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Year : 2014  |  Volume : 1  |  Issue : 1  |  Page : 37-40

Assessment of iatrogenic damage to proximal surfaces of adjacent teeth following crown preparation by final year dental students in Saudi Arabia

1 Associate Clinical Professor, Riyadh Colleges of Dentistry and Pharmacy, Riyadh, Saudi Arabia
2 Interns Riyadh Colleges of Dentistry and Pharmacy, Riyadh, Saudi Arabia

Date of Web Publication2-Jan-2014

Correspondence Address:
Bander Abdulwahhab
Royal Clinics of the Custodian of the Two Holy Mosques, Riyadh
Saudi Arabia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/WKMP-0056.124186

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Aim: The purpose of the following study is to measure the amount and frequency of iatrogenic damage to inter-proximal surfaces of adjacent teeth, following crown preparation, among undergraduate dental students in Riyadh Colleges of Dentistry and Pharmacy.
Materials and Methods: Teeth surfaces were examined on master casts, using ×2.5 magnifying loupes. The damage depth of the injured teeth was measured, with - a modified digital micrometer caliper (Whitworth's 6 inch Digital Caliper). To ensure that examined teeth surfaces were intact pre-operatively, they were confirmed with pretreatment radiographs.
Results: A sample of 180 teeth surfaces chosen randomly was examined of which only 111 samples done by undergraduate students with intact teeth surfaces were included. The 69 excluded samples either had carious or restored teeth surfaces or were done by practitioners other than dental students. Over Nearly 98% of examined teeth surfaces, adjacent to crown prepared teeth, were proximally injured. Through using specific measuring parameters, the most frequent type of damage was abrasion (58.7%). The most commonly damaged area found was the middle-third of the proximal surface. The damage extended to more than 50% of the proximal surface, in 63% of the total sample. The depth of the injury was more than 0.1 mm in 58% of the total sample. Damage was more frequent in maxillary teeth (60.4%), than mandibular teeth (39.6%).
Conclusion: Conventional crown preparation methods appear to result in significant damage to adjacent teeth surfaces; increasing caries risk potential, thermal sensitivity and periodontal disease. Therefore, protection of these surfaces and selection of the most appropriate instruments and preparation techniques are important.

Keywords: Crown preparation, dental students, iatrogenic damage, proximal surface

How to cite this article:
Abdulwahhab B, AlHati M, AlEnzi M, Babidan S. Assessment of iatrogenic damage to proximal surfaces of adjacent teeth following crown preparation by final year dental students in Saudi Arabia. Saudi J Oral Sci 2014;1:37-40

How to cite this URL:
Abdulwahhab B, AlHati M, AlEnzi M, Babidan S. Assessment of iatrogenic damage to proximal surfaces of adjacent teeth following crown preparation by final year dental students in Saudi Arabia. Saudi J Oral Sci [serial online] 2014 [cited 2023 Apr 2];1:37-40. Available from: https://www.saudijos.org/text.asp?2014/1/1/37/124186

  Introduction Top

An ideal preparation of the tooth should not damage the adjacent tooth in the slightest. This however is hard to achieve with literature documenting a high incidence of iatrogenic damage to adjacent teeth during crown preparation, [1],[2] cavity preparation [3],[4],[5],[6] and orthodontic stripping. [7],[8],[9] There are comparatively more data available on the incidence of iatrogenic damage during class II cavity preparations and orthodontic stripping than during crown preparations. [3],[5],[10] The few studies on crown preparation report a high incidence of damage to the adjacent tooth with rates as high as 89% [4] and 100%. [11]

The accidental damage of proximal teeth has been linked with increased caries susceptibility, periodontal disease and temperature sensitivity. [7] However given the potential for the enamel to remineralize following accidental traumatic injury, [12] it is important to not merely detect iatrogenic damage, but also quantify the extent of the damage. Although some authors have used scanning electron microscopy to describe iatrogenic damage on extracted teeth, the use of magnifying loupes and calipers have served to accurately detect and quantify iatrogenic damage to adjacent teeth.

The clinical performance of dental students is often an issue of debate and iatrogenic damage in teeth prepared by students is no different. Although some authors suggest that the inexperience and stress of a student cutting a cavity results in greater iatrogenic damage, others have documented less iatrogenic damage in teeth adjacent to class II cavities prepared by students. [5] There is however no comparable data for crown preparations done by students. Furthermore, there is a paucity of literature on the topic from the Middle East in general and Saudi Arabia in particular.

Given this gap of data, the aim of this investigation was to study the incidence and severity of iatrogenic damage to teeth adjacent to abutment teeth prepared by final year students in a Dental College in Saudi Arabia.

