Stephen J. Chu

Gingival Zenith Positions and Levels of the Maxillary Anterior Dentition

PURPOSE The location of the gingival zenith in a medial-lateral position relative to the vertical tooth axis of the maxillary anterior teeth remains to be clearly defined. In addition, the apex of the free gingival margin of the lateral incisor teeth relative to the gingival zeniths of the adjacent proximal teeth remains undetermined. Therefore, this investigation evaluated two clinical parameters: (1) the gingival zenith position (GZP) from the vertical bisected midline (VBM) along the long axis of each individual maxillary anterior tooth; and (2) the gingival zenith level (GZL) of the lateral incisors in an apical-coronal direction relative to the gingival line joining the tangents of the GZP of the adjacent central incisor and canine teeth under healthy conditions. MATERIALS AND METHODS A total of 240 sites in 20 healthy patients (13 females, 7 males) with an average age of 27.7 years were evaluated. The inclusion patient criteria were absence of periodontal disease, gingival recession, or gingival hypertrophy as well as teeth without loss of interdental papillae, spacing, crowding, existing restorations, and incisal attrition. GZP dimensions were measured with calibrated digital calipers for each individual tooth and within each tooth group in a medial-lateral direction from the VBM. GZLs were measured in an apical-coronal direction from a tangent line drawn on the diagnostic casts from the GZPs of the adjacent teeth. RESULTS This study demonstrated that all central incisors displayed a distal GZP from the VBM, with a mean average of 1 mm. Lateral incisors showed a deviation of the gingival zenith by a mean of 0.4 mm. In 97.5% of the canine population, the GZP was centralized along the long axis of the canine. The mean distance of the contour of the gingival margin in an apical-coronal direction of the lateral incisors (GZL) relative to gingival line joining the tangent of the adjacent central and canine GZPs was approximately 1 mm. CONCLUSION This investigation revealed a GZP mean value of 1 mm distal from the VBM for the central incisor tooth group. The lateral incisors showed a mean average of 0.4 mm. The canine tooth group demonstrated almost no deviations of the GZP from the VBM. The GZL of the lateral incisors relative to the adjacent central incisor and canine teeth were more coronal by approximately 1 mm. These data could be used as reference points during esthetic anterior oral rehabilitation. CLINICAL SIGNIFICANCE The information presented in this article can be clinically applied to reestablish the proper intratooth GZPs of the maxillary anterior teeth during periodontal crown lengthening or root coverage procedures. In addition, the intra-arch gingival level of the lateral incisor gingival zenith relative to the adjacent central and canine teeth can be appropriately established.

On the interfacial fracture of porcelain/zirconia and graded zirconia dental structures.

Porcelain fused to zirconia (PFZ) restorations are widely used in prosthetic dentistry. However, their susceptibility to fracture remains a practical problem. The failure of PFZ prostheses often involves crack initiation and growth in the porcelain, which may be followed by fracture along the porcelain/zirconia (P/Z) interface. In this work, we characterized the process of fracture in two PFZ systems, as well as a newly developed graded glass-zirconia structure with emphases placed on resistance to interfacial cracking. Thin porcelain layers were fused onto Y-TZP plates with or without the presence of a glass binder. The specimens were loaded in a four-point-bending fixture with the thin porcelain veneer in tension, simulating the lower portion of the connectors and marginal areas of a fixed dental prosthesis (FDP) during occlusal loading. The evolution of damage was observed by a video camera. The fracture was characterized by unstable growth of cracks perpendicular to the P/Z interface (channel cracks) in the porcelain layer, which was followed by stable cracking along the P/Z interface. The interfacial fracture energy GC was determined by a finite-element analysis taking into account stress-shielding effects due to the presence of adjacent channel cracks. The resulting GC was considerably less than commonly reported values for similar systems. Fracture in the graded Y-TZP samples occurred via a single channel crack at a much greater stress than for PFZ. No delamination between the residual glass layer and graded zirconia occurred in any of the tests. Combined with its enhanced resistance to edge chipping and good esthetic quality, graded Y-TZP emerges as a viable material concept for dental restorations.

Flapless postextraction socket implant placement in the esthetic zone: part 1. The effect of bone grafting and/or provisional restoration on facial-palatal ridge dimensional change-a retrospective cohort study.

