Arthur F. Hefti

Principles of periodontology.

Periodontal diseases are among the most common diseases affecting humans. Dental biofilm is a contributor to the etiology of most periodontal diseases. It is also widely accepted that immunological and inflammatory responses to biofilm components are manifested by signs and symptoms of periodontal disease. The outcome of such interaction is modulated by risk factors (modifiers), either inherent (genetic) or acquired (environmental), significantly affecting the initiation and progression of different periodontal disease phenotypes. While definitive genetic determinants responsible for either susceptibility or resistance to periodontal disease have yet to be identified, many factors affecting the pathogenesis have been described, including smoking, diabetes, obesity, medications, and nutrition. Currently, periodontal diseases are classified based upon clinical disease traits using radiographs and clinical examination. Advances in genomics, molecular biology, and personalized medicine may result in new guidelines for unambiguous disease definition and diagnosis in the future. Recent studies have implied relationships between periodontal diseases and systemic conditions. Answering critical questions regarding host-parasite interactions in periodontal diseases may provide new insight in the pathogenesis of other biomedical disorders. Therapeutic efforts have focused on the microbial nature of the infection, as active treatment centers on biofilm disruption by non-surgical mechanical debridement with antimicrobial and sometimes anti-inflammatory adjuncts. The surgical treatment aims at gaining access to periodontal lesions and correcting unfavorable gingival/osseous contours to achieve a periodontal architecture that will provide for more effective oral hygiene and periodontal maintenance. In addition, advances in tissue engineering have provided innovative means to regenerate/repair periodontal defects, based upon principles of guided tissue regeneration and utilization of growth factors/biologic mediators. To maintain periodontal stability, these treatments need to be supplemented with long-term maintenance (supportive periodontal therapy) programs.

Collaborative WHO Xylitol Field Study in French Polynesia

The value for caries prevention of partial sugar substitution by xylitol was tested in a 32-month nonrandomized comparative field study. A total of 746 6- to 12-year-old children living on three islands of the Polynesian archipelago were enrolled in the study. The children of one island representing the control group were supplied with toothbrushes and fluoridated dentifrice, and received regular instruction on oral hygiene. Otherwise, they maintained their customary dietary habits. The children of the other two islands were assigned to the xylitol group. They were enrolled in an identical oral health programme but, in addition, were regularly provided with xylitol-based sweets, i.e. chewing gums, candies, chocolate, ice lollies and gumdrops, at school on a daily basis in amounts corresponding to not more than 20 g xylitol/day. 468 children completed the study. The 195 participants of the control group showed an overall mean caries increment of 7.1 DMFS. In the xylitol group with 273 children a mean caries increment of 4.5 DMFS was measured. It is concluded that partial sugar substitution by xylitol is a useful tool in preventing caries and should be considered in addition to fluoridation and oral hygiene measures in public oral health programmes.

Three-dimensional fit of lithium disilicate partial crowns in vitro

OBJECTIVES A novel three-dimensional scanning technique was used to investigate the effects a one-step and a two-step impression methods can have on the three-dimensional fit of ceramic partial crowns. METHODS An acrylic model of a mandibular first molar was prepared to receive a partial coverage all-ceramic crown (mesio-occlusal-distal inlay preparation with reduction of all cusps and rounded shoulder finish line of buccal wall). Type IV plaster replicates were cast based on one-step single viscosity (OS/SV), one-step dual viscosity (OS/DV), and two-step dual viscosity (TS/DV) impressions. Five partial crowns were fabricated per impression method using hot-pressed lithium disilicate ceramics. Then, preparation and restorations were digitized using a non-contact, white-light scanner featuring self-calibrating optics (overall measurement uncertainty of <5μm). Data were entered into quality inspection software which superimposed the records (best-fit-algorithm), calculated fit-discrepancies for every pixel, and colour-coded the results to aid visualization. Furthermore, mean quadratic deviations (RMS) were computed and analyzed statistically with a 1-way ANOVA. Scheffés procedure was applied for multiple comparisons (α=0.05). RESULTS Mean RMS-values for marginal (internal) surfaces were: OS/SV 70 (20)μm, OS/DV 78 (34)μm, and TS/DV 107 (52)μm. Differences among impression techniques were statistically significant at p=0.006 (0.001). Qualitatively, occlusal ridges and preparation finish lines were over contoured, whereas inner occlusal boxes and the proximal-occlusal isthmus were under contoured. CONCLUSIONS OS/SV and OS/DV impressions resulted in statistically significantly smaller marginal and internal discrepancies than the two-step technique. CLINICAL SIGNIFICANCE Marginal and internal fit of hot-pressed lithium disilicate partial crowns depended on the employed impression technique. One-step impressions are preferred over two-step techniques in many day-to-day clinical situations, especially for the fabrication of partial coverage crown restorations.

