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Eye safety in dentistry

April 15, 2015
Authors Peter Arsenault, DMD, MS, and Amad Tayebi, ScD, Esq., discuss the inadequacy of the current dental mask and eyewear combination for protecting dental providers, as well as various types and sources of dental practice eye occupational hazards and the possible entry routes of dental debris toward practitioners’ eyes. The authors also present experimental work investigating the shortcomings of the current dental mask and eyewear combination for protecting dental providers’ eyes.

The objective of this article is to express an experimental, work-supported opinion of its authors regarding the inadequacy of the current dental mask and eyewear combination for protecting dental providers. The various types and sources of dental practice eye occupational hazards and the possible entry routes of dental debris toward the practitioner’s eyes are discussed. Experimental work investigating the shortcomings of the current dental mask and eyewear combination for protecting the dental provider’s eyes are presented.

Authors’ note: The opinions expressed in this article are solely those of the authors and do not represent opinions, positions, or recommendations—express or implied—made by The University of Massachusetts Lowell or by Tufts University. These opinions are based on Dr. Peter Arsenault’s extensive experience as a practicing dentist and as a professor of operative dentistry and Dr. Amad Tayebi’s extensive experience in the design and manufacturing of NIOSH-approved respiratory protection devices. In the interest of transparency, the authors hereby disclose that they are co-inventors of a patent covering a mask with debris deflector.

Types and sources of dental practice eye occupational hazards
By their nature, dental procedures involving drilling at very high speeds (180,000 rpm to 500,000 rpm) generate debris traveling at speeds of up to 50 mph. Such debris includes pieces of amalgam, tooth enamel, calculus, pumice, and broken dental burs along with blood-borne pathogens. In the absence of protective means, such debris may find its way to the eyes of the dental practitioner or dental assistant (Figure 1; Source: Google Photos).

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Possible entry routes of debris toward dental practitioners’ eyes
Normally, dentists, hygienists, and dental assistants wear masks and protective eyewear (glasses: prescription, nonprescription, and loupes) while performing dental procedures. Dental masks are available in a variety of designs and profiles, including pleated, molded cup, duckbill, and foldable styles. The most commonly used type is the pleated style. All dental mask styles provide protection of covered facial areas—primarily the nose, mouth, and portions of the cheeks—against splash.

Pleated dental masks are most preferred by dental practitioners since they are easy to wear and have low resistance to breathing.

Masks fitted with a full-face transparent shield are particularly desirable because a dental procedure can potentially generate the splashing of blood-borne pathogens and various debris. Masks with a full-face shield worn with appropriate eyewear underneath provide the most effective facial and eye protection against such safety hazards.

Referring to Figures 2 and 3, there are three possible routes dental debris may follow in order to reach the eye of a practitioner not wearing a full-face shield mask, namely:

  • Frontal Entry Routeby debris traveling perpendicular to the practitioner’s face. Glasses provide the necessary protection against such debris. They are required by OSHA Standard 1910.133(a) (1) and must meet ANSI Standard (Z87.1). Accordingly, fewer eye injuries are caused by such debris.
  • Sideways (right to left or left to right) Entry Routesby debris traveling tangential to the face. Side shields provide effective protection against such debris and are specifically required by OSHA Standard 1910.133(a) (2).
  • Bottom Gaps Entry Routes by debris traveling vertically and tangential to the face. Such debris may reach a practitioner’s eye through the open gaps (bottom gaps) between the lower rims of the lenses of the protective eyewear and the upper edge of the mask worn by the practitioner.

As discussed above, since Front Entry Route and Sideways Entry Routes are effectively blocked by the use of OSHA-required protective eyewear (OSHA Standard 1910.133(a)(1)) and side shields (OSHA Standard 1910.133(a)(2)), the Bottom Gaps Entry Routes are the most frequent, yet unaddressed, routes of eye-injury-causing debris.

Experimental work
A series of spray studies were conducted to evaluate the efficiency and safety of the current, typical personal protective equipment used in the dental setting.

The objective of the experimental spray studies were to evaluate the entry routes associated with the noted bottom gaps (the spaces between the wearer’s cheek or top edge of the worn mask and the bottom rim of the worn eyewear (see Figures 2 and 3) when a red-dyed spray was directed at the simulated practitioner’s face from different angles.

Experimental set-up and procedures
An apparatus was constructed to simulate the angles where a dentist or dental hygienist would most likely be relative to the patient and the dental handpiece used during typical dental procedures. (See Figures 4, 5, 6, and 7) Because of the nature of the study, a medium-size mannequin head was used as the subject as opposed to a “live” subject.
The medium-size human head mannequin was mounted and positioned to simulate the typical angular position and distance of the face of a dentist or a dental hygienist relative to the patient and operating dental handpiece during a dental procedure.

A spray bottle containing water-base red dye was used for spraying the dye solution at the mannequin head from the six o'clock (middle position), four o’clock, and eight o'clock positions (left and right positions) to simulate the average, typical angles that would be consistent with the dentist/patient operating positions and angles.

The first spray study consisted of the mannequin head wearing OSHA-compliant safety glasses with side shields along with a standard, flat ear loop mask (See Figure 8). The second spray study consisted of the mannequin head wearing a mask with a full-face shield without eyewear under the full-face shield/mask combination (See Figure 9).

