Alveolar ridge alterations after lateral guided bone regeneration with and without hyaluronic acid: a prospective randomized trial with morphometric and histomorphometric evaluation

OBJECTIVE

To clinically and histologically evaluate the potential effect of a cross-linked, high molecular weight hyaluronic acid (xHyA) on the outcomes of guided bone regeneration performed with a demineralized bovine bone mineral (DBBM) covered with a natural collagen membrane.

METHOD AND MATERIALS

Eleven patients (eight females and three males, mean age 53 years) with a total of 27 surgical sites were treated. Treatments were performed with either DBBM and natural collagen membrane fixed with tacks (group A) or DBBM mixed with xHyA and subsequently covered with natural collagen membrane (group B). Clinical evaluations were made at baseline (T1), immediately after guided bone regeneration (T2), and at the time of implant placement (T3). Additionally, at the time of implant placement, core biopsies were retrieved and submitted for histologic analysis.

RESULTS

Healing was uneventful in all cases. At 6 months, group B revealed a statistically significantly higher crestal ridge dimension compared to group A (P = .007). The histologic analysis revealed a tendency for greater mineralized tissue formation in group B compared to group A (67.5% versus 41.6%) and contained a higher amount of new bone (37.2%) and less DBBM residues (20.9%) than group A (12.8% new bone and 28.8% DBBM residues, respectively).

CONCLUSIONS

Within their limits, the present data indicate that, during guided bone regeneration with natural collagen membrane, the combination of DBBM and xHyA may improve the quality and quantity of bone formed with DBBM alone.

Properties of three collagen scaffolds in comparison with native connective tissue: an in-vitro study

PURPOSE

To evaluate collagen scaffolds (CS) in terms of their in vitro resorption behavior, surface structure, swelling behavior, and mechanical properties in physiologically simulated environments, compared with porcine native connective tissue.

MATERIALS AND METHODS

Three test materials-one porcine collagen matrix (p-CM), two acellular dermal matrices (porcine = p-ADM, allogenic = a-ADM)-and porcine native connective tissue (p-CTG) as a control material were examined for resorption in four solutions using a high-precision scale. The solutions were artificial saliva (AS) and simulated body fluid (SBF), both with and without collagenase (0.5 U/ml at 37 °C). In addition, the surface structures of CS were analyzed using a scanning electron microscope (SEM) before and after exposure to AS or SBF. The swelling behavior of CS was evaluated by measuring volume change and liquid absorption capacity in phosphate-buffered saline (PBS). Finally, the mechanical properties of CS and p-CTG were investigated using cyclic compression testing in PBS.

RESULTS

Solutions containing collagenase demonstrated high resorption rates with significant differences (p < 0.04) between the tested materials after 4 h, 8 h and 24 h, ranging from 54.1 to 100% after 24 h. SEM images revealed cross-linked collagen structures in all untreated specimens. Unlike a-ADM, the scaffolds of p-CM and p-ADM displayed a flake-like structure. The swelling ratio and fluid absorption capacity per area ranged from 13.4 to 25.5% among the test materials and showed following pattern: p-CM > a-ADM > p-ADM. P-CM exhibited higher elastic properties than p-ADM, whereas a-ADM, like p-CTG, were barely compressible and lost structural integrity under increasing pressure.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Collagen scaffolds vary significantly in their physical properties, such as resorption and swelling behavior and elastic properties, depending on their microstructure and composition. When clinically applied, these differences should be taken into consideration to achieve the desired outcomes.

Enamel Matrix Derivatives as an Adjunct to Alveolar Ridge Preservation-A Systematic Review

PURPOSE

To systematically assess the current evidence regarding the adjunctive application of enamel matrix derivatives (EMDs) during alveolar ridge preservation (ARP) following tooth extraction.

METHODS

A comprehensive literature search was conducted in MEDLINE, Cochrane Library, PsycINFO, Web of Science, Google Scholar, and Scopus to identify relevant randomized controlled clinical trials (RCTs). The primary outcome parameters of this systematic review were histomorphometric and radiographic data; secondary outcomes were the feasibility of implant placement after ARP as well as patient-related outcomes such as postoperative discomfort.

RESULTS

The search identified 436 eligible articles published from 2011 to 2022, but only five were ultimately included for data extraction (146 patients). Given the substantial heterogeneity among the included studies, no meta-analysis could be performed. The authors' qualitative analysis showed marginally improved outcomes regarding an increased percentage of new bone formation after tooth extraction and a reduction in postoperative discomfort.

CONCLUSIONS

Given the potential value of EMDs in other fields of regenerative dentistry, more consideration should be given to EMDs as an adjunctive treatment option in ARP. However, more well-controlled randomized clinical trials are necessary to evaluate the exact potential and impacts of EMDs.

