rays are the standard method for determining spatial discrepancies between structures and implants. Radiation exposure time is therefore unavoidable. We confirm here that radiation exposure time is considerably higher when relying on conventional impression methods, compared to photogrammetry. In the photogrammetry group, a single X-ray sufficed in all cases, while in the conventional group, an average of 3x more X-rays were required.

The initial studies assessing the PICDental® method indicated that it was a quick procedure, although intervention time was not a variable that was analyzed [17]. In the present study, intervention times proved to be constant for photogrammetry regardless of the number of implants and were considerably reduced with respect to conventional methods. The mean difference in intervention times between the two techniques was over 20 minutes and was clearly dependent on the number of implants in the case of the conventional


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techniques. These differences highlight the considerable experience and level of skills required to carry out impressions using conventional techniques. On the other hand, digital techniques can be learned relatively easily without extensive prior experience [18].

The number of connections/disconnections of the healing caps or the attachments in dental implants is also important. This is because repeating a procedure leads to an increase in bone resorption, which could, in turn, lead to further biological complications [19].

This study has demonstrated that photogrammetry reduces the number of connections and disconnections to almost half that of conventional methods. Also, with photogrammetry procedures, the frequency of connections/disconnections is independent of the number of implants applied. The PICDental® method determines the real spatial position of the implants from the beginning and no further registers are required.

Conclusion

This study has shown that, in cases of more than five implants, the PICDental® is more effective than the classic open-tray method for determining the spatial position in the mouth with a passive fit of not more than 0 mm. In addition, with photogrammetry, the impression does not need to be repeated and radiation exposure is reduced. Another positive outcome is a shorter and more predictable intervention time. Importantly, the procedure is also comfortable for patients.

Acknowledgements

Acknowledgements to PICDental Company for the support and the information facilitated. Acknowledgements to Mr. Juan Gómez for his close cooperation and help during the years of the study and his contribution to achieve this study at the dental office.

Conflict of Interest

No conflict of interest was reported in the present study.

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Volume 19 Issue 2 February 2020©All rights reserved by Rodríguez-Fernández Emilio., et al.









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cronicon · 2020. 1. 3. · cronicon open access ec dental science research article photogrammetry...

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