Study Highlights: Dental Practice-Based Research Networks


Assessing Outcomes of Cracked Teeth

Objectives: Cracked tooth syndrome (CTS) is a term applied to a presumptive diagnosis of incomplete tooth fracture that typically presents with consistent symptoms of pain to biting and temperature stimuli, especially cold. The purposes of this cracked tooth register are 1) to identify risk factors for predicting adverse outcomes in both symptomatic and asymptomatic cracked teeth; and 2: to evaluate outcomes of common treatments for symptomatic and asymptomatic cracked teeth. 

Methods: Practices were asked to assess for the presence of cracks in a randomly selected subject starting with a randomly selected posterior tooth.  Teeth were assessed via visual examination with magnification, tactile perception and transillumination.  To be included, a crack had to block transilluminated light.  Various patient-, tooth-, and crack-level criteria were assessed, along with treatment recommendations.  The goal is for each practice to enroll 12 asymptomatic and 8 symptomatic cracked teeth and follow them for a minimum of 1 year.  To aid in subject enrollment, practices could enroll any subject with a symptomatic cracked tooth that met inclusion criteria.

Results: To date, 36 practices in NW PRECEDENT have evaluated 634 subjects with either a symptomatic or asymptomatic cracked teeth.   Among 400 randomly selected subjects, 70% had at least one posterior cracked tooth, emphasizing how ubiquitous this condition is. In fact, one of the practitioners participating in this study noted, "This is a very important study.  Just participating in it has changed the way I think and practice." In addition, 93% of these teeth are asymptomatic, which provides a diagnostic and treatment problem for the dentist. A “watch and wait” approach must be used with caution, since 27% of cracked teeth showed at least one component of crack progression (e.g. length, depth, staining, direction, number of cracked surfaces, total number of cracks, periodontal pocket formation) in just one year. 

Conclusions: From analysis of preliminary data, closer examination of the characteristics of cracked teeth reveals that teeth with multiple cracks on multiple surfaces, and the presence of a restoration in the tooth of a younger (18-60 year old vs >60 year old) individual may help the dentist predict that the tooth is more likely to become symptomatic.  Fortunately, most cracked teeth are recommended for restorative treatment (92-95% of the time), resulting in less need for more invasive treatment (endodontic therapy, extraction). Further study will help to determine not only which cracked teeth are likely to get worse and when intervention should be accomplished, but also what treatments are most effective.


  1. T. Hilton, L. Mancl, Y. Coley, C. Baltuck, J.L. Ferracane, J. Peterson, N.W. PRECEDENT, Initial treatment recommendations for cracked teeth in Northwest PRECEDENT. IADR San Diego, CA, March 2011
  2. T. Hilton, L. Mancl, Y. Coley, J.L. Ferracane, C. Baltuck, E. Lubisich, A. Gilbert, L. Lowder, C. Barnes; J. Peterson, N.W. PRECEDENT, Assessing the Outcomes of Cracked Teeth in Northwest PRECEDENT, Accepted AADR Tampa, FL, March 2012
  3. T. Hilton, J.L. Ferracane, L. Mancl, Y. Coley, C. Baltuck, E. Lubisich, A. Gilbert, L. Lowder, C. Barnes; J. Peterson, N.W. PRECEDENT, Characteristics of Cracks in Teeth - Association with Symptoms, Accepted AADR Tampa, FL, March 2012


Remineralization of White Spot Lesions After Removal of Orthodontic Brackets

Objectives: White spot lesions (WSL) on teeth are a common sequela of orthodontic therapy, and can present a significant esthetic compromise.  We present preliminary data from a single-blinded randomized trial designed to assess the effectiveness of two agents commonly used to ameliorate WSL lesions.

Methods: Patients aged 12 to 20 were recruited from offices of orthodontists who belonged to Northwest PRECEDENT, a practice-based research network.  Patients had their orthodontic appliances removed less than 2 months from the time of enrollment, and had at least one WSL on their maxillary incisors.  Photographs were taken at enrollment , after which subjects were randomized to one of three arms:  1) a single application of PreviDent fluoride varnish (FV), 2) 8 week regimen of MI Paste Plus (MI), or 3) no active agent (control).  All patients received routine home care instructions and non-prescription fluoride toothpaste.  Eight weeks after enrollment, the patients were recalled  for follow-up photographs .  Before-and-after pairs of photographs were assessed by a panel of 5 dental professionals and a panel of 5 lay people.  The judges were asked to assess percent improvement of the WSL using a visual analog scale.   Self-assessment of improvement was also obtained.