Nonsurgical cleaning potential of deep-threaded implants and titanium particle release: A novel in vitro tissue model

OBJECTIVES

To measure the efficiency of three cleaning modalities on two implant designs with similar diameters but different thread depths as well as the presence of titanium particles.

METHODS

Sixty dyed implants (30 × 4.8 apically tapered (ATAP) and 30 × 5.0 fully tapered (FTAP)) were fixed in plastic models. The horizontal bone defects were surrounded with porcine soft tissue. Three instrumentation modalities were used to clean for 150 s: Curette (CUR), ultrasonic scaler (US), and air powder waterjet device (APWJ) with erythritol powder. Afterward, implants were photographed and scanning electron microscopic (SEM) images were taken. Titanium in the soft tissues was quantified in dissolved samples and histologically confirmed.

RESULTS

For ATAP and FTAP implants, the percentage of the cleaned surface was 26.4 ± 3.0 and 17.1 ± 2.4% for CUR, 33.7 ± 3.8% and 28.1 ± 2.3% for US, and 45.5 ± 4.1% and 24.7 ± 3.8% for APWJ, respectively. SEM images showed significant implant surface changes, especially after instrumentation with CUR and US, whereas APWJ had little to no effect. Most titanium residues were found after cleaning ATAP implants with CUR (152.0 ± 75.5), followed by US (89.5 ± 73.8) and APWJ (0.3 ± 0.8). For the FTAP implants, respective values accounted for 129.5 ± 58.6 μg and 67.0 ± 14.4 μg for CUR and US, respectively. No titanium residues were detected on ATAP with APWJ.

CONCLUSION

Based on in vitro data, erythritol-powered APWJ still appears to be the most efficient and gentle cleaning method. All three instruments, however, were found to have unprocessed areas depending on different implant designs, hence, clinical relevance for non-surgical approaches remains challenging and warrants further improvement.

Soft tissue related complications around anterior implants: commentary and clinical checklist

Implant-based rehabilitation is a clinical challenge, especially in the esthetic area. Numerous factors influence the outcome of the rehabilitation; however, the two main factors are the bone and soft-tissue deficiencies at the intended implant site. Peri-implant soft tissue complications can arise from a combination of factors that can be summarized in two categories: diagnostic errors and surgical planning management errors. Most of the complications can be corrected after each step of the treatment and even after the delivery of the prosthetic restoration with adequate soft tissue management in order to give the patient an esthetically pleasing outcome. The aims of this article are: to present the current literature, to propose a clinical checklist that will guide clinicians in evaluating the prognosis of the treatment utilizing soft tissue grafting, to illustrate a case series partially employing the proposed clinical checklist. The proposed checklist could be helpful in evaluating the prognosis of the treatment utilizing only soft tissue grafting. In clinical cases, in which the prognosis is classified as good, soft tissue management could be a viable treatment option before attempting more radical procedures like implant removal.

Bone envelope for implant placement after alveolar ridge preservation: a systematic review and meta-analysis

PURPOSE

To assess the dimensional establishment of a bony envelope after alveolar ridge preservation (ARP) with deproteinized bovine bone mineral (DBBM) in order to estimate the surgical feasibility of standard diameter implants placement without any additional augmentation methods.

METHODS

PubMed, Embase and CENTRAL databases were searched for suitable titles and abstracts using PICO elements. Inclusion criteria were as follows: randomized controlled trials (RCTs) comprising at least ten systemically healthy patients; test groups comprised placement of (collagenated) DBBM w/o membrane and control groups of no grafting, respectively. Selected abstracts were checked regarding their suitability, followed by full-text screening and subsequent statistical data analysis. Probabilities and number needed to treat (NNT) for implant placement without any further need of bone graft were calculated.

RESULTS

The initial database search identified 2583 studies. Finally, nine studies with a total of 177 implants placed after ARP with DBBM and 130 implants after SH were included for the quantitative and qualitative evaluation. A mean difference of 1.13 mm in ridge width in favour of ARP with DBBM could be calculated throughout all included studies (95% CI 0.28-1.98, t2 = 1-1063, I2 = 68.0%, p < 0.01). Probabilities for implant placement with 2 mm surrounding bone requiring theoretically no further bone augmentation ranged from 6 to 19% depending on implant diameter (3.25: 19%, RD = 0.19, C = 0.06-0.32, p < 0.01/4.0: 14%, RD = 0.14, C = 0.05-0.23, p < 0.01/5.0: 6%, RD = 0.06, C = 0.00-0.12, p = 0.06).

