Daniel A. Shugars

Non-carious cervical lesions

Non-carious cervical lesions are commonly encountered in clinical practice and present in a variety of forms. A knowledge of the aetiology of these lesions is important for preventing further lesions, halting progression of lesions already present, and determining appropriate treatment. The most commonly cited aetiological factors thought to lead to the development of cervical lesions are erosion, abrasion and tooth flexure. Evidence supports a multifactorial aetiology for non-carious cervical lesions. The purpose of this paper is to review the evidence for each of these aetiological factors as it relates to the development of non-carious cervical lesions. Specific features of cervical lesions linked to these factors, including their morphology, location, prevalence and distribution by age and sex will be discussed. Suggestions for future research into the cause and prevention of non-carious cervical lesions will be presented.

Meta-analysis of fixed partial denture survival: Prostheses and abutments

STATEMENT OF PROBLEM Few estimates of the probability of various outcomes associated with replacement of missing teeth with fixed partial dentures have been reported. Existing longitudinal studies have reported widely disparate results for the survival of fixed partial dentures, but these studies have used different definitions of failure and varying periods of follow-up. PURPOSE This study used meta-analysis to formulate annual probability estimates for three categories of fixed partial denture or abutment survival. METHODS A systematic review of the English language literature since 1960 identified eight studies that met the preset inclusion criteria. Estimated annual survival proportions were back-calculated based on the Kaplan-Meier model and these proportions were combined through a fixed effects model meta-analysis. The probabilities and corresponding 95% confidence intervals at 5, 10, and 15 years for the three categories of survival are reported. RESULTS For the aggregate population represented by the limited longitudinal studies available, this meta-analysis indicated that less than 15% of fixed partial dentures were removed or in need of replacement at 10 years; whereas, nearly one third were removed or in need of replacement at 15 years. Less than 5% of abutments were removed at 10 years.

A conceptual framework for understanding outcomes of oral implant therapy

The use of implants has expanded so rapidly that its effectiveness for many clinical situations has not been firmly established. Dentists are responsible for making appropriate therapeutic recommendations for the management of partial and complete edentulism. These decisions require an understanding of the consequences or outcome of treatment approaches. Outcome measures to evaluate the benefits of alternative therapies include longevity as well as physiologic, psychologic, and economic impacts. Future research should include outcome measures beyond implant prosthesis survival to more fully assess the practical impact of dental implants on the patients oral health and to determine the most cost-effective approaches for managing completely and partially edentulous patients.

Root caries risk indicators: a systematic review of risk models

OBJECTIVE To identify risk indicators that are associated with root caries incidence in published predictive risk models. METHODS Abstracts (n = 472) identified from a MEDLINE, EMBASE, and Cochrane registry search were screened independently by two investigators to exclude articles not in English (n = 39), published prior to 1970 (none), or containing no information on either root caries incidence, risk indicators, or risk models (n = 209). A full-article duplicate review of the remaining articles (n = 224) selected those reporting predictive risk models based on original/primary longitudinal root caries incidence studies. The quality of the included articles was assessed based both on selected criteria of methodological standards for observational studies and on the statistical quality of the modeling strategy. Data from these included studies were extracted and compiled into evidence tables, with information about the cohort location, incidence period, sample size, age of the study participants, risk indicators included in the model, root caries incidence, modeling strategy, significant risk indicators/predictors, and parameter estimates and statistical findings. RESULTS Thirteen articles were selected for data extraction. The overall quality of the included articles was poor to moderate. Root caries incidence ranged from 12% to 77% (mean ± SD = 45 ± 17%); follow-up time of the published studies was ≤ 10 years (range = 9; median = 3); sample size ranged from 23-723 (mean ± SD = 264 ± 203; median = 261); person-years ranged from 23 to 1540 (mean ± SD = 760 ± 556; median = 746). Variables most frequently tested and significantly associated with root caries incidence were (times tested; % significant; directionality): baseline root caries (12; 58%; positive); number of teeth (7; 71%; three times positive, twice negative), and plaque index (4; 100%; positive). Ninety-two other clinical and nonclinical variables were tested: 27 were tested three times or more and were significant between 9% and 100% of the times tested; and 65 were tested but never significant. CONCLUSIONS The root caries incidence indicators/predictors most frequently reported were root caries prevalence at baseline, number of teeth, and plaque index. This finding can guide targeted root caries prevention. There was substantial variation among published models of root caries risk in terms of variable selection, sample size, cohort location, assessment methods, incidence periods, association directionality, and analytical techniques. Future studies should emphasize variables frequently tested and often significant, and validate existing models in independent databases.