Effect of CNC-milling on the marginal and internal fit of dental ceramics: A pilot study

OBJECTIVES Machined restorations have been investigated for their preciseness before, while detailed information on the milling-step itself are lacking. Therefore, the aim of this laboratory study was to quantify the effect of a novel milling-procedure on the marginal and internal fit of ceramic restorations. METHODS An acrylic model of a lower left first molar was prepared to receive a ceramic partial crown and was duplicated by one step dual viscosity impressions. Gypsum casts were formed and laser-scanned to realize virtual datasets, before restorations were designed, exported (PRE) and machined from lithium disilicate blanks. Crowns were digitized by a structure-light-scanner to obtain post-milling-data (POST). PRE and POST were virtually superimposed on the reference tooth and subjected to computer-aided-inspection. Visual fit-discrepancies were displayed with colors, while root mean square deviations (RMSD) and degrees of similarity (DS) were computed and analysed by t-tests for paired samples (n=5, α=0.05). RESULTS The milling procedure resulted in a small increase of the marginal and internal fit discrepancies (RMSD mean: 3μm and 6μm, respectively). RMSD differences were not statistically significant (p=0.495 and p=0.160 for marginal and internal fit, respectively). These results were supported by the DS data. SIGNIFICANCE The products of digital dental workflows are prone to imprecisions. However, the present findings suggest that differences between computer-aided designed and actually milled restorations are small, especially when compared to typical fit discrepancies observed clinically. Imprecisions introduced by digital design or production processes are small.

Biomimetic mineralization: Long-term observations in patients with dentin sensitivity

OBJECTIVE Cervical tooth erosion is increasingly observed among adults and frequently associated with dentin sensitivity (DS). This study evaluated the effectiveness on DS of a biomimetic mineralization system (BIMIN) in comparison to the current standard treatment (Gluma(®) Desensitizer, Gluma). METHODS In this single-blind, 2-arm study, 40 patients with confirmed cervical DS were randomized to either the test group or the positive control group. A Visual-Analog-Scale (VAS) was used to assess DS following stimulation of the exposed dentin with a 2-s air blast. Assessments were made at baseline (pre-treatment), 2 days, 4, 8 and 12 weeks, and 12 months after treatment. Two-stage replicas were obtained from the treated teeth and gold sputtered at baseline, and 2 days, 3 and 12 months after treatment. Surface topography of the treated cervical lesions and occlusion of dentinal tubules were investigated using scanning electron microscopy (SEM). RESULTS Both treatments led to a statistically significant reduction (P<0.0001) in DS that persisted over the entire 12-month observation period. Differences in DS between the treatments were not statistically significant. SEM photomicrographs demonstrated that a mineral layer concealed the dentinal tubules in the test group. In contrast, numerous dentinal tubules remained visible in cervical defects that were treated with Gluma. SIGNIFICANCE A biomimetic mineralization kit was successfully used to treat patients exhibiting DS. The effect was similar to using Gluma, and was likely the result of the deposition of an enamel-like layer on the exposed cervical dentin.

Moving an incisor across the midline: A treatment alternative in an adolescent patient

A 13-year-old sought treatment for a severely compromised maxillary left central incisor and an impacted fully developed left canine. Extraction of both teeth became necessary. As the key component of the revised comprehensive treatment plan, the right maxillary central incisor was moved into the position of the left central incisor. All other maxillary teeth were moved mesially to close any gaps. Active orthodontic treatment was completed after 34 months. Frenectomy, minor periodontal surgeries, and bonded lingual retainers were used to improve aesthetics and stabilize the tooth positions. The patient was pleased with the treatment outcome. Cone-beam computed tomography provided evidence that the tooth movement was accompanied by a deviation of the most anterior portion of the median palatine suture. This observation may make relapse more likely if long-term retention cannot be ensured. Root resorption was not observed as a consequence of the major tooth movement.