CONCLUSION

ARP employing DBBM reduces ridge shrinkage on average by 1.13 mm and improves the possibility to place standard diameter implants with up to 2 mm circumferential bone housing; however, no ARP would have been necessary or additional augmentative bone interventions are still required in 4 out of 5 cases.

Horizontal Augmentation of Chronic Mandibular Defects by the Guided Bone Regeneration Approach: A Randomized Study in Dogs

Various biomaterial combinations have been studied focusing on their ability to stabilize blood clots and maintain space under soft tissue to support new bone formation. A popular combination is Deproteinized Bovine Bone Mineral (DBBM) placed with a native collagen membrane (NCM) tacked to native bone. In this study, we compared the outcome of this treatment option to those achieved with three different graft/membrane combinations with respect to total newly occupied area and the mineralized compound inside. After bi-lateral extraction of two mandibular premolars in five adult beagles L-shaped alveolar defects were created. A total of 20 defects healed for 6 weeks resulting in chronic type bone defects. At baseline, four options were randomly allocated to five defects each: a. DBBM + NCM with a four-pin fixation across the ridge; b. DBBM + RCLC (ribose cross-linked collagen membrane); c. DBBM + NPPM (native porcine pericardium membrane); and d. Ca-sulfate (CS) + RCLC membrane. Membranes in b/c/d were not fixed; complete tensionless wound closure was achieved by CAF. Termination after 3 months and sampling followed, and non-decalcified processing and toluidine blue staining were applied. Microscopic images obtained at standardized magnification were histomorphometrically assessed by ImageJ software (NIH). An ANOVA post hoc test was applied; histomorphometric data are presented in this paper as medians and interquartile ranges (IRs). All sites healed uneventfully, all sites were sampled and block separation followed before Technovit embedding. Two central sections per block for each group were included. Two of five specimen were lost due to processing error and were excluded from group b. New bone area was significantly greater for option b. compared to a. (p = 0.001), c. (p = 0.002), and d. (p = 0.046). Residual non-bone graft area was significantly less for option d. compared to a. (p = 0.026) or c. (p = 0.021). We conclude that collagen membranes with a prolonged resorption/barrier profile combined with bone substitutes featuring different degradation profiles sufficiently support new bone formation. Tacking strategy/membrane fixation appears redundant when using these biomaterials.

Gingival phenotype distribution in young Caucasian women and men - An investigative study

OBJECTIVES

To evaluate the relationship between gingival phenotype and tooth location based on selected index teeth ("Ramfjord") and assess possible differences between women and men.

MATERIAL AND METHODS

Thirty-six women and 20 men voluntarily participated in this investigation with an average age of 23 years (min: 19; max: 37). Gingival phenotypes (GP) were assessed by transparency of a periodontal probe through the buccal gingival margin.

RESULTS

A comparable and similar GP on all index teeth was only found in seven out of the 56 subjects, that is, thin or thick only: Five participants (three male/two female) showed a uniform and constantly thick and two females a constantly thin GP. While the majority of molars (94.6%; p = 0.006) showed a thick GP, premolars (61.6%; p = 0.09) as well as incisors (70.5%; p = 0.046) were predominantly categorized as thin. In addition, significantly thicker GP was in general observed for maxillary teeth (p = 0.001) but without differences between genders (p = 0.722).

CONCLUSION

No constant GP can be expected within one dentition. The use of the "Ramfjord teeth" may serve as a quick overview and reliable method to screen GP distribution.

Gingival phenotype assessment methods and classifications revisited: a preclinical study

Objective

To compare gingival phenotype assessment methods based on soft tissue transparency on different backgrounds and assessor experience levels.

Methods

For this purpose, 24 gingival specimens were retrieved from pig jaws with tissue thicknesses from 0.2 to 1.25 mm. Three methods were assessed: periodontal probe PCP12 (thin/thick), double-ended periodontal probe DBS12 (thin/moderate/thick) and colour-based phenotype probe CBP (thin/moderate/thick/very thick). Each sample was photographed with each probe underneath and categorized whether the probe was visible or not using different coloured backgrounds. To measure experience level influence, dentists, dental undergraduate students and laypersons (n = 10/group) performed the evaluation.

Results

PCP12 probe showed a threshold between 0.4 and 0.5 mm. To distinct between thin and moderate thick gingiva, a comparable range for DBS12 was found while moderate thickness was between 0.5 and 0.8 mm and for thick above 0.8 mm. CBP also showed a comparable threshold of 0.5 mm for thin versus moderate as compared with the other methods; above 0.8 mm, predominantly a very thick tissue was measured. In general, the background colour had a minor impact on PCP12 and DBS12, and investigator experience showed no clear influence on GP assessment.

