The International Journal of Periodontics & Restorative Dentistry © 2018 by QUINTESSENCE PUBLISHING CO, INC. PRINTING of TH

The International Journal of Periodontics & Restorative Dentistry

Increasing the Vertical Dimension of Occlusion: A Multicenter Retrospective Clinical Comparative Study on 100 Patients with Fixed Tooth-Supported, Mixed, and Implant-Supported Full-Arch Rehabilitations

Giacomo Fabbri, DDS1/Roberto Sorrentino, DDS, MSc, PhD2 The term vertical dimension of oc- Giorgio Cannistraro, DDS3/Francesco Mintrone, DDS4 clusion (VDO) refers to the distance Leonardo Bacherini, DDS5/Roberto Turrini, DDS6 between two selected anatomical Tiziano Bombardelli, MD, DDS7/Michele Nieri, MD, DDS8 or marked points in maximal inter- 6 Mauro Fradeani, MD, DDS cuspal position.1 It has been sug- gested that an increase in VDO This multicenter retrospective clinical study was aimed at comparing the effects of an might cause clinical drawbacks, such increase in vertical dimension of occlusion (VDO) in patients with fixed rehabilitations. as elevation of bite forces, muscle Expert clinicians retrospectively evaluated 100 patients treated with an increase hypersensitivity, symptoms of tem- of the VDO and fixed dental prostheses (FDPs) supported by teeth, implants, or both. The patients were divided into three study groups according to the type of poromandibular disorders, phonetic support of restorations in posterior areas, as follows: partially edentulous patients limitations, and teeth tenderness.2,3 with posterior teeth-supported rehabilitations and no implants in posterior segments However, modification of the VDO (group A), partially edentulous patients with posterior mixed rehabilitations and at least one osseointegrated implant in posterior segments (group B), and completely to increase the interarch distance is edentulous patients with posterior implant-supported rehabilitations (group C). crucial to optimal outcomes in some The new VDO was tested with mock-ups, temporary restorations, or removable prosthetic therapies. In fact, this ap- appliances. The patients were followed up for at least 1 year after the delivery of proach allows for many advantages, final restorations. Clinical variables were collected retrospectively, such as presence of referred self-reported bruxism and temporomandibular joint or muscle symptoms such as enhancement of the esthetic before treatment, extension of the dental arches, increase in VDO, restorative tooth display; correction of anterior materials, and functional complications. Descriptive statistics were analyzed; the three teeth relationships, improving hori- experimental groups were compared with one-way analysis of variance (ANOVA) zontal and vertical overlap; improve- followed by Tukey post hoc test for the quantitative variables and with logistic regression using the likelihood ratio test for the qualitative variables. Statistically ment of lip support; reduction or significant differences were reported among the experimental groups for functional avoidance of the need for surgical complications. Functional and prosthetic complications after the VDO increase crown-lengthening procedures and/ were not frequent. Functional complications were mainly noticed in group C but usually were no longer evident after 2 weeks. No significant differences were found or endodontic treatments; establish- between groups in terms of prosthetic complications and self-reported bruxism. ment of anatomical harmony, and Int J Periodontics Restorative Dent 2018;38:323–335. doi: 10.11607/prd.3295 minimization of occlusal tooth preparation, recovering vertical room for 1Private Practice, Cattolica, Italy. restorative materials. Due to these 2Research Professor, Department of Neurosciences, Reproductive and advantages, increase of the VDO is Odontostomatological Sciences, University of Naples, Naples, Italy. 3Private Practice, Castagnola delle Lanze, Italy. frequently performed in oral rehabil- 4Private Practice, Modena, Italy. itations, specifically to proceed with 5 Private Practice, Florence, Italy. minimally invasive approaches and 6Private Practice, Pesaro, Italy. 4,5 7Private Practice, Trento, Italy. to optimize prosthetic outcomes 8PhD Student, Department of Surgery and Translational Medicine, University of Florence, (Figs 1 to 4). Florence, Italy. The loss of tooth substance di- Correspondence to: Dr Giacomo Fabbri, Via del Porto 17 Cattolica, Rimini 47841, Italy. rectly affects the VDO and occlu- Fax + 39 0541 833322. Email: [email protected] sion, with consequences for both ©2018 by Quintessence Publishing Co Inc. function and esthetics. Despite the

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a b Fig 1 Case 1: A 34-year-old woman with a moderately worn dentition and esthetic concerns. (a) The esthetic and functional evaluations showed less-than-ideal teeth exposure at rest, altered tooth proportions, and a reduced horizontal overlap that compromised the correct disocclusion of the posterior teeth during anterior guidance. The increase in VDO (4 mm) in centric relation was crucial to preserve tooth structures and restore proper esthetics and function with correct horizontal and vertical overlap. The case was finalized with 28 lithium disilicate single crowns, monolithic in the posterior segments and layered in the anterior area. (b) The final prosthetic outcome after 7 years of function. The esthetic and the functional outcomes are completely preserved.