  Materials and Methods Top

Ethical approval for the study was obtained from the research center of the Riyadh Colleges of Dentistry and Pharmacy for the investigation.

Sample selection

The sample comprised randomly selected casts of patients who were treated by students in the clinics of the Dental College and who had received prosthodontics treatment requiring crown preparation. All casts had been poured using the two stage putty wash impression technique with a putty impression material (Express™ STD 3M ESPE, Seefeld, Germany) and a light body impression material (Express™ XT VPS, 3M ESPE). After examining and identifying the location of the examined teeth (upper-lower, posterior-anterior, right-left), only intact adjacent teeth were included in this study. Adjacent teeth were present with pretreatment bitewing radiographs for posterior teeth and periapical radiographs for anterior teeth, to ensure that they were intact pre-operatively. Casts that showed damage due to improper handling, casts with visible porosities and casts, which had been poured in alginate impressions were excluded from the study.

Measuring instrument

Master casts which met the inclusion criteria were examined, using magnifying ×2.5 loupes. The damage depth was measured with a Whitworth's 6 inch digital caliper (Whitworth, CA, USA), inserted horizontally and perpendicular to the floor, by ensuring a stable armrest. With the help of a mechanical engineer, the caliper was modified, by soldering a small pointed tip pin, to be able to reach the deepest area of injury [Figure 1]. Accordingly, each tooth was given a score according to a previously fixed index of Lussi and Gygax [4] [Table 1].
Figure 1: Modification of the caliper to measure the damage on the casts

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Table 1: Index for screening the casts for damage to the teeth

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Validity and specificity

To ensure inter-examiner reliability the scores of the defects on 20 randomly selected casts were measured by each of the assessors (SB, ME) Intra-examiner reliability was tested by making the examiners repeat the measurement on the same casts after 3 weeks. The Cronbach alpha for inter-examiner validity was 0.9, indicating satisfactory reliability. The intra-examiner Cronbach alpha was also 0.9.

The accuracy of the impression and the measuring tool was tested by measuring the bucco-lingual dimensions of the tooth immediately mesial to the abutment tooth on ten different casts and repeating the measurement in the patient's mouth. The Cronbach alpha score was 0.99 suggesting a margin of error of 0.2%.

Statistical analyses

The information and data from the completed laboratory study forms were entered into an electronic database (IBM SPSS® for Windows, ver. 15; IBM corp. Armonk, NY, USA) and statistical analysis (Chi-square test, P < 0.05) was carried out to interpret the results.

  Results Top

A total of 111 casts of tooth preparation, done by undergraduate students (51 male, 59 female), with intact tooth surfaces, were included in the study. Evidence of proximal damage was found on 98.2% of examined teeth surfaces, adjacent to crown prepared teeth. Only 2 casts showed no evidence of proximal damage. Damage was more frequent in maxillary teeth (60.4%) than in mandibular teeth (39.6%), posterior teeth (68.5%) than anterior teeth (31.5%) and the left side (65.8%), damaged more than the right side (34.2%).

The most frequent type of damage was abrasion, followed by abrasion and nicks, then nicks [Figure 2]. Nicks were more common among female students while abrasions were more common among male students [Table 2]. The most commonly damaged surface found was the middle-third of the proximal surface (46.8%).
Figure 2: Types of damage to the teeth; (a) nicks, (b) abrasion (c) both

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Table 2: Type of damage according to the gender of the operator

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The damage was located more vertically (occluso-cervically) than horizontally (bucco-lingualy) (40.5%). The damage extended to more than 50% of the proximal surface, in (63%) of injured teeth surfaces. The depth of the damage was more than 0.1 mm in 55.8% of the total sample [Chart 1 [Additional file 1]].

The Chi-square test and with P < 0.05 showed no significant differences, between the extent of damage and the operator's gender, neither between the location of damage nor its type and extent.

  Discussion Top

The results support the hypotheses of previous authors, that damage to the adjacent tooth is almost always inevitable while working on proximal areas. Interestingly, while previous studies have focused on the damage caused following box-preparations using conventional cavity preparation techniques, [4],[11],[13] this study confirmed that tooth preparation for prosthodontics abutments is at a great, if not greater risk.