Conclusion

Based on probe transparency and within the limitation of a preclinical study, we suggest GP differentiation into three entities: thin (< 0.5 mm; high risk), moderate (0.5–0.8 mm; medium risk) and thick (> 0.8 mm; low risk).

Clinical relevance

All three GP assessment methods are easy to perform and seem to have a high predictive value with a three entities classification for DBS12 and CBP.

Open healing of contained and non-contained extraction sockets covered with a ribose cross-linked collagen membrane: a pilot study

PURPOSE

This study investigated whether the placement of ribose cross-linked collagen (RCLC) membranes without primary soft tissue closure predictably resulted in sufficient alveolar ridge preservation in contained and non-contained extraction sockets.

METHODS

Membranes were positioned across extraction sockets, undermining full-thickness flaps, and the gingival margins were fixed by double-interrupted sutures without crossed horizontal mattress sutures for 1 week. In non-contained sockets, a bone substitute was used to support the membrane within the bony envelope. Radiographs and clinical images obtained 4 months later were analyzed by ImageJ software using non-parametric tests.

RESULTS

In 18 patients, 20 extraction sockets healed uneventfully and all sites received standard-diameter implants (4.1, 4.8, or 5.0 mm) without additional bone augmentation. Soft tissues and the muco-gingival border were well maintained. A retrospective analysis of X-rays and clinical photographs showed non-significant shrinkage in the vertical and horizontal dimensions (P=0.575 and P=0.444, respectively). The new bone contained vital bone cells embedded in mineralized tissues.

CONCLUSIONS

Within the limitations of this pilot study, open healing of RCLC membranes may result in sufficient bone volume for implant placement without additional bone augmentation in contained and non-contained extraction sockets.

Histological comparison of different compressive forces on particulate grafts during alveolar ridge preservation: a prospective proof-of-concept study

Purpose

The aim of this study was to determine the impact of different compressive forces on deproteinized bovine bone mineral (DBBM) particles covered by native bilayer collagen membrane (NBCM) during alveolar ridge preservation (ARP) in the molar area, and to identify any histomorphometric and clinical differences according to the compressive force applied.

Methods

Sockets were filled with DBBM after tooth extraction, and different compressive forces (30 N and 5 N, respectively) were applied to the graft material in the test (30 N) and control (5 N) groups. The DBBM in both groups was covered with NBCM in a double-layered fashion. A crossed horizontal mattress suture (hidden X) was then made. A core biopsy was performed using a trephine bur without flap elevation at the implant placement site for histomorphometric evaluations after 4 months. The change of the marginal bone level was measured using radiography.

Results

Twelve patients completed the study. The histomorphometric analysis demonstrated that the mean ratios of the areas of new bone, residual graft material, and soft tissue and the implant stability quotient did not differ significantly between the groups (P>0.05). However, the mean size of the residual graft material showed a significant intergroup difference (P<0.05).

Conclusions

The application of 2 compressive forces (5 N, 30 N) on particulate DBBM grafts during open-healing ARP in the posterior area led to comparable new bone formation, implant feasibility and peri-implant bone level.

Ridge preservation of compromised extraction sockets applying a soft cortical membrane: A canine proof-of-principle evaluation

OBJECTIVES

To explore whether placement of a soft cortical membrane can restore and regenerate the original alveolar ridge contour in deficient sockets.

MATERIALS AND METHODS

One Beagle dog was used in this proof-of-principle evaluation. In a first intervention, a standardized buccal dehiscence defect was artificially created at the distal roots of the 3rd and 4th mandibular premolars. Four weeks later, following endodontic treatment of the mesial roots, teeth were hemisected and the distal roots were extracted without raising a flap. A cortical membrane (Lamina®, Osteobiol) was placed outside of the bony envelope of the extraction socket to rebuild the buccal bone contour. Afterwards, sockets were filled with a collagen-modified porcine bone graft material (Gen-Os®, Osteobiol) to the level of the surrounding bone height. The socket orifice was closed with a porcine dermal matrix (Derma®). After four months, block specimens containing the socket-sites and remaining roots were retrieved, histologically processed and analyzed.

RESULTS

Surgery and post-operative healing were uneventful. Histologically, bone formation under the membrane was found, i.e. bony protrusions and ossicles by osteoblasts could be identified. Concomitantly, the membrane showed clear signs of degradation. Bone substitute was well integrated in newly formed bone and resorption of particles was found.

CONCLUSION

Three major observations were made in the present proof-of-principle study: (i) regeneration of a compromised socket seems possible when applying the presented approach, (ii) the soft cortical membrane was sufficiently stable to allow for the establishment of the contour and to inhibit soft tissue invasion and (iii) the applied xenogenic graft material was undergoing remodelling processes while allowing adequate bone regeneration.