a b Fig 2 Case 2: A 59-year-old woman affected by a grave occlusal, functional, and esthetic condition associated with temporomandibular disorder. (a) After a complete esthetic and functional evaluation, all the information necessary to create a wax-up was collected. The first step of the treatment was to asses the new interocclusal relationship using an indirect removable mock-up to evaluate the muscles and temporomandibular joint response at the new VDO in centric relation. An increase in the VDO in centric relation of 11 mm was made to achieve ideal functional and esthetic prosthetic outcomes. The case was concluded with a complete full-arch implant-supported rehabilitation in the maxilla and a teeth-supported prosthesis in the mandible with single crowns and veneers, with an implant-supported bridge from the mandibular right first premolar to first molar. (b) The final rehabilitation after 5 years of function showed an ideal stable occlusion with anterior and lateral guidance that allows the correct disocclusion of the posterior teeth during the function.

aforementioned advantages, arbi- either by increasing or decreasing it, literature review concerning the rela- trary increase of the VDO has always could cause serious problems such tionship between modification of the been a subject of debate in dentistry. as muscle pain, temporomandibu- VDO and TMJ disorders concluded Traditionally, changing the VDO has lar joint (TMJ) disorders, headaches, that many commonly held concepts not been considered a safe proce- and tooth grinding and clenching.6–8 related to this topic were not sup- dure. Several authors have reported On the contrary, in the last decades ported by scientific evidence and that the VDO is a specific and fixed several studies concluded that VDO that additional studies are neces- parameter that cannot be altered increase did not seem to be a haz- sary to understand this relationship when treating patients; moreover, es- ardous procedure when good occlu- more precisely.11 Moreover, several tablishment of an inadequate VDO, sal stability was achieved.9,10 A recent researchers have proven the ability of

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a b Fig 3 Case 3: A 62-year-old man with a severely worn dentition caused by attrition and erosion combined with self-reported bruxism. The increase in VDO (5 mm) in centric relation was mandatory to preserve tooth structures and restore ideal tooth proportions and correct function. An ideal posterior support was recreated by means of implants and restoration of the residual teeth with minimally invasive procedures, preserving the tooth structure and the vitality of the dental elements. The case was finalized using monolithic zirconia in the posterior areas and monolithic lithium disilicate in the anterior segments. (b) Final rehabilitation after 3 years of function. The increase in VDO allowed recreation of ideal teeth proportions with correct teeth exposure at rest and an ideal anterior occlusal relationship.

a b

Fig 4 Case 4: A 45-year-old man with severe reverse articluation refused orthodontic and surgical therapy. The occlusal relationship caused a dramatic functional condition associated with unsatisfactory esthetics. An increase in VDO (8 mm) in centric relation (CR) was essential to finalize the case with a satisfactory prosthetic outcome. In fact, the repositioning in CR combined with the increased VDO allowed recreation of a favorable arch relationship to be restored by minimally invasive lithium-disilicate single crowns. The new occlusal, functional, and esthetic situation realized with the wax-up was tested with a bonded mock-up for 3 months to determine the final prosthetic outcome. (b) The mock-up after 3 months of function, the new occlusal conditions completely integrated with a excellent esthetic and functional c response. The oral hygiene was maintained using interproximal toothbrushes. (c) Final rehabilitation after 3 years of function. The situation that was preliminarily tested with the mock-up was perfectly replicated in the final rehabilitation.

patients with implant-supported res- force12,13 and deficiency of periodon- torations. The combination of these torations to adapt to new VDO rela- tal structures14,15 are associated with factors may reduce patients’ abil- tionships; however, an increase in bite full-mouth implant-supported res- ity to compensate for VDO changes

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Fig 5 Representative patient from group A. The posterior support was provided by natural teeth only.

