Abstract
The purpose of this case control study is to determine the impact of screw-retained fixed cross-arch prostheses, supported by four osseointegrated implants, on articulation and oromyofunctional behaviour. Objective (acoustic analysis) and subjective assessment techniques were used to determine the overall intelligibility, phonetic characteristics and oromyofunctional behaviour at an average period of 7.3 months after placement of the fixed implant prosthesis in 15 patients and 9 age-matched controls with intact dentition and without prosthetic appliances. Overall satisfaction with the prosthesis was 87%, but 53% of the subjects mentioned an impact on speech. 87% of the subjects presented with one or more distortions of the consonants. The most common distortions were distortions of the sound /s/ (sigmatismus simplex, 40% and sigmatismus stridens, 33%), simplex /z/ (27%), insufficient frication of /ʃ/ (20%), /ʒ/ (20%), addental production of /d/ (20%), /t/ (20%) or /s/ sound (13%) and devoiced /d/ (7%). In the control group, no articulation disorders were noted. Oromyofunctional behaviour in both groups was normal. To what extent motor-oriented speech therapy (with focus on tongue function) immediately after periodontal treatment (after wound healing) would decrease the persistent phonetic distortions is a subject for further research.
The final process in speech production is articulation; the first processes are phonation and resonance. Articulation is the moulding of the airstream into recognisable speech sounds by several structures in the mouth, the articulators. The most important static or immovable articulators are the hard palate, the alveolar ridge and the teeth. The teeth, apart from serving a cosmetic purpose, also play a part in the articulation of speech sounds in several languages, including Dutch and Flemish (a language spoken in the northern part of Belgium). Along with the tongue, they are directly involved in the production of /f/ and /v/. They help to produce the frication in sounds such as /s/ and /z/ as the expiration passes over the lower edges of the incisor teeth.
Edentulism is often associated with functional and aesthetic burdens and is related to psychological problems possibly influencing daily activities. Any abnormality of the teeth, a missing tooth or replacement of one or more teeth could negatively affect or influence the production of specific speech sounds. Rehabilitation with fixed implant-supported prostheses (IFP) is a reliable and successful treatment alternative to conventional denture treatment on a long-term basis in completely and partially edentulous patients. The demand for this treatment has grown rapidly because of the increased expectation of a good quality of life, utility of the teeth and aesthetics in the middle-aged and/or older population. In daily clinical practice questions regarding oromyofunctional behaviour and especially speech production after implantation occur on a regular basis especially in professional or elite professional speakers, such as clients for whom even the smallest of articulation problems could have career consequences or could hamper the practice of their profession. In a questionnaire study on patients wearing removable full dentures in either mandible or maxilla it was revealed that phonetic problems were the reason for choosing implant borne prosthesis in 60% and 46% of the cases for the maxilla and mandible, respectively. In a similar study it was shown that phonetic concerns are more predominant in fully edentulous maxillary and mandibulary denture patients compared to partial denture wearers. Few studies have investigated the impact of cross-arch fixed prostheses on osseointegrated implants on speech characteristics and oromyofunctional behaviour, whereby the latter term refers to functions of the lip and tongue and the functions of blowing, sucking and swallowing. A data summary of the literature is provided in Table 1 .
