Ó
Operative Dentistry, 2018, 43-5, 501-507
Effect of Magnification
on the Precision of Tooth
Preparation in Dentistry
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M Eichenberger N Biner M Amato A Lussi P Perrin
Clinical Relevance
Magnification devices can improve the precision of tooth preparation by dentists.
SUMMARY cylindrical bur and water-cooling. The bound-
Objectives: To evaluate the impact of magnifi- ary line had to be touched but not erased.
cation aids on the precision of tooth prepara- Chair-side assistance was provided to simulate
tion under simulated clinical conditions. the clinical situation. Tooth 16 was prepared
under indirect vision via a dental mirror. Tooth
Methods and Materials: Two plastic blocks 36 was prepared under direct vision A) without
marked with a geometric shape were fixed in magnification aids, B) with Galilean loupes,
a dental phantom head: a circle as the distal 2.53 and light-emitting diode light, and C) with
surface of tooth 16 (UNS 3) and a y-shaped a microscope, 6.43 and coaxial light. The prep-
figure as the occlusal surface of tooth 36 (UNS aration procedure was performed three times
19). Sixteen dentists (mean age: 39 years; range: in different sequences of the magnification
26-67 years) prepared the geometric shapes devices and with a break of at least 1 week
from the inside to the boundary line with a between each procedure. The correctly pre-
Martina Eichenberger, Dr med dent, Department of Preven- pared contour and the incorrectly prepared
tive, Restorative and Pediatric Dentistry, University of Bern, areas were evaluated in relation to the whole
Bern, Switzerland circumference of the geometric shapes.
Nadine Biner, med dent, Department of Preventive, Restorative Results: For both values the precision was
and Pediatric Dentistry, University of Bern, Bern, Switzerland
significantly higher when a microscope was
Mauro Amato, Dr med dent, Department of Periodontology, used, followed by preparation using loupes;
Endodontology, and Cariology, University Centre for Dental
precision was lowest without magnification
Medicine, University of Basel, Basel, Switzerland
aids (p,0.0001). This was true for both indirect
Adrian Lussi, Prof Dr med dent, Dipl. Chem., Department of
and direct vision (p,0.05).
Preventive, Restorative and Pediatric Dentistry, University
of Bern, Bern, Switzerland Conclusions: Magnification devices improved
*Philippe Perrin, Dr med dent, Department of Preventive, the precision of tooth preparation under sim-
Restorative and Pediatric Dentistry, University of Bern, ulated clinical conditions.
Bern, Switzerland
*Corresponding author: Freiburgstrasse 7, Bern, 3010, INTRODUCTION
Switzerland; e-mail: philippe.perrin@zmk.unibe.ch
The use of magnification aids is widespread in
DOI: 10.2341/17-169-C
professions requiring manual dexterity and preci-
502 Operative Dentistry
sion. In dentistry, loupes and operating microscopes Visual Test
have become part of the normal equipment of many Each participating dentist underwent a near vision
dentists. They improve near visual acuity and help test as described by Eichenberger and others.5 The
to compensate for visual deficiencies.1-3 Recent test was performed without magnification aids but
studies with miniaturized visual tests on the basis with participants wearing their prescription glasses,
of microfilms have shown a high variability in the if needed. The distance was 300 mm, or the focal
near visual acuity of dentists. They found that acuity distance of the correction glasses.
declined with increasing age of dentists older than
40 years.1,3-6 The influence of magnification aids on Geometric Shapes
visual performance was evaluated in the same
studies. Galilean and Keplerian loupes improved Plastic teeth (OK T 14 and UK T 14, KaVo Dental
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near visual acuity and could compensate for presby- AG, Biberach, Germany) of a dental phantom head
opia in persons older than 40 years. The results of were prepared for the insertion of standardized
Keplerian loupes were superior to those of Galilean geometric shapes from a plastic block (A-PTM 99-
loupes due to their higher magnification. The 001, Frasaco, Tettnang, Germany). A geometric
performance of the operating microscope was out- circle was fixed as the distal surface of tooth 16
standing and highly superior compared with (universal numbering system: tooth 3) and a y-
loupes.1,3-5 These basic studies did not evaluate the shaped figure as the distal surface of tooth 36
influence of visual acuity on the quality of dental (universal numbering system: tooth 19) in order to
diagnostics and therapy, however. The subjective simulate a typical indirect and direct preparation
conviction that magnification devices improve the (Figure 1A,B). The plastic blocks were reversibly
precision of manual work is not supported by the fixed with superglue (Pattex flüssig 3g, Henkel,
weak scientific evidence in this field. Most studies of Düsseldorf, Germany), which allowed reuse of the
magnification aids and dental treatment are of low teeth for standardization purposes. The phantom
scientific rigor, such as expert opinions,7-10 case head with the teeth described earlier was positioned
reports,11-13 and case series.14,15 The few scientific on the dental chair habitually used by patients of the
studies that included a control group or followed a respective dentists to simulate a typical patient
standardized study design reported ambiguous re- setting.