and may compromise the survival Materials and Methods The patients were divided into of implant-supported restorations, three study groups according to the since the increase in bite forces and Study Population type of support of restorations in the reduction of the sensory percep- posterior areas, as follows: tion may lead to implant overload; This retrospective study was report- furthermore, bone loss, TMJ disorder ed according to the STROBE state- • Group A: patients with symptoms, and biomechanical prob- ment for improving the quality of posterior teeth-supported lems such as screw loosening and reports of observational studies in rehabilitations; no implants in fracture and chipping of veneering epidemiology.16 All patients signed posterior segments (molar and restorative materials causing failures a written consent form. premolar) (Fig 5) or complications of full-arch implant- The study subjects were select- • Group B: patients with supported prostheses can occur. To ed retrospectively from the patient posterior mixed rehabilitations; date, there is a lack of evidence re- directories of the private practices at least one osseointegrated garding the incidence of functional of six experienced prosthodontics. implant in posterior segments and prosthetic complications in pa- All patients were treated between (Figs 6 and 7) tients treated with a VDO increase by 2004 and 2014 with an increase of • Group C: completely means of teeth-supported, mixed, the VDO and FDPs supported by edentulous patients with and implant-supported restorations. teeth, implants, or both. The inclu- posterior implant-supported The present multicenter retrospec- sion criteria were patients with fixed rehabilitations (Fig 8) tive clinical study aimed at compar- rehabilitations in at least one arch ing the effects of an increase in VDO with an increase in VDO and at least Group A was made up of patients in patients with fixed rehabilitations. 1 year of follow-up after delivery of treated for severely worn dentition The null hypothesis stated that there final restorations. All patients with (Fig 3a), occlusal problems, or teeth was no association between the removable partial or complete den- compromised for biologic or biome- three experimental groups and the tures as antagonists were excluded chanical reasons. Only patients with- outcome variables. from the study. out implants in posterior segments

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Fig 6 Representative patient from group B. The posterior support was shared between natural teeth and a single implant at the site of the mandibular right first molar.

Fig 7 Representative patient from group B. The posterior support was shared between natural teeth and implants. were included in this group. The rehabilitations were finalized with crowns, veneers, overlays, table- tops, and three- and four-unit FDPs. The maximum follow-up time was 36.5 (± 24.1) months. Group B included patients provided with at least one implant in the posterior regions. This distinc- tion was made to investigate the influence of the presence of posterior osseointegrated implants on the patient’s adaptability after an Fig 8 Representative patient from group C. The posterior support was provided by increase in VDO. The dentoalveolar implants only.

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© 2018 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. 328 compensatory mechanism would al- From a clinical point of view, ative materials, since 3 mm is almost low for preservation of the original it is difficult to scientifically detect universally accepted as the mini- VDO,6 but in the same time it would any alteration of the VDO and the mum preparation height to guaran- allow for adaptation at the new diagnosis is mainly based on ob- tee sufficient resistance in posterior VDO. Consequently, the presence servation of interocclusal relation- teeth.21 Such an approach usually of single or multiple osseointegrat- ships, interdental proportions (ie, prevents the need for more invasive ed implants, particularly if placed short teeth), alteration of the curve surgical crown-lengthening proce- in the posterior areas where the of Spee, and soft tissues support (ie, dures that would lead to the loss of occlusal contacts are more intense, shortening of the lower face height, significant amounts of hard and soft could influence this compensatory inverted or toothless smile, angu- tissues, influence the emergence mechanism. This group was het- lar cheilitis).18 Shiny dental surfaces profiles, and cause the develop- erogeneous, including cases with and evident facets are considered ment of interdental black triangles.18 single and multiple implants sup- reliable clinical signs of attrition that porting single crowns (SCs), FDPs, usually match facets of the oppos- and full-arch prostheses opposing ing dentition in eccentric occlusion, Prosthodontic Procedures natural teeth and/or implants. The particularly in anterior teeth.19 maximum follow-up time was 36.5 In the present study, the cor- All the cases were treated with the (± 25.2) months. rect restoration of an altered VDO same prosthetic approach using Group C was made up of com- was based on a clinical evaluation simplified semiadjustable articula- pletely edentulous patients treated of functional, phonetic, and esthetic tors to evaluate the functional and with implant-supported full-arch parameters. In particular, occlusion occlusal parameters. Furthermore, prostheses at both arches: in these and bite relationships, the position all the cases were finalized in CR us- clinical conditions, the dentoal- of the incisal margins of the maxil- ing the bimanual manipulation tech- veolar compensatory mechanism is lary central incisors and their visibil- nique described by Dawson.22 completely absent. The maximum ity at rest, the resting and smiling lip The adjustable components on follow-up time was 56.6 (± 22.5) positions, analysis of the facial pro- semiadjustable articulators are com- months. file, soft tissue measurements at the monly set at the following average This partition of the treated lower facial third (ie, the distance be- values: condylar inclination at 25 to cases aimed at evaluating whether tween the point of the nose and the 35 degrees, progressive side shift the presence of implant-supported tip of the chin) and pronunciation of (ie, Bennett angle) at 7 to 15 de- restorations, and therefore partial or the S sound were considered.17,18 grees, and immediate side shift (ie, complete lack of the dentoalveolar Subsequent to anterior wear, Bennett movement) at 1 to 2 mm. In complex, could influence the reli- the mandible is usually located more the present study, all the operators ability of the VDO-increasing proce- anteriorly. By recording the horizon- used the following setting approach: dure, reducing the patient’s ability tal difference when the mandible is individualized condylar inclination, to adapt to the new VDO. in maximal intercuspation and cen- Bennett angle at 10 degrees, and tric relation (CR), interincisal room Bennett movement at 0 mm (since can be obtained for restorations.20 all patients were rehabilitated in CR, Diagnosis and Decision-Making The final preparation height was where immediate side shift does not Process reported to be a crucial determinant exist). A protrusive wax record was of the need for and magnitude of made to set individually the condy- The restoration of a correct VDO VDO increase.18 This amount was lar inclination. The protrusion of the should reflect the ideal dimension determined on the basis of the re- mandible brings the condyles down from the functional, esthetic, and sidual tooth structure and the room along the articular eminence of the comfort perspective.17 needed to incorporate the restor- temporal bone and the posterior