Soft tissue augmentation applying a collagenated porcine dermal matrix during second stage surgery: A prospective multicenter case series

BACKGROUND

The achievement and preservation of an adequate amount of soft tissue around implants is a critical factor for the prognosis of the treatment.

PURPOSE

To evaluate the effectiveness of a porcine dermal matrix applied during second stage implant surgery for horizontal soft tissue augmentation and preservation of dimensional stability.

MATERIALS AND METHODS

Twenty patients (mean age 50.2 ± 11.9 [SD] years) candidate to implant therapy and requiring soft tissue augmentation were recruited in four centers. Augmentation was performed in 24 cases. A porcine dermal matrix was placed into a buccal split-thickness pouch during uncovering surgery. Silicone impressions were taken before surgery (T0), 2 weeks later at suture removal (T2), 6 months (T3), and 24 months (T4) post augmentation. Dimensional changes of soft tissue were evaluated using superimposition of digitalized study casts.

RESULTS

Nineteen patients (23 implants) could be evaluated at 6 months and 13 patients (17 implants) at 24 months. After 6-month follow-up, there was a significant dimensional gain respect to baseline, averaging 0.83 ± 0.64 mm (P < .01). This did not change significantly at 24 months (0.77 ± 0.65 mm, P = .19). The gain was >0.5 mm in 65.2% and 64.7% of the cases, respectively. Soft tissue shrinkage averaged 34.2% ± 77.0% from T2 to T3 (P < .01) and did not change thereafter (P = .39). Shrinkage was more consistent in the posterior mandible than in the maxilla, but not significantly (P = .23 at 6-month and .36 at 24-month). No adverse events occurred.

CONCLUSION

Within the limitations of this prospective case series, the use of a porcine dermal matrix may provide consistent soft tissue augmentation that maintains up to 24-month follow-up, although graft shrinkage may occur in the first 6 months, depending on the location of surgery.

Dimensional Evaluation of Different Ridge Preservation Techniques with a Bovine Xenograft: A Randomized Controlled Clinical Trial

The objectives of this study were to determine the quantitative changes after different ridge preservation techniques (primary aim) and to assess the possibility of placing a dental implant, the bone quality, and the need for bone augmentation (secondary aim). A total of 35 patients who required extraction of at least one tooth (incisor, canine, or premolar) provided 35 single-gap extraction sites. After minimally invasive tooth removal, the sockets were randomly scheduled for one of four treatment modalities: placement of a deproteinized bovine bone mineral (DBBM; Endobon, Biomet 3i) covered with a soft tissue punch from the palate (T1); placement of DBBM alone (T2); placement of DBBM covered with a resorbable collagen membrane (OsseoGuard, Biomet 3i) (T3); or no additional treatment (T4). Silicone impressions were taken before and 6 months after extraction for quantitative-volumetric evaluation (primary outcome). The possibility of placing an implant, bone quality, and need for further bone augmentation were also noted (secondary outcomes). During the study period, no adverse events were observed. No statistically significant difference was found between the four treatments regarding the primary and secondary outcome parameters (P > .05). However, T4 showed double the buccal contour change, with the highest variance compared to the other three groups (T1 -0.874 ± 0.713; T2 -0.968 ± 0.344; T3 -1.26 ± 0.942; T4 -2.15 ± 1.349). Although no statistically significant difference was found between the four treatment modalities, placement of DBBM resulted in only half the contour change (< 1 mm) compared to control sites (> 2 mm). Ridge preservation with a DBBM with or without soft tissue punch should be considered in esthetically demanding cases and delayed or late implant placement.

Gingival biotype revisited-novel classification and assessment tool

OBJECTIVES

To evaluate the relationship between gingival biotypes and gingival thickness based on probe transparency through the gingival margin and to assess the sensitivity of a novel classification method.

MATERIAL AND METHODS

Sixty adult Caucasian subjects were stratified by their gingival biotype (GB) as defined by the transparency of a prototype double-ended periodontal probe through the buccal gingival margin into "thin" (30 subjects), "moderate" (15 subjects), and "thick" (15 subjects) GB. Three additional parameters were also assessed: gingival thickness (GT), probing depth (PD), and gingival width (GW).

RESULTS

Median GT was 0.43 mm (P _25% 0.32; P _75% 0.58) for thin, 0.74 mm (P _25% 0.58; P _75% 0.81) for moderate, and 0.83 mm (P _25% 0.74; P _75% 0.95) for thick GB, respectively. GT was statistically significant different for thin versus moderate and thin versus thick, respectively (Kruskal-Wallis test, p < 0.05; Dunn's test, thin versus moderate: p = 0.002; thin versus thick: p < 0.001; moderate versus thick: p = 0.089). GW was directly correlated with GT (Spearman correlation p < 0.01). The sensitivity of the new classification tool for diagnosing a thin GB was 91.3%. No adverse events or complications were reported.