Materials science has made great advances over the past few decades and tooth preparations have been modified to suit these advances. [6] However the basic method of preparation, the use of high speed burs, has remained largely unchanged over the past half century. The extent of damage to adjacent tooth during tooth preparation first began to receive attention in the 1970s. [3],[10] Despite emphasis being made in the literature on the need to protect adjacent teeth, there seems to be no change in the extent or prevalence of damage to the adjacent teeth across the decades. [1],[3],[8]

One of the important findings of this study was that although almost all the casts studied had signs of damage, only about half of them had damage greater than one third of the tooth surface. Authors have suggested that while minor damage to the adjacent tooth actually has the potential to remineralize, [5],[10],[12],[14] the defect may be misdiagnosed as caries on the follow-up X-ray. [12],[13] One of the limitations of this study is that the patients were not followed-up for complaints of sensitivity or possible development of caries. A follow-up study on these parameters could serve to shed more light on the nature of tooth damage and repair following iatrogenic damage.

Studies on practicing dentists have shown significantly lower incidence of damage in mandibular teeth than in maxillary teeth. [4],[5] Our results show that students had no significant difference in the incidence of damage, even though there were significant differences in the extent of damage to the maxillary and mandibular teeth. Similarly, our findings show no significant differences between damage to the right and left side of the patients' arches. This finding goes against the opinion of literature on periodontal treatment that has shown differences in patterns of efficiency and damage between right handed and left handed dentists. [15]

  Conclusion Top

The main aim of this study was to determine the incidence of iatrogenic damage during cavity preparation by students. An expansion of the study to include clinical follow-up of the patients and awareness of the instructors will clearly shed more light on what appears to be a serious problem during tooth preparation by undergraduate students.

  References Top

1.Moopnar M, Faulkner KD. Accidental damage to teeth adjacent to crown-prepared abutment teeth. Aust Dent J 1991;36:136-40.  Back to cited text no. 1
2.Coelho PG, Silva NR, Thompson VP, Rekow D, Zhang G. Effect of proximal wall height on all-ceramic crown core stress distribution: A finite element analysis study. Int J Prosthodont 2009;22:78-86.  Back to cited text no. 2
3.Boyde A, Knight PJ. Scanning electron microscope studies of Class II cavity margins. Matrix band application. Br Dent J 1972;133:331-7.  Back to cited text no. 3
4.Lussi A, Gygax M. Iatrogenic damage to adjacent teeth during classical approximal box preparation. J Dent 1998;26:435-41.  Back to cited text no. 4
5.Medeiros VA, Seddon RP. Iatrogenic damage to approximal surfaces in contact with Class II restorations. J Dent 2000;28:103-10.  Back to cited text no. 5
6.Peters MC, McLean ME. Minimally invasive operative care. II. Contemporary techniques and materials: An overview. J Adhes Dent 2001;3:17-31.  Back to cited text no. 6
7.Rossouw PE, Tortorella A. Enamel reduction procedures in orthodontic treatment. J Can Dent Assoc 2003;69:378-83.  Back to cited text no. 7
8.Arman A, Cehreli SB, Ozel E, Arhun N, Cetinºahin A, Soyman M. Qualitative and quantitative evaluation of enamel after various stripping methods. Am J Orthod Dentofacial Orthop 2006;130:131.e7-14.  Back to cited text no. 8
9.Zachrisson BU, Minster L, Ogaard B, Birkhed D. Dental health assessed after interproximal enamel reduction: Caries risk in posterior teeth. Am J Orthod Dentofacial Orthop 2011;139:90-8.  Back to cited text no. 9
10.Boyde A, Knight PJ, Jones SJ. Further scanning electron microscope studies of the preparation of class II cavities. Br Dent J 1972;132:447-57.  Back to cited text no. 10
11.Long TD, Smith BG. The effect of contact area morphology on operative dental procedures. J Oral Rehabil 1988;15:593-8.  Back to cited text no. 11
12.Mayne RJ, Cochrane NJ, Cai F, Woods MG, Reynolds EC. In-vitro study of the effect of casein phosphopeptide amorphous calcium fluoride phosphate on iatrogenic damage to enamel during orthodontic adhesive removal. Am J Orthod Dentofacial Orthop 2011;139:e543-51.  Back to cited text no. 12
13.Lussi A, Kronenberg O, Megert B. The effect of magnification on the iatrogenic damage to adjacent tooth surfaces during class II preparation. J Dent 2003;31:291-6.  Back to cited text no. 13
14.Piacentini C, Sfondrini G. A scanning electron microscopy comparison of enamel polishing methods after air-rotor stripping. Am J Orthod Dentofacial Orthop 1996;109:57-63.  Back to cited text no. 14
15.Canakci V, Tan U, Orbak R, Tezel A. Right- and left-handed dentists in periodontal therapy. Int J Neurosci 2002;112:1-14.  Back to cited text no. 15


  [Figure 1], [Figure 2]

  [Table 1], [Table 2]


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