The International Journal of Periodontics & Restorative Dentistry

© 2018 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. 329 teeth usually separate, depending Broach, Moyco Technologies) with on the amount of incisal guidance. A the Dawson technique. The amount 6.0 protrusive wax records the amount of VDO increase was evaluated for of separation. each case intraorally using fixed ana- 4.5 5.3 (± 1.6) The maxillary and mandibular tomical reference points in the ante- 3.0 3.9 arms of the articulator were sepa- rior areas of both arches, namely the (± 1.8) 3.2 rated and the protrusive wax placed gingival margins or the cemento (± 0.8) 1.5 between the casts until they were enamel junction (CEJ) of the anterior Increase in VDO (mm) Increase completely seated. Consequently, teeth. All the completely edentulous 0 Group A Group B Group C the condylar spheres moved down- patients in group C underwent a ward and forward as in the patients’ period of temporization by means mouths. The condylar inclination el- of fixed implant-supported screw- Fig 9 Mean (± SD) increase in VDO in the ement was then released and tilted retained provisional restorations experimental groups. down until it contacted the condylar fabricated to divide the prosthetic sphere; finally, it was secured. The space according to the principles aim of each prosthetic therapy was of complete removable dentures. to obtain an ideal occlusal stabil- Consequently, the reference points toms before treatment, extension of ity in CR, with posterior punctiform to evaluate the amount of the VDO the dental arches, increase in VDO contacts together with anterior and increase were set at implant necks or evaluated intraorally in the ante- lateral guidances. The following re- abutments. The new VDO was test- rior regions (in millimeters), material quirements to optimize occlusal sta- ed with mock-ups, temporary resto- used for the final prostheses, tech- bility were chosen: rations, or removable appliances for nique used to test the new VDO different periods in relation to the and period of testing, and func- • Stable stops on all teeth when needs of each clinical situation. tional complications within 2 weeks condyles were in CR with cusp After opening the VDO with and at 2 weeks, 6 weeks, 1 year, and tip to fossa contact temporary restorations, the pa- the last follow-up. The confounding • Anterior guidance in harmony tients were requested to function variables at baseline are reported with the border movement of normally for 2 months. If no signs in Table 1. The baseline for evalua- the envelope of function or symptoms of functional draw- tion of the functional complications • Disocclusion of all posterior backs or discomfort were noticed, was the day of the VDO increase by teeth during protrusive the restored VDO was considered means of mock-ups, temporary res- movements correct. In all the cases, the final torations, or removable appliances. • Disocclusion of all posterior prostheses maintained the VDO The considered functional compli- teeth on the nonworking side and all the functional and esthetic cations were tenderness, difficulty during lateral movements parameters tested with the provi- in chewing, difficulty with speech, • No interference of all posterior sional restorations. To be enrolled pain at teeth or implants, grinding, teeth on the working side in the present retrospective study, clenching, headache, muscle or during lateral anterior guidance the patients had to be followed up TMJ fatigue, and elevation of bite for at least 1 year after delivery of forces. The following prosthetic The new VDO was established the final restorations. complications were recorded sepa- considering esthetic and functional For each patient, different clini- rately: chipping of restoration ma- parameters through a compre- cal variables were collected retro- terials, biologic and biomechanical hensive clinical evaluation (Fig 9). spectively: age, sex, presence of complications, and occlusal wear. The CR record was obtained using self-reported bruxism and TMJ or At 6 weeks, 1 year, and the last a warm wax wafer (Moyco Union temporomandibular muscle symp- follow-ups, all the patients were