sults, and some authors found that magnification
devices per se did not lead to better diagnostics or Preparation Procedure
better treatment results.16-22 The cavities were prepared using a handpiece (5:1,
The aim of the present study was to evaluate the KaVo Dental), a cylindrical diamond bur (120-lm
impact of optical magnification on the precision of grit, 1-mm diameter, ISO 806 314 156 524 010 4.0,
tooth preparation under simulated clinical condi- Intensiv SA, Montagnola, Switzerland), water-cool-
tions. The null hypothesis was that magnification ing, and compressed air. Chair-side assistance was
has no influence on the precision of tooth prepara- provided by one of the authors (M.E.). The prepara-
tion. tion proceeded from inside to the boundary line, with
a predetermined limit of preparation depth between
METHODS AND MATERIALS 1.5 and 2.5 mm. This depth was indicated by the
colored layers in the plastic block. The black line of
Test Subjects the geometric shape had to be touched without
Sixteen dentists participated in the study (mean age: erasing it. The preparation time was limited to 5
39 years; median age: 31 years; range: 26-67 years). minutes. Tooth 16 was prepared under indirect
The dentists were employees of the dental school vision via a dental mirror (TOPvision FS Rhodium,
(n=10) and private dental practitioners (n=6). Hahnenkratt GmbH, Königsbach-Stein, Germany).
Inclusion criteria were 1) experience with dental Tooth 36 was prepared under direct vision, using the
loupes and operating microscopes and 2) near visual dental mirror to check the preparation. Each dentist
acuity in the range of a reference group of dentists as prepared the shape of tooth 16, followed by the shape
determined in an earlier study.5 The inclusion of tooth 36, under the following conditions:
threshold for experience was the daily use of both
loupes and a microscope, ascertained by questioning A. Naked eye, that is, no magnification devices
the participating dentists. Near visual acuity was except prescription glasses and customary oper-
assessed by a visual test. ating light
Eichenberger & Others: Tooth Preparation in Dentistry Using Magnification 503
camera (Leica DFC 495) and linked to a computer.
The ideal geometric shapes were superimposed to
the photographs of each preparation using the
program LAS V4.6.1 (Leica). These superimpositions
allowed the user to evaluate the correctly prepared
contour (mm) and the sum of overprepared and
underprepared areas (mm2). These values were set
in relation to the whole circumference and resulted
in two qualitative values for the preparation.
Statistical Analyses
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For statistical analysis, the software program R
version 3.3.0 (http://www.r-project.org/) was used.
The significance level was set at a=0.05. The
medians of the three preparation sequences were
used for the statistical analysis. Descriptive statistics
included minimum, maximum, mean, median, and
standard deviations. The numeric outcomes were
analyzed for differences between the three
experimental conditions (eye, loupe, microscope).
Because of the small sample size this was done using
a nonparametric analysis of variance for longitudinal
data according to Brunner and others.23 The p-values
were adjusted to take into account the multiple
comparisons using the Bonferroni-Holm correction.
Post hoc tests were performed without p-value
adjustment if global tests showed significant main
effects or interactions with other variables. Additional
questions (ie, on indirect vs direct vision) were
answered by performing post hoc Wilcoxon signed-
Figure 1. (A) The circle was fixed as the distal surface of tooth 16 to rank tests without p-value adjustment.
simulate the clinical situation of indirect preparation (viewed from the
12-o’clock position). (B) The y-shaped figure was fixed as the occlusal
surface of tooth 36 to simulate the clinical situation of direct RESULTS
preparation.
The near visual test resulted in a mean visual acuity
of 1.18, a median of 1.20, and a range of 0.86 to 1.57.
B. Customary Galilean loupes with coaxial light-
These values are within the range of the reference
emitting diode light source; 2.53 magnification group studied by Eichenberger and others.5 All test
factor subjects could therefore be included in the study.