CONCLUSION

GT differs significantly between the presented GB groups, hence, an alternative classification especially focusing on thin biotypes based on a modified periodontal probe might be advantageous. In addition, the presence of a thick gingiva is associated with a wide band of keratinized tissue.

CLINICAL RELEVANCE

This clinical setting might to be useful to identify high-risk patients with a very thin biotype and, consequently, higher risk for gingival recession after dental treatments.

Does chemical preconditioning contribute to the effectiveness of scaling and root planing? An in vitro pilot investigation

OBJECTIVES

A solution based on hypochlorite and amino acids was introduced to improve cleaning efficacy on the root surfaces. The purpose of this in vitro pilot study was to evaluate the time reduction and number of strokes required to clean untreated root surfaces in vitro.

METHODS

Sixty extracted human teeth displaying areas with subgingival calculus were assigned equally to one of three treatment groups (n = 20) according to the size of occupied areas, estimated by the number of pixels. The groups were assigned to either 30 s penetration time (I) or 300 s (II) or no pretreatment application (III). The weight for instrumentation was calibrated for a M25A curette (Deppeler/Switzerland) with 500 g. A new set of tools was used for each group, and each instrument was sharpened after single use by an EasySharp Device (Deppeler/Switzerland).

RESULTS

The time (in seconds) for instrumentation was recorded as follows: Group I: 32/23.5/50 (median/first quartile/third quartile); group II: 33/20/52.5; group III: 46.5/35.5/52.3. The results for the numbers of strokes were: Group I: 18/14.3/28; group II: 18.5/13/30.5; group III: 17.5/15/25. No statistically significant differences (P < 0.05) were found between the three groups for the variables 'time' and 'number of strokes'.

CONCLUSIONS

Within the limits of this in vitro pilot study, preconditioning of the calculus on root surfaces with an alkaline solution failed to reduce the number of strokes and time of instrumentation significantly.

Stage-two surgery using collagen soft tissue grafts: clinical cases and ultrastructural analysis

OBJECTIVE

To present the application of two different soft tissue grafts around dental implants during stage-two surgery. Furthermore, the ultrastructure of these materials is shown and discussed using scanning electron microscopy (SEM).

SUMMARY

Although soft tissue autografts may be currently regarded as the gold standard, harvesting of these grafts might lead to higher morbidity, longer chair time, and intra-/postoperative complications at the donor site. New developments in collagen scaff olds have provided an alternative to successfully replace autologous grafts in clinical practice. The SEM pictures clearly show the different composition of a bilayer scaff old (collagen matrix, CM) and a porcine acellular dermal matrix (ADM). These distinctive properties lead to different possible indications. Within the presented cases, ADM was used to augment the ridge contour and was placed into a buccal pouch to achieve complete coverage and an uneventful closed healing. On the other side, CM was left exposed to the oral cavity to successfully gain keratinized mucosa around and between two dental implants.

On the relationship between gingival morphotypes and different crown shape assessments in young Caucasians

OBJECTIVES

The objective of this study was to determine the relationship between crown length as well as crown width and gingival morphotypes (primary aim) and their correlation with tooth shape and papilla height (secondary aim).

MATERIAL AND METHODS

Thirty-six adult subjects were evaluated in this clinical study according to their gingival morphotype (GM) defined by transparency of a periodontal probe through the buccal gingival margin. Eighteen subjects comprised the thin entity group and 18 the control group thick entity, respectively. Besides crown length (CL) and crown width (CW), two different methods to assess crown shape (CW/CL ratio) were compared and analysis of their relation to papilla height was performed.

RESULTS

Nineteen female and 17 male volunteers were enrolled in this study, with a mean age of 24.9 years (±3.4; minimum 18, maximum 35). A statistical significant difference for the crown length could be detected between both groups (p < 0.05) but not for crown width. No significant difference was found for apical or coronal CW/CL ratio besides on tooth 22.

CONCLUSION

Within the limitations of this study and within this young Caucasian study population, only crown length seems to have an association with different gingival morphotypes. Furthermore, papilla height and crown shape do not have a clear correlation on tooth level.

CLINICAL RELEVANCE

Crown shape seems to be not a strong parameter in assessing the gingival morphotype.

Influence of local administration of pamidronate on extraction socket healing--a histomorphometric proof-of-principle pre-clinical in vivo evaluation

OBJECTIVES

To evaluate the influence of local administration of pamidronate histomorphometrically, adsorbed on a collagenated porcine bone substitute, on extraction socket healing.