Volume 38, Number 3, 2018

© 2018 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. 330 evaluated again for the presence study. Descriptive statistics were Dedicated software (JMP 10.0, of self-reported bruxism. This vari- performed using mean values and SAS Institute) was used for the sta- able was assessed based on patient standard deviations for the quanti- tistical analysis. The significance feedback and occlusal evaluations; tative variables and frequencies and value was set at P = .05. the freeway space was also re- percentages for the qualitative vari- corded to evaluate the interocclusal ables. Each patient was considered space in rest position. a statistical unit. The three experi- Results mental groups were compared with one-way ANOVA followed by Tukey The null hypothesis was rejected Statistical Analysis post hoc test for the quantitative since statistically significant differ- variables and with logistic regression ences were reported among the The experienced clinicians were using the likelihood ratio test for the experimental groups for functional trained to record the clinical study qualitative variables. The following complications, particularly up to 2 variables systematically to homog- were considered as outcome vari- weeks (P < .05). enize data as much as possible. ables: functional complications (at 2 The independent variable was weeks, 6 weeks, 1 year, and the final the type of rehabilitation. Three cat- follow-up), prosthetic complications, Study Population egories were considered as follows: and persistence of self-reported posterior teeth-supported FDPs bruxism at the final follow-up. As to In total, 100 patients from the den- (group A), posterior mixed resto- the latter, it was recorded only for tal practices of six experienced rations (group B), and completely patients who presented with self- clinicians were recruited for the implant-supported FDPs (group C). reported bruxism at baseline. The present retrospective study. Of The outcome variables were func- odds ratio (OR) and 95% confidence these, 25 patients had posterior tional complications, prosthetic interval (CI) between the three ex- teeth-supported FDPs (group A), complications, and persistence of perimental groups were calculated 56 patients had posterior mixed referred self-reported bruxism (ie, for the outcome variables. Stepwise FDPs (group B), and 19 patients had grinding or clenching). The con- forward and backward logistic re- complete implant-supported FDPs founding variables considered were gressions were performed to con- (group C). age, sex, center, presence of self- sider possible confounding variables reported bruxism at baseline, pres- using the following predictors: type ence of TMJ or muscle symptoms of rehabilitation (teeth, mixed, im- Descriptive Data before treatment, extension of the plants), age, sex, center, presence dental arches, increase in VDO (in of self-reported bruxism at baseline, At baseline, 57 women and 43 men millimeters) evaluated intraorally in presence of TMJ or muscle symp- were enrolled in the study. Their age the anterior regions, technique used toms before treatment, presence of ranged from 26 to 79 years; overall to test the new VDO (ie, mock-ups, at least 14 teeth per arch (yes/no), in- mean age was 52.8 (SD 11.3) years, provisional restorations, remov- crease in VDO (in millimeters) evalu- while the mean ages in the teeth- able appliances), time of VDO test- ated intraorally in anterior regions, supported, mixed-supported, and ing (in months), material used for technique used to test the new VDO implant-supported groups were the final restorations, and duration (ie, mock-ups, provisional restora- 48.6 (12.9), 52.6 (10.9) and 58.6 (7.3) of follow-up (in months). Sample tions, or removable appliances), time years, respectively (P = .0131). Of the size calculation was not performed. of VDO testing (in months), material patients, 44 were affected by self- and all patients with an increase in used for the final restorations (lithium reported bruxism and 22 presented VDO followed up for at least 1 year disilicate versus others), and duration with TMJ or muscle symptoms. As were included in the retrospective of follow-up (in months). to the qualitative data grouped by

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Table 1 Confounding Variables at Baseline and Frequency

Group A Group B Group C Total Variable (n = 25) (n = 56) (n = 19) (n = 100) P Sex

Men 11 (44%) 21 (38%) 11 (58%) 43 .3001 Women 14 (56%) 35 (62%) 8 (42%) 57 Dental center 1 3 (12%) 8 (14%) 0 (0%) 11 2 3 (12%) 11 (20%) 0 (0%) 14

3 10 (40%) 12 (21%) 16 (84%) 38 < .0001 4 5 (20%) 13 (23%) 2 (11%) 20 5 0 (0%) 10 (18%) 1 (5%) 11 6 4 (16%) 2 (4%) 0 (0%) 6 Self-reported bruxism 13 (52%) 24 (43%) 7 (37%) 44 .5843 Muscle or TMJ symptoms 6 (24%) 14 (25%) 2 (11%) 22 .3571 14 teeth per arch 23 (92%) 41 (73%) 6 (32%) 70 < .0001 Statistical significance set at P < .05 for likelihood ratio test.