A number of human comparison studies and case series have demonstrated the effectiveness of using a platform-switched implant-to-abutment connection to prevent peri-implant bone loss and subsequent soft tissue loss. To compare the bone around platform-switched and nonplatform-switched connections, adjacent pairs of both connection types were placed in a one-stage surgical procedure on each side of the mandibles of three monkeys (Macaca fascicularis). Eight weeks after abutment connection, histomorphometric analysis showed that both vertical and horizontal alveolar bone resorption had occurred around the nonplatform-switched implants, whereas bone was maintained vertically and new bone formed horizontally around the platform-switched implants.The dental literature has reported vertical soft tissue changes that can occur with immediate implant placement, bone grafting, and provisional restoration ranging from a gain or loss of 1.0 mm. However, little is known of the effects of facial-palatal collapse of the ridge due to these clinical procedures. Based upon treatment modalities rendered, an ensuing contour change can occur with significant negative esthetic consequences. The results of a retrospective clinical cohort study evaluating the change in horizontal ridge dimension associated with implant placement in anterior postextraction sockets are presented for four treatment groups: (1) group no BGPR = no bone graft and no provisional restoration; (2) group PR = no bone graft, provisional restoration; (3) group BG = bone graft, no provisional restoration; and (4) group BGPR = bone graft, provisional restoration. Bone grafting at the time of implant placement into the gap in combination with a contoured healing abutment or a provisional restoration resulted in the smallest amount of ridge contour change. Therefore, it is recommended to place a bone graft and contoured healing abutment or provisional restoration at the time of flapless postextraction socket implant placement.

Flapless Postextraction Socket Implant Placement, Part 2: The Effects of Bone Grafting and Provisional Restoration on Peri-implant Soft Tissue Height and Thickness- A Retrospective Study.

This article presents the results of evaluating the changes in peri-implant soft tissue dimensions associated with immediate implant placement into anterior postextraction sockets for four treatment groups: no BGPR (no bone graft, no provisional restoration), PR (no bone graft, provisional restoration), BG (bone graft, no provisional restoration), and BGPR (bone graft, provisional restoration). The vertical distance of the peri-implant soft tissue was greater for grafted sites than for nongrafted ones (2.72 mm vs 2.29 mm, P < .06). The facial soft tissue thickness at the gingival third also was greater for grafted than for nongrafted sites (2.90 mm vs 2.28 mm, P < .008) and for sites with provisional restorations compared to sites without them (2.81 mm vs 2.37 mm, P < .06), respectively. The net gain in soft tissue height and thickness was about 1 mm. The increases in vertical and horizontal dimensions for grafted sites were between 0.5 and 1.0 mm, as compared to sites with no bone graft and no provisional restoration.

Immediate Implant Placement into Extraction Sockets with Labial Plate Dehiscence Defects: A Clinical Case Series

PURPOSE To measure the buccal plate reconstruction of extraction sockets with labial plate dehiscence defects using a bone allograft in combination with an absorbable collagen membrane and a custom-healing abutment at the time of tooth removal. MATERIALS AND METHODS Ten patients underwent immediate implant placement and reconstruction of the buccal plate. Cone beam computed tomography (CBCT) was performed preextraction, immediately after bone grafting and implant placement (day 0), and between 6 and 9 months following implant surgery. Measurements were taken at three levels: coronal (L1), middle (L2), and apical (L3) level. RESULTS Implants placed into sockets with labial plate dehiscence defects demonstrated radiographic reformation of the labial plate dehiscence defect at 6 to 9 months posttreatment. The net gain in labial plate on cone beam computerized tomography (CBCT) in L1 and L2 was 3.0 mm, where 0 mm existed at pretreatment. The minimum amount of labial plate thickness of 2.0 mm was achieved in all treated sites, evaluated radiographically at 6 to 9 months postoperatively, in a single procedure, without flap elevation and maintaining the gingival architecture and satisfactory esthetics. CONCLUSION Placing an absorbable membrane, bone graft, and custom-healing abutment at the time of flapless anterior tooth extraction and immediate implant placement into a socket with a labial osseous dehiscence is a viable clinical technique to reconstitute the absence of the labial bone plate.

Laypersons' perception of facial and dental asymmetries.

The purpose of this article was to determine the individual visual perception thresholds of certain facial and dental discrepancies for a symmetric face model (SFM). A facial photograph of a female subjects smile was digitally manipulated into an artificially symmetric picture. Modifications were made on the SFM for shifts in the dental midline, nose, and chin (group 1) and cants of dental midline and incisal plane (group 2), resulting in a total of 24 different images divided into two groups. One-hundred randomly selected laypersons divided into two groups were used to evaluate each image according to their own personal beauty and esthetic criteria using a visual analog scale. The visual perception thresholds found for the SFM were 2 mm for a dental midline shift, 4 mm for nose deviation, 5 degrees for dental midline cant, and 3 degrees for frontal incisal plane cant. Chin deviations of 6 mm or less were not noticed. Dental midline shift, nose deviation, dental midline cant, and incisal plane cant relative to an SFM have an impact on the perception of facial attractiveness. Chin deviations did not have a statistically significant impact.