C. Operating microscope with integrated light
source (Leica, Heerbrugg, Switzerland); 6.43 The summarized data of both test teeth showed
magnification factor highly significant differences between the three exper-
imental conditions (eye, loupe, microscope) for the
The test was performed three times in different percentage of correctly prepared circumference and for
sequences (A-B-C; B-C-A; C-A-B) with a break of at the size of the incorrectly prepared area in relation to
least 1 week between the tests. the circumference (p,0.0001, Figures 2 and 3).
A separate analysis of the two teeth allowed a
Evaluation of the Prepared Geometrical comparison to be made between direct (tooth 36) and
Shapes indirect vision (tooth 16). The percentage of correctly
The unprepared surface of the geometrical shapes prepared circumferences is presented in Figure 4 for
was colored (Schwan-Stabilo Marker, Heroldsberg, the three optical conditions and the two teeth
Germany). Photographs of the geometric shapes separately. For both teeth the percentage of correctly
were taken at 103 magnification using a light prepared circumferences was significantly higher
microscope (Leica M 420) equipped with a video when a microscope was used, followed by Galilean
504 Operative Dentistry
difference between the naked eye, Galilean loupes,
and the microscope was significant (p,0.05). A
significant difference between direct and indirect
vision was noted for the naked eye (p=0.0052) but
not for the Galilean loupe (p=0.093) or the micro-
scope (p=0.597).
DISCUSSION
The literature on the effect of using magnification
devices on the precision of dental procedures is
controversial. To the best of our knowledge no
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standardized protocol has so far been used to test
the impact of loupes or an operating microscope on
the precision of tooth preparations. The aim of the
present study was to evaluate the effect of magnifi-
cation on tooth preparation under simulated clinical
conditions using a standardized protocol.
To avoid any bias due to limitations of dentists’
near vision, a standardized visual test at dental
working distance was performed on the study
participants.5 Most of the previous studies about the
impact of magnification devices on clinical skills have
not tested the dentists’ near visual performance,
although weak natural near visual acuity might
affect the dentists’ clinical performance.16,19,24-28
To prevent bias resulting from fatigue or training
effects, the dentists performed three preparation
cycles in rotating order of the visual conditions with
a break of at least 1 week between each procedure.
The median results of the three cycles were used for
Figure 2. The summarized data of both teeth showed that the
statistical analysis to exclude outliers by accidental
percentage of correctly prepared circumferences was significantly preparation defaults.
higher when a microscope was used (mean: 67.8%; standard
deviation [SD]: 17.6%), followed by loupes (mean: 44.9%; SD: The circle on the distal surface of tooth 16 and the
18.2%) and no magnification aids (mean: 31.2%; SD: 22.7%) y-shaped figure on the occlusal surface of tooth 36
(p,0.0001). were chosen to represent common cavities in these
Figure 3. Summarized data of both teeth showed that the incorrectly locations. The choice of these two locations also
prepared areas in relation to the circumference were significantly
lower when a microscope was used (mean: 0.021 mm2/mm; standard
allowed comparison of direct vs indirect vision
deviation [SD]: 0.015 mm2/mm), followed by loupes (mean: 0.045 corresponding to the clinical situation. The finding
mm2/mm; SD: 0.025 mm2/mm) and no magnification aids (mean: that direct vision allowed a significantly higher
0.076 mm2/mm; SD: 0.042 mm2/mm) (p,0.0001).
precision than indirect vision for preparations made
with the naked eye but not for those made using the
loupes, and was lowest with the naked eye (or microscope is of clinical interest and should be
wearing prescription glasses) (p,0.05). A signifi- further investigated.
cantly better performance under direct vision than
The precision of tooth preparation was measured
indirect vision was found for preparations made with
by two values: 1) the percentage of correctly
the naked eye (p=0.0076) and using the Galilean
prepared circumference quantified the general pre-
loupe (p=0.044). When dentists used the microscope,
cision, and 2) the dimensions of the incorrectly
the difference between direct and indirect vision was
prepared areas were quantified in relation to the
not significant (p.0.05).
circumference, thus giving a weight of the respective
The incorrectly prepared areas in relation to the imperfections. Both values showed that a highly
circumference (mm2/mm) are presented in Figure 5 significantly better performance was obtained using
for tooth 16 and tooth 36. For both teeth the the microscope, followed by Galilean loupes and,
Eichenberger & Others: Tooth Preparation in Dentistry Using Magnification 505
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Figure 4. Percentage of correctly prepared circumferences for direct vision (tooth 36) vs indirect vision (tooth 16). Performance under direct vision
was significantly better for preparations made with the naked eye and the Galilean loupe but not the microscope.