Bone Fluoride Concentrations after 16 Years of Drinking Water Fluoridation

The fluoride content of 147 pieces of vertebral cancellous bone, collected at autopsy from long-term residents in Basle, Switzerland, was determined. A statistical analysis of the results sustained the hypothesis of age-dependent fluoride accumulation in bone. No differences were found between sexes. 4 cases with severe chronic pyelonephritis had definitely elevated fluoride values.

Bonding with self-etching primers - pumice or pre-etch? An in vitro study

The purpose of this study was to compare the shear bond strengths (SBSs) of orthodontic brackets bonded with self-etching primer (SEP) using different enamel surface preparations. A two-by-two factorial study design was used. Sixty human premolars were harvested, cleaned, and randomly assigned to four groups (n = 15 per group). Teeth were bathed in saliva for 48 hours to form a pellicle. Treatments were assigned as follows: group 1 was pumiced for 10 seconds and pre-etched for 5 seconds with 37 per cent phosphoric acid before bonding with SEP (Transbond Plus). Group 2 was pumiced for 10 seconds before bonding. Group 3 was pre-etched for 5 seconds before bonding. Group 4 had no mechanical or chemical preparation before bonding. All teeth were stored in distilled water for 24 hours at 37°C before debonding. The SBS values and adhesive remnant index (ARI) score were recorded. The SBS values (± 1 SD) for groups 1-4 were 22.9 ± 6.6, 16.1 ± 7.3, 36.2 ± 8.2, and 13.1 ± 10.1 MPa, respectively. Two-way analysis of variance and subsequent contrasts showed statistically significant differences among treatment groups. ARI scores indicated the majority of adhesive remained on the bracket for all four groups. Pre-etching the bonding surface for 5 seconds with 37 per cent phosphoric acid, instead of pumicing, when using SEPs to bond orthodontic brackets, resulted in greater SBSs.

Cariogenicity of Topically Applied Sugar Substitutes in Rats under Restricted Feeding Conditions

The cariogenicity of frequent topical applications of water, sucrose, xylitol, sorbitol and sorbose was compared in a 20-day animal study under controlled feeding conditions. Osborne-Mendel rats were orally superinfected with Streptococcus mutans OMZ 176 and Actinomyces viscosus Ny 1 and received 25 daily ‘meals’of 0.4 g of diet 2000a containing 56%sucrose. Two topical applications were administered after each group of 5 programmed meals. The treatments significantly affected the fissure caries incidence. The highest scores were observed in the sucrose and sorbitol group. The number of fissure lesions in the xylitol and sorbose group did not significantly exceed that in the water group.

Implant Treatment in the Predoctoral Clinic: A Retrospective Database Study of 1091 Patients

PURPOSE This retrospective study was conducted at the Marquette University School of Dentistry to (1) characterize the implant patient population in a predoctoral clinic, (2) describe the implants inserted, and (3) provide information on implant failures. MATERIALS AND METHODS The study cohort included 1091 patients who received 1918 dental implants between 2004 and 2012, and had their implants restored by a crown or a fixed dental prosthesis. Data were collected from patient records, entered in a database, and summarized in tables and figures. Contingency tables were prepared and analyzed by a chi-squared test. The cumulative survival probability of implants was described using a Kaplan-Meier survival curve. Univariate and multivariate frailty Cox regression models for clustered observations were computed to identify factors associated with implant failure. RESULTS Mean patient age (±1 SD) at implantation was 59.7 ± 15.3 years; 53.9% of patients were females, 73.5% were Caucasians. Noble Biocare was the most frequently used implant brand (65.0%). Most implants had a regular-size diameter (59.3%). More implants were inserted in posterior (79.0%) than in anterior jaw regions. Mandibular posterior was the most frequently restored site (43%); 87.8% of implants were restored using single implant crowns. The overall implant-based cumulative survival rate was 96.4%. The patient-based implant survival rate was 94.6%. Implant failure risk was greater among patients than within patients (p < 0.05). Age (>65 years; hazard ratio [HR] = 3.2, p = 0.02), implant staging (two-stage; HR = 4.0, p < 0.001), and implant diameter (wide; HR = 0.4, p = 0.04) were statistically associated with implant failure. CONCLUSIONS Treatment with dental implants in a supervised predoctoral clinic environment resulted in survival rates similar to published results obtained in private practice or research clinics. Older age and implant staging increased failure risk, while the selection of a wide implant diameter was associated with a lower failure risk.