| Authors | Subjects ( n ) Sex, age (Y) |
Timing (months/years) |
Assessment technique | Results |
|---|---|---|---|---|
| *Haraldson et al. | * N = 21 *M/F: 5/16 *m.a.: 65 y (48–73y) |
*Postimplant 10 y after |
*Questionnaire Subitems: speech and chewing |
*Chewing: all could not chew as wished/more than half difficulty biting hard foods Speech: 29% (6/21) transient phonetic problems (but had also problems with dentures) |
| Lundqvist et al. | * N = 17 *M/F: 5/12 *m.a.: 54 y (32–66y) |
*pre- and postimplant Immediately, after 3–6 m. and after 3y. |
*Questionnaire Subitems: speech and chewing *Consensus perceptual evaluation of specific speech sounds (without further specifications) *Spectrograms of /s/ |
*Chewing: all could chew all kinds of food *Speech: half of the patients had some speech problems first 3–6 m. *Speech: 66% indistinct speech especially /s/ and /t/ sounds *Spectrograms: Differences in the articulation before and after treatment. Energy of /s/ in post implant condition was spread over whole frequency band. |
| Jemt | * N = 76 *M/F:48/28 *m.a.:60y (32–75y) |
*5 year follow-up with 3 assessments the first year and 4 check-ups/4y | *Questionnaire (yes/no answers) Subitem: speech |
*Speech problems especially present during first year: 32% (23/73), second year: 6% (4/70), third year 3% (2/68), fourth year: 2% (1/65), fifth year: 0% |
| Jacobs et al. | * N = 138 *M/F: 89/49 *m.a.: 59y (29–83y) *age and gender matched control group |
*Mean years since implantation: 9.3y. | *Speech: counting 60–70 *Articulation of a group of words and sentences containing specified speech sounds *Fast repetitive articulatory movements (3 times) *Oromyofunctional behaviour (tongue placement, lip posture, jaw relationship and swallowing) |
*Speech: significantly more of the subjects in the experimental group (84%) made 1 or more articulation errors in comparison with the control group (52%). * Articulation of /s/ /z/ and/or /t/ /d/ sounds significantly different *4/5 of the subjects satisfied with their speech *No sign. Diff. between satisfaction level of speech performance before and after implantation *No sign. diff. between experimental and control group |
| Yi et al. | * N = 40 *M/F: 19/21 *m.a.: 51y (42–65y) |
*Average follow-up period of 1.8y (1.1–2.9y) | *Questionnaire (provided 2 times) Subitems: chewing and phonetics |
*High values for phonetics and chewing comfort (0.8/1) *Significant improvement for chewing. |
| Göthberg et al. | * N = 78 *M/F: 32/46 *m.a.: 63y (40–80y) |
*Retrospective; during 3y after implantation | *Notes were made of the number of visits to a dentist during the 3-year period, the reason for the consultation and the treatment or intervention | * n = 2: restricted mouth opening * n = 1: tongue-thrust parafunction *Phonetic problems: mandible: 0%/maxilla: first year: 22%, (4/18), after two years 5% (1/18) |
| Sansone et al. | * N = 14 *M/F: 6/8 *m.a.: NS (41–78y) |
*Before, after 1 and 4 m of implantation | *Observation: chewing + swallowing
*Presence of phonetic and phonological deviations during spontaneous speech, connected speech (counting from 1 to 20, days of the week, months of the year) *Perceptual evaluation of the voice |
*No significant difference for chewing and swallowing; after dental treatment chewing alterations reduced and the presence of tongue thrusting was similar before and after 1 and 4 m. *No significant difference: 1/14 lisping *No significant difference: Predominantly absence of nasal air escape, present before treatment in 3/14, after treatment in 4/14 *No significant difference: little voice variations between assessments |
| Molly et al. | * N = 10 *M/F: 6/4 *m.a.: 54y (34–68y) |
*Before and 1, 3, 6 and 12 m after treatment | *Articulation: consensus perceptual evaluation: counting from 60 to 70, list of words including alveolars and labio-dental sounds, sentences and rapidly repeated sentences *acoustic analysis of /s/ to verify the energy level of the frequencies *oromyofunctional behaviour: position of the lip at ease, tongue at ease and during swallowing |
*10% (1/10) patient had disordered speech directly post surgery *40% (4/10) interdental /s/ and /z/ before surgery, which changed to addental articulation at 12 m postoperative *30% (3/10) strident /s/ and /z/ that changed into an addental or interdental pronunciation 1 year after surgery. *Oromyofunctional behaviour: most of the patients had addental tongue position during swallowing 1 year after surgery |
It is obvious from the available literature that there is a large disparity in study design, prosthetic treatment, assessment techniques and time of evaluation. Studies evaluating the speech in subjects with osseointegrated implants show conflicting results. Although Lundqvist et al. reported phonetic problems in 66% of patients, especially for the /s/ and /z/ sounds, Jacobs et al. found 84% of patients with disordered speech especially for /s/ /z/ /d/ and /t/ sounds. According to Molly et al. interdental phonation in the presurgical condition changed to addental articulation 12 months postoperatively.