MATERIAL AND METHODS

Two American Fox-hound dogs were used within this proof-of-principle study. Following endodontic treatment of the distal root of the three lower premolars, the teeth were hemisected, and the mesial roots were extracted flapless. The sockets were then loosely filled, in a split-mouth fashion, with a collagenated porcine bone substitute (Osteobiol Gen-Os; CPB), rehydrated either with 90 mg/ml pamidronate (Aredia(®) ; test) or with sterile saline (control). Extraction sockets were sealed with connective tissue punches obtained from the palate and secured with sutures. After 4 months of healing, specimens containing the socket sites and remaining roots were retrieved and histomorphometrically examined.

RESULTS

Histological evaluation of the sections revealed substantial differences in healing patterns. Control sites presented with various amounts of newly formed bone and no evidence of CPB inside the socket; in contrast, limited amounts of bone were observed at test sites, which were filled with CPB mainly embedded in connective tissue. Only minor differences were observed between test and control sites regarding vertical bone loss (buccal bone: -1.01 mm vs. -1.15 mm; lingual bone: -0.92 mm vs. -1.15 mm). Horizontal bone loss was nearly three times higher in control sites comparing to sites treated with pamidronate (-2.19 ± 1.81 mm vs. -0.80 ± 0.91 mm) at a level corresponding to 3 mm below the cemento-enamel junction (CEJ).

CONCLUSION

Local administration of pamidronate adsorbed on a collagenated porcine bone substitute in particulate form appeared to delay extraction socket healing, but may also reduce post-extraction dimensional changes in terms of horizontal bone width. Additionally, pamidronate appears to obstruct resorption of the porcine bone substitute.

On the relationship between gingival biotypes and gingival thickness in young Caucasians

OBJECTIVES

To evaluate a possible relationship between gingival biotypes and gingival thickness, papilla height and gingival width.

MATERIAL AND METHODS

Thirty-six adult subjects were stratified by their gingival biotype (GB), as defined by transparency of a periodontal probe through the buccal gingival margin, into "thin" (18 subjects) and "thick" (18 subjects) GB. Out of these, extreme cases (6 "very thin", 6 "very thick") were identified. Four different parameters were assessed: gingival thickness (GT), papilla height (PH), probing depth (PD) and gingival width (GW).

RESULTS

When comparing "thin" and "thick" GB, midfacial GT (0.40 ± 0.07 vs. 0.72 ± 0.11 mm; P < 0.0001), PH (3.76 ± 0.50 vs. 3.95 ± 0.41 mm, P = 0.02) and GW (3.01 ± 1.26 vs. 4.63 ± 0.86 mm, P = 0.04) were lower in the "thin" GB group. Further stratification into moderately and extremely "thin"/"thick" GB eliminated the differences between the moderate groups.

CONCLUSION

Our data support the traditional hypothesis that two different gingival biotypes with concomitant properties distinguishable by gingival transparency exist. In addition, we provide evidence that an alternative classification into "very thick", "moderate" and "very thin" biotypes might be advantageous, because the unique properties were seemingly primarily driven by subjects with extreme values.

Porcine dermal matrix for covering of recession type defects: a case series

OBJECTIVE

To study the clinical applicability of porcine dermal matrix for treatment of recession type defects.

METHOD AND MATERIALS

Twenty-eight gingival recessions in six patients were selected for root coverage procedures using a modified tunneling technique and porcine dermal matrix. As primary outcome, depth and width of gingival recession were assessed at baseline and at 6 and 12 months postoperatively. As a secondary outcome, the width of keratinized tissue was studied.

RESULTS

At 6 and 12 months postoperatively, mean root coverage was 65.52% and 56.82%, respectively. Complete root coverage was achieved in 42.86% of the treated defects.

CONCLUSION

Porcine dermal matrix may potentially be used as a replacement material for autologous tissue. However, complete root coverage was only achieved in less than half of the studied defects.

On the relationship between gingival biotypes and supracrestal gingival height, crown form and papilla height

OBJECTIVES

To determine the association between gingival biotypes and supracrestal gingival height (primary aim) and its relation to crown shape and papilla height (secondary aim).

MATERIALS AND METHODS

Eighty adult subjects were evaluated in this study. Based on the transparency of a periodontal probe through the buccal gingival margin, 38 subjects comprised the thin biotype group and 42 subjects comprised the thick biotype group, respectively. Three different parameters were clinically assessed: supracrestal gingival height (SGH) by bone sounding, crown width/crown length ratio and papilla height.