Provisional Restorations Used in Immediate Implant Placement Provide a Platform to Promote Peri-implant Soft Tissue Healing: A Pilot Study.

The use of an immediately placed provisional restoration that mirrors the cervical contours of the extracted tooth at the time of implant placement may provide a platform to promote peri-implant soft tissue healing. This study examined the association of sulcular bleeding at the time of initial disconnection of the provisional restoration with stability of the buccolingual ridge dimension following immediate implant placement. Eighteen immediate implants grafted with particulate bone were restored with a screw-retained, single-unit, provisional restoration and abutment. The presence of sulcular bleeding was recorded after 5 to 7 months of healing. Stability of the buccolingual ridge dimension at the level of the free marginal gingiva and 1, 2, 3, 5, 7, and 9 mm apical was estimated using the contralateral tooth as a control. Gingival bleeding was associated with the disconnection of the provisional restoration in 11 (61.1%) of the grafted implant sites. Bleeding upon initial disconnection of the provisional restoration was significantly correlated with smaller changes, or greater stability, in the buccolingual ridge dimension at each reference point from 0 to 3 mm apical to the free gingival margin. The use of anatomically contoured provisional restorations may provide a platform to promote peri-implant soft tissue healing and minimize remodeling of the buccolingual ridge dimension.

Color‐Matching Strategies for Non‐Vital Discolored Teeth: Part 1. Laboratory Ceramic Veneer Fabrication Solutions

UNLABELLED The following is a case report exemplifying the restorative and esthetic correction of a discolored stump shade of a non-vital tooth maxillary left central incisor tooth. Treatment options are non-vital bleaching of the root canal-treated tooth or esthetic restoration through an understanding of color and layered ceramics, where the latter was employed. Proper shade communication as well as additional facial tooth preparation and reduction are key clinical requirements in order to allow the ceramist adequate room to affect a color change without sacrificing translucency or vitality of the definitive restorations. CLINICAL SIGNIFICANCE Esthetic restorative correction of a discolored stump tooth shade can be managed with an understanding of color, shade communication, proper tooth preparation, and ceramic layering techniques.

Layperson’s preference regarding orientation of the transverse occlusal plane and commissure line from the frontal perspective

STATEMENT OF PROBLEM Facial asymmetries in features such as lip commissure and interpupillary plane canting have been described as common conditions affecting smile esthetics. When presented with these asymmetries, the clinician must choose the reference line with which to orient the transverse occlusal plane of the planned dental restorations. PURPOSE The purpose of the online survey described in this study was to determine lay preferences regarding the transverse occlusal plane orientation in faces that display a cant of the commissure line viewed from the frontal perspective. MATERIAL AND METHODS From a digitally created symmetrical facial model with the transverse occlusal plane and commissure line parallel to the interpupillary line (horizontal) and a model constructed in a previous study (control), a new facial model was created with 3 degrees of cant of the commissure line. Three digital tooth mountings were designed with different transverse occlusal plane orientations: parallel to the interpupillary line (A), parallel to the commissure line (B), and the mean angulation plane formed between the interpupillary and commissure line (C), resulting in a total of 4 images. All images, including the control, were organized into 6 pairs and evaluated by 247 selected laypersons through an online Web site survey. Each participant was asked to choose the more attractive face from each of the 6 pairs of images. RESULTS The control image was preferred by 72.9% to 74.5% of the participants compared with the other 3 images, all of which represented a commissure line cant. Among the 3 pairs which represent a commissure line cant, 59.1% to 61.1% preferred a transverse plane of occlusion cant (B and C) compared with a plane of occlusion parallel to the interpupillary, line and 61.1% preferred a plane of occlusion parallel to the commissure line (B) compared with the mean angulation plane (C). CONCLUSIONS Laypeople prefer faces with a commissure line and transverse occlusal plane parallel to the horizontal plane or horizon. When faces present a commissure line cant, laypeople prefer a transverse occlusal plane with a similar and coincident cant.

Color Matching Strategies for Non‐Vital Discolored Teeth: Part 2. In‐Vivo Bleaching Options for Discolored Teeth Preparations

UNLABELLED The following is a case report exemplifying the esthetic restorative and correction of a discolored substrate of a non-vital maxillary right lateral and central incisor tooth. Frequently, clinicians are presented with discolored teeth preparations after removal of a restoration and face difficult decision-making strategies in regards to materials selection, tooth preparation depth, and design. Part 2 will discuss the diagnosis and clinical bleaching treatment options when restoring non-vital discolored substrate preparations. The key is to know when such techniques should and can be applied with the associated esthetic clinical results. CLINICAL SIGNIFICANCE Esthetic restorative correction of discolored teeth preparations can be clinically managed with an understanding of non-vital bleaching concepts and techniques along with the associated risks and rewards.