Incidence rates for complete cusp fracture

OBJECTIVES Although complete cusp fracture is acknowledged to occur frequently, incidence rates have been reported rarely. This study determined incidence rates for complete coronal cusp fracture per person and per tooth type. METHODS All fractures presenting among enrollees in a dental health maintenance organization using two geographically isolated clinics were noted for 105 days. For a sample of these enrollees, likelihood of attending the clinic in the event of a fracture was assessed through a telephone survey, and the at-risk status of all teeth was determined through a record survey. Incidence rates were calculated for persons, and for individual tooth types for all complete fractures and for non-carious complete fractures. In addition, for posterior teeth the distribution of fractured cusps, and the severity of fractures were examined. RESULTS Per-person incidence rates for complete coronal fractures for all teeth were 89.0 and 72.7 per 1000 person years, respectively, for all fractures and for non-carious fractures. The rates for all anterior and all posterior teeth were 10.2 and 69.9, respectively, for all non-carious fractures. In mandibular posterior teeth, lingual cusps fractured twice as frequently as facial cusps, while the opposite was true for maxillary premolars. Among maxillary molars, the mesiofacial and distolingual cusps fractured most frequently. The large majority of fractures exposed dentin (95%), while pulpal exposure occurred infrequently (3%). A minority of fractures extended below the gingival crest (24%) or the DEJ (25%). CONCLUSIONS This is the first report of fracture incidence rates for enumerated persons and teeth at risk and as such helps define the magnitude of the problem for dentists and their patients.

Movement of Teeth Adjacent to Posterior Bounded Edentulous Spaces

Bounded edentulous spaces (BES)-a missing posterior tooth with intact adjacent teeth-are thought to lead to arch collapse resulting from the movement of adjacent teeth. To determine the rate of change in distance between teeth adjacent to a BES, we examined three successive measurable radiographs of 116 untreated posterior BES cases. The distance between the teeth (DBT) adjacent to the space was measured, and change in DBT (A DBT) between pre-extraction and follow-up radiographs was calculated. We used linear spline regression to construct models for tooth movement and to identify factors associated with A DBT. The mean A DBT was < 1 mm during the first year post-extraction, and the DBT continued to decrease at a successively slower rate each following year. Overall and for each tooth type, the greatest rates of decrease in DBT were seen in the zero to two-year period. In a multivariable model, time since extraction and tooth type were significantly associated with A DBT. These findings suggest that movement of teeth adjacent to a posterior BES after the first two years is usually gradual and minor within the time frame of this study.

Tooth-surface-specific Effects of Xylitol: Randomized Trial Results

The Xylitol for Adult Caries Trial was a three-year, double-blind, multi-center, randomized clinical trial that evaluated the effectiveness of xylitol vs. placebo lozenges in the prevention of dental caries in caries-active adults. The purpose of this secondary analysis was to investigate whether xylitol lozenges had a differential effect on cumulative caries increments on different tooth surfaces. Participants (ages 21-80 yrs) with at least one follow-up visit (n = 620) were examined at baseline, 12, 24, and 33 months. Negative binomial and zero-inflated negative binomial regression models were used to estimate incidence rate ratios (IRR) for xylitol’s differential effect on cumulative caries increments on root and coronal surfaces and, among coronal surfaces, on smooth (buccal and lingual), occlusal, and proximal surfaces. Participants in the xylitol arm developed 40% fewer root caries lesions (0.23 D2FS/year) than those in the placebo arm (0.38 D2FS/year; IRR = 0.60; 95% CI [0.44, 0.81]; p < .001). There was no statistically significant difference between xylitol and control participants in the incidence of smooth-surface caries (p = .100), occlusal-surface caries (p = .408), or proximal-surface caries (p = .159). Among these caries-active adults, xylitol appears to have a caries-preventive effect on root surfaces (ClinicalTrials.gov NCT00393055).