Table 2 Confounding Variables During Treatment

Group A Group B Group C Total Variable (n = 25) (n = 56) (n = 19) (n = 100) P Quantitative VDO increase (mm) 3.2 ± 0.8 3.9 ± 1.8 5.3 ± 1.6 4.1 ± 1.7 .0002 Test period (mo) 2.2 ± 4.6 4.6 ± 4.1 7.2 ± 2.9 4.6 ± 3.8 < .0001 Follow-up (mo) 36.5 ± 24.1 36.5 ± 25.2 56.6 ± 22.5 43.2 ± 25.5 0.0071 Qualitative Mock-up 25 (100%) 33 (59%) 1 (5%) 59 (59%) Provisional restorations 0 (0%) 21 (37%) 14 (74%) 35 (35%) < .0001 Removable appliances 0 (0%) 2 (4%) 4 (21%) 6 (6%) Lithium disilicate prosthesis 25 (100%) 51 (91%) 14 (74%) 90 (90%) .0090 Data are presented as mean ± SD for quantitative variables and frequency (percentage) for qualitative variables. Statistical significance was set at P < .05 for analysis of variance + Tukey post hoc test (quantitative variables) and likelihood ratio test (qualitative variables). type of restoration, 14 teeth per Outcome Data Functional Complications arch was rarely evidenced and statistically significant differences were The functional complications at 2 The functional complications (ie, dif- seen for center and in group C weeks, 6 weeks, 1 year, and final ficulty on speech and on chewing, (Table 1). follow-up are presented in Table 3. tenderness, soreness, clenching, Data regarding treatments are The implants group showed more increase in bite forces, TMJ or muscle presented in Table 2. The amount functional complications after 2 symptoms) progressively decreased of the VDO increase, the time of weeks and at the final follow-up; how- over time and usually disappeared VDO testing, and the duration of the ever, the complications tended to dis- after 2 weeks. From baseline to the follow-up were greater in group C. appear during the follow-up period. 1-year follow-up, these complications Lithium disilicate restorations and the There were no differences among decreased from 24% to 0% in group mock-up technique to test the new groups in prosthetic complications A, from 9% to 0% in group B, and VDO were more frequent in group A. and in self-reported bruxism. from 32% to 1% in group C. Difficulty

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Table 3 Qualitative Outcome Variables in Frequency Group A Group B Group C Total Variable (n = 25) (n = 56) (n = 19) (n = 100) P Patients with functional complications Baseline to 2 wk 6 (24%) 5 (9%) 6 (32%) 17 (17%) .0445 2 to 6 wk 2 (8%) 1 (2%) 2 (11%) 5 (5%) .2294 6 wk to 1 y 0 (0%) 0 (0%) 1 (5%) 1 (1%) – Patients with prosthetic complications 8 (32%) 16 (29%) 4 (21%) 28 (28%) .7103 Persistence of self-reported bruxism 7 (28%) 6 (11%) 4 (21%) 17 (17%) .1221 Statistical significance was set at P < .05 for likelihood ratio test. on speech was the most frequently self-reported bruxism at the 1-year B, and 21% (n = 4) in group C. The recorded drawback; neither TMJ or follow-up as well. The stepwise lo- most frequent complication was loss muscle symptoms nor increase in gistic regression for patients with of surface staining, noticed in 12% bite forces were reported. prosthetic complications selected (n = 3), 5% (n = 3), and 21% (n = 4) The stepwise logistic regression only center and duration of follow- of cases in groups A, B, and C, re- for patients with functional compli- up as predictor variables. In particu- spectively. In groups A and B, 2 (8%) cations yielded the same results at lar, there were significant differences and 8 (14%) chippings occurred, 2 weeks and at the last follow-up. between the centers (P = .0007), respectively. As to crown failures, Only the type of rehabilitation was and the longer the follow-up pe- 2 events (8%) were highlighted in selected as a predictor variable. The riod the more frequent was the per- group A and 4 (7%) were reported same result was achieved with the bi- sistence of self-reported bruxism in group B; 1 root (4%) fractured in variate analysis (likelihood ratio test: (OR = 1.05 for each further month group A while 1 root and 1 implant P = .0445). In particular, the differ- of follow-up; 95% CI: 1.02–1.11; (4%) failed in group B. No chipping ence was significant when comparing P = .0048). The results of the bivari- or crown or implant fractures were the mixed-supported and implant- ate analysis with the type of rehabili- reported in group C. supported groups (OR = 4.71; 95% tation as predictor variable was not The stepwise logistic regression CI: 1.24–18.80); conversely, no sig- significant P( = .1221; Table 2). In par- for patients with prosthetic compli- nificant differences were found ticular, the difference was not sig- cations selected only the duration comparing the teeth-supported nificant when comparing the mixed of follow-up as a predictor variable and implant-supported groups (OR and implants groups (OR = 4.00; (OR = 1.02 for each further month = 1.46; 95% CI: 0.38–5.68) and the 95% CI: 0.70–25.86), the teeth and of follow-up; 95% CI: 1.0004–1.04; teeth-supported and the mixed- implants groups (OR = 1.14; 95% P = .0465). The results of the bi- supported groups (OR = 3.22; 95% CI: 0.18–7.88), and the teeth and variate analysis with the type of CI: 0.88–12.5). mixed groups (OR = 3.45; 95% CI: rehabilitation as predictor vari- 0.85–16.67). able was not significant P( = .7103; Table 3). In particular, the differ- Persistence of Self-Reported ence was not significant comparing Bruxism Prosthetic Complications the mixed-supported and implant- supported groups (OR = 0.67; 95% The analysis of the persistence of Overall, prosthetic complications (ie, CI: 0.17–2.18), the teeth-supported self-reported bruxism considered chipping, crown/root/implant frac- and implant-supported groups only the patients who presented ture, loss of surface staining) pre- (OR = 0.57; 95% CI: 0.13–2.19), with this condition at baseline. Of sented a frequency of 32% (n = 8) and the teeth and mixed groups these 44 patients, 17 (39%) showed in group A, 30% (n = 17) in group (OR = 1.18; 95% CI: 0.41–3.23).

