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Part 1 of a Two-Part Series: Instrumenting Premolars

The complex root anatomy of these teeth poses a distinct challenge during hand instrumentation.

Part 1 of a Two-Part Series: Part two will discuss instrument selection for nonsurgical periodontal therapy and instrumentation technique for premolar teeth.

The complex root anatomy of these teeth poses a distinct challenge during hand instrumentation.

Mechanical debridement is an essential component of oral health care for patients with a healthy periodontium, gingival inflammation, or impaired junctional epithelium and loss of alveolar bone. Premolar teeth are challenging to instrument due to their complex root anatomy. Root debridement is often performed with the blended approach of power and manual instrumentation, followed by root planing with hand instruments.1,2 This two-part series on the hand instrumentation of premolar teeth will discuss root anatomy, instrument selection, and technique.Appropriate power or manual instrumentation involves not only selecting the best instrument for the task at hand, but also using the instrument effectively to reach proper endpoint(s) of care.


Knowledge of the root anatomy is of the utmost importance when instrumenting premolar teeth. During instrumentation, clinicians should create a mental image of the root to effectively select and instrument these narrow and anatomically challenging posterior teeth.

FIGURE 1. The mesial surface of the maxillary first premolar has a significant concavity adjoined to the coronal concavity.

Maxillary first premolar. The mesial surface of the maxillary first premolar has a significant concavity adjoined to the coronal concavity (Figure 1). In contrast, the distal root surface is flat with minimal to no root-surface concavity except coronal to the furcation. The mesial concavity is significant in instrumentation because it will be exposed with all degrees of periodontal conditions, from gingivitis to advanced periodontitis. The distal concavity will only be exposed during instrumentation of pocket depths greater than 5 mm or if significant clinical attachment loss (CAL) is present.

The furcation on this double-rooted tooth is located about 7 mm from the cementoenamel junction (CEJ) and the entire root length is about 14 mm. Therefore, the furcation will be exposed with severe periodontitis (ie, CAL of ≥ 5 mm and/or probing depth of ≥ 7mm),2 or with advancing moderate disease.

The location of the cervical line (ie, CEJ) is of interest when removing deposits from proximal surfaces. Premolar teeth have a mesial proximal curvature of 1 mm, and no curvature on the distal surface. This cervical line curvature, or lack thereof, is important for distinguishing calculus deposits from root-surface anatomy.

Additionally, the width of a premolar’s root near its cervix is important. One-half the width is used to gauge if an instrument’s working end can reach or overlap the midline of the proximal surface. The maxillary first premolar has a buccolingual diameter of 8 mm. The mesiodistal diameter at the cervix is 5.5 mm.

Maxillary second premolar. The single-rooted maxillary second premolar has proximal surfaces that are flat to slightly convex (Figure 2). These surfaces display concavities, grooves, and a possible furcation in the apical one-half of the root. Therefore, pocket depth and CAL may be encountered. The root length and other characteristics are the same as the maxillary first premolar.

FIGURE 2. The single-rooted maxillary second premolar has flat to slightly convex proximal surfaces.

Mandibular first premolar. The single-rooted mandibular first premolar has a convex root surface that tapers to the lingual (Figure 3). The coronal one-half of the root might have horizontal convexities. The apical one-third often has a concavity with a groove and bifurcation, which would be instrumented if the pocket depth is deep. This mandibular premolar is the same length as the maxillary premolars (14 mm); however, it is narrower at the cervix in the buccolingual dimension (6.5 mm).

Mandibular second premolar. The single-rooted mandibular second premolar has flat to slightly convex surfaces with small concavities on the mesial and distal in the middle one-half of the root (Figure 4). Therefore, the clinician will negotiate this anatomy with slight or moderate periodontitis and pocket depth up to 5 mm, as well as with advanced conditions. This premolar is longer than the other premolars (14.5 mm) and is 7 mm in the buccolingual dimension at the cervix.

Patients’ assessment information is important to consider when determining the root anatomy that may be encountered during mechanical debridement. A thorough oral assessment includes a comprehensive periodontal evaluation completed annually,3 or more frequently. The gingival contour, probing depths with or without bleeding, width of keratinized tissue, gingival recession, and CAL should be evaluated. Also, suppuration, furcation involvement, and mobility must be considered. The presence, degree, and distribution of gingival inflammation and biofilm, as well as radiographs are also important considerations for accurate diagnosis, prognosis, and treatment planning.3


FIGURE 3. The single-rooted mandibular first premolar has a convex root surface that tapers to the lingual.

A diagnosis of gingivitis vs periodontitis helps define the type of care needed. Treatment planning includes not only the length and number of appointments, but also the proper instruments for mechanical debridement.

Basic instrumentation, or scaling, of the premolars is indicated for healthy patients and those with gingival inflammation. Either a prophylaxis or scaling in the presence of generalized moderate or severe gingival inflammation is indicated for debridement of biofilm, calculus, and stain.4 For this type of care, various universal and area-specific curets can be used.

Although universal curets are shaped similarly, various tip lengths and widths are available. In instances of shallow periodontal pocket depth, a universal curet with a short shank and/or working end might be selected. Alternatively, a universal curet with a long working end may suffice for completing the debridement.

Pseudopocketing may be another consideration during instrument selection due to increased probing depths; however, in this case, the root anatomy described above will not be exposed. The pseudopocketing will cause the gingival tissue to increase in size with no apical migration of the junctional epithelium or destruction of the periodontal ligament and alveolar bone.5 For example, a pseudopocket measuring 6 mm requires debridement mostly on the crown with limited root-surface instrumentation. If, however, the 6 mm probing depth is a true periodontal pocket, the majority of the instrumentation will be on the root. Therefore, instrument selection for debridement cannot rely on probing depth alone.

FIGURE 4. The single-rooted mandibular second premolar has flat to slightly convex surfaces with small concavities on the mesial and distal in the middle one-half of the root.

Another consideration for instrument selection is reaching the midline effectively. The maximum premolar width at the cervix is 7 mm, so it is likely that the working ends of either universal or area-specific curets will reach and overlap the midline of the proximal surface. However, if deep periodontal pockets exist and mini- or micro-mini bladed area-specific instruments are used, the risk of not covering the proximal surface near the cervix increases because of the short working ends. In this case, both universal and area-specific curets can be employed to ensure adequate coverage of the proximal surface from the epithelial attachment to the CEJ.


Instrumenting premolar teeth presents a variety of challenges. Memorizing the potential anatomy and applying it to the clinical findings during hand instrumentation are key elements in maintaining health and promoting healing of the periodontal structures. Appropriate instrument selection for the different anatomy of premolar teeth is also integral to successful outcomes.


  1. Hodges KO. Instrument selection: philosophy and strategies. In: Hodges KO, ed. Concepts in Nonsurgical Periodontal Therapy. Independence, Kentucky: Delmar Cengage; 1998.
  2. American Academy of Periodontology. Task force report on the Update to the 1999 Classification of Periodontal Diseases and Conditions. J Periodontol. 2015;86:838–943.
  3. American Academy of Periodontology. Comprehensive periodontal therapy: a statement by the American Academy of Periodontology. J Periodontol. 2011;86:835–838.
  4.  CDT 2017 Dental Procedure Codes. 2016. Chicago: American Den- tal Association; 2016.
  5. American Academy of Periodontology. Glossary of Terms 2017. Available at: Accessed August 21, 2017.


From Dimensions of Dental Hygiene. September 2017;15(9):14, 16.

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