Design of the Xylitol for Adult Caries Trial (X-ACT)

BackgroundDental caries incidence in adults is similar to that in children and adolescents, but few caries preventive agents have been evaluated for effectiveness in adults populations. In addition, dentists direct fewer preventive services to their adult patients. Xylitol, an over-the-counter sweetener, has shown some potential as a caries preventive agent, but the evidence for its effectiveness is not yet conclusive and is based largely on studies in child populations.Methods/DesignX-ACT is a three-year, multi-center, placebo controlled, double-blind, randomized clinical trial that tests the effects of daily use of xylitol lozenges versus placebo lozenges on the prevention of adult caries. The trial has randomized 691 participants (ages 21-80) to the two arms. The primary outcome is the increment of cavitated lesions.DiscussionThis trial should help resolve the overall issue of the effectiveness of xylitol in preventing caries by contributing evidence with a low risk of bias. Just as importantly, the trial will provide much-needed information about the effectiveness of a promising caries prevention agent in adults. An effective xylitol-based caries prevention intervention would represent an easily disseminated method to extend caries prevention to individuals not receiving caries preventive treatment in the dental office.Trial RegistrationClinicalTrials.Gov NCT00393055

Prevalence of Third Molars With Caries Experience or Periodontal Pathology in Young Adults

PURPOSE We assessed the prevalence of caries experience and periodontal pathology on asymptomatic third molars in young adults. SUBJECTS AND METHODS Healthy subjects with 4 asymptomatic third molars were enrolled in an institutional review board-approved study during a 5-year period. Full mouth periodontal probing, 6 sites per tooth, was the measure of clinical periodontal status. The presence or absence of occlusal caries experience (carious lesions or restorations, including sealants) on third molars and on any surface of the first and second molars were assessed using a visual-tactile examination and panoramic radiographs. The primary outcome measures were at least 1 periodontal probing depth of at least 4 mm versus none and caries experience versus no caries experience. RESULTS The data were analyzed from 409 subjects, who averaged 25 years old. More subjects were female (53%) and white (76%). More subjects had at least 1 periodontal probing depth of 4 mm or deeper on a third molar (55%) than on the distal of a second molar (46%). These findings were more likely to be detected around a third molar in subjects with all third molars at the occlusal plane (72%) than in subjects with at least one third molar below (33%). Overall, fewer subjects were affected by third molar caries experience than first or second molars (24% vs 73%, respectively). Of the subset of subjects with all four third molars at the occlusal plane, 26% were affected by both third molar periodontal pathology and caries experience and 16% were caries and periodontal pathology free. CONCLUSIONS In these cross-sectional analyses, periodontal pathology was detected more frequently on third molars than on first and second molars and caries experience was detected more frequently on first and second molars than on third molars.

Changes Over Time in the Prevalence of Caries Experience or Periodontal Pathology on Third Molars in Young Adults

PURPOSE To assess the prevalence of caries experience and periodontal pathology on third molar teeth compared with first and second molars and teeth more anterior from subjects who had data collected over time in a longitudinal clinical study. PATIENTS AND METHODS Healthy subjects with 4 asymptomatic third molars and data for at least 4 years after enrollment were included in these analyses. The presence or absence of caries experience on the occlusal surface of the third molars and any surface of the first or second molars was assessed using a visual-tactile caries examination. Full mouth periodontal probing, 6 sites per tooth, was conducted as a measure of clinical periodontal status. The primary outcome measures were at least 1 periodontal probing depth of at least 4 mm versus none, and caries experience versus no caries experience. The prevalence of caries experience and periodontal pathologic findings at follow-up and the relationship of the occurrence between the third molars and teeth more anterior in the mouth were examined using McNemars statistics. RESULTS The follow-up was a median of 6.9 years (interquartile range 4.6 to 7.7 years) for 179 subjects, with a mean age of 29 years. More subjects were female (54%) and white (80%). At follow-up, 85% of the subjects had caries experience detected on the first or second molars, and only 50% had a third molar affected. In contrast, at follow-up, the presence of at least 1 periodontal probing depth of at least 4 mm was marginally more prevalent on the third molars than on the first or second molars (56% and 50%, respectively). Fewer subjects had third molars free of caries experience and periodontal pathology at follow-up compared with at enrollment (28% versus 38%, respectively). CONCLUSIONS The prevalence of both third molar caries experience and third molar periodontal pathology increased from baseline to the follow-up examination. At follow-up, the prevalence of caries experience was greater on the first or second molars than on the third molars, and periodontal pathology were greater on the third molars than on the more anterior teeth.