With the mannequin head in both studies mounted at the exact same position and angles with relation to the nozzle of the spray bottle, the nozzle was aimed at the mannequin head from the above-mentioned positions. Two complete spray shots from the spray bottle were generated from each of the three positions to evaluate possible entry routes for debris projectiles and associated procedural fluids. This was repeated for both mask set-ups.

V conclusion, results, and discussion
The first spray study was conducted with the mannequin head wearing a mask with full-face shield, (see Figure 9). With the head mounted as outlined (see Figures 4, 5, 6, and 7), two spray shots were directed at the mannequin head from the above-mentioned three positions. The results showed that a mask with a full-face shield provided complete and adequate facial protection from the typical spray and debris paths that a dental provider would encounter during a dental procedure (See Figures 10, 11, and 12). Note that the mannequin's eyes are clear from the spray dye (see Figure 12) indicating that the bottom gaps were adequately blocked while wearing the full-face shield/mask combination during the spray study.

The second spray study was conducted with the mannequin head wearing OSHA-compliant safety glasses with side shields and a flat, ear loop mask (see Figure 10). With the head mounted as outlined (See Figures 4, 5, 6, and 7), two spray shots were directed at the mannequin head from the same three positions. The results showed that the glasses with side shields blocked the frontal and side entry routes by debris traveling perpendicular to the practitioner’s face while not adequately closing the bottom gaps as the mask with full-face shield demonstrated (See Figures 13, 14, 15, 16, and 17).

As shown in Figures 13 and 14, it is clear that the spray dye covered the bottom rim of the safety glasses and the top edge of the mask while penetrating through the open bottom gaps and proceeding to the mannequin's eyes by traveling vertically and tangential to the face (See Figures 15, 16, and 17).

These findings demonstrate clearly that there is a major inadequacy and breach of the present dental mask and eyewear combination for protecting the eyes of a dental care provider. Closing the bottom gaps are essential to protect the eyes from dental debris along with blood-borne pathogens that may reach the eyes of the dental provider through such bottom gaps.

Peter Arsenault, DMD, MS, is a graduate of The University of Massachusetts where he received his Bachelor of Science and Master of Science degrees in plastics engineering, with a minor in chemistry. Dr. Arsenault worked in industry as an engineer before entering dental school. He earned his Doctor of Dental Medicine from Tufts University School of Dental Medicine in 1994. He completed a General Practice Residency at New England Medical Center in Boston, and then went on to private practice. He is a member of the American Dental Association, the New Hampshire and Massachusetts Dental Societies, the Academy of Sports Dentistry, and the Society of Plastics Engineers along with the Society of Materials Engineers. Dr. Arsenault has shown great interest in product development and intellectual property law and holds several US patents and patent-pending products relating to the dental field. Since 2005, Dr. Arsenault has taught at Tufts University School of Dental Medicine and is currently an associate professor and division head of operative dentistry in the Department of Prosthodontics and Operative Dentistry. He maintains a private practice in Salem, New Hampshire, and is the team dentist for the Lowell Spinners baseball club (the minor league affiliate of the Boston Red Sox). His emphasis on patient comfort and safety, as well as keeping up-to-date with the latest advancements in dentistry enable him to provide his patients with the best quality of care in the field. As a practicing dentist, he has recognized the shortcomings in eye safety wear for the practitioner. These shortcomings are what led him to i.shield.
Amad Tayebi, ScD, Esq., is a professor emeritus at the Plastics Engineering Department of the University of Massachusetts Lowell (UML). He joined the faculty of UML in 1978 and during his years of service received the Excellence in Teaching Award in the Plastics Engineering Department in 1998, 2000, 2002, 2005, and 2008. He also received the Exceeding Expectations Award from the UML Student Government in 2004. He retired in June 2010. Prior to joining the UML, he was an assistant/associate professor at Georgia Institute of Technology (Georgia Tech), from 1973 to 1978. In 1984, he cofounded a company for design and manufacturing of NIOSH (National Institute of Occupational Safety and Health)-approved respirators. In 1993, the company was granted the first approval number issued by NIOSH for respirators under the new more stringent approval requirements. The company (Better Breathing, Inc.) was acquired in 1996 by the largest US safety equipment company. Dr. Tayebi’s formal education and academic qualifications include a Bachelor of Science, with distinction and highest honors, in textile engineering, from Alexandria University (1964), a Master of Science Degree in textile technology, a mechanical engineer degree, and a doctor of science degree in mechanical engineering, with a minor in chemical engineering (surface chemistry and polymer physics), from the Massachusetts Institute of Technology (1970, 1972, and 1973) and a Juris Doctor from Massachusetts School of Law (2003). Dr. Tayebi is also an attorney (Commonwealth of Massachusetts) who is also admitted to practice patent law (United States Patent and Trademark Office). His areas of teaching include Processing and Design of Fibrous Materials, Fiber Reinforced Composites, Plastics Processing, Product Design, Thermodynamics, Fluid Mechanics, Particle and Rigid Body Dynamics, Statics, Principles of Design of Automated Assembly Systems, Capstone and Business Law for Engineers (Contracts, Products Liability and Intellectual Property Law).

Suggested reading
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