RESULTS

No statistical difference (P > 0.05) was detected neither for the correlation between different biotypes (thick/thin) and SGH nor for the association of biotypes and crown width/crown length ratio. Papilla height was only significantly increased (P ≤ 0.05) in the area of teeth no. 21/22 for the thin periodontal biotype. Intra-examiner deviation was found to be very low for all clinical parameters (percentile agreement > 95%).

CONCLUSIONS

Within the limits of this study, we found that in young Caucasians (i) soft tissue dimensions seem to be similar between biotypes (ii) and the traditional hypothesis that a thick gingiva merges with broad-short crown shape and flat papillae and a thin gingiva with a narrow-long crown shape and high scalloping, may be questionable.

Stability of serum eye drops after storage of 6 months

PURPOSE

Serum eye drops are used for the treatment of ocular surface disease (eg, Sicca syndrome). The objective of this experimental study was to investigate whether they maintain their wound-healing potency after a prolonged storage of 6 months at -20 °C and to find a parameter that can serve as a quality and stability indicator.

METHODS

After obtaining whole blood from 10 volunteers and preparing 100% (AS100), 50% (AS50), and 20% (AS20) serum eye drops, epitheliotrophic factors including EGF, fibronectin, vitamins A and E, albumin, and immunoglobulin A were quantified before and after storage for 7 days at 6 °C or 3 and 6 months at -20 °C. Human corneal epithelial (HCE) cell lines were used to investigate proliferation, migration, and overall wound healing potency of the cells in response to different serum preparations. The proliferation, migration, and wound healing of HCE cells were measured after incubation with different serum eye drop concentrations and after different storage conditions.

RESULTS

The concentration of epidermal growth factor, fibronectin, vitamins A and E, immunoglobulin A, and albumin showed no significant reduction over the test period. Proliferation, migration, and wound healing of HCE cells was significantly better after incubation with undiluted serum in comparison with diluted serum. No significant loss of cytokine concentration, wound healing, and proliferation effect in HCE culture of AS100, AS50, and AS20 could be detected over the 6 months of storage.

CONCLUSIONS

The concentration of a spectrum of cytokines involved in corneal epithelial wound healing and the epitheliothrophic effect of serum are not significantly changed after a prolonged storage of 6 months at -20 °C. Hence, it seems justifiable to provide patients with appropriate freezer capacity with a 6-month supply of autologous serum eye drops. Albumin--which is known to be relevant for ocular surface health--could serve as a cost-effective parameter for stability controls.

Root coverage with a modified lateral sliding flap - a case series

The necessity of surgical root coverage is often encountered in daily clinical practice, mainly because of esthetic reasons. Despite the variety of available surgical techniques, delicate clinical scenarios may require refined surgical therapy approaches. The presented double sliding flap technique is designed to meet the special requirements encountered in the often-fragile incisal mandibular area. This surgical approach combines two laterally repositioned flaps with the dissection of the frenulum, to cover two deep neighboring recessions in the area of the central incisors. Providing that correct indication and adequate surgical tissue handling are used, this complex and advanced technique may have the potential to achieve complete longterm root coverage and an esthetically satisfying treatment outcome.

Structural basis for the nucleic acid binding cooperativity of bacteriophage T4 gene 32 protein: the (Lys/Arg)3(Ser/Thr)2 (LAST) motif

To identify the functional residues of the N-terminal B region of bacteriophage T4 gene 32 protein involved in its cooperative binding to single-stranded nucleic acids, a process dependent on homotypic protein-protein interaction, we have studied the interaction of the protein with synthetic peptides containing different portions of this domain. Gel-permeation chromatography showed that a 6-acryloyl-2-dimethylaminonaphthalene (acrylodan)-labeled fluorescent peptide corresponding to the first 17 residues of gene 32 protein formed a complex with whole protein. The fluorescence was blue-shifted 14 nm upon interaction with intact protein, and somewhat less so (7-11 nm) with cleavage products of the protein lacking B domains. The intrinsic tryptophan fluorescence of whole and truncated protein was quenched by this peptide and by the nonderivatized peptide. The peptide bound tightly to truncated protein at both 0.015 and 0.44 M Na+, with a stoichiometry of 1:1. Similar tryptophan quenching or acrylodan blue shifts were obtained with peptides corresponding to residues 1-9 and 3-8, but not residues 1-4, 5-9, or 5-17, indicating that the essential amino acids are contained within positions 3-8, Lys-Arg-Lys-Ser-Thr-Ala. Several other DNA binding proteins contain a LAST motif with documented involvement of these residues in nucleic acid interaction. The amino acid and coding sequence of residues 110-114, a region proposed to be involved in nucleic acid binding, is virtually identical to that of residues 3-7. Based on these observations, we have formulated a model for the cooperative interactions of gene 32 protein with single-stranded nucleic acids.