Sigmatism stridens (the production of the /s/ sound accompanied with a whistle sound) changed to addental (the production of the /s/ sound with the tongue tip against the central incisors instead of against the upper alveolus) or interdental (the production of the /s/ sound with the tongue tip between the central incisors instead of against the upper alveolus) articulation 1 year after implantation. Other authors have not observed this phenomenon.
Comparison between the studies listed in Table 1 is difficult, because different speech assessment techniques (questionnaires, perceptual evaluation, acoustic analysis) and different speech samples (counting, words and sentences) were used. Most of these lack a perceptual consensus evaluation. A perceptual consensus evaluation was performed only in the studies of Lundqvist et al. and Molly et al. The timing of assessment before and/or after implant prosthetic rehabilitation also differed, ranging from a few months to many years after finalizing the implant-supported restoration. An age and gender related control group was only used in the study by Jacobs et al.
The main purpose of this case control group study design is to determine the impact of screw-retained, fixed cross-arch prostheses, supported by four osseointegrated implants (known in dental literature as the all-on-four concept) on articulation and oromyofunctional behaviour in Flemish subjects by means of subjective and objective assessment techniques (after an initial adaptation period of on average 7.3 months). Based on an in-depth analysis of existing literature, normal speech intelligibility with the presence of minor phonetic disorders and slightly impaired oromyofunctional behavioural patterns are hypothesized. This information may lead to clinical guidelines regarding implant and prosthetic planning and be useful to dentists, orthodontists, periodontists, oral surgeons and speech language pathologists especially when treating professional speakers.
Methods and materials
This study was approved by the human subject committee of the University Hospital of Gent, Belgium.
The subjects participating in this clinical investigation were all part of a prospective clinical trial aiming to evaluate implant related treatment outcome. 20 consecutively treated participants (6 males and 14 females) were studied. All patients complained of retention problems of the removable appliance, loss of function and/or aesthetic appearance and were referred to the Department of Oral and Maxillofacial Surgery of the University Hospital Gent, Belgium. At the time of intake, all patients complained of pain and discomfort during eating, relaxing problems and oromyofunctional dysfunction. All patients were in good health and none had a history of cleft palate, craniofacial deformities, cognitive deficiency or neuromotor dysfunction. Nine patients were edentulous in the maxilla, 11 were edentulous in the mandible. The opposite jaw could consist of natural teeth, a removable prosthesis or a fixed prosthetic rehabilitation. All patients had to be edentulous in the treated jaw for at least 8 weeks prior to implant surgery to allow for initial bone remodeling and soft tissue healing after extraction 17 of the 20 subjects (9 women and 8 men) responded positively and agreed to participate to this independent logopaedic assessment. Two patients were ill at the time of the assessments. All 15 patients (9 men and 6 women) with a mean age of 48 years (range 43–75 years) received a logopaedic assessment (of overall intelligibility, articulation, oromyofunctional behaviour and an acoustic analysis) on average 7.3 months (range 6–8 months) after rehabilitation with a final screw retained cross arch implant-supported prosthesis in either mandible or maxilla. This time frame was chosen to allow for initial adaptation of the new appliance. Whenever a removable denture was present in the maxilla, it received a new set-up of teeth to maximize the occlusion. This was a prerequisite according to the treatment protocol to spread the loading forces equally on all four implants. Hearing (normal hearing is necessary for normal development and production of speech) was assessed for both ears separately at standard audiometric frequencies. All participants had hearing thresholds better than 20 dB in their poorer ear. No patients were professional speakers.