Figure 5. Incorrectly prepared areas for direct vision (tooth 36) vs indirect vision (tooth 16). Performance under direct vision was significantly better
for preparations made with the naked eye but not for those made using loupes or the microscope.
lastly, the naked eye (with prescription glasses if CONCLUSION
needed). The results indicate a direct influence of
Magnification devices improved the precision of
magnification devices on the precision of dental
tooth preparations in a simulated clinical setting.
work. This supports commonly expressed expert
Highly significant differences were noted between
opinions29-31 but is in contrast to the results of some
preparations made using the optically sophisticated
experimental studies,16,17,20 where magnification
operating microscope, Galilean loupes with coaxial
aids per se did not lead to better clinical outcomes.
illumination and the naked eye (plus prescription
The inclusion criterion of daily use by the study
glasses if needed). This was true for direct and
subjects of all magnification aids tested is essential
indirect vision. The protocol evaluated in this study
to avoid bias resulting from lack of expertise. This
strict inclusion criterion has not been described in allowed for an objective assessment of different
earlier studies and might be a possible explanation impacts, for example, magnification aids and direct
for the different outcomes. This criterion, on the vs indirect vision, on the precision of tooth prepara-
other hand, drastically limits the number of poten- tion.
tial test subjects and caused the restriction on
Galilean loupes in this study. Since earlier studies Acknowledgments
showed a superior visual performance of Keplerian The authors would like to thank Isabel Hug (Department of
loupes, it would be interesting to evaluate their Restorative, Preventive and Pediatric Dentistry, School of
impact in a future study. The effects of age and near Dental Medicine, University of Bern, Bern, Switzerland) for
the evaluation of the prepared geometrical shapes and Gabriel
visual acuity were not further investigated due to Fischer (significantis GmbH, Niederwangen b. Bern, Switzer-
the limited number of participants. land) for the statistical analysis.
506 Operative Dentistry
Regulatory Statement 13. Weinstein T, Rosano G, Del Fabbro M, & Taschieri S
(2010) Endodontic treatment of a geminated maxillary
This study was conducted in accordance with all the
provisions of the local human subjects oversight committee second molar using an endoscope as magnification device
guidelines and policies of the Kantonale Ethikkommission International Endodontic Journal 43(5) 443-450.
Bern. There was no approval number or code and documen- 14. Brito M Jr, Moreira G Jr, Normanha JA, Faria-e-Silva
tation was provided. AL, Camilo CC, Savioli RN, & Saquy PC (2013) Midbuccal
canals of maxillary molars evaluated by cone-beam
Conflict of Interest computed tomography: Endodontic management of two
The authors of this manuscript certify that they have no cases Brazilian Dental Journal 24(6) 575-579.
proprietary, financial, or other personal interest of any nature 15. Albuquerque DV, Kottoor J, Dham S, Velmurugan N,
or kind in any product, service, and/or company that is Abarajithan M, & Sudha R (2010) Endodontic manage-
presented in this article. ment of maxillary permanent first molar with 6 root
Downloaded from http://meridian.allenpress.com/operative-dentistry/article-pdf/43/5/501/1837088/17-169-c.pdf by India user on 29 July 2024
canals: 3 case reports Oral Surgery, Oral Medicine, Oral
(Accepted 14 August 2017) Pathology, Oral Radiology, and Endodontics 110(4)
e79-e83.
REFERENCES
16. Lussi A, Kronenberg O, & Megert B (2003) The effect of
1. Eichenberger M, Perrin P, Ramseyer ST, & Lussi A (2015) magnification on the iatrogenic damage to adjacent tooth
Visual acuity and experience with magnification devices surfaces during class II preparation Journal of Dentistry
in Swiss dental practices Operative Dentistry 40(4) 31(4) 291-296.
E142-E149.
17. Neuhaus KW, Jost F, Perrin P, & Lussi A (2015) Impact
2. Perrin P, Eichenberger M, Neuhaus KW, & Lussi A (2016) of different magnification levels on visual caries detection
Visual acuity and magnification devices in dentistry with ICDAS Journal of Dentistry 43(12) 1559-1564.
Swiss Dental Journal 126(3) 222-235.