The International Journal of Periodontics & Restorative Dentistry

Freeway Space are unable to withstand even physi- used, the operator should be aware ologic occlusal forces and start to of its limitations; the combination of The mean freeway space was 2.7 tip sideways, resulting in a collapsed more than one method is recom- (± 0.7) mm at last follow-up. By group, bite due to overclosure of the jaws.11 mended in daily clinical practice to the mean values were 2.5 (± 0.7) mm In the last decade, adhesive overcome such limitations. In partic- in group A, 2.6 (± 0.8) mm in group dentistry has significantly improved ular, facial esthetics and physiologic B, and 3.1 (± 0.7) mm in group C. in terms of physical and mechani- rest position were the most com- The differences between the cal properties, allowing for additive monly used approaches to establish groups were significant P( = .0211). restorative approaches.24 Subse- a correct VDO.17 These were used in In particular, according to Tukey quently, interest has grown in using the present clinical study. post hoc test, the difference was resin materials to manage tooth The retrospective clinical evalua- significant between the mixed wear, as these offer a more con- tion performed in the present study and implants groups (difference servative approach by preserving showed that functional and pros- 0.5 mm; 95% CI: 0.02–0.94 mm) and existing tooth structure in contrast thetic complications associated with between the teeth and implants to more invasive conventional treat- a VDO increase occurred in 17% and groups (difference 0.6 mm; 95% ment options.4,25 However, the lack 29% of patients, respectively, with an CI: 0.06–1.11 mm). The difference of evidence-based guidelines and average follow-up of 40.3 months. was not significant between the clinical recommendations for the Functional complications appeared teeth and mixed groups (difference management of tooth wear further within the first 2 weeks and usually 0.1 mm; 95% CI: −0.3–0.5 mm). challenges the treatment planning decreased each week. In some cas- and decision-making processes.25,26 es, it was necessary to adjust the oc- Recent systematic reviews have clusion with selective grinding, while Discussion reported that clinical studies did in other clinical situations no proce- not present sufficient evidence to dures were needed. The pretreat- Loss of VDO (or bite collapse) can make clear clinical recommenda- ment self-reported bruxism showed occur in the presence of attrition tions for the management of worn a partial or complete regression in and/or chemical erosion23 (ie, occlu- dentition. Nonetheless, a series of 61% of the patients immediately sal wear), particularly when bruxer approaches were common among after the prosthetic therapy: not patients grind their teeth aggres- clinicians, including the use of CR; significant differences were found sively, reducing the biting surfaces the use of resin and glass ceramics, between all the groups, in terms of so that the maxilla and mandible respectively, as temporary and final permanence of self-reported brux- rotate closer together than normal. restorative materials; and the use ism. However, at the last follow-up This can sometimes be compen- of occlusal splints to protect the re- visit a relapse of the bruxism was sated by progressive, slow extru- stored dentition.26,27 observed in 70% of the patients in sion and supereruption of opposing A recent systematic review this group. This is partially in line with teeth. In the presence of occlusal pointed out that there are many recent publications regarding the parafunctions, however, aggressive methods available to estimate a correlation between bruxism and oc- bruxers usually grind tooth struc- proper VDO; however, such meth- clusion.28,29 Thus, the clinical evalua- tures at a greater rate than passive ods are empirical and there is a lack tion of the cases treated in this study extrusion can compensate for.18 of scientific evidence and univocally showed only an immediate and tem- Moreover, loss of VDO can oc- accepted techniques to precisely porary positive effect of the occlusal cur in nonbruxer patients when determine the VDO. Clinical judg- therapies on the bruxism activity. enough teeth are lost due to decay ment and dentist preferences play In agreement with previous clini- and/or periodontal disease. The re- a paramount role in the assessment cal investigations, functional compli- maining teeth and supporting bone of the VDO. Whatever approach is cations were more frequent in cases