For the comparison of the overall satisfaction, the articulatory and acoustic characteristics and the oromyofunctional behaviour a control group of 9 subjects with an intact dentition of at least 28 natural teeth (without missing teeth, implants or removable prosthesis) and a mean age of 47.6 years (range 22–61 years) was randomly assembled. These control subjects were selected based on the following criteria: none of the patients had a history of cleft palate, craniofacial deformities, cognitive deficiency or neuromotor dysfunction. Hearing was assessed for both ears separately at standard audiometric frequencies. All participants had hearing thresholds better than 20 dB in their poorer ear. A Mann–Whitney U -test showed that the mean chronological age of the single-tooth implant subjects and the control subjects did not differ significantly ( p < 0.05).
Surgical and prosthetic treatment
Prior to surgery, the removable prostheses were adapted for computed tomography (CT) radiographic examination allowing virtual planning of the ideal implant location. Using the Nobel Guide planning system (Nobel, Biocare, Göteborg, Sweden). Stereolithic guide plates were constructed for flapless guided surgery whereby 4 implants were installed according to the ‘all-on-four’ treatment concept. Surgery was performed under local anaesthesia and all patients received 4 implants in the maxilla or mandible. The most anterior implants are located both at the position of the second incisor and perpendicular into the alveolar crest. The two posterior implants are directed under 30 degree angulation to avoid the sinus in the maxilla and the mandibular nerve in the mandible. The two latter implants have their screw access holes at the second bicuspid. Implants are placed without mucoperiosteal elevation, known as flapless surgery, based on the virtual planning and with the guide plate firmly attached to the bone with fixation pins ( Fig. 1 ).
After implant installation, the guide plate was deconnected and the conical multi-unit abutments were connected on the anterior implants and angulated abutments were installed on the posterior implants to correct for the angulation discrepancy. A transfer model, obtained after impression, allowed the dental technician to modify the denture into a provisional screw-retained bridge by chemically bond provisional titanium cylinders into the acryl denture. The latter was reinforced with a glass-fibre or metal reinforcement to avoid fractures under loading. Given the most distal implant was positioned at the second premolar the provisional bridge contained 10 teeth. To minimize the risk for fractures, a cantilever posterior to the last implant was avoided in the provisional bridge. The implant embrasures were sufficiently widened to allow interproximal cleaning measures with interdental brushes. The abutments were torqued into place at 35 N cm according to the manufacturer’s guidelines. The prostheses were screw retained within 2 days after surgery and occlusion/articulation was adapted by grinding and polishing whenever necessary. Patients received oral hygiene instructions and reinforcement at regular time intervals. As the surgery was flapless, there was no suturing of the soft tissues and minimal swelling occurred. The provisional restoration was replaced by a conventional final 12 units screw-retained jaw anchored bridge 3–4 months after initial treatment.
Surgical and prosthetic treatment
Prior to surgery, the removable prostheses were adapted for computed tomography (CT) radiographic examination allowing virtual planning of the ideal implant location. Using the Nobel Guide planning system (Nobel, Biocare, Göteborg, Sweden). Stereolithic guide plates were constructed for flapless guided surgery whereby 4 implants were installed according to the ‘all-on-four’ treatment concept. Surgery was performed under local anaesthesia and all patients received 4 implants in the maxilla or mandible. The most anterior implants are located both at the position of the second incisor and perpendicular into the alveolar crest. The two posterior implants are directed under 30 degree angulation to avoid the sinus in the maxilla and the mandibular nerve in the mandible. The two latter implants have their screw access holes at the second bicuspid. Implants are placed without mucoperiosteal elevation, known as flapless surgery, based on the virtual planning and with the guide plate firmly attached to the bone with fixation pins ( Fig. 1 ).