Results: Of the 102 subjects, 36 received FV, 30 received MI, and 36 received no active treatment.  The mean improvements assessed by the professional panel were 28%, 21%, and 30% in the FV, MI, and control groups, respectively.  Results from the lay panel were 32%, 30%, and 27%, respectively.   These rates were not significantly different  in either panel of judges.  Self assessment of improvement was 38%, 37%, and 38%, respectively, indicating no significant difference among subjects in the three groups.

Conclusions: In this study, preliminary data indicates that neither PreviDent varnish nor MI Paste Plus are more effective than normal home care over an 8 week period.


  1. G. Huang, B. Roloff-Chiang, S. Shalchi, B. Mills, C. Spiekerman, A. Korpak, and N.W. PRECEDENT, Treatment of White Spot Lesions: A Randomized Clinical Trial, Accepted AADR Tampa, FL, March 2012

PEARL Network

Single Tooth Endodontic and Restorative Treatment Outcomes: PEARL Interim Findings

Patients and their oral health providers routinely face difficult treatment decisions trying to decide the best oral treatment outcomes for their health and well-being.  Making choices based on “generalizable data” is essential for provider decision making and evidence based dental treatment.  The PEARL Network clinical study PRL0705 - “Outcomes for Endodontic Treatment and Restoration of Teeth in Dental Practice” directly assessed treatment outcomes in general dental practice along with patient reported outcomes (PROs).  The study found total failure rates, defined both from the provider and the patient perspective to be significantly higher than previously reported in the literature.  These findings should be carefully considered when weighing treatment options. JADA, May 2012.

PEARL Non-carious Cervical Lesion RCT Baseline and Sleep Bruxism Findings

This study is the longest duration hypersensitivity study conducted to date.  The study design provides an answer to a clinical question of what is the best treatment option for non-carious cervical lesions.  This three arm study compared the use of an FDA approved dentifrice containing potassium nitrate, against placement of a sealant, and resin based composite.  Additionally, during the recall visits impressions were taken of the lesions to assess the integrity of the treatments and subjected to scanning electron microscope evaluation.  This study is the first randomized controlled study conducted in a dental PBRN with patients randomized in the practitioner's office and demonstrated an extraordinary level of practitioner and patient compliance (97%), well above industry standards.  The PEARL Network found that the use of a sealant, a dentin bonding agent followed resin based composite restoration significantly lowered both calibrated air blast and patient reported sensitivity compared to the reduction achieved with a potassium nitrate dentifrice at all recalls through the 6 months of the study.  Laboratory evaluation of follow up impressions of the lesion and restorations indicates that open dentinal tubules may not correlate with patient sensitivity.  The manuscript is currently in preparation.


Lessons Learned During the Conduct of Clinical Studies in the Dental PBRN

This article discusses the 23 main substantive and methodologic lessons learned by DPBRN as it conducted its studies in the 2005-2012 funding cycle.  DPBRN demonstrated that large numbers of practitioner-investigators and patients can be enrolled in PBRN studies (more than 70,000 participant units); from a broad range of practice types; for a broad range of study topics, enrollments sizes, and study designs; that patient acceptance is high; and that practitioners can be effectively engaged at every step of the research process (from idea generation, to data collection, to presentation of results, to incorporation of DPBRN evidence into daily clinical practice).  With its studies that have had to do with overlaps between dentistry and medicine (a total of 5 studies about smoking cessation, bisphosphonate-associated osteonecrosis of the jaw, and diabetes screening topics), DPBRN has demonstrated that it can utilize its large existing infrastructure to quickly evaluate emerging health problems and to conduct research on topics that are of interest to oral health and systemic disease.  DPBRN has completed a total of 22 studies (listed at [1]).  So far, these studies have led to 56 peer-reviewed publications in print, in press, or accepted (listed at [2]), with another 13 under review by peer-reviewed journals (listed at [2]), and an additional 16 in development. 
Gilbert GH, Richman JS, Gordan VV, Rindal DB, Fellows JL, Benjamin PL, Wallace-Dawson M, Williams OD, for The DPBRN Collaborative Group. Lessons learned during the conduct of clinical studies in The Dental PBRN. Journal of Dental Education 2011; 75(4): 453-465.

Repair or Replacement of Defective Restorations by Dentists in the Dental PBRN 

This article is an example of a line of research in DPBRN having to do with less surgically-invasive approaches to the treatment of early dental caries and defective restorations.  This overall line of research has provided evidence that DPBRN participation fostered movement of scientific evidence into routine practice.  Practitioner-investigators are open to changing how they treat patients as a result of engaging fellow practitioner-investigators in the scientific process.

Gordan VV, Riley JL III, Geraldeli S, Rindal DB, Qvist V, Fellows JL, Kellum HP, Gilbert GH, for The DPBRN Collaborative Group.  Repair or replacement of defective restorations by dentists in The Dental PBRN. Journal of the American Dental Association 2012; accepted for publication.


Last Reviewed on
February 2018