18. Taschieri S, Weinstein T, Tsesis I, Bortolin M, & Del
3. Perrin P, Ramseyer ST, Eichenberger M, & Lussi A (2014) Fabbro M (2013) Magnifying loupes versus surgical
Visual acuity of dentists in their respective clinical microscope in endodontic surgery: A four-year retrospec-
conditions Clinical Oral Investigations 18(9) 2055-2058. tive study Australian Endodontic Journal 39(2) 78-80.
4. Eichenberger M, Perrin P, Neuhaus KW, Bringolf U, & 19. Hoerler SB, Branson BG, High AM, & Mitchell TV (2012)
Lussi A (2013) Visual acuity of dentists under simulated Effects of dental magnification lenses on indirect vision: A
clinical conditions Clinical Oral Investigations 17(3) pilot study Journal of Dental Hygiene 86(4) 323-330.
725-729.
20. Mitropoulos P, Rahiotis C, Kakaboura A, & Vougioukla-
5. Eichenberger M, Perrin P, Neuhaus KW, Bringolf U, & kis G (2012) The impact of magnification on occlusal
Lussi A (2011) Influence of loupes and age on the near caries diagnosis with implementation of the ICDAS II
visual acuity of practicing dentists Journal of Biomedical criteria Caries Research 46(1) 82-86.
Optics 16(3) 035003.
21. Smadi L, & Khraisat A (2007) Detection of a second
6. Perrin P, Neuhaus KW, & Lussi A (2014) The impact of mesiobuccal canal in the mesiobuccal roots of maxillary
loupes and microscopes on vision in endodontics Interna- first molar teeth Oral Surgery, Oral Medicine, Oral
tional Endodontic Journal 47(5) 425-429. Pathology, Oral Radiology, and Endodontics 103(3)
7. Sitbon Y, & Attathom T (2014) Minimal intervention e77-e81.
dentistry II: Part 6. Microscope and microsurgical 22. Donaldson ME, Knight GW, & Guenzel PJ (1998) The
techniques in periodontics British Dental Journal effect of magnification on student performance in pediat-
216(9) 503-509. ric operative dentistry Journal of Dental Education
8. Sitbon Y, Attathom T, & St-Georges AJ (2014) Minimal 62(11) 905-910.
intervention dentistry II: part 1. Contribution of the 23. Brunner E, Domhof S, & Langer F (2002) Nonparametric
operating microscope to dentistry British Dental Journal Analysis of Longitudinal Data in Factorial Experiments
216(3) 125-130. Wiley, New York NY.
9. Mamoun J (2013) Use of high-magnification loupes or 24. Forgie AH, Pine CM, & Pitts NB (2001) Restoration
surgical operating microscope when performing dental removal with and without the aid of magnification
extractions New York State Dental Journal 79(3) 28-33. Journal of Oral Rehabilitation 28(4) 309-313.
10. Malterud MI (2013) Magnification: You can’t effectively 25. Forgie AH, Pine CM, & Pitts NB (2002) The use of
practice minimally invasive biomimetic dentistry without magnification in a preventive approach to caries detection
it General Dentistry 61(3) 14-17. Quintessence International 33(1) 13-16.
11. Kottoor J, Paul KK, Mathew J, George S, & Roy A (2014) 26. Haak R, Wicht MJ, Hellmich M, Gossmann A, & Noack
A permanent mandibular second molar with seven root MJ (2002) The validity of proximal caries detection using
canal systems Quintessence International 45(5) 381-383. magnifying visual aids Caries Research 36(4) 249-255.
12. Kottoor J, Sudha R, & Velmurugan N (2010) Middle distal 27. Buhrley LJ, Barrows MJ, BeGole EA, & Wenckus CS
canal of the mandibular first molar: a case report and (2002) Effect of magnification on locating the MB2 canal
literature review International Endodontic Journal 43(8) in maxillary molars Journal of Endodontics 28(4)
714-722. 324-327.
Eichenberger & Others: Tooth Preparation in Dentistry Using Magnification 507
28. Maggio MP, Villegas H, & Blatz MB (2011) The effect of 30. van Gogswaardt DC (1990) [Dental treatment methods
magnification loupes on the performance of preclinical using the loupe]. ZWR Das Deutsche Zahnärzteblatt 99(8)
dental students Quintessence International 42(1) 45-55. 614-617.
29. Friedman MJ (2004) Magnification in a restorative dental 31. Woo GC, & Ing B (1988) Magnification devices for the
practice: From loupes to microscopes Compendium of presbyopic dentist. Journal of the Canadian Dental
Continuing Education in Dentistry 25(1) 48, 50, 53-45. Association 54(6) 447-449.
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