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© 2018 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER. 334 of restorations supported complete- be extremely reliable due to the re- that maintaining good occlusal sta- ly by implants (group C). A longer duced thickness and the temporary bility plays a paramount role.6–18 period of adaptive parafunctional luting procedures. In case of com- The main limitations of the pres- activity was reported with these pletely implant-supported restora- ent study were the retrospective prostheses due to the lack of sen- tions, the VDO increase seemed not evaluation and the presence of dif- sory feedback from the periodontal to influence the incidence of pros- ferent prosthodontists. However, as ligament; consequently, more me- thetic complications compared to to generalizability, all the cases were chanical complications can occur on the other groups. Similarly, the per- treated by experienced prosth- implant restorations after an increase manence of self-reported bruxism odontists and this could have posi- in the VDO.30,31 In the present study, seemed not to be correlated to the tively influenced the results. difficulties with speech was the most type of restoration. Conversely, this frequent complication in the implant was significantly influenced by the group. This is probably due to the centers that performed the clinical Conclusions prosthetic volume; in some cases, treatments and was more evident as particular cases of severe atrophy, the follow-up increased. This could Within the limitations of the pres- the preostheses can be bulky. VDO indicate that the operators’ evalua- ent retrospective multicenter clini- increases were usually higher in this tion influenced the outcomes and cal study, the following conclusions group than in the other groups be- that the risk of relapse is higher over can be drawn: cause in completely edentulous pa- time. Consequently, it is possible to tients the original VDO was often state that bruxism could not be suc- • The presence of functional completely lost. The observed com- cessfully treated by means of occlu- and prosthetic complications plications were temporary except for sal rehabilitations because relapse after the VDO increase was not one patient with severe atrophy who can occur after a long period. frequent. maintained moderate difficulty with The results obtained in the • Functional complications were speech due to the prosthesis vol- present clinical study were in accor- mainly noticed in completely ume. Clinicians must carefully con- dance with other clinical investiga- implant-supported rehabilita- sider this aspect in the treatment of tions aimed at evaluating the same tions but usually were no longer completely edentulous patients by variables.3,6,10,11 The achievement evident after 2 weeks. means of fixed implant-supported of a stable posterior occlusion is • No significant differences were restorations. crucial before considering any in- found between groups in terms Not significant differences in crease in VDO.18 At present, increas- of prosthetic complications and terms of functional complications ing the VDO can be considered a self-reported bruxism. were observed between the teeth safe procedure; any consequential • When necessary and if properly and mixed groups. The VDO testing signs and symptoms have been re- performed, increase of the period for the mixed and implant ported to be self-limiting.18 In the VDO can be considered a safe groups was higher than that for the presence of worn dentition, increas- and viable clinical procedure teeth group; in fact, in case of teeth- ing the VDO resulted in occlusion that could cause moderate supported posterior rehabilitations reestablishment in 91% of patients discomfort within the first treated with minimally invasive ap- after 18 months of function.32 The 2 weeks with a subsequent proaches, reliable temporary resto- limited scientific evidence available resolution of all symptoms. rations are difficult to retain for long suggests that the stomatognathic • Based on the present results, periods. In case of ultrathin occlu- system has great ability to adapt however, prosthetic changes sal reconstruction, the temporary rapidly to moderate increases in the in dental occlusion are not phase with acrylic and bis-acrylic VDO of up to 5 mm without any sig- acceptable as strategies for resin material or composite cannot nificant clinical consequences and solving bruxism.

The International Journal of Periodontics & Restorative Dentistry

Acknowledgments 11. Moreno-Hay I, Okeson JP. Does altering 21. Goodacre CJ, Campagni WV, Aquilino the occlusal vertical dimension produce SA. Tooth preparations for complete temporomandibular disorders? A lit- crowns: An art form based on scien- This was a self-founded retrospective clinical erature review. J Oral Rehabil 2015;42: tific principles. J Prosthet Dent 2001;85: study. The authors reported no conflicts of 875–882. 363–376. interest related to this study. 12. Goodacre CJ, Bernal G, Rungcharas- 22. Dawson PE. Functional Occlusion: From saeng K, Kan JY. Clinical complications TMJ to Smile Design. St Louis: Mosby, with implants and implant prostheses. 2006. J Prosthet Dent 2003;90:121–132. 23. Bartlett D. A personal perspective and 13. Carlsson GE, Lindquist LW. 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